BACKGROUND Orai1 is a critical ion channel subunit, best recognized as a mediator of store-operated Ca2+ entry (SOCE) in nonexcitable cells. SOCE has recently emerged as a key contributor of cardiac hypertrophy and heart failure but the relevance of Orai1 is still unclear. METHODS To test the role of these Orai1 channels in the cardiac pathophysiology, a transgenic mouse was generated with cardiomyocyte-specific expression of an ion pore-disruptive Orai1R91W mutant (C-dnO1). Synthetic chemistry and channel screening strategies were used to develop 4-(2,5-dimethoxyphenyl)-N-[(pyridin-4-yl)methyl]aniline (hereafter referred to as JPIII), a small-molecule Orai1 channel inhibitor suitable for in vivo delivery. RESULTS Adult mice subjected to transverse aortic constriction (TAC) developed cardiac hypertrophy and reduced ventricular function associated with increased Orai1 expression and Orai1-dependent SOCE (assessed by Mn2+ influx). C-dnO1 mice displayed normal cardiac electromechanical function and cellular excitation-contraction coupling despite reduced Orai1-dependent SOCE. Five weeks after TAC, C-dnO1 mice were protected from systolic dysfunction (assessed by preserved left ventricular fractional shortening and ejection fraction) even if increased cardiac mass and prohypertrophic markers induction were observed. This is correlated with a protection from TAC-induced cellular Ca2+ signaling alterations (increased SOCE, decreased [Ca2+]i transients amplitude and decay rate, lower SR Ca2+ load and depressed cellular contractility) and SERCA2a downregulation in ventricular cardiomyocytes from C-dnO1 mice, associated with blunted Pyk2 signaling. There was also less fibrosis in heart sections from C-dnO1 mice after TAC. Moreover, 3 weeks treatment with JPIII following 5 weeks of TAC confirmed the translational relevance of an Orai1 inhibition strategy during hypertrophic insult. CONCLUSIONS The findings suggest a key role of cardiac Orai1 channels and the potential for Orai1 channel inhibitors as inotropic therapies for maintaining contractility reserve after hypertrophic stress.

中文翻译：

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Orai1 通道抑制可在压力过载后保持左心室收缩功能和正常的 Ca2+ 处理。

背景 Orai1 是一个关键的离子通道亚基，最被认为是非兴奋细胞中钙池操纵的 Ca2+ 进入 (SOCE) 的介体。SOCE 最近已成为心脏肥大和心力衰竭的关键因素，但 Orai1 的相关性仍不清楚。方法 为了测试这些 Orai1 通道在心脏病生理学中的作用，我们生成了一只转基因小鼠，其心肌细胞特异性表达了离子孔破坏性 Orai1R91W 突变体 (C-dnO1)。合成化学和通道筛选策略被用于开发 4-(2,5-二甲氧基苯基)-N-[(吡啶-4-基)甲基]苯胺 (以下简称 JPIII), 一种小分子 Orai1 通道抑制剂适用于体内递送。结果 经受横向主动脉缩窄术 (TAC) 的成年小鼠发生心脏肥大和心室功能降低，这与 Orai1 表达增加和 Orai1 依赖性 SOCE（通过 Mn2+ 流入评估）相关。尽管 Orai1 依赖性 SOCE 减少，但 C-dnO1 小鼠显示出正常的心脏机电功能和细胞兴奋-收缩耦合。TAC 后五周，C-dnO1 小鼠免受收缩功能障碍（通过保留的左心室缩短分数和射血分数评估），即使观察到心脏质量增加和促肥大标记物诱导。这与防止 TAC 诱导的细胞 Ca2+ 信号改变（增加 SOCE，降低 [Ca2+]i 瞬变幅度和衰减率，降低 SR Ca2+ 负荷和抑制细胞收缩力）和来自 C-dnO1 小鼠的心室心肌细胞中的 SERCA2a 下调，与 Pyk2 信号减弱相关。TAC 后 C-dnO1 小鼠心脏切片中的纤维化也较少。此外，在 TAC 5 周后用 JPIII 治疗 3 周证实了 Orai1 抑制策略在肥大损伤期间的转化相关性。结论 这些发现表明心脏 Orai1 通道的关键作用以及 Orai1 通道抑制剂作为正性肌力疗法在肥厚性应激后维持收缩力储备的潜力。在 TAC 5 周后用 JPIII 治疗 3 周证实了 Orai1 抑制策略在肥大性损伤期间的转化相关性。结论 研究结果表明心脏 Orai1 通道的关键作用以及 Orai1 通道抑制剂作为正性肌力疗法在肥大应激后维持收缩力储备的潜力。在 TAC 5 周后用 JPIII 治疗 3 周证实了 Orai1 抑制策略在肥大性损伤期间的转化相关性。结论 这些发现表明心脏 Orai1 通道的关键作用以及 Orai1 通道抑制剂作为正性肌力疗法在肥厚性应激后维持收缩力储备的潜力。