Altered disposition of acetaminophen in Nrf2-null and Keap1-knockdown mice

Toxicol Sci. 2009 May;109(1):31-40. doi: 10.1093/toxsci/kfp047. Epub 2009 Feb 26.

Abstract

Acetaminophen (AA) is a widely used antipyretic drug that causes hepatotoxicity at high doses. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that mitigates electrophilic stress from AA by inducing genes, such as NAD(P)H:quinone oxidoreductase 1 (Nqo1), multidrug resistance-associated proteins (Mrps), and glutathione (GSH) synthesis enzymes. To determine whether Nrf2 activation alters the biotransformation and excretion of AA, male wild-type, Nrf2-null, and Keap1 (Kelch-like ECH-associated protein 1)-knockdown (Keap1-kd) mice (which have increased activation of Nrf2) were administered a single subtoxic dose of AA (50 mg/kg, iv), after which, AA and its metabolites (AA-glucuronide [AA-GLUC]; AA-sulfate [AA-SULF]; AA-glutathione [AA-GSH]) were quantified in plasma, bile, and liver. AA-GLUC concentrations were reduced in plasma and elevated in livers of Nrf2-null mice due to decreased glucuronidation activity and lower expression of the basolateral efflux transporter Mrp3. In contrast, Keap1-kd mice had higher plasma and lower hepatic AA-GLUC concentrations, due to higher Mrp3 expression. Lower glucuronidation activity of Nrf2-null mice increased the proportion of AA available for sulfation, resulting in elevated AA-SULF concentrations in plasma, bile, and liver. Decreased AA-sulfation activity in Keap1-kd mice resulted in lower AA-SULF concentrations. AA-GSH conjugates were increased in Nrf2-null mice and tended to be lower in Keap1-kd mice. Furthermore, Nqo1, an enzyme capable of detoxifying the reactive intermediate of AA metabolism, N-acetyl-p-benzoquinone imine (NAPQI), had 85% lower activity in Nrf2-null mice and 415% higher activity in Keap1-kd mice relative to wild-type. In conclusion, lack of Nrf2 results in decreased AA glucuronidation, leading to increased AA available for NAPQI formation and decreased efflux of AA-GLUC via Mrp3; however, activation of Nrf2, as in Keap1-kd mice, results in decreased sulfotransferase activity, decreased AA-SULF formation, and enhanced elimination of AA-GLUC due to increased expression of Mrp3.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acetaminophen / administration & dosage
  • Acetaminophen / analogs & derivatives
  • Acetaminophen / analysis
  • Acetaminophen / blood
  • Acetaminophen / metabolism
  • Acetaminophen / pharmacokinetics*
  • Adaptor Proteins, Signal Transducing / genetics*
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Bile / chemistry
  • Biotransformation
  • Carrier Proteins / metabolism
  • Cytoskeletal Proteins / genetics*
  • Cytoskeletal Proteins / metabolism
  • Gene Knockdown Techniques
  • Guinea Pigs
  • Kelch-Like ECH-Associated Protein 1
  • Liver / chemistry
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Microscopy, Fluorescence
  • Microsomes, Liver / metabolism
  • NAD(P)H Dehydrogenase (Quinone)
  • NADPH Dehydrogenase / metabolism
  • NF-E2-Related Factor 2 / genetics*
  • NF-E2-Related Factor 2 / metabolism

Substances

  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Cytoskeletal Proteins
  • Keap1 protein, mouse
  • Kelch-Like ECH-Associated Protein 1
  • NF-E2-Related Factor 2
  • Nfe2l2 protein, mouse
  • Acetaminophen
  • acetaminophen glucuronide
  • NAD(P)H Dehydrogenase (Quinone)
  • Nqo1 protein, mouse
  • NADPH Dehydrogenase
  • acetaminophen sulfate ester
  • 3-(glutathion-S-yl)acetaminophen