Introduction: Hepatic stellate cells (HSC) and myofibroblasts may be relevant stromal drivers of human hepatocellular carcinoma (HCC). It was hypothesised that targeted inhibition of αv integrin-mediated TGF-β activation, by HSC or hepatocytes, may result in reduced peri-tumoural and intra-tumoural extracellular matrix formation, and reduced hepatic carcinogenesis. The role of HSC in acute liver injury is less well characterised. It was anticipated that integrin signalling on HSC and hepatocytes might also be relevant in the acute setting. The emerging technique of intravital microscopy (IVM) allows detailed, real-time investigation of the cellular processes involved in hepatocyte injury, cell death and repair. It was hypothesised that this could be coupled with mouse models of HCC and acute liver injury, to perform sequential imaging under anaesthesia. Aims: (i) To determine the effect of targeted inhibition of αv integrins on HSC and hepatocytes, during hepatocarcinogenesis, in a mouse model of HCC. (ii) To investigate the effect of targeted inhibition of αv and other integrins on HSC, hepatocytes, and liver sinusoidal endothelial cells (LSEC), during acute liver injury, in the mouse model of paracetamol-induced liver injury. (iii) To develop IVM of the liver, via an abdominal imaging window, with optimisation of surgical and imaging techniques, to allow sequential imaging of the same animal. Methods: The diethylnitrosamine (DEN)-induced mouse model of hepatocarcinogenesis was used, and PDGFRβ-Cre;αvfl/fl and Alb-Cre;αvfl/fl mice were employed to deplete αv integrins on HSC and hepatocytes respectively. Tumours were harvested at 40 weeks post-DEN. Tumour size and number was evaluated in all animals. PDGFRβ-Cre;αvfl/fl and Alb-Cre;αvfl/fl mice were used in the paracetamol model, to investigate the role of αv integrins in acute liver injury. PDGFRβ-Cre;β8fl/fl and Alb-Cre;β 8fl/fl animals were also tested in this model. The role of integrins in liver sinusoidal endothelial cells (LSEC) during paracetamol-induced liver injury was evaluated using Cdh5-Cre mice. IVM of the liver was performed by surgical implantation of an abdominal imaging window, consisting of a titanium ring and coverslip, secured in place with a purse string suture. Fluorescent reporter mice were used to identify hepatic and vascular architecture, and other label-free microscope technologies were utilised to image collagen, lipid distribution, necrotic areas and blood flow within tissues. Results: In large cohorts of PDGFRβ-Cre;αvfl/fl, Alb-Cre;αvfl/fl, and control animals, there was no difference in mean tumour size or number, at 40 weeks. Targeted inhibition of α v integrins and β 8 integrin on hepatocytes, HSC or LSEC was not protective in paracetamol-induced liver injury. IVM of the liver can be performed on animals with HCC and throughout paracetamol-induced liver injury, to obtain high quality, real-time images of multiple cell lineages and the hepatic microenvironment. Conclusions: The role of TGF-β in HCC pathogenesis is complex and context-dependent. Targeted loss of αv integrin did not result in reduction in tumour burden in this non-cirrhotic model of HCC. IVM of the liver is a powerful tool to quantify inflammatory infiltrates and assessment of vascular remodelling throughout the course of acute liver injury and regeneration, providing insights into the biological processes determining recovery.

Peu de données sont disponibles sur le devenir à long terme après un choc septique. De plus le foie, organe clé dans la réponse de l’hôte à l’agression pourrait jouer un rôle important concernant le devenir à long terme. Dans une cohorte de patients chirurgicaux en choc septique, nous avons observé une mortalité élevée à 6 mois et une altération de la qualité de vie parmi les survivants par rapport à la population générale. Toutefois, celle-ci tend à s’améliorer au cours du temps. Dans un second travail, nous avons observé que la dysfonction hépatique précoce évaluée par le score SOFA dans les 24 heures qui suivait l’introduction des vasopresseurs n’avait pas d’impact sur la mortalité et la qualité de vie à long terme dans une cohorte multicentrique de patients médico-chirurgicaux en choc septique. Au contraire, l’apparition secondaire ou l’aggravation d’une dysfonction hépatique était associée à une surmortalité jusque 6 mois après l’épisode de choc septique. Afin d’approfondir par une approche expérimentale les mécanismes impliqués dans la dysfonction septique hépatique, nous avons mis au point un modèle in vitro de co-cultures hépatocytes-macrophages soumis au LPS. A partir de ce modèle, nous avons montré qu’une catécholamine telle que l’adrénaline, jouait un rôle dans la pérennisation d’une inflammation péri hépatique locale par un mécanisme AMPc dépendant mais epac/PKa indépendant. / Knowledge regarding long-term outcome after septic shock is limited. Additionally, the liver, which plays a key role during the septic illness, could significantly impact the long term outcome. First, in a surgical cohort of septic shock patients, we found that the 6-month mortality rate remained high. Baseline health-related quality of life (HRQOL) was found to be lower than in the general population and although HRQOL improved 6 months after the onset of septic shock, HRQOL remained lower than in the general population. In a second work including a large multicenter cohort of septic patients, we found a significant relationship between the occurrence or the worsening of liver dysfunction during the course of septic shock and mortality at 6 months; however, this relationship was not found in the patients with baseline liver dysfunction. At last, experimentally, we established a hepatocyte-macrophage co-culture model and septic shock was mimicked by lipopolysaccharide (LPS) treatment. We found that a catecholamine frequently used in septic shock such as epinephrine was able to shift the innate immune response toward a pro-inflammatory environment even when a low anti-inflammatory response was observed in macrophages and these effects were cAMP dependent but PKA/epac independent.

Les objectifs de cette thèse sont de déterminer les mécanismes cellulaires et moléculaires mis en jeu lors de la co-exposition de cellules hépatiques à l'éthanol, un toxique alimentaire, et au benzo[a]pyrène (B[a]P), un important contaminant de l’environnement émis lors de combustions incomplètes. L’exposition d’hépatocytes primaires de rat pendant 8h favorise leur collaboration via l’induction d’une déplétion membranaire en cholestérol par le B[a]P, ce qui facilite l’action de l’éthanol à déstabiliser les lysosomes via la phospholipase C-1 pour entraîner la mort par apoptose. Lors d’une exposition répétée sur 96h dans les cellules WIF-B9, celles-ci provoquent une mort précoce par nécrose suivie d’une apoptose tardive via leurs métabolismes. Leur toxicité impliquerait un remodelage membranaire et un stress oxydant avec la production d’espèces réactives de l’oxygène et la variation de l’homéostasie du fer. / The aim of this work is to determine cellular and molecular mechanisms implicated in the co-exposure to ethanol, a dietary toxic substance, and benzo[a]pyrene (B[a]P), a major environmental contaminant, found during incomplete combustions. Primary rat hepatocytes exposed during 8h showed a cooperation effect between the two molecules through the depletion of membrane cholesterol by B[a]P, which promote ethanol action to destabilize lysosomes through phospholipase C-1 and facilitate apoptosis cell death. After repeated exposure during 96h of WIF-B9 cells, these two molecules provoke an early cell death by necrosis and a late apoptosis through their metabolisms. Their toxic effects implicate membrane remodeling and oxidative stress with reactive oxygen species production and modifications in iron pool.

Aquatic organisms in response to toxic insults from environmental pollutants activate defence systems including the aryl hydrocarbon receptor (AhR) in an attempt to metabolize and excrete these toxicants and their metabolites. These detoxification mechanisms however may come with certain energetic costs. I hypothesize that the activation of the AhR by β-Naphthoflavone (β-NF), a model AhR agonist, results in increased energetic costs requiring metabolic reorganization in rainbow trout hepatocytes. While the results obtained suggest that there are no significant energetic costs of AhR activation, analysis of enzyme activities suggests possible metabolic reorganization. This study also showed significant changes in cellular processes in hepatocytes over the incubation periods which previously were not reported. Furthermore, for the first time in fish hepatocytes, metabolic flux analysis (MFA) was used to examine intra-cellular metabolism, the applicability of which is discussed.

Les hépatocytes humains adultes en culture primaire (HHCP) ont de nombreuses applications en physiopathologie hépatique, en pharmacologie et en biothérapie, mais sont limitées par leur faible disponibilité. Les cellules souches embryonnaires humaines (hES) sont une source prometteuse pour l'obtention d'hépatocytes en grande quantité. Nous avons développé un modèle in vitro de différenciation de hES en hépatocytes en reproduisant toutes les étapes de l'ontogenèse hépatique. Au cours de la différenciation, l'expression de 41 gènes marqueurs du foie a été étudiée et comparée aux HHCP, au foie fœtal et aux progéniteurs hépatiques issus du foie adulte. Les résultats démontrent qu'au bout de 21 jours de différenciation, les cellules souches embryonnaires différenciées en hépatocytes (hES-Hep) ont atteint un état de maturation équivalente aux hépatocytes fœtaux aux alentours de 20 semaines de gestation. L'expression forcée du xénorécepteur CAR dans les hES-Hep a induit l'expression des gènes de la détoxification et la biotransformation de midazolam, un substrat de CYP3A4. Ces résultats pourront contribuer au développement de cultures de hES-Hep comme alternative aux HHCP pour les études du métabolisme des xénobiotiques et pour la thérapie cellulaire. / Primary cultures of human adult hepatocytes (PCHH) have widespread potential applications in liver physiopathology , pharmacology, and cell-based therapies, but are currently limited by poor availability. Human embryonic stem cells (hES) are a promising source for the generation of hepatocytes in large quantities. In this study, we differentiated hES into hepatocytes by mimicking in vitro the various stages of hepatic ontogenesis. We analyzed the expression of a panel of 41 liver marker genes in hepatocyte-like cells derived from hES (hES-Hep) in comparison with PCHH, fetal liver and progenitors obtained from adult liver. The data revealed that after 21 days of differentiation ES-Hep are representative of fetal hepatocytes at around 20 weeks of gestation. The forced expression of the xenoreceptor CAR in hES-Hep induced the expression of detoxification genes as well as the biotransformation of midazolam, a substrate of CYP3A4. These results may contribute to the development of hES-Hep cultures as an alternative to PCHH for studies of xenobiotic metabolism and for cell-based therapies.

Orientador: Maria Luiza Silveira Mello / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-22T06:29:06Z (GMT). No. of bitstreams: 1 Ghiraldini_FlaviaGerelli_D.pdf: 75704253 bytes, checksum: 9d1afc3cebcffd05000b5efb25d3996d (MD5) Previous issue date: 2013 / Resumo: O diabetes mellitus do tipo I (DM1) caracteriza-se pela ocorrência de insulite com consequente hiperglicemia e poliuria. Alterações celulares estruturais e metabólicas decorrentes do aumento da glicemia podem provocar fenótipos de envelhecimento precoce. O envelhecimento celular e resultado de fatores intrínsecos e extrínsecos, que alteram a estrutura e a organização da cromatina e que, consequentemente, afetam a expressão gênica. As sirtuinas, deacetilases NAD+-dependentes, estão envolvidas na transcrição gênica, reparo de DNA, transcrição do rDNA, regulação metabólica e remodelação cromatinica. As sirtuinas nucleares, especialmente Sirt1 e Sirt6 estão envolvidas com o envelhecimento precoce, no metabolismo de glicose e na resposta a inflamação. O presente trabalho teve como objetivo geral comparar os processos de remodelação cromatinica em hepatocitos sob o efeito da hiperglicemia e do envelhecimento, usando-se modelo animal (camundongos). Um modelo de cultura celular (HepG2) foi também utilizado para estudo de efeitos da hiperglicemia, utilizando-se como metodologias analisem morfológicas e moleculares. Foi observado um aumento em conteúdo de DNA e em acessibilidade da cromatina a MNase mais acentuado em hepatocitos de animais DM1 do que de idosos. O aumento na abundancia de Sirt1 em animais hiperglicêmicos não refletiu em sua maior atividade, enquanto em idosos houve um decréscimo generalizado nesses parâmetros e aumento da aceptilação de sítios histónicos. Em animais DM1, Sirt6 apresentou abundancia semelhante à de Sirt1, possivelmente devido à alta fragmentação de DNA observada nesses animais, diferente do ocorrido em idosos. Ambos os animais DM1 e idosos apresentaram baixa relação área AgNOR+/área nuclear. Em animais diabéticos isto foi devido ao aumento na área nuclear, enquanto nos idosos, foi devido à diminuição na área AgNOR+ e aumento na área nuclear. O aumento na metilação de rDNA na porção 18S e a baixa abundancia de Sirt7 confirmam diminuição no metabolismo celular no envelhecimento. Em hepatocitos de camundongos DM1 e idosos foi observado genes diferencialmente expressos relacionados à inflamação. Admite-se que no primeiro caso este achado seja devido à natureza auto-imune da doença, enquanto no segundo possa ser um indício de inflamação naturalmente encontrada em processos de envelhecimento. Em animais DM1, a expressão diferenciada de genes envolvidos com metabolismo de lipídios poderia contribuir para com a peroxidação lipídica e produção de ROS levando a esteatose hepática. Nas células HepG2, alterações na expressão dos genes Apoe, Igfbp1 e Foxo1, ocorridas em meio de cultura hiperglicêmicas, tornaram-se revertidas quando as células foram retornadas a normoglicemia. Contudo, as abundancias das marcações epigenéticas nos promotores desses genes decresceram progressivamente, indicação de uma memória hiperglicêmica, dado não observado em modelo animal. A análise do fenótipo nuclear dessas células indicou possível indução da proliferação celular quando retornadas a normoglicemia. A inibição de sirtuinas aumentou o conteúdo Feulgen-DNA e o contraste entre cromatina condensada e não-condensada, indicativo de atuação na proliferação celular e na remodelação cromatinica. DM1 e envelhecimento, portanto, não podem ser considerados fenômenos idênticos, pois enquanto no primeiro ha um mecanismo compensatório que promove alterações genéticas, epigenéticas e remodelação cromatinica, no segundo ha um decréscimo generalizado no metabolismo celular levando a modificações diferentes nos mesmos parâmetros / Abstract: Diabetes mellitus type I (DM1) is characterized by insulitis and consequent hyperglycemia and polyuria. Structural and metabolic changes in the cell caused by hyperglycemia might induce an early-ageing phenotype. Both intrinsic and extrinsic agents might contribute to cellular ageing thus leading to chromatin structural changes and differential gene expression. Sirtuins, NAD+-dependent deacetilases, play a role in cell metabolism, transcription, DNA repair and chromatin remodeling. Sirt1 and Sirt6, especially, are nuclear proteins related to early-ageing, glucose metabolism and inflammatory response. The general purpose of the present work was to compare processes of chromatin remodeling in hepatocytes under the effects of hyperglycemia and aging, using mouse models. A model using cells in culture (HepG2) was also used to study the effects caused by hyperglycemia. The methodology used involved morphological and molecular analysis. An increase in DNA content and chromatin accessibility to MNAse was found more pronounced in hepatocytes from DM1 than from aged mice. Despite the high abundance of Sirt1 in DM1 animals, its activity was not proportionally high, whereas in old animals there was a reduction in these parameters, increasing the acetylation of Sirt1-histonic sites. In DM1 mice, Sirt6 presented similar abundance as Sirt1, possibly due to the high DNA fragmentation, different to what was found in aged animals. Both DM1 and normoglycemic old mice presented a decrease in AgNOR+ area/nuclear area ratio. While in DM1 animals it was a result from the increase in nuclear area, in old animals it was a combination of increased nuclear areas and decreased AgNOR+ areas. The DNA methylation increase in the 18S rDNA region and the decrease in Sirt7 abundance in the hepatocytes from old mice support the hypothesis of diminished cellular metabolism. Differential expression analysis for DM1 and old mouse hepatocytes presented a high number of genes involved in the inflammatory response. While in the former it could be an autoimmune characteristic of the disease, in the latter it might be an evidence of inflammatory state naturally associated with aging. Moreover, DM1 mice also presented differential gene expression related to lipid metabolism, which could contribute to increase lipid peroxidation and ROS production leading to hepatic steatosis. HepG2 cells showed changes in Apoe, Igfbp1 and Foxo1 expression in hyperglycemic medium and they were reverted when the cells returned to normoglycemic medium. The epigenetic marks, however, presented a progressive decrease in abundance, indicative of a hyperglycemic memory, which was not observed in DM1 animals. The nuclear phenotype in HepG2 cells under these same experimental conditions indicated a possible induction in cellular proliferation when the cells were returned to the normoglycemic medium. Inhibition of sirtuins increased the contrast between condensed and non-condensed chromatin and the Feulgen-DNA content, indicating a role in cell division and chromatin remodeling. Therefore, DM1 and ageing cannot be considered as identical processes, because while in DM1 there is a compensatory mechanism that induces changes in epigenetic marks, chromatin remodeling and differential gene expression, there is a general decrease in cell metabolism under aging that leads to different changes in the same parameters / Doutorado / Biologia Celular / Doutor em Biologia Celular e Estrutural

Dihydromyricetin (DMH) is a natural flavonoid compound with positive effects on the human organism. In traditional Chinese medicine, plants containing DMH were used to treat liver diseases and to reduce alcohol intoxication. The effects of DHM on ethanol metabolism are not yet completely understood. Effects of DHM during alcohol intoxication were studied on primary hepatocytes of rats. DCFDA and DHR probes were used to prove that DHM (depending on concentration) reduces the number of reactive oxygen and nitrogen species in primary hepatocytes. However, the hepatoprotective effects of DHM were not achieved when presence of the alanine aminotransferase (ALT) was used to measure the damage of cells exposed to alcohol. Further, the effects of DHM on alcohol metabolism were studied in vivo. Rats were administered with single dose of ethanol or ethanol combined with DHM. Measured blood levels of ethanol and acetaldehyde show that DHM has no effects on the rate or levels of alcohol metabolism. The effects of DHM were also studied with repeated alcohol administration. In the group that was administered also DHM, increased blood levels of ethanol were measured. This points that DHM slow down the metabolic rate of ethanol. Obtained results did not prove any positive effects of DHM on alcohol metabolism....

The main objective of this study was the application and comparison of different assays in assessing toxicity of cyanobacterial samples, and also characterizing toxicity of the field samples. Therefore, toxicity of purified microcystin-LR (MC-LR) and cyanobacterial samples collected from the Hartbeespoort (HBP) Dam (winter and summer seasons of 2005/2006) and Kruger National Park (KNP) were investigated and compared using the ELISA, mouse bioassay, catfish primary hepatocytes (in vitro assay) and protein phosphatase inhibition (PPi) assays. During sampling in the summer season at the HBP Dam, the dam surface was covered with a thick-green layer of cyanobacterial scum and a foul smell coming from the water surface was always present. Only blue-green streaks of cyanobacteria covered the dam surface during the winter season. All HBP Dam samples (winter and summer samples) and KNP samples (Nhlanhanzwani Dam, Mpanama Dam and Sunset Dam) were dominated by Microcystis aeruginosa with the exception of Makhohlola Dam samples which were found to have no cyanobacteria. The World Health Organization (WHO) has proposed a guideline value for human use of 1.0 µg/L (0.001 mg/L) for MC-LR, the most common microcystin (MC) variant, in drinking water (WHO 1998), whereas 2 000 Microcystis cells/mL have been recommended as the limit of cyanobacteria in drinking water for animals (DWAF 1996). Cyanotoxin concentrations exceeding the prescribed guideline value were detected in all HBP Dam samples (ELISA results ranging between 3.67 to 86.08 mg/L; PPi results ranging between 2.99 to 54.90 mg/L) and KNP samples (ELISA results ranging between 0.1 to 49.41 mg/L; PPi results ranging between 0.006 to 10.95 mg/L) using both the ELISA and PPi assays. In the current study, a dose of about 175 µg/kg of purified MC-LR was demonstrated to be lethal in male CD-1 SPF mice. The HBP Dam summer samples and Nhlanganzwani Dam samples were the only cyanobacterial samples that resulted in death (acute toxicity) of mice. In order to be able to investigate further the in vivo effects of cyanotoxins, transmission electron microscopy (TEM) was used to complement results obtained from the in vivo assay. Ultrastructural changes of varying degree were observed in livers of mice exposed to both the HBP Dam winter and summer samples. Early stages of hepatocyte to hepatocyte disassociation, slight vesiculation of endoplasmic reticulum (ER) and swollen mitochondria were the most significant ultrastructural changes produced in mouse hepatocyte tissues by the HBP Dam winter samples. The most significant ultrastructural changes produced in mouse hepatocyte tissues by the HBP Dam summer samples were massive hepatic haemorrhage indicated by the appearance of erythrocytes between hepatocytes and the extensive vesiculation of ER. This is the first time that the African sharptooth catfish primary hepatocyte model has been used to assess the hepatotoxicity of purified MC-LR and cyanotoxin-containing water samples. In this study, the toxicity of cyanobacterial samples and purified MC-LR to cause hepatotoxicity in mice was confirmed in vitro using the catfish primary cell line. A comparison among the cyanobacterial samples using EC50 showed the following hepatotoxicity trend in the catfish primary cell line: HBP Dam summer samples > Nhlanganzwani Dam samples > HBP Dam winter samples > Mpanama Dam samples > Sunset Dam samples > Makhohlola Dam samples. The HBP Dam samples were the most hepatotoxic and Makhohlola Dam samples were the least hepatotoxic. The EC50 for purified MC-LR using the catfish primary hepatocytes was about 91 nM. A statistical comparison of the assays used in this study (i.e. ELISA, PPi, mouse test and cytotoxicity [catfish primary hepatocyte] assays) was performed based on the Kappa coefficient (K). An almost perfect agreement (K > 0.80) was observed between the mouse test and cytotoxicity assay; mouse test and ELISA; cytotoxicity assay and ELISA; and ELISA and PPi assay. In conclusion, field samples collected during the summer season were found to have very high levels of toxins and a higher degree of toxicity when compared to the winter samples. The cytotoxicity assay using African sharptooth catfish (Clarias gariepinus) primary hepatocytes has been shown for the first time to produce results similar to those observed when using the mouse bioassay in assessing cyanobacterial toxicity. Therefore, this primary cell line may be used as a potential alternative to the mouse assay in toxicity testing of cyanotoxins. Three KNP dams (Nhlanganzwani Dam, Mpanama Dam and Sunset Dam) investigated in this study were found to contain Microcystis aeruginosa. All four KNP dams (Nhlanganzwani Dam, Mpanama Dam, Makhohlola Dam and Sunset Dam) had cyanotoxin levels above the prescribed guideline value, which is of concern and warrants further investigations to the effects on wildlife in the park. Future studies will include use of High Performance Liquid Chromatography (HPLC) to investigate the toxin profile of the field samples in order to fully describe the different classes/or types of toxins present in the samples. More validation studies that could give a more comprehensive understanding about the sensitivity of the catfish primary cell line for microcystins will also be undertaken. / Dissertation (MSc (Paraclinical Studies))--University of Pretoria, 2007. / Paraclinical Sciences / unrestricted

Les transporteurs membranaires jouent un rôle primordial dans la pharmacocinétique de médicaments mais aussi dans le transport de composés endogènes. La maîtrise de modèle in vitro permettant d’évaluer leur implication dans des interactions médicamenteuses, notamment au niveau hépatique, est donc primordiale. L’utilisation de ces modèles permettra aussi de déterminer l’impact potentiel de contaminants environnementaux, comme les particules diesel, sur l’expression fonctionnelle de transporteurs. Nos résultats démontrent la fiabilité de modèles hépatocytaires (hépatocytes et cellules d’hépatome HepaRG) en culture monocouche pour l’étude du transport membranaire de médicaments. Grâce à ces modèles, nous avons mis en évidence que des extraits de particules diesel (DEPe) peuvent modifier l’expression et/ou la fonction de transporteurs membranaires hépatiques, les Organic Anion Polypeptide Transporter (OATP) et les Multidrug Resistance associated Protein (MRP). Au niveau pulmonaire, les DEPe peuvent aussi augmenter l’expression du complexe LAT1/CD98hc, un complexe protéique de transport d’acides aminés souvent associé à de mauvais pronostics dans les cas de cancer du poumon. En conclusion, nos résultats mettent en évidence que les DEPe peuvent intervenir dans la régulation de l’activité et de l’expression de transporteurs membranaires tant au niveau hépatique qu’au niveau pulmonaire. / Membrane transporters play a major role in the pharmacokinetic of drugs and in the transport of endogenous compounds. The development of in vitro models for the study of their expression and activity is therefore important to consider, notably for analyzing their interactions with drugs or environmental contaminants such as diesel exhaust particles. Our results demonstrated the reliability of hepatocytic cells (hepatocytes and highly differentiated hepatoma HepaRG cells) in monolayer culture for the study of membrane transport of drugs. Using these models allowed us to demonstrate that extracts of diesel exhaust particles (DEPe) can alter the expression and / or function of major liver transporters such as organic anion transporting polypeptides (OATP) and Protein Multidrug associated Resistance (MRP). In lung cells, DEPe can increase the expression of complex LAT1 / CD98hc a protein complex, that is associated with poor prognosis in lung cancer. In conclusion, our results demonstrated that DEPe can regulate activity and expression of membrane transporters at hepatic and lung level.

Enterococcus faecalis est une bactérie commensale du microbiote intestinal humain. Inoffensive chez l'homme sain, E. faecalis est aussi un pathogène opportuniste. En conditions de dysbiose post-antibiotique, E. faecalis peut devenir une espèce dominante, traverser la barrière intestinale avant de disséminer. E. faecalis se classe désormais comme la troisième cause d'infections nosocomiales dans le monde. La pathogénie de E. faecalis est un processus multifactoriel dont les mécanismes cellulaires de son interaction avec l'hôte sont encore mal compris. À l'aide de modèles cellulaires d'infection et de modèles in vivo, nous avons entrepris de caractériser le rôle du facteur de virulence ElrA pendant l'infection cellulaire.Notre objectif était également de déterminer si FHL2, un partenaire eucaryote de ElrA, était impliqué dans l'infection par E. faecalis et de determiner l'impact de l'interaction ElrA-FHL2. Nous avons démontré que ElrA agit comme une cape d'invisibilité permettant à E. faecalis de ne pas être détecté par des macrophages. Nous avons également montré que FHL2 est impliqué dans la défense de l’hôte contre l'infection par E. faecalis, mais ce rôle implique partiellement ElrA. Parallèlement, nous avons montré pour la première fois que E. faecalis est capable de se multiplier dans les hepatocytes. En conclusion, ce travail apporte de nouvelles perspectives sur les interactions de E. faecalis avec son hôte. / Enterococcus faecalis is a core member of the human gut microbiota. Harmless for healthy humans, it is able to cause disease in susceptible patients under antibiotic-induced microbiota alteration. Nowadays, E. faecalis ranks as the third cause of nosocomial infections worldwide. E. faecalis pathogenicity is a multifactorial process but the cellular mechanisms of its interaction with the host remain poorly understood. Using cellular models of infection and in vivo models, we aimed to characterize the role of the virulence factor ElrA during cellular infection. Our goal was also to determine if FHL2, an ElrA eukaryotic partner, was implicated in E. faecalis infection and the impact of ElrA-FHL2 interaction. We have demonstrated that ElrA acts as an invisibility cloak allowing E. faecalis to avoid macrophage recognition. Also, we have shown that FHL2 is implicated in the defense against E. faecalis infection, involving partially ElrA. In parallel, we showed that intracellular replication of E. faecalis in hepatic cells. Altogether, our work provides new insights in E. faecalis interactions with the host cell.