Acute Liver Failure (ALF) is a devastating ailment with a high mortality rate and limited treatment alternatives. This study presents a methodology for the design and development of a bio-artificial bioreactor to be used in a Bio-Artificial Liver Support System. The system will ultimately be used either to bridge a patient to orthotopic liver transplant (OLT), the only current cure for end stage ALF, or spontaneous recovery. Methods to optimize and visualize the flow and related mass transfer in the BR are presented. The use of magnetic resonance imaging (MRI), scanning electron microscopy (SEM) and simple testing methodology is applied with emphasis on modeling the flow conditions in the BR. The bioreactor (BR) used in the Bio-Artificial Liver Support System (BALSS), currently under-going animal trials at the University of Pretoria, was modeled and simulated for the flow conditions in the device. Two different perfusion steps were modeled including the seeding of hepatocyte cells and later the clinical perfusion step. It was found that the BR geometry was not optimal with “dead spots” and regions of retarded flow. This would restrict the effective transport of nutrients and oxygen to the cells. The different perfusion rates for the seeding and clinical perfusion steps allowed for different velocity contours with cells seeing inconsistent flow patterns and mass transfer gradients. An optimized BR design is suggested and simulated, that effectively reduces the areas of retarded flow (dead spots) and increases the flow speed uniformly through the BR to an order of magnitude similar to that found in the sinusoidal range. The scaffolding volume was also decreased to allow a larger local cell density promoting cell-cell interaction. Finally a summarized design table for the design of a hepatic BR is presented. / Dissertation (MEng (Mechanical))--University of Pretoria, 2008. / Mechanical and Aeronautical Engineering / unrestricted

In this thesis I examined molecular mechanisms involved in acute and chronic liver injury, and also studied basic pathways mediating tumour promotion. Acute hepatic failure secondary to paracetamol poisoning is associated with high mortality. C-jun (NH2) terminal kinase (JNK) is a member of the mitogen activated protein kinase family and is a key intracellular signaling molecule involved in the control of cell fate. Paracetamol induced hepatic JNK activation in both human and murine paracetamol hepatotoxicity, and in a murine model preceded the onset of hepatocyte death. JNK inhibition in vivo (using two JNK inhibitors with different mechanisms of action) markedly reduced mortality in murine paracetamol hepatotoxicity. In addition, delayed administration of JNK inhibitor was more effective than N-acetylcysteine following paracetamol poisoning in mice. JNK inhibition was not protective in acute carbon tetrachloride or anti-Fas antibody mediated hepatic injury, suggesting specificity for the role of JNK in paracetamol hepatotoxicity. Furthermore, disruption of the JNK1 or JNK2 genes did not protect against paracetamol-induced hepatic damage. Pharmacological JNK inhibition had no effect on paracetamol metabolism, but markedly inhibited hepatic TNF-alpha production following paracetamol poisoning. These data demonstrate a central role for JNK in the pathogenesis of paracetamol induced liver failure, thereby identifying JNK as an important therapeutic target in the treatment of paracetamol hepatotoxicity. Liver fibrosis with loss of tissue architecture and subsequent hepatic failure represents a massive healthcare burden worldwide. Expression of Galectin-3 (a beta-galactoside binding animal lectin) is upregulated in established human fibrotic liver disease, during the development of experimental liver fibrosis and is temporally and spatially related to the induction and resolution of experimental hepatic fibrosis. Disruption of the gene encoding Galectin-3 blocks transdifferentiation of precursors to myofibroblasts in vitro and in vivo, markedly attenuating hepatic scarring in a murine model of liver fibrosis. Inhibition of Galectin-3 expression by siRNA in primary murine and human hepatic stellate cells significantly reduced myofibroblast activation and procollagen(I) expression. The reduction in hepatic fibrosis observed in the Galectin-3-/- mouse occurred despite equivalent liver injury and inflammation, and similar tissue expression of TGF-beta. TGF-beta failed to transactivate Galectin-3-/- hepatic stellate cells, in contrast with wild type hepatic stellate cells. However TGF-beta stimulated signaling via Smad-2 and 3 was equivalent in both Galectin-3-/- and wild type hepatic stellate cells indicating that Galectin-3 is required for TGF-beta mediated myofibroblast activation and matrix production. This supports a novel and important mechanistic role for Galectin-3 in the regulation of myofibroblast activation and consequent liver fibrosis. Finally, in vivo siRNA knockdown of Galectin-3 inhibited myofibroblast activation following hepatic injury and may therefore provide a novel therapeutic approach to the prevention and treatment of liver fibrosis. CD98hc (a ligand for Galectin-3) constitutively and specifically associates with beta1 integrins and is highly expressed on the surface of human tumour cells irrespective of the tissue of origin. CD98hc promotes both anchorage- and serum-independent growth. Using chimeras of CD98hc and the type II membrane protein CD69 demonstrated that the transmembrane domain of CD98hc is necessary and sufficient for integrin association in cells. Furthermore, CD98hc/β1 integrin association is required for focal adhesion kinase-dependent phosphoinositol 3-hydroxykinase activation and cellular transformation. Amino acids 82-87 in the putative cytoplasmic/transmembrane region appear to be critical for the oncogenic potential of CD98hc and provide a novel mechanism for tumour promotion by integrins.

Infections in patients with acute liver failure (ALF) and acute liver injury (ALI) are a frequent occurrence. Because ALF and ALI patients share many of the same clinical features as patients with severe sepsis and septic shock, identifying an infection based upon clinical manifestations is extremely difficult. Bacterial culture and sensitivity reports require 24 to 72 hours to be finalized after the need for a culture is suspected and obtained. During this time period, ALF and ALI patients are either not receiving required antibiotic therapy, receiving antibiotic therapy that is not required or not appropriate for the infecting bacterial pathogen, or receiving the correct antibiotic prophylaxis. Receiving an antibiotic that is not needed or inappropriate adds another level of complexity to the ALF and ALI patients because antibiotics may exacerbate liver dysfunction. The purpose of this study was to determine the utility of serum procalcitonin concentrations (SPCTC) as a biomarker of bacterial infections in patients with acute liver failure (ALF) and acute liver injury (ALI). This three part study measured SPCTC retrospectively on samples from ALF and ALI patients who were prospectively enrolled in the United States Acute Liver Failure Study Group (USALFSG) ALF and ALI studies. In the first part of the study, subjects were categorized according to how many SIRS continuum components they had and whether there was a documented infection. In the second part, serial samples on subjects who developed infections were identified. And, in the third part, serial samples on subjects diagnosed with infection on day one of the study and categorized based upon transplant free survival (TFS) or death and/or liver transplant (DoT) were identified. Procalcitonin was not found to be useful in identifying infection in the ALF and ALI patient populations. A cut-off for indication of infection was calculated to be 1.62 ng/mL using receiver operator curve (ROC) analysis. Despite the fact that there was an overall increase in SPCTC as the severity of illness increased in patients with a documented infection, there were confounding variables including antibiotic use, missing data, and small sample size that may have contributed to the poor sensitivity and specificity (0.643 and 0.620 respectively) calculated as part of the ROC analysis. SPCTC values appeared to be increased in subject with acetaminophen (APAP) toxicity and may have affected the cut-off, sensitivity, and specificity results. Increased SPCTC values were seen in APAP subjects who did not have a documented infection. It is unknown at this time if the SPCTC were increase due to liver damage, an undiagnosed infection, or as a result of increase cytokine production due to the APAP toxicity. Serial PCT concentrations in patients who achieved TFS showed a greater decrease over time than those of patients who died or received a liver transplant, however, the TFS group contained a large portion of APAP subjects. Further prospective studies are needed to determine the extent of interference with SPCTC in patients with APAP toxicity and to better define the PCT concentration cut-off between infection and no infection in the ALF and ALI populations.

Hepatite é uma condição inflamatória do fígado que pode ser autolimitada ou pode progredir para um quadro de fibrose, cirrose ou câncer. Uma das consequências mais graves associada ao dano hepático é a insuficiência hepática aguda (também conhecida como insuficiência hepática fulminante), cujas etiologias mais comuns são as infecções virais, a autoimunidade e o uso de medicamentos. Conhecendo as atividades biológicas das moléculas presentes na saliva dos insetos hematófagos, e com base em resultados anteriores do nosso grupo de pesquisa, acreditamos que os componentes salivares do mosquito Aedes aegypti possam ser empregados na prevenção e/ou tratamento de doenças inflamatórias. Assim, para avaliar o potencial terapêutico da saliva de A. aegypti em quadros de insuficiência hepática aguda, empregamos um modelo experimental amplamente utilizado para o estudo da hepatite autoimune, a hepatite experimental aguda induzida por concanavalina A (Con A) e um modelo de hepatotoxicidade induzida por acetaminofeno (APAP), comumente empregado para o estudo da lesão hepática induzida por fármaco. Nossos resultados demonstram que a exposição de animais às picadas de mosquitos A. aegypti reduz os níveis das enzimas alanino aminotransferase (ALT) em ambos os modelos e de aspartato aminotransferase (AST) no modelo de hepatite induzida por Con A. Além disso, o tratamento com a saliva foi capaz de reduzir os níveis de citocinas séricas IFN-&gamma, IL-6 e IL-2, bem como a expressão de IFN-&gamma no fígado no modelo de hepatite experimental aguda induzida por Con A e as citocinas séricas TNF-, IL-6, IL1 e IL-10 no modelo de hepatite tóxica induzida por APAP. Os animais injetados com Con A apresentaram um aumento das frequências de populações de células NK e macrófagos e a exposição às picadas reduziu essas alterações para níveis próximos aos do grupo controle. Da mesma maneira, a exposição aos mosquitos também reduziu as populações de células dendríticas, macrófagos e células NKT, que se apresentaram aumentadas no grupo de animais injetados com APAP. Tais dados demonstram que a saliva de A. aegypti é capaz de proteger os animais dos efeitos deletérios das hepatites avaliadas, devido à sua capacidade de modular a resposta inflamatória nos animais experimentais. Estudos futuros poderão caracterizar as moléculas responsáveis por essa atividade biológica, destacando seu potencial uso como opção para prevenção e/ou tratamento destas condições. / Hepatitis is an inflammatory condition of the liver that can be self-limiting or progress to fibrosis, cirrhosis or cancer. One of the most severe consequences associated with the hepatic damage is the acute liver failure (also known as fulminant hepatic failure). being viral infections, autoimmunity and use of medications the most common etiologies. Knowing the biological activities of the compounds present in the saliva of hematophagous insects, and based on previous results from our group, we believe that the salivary components of Aedes aegypti mosquitoes can be employed in the prevention and/or treatment of inflammatory diseases. Thus, to evaluate the therapeutic potential of A. aegypti mosquito saliva in acute liver failure, we employed a well-established model for the study of autoimmune hepatitis, acute experimental hepatitis induced by concanavalin A (Con A), and a model of hepatotoxicity induced by acetaminophen (APAP) commonly employed to study drug-induced liver injury. Our results demonstrate that the exposure of animals to A. aegypti mosquito bites reduces alanine aminotransferase (ALT) enzyme levels in both models and aspartate aminotransferase (AST) in the acute experimental hepatitis induced by Con A. In addition, the treatment with saliva was able to reduce the levels of the serum cytokines IFN-&gamma, IL-6 and IL-2, as well as the expression of hepatic IFN-&gamma in the in the model of acute experimental hepatitis induced by ConA as well as the serum cytokines TNF-, IL-6, IL-1, and IL-10 in the APAP-induced toxic hepatitis model. Animals injected with Con A presented an increase in the frequencies of NK cells and macrophages populations, and the exposure to the bites reduced this changes to levels close to that found in the control group. Likewise, mosquito exposure also reduced the populations of dendritic cells, macrophages and NKT cells that were increased in the group of animals injected with APAP. These data demonstrate that A. aegypti saliva is able to protect animals from the deleterious effects of the evaluated hepatitis, due to its ability to modulate the inflammatory response of the experimental animals. Future studies might characterize the molecules responsible for this biological activity, highlighting their potential use as an option for prevention and/or treatment of these conditions.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2013-11-06T17:30:24Z No. of bitstreams: 1 Felipe Miranda Santos Potencial terapeutico das S-nitroglutationa-.pdf: 5390094 bytes, checksum: 048e66640081905e53e87d3353d7c25c (MD5) / Made available in DSpace on 2013-11-06T17:30:24Z (GMT). No. of bitstreams: 1 Felipe Miranda Santos Potencial terapeutico das S-nitroglutationa-.pdf: 5390094 bytes, checksum: 048e66640081905e53e87d3353d7c25c (MD5) Previous issue date: 2012 / Fundação Oswaldo Cruz. Centro de Pesquisa Gonçalo Moniz. Salvador, BA, Brasil / Universidade Federal da Bahia. Faculdade de Farmácia. Salvador, BA, Brasil / A intoxicação pelo paracetamol é a principal causa de insuficiência hepática aguda (IHA) em vários países do ocidente. A hepatotoxicidade é mediada por um metabólito intermediário reativo que depleta as reservas do antioxidante endógeno glutationa (GSH). O tratamento precoce com n-acetilcisteína (NAC) é recomendado para restabelecer a concentração fisiológica de GSH. A snitrosoglutationa (GSNO) é uma molécula antioxidante derivada do GSH capaz de reduzir o estresse oxidativo em diversos sistemas celulares e modelos experimentais. OBJETIVO: Avaliar se GSNO é capaz de reduzir a taxa de mortalidade, extensão da necrose hepática, manifestações bioquímicas e comparar sua eficácia com NAC e GSH no tratamento da IHA experimental induzida por paracetamol. METODOLOGIA: Camundongos isogênicos machos da linhagem C57Bl/6 foram tratados por três semanas com água suplementada com etanol a 10%. Os animais foram divididos em cinco grupos. O grupo 1 (controle negativo) recebeu solução salina 0,9%. Os demais grupos receberam 300 mg/Kg de paracetamol para indução de IHA. Após 3 horas, o grupo 2 (controle positivo) foi tratado com salina tamponada com fosfato (PBS) e os grupos 3, 4 e 5 foram tratados, respectivamente, com 600 Umol/kg de NAC, GSH e GSNO. A eutanásia foi feita 12 horas após a indução de IHA. A extensão da necrose hepática foi avaliada por morfometria através do software IMAGEPRO-PLUS. Os níveis séricos de transaminases e fosfatase alcalina foram avaliados como marcadores bioquímicos de lesão hepática. A taxa de mortalidade foi avaliada em um experimento independente, após uma dose de 350 mg/Kg de paracetamol. RESULTADOS: O tratamento com GSNO 600 Umol/kg aumentou a taxa de sobrevida em relação aos grupos tratados com NAC ou PBS. Entretanto, não houve diferença de mortalidade entre os grupos GSNO e GSH. A avaliação morfométrica revelou menor extensão de necrose hepática nos animais tratados com GSNO em comparação com NAC e PBS. Houve redução de atividade sérica de ALT, mas não de AST no grupo GSNO em comparação com PBS e NAC. Os níveis séricos de fosfatase alcalina, albumina, ureia e creatinina não apresentaram diferenças entre os diversos grupos. CONCLUSÃO: O tratamento com GSNO aumenta a taxa de sobrevida e reduz a extensão de necrose hepática na IHA experimental por paracetamol. O GSNO apresenta eficácia superior à NAC e idêntica ao GSH em dose equimolar. Estes achados sugerem que o efeito protetor do GSNO parece independer da porção nitroso da molécula. Possíveis mecanismos de proteção extra-hepáticos merecem ser investigados / Paracetamol overdose is the main cause of acute liver failure (ALF) in western countries. The hepatotoxicity is mediated by a reactive metabolite that depletes the pool of glutathione (GSH), an endogenous antioxidant molecule. Early treatment with n-acetylcysteine (NAC) is recommended to replenish the pool of GSH. S-nitrosoglutathione (GSNO) is a potent antioxidant molecule that reduces oxidative stress in several cellular systems and experimental models. OBJECTIVE: To evaluate if GSNO reduces the mortality rate, the hepatocelular necrosis extension and to compare its therapeutic efficacy with NAC and GSH in experimental ALF induced by paracetamol. METHODS: Male mice were treated for three weeks with alcohol 10% orally. The animals were divided in five groups. Group 1 (negative control) received saline 0.9%. All the other groups received 300 mg/Kg paracetamol for induction of ALF. After 3 hours, group 2 (positive control) received phosphate buffered saline (PBS) and groups 3, 4 and 5 were treated respectively with 600 Umol/kg of NAC, GSH and GSNO. The animals were sacrificed after 12 hours of induction of ALF. The area of liver necrosis was evaluated by morphometric analysis with the software IMAGEPRO. Transaminases and alkaline phosfatase were determined as markers of liver injury. Mortality rate was evaluated in an independent experiment after a dose of 350 mg/Kg of paracetamol. RESULTS: GSNO treatment (600 Umol/kg) significantly improved the survival rate compared to PBS and NAC treatments. There was no statistical difference in survival rate between GSNO and GSH groups. In addition, GSNO attenuated the area of liver necrosis in comparison to NAC and PBS, but not to GSH. GSNO reduced the serum ALT, but not AST activity in comparison to PBS and NAC. There was no statistical difference in alkaline phosphatase, urea, creatinine and albumin among the groups that received paracetamol. CONCLUSION: GSNO treatment augmented survival rate and reduced the area of liver necrosis in comparison to NAC, but was equally as effective as GSH. These findings suggest that the hepatoprotector effect of GSNO is independent of the nitroso moiety of the molecule. Potential extra-hepatic mechanisms remain to be evaluated.

Introduction The development of an appropriate animal model of ALF is paramount for the understanding of the disease pathogenesis and evaluation of potential therapeutic approaches. Acute liver failure (ALF) is a severe, usually rapidly progressive disease characterized by high mortality (60 - 90 %). Besides acute liver transplantation which faces a shortage of donors, the only possible therapeutic alternative is applying biological or non-biological liver support systems. To confirm the effectiveness of these methods, clinically relevant model of ALF on a large laboratory animal is essential. Surgically induced ALF models seem to be more reliable than models based on chemical intoxication. Ideal model of ALF has not yet been published. Surgical models are usually performed with devascularisation, large liver resection or hepatectomy. The aim of this work was to introduce three surgical models of ALF and evaluate their usefulness for testing biological and non-biological liver support systems. Materials and Methods Female laboratory pig weighing 35 - 45 kg was used for the experimental study. After induction of general anesthesia the thermodilution catheter was introduced via jugular vein. Femoral artery and vein were cannulated for invasive blood pressure monitoring and for infusions and...

What is known and objective: Amiodarone, a commonly used class III antiarrhythmic agent notable for a relatively long half-life of up to 6 months and its pronounced adverse effect profile, is used for both acute and chronic management of cardiac arrhythmias. Chronic use of amiodarone has been associated with asymptomatic hepatotoxicity; however, acute toxicity is thought to be uncommon. There are only six reported cases of acute liver failure (ALF) secondary to amiodarone. In all these cases the outcome of death during the same hospitalization resulted. We aimed to report the only case of acute liver failure secondary to amiodarone infusion in the existing literature where the patient survived. Case summary: A 79-year-old woman admitted with atrial flutter was being treated with intravenous (IV) amiodarone when she abruptly developed coagulopathy, altered mental status and liver enzyme derangement. She was diagnosed with acute liver failure (ALF) secondary to an amiodarone adverse drug reaction, with a calculated score of seven on the Naranjo adverse drug reaction probability scale. Amiodarone was immediately withheld, and N-acetylcysteine (NAC) was initiated. Clinical improvement was seen within 48 hours of holding the drug and within 24 hours of initiating NAC. On post-hospital follow-up visit she was reported to have complete recovery. What is new and conclusion: This report emphasizes the importance of monitoring liver enzymes and mental status while a patient is being administered IV amiodarone. N-acetylcysteine administration may have possibly contributed to the early and successful recovery from ALF in our patient. To date, she is the only patient in the existing literature who has been reported to survive ALF secondary to amiodarone administration.

Quinolones are a group of antibiotics that have gained significant popularity on a global scale since the end of the last century. This popularity was predominantly based on their proven potency, broad coverage against a wide range of bacteria, in addition to possessing a favorable pharmacologic profile. Whereas quinolone-associated adverse reactions are generally tolerable and self-limiting, some reactions have generated heightened concerns due to their serious nature, which have resulted in label changes or even market withdrawal in some instances. This thesis investigates the association between quinolone antibiotics and two adverse reactions of an acute and serious nature: acute liver failure and retinal detachment. Each adverse reaction is investigated through integrating evidence from three studies utilizing different designs based on data from different sources, with each source offering a unique perspective on this issue. The first study type (chapter 2 for acute liver failure ‘ALF’ and Chapter 5 for retinal detachment ‘RD’) analyzes spontaneous reports submitted to the US Food & Drug Administration (FDA) adverse event reporting system database. Chapters 3 and 6 systematically identified all relevant (published and unpublished) clinical trials for occurrences of ALF and RD, respectively, among trial participants. Finally, chapters 4 (ALF) and 7 (RD) involved case-control analysis of a major US database of electronic health records for nearly 70 million inpatients admitted to more than 500 hospitals between 2000 and 2016. The FAERS analysis revealed a positive ALF signal with ciprofloxacin and a marginal signal for RD with moxifloxacin. Examination of the evidence from clinical trials revealed only two cases of ALF, one associated with gemifloxacin and one with moxifloxacin. No cases of RD were reported in any of the identified clinical trials. Primary analyses of the Health Facts® data revealed no overall association between quinolones and the risk of ALF or RD. However, elevated risk was identified in some subgroups, including African Americans (ALF, RD), Caucasians (ALF), women (ALF, RD), men (ALF), those ≤60 years of age (ALF) or 56-70 years of age (RD), and those with no or few comorbidities (ALF). Evidence from analyses of data from spontaneous reports and clinical trials provided some evidence for an elevated risk of ALF or RD following the systemic administration of quinolone antibiotics. Some evidence of elevated risk was also identified in the case-control analyses of inpatient EHR records. Findings from our six epidemiologic studies are in line with current advisories by FDA and Health Canada.

L’encéphalopathie hépatique (EH) se développe chez les patients atteints d’une maladie du foie et se caractérise par de nombreuses anomalies neuropsychiatriques. L’insuffisance hépatique aiguë (IHA) se caractérise par une perte progressive de l’état de conscience, par une augmentation rapide de l’œdème cérébral et une augmentation de la pression intracrânienne entraînant une herniation cérébrale et la mort. Plusieurs facteurs sont responsables du développement de l’EH mais depuis une centaine d’années, l’hyperammonémie qui peut atteindre des concentrations de l’ordre de plusieurs millimolaires chez les patients atteints d’IHA aux stades de coma est considérée comme un facteur crucial dans la pathogenèse de l’EH. La présente thèse comprend 4 articles suggérant l’implication de nouveaux mécanismes pathogéniques dans le développement de l’EH et de l’œdème cérébral associés à l’IHA et tente d’expliquer l’effet thérapeutique de l’hypothermie et de la minocycline dans la prévention de l’EH et de l’œdème cérébral: 1. L’IHA induite par dévascularisation hépatique chez le rat se caractérise par une augmentation de la production de cytokines pro-inflammatoires cérébrales (IL-6, IL-1, TNF-). Cette observation constitue la première évidence directe que des mécanismes neuro-inflammatoires jouent une rôle dans la pathogenèse de l’EH et de l’œdème cérébral associés à l’IHA (Chapitre 2.1, articles 1 et 2). 2. L’activation de la microglie telle que mesurée par l’expression de marqueurs spécifiques (OX42, OX-6) coïncide avec le développement de l’encéphalopathie (stade coma) et de l’œdème cérébral et s’accompagne d’une production accrue de cytokines pro-inflammatoires cérébrales (Chapitre 2.1, article 1 et 2). 3. Un stress oxydatif/nitrosatif causé par une augmentation de l’expression de l’oxyde nitrique synthétase et une augmentation de la synthèse d’oxyde nitrique cérébral participe à la pathogénèse des complications neurologiques de l’IHA (Chapitre 2.3, articles 3 et 4). 4. Des traitements anti-inflammatoires tels que l’hypothermie et la minocycline peuvent constituer de nouvelles approches thérapeutiques chez les patients atteints d’IHA (Chapitre 2.1, article 1; Chapitre 2.2, article 2). 5. Les effets bénéfiques de l’hypothermie et de la minocycline sur les complications neurologiques de l’IHA expérimentale s’expliquent, en partie, par une diminution du stress oxydatif/nitrosatif (Chapitre 2.3, article 3; Chapitre 2.4, article 4). / Hepatic encephalopathy (HE) contains a spectrum of neuropsychiatric abnormalities observed in patients with liver disease. A quick worsening of consciousness and increasingly growing cerebral edema, high intracranial pressure, which leads to cerebral herniation and death, are characteristics of acute liver failure (ALF). Multiple factors are found responsible for the development of HE, whereas, over 100 years, hyperammonia is considered the most crucial factor in defining the pathogenesis of HE in ALF, which can increase to millimolar concentrations in the brain at the coma stages of HE. The present thesis comprises 4 articles, which demonstrates new pathogenic mechanisms involved in the development of HE and cerebral edema in ALF, and elucidates part of the therapeutic mechanism of hypothermia and minocycline in the prevention of HE and cerebral edema during ALF. The major findings are listed below: (1) Experimental ALF leads to the increase in brain production of proinflammatory cytokines (IL-6, IL-1, TNF-α), and provides the first direct evidence that central inflammatory mechanisms play a role in the pathogenesis of the encephalopathy and brain edema in ALF (chapter 2.1 - article 1; chapter 2.1 - article 2). (2) Activation of cerebral microglia, measured by OX-42, OX-6, predicts the presence of severe encephalopathy (coma) and brain edema in rats with ischemic ALF, which accompanies the increased production of brain proinflammatory cytokines (chapter 2.1 - article 1; chapter 2.2 - article 2). (3) Oxidative/nitrosative stress participates in the pathogenesis of brain edema and its complications in experimental ALF animals with ischemic liver failure. The increases in cerebral NOS isoform expression caused by ALF were sufficient to cause increased NO production in the brain (chapter 2.3 - article 3; chapter 2.4 - article 4). (4) Anti-inflammatory treatment, such as hypothermia or antibiotics, may be beneficial in patients with ALF (chapter 2.1 - article 1; chapter 2.2 - article 2). (5) The beneficial effect of both hypothermia and minocycline on the neurological complications of experimental ALF is mediated, at least in part, by reduction of brain-derived oxidative/nitrosative stress (chapter 2.3 - article 3; chapter 2.4 - article 4).

L’encéphalopathie hépatique (EH) se développe chez les patients atteints d’une maladie du foie et se caractérise par de nombreuses anomalies neuropsychiatriques. L’insuffisance hépatique aiguë (IHA) se caractérise par une perte progressive de l’état de conscience, par une augmentation rapide de l’œdème cérébral et une augmentation de la pression intracrânienne entraînant une herniation cérébrale et la mort. Plusieurs facteurs sont responsables du développement de l’EH mais depuis une centaine d’années, l’hyperammonémie qui peut atteindre des concentrations de l’ordre de plusieurs millimolaires chez les patients atteints d’IHA aux stades de coma est considérée comme un facteur crucial dans la pathogenèse de l’EH. La présente thèse comprend 4 articles suggérant l’implication de nouveaux mécanismes pathogéniques dans le développement de l’EH et de l’œdème cérébral associés à l’IHA et tente d’expliquer l’effet thérapeutique de l’hypothermie et de la minocycline dans la prévention de l’EH et de l’œdème cérébral: 1. L’IHA induite par dévascularisation hépatique chez le rat se caractérise par une augmentation de la production de cytokines pro-inflammatoires cérébrales (IL-6, IL-1, TNF-). Cette observation constitue la première évidence directe que des mécanismes neuro-inflammatoires jouent une rôle dans la pathogenèse de l’EH et de l’œdème cérébral associés à l’IHA (Chapitre 2.1, articles 1 et 2). 2. L’activation de la microglie telle que mesurée par l’expression de marqueurs spécifiques (OX42, OX-6) coïncide avec le développement de l’encéphalopathie (stade coma) et de l’œdème cérébral et s’accompagne d’une production accrue de cytokines pro-inflammatoires cérébrales (Chapitre 2.1, article 1 et 2). 3. Un stress oxydatif/nitrosatif causé par une augmentation de l’expression de l’oxyde nitrique synthétase et une augmentation de la synthèse d’oxyde nitrique cérébral participe à la pathogénèse des complications neurologiques de l’IHA (Chapitre 2.3, articles 3 et 4). 4. Des traitements anti-inflammatoires tels que l’hypothermie et la minocycline peuvent constituer de nouvelles approches thérapeutiques chez les patients atteints d’IHA (Chapitre 2.1, article 1; Chapitre 2.2, article 2). 5. Les effets bénéfiques de l’hypothermie et de la minocycline sur les complications neurologiques de l’IHA expérimentale s’expliquent, en partie, par une diminution du stress oxydatif/nitrosatif (Chapitre 2.3, article 3; Chapitre 2.4, article 4). / Hepatic encephalopathy (HE) contains a spectrum of neuropsychiatric abnormalities observed in patients with liver disease. A quick worsening of consciousness and increasingly growing cerebral edema, high intracranial pressure, which leads to cerebral herniation and death, are characteristics of acute liver failure (ALF). Multiple factors are found responsible for the development of HE, whereas, over 100 years, hyperammonia is considered the most crucial factor in defining the pathogenesis of HE in ALF, which can increase to millimolar concentrations in the brain at the coma stages of HE. The present thesis comprises 4 articles, which demonstrates new pathogenic mechanisms involved in the development of HE and cerebral edema in ALF, and elucidates part of the therapeutic mechanism of hypothermia and minocycline in the prevention of HE and cerebral edema during ALF. The major findings are listed below: (1) Experimental ALF leads to the increase in brain production of proinflammatory cytokines (IL-6, IL-1, TNF-α), and provides the first direct evidence that central inflammatory mechanisms play a role in the pathogenesis of the encephalopathy and brain edema in ALF (chapter 2.1 - article 1; chapter 2.1 - article 2). (2) Activation of cerebral microglia, measured by OX-42, OX-6, predicts the presence of severe encephalopathy (coma) and brain edema in rats with ischemic ALF, which accompanies the increased production of brain proinflammatory cytokines (chapter 2.1 - article 1; chapter 2.2 - article 2). (3) Oxidative/nitrosative stress participates in the pathogenesis of brain edema and its complications in experimental ALF animals with ischemic liver failure. The increases in cerebral NOS isoform expression caused by ALF were sufficient to cause increased NO production in the brain (chapter 2.3 - article 3; chapter 2.4 - article 4). (4) Anti-inflammatory treatment, such as hypothermia or antibiotics, may be beneficial in patients with ALF (chapter 2.1 - article 1; chapter 2.2 - article 2). (5) The beneficial effect of both hypothermia and minocycline on the neurological complications of experimental ALF is mediated, at least in part, by reduction of brain-derived oxidative/nitrosative stress (chapter 2.3 - article 3; chapter 2.4 - article 4).