Aims Ischemia/reperfusion (I/R) injury is an important complication of reperfusion therapy for acute myocardial infarction, extremely compromising the cardiac benefits of revascularization, however, specific and efficient treatment for cardiac I/R injury is still lacking. Isthmin-1 (ISM1) is a novel adipokine, and plays indispensable roles in regulating glycolipid metabolism and cell survival. The present study aims to investigate the potential role and molecular mechanism of ISM1 in cardiac I/R injury using gain- and loss-of-function approaches. Methods and Results Cardiac-specific ISM1 overexpression and silence were achieved using an adeno-associated virus serotype 9 system, and then these mice were subjected to I/R surgery, followed by biochemical test, echocardiography and histopathologic examinations, etc. Meanwhile, neonatal rat cardiomyocytes (NRCMs) with ISM1 silence or overexpression also received simulated I/R (sI/R) injury to further verify its role in vitro. The potential downstream pathways and molecular targets of ISM1 were screened by RNA-sequencing. We also treated injured mice and NRCMs with recombinant ISM1 (rISM1) to explore whether supplementation with ISM1 was sufficient to protect against I/R injury. Furthermore, acute myocardial infarction patients with percutaneous coronary intervention (PCI) and paired healthy controls were included to reveal the clinical relevance of circulating ISM1. Cardiac-specific ISM1 silencing aggravated while ISM1 overexpression alleviated I/R-induced acute cardiac injury and cardiac remodeling and dysfunction. Mechanistically, ISM1 targeted αvβ5 integrin to facilitate the nuclear accumulation of nuclear transcription factor Y subunit alpha, transcriptionally increased soluble guanylyl cyclase beta subunit expression, and eventually enhanced cGMP generation. Besides, we confirmed that treatment with rISM1 before or after reperfusion could confer cardioprotective effects in mice. Clinically, lower ISM1 levels post-PCI was associated with worse outcome in patients. Conclusion ISM1 can protect against cardiac I/R injury through cGMP-PKG signaling pathway, and it is a promising therapeutic and predictive target of cardiac I/R injury.

中文翻译：

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Isthmin-1通过cGMP-PKG信号通路减轻心脏缺血/再灌注损伤

缺血/再灌注（I/R）损伤是急性心肌梗死再灌注治疗的重要并发症，极大地损害了血运重建对心脏的益处，但目前仍缺乏针对心脏I/R损伤的特异性和有效的治疗方法。 Isthmin-1 (ISM1) 是一种新型脂肪因子，在调节糖脂代谢和细胞存活中发挥着不可或缺的作用。本研究旨在利用功能获得和丧失的方法研究 ISM1 在心脏 I/R 损伤中的潜在作用和分子机制。方法与结果利用腺相关病毒血清型9系统实现心脏特异性ISM1过表达和沉默，然后对这些小鼠进行I/R手术，随后进行生化检查、超声心动图和组织病理学检查等。 ISM1沉默或过度表达的心肌细胞（NRCM）也接受了模拟I/R（sI/R）损伤，以进一步验证其体外作用。通过RNA测序筛选ISM1的潜在下游途径和分子靶标。我们还用重组 ISM1 (rISM1) 治疗受伤的小鼠和 NRCM，以探讨补充 ISM1 是否足以预防 I/R 损伤。此外，还纳入了接受经皮冠状动脉介入治疗 (PCI) 的急性心肌梗死患者和配对的健康对照，以揭示循环 ISM1 的临床相关性。心脏特异性 ISM1 沉默加剧，而 ISM1 过表达减轻 I/R 诱导的急性心脏损伤以及心脏重塑和功能障碍。从机制上讲，ISM1靶向αvβ5整合素以促进核转录因子Y亚基α的核积累，转录增加可溶性鸟苷酸环化酶β亚基的表达，并最终增强cGMP的产生。此外，我们证实在再灌注之前或之后用rISM1治疗可以赋予小鼠心脏保护作用。临床上，PCI 后 ISM1 水平较低与患者预后较差相关。结论 ISM1可以通过cGMP-PKG信号通路预防心脏I/R损伤，是心脏I/R损伤的一个有前景的治疗和预测靶点。