Mitochondrial respiratory chain activity is associated with severity, corticosteroid response and prognosis of alcoholic hepatitis.

BACKGROUND AND AIMS: Little is known about the extent of mitochondrial respiratory chain (MRC) activity dysfunction in patients with alcoholic hepatitis (AH). We aimed to assess the hepatic MRC activity in AH patients and its potential impact on the severity and prognosis of this life-threatening liver disease. METHODS: MRC complexes were measured in liver biopsies of 98 AH patients (non-severe, 17; severe, 81) and in 12 histologically normal livers (NL). Severity was assessed according to Maddrey's Index and MELD score. Corticosteroid response rate and cumulative mortality were also evaluated. RESULTS: The activity of the five MRC complexes was markedly decreased in the liver of AH patients compared with that of NL subjects, being significantly lower in patients with severe AH than in those with non-severe AH. There was a negative correlation between the activity of all MRC complexes and the severity of AH. Interestingly, only complex I and III activities showed a significant positive correlation with the corticosteroid response rate and a significant negative correlation with the mortality rate at all-time points studied. In a multivariate regression analysis, besides the MELD score and the corticosteroid response rate, complex I activity was significantly associated with 3-month mortality (OR = 6.03; p = 0.034) and complex III activity with 6-month mortality (OR = 4.70; p = 0.041) in AH patients. CONCLUSION: Our results indicate that MRC activity is markedly decreased in the liver of AH patients, and, particularly, the impairment of MRC complexes I and III activity appears to have a significant impact on the clinical outcomes of patients with AH.

Protein tyrosine phosphatase 1b deficiency protects against hepatic fibrosis by modulating nadph oxidases.

Inflammation is typically associated with the development of fibrosis, cirrhosis and hepatocellular carcinoma. The key role of protein tyrosine phosphatase 1B (PTP1B) in inflammatory responses has focused this study in understanding its implication in liver fibrosis. Here we show that hepatic PTP1B mRNA expression increased after bile duct ligation (BDL), while BDL-induced liver fibrosis was markedly reduced in mice lacking Ptpn1 (PTP1B-/-) as assessed by decreased collagen deposition and α-smooth muscle actin (α-SMA) expression. PTP1B-/- mice also showed a significant increase in mRNA levels of key markers of monocytes recruitment (Cd68, Adgre1 and Ccl2) compared to their wild-type (PTP1B+/+) littermates at early stages of injury after BDL. Interestingly, the lack of PTP1B strongly increased the NADPH oxidase (NOX) subunits Nox1/Nox4 ratio and downregulated Cybb expression after BDL, revealing a pro-survival pattern of NADPH oxidase induction in response to liver injury. Chimeric mice generated by transplantation of PTP1B-/- bone marrow (BM) into irradiated PTP1B+/+ mice revealed similar hepatic expression profile of NOX subunits than PTP1B-/- mice while these animals did not show differences in infiltration of myeloid cells at 7 days post-BDL, suggesting that PTP1B deletion in other liver cells is necessary for boosting the early inflammatory response to the BDL. PTP1B-/- BM transplantation into PTP1B+/+ mice also led to a blockade of TGF-ß and α-SMA induction after BDL. In vitro experiments demonstrated that deficiency of PTP1B in hepatocytes protects against bile acid-induced apoptosis and abrogates hepatic stellate cells (HSC) activation, an effect ameliorated by NOX1 inhibition. In conclusion, our results have revealed that the lack of PTP1B switches NOX expression pattern in response to liver injury after BDL and reduces HSC activation and liver fibrosis.

Omentectomy Prevents Metabolic Syndrome By Reducing Appetite and Body Weight In A Diet-Induced Obesity Rat Model.

Visceral fat deposition is associated with impairment of glucose and lipid metabolism while leptin levels are frequently related to subcutaneous fat area. At present, there is considerable controversy regarding the role of visceral adipose tissue accumulation in the development of metabolic syndrome (MS). Here we show the effects of omentectomy on the liver and MS in a diet induced obesity rat model. Our results reveal that undergoing omentectomy previously the establishment of the diet-induced-obesity reduced significantly body weight gain and avoid the development of MS, including non-alcoholic fatty liver disease. Intriguingly, the significantly lower body weight gain was due to decreased food intake. Omentum drives obesity progression through leptin resistance mediated by C-reactive protein, Interleucin (IL)-6 and high lipolysis activity. Omentum removal reversed immediately the increased plasma levels of CRP and IL-6 and gradually food intake, weight gain, and features of MS in diet-induced-obesity. Omentectomy caused no changes in normal-weigh-rats. This report displays causal mechanism by which omentum promotes obesity and propose omentectomy as a promising procedure in MS prevention.

Interlobar Artery Resistive Index predicts Acute-on-Chronic Liver Failure Syndrome in Cirrhotic Patients with Acute Decompensation.

INTRODUCTION: Patients with acutely decompensated (AD) cirrhosis are at risk for developing acute-on-chronic liver failure (ACLF) syndrome. This syndrome is associated with a high short-term mortality rate. The aim of our study was to identify reliable early predictors of developing ACLF in cirrhotic patients with AD. PATIENTS AND METHODS: We assessed 84 cirrhotic patients admitted for AD without ACLF on admission. We performed routine blood testing and detailed ultrasound Doppler studies of systemic arteries and mayor abdominal veins and arteries. We also calculated liver-specific and intensive care unit predictive scores. The area under the ROC curve (AUROC) was calculated for all variables that were significantly different between patients who developed ACLF and those who did not. Sensitivity, specificity, positive and negative predictive values, as well as diagnostic accuracy predicting the short-term development of ACLF were determined. RESULTS: of the 84 patients, 23 developed ACLF whereas 61 did not. In the univariate analysis, serum levels of creatinine and urea, prothrombin time ratio, MELD score, portal vein and femoral artery flow velocity as well as the renal and interlobar artery resistive indices (RI) were associated with the short-term development of ACLF. However, only interlobar artery RI had independent predictive value in the multivariate analysis. The AUROC value for RI of the interlobar arteries was 0.9971. CONCLUSION: On the first day of admission, ultrasound measurement of the RI of the interlobar arteries recognizes with high predictive accuracy those cirrhotic patients admitted with AD who will develop ACLF during hospital admission.

NADPH oxidase is implicated in the pathogenesis of oxidative phosphorylation dysfunction in mice fed a high-fat diet.

The aim of this study was to evaluate the role of NADPH oxidase (NADPHox) in the pathogenesis of oxidative phosphorylation (OXPHOS) dysfunction as found in mice fed a high-fat diet (HFD). C57BL/6J mice were distributed in four groups: WT/SCD: six wild-type (WT) mice fed a standard chow diet (SCD); WT/HFD, six WT mice fed a HFD; NOX2(-/-)/SCD, six NADPHox-deficient mice on a SCD; (4) NOX2(-/-)/HFD, six NADPHox-deficient mice on a HFD. After 32 weeks, we studied the liver for: histology; OXPHOS complex activity; fully assembled OXPHOS complexes and their subunits; gene expression of OXPHOS subunits; oxidative and nitrosative stress; and oxidative DNA damage. In the liver of WT/HFD mice, we found a significant decreased in the activity of all OXPHOS complexes, in fully assembled complexes, in the amount of OXPHOS subunits, and in gene expression of mitochondrial DNA-encoded subunits. 8-hydroxy-2'-deoxyguanosine was only increased in mitochondrial DNA. The liver of NOX(-/-)/HFD mice showed mild steatosis but no non-alcoholic steatohepatitis (NASH) lesions were found. OXPHOS activity, OXPHOS subunits, and assembly of subunits into OXPHOS complexes were normal in these mice. We conclude that this study shows that NADPH deficiency protects mice from developing OXPHOS dysfunction and NASH caused by a HFD.

Simvastatina: desde el colesterol al óxido nítrico, desde la cardiopatía isquémica a la hipertensión portal / Simvastatin - From cholesterol to nitric oxide, from ischemic heart disease to portal hypertension

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In vitro treatment of HepG2 cells with saturated fatty acids reproduces mitochondrial dysfunction found in nonalcoholic steatohepatitis.

Activity of the oxidative phosphorylation system (OXPHOS) is decreased in humans and mice with nonalcoholic steatohepatitis. Nitro-oxidative stress seems to be involved in its pathogenesis. The aim of this study was to determine whether fatty acids are implicated in the pathogenesis of this mitochondrial defect. In HepG2 cells, we analyzed the effect of saturated (palmitic and stearic acids) and monounsaturated (oleic acid) fatty acids on: OXPHOS activity; levels of protein expression of OXPHOS complexes and their subunits; gene expression and half-life of OXPHOS complexes; nitro-oxidative stress; and NADPH oxidase gene expression and activity. We also studied the effects of inhibiting or silencing NADPH oxidase on the palmitic-acid-induced nitro-oxidative stress and subsequent OXPHOS inhibition. Exposure of cultured HepG2 cells to saturated fatty acids resulted in a significant decrease in the OXPHOS activity. This effect was prevented in the presence of a mimic of manganese superoxide dismutase. Palmitic acid reduced the amount of both fully-assembled OXPHOS complexes and of complex subunits. This reduction was due mainly to an accelerated degradation of these subunits, which was associated with a 3-tyrosine nitration of mitochondrial proteins. Pretreatment of cells with uric acid, an antiperoxynitrite agent, prevented protein degradation induced by palmitic acid. A reduced gene expression also contributed to decrease mitochondrial DNA (mtDNA)-encoded subunits. Saturated fatty acids induced oxidative stress and caused mtDNA oxidative damage. This effect was prevented by inhibiting NADPH oxidase. These acids activated NADPH oxidase gene expression and increased NADPH oxidase activity. Silencing this oxidase abrogated totally the inhibitory effect of palmitic acid on OXPHOS complex activity. We conclude that saturated fatty acids caused nitro-oxidative stress, reduced OXPHOS complex half-life and activity, and decreased gene expression of mtDNA-encoded subunits. These effects were mediated by activation of NADPH oxidase. That is, these acids reproduced mitochondrial dysfunction found in humans and animals with nonalcoholic steatohepatitis.

High-fat diet decreases activity of the oxidative phosphorylation complexes and causes nonalcoholic steatohepatitis in mice.

Nonalcoholic fatty liver disease (NAFLD) is the most frequent histological finding in individuals with abnormal liver-function tests in the Western countries. In previous studies, we have shown that oxidative phosphorylation (OXPHOS) is decreased in individuals with NAFLD, but the cause of this mitochondrial dysfunction remains uncertain. The aims of this study were to determine whether feeding mice a high-fat diet (HFD) induces any change in the activity of OXPHOS, and to investigate the mechanisms involved in the pathogenesis of this defect. To that end, 30 mice were distributed between five groups: control mice fed a standard diet, and mice on a HFD and treated with saline solution, melatonin (an antioxidant), MnTBAP (a superoxide dismutase analog) or uric acid (a scavenger of peroxynitrite) for 28 weeks intraperitoneously. In the liver of these mice, we studied histology, activity and assembly of OXPHOS complexes, levels of subunits of these complexes, gene expression of these subunits, oxidative and nitrosative stress, and oxidative DNA damage. In HFD-fed mice, we found nonalcoholic steatohepatitis, increased gene expression of TNFα, IFNγ, MCP-1, caspase-3, TGFß1 and collagen α1(I), and increased levels of 3-tyrosine nitrated proteins. The activity and assembly of all OXPHOS complexes was decreased to about 50-60%. The amount of all studied OXPHOS subunits was markedly decreased, particularly the mitochondrial-DNA-encoded subunits. Gene expression of mitochondrial-DNA-encoded subunits was decreased to about 60% of control. There was oxidative damage to mitochondrial DNA but not to genomic DNA. Treatment of HFD-fed mice with melatonin, MnTBAP or uric acid prevented all changes observed in untreated HFD-fed mice. We conclude that a HFD decreased OXPHOS enzymatic activity owing to a decreased amount of fully assembled complexes caused by a reduced synthesis of their subunits. Antioxidants and antiperoxynitrites prevented all of these changes, suggesting that nitro-oxidative stress played a key role in the pathogenesis of these alterations. Treatment with these agents might prevent the development of NAFLD in humans.

Experience of the endoscopist increases detection rates of smaller size and higher histological grade polyps.

BACKGROUND: Adenoma and polyp detection rates (ADR and PDR, respectively) are important indicators of endoscopy quality, particularly in colorectal carcinoma screening. OBJECTIVE: To assess the influence of the endoscopist's experience on the ADR and PDR. PATIENTS AND METHODS: In this study, 9635 colonoscopies were screened during a 5-year period. Only 5738 were finally analyzed due to exclusion criteria. The endoscopists were separated in three groups of experience according to the number of colonoscopies performed in the past (yearly and total). The number of polyps and adenomas, as well as the size and histology of these polyps were recorded. RESULTS: The ADR and PDR were similar regardless of the experience of the endoscopist, but those with more experience clearly found more polyps of less than 10 mm (P = 0.01) and of less than 3 mm (P < 0.0001). Most of the differences were due to a higher number of flat polyps detected by the experienced group. This study also shows that more experienced endoscopists detect adenomas with more advanced histology (P < 0.0001). CONCLUSION: Even though the ADR and PDR are similar in all groups of endoscopists, the less experienced endoscopists could be missing some of the smaller polyps, sometimes with more advanced histology.

Pioglitazone leads to an inactivation and disassembly of complex I of the mitochondrial respiratory chain.

BACKGROUND: Thiazolidinediones are antidiabetic agents that increase insulin sensitivity but reduce glucose oxidation, state 3 respiration, and activity of complex I of the mitochondrial respiratory chain (MRC). The mechanisms of the latter effects are unclear. The aim of this study was to determine the mechanisms by which pioglitazone (PGZ), a member of the thiazolidinedione class of antidiabetic agents, decreases the activity of the MRC. In isolated mitochondria from mouse liver, we measured the effects of PGZ treatment on MRC complex activities, fully-assembled complex I and its subunits, gene expression of complex I and III subunits, and [3H]PGZ binding to mitochondrial complexes. RESULTS: In vitro, PGZ decreased activity of complexes I and III of the MRC, but in vivo only complex I activity was decreased in mice treated for 12 weeks with 10 mg/kg/day of PGZ. In vitro treatment of isolated liver mitochondria with PGZ disassembled complex I, resulting in the formation of several subcomplexes. In mice treated with PGZ, fully assembled complex I was increased and two additional subcomplexes were found. Formation of supercomplexes CI+CIII2+CIVn and CI+CIII2 decreased in mouse liver mitochondria exposed to PGZ, while formation of these supercomplexes was increased in mice treated with PGZ. Two-dimensional analysis of complex I using blue native/sodium dodecyl sulfate polyacrylamide gel electrophoresis (BN/SDS-PAGE) showed that in vitro PGZ induced the formation of four subcomplexes of 600 (B), 400 (C), 350 (D), and 250 (E) kDa, respectively. Subcomplexes B and C had NADH:dehydrogenase activity, while subcomplexes C and D contained subunits of complex I membrane arm. Autoradiography and coimmunoprecipitation assays showed [3H]PGZ binding to subunits NDUFA9, NDUFB6, and NDUFA6. Treatment with PGZ increased mitochondrial gene transcription in mice liver and HepG2 cells. In these cells, PGZ decreased intracellular ATP content and enhanced gene expression of specific protein 1 and peroxisome-proliferator activated receptor (PPAR)γ coactivator 1α (PGC-1α). CONCLUSIONS: PGZ binds complex I subunits, which induces disassembly of this complex, reduces its activity, depletes cellular ATP, and, in mice and HepG2 cells, upregulates nuclear DNA-encoded gene expression of complex I and III subunits.

Sp1 and Sp3 transcription factors mediate leptin-induced collagen α1(I) gene expression in primary culture of male rat hepatic stellate cells.

Mechanisms by which leptin stimulates collagen α(1)(I) [Col1a(I)] gene expression are unclear. The purposes of this study were to identify the trans-acting factors and cis-acting elements in Col1a(I) promoter involved in this effect as well as the pathways that are implicated. In primary cultures of rat hepatic stellate cells (HSCs), we measured the effects of leptin on Col1a(I) gene and protein expression and on the binding of nuclear proteins to the Col1a(I) promoter. We found that leptin increased Col1a(I) gene and protein expression in activated HSCs. Transient transfections showed that leptin exerted its effects through elements located between -220 and -112 bp of the Col1a(I) promoter. Gel retardation assays demonstrated that leptin induced the binding of transcription factors specific protein (Sp)-1 and Sp3 to two elements located between -161 and -110 bp of the Col1a(I) promoter. Leptin-induced Sp1/Sp3 phosphorylation, but this effect was suppressed by inhibiting or silencing Janus kinase-2, phosphatidylinositol-3-kinase, nonphagocytic adenine dinucleotide phosphate (NADPH) oxidase, or ERK1/2, by the use of antioxidants or catalase, or by preventing protein-aldehyde adduct formation. Leptin provoked oxidative stress, aldehyde-protein adduct formation, and increased gene expression of some components of the NADPH oxidase complex. In conclusion, in HSCs, leptin up-regulates Col1a(I) gene expression after activating NADPH oxidase, inducing oxidative stress, aldehyde-protein adduct formation, and ERK1/2 phosphorylation, which in turn activates Sp1/Sp3 and provokes the binding of these two factors to regulatory elements located between -161 and -110 bp of the Col1a(I) promoter. These findings may contribute to a better understanding of mechanisms involved in the leptin-induced liver fibrosis.

Protein-tyrosine phosphatases are involved in interferon resistance associated with insulin resistance in HepG2 cells and obese mice.

Insulin resistance is a risk factor for non-response to interferon/ribavirin therapy in patients with chronic hepatitis C. The aim of this study was to determine the role played by protein-tyrosine phosphatases (PTPs) in the absence of interferon-α (IFNα) response associated with insulin resistance. We induced insulin resistance by silencing IRS-2 or by treating HepG2 cells with tumor necrosis factor-α (TNFα) and analyzed insulin response by evaluating Akt phosphorylation and IFNα response by measuring Stat-1 tyrosine phosphorylation and 2',5'-oligoadenylate synthase and myxovirus resistance gene expression. The response to IFNα was also measured in insulin-resistant obese mice (high fat diet and ob/ob mice) untreated and treated with metformin. Silencing IRS-2 mRNA induces insulin resistance and inhibits IFNα response. Likewise, TNFα suppresses insulin and IFNα response. Treatment of cells with pervanadate and knocking down PTP-1B restores insulin and IFNα response. Both silencing IRS-2 and TNFα treatment increase PTP and PTP-1B activity. Metformin inhibits PTP and improves IFNα response in insulin-resistant cells. Insulin-resistant ob/ob mice have increased PTP-1B gene expression and activity in the liver and do not respond to IFNα administration. Treatment with metformin improves this response. In HepG2 cells, insulin resistance provokes IFNα resistance, which is associated with an increased PTP-1B activity in the liver. Inhibition of PTP-1B activity with pervanadate and metformin or knocking down PTP-1B reestablishes IFNα response. Likewise, metformin decreases PTP-1B activity and improves response to IFNα in insulin-resistant obese mice. The use of PTP-1B inhibitors may improve the response to IFNα/ribavirin therapy.

Melatonin improves mitochondrial respiratory chain activity and liver morphology in ob/ob mice.

In previous studies, we have shown that mitochondrial respiratory chain (MRC) activity is decreased in patients with nonalcoholic steatohepatitis and in ob/ob mice and that peroxynitrite plays a pathogenic role. The present study examined whether melatonin, a peroxynitrite scavenger, prevents: (i) the in vitro effects of peroxynitrite on normal mitochondrial proteins and (ii) the development of nonalcoholic liver disease, MRC dysfunction and proteomic changes found in the mitochondrial complexes from ob/ob mice. We studied MRC activity, assembly of mitochondrial complexes and its subunits in normal mitochondrial proteins exposed to peroxynitrite in the absence and presence of melatonin. The same studies were done in mitochondrial proteins from ob/ob mice untreated and treated with melatonin. Preincubation of mitochondrial proteins from wild-type mice with melatonin prevented 3-tyrosine nitration of these proteins, eliminated the reduction in the MRC activity, the defect in the assembly of mitochondrial complexes and degradation of their subunits induced by peroxynitrite in vitro. Moreover, treatment of ob/ob mice with 10 mg/kg/day melatonin for 12 wk reduced oxidative and nitrosative stress, prevented the loss of MRC activity, protected their complexes and subunits from degradation, and favored assembling of mitochondrial complexes. In addition, this treatment improved fatty liver, decreased hepatic triglyceride concentration and increased apolipoprotein B100 in liver tissue. In conclusion, melatonin prevents the effects of peroxynitrite on mitochondrial proteins in vitro and administration of melatonin to ob/ob mice normalizes liver morphology, mitochondrial dysfunction and assembly of MRC complexes.

Mitochondrial complex I subunits are decreased in murine nonalcoholic fatty liver disease: implication of peroxynitrite.

We investigate the cause of the low activity of mitochondrial complex I found in ob/ob mice with nonalcoholic fatty liver disease. In mitochondrial proteins from ob/ob mice, we assessed complex I activity, fully assembled complex I, and its subunits, oxygen consumption, gene expression of complex I subunits, and oxidative damage to DNA. In mitochondrial proteins from the liver of ob/ob mice, complex I activity, fully assembly of this complex and complex I subunits were markedly reduced. Likewise, gene expression of mitochondrial DNA-encoded subunits was significantly decreased in obese mice, but not nuclear DNA-encoded subunits. Treatment of obese mice with uric acid, anti-TNFalpha antibody or a mimic of manganese superoxide dismutase normalized all these abnormalities. "In vitro" addition of peroxynitrite to mitochondrial proteins from wild-type mice reproduced the abnormalities found in ob/ob mice (decreased complex I activity, the amount of fully assembled complex I, and its subunits, and mitochondrial oxygen consumption). Low activity of complex I found in ob/ob mice can be ascribed to a reduced amount of fully assembled complex, which may be attributed to degradation and reduced synthesis of its subunits by peroxynitrite. Exposure of mitochondrial proteins from normal mice to peroxynitrite reproduced the proteomic abnormalities present in ob/ob mice.

Fibronectin increases survival of rat hepatic stellate cells--a novel profibrogenic mechanism of fibronectin.

UNLABELLED: The aims of this study were to determine whether fibronectin increases survival of hepatic stellate cells (HSCs) in starving conditions, and to identify the signal transduction pathways involved in this effect. METHODS: Primary culture of rat HSCs were plated on fibronectin-uncoated or coated culture wells, and grown in the presence of 0.2% or 20% fetal calf serum. Cell apoptosis was measured by an ELISA procedure. Signal transduction pathways were analyzed by inhibiting major intracellular transduction pathways with appropriated inhibitors and by detecting phosphorylated proteins. RESULTS: Fibronectin increased survival of serum deprived HSCs. This effect was abrogated by the presence of the RGD peptide, by silencing FAK expression, and by inhibiting PI3K with LY294002 or wortmannin. Growth of HSCs on fibronectin induced integrin alpha5beta1 expression, tyr397, ser473, and ser136 phosphorylation of FAK, Akt, and Bad, respectively, and the binding of phosphorylated Bad to 14-3-3 proteins. Likewise, fibronectin increased Bcl2/Bax ratio and reduced release of mitochondrial cytochrome c into the cytoplasm, formation of apoptosome, and caspase 9 and 3 activity. These effects were avoided by treatment of cells with PI3K inhibitors. CONCLUSION: Fibronectin increases survival of HSCs via a pathway involving integrin alpha5beta1 receptors, FAK, PI3K, Akt and proteins of Bcl2 family.

Interferon alpha increases metalloproteinase-13 gene expression through a polyomavirus enhancer activator 3-dependent pathway in hepatic stellate cells.

BACKGROUND/AIMS: To determine the effects of IFNalpha on MMP-13 gene expression in primary culture of hepatic stellate cells. METHODS: We measured MMP-13 mRNA, MMP-13 protein, MMP-13 luciferase activity, binding of AP1 and PEA3 to DNA, and binding of PEA3 to Jak1 and Stat1. RESULTS: IFNalpha increased MMP-13 mRNA, MMP-13 protein, and luciferase activity in cells transfected either with a luciferase plasmid driven by the MMP-13 promoter or with the same plasmid in which the AP1 binding site has been mutated. IFNalpha induced the binding of nuclear proteins to a radiolabeled PEA3 probe, but not to a AP1 probe. Supershift assays demonstrated that PEA3 and Stat1 are implicated in the formation of this complex. Immunoprecipitation assays showed that PEA3 interacts physically with Stat1 and that IFNalpha treatment increases this interaction. Downregulation of PEA3 or JAK1 with appropriated siRNAs or mutation of the PEA3 binding site in the MMP-13 promoter abrogated the effects of IFNalpha on MMP-13 gene expression. Finally, IFNalpha induced the binding of PEA3 to JAK1, as well as PEA3 tyrosine and serine phosphorylation. CONCLUSIONS: IFNalpha determines the binding of PEA3 to JAK1 and its tyrosine phosphorylation. Activated PEA3 binds to MMP-13 promoter and activates its expression.

Effects of rosiglitazone on the liver histology and mitochondrial function in ob/ob mice.

UNLABELLED: Insulin resistance is present in almost all patients with nonalcoholic steatohepatitis (NAFLD), and mitochondrial dysfunction likely plays a critical role in the progression of fatty liver into nonalcoholic steatohepatitis. Rosiglitazone, a selective ligand of peroxisome proliferator-activated receptor gamma (PPARgamma), is an insulin sensitizer drug that has been used in a number of insulin-resistant conditions, including NAFLD. The aim of this study was to analyze the effects of rosiglitazone on the liver histology and mitochondrial function in a model of NAFLD. All studies were carried out in wild-type and leptin-deficient (ob/ob) C57BL/6J mice. Ob/ob mice were treated with 1 mg/kg/day, and activity of mitochondrial respiratory chain (MRC), beta-oxidation, lipid peroxidation, glutathione content in mitochondria, and 3-tyrosine-nitrated proteins in mitochondria were measured. In addition, histological and ultrastructural changes induced by rosiglitazone were also noted. Rosiglitazone treatment increased liver steatosis, particularly microvesicular steatosis. In these animals, mitochondria were markedly swollen with cristae peripherally placed. In ob/ob mice, this drug increased PPARgamma protein expression and lipid peroxide content in liver tissue and decreased glutathione concentration in mitochondria. Rosiglitazone suppressed the activity of complex I of the MRC in ob/ob mice, but did not affect beta-oxidation. 3-Tyrosine nitrated mitochondrial proteins, significantly increased in ob/ob mice, were not modified by rosiglitazone treatment. CONCLUSION: Treatment of ob/ob mice with rosiglitazone did not reverse histological lesions of NAFLD or improve MRC activity. On the contrary, rosiglitazone reduced activity of complex I and increased oxidative stress and liver steatosis.

Uric acid and anti-TNF antibody improve mitochondrial dysfunction in ob/ob mice.

The mechanisms responsible for low mitochondrial respiratory chain (MRC) activity in the liver of patients with nonalcoholic steatohepatitis are unknown. In this study, we examined the cause of this dysfunction in ob/ob mice. Forty-six mice were distributed in six groups: group I: C57BL/6J mice; group II: C57BL/6J Lep(-/-) mice (ob/ob); group III, ob/ob mice treated with manganese [III] tetrakis (5,10,15,20 benzoic acid) porphyrin (MnTBAP); group IV, ob/ob mice treated with IgG1 immunoglobulin; group V, ob/ob mice treated with anti-TNF antibody; group VI: ob/ob mice treated with uric acid. In liver tissue, we measured MRC activity, fatty acid beta-oxidation, tumor necrosis factor (TNF), inducible nitric oxide synthase (iNOS), 3-tyrosine-nitrated proteins, 3-tyrosine-nitrated mitochondrial proteins, including cytochrome c and ND4 subunit of complex I. MRC activity was decreased in ob/ob mice. TNF levels, iNOS protein expression, and tyrosine nitrated proteins were markedly increased in the liver of ob/ob mice. In these animals, mitochondrial proteins were markedly tyrosine nitrated, particularly the ND4 subunit of complex I and cytochrome c. Treatment of these animals with uric acid, a peroxynitrite scavenger, anti-TNF antibody, or MnTBAP decreased tyrosine nitrated proteins, improved the activity of MRC complexes, and led to a marked regression of hepatic steatosis and inflammation. In conclusion, MRC dysfunction and liver lesions found in ob/ob mice are likely to reflect the tyrosine nitration of mitochondrial proteins by peroxynitrite or a peroxynitrite-derivate radical. Increased hepatic TNF and iNOS expression might enhance peroxynitrite formation and inhibition of MRC complexes.

Factors associated with the presence of nonalcoholic steatohepatitis in patients with chronic hepatitis C.

OBJECTIVES: The aim of this study was to identify factors associated with the presence of nonalcoholic steatohepatitis (NASH) in patients with chronic hepatitis C (CHC). METHODS: We studied 98 patients with CHC [47 with NASH (group HCV/NASH), 51 without NASH (group HCV)] and 85 with NASH not infected with hepatitis C virus (HCV) (group NASH). We determined factors associated with the presence of NASH in patients with hepatitis C. RESULTS: Group HCV/NASH patients resembled those with NASH. Body mass index (BMI) was higher in group HCV/NASH than in group HCV, but was similar to group NASH. Most HCV/NASH patients had risk factors for NASH. In patients infected with HCV, NASH and NASH-related lesions were independently associated with BMI, while steatosis score was associated with HCV genotype 3 and BMI. Fibrosis stage was independently associated with steatosis, necroinflammatory activity index, and NASH lesions. CONCLUSION: While HCV genotype 3 infection and BMI are associated with the presence of steatosis in CHC, BMI is the only factor independently associated with the presence of NASH in these patients. We suggest that overweight-related factors might induce NASH in CHC patients.

Interleukin-6 increases rat metalloproteinase-13 gene expression through Janus kinase-2-mediated inhibition of serine/threonine phosphatase-2A.

Interleukin-6 (IL-6) increases metalloproteinase-13 (MMP-13) gene expression by increasing phosphorylated c-Jun and by inhibiting serine/threonine phosphatase-2A (PP2A) activity. We investigated the mechanisms by which IL-6 induces c-Jun phosphorylation and PP2A inactivation in Rat-1 fibroblasts. We show that IL-6 increased MMP-13 mRNA, phosphorylated c-Jun, and activator protein 1 (AP1) binding activity without increasing c-Jun-N-terminal kinase (JNK) activity. These effects did not seem to be mediated by ERK, p38 MAP kinase, phosphatidylinositol-3-kinase, calmoduline-dependent protein kinase, protein kinase C (PKC) or protein kinase A since inhibition with specific inhibitors did not abrogate these effects. IL-6 increases PP2A catalytic subunit tyrosine phosphorylation. Inhibition of the tyrosine kinase Jak2, with the specific inhibitor AG490, abrogated this effect. Likewise, this Jak2 inhibitor blocked the effects of IL-6 on c-Jun phosphorylation, AP1 binding activity and metalloproteinase-13 gene expression. We conclude that IL-6 increases MMP-13 gene expression by activation of Jak2, resulting in tyrosine phosphorylation of the catalytic subunit of PP2A, which in turn decreases PP2A activity and prolongs c-Jun phosphorylation.