L-type Cav1.3 (alpha1D) calcium channels as targets for controlling heart failure related ventricular arrhythmias – CANTATA

Ventricular arrhythmias (VAs) constitute a major issue in heart failure (HF), as they cause overt mortality in patients. The mechanisms underlying VAs in HF are incompletely understood, hampering development of therapeutic strategy to prevent their occurrence. There is evidence indicate that regions of the failing ventricle are endowed with an intrinsic automaticity enabling the occurence of generalized arrhythmias. Ion channels are the fundamental building blocks that determine the cardiac electrical activity and thus arrhythmias, which represent the end product of abnormal ion channel structure, number, or function. Actually, most fatal arrhythmias in experimental HF are initiated by non-reentrant mechanisms that arise from abnormal ventricular automaticity or triggered activity, in which action potential (AP) prolongation and aberrant Ca2+ fluxes are a recurrent theme. The heart expresses two isoforms of L-type Ca2+ channels, Cav1.2 and Cav1.3. The Cav1.2 couples excitation to contraction in the ventricle, whereas the Cav1.3 confers automaticity to the sinoatrial node but is not expressed in the healthy adult ventricle. However, pilot data from the consortium teams indicate de novo Cav1.3 expression in failing human ventricles, reminiscent of the foetal reprogramming of cardiac gene expression in HF. Furthermore, we observe that selective blockade of Cav1.3 prevents VAs in mouse model of HF secondary to hypertension. Since Cav1.3 generates automaticity, we hypothesize that this channel is a potential candidate in the generation of VAs in the failing ventricle. Throughout interdisciplinary approaches, from molecule to organism, and sharing materials from two internationally recognized leading and complementary partners that conduct synergetic state-of-the art research in the field of function of cardiac ion channels and arrhythmia, we propose a proof of concept project to validate this novel role of Cav1.3 in HF and show that pharmacologic inhibition or molecular knockdown of Cav1.3 expression in failing hearts prevents VAs. We will explore Cav1.3 expression in human HF hearts of different etiologies. We will study the spatio-temporal expression of Cav1.3 and Cav1.2 in different experimental model of hearts with HF and attempt to establish a correlation between these data and the onset and duration of VA, as a function of pathology and gender both in vivo using endocardial exploration of heart rhythm and ex vivo using isolated Langendorff perfused hearts. We will induce HF in mice in which Cav1.2 channels have been rendered insensitive to dihydropyridines - enabling Cav1.3 to be selectively blocked - to investigate the ability of Cav1.3 selective pharmacological inhibition to suppress arrhythmia in the failing ventricle. We will also investigate the mechanism of generation of ectopic automaticity by Cav1.3 and the impact of cAMP-PKA dependent regulation of both Cav1.3 and Cav1.2 in this process. In mirror-like way, we will knockdown endogenous expression of Cav1.3 in cardiomyocytes derived from human pluripotent stem cells (hiPSC-CM) and in HF mouse model using AAV9-mediated knockdown of Cav1.3. In these human derived and mice models of Cav1.3 knockdown, we will study alterations in myocyte excitability and intracellular Ca2+ dynamics, we will identify regulatory Cav1.3 protein partners and test the capability of genetic silencing of Cav1.3 to prevent arrhythmia. The overarching goal of this project is to delineate the pathophysiological role of de novo Cav1.3 channels expression in HF. The combined basic knowledge gained from our project might be used to develop new anti-arrhythmic drugs based on Cav1.3 inhibition. In addition, our project will provide proof-of-concept to begin developing directed gene therapy to knockdown ventricular expression of Cav1.3. In summary, the CANTATA program will establish a new concept in HF, which may help alleviate one of the modern society’s greatest health burdens, the malignant VAs.