Unnatural verticilide enantiomer inhibits type 2 ryanodine receptor-mediated calcium leak and is antiarrhythmic

Abstract

Ca2+ leak via ryanodine receptor type 2 (RyR2) can cause potentially fatal arrhythmias in a variety of heart diseases and has also been implicated in neurodegenerative and seizure disorders, making RyR2 an attractive therapeutic target for drug development. Here we synthesized and investigated the fungal natural product and known insect RyR antagonist (−)-verticilide and several congeners to determine their activity against mammalian RyR2. Although the cyclooligomeric depsipeptide natural product (−)-verticilide had no effect, its nonnatural enantiomer [ent-(+)-verticilide] significantly reduced RyR2-mediated spontaneous Ca2+ leak both in cardiomyocytes from wild-type mouse and from a gene-targeted mouse model of Ca2+ leak-induced arrhythmias (Casq2−/−). ent-(+)-verticilide selectively inhibited RyR2-mediated Ca2+ leak and exhibited higher potency and a distinct mechanism of action compared with the pan-RyR inhibitors dantrolene and tetracaine and the antiarrhythmic drug flecainide. ent-(+)-verticilide prevented arrhythmogenic membrane depolarizations in cardiomyocytes without significant effects on the cardiac action potential and attenuated ventricular arrhythmia in catecholamine-challenged Casq2−/− mice. These findings indicate that ent-(+)-verticilide is a potent and selective inhibitor of RyR2-mediated diastolic Ca2+ leak, making it a molecular tool to investigate the therapeutic potential of targeting RyR2 hyperactivity in heart and brain pathologies. The enantiomer-specific activity and straightforward chemical synthesis of (unnatural) ent-(+)-verticilide provides a compelling argument to prioritize ent-natural product synthesis. Despite their general absence in nature, the enantiomers of natural products may harbor unprecedented activity, thereby leading to new scaffolds for probe and therapeutic development.

Molecular and tissue mechanisms of catecholaminergic polymorphic ventricular tachycardia

“…For example, human cardiomyocyte models of CPVT generated from patient-specific induced pluripotent stem cells (iPSCs) also exhibit DADs and action potentials triggered by spontaneous calcium release (Novak et al 2012(Novak et al , 2015. Drug efficacy in isolated ventricular cardiomyocytes can predict anti-arrhythmic efficacy in mouse models and in humans with CPVT (Knollmann, 2011;Batiste et al 2019). Furthermore, CPVT patients frequently present with atrial tachycardia or atrial fibrillation that can occur prior to or during their ventricular tachycardia (Leenhardt et al 1995).…”

“…Dantrolene, a drug used clinically to treat hyperactive skeletal muscle calcium release, decreased exercise-induced ventricular ectopy in some but not all CPVT patients (Penttinen et al 2015). Our group recently reported J Physiol 598.14 the discovery of ent-verticilide, a cyclic depsipeptide that has nanomolar potency, is selective for RyR2 over RyR1, and exhibits anti-arrhythmic efficacy in vivo (Batiste et al 2019). Another promising drug target is the calmodulin-dependent serine-threonine protein kinase II (CaMKII) (Fig.…”

ArrhythmoGenoPharmacoTherapy

“…Genetic analyses and findings led to the conclusion that chromosomal area of 1q42-q43 genes is probably closely connected to the function of ryanodine receptor (RyR)-calcium-release channels in cardiac tissues (Priori et al, 2001;Marks et al, 2002). Based on these aforementioned publications, it was suggested that potential inhibitors of RyR, especially RyR2, could be an important antiarrhythmic target for the development of new therapeutic agents (Bongianino et al, 2017;Batiste et al, 2019).…”

“…However, other antiarrhythmic agents initially classified by Vaughan Williams (1975), which are used in clinical therapy against hypoxia-or ischemia-induced arrhythmias e.g., beta adrenergic receptor blockers and calcium channel antagonists, should be avoided for the therapeutic management of arrhythmias with prolonged QT interval. A promising future approach, under experimental conditions to manage the CPVTinitiated QT prolongation, was published by Batiste et al (2019) showing that an unnatural verticilide enantiomer inhibits the function of RyR2-mediated calcium leak, which inhibits QT prolongation, and prevents life threatening arrhythmias.…”

Efficacy of Flecainide in Catecholaminergic Polymorphic Ventricular Tachycardia Is Mutation-Independent but Reduced by Calcium Overload

“…Although disputed by Bannister et al (2015) the most plausible explanation is that flecainide acts directly on RyR2 by blocking its open state, and thereby reduces the amount of Ca 2+ released during spontaneous openings of RyR2 channel clusters measured as Ca 2+ sparks (Hilliard et al, 2010). The hypothesis that flecainide inhibits RyR2 channels is supported by work indicating that flecainide suppresses RyR2-mediated SR Ca 2+ efflux (e.g., Ca 2+ spark mass) in permeabilized cardiomyocytes under experimental conditions that render Na + channels inactivated (Hilliard et al, 2010; Savio-Galimberti and Knollmann, 2015; Batiste et al, 2019). In contrast, Sikkel et al (2013) proposed that Na + channel block alone is responsible for Flecainide’s efficacy in CPVT.…”