A Novel Neuroprotective Strategy for Ischemic Stroke: Transient Mild Acidosis Treatment by CO2 Inhalation at Reperfusion

• Published in: Journal of cerebral blood flow and metabolism Vol. 34; no. 2; pp. 275 - 283
• Main Authors: Fan, Yan-Ying, Shen, Zhe, He, Ping, Jiang, Lei, Hou, Wei-wei, Shen, Yao, Zhang, Xiang-Nan, Hu, Wei-Wei, Chen, Zhong
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.02.2014; Sage Publications Ltd; Nature Publishing Group
• Subjects: Acidosis - blood; Acidosis - chemically induced; Acidosis - drug therapy; Animals; Brain Ischemia - blood; Brain Ischemia - drug therapy; Brain Ischemia - physiopathology; Carbon Dioxide - pharmacology; Male; Mice; Neuroprotective Agents - pharmacology; Original; Reperfusion Injury - blood; Reperfusion Injury - drug therapy; Reperfusion Injury - physiopathology; Sodium Bicarbonate - blood; Stroke - blood; Stroke - drug therapy; Stroke - physiopathology; acidosis treatment; mPTP; cerebral ischemia; neuroprotection
• ISSN: 0271-678X; 1559-7016
• DOI: 10.1038/jcbfm.2013.193

Acidosis is one of the key components in cerebral ischemic postconditioning that has emerged recently as an endogenous strategy for neuroprotection. We set out to test whether acidosis treatment at reperfusion can protect against cerebral ischemia/reperfusion injury. Adult male C57BL/6 J mice were subjected to 60-minute middle cerebral arterial occlusion followed by 24-hour reperfusion. Acidosis treatment by inhaling 10%, 20%, or 30% CO2 for 5 or 10 minutes at 5, 50, or 100 minutes after reperfusion was applied. Our results showed that inhaling 20% CO2 for 5 minutes at 5 minutes after reperfusion-induced optimal neuroprotection, as revealed by reduced infarct volume. Attenuating brain acidosis with NaHCO3 significantly compromised the acidosis or ischemic postconditioning-induced neuroprotection. Consistently, both acidosis-treated primary cultured cortical neurons and acute corticostriatal slices were more resistant to oxygen–glucose deprivation/reperfusion insult. In addition, acidosis inhibited ischemia/reperfusion-induced apoptosis, caspase-3 expression, cytochrome c release to cytoplasm, and mitochondrial permeability transition pore (mPTP) opening. The neuroprotection of acidosis was inhibited by the mPTP opener atractyloside both in vivo and in vitro. Taken together, these findings indicate that transient mild acidosis treatment at reperfusion protects against cerebral ischemia/reperfusion injury. This neuroprotection is likely achieved, at least partly, by inhibiting mPTP opening and mitochondria-dependent apoptosis.