High sensitivity of Nrf2 knockout mice to acetaminophen hepatotoxicity associated with decreased expression of ARE-regulated drug metabolizing enzymes and antioxidant genes.

Abstract

Nrf2, which belongs to the basic leucine zipper (bZip) transcription factor family, has been implicated as a key molecule involved in antioxidant-responsive element (ARE)-mediated gene expression. In order to examine the role of Nrf2 in protection against xenobiotic toxicity, the sensitivity of nrf2 knockout mice to acetaminophen (N-acetyl-4-aminophenol (APAP)) was analyzed. The saturation of detoxification pathways after high levels of exposure to APAP is known to induce hepatotoxicity. Two factors important in its detoxification are UDP-glucuronosyltransferase (UDP-GT), an ARE-regulated phase-II drug-metabolizing enzyme, and glutathione (GSH), an antioxidant molecule whose synthesis depends on ARE-regulated gamma-glutamylcysteine synthetase (gammaGCS). Two- to 4-month-old male mice were orally administered a single dose of APAP at 0, 150, 300, or 600 mg/kg. Doses of 300 mg/kg APAP or greater caused death in the homozygous knockout mice only, and those that survived showed a greater severity in hepatic damage than the wild-type mice, as demonstrated by increased plasma alanine aminotransferase activity, decreased hepatic non-protein sulfhydryl (NPSH) content, and centrilobular hepatocellular necrosis. The high sensitivity of Nrf2-deficient mice was confirmed from observations made at 0, 2, 8, and 24 h after dosing with 300 mg/kg APAP; increased anti-APAP immunoreactivity was also noted in their livers at 2 h. Untreated homozygous knockout mice showed both a lower UDP-GT activity and NPSH content, which corresponded to decreased mRNA levels of UDP-GT (Ugt1a6) and the heavy chain of gammaGCS, respectively. These results show that Nrf2 plays a protective role against APAP hepatotoxicity by regulating both drug metabolizing enzymes and antioxidant genes through the ARE.

• Authors: A Enomoto, K Itoh, E Nagayoshi, J Haruta, T Kimura, T O'Connor, T Harada, M Yamamoto
• Journal: Toxicological sciences : an official journal of the Society of Toxicology (Toxicol Sci) Vol. 59 Issue 1 Pg. 169-77 (Jan 2001) ISSN: 1096-6080 [Print] United States
• PMID: 11134556 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DNA-Binding Proteins
• NF-E2-Related Factor 2
• Nfe2l2 protein, mouse
• RNA, Messenger
• Trans-Activators
• Acetaminophen
• Glucuronosyltransferase
• Alanine Transaminase
• Glutamate-Cysteine Ligase
• Glutathione

Topics

• Acetaminophen (administration & dosage, pharmacokinetics, toxicity)
• Alanine Transaminase (blood)
• Animals
• Chemical and Drug Induced Liver Injury (genetics, metabolism, prevention & control)
• DNA-Binding Proteins (deficiency, genetics, metabolism)
• Dose-Response Relationship, Drug
• Fluorescent Antibody Technique, Indirect
• Gene Expression Regulation, Enzymologic
• Glucuronosyltransferase (genetics, metabolism)
• Glutamate-Cysteine Ligase (genetics, metabolism)
• Glutathione (analysis, genetics, metabolism)
• Heterozygote
• Homozygote
• Male
• Mice
• Mice, Inbred ICR
• Mice, Knockout
• Microsomes, Liver (drug effects, enzymology)
• NF-E2-Related Factor 2
• RNA, Messenger (metabolism)
• Reverse Transcriptase Polymerase Chain Reaction
• Trans-Activators (deficiency, genetics, metabolism)