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 本申请提出了研究cGMP和cGMP-1通过其调节的新机制。 依赖性蛋白激酶I（PKGI）维持钙稳态，对抗室性心动过速（VT）。 糖尿病心脏在急性心肌梗死的情况下。糖尿病（DM）与心脏骤停的增加有关。 死亡（SCD），但糖尿病中糖尿病发生的分子和细胞机制仍不完全 明白T波交替（TWA）是体表心电图上的一种频率依赖性搏动波动， 与危及生命的室性心律失常有关。T波电交替已被描述在患者 II型糖尿病患者中，GSK 3 β活性亢进与DMII的继发性效应有关，但知之甚少 关于交替糖的机制及其在患者或小鼠VT发病机制中的特定作用， II型DM的型号。对程控心室刺激的VT诱导已被用于 识别心脏易发生室性心动过速的患者。目前的初步数据 本申请在两个单独的模型中鉴定了VT和TWA的显著诱导： DMII，以及高脂肪高蔗糖（HFHS）喂养的胰岛素不敏感小鼠模型。更重要的是我们 已经证明这些小鼠在心肌梗死后会发生严重的自发性心律失常 （密歇根州）。我们已经观察到，在上述两种情况下，细胞内信号分子cGMP均减少 模型此外，主要心血管cGMP效应物蛋白激酶G Iα（PKGIα）的遗传破坏 导致T波交替和高度诱导性VT，提供了该激酶在 VT在体内的发病机制。补救实验表明，cGMP- 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， GSK 3 β抑制剂TWS-119可减轻VT。基于这些和已发表的数据，提示GSK 3 β是PKG 1 α 底物，本申请提出测试PKGIα既对抗诱导型， 通过调节GSK 3 β活性，在糖尿病心脏中自发性MI后VT。我们提出3个具体的 目的：1）确定PDE抑制剂增加DMII心脏PKGI的抗心律失常作用， 鸟苷酸环化酶激活剂; 2）确定PKGIα功能障碍的生理机制 通过对Ca稳态的影响易诱发和MI后VT和交替; 3）确定 DMII中cGMP-PKG信号传导中断促进VT的下游信号传导机制 心这些研究产生的数据将确定PKGIα信号在VT调节中的作用 在DM II心脏中，有可能将PKGI的药理学调节确定为一种新的抗糖尿病药物。 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.