Coupling of Ca 2+ to CREB Activation and Gene Expression in Intact Cerebral Arteries From Mouse

Abstract

Abstract —Pathological changes of the vasculature are characterized by changes in Ca 2+ handling and alterations in gene expression. In neurons and other cell types, [Ca 2+ ] i often drives changes in gene expression. However, the relationship between Ca 2+ signaling and gene expression in vascular smooth muscle is not well understood. This study examines the ability of Ca 2+ influx through voltage-dependent, L-type Ca 2+ channels (VDCCs) and Ca 2+ release through ryanodine receptors (RyRs) to activate the transcription factor, cAMP-responsive element binding protein (CREB), and increase c- fos levels in intact cerebral arteries. Membrane depolarization increased the fraction of nuclei staining for phosphorylated CREB (P-CREB) and levels of c- fos mRNA in intact mouse cerebral arteries. Ryanodine, which inhibits RyRs, increased P-CREB staining and c- fos levels. Forskolin, an activator of adenylyl cyclase, and sodium nitroprusside, an NO donor, increased P-CREB and c- fos levels. Nisoldipine, an inhibitor of VDCCs, reversed the effects of depolarization and ryanodine on P-CREB and c- fos levels, but not the effects of forskolin or sodium nitroprusside. Inhibition of Ca 2+ /calmodulin-dependent protein kinase (CaM kinase) blocked increases in P-CREB and c- fos levels seen with membrane depolarization, suggesting that CaM kinase has an important role in the pathway leading from Ca 2+ influx to CREB-mediated changes in c- fos levels. Our data suggest that membrane depolarization increases [Ca 2+ ] i through activation of VDCCs, leading to increased P-CREB and c- fos , and that RyRs have a profound effect on this pathway by indirectly regulating Ca 2+ entry through VDCCs. These results provide the first evidence of Ca 2+ regulation of CREB and c- fos in arterial smooth muscle.