title: Tolerance to acetaminophen hepatotoxicity in the mouse model of autoprotection is associated with induction of flavin-containing monooxygenase-3 (FMO3) in hepatocytes.
abstract: Acetaminophen (APAP) pretreatment with a hepatotoxic dose (400 mg/kg) in mice results in resistance to a second, higher dose (600 mg/kg) of APAP (APAP autoprotection). Recent microarray work by our group showed a drastic induction of liver flavin containing monooxygenase-3 (Fmo3) mRNA expression in our mouse model of APAP autoprotection. The role of liver Fmo3, which detoxifies xenobiotics, in APAP autoprotection is unknown. The purpose of this study was to characterize the gene regulation and protein expression of liver Fmo3 during APAP hepatotoxicity. The functional consequences of Fmo3 induction were also investigated. Plasma and livers were collected from male C57BL/6J mice over a period of 72 h following a single dose of APAP (400 mg/kg) to measure Fmo3 mRNA and protein expression. Although Fmo3 mRNA levels increased significantly following APAP treatment, protein expression changed marginally. In contrast, both Fmo3 mRNA and protein expression were significantly higher in APAP autoprotected livers. Unlike male C57BL/6J mice, female mice have ∼80-times higher constitutive Fmo3 mRNA levels and are highly resistant to APAP hepatotoxicity. Coadministration of APAP with the FMO inhibitor methimazole rendered female mice susceptible to APAP hepatotoxicity, with no changes in susceptibility detected in male mice. Furthermore, a human hepatocyte cell line (HC-04) clone over-expressing human FMO3 showed enhanced resistance to APAP cytotoxicity. Taken together, these findings establish for the first time induction of Fmo3 protein expression and function by xenobiotic treatment. Our results also indicate that Fmo3 expression and function plays a role in protecting the liver from APAP-induced toxicity. Although the mechanism(s) of this protection remains to be elucidated, this work describes a novel protective function for this enzyme.
authors: Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269.
authors: Swetha
authors: S
authors: Rudraiah
authors: Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269.
authors: Philip R
authors: PR
authors: Rohrer
authors: Cellular Dynamics International, Madison, Wisconsin 53711.
authors: Igor
authors: I
authors: Gurevich
authors: Rutgers University, Office of Translational Science, New Brunswick, New Jersey 08901.
authors: Michael J
authors: MJ
authors: Goedken
authors: Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269.
authors: Theodore
authors: T
authors: Rasmussen
authors: US EPA, National Health and Environmental Effects Research Laboratory, Research Triangle Park, North Carolina 27711.
authors: Ronald N
authors: RN
authors: Hines
authors: Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut 06269 jose.manautou@uconn.edu.
authors: José E
authors: JE
authors: Manautou
mesh_terms: D000082:Acetaminophen / Q000008:administration & dosage / Q000633:toxicity*; D000410:Alanine Transaminase / Q000378:metabolism; D000818:Animals; D056486:Chemical and Drug Induced Liver Injury / Q000201:enzymology* / Q000209:etiology / Q000517:prevention & control*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D004790:Enzyme Induction; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D010105:Oxygenases / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000082:Acetaminophen; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming); D000410:Alanine Transaminase
keywords: Fmo3; acetaminophen; autoprotection; hepatotoxicity; inhibitor; methimazole