Gilles Ponchel

Mechanisms of S-nitrosothiols intestinal permeability and NO store formation within vascular wall to improve NO oral delivery systems

Keywords: S-nitrosoglutathione, particles, oral delivery systems, nitric oxide storage, intestinal permeability

bright ideas and optimism on work always inspired me. I learned a lot from Marianne about Pharmaceutics. She let me know the importance of standardization and details in experiments. She always spends her time listening to all the developments in my work and providing help and support every step of the way. I am lucky to have these two supervisors and friends: not only guided me in the thesis, but also helped me make my casual life easier in France.

I gratefully acknowledge Pr. Hu (my supervisor during master study in Wuhan University), Pr. Maincent (Université de lorraine) and Pr. Leroy (Université de lorraine).

They provided me this precious opportunity to start my PhD here. Pr. Hu taught me a lot about basic experiment knowledge during the three years of master study in Wuhan.

Pr. Maincent gave me a lot of useful suggestions of the formulation part and Pr. Leroy let me know the importance of serous and detailed attitude in the experiments.

I would like to express my thanks to Ariane Boudier (leader of EA3452), Anne Sapin-Minet and Igor Clarot for their supporting and advices during the experiments and life. Their smile and words always comfort and inspire me especially during the discussion.

I would like to express my gratitude to Isabelle Lartaud, Isabelle Fries and Caroline Perrin-Sarrado for their help and contributions about the work during pharmacological evaluations.

My grateful words should go to Philippe Giummelly. for his help on GSNO preparation, apparatus validation as well as the operation teaching on different apparatus.

I also need to express truthful gratitude to Arnaud, Romain, Justine, Jordan and Margaux… for their help and suggestions during the cooperation and daily experiments. Special gratitude is sent to Hui and Haiyan, who accompanied and help me from my master study to PhD work. I also own my sincere gratitude to Pascale, Nathalie and all my colleges for their help at any time for any cases.

At last, the deepest thanks and heartfelt goes to my parents in China, who have always supported me about every decision, that motivated me to keep going. 7. Mass balance for all tested treatments (initial amount 50 nmol) after 4 h of permeability from the apical compartment at pH 6.4 to the basolateral compartment at pH 7.4. Mean ± sem of three independent experiments done in duplicate………..…91 Article 3 Table 1. Pharmacodynamic parameters calculated from phenylephrine concentration curves established on endothelium-intact and endothelium removed aortae subjected or not to 2 μM of S-nitrosoglutathione (GSNO), S-nitroso-N-acetylcysteine (NACNO), S-nitroso-Nacetylpenicillamine (SNAP) or sodium nitroprusside (SNP) treatment...121

Scientific works

Oral presentations (international congress)

Article 4

Table 1. Mass balance of NOx species for GSNO, GSNO-NP and GSNO-MPs

Aperçu de la thèse

Chapter 1. Introduction 1.1 Nitric oxide

Nitric oxide (NO) is a gaseous radical, whose biosynthesis and cellular signaling mechanisms were discovered in the 1980's [1][2][3][4] . As one of the most important signaling molecule, NO is involved in different organs and systems (such as cardiovascular system 5,6 , immune system 2,3 and nervous system 7 ) where it is responsible for modulating various effects 8,9 (Figure 1). Among others, NO can be regarded as a potent vasodilator, a regulator of platelet adhesion, a neurotransmitter, an antimicrobial agent, a tumor mediator and an angiogenesis promoter 10,11 . Thus, researchers from different disciplines have proposed NO as a potential therapeutic. 1.2 Nitric oxide and cardiovascular diseases (CVD)

Nitric oxide in the cardiovascular system

In cardiovascular system [15][16][17] , eNOS is mainly expressed in endothelial cells but also in platelets, cardiac myocytes and smooth muscle cells (SMCs); nNOS is basically expressed in the sarcoplasmic reticulum from cardiac myocytes, in autonomic cardiac neurons as well as ganglia or within vascular smooth muscle cells (VSMCs) (Figure 3).

However, only under oxidative or pro-inflammatory conditions, iNOS will be expressed in a large range of cells such as endothelial cells, cardiac myocytes, nerve cells, VSMCs, leukocytes and fibroblasts. NO regulates cardiovascular system via two distinct pathways: one is the activation of the soluble guanylate cyclase (sGC) followed with the downstream stimulation of Protein Kinase G (PKG), and one direct pathway through proteins S-nitrosation (the binding of a NO moiety on a thiol group from a cysteine residue to form an RSNO).

In vessels, NO synthesized by eNOS triggers the relaxation of VSMCs as well as inhibits their proliferation 17,18 . After its diffusion to the vessel lumen, it also mediates angiogenesis and inhibits platelet aggregation and thrombosis.

In erythrocytes, NO reacts with the Fe 2+ heme of oxyhemoglobin and produce nitrate ions. Then, the nitrate reductase existing in mammalian tissues reduces nitrate ions (NO3 -) to nitrite ions (NO2 -). In fact, deoxygenated hemoglobin has a nitrite reductase activity, which reduces NO2 -to NO in hypoxic and acidic environments. In addition, reversible S-nitrosation of the Cys 93 of hemoglobin might transport NO for its subsequent release in hypoxic tissues. The reduction of NO2 -and/or S-nitrosation of hemoglobin promotes NO release followed by-immediate relaxation of hypoxic tissues 19 . The diffusion and bioavailability of NO in VSMCs are regulated by hemoglobin-α (Hb-α) at the myoendothelial junction and by cytoglobin in muscle cells.

In addition, NO synthesized through nNOS in the VSMCs also help to regulate the vascular tone [20][21][22] .

In cardiac myocytes, the main roles of NO are the regulation of cardiac contractility through the modulation of the excitation-contraction coupling, relaxation, and mitochondrial respiration. In addition, the action of nNOS expressed in cardiac nerves and postsynaptic eNOS can reinforce the parasympathetic (vagal) transmission through modulating the sympathetic-parasympathetic balance, which finally reduces the heart rate 18 .

NO signaling in vascular beds in health and disease.

Under physiological conditions (Figure 4a), NO synthesized by eNOS inhibits platelet aggregation and thrombosis. Basically, NO activates soluble guanylate cyclase in VSMCs by coordination to the ferrous prosthetic of the heme moiety (which is nitrosylation) which converts the guanosine-5'-triphosphate (GTP) to cyclic guanosine monophosphate (cGMP). Then, the PKG will be activated in the SMCs. Both cGMP and PKG lowered the intracellular Ca 2+ levels through stimulating its reuptake by sarcoplasmic/ endoplasmic reticulum calcium-ATPase and its extrusion through the plasma membrane calcium-transporting ATPase 15 . In addition, the efflux of K + will also be triggered by PKG through the large-conductance Ca 2+ -sensitive potassium channel, which will hyperpolarize the cell and reduce Ca 2+ entry through the L-type calcium channel. At last, PKG promotes the dephosphorylation of the myosin light chain through the associated phosphatase. Together these modifications mediate vasorelaxation. Perivascular adipose tissue (PVAT) contributes to this effect under healthy conditions by releasing NO and adiponectin, which activates NO production in SMCs 15,18,21 .

NO storage

The first target of NO is sGC, the soluble isoform of the guanylate cyclase 5 .

However, it is now known that many actions of NO are in fact independent of cGMP. It has been reported that the cGMP-independent NO signaling pathways are attributed to S-nitrosation of structurally and functionally important cysteine residues 9 . In fact, the S-nitrosation process will produce different S-nitrosothiols (RSNOs), which are the main components of 'NO storage pool' in the body. NO synthesized from NOSs or coming from exogenous sources will be transferred into different NO storage forms like nitrite ions, RSNOs, N-nitroso proteins and other compounds like iron-nitrosylcomplexes (Figure 5). These compounds can act as NO donors or may even possess intrinsic NO-like activity 16,25 .

Nitric oxide donors

An exogenous supply of NO is needed to restore deficient NO levels. Indeed, by applying gaseous NO directly via inhalation, the pulmonary hypertension was relieved without systemic vasodilation and hypotension 29 . However, this application is still limited by several shortcomings: such as, its rapid inactivation when stopping NO administration due to the short half-time of NO; complex operation conditions with high cost (specific tanks); lack of possibility to treat pathologies at distant sites (NO cannot reach more than lungs when applied through inhalation). Therefore, a lot of compounds showing the ability to release NO have been investigated for cardiovascular diseases treatment and some of them (eg, nitroprusside and nitroglycerin) are or even have been used in clinic for decades [30][31][32] . According to different mechanism of NO formation, some of them are direct NO donors (including NO gas) whereas others require metabolism 33 . This will be discussed in the following sections. In addition, two families (related to our work) among the several new NO donors will be presented: amidoximes and RSNOs.

Direct Donors

Compounds, which release NO directly are pharmacological agents with either a nitroso (S-N=O) or nitrosyl (metal•NO) functional group. These direct donors can spontaneously release NOx species (nitric oxide related species: different redox forms of nitrogen monoxides produced by the donor molecule). The most common members of direct donors are NO gas, sodium nitroprusside, and sodium trioxodinitrate (Angeli's salt). NO gas is the most direct form but the complex conditions for inhalation and the short half time of NO (within second) limits its application 34 . In sodium nitroprusside (SNP), NO is coordinated to iron as a nitrosyl group (also connected to 5 nitrile ions) in a square bipyramidal complex 35 . Under physiological conditions, NO can be released spontaneously from the parent chemical structure. For decades, SNP was widely used for the acute treatment of heart failure and hypertension. However, the application of SNP was limited due to parenteral administration, tolerance and side effects (potential thiocyanate toxicity for long-time administration) 36 . Thus, SNP has been withdrawn from European market in 2017. In Angeli's salt, NO -, a reduced form of NO, is released spontaneously under physiological conditions. Distinct from other redox forms of NO, NO -has an unique effect on vascular smooth muscle: the relaxation mediated by NO -from Angeli's salt were more prolonged than those induced by NO 37,38 .

Besides, compounds like Diethylamine/NO and diethylenetriamine/NO (which belong to diazeniumdiolate or NONOate [N(O)NO] class) can also release NO spontaneously 39 . In these two compounds, NO is covalently linked to diethylamine and diethylenetriamine. It has been proved that diazeniumdiolates can protect the neuro system from the neurotoxicity induced by hydrogen peroxide through a rat model 40 .

Other heterocyclic compounds include the oxatriazolium class (sydnonimines) and the furoxan class 41 . These two kinds of NO donors can release NO directly using some cofactors (oxidants for sydnonimines and thiols for furoxans) 42 .

Donors Requiring Metabolism

NO donors requiring metabolism to release NO are also widely used. For example, the two classic nitrovasodilator families, nitrite esters and organic nitrates (like amyl nitrite, isosorbide dinitrate and isosorbide 5-mononitrate nitroglycerin, shown in Figure 7), have been used in cardiovascular diseases for a long time. However, there are several limitations for these NO donors, including tolerance (i.e. the loss of therapeutic effect under chronic administration), limited bioavailability, low selectivity as well as potentially adverse hemodynamic effects 43,44 . Though these limitations, these drugs are still one the main therapeutics for cardiovascular diseases treatment. As these organic nitrate esters are prodrugs, they require enzymes to generate NO in the body.

The main enzyme systems involved in the metabolism of organic nitrate/ nitrite esters is located within microsomal membranes. A lot of evidences suggest that the cytochrome P-450 (CYP450), the presence of NADPH oxidase as well as the activity of glutathione-S-transferase, are necessary in the metabolic processes of both denitration and reduction of organic nitrate esters to authentic NO 45,46 . It has also been proved that the tolerance of these NO donors is related to the increasing angiotensin II-dependent vascular superoxide anion production from NAD(P)H oxidase and eNOS 47,48 . Superoxide anion then reacts with NO generated from the NO donors, producing peroxynitrite ions (OONO -) 49 . In addition, the tolerance to organic nitrates is also associated with the cross-tolerance to endothelium-derived NO, both by the oxidative inactivation of this endogenous NO to peroxynitrite ions and by the "uncoupling" of eNOS activity 50,51 .

Cytochromes P450 pathway

The first step of the oxidation by NOS resembles a classical P-450 dependent monooxygenation, which is not the case of the second step since it consumes only 0.5 mol of NADPH. This reaction has been the subject of study of many researchers, which have proven that the oxidation of not only the NHA, but also other arginine-mimetics like amidoximes, can be done by the CYP450.

It has been proven by previous work, that many molecules presenting the C=N-OH function like benzamidoximes, ketoximes, guanidoximes, and arylamidoximes are capable of releasing NO in the presence of CYP450, NADPH and dioxygen.

One of the studied molecules that released important quantities of NO is 4chlorobenzamidoxime 54 (Figure 9). In this thesis, some new amidoximes molecules have been evaluated in the article 1, as follows:

S-nitrosothiols

As described in the Figure 5 and6, RSNOs (such as GSNO and Snitrosoproteins) can be synthesized through different ways in the body. RSNOs are regarded as promising candidates for the treatment of cardiovascular diseases because of their advantages over the existing drugs: they do not share the shortcomings of organic nitrates and nitroprusside, including oxidative stress or tolerance induction. Several initial clinical studies showed that RSNOs may be of benefit in different cardiovascular diseases 55 . As shown in Figure 10, members of this class include GSNO, S-nitroso-N-acetyl-penicillamine (SNAP),

S-nitroso-N-acetyl-L-cysteine (NACNO)…

The stability and biological chemistry of RSNOs

One of the most important parameters for the degradation of S-nitrosothiols are metal ions (specifically copper and iron). Even traces of contaminating metal ions can degrade RSNOs, that is why published half-lives for Snitrosothiols are more a measure of water purity than of compound stability 56 if no metal ion chelator is used. The common biological S-nitrosothiols are stable for several hours in the presence of the metal ion chelator diethylenetriaminepentaacetic acid. Their stabilities decrease in the order GSNO>SNAP>S-nitrosohomocysteine>S-nitrosocysteine in the absence of the metal ion chelator in pH 7.4 phosphate buffer 57 . The decomposition caused by copper (II) leads to the formation of nitric oxide without any thiyl radicals formation, which indicates that the breakdown mechanism of S-NO bond is not homolysis 57 . Another parameter accelerating RSNOs degradation is the light.

Unlike copper (II), photolysis promote the hemolytic cleavage of the S-NO bond 58 . A strong direct light can significantly reduce RSNOs concentration. The room light is sufficient to produce a small quantity of nitric oxide in a solution of RSNOs. So, RSNOs (powders or solutions) should be stored in the dark. In addition, thermal decomposition is also regarded as a key factor for the decomposition of RSNOs 57 . The mechanism of this appears to be similar to photolysis, with homolytic cleavage producing NO and an alkyl thiyl radicals.

There are still other parameters, which will decrease the stability of RSNOs like enzymatic decomposition: for example, GGT can cause the decomposition of GSNO 59 . Several enzymes are involved in the degradation of RSNOs and they will be discussed later in the manuscript (in vivo metabolism of GSNO).

RSNOs are biologically involved in 3 main reactions (Figure 11): nitric oxide release, transnitrosation and S-thiolation 60 .

Nitric oxide release

As mentioned above, nitric oxide is easily generated from RSNOs in the presence of metal ions such as copper ions, iron ions and reducing agents. This reaction is reversible because its products are still a thiol and a Snitrosothiol 61 . When the transition occurs from a relatively stable S-nitrosothiols (e.g. GSNO or SNAP) to the thiol function of cysteine amino acid, a relatively unstable S-nitrosocysteine will be formed. S-nitrosocysteine can decompose and release NO in the presence of Cu + or spontaneously 62,63 . Transnitrosation represents an important way to transfer 'NO' from species to species inside cells, which is regarded as a potential mechanism for the modification of protein activity 64 .

S-Thiolation

S-thiolation reaction occurs through the nucleophilic attack of the sulfur of RSNOs by a thiolate anion, producing a disulfide and nitroxyl anion 65,66 . The Sthiolation of proteins has been regarded for a long time as an intracellular response to oxidative stress. When enzymes were incubated with RSNOs, both S-nitrosation and S-thiolation occured 67,68 . However, exposure of cells to nitrogen oxides led to extensive intracellular S-thiolation 69 . Thus, S-thiolation is a more stable modification than S-nitrosation.

In addition to these three biological reactions, some RSNOs can have direct effects. On the one hand, it has been suggested that GSNO acts as a substrate for several enzymes utilizing glutathione (GSH), such as the GGT and the glutathione peroxides 59 . On the other hand, several RSNOs like GSNO, SNAP can S-nitrosate sGC, which will inactivate the enzyme 70 .

GSNO

GSNO, as one of the main intracellular RSNOs, seems to be a good choice as drug candidate with several advantages over others RSNOs: i) GSNO is a physiologic RSNOs with no side effects. ii) it is relatively stable compared to other endogenous RSNOs; iii) dedicated enzymes like the GGT are able to catalyze the release of NO only from GSNO and not from other natural (e.g. Snitrosoalbumin) nor synthetic RSNOs (e.g. NACNO and SNAP).

Chemical Synthesis of GSNO

GSNO is easy to synthesize through the reaction between GSH and nitrous acid. This reaction is efficient and fast with high yield. Unlike most low-molecular weight RSNOs, GSNO can be precipitated with acetone, which results in a pink solid powder. Other nitrosating agents could be used for GSNO synthesis, such as nitrosonium, nitrosonium chloride, tetrafluoroborate, dinitrogen tetraoxide and dinitrogen trioxide 59,71 . However, reaction between GSH and nitrous acid is the most frequently used with both a simple procedure and a high yield. The original study by Hart 72 showed an extinction coefficient for GSNO of 922 M -1 cm -1 at λmax = 335 nm, which is in agreement with the result measured in our lab with the value as 922 M -1 cm -1 at λmax = 334 nm 73 . As GSNO is easy to degrade under all these conditions, it is important to develop dosage forms to protect GSNO from degradation for the different therapeutic applications.

In vitro stability

In vivo metabolism

A summary of the four main enzymatic metabolisms of GSNO is presented in Figure 12. They will be subsequently discussed in the text.

GSNO reductase (GSNOR) and carbonyl reductase 1 (CR1):

These two enzymes are able to catabolize GSNO without any release of NO. GSNO reductase reduces GSNO using NADH as a cofactor. The product GSNHOH is an intermediate, which can either rearrange and being hydrolyzed to produce GSO2H and ammonia or react with GSH and produce GSSG and NH2OH 74 . Through catalyzing the breakdown of GSNO, GSNOR can modulate intracellular reactive nitric oxide availability. In addition, it can also indirectly regulate RSNOs through GSNO-mediated protein S-nitrosation 75 .

Compared with GSNOR, CR1 is one of the most recent addition to the list of GSNO reducing enzymes 76 . Similar to GSNOR, the catalytic reaction of GSNO by Carbonyl reductase 1 produces the same intermediate product.

Thioredoxin system (Trx) and Protein disulfide isomerase (PDI):

The thioredoxin superfamily is a large multigene family that contains five main protein groups: Trx, PDI, glutaredoxins, glutathione peroxidases, and glutathione-S-transferases. All the members share a common structural arrangement and are major players in oxidative protein folding. Among them, Trx and PDI play important roles in the metabolism of GSNO.

The thioredoxin system plays a critical role in both control and maintenance of redox homeostasis, and this system comprises three main members: Trx, TrxR, and NADPH 77 . Trx has two isoforms: Trx1 mainly localizes in the cytosol and the nucleus; Trx2 localizes in the mitochondria. Through their vicinal dithiols at the active site, they are able to reduce protein disulfides. Reduced Trx (Trx-(SH)2) reacts directly with a protein disulfide and produces a reduced protein dithiol and oxidized Trx (Trx-S2). Although Trx has been regarded as a target of S-nitrosation for a long time, it has also been identified as a main player in the reduction of low-molecular weight and protein S-nitrosothiols. Trx plays a critical role in both denitrosation and transnitrosation reactions [78][79][80] .In denitrosation, reduced Trx reacts directly with the low-molecular weight RSNOs (like GSNO) and protein RSNOs. In transnitrosation, Trx is S-nitrosated, leaving behind a thiol. Then, the S-nitrosated Trx will be turned over and nitroxyl will be released to form oxidized Trx. The oxidized Trx can be reduced by the TrxR and NADPH.

The Trx system has been hypothesized as the primary regulator of the S-nitroso proteome in most tissues because of its more ubiquitous expression than GSNO reductase and carbonyl reductase 59 .

PDI is an enzyme has two catalytic sites composed of two cysteine residues, which catalyzes the breakage and formation of disulfide bonds between cysteine residues in proteins to fold proteins. The catalyzing mechanism of PDI is similar to RSH-RSNOs exchange reaction 81 . The protein disulfide isomerase regulates intracellular transfer of nitric oxide through catalyzing transnitrosation and denitrosation. It has been reported that PDI can denitrosate GSNO and it is suggested that NO released through this reaction combines with dioxygen in the hydrophobic environment and generates N2O3 82 .

This "NO-charged PDI" can perform both intramolecular and intermolecular Snitrosation reactions. Reduced PDI can denitrosate S-nitrosated PDI to release NO.

γ-glutamyltranspeptidase (GGT):

As an enzyme on the extracellular cell surface, the γglutamyltranspeptidase is involved in the catabolism of GSH and GSH adducts and the processing of thiol-based leukotrienes 83 . The enzyme transfers the γglutamate group from glutathione and leaves cysteinyl-glycine through either hydrolysis or in the presence of a co-substrate like glycyl-glycine 84 . It has been reported that GGT can use GSNO as a substrate, producing Snitrosocysteinylglycine to accelerate the degradation of GSNO. GGT appears to work when GSH crosses cell membranes to deliver extracellular cysteine 83 .

In addition, the substrates for GGT include many substituted derivatives of GSH, and GSSG, and GGT acts to degrade and recycle both GSSG and the products of glutathione S-transferase activity 85 .

Other enzymes-dependent mechanisms

In has been suggested that other enzymes also play a role in the metabolism/degradation of GSNO. These enzymes include glutathione peroxidase 86 , xanthine oxidase 87 and CuZn superoxide dismutase 88 . In the work of Hou et al 86 , glutathione peroxidase alone catalyzed the GSNO, without the presence of any thiol or H2O2. Under aerobic conditions, xanthine oxidase showed its ability to induce the decomposition of GSNO in the presence of purine or pteridine substrates 87 . CuZn superoxide dismutase 88 was able to catalyze the GSNO decomposition in the presence of GSH and result in the production of NO. Through these enzymes, the reaction products are nitric oxide, GSH or glutathione disulfide. However, it has been shown by kinetic measurements that their reactions are much less efficient than the other enzymes (GSNOR, Trx system or GGT) 89 .

GSNO related delivery systems and therapeutic potentials

Due to the low stability of GSNO in vitro and in vivo, an ideal formulation should protect it from decomposition while ensuring suitable localization and kinetics of drug delivery. GSNO, as a small hydrophilic drug, could diffuse very easily, which may cause two issues: low encapsulation efficiency (during formulation process) and initial burst (i.e. massive drug release over a short time period after administration). The main delivery systems previously reported for GSNO will be discussed in detail in the following sections. They were categorized according to the administration route: (i) intravenous, (ii) topical, (iii)parenteral other than intravenous (implants) and (iv) oral.

Intravenous administration

Intravenous (IV) therapy delivers liquids directly into a vein. The therapeutic potential of GSNO was evaluated in humans through IV administration, focusing on its ability to effectively decrease platelet aggregation and blood pressure (as shown in Table 1). GSNO showed its antiplatelet effect at low dosage (2.5 mg IV for healthy women) without hemodynamic changes 90 .

Similarly, Moncada et al. 91 have reported that when applied to patients undergoing percutaneous transluminal coronary angioplasty, small IV doses (4.4. nmol/kg/min) of GSNO inhibited platelet aggregation without decreasing blood pressure. These results have been supported by several similarly designed experiments, which applied low dosage GSNO to reduce platelet aggregation 28,[92][93][94] as well as embolization [95][96][97] . It has been suggested that the antiplatelet effect of GSNO is driven by the high expression of cell surface protein disulfide isomerase on platelets surface, catalyzing the release of NO 98 . However, at higher dosage GSNO caused hypotension to healthy adults 98 , which come from the vasodilation effect of NO. Indeed Rassaf 100 described that infusion of GSNO at 30 µmol over 1 minute induces vasodilation and causes hypotension to healthy adult humans. All these studies reported pharmacological effects (anti-platelet aggregation, embolization and hypotension) of GSNO with minimal or no side effects.

Through IV, GSNO was not only administrated as a solution, but also as a suspension of nanoparticles in some preclinical studies. For example, Duong 101 and his group obtained self-assembled nanoparticles through GSNOconjugated diblock copolymers (2-vinyl-4,4-dimethyl-5-oxazolone and oligoethylene glycolmethacrylate), which showed a high stability with sustained release (over 80% of NO released from the nanoparticles after 24 h in the presence of ascorbic acid). After decoration with vitamin A for liver targeting (the therapeutic aim was reducing portal hypertension), these nanoparticles were intravenously administrated to rats (with GSNO concentration equivalent to 500 µM in rat blood). They preferentially accumulated in the liver as expected, so they could be applied to alleviate liver fibrosis and portal hypertension. Delivery of GSNO through IV route has several merits, such as rapid onset drug effect, direct delivery to the blood and precise control of drug quantities. However, low patient compliance and short drug duration time are the main drawbacks of intravenous delivery. Thus, other delivery systems of GSNO have been developed. After a single subcutaneous administration to healthy rats, these formulations showed a less pronounced but more sustained hypotension compared to free drug, and were able to prevent transient platelet hyper-responsiveness.

Moreover, in a rat model, a single administration 2 h after induction of a stroke provided cerebroprotection (histological and functional benefits), while free drug was deleterious. Similarly, other scaffolds were developed such as nanocomposites made of polyhedral oligomeric silsesquioxane/poly(carbonateurea) urethane by de Mel 118 , and PLGA)/ PEG/PCL stents by Acharya 119 . All these implants were developed as the treatment methods for cardiovascular diseases and they showed a stable, sustained and consistent release of NO from 1 day to several weeks in vitro. Studies about GSNO delivery mainly focused on parenteral and topical administrations, whereas a little attention has been paid to its oral delivery (Table 4). As one of the most preferred administration methods, oral delivery has several advantages over other routes such as compliance and convenience of patient (which helps to increase therapeutic efficacy), lower cost of production considering the manufactured conditions (sterility is unnecessary).

In addition, oral route is interesting for physiological reasons: the gastrointestinal tract supplies extensive surface (300 to 400 m 2 ) 120 for drugs absorption but also poses challenges to prevent their degradation.

In the work of Shunmugavel et al. 121 , free GSNO was directly applied orally to rats with spinal cord injury. Then ameliorated inflammatory sequelae were observed in bladder and renal tissues, compared with control group. Similarly, several other applications have been proposed for oral administration of GSNO to animals: Giri et al. 122 used the GSNO to inhibit proliferation of chemo responsive and chemo resistant ovarian cancer cell lines with oral dosage 1 mg/kg to rats. In the work of Nath et al. 123 the progression of a chronic experimental autoimmune encephalomyelitis was slowed in mice after applying GSNO. In a rat model of experimental autoimmune uveitis 124 , a significant suppression of inflammatory mediators was shown after oral administration of GSNO. However, due to the degradation of GSNO along the gastrointestinal tract, high dosage of free GSNO (1 mg/kg) has to be used in these experiments.

In order to protect GSNO from degradation, several particles adapted to oral route administration have been developed in our lab. For example, Wu et al developed GSNO-loaded nanoparticles 125 (GSNO-NP) using polymer Eudragit® RL PO through a double emulsion/solvent evaporation method, and they showed a protection and a sustained release of GSNO. GSNO-NP were then embedded into an alginate, chitosan, or alginate/chitosan matrix to form nanocomposite particles 126,127 (GSNO-aNCP, GSNO-cNCP and GSNO-acNCP, respectively). All these nanocomposites showed higher encapsulation efficiency and better sustained release of GSNO. The GSNO-acNCP also led to the formation of a NO store in the aorta wall after a single oral administration to rats.

Gastrointestinal barrier

All along the gastrointestinal tract various parameters can trigger RSNOs decomposition: enzymes and metal ions (described in the degradation of RSNOs) as well as pH variations. For the stomach, it produces gastric juice, which contains potassium chloride, sodium chloride and hydrochloric acid (HCl). The HCl keeps the acidic environment at pH 1.5 to 3.5 and induces the degradation of proteins and peptides into aminoamides. After entering the duodenum, pH increased rapidly from 2 to 6. The extreme pH and rapid change may accelerate the degradation of RSNOs and decrease its bioavailability. In addition, the enzymes or the metal ions existing in the gastrointestinal tract can also cause GSNO decomposition.

The barrier of intestine is a complex multilayer system which is composed of an external "physical" barrier and an inner immunological barrier 128 . The epithelial cell layer is covered with two mucus layers, which forms the protective external barrier. The single epithelial cells layer interspersed with various other cells, such as goblet cells, which produce mucus, Paneth cells, which produce anti-microbial peptide, as well as enterocytes M-cells, which specialize in luminal sampling. All of these cells forms the main barrier between the outside world and the proper function in the body. The layer under epithelium is the lamina propria, where exists various innate and adaptive immune cells such as B cells, T cells, mast cells, eosinophils and macrophages. All of these consist of the immune system, which responds with "toleragenic-reaction" or "active" eradication towards foreign antigens. The intestinal barrier plays an important role in the absorption and the bioavailability of drugs through oral administration [129][130][131] .

Epithelial cells lining is a kind of tight junctions that repels harsh fluids, which may injure mucosa. The transport of drugs through the cells is the key factor of bioavailability (will be discussed in the Chapter 2). The mucus blanket is secreted by mucosal neck cells and surface epithelial cells. It forms a gel-like coating on the surface of mucosa with protecting effect. The bicarbonate is also secreted by epithelial cells.

All these mucosal barriers prevent drugs (like GSNO) from entering blood vessels.

With the viscosity and interactive nature, the mucus layers offer a resistance to the diffusion of drugs and limit their bioavailability. In addition, GSNO/RSNOs is also easy to be degraded during the gastrointestinal tract, via the different enzymes (such as Trx, PDI, GGT) on the cells.

Nanoparticles/microparticles for oral delivery of biological molecules

The bioavailability of biological molecules is always reduced by their susceptibility to degradation and low penetration across the intestinal barrier. Thus, the challenge to deliver GSNO through the oral route is to improve its bioavailability. Several strategies are on ongoing investigations such as chemical modification, encapsulation, use of absorption enhancers… Among all the methods, encapsulation into nanoparticles/microparticles seems to have advantages over others 131 :

1. The size and surface characteristics of particles are easy to manipulate to achieve drug targeting after administration.

2. The control of particles and the sustain of drug release will help to increase therapeutic efficacy with less side effects.

3. The degradation of particles and their controlled release effect can be modulated through the choice of matrix constituents.

4. Particles provide a good protection for drugs through the gastrointestinal tract and preserve the drug activity 5. Intestinal permeability can be enhanced using different polymers.

Nanoparticles targeting the gastrointestinal tract

The main aims to design nanoparticles to deliver biomolecular drugs are to control their size, surface properties and release kinetic parameters in order to get site-specific action with therapeutic drug concentrations. According to the targeted sites, developed nanoparticles can be classified into stomach targeting, small intestine targeting, intestinal lymphatic system targeting as well as colon targeting 129 (Figure 13).

Stomach targeting nanoparticles

Most of the nanoparticles designed to target the stomach were applied to increase the gastric retention using mucoadhesive polymer such as chitosan. As a natural polysaccharide composed of N-acetyl-D-glucosamine and β-(1-4)-linked Dglucosamine 132 , chitosan contains amines, which can interact with negatively charged sugars on mucin and thus is widely used as mucoadhesive reagent. However, chitosan is easy to dissolve in acidic pH, so it should be complexed with polyanions to prevent its rapid dissolution. For example, Chang et al. 133 developed amoxicillin-loaded nanoparticles through complexing chitosan and poly-glutamic acid polyelectrolytes, which can be used for the treatment of H. pylori infections. In another investigation, Lin et al. 134 described fucose-chitosan-heparin nanoparticles crosslinked with genipin and loaded with berberine, which have the potential to treat H. pylori infection.

Small intestinal targeting nanoparticles

Targeting the small intestine has been regarded as a useful way to improve systemic absorption of drugs such as vaccines, peptides, proteins and other macromolecules. This kind of nanoparticles often uses enteric polymers alone or complexed with other polymers, to protect drug from decomposition in the stomach and/or to get specific site release 129 . In order to target small intestine, He and colleagues 135 fabricated insulin-loaded solid lipid nanoparticles with a vitamin B12 stearate conjugate for targeting. These nanoparticles presented more than 2-fold higher bioavailability compared to non-modified ones. Similar nanoparticles were synthesized by Verma 136 , through coating insulin-loaded calcium phosphate nanoparticles (Insu-Cap NPs) with sodium alginate and chitosan-vitamin layer congaing B12 conjugate.

Intestinal lymphatic system targeting nanoparticles

The targeting of nanoparticles to the intestinal lymphatic system has been extensively tested for improving drugs bioavailability especially for the ones with extensive degradation along gastrointestinal tract and/or hepatic first-pass metabolism.

For lymphatic system targeting, various fatty acid monoglycerides, diglycerides and triglycerides were applied. Alex et al. 137 improved oral bioavailbility of lopinavir, a drug with low water solubility and low bioavailability, part of the highly active antiretroviral therapy, using glyceryl behenate solid lipid nanoparticles. During the work of Zhang et al. 138 , candesartan cilexetil-loaded glyceryl monostearate nanoparticles were obtained and turned out to improve the in oral bioavailability of the drug in rats around 12-fold.

Colon targeting nanoparticles

The majority of formulation designed to target colon through oral route are mainly applied to treat inflammatory bowel diseases (IBD). To target the colon, pH sensitive polymers are commonly used alone or in combination with other polymers, which assist to target like azo containing moieties. Among all these polymers, Eudragit S is the most frequently used. For example, the group of Gugulothu 139 developed pH sensitive nanoparticles using Eudragit S100. These nanoparticles contained curcumin and celecoxib, which can be used for the treatment of IBD. After oral administration to

Trinitrobenzene sulfonic acid induced rats, nanoparticles significantly lowered inflammatory cell activity in rat colon homogenates compared to the free drug.

Microparticles for oral delivery

Similar with nanoparticles, microparticles offer numerous advantages such as targeted delivery, protection of drug during gastrointestinal tract, and intestinal permeability enhancement according to the polymer applied. Despite the impressive progress made in targeting delivery, which allows good drug protection with less side effects, only a few drug-delivering nanoparticles have really reached the market. The following shortcomings are the main limits to their development 140,141 :

1. Low drug loading capacity. The drug loading (the weight of drug compared with the weight of carrier material) of nanoparticles is usually less than 5% 142 . Due to this poor value, either the quantity of drug administrated is not enough to reach a pharmacologically active concentration at the target, or the required quantity of carrier material is too great, producing toxicity or other side-effects.

2. Burst release. The other main limit of nanoparticles is the rapid drug release after administration. It may come mainly from either the quick release of drug simply adsorbed or anchored at the surface of nanoparticles, or from its fast across the short length radius of nanoparticles. As a result, a significant part of drug will be released before reaching targets, leading to low efficacy as well as side-effects.

Compared with nanoparticles, microparticles usually offer better drug loading as well as longer sustained release time. On the one hand, with bigger size, microparticles can load more drugs than nanoparticles with the same amount of polymer. On the other hand, as the mechanisms of drug release from particles (especially polymeric particles) include diffusion, particle erosion and degradation (for nanoparticle using biodegradable material), it takes a longer time for erosion-triggers to penetrate the particle, and to the drugs or debris to release out in the bigger microparticles [142][143][144] .

Transport mechanism through intestinal barrier

The main routes which drugs cross the intestine membrane can be divided into two pathways: paracellular pathway and transcellular pathway. Paracellular pathway means drugs cross through the aqueous pores at the tight junctions between the intestinal cells while transcellular pathway requires drug diffusion across the lipid cell membrane. The mechanism of intestinal transport can also be divided into passive diffusion or active transport. The active transport can be divided by two part: influx and efflux. A lot of influx transporters are expressed by the small intestinal mucosa. Influx is important for the absorption of nutrients and vitamins, it also plays important roles in the drugs absorption, such as the large neutral amino acids, di-/tripeptides, nucleosides bile acids, and monocarboxylic acid transporters. However, the main function of efflux is as an absorptive barrier to limit oral bioavailability of many drugs and xenobiotics. These transporters include breast cancer resistance protein, Pglycoprotein, organic ion transporters and multi-drug resistance-associated protein 145- 147 .

In order to apply RSNOs through the oral delivery route, it is important to know more about the intestinal permeability of different RSNOs. Different mechanisms could be involved in the absorption of molecules through the intestinal barrier: paracellular way, transcellular way (including carrier-mediated way as well as receptor-mediated transport) 128,129 (Figure 14).

Paracellular transport

In paracellular transport, molecules cross the epithelium through the intercellular spaces between the epithelial cells. As a passive transport, the paracellular transport always results from diffusion and is controlled by the tight junctions. The tight junctions are the main barriers that limit the permeation rate during the paracellular transport of ions and large molecules 148 . The size of the paracellular space is around 10 Å and the sizes of aqueous pores resulting from epithelial tight junctions differ from their location:

7-9 Å, approximately 3-4 Å and 8-9 Å in human jejunum, ileum, and colon, respectively 149 . Thus, molecules with a radius above 15 Å (around 3.5 kDa) cannot be transported through the paracellular way 150 . Furthermore, tight junctions represent only around 0.01% of the total area on the intestine surface 151 . In addition, paracellular transport varies depending on electrical resistance among epithelia but is not largely influenced by the physicochemical properties of drugs, such as lipophilicity or hydrogen bonding capacity 152,153 .

Transcellular transport

The transcellular transport occurs by transcytosis across intestinal epithelial cells, a special process through which cells take up particles. A typical example of transcellular transport is the transport of glucose from the intestinal lumen to the extracellular side through epithelial cells. An endocytic process takes place first at the cell apical membrane, followed with transport through the cell and finally release of glucose at the basolateral side 154 . Compared with the apical membrane, the basolateral membrane is thinner and more permeable due to the low protein-to-lipid ratio. Two key factors are significant to the transcellular transport: (i) physicochemical properties of molecular or particles, such as liophilicity, size, charge and hydrogen bond potential (ii) physiology of the gastrointestinal tract 155,156 . The two primary intestinal cells for transport are enterocytes and M cells. Enterocytes are the main cells lining the gastrointestinal tract whereas M cells represent a very small proportion of the intestinal epithelium 157 . M cells are mainly located in the epithelium of Peyer's patches and they deliver peptides and proteins from the lumen to the underlying lymphoid tissues to help inducing immune responses. M cells can transport a wide variety of materials with their high transcytosis capacity 158,159 . M cells take up particles, macromolecules and microorganisms through adsorptive endocytosis via clathrin-coated pits and vesicles, fluid phase endocytosis and phagocytosis 160 .

Carrier-mediated transport is an active absorption, which requires energy and carriers to uptake specific molecules. The carrier recognizes the target molecules and transport them even against the concentration gradient. Through carrier-mediated transport, drugs can be transferred across the intestine barrier and then released into circulation 161 . The process is especially adapted to small hydrophilic molecules 162 , such as small di/tripeptides, amino acids and monosaccharides 163 .

Protein drugs are the main clients in receptor-mediated transport. During this process, protein drugs usually act as a receptor for surface-attached ligands or as a receptor-specific ligand for surface-attached receptors 164 . It has been reported that receptor-mediated transport can be exploited to increase a protein bioavailability through oral delivery. The receptor-mediated transport comprises cell invagination, resulting in the formation of a vesicle. This transportation is called endocytosis and includes pinocytosis and phagocytosis, or the receptor-mediated potocytosis (nonclathrin-mediated) and endocytosis (clathrin-mediated).

As both carrier-and receptor-mediated transport also drive the target molecule into circulation through the cell or cell membrane, they can be regarded as transcellular pathways.

Intestinal permeability measurement with Caco-2 cell monolayer model

It is critical to select the right techniques to assess the intestinal permeability of drugs. A wide range of methods have been applied to measure the intestinal permeability according to the different settings (in vivo, ex vivo or in vitro). The in vivo measurement is the most direct method to check the intestinal permeability. For example, the typical measurement for intestinal permeability in humans is testing the urinary excretion of lactulose and mannitol (non-metabolized sugars) after oral administration over a 6 h period. The ratio of lactulose/mannitol can reflect the intestinal permeability state 165 . In addition, the in vivo measurement method has also been applied in the animal studies after oral gavage of PEG, sugars, or fluorescently labeled dextrans followed by detection in the blood or urine 166,167 . However, in vivo measurement is time-consuming and has several drawbacks, such as variation between the humans and animals or just the different genotype and phenotype of humans 165 . Ex vivo test is another method applied to the intestinal permeability. One of the commonly used is Ussing Chamber, which mimics the in vivo compartmentalization between the intestine lumen and the intestine mucosa 168 . An intestine segment separates the system into two compartments (donor and acceptor) with equal volumes. Through adding different permeability markers (such as sodium fluorescein (paracellular), propranolol (transcellular), mannitol…) to donor compartment and harvesting in acceptor compartment, the intestinal permeability can be measured. This method is limited by its short time of measurement because of the low ex vivo viability (approximately 2 h) 168 .

Compared with in/ex vivo, the in vitro models have several advantages such as lower cost, high accessibility and higher throughput. Furthermore, it may reduce the use of animals for experimental purposes 169 . Cell monolayer cultures have been regarded as one of the most important models for intestinal permeability. Through incubating the differentiated intestinal epithelial cells (such as Caco-2, HT-29, and T-84 cells) on semipermeable filter, an oriented cell monolayer is formed thus defining an apical and a basolateral compartment 170 . Among these different cell lines, Caco-2 is the most widely applied to mimic the intestinal epithelial barrier. Despite Caco-2 cells were derived from human colorectal adenocarcinoma, they are close to enterocytes from small intestine after differentiation and polarization 171 . For many compounds, strong correlations have been observed between permeability (passive transcellular and paracellular) across Caco-2 cell monolayers and oral bioavailability in humans 172,173 . Thus, this in vitro model has also been applied to rapidly predict the intestinal permeability of a as well as the pathways utilized during transport 174,175 .

Biopharmaceutical Classification System

The drugs are categorized into 4 classes according to the Biopharmaceutical Classification System (BCS) based on the solubility and permeability to biomembranes (as shown in Figure 15 176 ). The BSC is regarded as a guideline for the formulation scientists, for the proper selection and design of the formulation of different drug substance. Class II: These drugs have low solubility but high permeability, thus, the dissolution rate becomes the key parameter for bioavailability. These drugs display variable bioavailability and need enhancement of their dissolution rate to improve their bioavailability. They are also suitable for controlled drug delivery.

Class III: Permeation through the intestinal membrane becomes the rate-determining step for drugs of Class III. As absorption is limited by permeation rate, their bioavailability is independent of drug release from the dosage form. These drugs are problematic for controlled release application and they need improvement of intestinal permeability to enhance the bioavailability.

Class IV: Drugs belonging to this class exhibit poor and variable bioavailability. Several parameters govern their bioavailability, such as intestinal permeability, rate of dissolution, gastric emptying, and so on. They are generally not suitable for oral drug delivery.

Thus, it is important to make clear the mechanism about the intestinal permeability of different RSNOs and which class it belongs to. In the article 2, intestinal permeability of three different RSNOs (GSNO, NACNO and SNAP) have been tested through a

Caco-2 monolayer transwell model:

NO storage

In the previous work of our lab 127 , nitric oxide storage has been found in the vascular wall after the administration of GSNO loaded nanocomposite to Wistar rats.

As described in the Chapter 1, S-nitrosothiol (RSNOs) is one of the main NO storage forms in our body. The transnitrosation (such as transfer NO from cysteine residue to another, from GSNO to other proteins) plays an important role in both the production and degradation of RSNOs. Several studies have proven the existence of NO stores.

For example, photosensitive NO stores have been identified through the relaxation of precontracted blood vessels after exposition to light 177,178 . In further study, photosensitivity was lost after exposed the endothelium removed vessels repeatedly exposed to light, but it recovered when these vessels were exposed to a NO donor 179 .

Another evidence is the relaxation effect of blood vessels after adding the low molecular weight thiols like N-acetylcysteine (NAC). NAC can displace NO from other high molecular weight RSNOs then produce NO to vasodilate the vessels 180 . The existence of NO stores has been proposed as the explanation for the persistence of endothelium-dependent relaxion effects after using inhibitors to block the NO synthase 181 . It is also the reason for the lasting hyporesponsiveness of vessels to vasoconstrictors elicited by NO donors 182 . To conclude, all these studies proven the existence of NO stores and support the idea that S-nitrosation of thiols in tissues is a mechanism of NO stores (RSNOs) formation from which NO can be subsequently released.

Main forms of NO storage

In fact, RSNOs and dinitrosyl iron complexes (DNIC) are the two main forms of NO transport and storage in the organism. These two types of compounds can be of high or low molecular weight. The protein complexes are usually more stable compared to the one with low molecular weight. Among the low molecular weight nitrosothiols, S-nitrosocysteine has the closest physicochemical and virtually identical vasodilatory properties to endothelium derived relaxing factor 183 . GSNO has been regarded as the intermediate between NOS activation and free NO formation. It was suggested that NOS nitrosates glutathione to form GSNO, which releases NO in the presence of Cu +179,184,185 . In addition, low molecular weight RSNOs can also pass NO to the cysteine residues of proteins through transnitrosylation 186 . S-nitrosylation or Snitrosation of certain proteins give rise to NO transport-storage forms such as S-nitrosoalbumin 187,188 and S-nitrosohemoglobin (SNO-Hb) 189 . Iron-nitrosyl-hemoglobin is formed through the interaction of heme-Fe(II) with NO. Under high O2 pressure, NO moiety is then transfer from the heme group to the cysteine 93 residue of Hb, resulting in the formation of SNO-Hb. Conversely, NO is released from SNO-Hb when O2 tension decreases. This results in vasodilation and the improvement of tissue perfusion and gas exchange 190 . In addition, S-nitrosoalbumin also serves as an important NOtransporter.

Except RSNOs, DNIC with thiol-containing ligands [(RS)2Fe(NO)2] are other possible endogenous NO storage form 191 . DNIC were found in animal tissues over 50 years ago via their specific electron paramagnetic resonance signal 192 . The main biological activity of DNIC is due to release of NO, transfer NO to cysteine group of proteins, or transfer Fe(NO)2 groups to proteins dithiols to form new DNIC. In the work of Galagan 193 , exogenous DNIC were administrated to rats and resulted in quickly spread over tissues followed with hypotensive effects.

These two kinds of NO storage forms (RSNOs and DNIC) are capable of interconversions according to the level of Fe 2+ , NO, as well as low molecular weight thiols in the cell (Figure 16). When thiols content decreases, both DNIC and RSNOs amount decrease. When NO level decreases while the thiols and iron concentration remain constant, DNIC and RSNOs mainly serve as NO donors, which transfer NO to the acceptor cell. Excessive iron accelerates RSNOs dissociation more than DNIC dissociation. NO is principally stabilized in the form of RSNOs with excessive thiols as compared to iron 194 . Apparently, RSNOs is the main NO transport form between the cells. When RSNOs arrives in the region where content of non-heme iron and thiols increased, it initiates DNIC formation, while dissociation of DNIC releases NO 195,196 .

S-nitroso-proteins and its functional significance

As one of the main forms of NO storage in organisms, S-nitroso-proteins (such as SNO-Hb and S-nitrosoalbumin) play an important role in the transport and prolong the lifetime of NO. However, the S-nitrosation and denitrosation of proteins (enzymes) may also change their activity. For example, cysteine 69 (C69) is the nitrosable thiol of Trx 198 .

It has been suggested that the S-nitrosation of C69 results in the increase of Trx activity compared with control. Whereas, this increase is not inducible using the C69S mutant Trx 199 . In addition, the enzyme PDI, a member of thioredoxin superfamily, has also proven to be nitrosable in vitro 200 . Some investigations have shown that PDI losses its activity after S-nitrosation with a fivefold excess of the SNO donor 201 . However, no data has been presented about the existence of PDI-SNO in vivo. Caspases are a family of proteolytic enzymes that play important role in cellular death. SNO is believed to exert a portion of its anti-apoptotic effects via nitrosation of cysteine from the active site of at least two members from the caspase family 202 . To conclude, S-nitrosation activity is of significance to the activity of enzyme.

Endothelial dysfunction

Endothelial dysfunction is characterized by the decrease of the bioavailability of vasodilators, especiallyNO, and/or an increased production of endothelium derived contracting factors 203 . It is involved in most forms of cardiovascular diseases, such as atherosclerosis, hypertension, peripheral artery disease, chronic heart failure, coronary artery disease, diabetes, and chronic renal failure.

Several factors participate in the formation of endothelial dysfunction, such as cardiovascular risk factors including aging, smoking, hypertension, hyperglycemia, hypercholesterolemia, and genetic factors like family premature atherosclerotic disease history 203,204 . Endothelial dysfunction causes a chronic inflammatory process with a reduction of antithrombotic factors as well as an increase in prothrombotic products and vasoconstrictors, resulting in abnormal vasoreactivity and elevating risk of cardiovascular diseases 203,205,206 (Figure 17). In addition, endothelial dysfunction has also been related to obesity, elevated C-reactive protein, and chronic systemic infection [207][208][209][210][211][212] . As the imbalance in the production of vasodilating factors (NO) is the key point of endothelial dysfunction, the formation of a NO store may restore the physiological role of NO which helps counteracting endothelial dysfunction.

To make clear the NO storage in vascular wall, different rat aorta (endothelium Chapter 4: Nano or micro? Three different particles to deliver GSNO through oral route.

As described in the chapter 2, GSNO showed a middle-class intestinal permeability preferentially through transcellular way. It was therefore postulated that GSNO can be administrated via the oral route. Oral delivery of GSNO seems to be a good method to apply GSNO with its advantages such as patient compliance, convenience, low cost, non-injection as well as lower infection risk. These merits are important especially when applied to chronic disease like cardiovascular diseases.

However, GSNO is easy to degrade through different in vitro parameters and enzymes in vivo. The protection of GSNO through gastrointestinal tract is crucial for its applications through oral administration route. As shown in Tables 1234, few oral formulations have been developed to deliver GSNO, which is a small hydrophilic molecule and easy to diffuse. To develop GSNO-loaded formulation through oral administration adapted to CVD application, several factors should be considered:

1. Material adapted to oral route.

Efficient encapsulation efficiency of GSNO

3. Sustained release 4. Intestinal permeability enhancement

Stability of encapsulated GSNO

As described in the Chapter 1, GSNO-NP have been developed in our lab using polymer Eudragit® RL PO through a water-in-oil-in-water (W/O/W) double emulsion/solvent evaporation method. In addition, microparticles share the advantages of nanoparticles but with additional ones such as higher drug loading and longer sustained release time. Thus, modification of GSNO-NP was considered in order to reach the four requirements above.

Eudragit® RL PO:

The proper selection of material is of significant importance to develop a formulation. Eudragit® RL PO used in the GSNO-NP preparation belongs to Eudragit® family, which are nonabsorbable (in water), non-biodegradable and nontoxic polymers. Eudragit® RL PO is a copolymer consisting of methyl methacrylate, ethyl acrylate and methacrylic acid ester (low content) with quaternary ammonium groups. As a solid substance (white powder) with a faint amine-like smell, Eudragit® RL PO is used as coating material to get sustained drug release and is also suitable for matrix structures. It is widely used in the development of drug delivery systems such as mucoadhesive tablets, nanoparticles, solid dispersions. Singh et al 213 .

described that Eudragit® RLPO with iron oxide combination presented a high-level potential for developing gastroretentive and mucoadhesive drug delivery systems.

Pandey et al 214 developed a site-specific patch using Eudragit® RLPO and RSPO, with a 12 h sustained release as well as mucoadhesion effect. Thus, Eudragit RLPO is a good candidate polymer for oral delivery system with sustained release.

Double emulsion (W/O/W and S/O/W)

After determining the polymer used to prepare the particles, the next step is to choose the preparation process. Several methods are potentially useful for the nano/microparticles preparation. One of the most common is single emulsion, it can encapsulate drugs, which are poorly soluble or lipophilic drugs successfully but it is not suitable for the highly water-soluble drugs. This problem can be solved using the double emulsion technique (also called "multiple emulsion") 215 .

Water in oil in water (W/O/W) double emulsion

The water in oil in water double emulsions separate the internal aqueous phase from external aqueous phases using an oil layer. The oil layer in the middle acts as a liquid membrane to constrain the hydrophilic drugs inside. Thus, this double emulsion system is regarded as a good candidate for controlled release of hydrophilic drugs.

The water in oil in water double emulsion/solvent evaporation is the main method to prepare W/O/W microparticles. As shown in Figure 18, drugs are dissolved in an aqueous phase (inner aqueous phase, W1). W1 is then emulsified in an oil phase which is always the solution of polymer, resulting in the water in oil emulsion (W1/O).

Then, this primary emulsion (W1/O) is dispersed in another aqueous phase (outside aqueous phase, W2) to produce the W1/O/W2 double emulsions. After removing the organic solvent through evaporation, the double emulsion particles can be collected through centrifugation or filtration 216 .

General discussion, conclusions and perspectives

General discussion

As an important second messenger, nitric oxide plays important roles in our body.

NO deficiency is one of the key factors for the CVD. Due to its short half-time and the inconvenience of its application as gas, NO donors are good candidate drugs for CVD treatment. NO donors decompose in the body to generate NO or NO-derived species.

NO donors have been applied in CVD for many years, in particular sodium nitroprusside for the treatment of hypertensive emergencies and organic nitrates for angina pectoris. However, long-term administration of organic nitrates generates tolerance, oxidative stress and other side effects. New NO donors, especially RSNOs offer advantages over existing drugs. They do not share side effects with organic nitrates and initial clinical studies suggest their therapeutic potential in a variety of cardiovascular disorders.

However, the application of RSNOs is limited by their poor stability. RSNOs are sensitive to different parameters in vitro (such as metal ions, light, oxygen, light, temperature) and are easy to be degraded by enzymes in vivo (as described in chapter 1).

In order to apply RSNOs to chronic CVD, oral delivery system with sustained release effect sounds like the best choice. In previous studies of our lab, Wu et al 127 developed GSNO-acNCP. After a unique oral administration of these GSNO-acNCP to Wistar rats, GSNO permeated through intestine and entered into vessels, resulting in the formation of a NO store within the vascular wall. However, some drawbacks arose: GSNO-acNCP are not easy to reproduce due to a time-consuming and multi-steps process of production; and they should be prepared right before administration due to their low stability as suspensions.

In this study, we aimed at evaluating the future of RSNOs to treat cardiovascular diseases through oral route and at developing suitable delivery systems. To that purpose we:

1. Made clear the intestinal permeability mechanisms of different RSNOs 2. Evaluated RSNOs capacity to form a bioavailable NO store within the vascular wall 3. Optimized the oral delivery system for S-nitrosoglutathione

The oral bioavailability of proteins, peptides or drugs depends mainly on their intestinal absorption 220,221 . As the RSNOs studied here are derived from peptides (GSH)

or amino acids (cysteine, valine), it is therefore critical for us to evaluate the intestinal permeability (free or from particles). In the article 2, the intestinal permeability of RSNOs have been followed through the quantification of different NOx species (RSNOs, NO2 -and NO3 -). Indeed, as described in chapter 1, RSNOs are easy to degrade and produce NO2 -and NO3 -. NO2 -and NO3 -are capable of interconversion or able to release NO in a physiological environment, so both of them have been regarded

as meaningful parts of NO intestinal permeability. Basically, NO, NO2 -and NO3 - constitute a complex biological cycle under physiological conditions in mammals.

Several different mechanisms are thought to be involved in this cycling, such as reduction or oxidation through bacteria [222][223][224] , hemoglobin [225][226][227] or other heme proteins 228 , NOS 229,230 , xanthine oxidoreductase [231][232][233][234][235] , hypoxia 236 , acid catalyzed 237- 240 , and UV radiation 241 . Nitrate ions in the blood can be circled and concentrated in the salivary glands and secreted into our mouth [222][223][224] , where they are finally reduced to nitrite ions. Nitrite ions can also be reduced to NO under acidic conditions in the stomach 242 , and enter the blood vessels as RSNOs after permeating the intestine.

Nitrite ions in the blood are reduced by enzymes (such as xanthine oxidoreductase) or via hemoglobin under hypoxic conditions. Thus, NO2 -and NO3 -can also be regarded as possible NO sources in the body.

In order to develop the proper formulation for RSNOs oral delivery, RSNOs were classified according to the BCS. BCS is a system which has been widely used to differentiate the drugs according to their solubility and intestinal permeability. The After permeating the intestine barrier, RSNOs enter in the bloodstream where they promote the formation of NO store. This latter is vital to vascular homeostasis, as described in the chapter 3, thus the reconstitution of this stock is mandatory in the context of cardiovascular diseases linked to NO depletion. In the literature, two main methods were described to evaluate the vascular NO store: one is the relaxation of vessels representing the existence of photosensitive NO store, during the exposure of the precontracted blood vessels to light [178][179][180] ; the other is the usage of NO scavengers such as low molecular weight thiols. For example, NAC can displace NO from the NO store especially from S-nitrosated proteins or protein-bound dinitrosyl-iron complexes.

Thus, the relaxation induced by NAC in precontracted vessels also indicates the presence of a NO store 181,250 . We evaluated the NO store produced by GSNO, SNAP and NACNO on endothelium-intact and endothelium-removed aortae in order to mimic healthy condition and endothelial dysfunction, respectively. As shown in article 3, the three RSNOs, with NACNO as the leader, were able to form a NO store within the aorta, no matter which kind of aorta was studied. The NAC-induced vasodilation protocol confirmed also the superiority of NACNO, being the RSNOs forming the highest NO store with the highest bioavailability in both types of aortae. This may probably due to the mechanism of NACNO incorporation into cells using the L-type amino acid transporter without metabolism 251,252 , whereas other RSNOs (GSNO and SNAP) transfer into cells using enzymes activity present either on the endothelium or on smooth muscle cells 253,254 . Moreover, the NO store produced by NACNO induces also a higher hyporeactivity to vasoconstrictor than other NO donors. In addition, all these NO donors showed their ability to counteract the vasoconstriction induced by phenylephrine in endothelium-removed aorta. It has been illustrated that endogenous NO or NO derived from exogenous NO donors is responsible for the vascular hyporeactivity to vasoconstrictors 255,256 . In fact, in the study of Alencar et al. 250 , they induced NO storage in rat aorta by administration of GSNO through infusion, which finally caused similar aortic hyporeactivity to vasoconstrictors like phenylephrine. In our study, we have not only checked the ability of RSNOs to induce NO store as well as its vasoactivity, but we also linked this pharmacological action to the quantification of NOx species either in endothelium-intact or endothelium-removed aortae.

Phenylephrine effect on vessels is a balance between the activation of alpha-1 adrenergic receptors on smooth muscle cells (vasoconstriction) and alpha-1 adrenergic receptors on endothelial cells (leading to the activation of the NO/sGC signaling pathway and then attenuation of the vasoconstriction). We confirmed that the vasoconstriction induced by agonists of alpha-1 adrenergic receptors was modified by three different RSNOs treatment only in endothelium-removed aortae, which has been supported by the work of others (mainly treatment of GSNO and DNIC) 127,250,257,258 . In addition, it was suggested that S-nitrosation of alpha-1 adrenergic receptors by RSNOs was also one possible mechanism of alpha-1 adrenergic receptors inhibition 259 . To conclude, RSNOs, in particular NACNO, are able to induce NO storage, which present a benefit to restore NO-related functions especially when the endothelium is absent (mimic of endothelial dysfunction).

For the quantification of the NO store, a lot of work has been focused on the optimization of the DAN/DAN+Hg 2+ method. We first transferred the DAN/DAN+Hg 2+ method from simple media (PBS, Kreb's buffer…) to the quantification in more complex media like cell lysates from smooth muscle cells (article 1) or intestinal cells (article 2).

Basically, the cells were lysed in a medium containing a complex of sodium tetraborate and L-serine 260 (as GGT inhibitor) as well as N-ethylmaleimide 261 (free thiols blocker)

and the NOx species were quantified with the DAN/DAN+Hg 2+ method. However, with a more complex matrix and lower concentrations of NOx species, the quantification in tissues like aortae (article 3) is more difficult. First, the tissues (aorta) were crushed in liquid nitrogen with a mortar and then reacted directly with an overdosage of DAN+Hg 2+ reagent in acidic solution. During this procedure, by avoiding lysis buffer, the dilution of samples has been eliminated. However, this method did not enable us to quantify nitrite ions and RSNOs separately, but small amount of NOx species (nitrite ions + RSNOs) could be quantified.

After studying the ability of RSNOs to cross the intestinal barrier and developing suitable methodology to study the NO store in vascular wall they can trigger, we also developed an oral delivery system to administer them. This formulation is aimed at protecting the RSNOs from degradation all along the gastrointestinal tract, increasing their intestinal permeability as well as their release time. Regarding articles 2 and 3, NACNO seems to be the best drug candidate to formulate with both the highest intestinal permeability and the induction of the highest and most bioavailable NO store compared to SNAP and GSNO. However, we choose GSNO as the RSNOs model in the preparation of oral delivery systems due to its several advantages: it is a physiological RSNOs and its skeleton, reduced GSH, is very abundant in the body, which means lower side effects; GSNO can be synthesized and stored as solid, which is a prerequisite for the preparation of S/O/W particles (NACNO cannot). Thus, GSNO was chosen as the drug candidate to prepare oral delivery systems.

As it has a simple and reproducible preparation method with efficient encapsulation efficiency (about 30%), the GSNO-NP 125 has been chosen as the starting material for optimization. In recent literature 115,219 , different RSNOs were successfully encapsulated in PLGA microparticles through S/O/W double emulsion. As described in chapter 1 and chapter 3, microparticles display several advantages over nanoparticles such as higher loading capacity as well as longer sustained release time.

Moreover, among microparticles, S/O/W microparticles are often described as surpassing W/O/W microparticles, with possible higher encapsulation efficiency as well as better release profile. So, two different types of particles (GSNO-MPW and GSNO-MPS) were obtained through the modification of the energy of the 2 nd emulsion and the inner phase during GSNO-NP preparation. However, the encapsulation efficiency of these two microparticles kept similar to the GSNO-NP. This may result from the quick diffusion of GSNO as a small hydrophilic molecular, and regarding the GSNO-MPS it may also result from the big size of inner solid GSNO powder. Increasing the encapsulation efficiency was not our principal aim, but it could be beneficial, as high encapsulation efficiency presents several advantages: 1) efficient therapeutic effects with higher possible drug concentration; 2) economical and fewer side effects with less excipient like polymer; 3) compliance of patient with less dosage and lower frequencies.

In the work of Castellanos 262 et al, the EE of PLGA-Bovine serum albumin W/O/W MP (less than 40%) has been enhanced to 80% using S/O/W process. However, for our particles, the encapsulation efficiency still kept around 30% (corresponding to a load of 0.02 μmol GSNO/mg particles). Nevertheless, microparticles presented a sustained release time (2-4 hours) compared to GSNO-NP.

Stabilizing the formulations to get storable and easy-to-transport products was however a key objective of our work. Transforming particles suspensions to dry drug products can indeed provide several advantages 263 , such as easier delivery and storage of the drug product, with long stability. Several methods could be applied to remove the liquid medium and get dry drug products [263][264][265] : spray-drying, direct drying, vacuum drying, lyophilization and so on. However, with the low stability of GSNO, it is important to control the environment during the drying of GSNO loaded particles, such as the light, oxygen, temperature, and to get a low residual water content.

Lyophilization, often used for pharmaceutics, can achieve those requirements and therefore was tested in this work. However, microparticles powders displayed a high residual water content after lyophilization, which may be related to the lyophilization process or the hygroscopic properties of GSNO. Lyophilization is a stressful process for both the particles and the drug. We did not explore in this work the optimization of this complex process, in particular because we had nor the time neither the suitable apparatus to do it properly. It might also be difficult to obtain lower residual water content without destroying the drug, due to its peptidic, hygroscopic and labile nature.

Even with their high residual water content, our particles had a satisfying stability, lower for GSNO-MPS (one month) than for GSNO-NP (more than 3 months). Besides, all these three types of particles displayed an enhancement of GSNO intestinal permeability: GSNO-NP promoted the intestinal permeability of GSNO to the middle of medium class whereas GSNO-MPW and GSNO-MPS enhanced GSNO to the high permeability class. This improvement may be attributed to the positive charge at the surface of particles, which comes from the methacrylic acid and ethylacrylate polymer (Eudragit). The particles may interact with intestinal cells (negative charge) and cause an increase in bioavailability, enhanced in the case of microparticles by a sustained NO delivery. These microparticles seem to be good candidates for the oral delivery of GSNO.

When applying RSNOs through oral administration, they have to cross not only the intestinal epithelium (after surviving the harsh conditions in the upper tract), but also the mucus layer and the intestinal microbiota. The drug delivery system might offer some key features for the interaction with the mucus layer. In the meantime, NO, the main product of RSNOs decomposition, has anti-bacterial effect through several possible ways 266,267 : it attacks DNA of bacterial, disturbs protein (enzymes) synthesis and damages the amino acids in membrane. GSNO and NACNO are bactericidal against common Gram-negative and Gram-positive pathogens [267][268][269] . GSNO is bactericidal at low concentrations (4.6 ± 3.2 mM), which are safe to human cells:

around twice the concentration of GSNO in serum 269,270 . The antibacterial effect of NACNO not only comes from NO but also from NAC. On the one hand, the interaction of RSNOs with microbiota in intestine provides another application of RSNOs loaded particles; on the other hand, the interaction may decrease the bioavailability of RSNOs in the treatment of CVD. Thus, it could be important to evaluate the impact of GSNO loaded particles/free GSNO on the intestinal flora of animals if we want to apply them to the in vivo experiment.

amidoximes functions was the most potent molecule for NO release with cytocompatibility with human smooth muscle cells. In order to study its potentiality for CVD, its intestinal permeability and ability to induce NO storage could also be evaluated using similar experiments as in article 2 and 3. During these procedures, the logP value may also guide the selection of amidoximes molecule. According to 'Lipinski's Rule of 5' (developed at Pfizer) the logP of a compound intended for oral administration should be smaller than 5 271 . A suitable logP value is important for the oral administration, a more lipophilic compound (logP > 5) will have low aqueous solubility and result in compromising bioavailability; or it may be easy sequestered by fatty tissue and difficult to excrete. Normally, for oral administration through intestinal absorption, the idea logP value is 1.35-1.8 271,272 . The amidoximes tested in article 1 had logP values between 0 and 2, thus suitable for oral administration and also probably easier to encapsulate into polymeric formulations than GSNO (logP -2.7) with more sustained release. However, the decomposition of amidoximes exclusively by CYP450 could raise a tolerance issue under chronic administration, as observed with organic nitrates.

The future of RSNOs application either in free or formulated form will pass by an evaluation of their in vivo properties after oral administration. First the pharmacokinetic of these compounds should be followed using methods developed in the literature 273 , especially, the one based on N 15 developed in our lab 62,63 . Indeed, Yu et al, developed a DAN assay followed by liquid chromatography with tandem mass spectrometry based on N 15 quantification. This method deciphers between naturally occurring NOx species (nitrite ions, nitrate ions and RSNOs) and N 15 enriched administrated GSNO.

This method was validated on Caco-2 cell 274 as well as intestine tissue 275 (Ussing chamber) with a 5 nM limit of quantification (for memory, Griess method has a limit of quantification about 10 -6 to 10 -5 M whereas DAN with 10 -7 to 2*10 -6 M). The possibility to quantify NOx species in the nanomolar range, in cells and in tissues, will render easier the in vivo pharmacokinetic studies (release, distribution, degradation and excretion) of RSNOs and RSNOs formulations.

In addition, the study of the effects of RSNOs on the intestinal mucus and flora could also be interesting. As RSNOs have anti-bacterial effect, the intestinal flora balance may be destroyed, which may cause the changes of intestinal absorption of RSNOs. In addition, some of RSNOs could be degraded during the reaction with different bacteria during the intestinal tract. As described by Björne et al. 276 , nitritecontaining human saliva increases not only gastric mucosal blood flow but also mucus thickness in the rat. Similarly, the degradation of RSNOs can produce nitrite, which could change the thickness of mucus and impact the intestinal permeability of RSNOs

The description of the vascular NO store should be also continued in terms of localization and identification. The NO store could be localized within vascular wall either by comparing the quantity of NO store in the whole versus in an endotheliumremoved vessel, or by immunofluorescence microscopy. To further make clear if the NO store is within organelles, in extracellular matrix, or in the cytosol, we can use an intracellular NO probe such as 4,5-Diaminofluorescein diacetate 277 , combined with specific probes of each cell compartment or tissue layer. The identification of Snitrosated proteins forming the NO store in the vascular wall could be achieved using the biotin switch method coupled with mass spectrometry already developed in the lab 278 . S-nitrosated proteins identification might help us to find new NO target and will open further studies on the impact of the S-nitrosation process on these proteins' activity and/or expression.

As mentioned in the discussion part, NACNO could be an interesting treatment for CVD, so we can also prepare NACNO loaded nanoparticles and microparticles through W/O/W method, starting from NACNO solutions. However, the initial NACNO concentration after preparation is always 0.01 M in our lab, which is six times lower than the one of GSNO (about 0.06 M). Thus, NACNO solution should be condensed to get a higher concentration before particles preparation. In addition, NACNO cannot Lyophilization has been applied to get long time stability. However, the stability time of microparticles (1 month) is less than nanoparticles (3 months). To get a longer stability time (more than 3 months or longer), we can optimize the lyophilization procedure for GSNO loaded particles according to the property of GSNO: the annealing procedure to decrease the duration time; the temperature and duration time of primary drying and second drying [281][282][283] .

It is possible to enhance the encapsulation efficiency and to sustain the release through different methods:

1. Choose the proper Eudragit: It has been suggested that the mechanism of drug release from dosage forms coated with Eudragit is mainly through control of fluid permeation with subsequent dissolution and diffusion of the active substance. However, the pores of Eudragit films have been shown to be larger (which means the diffusion of the drug through these pores is higher) in Eudragit RL films than in Eudragit RS films. The larger pores can cause the quick release speed of GSNO from the particles.

Besides, the high permeability of Eudragit RL PO may also induce the low drug loading capacity 284,285 .

2. Use two different emulsifiers to prepare the double emulsion. In the double emulsion of these three particles, only one surfactant Kolliphor P188 has been applied as emulsifier. The polymer Eudragit RL PO acts partly as emulsifier, which may be not so efficient.

After optimization of the particles, we can obtain different particles and choose the right one (size, encapsulation efficiency, release, dosage) for in vivo experiments.

Then, capacity of chosen particles to counteract CVD can be determined through in 4, 129.4, 120.6, 120.4, 114.4, 66.3, 27.7, 21.7, 15.9. 6, 134.7, 119.9, 119.8, 115.8, 104.9, 67.8, 28.6, 23.0, 17.7.

Amidoximes Synthesis Conditions

Oxidation of amidoximes using rat liver microsomes

The incubation media was prepared by mixing the substrate (111 μM) with rat liver microsomes (0.25 mg of proteins) and 148 mM phosphate buffer pH 7.4 (final volume, 450 μL). This media was pre-incubated for 1 min at 37°C. NADPH (1.11 mM) was added to start the reaction and the mixture was incubated for 10 min at 37°C. The reaction was stopped by heating the mixture for 3 min at 100°C. The proteins were precipitated by centrifugation for 15 min at 10000 rpm at 4°C.

Griess assay

Briefly, 100 µL of sample were diluted with 100 µL acetoacetic solution 11% (v/v) (pH 2.5) and added with 40 µL of sulfanilamide solution in 0.4 M HCl. Finally, the diazonium salt formed was made to react with 10 µL of a 0.6% (w/v) N- (1-naphthyl) ethylenediamine solution in 0.4 M HCl to form a chromophoric azo product that absorbs at 540 nm. Results are expressed as means ± standard error of the mean (SEM). Statistical analyses were performed using oneway ANOVA test followed by Bonferroni's multiple comparisons test. The GraphPad Prism software (GraphPad Software version 5.0, San Diego, USA) was used for all the presented results.

Cytocompatibility assay

HVSMC cells (CRL-1999, ATCC, USA) were grown in F-12K (ATCC-30-2004) medium supplemented with 10% (v/v) fetal bovine serum, 1 % (v/v) penicilline-streptomycin cocktail (10000 units penicillin and 10 mg streptomycin per mL), 0.01 mg/mL insuline, 0.05 mg/mL acid ascorbic, 10 mM TES, 0.01 mg/mL transferrine, 10 ng/mL sodium selenite, 0.03 mg/mL ECGS et 10 mM HEPES. Cells were cultured at 37°C under 5% (v/v) CO2 in a humidified incubator. HVSMC cells were seeded at 6.25×10 4 cells/cm 2 in 96-wells plates for 24 h before being incubated with amidoximes 2. After 24 h at 37°C with 0.001 to 100 µM of compounds 2, cytocompatibility regarding metabolic activity was checked using the MTT assay. Briefly, 0.5 mg/mL MTT was incubated with the cells for 3 h. Then, 50 µL DMSO was added under stirring for 5 min to extract the formazan crystals. The absorbance was read at 570 nm with a reference at 630 nm using EL 800 microplate reader (Bio-TEK Instrument, INC ® , France). Metabolic activity in the presence of treatments was compared to the control condition.

NO release experiments

The reference GSNO was synthesized as previously described by Parent et al. 1 Briefly, reduced glutathione (GSH) was incubated with an equivalent amount of sodium nitrite under acidic conditions (0.626 M HCl). The concentration of GSNO was calculated using the specific molar absorbance of S-NO bond at 334 nm (ε = 922 M -1 cm -1 ) and the Beer-Lambert law.

HVSMC cells were seeded at 6,400 cells/cm 2 in 6-wells plates 48 h before incubation with amidoximes 2. After 1 h at 37°C with 100 µM (a concentration of 50 µM was used for 2d) of each amidoxime, or 100 µM of GSNO, cells were washed with PBS and lysed in 50 mM of Tris, 150 mM of NaCl, 1% of Igepal CA-630 (v/v), 0.1% of SDS (v/v), 1 mM of EDTA, 0.1 mM of neocuproine, 20 mM of sodium tetraborate and 10 mM of NEM. RSNO and nitrite ions were immediately quantified using a fluorimetric method as previously described by Wu et al. 2 Briefly, N2O3 generated from acidified nitrite ions reacts with 1.05 mM 2,3-diaminonaphthlene with or without 1.05 mM of HgCl2 producing naphthotriazole that emit fluorescence at 415 nm after excitation at 375 nm (JASCO FP-8300, France). Les S-nitrosothiols (RSNO) comme le S-nitrosoglutathion (GSNO) sont des donneurs de monoxyde d'azote (NO) prometteurs pour le traitement des maladies cardiovasculaires. Cependant, ce sont des candidats médicaments peu stables. Précédemment, des nanoparticules chargées en GSNO (GSNO-NP) ont été incluses dans une matrice d'alginate/chitosan. Les particules composites ainsi produites avaient une bonne encapsulation et une libération prolongée de GSNO. De plus, leur administration orale à des rats produisait un stock de NO au niveau de la paroi de l'aorte. Elles avaient cependant plusieurs limitations : préparation et caractérisation longues, manque de stabilité et de reproductibilité. Ce travail avait donc trois objectifs : (1) déterminer le mécanisme d'absorption intestinale des RSNO non formulés ; (2) évaluer la capacité des RSNO non formulés à créer un stock vasculaire de NO ; 3) optimiser la formulation de GSNO. Nous avons montré, dans un modèle in vitro de barrière intestinale, que la perméabilité intestinale de GSNO, S-nitroso-Nacétylcystéine (NACNO) et S-nitroso-N-acetylpénicillamine (SNAP) se fait par un mécanisme passif, principalement par voie transcellulaire (également paracellulaire pour SNAP), avec une perméabilité moyenne. Après avoir traversé la barrière intestinale, les RSNO atteindront les vaisseaux sanguins. Pour comparer leur capacité à former un stock vasculaire de NO dans des aortes (avec endothélium intact ou retiré), nous avons quantifié le stock, vérifié sa biodisponibilité pour la vasorelaxation et évalué son impact sur une vasoconstriction induite par la phénylephrine (PHE). L'incubation des aortes avec les RSNO augmente le stock basal de NO par un facteur trois à cinq. Ce stock est mobilisable pour induire la vasorelaxation et efficace pour diminuer la réactivité vasculaire à la PHE (NACNO>GSNO = SNAP), seulement dans les aortes dont l'endothélium a été retiré. Comme la perméabilité intestinale des RSNO est moyenne, l'intégration du GSNO dans une formulation appropriée est nécessaire. Vu l'impossibilité de résoudre les problèmes liés aux particules composites, le protocole de production des GSNO-NP a été modifié pour produire des microparticules (deux types selon l'état liquide ou solide de GSNO dans la phase interne de l'émulsion). Les deux types de microparticules avaient une libération de GSNO ralentie par rapport aux GSNO-NP. Les nano-comme les microparticules ont pu être stabilisées par lyophilisation, et amélioraient la perméabilité intestinale de GSNO (jusqu'à une forte perméabilité avec les microparticules). Par conséquent, une administration orale de nano/microparticules chargées en GSNO/RSNO pourrait représenter une nouvelle approche thérapeutique pour les maladies cardiovasculaires.

Mots clés : S-nitrosoglutathion, particules, systèmes de délivrance pour la voie orale, stockage de monoxyde d'azote, perméabilité intestinale Mechanisms of S-nitrosothiols intestinal permeability and NO store formation within vascular wall to improve NO oral delivery systems S-nitrosothiols (RSNOs) such as S-nitrosoglutathione (GSNO) are promising nitric oxide (NO) donors for cardiovascular diseases treatment. However, they are poorly stable drug candidates. In previous studies, GSNO-loaded nanoparticles (GSNO-NP) were embedded into an alginate/chitosan matrix. Resulting nanocomposite particles showed high encapsulation and sustained release of GSNO, and led to the formation of a NO store in the wall of aorta after a single oral administration to rats. However, these nanocomposite particles have several limitations such as time-consuming preparation, lack of both stability and reproducibility. This thesis work aimed at: 1) Elucidate the mechanism of free RSNOs intestinal absorption; 2) Evaluate ability of free RSNOs to form a vascular NO store; 3) Optimize the GSNO formulation. In this study, we showed that the intestinal permeability (in vitro model of intestinal barrier) of GSNO, S-nitroso-N-acetylcysteine (NACNO) and S-nitroso-N-acetylpenicillamine (SNAP) was a passive diffusion, following the transcellular pathway (and also the paracellular way for SNAP) and belonging to the medium permeability class. After crossing the intestinal barrier, RSNOs will reach the vasculature. In order to compare the ability of free RSNOs to form a vascular store of NO either in endothelium-intact or endothelium-removed aortae, we quantified the store, verified its bioavailability for vasorelaxation and evaluated its impact on phenylephrine (PHE)-induced vasoconstriction. Incubation with RSNOs increased the basal NO store three to five times. This store is still bioavailable to induce vasorelaxation and efficient to induce vascular hyporeactivity to PHE (NACNO> GSNO = SNAP) only in endothelium-removed aortae. As intestinal permeability of RSNOs was in the medium class, the integration of GSNO into an appropriate delivery system is essential. Limitations of previously developed nanocomposites particles were impossible to bypass so the production process of GSNO-NP was modified (liquid or solid GSNO in the internal phase of the emulsion) to produce microparticles. Both kinds of microparticles exhibited a slower release of GSNO than GSNO-NP. Nano-and microparticles were stable after lyophilization and presented an enhancement of GSNO intestinal permeability (up to high permeability class for microparticles). Thus, oral administration of GSNO/RSNO loaded nano/micro particles seems to be a promising avenue for the treatment of cardiovascular diseases.

Publications ( 1 )

 1 *Bonetti, J. & *Zhou, Y., Parent, M., Clarot, I., Yu, H., Fries-Raeth, I., Leroy, P., Lartaud, I. & Gaucher, C. (2018). Intestinal absorption of S-nitrosothiols: Permeability and transport mechanisms. Biochemical pharmacology (IF = 4.8), 155, 21-31. * equal contribution (2) Sahyoun, T., Gaucher, C., Zhou, Y., Ouaini, N., Schneider, R., & Arrault, A. (2018). Synthesis of novel mono and bis nitric oxide donors with high cytocompatibility and release activity. Bioorganic & medicinal chemistry letters (IF = 2.53), 28(20), 3329-3332 (3) *Perrin-Sarrado. C. & *Zhou, Y., Salgues. V., Parent, M., Giummelly.P., Lartaud.I. & Gaucher, C. S-nitrosothiols as potential therapeutics to induce a mobilizable vascularstore of nitric oxide to counteract endothelial dysfunction (under review). Biochemical pharmacology (IF = 4.8), * equal contribution (4) Zhou, Y., Gaucher, C., Fries-Raeth, I. Hobbekaya, M., Martin, C., Sapin-Minet, A… & Parent, M. Enhancing intestinal permeability of nitric oxide with storable microparticles for S-nitrosoglutathione oral delivery (submitted) Journal: International Journal of Pharmaceutics (IF = 4.2).

( 1 ) 2 Table 1 .

 121 Zhou, Y., Gaucher, C., Fries-Raeth, I. & Parent, M. Nano or micro: 3 different particles to deliver and protect S-nitrosoglutathione for oral route administration: COST meeting, 25th to 27th March 2019 in Luxemburg. (published in Proceedings) (2) Parent, M., Zhou, Y., Bonetti, J., Perrin-Sarrado, C., Lartaud, I., Sapin-Minet, A. & Gaucher, C. Antioxidant properties of S-nitrosoglutathione and nanotechnologies: COST meeting, 25th to 27th March 2019 in Luxemburg. (published in Proceedings) (3) Zhou, Y., Gaucher, C., Fries-Raeth, I., Hobbekaya, M-A., Martin, C. & Parent, M. Nano-versus micro-particles for S-nitrosoglutathione formulation: PDDS meeting, 24th to 26th June 2019 in Marne-La-Vallée, France. Poster communications (1) Zhou, Y., Gaucher, C., Parent, M. :Système d'administration orale de Snitrosoglutathion pour les maladies cardiovasculaires. DocLor -Doctorial de Lorraine 2018, April 16th to 20th, 2018 in La Bolle Saint-Dié (France) (2) Zhou, Y., Gaucher, C., Fries-Raeth, I., Hobbekaya, M-A., Martin, C. & Parent, M: Nano-versus Micro-particles for S-nitrosoglutathione formulation. Formulation Days 2019, January 10th to 11th, 2019 in Lyon (France). Introduction Table 1. GSNO related intravenous delivery systems................................................59 Table 2. GSNO related topical delivery systems........................................................63 Table 3. GSNO loaded implants. ...............................................................................66 Table 4. GSNO related oral delivery systems. ...........................................................69 Article Standard curves validation parameters for S-nitrosothiols (RSNO), nitrite ions (NO2 -) and nitrate ions (NO3 -) in HBSS with Ca 2+ /Mg 2+ . Mean ± sem; n = 3...............85 Table 2. Values of apparent permeability coefficient (Papp) for NOx species (RSNO + NO2 -+ NO3 -) and the RSNO molecular form after 4 h of permeation from the apical to the basolateral compartment. nd: not determined, LOQ: Limit of quantification. Mean ± sem of four independent experiments done in duplicate..........................................86 Table 3. Mass balance for each treatment (initial amount: 50 nmol) after 4 h of permeation from the apical to the basolateral compartment. Mean ± sem of four independent experiments done in duplicate................................................................87 Table 4. Values of apparent permeability coefficient (Papp) for NOx species (RSNO + NO2 -+ NO3 -) and the RSNO form after 4 h of permeation from basolateral to apical compartment. nd: not determined, LOQ: Limit of quantification. Mean ± sem of four independent experiments done in duplicate................................................................88 Table 5. Mass balance for each tested treatment (initial amount 150 nmol) after 4 h of permeability from the basolateral to the apical compartment. Mean ± sem of four independent experiments done in duplicate...............................................................89 Table 6. Values of apparent permeability coefficient (Papp) for NOx species (RSNO + NO2 -+ NO3 -) and the RSNO form after 4 h of permeability study from the apical compartment (pH 6.4) to the basolateral compartment (pH 7.4). Mean ± sem of three independent experiments done in duplicate...............................................................90 Table

conditions after 1 hFigure 1 .Figure 2 . 1 :Fig. 1 .Fig. 2 . 2 :Fig. 1 .Fig. 2 .Fig. 1 .Fig. 2 .Figure 1 .Figure 2 .Figure 4 .

 11211221212124 Figures

  La réduction de la taille des grains de GSNO (de 40 µm à moins de 10 µm) initiée en collaboration avec la société StaniPharm devrait, d'après la littérature, conduire à une meilleure encapsulation et à une libération prolongée de GSNO avec les microparticules S/H/E. Cependant, les premiers essais en fluide supercritique présentés dans cet article n'ont pas été concluants, à cause de la grande fragilité et de l'hydrophilie du GSNO. Par ailleurs, les paramètres critiques des particules (taille et contenu en GSNO) sont maintenus jusqu'à 1 mois après lyophilisation et stockage à 4°C pour les microparticules et jusqu'à 3 mois pour les nanoparticules. Les suspensions fraîches de particules n'étant stables qu'une journée, cette stabilisation représente une avancée majeure, car elle permettra d'optimiser les campagnes de préparation des particules et de les envoyer éventuellement vers d'autres laboratoires pour la réalisation de tests précliniques. Les particules chargées en GSNO développées pourraient ainsi représenter une nouvelle opportunité thérapeutique pour un traitement chronique, par voie orale, des pathologies associées avec un déficit en monoxyde d'azote Pour conclure, les objectifs de ce travail étaient de mettre en évidence les mécanismes de la perméabilité intestinale de différents S-nitrosothiols et leur capacité à former un stock de NO mobilisable dans la paroi vasculaire, ainsi que de développer des formulations adaptées pour le traitement oral des maladies cardiovasculaires. Nous avons démontré : 1) que les trois RSNO étudiés peuvent être administrés par voie orale (avec une perméabilité intestinale moyenne) ; 2) qu'ils peuvent tous trois former un stock vasculaire de NO mobilisable pour une vasorelaxation ou pour induire une hyporéactivité à un agent vasoconstricteur. Tout ceci dans le cadre d'un endothélium lésé, ce qui est prometteur dans le contexte des maladies cardiovasculaires, souvent liées à une dysfonction endothéliale ; et 3) qu'il est possible d'augmenter significativement la perméabilité intestinale du GSNO grâce à des formulations, en particulier les microparticules obtenues par la méthode d'émulsion solide-huile-eau. Ce travail ouvre de nombreuses perspectives à la fois pharmacologiques et galéniques. Par exemple, une localisation plus fine du stock vasculaire de NO ainsi qu'une identification des protéines nitrosées (par une technique de biotin-switch associée à la spectrométrie de masse, déjà développée dans l'équipe) pourrait être entreprise afin de mettre au jour de nouvelles cibles de NO. Idéalement, les méthodes analytiques devraient également permettre de réaliser une pharmacocinétique complète des RSNO administrés (libres ou formulés). En ce qui concerne la formulation, de nombreuses optimisations pourraient être recherchées (meilleure encapsulation, libération plus longue, encapsulation d'autres donneurs de NO -RSNO, amidoximes, ou autres-, co-encapsulation de différents principes actifs, modification des polymères par exemple avec des groupements donneurs de NO, …). Cependant, les formulations développées dans ce travail pourraient d'ores et déjà être administrées chez l'animal sain, pour vérifier la formation du stock vasculaire de NO, ou dans des modèles pathologiques (athérosclérose ou accident vasculaire cérébral, par exemple).

Figure 1 .

 1 Figure 1. An overview of nitric oxide (NO) physiological activities in various systems 10 .

Figure 2 .

 2 Figure 2. The synthesis of nitric oxide by nitric oxide synthases 12 .

Figure 3 .

 3 Figure 3. NO in the cardiovascular system 15 . NO, nitric oxide; eNOS, endothelial nitric oxide synthase; VSMC, vascular smooth muscle cell; NO2 -, nitrite ions; Hb-α, haemoglobin-α; CYGB, cytoglobin; nNOS, neuronal nitric oxide synthase; β1, adrenergic receptor β1; ACh, acetylcholine; m2, muscarinic acetylcholine receptor m2; NA, noradrenaline; SNO, Snitrosothiol; SR, sarcoplasmic reticulum; T-tubule, transverse-tubule.

Figure 4 .

 4 Figure 4. NO signaling in cardiovascular system under physiological (left) and pathological (right) conditions 15 . NO, nitric oxide; eNOS, endothelial nitric oxide synthase; sGC, soluble guanylate cyclase; PKG, protein kinase G; SMCs, smooth muscle cells; SERCA, sarcoplasmic/ endoplasmic reticulum calcium-ATPase; PMCA, plasma membrane calcium-transporting ATPase; BKCa, Ca 2+ -sensitive potassium channel; LTCC, L-type calcium channel; MLCP, myosin light chain through the associated phosphatase; PVAT, Perivascular adipose tissue; APN, adiponectin; NADPH ox, NADPH oxidase; O2 -, superoxide anion; TNF, Tumour necrosis factor; LK, leukocyte; MLCK, myosin light chain kinase; SR, sarcoplasmic reticulum.

Figure 5 .

 5 Figure 5. S-nitrosothiols (RSNOs) formation and degradation in the body 25 .

Figure 6 .

 6 Figure 6. Potential mechanisms of S-nitrosothiols and S-nitrosoproteins formation and degradation 26 . NOS, nitric oxide synthases; GSNO, S-nitrosoglutathione; GSNOR, GSNO reductase; CBR1, carbonyl reductase 1; Trx, thioredoxin; TrxR, thioredoxin reductase.

Figure 7 .

 7 Figure 7. Structures of conventional organic nitrates and nitrite esters 42 .

Figure 8 .

 8 Figure 8. Structure of amidoxime function.

Figure 9 .

 9 Figure 9. Structure of 4-chlorobenzamidoxime.

  Tanya Sahyoun a,c , Caroline Gaucher b , Yi Zhou b , Naï m Ouaini c , Raphaël Schneider d* , Axelle Arrault a* a Laboratoire de Chimie Physique Macromoléculaire, Université de Lorraine, CNRS, LCPM, F-54000 Nancy, France b Université de Lorraine, CITHEFOR, F-54000 Nancy, France c Faculty of Sciences, Holy Spirit University of Kaslik, BP446, Jounieh, Mount Lebanon, Lebanon d Laboratoire Réactions et Génie des Procédés, Université de Lorraine, CNRS, LRGP, F-54000 Nancy, France

Figure 10 .

 10 Figure 10. Structure of GSNO, NACNO and SNAP 56,57 .

Figure 11 .

 11 Figure 11. Biological activity of RSNOs 60 .

  Copper (II) can directly and catalytically decompose RSNOs. This reaction generates nitric oxide and thiol disulfide but does not appear to proceed through a thiyl radical intermediate. The mechanism is fairly well established:TransnitrosationIn transnitrosation process, the nitroso functional group is transferred from one S-nitrosothiol to another thiol function. Transnitrosation occurs by nucleophilic attack of the thiolate anion on the nitrogen of the S-nitrosothiol.

  Similar with other RSNOs introduced above, GSNO shows a low stability in aqueous solutions. A possible explanation is the mesomerization of the S-NO bond. The distribution of those mesomers depends on the electrophile and nucleophile groups in the S-NO bond environment. Published half-lives of GSNO are not unified and are clearly conditiondependent. Basically, several mechanisms are involved in the decomposition of GSNO, including S-NO bond homolysis in the thermal/photolysis decomposition, metal ion-catalyzed (mainly Cu 2+ ) decomposition, heterolysis, and hydrolysis.

Figure 12 .

 12 Figure 12. In vivo metabolism of GSNO through different enzymes: 1. GSNO

Figure 13 .

 13 Figure 13. Nanoparticles targeted to the gastrointestinal tract 129 .

Figure 14 .

 14 Figure 14. mechanisms of molecules crossing through the intestinal barrier 131 . (a) receptor-mediated transport; (b) carrier-mediated transport; (c) paracellular transport; (d) transcellular transport; and (e) M cell mediated transport (i.e., phagocytosis by M cells).

Figure 15 .

 15 Figure 15. drugs classification according to the Biopharmaceutical Classification System (BCS)

Figure 16 .

 16 Figure 16. NO storage in the form of S-nitrosothiols (RS-NO), dinitrosyl iron complexes (DNIC) with protein ligands, and low molecular weight DNIC 197 .

Figure 17 .

 17 Figure 17. The various factors that affect the endothelium and the consequences of endothelial dysfunction 204 .

  intact and removed) have been incubated with different NO donors to induce NO storage. The vasoactivity of NO storage has also been tested, as shown in article 3: vascular store of nitric oxide to counteract endothelial dysfunction. Les S-nitrosothiols : de potentiels médicaments induisant la formation d'un stock mobilisable de monoxyde d'azote au sein des vaisseaux afin de contrer la dysfonction endothéliale. Caroline Perrin-Sarrado # , Yi Zhou # , Valérie Salgues, Marianne Parent, Philippe Giummelly, Isabelle Lartaud, Caroline Gaucher* # Les deux auteurs ont contribué à parts égales à ce travail. Article soumis au journal Biochemical Pharmacology le 28 juin 2019. (FI : 4,7). Q1 Pharmacology and Pharmacy).

  Figure 3.

Figure 10 .

 10 Figure 10. Scheme of the preparation procedure for drug loaded microparticles by the double emulsion solvent evaporation method 215 .

Figure 1 .

 1 Figure 1.

Figure 2 .

 2 Figure 2.

  Figure 3.

  Figure 5.

  Figure 6.

  Figure 7.

  permeability of three different RSNOs (physiologic GSNO and two synthetic RSNOs: SNAP and NACNO) was evaluated using an in vitro model of intestinal barrier made of Caco-2 cells, which has been widely used for intestinal permeability evaluation and drug screening243,244 . As presented in article 2, NACNO showed the highest Papp value, which means the best intestinal permeability of these three RSNOs. GSNO displayed similar intestinal permeability as SNAP. However, all the three RSNOs belong to the medium intestinal permeability class. The intestinal permeability of NACNO belongs to the middle of medium class and GSNO and SNAP belong to the beginning of medium class. So, NACNO tends to be closer to the class I type drugs (according to BCS) and should be a better option for formulations than other RSNOs (GSNO and SNAP).However, these three RSNOs display different biological properties linked to their own chemical structures. SNAP and NACNO are synthetic RSNOs derived from valine and cysteine, respectively. Furthermore, SNAP is made of N-acetyl-D-penicillamine an antiinflammatory drug, used to treat rheumatoid polyarthritis, with an antioxidant thiol function. NACNO is made of N-acetyl-L-cysteine, a mucolytic, showing an antioxidant activity linked to the thiol function of the cysteine. Less RSNOs and nitrite ions have been found in the cells incubated with SNAP compared to NACNO and GSNO. We speculated that SNAP may cross the intestine mainly through paracellular way, whereas NACNO and GSNO mainly through transcellular way. In fact, SNAP has been shown to promote intestinal absorption of different model drugs (insulin, fluoresceinlabelled compounds) by reversible opening of tight junctions245,30 . In addition, we demonstrated that the transport of RSNOs through the intestine barrier is driven by passive diffusion rather than active transport. With high solubility and medium intestinal permeability, RSNOs can be regarded as drugs classified between class I and class III according to BCS. As described byLe Ferrec et al. 249 , the results obtained in vitro with high permeability molecules (class I and class II) can be easily transposed to in vivo intestinal absorption unlike results obtained for low permeability molecules (class III and class IV). Thus, RSNOs can be regarded as suitable for oral administration route with their medium class of permeability.

  be entrapped through S/O/W double emulsion method without way to isolate NACNO solid powder. The post-S-nitrosation of NAC (previously encapsulated as solid powder) with NaNO2 might be another potent way to get NACNO S/O/W microparticles. As described in the work of Nacharaju 279 et al, NACNO loaded nanoparticles were successfully prepared through the S-nitrosation of NAC by NaNO2. These nanoparticles were suspended in tetramethoxysilane based sol-gel and showed long time (24 h) release. In addition, Souza 280 et al have found a novel way to deliver NACNO through the oral route using the intratablet S-nitrosation of NAC. Basically, a tablet containing NAC and NaNO2 powder were obtained and NACNO was sustain released during the absorption of water. Thus, NACNO loaded particles can be obtained with W/O/W method through direct encapsulation, and with S/O/W by indirect way.

  vivo experiments after oral administration to murine model of atherosclerosis or stroke

1 H

 1 NMR (300 MHz, DMSO-d6, 25°C): δ = 7.31-7.25 (m, 2H, Har), 6.94-6.90 (m, 3H, Har), 3.99 (t, J = 6.0 Hz, 2H, O-CH2), 2.57 (t, J = 6.9 Hz, 2H, CN-CH2), 1.83-1.69 (m, 4H, (CH2)2). 13 C NMR (75 MHz, DMSO-d6, 25°C): δ = 158.

  IR (neat): 3398 (br), 2924 (w), 2875 (w), 2246 (w), 1598 (m), 1495 (m), 1474 (m), 1427 (w), 1394 (w), 1294 (w), 1243 (s), 1173 (w), 1081 (w), 1058 (w(300 MHz, CDCl3, 25°C): δ = 7.60-7.57 (m, 2H, Har), 6.95-6.92 (m, 2H, Har), 4.06 (t, J = 5.6 Hz, 2H, O-CH2), 2.46 (t, J = 6.8 Hz, 2H, CN-CH2), 2.03-1.84 (m, 4H, (CH2)2) 13 C NMR (75 MHz, CDCl3, 25°C): δ= 162.

2

 2

Intracellular

  RSNO and nitrite ions were quantified after 1 h of incubation with different treatment (amidoxime or GSNO) in contact with smooth muscle cells. Control cells incubated 13 C NMR Analysis: solvent DMSO-d6 HPLC Analysis Rt = 13.942, Area percentage = 95.183 % Mécanismes de franchissement de la barrière intestinale et de stockage vasculaire des S-nitrosothiols pour l'amélioration de formulations orales de NO

Article 1: Synthesis of Novel Mono and Bis Nitric Oxide Donors with High Cytocompatibility and Release Activity

	P450. Les résultats de l'étude de nouvelles molécules synthétiques, mono ou bis-
	Le monoxyde d'azote (NO) est un gaz radicalaire impliqué dans la signalisation amidoxime, sont présentés dans l'article 1.
	des systèmes cardiovasculaires, immunitaires et nerveux. Au sein du système Tanya Sahyoun, Caroline Gaucher, Yi Zhou, Naï m Ouaini, Raphaël Schneider, cardiovasculaire, la première cible de NO est la guanylate cyclase soluble (GCs) dont l'activation permet la synthèse de GMPc, un second messager médiant la relaxation Axelle Arrault.
	vasculaire. Ceci constitue la voie de signalisation NO/GCs/GMPc. Cependant, le Quatre composés comportant une ou deux fonctions amidoximes ont été synthétisés :
	mécanisme d'action de NO emprunte également des voies de signalisation (1) Le composé 2a-b contenant une fonction amidoxime aromatique, (2) le composé
	indépendantes de la voie NO/GCs/GMPc, comme la S-nitrosation. La S-nitrosation 2c présentant une fonction amidoxime aliphatique, et (3) le composé 2d présentant
	correspond à la formation d'un lien covalent entre la fonction thiol d'un résidu cystéine deux fonctions amidoxime, une aromatique et une autre aliphatique. La capacité de
	et NO. Elle est considérée comme une modification post-traductionnelle des protéines, ces composés à libérer du monoxyde d'azote (NO) a été évaluée in vitro en tirant partie
	du métabolisme oxydant de cytochromes P450 de microsomes de foie de rats. Les
	résultats obtenus démontrent que toutes les fonctions amidoxime des composés
	synthétisés sont capables de libérer NO, avec une plus grande capacité pour le
	composé 2a qui possède une fonction amidoxime aromatique. De plus, toutes les
	amidoximes testées sont cytocompatibles vis-à-vis de cellules musculaires lisses
	humaines. En utilisant la formation de S-nitrosothiols intracellulaires comme marqueur
	de la biodisponibilité de NO, les composés 2a et 2c ont montré leur capacité à délivrer
	candidats médicaments. IIs constituent en effet des prodrogues de NO, dont la une plus grande quantité de NO que la molécule de référence (4-
	biodisponibilité est considérablement diminuée au cours des pathologies chlorobenzamidoxime). Ainsi, les amidoximes sont capables de traverser la membrane
	cardiovasculaires. Les donneurs de NO comme les dérivés nitrés sont utilisés depuis cellulaire pour être ensuite oxydées par les CYP450 des cellules musculaires lisses.
	de nombreuses années dans le traitement de l'angor dans le cadre de sa prévention En revanche, la bis-amidoxime aromatique/
	et en cas de crise. Cependant, les dérivés nitrés sont sujets au phénomène de
	tolérance (perte d'effet thérapeutique lors d'administration chronique), présentent une
	faible biodisponibilité et une faible sélectivité. Ils sont également responsables de
	l'amplification du stress oxydant déjà installé au cours des pathologies
	cardiovasculaires.
	Ainsi, d'autres molécules donneuses de NO sont actuellement à l'étude. Parmi
	celles-ci nous nous sommes d'abord intéressés aux amidoximes. La fonction
	amidoxime est physiologiquement produite lors de la synthèse de NO catalysée par
	les NO synthases. En effet, au cours de cette catalyse en deux étapes, l'arginine est
	d'abord N-hydroxylée en N-hydroxyarginine présentant une fonction amidoxime. Cette
	fonction amidoxime est capable de libérer NO sous l'action oxydative des cytochromes

aussi importante que la phosphorylation pour la modulation des activité/expression protéiques. La S-nitrosation forme des S-nitrosothiols comme les S-nitrosoprotéines, S-nitrosopeptides ou S-nitrosoacides aminés. En plus de moduler les voies de signalisation, ces S-nitrosothiols représentent également une forme de stockage et de transport de NO dont la demi-vie à l'état radicalaire n'est que de quelques secondes.

Ainsi, à l'état radicalaire, le rayon d'action de NO ne peut dépasser quelques micromètres. Ces S-nitrosothiols sont depuis quelques années considérés comme des

aliphatique 2d est de grand intérêt car sa capacité à délivrer NO et par la suite à augmenter le stockage de NO dans les cellules via la formation de S-nitrosothiols intracellulaires est similaire aux amidoximes 2a et 2b. En effet, en considérant que la bis-amidoxime 2d a été étudiée à une concentration

	D'autres donneurs de NO dérivant des S-nitrosothiols, formes physiologiques de
	transport et de stockage de NO, sont également à l'étude. Parmi ces S-nitrosothiols,
	nous pouvons citer le S-nitrosoglutathion (GSNO), la S-nitroso-N-acétyl-L-cystéine
	(NACNO) et le S-nitroso-N-acétyl-pénicillamine (SNAP). Les S-nitrosothiols sont
	considérés comme des candidats médicaments d'avenir, puisqu'ils ne présentent pas
	les effets indésirables de dérivés nitrés précédemment énumérés. Les RSNO sont
	dénués de toxicité aigüe, et de par l'existence physiologique de certains d'entre eux,
	ils ne présentent probablement aucun risque dans le cadre d'application répétée. Ceci
	est d'autant plus important que les pathologies cardiovasculaires sont, pour la plupart,
	des affections chroniques nécessitant un traitement sur le long terme. Dans ce
	contexte, la voie d'administration orale de ces molécules est la plus indiquée du point
	de vue des patients (facilité, faible contrainte conduisant à une meilleure observance).
	De plus, la voie orale présente des avantages physiologiques comme une grande
	surface d'absorption (300 à 400 m 2 ). Néanmoins, la barrière intestinale constitue un
	obstacle important à franchir pour ces molécules de nature peptidique ou protéique,
	avec une liaison nitrosothiol fragile. Ainsi, une deuxième étude a été menée sur les
	mécanismes d'absorption intestinale des S-nitrosothiols (Article 2).
	deux fois plus faible que celle des composés 2a et 2b, nous pouvons conclure que le
	composé 2d est la molécule la plus performante de tous les composés donneurs de
	NO testés ici.

Article 2: Intestinal absorption of S-nitrosothiols: permeability and transport mechanisms Absorption intestinale des S-nitrosothiols : Mécanismes de transport et de perméabilité

	Justine Bonetti # , Yi Zhou # , Marianne Parent, Igor Clarot, Haiyan Yu, Isabelle Fries-
	Raeth, Pierre Leroy, Isabelle Lartaud, Caroline Gaucher*

# Les

deux auteurs ont contribué à parts égales à ce travail.

	7,4, pH proche de sa partie distale. Au travers de cet article, nous avons déterminé les
	mécanismes de perméabilité intestinale des RSNO et prouvé que leur administration
	par voie orale était possible. Après avoir franchi la barrière intestinale, les S-
	nitrosothiols rejoignent le compartiment vasculaire où ils joueront leurs rôles de
	transporteurs puis de donneurs de NO pour restaurer le pool vasculaire de NO. Ce
	pool se retrouve ainsi sous deux formes, une forme circulante dans le flux sanguin et
	une forme tissulaire stockée dans la paroi vasculaire. Ainsi, la prochaine étape de cette
	étude a consisté à comparer la capacité des différents S-nitrosothiols à promouvoir la
	Au cours du vieillissement ou du développement des pathologies cardiovasculaires, formation d'un stock au sein de la paroi aortique et de vérifier si ce stock est mobilisable
	une diminution de la biodisponibilité du monoxyde d'azote (NO) est observée. Afin de pour la vasodilation, faisant preuve de sa biodisponibilité. Enfin, les propriétés
	restaurer une concentration physiologique de NO, les S-nitrosothiols (RSNO) font protectrices des fonctions endothéliales des S-nitrosothiols ont été évaluées sur des
	partie des donneurs de NO envisagés comme principes actifs potentiels. Les RSNO aortes dénuées d'endothélium (Article 3).
	sont la forme physiologique de stockage et de transport de NO dans l'organisme, lui
	assurant ainsi une demi-vie supérieure à sa forme libre radicalaire (< 0,5 s). La plupart
	des pathologies cardiovasculaires nécessitent un traitement chronique pour lequel la
	voie orale est plébiscitée. Cependant, l'absorption intestinale des RSNO, première
	limite à leur biodisponibilité vasculaire, n'a jamais été étudiée. Ainsi, à l'aide d'un
	modèle in vitro de barrière intestinale (Caco-2), cette étude vise à élucider les
	mécanismes de perméabilité intestinale (passifs ou actifs, voie paracellulaire ou
	transcellulaire) et à prédire le site d'absorption intestinale préférentiel des RSNO. Dans
	notre étude, trois RSNO, le S-nitrosoglutathion (GSNO), la S-nitroso-N-acétylcystéine
	(NACNO), la S-nitroso-N-acétyl-D-pénicillamine (SNAP), qui diffèrent de par le
	squelette transportant NO, ont été évalués. Ces squelettes transporteurs de NO
	confèrent des propriétés physico-chimiques (lipophilie) et des activités biologiques
	(antioxydantes et/ou anti-inflammatoires) différentes aux RSNO. Ainsi, en montrant à
	l'aide de ce modèle la perméabilité apparente moyenne des RSNO, associée à leur
	forte solubilité, cette étude a permis de placer ces molécules entre la classe I et la
	classe III du Système de Classification Biopharmaceutique. L'évaluation
	bidirectionnelle de la perméabilité a également solutionné le mécanisme de
	perméabilité de RSNO selon un phénomène passif. De plus, GSNO et NACNO suivent
	préférentiellement la voie transcellulaire alors que SNAP préfère la voie paracellulaire.
	Finalement, le squelette transportant NO a une influence sur le site d'absorption des
	RSNO, puisque la perméabilité de NACNO est favorisée à pH 6,4, pH proche de la
	partie proximale du jéjunum, alors que celles de GSNO et SNAP sont meilleures à pH

Article 3: S-nitrosothiols as potential therapeutics to induce a mobilizable vascular store of nitric oxide to counteract endothelial dysfunction. Les S-nitrosothiols : de potentiels médicaments induisant la formation d'un stock mobilisable de monoxyde d'azote au sein des vaisseaux afin de contrer la dysfonction endothéliale.

	Caroline Perrin-Sarrado # , Yi Zhou # , Valérie Salgues, Marianne Parent, Philippe
	Giummelly, Isabelle Lartaud, Caroline Gaucher*

#

Les deux auteurs ont contribué à parts égales à ce travail.

	testés à l'aide de la N-acétylcystéine. Ensuite la capacité de ce stock à s'opposer à la Dans ce contexte, trois stratégies de formulation de GSNO basées sur des procédés Article 4:
	vasoconstriction produite par la phényléphrine (PHE) a été appréciée. de double émulsion/évaporation de solvant ont été comparées (Article 4).
	Tous les RSNO étudiés ont été capables de générer un stock de NO trois à cinq fois
	supérieur à la quantité basale de NOx au sein des artères contrôle. NACNO était le
	plus performant de tous les RSNO pour produire un stock vasculaire biodisponible
	pour la vasorelaxation et pour induire une hyporéactivité à la PHE des artères sans
	endothélium. L'efficacité de GSNO et SNAP était équivalente, et supérieure à celle de
	SNP. Au sein des artères avec endothélium, le stock de NO s'est également formé,
	Article soumis au journal Biochemical Pharmacology le 28 juin 2019, en révision cependant il s'est avéré moins disponible pour la vasorelaxation et n'a pas influencé
	la vasoconstriction induite par la PHE.
	La dysfonction endothéliale prédispose au développement de certaines pathologies En conclusion, les RSNO, et NACNO plus particulièrement, sont capable de restaurer
	cardiovasculaires. Elle est définie comme un déséquilibre entre la production de la biodisponibilité de NO en créant un stock fonctionnel de NO au sein de la paroi des
	substances vasodilatatrices comme le monoxyde d'azote (NO) et de substances vaisseaux sanguins et de façon plus marquée quand l'endothélium est absent. Ce
	vasoconstrictrices. Afin d'assurer ses fonctions physiologiques, NO, un radical gazeux phénomène a été associé à une hyporéactivité de l'artère à un agent vasoconstricteur
	à demi-vie très courte, a besoin d'être stocké et transporté jusqu'à son site d'action. comme la PHE. Des traitements à base de RSNO pourraient donc présenter un
	Les S-nitrosothiols (RSNO) comme le S-nitrosoglutathion (GSNO) représentent la bénéfice pour restaurer les fonctions NO-dépendantes dans des états pathologiques
	principale forme physiologique de stockage de NO au sein du système vasculaire. Le associés à un endothélium lésé.
	stock de NO formé par les RSNO reste alors biodisponible pour déclencher la Ainsi, toutes ces études mettent en évidence que NACNO est le S-nitrosothiol qui
	vasorelaxation. Ainsi, les RSNO représentent une classe émergente de donneurs de franchit le mieux la barrière intestinale et qui produit le stock de NO vasculaire le plus
	NO pour restaurer la biodisponibilité de NO au cours des troubles cardiovasculaires. grand et le plus biodisponible.
	Le but de cette étude est de comparer la capacité des S-nitrosothiols à produire un Dans la dernière partie de ce travail, nous nous sommes intéressés au développement
	stock vasculaire de NO au sein d'artères dont l'endothélium est intact ou d'artères dont de formulations particulaires adaptées à la voie orale et permettant d'augmenter la
	l'endothélium a été retiré. Un RSNO physiologique, le GSNO, ainsi que deux RSNO biodisponibilité des S-nitrosothiols. Malgré la supériorité de NACNO dans les études
	synthétiques, la S-nitroso-N-acétylcystéine (NACNO) et la S-nitroso-N-précédentes, c'est le GSNO qui a été utilisé pour cette étude. En effet, il présente
	acétylpénicillamine (SNAP) ont été testés, permettant ainsi d'évaluer le potentiel certains avantages. D'une part, il est physiologique (contrairement à NACNO) et a été
	thérapeutique des RSNO pour compenser la dysfonction endothéliale. Le utilisé dans la majorité des essais cliniques. D'autre part, seul GSNO peut être obtenu
	nitroprussiate de sodium (SNP), un médicament bénéficiant déjà d'une autorisation de sous la forme d'un produit à la fois pur et solide (ce qui permet plus de libertés dans la
	mise sur le marché, a été utilisé comme donneur de NO contrôle non RSNO. Les deux formulation).
	types d'artères (avec ou sans endothélium) utilisées dans cette étude ont été isolées En ce qui concerne le procédé de formulation galénique, il doit être adapté à ces
	de rats Wistar mâles normotendus et exposées aux donneurs de NO. Ensuite, les molécules particulièrement fragiles et hydrophiles, tout en respectant le cahier des
	espèces dérivées de NO (NOx) représentant le stock intravasculaire de NO, ont été charges pour la voie orale : polymère adapté, charge en principe actif suffisante,
	quantifiées en utilisant la sonde diaminonaphthalène couplée aux ions mercuriques. libération appropriée, stabilité des caractéristiques des particules obtenues pour
	La biodisponibilité du stock de NO et sa capacité à produire la vasorelaxation ont été faciliter leur utilisation, amélioration de la perméabilité intestinale sans cytotoxicité…

Enhancing intestinal permeability of nitric oxide with storable microparticles for S-nitrosoglutathione oral delivery. Des microparticules préparables à l'avance pour la délivrance de S- nitroglutathion par voie orale et capables d'augmenter la perméabilité intestinale du monoxyde d'azote Yi

Zhou, Caroline Gaucher, Isabelle Fries, Mehmet Hobekkaya, Charlène Martin, Clément Leonard, Frantz Deschamps, Anne Sapin-Minet, Marianne Parent* Article soumis au journal International Journal of Pharmaceutics le 21 août 2019 Trois sortes de particules encapsulant du S-nitrosoglutathion (GSNO), un donneur physiologique de monoxyde d'azote, ont été préparées à partir des mêmes matériaux mais avec des procédés modifiés de double émulsion/évaporation de solvant : eau dans huile dans eau (E/H/E) ou solide dans huile dans eau (S/H/E). Les nano-et microparticules obtenues par la méthode E/H/E ont été comparées aux microparticules obtenues par la méthode S/H/E en ce qui concerne leur taille, leur capacité à encapsuler le GSNO et à le libérer in vitro. La cytocompatibilité des particules vis-à-vis des cellules intestinales ainsi que leur capacité à améliorer la perméabilité intestinale du GSNO in vitro (modèle de barrière intestinale constituée par les cellules Caco-2 différenciées) ont été évaluées. L'efficacité d'encapsulation du GSNO est la même (environ 30 %) pour les trois sortes de particules mais les microparticules (S/H/E > E/H/E) présentent un profil de libération plus lent du GSNO in vitro et améliorent significativement la perméabilité intestinale de GSNO. Cette perméabilité apparente élevée lorsqu'il est encapsulé dans les microparticules, associée à une solubilité élevée, fait passer GSNO en classe III de la classification biopharmaceutique.

Table 1 . GSNO related intravenous delivery systems

 1 These films enhanced the vaginal blood perfusion in a rat model and showed no cytotoxic effects, which means they might be regarded as potential treatments for female sexual arousal disorder.

	Formulation type	Effects	Application	Note	Dosage (eq infusion rate) Ref
			Young healthy women		2.5 mg GSNO over 30 min (about 4.1 nmol/kg/min)	90
				No
		Inhibition of platelet activation	Patients with unstable angina and patients with acute	hemodynamic changes were observed	2.2 or 4.4. nmol/kg/min	91
			myocardial infarction
			Coronary bypass patients		40 nmol/min (0.67 nmol/kg/min)	92
	Free GSNO	Reduced hypertension and platelet aggregation	Preeclamptic pregnant women		50-250 µg/min for 60-90 min (2.5 to 12.5 nmol/kg/min)	93
		Inhibition of platelet activation	Percutaneous transluminal coronary angioplasty patients	No observed hemodynamic changes were	Not mentioned	94
		Reduced embolization	Endarterectomy patients, Carotid angioplasty patients	Dose titrated not to induce hypotension	2.2 or 4.4. nmol/kg/min	95-97

(especially airway mucosa) as well. It was reported that mucosal GSNO can induce bronchodilation by releasing NO, which is an important therapeutic agent in pulmonary diseases such as asthma

103

. In the study of

Hurley et al. 104

, a nebulized GSNO inhaler effectively improved oxygenation in cystic fibrosis patients. However, a lot of studies reported in the literature with interesting results only include in vitro and preclinical tests on cells or animals. For example, through incorporation of GSNO into poly(ethylene glycol) (PEG) matrices, Seabra et al.

105

obtained a formulation suitable for topical administration and showed its potential to enhance the percutaneous absorption of NO. In addition,

Seabra et al. 106,107

also succeeded in incorporating GSNO into films of blended poly(vinyl alcohol)/poly(vinyl pyrrolidone) (PVA/PVP). These films could be with antibacterial effects. In the work of

Yoo et al. 110

, GSNO was incorporated into films made of three different materials (Carbopol, hydroxypropyl methylcellulose (HPMC) and PEG).

were obtained through solid-in-oil-in-water (S/O/W) double emulsion with solvent evaporation technology. These microparticles were applied onto skin lesions infected with methicillin-resistant Staphylococcus aureus and enhanced drastically their healing, in a rat model.

Table 2 . GSNO related topical delivery systems

 2

	Formulation type	Polymer	Effects or treatments	Administration area	Note	Ref
			local microcirculatory
	Hydrogel	F-127	flux increase without any systemic side	Human skin		102
			effects
	Free GSNO		Bronchodilation	Pig lung		103
	Patent inhalation		Improving oxygenation without any systemic side effect	Lung of cystic fibrosis patients		104
	Matrices	PEG	Potential to enhance the percutaneous absorption	Not mentioned		105
		PVA/PVP	Accelerate the wound healing in diabetes Not mentioned		106,107
	Films	PVA	Local vasodilation promotion effects or as dermal wound dressing	Human skin		108
		Chitosan	Wound healing and antibacterial effects	Rat skin		109

intermediate cells anchorage with an increase in protein production while cellular metabolic activity and redox balance were maintained. These preliminary results could pave the way for a potential application in cardiovascular tissue engineering. In addition,

Parent et al. 117

also developed in situ GSNO-loaded formulations (implants and microparticles) using PLGA.

Table 3 . GSNO loaded implants

 3

	Formulation type	Polymer	Effects	Application	Note	Ref
	Scaffolds	PLGA/ PCL	Cardiovascular tissue engineering			116
					Longer and slight hypotension
	Microparticles	PLGA	Potential treatment of stroke	Rats with stroke	effect, ability to prevent transient well as to provide platelet hyper-responsiveness as	117
					cerebroprotection after stroke
		Polyhedral oligomeric
	Nanocomposite	silsesquioxane/poly(carbonate-	CVD			118
		urea) urethane
	Polymeric stents	PLGA/ PEG / PCL	Antiplatelet			119

Table 4 . GSNO related oral delivery systems

 4

	Formulation type	Polymer	Effects	Application	Note	Ref
			Ameliorates inflammatory
			sequelae observed in bladder	Spinal cord injury induced rats		121
			and renal tissues
			Inhibited proliferation of
			chemoresponsive and chemoresistant ovarian cancer	Rats		122
	Free GSNO		cell lines
			Reduced disease progression in chronic models	Experimental autoimmune encephalomyelitis mice		123
			Significantly suppressed the levels of inflammatory mediators in the retinas of EAU mice	Experimental autoimmune uveitis (eau)		124
	Nanoparticles	Eudragit				125
		Eudragit,				126
	Nanocomposite	alginate, chitosan		Rats	NO store formation in the vessel wall	127

Table 1 .

 1 Conditions used for the synthesis of amidoximes 2.

	Entry	Product	Conditions	Yield
				(%)
	1	2a	NH2OH.HCl (3 x 2eq), Na2CO3 (3 x 2 eq), EtOH, reflux	98
	2	2b	NH2OH.HCl (2 x 2eq), Na2CO3 (2 x 2 eq), EtOH, reflux	95
	3	2c NH2OH.HCl (2 x 2eq), Na2CO3 (2 x 2 eq), EtOH, reflux	37
	4	2c	NH2OH 50 wt. % in H2O (1.5 eq), EtOH, reflux	60
	5	2d	NH2OH 50 wt. % in H2O (2.5 eq), EtOH, reflux	40

Rt = 13.433, Area percentage = 98.886 %

Rt = 10.859, Area percentage = 96.731 %

Acknowledgements

The completion of my PhD thesis would not have been possible without the support of many people whom I wish to thank for their contributions and diligent efforts. I would like to express my sincerely thanks to Pr. Ponchel (Université Paris-Sud), Pr. Demougeot (Université de Franche-Comté), Dr. Elhabiri (DR-CNRS, Université de Strasbourg) and Dr. Boura (MCU, Université de Lorraine) for accepting to be my reviewers of this work. To Pr. Ponchel and Dr. Boura, thank you for their participation in this thesis committee and valuable comments which have enriched this work. I would like to express my deepest and sincere gratitude to my supervisors: Caroline Gaucher and Marianne Parent, who supported me during the all the research and writing of this thesis. Caroline had a large impact on my work by sharing her insight and experience. I deeply appreciate her smart mind and efficient work capacity. Her

List of tables, figures and abbreviations

Tables Please find the Appendix A from page 206 to 222.

Chapter 2: Intestinal permeability of S-nitrosothiols

Conclusion and Perspectives

This work aims at making clear the mechanisms of intestinal permeability of different RSNOs as well as their ability to form NO store within the vascular wall, which helps to improve RSNOs-loaded oral delivery system dedicated to CVD treatment. We demonstrated that:

1. All the three RSNOs can cross the intestinal barrier (medium class of permeability) by passive diffusion. GSNO and NACNO preferentially cross intestinal barrier by the transcellular pathway and SNAP followed not only the transcellular but also paracellular way. They belong to class I or class III according to BCS and can be administrated through oral route.

2. All RSNOs showed their ability to induce the formation of a NO store, which represent a three to five times increase in NOx species content inside aorta (endothelium-intact or endothelium-removed). The vascular NO store, produced by each RSNOs (NACNO was the most potent), was available for vasorelaxation and induced hyporeactivity to the vasoconstrictive agent PHE. RSNOs, particularly NACNO, are able to restore NO bioavailability within the vascular wall, especially for the endothelium-removed aortae. They can be regarded as potent therapeutics to counteract endothelial dysfunction.

3. Two microparticles types (GSNO-MPW and GSNO-MPS) were obtained through the modification of GSNO-NP preparation with similar encapsulation efficiency (about 30%) but longer GSNO release time (more than 2 hours). Through lyophilization, all these three particles were transferred to powders with long time stability (more than 3 months for GSNO-NP and 1 month for two microparticles). In addition, all these three particles presented an ability to enhance the intestinal permeability of GSNO. They might represent a good choice for chronic oral treatment of NO deficiency caused pathologies like CVD.

With regard to these studies, several parts deserve further study or our attention.

In the study of amidoxime (article 1), compound 2d bearing aromatic and aliphatic ), rat liver microsomes (20 mg/mL in saccharose), hydroxylamine hydrochloride (99%), hydroxylamine solution 50 wt. % in H2O were purchased from Sigma-Aldrich. 4hydroxybenzamidoxime (>98%) and 4-methoxybenzamidoxime (99%) were purchased from Alfa Aesar. Potassium cyanide (KCN, ≥97%) was purchased from Merck. Calcium carbonate (Na2CO3, ≥99.8%) was purchased from Carl Roth. Commercial products were used as received.

Ultrapure deionized water (>18.2MΩ.cm) was used to prepare all the solutions. The cells used were from human smooth muscular cells issued from human thoracic aorta (CRL-1999).

Characterization

All reactions were monitored by TLC silica plates. Melting points were measured on a Buchi M-560 Melting Point apparatus. FT-IR spectra were recorded by a Bruker Tensor 27 spectrometer equipped with liquid nitrogen cooled MCT-detector. FT-IR spectra were obtained at 6 cm -1 resolution using the Attenuated Total Reflectance (ATR) technique. NMR spectra were measured with a Bruker Avance 300 (300 MHz for 1 The absorbance for the Griess assay was measured by using EL 800 microplate reader (Bio-TEK Instrument, INC®, France). All fluorescence for DAN assay was measured by using the FP-8300iRM fluorescence spectrophotometer (JASCO, France) coupled with FMP Micro-well plate reader.

Synthesis of nitriles 1c and 1d

To a stirred solution of the bromo derivative (15 mmol) in DMF (15 mL), was added potassium cyanide (4 eq). The mixture was heated to reflux for 72 h. After cooling to room temperature, the mixture was filtered over sintered glass and Celite and the solvent evaporated under reduced pressure. The residue was extracted with ethyl acetate (4 x 40 mL) and the organic phase washed with a 1M NaOH. The organic layer was dried over MgSO4 and concentrated. The product was purified by flash chromatography using ethyl acetate/petroleum ether (8/2) as eluent.

5-Phenoxy-pentanenitrile 1c

with PBS added with 0.1% DMSO were under the limit of detection for both RSNO and nitrite ions.

Analytical data for lead compounds