Targeting the endothelial clock to treat perioperative myocardial ischemia

心肌缺血(MI)是世界范围内主要的死亡原因之一。目前，主要的治疗方法是 急性心肌梗死仍然是早期血运重建。然而，血运重建后的再灌注损伤是一种 心肌损伤的重要原因。事实上，患者的一年死亡率高达42%。 围手术期心肌梗死后再血运重建。虽然内皮细胞损伤已被认为是一种 作为心肌缺血再灌注损伤的关键因素，目前尚无内皮保护策略建立。 我们最近率先在光诱导的昼夜节律蛋白周期2(PER2)中扮演了一个新的角色 对MI的保护。光暴露策略靶向和操纵PER2功能的研究揭示 将小鼠置于强烈而不是环境光条件下一周(14小时光照：10小时黑暗， 10,000 LUX，全光谱，带紫外线滤光片)提供强大的心脏保护。作为根本机制，我们 发现强光增强了心脏PER2的昼夜节律幅度。没想到，后来 研究表明，PER2的这种幅度增强建立了一种心脏保护和低氧 诱导因子1α(HIF1a)-未损伤心脏中类似的信号环境。昼夜节律幅度 增强在不同的环境中被认为是一种保护机制，目前正在 严密的调查。然而，潜在的机制还没有被很好地理解。一种全基因组阵列 强光诱导的基因调控发现，强光上调了HIF1a调节的基因和 未损伤心脏中的内皮保护性血管生成素样蛋白4这一发现表明 内皮细胞表达的PER2在光诱导的心脏保护中的关键作用。事实上，使用老鼠和 内皮特异性PER2的缺失，我们证明了光引起的心脏保护是完全的 废止了。此外，强光处理显著改善了血管内皮细胞屏障功能 心肌缺血，这是内皮细胞PER2特异性的。因此，我们假设振幅 扩增内皮细胞PER2通过诱导HIF1a-ANGPTL4促进血管完整性 心肌梗死患者的心肌功能。为了解决这个问题，我们设计了三个具体目标：1.将药物导致的PER2定义为 心肌梗死的内皮屏障保护策略，2.药物诱导HIF1a增加昼夜节律的研究 3.研究血管内皮细胞ANGPTL4作为血管内皮生长因子受体的下游靶点 强烈的光照可引起心脏保护。 这些研究的主要目标是表征新的、基于光的治疗靶点，这些靶点可以 经过药理修饰，在心脏保护方面与强光疗法一样有效。通过 研究新的内皮靶向策略，这项提议有望识别新的、高影响的 缺血后心肌保护的治疗方法可有效地预防或 减轻大手术患者心肌缺血组织损伤。

Myocardial ischemia (MI) is one of the leading causes of death worldwide. Currently, the mainstay therapy of acute MI remains early revascularization. However, reperfusion injury following revascularization is a significant cause of myocardial damage. In fact, 1-year mortality rates are as high as 42% in patients undergoing revascularization after perioperative MI. While endothelial damage has been recognized as a critical contributor to myocardial IR-injury, no endothelial-protective strategy has been established yet. We recently pioneered a novel role for the light elicited circadian rhythm protein Period 2 (PER2) in protection from MI. Investigation of light exposure strategies to target and manipulate PER2 function revealed that housing mice under intense instead of ambient light conditions for one week (14h light:10h darkness, 10,000 LUX, full-spectrum with UV filter) mediates robust cardioprotection. As the underlying mechanism, we discovered that intense light enhanced the circadian amplitude of cardiac PER2. Unexpectedly, subsequent studies revealed that this ‘amplitude enhancement’ of PER2 established a cardioprotective and hypoxia inducible factor 1 alpha (HIF1A)-similar signaling environment in the uninjured heart. Circadian amplitude enhancement has been implicated as a protective mechanism in different settings and is currently under intense investigation. However, the underlying mechanisms are not well understood. A whole-genome array on intense light elicited gene regulation uncovered that intense light upregulated the HIF1A-regulated and endothelial-protective Angiopoietin-like 4 (ANGPTL4) protein in the uninjured heart. This discovery pointed towards a critical role for endothelial expressed PER2 in light-elicited cardioprotection. Indeed, using mice with endothelial-specific deletion of Per2, we demonstrated that light elicited cardioprotection was completely abolished. Moreover, intense light pretreatment significantly improved endothelial barrier function following myocardial ischemia, which was endothelial PER2 specific. Therefore, we hypothesize that amplitude amplification of endothelial PER2 boosts vascular integrity via induction of HIF1A-ANGPTL4 which improves myocardial function in MI. To address this, we designed three specific aims: 1. Define drug-elicited PER2 as an endothelial-barrier-protective strategy in MI, 2. Study drug induced HIF1A to increase the circadian amplitude and to overcome Per2 deficiency, 3. Study endothelial ANGPTL4 as a downstream target of intense light elicited cardioprotection. The main goal of these studies is to characterize novel, light-based therapeutic targets that can be modified pharmacologically and are as effective as an intense light treatment in cardioprotection. By investigating novel endothelium-targeting strategies, this proposal promises to identify new, high-impact therapeutic approaches for post-ischemic myocardial protection that could effectively be used to prevent or attenuate ischemic tissue injury of the myocardium in patients undergoing major surgery.