Fas receptor-deficient lpr mice are protected against acetaminophen hepatotoxicity due to higher glutathione synthesis and enhanced detoxification of oxidant stress.

Acetaminophen (APAP) overdose is a classical model of hepatocellular necrosis; however, the involvement of the Fas receptor in the pathophysiology remains controversial. Fas receptor-deficient (lpr) and C57BL/6 mice were treated with APAP to compare the mechanisms of hepatotoxicity. Lpr mice were partially protected against APAP hepatotoxicity as indicated by reduced plasma ALT and GDH levels and liver necrosis. Hepatic Cyp2e1 protein, adduct formation and hepatic glutathione (GSH) depletion were similar, demonstrating equivalent reactive metabolite generation. There was no difference in cytokine formation or hepatic neutrophil recruitment. Interestingly, hepatic GSH recovered faster in lpr mice than in wild type animals resulting in enhanced detoxification of reactive oxygen species. Driving the increased GSH levels, mRNA induction and protein expression of glutamate-cysteine ligase (gclc) were higher in lpr mice. Inducible nitric oxide synthase (iNOS) mRNA and protein levels at 6h were significantly lower in lpr mice, which correlated with reduced nitrotyrosine staining. Heat shock protein 70 (Hsp70) mRNA levels were substantially higher in lpr mice after APAP.

CONCLUSIONS

Our data suggest that the faster recovery of hepatic GSH levels during oxidant stress and peroxynitrite formation, reduced iNOS expression and enhanced induction of Hsp70 attenuated the susceptibility to APAP-induced cell death in lpr mice.