Reduction of myocardial damage during acute ischemia

减少急性缺血期间的心肌损伤

• 批准号: 8148332
• 负责人: Mark Talan
• 金额: $ 21.76万
• 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/8148332
• 关键词: Acute; Ischemia; Myocardial

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. I. Erythropoietin reduces the myocardial ischemic damage. Erythropoietin (EPO), natural stimulant of erythropoiesis, recently emerged as a potential antiapoptotic factor with neuroprotective properties. We have demonstrated that the antiapoptotic effects of EPO also resulted in cardioprotection. In experiments in rats we showed that single systemic administration of recombinant human EPO (3000 IU/kg) immediately after permanent ligation of a coronary artery results in 75% reduction of the size of myocardial infarction eight weeks later. During eight weeks after induction of myocardial infarction, left ventricular remodeling and function decline in EPO treated rats was significantly attenuated and statistically was not different from that in sham operated animals. Twenty-four hours after ligation of coronary artery, the number of apoptotic myocytes measured in the myocardial risk area (area immediately adjacent to the infarct site) was reduced by half in the EPO treated rats compared with untreated animals. In subsequent experiments we established that a single intravenous dose of 3000 IU/kg is cardioprotective up to 12 hrs after coronary ligation, but it loses its cardioprotective properties after 24 hrs. If animals are treated with EPO immediately after coronary ligation, the treatment dose can be reduced up to 150 IU/kg (usual, FDA-approved dose for the treatment of anemia) without the loss of effectiveness; however, the therapeutic window in this case is also reduced to 4 hrs. In additional experiments, we showed that repeated daily EPO injections do not have any added benefits comparing with a single injection immediately after coronary ligation. II. Therapeutic window of cardioprotective properties of Erythropoietin in experimental ischemic-reperfusion model. While effective doses and the therapeutic window of EPO in the experimental model of permanent ligation of a coronary artery were well established in our previous studies (see I above), most published experimental studies on cardioprotective properties of EPO were based on more a clinically relevant model - temporary myocardial ischemic followed by reperfusion. In those reports, the EPO was injected either preventively, prior to interruption of myocardial circulation, or at the moment of restoration of circulation. Both scenarios are logistically not feasible in a clinical setting, where experimental treatment most likely will be following the interventional revascularization. In the present study we employed a rat ischemic/reperfusion model. The time of ischemia was chosen as 2 hrs - the average time between the onset of the symptoms of heart attack and implementation of clinical intervention to restore circulation in the hospital (data for USA). After 2 hrs of ischemia the circulation was restored. A single dose of EPO, 3000 IU/kg, was injected intraperitoneal either at the moment of restoration of myocardial circulation or 2 hrs later. The size of the ensuing MI, as well as the extent of apoptosis and inflammation in the area at risk were assessed histologically 24 hrs following the onset of ischemia. Results indicated that the effects of EPO applied at the moment of reperfusion were comparable with effects of EPO described for the model of a permanent coronary ligation with respect to MI size and apoptosis: MI size was significantly reduced in EPO-treated compared to untreated animals and the extent of apoptosis was significantly attenuated. However, the EPO injected 2 hrs following reperfusion did not affect either ensuing MI size or the apoptosis in the area at risk. Results, while preliminary at this time, are important for design of future clinical trials.

该项目的主要目的是对心肌缺血动物模型进行临床前实验，以阐明心肌细胞死亡的机制和随后CHF的发展，并评估不同治疗方式的潜力。最终目的是限制心肌损伤的程度，预防或减轻CHF的发展。 I.促红细胞生成素可减轻心肌缺血损伤。 促红细胞生成素（EPO）是一种天然的促红细胞生成素，近年来被认为是一种具有神经保护作用的抗凋亡因子。我们已经证明，EPO的抗凋亡作用也导致心脏保护。在大鼠的实验中，我们表明，在冠状动脉永久结扎后立即单次全身给予重组人EPO（3000 IU/kg），8周后心肌梗死面积减少75%。在诱导心肌梗死后8周内，EPO治疗组大鼠的左室重构和功能下降明显减轻，与假手术组相比无统计学差异。结扎冠状动脉后24小时，在心肌危险区（紧邻梗死部位的区域）中测量的凋亡心肌细胞的数量在EPO治疗的大鼠中与未治疗的动物相比减少了一半。在随后的实验中，我们确定了3000 IU/kg的单次静脉内剂量在冠状动脉结扎后长达12小时具有心脏保护作用，但在24小时后失去其心脏保护特性。如果在冠状动脉结扎后立即用EPO治疗动物，则治疗剂量可以减少至150 IU/kg（通常，FDA批准的治疗贫血的剂量）而不丧失有效性;然而，在这种情况下，治疗窗也减少至4小时。 在另外的实验中，我们表明，与冠状动脉结扎后立即单次注射相比，每天重复注射EPO没有任何额外的益处。 二.促红细胞生成素在实验性缺血再灌注模型中心脏保护特性的治疗窗。 虽然在我们以前的研究中已经很好地确定了EPO在永久性结扎冠状动脉的实验模型中的有效剂量和治疗窗（参见上文I），但大多数关于EPO的心脏保护特性的已发表的实验研究更多地基于临床相关模型-暂时性心肌缺血随后再灌注。在这些报告中，EPO是在心肌循环中断之前或在循环恢复时预防性注射的。这两种情况在临床环境中逻辑上都不可行，其中实验性治疗最有可能在介入血运重建后进行。在本研究中，我们采用了大鼠缺血/再灌注模型。缺血时间选择为2小时-心脏病发作症状发作和实施临床干预以恢复医院循环之间的平均时间（美国数据）。缺血2小时后，循环恢复。在心肌循环恢复时或2小时后腹腔注射EPO 3000 IU/kg。在缺血发作后24小时，组织学上评估随后的MI的大小，以及处于危险区域的细胞凋亡和炎症的程度。结果表明，在再灌注时应用的EPO的效果与永久性冠状动脉结扎模型中描述的EPO对MI大小和细胞凋亡的效果相当：与未处理的动物相比，EPO处理的动物MI大小显著减小，细胞凋亡的程度显著减弱。 然而，再灌注后2小时注射EPO并不影响随后的MI大小或危险区域的细胞凋亡。 结果虽然是初步的，但对未来临床试验的设计很重要。