Donepezil-induced degradation of hERG potassium channel via lysosomal pathway is exacerbated by hypoxia

Donepezil (DPZ), an acetylcholinesterase inhibitor for Alzheimer's disease, has drawn attention for causing prolonged QT interval and torsade de pointes (TdP). Acquired long QT syndrome (acLQTS) is usually caused by blockage of the cardiac potassium current I_Kr/hERG, which is essential for cardiac repolarization. This study aimed to investigate DPZ's effect on hERG channel and its cardiotoxic mechanism, particularly focusing on whether hypoxia increases the risk of DPZ-induced acLQTS. To explore these, we employed western blotting to analyze protein levels, the patch clamp technique to measure hERG current and the action potentials of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Additionally, immunoprecipitation was utilized to detect protein-protein interactions. Finally, optical mapping monitored guinea pig ECGs and APD, providing in vivo insights. Our results indicate that 24-h incubation with DPZ inhibits hERG protein levels and current in the plasma membrane. Mechanistically, DPZ induces an imbalance in hERG protein acetylation/ubiquitination and decreases the stability of hERG by promoting HDAC6 expression, and the ubiquitinated hERG protein was degraded at lysosomes via K63-polyubiquitin chains. DPZ affects hERG membrane protein via two pathways: it accelerates endocytosis and directs degradation via CHMP3 (a sorting protein of ESCRT-III), while inhibiting recycling through Rab11. Hypoxia exacerbates DPZ-induced hERG degradation and APD prolongation in guinea pigs and hiPSC-CMs. Collectively, DPZ reduces hERG protein stability in the membrane, promoting its degradation in lysosomes. Hypoxia further exacerbates the risk of arrhythmia caused by DPZ. These findings remind us to pay attention to acLQTS induced by DPZ inhibition of hERG in clinical applications.