Reduction of myocardial damage during acute ischemia

减少急性缺血期间的心肌损伤

• 批准号: 8552489
• 负责人: Mark Talan
• 金额: $ 34.89万
• 依托单位: NATIONAL INSTITUTE ON AGING
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8552489
• 关键词: Acute; Acute myocardial infarction; Affect; Anemia; Animal Experiments; Animal Model; Anti-Inflammatory Agents; Anti-inflammatory; Antioxidants; Apoptosis; Apoptotic; Area; Attenuated; Binding; Blood Circulation; Bolus Infusion; Cardiac; Cardiac Myocytes; Cell Survival; Cells; Cessation of life; Chronic; Clinical Trials; Clinical Trials Design; Collaborations; Consensus; Coronary; Coronary Circulation; Coronary Occlusions; Coronary artery; Deterioration; Developed Countries; Development; Dose; Echocardiography; Elderly; Erythropoiesis; Erythropoietin; Erythropoietin Receptor; Etiology; Experimental Models; Goals; Heart; Heart failure; Hematocrit procedure; Histologic; Human; In Vitro; Infarction; Inflammation; Injection of therapeutic agent; Ischemia; Left Ventricular Remodeling; Left ventricular structure; Ligation; Measures; Mitochondria; Modality; Modeling; Morbidity - disease rate; Myocardial; Myocardial Infarction; Myocardial Ischemia; Myocardium; Operative Surgical Procedures; Outcome; Oxidative Stress; Patients; Peptides; Permeability; Pharmacologic Substance; Phase; Phase II Clinical Trials; Property; Pyroglutamate; Rattus; Reactive Oxygen Species; Reperfusion Therapy; Reporting; Research Personnel; Reticulocytes; Risk; Severities; Structure; Surface; Symptoms; Testing; Therapeutic; Therapeutic Effect; Therapeutic Intervention; Time; Tissues; Trauma; Work; base; brain tissue; cationic antimicrobial protein CAP 37; cytokine; design; follow-up; functional decline; in vivo; mortality; myocardial infarct sizing; pre-clinical; prevent; programs; recombinant human erythropoietin; research study; restoration; small molecule; success; translational study

The broad objective of this program is to perform preclinical experimentation on animal models of myocardial ischemia to elucidate the mechanisms of cellular death in the myocardium and development of the subsequent CHF and to evaluate the potential of different therapeutic modalities. The ultimate goal is to limit the extent of myocardial damage and to prevent or attenuate the development of CHF. Erythropoietin (EPO), a cytokine known to stimulate erythropoiesis and widely used to treat the anemia of different etiology, had been recently reported to suppress apoptosis and to reduce the extent of damage in brain tissue following experimental ischemia or trauma. We had reported that, similar to brain tissue, a single systemic injection of recombinant human EPO following coronary ligation reduce apoptosis in the myocardial area at risk, attenuated the early left ventricular remodeling, and, eight weeks later, resulted in the reduction of the infarct size and the extent of structural and functional deterioration of the heart. We had also reported the results of studies that defined therapeutic doses and the therapeutic window of rhEPO in the rat model of MI. However, repeated dosing of rhEPO obviously causes a marked elevation of hematocrit. Moreover, it has been reported that even a single injection of rhEPO resulted in a significant elevation of the level of reticulocytes, which could represent an additional risk for MI patients. Therefore, it would be advantageous to have a compound that would have tissue protective properties of EPO without its erythropoietic effect. The purpose of the current studies was to investigate the possible therapeutic effects of a small molecule designed by Warren Pharmaceutical on the basis of EPO structure, a pyroglutamate helix B surface peptide (pHBP) that includes only a part of the EPO molecule that does not bind to EPO receptor and thus, is not erythropoietic, but retains tissue protective properties of EPO. This work had been done in collaboration with researchers from Warren Pharmaceutical and with Drs. Sollott and Boheler of the LCS. We compared the ability of pHBP and EPO to protect cardiac myocytes from oxidative stress in vitro and cardiac tissue from ischemic damage in vivo. HBP, similar to EPO, increased the reactive oxygen species (ROS) threshold for induction of the mitochondrial permeability transition by 40%. In an experimental model of myocardial infarction induced by permanent ligation of a coronary artery in rats, a single bolus injection of 60 g/kg of pHBP immediately after coronary ligation, similar to EPO, reduced apoptosis in the myocardial area at risk, examined 24 h later, by 80% and inflammation by 34%. Myocardial infarction (MI) measured 24 h after coronary ligation was similarly reduced by 50% in both pHBP- and EPO-treated rats. Two wks after surgery, left ventricular remodeling and functional decline assessed via echocardiography were significantly and similarly attenuated in pHBP- and EPO-treated rats, and MI size was reduced by 25%. The effect was retained during the 6-wk follow-up. A single bolus injection of pHBP immediately after coronary ligation was effective in reduction of MI size in a dose as low as 1 g/kg, but was ineffective at a 60 g/kg dose if administered 24 h after MI induction. We conclude that pHBP is equally cardioprotective with EPO and deserves further consideration as a safer alternative to rhEPO in the search for therapeutic options to reduce myocardial damage following blockade of the coronary circulation. Despite positive outcomes observed in the vast majority of animal experiments demonstrating strong cardioprotective properties of rhEPO in the models of myocardial infarction, the results of several phase II clinical trials in humans concluded recently were far less encouraging. As a result, the enthusiasm for this new possible therapeutic intervention was greatly diminished. We postulated that time that elapsed between symptoms onset and rhEPO administration in negative clinical trials was much longer that in successful animal experiments. To test a hypothesis that in negative clinical trials of erythropoietin in patients with acute myocardial infarction (MI) the erythropoietin (rhEPO) could be administered outside the narrow therapeutic window, we designed an animal experiment that imitated that general design of clinical trials. MI was induced in rats either by a permanent ligation of a descending coronary artery or by a 2-hr occlusion followed by a reperfusion. rhEPO, 3000 IU/kg, was administered intraperitoneally at the time of reperfusion, 4 hrs after beginning of reperfusion, or 6 hrs after permanent occlusion. MI size was measured histologically 24 hrs after coronary occlusion. The area of myocardium at risk was similar among groups. The MI size in untreated rats averaged 42% of area at risk, or 24% of left ventricle, and was reduced by more than 50% (p<0.001) in rats treated with rhEPO at the time of reperfusion. The MI size was not affected by treatment administered 4 hrs after reperfusion or 6 hrs after permanent coronary occlusion. Therefore, our study in a rat experimental model of MI demonstrates that rhEPO administered within 2 hrs of a coronary occlusion effectively reduces MI size, but when rhEPO was administered following a delay similar to that encountered in clinical trials, it had no effect on MI size. Results of our experiment strongly indicate that clinical trials that failed to demonstrate rhEPO efficacy in patients with MI may have missed a narrow therapeutic window defined in animal experiments.

该计划的主要目标是在心肌缺血的动物模型上进行临床前实验，以阐明心肌细胞死亡和随后的CHF发展的机制，并评估不同治疗方式的潜力。最终目的是限制心肌损害的程度，预防或减轻CHF的发展。 促红细胞生成素(EPO)是一种已知的刺激红细胞生成的细胞因子，被广泛用于治疗不同原因的贫血，最近有报道称它能抑制实验性脑缺血或创伤后的细胞凋亡，减轻脑组织的损伤程度。我们曾报道，与脑组织类似，冠状动脉结扎后一次性全身注射重组人促红细胞生成素可减少危险心肌区域的细胞凋亡，减轻早期左室重构，并在8周后导致心肌梗死范围缩小以及心脏结构和功能恶化的程度。我们还报道了确定重组人促红细胞生成素在心肌梗死大鼠模型中的治疗剂量和治疗窗口的研究结果。然而，重复剂量的重组人促红细胞生成素明显引起红细胞压积的显著升高。此外，据报道，即使是一次注射重组人促红细胞生成素也会导致网织红细胞水平显著升高，这可能是MI患者的额外风险。因此，具有EPO的组织保护特性而不具有其红细胞生成作用的化合物将是有利的。本研究的目的是探讨Warren制药公司根据EPO结构设计的一种小分子的可能的治疗作用。EPO结构是一种焦谷氨酸螺旋B表面肽(PHBP)，它只包含EPO分子的一部分，该分子不与EPO受体结合，因此不是促红细胞生成素，但保留了EPO的组织保护特性。 这项工作是与沃伦制药公司的研究人员以及LCS的Sollott和Boheler博士合作完成的。我们比较了PHBP和EPO在体外保护心肌细胞免受氧化应激的能力，以及在体内保护心肌组织免受缺血损伤的能力。与EPO类似，HBP使诱导线粒体通透性转变的ROS阈值增加了40%。在永久性结扎大鼠冠状动脉造成的心肌梗死模型上，冠状动脉结扎后立即单次注射60g/kg PHBP，与促红细胞生成素相似，可减少危险心肌区域的细胞凋亡，24小时后检查，减少80%，炎症减少34%。冠状动脉结扎后24小时测得的心肌梗死(MI)在PHBP和EPO治疗的大鼠中相似地减少了50%。术后两周，用PHBP和EPO治疗的大鼠，超声心动图评估的左心室重塑和功能衰退明显减弱，心肌梗死面积缩小25%。在6wk的随诊过程中，效果得以保留。冠状动脉结扎后即刻单次注射PHBP可有效缩小心肌梗死面积，剂量低至1g/kg，但在诱导后24 h注射60g/kg则无效。我们的结论是，PHBP与EPO具有同等的心脏保护作用，在寻找减少冠脉循环阻断后心肌损害的治疗方案时，值得进一步考虑作为rhEPO的更安全替代品。 尽管在绝大多数动物实验中观察到了积极的结果，表明在心肌梗死模型中重组人促红细胞生成素具有强大的心脏保护作用，但最近在人类身上得出的几项II期临床试验的结果远远不那么令人鼓舞。结果，人们对这种新的可能的治疗干预的热情大大降低。我们推测，在阴性临床试验中，从症状出现到给予重组人促红细胞生成素的时间比在成功的动物实验中要长得多。为了验证一个假设，即在急性心肌梗死(MI)患者的促红细胞生成素(RhEPO)阴性临床试验中，促红细胞生成素(RhEPO)可以在狭窄的治疗窗口之外使用，我们设计了一个模仿临床试验总体设计的动物实验。 通过永久性结扎冠状动脉降支或闭塞2小时后再灌流的方法诱导大鼠心肌梗死。在再灌流时、再灌流开始后4h或永久阻断后6h，分别给予重组人促红细胞生成素3000IU/kg。冠状动脉闭塞后24小时行组织学测量心肌梗死大小。不同组间的危险心肌面积相似。未治疗的大鼠心肌梗死面积平均为危险面积的42%，或左心室的24%，而重组人促红细胞生成素治疗的大鼠再灌流时心肌梗死面积缩小了50%以上(p&lt；0.001)。心肌梗死大小不受再灌注后4h或永久闭塞后6h给药的影响。因此，我们在大鼠实验性心肌梗死模型上的研究表明，在冠状动脉闭塞后2小时内给予重组人促红细胞生成素有效地缩小了心肌梗死大小，但当重组人促红细胞生成素在与临床试验中遇到的延迟类似的时间后给予时，对心肌梗死大小没有影响。我们的实验结果强烈表明，未能证明重组人促红细胞生成素对心肌梗死患者有效的临床试验可能错过了动物实验中定义的一个狭窄的治疗窗口。