Kanaporis Giedrius, Treinys Rimantas, Fischmeister Rodolphe, Jurevičius Jonas
Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania.
INSERM UMR-S 1180, Univ Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France.
PLoS One. 2017 Aug 31;12(8):e0184246. doi: 10.1371/journal.pone.0184246. eCollection 2017.
Metabolic stress evoked by myocardial ischemia leads to impairment of cardiac excitation and contractility. We studied the mechanisms by which metabolic inhibition affects the activity of L-type Ca2+ channels (LTCCs) in frog ventricular myocytes. Metabolic inhibition induced by the protonophore FCCP (as well as by 2,4- dinitrophenol, sodium azide or antimycin A) resulted in a dose-dependent reduction of LTCC current (ICa,L) which was more pronounced during β-adrenergic stimulation with isoprenaline. ICa,L was still reduced by metabolic inhibition even in the presence of 3 mM intracellular ATP, or when the cell was dialysed with cAMP or ATP-γ-S to induce irreversible thiophosphorylation of LTCCs, indicating that reduction in ICa,L is not due to ATP depletion and/or reduced phosphorylation of the channels. However, the effect of metabolic inhibition on ICa,L was strongly attenuated when the mitochondrial F1F0-ATP-synthase was blocked by oligomycin or when the cells were dialysed with the non-hydrolysable ATP analogue AMP-PCP. Moreover, increasing the intracellular pH buffering capacity or intracellular dialysis of the myocytes with an alkaline solution strongly attenuated the inhibitory effect of FCCP on ICa,L. Thus, our data demonstrate that metabolic inhibition leads to excessive ATP hydrolysis by the mitochondrial F1F0-ATP-synthase operating in the reverse mode and this results in intracellular acidosis causing the suppression of ICa,L. Limiting ATP break-down by F1F0-ATP-synthase and the consecutive development of intracellular acidosis might thus represent a potential therapeutic approach for maintaining a normal cardiac function during ischemia.
心肌缺血诱发的代谢应激会导致心脏兴奋和收缩能力受损。我们研究了代谢抑制影响青蛙心室肌细胞中L型钙通道（LTCCs）活性的机制。由质子载体FCCP（以及2,4-二硝基苯酚、叠氮化钠或抗霉素A）诱导的代谢抑制导致LTCC电流（ICa,L）呈剂量依赖性降低，在用异丙肾上腺素进行β-肾上腺素能刺激时这种降低更为明显。即使存在3 mM细胞内ATP，或者当细胞用cAMP或ATP-γ-S进行透析以诱导LTCCs发生不可逆的硫代磷酸化时，ICa,L仍会因代谢抑制而降低，这表明ICa,L的降低并非由于ATP耗竭和/或通道磷酸化减少。然而，当线粒体F1F0-ATP合酶被寡霉素阻断时，或者当细胞用不可水解的ATP类似物AMP-PCP进行透析时，代谢抑制对ICa,L的影响会大大减弱。此外，增加细胞内pH缓冲能力或用碱性溶液对心肌细胞进行细胞内透析会强烈减弱FCCP对ICa,L的抑制作用。因此，我们的数据表明，代谢抑制会导致以反向模式运行的线粒体F1F0-ATP合酶过度水解ATP，这会导致细胞内酸中毒，从而抑制ICa,L。因此，限制F1F0-ATP合酶的ATP分解以及随后发生的细胞内酸中毒可能代表一种在缺血期间维持正常心脏功能的潜在治疗方法。
