D-Galactosamine-induced mouse hepatic apoptosis: Possible involvement withtumor necrosis factor, but not with caspase-3 activity

We investigated whether tumor necrosis factor (TNF) and caspase-3 activity are involved in the induction of hepatocellular apoptosis in D-galactosamin e (D-GalN)-induced hepatotoxicity in mice. Acute hepatotoxicity was induced by the intraperitoneal injection of D-GalN into female BALB/c mice. D-GalN (0.75-3.0 g/kg) increased the serum glutamate pyruvate transaminase (s-GPT ) activity and the percentage of liver DNA fragmentation, an indicator of h epatotoxicity, after 48 h, in a dose-dependent manner. Furthermore, after D -GalN (3.0 g/kg) administration, increased liver DNA fragmentation was dete cted biochemically at 24 h, then increased s-GPT activity accompanied by in creased liver DNA fragmentation was observed after 48 h. The serum TNF (s-T NF) level and the TNF mRNA expression in the liver after D-GalN (3.0 g/kg, i.p,) administration were examined by an ELISA kit and reverse transcriptio n polymerase chain reaction (RT-PCR), respectively, to investigate the rela tion between the s-GPT activity and liver DNA fragmentation. The s-TNF leve l and TNF mRNA expression in the liver after D-GalN (3.0 g/kg) administrati on were detected earlier than liver DNA fragmentation, then increased with time. However, there was almost no association of caspase-3 activity with t he increase in liver DNA fragmentation. Increases in the s-TNF level, TNF m RNA expression and the percentage of DNA fragmentation in the liver and s-G PT activity were inhibited by dexamethasone (Dex; 0.4-2.5 mg/kg, i.p,) in a dose-dependent manner. Based on these findings, it was considered that the intracellular apoptosis signal in D-GalN-induced hepatotoxicity in mice di d not depend on caspase-3 activity and that other signals mediated by TNF m ay be involved.