Ca2+-Permeable Acid-sensing Ion Channels and Ischemic Brain Injury |
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Authors: | Z-G Xiong X-P Chu RP Simon |
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Institution: | (1) Robert S. Dow Neurobiology Laboratories, Legacy Clinical Research Center, 1225 NE 2nd Ave, Portland, OR 97232, USA |
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Abstract: | Acidosis is a common feature of brain in acute neurological injury, particularly in ischemia where low pH has been assumed
to play an important role in the pathological process. However, the cellular and molecular mechanisms underlying acidosis-induced
injury remain unclear. Recent studies have demonstrated that activation of Ca2+-permeable acid-sensing ion channels (ASIC1a) is largely responsible for acidosis-mediated, glutamate receptor-independent,
neuronal injury. In cultured mouse cortical neurons, lowering extracellular pH to the level commonly seen in ischemic brain
activates amiloride-sensitive ASIC currents. In the majority of these neurons, ASICs are permeable to Ca2+, and an activation of these channels induces increases in the concentration of intracellular Ca2+ (Ca2+]i). Activation of ASICs with resultant Ca2+]i loading induces time-dependent neuronal injury occurring in the presence of the blockers for voltage-gated Ca2+ channels and the glutamate receptors. This acid-induced injury is, however, inhibited by the blockers of ASICs, and by reducing
Ca2+]o. In focal ischemia, intracerebroventricular administration of ASIC1a blockers, or knockout of the ASIC1a gene protects brain
from injury and does so more potently than glutamate antagonism. Furthermore, pharmacological blockade of ASICs has up to
a 5 h therapeutic time window, far beyond that of glutamate antagonists. Thus, targeting the Ca2+-permeable acid-sensing ion channels may prove to be a novel neuroprotective strategy for stroke patients. |
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Keywords: | Acidosis Ischemia Ca2+ toxicity Neurons Patch clamp |
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