Effects of ethanol on the expression of immediate-early genes in nerve cells

Immediate-early genes of the fos and jun families encode proteins that dimerize to form a complex of activator protein 1 and regulate the expression of a number of genes in the nervous system. Ethanol has previously been shown to induce alterations in expression of fos and jun genes in the brain. The present study examined the effects of ethanol on the expression of c-fos, fosB, c-jun, junB and junD genes in human neuroblastoma SH-SY5Y cells. Prior to the investigation of ethanol effects, the basal and agonist-stimulated expression of these genes were characterized. A constitutive expression of c-jun and junD was observed in unstimulated cells, whereas transcripts of c-fos, fosB and junB could not be detected. Stimulation with carbachol and TPA induced expression of all these genes but the expression patterns differed among individual genes. The expression of c-fos, fosB and junB induced by carbachol was primarily mediated through protein kinase C, whereas the carbachol-stimulated expression of c-jun and junD was mainly regulated via calcium/calmodulin-dependent kinase II. Long-term ethanol exposure increased the expression of c-jun and junD and potentiated the carbachol-stimulated expression of c-fos, fosB and junB. On the other hand, acute ethanol selectively attenuated the basal and phorbol ester-stimulated expression of junD, leaving the expression of c-jun and junB unaffected. Thus, junD seems to be sensitive to both acute and long-term ethanol exposure. The potentiation of carbachol-stimulated c-fos, fosB and junB expression after long-term ethanol exposure was primarily mediated via M1 receptors and protein kinase C. Neither long-term nor acute ethanol exposure influenced the degradation of the junD mRNA, which indicates that it is the transcription of the gene which is affected by ethanol. These results support the view that expression of fos and jun genes is involved in the ethanol-induced changes in the function of nerve cells.