Inhibition of intermittent calcium‐activated potassium channel (SK4) attenuates Ang II‐induced hypertrophy of human‐induced stem cell‐derived cardiomyocytes via targeting Ras–Raf–MEK1/2–ERK1/2 and CN–NFAT signaling pathways

Cardiac hypertrophy caused by angiotensin II (Ang II) is essential for the pathological process of heart failure. The intermediate calcium-activated potassium channel (SK4) has been shown to be involved in the process of the inflammatory response, cell proliferation, and apoptosis. However, the role of SK4 in cardiac hypertrophy has not been elucidated. Cardiac hypertrophy in human-induced pluripotent stem cells-derived cardiomyocytes (HiPSC-CMs) was induced by Ang II. Cells were transfected with SK4 adenovirus or treated with SK4 inhibitor (TRAM-34). TUNEL staining was used to assess the levels of apoptosis. Real-time polymerase chain reaction and Western blot analysis were used to measure messenger RNA (mRNA) and protein levels, respectively. The present results showed that SK4 expression was upregulated in HiPSC-CMs stimulated by Ang II. The downregulation of SK4 by a specific inhibitor TRAM-34 markedly ameliorated cardiac hypertrophy (reflected by the mRNA levels of atrial natriuretic peptide, brain natriuretic peptide, and β-myosin heavy chain) and apoptosis (reflected by the level of Caspase 3, Bax, and Bcl-2) induced by Ang II treatment. The action of SK4 in cardiac hypertrophy was mediated by Ras-Raf-mitogen-activated protein kinases 1/2 (MEK1/2)-extracellular-regulated protein kinases 1/2 (ERK1/2) and calcineurin (CN)-nuclear factors of activated T cells (NFAT) activation. Our studies demonstrated that inhibition of SK4 significantly alleviated cardiac hypertrophy induced by Ang II in hiPSC-CMs by targeting Ras-Raf-MEK1/2-ERK1/2 signaling and CN-NFAT signaling pathway. Our studies suggest that SK4 may serve as a potential therapeutic target that could delay hypertrophy.