ABSTRACT
Inflammation mediated by activated microglia cells has been shown to contribute to the pathogenesis of Alzheimer disease (AD) [1]. Microglia are the immune cells in the central nervous system, and when activated they secrete the lipid-derived mediator prostaglandin E2 (PGE2), the cytokine interleukin-1beta (IL-1beta), and other inflammatory mediators. Apolipoprotein E isoform 4 (apoE4), coded for by the gene APOE4 (epsilon4), has been shown to correlate with higher risk of onset of AD, as well as with increased severity of other diseases with a neuroinflammatory component. This study investigated isoform-specific effects of apoE on the regulation of PGE2, COX2, and IL-1beta expression. Two physiologically relevant preparations of apoE displayed an isoform-specific effect on inflammation in primary adult microglia cultured from adult rat brain cortex. Specifically, apoE4 alone, but not the more common isoform apoE3, stimulated secretion of PGE2 and IL-1beta. The increase in PGE2 release stimulated by apoE4 was not accompanied by the upregulation of the COX-2 enzyme in microglia.
Subject(s)
Alzheimer Disease/metabolism , Alzheimer Disease/physiopathology , Apolipoproteins E/metabolism , Dinoprostone/biosynthesis , Inflammation/metabolism , Inflammation/physiopathology , Interleukin-1/biosynthesis , Microglia/metabolism , Prostaglandin-Endoperoxide Synthases/biosynthesis , Protein Isoforms/metabolism , Animals , Cyclooxygenase 2 , Rats , Rats, Sprague-DawleyABSTRACT
Alzheimer disease (AD) involves glial inflammation associated with amyloid plaques. The role of the microglial cells in the AD brain is controversial, as it remains unclear if the microglia form the amyloid fibrils of plaques or react to them in a macrophage-phagocytic role. Also, it is not known why microglia are preferentially associated with some amyloid plaque types. This review will provide substantial evidence to support the phagocytic role of microglia in the brain as well as explain why microglia are generally associated with specific plaque types that may be explained through their unique mechanisms of formation. In summary, the data presented suggests that plaque associated microglial activation is typically subsequent to specific amyloid plaque formations in the AD brain.
