CALCIUM ION-DEPENDENT SIGNALING AND MITOCHONDRIAL DYSFUNCTION - MITOCHONDRIAL CALCIUM-UPTAKE DURING HORMONAL-STIMULATION IN INTACT LIVER-CELLS AND ITS IMPLICATION FOR THE MITOCHONDRIAL PERMEABILITY TRANSITION
CALCIUM ION-DEPENDENT SIGNALING AND MITOCHONDRIAL DYSFUNCTION - MITOCHONDRIAL CALCIUM-UPTAKE DURING HORMONAL-STIMULATION IN INTACT LIVER-CELLS AND ITS IMPLICATION FOR THE MITOCHONDRIAL PERMEABILITY TRANSITION
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DOI：
10.1016/0925-4439(95)00015-v
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发表时间：
1995-05-24
影响因子：
6.2
通讯作者：
WANG, XL
中科院分区：
文献类型：
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作者：
HOEK, JB;FARBER, JL;WANG, XL
升高胞质Ca 2+浓度的激素（[Ca 2 +]（cyt））通常使用Ca 2+作为信使来激活线粒体内代谢过程。然而，线粒体Ca2+水平也调节线粒体渗透性转换（MPT）的激活，这是一个涉及跨内膜和外膜组装高电导蛋白质孔的过程。对完整肝细胞的研究表明，MPT是缺氧或呼吸抑制剂诱导的细胞杀伤中的关键步骤。在这项研究中，我们使用新鲜分离的肝细胞来研究加压素或其他激动剂引起的[Ca2+]（cyt）升高在多大程度上导致线粒体中Ca2+积聚，以及这种治疗如何影响线粒体对MPT的敏感性。在用毛地黄皂苷透化之前，将肝细胞与加压素、胰高血糖素或毒胡萝卜素（内质网Ca 2+泵的抑制剂）一起孵育。线粒体Ca2+的积累，通过以下离子霉素诱导的Ca2+释放透化细胞和线粒体肿胀进行了研究，通过以下环孢菌素A敏感的光散射变化引起的氧化苯砷和鱼藤酮。结果表明，提高[Ca2+]（cyt）的试剂导致线粒体中显著的Ca2+积累。用加压素和胰高血糖素的组合或用含有毒胡萝卜素的孵育物获得过量的Ca2+积累（超过基础水平的10倍增加）。这些条件也与鱼藤酮诱导的线粒体肿胀显着增加。然而，更温和的增加线粒体Ca2+含量后，单独用加压素处理细胞没有增强肿胀反应，相反，加压素抑制线粒体肿胀相比，控制孵育。加压素也部分抑制与毒胡萝卜素治疗相关的肿胀，虽然它没有显着影响在这些条件下的Ca2+积累。佛波酯模拟了加压素的这种作用，表明蛋白激酶C的作用。这些数据表明，线粒体Ca2+积累[Ca2+]（细胞色素）升高后，增强了对MPT激活的敏感性，这是一种可能在缺氧或响应其他挑战时增加细胞损伤的反应。然而，激素也会激活细胞中抑制MPT的保护性反应。
Hormones that elevate cytosolic Ca2+ concentrations ([Ca2+](cyt)) often use Ca2+ as a messenger to activate intramitochondrial metabolic processes. However, the mitochondrial Ca2+ level also regulates the activation of the mitochondrial permeability transition (MPT), a process that involves the assembly of a high conductance proteinaceous pore across the inner and outer membrane. Studies on intact liver cells indicate that the MPT is a critical step in the cell killing induced by anoxia or respiratory inhibitors. In this study, we used freshly isolated hepatocytes to investigate to what extent the elevation of [Ca2+](cyt) by vasopressin or other agonists causes Ca2+ accumulation in the mitochondria and how this treatment affects the mitochondrial susceptibility to undergo the MPT. Hepatocytes were incubated with vasopressin, glucagon, or with thapsigargin (an inhibitor of the endoplasmic reticulum Ca2+ pump) prior to permeabilization with digitonin. Mitochondrial Ca2+ accumulation was determined by following the ionomycin-induced Ca2+ release in permeabilized cells and mitochondrial swelling was studied by following cyclosporin A-sensitive light scattering changes induced by phenylarsenoxide and rotenone. The results indicate that agents that elevate [Ca2+](cyt) cause a significant Ca2+ accumulation in the mitochondria. Excessive Ca2+ accumulation (> 10-fold increase over basal levels) was obtained with the combination of vasopressin and glucagon or with incubations containing thapsigargin. These conditions were also associated with a marked increase in rotenone-induced mitochondrial swelling. However, the more modest increase in mitochondrial Ca2+ content after treating cells with vasopressin alone did not enhance the swelling response; instead, vasopressin suppressed mitochondrial swelling compared to control incubations. Vasopressin also partly suppressed the swelling associated with thapsigargin treatment, although it did not significantly affect the Ca2+ accumulation under these conditions. This effect of vasopressin was mimicked by phorbol ester, suggesting a role for protein kinase C. The data indicate that mitochondrial Ca2+ accumulation following elevation of [Ca2+](cyt) enhances the susceptibility for activation of the MPT, a response that may increase cell injury during anoxia or in response to other challenges. However, hormones also activate protective responses in the cell that suppress the MPT.