Pioglitazone ameliorates nonalcoholic steatohepatitis by down-regulating hepatic nuclear factor-kappa B and cyclooxygenases-2 expression in rats

摘要

Background Pioglitazone is effective in nonalcoholic steatohepatitis (NASH),but the mechanisms of action are not completely understood.This study was designed to investigate the effects of pioglitazone on hepatic nuclear factor-kappa B (NF-κB) and cyclooxygenases-2 (COX-2) expression in NASH rats.Methods Thirty Sprague-Dawley male rats were randomly assigned to a control group (n=10),NASH group (n=10),and pioglitazone treatment group (n=10).Liver tissues were processed for histology by hematoxylin & eosin and Masson stained.Serum alanine aminotransferase (ALT),cholesterol,triglyceride,fasting blood glucose (FBG),fasting insulin (FINS) levels and biochemical parameters of antioxidant enzyme activities,tumor necrosis factor alpha (TNF-α),prostaglandin E2 (PGE2) levels in serum and liver were measured.The mRNA and protein expression of peroxisome proliferator-activated receptor gamma (PPARy),NF-κB and COX-2 were determined by real-time polymerase chain reaction,Westem blotting and immunohistochemistry.One-way analysis of variance (ANOVA) and Wilcoxon's signed-rank test was used for the statistical analysis.Results There were severe steatosis,moderate inflammatory cellular infiltration and fibrosis in NASH rats.After pioglitazone treatment,steatosis,inflammation and fibrosis were significantly improved compared with the NASH group(X2=20.40,P ＜0.001; )X2=20.17,P ＜0.001; X2=13.98,P=0.002).Serum ALT,cholesterol,triglyceride,FBG,FINS levelswere significantly elevated in the NASH group (P ＜0.05).In the NASH group,total anti-oxidation competence (T-AOC),superoxide dismutase (SOD),catalase (CAT),glutathione peroxidase (GSH-PX) and malondialdehyde (MDA) levels inserum and liver were conspicuous disordered than those parameters in the control group.Meanwhile,TNF-α and PGE2levels in serum and liver were significantly increased compared with the control group.Immunohistochemistry showedNF-KB and COX-2 expression in liver was significantly elevated.However,PPARy level was decreased in the NASHgroup.Real-time PCR and Western blotting revealed mRNA and protein expression of COX-2 were increased in theNASH group compared with the control group (0.57±0.08 vs.2.83±0.24; 0.38±0.03 vs.1.00±0.03,P＜0.001 and,P=0.004,respectively).After pioglitazone intervention,all of those parameters markedly improved (P ＜0.05 or P ＜0.01 ).Conclusion Down-regulating hepatic NF-κB and COX-2 expression,at least in part,is one of the possible therapeutic mechanisms of pioglitazone in NASH rats.