Monceau Virginie, Belikova Yulia, Kratassiouk Gueorgui, Robidel Estelle, Russo-Marie Françoise, Charlemagne Daniele
Institut National de la Santé et de la Recherche Médicale (INSERM) U-689, Centre de Recherche Cardiovasculaire INSERM-Lariboisière, Paris Cedex 10, France.
Am J Physiol Heart Circ Physiol. 2006 Aug;291(2):H965-71. doi: 10.1152/ajpheart.01053.2005. Epub 2006 Feb 24.
Annexin A5 is a Ca2+-dependent phospholipid binding protein well known for its high phosphatidylserine affinity. In vitro, translocation to sarcolemma and externalization of endogenous annexin A5 in the cardiomyocyte has recently been demonstrated to exert a proapoptotic effect. To determine whether these in vitro findings occurred in vivo, we performed myocardial infarction (MI) and studied the time course of apoptosis and annexin A5 localization (0.5 to 8 h) in the border zone around the infarcted area. This zone that was defined as Evans blue unstained and triphenyltetrazolium chloride (TTC) stained, represented 42.3 +/- 5.5% of the area at risk and showed apoptotic characteristics (significant increases in caspase 3 activity 2.3-fold at 0.5 h; P < 0.05), transferase-mediated dUTP nick-end labeling-positive cardiomyocytes (15.8 +/- 0.8% at 8 h), and DNA ladder. When compared with sham-operated rats, we found that in this area, annexin A5 was translocated to the sarcolemma as early as 0.5 h after MI and that translocation increased with time. Moreover, the amount of annexin A5 was unchanged in the border zone and decreased in the infarcted area after 1 h (77.1 +/- 4.8%; P < 0.01 vs. perfused area), suggesting a release in the latter but not in the former. In conclusion, we demonstrated that annexin A5 translocation is an early and rapid event of the whole border zone, likely due to Ca2+ increase. Part of this translocation occurred in areas where apoptosis was later detected and suggests that in vivo as in vitro annexin A5 might be involved in the regulation of early apoptotic events during cardiac pathological situations.
膜联蛋白A5是一种依赖钙离子的磷脂结合蛋白，以其对磷脂酰丝氨酸的高亲和力而闻名。最近有研究表明，在体外，心肌细胞内源性膜联蛋白A5易位至肌膜并外化可发挥促凋亡作用。为了确定这些体外研究结果是否在体内发生，我们进行了心肌梗死（MI）实验，并研究了梗死区域周围边界区凋亡的时间进程以及膜联蛋白A5的定位（0.5至8小时）。该区域被定义为伊文思蓝未染色且氯化三苯基四氮唑（TTC）染色的区域，占危险区域面积的42.3±5.5%，并呈现出凋亡特征（半胱天冬酶3活性在0.5小时时显著增加2.3倍；P<0.05）、转移酶介导的dUTP缺口末端标记阳性心肌细胞（8小时时为15.8±0.8%）以及DNA梯带。与假手术大鼠相比，我们发现，在该区域，心肌梗死后0.5小时膜联蛋白A5就最早易位至肌膜，且易位随时间增加。此外，膜联蛋白A5在边界区的量在1小时后无变化，而在梗死区域减少（77.1±4.8%；与灌注区域相比，P<0.01），这表明后者有释放而前者没有。总之，我们证明膜联蛋白A5易位是整个边界区早期且快速发生的事件，可能是由于钙离子增加所致。部分这种易位发生在后来检测到凋亡的区域，这表明在体内如同在体外一样，膜联蛋白A5可能参与心脏病理状态下早期凋亡事件的调控。
