EXPRESSION OF CYCLOOXYGENASE-1/-2, MICROSOMAL PROSTAGLANDIN-E SYNTHASE-1 AND E-PROSTANOID RECEPTOR 2 AND REGULATION OF INFLAMMATORY MEDIATORS BY PGE2 IN THE AMOEBOID MICROGLIA IN HYPOXIC POSTNATAL RATS AND MURINE BV-2 CELLS

This study aimed to investigate the effect of hypoxia on the expression of cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), microsomal prostaglandin-E synthase (mPGES-1), E-prostanoid receptor 2 (EP2) in microglia; and the roles of EP2-cyclic adenosine monophosphate (cAMP) signaling pathway in the prostaglandin E-2 (PGE(2)) regulation of inflammatory mediators released by hypoxic BV-2 cells. Immunoexpression of COX-1, COX-2, mPGES-1 and EP2 was localized in the amoeboid microglial cells (AMC), a nascent brain macrophage in the developing brain, as confirmed by double labeling with OX-42 and lectin, specific markers of microglia. AMC emitted a more intense immunofluorescence in hypoxic rats when compared with the matching controls. In postnatal rats subjected to hypoxia, mRNA and protein expression levels of COX-1, COX-2 and mPGES-1 along with tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), inducible nitric-oxide synthase (iNOS) and PGE(2) product in the callosal tissue were significantly increased. The results were shared in the BV-2 cells except for COX-1 mRNA and protein whose levels remained unaltered. Interestingly, treatment with EP2 antagonist AH-6809 resulted in suppression of hypoxia induced EP2, IL-1 beta and iNOS mRNA and protein expression, TNF-alpha protein expression and intracellular cAMP level in BV-2 cells. It is suggested that PGE(2) may regulate above inflammatory mediators in the activated microglia via EP2-cAMP signaling pathway in hypoxic conditions. (C) 2009 IBRO. Published by Elsevier Ltd. All rights reserved.