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 microM, 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 start of treatment. Tumor necrosis factor-alpha is not indispensable for the development of cytotoxicity but aggravates it and leads to a time shift towards earlier times. Lipid peroxidation is low with alpha-amanitin alone even at 36 h but markedly increased by cotreatment with tumor necrosis factor-alpha. The antioxidant silibin prevents the effect of tumor necrosis factor-alpha, 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 inducing effect of TNF-alpha on the expression of this enzyme. The gene expression of endogenous tumor necrosis factor-alpha in the hepatocytes is not increased 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.
El-Bahay
C
C
Institute of Toxicology, University of Düsseldorf, Düsseldorf, Germany.
Gerber
E
E
Horbach
M
M
Tran-Thi
Q H
QH
Röhrdanz
E
E
Kahl
R
R
D000546:Amanitins / Q000633:toxicity*; D000818:Animals; D015152:Blotting, Northern; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D008099:Liver / Q000166:cytology* / Q000187:drug effects; D008297:Male; D014176:Protein Biosynthesis; D012313:RNA / Q000032:analysis / Q000302:isolation & purification; D051381:Rats; D017208:Rats, Wistar; D012838:Silymarin / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology / Q000502:physiology*
D000546:Amanitins; D012838:Silymarin; D014409:Tumor Necrosis Factor-alpha; D012313:RNA; D013482:Superoxide Dismutase