The Effects Of Nf-κB And Oxidative Stress In The Pathogenesis Of Alcoholic Fatty Liver And Its Suppression By Silymarin

Background The mechanisms by which ethanol causes fatty liver have notcompletely been clear yet. Ethanol-induced oxidative stress and effects of cytokineappear to play a major role in alcoholic fatty liver. Nuclear factor-kappa B (NF-κB) is aubiquitous transcription factor that is activated by a variety of cytokines,and is a keyregulator in the inflammatory response to stimulus. Emerging attention has beenfocused on the regulation and function of NF-κB during liver injury. NF-κB activationhave been implicated as mediators of alcoholic fatty liver. Silymarin which is a safe,stable and effective liver protective drugs has a strong antioxidant effect, but itsmechanisms of action have still not been well established. Therefore, to establish themodel of alcoholic fatty liver, clarify the effects of NF-κB and oxidative stress inpathogenesy of alcoholic fatty liver and explore the role of silymarin on oxidative stressand NF-κB expression in alcoholic fatty liver are important.Objective To establish the model of alcoholic fatty liver and investigate the effects ofNF-κB and oxidative stress in pathogenesy of alcoholic fatty liver and explore the roleof silymarin on oxidative stress and NF-κB expression in alcoholic fatty liver.Methods The model of rat’s alcoholic fatty liver was induced by intragastric infusion ofethanol and high-fat diet for six weeks. All rats were randomly divided into normalcontrol group(n=10),model group(n=15) and silymarin groups(100mg/kg,150mg/kg,200 mg/kg; n=15, respectively). The normal control group received normal saline by gavage,and the others were prepared with ethanol administration by gavage twice a day. Thedaily doses of ethanol for the rats of the model and silymarin groups were6g/kg/d inthe first week and then increased progressively every week up to a maximum of8g/kg/d in a further5weeks. In the silymarin groups, silymarin was gavaged two hoursafter the administration of the first ethanol every day at the doses of100mg/kg/d,150mg/kg/d and200mg/kg/d. During the experiment, general appearanceof rats was observed. At the end of experiment,all of the rats were anesthetized andsacrificed.Histopathological changes were assessed by hematoxylin and eosin(HE)staining.The activities of alanine transarninase(ALT) and aspartateaminotransferase(AST), the levels of total bilirubin(TBIL),total cholesterol(TC) andtriglyceride(TG) in serum were detected with routine laboratory methods using anautoanalyzer. The activities of superoxide dismutase (SOD) and glutathioneperoxidase(GPx) and the level of malondialdehyde (MDA) in liver homogenates weremeasured by spectrophotometry. The TG content in liver tissue was determined byspectrophotometry. The expression of nuclear factor-κB (NF-κB), intercellular adhesionmolecule-1(ICAM-1) and interleukin-6(IL-6) in the liver were analyzed byimmunohistochemistry.Results At the end of the6th week, alcohol could induce obvious steatosis of liver.Compared with normal control group, a greater accumulation of fat droplets, variousdegrees of diffuse hepatic steatosis and intralobular inflammation could be foundobviously in model group. The activities of AST and ALT were increased in modelgroup(P<0.05and P<0.01,respectively) compared with normal control group. Similarly,the levels of TBIL and TG were significantly higher in model group than those innormal control group(P<0.05and P<0.01,respectively). Compared with normal controlgroup，the MDA content in liver homogenates was remarkably higher and SOD and GPx activities were markedly lower in model group(P<0.01).The level of TG wassignificantly higher in model group than that in normal control group(P<0.01).Theexpression level of NF-κB P65,ICAM-1and IL-6in rat liver was also notablelyincreased in model group compared with normal control group(P<0.01). Compared withmodel group, silymarin(150mg/kg,200mg/kg) effectively improved histologicaldamage situation(P<0.05and P<0.01,respectively).The activities of ALT and AST andthe level of TBIL in silymarin treatment group（200mg/kg）were markedly lower than inmodel group(P <0.05). Compared with model group,silymarin（100mg/kg,150mg/kg,200mg/kg） notablely decreased MDA content（P<0.01）and increased GPx activity(P<0.05),and silymarin （150mg/kg,200mg/kg） remarkably increased SOD activity（P<0.01）. Silymarin（150mg/kg,200mg/kg）significantly decreased TG content in livertissue compared with model group(P<0.01).Additionally, compared with model group,silymarin（150mg/kg,200mg/kg） markedly downregulated the expression of NF-κBP65, ICAM-1and IL-6in liver tissue（P<0.01）.Conclusions1.NF-κB and oxidative stress may have a role in the pathogenesis ofalcoholic fatty liver.2.Silymarin’s protective effects on alcoholic fatty liver may berelated to inhibiting the expression of NF-κB and alleviating oxidative stress.