RESUMO
The Alzheimer's disease (AD) brain is characterized by plaques containing beta-amyloid (Abeta) protein surrounded by astrocytes and reactive microglia. Activation of microglia by Abeta initiates production of reactive oxygen species (ROS) by the plasmalemmal NADPH oxidase; the resultant oxidative stress is thought to contribute to neurodegeneration in AD. We have previously shown that Abeta upregulates a chloride current mediated by the chloride intracellular channel 1 (CLIC1) protein in microglia. We now demonstrate that Abeta promotes the acute translocation of CLIC1 from the cytosol to the plasma membrane of microglia, where it mediates a chloride conductance. Both the Abeta induced Cl(-) conductance and ROS generation were prevented by pharmacological inhibition of CLIC1, by replacement of chloride with impermeant anions, by an anti-CLIC1 antibody and by suppression of CLIC1 expression using siRNA. Thus, the CLIC1-mediated Cl(-) conductance is required for Abeta-induced generation of neurotoxic ROS by microglia. Remarkably, CLIC1 activation is itself dependent on oxidation by ROS derived from the activated NADPH oxidase. We therefore propose that CLIC1 translocation from the cytosol to the plasma membrane, in response to redox modulation by NADPH oxidase-derived ROS, provides a feedforward mechanism that facilitates sustained microglial ROS generation by the NAPDH oxidase.
Assuntos
Peptídeos beta-Amiloides/farmacologia , Encéfalo/citologia , Canais de Cloreto/fisiologia , Microglia/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animais , Anticorpos/farmacologia , Encéfalo/metabolismo , Células Cultivadas , Canais de Cloreto/imunologia , Glicolatos/farmacologia , Proteínas de Fluorescência Verde/biossíntese , Humanos , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Transgênicos , Mutação/fisiologia , Técnicas de Patch-Clamp , Presenilina-1/genética , Transporte Proteico/efeitos dos fármacos , Transporte Proteico/fisiologia , RNA Interferente Pequeno/farmacologia , Ratos , Proteínas tau/genéticaRESUMO
Oxidative stress, characterized by overproduction of reactive oxygen species (ROS), is a major feature of several pathological states. Indeed, many cancers and neurodegenerative diseases are accompanied by altered redox balance, which results from dysregulation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In this review, we consider the role of the intracellular chloride channel 1 (CLIC1) in microglial cells during oxidative stress. Following microglial activation, CLIC1 translocates from the cytosol to the plasma membrane where it promotes a chloride conductance. The resultant anionic current balances the excess charge extruded by the active NADPH oxidase, supporting the generation of superoxide by the enzyme. In this scenario, CLIC1 could be considered to act as both a second messenger and an executor.