Cytochrome P4502E1 inhibition by propylene glycol prevents acetaminophen (paracetamol) hepatotoxicity in mice without cytochrome P4501A2 inhibition.
Acetaminophen hepatotoxicity is associated with its biotransformation to the reactive metabolite N-acetyl-p-benzoquinone imine that binds to protein. Two forms of cytochrome P450, CYP2E1 and CYP1A2, have been implicated as primarily responsible for the bioactivation. To determine the relative contributions of these P450's, overnight fasted male NMRI mice were pretreated with 10 ml of 50% v/w propylene glycol/kg or fluvoxamine (10 mg/kg) at -80 and -20 min. relative to acetaminophen dosing to inhibit CYP2E1 and CYP1A2, respectively. Mice were sacrificed at 0.5 or 4 hr after a hepatotoxic dose of acetaminophen (300 mg/kg). Propylene glycol or propylene glycol plus fluvoxamine, but not fluvoxamine alone protected against acetaminophen hepatotoxicity as indicated by abolished increase in serum alanine aminotransferase activity, less depletion of hepatic glutathione and lower liver:body weight ratios. Propylene glycol inhibited the activity of CYP2E1 as indicated by 84% reduction in the clearance of 3 mg/kg dose of chlorzoxazone, whereas fluvoxamine inhibited the activity of CYP1A2 as indicated by 40% reduction in the clearance of a 10 mg/kg dose of caffeine. For this animal model, the data are consistent with the notion that hepatoxicity is associated with bioactivation of acetaminophen by CYP2E1 but not by CYP1A2.
D000082:Acetaminophen / Q000037:antagonists & inhibitors* / Q000633:toxicity; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology / Q000627:therapeutic use*; D002110:Caffeine / Q000493:pharmacokinetics; D019392:Cytochrome P-450 CYP2E1; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D010089:Oxidoreductases, N-Demethylating / Q000037:antagonists & inhibitors*; D019946:Propylene Glycol; D011409:Propylene Glycols / Q000494:pharmacology / Q000627:therapeutic use*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D065607:Cytochrome P-450 Enzyme Inhibitors; D011409:Propylene Glycols; D000082:Acetaminophen; D002110:Caffeine; D019946:Propylene Glycol; D003577:Cytochrome P-450 Enzyme System; D019392:Cytochrome P-450 CYP2E1; D010089:Oxidoreductases, N-Demethylating