The involvement of cytochrome P4502E1 in 2-bromoethanol-induced hepatocyte cytotoxicity.
The cytotoxicity of 2-bromoethanol towards hepatocytes isolated from rats was concentration-dependent (EC(50)100 mu M, 2 hr). Bromoacetaldehyde was more toxic (EC(50)60 mu M, 2 hr) and bromoacetic acid was less toxic (EC(50)150 mu M, 2 hr). Glutathione (GSH) depletion occurred before cytotoxicity ensued and GSH depleted hepatocytes were more susceptible to 2-bromoethanol. Lipid peroxidation increased steadily 1 hr after 2-bromoethanol addition and antioxidants, iron chelators or hypoxia prevented 2-bromoethanol induced lipid peroxidation and cell lysis. Alcohol dehydrogenase inhibitors, methyl pyrazole or dimethyl sulfoxide only partly prevented 2-bromoethanol induced GSH depletion, lipid peroxidation and cytotoxicity. However, cytochrome P4502E1 (CYP2E1) inhibitors/substrates were more effective at preventing 2-bromoethanol-induced GSH depletion, lipid peroxidation and cytotoxicity suggesting that 2-bromoethanol is mostly metabolically activated by CYP2E1. Also, hepatocytes isolated from CYP2E1 induced rats were more susceptible to 2-bromoethanol and hepatocytes isolated from rats pretreated with carbon disulfide to inactivate CYP2E1 were more resistant to 2-bromoethanol treatment. Formation of S-(formylmethyl)glutathione during 2-bromoethanol metabolism by microsomal mixed function oxidase in the presence of GSH was also prevented by cytochrome P4502E1 inhibitors/substrates or by Anti-Rat CYP2E1. Furthermore, aldehyde dehydrogenase inhibitors-cyanamide or chloral hydrate increased 2-bromoethanol dependent hepatocyte susceptibility. This suggests that 2-bromoethanol is preferably metabolised by CYP2E1 dependent monoxygenase to form 2-bromoacetaldehyde which causes cell lysis as a result of GSH depletion and lipid peroxidation.
Khan
S
S
Faculty of Pharmacy, University of Toronto, Ontario, Canada.
Sood
C
C
O'Brien
P J
PJ
D000433:1-Propanol / Q000633:toxicity; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001711:Biotransformation / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002470:Cell Survival / Q000187:drug effects; D056486:Chemical and Drug Induced Liver Injury / Q000201:enzymology* / Q000378:metabolism; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism*; D000431:Ethanol / Q000031:analogs & derivatives* / Q000633:toxicity; D005978:Glutathione / Q000378:metabolism; D007502:Iron Chelating Agents / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D020005:Propanols; D051381:Rats; D017207:Rats, Sprague-Dawley
D000975:Antioxidants; D007502:Iron Chelating Agents; D020005:Propanols; D000431:Ethanol; C006463:allyl alcohol; D000433:1-Propanol; D019392:Cytochrome P-450 CYP2E1; D005978:Glutathione; C025475:ethylene bromohydrin