Zhang Hong Yan, McPherson Bradley C, Liu Huiping, Baman Timir S, Rock Peter, Yao Zhenhai
Department of Anesthesiology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Am J Physiol Heart Circ Physiol. 2002 Apr;282(4):H1395-403. doi: 10.1152/ajpheart.00683.2001.
Oxygen radicals and protein kinase C (PKC) mediate ischemic preconditioning. Using a cultured chick embryonic cardiomyocyte model of hypoxia and reoxygenation, we found that the oxygen radicals generated by ischemic preconditioning were H(2)O(2). Like preconditioning, H(2)O(2) selectively activated the epsilon-isoform of PKC in the particulate compartment and increased cell viability after 1 h of hypoxia and 3 h of reoxygenation. The glutathione peroxidase ebselen (converting H(2)O(2) to H(2)O) and the superoxide dismutase inhibitor diethyldithiocarbamic acid abolished the increased H(2)O(2) and the protection of preconditioning. PKC activation with phorbol 12-myristate 13-acetate increased cell survival; the protection of preconditioning was blocked by epsilonV(1-2), a selective PKC-epsilon antagonist. Similar to preconditioning, the protection of PKC activation was abolished by mitochondrial K(ATP) channel blockade with 5-hydroxydecanoate or by GABA receptor stimulation with midazolam or diazepam. In addition, PKC, mitochondrial ATP-sensitive K(+) (K(ATP)) channels, and GABA receptors had no effects on H(2)O(2) generated by ischemic preconditioning before prolonged hypoxia and reoxygenation. We conclude that H(2)O(2) opens mitochondrial K(ATP) channels and inhibits GABA receptors via activating PKC-epsilon. Through this signal transduction, preconditioning protects ischemic cardiomyocytes.
氧自由基和蛋白激酶C（PKC）介导缺血预处理。利用培养的鸡胚心肌细胞缺氧复氧模型，我们发现缺血预处理产生的氧自由基是H₂O₂。与预处理一样，H₂O₂能选择性激活微粒体部分的PKCε亚型，并在缺氧1小时和复氧3小时后提高细胞活力。谷胱甘肽过氧化物酶依布硒啉（将H₂O₂转化为H₂O）和超氧化物歧化酶抑制剂二乙二硫代氨基甲酸盐消除了H₂O₂的增加及预处理的保护作用。用佛波酯12 - 肉豆蔻酸酯13 - 乙酸酯激活PKC可提高细胞存活率；选择性PKCε拮抗剂εV(1 - 2)可阻断预处理的保护作用。与预处理相似，用5 - 羟基癸酸阻断线粒体ATP敏感性钾（KATP）通道或用咪达唑仑或地西泮刺激GABA受体可消除PKC激活的保护作用。此外，在长时间缺氧和复氧之前，PKC、线粒体ATP敏感性钾（KATP）通道和GABA受体对缺血预处理产生的H₂O₂没有影响。我们得出结论，H₂O₂通过激活PKCε打开线粒体KATP通道并抑制GABA受体。通过这种信号转导，预处理可保护缺血心肌细胞。
