A Role of PKG1a and Inhibitors of cGMP Phosphodiesterase in Post MI VT in Mouse Models for Type II Diabetes and Metabolic Syndrome

项目摘要 目前的应用建议研究cGMP和cGMP- 依赖蛋白激酶I(PKGI)维持钙稳态和抗室性心动过速(VT) 糖尿病心脏在急性心肌梗死中的设置。糖尿病(DM)与心脏骤停的增加有关 死亡(SCD)，但糖尿病心律失常发生的分子和细胞机制仍不完全 明白了。T波交替(TWA)是体表EKG上的一种依赖于速率的搏动 与危及生命的室性心律失常有关。T波交替波已被描述为患者 对于II型糖尿病，GSK3β的过度活动与DMII的继发效应有关，但鲜为人知 关于Alternans的机制及其在患者或小鼠VT发病中的特殊作用 适用于类型II DM的型号。室性心动过速对程序性心室刺激的应答性已被用于 确定心脏易发生室性心动过速的患者。当前的初步数据 应用发现VT和TWA在两个不同的模型中具有显著的诱导性：DB/DB小鼠模型 DMII，并在高脂高糖(HFHS)喂养的小鼠中建立胰岛素不敏感模型。更重要的是，我们 已经证明，这些小鼠在心肌梗死后会出现严重的自发性心律失常 (Mi)。我们观察到，在上述两种情况下，细胞内信号分子cGMP均减少。 模特们。此外，主要的心血管cGMP效应因子蛋白激酶G Iα(PKGIα)的遗传破坏 导致T波交替和高度诱导性室性心动过速，提供了直接证据，证明该激酶在 室性心动过速的体内发病机制。救援实验表明，cGMP-1对cGMP有增强作用。 选择性磷酸二酯酶5抑制剂西地那非可消除DB/DB和HFHS小鼠的VT和TWA，而 β抑制剂TWS-119可减弱室性心动过速。根据这些和公布的数据，GSK3β是一个PKG1α 底物，当前的应用程序建议测试PKGIα既反对可诱导的又反对 糖尿病心脏自发性心肌梗死后室性心动过速通过调节GSK3β活性实现。我们提出3个具体的建议 目的：1)研究PDE抑制剂对DMII心脏PKGI增强的抗心律失常作用 鸟苷环化酶激活剂；2)确定PKGIα功能障碍的生理机制 通过对钙稳态的影响，易诱发和诱发MI后室性心动过速和交替；3)测定 干扰cGMP-PKG信号促进DMII中VT的下游信号机制 心。这些研究产生的数据将确定PKGIα信号在室速调节中的作用 并有可能确定PKGI作为一种新的抗心律失常药物的药理调节 糖尿病患者的治疗策略。

Project Summary The current application proposes to investigate the novel mechanisms through which cGMP and the cGMP- dependent protein kinase I (PKGI) maintain Ca homeostasis and oppose ventricular tachycardia (VT) in the diabetic heart in the setting of acute MI. Diabetes mellitus (DM) is associated with an increase in sudden cardiac death (SCD), but the molecular and cellular mechanisms of arrhythmogenesis in DM remain incompletely understood. T-Wave alternans (TWA) is a rate dependent beat-to-beat fluctuation on the surface EKG that has been associated with life threatening ventricular arrhythmias. T-wave alternans has been described in patients with Type II DM, and hyperactivity of GSK3β has been implicated in secondary effects of DMII, but little is known regarding the mechanism of alternans and its specific role in the pathogenesis of VT in patients, or in mouse models for Type II DM. Inducibility of VT in response to programmed ventricular stimulation has been used to identify patients whose hearts are predisposed to the development of VT. Preliminary data in the current application identify significant inducibility of VT and of TWA in two separate models: the Db/Db mouse model of DMII, and in the High Fat High Sucrose (HFHS) fed mouse model of insulin insensitivity. More importantly, we have demonstrated that these mice develop severe spontaneous arrhythmias following myocardial infarction (MI). We have observed that the intracellular signaling molecule cGMP is decreased in both of these above models. Further, genetic disruption of the primary cardiovascular cGMP effector, Protein Kinase G Iα (PKGIα) leads to T-wave alternans and highly inducible VT, providing direct evidence that this kinase plays a role in the pathogenesis of VT in vivo. Rescue experiments demonstrate that augmentation of cGMP with the cGMP- selective phosphodiesterase 5 inhibitor sildenafil abolishes VT and TWA in the Db/Db and HFHS mice, while the GSK3β inhibitor TWS-119 attenuates VT. Based on these and published data implicating GSK3β as a PKG1α substrate, the current application proposes to test the hypothesis that PKGIα opposes both inducible and spontaneous post MI VT in the diabetic heart through the regulation of GSK3β activity. We propose 3 Specific Aims: 1) Determine the anti-arrhythmic effects of PKGI augmentation in the DMII heart by PDE inhibitors and Guanylate cyclase activators; 2) Determine the physiologic mechanisms by which PKGIα dysfunction predisposes to inducible and post MI VT and alternans via an effect on Ca homeostasis; 3) Determine the downstream signaling mechanisms through which disruption of cGMP-PKG signaling promotes VT in the DMII heart. The data generated from these studies will determine the role of PKGIα signaling in the regulation of VT in the DM II heart and has the potential to identify pharmacologic modulation of PKGI as a novel anti-arrhythmic strategy in patients with DM.