Mitochondrial uncoupling downregulates calsequestrin expression and reduces SR Ca2+ stores in cardiomyocytes
Mitochondrial uncoupling downregulates calsequestrin expression and reduces SR Ca2+ stores in cardiomyocytes
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DOI：
10.1093/cvr/cvq180
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发表时间：
2010-10-01
影响因子：
10.8
通讯作者：
Tavi, Pasi
中科院分区：
文献类型：
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作者：
Hanninen, Sandra L.;Ronkainen, Jarkko J.;Tavi, Pasi
线粒体心肌病与心肌细胞钙信号的有害重塑有关，部分原因是肌浆网(SR)钙缓冲钙调素(CASQ2)的表达受到抑制。本研究旨在探讨线粒体功能受损是否直接导致CASQ2表达下调。用线粒体解偶联剂4-三氟甲氧基苯肼(FCCP)诱导培养的新生大鼠心肌细胞线粒体应激。用共聚焦显微镜分别用荧光指示剂Fluo-4和MitoSOX红测量了细胞内的钙瞬变和活性氧物种(ROS)。线粒体应激导致心肌细胞钙调素(CASQ2)浓度依赖性下调，心肌细胞钙信号发生改变，同时肌浆网钙离子含量降低，钙离子放电幅度和持续时间降低。Caspase3、p38和P53抑制剂对FCCP诱导的CASQ2下调无影响，但可被ROS清除剂N-乙酰半胱氨酸(NAC)减弱。重要的是，NAC不仅减少了FCCP诱导的ROS的产生，而且还恢复了Ca~(2+)信号、SR Ca~(2+)含量和Ca~(2+)触发特性以控制水平。线粒体解偶联导致CASQ2表达的快速转录变化，表现为Ca~(2+)信号的受损，这些变化可以被ROS清除剂阻止。由于线粒体功能受损与几种心脏疾病以及正常衰老有关，这里描述的机制可能涉及广泛的心脏疾病。
Mitochondrial cardiomyopathy is associated with deleterious remodelling of cardiomyocyte Ca2+ signalling that is partly due to the suppressed expression of the sarcoplasmic reticulum (SR) Ca2+ buffer calsequestrin (CASQ2). This study was aimed at determining whether CASQ2 downregulation is directly caused by impaired mitochondrial function.Mitochondrial stress was induced in cultured neonatal rat cardiomyocytes by means of the mitochondrial uncoupler carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP). Ca2+ transients and reactive oxygen species (ROS) were measured by confocal microscopy using the indicators fluo-4 and MitoSOX red, respectively. Mitochondrial stress led to concentration-dependent downregulation of calsequestrin (CASQ2) and changes in the Ca2+ signals of the cardiomyocytes that were accompanied by reduction in SR Ca2+ content and amplitude and duration of Ca2+ sparks. Caspase 3, p38, and p53 inhibitors had no effect on FCCP-induced CASQ2 downregulation; however, it was attenuated by the ROS scavenger N-acetylcysteine (NAC). Importantly, NAC not only decreased FCCP-induced ROS production, but it also restored the Ca2+ signals, SR Ca2+ content, and Ca2+ spark properties to control levels.Mitochondrial uncoupling results in fast transcriptional changes in CASQ2 expression that manifest as compromised Ca2+ signalling, and these changes can be prevented by ROS scavengers. As impaired mitochondrial function has been implicated in several cardiac pathologies as well as in normal ageing, the mechanisms described here might be involved in a wide spectrum of cardiac conditions.