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Dominique Pessayre

Publications and source records attributed to Dominique Pessayre.

At least 19 recordsLinked to original sources
PubMed2006

Dexamethasone hepatic induction in rats subsequently treated with high dose buprenorphine does not lead to respiratory depression.

In humans, asphyxic deaths and severe poisonings have been attributed to high-dosage buprenorphine, a maintenance therapy for heroin addiction. However, in rats, intravenous buprenorphine at doses up to 90 mg kg(-1) was not associated with significant effects on arterial blood gases. In contrast, norbuprenorphine, the buprenorphine major cytochrome P450 (CYP) 3A-derived metabolite, is a potent respiratory depressant. Thus, our aim was to study the consequences of CYP3A induction on buprenorphine-associated effects on resting ventilation in rats. We investigated the effects on ventilation of 30 mg kg(-1) buprenorphine alone or following cytochrome P450 (CYP) 3A induction with dexamethasone, using whole body plethysmography (N=24) and arterial blood gases (N=12). Randomized animals in 4 groups received sequential intraperitoneal dosing with: (dexamethasone [days 1-3]+buprenorphine [day 4]), (dexamethasone solvent [days 1-3]+buprenorphine [day 4]), (dexamethasone [days 1-3]+buprenorphine solvent [day 4]), or (dexamethasone solvent [days 1-3]+buprenorphine solvent [day 4]). Buprenorphine alone caused a significant rapid and sustained increase in the inspiratory time (P<0.001), without significant effects on the respiratory frequency, the tidal volume, the minute volume, or arterial blood gases. In dexamethasone-pretreated rats, there was no significant alteration in the respiratory parameters, despite CYP3A induction and significant increase of the ratio of plasma norbuprenorphine-to-buprenorphine concentrations. In conclusion, dexamethasone did not modify the effects of 30 mg kg(-1) buprenorphine on rat ventilation. Our results suggest a limited role of drug-mediated CYP3A induction in the occurrence of buprenorphine-attributed respiratory depression in addicts.

Animals↗
PubMed2006

Partial Beclin 1 silencing aggravates doxorubicin- and Fas-induced apoptosis in HepG2 cells.

AIM: To investigate the role of Beclin 1 on the susceptibility of HepG2 cells to undergo apoptosis after anti-Fas antibody or doxorubicin treatment. METHODS: Beclin 1 silencing was achieved using RNA interference. DNA ploidy, the percentage of apoptotic cells and the mitochondrial membrane potential were assessed by flow cytometry. Levels of Beclin 1, Bcl-X(L) and cytochrome c, and the cleavage of poly (ADP-ribose) polymerase (PARP) were assayed by using Western blots. RESULTS: Beclin 1 expression decreased by 75% 72 h after Beclin 1 siRNA transfection. Partial Beclin 1 silencing significantly increased the percentage of subG1 cells 24 and 40 h after treatment with doxorubicin or anti-Fas antibody, respectively, and this potentiation was abrogated by treatment with a pan-caspase inhibitor. Partial Beclin 1 silencing also increased PARP cleavage, mitochondrial membrane depolarization and cytosolic cytochrome c. The pro-apoptotic consequences of partial Beclin 1 silencing were not associated with a decline in Bcl-X(L) expression. CONCLUSION: Partial Beclin 1 silencing aggravates mitochondrial permeabilization and apoptosis in HepG2 cells treated with an anti-Fas antibody or with doxorubicin.

Antibiotics, Antineoplastic↗
PubMed2006

The anti-inflammatory drug, nimesulide (4-nitro-2-phenoxymethane-sulfoanilide), uncouples mitochondria and induces mitochondrial permeability transition in human hepatoma cells: protection by albumin.

Like other nonsteroidal anti-inflammatory drugs, nimesulide (4-nitro-2-phenoxymethane-sulfoanilide) triggers hepatitis in a few recipients. Although nimesulide has been shown to uncouple mitochondrial respiration and cause hepatocyte necrosis in the absence of albumin, mechanisms for cell death are incompletely understood, and comparisons with human concentrations are difficult because 99% of nimesulide is albumin-bound. We studied the effects of nimesulide, with or without a physiological concentration of albumin, in isolated rat liver mitochondria or microsomes and in human hepatoma cells. Nimesulide did not undergo monoelectronic nitro reduction in microsomes. In mitochondria incubated without albumin, nimesulide (50 microM) decreased the mitochondrial membrane potential (DeltaPsim), increased basal respiration, and potentiated the mitochondrial permeability transition (MPT) triggered by calcium preloading. In HUH-7 cells incubated for 24 h without albumin, nimesulide (1 mM) decreased the DeltaPsim and cell NADPH and increased the glutathione disulfide/reduced glutathione ratio and cell peroxides; nimesulide triggered MPT, ATP depletion, high cell calcium, and caused mostly necrosis, with rare apoptotic cells. Coincubation with either cyclosporin A (an MPT inhibitor) or the combination of fructose-1,6-diphosphate (a glycolysis substrate) and oligomycin (an ATPase inhibitor) prevented the decrease in DeltaPsim, ATP depletion, and cell death. A physiological concentration of albumin abolished the effects of nimesulide on isolated mitochondria or HUH-7 cells. In conclusion, the weak acid, nimesulide, uncouples mitochondria and triggers MPT and ATP depletion in isolated mitochondria or hepatoma cells incubated without albumin. However, in the presence of albumin, only a fraction of the drug enters cells or organelles, and uncoupling and toxicity are not observed.

Animals↗
PubMed2006

Protein kinase PKC delta and c-Abl are required for mitochondrial apoptosis induction by genotoxic stress in the absence of p53, p73 and Fas receptor.

Doxorubicin, cis-diamminedichloroplatinum (II) and 5-fluorouracil used in chemotherapy induce apoptosis in Hep3B cells in the absence of p53, p73, and functional Fas. Since mediators remain unknown, the requirement of PKC delta (PKCdelta) and c-Abl was investigated. Suppression of c-Abl or PKCdelta expression using SiRNAs impaired PARP cleavage, Gleevec and/or rottlerin inhibited the induction of the subG1 phase and the increase of reactive oxygen species level. Co-precipitations and phosphorylations to mitochondria of c-Abl, PKCdelta and Bcl-X(L/s) were induced. A depolarization of the mitochondrial membrane and activations of caspase-2 and -9 were observed. We propose that, in the absence of p53, p73 and Fas, genotoxic drugs could require both PKCdelta and c-Abl to induce apoptosis through the mitochondrial pathway.

Apoptosis↗
PubMed2006

Genetic polymorphisms in antioxidant enzymes modulate hepatic iron accumulation and hepatocellular carcinoma development in patients with alcohol-induced cirrhosis.

Manganese superoxide dismutase (MnSOD) converts the superoxide anion into H(2)O(2), which, unless it is detoxified by glutathione peroxidase 1 (GPx1), can increase hepatic iron and can react with iron to form genotoxic compounds. We investigated the role of Ala/Val-MnSOD and Pro/Leu-GPx1 polymorphisms on hepatic iron accumulation and hepatocellular carcinoma development in patients with alcoholic cirrhosis. Genotypes were determined in 162 alcoholic patients with cirrhosis but without hepatocellular carcinoma initially, who were prospectively followed up for hepatocellular carcinoma development. We found that patients with two Val-MnSOD alleles (slow H(2)O(2) production) and two Pro-GPx1 alleles (presumably quick H(2)O(2) detoxification) had a lower risk of hepatocellular carcinoma development than other patients (chi(2) trend test, P = 0.001; log-rank, P = 0.0009). Indeed, hepatocellular carcinoma percentage was 0% in subjects with this "2Val-MnSOD/2Pro-GPx1" genotype versus 16%, 27%, and 32% in "2Val-MnSOD/1or2Leu-GPx1," "1or2Ala-MnSOD/2Pro-GPx1," and "1or2Ala-MnSOD/1or2Leu-GPx1" patients, respectively. The percentage of patients with stainable hepatic iron increased progressively with these genotypic associations: 22%, 28%, 50%, and 53%, respectively (chi(2) trend test, P = 0.005). Stainable iron was a risk factor for hepatocellular carcinoma (log-rank, P = 0.0002; relative risk, 3.40). In conclusion, polymorphisms in antioxidant enzymes modulate hepatic iron accumulation and hepatocellular carcinoma development in French alcoholic patients with cirrhosis.

Alleles↗
PubMed2006

Mitochondrial dysfunction in NASH: causes, consequences and possible means to prevent it.

Calorie-enriched diet and lack of exercise are causing a worldwide surge of obesity, insulin resistance and lipid accretion in liver (i.e. hepatic steatosis), which can lead to steatohepatitis. Steatosis and nonalcoholic steatohepatitis (NASH) can also be induced by drugs such as amiodarone, tamoxifen and some antiretroviral drugs, including stavudine and zidovudine. There is accumulating evidence that mitochondrial dysfunction (more particularly respiratory chain deficiency) plays a key role in the physiopathology of NASH whatever its initial cause. In contrast, the mitochondrial beta-oxidation of fatty acids can be either increased (as in insulin resistance-associated NASH) or decreased (as in drug-induced NASH). However, in both circumstances, generation of reactive oxygen species (ROS) by the damaged respiratory chain can be augmented. ROS generation in an environment enriched in lipids in turn induces lipid peroxidation which releases highly reactive aldehydic derivatives (e.g. malondialdehyde) that have diverse detrimental effects on hepatocytes and other hepatic cells. In hepatocytes, ROS, reactive nitrogen species and lipid peroxidation products further impair the respiratory chain, either directly or indirectly through oxidative damage to the mitochondrial genome. This consequently leads to the generation of more ROS and a vicious cycle occurs. Mitochondrial dysfunction can also lead to apoptosis or necrosis depending on the energy status of the cell. ROS and lipid peroxidation products also increase the generation of several cytokines (TNF-alpha, TGF-beta, Fas ligand) playing a key role in cell death, inflammation and fibrosis. Recent investigations have shown that some genetic polymorphisms can significantly increase the risk of steatohepatitis and that several drugs can prevent or even reverse NASH. Interestingly, most of these drugs could exert their beneficial effects by improving directly or indirectly mitochondrial function in liver. Finding a drug, which could fully prevent oxidative stress and mitochondrial dysfunction in NASH is a major challenge for the next decade.

Animals↗
PubMed2005

Ethanol increases mitochondrial cytochrome P450 2E1 in mouse liver and rat hepatocytes.

Enhanced hepatic levels of cytochrome P450 2E1 (CYP2E1) may play a key role in the pathogenesis of some liver diseases because CYP2E1 represents a significant source of reactive oxygen species. Although a large fraction of CYP2E1 is located in the endoplasmic reticulum, CYP2E1 is also present in mitochondria. In this study, we asked whether ethanol, a known inducer of microsomal CYP2E1, could also increase CYP2E1 within mitochondria. Our findings indicated that ethanol increased microsomal and mitochondrial CYP2E1 in cultured rat hepatocytes and in the liver of lean mice. This was associated with decreased levels of glutathione, possibly reflecting increased oxidative stress. In contrast, in leptin-deficient obese mice, ethanol administration did not increase mitochondrial CYP2E1, nor it depleted mitochondrial glutathione, suggesting that leptin deficiency hampers mitochondrial targeting of CYP2E1. Thus, ethanol intoxication increases CYP2E1 not only in the endoplasmic reticulum but also in mitochondria, thus favouring oxidative stress in these compartments.

Animals↗
PubMed2005

Peroxynitrite-induced mitochondrial and endonuclease-mediated nuclear DNA damage in acetaminophen hepatotoxicity.

Intracellular sources of peroxynitrite formation and potential targets for this powerful oxidant and nitrating agent have not been identified after acetaminophen (AAP) overdose. Therefore, we tested the hypothesis that peroxynitrite generated in mitochondria may be responsible for mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) damage. C3Heb/FeJ mice were treated with 300 mg/kg AAP and monitored for up to 12 h. Loss of mtDNA (assayed by slot blot hybridization) and substantial nDNA fragmentation (evaluated by anti-histone enzyme-linked immunosorbent assay, terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, and agarose gel electrophoresis) were observed as early as 3 h after AAP overdose. Analysis of nitrotyrosine protein adducts in subcellular fractions established that peroxynitrite was generated predominantly in mitochondria beginning at 1 h after AAP injection. Delayed treatment with a bolus dose of glutathione (GSH) accelerated the recovery of mitochondrial glutathione, which then effectively scavenged peroxynitrite. However, mtDNA loss was only partially prevented. Despite the absence of nitrotyrosine adducts in the nucleus after AAP overdose, nDNA damage was almost completely eliminated with GSH administration. A direct comparison of nDNA damage after AAP overdose with nDNA fragmentation during tumor necrosis factor receptor-mediated apoptosis showed similar DNA ladders on agarose gels but quantitatively different results in three other assays. We conclude that peroxynitrite may be partially responsible for mtDNA loss but is not directly involved in nDNA damage. In contrast, nDNA fragmentation after AAP overdose is not caused by caspase-activated DNase but most likely by other intracellular DNase(s), whose activation is dependent on the mitochondrial oxidant stress and peroxynitrite formation.

Acetaminophen↗
PubMed2005

Alcohol increases tumor necrosis factor alpha and decreases nuclear factor-kappab to activate hepatic apoptosis in genetically obese mice.

Both obesity and alcohol can cause oxidative stress, cytokine induction, and steatohepatitis. To determine the consequences of their combination, we compared the hepatic effects of moderate ethanol binges in lean and obese ob/ob mice. Mice received water or ethanol (2.5 g/kg) by gastric intubation daily for 4 days, and were killed 2 hours after the last administration. Some obese mice also received pentoxifylline, an inhibitor of tumor necrosis factor-alpha (TNF-alpha) production, before each ethanol administration. In lean mice, these moderate ethanol doses did not increase plasma TNF-alpha and hepatic caspase-3 activity, but triggered some apoptotic hepatocytes. Naive ob/ob mice had a few necrotic and apoptotic hepatocytes, but exhibited little oxidative stress, possibly because of adaptive increases in manganese superoxide dismutase, heat shock protein 70 (Hsp70), mitochondrial cytochrome c, and mitochondrial DNA. Alcohol administration to ob/ob mice did not increase oxidative stress despite increased CYP2E1, but increased plasma TNF-alpha, further increased Hsp70, and profoundly decreased p65 nuclear factor kappaB (NF-kappaB) protein and DNA-binding activity in nuclear extracts. Caspase-3 was activated, and more apoptotic hepatocytes were found in intoxicated obese mice than naive obese mice. In intoxicated obese mice, pentoxifylline fully prevented the increase in plasma TNF-alpha the decrease in nuclear NF-kappaB activity, and the increase in hepatic caspase-3, and it also decreased hepatic triglycerides. In conclusion, obese mice develop adaptations that may limit oxidative stress. Moderate ethanol intoxication does not increase oxidative stress in obese mice, but increases TNF-alpha and also decreases nuclear NF-kappaB activity, thus unleashing the apoptotic effects of TNF-alpha.

Animals↗
PubMed2005

Potent induction of apoptosis in human hepatoma cell lines by targeted cytotoxic somatostatin analogue AN-238.

BACKGROUND/AIMS: The efficacy of a targeted cytotoxic hybrid somatostatin analogue AN-238 and of its superactive radical 2-pyrrolinodoxorubicin (AN-201) to induce apoptosis of HepG2 and Hep3B human hepatoma cell lines were studied. AN-238 was designed to selectively target tumor cells expressing somatostatin receptor subtypes (sst(s)). Its effects on HepG2 or Hep3B cells displaying or lacking tumor suppressor p53, respectively, were compared. Normal rat isolated hepatocytes were also tested. METHODS: sst(s) were characterized by binding assays and RT-PCR. Cytotoxicity was quantified by flow cytometry. DNA fragmentation was studied by gel electrophoresis, PARP cleavage by Western blot and ROS formation using fluorescent probes. RESULTS: Specific binding of iodinated RC-160 to HepG2 and Hep3B cells, and its displacement by AN-238 was characterized. mRNA for hsst(2A) was found in both cell lines. Flow cytometry showed a stronger effect of AN-238 than AN-201 to induce sub-G1 phase. DNA fragmentation, nuclear bodies, and PARP cleavage were observed. In addition, AN-238 increased formation of ROS more potently than AN-201. However, no inductions of DNA fragmentation by AN-201 or AN-238 were observed on rat hepatocytes. CONCLUSIONS: Our results indicate that, in liver cancer, the cytotoxic somatostatin analogue AN-238 is a powerful agent that can induce apoptosis, through sst(s) and independently of p53.

Apoptosis↗
PubMed2005

Genetic dimorphism in superoxide dismutase and susceptibility to alcoholic cirrhosis, hepatocellular carcinoma, and death.

BACKGROUND AND AIMS: A genetic dimorphism encodes for either alanine (Ala) or valine (Val) in the mitochondrial targeting sequence of manganese superoxide dismutase (MnSOD), and modulates its mitochondrial import. However, the role of this dimorphism in the susceptibility of alcoholic patients to develop cirrhosis is controversial, and its influence on the occurrence of hepatocellular carcinoma (HCC) and death in patients with alcoholic cirrhosis is unknown. METHODS: We compared MnSOD genotypes in 94 control subjects and 264 patients with alcoholic cirrhosis. Patients were included at the time of the first liver biopsy examination showing cirrhosis, and were followed-up prospectively. RESULTS: Alcohol consumption was similar, whatever the patients' genotype. At inclusion, the percentage of Val/Val homozygotes was lower in patients than in controls (16% vs. 31%), whereas the percentage of Ala/Ala homozygotes was higher in patients than in controls (30% vs. 21%) ( P = .008). During follow-up evaluation, only 9% of Val/Val patients developed HCC, vs. 30% and 29% of Ala/Val and Ala/Ala patients, respectively ( P = .02). Only 28% of Val/Val patients died or were transplanted, vs. 49% and 50% of Ala/Val and Ala/Ala patients, respectively ( P = .03). Because of the progressive decrease in surviving Ala patients, the genotypic distribution in patients surviving for 5 or 10 years no longer differed from the genotypic distribution in controls. CONCLUSIONS: The presence of at least 1 Ala MnSOD allele increases the risk for developing cirrhosis in French alcoholics, and increases the rates of HCC development and death in cirrhotic patients.

Carcinoma, Hepatocellular↗
PubMed2005

The manganese superoxide dismutase Ala16Val dimorphism modulates both mitochondrial import and mRNA stability.

A genetic dimorphism incorporates either alanine (Ala) or valine (Val) in the mitochondrial targeting sequence (MTS) of manganese superoxide dismutase (MnSOD). The Ala-MTS confers a 40% higher MnSOD activity than the Val-MTS after import into isolated mitochondria in vitro. The present study aimed to characterize functional consequences in whole cells. HuH7 human hepatoma cells were transfected with vectors encoding for the human Ala- or Val-MnSOD variants fused to a Myc-His-tag. The Ala-variant resulted in four-fold higher levels of the mature exogenous protein and MnSOD activity than the Val-variant. Studies with a proteasome inhibitor indicated that precursor proteins are either imported into the mitochondria or degraded by the proteasome. Despite identical levels 8 h after transfection, mRNA levels at 36 h were two-fold higher for the Ala-encoding mRNA than the Val-mRNA. Decreasing the mitochondrial membrane potential decreased both MnSOD mitochondrial import and its mRNA levels. Much larger differences in the activity of the human Val- and Ala-MnSOD variants are observed in whole cells rather than after import experiments performed in vitro. First, the slowly imported Val-MnSOD is degraded by the proteasome in cells. Second, the slower mitochondrial import of the Val-variant may be associated with decreased mRNA stability, possibly due to impaired cotranslational import.

Alanine↗
PubMed2004

Subliminal Fas stimulation increases the hepatotoxicity of acetaminophen and bromobenzene in mice.

The hepatotoxicity of several drugs is increased by mild viral infections. During such infections, death receptor ligands are expressed at low levels, and most parenchymal cells survive. We tested the hypothesis that subliminal death receptor stimulation may aggravate the hepatotoxicity of drugs, which are transformed by cytochrome P-450 cytochrome P-450 into glutathione-depleting reactive metabolites. Twenty-four-hour-fasted mice were pretreated with a subtoxic dose of the agonistic Jo2 anti-Fas antibody (1 microg per mouse) 3 hours before acetaminophen (500 mg/kg) or 1 hour before bromobenzene (400 mg/kg) administration. Administration of Jo2 alone increased hepatic inducible nitric oxide synthase nitric oxide synthase but did not modify serum alanine aminotransferase (ALT), hepatic adenosine triphosphate (ATP), glutathione (GSH), cytochrome P-450, cytosolic cytochrome c, caspase-3 activity or hepatic morphology. However, pretreating mice with Jo2 further decreased both hepatic GSH and ATP by 40% 4 hours after acetaminophen administration, and further increased serum ALT and the area of centrilobular necrosis at 24 hours. In mice pretreated with the Jo2 antibody before bromobenzene administration, hepatic GSH 4 hours after bromobenzene administration was 51% lower than in mice treated with bromobenzene alone, and serum ALT activity at 24 hours was 47-fold higher. In conclusion, administration of a subtoxic dose of an agonistic anti-Fas antibody before acetaminophen or bromobenzene increases metabolite-mediated GSH depletion and hepatotoxicity. Subliminal death receptor stimulation may be one mechanism whereby mild viral infections can increase drug-induced toxicity.

Acetaminophen↗
PubMed2004

Mitochondrial injury in steatohepatitis.

Rich diet and lack of exercise are causing a surge in obesity, insulin resistance and steatosis, which can evolve into steatohepatitis. Patients with non-alcoholic steatohepatitis have increased lipid peroxidation, increased tumour necrosis factor-alpha (TNF-alpha) and increased mitochondrial beta-oxidation rates. Their in-vivo ability to re-synthesize ATP after a fructose challenge is decreased, and their hepatic mitochondria exhibit ultrastructural lesions, depletion of mitochondrial DNA and decreased activity of respiratory chain complexes. Although the mechanisms for these effects is unknown, the basal cellular formation of reactive oxygen species (ROS) may oxidize fat deposits to cause lipid peroxidation, which damages mitochondrial DNA, proteins and cardiolipin to partially hamper the flow of electrons within the respiratory chain. This flow may be further decreased by TNF-alpha, which can release cytochrome c from mitochondria. Concomitantly, the increased mitochondrial fatty acid beta-oxidation rate augments the delivery of electrons to the respiratory chain. Due to the imbalance between a high electron input and a restricted outflow, electrons may accumulate within complexes I and III, and react with oxygen to form the superoxide anion radical. Increased mitochondrial ROS formation could in turn directly oxidize mitochondrial DNA, proteins and lipids, enhance lipid peroxidation-related mitochondrial damage, trigger hepatic TNF-alpha formation and deplete antioxidants, thus further blocking electron flow and further increasing mitochondrial ROS formation. Mitochondrial dysfunction plays an important role in liver lesions, through the ROS-induced release of both biologically active lipid peroxidation products and cytokines. In particular, the up-regulation of both TNF-alpha and Fas triggers mitochondrial membrane permeability and apoptosis. The ingestion of apoptotic bodies by stellate cells stimulates fibrogenesis, which is further activated by lipid peroxidation products and high leptin levels. Chronic apoptosis is compensated by increased cell proliferation, which, together with oxidative DNA damage, may cause gene mutations and cancer.

Adipocytes↗
PubMed2004

Effects of zidovudine, stavudine and beta-aminoisobutyric acid on lipid homeostasis in mice: possible role in human fat wasting.

OBJECTIVE: Although mitochondrial DNA (mtDNA) depletion could play a role in nucleoside reverse transcriptase inhibitor-induced lipoatrophy, poor correlations between fat mtDNA levels and lipoatrophy suggest additional mechanism(s). Stavudine (d4T), zidovudine (AZT) and the thymine catabolite, beta-aminoisobutyric acid (BAIBA), but not zalcitabine (ddC) or didanosine (ddI), can increase fatty acid oxidation in liver mitochondria and plasma ketone bodies in mice. Since fat oxidation in non-adipose tissue can influence body adiposity, we sought to determine whether d4T, AZT and BAIBA can cause lipoatrophy in mice by this catabolic mechanism. METHODS: Lean or obese ob/ob mice were treated for 6 weeks with d4T, AZT or BAIBA, and lean mice with ddC or ddI. Body fat mass was assessed by dual energy X-ray absorptiometry, and mtDNA by Slot blot hybridization in epididymal fat. RESULTS: Whereas ddC or ddI did not change plasma beta-hydroxybutyrate and body fat mass, d4T, AZT and BAIBA increased plasma beta-hydroxybutyrate in lean mice suggesting increased hepatic fatty acid oxidation and ketogenesis. Despite unchanged food consumption, a supra-pharmacological dose of d4T tended to decrease, whilst AZT and BAIBA decreased body fat mass. Fat mtDNA and plasma triglycerides, cholesterol, glucose, insulin, leptin and adiponectin levels were unchanged. In obese mice, d4T, AZT and BAIBA did not increase plasma beta-hydroxybutyrate, and only AZT decreased body fat mass without reducing fat mtDNA. CONCLUSIONS: d4T and AZT can enhance hepatic fat oxidation and cause fat wasting, without decreasing adipose tissue mtDNA and without causing insulin resistance in mice. BAIBA, a thymine catabolite, reproduces these effects. These catabolic effects could play a role in the lipoatrophy, which can occur in AZT- or d4T-treated patients.

Aminoisobutyric Acids↗
PubMed2003

Downregulation of cytochromes P450 in growth-stimulated rat hepatocytes: role of c-Myc induction and impaired C/EBP binding to DNA.

BACKGROUND/AIMS: Several cytochromes P450 (CYPs) are expressed in differentiated hepatocytes, but downregulated in growth-stimulated cells. We determined the signals involved in CYP downregulation by epidermal growth factor (EGF). METHODS: Rat hepatocytes were cultured with or without diverse substances for 72 h and EGF for the last 48 h. RESULTS: EGF increased c-myc mRNA and protein, and decreased CYP mRNAs and proteins; both effects were prevented by two agents blocking c-myc transcription (retinoic acid and DMSO) and two antisense c-myc oligomers. Despite unchanged CCAAT-enhancer binding protein alpha (C/EBPalpha) and increased C/EBPbeta levels, nuclear proteins of EGF-treated cells did not bind to a C/EBP DNA probe in a gel mobility shift assay. This binding was restored when cells were co-treated with both EGF and c-myc antisense oligomers (preventing c-Myc induction). The N-terminal c-Myc domain added to control nuclear extracts prevented C/EBP DNA binding. A monoclonal anti-c-Myc antibody co-immunoprecipitated c-Myc, C/EBPalpha and C/EBPbeta from nuclear extracts. In cells not treated with EGF, an antisense C/EBPalpha oligomer decreased CYP expression. CONCLUSIONS: EGF overexpresses c-Myc, decreases C/EBP binding to DNA and downregulates CYPs. We suggest that c-Myc may form inactive complexes with C/EBPs, thus decreasing C/EBP-mediated CYP transactivation.

Animals↗
PubMed2003

Alcohol and hepatitis C virus core protein additively increase lipid peroxidation and synergistically trigger hepatic cytokine expression in a transgenic mouse model.

BACKGROUND/AIMS: Alcohol consumption accelerates the appearance of liver fibrosis and hepatocellular carcinoma in patients with chronic hepatitis C virus (HCV) infection, but the mechanisms of these interactions are unknown. We therefore investigated the effects of chronic ethanol consumption in HCV core protein-expressing transgenic mice. METHODS: Ethanol was progressively added (up to 20%) to the drinking water that was given ad libidum. RESULTS: In vivo fatty acid oxidation was not inhibited by ethanol consumption and/or HCV core expression. Both chronic ethanol consumption and HCV core expression decreased hepatic lipoprotein secretion and caused steatosis, but had no additive effects on lipoprotein secretion or steatosis. However, chronic ethanol consumption and HCV core protein additively increased lipid peroxidation and acted synergistically to increase the hepatic expression of transforming growth factor-beta (TGF-beta) and, to a less extent, tumor necrosis factor-alpha (TNF-alpha). CONCLUSIONS: HCV core protein expression and chronic alcohol consumption have no effects on in vivo fatty acid oxidation and do not additively impair hepatic lipoprotein secretion, but additively increase hepatic lipid peroxidation and synergistically increase hepatic TNF-alpha and TGF-beta expression. These effects may be involved in the activation of fibrogenesis and the development of hepatocellular carcinoma in patients cumulating alcohol abuse and HCV infection.

Animals↗