Cristian Piras

Yongzhi Guo

Alessio Soggiu

Metasu Chanrot

Viviana Greco

Andrea Urbani

Gilles Charpigny

Luigi Bonizzi

Dr Paola Roncada
email: paola.roncada@istitutospallanzani.it

Patrice Humblot

Metasu Chanrot Bc

Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge

scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche

Molecular BioSystems Accepted Manuscript

Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28.

Molecular BioSystems Accepted Manuscript

Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28.

Introduction

Due to negative genetic correlations between milk production traits, and reproduction and health traits 1 the genetic selection for high milk production potential has been associated in dairy cows with a reduction in fertility and an increased sensitivity to diseases 2,3 . Modern dairy cows are at high risk of suffering from uterine disease following calving and the number of exposed cows reached several millions per year in EU [2][3][4][5] . Exposed cows have low fertility, extended unproductive periods with high culling rates 5,6 thus affecting herd economy since rearing replacement animals is one of the main source of economic losses and welfare due to short life. More costs result from treatment and associated milk withdrawal. The total costs of diagnosed uterine diseases, for farmers, dairy and breeding industries has been reported to reach 1.4 billion €/year in EU 6 . This figure may be underestimated due to undiagnosed forms of uterine dysfunction leading to idiopathic infertility. Dystocia and retained placenta predispose to uterine disease due to disruption of physical barriers to infection and perturbation of immune responses that should eliminate pathogens 7 . Metabolic imbalance is also influencing these processes as strong negative energy balance was reported to depress gene expression in relation to immunity in uterine tissue [8][9][10] . In most epithelia, specific strains of Escherichia coli (E. coli) are major sources of infection. For the cow endometrium, E. coli is one of the most prevalent bacteria isolated in metritis 6,11,12 and paves the way for infection by other bacteria or viruses 13,14 . A major component explaining the pathogenicity of E coli is related to the interaction of LPS with the host tissue 12,15 . E coli LPS provokes the inflammation of the endometrium through a cascade of events well conserved in different tissues. The presence and the involvement of TLR4 in epithelial and stromal cells of the bovine endometrium has already been demonstrated by Cronin and colleagues 16 . LPS binding to Toll like 4 receptors triggers the production of pro-inflammatory cytokines, the attraction of immune cells in stromal tissue and a shift between PGF2α and PGE2 production by the endometrium. The deregulation of cytokines, chemokines, growth factors and major histocompatibility complexes (MHC) is a part of the inflammatory processes affecting epithelial barriers. Diagnosed clinical symptoms are the basis for treatment. However, acute uterine infections are often followed by an asymptomatic persistent inflammation which remains untreated. For instance in the cow, it has been shown that the undiagnosed persistence of inflammation of the endometrium following infection contracted at parturition 7,17 perturbs later the embryo-maternal interactions necessary to establish successful implantation thus impairing fertility 5,6 . However, the role of endometrial cells and more especially epithelial cells in the persistence of inflammation and mechanisms involved in infertility at this stage of pregnancy still have to be elucidated. Successful implantation requires a balanced and accurate molecular communication between conceptus and maternal endometrium. Even a small imbalance due to former bacterial infection /LPS stimulation could affect negatively the dialogue between the mother and the embryo necessary for the establishment of pregnancy 18 . The increased activation of NFκB and the secretion of proinflammatory and chemotactic cytokines that proved the activation of CD14 receptor was demonstrated bronchial epithelial cell lines 19 . The occurrence of endometritis linked to the production of cytokines has already been investigated through the analysis of mRNA expression 20 . The overexpression of IL-1alpha and IL-1-RN mRNA and the down-regulation of cPGES mRNA have been reported in cows with subclinical endometritis when compared to healthy cows. Authors found as well that the expression of CXCL5, IL1B, IL8 and TNF mRNA was significantly higher in cows with subclinical or clinical endometritis. This result came from analysis of mRNA expression of the transcripts involved in prostaglandin synthesis in the bovine endometrium 20,21 . The deregulation of these pathways induced by LPS in endometrial cells, was further illustrated by Oguejiofor et al., 2015, while using a wider transcriptomic approach. Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI :

Molecular BioSystems Accepted Manuscript

10.1039/c6mb00723f

The differential protein expression in caruncular and intercaruncular areas during peri-implantation period has been described in ewes 18 . Authors used LC-MS/MS technique and highlighted the important role of structural proteins as actin in the implantation process.

A differential proteomics profiling of cows with endometritis has already been performed by using 2D electrophoresis on endometrial tissue 22 . Among differentially expressed proteins between healthy cows and endometritis cows, proteins such as peroxiredoxin and heat shock proteins were overexpressed 22 .

As described above, the response of endometrial tissue in terms of pro-inflammatory factors has already been documented from in vivo material generally combining different types of cells resulting in some heterogeneity of the analyzed tissue. Other limitations may have resulted from former proteomic approaches. Due to this, in the present study we investigated the changes induced by LPS at different concentration on a homogenous population of post-primary bovine endometrial epithelial cells (bEECs) and by using two complementary proteomics approaches (2D electrophoresis and shotgun MS analysis). By using this combination, it was expected to find proteins patterns that may reveal the consequences of previous infection in the endometrial epithelium.

The information brought here showing that a multiplicity of pathways are deregulated by LPS provides new insights on the mechanisms involved in persistent inflammation following bacterial infection and suggest new perspectives to limit the impact of inflammation on the endometrial epithelium.

Material and methods

Sample selection and endometrial epithelial cell culture.

Bovine uteri without any morphological signs of inflammation were collected from a slaughter house and brought back on ice to laboratory within 1 hour after collection. Stage of the estrus cycle was determined at first from ovarian morphology and presence or absence of mucus in the uterine body. Genital tracts from 9 cows, showing an orange CL >15mm diameter and without abundant mucus were estimated to be associated with luteal phase 23 and subsequently used for cell culture. Stage of the cycle was further confirmed by histology from measurement of number of cross sections of the glands in full sections of the endometrium taken 5 cm from the tip of the horn 24. The left uterine horns were dissected and cut into 5-6 cm long and 4-5 mm deep pieces. Uterine tissue was digested with collagenase IV (C5138, Sigma) and hyaluronidase (250 U/mL; H3506, Sigma) diluted in PBS (phosphate-buffered saline) plus 2% BSA while stirring for 2 hours at 39°C. The suspension was then filtered through a 250 µm gauze to remove residual mucus and undigested tissue. The filtrate was then passed through a 40 µm nylon sieve, which allowed the fibroblast and blood cells to pass through while epithelial cells were retained. Epithelial cells were collected from the filter by backwashing with 30 mL PBS. Cells were centrifuged at 170 g for 6 minutes and the pellet was re-suspended in 3 mL of PBS. To disperse pellet into a single cell suspension, cells were disrupted by passing through a fine gauge needle. Then, cells were cultured in F- Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f performed at 5-6 days when epithelial cells attained 80 to 90% confluence. The process was renewed until passage 4 and cells exposed to LPS challenge. LPS powder was dissolved in water 5 mg/ml as a stock. Before challenge, the adjusted concentrations of LPS and media were completely mixed. At 72 hours following LPS challenge, the supernatant was removed and non-adherent (floating) cells in media were counted under microscope by using a burker neubauer chamber (hemocytometer, 40443001, Hecht Assistent®, Rhon, Germany). The attached cells were then detached with trypsin (TrypleTMExpress, gibco®, Waltham, USA). Cells were exposed systematically two times to 4 mL trypsin at 39°C for 4 minutes. Flasks were then checked for remaining cells. This protocol was applied again when some cells remained attached. After trypsinization, all cells were pipetted from flasks and then transferred into 15 mL falcon tubes. The solution was gently mixed for 2-3 seconds and 70 µL taken and mixed with the same volume of trypan blue solution (T8154 trypan blue solution 0.4%, Sigma®, St.Louis, MO, USA) in Eppendorf tubes. Then, 10 µL of mixed solution was immediately transferred to the counting chamber (same as above) following manufacturer's instructions. The living cells were detached with trypsin and pellets of 2 to 3 million post-primary cells per group were collected and immediately deep frozen (-80°c) until subsequent proteomic analyzes 23 .

LPS Challenges

In preliminary experiments, epithelial endometrial cells were exposed to a wide range of concentrations of LPS reflecting concentrations found in uterine fluid in case of clinical endometritis 24 and cell survival was estimated 25 . The dosages of LPS used in the present experiment (Sigma L2630 E.coli O111:B4, 0 as controls, 8 and 16 µg/ml) were chosen according to epithelial cell survival at 72 hours which was shown to be maximal with 8 µg/ml LPS (+30 to + 40% living cells when compared to controls). This increase in cell survival progressively vanished with increasing dosage, cell survival being not different from controls following addition of 16 µg/ml and being lower than controls at higher dosages. LPS challenges (0, 8 and 16 µg/ml LPS) were applied on cells issued from 9 different cows (in 3 series of 3 cows). Living cells were counted by trypan blue staining and cell survival profiles at 72 hours obtained from this precise subset of cows, measured as (number of cells "LPS treated"number of cells "controls" / number of cells "controls") were analyzed by ANOVA (SAS ver 9.2, proc GLM). Effects of cow, series of experiments and LPS dosage on cell survival were analyzed by ANOVA (SAS Ver 9.2, proc GLM). The cow ID (9 levels; 3 different cows in each of 3 series), the series No (3 levels) and LPS dosage (2 levels) were included in the model as well as LPS x cow and LPS x series interactions. The tests were made while comparing the LSmean ratio, observed for a given factor (or second order interactions) to 0, which should be the mean value observed if these ratios were distributed at random. LS means ratios (either negative or positive) corresponding to the effect of LPS differing from 0 at p<0.05 were considered as significant.

Proteomics analyses

Proteomic analyses have been performed according to Figure 1. All 9 biological replicates have been analyzed in groups of three through 2D electrophoresis followed by MALDI TOF MS for protein identification. Moreover, the first three biological replicates have been analyzed through label-free nanoflow liquid chromatography mass spectrometry (nLC-MS E ) analysis and each run was performed in triplicate.

Extraction of cell samples

Cellular pellets (cell amounts per pellet varied from 1,6x10 6 to 3,3x10 The gels have been then removed from the plates, washed three times with double-distilled water and stained over night (ON) with Coomassie Brilliant Blue. Gels have been digitized using an Imagescanner III (GE Healthcare) and image analysis was performed using SameSpots software (Version 4.5, Nonlinear Dynamics U.K.). Spots with a p value lower than 0.05 were manually excised and subjected to mass spectrometry (MS) analysis and protein identification. The protein identification was performed according to the methodological protocol previously described [26][27][28][29] . Briefly, after steps of dehydration, reduction and alkylation, single spots were digested with a solution of 0.01 µg/µl of porcine trypsin (Promega, Madison, WI) at 37 °C for 16 h. Peptides were concentrated using C18 ZipTip (Millipore) and then were spotted on a Ground Steel plate (Bruker-Daltonics, Bremen, Germany).

MALDI TOF TOF MS Analysis

The Peptide Mass Fingerprinting Analysis was performed according to Piras et al 30 Briefly, the MS analysis was performed on an Ultraflex III MALDI-TOF/TOF spectrometer (Bruker-Daltonics) in positive reflectron mode and MS spectra were analyzed by FlexAnalysis 3. To confirm the PMF identifications, the instrument was switched in LIFT mode with 4-8 × 10 3 laser shots using the instrument calibration file. For the fragmentation, precursor ions were manually selected and the precursor mass window was automatically set. Each MS/MS spectra acquired were processed by spectra baseline subtraction, smoothing (Savitsky-Golay) and centroiding using Flex-Analysis 3.3 software. For searching analysis, these parameters were set: carbamidomethylation of cysteines and oxidation on methionine respectively among fixed and variable modifications; maximum of one missed cleavage; the mass tolerance to 50 ppm for precursor ions and to a maximum of 0.5 Da for fragments. The taxonomy was restricted to Bos taurus. The confidence interval for protein identification was set to 95% (p < 0.05) and only peptides with an individual ion score above the identity threshold were considered correctly identified.

Molecular BioSystems Accepted Manuscript

Statistical analysis for validation of 2-DE dataset

For a subset of 5 proteins, the repeatability of the results over the 3 series of analyses has been studied. From mean MS results from the 3 technical replicates of each sample the ratio of expression when compared to control was calculated and results analyzed by ANOVA (SAS Ver 9.2, proc GLM). The cow ID (9 levels; 3 different cows in each of 3 series), the series No (3 levels) and LPS dosage (2 levels) were included in the model as well as LPS x cow and LPS x series interactions. The tests were made while comparing the LSmean ratio, observed for a given factor (or second order interactions) to 0, which should be the mean value observed if these ratios were distributed at random. For a given protein, ratios of expression (either negative or positive) corresponding to the effect of LPS differing from 0 at p<0.05 were considered as significant through the 3 series of experiments.

Expression Analysis by nLC-MS E .

Label-free nanoflow liquid chromatography mass spectrometry (nLC-MS E ) was performed as previously described in [30][31][32] . Briefly, the protein extracts of nine biological samples (3 dosages LPS from cell culture from 3 cows) were precipitated with a cold mix of Ethanol, Methanol, and Acetone (ratio 2: . The list of normalized proteins was screened according to the following criteria: protein identified in at least 2 out of 3 runs of the same sample with a fold change of regulation higher than +/-20%; We considered significant only differentially expressed proteins with a p value < 0.05. Finally, the GO Molecular function classification from the Panther Classification System 33 was used to allocate the differentially expressed proteins into functional groups according to the best fitness in the biological system analyzed.

1:1, v/v),

Results

Cell survival profiles following LPS challenges

The profile of cell survival following LPS challenges made in the subset of cows used in this study was very similar to those observed in former experiments. A strong increase in cell survival was observed with the 8 µg/ml LPS dosage (+24%, p<0.0001) whereas results were not different from controls for the 16 µg/ml LPS group (0.4%, NS).

Proteomic profiling from 2D electrophoresis coupled with MALDI TOF TOF

From 2D electrophoresis and imaging analyses a total of 1096 different spots were visualized (Figure 2) from pellets of endometrial epithelial cells and proteins subsequently identified from MALDI TOF TOF MS analysis. From those, a total of 7 proteins were found to be differentially expressed between controls and LPS treated samples (Table 1).

The different types of responses obtained according to LPS dosage are presented in Figure 3.

Results obtained by 2D electrophoresis coupled with MALDI TOF identification revealed that response to LPS was similar over the 3 groups of experiments for 5 proteins especially for the 8µg/ml dosage whereas response was more variable for the 16µg/ml LPS dosage. For all these proteins no significant interaction between LPS dosage and series was found. Annexin 2 was significantly under expressed for the 8µg/ml dosage (p<0.02) but only a similar trend was observed for the 16µg/ml LPS dosage (Figure 4). On the contrary, Eukaryotic Initiation Factor 4A1 (EIF 4A1), Protein Disulfide isomerase (PDIA3), Superoxide Dismutase and Transketolase were significantly overexpressed following the 8µg/ml LPS challenge (p<0.001 to p<0.05). Similar effects were seen with 16µg/ml but only a trend was seen for EIF 4A1. For all proteins, differences between 8 and 16µg/ml LPS are nonsignificant.

Proteomic profiling from shotgun MS and analysis of differentially expressed pathways.

Shotgun MS analysis qualitatively identified a total of 226145 EMRTs and 160 proteins across all conditions. Quantification was performed following analysis of EMRTs and protein normalization. 34,35 The overall statistical analysis from shotgun MS highlighted 35 differentially expressed proteins between the three different experimental groups (Table 1, fig. 5). These divide into 25 up regulated and 10 down regulated for at least one of the LPS dosage when compared to controls (p<0.05).

From Panther Classification System and use of GO Molecular function classification the differentially expressed proteins clustered well in structural proteins, metabolism proteins (energy metabolism), transcription and protein synthesis, oxidative stress, cell growth/apoptosis, immune response, and chromatin DNA binding pathways. Structural/Cytoskeleton, calcium metabolism and membrane properties: Structural proteins such as actin, peripherin and related proteins that contribute to actin stabilization and anchorage on plasma membrane such as radixin and tropomyosin alpha 1 chain are strongly down-regulated in both LPS groups in comparison to control group. On the contrary, Tropomyosin alpha 3 chain is upregulated with both LPS dosages. Proteins involved in cell membrane function and calcium metabolism are either down (annexin A1 and annexin A2, both LPS dosages) or up regulated (calreticulin both LPS dosages). Protein disulfide isomerase (P4HB) and protein disulfide isomerase A3 (PDIA3) are both upregulated. In addition, a strong down-regulation of a protein with proteolytic activity (Cathepsin) and an up-regulation of a strong inhibitor of endopeptidases (Cystatin-B) in LPS8 group versus control group were observed.

Molecular BioSystems Accepted Manuscript

Energy Metabolism: All proteins clustering in this category are strongly upregulated for both LPS dosages. This includes phosphoglycerate mutase, glyceraldehyde-3-phosphate deshydrogenase, triosephosphate isomerase and β enolase, all of them being part of the glycolytic process.

Oxidative stress: All proteins involved in oxidative stress response and protein folding and refolding have been found to be overexpressed following LPS treatment. Among them peroxiredoxin, protein disulfide-isomerase, protein disulfide-isomerase A3, endoplasmin, SH3 domain binding glutamic acid rich like protein 3 and heat shock related 70KDA protein -2. For most of them overexpression is a little bit higher with the 16 than for the 8 µg/ml LPS dosage, but response is already very significant with 8 µg/ml. Transcription processes: Proteins such as transcription, initiation and elongation factors and ribonucleoproteins involved at different steps of the transcription process have been also found to be overexpressed in the groups of cells challenged with LPS. This includes elongation factor 1-alpha, elongation factor 1-delta, elongation factor 2, eukariotic initiation factor 4A-1 (EIF4A-1), heterogeneous nuclear ribonucleoprotein A1 and 60S acidic ribosomal protein P2. For all of them except EIF4A-1 changes in expression are more pronounced for the 16 than for the 8 µg/ml LPS dosage.

Cell growth/ cell cycle/ proliferation /apoptosis: Differentially expressed proteins involved in these pathways dispatch in up-(78 kDa glucose-regulated protein, phosphoglycerate kinase 1) and downregulated ones (three different types of metallothioneins (-1, -1A, -2) and galectin-1). Galectin -1 (regulating apoptosis) is downregulated for both LPS dosages whereas the 3 metallothioneins (involved in negative regulation of growth/ proliferation) are only up regulated significantly for the 8 µg/ml LPS dosage.

Immune response:

Histone H2B type 1 (involved in innate immune response in mucosa as a defense mechanism against bacteria) and14 -3-3 protein zeta delta (involved in response proteins from bacterial origin) are strongly upregulated with the 16 µg/ml LPS dosage (no change with 8) whereas alpha enolase (stimulating IgG production, pro-inflammatory and involved in allergy mechanisms) is strongly upregulated with both LPS dosages. Chromatin / DNA binding proteins: Histones H2A type 1, H2A.J, H2B type 1-K are more strongly down regulated with the 16 than with 8µg/ml LPS dosage whereas Histone H4 is more deregulated with 8. On the contrary, Histone H2B type 1-N, has been found to be upregulated in the LPS16 group. The whole panel of differentially expressed proteins, their relationships and sense of deregulation has been represented through an interactomic analysis performed with STRING 10 36 (Figure 6).

Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f

Discussion LPS used at concentrations in the range of those found from in vivo studies at 72 hours after challenge of bEECs, induce either a strong increase in cell number (8µg/ml dosage) or no change in epithelial cell survival (16µg/ml dosage) 25 . These results are in agreement with studies reporting that LPS induced an increase in epithelial cell proliferation from different tissues [37][38][39] . Differences with results showing an inhibition of epithelial cell number 40,41 could be partly due to the dosage of LPS that induced an inhibition with the highest LPS dose (16µg/ml dosage). However, despite this increase in the number of living cells with a normal morphological appearance, the results of the present study reveal that many changes in protein expression occur following exposure of bEECs to E coli LPS showing that several functions of these cells were highly de-regulated. The consequences of observed changes in protein expression for cell function and possible implications for implantation will be discussed according to the molecular function retrieved from GO annotations.

Structural/Cytoskeleton, calcium metabolism and membrane properties Actin and peripherin have been found to be down-regulated with both LPS dosages. These proteins play a key role as structural constituents of cytoskeleton. Such changes in actin remodeling after LPS stimulation have already been described in macrophages and changes in cell mobility have been reported from the same study 42 . The down regulation of actin 2 in this model could also be linked to a rearrangement of other structural proteins following LPS stimuli. This is supported by changes in the regulation of PHB4 and PDIA3 which controls the cleavage and rearrangement of disulfite bounds both inside and outside the cell, modifying proteins attached to cell or nascent proteins. Annexin A1 and annexin A2 were down-regulated by LPS. They are both involved in calcium metabolism. Annexins are considered as scaffolding proteins which participate in membrane dynamics. In particular, annexin A2, that has structural similarities to annexin A1, has been shown to exhibit anti-inflammatory activities in several animal models of inflammation [43][44][45][46][47] . This protein has been included here in the calcium metabolism proteins because of its calcium binding properties and dependent activity. However, beside these properties in relation with GO annotations, structural activities linked to lipid bilayer and lipid rafts and to actin binding have been reported as well 48 . The regulation of annexins and actin are following the same trend. The anti-inflammatory properties of annexins and the down-regulation observed here are in agreement with the pro-inflammatory role of LPS.

On the contrary, we observed an over-expression of calreticulin which is mainly involved in calcium metabolism and in protein folding (Figure 6). As a chaperone protein, calreticulin is also linked with HSP90. This protein is expressed on the cellular surface and its putative role in cell adhesion, migration or apoptosis has been documented 49 . In addition, calreticulin modulates integrin-dependent Ca 2+ signaling [Michalak et al., 1999] and different patterns of expression have been reported during implantation in mice [Cheng et al., 2009].This protein is expressed on the cellular surface and its putative role in cell adhesion, migration or apoptosis has been documented 49 . In addition, calreticulin modulates integrin-dependent Ca 2+ signaling 50 and different patterns of expression have been reported during implantation in mice 51 . The signification of its overexpression in our model in relation with the above still has to be elucidated. The full mechanism by which LPS provokes these changes remains to be deciphered. However, our results suggest that LPS destabilizes cell structure and modify cell membrane properties in a way cell adhesion is reduced. To our knowledge, the possible roles of LPS in altering such functions have not been much described before especially in relation with implantation. The changes observed could be of considerable importance while considering the role of adhesion molecules and membrane function in this process.

Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f

Another response to LPS in relation with cell structure could be part of a defense mechanism contributing to inhibit protease activity through down-regulation of the protease cathepsin and upregulation of the peptidase inhibitor Cystatin-B. As Cystatin-B is an inhibitor of cathepsin protease, the trend of expression of these two proteins is consistent and such changes may protect cells from proteolytic activity. The role of this anti-protease mechanism and its relation with the changes reported above in cell structure and membrane permeability requires further investigation.

Energy Metabolism

Differentially expressed proteins related to energy metabolism proteins were all found to be overexpressed in both LPS groups when compared to controls. These proteins are mostly glycolytic proteins as Phosphoglycerate mutase, Glyceraldehyde-3-phosphate dehydrogenase, Triosephosphate isomerase, Beta-enolase OS and Alpha-enolase. The interactomic analysis (Figure 6) shows clearly that energy metabolism occupies a very central place in this system. This is consistent with the fact that LPS induced glycolysis which has been constantly reported in literature from other tissues and other species [52][53][54] determines other cell responses thus contributing in many ways to the development of pathological processes.

Oxidative stress response

Even if this in vitro model is working outside the in vivo machinery and based on a single population of cells, many proteins involved in this pathway and in protection from oxidative stress are deregulated showing the key role of LPS while inducing oxidative stress. They occupy a place close to proteins involved in metabolism (Figure 6) and most of them may result from LPS induced glycolysis changes. The only protein that is not linked with other proteins, in this interactomic analysis, is the SH3 domain-binding glutamic acid-rich-like protein 3 that, according to GO classification, was related to cell redox homeostasis and is also involved in regulation of actin cytoskeleton organization. Interestingly, our results confirm also the up-regulation of Peroxiredoxin-1, which has been described as a strong promoter of inflammation through stimulation of the synthesis of proinflammatory cytokines such as interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) [START_REF] Liu | Mediators of inflammation[END_REF] . Changes in cytokines were not evidenced from this epithelial cells model. However, the up-regulation of Peroxiredoxin-1 and other pro-inflammatory molecules such as Enolases may represent an important link between LPS stimulation and the generation of inflammatory cascade in surrounding cells.

Translation Process/protein synthesis, regulation of cell cycle and proliferation

As for the energy metabolism, several proteins involved in protein biosynthesis such as initiation and elongation factors have been found to be strongly up-regulated. This demonstrates that the translation machinery is stimulated by LPS. The strong links between these proteins in the interactome and their upregulation is very consistent with the role of this family of factors in the stimulation of cell growth and proliferation [START_REF] Shahbazian | [END_REF]57 and the present changes in this phenotype induced by LPS. In addition to the above, other proteins have been reported, from their GO annotated molecular functions, to be related with regulation of cell cycle and cell proliferation. In this case, the interpretation of the interactomic analysis is more complex than for other functions. A strong link was found, with a high significant value, between Transketolase, Phosphoglycerate kinase 1 and 78 kDa glucose-regulated protein, the latest being linked to the above translation machinery. From GO molecular functions, all these proteins are involved in regulation of cellular growth, epithelial cells differentiation and act as positive regulators of cell migration. As for proteins involved in translation their up-regulation is consistent with the proliferative phenotype observed following LPS challenge. No links were found between the above and metallothioneins nor galectin-1. Metallothioneins were found here to be up-regulated only in cells exposed to 8µg/ml LPS and galectin-1 is down regulated for both LPS dosages. These proteins are classified, from GO annotated molecular functions, as involved in negative regulation of growth. The up-regulation of metallothioneins looks in contrast with the growing phenotype observed in our model. However, their up-regulation could be related to a compensatory mechanism from cells to counteract the proliferative response induced by the activation of metabolism and transcription machinery. This response could be also associated to different functions as these proteins have been reported to be involved in bactericidal activity and nitric oxide production following LPS stimulation 58 .

Molecular BioSystems Accepted Manuscript

Immune response; relationships with establishment of pregnancy Our results showing that 14-3-3 protein zeta/delta is up-regulated in the LPS16 group versus control group is consistent with former functions of this protein described in literature. It's major role in the regulation of corneal epithelial proliferation and differentiation in corneal mice cell culture has been reported 59 . This protein has been shown to be also involved in the regulation of the production of cytokines 60 and, the gamma proteoform, is up-regulated during LPS-induced cardiomyocytes injury 61 . Its major role in Toll-like receptors activation has also been demonstrated and its involvement in the lipopolysaccharide-induced production of tumor necrosis factor by macrophages has been documented 62 . A recent study demonstrated that 14-3-3γ was able to attenuate the LPS-induced inflammatory responses and to induce the proliferation of dairy cow mammary epithelial cells 63 . The up-regulation of this protein we observed may be part of a similar anti-inflammatory mechanism taking place in our model in response to LPS. One of the most interesting finding in our results in relation with establishment of pregnancy is the strong down-regulation of galectin-1 induced by LPS. To our knowledge this has not been reported before. Galectin-1 has been mostly studied in human and rodents and has been shown to be expressed in the bovine endometrium 64 . In the human, this protein is abundantly expressed in the non-immune cells at the fetus-maternal interface, down regulates the production of pro-inflammatory cytokines and promotes maternal immune tolerance 65 . In the mouse, Yakushina et al., 2015 66 shown that galectin-1 stimulates the differentiation of CD4+ cells into T-regulatory cells then being one of the key molecules involved in immune-tolerance. Probably as the result of the above, low expression in the endometrium has been associated to an increased frequency of early pregnancy failures and miscarriages 67,68 .

As part of the metabolic changes both α and β-enolase are both up-regulated following challenges with similar responses for both LPS dosages. Among other roles, α-enolase has been reported as an allergenic molecule with immune and strong pro-inflammatory properties [69][70][71] . In rats, high expression of α-enolase has been associated with increased numbers of CD4+ T cells and immuno rejection in an allograft transplantation model 72 .

The impact of immune imbalance induced by deregulations of galectin-1 and α-enolase on the establishment of pregnancy has to be demonstrated in the bovine through functional studies. If existing and persistent, the lack of immunosuppression induced by LPS through down regulation of galectin-1 and up-regulation of pro-inflammatory processes through enolases could be part of the mechanisms altering implantation success even in the absence of bacterial infection.

Chromatin and DNA binding

A differential expression of several DNA binding proteins such as histones has been found. As said before for other processes, the interactome picture is quite complex here with 4 of them under expressed and 2 over expressed following LPS challenge and more specific work is needed to decipher the mechanisms explaining the overexpression of some specific histones and the downregulation of some other isoforms. However, from the 4 histones under expressed we found 2 (Histone H2A type1 and H2AJ) which are associated with chromatin silencing consistent with the over expression of many pathways. The over expression of Histones H2B type1 and H2B type1N following exposure to the 16µg/ml dosage is also consistent with their roles in innate immune

Molecular BioSystems Accepted Manuscript

Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28.

View Article Online DOI: 10.1039/C6MB00723F

Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f

response in mucosa and DNA protein binding. Effectively, some histones, such as H2B type1, could represent LPS binding proteins 73 and their differential expression could contribute to the formation of an antimicrobial and of an endotoxin-neutralizing barrier against microorganisms 74 .

Conclusion

This study shows that many pathways involved in a wide range of functions are affected by LPS. Some were awaited, and the corresponding changes in mRNAs and proteins described. However, even for these pathways which have been studied intensively and largely documented, such as the immune response, this proteomic approach reveals that deregulation occurs for specific molecules which have not been described in former studies and /or not related to the role of LPS and its possible impacts on the establishment of pregnancy. Taken together, the results from this cow model based on a pure population of epithelial cells provide evidence that LPS induces the activation of proinflammatory mechanisms and at the same time down regulates signals reported to be involved in immune-tolerance in other species (such as Galectin-1). The persistence of changes possibly induced by LPS due to exposure to pathogens during the post-partum period and their subsequent implication in fertility failures at time of establishment of pregnancy deserves further investigations.

Aknoledgments

This work was performed with the financial support of the EU project "PROLIFIC" (grant KBBE 311776-PR and PH) and of Rajamangala University of Technology Srivijaya (RMUTSV, Thailand).

Molecular BioSystems Accepted Manuscript

Published on 21

 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28. View Article Online DOI: 10.1039/C6MB00723F

Published on 21

 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28. View Article Online DOI: 10.1039/C6MB00723F Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f

Figure legends Figure 1 :

 legends1 Figure legendsFigure1: Strategy for the proteomic analyses. Left part of graph 2D Electrophoresis and Maldi TOF TOF. All cell pellets from 9 cows (3 samples per cow, Control CTRL and LPS treated cells; LPS 8 µg/ml, LPS 16 µg/ml) were analyzed following separation of protein spots by 2D gel electrophoresis and identification of spots by image analysis (Progenesis), gel spots were digested and then differentially expressed (DE) proteins identified by MALDI TOF-TOF MS (Ultraflex III, Bruker) and quantified. Right part nLC-MS/MS analysis was performed in the first series of three cows (3 samples per cow as above) peptide separation and identification was done following tryptic digestion of total protein extracts. Assays were run in triplicate for each sample in each type of analysis.

Figure 2 :

 2 Figure 2: Representative image of 2D map of one biological replicate.

Figure 3 :

 3 Figure3: Differentially expressed proteins observed from 2D electrophoresis followed by MALDI TOF TOF MS analysis in response to LPS (CTRL Control, LPS 8µg/ml, LPS 16µg/ml). For each bar is reported the mean ± SD value of nine biological replicates (n=9). Proteins follow the survival profile of epithelial cells (PDIA3 Protein Disulfide Isomerase) or is inverse (ANXA2 Annexin 2). Significance (* p<0.05, ** p<0.01) indicates differential expression between treated samples and controls.

Figure 4 :

 4 Figure 4:Mean response for 5 differentially expressed proteins following 3 series of LPS challenge with 8 and 16µg/ml LPS (each bar from 9 individual cows). Results are expressed as ratios when compared to controls and for each LPS dosage, significance of differences are tested against 0; * p<0.05, ** p<0.01, *** p<0.001. For all proteins, differences between 8 and 16µg/ml LPS are nonsignificant.

Figure 5 :

 5 Figure 5: Results from shotgun analysis, proteins significantly overexpressed and under-expressed following challenge of endometrial epithelial cells with 8 (orange bars) or 16 µg/ml LPS (grey bars) when compared to controls (blue bars), * p< 0.05, ** p<0.01.

Figure 6 .

 6 Figure 6. Protein legend STRING protein-protein interaction analysis. The string name of each protein represented in the figure is indicated in the 4 th column of table 1.

Figure 1 :

 1 Figure 1: Strategy for the proteomic analyses. Left part of graph 2D Electrophoresis and Maldi TOF TOF. All cell pellets from 9 cows (3 samples per cow, Control CTRL and LPS treated cells; LPS 8 µg/ml, LPS 16 µg/ml) were analyzed following separation of protein spots by 2D gel electrophoresis and identification of spots by image analysis (Progenesis), gel spots were digested and then differentially expressed (DE) proteins identified by MALDI TOF-TOF MS (Ultraflex III, Bruker) and quantified. Right part nLC-MS/MS analysis was performed in the first series of three cows (3 samples per cow as above) peptide separation and identification was done following tryptic digestion of total protein extracts. Assays were run in triplicate for each sample in each type of analyse.

Figure 3 :

 3 Figure 3: Differentially expressed proteins observed from 2D electrophoresis followed by MALDI TOF TOF MS analysis in response to LPS (CTRL Control, LPS 8µg/ml, LPS 16µg/ml). For each bar is reported the mean ± SD value of nine biological replicates (n=9). Proteins follow the survival profile of epithelial cells (PDIA3 Protein Disulfide Isomerase) or is inverse (ANXA2 Annexin 2). Significance (* p<0.05, ** p<0.01) indicates differential expression between treated samples and controls.

Figure 4 :

 4 Figure4: Mean response for 5 differentially expressed proteins following 3 series of LPS challenge with 8 and 16µg/ml LPS (each bar from 9 individual cows). Results are expressed as ratios when compared to controls and for each LPS dosage, significance of differences are tested against 0; * p<0.05, ** p<0.01, *** p<0.001. For all proteins, differences between 8 and 16µg/ml LPS are non-significant.

  Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28. FPR) of the identification algorithm under 1% and 200 fmol of the enolase internal standard set as calibration protein concentration. The most reproducible proteotypic peptides for retention time and intensity of enolase digestion (m/z 814.49; m/z 1159.59; m/z 1288.70; m/z 1755.95; m/z 1840.91, m/z 2441.12) were used to normalize the EMRTs table. The expression analysis was performed considering 3 technical replicates available for each experimental condition (i.e., one experimental condition, control, LPS 8 and LPS 16 groups, × three biological replicates × three technical replicates)

	View Article Online
	Each sample was run in three technical replicates. For qualitative and quantitative analysis, LC-MS
	data from three replicates experiments for each nine samples were processed using ProteinLynx
	GlobalServer v.3.0.2 (PLGS, Waters Corporation). Protein identifications were obtained with the
	embedded ion accounting algorithm of the software searching into UniProtKB/Swiss-Prot Bos taurus
	database release 2013_12 (25 245 entries) to which the sequence of enolase (UniProtKB/Swiss-Prot

then dissolved in 6 M Urea, 100 mM Tris pH 7.5 and digested 50:1 (w⁄w) with sequence grade trypsin (Promega, Madison, WI, USA) at 37°C overnight after reduction with 10 mM DTT and alkylation with 20 mM IAA. The reaction was stopped by adding a final concentration of 0.1% TFA. Separation of tryptic peptides and subsequent qualitative and quantitative nLC-MS E analysis were performed by nanoACQUITY UPLC System (Waters Corp., Milford, MA) coupled to a Q-Tof Premier mass spectrometer (Waters Corp., Manchester, U.K.). An amount of 200 fmol/µl of digestion of Enolase from Saccharomyces cerevisiae was added to each sample as internal standard, then a final concentration of 0.6 µg of protein digestion was loaded on column for peptides separation. Peptides were loaded onto a Symmetry C18 5 µm, 180 µm x 20 mm precolumn (Waters Corp.) and subsequently separated by a 170 min reversed phase gradient at 250 nL/min (3-40% CH 3 CN over 145 min) using a NanoEase BEH C18 1.7 µm, 75 µmX25 cm nanoscale LC column (Waters Corp.) maintained at 35 °C. The Q-Tof Premier mass spectrometer directly coupled to the chromatographic system operated in ''Expression Mode'' switching between low (4 eV) and high (15-40 eV) collision energies on the gas cell, using a scan time of 1.5 s per function over

50-1990

m/z. The processing of low and elevated energy, added to the data of the reference lock mass, provides a time-aligned inventory of accurate mass-retention time components for both the low and elevated-energy (EMRT, exact mass retention time). AC: P00924) was appended. The search parameters were set at: automatic tolerance for precursor ions and for product ions, minimum 3 fragment ions matched per peptide, minimum 7 fragment ions matched per protein, minimum 2 peptide matched per protein, 1 missed cleavage, carbamydomethylation of cysteines and oxidation of methionines as fixed and variable modifications,

Molecular BioSystems Accepted Manuscript

DOI: 10.1039/C6MB00723F Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f

false positive rate (

  Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28.

	View Article Online

DOI: 10.1039/C6MB00723F Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f

  Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28.

	View Article Online
	DOI: 10.1039/C6MB00723F

Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f

  Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28. Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28. Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28. Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28. Published on 21 December 2016. Downloaded by University of Newcastle on 25/12/2016 08:31:28.Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f

	View Article Online View Article Online View Article Online View Article Online View Article Online
	DOI: 10.1039/C6MB00723F DOI: 10.1039/C6MB00723F DOI: 10.1039/C6MB00723F DOI: 10.1039/C6MB00723F DOI: 10.1039/C6MB00723F
	Molecular BioSystems Accepted Manuscript Molecular BioSystems Accepted Manuscript Molecular BioSystems Accepted Manuscript Molecular BioSystems Accepted Manuscript

Table 1 .

 1 Cell growth/cell cycle/proliferation/apoptosisComment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P.,Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723fTable representing the whole dataset of the differentially expressed proteins identified through shtogun MS analysis and 2D electrophoresis (* p<0.05, ** p<0.01, *** p<0.001).

	* *	* *					* *	* *
		UNIQUE	UNIQUE	UNIQUE	UNIQUE	UNIQUE	UNIQUE

Comment citer ce document : Piras, C., Guo, Y., Soggiu, A., Chanrot, M., Greco, V., Urbani, A., Charpigny, G., Bonizzi, L., Roncada, P., Humblot, P. (2017). Changes in protein expression profiles in bovine endometrial epithelial cells exposed to E coli LPS challenge. Molecular Biosystems, 13 (2), 392-405. DOI : 10.1039/c6mb00723f

Published on 21 December 2016. Downloaded by University of Newcas