Sun Hong-Shuo, Xu Baofeng, Chen Wenliang, Xiao Aijiao, Turlova Ekaterina, Alibraham Ammar, Barszczyk Andrew, Bae Christine Y J, Quan Yi, Liu Baosong, Pei Lin, Sun Christopher L F, Deurloo Marielle, Feng Zhong-Ping
Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Pharmacology & Toxicology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
Exp Neurol. 2015 Jan;263:161-71. doi: 10.1016/j.expneurol.2014.10.003. Epub 2014 Oct 18.
Neonatal hypoxic-ischemic brain injury and its related illness hypoxic-ischemic encephalopathy (HIE) are major causes of nervous system damage and neurological morbidity in children. Hypoxic preconditioning (HPC) is known to be neuroprotective in cerebral ischemic brain injury. K(ATP) channels are involved in ischemic preconditioning in the heart; however the involvement of neuronal K(ATP) channels in HPC in the brain has not been fully investigated. In this study, we investigated the role of HPC in hypoxia-ischemia (HI)-induced brain injury in postnatal seven-day-old (P7) CD1 mouse pups. Specifically, TTC (2,3,5-triphenyltetrazolium chloride) staining was used to assess the infarct volume, TUNEL (Terminal deoxynucleotidyl transferase mediated dUTP nick end-labeling) to detect apoptotic cells, Western blots to evaluate protein level, and patch-clamp recordings to measure K(ATP) channel current activities. Behavioral tests were performed to assess the functional recovery after hypoxic-ischemic insults. We found that hypoxic preconditioning reduced infarct volume, decreased the number of TUNEL-positive cells, and improved neurobehavioral functional recovery in neonatal mice following hypoxic-ischemic insults. Pre-treatment with a K(ATP) channel blocker, tolbutamide, inhibited hypoxic preconditioning-induced neuroprotection and augmented neurodegeneration following hypoxic-ischemic injury. Pre-treatment with a K(ATP) channel opener, diazoxide, reduced infarct volume and mimicked hypoxic preconditioning-induced neuroprotection. Hypoxic preconditioning induced upregulation of the protein level of the Kir6.2 isoform and enhanced current activities of K(ATP) channels. Hypoxic preconditioning restored the HI-reduced PKC and pAkt levels, and reduced caspase-3 level, while tolbutamide inhibited the effects of hypoxic preconditioning. We conclude that K(ATP) channels are involved in hypoxic preconditioning-induced neuroprotection in neonatal hypoxic-ischemic brain injury. K(ATP) channel openers may therefore have therapeutic effects in neonatal hypoxic-ischemic brain injury.
新生儿缺氧缺血性脑损伤及其相关疾病缺氧缺血性脑病（HIE）是儿童神经系统损害和神经疾病的主要原因。已知缺氧预处理（HPC）对脑缺血性脑损伤具有神经保护作用。K（ATP）通道参与心脏的缺血预处理；然而，神经元K（ATP）通道在脑HPC中的作用尚未得到充分研究。在本研究中，我们研究了HPC在出生后7天（P7）的CD1小鼠幼崽缺氧缺血（HI）诱导的脑损伤中的作用。具体而言，使用TTC（2,3,5-三苯基氯化四氮唑）染色评估梗死体积，TUNEL（末端脱氧核苷酸转移酶介导的dUTP缺口末端标记）检测凋亡细胞，蛋白质印迹法评估蛋白质水平，膜片钳记录测量K（ATP）通道电流活性。进行行为测试以评估缺氧缺血损伤后的功能恢复。我们发现缺氧预处理减少了梗死体积，减少了TUNEL阳性细胞的数量，并改善了新生儿小鼠在缺氧缺血损伤后的神经行为功能恢复。用K（ATP）通道阻滞剂甲苯磺丁脲预处理可抑制缺氧预处理诱导的神经保护作用，并加重缺氧缺血损伤后的神经退行性变。用K（ATP）通道开放剂二氮嗪预处理可减少梗死体积，并模拟缺氧预处理诱导的神经保护作用。缺氧预处理诱导Kir6.2亚型蛋白水平上调，并增强K（ATP）通道的电流活性。缺氧预处理恢复了HI降低的PKC和pAkt水平，并降低了caspase-3水平，而甲苯磺丁脲抑制了缺氧预处理的作用。我们得出结论，K（ATP）通道参与新生儿缺氧缺血性脑损伤中缺氧预处理诱导的神经保护作用。因此，K（ATP）通道开放剂可能对新生儿缺氧缺血性脑损伤具有治疗作用。
