Jiangsu Province Key Laboratory of Anesthesiology, Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, NMPA Key Laboratory for Research and Evaluation of Narcotic and Psychotropic Drugs, Xuzhou Medical University, 209 Tongshan Rd, Xuzhou, 221004, Jiangsu, China.
Department of Otolaryngology Head and Neck Surgery, Shengjing Hospital, China Medical University, Shenyang, 110122, Liaoning, China.
Basic Res Cardiol. 2022 Apr 7;117(1):20. doi: 10.1007/s00395-022-00930-x.
Accumulating evidence suggests that autophagy dysfunction plays a critical role in myocardial ischemia/reperfusion (I/R) injury. However, the underling mechanism of malfunctional autophagy in the cardiomyocytes subjected to I/R has not been well defined. As a result, there is no effective therapeutic option by targeting autophagy to prevent myocardial I/R injury. Here, we used both an in vitro and an in vivo I/R model to monitor autophagic flux in the cardiomyocytes, by exposing neonatal rat ventricular myocytes to hypoxia/reoxygenation and by subjecting mice to I/R, respectively. We observed that the autophagic flux in the cardiomyocytes subjected to I/R was blocked in both in vitro and in vivo models. Down-regulating a lysosomal cationic channel, TRPML1, markedly restored the blocked myocardial autophagic flux induced by I/R, demonstrating that TRPML1 directly contributes to the blocked autophagic flux in the cardiomyocytes subjected to I/R. Mechanistically, TRPML1 is activated secondary to ROS elevation following ischemia/reperfusion, which in turn induces the release of lysosomal zinc into the cytosol and ultimately blocks the autophagic flux in cardiomyocytes, presumably by disrupting the fusion between autophagosomes and lysosomes. As a result, the inhibited myocardial autophagic flux induced by TRPML1 disrupted mitochondria turnover and resulted in mass accumulation of damaged mitochondria and further ROS release, which directly led to cardiomyocyte death. More importantly, pharmacological and genetic inhibition of TRPML1 channels greatly reduced infarct size and rescued heart function in mice subjected to I/R in vivo by restoring impaired myocardial autophagy. In summary, our study demonstrates that secondary to ROS elevation, activation of TRPML1 results in autophagy inhibition in the cardiomyocytes subjected to I/R, which directly leads to cardiomyocyte death by disrupting mitochondria turnover. Therefore, targeting TRPML1 represents a novel therapeutic strategy to protect against myocardial I/R injury.
越来越多的证据表明，自噬功能障碍在心肌缺血/再灌注（I/R）损伤中起着关键作用。然而，在 I/R 作用下心肌细胞中自噬功能障碍的潜在机制尚未得到很好的定义。因此，目前还没有通过靶向自噬来预防心肌 I/R 损伤的有效治疗方法。在这里，我们使用体外和体内 I/R 模型来监测心肌细胞中的自噬流，分别通过使新生大鼠心室肌细胞经历缺氧/复氧和使小鼠经历 I/R。我们观察到，在体外和体内模型中，I/R 作用下的心肌细胞自噬流被阻断。下调溶酶体阳离子通道 TRPML1 可显著恢复 I/R 诱导的阻断的心肌自噬流，表明 TRPML1 直接导致 I/R 作用下心肌细胞中阻断的自噬流。在机制上，TRPML1 是在缺血/再灌注后 ROS 升高的继发作用下被激活的，这反过来又导致溶酶体锌释放到细胞质中，并最终阻断心肌细胞中的自噬流，可能是通过破坏自噬体与溶酶体之间的融合。结果，TRPML1 诱导的抑制性心肌自噬流破坏了线粒体周转，导致受损线粒体的大量积累和进一步的 ROS 释放，这直接导致心肌细胞死亡。更重要的是，TRPML1 通道的药理学和遗传学抑制通过恢复受损的心肌自噬，大大减少了体内 I/R 小鼠的梗死面积并挽救了心脏功能。总之，我们的研究表明，继发于 ROS 升高，TRPML1 的激活导致 I/R 作用下心肌细胞中的自噬抑制，通过破坏线粒体周转直接导致心肌细胞死亡。因此，靶向 TRPML1 代表了一种保护心肌免受 I/R 损伤的新治疗策略。
