IPTAKALIM PROTECTS AGAINST HYPOXIC BRAIN INJURY THROUGH MULTIPLE PATHWAYS ASSOCIATED WITH ATP-SENSITIVE POTASSIUM CHANNELS

The rapid and irreversible brain injury produced by anoxia when stroke occurs is well known. Cumulative evidence suggests that the activation of neuronal ATP-sensitive potassium (K-ATP) channels may have inherent protective effects during cerebral hypoxia, yet little information regarding the therapeutic effects of K-ATP channel openers is available. We hypothesized that pretreatment with a K-ATP channel opener might protect against brain injury induced by cerebral hypoxia. In this study, adult Wistar rats were treated with iptakalim, a new K-ATP channel opener, which is selective for SUR2 type K-ATP channels, by intragastric administration at doses of 2, 4, or 8 mg/kg/day for 7 days before being exposed to simulated high altitude equivalent to 8000 m in a decompression chamber for 8 h leading to hypoxic brain injury. By light and electron microscopic images, we observed that hypobaric hypoxia-induced brain injury could be prevented by pretreatment with iptakalim. It was also observed that the permeability of the blood-brain barrier, water content, Na+ and Ca2+ concentration, and activities of Na+,K+-ATPase, Ca2+-ATPase and Mg2+-ATPase in rat cerebral cortex were increased and the gene expression of the occludin or aquaporin-4 was down- or upregulated respectively, which could also be prevented by the pretreatment with iptakalim at doses of 2, 4, or 8 mg/kg in a dose-dependent manner. Furthermore, we found that in an oxygen-and-glucose-deprived model in ECV304 cells and rat cortical astrocytes, pretreatment with iptakalim significantly increased survived cell rates and decreased lactate dehydrogenate release, which were significantly antagonized by glibenclamide, a K-ATP channel blocker. We conclude that iptakalim is a promising drug that may protect against brain injury induced by acute hypobaric hypoxia through multiple pathways associated with SUR2-type K-ATP channels, suggesting a new therapeutic strategy for stroke treatment. (C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.