Microtubules are more stable and more highly acetylated in ethanol-treated hepatic cells.
OBJECTIVE
Chronic alcohol consumption can lead to serious liver disease. Although the disease progression is clinically well-described, the molecular basis for alcohol-induced hepatotoxicity is not understood.


METHODS
We examined hepatocyte-specific, alcohol-induced alterations in microtubule dynamics in WIF-B cells. These cells provide an excellent model for studying alcohol-induced hepatotoxicity; they remain differentiated in culture and metabolize alcohol.


RESULTS
Consistent with reports in other hepatic systems, microtubule polymerization in ethanol-treated WIF-B cells was impaired. However, when viewed by epifluorescence, the microtubules in ethanol-treated cells resembled stable polymers. Antibodies to acetylated alpha-tubulin confirmed their identity morphologically and revealed biochemically that ethanol-treated cells had approximately three-fold more acetylated alpha-tubulin than control cells. Livers from ethanol-fed rats also contained increased levels of acetylated alpha-tubulin. Consistent with increased acetylated alpha-tubulin levels, microtubules in ethanol-treated WIF-B cells were more stable. Because stability increased with increased time of ethanol exposure or concentration, was prevented by 4-methylpyrazole and was potentiated by cyanamide, we conclude that increased acetylation requires alcohol metabolism and is likely to be mediated by acetaldehyde.


CONCLUSIONS
Ethanol metabolism impairs tubulin polymerization, but once microtubules are formed they are hyperstabilized. These ethanol-induced alterations in microtubule integrity likely have profound effects on hepatocyte function.
Kannarkat
George T
GT
Department of Biology, The Catholic University of America, 620 Michigan Avenue, NE, Washington, DC 20064, USA.
Tuma
Dean J
DJ
Tuma
Pamela L
PL
D000079:Acetaldehyde / Q000378:metabolism; D000107:Acetylation / Q000187:drug effects; D000818:Animals; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D002492:Central Nervous System Depressants / Q000493:pharmacokinetics / Q000633:toxicity*; D000431:Ethanol / Q000493:pharmacokinetics / Q000633:toxicity*; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008108:Liver Diseases, Alcoholic / Q000378:metabolism / Q000473:pathology*; D008113:Liver Neoplasms; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism; D011108:Polymers / Q000378:metabolism; D051381:Rats
D002492:Central Nervous System Depressants; D011108:Polymers; D000431:Ethanol; D000079:Acetaldehyde