Al-Othman Reham, Al-Jarallah Aishah, Babiker Fawzi
Department of Biochemistry, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait.
Department of Physiology, College of Medicine, Kuwait University, Kuwait City, Kuwait.
Front Pharmacol. 2024 Nov 14;15:1398630. doi: 10.3389/fphar.2024.1398630. eCollection 2024.
High-density lipoprotein (HDL) protects against myocardial ischemia-reperfusion (I/R) injury. Mammalian target of rapamycin complexes 1 and 2 (mTORC1 and mTORC2) play opposing roles in protecting against I/R injury, whereby mTORC1 appears to be detrimental while mTORC2 is protective. However, the role of HDL and mTORC signaling in protecting against I/R in hypertensive rodents is not clearly understood. In this study, we investigated the involvement of mTORC1 and mTORC2 in HDL-mediated protection against myocardial I/R injury in normotensive Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHR).
Hearts from WKY and SHR were subjected to I/R injury using a modified Langendorff system. Hemodynamics data were collected, and infarct size was measured. Rapamycin and JR-AB2-011 were used to test the role of mTORC1 and mTORC2, respectively. MK-2206 was used to test the role of Akt in HDL-mediated cardiac protection. The expression levels and the activation states of mediators of mTORC1 and mTORC2 signaling and myocardial apoptosis were measured by immunoblotting and/or enzyme-linked immunosorbent assay (ELISA).
HDL protected hearts from WKY and SHR against I/R injury as indicated by significant improvements in cardiac hemodynamics and reduction in infarct size. HDL induced greater protection in WKY compared to SHR. HDL treatment attenuated mTORC1 signaling in WKY by reducing the phosphorylation of P70S6K (mTORC1 substrate). In SHR however, HDL attenuated mTORC1 signaling by reducing the levels of phospho-mTORC1, Rag C (mTORC1 activator), and phospho-PRAS40 (mTORC1 inhibitor). HDL increased the phosphorylation of mTORC2 substrate Akt, specifically the Akt2 isoform in SHR and to a greater extent in WKY. HDL-induced protection was abolished in the presence of Akt antagonist and involved attenuation of GSK, caspases 7 and 8 activation, and cytochrome C release.
HDL mediates cardiac protection via attenuation of mTORC1, activation of mTORC2-Akt2, and inhibition of myocardial apoptosis. HDL regulates mTORC1 and mTORC2 signaling via distinct mechanisms in normotensive and hypertensive rats. HDL attenuation of mTORC1 and activation of mTORC2-Akt2 signaling could be a mechanism by which HDL protects against myocardial I/R injury in hypertension.
高密度脂蛋白（HDL）可预防心肌缺血再灌注（I/R）损伤。雷帕霉素复合物1和2（mTORC1和mTORC2）在预防I/R损伤中发挥相反作用，其中mTORC1似乎有害而mTORC2具有保护作用。然而，HDL和mTORC信号通路在高血压啮齿动物预防I/R中的作用尚不清楚。在本研究中，我们调查了mTORC1和mTORC2在正常血压的Wistar Kyoto（WKY）大鼠和自发性高血压大鼠（SHR）中HDL介导的心肌I/R损伤保护作用中的参与情况。
使用改良的Langendorff系统对WKY和SHR的心脏进行I/R损伤。收集血流动力学数据并测量梗死面积。分别使用雷帕霉素和JR-AB2-011来测试mTORC1和mTORC2的作用。使用MK-2206来测试Akt在HDL介导的心脏保护中的作用。通过免疫印迹和/或酶联免疫吸附测定（ELISA）测量mTORC1和mTORC2信号通路介质以及心肌细胞凋亡的表达水平和激活状态。
HDL保护WKY和SHR的心脏免受I/R损伤，表现为心脏血流动力学显著改善和梗死面积减小。与SHR相比，HDL对WKY的保护作用更强。HDL处理通过降低P70S6K（mTORC1底物）的磷酸化来减弱WKY中的mTORC1信号通路。然而，在SHR中，HDL通过降低磷酸化mTORC1、Rag C（mTORC1激活剂）和磷酸化PRAS40（mTORC1抑制剂）的水平来减弱mTORC1信号通路。HDL增加了mTORC2底物Akt的磷酸化，特别是在SHR中的Akt2亚型，在WKY中增加的程度更大。在存在Akt拮抗剂的情况下，HDL诱导的保护作用被消除，并且涉及GSK、半胱天冬酶7和8激活以及细胞色素C释放的减弱。
HDL通过减弱mTORC1、激活mTORC2-Akt2和抑制心肌细胞凋亡来介导心脏保护作用。HDL在正常血压和高血压大鼠中通过不同机制调节mTORC1和mTORC2信号通路。HDL对mTORC1的减弱和mTORC2-Akt2信号通路的激活可能是HDL预防高血压中心肌I/R损伤的一种机制。
