Elevated level of serum Mn-superoxide dismutase in patients with primary biliary cirrhosis: possible involvement of free radicals in the pathogenesis in primary biliary cirrhosis.

Serum Mn-superoxide dismutase (Mn-SOD) was determined in patients with various liver diseases including 31 patients with primary biliary cirrhosis (PBC), 46 with hepatocellular carcinoma (HCC), 17 with liver cirrhosis (LC), 23 with chronic hepatitis (CH) and 12 patients with obstructive jaundice with an enzyme-linked immunosorbent assay using a specific monoclonal antibody. The serum level in patients with PBC (407 +/- 35 ng/ml, mean +/- SEM; n = 31) was significantly increased (p less than 0.01) compared with those of other liver diseases. Mn-SOD level did not correlate with total bilirubin level, gamma-glutamyl transpeptidase activity, alkaline phosphatase activity, alanine aminotransferase activity, IgM, or with ceruloplasmin level in the sera of the patients. When the patients with PBC were histologically subdivided into four groups according to Scheuer's classification (Scheuer PJ. Primary biliary cirrhosis. In: Scheuer PJ, ed. Liver biopsy interpretation. 3rd ed. London: Bailliere Tindall, 1980:47-56), a high level of serum Mn-SOD was noticed in the early stage as well as in the advanced stage of the disease. Immunoblot analysis confirmed the reactivity and specificity of the monoclonal antibody to the enzyme protein in the patients' sera. Immunostaining of a liver biopsy specimen from the patients with PBC revealed increased expression of the enzyme protein in damaged epithelial cells of interlobular bile ducts, bile ductules, and degenerated hepatocytes. These data suggested that free radicals including superoxide anion are possibly involved in the pathogenesis of the disease and Mn-SOD may play some role in a protection against the superoxide anion.