Suppression of Alzheimer-associated inflammation by microglial prostaglandin-E2 EP4 receptor signaling.

ABSTRACT: A persistent and nonresolving inflammatory response to accumulating A? peptide species is a cardinal feature in the development of Alzheimer's disease (AD). In response to accumulating A? peptide species, microglia, the innate immune cells of the brain, generate a toxic inflammatory response that accelerates synaptic and neuronal injury. Many proinflammatory signaling pathways are linked to progression of neurodegeneration. However, endogenous anti-inflammatory pathways capable of suppressing A?-induced inflammation represent a relatively unexplored area. Here we report that signaling through the prostaglandin-E2 (PGE2) EP4 receptor potently suppresses microglial inflammatory responses to A?42 peptides. In cultured microglial cells, EP4 stimulation attenuated levels of A?42-induced inflammatory factors and potentiated phagocytosis of A?42. Microarray analysis demonstrated that EP4 stimulation broadly opposed A?42-driven gene expression changes in microglia, with enrichment for targets of IRF1, IRF7, and NF-?B transcription factors. In vivo, conditional deletion of microglial EP4 in APPSwe-PS1?E9 (APP-PS1) mice conversely increased inflammatory gene expression, oxidative protein modification, and A? deposition in brain at early stages of pathology, but not at later stages, suggesting an early anti-inflammatory function of microglial EP4 signaling in the APP-PS1 model. Finally, EP4 receptor levels decreased significantly in human cortex with progression from normal to AD states, suggesting that early loss of this beneficial signaling system in preclinical AD development may contribute to subsequent progression of pathology.

SUBMITTER: Woodling NS 

PROVIDER: S-EPMC3996215 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature