Acetaminophen-Induced Hepatotoxicity and Protein Nitration in Neuronal Nitric-Oxide Synthase Knockout Mice

Abstract

In overdose acetaminophen (APAP) is hepatotoxic. Toxicity occurs by metabolism to N-acetyl-p-benzoquinone imine, which depletes GSH and covalently binds to proteins followed by protein nitration. Nitration can occur via the strong oxidant and nitrating agent peroxynitrite, formed from superoxide and nitric oxide (NO). In hepatocyte suspensions we reported that an inhibitor of neuronal nitric-oxide synthase (nNOS; NOS1), which has been reported to be in mitochondria, inhibited toxicity and protein nitration. We recently showed that manganese superoxide dismutase (MnSOD; SOD2) was nitrated and inactivated in APAP-treated mice. To understand the role of nNOS in APAP toxicity and MnSOD nitration, nNOS knockout (KO) and wild-type (WT) mice were administered APAP (300 mg/kg). In WT mice serum alanine aminotransferase (ALT) significantly increased at 6 and 8 h, and serum aspartate aminotransferase (AST) significantly increased at 4, 6 and 8 h; however, in KO mice neither ALT nor AST significantly increased until 8 h. There were no significant differences in hepatic GSH depletion, APAP protein binding, hydroxynonenal covalent binding, or histopathological assessment of toxicity. The activity of hepatic MnSOD was significantly lower at 1 to 2 h in WT mice and subsequently increased at 8 h. MnSOD activity was not altered at 0 to 6 h in KO mice but was significantly decreased at 8 h. There were significant increases in MnSOD nitration at 1 to 8 h in WT mice and 6 to 8 h in KO mice. Significantly more nitration occurred at 1 to 6 h in WT than in KO mice. MnSOD was the only observed nitrated protein after APAP treatment. These data indicate a role for nNOS with inactivation of MnSOD and ALT release during APAP toxicity.

Protective Properties of 2-Acetylcyclopentanone in a Mouse Model of Acetaminophen Hepatotoxicity

“…3, A-C). Thereafter, biomarker activity increased rapidly, and at the 24 time point, the mean peak levels achieved were remarkably elevated indicating significant hepatocyte damage (Agarwal et al, 2012;Jaeschke, 1990), e.g., mean (6 S.E.M.) 24-hour AST levels were 18,100 6 3300 IU/l, which represents more than a 110-fold increase relative to the pooled control, 160 6 20 IU/l (Fig.…”

Systems Biology Investigation to Discover Metabolic Biomarkers of Acetaminophen-Induced Hepatic Injury Using Integrated Transcriptomics and Metabolomics

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The dual role of osteopontin in acetaminophen hepatotoxicity

“…Although they may be identified as necrotic, not all necrotic hepatocytes die with the release of ALT. Thus, it is not surprising to observe a discrepancy between the necrosis and the ALT results in reports [28,36,37] . On the basis of ALT results, we conclude that OPN-mediated inflammatory response plays an important role in the progression of APAP hepatotoxicity.…”