[Role of store-operated Ca2+ channels in primary hepatocytes under conditions of calcium overload and ethanol-induced injury].

OBJECTIVE:To investigate the role of store-operated calcium channels (SOCs) in primary hepatocytes under conditions of calcium overload and ethanol-induced injury. METHODS:The in vitro model of chronic ethanol-induced hepatocyte injury was established using primary hepatocytes isolated from Sprague-Dawley rats. Ethanol-induced changes (24, 48 and 72 h; 50, 100, 200, 400 and 800 mmol/L) in expression of the SOCs proteins stromal interaction molecule 1 (STIM1) and calcium release-activated calcium channel protein 1 (Oria1) were detected by qualitative PCR analysis (mRNA) and western blotting (protein). The possible role of these two SOCs proteins in the ethanol-induced extracellular calcium influx and related liver cell injury was determined by treating the cell system with various channel blockers (EGTA, La3+, and 2-APB). Cell viability was determined by MTT assay and cytosolic free calcium ion concentration was determined by flow cytometry. RESULTS:After 24 h of exposure to 0 (untreated) to 800 mM/L ethanol, the cell viability was reduced in a concentration-dependent manner. The 400 mmol/L concentration of ethanol decreased cell viability by 57.34% +/- 2.34%. and was chosen for use in subsequent experiments. Compared with the untreated control cells, the ethanol-treated cells showed significantly up-regulated mRNA and protein expression of both STIM1 and Orai1 at all times examined, suggesting that the ethanol-stimulated expression of STIM1 and Orai1 could persist for at least 72 h. The ethanol treatment induced increase in cytoplasmic calcium levels was significantly (and similarly) reduced by co-treatment with any of the three channel blockers. CONCLUSION:Chronic ethanol exposure can increase the expression of STIM1 and Orai1 in primary liver cells, suggesting that ethanol may increase extracellular calcium influx by up-regulating expression of these SOCs protein molecules, ultimately aggravating liver cell damage.