虎杖苷通过靶向抑制Ca2+/calmodulin激活的calcineurin-NFAT信号通路治疗心肌肥大的研究

心肌肥大是一种有害的心脏病理性重构，防治其发生对降低心血管疾病死亡率意义重大。Ca2+/钙调素激活的calcineurin-NFAT信号通路是心肌肥大发生的重要机制，通过抑制细胞内钙信号可阻止该通路激活，降低心肌肥大发生，但却带来心肌收缩力减弱的副作用。我们前期工作发现，多酚类化合物虎杖苷通过多靶点效应对心脏兴奋－收缩偶联发挥神奇的调节作用：一方面虎杖苷能有效降低细胞内钙信号，另外，它还增加肌原纤维对Ca2+敏感性，不降低心肌收缩力。因此，我们提出虎杖苷是一种可抑制calcineurin-NFAT信号通路治疗心肌肥大的理想药物之假设。拟开展以下研究：1. 通过复制心肌肥大的细胞和动物模型，查明虎杖苷治疗心肌肥大的作用；2. 通过分子生物学、膜片钳、激光共聚焦等技术，查明虎杖苷对calcineurin-NFAT信号通路的作用及其钙信号机制。为探寻心肌肥大治疗新药和作用机理提供理论和实验依据。

Cardiac hypertrophy is a detrimental pathological remodeling of the heart. The presence of left ventricular hypertrophy is the main risk factor for subsequent development of heart failure in man. Prevention of hypertrophy is important for decreasing morbidity and mortality of cardiovascular diseases. It is well established that Ca2+/calmodulin-activated calcineurin-NFAT signaling pathway is an important and common signaling pathway for the pathogenesis of hypertrophy. Inhibition of calcineurin activity with its inhibitors, such as cyclosporine A (CsA) and FK506, has been reported to have therapeutic effect on prevention of the development of hypertrophy in cultured neonatal cardiomyocytes, as well as in pressure overload-induced hypertrophic animal models. However, inhibition of calcineurin activity will induce other severe diseases because calcineurin-NFAT signaling pathway also participates in immune regulation. An alternative method for suppression of calcineurin-NFAT pathway is to inhibit Ca2+ signaling in cardiac myocytes. It has been suggested that L-type Ca+ channel blockers can prevent the development of hypertrophy by suppression of calcineurin-NFAT signaling pathway through inhibiting L-type Ca2+ current (ICa) and systolic Ca2+ transient. However, Ca2+ channel blockers have apparent side effect of suppressing cardiac contractility. Therefore, it is important to develop anti-hypertrophic drugs or methods that can inhibit intracellular Ca2+ signaling without compromising cardiac contractility. Our preliminary results show that polydatin, a resveratrol glucoside, had direct actions on cardiac Ca2+ signaling and excitation-contraction (EC) coupling through targeting on multiple Ca2+ transporter proteins and contractile myofilament. Polydatin decreased L-type Ca2+ current and systolic Ca2+ transient. To our surprise, polydatin had no effect or slightly increased cardiac contractility, for polydatin increased myofilament Ca2+ sensitivity. Therefore, we propose that polydatin is an ideal anti-hypertrophic drug by suppression of Ca2+-activated calcineurin-NFAT signaling pathway. To testify this hypothesis, we will firstly explore the effect of polydatin on the pathogenesis of phenylephrine-induced hypertrophy in cultured neonatal cardiac myocytes, and in pressure overload-induced hypertrophic mouse and dog models. Secondly, we will investigate the contribution of calcineurin-NFAT signaling pathway in polydatin treatment of hypertrophy. Furthermore, we will examine Ca2+-related mechanisms underlying polydatin suppression of calcineurin-NFAT signaling pathway. Through these efforts, we will try to discover the potential role of polydatin in the treatment of hypertrophy and elucidate the underlying mechanisms.