title: 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.
authors: Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors: Rakhee
authors: R
authors: Agarwal
authors: Leah
authors: L
authors: Hennings
authors: Tonya M
authors: TM
authors: Rafferty
authors: Lynda G
authors: LG
authors: Letzig
authors: Sandra
authors: S
authors: McCullough
authors: Laura P
authors: LP
authors: James
authors: Lee Ann
authors: LA
authors: MacMillan-Crow
authors: Jack A
authors: JA
authors: Hinson
mesh_terms: D000082:Acetaminophen / Q000633:toxicity*; D000410:Alanine Transaminase / Q000097:blood; D018712:Analgesics, Non-Narcotic / Q000633:toxicity*; D000818:Animals; D001219:Aspartate Aminotransferases / Q000097:blood; D015153:Blotting, Western; D056486:Chemical and Drug Induced Liver Injury / Q000201:enzymology* / Q000473:pathology; D003545:Cysteine / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology / Q000378:metabolism; D008099:Liver / Q000473:pathology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000502:physiology*; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D018712:Analgesics, Non-Narcotic; D009566:Nitrates; D000082:Acetaminophen; D052248:Nitric Oxide Synthase Type I; D013482:Superoxide Dismutase; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D003545:Cysteine