Kir6.2-containing ATP-sensitive potassium channels protect cortical neurons from ischemic/anoxic injury in vitro and in vivo

Abstract

ATP-sensitive potassium (K ATP) channels are weak inward rectifiers that appear to play an important role in protecting neurons against ischemic damage. Cerebral stroke is a major health issue, and vulnerability to stroke damage is regional within the brain. Thus, we set out to determine whether K ATP channels protect cortical neurons against ischemic insults. Experiments were performed using Kir6.2 −/− K ATP channel knockout and Kir6.2 +/ + wildtype mice. We compared results obtained in Kir6.2 −/− and wildtype mice to evaluate the protective role of K ATP channels against focal ischemia in vivo, and, using cortical slices, against anoxic stress i n vitro. Immunohistochemistry confirmed the presence of K ATP channels in the cortex of wildtype, but not Kir6.2 −/−, mice. Results from in vivo and in vitro experimental models indicate that Kir6.2-containing K ATP channels in the cortex provide protection from neuronal death. Briefly, in vivo focal ischemia (15 min) induced severe neurological deficits and large cortical infarcts in Kir6.2 −/− mice, but not in wildtype mice. Imaging analyses of cortical slices exposed briefly to oxygen and glucose deprivation (OGD) revealed a substantial number of damaged cells (propidium iodide–labeled) in the Kir6.2 −/− OGD group, but few degenerating neurons in the wildtype OGD group, or in the wildtype and Kir6.2 −/− control groups. Slices from the three control groups had far more surviving cells (anti-NeuN antibody-labeled) than slices from the Kir6.2 −/− OGD group. These findings suggest that stimulation of endogenous cortical K ATP channels may provide a useful strategy for limiting the damage that results from cerebral ischemic stroke.