The Role Of Prostaglandin E2Receptor Sutvpe2(Ep2)in α-synuclein Induced Microglial Activation

BackgroundRecently several studies have indicated that an inflammatory process characterized by activation of resident microglia, likely either initiates or aggravates nigral neurodegeneration in Parkinson’s disease (PD). Abnormal a-Synuclein aggregation (a major component of Lewy bodies) plays an important role in PD pathogenesis. A growing body of evidence from in vivo and in vitro studies shows that extracellular a-synuclein can indeed trigger the activation of microglia and therefore induce a lethal cascade of neuroinflammation leading to the dopaminergic neuronal death in PD pathogenesis. In our previous study, we demonstrated that ablation of EP2(one of the four receptors of PGE2) significantly enhanced microglia mediated ex vivo clearance of a-synuclein aggregates while significantly attenuated neurotoxicity and extent of a-synuclein aggregation in mice treated with a parkinsonian toxicant1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. However, the mechanisms by which EP2regulates the activation of microglia induced by a-synuclein are not fully understood.Objectives(1) To confirm that aggregated a-synuclein can activate microglia (2) To investigate the role of EP2in regulating microglial activation induced by α-synucleinMethodsThe activation of microglia was measured by (1) CD11b expression level (immunocytochemistry),(2) neurotoxic factor production:IL-1, IL-6, NO, PGE2(RT-PCR, Griess reagent and ELISA) and (3) phagocytotic activity (Fluorescent Microspheres and Flow cytometry) in BV-2cell line (a murine microglial cell) as well as primary rat microglia culture.ResultsPart Ⅰ Aggregated α-synuclein induced BV2and primary microglial activation by increasing IL-1β, IL-6, COX-2, iNOS mRNA levels, stmulating NO and PGE2release and enhancing phagocytosis compared to the control group.Part Ⅱ Antagonism of EP2by AH6809further activated microglia by increasing CD11b expression level and enhancing phagocytosis while reducing NO and PGE2release compared to the α-synuclein treated group.Part Ⅲ Inhibition of cAMP production reduced α-synuclein induced NO and PGE2release in microglia, which is similar with that of EP2antagonism.ConclusionPart Ⅰ Aggregated α-synuclein can activate microglia resulting in increasing the releases of proinflammatory cytokine and enhancing its phagocytic capacity.Part Ⅱ Antagonism of EP2can regulate α-synuclein induced microligal activation by reducing the release of proinflammatory factors while enhancing its phagocytosisPartⅢ The regulation of EP2on α-synuclein induced microligal activation is mediated by EP2/cAMP pathway.