Chronic Ethanol Treatment Impairs Rac and Cdc42 Activation in Rat Hepatocytes

• Published in: Alcoholism, clinical and experimental research Vol. 30; no. 7; pp. 1208 - 1213
• Main Authors: Schaffert, Courtney S., Todero, Sandra L., Casey, Carol A., Thiele, Geoffrey M., Sorrell, Michael F., Tuma, Dean J.
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.07.2006; Lippincott Williams & Wilkins
• Subjects: Alcoholism and acute alcohol poisoning; Animals; Biological and medical sciences; cdc42 GTP-Binding Protein - drug effects; Cdc42 GTPase; Cell Adhesion - drug effects; Cell Culture Techniques; Collagen Type IV; Ethanol - pharmacology; Experimental Model for Alcoholic Liver Disease; Hepatocyte-Extracellular Matrix Interactions; Hepatocytes - drug effects; Male; Medical sciences; rac GTP-Binding Proteins - drug effects; Rac GTPase; Rats; Rats, Wistar; rhoA GTP-Binding Protein - drug effects; RhoA GTPase; Signal Transduction - drug effects; Toxicology; Rac GTPase; Rat; Hepatocyte-Extracellular Matrix Interactions; Experimental Model for Alcoholic Liver Disease; Hepatic disease; Esterases; Activation; RhoA GTPase; Alcoholic beverage; Hepatocyte; Extracellular matrix; Cdc42 GTPase; Ethanol; Digestive system; Enzyme; Triphosphoric monoester hydrolases; Alcoholism; Rodentia; dGTPase; Vertebrata; Chronic; Mammalia; Treatment; Animal; Digestive diseases; Hydrolases; Models
• ISSN: 0145-6008; 1530-0277
• DOI: 10.1111/j.1530-0277.2006.00135.x

Background: The effects of chronic ethanol feeding on rat hepatocytes have been shown to include impaired cell–extracellular matrix (ECM) adhesion events, such as decreased attachment and spreading as well as increased integrin–actin cytoskeleton association. These results, observed previously by this laboratory, are highly suggestive of impaired actin cytoskeleton reorganization, an event mediated by differential activation of the Rho family GTPases Rac, Cdc42, and RhoA. Therefore, the purpose of this study was to examine the effects of chronic ethanol administration on these GTPases. Methods: Male Wistar rats were pair‐fed 4 to 5 weeks with a liquid diet containing either ethanol (as 36% of total calories) or isocaloric carbohydrate. Hepatocytes were isolated and plated on collagen IV up to 24 hours. At specific times, the hepatocytes were lysed and these lysates were analyzed for RhoA, Cdc42, and Rac activation. Results: In freshly isolated hepatocytes from ethanol‐fed rats, the GTP‐bound (active) forms of Rac and Cdc42 were significantly decreased compared with pair‐fed control rats, while the GTP‐bound form of RhoA was not significantly altered. These ethanol‐induced impairments in Rac and Cdc42 activation persisted even after plating the hepatocytes on collagen IV. Additionally, chronic ethanol treatment did not directly affect GTP binding of Cdc42 and Rac, as incorporation of GTPγS was not affected. Conclusions: Chronic ethanol administration selectively impairs Rac and Cdc42 activation in rat hepatocytes. As activation of these 2 GTPases is crucial for efficient cell attachment and spreading on ECM substrates, the results from this study suggest that the ethanol‐induced impairments in Rac and Cdc42 activation are responsible for the impaired hepatocyte–ECM adhesion events observed previously by our laboratory. Furthermore, these results raise the intriguing possibility that these GTPases are involved in other ethanol‐induced functional impairments, such as protein trafficking and receptor‐mediated endocytosis.