Mechanism of Liver Injury during Obstructive Jaundice: Role of Nitric Oxide, Splenic Cytokines, and Intestinal Flora

To elucidate the roles of enteric bacteria and immunological interactions among liver, spleen and intestine in the pathogenesis of liver injury during obstructive jaundice, we studied the effects of antibiotics and splenectomy on bile-duct-ligated C57BL mice. When animals were subjected to bile-duct-ligation (BDL), plasma levels of bilirubin, alanine aminotransferase and aspartate aminotransferase increased markedly. However, the increases in plasma transaminases were significantly lower in splenectomized or antibiotics-treated groups than in the control BDL group. Histological examination revealed that liver injury was also low in the two groups. BDL markedly increased plasma level of interferon-γ (IFN-γ) and the expression of inducible nitric oxide synthase (iNOS) in liver and spleen. These changes were suppressed either by splenectomy or administration of antibiotics. Kinetic analysis revealed that BDL-induced liver injury and the increase of interleukin-10 (IL-10) and INF-γ were lower in iNOS(−/−) than in wild type animals. BDL markedly increased the expression of IgA in colonic mucosa. These observations suggest that enteric bacteria, nitric oxide and cytokines including IFN-γ and IL-10 derived from spleen and intestines form a critical network that determines the extent of liver injury during obstructive jaundice.