Kupffer cell-derived cytokines are believed to play pivotal paracrine roles in the pathogenesis of alcoholic liver disease (ALD). To evaluate this hypothesis, Kupffer cell gene expression of tumor necrosis factor-alpha ( m a ) , interleukin (IL)-6, and transforming growth factor-beta 1 (TGFP1) were directly examined in the rat model of ALD. Kupffer cells were isolated from the model after 10 and 17 weeks of intragastric ethanol infusion. These two durations resulted in focal hepatocellular in- jury and liver fibrogenesis, respectively. Oxidative stress as assessed by the hepatic level of thiobarbituric acid reacting substances, was evident at 10 weeks but more pronounced at 17 weeks. The steady state messenger RNA (mRNA) levels of the cytokines were examined by Northern blot analysis using RNA samples from freshly isolated Kupffer cells, and the release of the cyto- kines was quantitated ex uiuo using a 3-day culture. The mRNA levels of TNFa and TGFPl were significantly increased by 183% and 204% at 10 weeks and 231% and 295% at 17 weeks in the ethanol-fed rats, respectively.
Ex uiuo release of T " activity by control Kupffer cells was undetectable or very low (<2U/105 celldl8 hours) at both time points, but the cells from the ethanol-fed animals secreted appreciably more TNF (27.8 2 7.6 U at 10 weeks and 40.4 2 10.3 U at 17 weeks). The release of the latent TGFPl protein was also coordinately increased by 143% at 10 weeks and 238% at 17 weeks. IL-6 mRNA expression was minimal at 10 weeks, but enhanced most prominently (790%) at 17 weeks, with the ex uiuo release of this cytokine increased 4-fold at the latter time point. These results show coordinate induction of TNFcy, TGFP, and IL-6 expression by Kupffer cells in progression of experimental ALD and support their paracrine roles in the ALD pathogenesis. In particular, the marked induction of Kupffer cell IL-6 gene expres-Abbreviations: ALD, alcoholic liver disease; TNFa, tumor necrosis factoralpha; IL, interleukin; TGF, transforming growth factor; mRNA, messenger RNA.