Yitzhaki Smadar, Hochhauser Edith, Porat Eyal, Shainberg Asher
The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, 52900 Israel.
J Mol Cell Cardiol. 2007 Nov;43(5):653-62. doi: 10.1016/j.yjmcc.2007.07.060. Epub 2007 Aug 7.
Previously we found that uridine-5'-triphosphate (UTP) significantly decreased cultured cardiomyocyte death, induced by hypoxia via activating P2Y(2) receptors, reduced infarct size and maintained higher ATP levels in an in vivo model. Mitochondrial contribution to the progression of cardiomyocyte injury in ischemia/hypoxia is well known. However, the protective effects of UTP in cardiac cells with a respiratory chain deficiency are poorly elucidated. The aim of our study was to further define the role of UTP on mitochondrial functional tolerance following chemical and/or ischemic stress in in vivo and in vitro models. Cardiac mitochondrial function was tested 24 h post left anterior descending (LAD) ligation in UTP (0.44 microg/kg)-treated rats. UTP's beneficial effect in LAD-ligated hearts was expressed by improved mitochondrial activity (Complexes I, II and IV). In the in vitro model, cultured cardiomyocytes were pretreated with 50 microM UTP prior to hypoxic and/or chemical stress with rotenone or sodium azide. Pretreatment with UTP maintained increased ATP levels as well as mitochondrial membrane potential and reduced lactate dehydrogenase (LDH) release. A modest reduction (12%) in the mitochondrial membrane potential was demonstrated when the cultured cardiomyocytes were subjected to UTP. This reduction was abolished by the P2Y receptor antagonist, reactive blue 2, but not with 5 hydroxydecanoate, a mitochondrial K(ATP) channel inhibitor, or by BAPTA-AM, the intracellular calcium chelator. We suggest that UTP may act as an uncoupling agent, which exerts a modest mitochondrial depolarization, resulting in a reduction of Ca(2+) uptake, preserving mitochondrial activity, thereby reducing cell damage during hypoxia.
此前我们发现，尿苷-5'-三磷酸（UTP）可通过激活P2Y(2)受体，显著减少缺氧诱导的培养心肌细胞死亡，缩小梗死面积，并在体内模型中维持较高的ATP水平。线粒体在缺血/缺氧心肌细胞损伤进展中的作用已广为人知。然而，UTP对呼吸链缺陷心肌细胞的保护作用尚不清楚。我们研究的目的是在体内和体外模型中进一步明确UTP在化学和/或缺血应激后对线粒体功能耐受性的作用。在UTP（0.44微克/千克）处理的大鼠中，于左冠状动脉前降支（LAD）结扎后24小时检测心脏线粒体功能。UTP对LAD结扎心脏的有益作用表现为线粒体活性（复合体I、II和IV）的改善。在体外模型中，在用鱼藤酮或叠氮化钠进行缺氧和/或化学应激之前，用50微摩尔/升UTP预处理培养的心肌细胞。UTP预处理可维持ATP水平升高以及线粒体膜电位，并减少乳酸脱氢酶（LDH）释放。当培养的心肌细胞接受UTP处理时，线粒体膜电位有适度降低（12%）。P2Y受体拮抗剂反应性蓝2可消除这种降低，但线粒体K(ATP)通道抑制剂5-羟基癸酸或细胞内钙螯合剂BAPTA-AM则不能。我们认为，UTP可能作为一种解偶联剂，发挥适度的线粒体去极化作用，导致Ca(2+)摄取减少，保持线粒体活性，从而减少缺氧期间的细胞损伤。
