Cohen M V, Liu Y, Liu G S, Wang P, Weinbrenner C, Cordis G A, Das D K, Downey J M
Department of Medicine, University of South Alabama College of Medicine, Mobile, USA.
Circulation. 1996 Oct 1;94(7):1713-8. doi: 10.1161/01.cir.94.7.1713.
Activation of protein kinase C (PKC) is thought to be a critical step in ischemic preconditioning. Many receptor agonists activate PKC via stimulation of phospholipase C (PLC), which degrades membrane phospholipids to diacylglycerol (DAG), an important PKC cofactor. However, adenosine receptors, critical components of the prototypical preconditioning pathway, are not thought to couple to PLC in the cardiomyocyte. We therefore tested whether ischemic preconditioning or adenosine might instead activate phospholipase D (PLD) to produce DAG.
PLD activity was measured in isolated rabbit hearts. Ischemic injury was evaluated in either isolated rabbit hearts or dispersed myocytes. PLD activity doubled from a control level of 74.8 +/- 10.0 to 140.0 +/- 11.5 mumol.min-1.g-1 (P < .025) after two 5-minute periods of global ischemia separated by 5 minutes of reperfusion. A similar increase was noted after the heart had been exposed to (R)-N6-(2-phenylisopropyl)-adenosine [(R)-PIA] for 20 minutes. When sodium oleate, which activates PLD, was administered to isolated hearts before a 30-minute coronary occlusion, infarct size (15.6 +/- 2.0% of the risk zone) was significantly smaller than in untreated hearts (30.4 +/- 2.2%; P < .01). Exposure to sodium oleate significantly prolonged the rate of isolated myocyte survival during simulated ischemia. Propranolol 100 mumol/L, which blocks DAG production from metabolites produced by PLD catalysis, completely abolished the protective effects of both metabolic preconditioning and (R)-PIA exposure in myocytes.
We conclude that PLD stimulation is involved in the protection of ischemic preconditioning in the rabbit heart.
蛋白激酶C（PKC）的激活被认为是缺血预处理中的关键步骤。许多受体激动剂通过刺激磷脂酶C（PLC）来激活PKC，PLC可将膜磷脂降解为二酰甘油（DAG），这是一种重要的PKC辅助因子。然而，腺苷受体作为典型预处理途径的关键组成部分，在心肌细胞中并不被认为与PLC偶联。因此，我们测试了缺血预处理或腺苷是否可能通过激活磷脂酶D（PLD）来产生DAG。
在离体兔心脏中测量PLD活性。在离体兔心脏或分离的心肌细胞中评估缺血损伤。在经历两次5分钟的全心缺血（中间间隔5分钟再灌注）后，PLD活性从对照水平的74.8±10.0μmol·min⁻¹·g⁻¹增加了一倍，达到140.0±11.5μmol·min⁻¹·g⁻¹（P<.025）。在心脏暴露于（R）-N6-（2-苯异丙基）-腺苷[（R）-PIA]20分钟后也观察到类似的增加。当在30分钟冠状动脉闭塞前向离体心脏给予激活PLD的油酸钠时，梗死面积（占危险区的15.6±2.0%）明显小于未处理的心脏（30.4±2.2%；P<.01）。暴露于油酸钠可显著延长模拟缺血期间分离心肌细胞的存活时间。100μmol/L的普萘洛尔可阻断PLD催化产生的代谢产物生成DAG，它完全消除了代谢预处理和（R）-PIA暴露对心肌细胞的保护作用。
我们得出结论，PLD刺激参与了兔心脏缺血预处理的保护作用。
