NORADRENERGIC REGULATION OF PERIOD1 EXPRESSION IN SPINAL ASTROCYTES IS INVOLVED IN PROTEIN KINASE A, C-JUN N-TERMINAL KINASE AND EXTRACELLULAR SIGNAL-REGULATED KINASE ACTIVATION MEDIATED BY alpha1- AND beta2-ADRENOCEPTORS

摘要

Our recent data suggest that noradrenaline (NA) regulates expression of Per1 mRNA in rat C6 cells, as a model of brain astrocytes, by two distinct NA-mediating pathways. Although C6 cells possess potential astrocyte-type characteristics, we hypothesize that astrocytes located in a distinct tissue or organ play specific roles consistent with their own unique functions in response to the surrounding environment. We have herein found in primary rat spinal astrocytes using real-time RT-PCR that NA induced robust transient increases in Per1, Cry1, Cry2 and Bmal1 mRNA expression. Cry1, Cry2 and Bmal1 expressions induced by NA were attenuated by transfection of Per1 small interference RNA (siRNA). The effect of NA on Per1 expression was partially blocked by either prazosin (a selective antagonist of alpha1-adrenoceptor) or ICI118551 (a selective antagonist of beta2-adrenoceptor), and completely blocked by the combination of both antagonists. Treatment with H89 (a protein kinase A [PKA] inhibitor), SP600125 (a c-Jun N-terminal kinase [JNK] inhibitor), or PD98059 (an extracellular signal-regulated kinase [ERK] inhibitor), partially inhibited NA-induced Per1 mRNA expression, and the combination of these three inhibitors inhibited expression to nearly a non-stimulated level. Furthermore, NA phosphorylated not only ERK but also JNK1, an effect that was detected by western blotting. These actions were inhibited only by prazosin, and not by ICI118551. In addition, we found that NA induced phosphor-ylation of transcription-related proteins such as cAMP response element binding protein (CREB) and c-Jun. These phosphorylation processes were regulated through distinct pathways: CREB phosphorylation was dependent on the PKA and JNK pathways but c-Jun phosphorylation was mediated by the ERK and JNK pathways. These results suggest that Per1 plays a key role in noradrenergic regulation on clock gene expression in spinal astrocytes and activation of alpha1 and beta2 adrenoceptors are o...