Preferential involvement of Na+/Ca2+ exchanger type-1 in the brain damage caused by transient focal cerebral ischemia in mice

The Na+/Ca2+ exchanger (NCX), an ion-transporter located in the plasma membrane of neuronal cells, contributes to intracellular Ca2+ homeostasis. Within the brain, three isoforms (NCX1, NCX2, and NCX3) are widely distributed. However, it is not clear to what extent these isoforms are involved in ischemic brain damage in mammals. We therefore used genetically altered mice and isoform-selective NCX inhibitors in a model of transient focal ischemia to investigate the role of each NCX isoform in ischemic brain damage. NCX isoform-mutant mice (NCX1+/−, NCX2+/−, and NCX3+/−) and wild-type mice were subjected to 90 min of middle cerebral artery occlusion (MCAO) followed by 24 h of reperfusion. One of three NCX inhibitors [SN-6, KB-R7943, or SEA0400 (3 or 10 mg kg−1, i.p.)] was administered to ddY mice at 30 min before more prolonged (4-h) MCAO followed by 24 h of reperfusion. After transient MCAO reperfusion, the cerebral infarcts in NCX1+/− mice, but not those in NCX2+/− or NCX3+/− mice, were significantly smaller than those in wild-type mice. SN-6 and SEA0400, which are more selective for the NCX1 isoform, significantly reduced the infarct volume at 10 mg/kg. In contrast, KB-R7943, which is more selective for NCX3, did not. These results suggest that the NCX1 isoform may act preferentially (vs. the NCX2 and NCX3 isoforms) to exacerbate the cerebral damage caused by ischemic insult in mice, and that NCX1-selective inhibitors warrant investigation as a potential therapeutic agents for stroke.

► Cerebral infarcts were smaller in NCX1+/− mice than in wild-type mice. ► Cerebral infarcts did not differ between NCX2+/− and NCX3+/− mice and wild-type mice. ► Selective NCX1 inhibitors significantly reduced infarct volume in ddY mice.