Division of Cardiology, Medical University of Graz, Austria.
Br J Pharmacol. 2012 Oct;167(3):493-504. doi: 10.1111/j.1476-5381.2012.01995.x.
Ca²⁺ leak from the sarcoplasmic reticulum (SR) via ryanodine receptors (RyR2s) contributes to cardiomyocyte dysfunction. RyR2 Ca²⁺ leak has been related to RyR2 phosphorylation. In these conditions, JTV519 (K201), a 1,4-benzothiazepine derivative and multi-channel blocker, stabilizes RyR2s and decrease SR Ca²⁺ leak. We investigated whether JTV519 stabilizes RyR2s without increasing RyR2 phosphorylation in mice and in non-failing human myocardium and explored underlying mechanisms.
SR Ca²⁺ leak was induced by ouabain in murine cardiomyocytes. [Ca²⁺]-transients, SR Ca²⁺ load and RyR2-mediated Ca²⁺ leak (sparks/waves) were quantified, with or without JTV519 (1 µmol·L⁻¹). Contribution of Ca²⁺ -/calmodulin-dependent kinase II (CaMKII) was assessed by KN-93 and Western blot (RyR2-Ser(2814) phosphorylation). Effects of JTV519 on contractile force were investigated in non-failing human ventricular trabeculae.
Ouabain increased systolic and diastolic cytosolic Ca²⁺ , SR [Ca²⁺], and SR Ca²⁺ leak (Ca²⁺ spark (SparkF) and Ca²⁺ wave frequency), independently of CaMKII and RyR-Ser(2814) phosphorylation. JTV519 decreased SparkF but also SR Ca²⁺ load. At matched SR [Ca²⁺], Ca²⁺ leak was significantly reduced by JTV519, but it had no effect on fractional Ca²⁺ release or Ca²⁺ wave propagation velocity. In human muscle, JTV519 was negatively inotropic at baseline but significantly enhanced ouabain-induced force and reduced its deleterious effects on diastolic function.
JTV519 was effective in reducing SR Ca²⁺ leak by specifically regulating RyR2 opening at diastolic Ca²⁺ in the absence of increased RyR2 phosphorylation at Ser(2814) , extending the potential use of JTV519 to conditions of acute cellular Ca²⁺ overload.
肌浆网（SR）通过兰尼碱受体（RyR2s）的 Ca²⁺渗漏导致心肌细胞功能障碍。RyR2 Ca²⁺渗漏与 RyR2 磷酸化有关。在这些情况下，1,4-苯并噻嗪衍生物和多通道阻滞剂 JTV519（K201）稳定 RyR2s 并减少 SR Ca²⁺渗漏。我们研究了 JTV519 是否在不增加 RyR2 磷酸化的情况下稳定 RyR2s，在小鼠和非衰竭的人类心肌中，并探讨了潜在的机制。
哇巴因诱导小鼠心肌细胞 SR Ca²⁺渗漏。用 JTV519（1μmol·L⁻¹）检测[Ca²⁺]-瞬变、SR Ca²⁺负荷和 RyR2 介导的 Ca²⁺渗漏（火花/波）。用 KN-93 和 Western blot（RyR2-Ser(2814)磷酸化）评估 Ca²⁺/钙调蛋白依赖性激酶 II（CaMKII）的贡献。在非衰竭的人心室小梁中研究 JTV519 对收缩力的影响。
哇巴因增加了收缩期和舒张期胞浆Ca²⁺、SR [Ca²⁺]和 SR Ca²⁺渗漏（Ca²⁺火花（SparkF）和 Ca²⁺波频率），与 CaMKII 和 RyR-Ser(2814)磷酸化无关。JTV519 减少了 SparkF，但也减少了 SR Ca²⁺负荷。在匹配的 SR [Ca²⁺]下，JTV519 显著减少 Ca²⁺渗漏，但对分数性 Ca²⁺释放或 Ca²⁺波传播速度没有影响。在人类肌肉中，JTV519 在基础状态下具有负性肌力作用，但显著增强哇巴因诱导的力，并减少其对舒张功能的有害影响。
JTV519 在没有增加 RyR2 Ser(2814)磷酸化的情况下，通过在舒张期Ca²⁺特异性调节 RyR2 的开放，有效减少了 SR Ca²⁺渗漏，从而扩展了 JTV519 在急性细胞 Ca²⁺过载情况下的潜在用途。
