transforming-growth-factor-beta and Hepatitis--Animal

Liver fibrosis is a severe, life-threatening clinical condition resulting from nonresolving hepatitis of different origins. IL-17A is critical in inflammation, but its relation to liver fibrosis remains elusive. We find increased IL-17A expression in fibrotic livers from HBV-infected patients undergoing partial hepatectomy because of cirrhosis-related early-stage hepatocellular carcinoma in comparison with control nonfibrotic livers from uninfected patients with hepatic hemangioma. In fibrotic livers, IL-17A immunoreactivity localizes to the inflammatory infiltrate. In experimental carbon tetrachloride-induced liver fibrosis of IL-17RA-deficient mice, we observe reduced neutrophil influx, proinflammatory cytokines, hepatocellular necrosis, inflammation, and fibrosis as compared with control C57BL/6 mice. IL-17A is produced by neutrophils and T lymphocytes expressing the Th17 lineage-specific transcription factor Retinoic acid receptor-related orphan receptor γt. Furthermore, hepatic stellate cells (HSCs) isolated from naive C57BL/6 mice respond to IL-17A with increased IL-6, α-smooth muscle actin, collagen, and TGF-β mRNA expression, suggesting an IL-17A-driven fibrotic process. Pharmacologic ERK1/2 or p38 inhibition significantly attenuated IL-17A-induced HSC activation and collagen expression. In conclusion, IL-17A(+) Retinoic acid receptor-related orphan receptor γt(+) neutrophils and T cells are recruited into the injured liver driving a chronic, fibrotic hepatitis. IL-17A-dependent HSC activation may be critical for liver fibrosis. Thus, blockade of IL-17A could potentially benefit patients with chronic hepatitis and liver fibrosis.

Topics: Actins; Adult; Animals; Carbon Tetrachloride Poisoning; Carcinoma, Hepatocellular; Chemical and Drug Induced Liver Injury; Collagen; Cytokines; Female; Gene Expression Regulation; Hemangioma; Hepatectomy; Hepatic Stellate Cells; Hepatitis B, Chronic; Hepatitis, Animal; Humans; Interleukin-17; Liver Cirrhosis; Liver Neoplasms; Male; MAP Kinase Signaling System; Mice; Mice, Knockout; Middle Aged; Neutrophils; Nuclear Receptor Subfamily 1, Group F, Member 3; Protein Kinase Inhibitors; Receptors, Interleukin-17; Recombinant Proteins; Th17 Cells; Transforming Growth Factor beta

The etiology of autoimmune liver disease is poorly understood. BALB/c mice deficient in the immunoregulatory cytokine TGF-beta1 spontaneously develop necroinflammatory liver disease, but the immune basis for the development of this pathology has not been demonstrated. Here, we show that BALB/c-TGF-beta1(-/-) mice exhibit abnormal expansion in hepatic mononuclear cells (MNCs) compared with wild-type littermate control mice, particularly in the T cell and macrophage lineages. To test whether lymphocytes of the adaptive immune system are required for the spontaneous development of necroinflammatory liver disease, BALB/c-TGF-beta1(-/-) mice were rendered deficient in B and T cells by crossing them with BALB/c-recombinase-activating gene 1(-/-) mice. BALB/c-TGF-beta1(-/-)/recombinase-activating gene 1(-/-) double-knockout mice showed extended survival and did not develop necroinflammatory liver disease. The cytolytic activity of BALB/c-TGF-beta1(-/-) hepatic lymphocytes was assessed using an in vitro CTL assay. CTL activity was much higher in BALB/c-TGF-beta1(-/-) hepatic MNCs compared with littermate control hepatic MNCs and was particularly pronounced in the CD4(+) T cell subset. Experimental depletion of CD4(+) T cells in young BALB/c-TGF-beta1(-/-) mice prevented the subsequent development of necroinflammatory liver disease, indicating that CD4(+) T cells are essential for disease pathogenesis in vivo. These data definitively establish an immune-mediated etiology for necroinflammatory liver disease in BALB/c-TGF-beta1(-/-) mice and demonstrate the importance of CD4(+) T cells in disease pathogenesis in vivo. Furthermore, TGF-beta1 has a critical role in homeostatic regulation of the hepatic immune system, inhibiting the development or expansion of hepatic cytolytic CD4(+) T cells.

Topics: Animals; Autoimmune Diseases; CD4-Positive T-Lymphocytes; Crosses, Genetic; Cytotoxicity, Immunologic; Female; Genetic Predisposition to Disease; Hepatitis, Animal; Immunity, Cellular; Lymphocyte Depletion; Male; Mice; Mice, Inbred BALB C; Mice, Knockout; Necrosis; T-Lymphocyte Subsets; Transforming Growth Factor beta; Transforming Growth Factor beta1

Autoimmune hepatitis (AIH) in humans arises spontaneously in genetically susceptible individuals and is associated with the presence of Th1 cells in the liver. The understanding of AIH has advanced more slowly than that of other organ-specific autoimmune diseases, however, largely because of the lack of an appropriate animal model. We now describe a new mouse model characterized by spontaneous development of necroinflammatory hepatitis that is restricted by genetic background. Mice deficient in the immunomodulatory cytokine TGF-beta1 were extensively back-bred to the BALB/c background. The BALB/c background dramatically modified the phenotype of TGF-beta1(-/-) mice: specifically, BALB/c-TGF-beta1(-/-) mice developed a lethal necroinflammatory hepatitis that was not observed in TGF-beta1(-/-) mice on a different genetic background. BALB/c background TGF-beta1(-/-) livers contained large numbers of activated CD4(+) T cells that produced large quantities of IFN-gamma, but little IL-4, identifying them as Th1 cells. BALB/c background TGF-beta1(-/-)/IFN-gamma(-/-) double knockout mice, generated by cross-breeding, did not develop necroinflammatory hepatitis, demonstrating that IFN-gamma is mechanistically required for its pathogenesis. This represents the first murine model of hepatitis that develops spontaneously, is restricted by genetic background, and is dependent upon the Th1 cytokine IFN-gamma, and that thus recapitulates these important aspects of AIH.

Topics: Animals; Autoimmune Diseases; Cell Differentiation; Crosses, Genetic; Genetic Predisposition to Disease; Hepatitis, Animal; Interferon-gamma; Liver; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Inbred Strains; Mice, Knockout; Necrosis; Survival Rate; Th1 Cells; Th2 Cells; Transforming Growth Factor beta; Transforming Growth Factor beta1

Tumor necrosis factor (TNF)alpha, a pivotal cytokine involved in inflammation, is produced primarily by Kupffer cells in the liver. It has been shown that inactivation of Kupffer cells prevents alcohol-induced liver injury; therefore, the purpose of this study was to determine if neutralizing anti-TNF-alpha antibody is also effective. Male Wistar rats were exposed to ethanol (11 to 12 g x kg(-1) x d[-1]) continuously for up to 4 weeks via intragastric feeding using an enteral feeding model. Before ethanol exposure, polyclonal anti-mouse TNF-alpha rabbit serum was injected (2.0 mg/kg intravenously). There were no significant differences in body weight, mean ethanol concentration, or cyclic patterns of ethanol in urine when ethanol- and ethanol plus antibody-treated groups were compared. Expression of TNF-alpha and macrophage inflammatory protein 2 (MIP-2) messenger RNA (mRNA), determined using reverse transcription-polymerase chain reaction, was three- to four-fold higher in livers of ethanol-treated rats than in those of rats fed an ethanol-free, high-fat control diet. In addition, MIP-2 levels were also elevated when detected by Northern blot analysis. Anti-TNF-alpha antibody did not affect expression of mRNA for interleukin (IL) 1alpha, IL-6, transforming growth factor beta1, or TNF-alpha. However, MIP-2 mRNA expression, which is regulated by TNF-alpha, was decreased significantly by anti-TNF-alpha antibody treatment. Serum aspartate transaminase levels were elevated in ethanol-treated rats to 136 +/- 12 IU/L after 4 weeks but only reached 90 +/- 5 IU/L (P < .05) in rats treated with anti-TNF-alpha antibody. The hepatic inflammation and necrosis observed in ethanol-fed rats were attenuated significantly by antibody treatment, and steatosis was not. These results support the hypothesis that TNF-alpha plays an important role in inflammation and necrosis in alcohol-induced liver injury and that treatment with anti-TNF-alpha antibody may be therapeutically useful in this disease.

Topics: Animals; Antibodies; Aspartate Aminotransferases; Blotting, Northern; Chemokine CXCL2; Chemotactic Factors; Dietary Fats; DNA Primers; Ethanol; Hepatitis, Animal; Interleukin-1; Interleukin-6; Liver Cirrhosis, Alcoholic; Male; Monokines; Rabbits; Rats; Rats, Wistar; RNA, Messenger; Transforming Growth Factor beta; Tumor Necrosis Factor-alpha