ERLAD-hERG axis and L-type calcium channel activation mediate cholesterol-induced acquired long QT syndrome-related cardiotoxicity.

High cholesterol is a key cardiovascular risk factor that can modulate cardiac electrophysiology and promote acquired long QT syndrome (acLQTS)-related cardiotoxicity, a potentially life-threatening condition associated with QT prolongation, torsade de pointes, and sudden cardiac death. This study investigated the effects of cholesterol overload on human Ether-à-go-go-Related Gene (hERG/Kv11.1; encoded by KCNH2) potassium channels and L-type calcium channels (LTCC; mainly Cav1.2/CACNA1C in cardiomyocytes), as well as the underlying mechanisms of acLQTS-related cardiotoxicity, using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), whole-cell patch clamp, quantitative real-time PCR (qRT-PCR), Western blotting, immunoprecipitation, fluorescence imaging, and a high-cholesterol diet guinea pig model with rosuvastatin intervention combined with optical mapping. The results showed that transient cholesterol exposure inhibited hERG tail current amplitude and accelerated channel inactivation, with the effect showing a Y652-dependent component, while also enhancing LTCC activity. Mechanistically, cholesterol overload triggered endoplasmic reticulum (ER) stress, impaired hERG proteostasis, and promoted ER-to-lysosome-associated degradation (ERLAD) of hERG. This process was associated with CANX-mediated recognition of abnormal hERG and FAM134B-LC3B-related autophagic-lysosomal processing, contributing to reduced total hERG expression and membrane-localized mature hERG. FAM134B overexpression partially preserved hERG expression and attenuated cholesterol-induced ER stress/autophagy-related abnormalities. In vivo, rosuvastatin improved lipid profiles and cardiac remodeling in high-cholesterol guinea pigs but was associated with more pronounced action potential duration (APD) and QT interval prolongation under high-cholesterol conditions. These findings suggest that cholesterol overload may increase susceptibility to hERG-related repolarization abnormalities during rosuvastatin exposure and highlight the importance of cholesterol management and electrocardiographic (ECG) monitoring in hypercholesterolemic settings.