EFFECT OF DRUGS UPON MYOCARDIAL HYPOXIA

单次或多次短暂的心肌缺血，在长时间的缺血之前，已被证明可以显着减少心肌梗死面积，这种现象称为缺血预处理（IPC）。 IPC发生在两个阶段，其中心脏保护作用仅持续1-2小时的急性期和在1 - 2 -24小时再次发生并持续48-96小时的延迟期。 我们的实验室首次证明，内源性阿片类物质通过δ（δ）阿片受体起作用，并增强三磷酸腺苷敏感性钾通道（KATP通道）的开放是触发和维持完整大鼠心脏急性和延迟IPC的关键因素。 基于这些发现，本提案的长期目标是阐明δ 1-阿片受体激活导致大鼠心脏中急性和/或延迟PC的细胞内信号传导途径。 待检验的主要假设是δ 1-阿片受体的激活通过激活几种细胞内激酶途径产生急性和延迟PC，所述细胞内激酶途径包括酪氨酸激酶（TK）、蛋白激酶C（PKC）和促分裂原活化蛋白激酶（MAPK）级联，其导致线粒体KATP通道（mito KATP）的激活和心脏保护。 实验将在离体缓冲液灌注大鼠心脏和完整血液灌注大鼠心脏中进行。 我们将通过选择性药理学探针、免疫细胞化学和Western印迹分析，来确定TK、PKC的不同亚型以及MAPK途径的3个主要组分，细胞外信号调节激酶（ERK 1/2）、Jun N-末端激酶（JNK）和p38 MAPK在阿片诱导的PC中的作用。 我们将使用2个指标，即器官水平的梗死面积和亚细胞水平的线粒体功能，来评估离体和完整心脏长时间缺血和再灌注后的心肌损伤。 将通过测量ATP合成速率、线粒体膜电位和线粒体耗氧量来评估线粒体KATP通道功能。 在存在和不存在mito KATP的激动剂或拮抗剂的情况下，从对照、阿片样物质和IPC处理的心脏收获线粒体，以确定该亚细胞器在心脏保护中的作用。阿片类药物产生延迟PC的机制将与热休克反应进行比较，作为比较的标准。 该研究结果新颖，具有重要的临床意义，可能成为治疗急性或慢性缺血性心脏病患者的有效新手段。 该项目特别令人兴奋，因为许多阿片类激动剂已经提供给医生，在患者中实施这一概念之前可能不需要长时间的药物开发。

Single or multiple brief periods of myocardial ischemia prior to a prolonged period of ischemia have been shown to produce a marked reduction in myocardial infarct size, a phenomenon termed ischemic preconditioning (IPC). IPC occurs in two phases, an acute phase in which the cardioprotective effects only persist for 1-2 hours and a delayed phase which reoccurs at 12-24 hours and persists for 48-96 hours. Our laboratory was the first demonstrate that endogenous opioids acting via a delta (delta) opioid receptor and enhanced opening of the adenosine-triphosphate sensitive potassium channel (KATP channel) were key factors in triggering and maintaining acute and delayed IPC in the intact rat heart. Based on these findings, the long- term goal of the present proposal is to elucidate intracellular signalling pathways by which delta1-opioid receptor activation leads to acute and/or delayed PC in the rat heart. The major hypothesis to be tested is that activation of the delta1-opioid receptor produces acute and delayed PC by activating several intracellular kinase pathways consisting of tyrosine kinase (TK), protein kinase C (PKC) and the mitogen-activated protein kinase (MAPK) cascade which leads to activation of the mitochondrial KATP channel (mito KATP) and cardioprotection. Experiments will be performed in isolated buffer-perfused rat hearts and intact blood-perfused rat hearts. By use of selective pharmacological probes, immunocytochemistry and Western blot analysis, we will determine the role of TK, different isoforms of PKC and the 3 major components of the MAPK pathway, extracellular signal- regulated kinase (ERK 1/2), Jun N-terminal kinase (JNK) and p38 MAPK in opioid-induced PC. We will use 2 indices, infarct size at the organ level and mitochondrial function at the subcellular level, to assess myocardial injury following prolonged ischemia and reperfusion in isolated and intact hearts. Mitochondrial KATP channel function will be assessed by measurements of ATP synthesis rates, mitochondrial membrane potential and mitochondrial oxygen consumption. Mitochondria will be harvested from control, opioid- and IPC-treated hearts in the presence and absence of agonists or antagonists of mito KATP to determine the role of this subcellular organelle in cardioprotection. Mechanisms of delayed PC produced by opioids will be compared to the heat shock response as a standard of comparison. The results of the proposal are novel and have great clinical significance and may result in an effective new means of treating patients with acute or chronic ischemic heart disease. This project is particularly exciting since many opioid agonists are already available to physicians and a long period of drug development may not be necessary before implementing this concept in patients.