Department of Cardiology, First Affiliated Hospital, China Medical University, Shenyang, Liaoning 110001, China.
Chin Med J (Engl). 2009 Oct 5;122(19):2360-5.
Apoptosis is a major cause of ischemic heart dysfunction. Apelin, the endogenous ligand for the G-protein-coupled APJ receptor, has been reported to exert cardioprotective effects during myocardial injury. The aim of this study was to investigate the effects of apelin on apoptosis of rat cardiomyocytes induced by glucose deprivation (GD) and study the related signaling pathway.
Apelin and APJ mRNA expression were determined by RT-PCR in neonatal rat cardiomyocytes during different durations of GD. Cardiomyocyte apoptosis was detected by annexin V-FITC/propidium iodide (PI) staining after GD for 12 hours with or without apelin-13 (10 and 100 nmol/L) pretreatment. Protein levels of Akt and the mammalian target of rapamycin (mTOR) as well as cell apoptosis were detected in the presence or absence of LY294002 (a phosphatidylinositol 3-kinases (PI3K) inhibitor) or rapamycin (a mTOR inhibitor).
Apelin mRNA expression was up-regulated when cardiomyocytes were exposed to GD for 6, 12, 18, and 24 hours compared with the base level (P > 0.05, P < 0.01, P < 0.01, P < 0.01). However, when cardiomyocytes were exposed to GD for up to 36 hours, apelin mRNA expression was 17% lower than the base level (P < 0.05). APJ mRNA expression paralleled that of apelin. Apelin-13 pretreatment at 100 nmol/L significantly inhibited GD-induced cardiomyocyte apoptosis (P < 0.05) and increased Akt and mTOR phosphorylation (P < 0.01, P < 0.01). At the same time apelin-13 (100 nmol/L) up-regulated Bcl-2 protein expression and down-regulated Bax and cleaved caspase-3 expression (P < 0.01, P < 0.05, P < 0.05). The anti-apoptotic effect of apelin-13 was blocked by LY294002 (P < 0.01) but not by rapamycin.
The endogenous apelin-APJ system is compensatorily up-regulated and ultimately down-regulated following sustained myocardial ischemia. Apelin protects against ischemic cardiomyocyte apoptosis via activation of the PI3K/Akt pathway.
细胞凋亡是缺血性心脏功能障碍的主要原因。Apelin 是 G 蛋白偶联受体 APJ 的内源性配体，已有研究报道其在心肌损伤时发挥心脏保护作用。本研究旨在探讨 Apelin 在葡萄糖剥夺（GD）诱导的大鼠心肌细胞凋亡中的作用，并研究相关信号通路。
通过 RT-PCR 检测不同 GD 时间点新生大鼠心肌细胞中 Apelin 和 APJ mRNA 的表达。GD 12 小时后，用 Annexin V-FITC/PI 染色检测 Apelin-13（10 和 100 nmol/L）预处理后心肌细胞的凋亡。在存在或不存在 LY294002（PI3K 抑制剂）或 rapamycin（mTOR 抑制剂）的情况下，检测 Akt 和哺乳动物雷帕霉素靶蛋白（mTOR）的蛋白水平以及细胞凋亡。
与基础水平相比，GD 6、12、18 和 24 小时时，心肌细胞 Apelin mRNA 表达上调（P>0.05，P<0.01，P<0.01，P<0.01）。然而，当心肌细胞 GD 36 小时时，Apelin mRNA 表达比基础水平低 17%（P<0.05）。APJ mRNA 表达与 Apelin 平行。100 nmol/L Apelin-13 预处理可显著抑制 GD 诱导的心肌细胞凋亡（P<0.05），并增加 Akt 和 mTOR 磷酸化（P<0.01，P<0.01）。同时，Apelin-13（100 nmol/L）上调 Bcl-2 蛋白表达，下调 Bax 和 cleaved caspase-3 表达（P<0.01，P<0.05，P<0.05）。Apelin-13 的抗凋亡作用被 LY294002 阻断（P<0.01），但不受 rapamycin 影响。
在持续心肌缺血后，内源性 Apelin-APJ 系统代偿性上调，最终下调。Apelin 通过激活 PI3K/Akt 通路保护缺血性心肌细胞凋亡。
