Deletion of TRAAK Potassium Channel Affects Brain Metabolism and Protects against Ischemia

Abstract

Cerebral stroke is a worldwide leading cause of disability. The two-pore domain K+ channels identified as background channels are involved in many functions in brain under physiological and pathological conditions. We addressed the hypothesis that TRAAK, a mechano-gated and lipid-sensitive two-pore domain K+ channel, is involved in the pathophysiology of brain ischemia. We studied the effects of TRAAK deletion on brain morphology and metabolism under physiological conditions, and during temporary focal cerebral ischemia in Traak-/- mice using a combination of in vivo magnetic resonance imaging (MRI) techniques and multinuclear magnetic resonance spectroscopy (MRS) methods. We provide the first in vivo evidence establishing a link between TRAAK and neurometabolism. Under physiological conditions, Traak-/- mice showed a particular metabolic phenotype characterized by higher levels of taurine and myo-inositol than Traak+/+ mice. Upon ischemia, Traak-/- mice had a smaller infarcted volume, with lower contribution of cellular edema than Traak+/+ mice. Moreover, brain microcirculation was less damaged, and brain metabolism and pH were preserved. Our results show that expression of TRAAK strongly influences tissue levels of organic osmolytes. Traak-/- mice resilience to cellular edema under ischemia appears related to their physiologically high levels of myo-inositol and of taurine, an aminoacid involved in the modulation of mitochondrial activity and cell death. The beneficial effects of TRAAK deletion designate this channel as a promising pharmacological target for the treatment against stroke. © 2012 Laigle et al.