ABSTRACT
Introduction: Chloroquine (CQ) and its derivate hydroxychloroquine (HCQ) are successfully deployed for different diseases beyond the prophylaxis and treatment of malaria. Both substances exhibit antiviral properties and have been proposed for prophylaxis and treatment of COVID-19 caused by SARS-CoV-2. CQ and HCQ cause similar adverse events including life-threatening cardiac arrhythmia generally based on QT-prolongation, which is one of the most reported adverse events for both agents associated with the treatment of COVID-19. Various drugs known to induce QT-prolongation have been proven to exert local anesthetic (LA)-like properties regarding their impact on the cardiac Na+ channel Nav1.5. Inhibition of Nav1.5 is considered as the primary mechanism of cardiotoxicity caused by LAs. However, the mechanism of the arrhythmogenic effects of CQ and HCQ related to Nav1.5 has not yet been fully investigated. Therefore, the exact mechanism of how CQ and HCQ affect the sodium currents generated by Nav1.5 need to be further elucidated. Objective: This in vitro study aims to investigate the effects of CQ and HCQ on Nav1.5-generated sodium currents to identify possible LA-like mechanisms that might contribute to their arrhythmogenic properties. Methods: The effects of CQ and HCQ on Nav1.5-generated sodium currents by HEK-293 cells expressing either wild-type human Nav1.5 or mutant Nav1.5 F1760A are measured using the whole-cell patch-clamp technique. Results: Both agents induce a state-dependent inhibition of Nav1.5. Furthermore, CQ and HCQ produce a use-dependent block of Nav1.5 and a shift of fast and slow inactivation. Results of experiments investigating the effect on the LA-insensitive mutant Nav1.5-F1760A indicate that both agents at least in part employ the proposed LA-binding site of Nav1.5 to induce inhibition. Conclusion: This study demonstrated that CQ and HCQ exert LA-typical effects on Nav1.5 involving the proposed LA binding site, thus contributing to their arrhythmogenic properties.