The Immune Mechanism In Alcoholic Liver Disease

Chronic alcohol consumption leads to alcoholic liver disease(ALD).ALD presents as a broad spectrum of disorders,ranging from simple fatty liver to more severe forms of liver injury,including alcoholic hepatitis(AH),cirrhosis,and super imposed hepatocellular carcinoma(HCC).The pathogenesis of ALD is complicated,including the affect on various types of cells in the liver and gut via alcohol and its toxic metabolic product,production of reactive oxygen species(ROS),and inflammatory cascade response.Several risk factors for ALD have been identified.These include aflatoxin,obesity,and hepatitis virus infection.In addition to metabolic system,immune system also participate in the progress of ALD.Early studies indicated that ethanol consumption leaded to elevation of hepatic LPS levels,which target CD14/TLR4 receptors that are elevated after ethanol consumption,leading to production of proinflammatory cytokines such as IL-6,TNF-?,IL-1? and ROS,and subsequent liver injury,and then recruitment of NKT cells and neutrophils,leading to the progress of ALD.In addition,alcohol inhibition of NK/IFN-y could be an important mechanism contributing to alcohol-induced liver fibrosis and alcohol acceleration of liver fibrosis.However,little is known about the potential immunological mechanisms by which ethanol affects tumor progression,especially the changes of immune cells and the interactive mechanisms between cells.In our study,we used two animal models for exploring these details.The main results in the study including the two aspects are shown as followed.1.Chronic alcohol consumption promotes diethylnitrosamine-induced hepatocarcinogenesis via immune disturbances Here,adult male mice were administered multiple doses of diethylnitrosamine(DEN).Four and a half months later,the DEN-treated mice were placed on a liquid Lieber-DeCarli control diet or diet containing 5%ethanol for 2.5 months.At the end of the study,the data showed that ethanol feeding exacerbates the progression of hepatic tumors(characterized by the ratio of liver weight to body weight,and the tumor volume and diameter)in DEN-treated mice.Mechanistically,compared with the pair-fed mice in the DEN + C group,the mice in the DEN + E group exhibited significantly higher ALT and hepatic mRNA levels of IL-6 and IL-17A.Chronic alcohol consumption aggravates inflammation.Notably,compared with pair-fed mice in the DEN + C group,mice in the DEN + E group showed more fibrous septa in liver sections,as visualized by Sirius red staining.The mRNA expression of the fibrosis-related genes CollA1,MMP2,a-SMA,GFAP and TIMP1 and the EMT-related genes snail,E-cadherin,and MMP9 in the liver were higher in the DEN+E group than in the DEN+C group.These data indicated chronic alcohol consumption aggravated inflammation,fibrosis,and epithelial-mesenchymal transition(EMT)in the pathological process of HCC.Besides,chronic alcohol consumption decreased the number of antitumor CD8+ T cells but increased the number of tumor-associated macrophages(TAMs)in the liver in DEN-initiated tumorigenesis.Moreover,TAMs were prone to be M2 phenotype after alcohol consumption.Conclusions:These data demonstrate that chronic alcohol consumption exacerbates DEN-induced hepatocarcinogenesis by enhancing protumor immunity via increasing tumor-associated macrophage infiltration,impairing antitumor immunity via reducing antitumor CD8+ T cells,and aggravating hepatic pathological injury.2.Suppression of NK cell activity by regulatory NKT10 cells in alcoholic liver diseaseSince IFN-y is an important effector molecule produced by NK cells,and alcohol inhibition of NK/IFN-y could be an important mechanism contributing to liver fibrosis.Here,using a chronic plus single-binge ethanol consumption mouse model,we depleted the NK cells in the C57BL/6 female mice using anti-asialo GM1(AsGM1)antibody.Mice receiving anti-AsGM1 antibody displayed decreased serum alanine aminotransferase(ALT)levels but higher hepatic triglyceride(TG)levels and pan-lobular steatosis.Meanwhile,GKO mice displayed significantly more severe liver damageand steatosisthan WT mice.INF-y could clearly downregulate the expression levels of several lipogenesis(Srebp-1,Fas,,Acc,Gpat and Scdl)and fatty acid uptake(Fat)genes in primary hepatocytes in a dose-dependent manner in vitro.These data hinted that NK cells and IFN-? played protective roles against liver steatosis in alcoholic steatohepatitis.Besides,we found that IL-10-/-mice displayed increase in the frequency,absolute number,and function of hepatic NK cells compared with WT mice.Meanwhile,liver damage and steatosis were obviously alleviated in IL-10-/-mice compared with WT controls.Furthermore,the depletion of NK cells in ethanol-exposed IL-10-/-mice diaplayed severe liver injury and steatosis.These data demonstrated that IL-10 is upstream of NK cells and is required for the suppression of the recruitment and functions of NK cells and promotes alcoholic steatohepatitis.Prvious research in our lab showed that iNKT-derived IL-10 increased notably following excessive alcohol consumption(unpublished data).So we adoptively transferred hepatic iNKT cells from 10-day ethanol-containing diet-fed WT or IL-10-/-mice into Ja18-/-mice undergoing chronic-binge treatment.As expected,the mice that received WT iNKT cells showed decreases in the frequency,absolute number,degranulation and IFN-? release of hepatic NK cells compared with controls,accompanied by significantly more severe alcohol-induced liver injury and steatosis.However,when Ja18-/-mice received the transfer of IL-10-deficient iNKT cells,the number and functions of NK cells were restored,and the pathogenesis of alcoholic steatohepatitis was alleviated.These data straightway provide evidence that IL-10 from iNKT cells antagonizes the protective role of NK cells in alcoholic steatohepatitis.Conclusions:Our study demonstrate that NK cells and IFN-? play protective roles against alcoholic liver steatosis in a chronic plus single-binge ethanol consumption mouse model.IL-10 produced from a regulatory subset of iNKT cells is responsible for the suppression of the protective roles of hepatic NK cells and contributes to the development of alcoholic liver steatosis.