G Protein Associated With The Pathogenesis Of Alcoholic Fatty Liver And The Proliferation Inhibitory Effect Of Melatonin On HCC HepG2

Aim To investigate the effect of G-protein signaling on the pathogenesis of alcoholic fatty liver and the putative inhibition of HepG2 proliferation with MT treatment. Method SD rats were treated with high fatty diet in combination with different doses of ethanol for 6 weeks, and the model of alcoholic fatty liver was established in rats. By the end of the 6th week, all rats were sacrificed, the serum level of ALT, AST, TG, TC, HDL-C were measured respectively, and the frozen sections of liver were stained with Oil Red O and observed by microscope. The proliferation of HepG2 cell in vitro was observed by MTT method. The expressions of Gαi1, Gαi2, Gαi3, Gαs were detected by western blot. The level of cAMP was determined by RIA. Result The serum levels of ALT, AST, TG, TC were increased significantly in model groups. HE dying and Oil Red O stain results demonstrated apparent fat accumulation in rat liver with alcohol treatment. When Combined with high fatty diet, ethanol could significantly decrease the expression of Gαi1, Gαi2 and Gαi3, meanwhile, OPN also dramatically increase in model groups and show a dose-positive relation. Melatonin inhibited proliferation of HepG2 in a time- and concentration-dependent manner. To determine whether this inhibitory effect has a relationship with G protein-cAMP-dependent signal pathway, the level of cAMP and expression of G-protein in HepG2 cell were detected at different time-points (0min, 15min, 30min, 45min, 60min, 90min and 120min) after treatment of melatonin(10-5 mol·L-1). Western blot results showed that treatment of melatonin for 30min significant decreased the expression of Gαi1, Gαi2, Gαi3 and had no obviously effects on the expression of Gαs. Meanwhile, melatonin had a tendency to decrease the level of cAMP but no statistical difference. Conclusion The underlied mechanism of alcoholic liver disease may involve G protein–related downstream signaling, as well as OPN. Melatonin inhibits proliferation of HepG2 cell in a time- and concentration- dependent manner in vitro. This inhibitory effect maybe possibly mediated through G-protein-cAMP signal pathway.