by Wong Wing-yee, Felice. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 144-166). / Abstract also in Chinese. / Acknowledgements --- p.i / List of Abbreviations --- p.ii / Abstract --- p.iv / Abstract (Chinese Version) --- p.vi / Table of Contents --- p.viii / List of Tables --- p.xii / List of Figures --- p.xiv / List of Appendices --- p.xvi / Chapter Chapter I --- Literature Review / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Background of Cytochrome P450 --- p.3 / Chapter 2.1 --- Discovery --- p.3 / Chapter 2.2 --- Tissue Distribution --- p.3 / Chapter 2.3 --- Structure and Functions --- p.7 / Chapter 2.4 --- Nomenclature of the P450 Superfamily --- p.10 / Chapter 3. --- Cytochrome P450 2E1 (CYP2E1) --- p.11 / Chapter 3.1 --- Discovery --- p.11 / Chapter 3.2 --- Tissue Distribution --- p.12 / Chapter 3.3 --- Substrates and Inducers --- p.13 / Chapter 3.4 --- Toxicological Role of CYP2E1 --- p.15 / Chapter 4. --- CYP2E1-knockout Mouse Model --- p.17 / Chapter Chapter II --- Carbon Tetrachloride (CC14) Study / Chapter 1. --- Introduction --- p.19 / Chapter 1.1 --- General Properties and Usage of CC14 --- p.19 / Chapter 1.2 --- Toxicological Aspects of CC14 --- p.19 / Chapter 1.3 --- Mechanism of CCl4-induced Hepatotoxicity --- p.20 / Chapter 1.4 --- Role of CYP2E1 in CCl4-induced Hepatotoxicity --- p.23 / Chapter 1.5 --- Objectives of the Study --- p.27 / Chapter 2. --- Materials and Methods --- p.29 / Chapter 2.1 --- Chemicals and Materials --- p.29 / Chapter 2.2 --- Animals --- p.29 / Chapter 2.3 --- Acute CC14 Treatment --- p.29 / Chapter 2.4 --- Preparation of Microsomal Fractions --- p.30 / Chapter 2.5 --- Determination of Microsomal Protein Concentration --- p.31 / Chapter 2.6 --- Determination of Serum Aminotransferase Activities --- p.31 / Chapter 2.7 --- Liver Histology --- p.32 / Chapter 2.8 --- Hepatic Microsomal CYP2E1 Activity -p-nitrophenol Assay --- p.34 / Chapter 2.9 --- SDS-PAGE and Western Blot Analysis --- p.35 / Chapter 2.10 --- Detection of Lipid Peroxidation in vitro and in vivo --- p.35 / Chapter 2.10.1 --- In vitro Lipid Peroxidation - 2-Thiobarbituric Acid (TBA) assay --- p.35 / Chapter 2.10.2 --- In vivo Lipid Peroxidation - Microsomal Conjugated Dienes Detection --- p.36 / Chapter 2.11 --- Hepatic Lipid Fatty Acid Composition Analysis --- p.39 / Chapter 2.11.1 --- Lipid Extraction --- p.39 / Chapter 2.11.2 --- Thin Layer Chromatography --- p.39 / Chapter 2.11.3 --- Methylation --- p.40 / Chapter 2.11.4 --- Gas Chromatography --- p.40 / Chapter 2.12 --- Statistical Analysis --- p.41 / Chapter 3. --- Results --- p.42 / Chapter 3.1 --- "Mortality, Liver Weight and Liver Color" --- p.42 / Chapter 3.2 --- Hepatotoxicity --- p.42 / Chapter 3.2.1 --- Serum ALT and AST activities --- p.42 / Chapter 3.2.2 --- Liver Histology --- p.45 / Chapter 3.3 --- CYP2E1-catalysed PNP Activities and CYP2E1 Protein Levels --- p.49 / Chapter 3.3.1 --- CYP2El-catalyzed PNP Activities --- p.49 / Chapter 3.3.2 --- CYP2E1 Protein Levels --- p.52 / Chapter 3.4 --- Lipid Peroxidation --- p.52 / Chapter 3.4.1 --- In vitro Lipid Peroxidation --- p.52 / Chapter 3.4.2 --- In vivo Lipid Peroxidation --- p.54 / Chapter 3.5 --- Hepatic Lipid Fatty Acid Composition --- p.56 / Chapter 3.5.1 --- Fatty Acid Composition in Hepatic Phospholipid --- p.56 / Chapter 3.5.2 --- Fatty Acid Composition in Hepatic Microsomal Phospholipid --- p.59 / Chapter 3.5.3 --- Fatty Acid Composition in Hepatic Triglyceride --- p.61 / Chapter 4. --- Discussion --- p.63 / Chapter 4.1 --- CYP2E1 is Required in CCl4-mediated Hepatotoxicity --- p.63 / Chapter 4.2 --- CYP2E1 is Degraded following CC14 Exposure --- p.65 / Chapter 4.3 --- CYP2E1 is Required in CCl4-induced Lipid Peroxidation --- p.67 / Chapter 4.4 --- CYP2E1 is Required in CCl4-induced Hepatic Phospholipid Depletion --- p.70 / Chapter 4.5 --- CYP2E1 is Required in CCl4-induced Hepatic Triglyceride Accumulation --- p.72 / Chapter 5. --- Conclusion --- p.76 / Chapter Chapter III --- Chronic Ethanol Consumption Study / Chapter 1. --- Introduction --- p.77 / Chapter 1.1 --- Multiple Metabolic Pathways for Ethanol Metabolism --- p.77 / Chapter 1.2 --- Metabolism of Ethanol by the Microsomal Ethanol Oxidizing System --- p.79 / Chapter 1.3 --- Role of CYP2E1 in Ethanol Metabolism --- p.82 / Chapter 1.4 --- Role of CYP2E1 in Alcoholic Liver Disease and Associated Oxidative Stress --- p.84 / Chapter 1.5 --- Objectives of the Study --- p.89 / Chapter 2. --- Materials and Methods --- p.90 / Chapter 2.1 --- Chemicals and Materials --- p.90 / Chapter 2.2 --- Animals --- p.90 / Chapter 2.3 --- Chronic Ethanol Treatment --- p.90 / Chapter 2.3.1 --- Ethanol Diet Composition --- p.90 / Chapter 2.3.2 --- Ethanol Feeding --- p.90 / Chapter 2.4 --- Monitoring of Blood Ethanol Levels --- p.96 / Chapter 2.5 --- Preparation of Microsomal Fractions --- p.96 / Chapter 2.6 --- Determination of Microsomal Protein Concentration --- p.97 / Chapter 2.7 --- Determination of Serum Aminotransferase Activities --- p.98 / Chapter 2.8 --- Liver Histology --- p.98 / Chapter 2.9 --- SDS-PAGE and Western Blot Analysis --- p.99 / Chapter 2.10 --- Hepatic Fatty Acid Composition Analysis --- p.100 / Chapter 2.10.1 --- Lipid Extraction --- p.100 / Chapter 2.10.2 --- Thin Layer Chromatography --- p.101 / Chapter 2.10.3 --- Methylation --- p.101 / Chapter 2.10.4 --- Gas Chromatography --- p.102 / Chapter 2.11 --- Statistical Analysis --- p.103 / Chapter 3. --- Results --- p.104 / Chapter 3.1 --- Average Food Consumption --- p.104 / Chapter 3.2 --- Average Ethanol Consumption for Ethanol Liquid Diet Feeding Group --- p.104 / Chapter 3.3 --- Body Weight Gain --- p.104 / Chapter 3.4 --- Blood Ethanol Levels --- p.108 / Chapter 3.5 --- "Mortality, Liver Weight and Liver Color" --- p.108 / Chapter 3.6 --- Serum ALT and AST Activities --- p.110 / Chapter 3.7 --- Liver Histology --- p.114 / Chapter 3.8 --- Western Blot Analysis --- p.119 / Chapter 3.9 --- Hepatic Lipid Fatty Acid Composition --- p.119 / Chapter 3.9.1 --- Fatty Acid Composition in Hepatic Phospholipid --- p.119 / Chapter 3.9.2 --- Fatty Acid Composition in Hepatic Triglyceride --- p.123 / Chapter 4. --- Discussion --- p.126 / Chapter 4.1 --- Nutrients Displacement after Chronic Ethanol Consumption --- p.126 / Chapter 4.2 --- Varied Blood Ethanol Levels after Chronic Ethanol Consumption --- p.127 / Chapter 4.3 --- Increase in CYP2E1 Levels after Chronic Feeding of Ethanolin WT mice --- p.127 / Chapter 4.4 --- Lack of Evidence Indicating the Development of Ethanol- Induced Liver Injury --- p.129 / Chapter 4.4.1 --- No Elevations in Serum ALT and AST Activities --- p.129 / Chapter 4.4.2 --- Normal Liver Histology --- p.130 / Chapter 4.4.3 --- Lack of Triglyceride Accumulation --- p.131 / Chapter 4.4.4 --- Elevations in Hepatic PL --- p.132 / Chapter 4.5 --- Possible Reasons for the Absence of Liver Damage after Chronic Ethanol Consumption in our Mouse Model --- p.134 / Chapter 5. --- Conclusion --- p.137 / Chapter Chapter IV --- Concluding Remarks / Chapter 1. --- A Comparison between Acute CC14 Study and Chronic Ethanol Consumption Study --- p.139 / Chapter 1.1 --- Regulation of CYP2E1 Expression --- p.139 / Chapter 1.2 --- Free Radical Production Involved in CC14- and Chronic Ethanol Consumption-Mediated Liver Injury --- p.140 / Chapter 1.3 --- An Overall Comparison between CC14 study and Chronic Ethanol Consumption Study --- p.140 / Chapter 2. --- Future Studies --- p.142 / Chapter 2.1 --- Acute CC14 Study --- p.142 / Chapter 2.1.1 --- Calcium Homeostasis Studies --- p.142 / Chapter 2.1.2 --- Spin Trapping Studies --- p.142 / Chapter 2.2 --- Chronic Ethanol Study --- p.142 / Chapter 2.2.1 --- "Generation of a Heterozygous ""Ethanol-Sensitive"" Mouse Strain (SV/129/ter x C57BL/6)" --- p.143 / Chapter 3. --- Concluding Remarks --- p.143 / References --- p.144 / Appendix --- p.167

Diabetic pregnancy is associated with increased risk of congenital malformations. Previous studies have shown that maternal diabetes can interact with the vitamin A metabolite, all-trans retinoic acid (RA), in increasing embryonic susceptibility to caudal regression and neural tube defects. The aim of this thesis is to investigate the cellular and molecular mechanisms that underlie this interaction. / First hypothesis. RA concentration in the embryo is tightly regulated by the synthesizing enzyme retinaldehyde dehydrogenase type II (RALDH2), and the degrading enzyme CYP26. Alteration in expression levels of these enzymes under maternal diabetes may affect the availability of RA and thus its teratogenicity. / In conclusion, results of this thesis provide insight into the mechanism of how maternal diabetes interacts with RA in enhancing embryonic susceptibility to congenital malformations. This is also the first report to show that maternal diabetes alters RA homeostasis. (Abstract shortened by UMI.) / Second hypothesis. The transfer of RA to the nucleus for molecular action is regulated by cytoplasmic cellular retinoic acid binding proteins CRABP-I and CRABP-II. Alteration in expression levels of these binding proteins under maternal diabetes may affect the amount of RA reaching the nucleus and thus its teratogenicity. / Third hypothesis. The action of RA is mediated via different nuclear retinoic acid receptors (RAR) and retinoid X receptors (RXR). Alteration in expression levels of these receptors under maternal diabetes may affect the efficacy of RA signal transduction and thus its teratogenicity. / Three hypotheses are proposed to explain the underlying mechanism of increased embryonic susceptibility to RA teratogenicity under maternal diabetes: / To investigate these hypotheses, expression levels of various genes in different groups were compared. Result show that there are no significant differences in mRNA expression levels of CRABP-I, CRABP-II, RARgamma, RARgamma and RXRalpha between embryos of diabetic and non-diabetic mice with or without RA treatment. In contrast, expression levels of Raldh2 and CYP26 are significantly reduced in embryos of diabetic mothers, and in embryos of non-diabetic mice cultured in vitro in hyperglycemic conditions. Moreover, embryos of diabetic mice show significantly reduced response to RA-induced up-regulation of CYP26. These findings suggest that the rate of degradation of RA is slower in embryos of diabetic mice and thus the teratogenic effect of RA is enhanced. / Leung Bo Wah. / "July 2005." / Adviser: Alisa S. W. Shum. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3779. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 158-198). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

A fim de prevenir a rejeição do órgão transplantado pelo hospedeiro, se faz necessário o uso de drogas imunossupressoras, como a ciclosporina, que pode levar ao aparecimento de efeitos colaterais como hipertensão arterial, nefrotoxicidade, hepatotoxicidade, e hiperplasia gengival medicamentosa (HGM), que pode ser potencializada se bloqueadores de canal de cálcio como a nifedipina forem associados a fim de controlar a pressão arterial. A patogênese da HGM ainda é incerta, entretanto fatores como a presença de cálculo e placa, concentração plasmática da droga, idade e fatores hormonais podem influenciar as características clínicas e o desenvolvimento da HGM. Recentemente, alguns vírus têm sido associados com a HGM. O HPV (Papiloma Vírus Humano) tem sido associado com casos severos de HGM, enquanto que o EBV (Vírus Epstein-Barr) é associado ao aparecimento de desordens linfoproliferativas pós transplante, que se apresentam como HGM. O objetivo deste trabalho foi avaliar a freqüência e o grau da HGM em pacientes transplantados renais (TR), identificar o EBV e HPV na HGM destes pacientes, e correlacionar a HGM, índice de placa, presença de cálculo e presença do EBV e HPV nos pacientes TR. Foram examinados os prontuários de 58 pacientes TR atendidos no CAPEFOUSP, e os dados com relação à medicação imunossupressora em uso e presença ou ausência de HGM foram registrados. Foram contatados 15 pacientes TR, dos quais foram colhidos dados demográficos, história médica, drogas em uso e história dental. No exame intra-oral foram observados o índice de placa, grau da HGM e presença de cálculo. A HGM foi removida e enviada a Disciplina de Patologia Bucal para análise microscópica. Os espécimes removidos foram comparados com um grupo controle composto por 20 casos de hiperplasia gengival inflamatória. Ambos os grupos foram submetidos ao exame de rotina, enfatizando a presença de coilócitos e a análise molecular, com hibridização in situ para o EBV (sondas EBER e Lytic) e HPV (sonda de amplo espectro e tipos 6/11, 16/18 e 31/33 nos casos positivos para a sonda de amplo espectro). 42% dos pacientes apresentaram HGM grau 1, 50% grau 2 e 8% grau 3. Cálculo estava presente em 50% dos pacientes. O índice de placa médio encontrado foi de 72%. Todas as amostras gengivais removidas cirurgicamente apresentaram um quadro histopatológico compatível com HGM. Os coilócitos estavam presentes em 100% dos casos do grupo de estudo e em 80% dos casos do grupo controle. O HPV esteve presente em 20% dos casos do grupo de estudo e em 10% do grupo controle. O EBV estava presente em 100% dos casos do grupo de estudo e em 90% dos casos do grupo controle, para ambas as sondas, entretanto no grupo de estudo foi observada uma expressão maior do EBV, tanto em quantidade de células marcadas, como em áreas mais profundas. Concluímos que a maioria dos pacientes TR apresentou HGM leve a moderada; EBV foi encontrado em todos os pacientes TR, caracterizando uma infecção oportunista, enquanto que o HPV foi encontrado nas mesmas proporções nos pacientes TR e no grupo controle; não foi encontrada correlação entre índice da HGM, índoce de placa, presença de cálculo e presença do EBV e HPV. / In order to prevent graft rejection in organ transplantation, is necessary the use of immunosuppressive drugs, as cyclosporin, that has several side effects, such as high blood pressure, nephrotoxicity, hepatotoxicity and gingival overgrowth (GO), that can be increased if calcium channel blockers, such as nifedipine, are associated in order to control de blood pressure. The pathogenesis of GO is still uncertain, but some factors such as the presence of calculus and plaque, drug plasmatic concentration, age and hormonal factors can influence the clinical aspects and development of GO. Recently some virus have been associated to GO as well. HPV (Human Papilloma Virus) have been associated to severe cases of GO and EBV (Epstein-Barr Virus) have been associated to posttransplantation lymphoproliferative disorders presenting as GO. The aim of this work was to evaluate GO incidence and score in renal transplant patients (RTP), identify EBV and HPV in GO from RTP, and correlate GO, plaque score, presence of calculus, and presence of EBV and HPV in RTP. We reviewed 58 charts from RTP attending to Special Care Dentistry Center (CAPE-FOUSP). Immunosuppressant drugs and presence or absence of GO were registered. 15 RTP were asked to show up in order to be examined. We collected demographic data, medical history, drugs in use and dental history. In intra-oral exam we observed plaque score, GO score and presence of calculus. GO were removed and sent to Oral Pathology Department for microscopic analysis. GO was compared to a control group composed by 20 cases of inflammatory gingival hyperplasia and both groups were submitted to routine exam emphasizing the presence of koilocytes and to molecular analysis with in situ hybridization for EBV (EBER and Lytic probes) and for HPV (wide spectrum probe and 6/11, 16/18, 31/33 types in cases where wide spectrum were positive). 42% of the patients presented GO score 1, 50% score 2 and 8% score 3. Calculus were presented in 50% of the patients. The average of plaque score was 72%.All GO specimens removed had a histopathological exam compatible with drug induced gingival overgrowth. Koilocytes were presented in 100% of study group (SG) and in 80% of control group (CG). HPV were presented in 20% of the SG and in 10% of the CG. EBV was presented in 100% of SG and in 90% of CG, for both probes, but in SG it could be observed in deeper areas of the epithelium and in a more pronounced expression. We concluded that most RTP presented mild to moderate GO, EBV were found in all RTP, characterizing an opportunistic infection, while HPV were found in the same proportions than in the control group and there were no statistical correlation between GO, plaque score, presence of calculus and presence of EBV and HPV.

This purpose of this study was to explore social workers’ perspectives of drug-induced psychosis. More specifically, it sought to determine how knowledgeable clinical social workers are on the impact illicit drug use on the development of psychotic disorders. The study also aimed to discover clinical social workers’ perspectives regarding the influence of illicit drug use on the development of psychotic illnesses. This study used mixed methods approach in attempt to solve the research question. The quantitative portion of the research, an anonymous survey, allowed for the assessment of social workers’ knowledge of drug-induced psychosis. The qualitative portion of the research, individual interviews and a focus group, allowed for a comparison of social workers’ experiences from having encountered drug-induced psychosis in clinical practice. The qualitative findings produced insight that highlighted common themes that can be explored further in future research within the context of clinical social work practice.

Hydroxyurea is a teratogen; treatment of dams during organogenesis causes various malformations. Administration of a free radical scavenger ameliorates the embryotoxicity of hydroxyurea, suggesting that oxidative stress mediates this toxicity. The goal of this thesis was to test the hypothesis that superoxide, a reactive oxygen species, is involved. Superoxide dismutase 1 (SOD1) is an antioxidant enzyme that converts superoxide to hydrogen peroxide. To elucidate the role of superoxide in mediating hydroxyurea teratogenicity, dams that were wildtype or hemizygous for hSOD1 were treated on gestation day 9 with saline (control) or hydroxyurea (400 or 600 mg/kg). Fetal death rate and weight were affected similarly by hydroxyurea treatment in litters from wildtype and hemizygous dams. However, fetuses from hemizygote dams exposed to 600 mg/kg hydroxyurea had fewer specific external and skeletal malformations when compared to wildtype dams. These data suggest that superoxide dismutase 1 protects fetuses against specific consequences of oxidative insult during organogenesis.

5-Bromo-2'-deoxyuridine (BrdU), a thymidine analogue, is genotoxic and teratogenic. The exposure of mouse embryos to BrdU at doses that cause malformations induces oxidative stress and an embryonic stress response characterized by an increase in c-Fos dependent AP-1 DNA binding. The goal of this thesis was to test the hypothesis that development is disturbed at sites where BrdU is incorporated into DNA, triggering oxidative stress and c-Fos induction. Gestation day 9 CD-1 mice were treated with BrdU and embryos were obtained for immunolocalization of BrdU, 8-oxoguanine, a biomarker for oxidative stress, and c-Fos. BrdU incorporation into DNA was dispersed throughout the embryo. In contrast, the staining for 8-oxoguanine and c-Fos were highest in the neuroepithelium. BrdU incorporation was not affected by the pre-administration of N-acetyl-cysteine (NAC), an anti-oxidant, although both 8-oxoguanine and c-Fos staining were decreased. Thus, the response of the embryo to insult is tissue specific.

Un lien entre certaines dysfonctions du système sérotoninergique et la survenue de valvulopathies a été suggéré par les lésions valvulaires observées au cours de l’utilisation chronique de certains agonistes des récepteurs 5-HT2 (dérivés de l’ergot de seigle, fenfluramine) et les atteintes tumorales carcinoïdes (qui entrainent une augmentation des taux de 5-HT circulante). Les lésions dégénératives associent une fibrose, une sténose et/ou une régurgitation des valves pouvant conduire à de nombreuses complications cardiovasculaires. À l’heure actuelle, il n’existe aucune thérapeutique pouvant freiner ou faire régresser les lésions. Nos travaux démontrent à partir de modèles animaux et cellulaires, l’implication effective des récepteurs 5-HT2B et 5-HT2A dans l’initiation des lésions. L’analyse histologique des valves à partir de nos modèles animaux a révélé la contribution des cellules endothéliales au cours des stades précoces. Ces cellules sont des progéniteurs endothéliaux (CD34+) recrutés à partir de la moelle au sein de la valve sous la stimulation des récepteurs 5-HT2 et par un mécanisme intracellulaire impliquant la eNOS. Des travaux ultérieurs permettront de mieux caractériser les différents types cellulaires et les biomarqueurs d’initiation du processus afin de déterminer de nouvelles pistes thérapeutiques. / Several studies have reported a strong correlation between the development of cardiac valve injury and some dysfunctions of the serotonergic system. Valve lesions are observed during the chronic use of some 5-HT2 receptors agonists (ergot derivates or fenfluramine derivatives) or are secondary to metastatic carcinoid tumours (with increased circulating 5-HT amount). These lesions show fibrosis, with thickened leaflets, valves stenosis and/or regurgitation followed by several cardiovascular complications. There is no medical treatment to stop or alter the natural course of the lesions. Surgical replacement by prosthesis is the only effective therapy. Our study based on animal and cellular pharmacological models, demonstrates the serotonergic system contribution through 5-HT2B and 5-HT2A receptors in the pathogenesis of valve degeneration. Histological analysis of the lesions reveals the contribution of endothelial cells to the initiation process. These cells are probably endothelial progenitors (CD34+) recruited inside the valve implying a NO-dependent mechanism. Further studies will characterize the specific cells to find biomarkers of valve remodelling initiation and at term, will identify best therapeutic targets around the serotonergic system.

La cholestase intrahépatique représente environ 40% des lésions hépatiques induites par les médicaments et se caractérise par une accumulation intracellulaire des acides biliaires (AB). Les mécanismes impliqués sont encore mal connus et sa prédiction reste difficile. Le but de ce travail était de caractériser dans la cholestase d’origine médicamenteuse et de développer des méthodes de screening pour sa prédiction précoce, en utilisant la lignée humaine hépatique HepaRG et les hépatocytes humains. Tout d’abord, nous avons démontré que la motilité des canalicules biliaires (CB) est indispensable à la clairance des AB et requiert une alternance de phosphorylation/déphosphorylation de la chaine légère de la myosine (MLC), contrôlé par la voie Rho-kinase/Myosin Light Chain Kinase (ROCK/MLCK). Nous avons ensuite montré pour la première fois que les médicaments cholestatiques altèrent la voie ROCK/MLCK/MLC et la dynamique des CB. En utilisant la famille des antibiotiques résistant à la pénicillinase, dont fait partie la flucloxacilline, responsable de nombreux cas de cholestase, nous avons observé que la dérégulation de ROCK pouvait se faire par activation de HSP27, associée aux voies de signalisation PKC/P38 et PI3K/AKT. Enfin, nous avons montré une capacité variable des médicaments cholestatiques à moduler les profils des AB. En effet, les médicaments cholestatiques majeurs induisent une accumulation préférentielle des AB hydrophobes toxiques, in vitro, dans les premières 24h, qui résulte d’une inhibition de leur amidation. Au total, l’ensemble du travail a permis de progresser dans la compréhension des mécanismes impliqués dans la cholestase d’origine médicamenteuse et de mettre en évidence de nouveaux biomarqueurs utiles pour sa prédiction. / Intrahepatic cholestasis represents around 40% of drug-induced liver injuries and is characterized by intracellular accumulation of bile acids (BA); mechanisms involved and its accurate prediction remains challenging. The aim of the current work was to characterize the mechanisms involved in drug-induced cholestasis and to develop screening methods for its early prediction, using human differentiated HepaRG and primary human hepatocytes. First, we demonstrated that bile canaliculi (BC) motility is essential for BA clearance and requires alternating phosphorylation/dephosphorylation of myosin light chain (MLC) that is controlled by the Rho-kinase/Myosin Light Chain Kinase (ROCK/MLCK) signaling pathway. Then, we showed, for the first time that cholestatic drugs could alter the ROCK/MLCK/MLC pathway and BC dynamics. Using the penicillinase-resistant antibiotics family, including flucloxacillin that is responsible for many cases of cholestasis, we found that deregulation of ROCK could be modulated by HSP27, associated with PKC/P38 and PI3K/AKT signaling pathways. Finally, we evidenced variable potency of cholestatic drugs to modulate BA profiles. Indeed, the well-known cholestatic drugs induced a preferential accumulation of unconjugated toxic hydrophobic BA in vitro within the first 24h that resulted from inhibition of their amidation. Altogether, these data bring new information on the understanding of the mechanisms involved in drug-induced cholestasis and highlight new morphological and molecular predictive biomarkers of drug-induced cholestasis.

La cholestase est l'une des manifestations les plus courantes des lésions induitespar des médicaments. Dans 40% des cas elle n’est pas prévisible; une meilleure prédictibilité représente donc un défi majeur. Tout d'abord, nous avons démontré que les cellules hépatiques humaines HepaRG différenciées sont un modèle approprié pour étudier la cholestase induite par les médicaments en comparant la localisation et l’activité des transporteurs d'influx et d'efflux avec les hépatocytes humains primaires. Tous les transporteurs d'efflux et d’influx testés ont été correctement localisés au niveau des membranes canaliculaire (BSEP, MRP2, MDR1 et MDR3) et basolatéral (NTCP, MRP3) et sont fonctionnels. En outre, ces cellules expriment également les enzymes qui métabolisent les acides biliaires (ABs) et ont la capacité de les synthétiser et de les conjuguer avec la taurine, la glycine et le sulfate, à un taux similaire à celui des hépatocytes primaires. Des changements ont été observés sur la répartition des ABs totaux après traitements de cellules HepaRG par un médicament cholestatique, la cyclosporine A (CsA), de manière concentration- dépendante. L'inhibition de l'efflux et de l'influx de taurocholate a été observée après 15 min et 1 h respectivement. Ces premiers effets ont été associés à la dérégulation de la voie des cPKC et l'induction d’un stress du réticulum endoplasmique puis d’un stress oxydant. Nous avons également montré pour la première fois une accumulation intracellulaire d’ABs endogènes avec un médicament cholestatique in vitro. En outre, notre travail apporte des preuves que la motilité des canalicules biliaires (BC) est indispensable à la clairance des ABs. La voie ROCK et le complexe actomyosine sont fortement impliqués. Nous avons fourni la première démonstration que la voie ROCK et les dynamiques des BC sont des cibles majeures des composés cholestatiques. Nos données devraient contribuer à l'élaboration de méthodes de screening pour la prédiction précoce des effets secondaires induits par les médicaments cholestatiques. / Cholestasis is one of the most common manifestations of drug-induced liver injury (DILI). Since up to now it is unpredictable in 40% of all cases its accurate prediction represents a major challenge. First, we validated that differentiated HepaRG human liver cells are a suitable in vitro model to study drug-induced cholestasis, by comparing localization of influx and efflux transporters and their functional activity in these cells and primary human hepatocytes. All tested influx and efflux transporters were correctly localized to canalicular (BSEP, MRP2, MDR1, and MDR3) or basolateral (NTCP, MRP3) membrane domains and were functional. In addition, the HepaRG cell line also exhibits bile acids (BAs) metabolizing enzymes and has the capacity to synthesize BAs and to further amidate these BAs with taurine and glycine as well as sulfate, at a rate similar to that of primary hepatocytes. Concentration- dependent changes were observed in total BAs disposition after treatment of HepaRG cells by the cholestatic drug cyclosporine A (CsA). Inhibition of efflux and uptake of taurocholate was evidenced as early as 15 min and 1 h respectively. These early effects were associated with deregulation of cPKC pathway and induction of endoplasmic reticulum stress that preceded generation of oxidative stress. We also showed for the first time intracellular accumulation of endogenous BAs by a cholestatic drug in vitro. In addition, our work brings evidences that motility of bile canaliculi (BC) is essential for BAs clearance where ROCK pathway and actomyosin complex are highly implicated. We provided the first demonstration that ROCK pathway and BC dynamics are major targets of cholestatic compounds. Our data should help in the development of screening methods for early prediction of drug-induced cholestatic side effects.

Il est estimé aujourd’hui que plus de 350 médicaments peuvent induire des lésions hépatiques entraînant différentes manifestations cliniques telles qu’une hépatite cytolytique, une stéatose voire une cirrhose. Bon nombre de médicaments hépatotoxiques induisent un dysfonctionnement mitochondrial. Cependant, les mécanismes induisant de tels effets délétères ne sont pas tous élucidés, en particulier ceux concernant l’ADN mitochondrial (ADNmt) et son homéostasie, qui ne sont pas souvent explorés. De plus, il existe peu d’informations concernant l’hépatotoxicité médicamenteuse dans un contexte de stéatose induite par l’obésité. Ainsi, l’objectif de ce travail a été tout d’abord de mettre au point un modèle de stéatose dans les cellules de la lignée hépatocytaire humaine HepaRG afin d’étudier ensuite, les effets de neuf médicaments hépatotoxiques et vraisemblablement mitochondriotoxiques – l’amiodarone, l’atorvastatine, la carbamazépine, l’imipramine, la lovastatine, la perhexiline, le ritonavir, la terbinafine et la troglitazone – sur l’homéostasie de l’ADNmt dans un contexte ou non de stéatose. En utilisant des concentrations peu ou non cytotoxiques, nous avons trouvé que parmi les neuf médicaments étudiés, le ritonavir et l’imipramine ont induit des effets mitochondriaux suggérant une altération de la traduction mitochondriale. De façon notable, la toxicité du ritonavir était plus importante dans les cellules non-stéatosées. De plus, aucun des neuf médicaments n’a induit de diminution des quantités d’ADNmt. Cependant, les quantités accrues d’ADNmt ont été retrouvées avec six des neuf médicaments, et notamment dans les cellules non-stéatosées. Cela était par ailleurs accompagné d’une modulation de l’expression des différents facteurs impliqués dans la biogenèse mitochondriale (PGC-1α, PGC-1β, AMPK, etc.). Ainsi, ces données laissent supposer qu’une altération de la traduction mitochondriale peut ne pas être une événement rare et que l’augmentation des quantités d’ADNmt et la modulation de la biogenèse mitochondriale pourraient être une réponse adaptative fréquente à des altérations mitochondriales pouvant être amoindrie par la stéatose. / It is currently estimated that more than 350 drugs can induce liver injury with different clinical presentations such as hepatic cytolysis, steatosis, even cirrhosis. Many hepatotoxic drugs can induce mitochondrial damage and dysfunction. However, not all mechanisms that lead to such deleterious effects are clarified, especially those concerning mitochondrial DNA (mtDNA) and its homeostasis, which are not often investigated. Moreover, there is little information regarding the impact of non alcoholic fatty liver disease (NAFLD) on drug-induced liver injury. Thus, the aim of this work was, first of all, to develop a model of NAFLD in the hepatic cell line HepaRG in order to study further effects of nine hepatotoxic and presumably mitochondriotoxic drugs – amiodarone, atorvastatin, carbamazepine, imipramine, lovastatin, perhexiline, ritonavir, terbinafine and troglitazone –, on mtDNA homeostasis in the context of NAFLD or not. By using drug concentrations that did not induce major cytotoxicity, we found that, among the nine drugs, studied, ritonavir and imipramine induced mitochondrial effects suggesting alteration of mtDNA translation. Notably, ritonavir toxicity was stronger in non-steatotic cells. Furthermore, none of the nine drugs decreased mtDNA levels. However, increased mtDNA was observed with six drugs, especially in non-steatotic cells. This result was also accompanied by a modulation of the expression of various factors involved in mitochondrial biogenesis (e.g. PGC-1α, PGC-1β, AMPK).Therefore, this data suggests that drug-induced impairment of mtDNA translation may not be a rare event and increased mtDNA levels and modulation of mitochondrial biogenesis could be a frequent adaptive response to mitochondrial impairments, which could be dampened by steatosis.