Elevated cytosolic Na+ decreases mitochondrial Ca2+ uptake during excitation-contraction coupling and impairs energetic adaptation in cardiac myocytes
Elevated cytosolic Na+ decreases mitochondrial Ca2+ uptake during excitation-contraction coupling and impairs energetic adaptation in cardiac myocytes
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DOI：
10.1161/01.res.0000232546.92777.05
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发表时间：
2006-07-21
影响因子：
20.1
通讯作者：
O'Rourke, Brian
中科院分区：
文献类型：
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作者：
Maack, Christoph;Cortassa, Sonia;O'Rourke, Brian
线粒体Ca2+([Ca2+]m)调节氧化磷酸化，从而有助于心肌细胞的能量供应和需求匹配。线粒体通过Ca2+单转运体（MCU）吸收Ca2+，并通过线粒体Na+/Ca2+交换器（mNCE）将其挤出。线粒体是快速吸收Ca2+，以搏动为基础，还是缓慢吸收，通过暂时整合细胞质Ca2+([Ca2+](c))瞬态，这是有争议的。此外，虽然线粒体Ca2+外溢受mNCE控制，但细胞内Na+升高（[Na+](i)）是否影响线粒体Ca2+摄取和生物能量学尚不清楚。为了监测[Ca2+](m)，我们在豚鼠心肌细胞线粒体上装载rhod-2-乙酰氧基甲酯（rhod-2 AM），并在rhod-2透析出细胞质后用indo-1监测[Ca2+](c)。电压箝位去极化引起的[Ca2+](c)瞬态伴随着快速[Ca2+](m)瞬态，其振幅（Delta）与δ [Ca2+](c)线性相关。在β -肾上腺素能刺激下，[Ca2+](m)的衰减速度比[Ca2+](c)慢约2.5倍，当δ [Ca2+](c)的振幅或频率增加时，导致[Ca2+](m)的舒张累积。MCU阻滞剂Ru360降低δ [Ca2+](m)并增加δ [Ca2+](c)，而mNCE抑制剂CGP-37157增强舒张期[Ca2+](m)积累。升高[Na+](i)从5到15 mmol/L加速线粒体Ca2+衰变，从而降低收缩期和舒张期[Ca2+](m)。随着工作量的逐渐或突然变化，降低的烟酰胺腺嘌呤二核苷酸（NADH）水平维持在5 mmol/L [Na+](i)，但在15 mmol/L时，NADH池被部分氧化。结果表明：(1)在[Ca2+](c)瞬态过程中，线粒体快速吸收Ca2+并有助于快速缓冲；(2) [Na+]升高(i)损害线粒体Ca2+摄取，从而影响能量供需匹配。后一种效应可能对[Na+]升高的心脏疾病有影响(1)。
Mitochondrial Ca2+([Ca2+]m) regulates oxidative phosphorylation and thus contributes to energy supply and demand matching in cardiac myocytes. Mitochondria take up Ca2+ via the Ca2+ uniporter (MCU) and extrude it through the mitochondrial Na+/Ca2+ exchanger (mNCE). It is controversial whether mitochondria take up Ca2+ rapidly, on a beat-to-beat basis, or slowly, by temporally integrating cytosolic Ca2+([Ca2+](c)) transients. Furthermore, although mitochondrial Ca2+ efflux is governed by mNCE, it is unknown whether elevated intracellular Na+([Na+](i)) affects mitochondrial Ca2+ uptake and bioenergetics. To monitor [Ca2+](m), mitochondria of guinea pig cardiac myocytes were loaded with rhod-2-acetoxymethyl ester (rhod-2 AM), and [Ca2+](c) was monitored with indo-1 after dialyzing rhod-2 out of the cytoplasm. [Ca2+](c) transients, elicited by voltage-clamp depolarizations, were accompanied by fast [Ca2+](m) transients, whose amplitude (Delta) correlated linearly with Delta[Ca2+](c). Under beta-adrenergic stimulation, [Ca2+](m) decay was approximate to 2.5-fold slower than that of [Ca2+](c), leading to diastolic accumulation of [Ca2+](m) when amplitude or frequency of Delta[Ca2+](c) increased. The MCU blocker Ru360 reduced Delta[Ca2+](m) and increased Delta[Ca2+](c), whereas the mNCE inhibitor CGP-37157 potentiated diastolic [Ca2+](m) accumulation. Elevating [Na+](i) from 5 to 15 mmol/L accelerated mitochondrial Ca2+ decay, thus decreasing systolic and diastolic [Ca2+](m). In response to gradual or abrupt changes of workload, reduced nicotinamide-adenine dinucleotide (NADH) levels were maintained at 5 mmol/L [Na+](i), but at 15 mmol/L, the NADH pool was partially oxidized. The results indicate that (1) mitochondria take up Ca2+ rapidly and contribute to fast buffering during a [Ca2+](c) transient; and (2) elevated [Na+](i) impairs mitochondrial Ca2+ uptake, with consequent effects on energy supply and demand matching. The latter effect may have implications for cardiac diseases with elevated [Na+](i).