Sasaki Toshiki, Shishido Tetsuro, Kadowaki Shinpei, Kitahara Tatsuro, Suzuki Satoshi, Katoh Shigehiko, Funayama Akira, Netsu Shunsuke, Watanabe Tetsu, Goto Kaoru, Takeishi Yasuchika, Kubota Isao
Department of Cardiology, Pulmonology, and Nephrology, Yamagata University School of Medicine, 2-2-2 Iidanishi, Yamagata, 9909585, Japan.
Heart Vessels. 2014 Jan;29(1):110-8. doi: 10.1007/s00380-013-0366-6. Epub 2013 May 30.
Early coronary reperfusion of the ischemic myocardium is a desired therapeutic goal for the preservation of myocardial function. However, reperfusion itself causes additional myocardium injuries. Activation of the diacylglycerol-protein kinase C (DAG-PKC) cascade has been implicated in the cardioprotective effects occurring after ischemia/reperfusion (I/R). DAG kinase (DGK) controls cellular DAG levels by converting DAG to phosphatidic acid, and may act as an endogenous regulator of DAG-PKC signaling. In the present study, we examined the functional role of DGKα in cardiac injury after I/R in in vivo mouse hearts. We generated transgenic mice with cardiac-specific overexpression of DGKα (DGKα-TG). The left anterior descending coronary artery was transiently occluded for 20 min and reperfused for 24 h in DGKα-TG mice and wild-type littermate (WT) mice. The levels of phosphorylation activity of PKCε, extracellular-signal regulated kinase (ERK) 1/2, and p70 ribosomal S6 kinase (p70S6K) were increased after I/R in WT mouse hearts. However, in DGKα-TG mice, activation of PKCε, ERK1/2, and p70S6K was attenuated compared to WT mice. After 24 h, Evans blue/triphenyltetrazolium chloride double staining and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining showed that DGKα-TG mice had significantly larger myocardial infarctions and larger numbers of TUNEL-positive cardiomyocytes than WT mice. Echocardiography and cardiac catheterization revealed that left ventricular systolic function was more severely depressed in DGKα-TG mice than in WT mice after I/R. These findings suggest that DGKα exacerbates I/R injury by inhibiting the cardioprotective effects of PKCε, ERK1/2, and p70S6K activation.
早期对缺血心肌进行冠状动脉再灌注是保护心肌功能的理想治疗目标。然而，再灌注本身会导致额外的心肌损伤。二酰基甘油-蛋白激酶C（DAG-PKC）级联反应的激活与缺血/再灌注（I/R）后出现的心脏保护作用有关。二酰基甘油激酶（DGK）通过将DAG转化为磷脂酸来控制细胞内DAG水平，并可能作为DAG-PKC信号的内源性调节因子。在本研究中，我们检测了DGKα在体内小鼠心脏I/R后心脏损伤中的功能作用。我们构建了心脏特异性过表达DGKα的转基因小鼠（DGKα-TG）。在DGKα-TG小鼠和野生型同窝小鼠（WT）中，将左冠状动脉前降支短暂闭塞20分钟，然后再灌注24小时。I/R后，WT小鼠心脏中PKCε、细胞外信号调节激酶（ERK）1/2和p70核糖体S6激酶（p70S6K）的磷酸化活性水平升高。然而，与WT小鼠相比，DGKα-TG小鼠中PKCε、ERK1/2和p70S6K的激活减弱。24小时后，伊文思蓝/氯化三苯基四氮唑双重染色和末端脱氧核苷酸转移酶dUTP缺口末端标记（TUNEL）染色显示，DGKα-TG小鼠的心肌梗死面积明显大于WT小鼠，TUNEL阳性心肌细胞数量也更多。超声心动图和心脏导管检查显示，I/R后DGKα-TG小鼠的左心室收缩功能比WT小鼠受到更严重的抑制。这些发现表明，DGKα通过抑制PKCε、ERK1/2和p70S6K激活的心脏保护作用而加重I/R损伤。
