Modulation of p-adrenergic and myofilament responses by Cardiac Resynchronization

心脏起搏治疗（CRT）是新世纪心力衰竭治疗的主要新进展。它使用双心室起搏刺激来抵消传导延迟，从而改善受影响患者的收缩协调。在急性和慢性改善休息和储备收缩功能的治疗中，它是独一无二的，因为它也提高了生存率。本PPG的总体主题是，通过了解这是如何在细胞和分子水平上完成的，将产生重要的新见解，以最佳地使用CRT，并更普遍地用于心力衰竭治疗。我们最近的工作表明，心肌细胞静息和β-肾上腺素能刺激功能在不同步心力衰竭（DHF）中明显受到抑制，而CRT则大大增强了这两种功能。其机制包括β-1受体数量的适度增加、腺苷酸环化酶活性的增强以及抑制性G蛋白偶联的显著抑制，这些抑制性G蛋白偶联可能与G偶联信号蛋白3调节剂的负调节有关。新的数据显示，CRT增强的肌丝钙反应也有贡献，并伴随着几种调节性细丝蛋白的磷酸化变化。这些变化在总是同步收缩的心脏中也没有观察到，但在先前DHF心脏中恢复同步性似乎是特异性的。本项目的目标是确定CRT诱导的肌钙和β-肾上腺素能/Gi偶联变化介导的收缩储备改善的机制。目的1研究犬模型中肌丝敏感性改变的机制，测试其与ATP利用的耦合，以及在皮肤肌肉和肌细胞制备物中的翻译后变化的作用。目的2和3测试CRT如何独特地调节β-AR储备，重点是RGS蛋白抑制Gi信号传导的作用和β-β 2激活效应的变化。这项工作使用狗模型，以及DHF和CRT的新小鼠模型，使一般缺乏RGS 2，-3或-4的小鼠的研究能够更直接地测试这种调节的影响。这些数据可能产生适合CRT的心脏的新的潜在生物标志物，并为可能影响更广泛患者人群的心力衰竭治疗的成功治疗提供新的见解。

Cardiac resynchronization therapy (CRT) is the major new advance in heart failure treatment in the new millennium. It uses bi-ventricular pacing stimulation to offset conduction delay and thereby improve contraction coordination in affected patients. It is unique among treatments that acutely and chronically improve rest and reserve systolic function, as it also improves survival. The overall theme ofthis PPG is that by understanding how this is accomplished at the cellular and molecular level will yield important new insights into optimally using CRT, and for heart failure therapy more generally. Our recent work showed myocyte rest and beta-adrenergic stimulated function are markedly depressed in dyssynchronous heart failure (DHF) and both are greatly enhanced by CRT. Mechanisms included a modest rise in beta-1 receptor number, enhanced adenylate cyclase activity, and a marked suppression of inhibitory G-protein coupling potentially linked to negative modulation by regulator of G-coupled signaling protein 3. New data shows enhanced myofilament calcium responsiveness with CRT also contributes, and is accompanied by phosphorylation changes in several regulatory thin filament proteins. These changes are not observed in hearts that develop failure with always synchronous contraction either, but appear specific to having synchrony restored in a previously DHF heart. The goal of this project is to determine the mechanisms underlying improved contractile reserve mediated by myofilament-calcium and beta-adrenergic/Gi-coupled changes induced by CRT. Aim 1 studies the mechanisms of altered myofilament sensitivity in our canine models, testing its coupling to ATP utilization, and role of post-translational changes in skinned muscle and myocyte-preparations. Aims 2 and 3 test how CRT uniquely modulates beta-AR reserve, focusing on the role of RGS protein suppression of Gi signaling and changes in betai-beta2 activation effects. This work uses the dog model, as well as a new mouse model of DHF and CRT to enable studies of mice generically lacking RGS2, -3, or -4 to more directly test the impact of this regulation. These data may yield novel potential biomarkers for hearts amenable to CRT, and provide novel insights into a successful therapy that could impact heart failure treatment in the broader patient population.