Cardiac subsarcolemmal and interfibrillar mitochondria display distinct responsiveness to protection by diazoxide.
Cardiac subsarcolemmal and interfibrillar mitochondria display distinct responsiveness to protection by diazoxide.
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DOI：
10.1371/journal.pone.0044667
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Jahangir A
中科院分区：
文献类型：
--
作者：
Holmuhamedov EL;Oberlin A;Short K;Terzic A;Jahangir A
心肌肌膜下（SSM）和肌原纤维间（IFM）线粒体亚群具有不同的生化特性，其蛋白质和脂质组成、呼吸和蛋白质合成能力以及对代谢挑战的敏感性不同，但其对心脏活性心脏保护疗法的反应性尚未得到表征。本研究评估了两种线粒体亚群对二氮嗪（一种靶向线粒体的心脏保护剂）的不同反应性。线粒体亚群新鲜分离的大鼠心室和他们的形态进行了评估，通过电子显微镜和酶活性测定使用标准的生化协议与读板器。使用琥珀酸作为底物，从状态3呼吸评估氧化磷酸化。使用标准Ca 2+和TPP+离子选择性电极评估钙动力学和Ca 2+依赖的线粒体渗透性转换（MPT）孔和线粒体膜电位的状态。与IFM相比，分离的SSM对Ca 2+过负荷介导的三磷酸腺苷（ATP）合成抑制表现出更高的敏感性，ATP产生减少（SSM中从375±25至83±15 nmol ATP/min/mg蛋白，IFM中从875±39至583±45 nmol ATP/min/mg蛋白）。此外，与IFM相比，SSM表现出降低的Ca 2+积累能力（SSM和IFM中分别为230±13 nmol Ca 2 +/mg蛋白质与450±46 nmol Ca 2 +/mg蛋白质），表明MPT孔开放的Ca 2+敏感性增加。尽管对应激的敏感性增强，但SSM对二氮嗪（100 μM）对Ca 2+过载介导的ATP合成抑制的保护作用更敏感（SSM和IFM分别为67%和2%）。这些结果为心肌SSM和IFM对Ca 2+依赖性代谢应激的不同敏感性和二氮嗪对线粒体能量学的保护作用提供了证据。
Cardiac subsarcolemmal (SSM) and interfibrillar (IFM) mitochondrial subpopulations possess distinct biochemical properties and differ with respect to their protein and lipid compositions, capacities for respiration and protein synthesis, and sensitivity to metabolic challenge, yet their responsiveness to mitochondrially active cardioprotective therapeutics has not been characterized. This study assessed the differential responsiveness of the two mitochondrial subpopulations to diazoxide, a cardioprotective agent targeting mitochondria. Mitochondrial subpopulations were freshly isolated from rat ventricles and their morphologies assessed by electron microscopy and enzymatic activities determined using standard biochemical protocols with a plate reader. Oxidative phosphorylation was assessed from State 3 respiration using succinate as a substrate. Calcium dynamics and the status of Ca2+-dependent mitochondrial permeability transition (MPT) pore and mitochondrial membrane potential were assessed using standard Ca2+ and TPP+ ion-selective electrodes. Compared to IFM, isolated SSM exhibited a higher sensitivity to Ca2+ overload-mediated inhibition of adenosine triphosphate (ATP) synthesis with decreased ATP production (from 375±25 to 83±15 nmol ATP/min/mg protein in SSM, and from 875±39 to 583±45 nmol ATP/min/mg protein in IFM). In addition, SSM exhibited reduced Ca2+-accumulating capacity as compared to IFM (230±13 vs. 450±46 nmol Ca2+/mg protein in SSM and IFM, respectively), suggestive of increased Ca2+ sensitivity of MPT pore opening. Despite enhanced susceptibility to stress, SSM were more responsive to the protective effect of diazoxide (100 μM) against Ca2+ overload-mediated inhibition of ATP synthesis (67% vs. 2% in SSM and IFM, respectively). These results provide evidence for the distinct sensitivity of cardiac SSM and IFM toward Ca2+-dependent metabolic stress and the protective effect of diazoxide on mitochondrial energetics.
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影响因子：
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影响因子：
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