Abstract 20923: Knockout Mice With Gene Ablation of the Acid-Extruding Membrane Protein Nbcn1 Develop Neuroprotection
Acidification is observed in stroke ranging between pH 6.1 and 6.5 in focal and global ischemia. This acidification induces deleterious effects including release of protease and calcium, activation of acid-sensing ion channels, mitochondrial destruction, and more. The pathological aspects of acidification have been well documented; nonetheless our understanding of how pH contributes to neuronal death in cerebral ischemia is still incomplete. Here, we examined the vulnerability of NBCn1 knockout mice to neuronal death induced by brain insults. Compared to wild-type littermates, NBCn1 knockout mice develop low plasma and CSF pH. To determined neuroprotective effect, mice were administered with NMDA (75 mg/kg body weight; intraperitoneal injection; 8 males for each group of knockouts and wild types). Knockout mice showed substantially reduced expression and activity of active caspase-3, and low TUNEL staining. Thus, knockout mice exhibit reduced neuronal death. In cultures of hippocampal neurons from postnatal P5 mice, knockout mouse neurons had reduced NMDA-mediated excitotoxicity, determined by LDH release (p < 0.05; n = 6 for each; two-way ANOVA with Bonferroni post-test). Determined by cGMP production in the presence of the NOS blocker L-NAME, neurons from knockouts showed a significantly low nNOS activity (p < 0.05). The basal cGMP production was slightly higher in knockouts probably due to low intracellular pH; however there was no increase in cGMP production after NMDA treatment. Thus, the nNOS/NMDAR pathway was altered in knockouts. In other experiments, mice (11 week old) were subjected to cerebral infarction by a unilateral occlusion of the common carotid artery plus hypoxia (7.5% oxygen). Determined by triphenyltetrazolium chloride staining 24 h after surgery, we found that, while wild type mice showed sizable infarction, knockout mice had no discernible injury. White matters in the striatum and external capsule in the ipsilateral hemisphere were destructed in wild type mice, whereas the corresponding regions in knockout mice were normal. We conclude that NBCn1 deletion protects neurons from acute brain insults.
Author Disclosures: H. Park: None. J.A. jones: None. Y. Sun: None. C. Kuan: None. I. Choi: None.
- © 2016 by American Heart Association, Inc.