Decreased neuronal death in Na+/H+ exchanger isoform 1-null mice after in vitro and in vivo ischemia.
Na+/H+ exchanger isoform 1 (NHE1) is a major acid extrusion mechanism after intracellular acidosis. We hypothesized that stimulation of NHE1 after cerebral ischemia contributes to the disruption of Na+ homeostasis and neuronal death. In the present study, expression of NHE1 was detected in cultured mouse cortical neurons. Three hours of oxygen and glucose deprivation (OGD) followed by 21 h of reoxygenation (REOX) led to 68 +/- 10% cell death. Inhibition of NHE1 with the potent inhibitor cariporide (HOE 642) or genetic ablation of NHE1 reduced OGD-induced cell death by approximately 40-50% (p < 0.05). In NHE1(+/+) neurons, OGD caused a twofold increase in [Na+]i, and 60 min REOX triggered a sevenfold increase. Genetic ablation of NHE1 or HOE 642 treatment had no effects on the OGD-mediated initial Na+(i) rise but reduced the second phase of Na+(i) rise by approximately 40-50%. In addition, 60 min REOX evoked a 1.5-fold increase in [Ca2+]i in NHE1(+/+) neurons, which was abolished by inhibition of either NHE1 or reverse-mode operation of Na+/Ca2+ exchange. OGD/REOX-mediated mitochondrial Ca2+ accumulation and cytochrome c release were attenuated by inhibition of NHE1 activity. In an in vivo focal ischemic model, 2 h of left middle cerebral artery occlusion followed by 24 h of reperfusion induced 84.8 +/- 8.0 mm3 infarction in NHE1(+/+) mice. NHE1(+/+) mice treated with HOE 642 or NHE1 heterozygous mice exhibited a approximately 33% decrease in infarct size (p < 0.05). These results imply that NHE1 activity disrupts Na+ and Ca2+ homeostasis and contributes to ischemic neuronal damage.
Luo
Jing
J
Department of Physiology, University of Wisconsin Medical School, Madison, Wisconsin 53792, USA.
Chen
Hai
H
Kintner
Douglas B
DB
Shull
Gary E
GE
Sun
Dandan
D
D000818:Animals; D002545:Brain Ischemia / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D027682:Cation Transport Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D016923:Cell Death / Q000235:genetics / Q000502:physiology; D015687:Cell Hypoxia / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000235:genetics; D005260:Female; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000201:enzymology* / Q000473:pathology; D011247:Pregnancy; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology
D027682:Cation Transport Proteins; D008565:Membrane Proteins; C490997:Slc9a1 protein, mouse; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers