Mephedrene-Induced Cardiac Electrophysiological and Molecular Alterations: An Integrated In Vitro and In Vivo Study

Mephedrene, a psychoactive stimulant structurally related to methamphetamine, has recently emerged on illicit markets. Although methamphetamine-like compounds are known to stimulate the central nervous system and elevate cardiovascular risk, the pharmacological and toxicological characteristics of mephedrene, particularly its cardiotoxic potential, are poorly defined. Cardiotoxicity was evaluated using integrated in vitro and in vivo approaches. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were assessed for electrophysiological alterations by multi-electrode array (MEA) recordings, cell viability by WST-1 assay, and sarco/endoplasmic reticulum Ca²⁺-ATPase 2 (SERCA2) expression by Western blotting. In vivo electrocardiography (ECG) was recorded in rats following intravenous mephedrene administration (5 or 15 mg/kg). WST-1 assays revealed a significant decline in cell viability from 300 μM. MEA analysis showed reductions in Fridericia-corrected field potential duration (FPDcF) and beat period at 10 μM and a decrease in spike amplitude at 50 μM. Western blots demonstrated SERCA2 downregulation at 50 and 100 μM, consistent with impaired Ca²⁺ handling. In vivo, mephedrene produced significant QT interval prolongation at 5 and 15 mg/kg, with a dose-dependent increase. This study provides the first integrated evidence that mephedrene induces concentration-dependent disturbances in cardiac electrophysiology, viability, and Ca²⁺-regulatory mechanisms in vitro and prolongs QT intervals in vivo. These findings indicate substantial cardiovascular risk associated with mephedrene exposure and underscore the need for toxicological surveillance and regulatory action to mitigate potential public health harms posed by emerging novel psychoactive substances.