Approved drugs ezetimibe and disulfiram enhance mitochondrial Ca2+ uptake and suppress cardiac arrhythmogenesis.

BACKGROUND AND PURPOSE: Treatment of cardiac arrhythmia remains challenging due to severe side effects of common anti-arrhythmic drugs. We previously demonstrated that mitochondrial Ca2+ uptake in cardiomyocytes represents a promising new candidate structure for safer drug therapy. However, druggable agonists of mitochondrial Ca2+ uptake suitable for preclinical and clinical studies are still missing. EXPERIMENTAL APPROACH: Herewe screened 727 compounds with a history of use in human clinical trials in a three-step screening approach. As a primary screening platform we used a permeabilized HeLa cell-based mitochondrial Ca2+ uptake assay. Hits were validated in cultured HL-1 cardiomyocytes and finally tested for anti-arrhythmic efficacy in three translational models: a Ca2+ overload zebrafish model and cardiomyocytes of both a mouse model for catecholaminergic polymorphic ventricular tachycardia (CPVT) and induced pluripotent stem cell derived cardiomyocytes from a CPVT patient. KEY RESULTS: We identifiedtwo candidate compounds, the clinically approved drugs ezetimibe and disulfiram, which stimulate SR-mitochondria Ca2+ transfer at nanomolar concentrations. This is significantly lower compared to the previously described mitochondrial Ca2+ uptake enhancers (MiCUps) efsevin, a gating modifier of the voltage-dependent anion channel 2, and kaempferol, an agonist of the mitochondrial Ca2+ uniporter. Both substances restored rhythmic cardiac contractions in a zebrafish cardiac arrhythmia model and significantly suppressed arrhythmogenesis in freshly isolated ventricular cardiomyocytes from a CPVT mouse model as well as induced pluripotent stem cell derived cardiomyocytes from a CPVT patient. CONCLUSION AND IMPLICATIONS: Taken together we identified ezetimibe and disulfiram as novel MiCUps and efficient suppressors of arrhythmogenesis and as such as, promising candidates for future preclinical and clinical studies.

Suppression of Arrhythmia by Enhancing Mitochondrial Ca2+ Uptake in Catecholaminergic Ventricular Tachycardia Models.

Cardiovascular disease-related deaths frequently arise from arrhythmias, but treatment options are limited due to perilous side effects of commonly used antiarrhythmic drugs. Cardiac rhythmicity strongly depends on cardiomyocyte Ca2+ handling and prevalent cardiac diseases are causally associated with perturbations in intracellular Ca2+ handling. Therefore, intracellular Ca2+ transporters are lead candidate structures for novel and safer antiarrhythmic therapies. Mitochondria and mitochondrial Ca2+ transport proteins are important regulators of cardiac Ca2+ handling. Here we evaluated the potential of pharmacological activation of mitochondrial Ca2+ uptake for the treatment of cardiac arrhythmia. To this aim,we tested substances that enhance mitochondrial Ca2+ uptake for their ability to suppress arrhythmia in a murine model for ryanodine receptor 2 (RyR2)-mediated catecholaminergic polymorphic ventricular tachycardia (CPVT) in vitro and in vivo and in induced pluripotent stem cell-derived cardiomyocytes from a CPVT patient. In freshly isolated cardiomyocytes of RyR2R4496C/WT mice efsevin, a synthetic agonist of the voltage-dependent anion channel 2 (VDAC2) in the outer mitochondrial membrane, prevented the formation of diastolic Ca2+ waves and spontaneous action potentials. The antiarrhythmic effect of efsevin was abolished by blockade of the mitochondrial Ca2+ uniporter (MCU), but could be reproduced using the natural MCU activator kaempferol. Both mitochondrial Ca2+ uptake enhancers (MiCUps), efsevin and kaempferol, significantly reduced episodes of stress-induced ventricular tachycardia in RyR2R4496C/WT mice in vivo and abolished diastolic, arrhythmogenic Ca2+ events in human iPSC-derived cardiomyocytes.