Lead and calcium produce rod photoreceptor cell apoptosis by opening the mitochondrial permeability transition pore
Lead and calcium produce rod photoreceptor cell apoptosis by opening the mitochondrial permeability transition pore
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DOI：
10.1074/jbc.275.16.12175
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发表时间：
2000-04-21
影响因子：
4.8
通讯作者：
Fox, DA
中科院分区：
文献类型：
--
作者：
He, LH;Poblenz, AT;Fox, DA
钙超载被认为在化学诱导和遗传性视网膜变性的视杆细胞凋亡过程中起重要作用，然而，这一假设尚未得到直接验证。我们开发了一种利用离体大鼠视网膜的体外模型，以确定Ca 2+和/或Pb 2+诱导的视网膜变性的机制。共聚焦显微镜，组织学和生物化学研究确定，升高的[Ca 2 +]和/或[Pb 2 +]定位于光感受器，并产生杆选择性凋亡。Ca ~（2+）和/或Pb ~（2+）诱导线粒体去极化、肿胀和细胞色素c释放。随后，caspase-9和caspase-3被依次激活。Caspase-7和caspase-8未被激活。Ca ~（2+）和Pb ~（2+）的作用是相加的，可被线粒体通透性转换孔（PTP）抑制剂环孢菌素A完全阻断，而钙调神经磷酸酶抑制剂FK 506则无此作用。半胱天冬酶抑制剂carbobenzoxy-Leu-Glu-His-Asp-CH 2F和carbobenzoxy-Asp-Glu-Val-AspCH（2）F，但不是carbobenzoxy-Ile-Glu-Thr-Asp-CH 2F，差异性地阻断线粒体后事件。杆中还原型和氧化型谷胱甘肽和吡啶核苷酸的水平不变。我们的研究结果表明，杆线粒体是Ca 2+和Pb 2+的靶位点。此外，他们认为，Ca 2+和Pb 2+结合到PTP的内部金属（Me 2+）结合位点，随后打开PTP，这启动了细胞色素c-caspase级联的杆细胞凋亡。
Calcium overload is suggested to play a fundamental role in the process of rod apoptosis in chemical-induced and inherited retinal degenerations, However, this hypothesis has not been tested directly. We developed an in vitro model utilizing isolated rat retinas to determine the mechanisms underlying Ca2+- and/or Pb2+-induced retinal degeneration. Confocal microscopy, histological, and biochemical studies established that the elevated [Ca2+] and/or [Pb2+] were localized to photoreceptors and produced rod-selective apoptosis. Ca2+ and/or Pb2+ induced mitochondrial depolarization, swelling, and cytochrome c release. Subsequently caspase-9 and caspase-3 were sequentially activated. Caspase-7 and caspase-8 were not activated. The effects of Ca2+ and Pb2+ were additive and blocked completely by the mitochondrial permeability transition pore (PTP) inhibitor cyclosporin A, whereas the calcineurin inhibitor FK506 had no effect. The caspase inhibitors carbobenzoxy-Leu-Glu-His-Asp-CH2F and carbobenzoxy-Asp-Glu-Val-AspCH(2)F, but not carbobenzoxy-Ile-Glu-Thr-Asp-CH2F, differentially blocked post-mitochondrial events. The levels of reduced and oxidized glutathione and pyridine nucleotides in rods were unchanged. Our results demonstrate that rod mitochondria are the target site for Ca2+ and Pb2+. Moreover, they suggest that Ca2+ and Pb2+ bind to the internal metal (Me2+) binding site of the PTP and subsequently open the PTP, which initiates the cytochrome c-caspase cascade of apoptosis in rods.