Amyloid-beta protein oligomer at low nanomolar concentrations activates microglia and induces microglial neurotoxicity.

ABSTRACT: Neuroinflammation and associated neuronal dysfunction mediated by activated microglia play an important role in the pathogenesis of Alzheimer disease (AD). Microglia are activated by aggregated forms of amyloid-? protein (A?), usually demonstrated in vitro by stimulating microglia with micromolar concentrations of fibrillar A?, a major component of amyloid plaques in AD brains. Here we report that amyloid-? oligomer (A?O), at 5-50 nm, induces a unique pattern of microglia activation that requires the activity of the scavenger receptor A and the Ca(2+)-activated potassium channel KCa3.1. A?O treatment induced an activated morphological and biochemical profile of microglia, including activation of p38 MAPK and nuclear factor ?B. Interestingly, although increasing nitric oxide (NO) production, A?O did not increase several proinflammatory mediators commonly induced by lipopolyliposaccharides or fibrillar A?, suggesting that A?O stimulates both common and divergent pathways of microglia activation. A?O at low nanomolar concentrations, although not neurotoxic, induced indirect, microglia-mediated damage to neurons in dissociated cultures and in organotypic hippocampal slices. The indirect neurotoxicity was prevented by (i) doxycycline, an inhibitor of microglia activation; (ii) TRAM-34, a selective KCa3.1 blocker; and (iii) two inhibitors of inducible NO synthase, indicating that KCa3.1 activity and excessive NO release are required for A?O-induced microglial neurotoxicity. Our results suggest that A?O, generally considered a neurotoxin, may more potently cause neuronal damage indirectly by activating microglia in AD.

SUBMITTER: Maezawa I 

PROVIDER: S-EPMC3030372 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature