Extracellular adenosine 5′‐triphosphate elicits the expression of brain‐derived neurotrophic factor exon IV mRNA in rat astrocytes

AbstractA growing body of recent evidence indicates that ATP plays an important role in neuronal–glial communications. In this study, the authors demonstrated that extracellular ATP elicits the gene expression of brain‐derived neurotrophic factor (BDNF), especiallyBDNFexon IV mRNA, in primary cultured rat cortical astrocytes but not in neurons. To investigate the mechanism by which ATP inducesBDNFexon IV mRNA expression, the authors used immortalized astrocyte cell line RCG‐12. ATP dose‐dependently increased the expression ofBDNFexon IV mRNA and activatedBDNFpromoter IV. P2Y receptor agonists (ADP and 2MeS‐ADP) but not a P2X receptor agonist (αβMeATP) induced the expression ofBDNFexon IV mRNA. Moreover, ATP‐inducedBDNFexon IV mRNA upregulation was inhibited by a P2Y antagonist (MRS2179) but not by P2X antagonists (TNP‐ATP and PPADS). These findings suggest the involvement of P2Y receptors in the ATP‐induced transcription of theBDNFgene. Among the signal transduction inhibiters examined in this study, intracellular Ca2+chelator (BAPTA‐AM) and Ca2+/calmodulin‐dependent kinase (CaM kinase) inhibitors (KN‐93 and W‐7) attenuated ATP‐inducedBDNFexon IV mRNA upregulation. ATP transiently induced the phosphorylation of cAMP‐responsive element‐binding protein (CREB). ATP‐induced CREB phosphorylation was repressed by P2Y antagonists, BAPTA‐AM, and CaM kinase inhibitors. Overexpression of dominant negative CREB mutants reduced the activation ofBDNFpromoter IV and attenuated the upregulation ofBDNFexon IV mRNA expression. These results suggest that ATP induces BDNF expression through P2Y receptor followed by the activation of CaM kinase and CREB in astrocytes. These mechanisms are likely to contribute to the enhancement of neuronal–glial networks. © 2008 Wiley‐Liss, Inc.