EP2 Receptor Signaling Pathways Regulate Classical Activation of Microglia

• Type of Material: Article
• Authors: Yi Quan, Emory University; Jianxiong Jiang, Emory University; Raymond Dingledine, Emory University
• Language: English
• Date: 2013-02-12
• Publisher: American Society for Biochemistry and Molecular Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.
• Final Published Version (URL): http://dx.doi.org/10.1074/jbc.M113.455816
• Title of Journal or Parent Work: Journal of Biological Chemistry
• ISSN: 0021-9258
• Volume: 288
• Issue: 13
• Start Page: 9293
• End Page: 9302
• Grant/Funding Information: This work was supported, in whole or in part, by National Institutes of Health Grants U01NS058158 and R21NS074169 (both to R. D.) from the NINDS and the Countermeasures against Chemical Threats (CounterACT) Program, National Institutes of Health Office of the Director.; This work was also supported by the Epilepsy Foundation (to J. J.).
• Keywords: PKA; Epac; inflammation; cytokine; microglia; EP2; prostaglandins; protein kinase A
• Research Categories: Health Sciences, Pharmacology

Abstract

Activation of EP2 receptors by prostaglandin E2 (PGE2) promotes brain inflammation in neurodegenerative diseases, but the pathways responsible are unclear. EP2 receptors couple to Gαs and increase cAMP, which associates with protein kinase A (PKA) and cAMP-regulated guanine nucleotide exchange factors (Epacs). Here, we studied EP2 function and its signaling pathways in rat microglia in their resting state or undergoing classical activation in vitro following treatment with low concentrations of lipopolysaccharide and interferon-γ. Real time PCR showed that PGE2 had no effect on expression of CXCL10, TGF-β1, and IL-11 and exacerbated the rapid up-regulation of mRNAs encoding cyclooxygenase-2, inducible NOS, IL-6, and IL-1β but blunted the production of mRNAs encoding TNF-α, IL-10, CCL3, and CCL4. These effects were mimicked fully by the EP2 agonist butaprost but only weakly by the EP1/EP3 agonist 17-phenyl trinor PGE2 or the EP4 agonist CAY10598 and not at all by the EP3/EP1 agonist sulprostone and confirmed by protein measurements of cyclooxygenase-2, IL-6, IL-10, and TNF-α. In resting microglia, butaprost induced cAMP formation and altered the mRNA expression of inflammatory mediators, but protein expression was unchanged. The PKA inhibitor H89 had little or no effect on inflammatory mediators modulated by EP2, whereas the Epac activator 8-(4-chlorophenylthio)-2′-O-methyladenosine 3′,5′-cyclic monophosphate acetoxymethyl ester mimicked all butaprost effects. These results indicate that EP2 activation plays a complex immune regulatory role during classical activation of microglia and that Epac pathways are prominent in this role.