Influence of tumor necrosis factor-alpha and silibin on the cytotoxic action of alpha-amanitin in rat hepatocyte culture

Tumor necrosis factor-alpha is assumed to play a role in toxic liver damage . We examined whether exogenous tumor necrosis factor-alpha must be present for alpha-amanitin cytotoxicity in rat hepatocyte culture, alpha-Amanitin at a concentration of 0.1 mu M, which is close to that found in intoxicated patients, inhibits RNA and protein synthesis within 12 h but cytotoxicity only occurs after a latency period and is pronounced at 36 h after the star t of treatment. Tumor necrosis factor-alpha is not indispensable for the de velopment of cytotoxicity but aggravates it and leads to a time shift towar ds earlier times. Lipid peroxidation is low with alpha-amanitin alone even at 36 h but markedly increased by cotreatment with tumor necrosis factor-al pha. The antioxidant silibin prevents the effect of tumor necrosis factor-a lpha, indicating an involvement of reactive oxygen species. alpha-Amanitin alone does not increase but dose-dependently inhibits the expression of the antioxidant enzyme manganous superoxide dismutase and decreases the induci ng effect of TNF-alpha on the expression of this enzyme. The gene expressio n of endogenous tumor necrosis factor-alpha in the hepatocytes is not incre ased but rather inhibited by alpha-amanitin treatment. The results suggest that alpha-amanitin causes delayed cytotoxicity following rapid inhibition of RNA and protein synthesis and that tumor necrosis factor-alpha shortens the latency period and aggravates the cytotoxicity by a mechanism which may involve reactive oxygen species. (C) 1999 Academic Press.