MOE Engineering Center of Hematological Disease, MOH Key Lab of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China.
Department of Cardiology, Suzhou Municipal Hospital, Suzhou, Jiangsu Province, China.
Biomed Pharmacother. 2020 Nov;131:110787. doi: 10.1016/j.biopha.2020.110787. Epub 2020 Sep 30.
Acute myocardial infarction (AMI) is one of the deadliest diseases worldwide. The search for countermeasures to reduce cardiomyocytes death in the infarcted area has always been the focus of research. Ubiquitin (UB) is a small polypeptide mainly involved in proteasome-mediated protein degradation in cells, whereas extracellular UB in body fluids can also function through its receptor CXC chemokine receptor type 4 (CXCR4). This study aimed to explore the functional roles of extracellular UB in cardiomyocytes during ischemia/hypoxia (I/H).
H9C2 cells were subjected to I/H treatment and cell injury was evaluated by cell viability, morphology changes and apoptosis rate. UB expression and levels of ubiquitinated proteins after I/H injury were measured. The effects of extracellular UB on I/H-induced cardiomyocytes apoptosis and the possible underlying mechanisms were studied.
I/H injury induced the decrease of cell viability as well as enhanced impaired cell morphology and apoptosis rate in H9C2 cells. Levels of UB mRNA and ubiquitinated proteins were significantly up-regulated after I/H treatment, whereas the concentration of extracellular UB in the conditioned media did not show significant change and the intracellular mono-UB levels in cells were down-regulated. Extracellular UB treatment protected cardiomyocytes from I/H injury by inhibiting the overactivation of mitochondria-dependent apoptosis pathway and up-regulating autophagy level. Inhibition of CXCR4 receptor using AMD3100 abolished cardioprotective effects of extracellular UB.
The up-regulation of UB was suggested to be an adaptive response to resist I/H-induced cardiomyocytes apoptosis, and additional extracellular UB treatment might serve as a new potential therapeutic drug for AMI.
急性心肌梗死（AMI）是全球范围内最致命的疾病之一。寻找减少梗死区心肌细胞死亡的对策一直是研究的重点。泛素（UB）是一种主要参与细胞内蛋白酶体介导的蛋白质降解的小多肽，而体液中的细胞外 UB 也可以通过其受体 CXC 趋化因子受体 4（CXCR4）发挥作用。本研究旨在探讨细胞外 UB 在缺血/缺氧（I/H）期间对心肌细胞的功能作用。
将 H9C2 细胞进行 I/H 处理，并通过细胞活力、形态变化和凋亡率评估细胞损伤。测量 I/H 损伤后 UB 表达和泛素化蛋白水平。研究细胞外 UB 对 I/H 诱导的心肌细胞凋亡的影响及其可能的潜在机制。
I/H 损伤导致 H9C2 细胞活力下降，细胞形态受损，凋亡率增加。I/H 处理后 UB mRNA 和泛素化蛋白水平明显上调，而条件培养基中外泌体 UB 浓度无明显变化，细胞内单 UB 水平下调。细胞外 UB 处理通过抑制线粒体依赖性凋亡途径的过度激活和上调自噬水平来保护心肌细胞免受 I/H 损伤。使用 AMD3100 抑制 CXCR4 受体可消除细胞外 UB 的心脏保护作用。
UB 的上调被认为是抵抗 I/H 诱导的心肌细胞凋亡的一种适应性反应，额外的细胞外 UB 治疗可能成为 AMI 的一种新的潜在治疗药物。
