| Background and Aims: Alcoholic liver disease (ALD) is a major causeof morbidity and mortality worldwide. The spectrum of ALD ranges fromfatty liver to hepatic inflammation, necrosis, progressive fibrosis andhepatocellular carcinoma. Although it is now well established that the riskof developing ALD increases with increasing alcohol consumption, it alsois known that not all alcoholics develop clinically overt alcoholic liverinjury. It is presumed that other factors, such as sex, geneticcharacteristics, and environmental influences play a role in the genesis ofALD. This study examined the possible role of endotoxemia (fromincreased gut permeability) as a trigger factor of hepatic fibrosis inalcoholics by using a rat model of chronic alcohol feeding.Methods: Forty eight Sprague-Dawley rats were randomly divided asfour groups and fed isocaloric Liber-DeCarli liquid diets±alcohol for8weeks or10weeks. Plasma concentrations of LPS in portal veins fromthese rats were determined by spectrophotometric method. Liver samplesfrom rats were examined for TLR4and TGF-β1mRNA by in situhybridization. Immunohistochemistry was used to determine FSP-1andvimentin for identification of HSC while F4/80for recognition of Kupffercells in serial sections of liver tissues. Computer image analysis was performed to measure the integrated optimal density (IOD) ofFSP-1-positive HSC and TLR4mRNA-positive cells. Collagen I andα-SMA protein from liver samples were determined by Western blotwhile IL-1, IL-6, TNF-α and TGF-β1mRNA detected by RT-PCR.Histological characteristics were evaluated by H and E staining andMasson Trichrome stain.Results: Liver tissues stained with Masson’s Trichrome staining hasshowed that there was a perisinusoidal fibrosis in rats fed ethanol for10weeks compared with normal food-fed rats, which was consistent withcollagen I stain by Western blot. Immunohistochemical stain showedthere were abundant activated HSC and some Kupffer cells in livers ofrats fed ethanol for10weeks, but a few HSC were seen in rats fed normalfood. There were significantly higher LPS levels in portal veins inalcohol-fed rats for10weeks compared with rats fed the control diet for10weeks, but LPS was not increased in alcohol-fed rats for8weeks,suggesting chronic drinking of alcohol increasing gut permeability. In situhybridization analysis showed that a significant increase of TLR4mRNAcould be detected in abundant hepatocytes and some activated HSC andKupffer cells in livers of rats fed ethanol diet for10weeks, but in fewerendothelial cells of central vein or hepatocytes in either normal food-fedrats for10weeks or ethanol-fed rats for8weeks. Bivariate correlationanalysis showed that there was a positive correlation between the expression intensity of TLR4mRNA in livers and the levels of plasmaLPS in the portal vein of rats fed ethanol for10weeks(r=0.856;p<0.05), furthermore, the expressions of proinflammatorycytokine mRNA including IL-1, IL-6, and TNF-α as well as profibrogenicfactor TGF-β1mRNA were increased in liver samples of rats fed ethanolfor10weeks compared with rats fed normal food.Conclusion:The plasma LPS levels in portal vein of rats are significantlyincreased in chronic drinking of alcohol, which activates TLR4signalingpathway of Kupffer cells and HSC in liver of these rats. Theproinflammatory cytokines and TGF-β1as key gene products in responseto LPS-TLR4pathway can activate HSC, which may further result inhepatic fibrosis. |
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