Inhibition of CYP2E1 leads to decreased malondialdehyde-acetaldehyde adduct formation in VL-17A cells under chronic alcohol exposure.
OBJECTIVE
Ethanol metabolism leads to the formation of acetaldehyde and malondialdehyde. Acetaldehyde and malondialdehyde can together form malondialdehyde-acetaldehyde (MAA) adducts. The role of alcohol dehydrogenase (ADH) and cytochrome P4502E1 (CYP2E1) in the formation of MAA-adducts in liver cells has been investigated.


METHODS
Chronic ethanol treated VL-17A cells over-expressing ADH and CYP2E1 were pretreated with the specific CYP2E1 inhibitor - diallyl sulfide or ADH inhibitor - pyrazole or ADH and CYP2E1 inhibitor - 4-methyl pyrazole. Malondialdehyde, acetaldehyde or MAA-adduct formation was measured along with assays for viability, oxidative stress and apoptosis.


RESULTS
Inhibition of CYP2E1 with 10 μM diallyl sulfide or ADH with 2mM pyrazole or ADH and CYP2E1 with 5mM 4-methyl pyrazole led to decreased oxidative stress and toxicity in chronic ethanol (100 mM) treated VL-17A cells. In vitro incubation of VL-17A cell lysates with acetaldehyde and malondialdehyde generated through ethanol led to increased acetaldehyde (AA)-, malondialdehyde (MDA)-, and MAA-adduct formation. Specific inhibition of CYP2E1 or ADH and the combined inhibition of ADH and CYP2E1 greatly decreased the formation of the protein aldehyde adducts. Specific inhibition of CYP2E1 led to the greatest decrease in oxidative stress, toxicity and protein aldehyde adduct formation, implicating that CYP2E1 accelerates the formation of protein aldehyde adducts which can be an important mechanism for alcohol mediated liver injury.


CONCLUSIONS
CYP2E1-mediated metabolism of ethanol leads to increased AA-, MDA-, and MAA-adduct formation in liver cells which may aggravate liver injury.
Life Science Division, AU-KBC Research Centre, MIT Campus of Anna University, Chromepet, Chennai-600044, India.
Kavitha
K
Swaminathan
Dahn L
DL
Clemens
Aparajita
A
Dey
D000079:Acetaldehyde / Q000378:metabolism*; D000426:Alcohol Dehydrogenase / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D000498:Allyl Compounds / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D019392:Cytochrome P-450 CYP2E1 / Q000096:biosynthesis; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004334:Drug Administration Schedule; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000431:Ethanol / Q000008:administration & dosage / Q000633:toxicity*; D000077604:Fomepizole; D056945:Hep G2 Cells; D006801:Humans; D008315:Malondialdehyde / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013440:Sulfides / Q000494:pharmacology
D000498:Allyl Compounds; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004791:Enzyme Inhibitors; D011720:Pyrazoles; D017382:Reactive Oxygen Species; D013440:Sulfides; D000431:Ethanol; C031280:pyrazole; D008315:Malondialdehyde; C038491:allyl sulfide; D000077604:Fomepizole; D000426:Alcohol Dehydrogenase; D019392:Cytochrome P-450 CYP2E1; D053148:Caspase 3; D000079:Acetaldehyde