Esophageal Cancer-Related Gene-4 Contributes to Lipopolysaccharide-Induced Ion Channel Dysfunction in hiPSC-Derived Cardiomyocytes

Background and purpose: Esophageal cancer-related gene-4 (ECRG4) participate in inflammation process and can interact with the innate immunity complex TLR4-MD2-CD14 on human granulocytes. In addition, ECRG4 participate in modulation of ion channel function and electrical activity of cardiomyocytes. However, the exact mechanism is unknown. This study aimed to test our hypothesis that ECRG4 contributes to inflammation-induced ion channel dysfunctions in cardiomyocytes.

Methods: Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) generated from three donors were treated with lipopolysaccharide (LPS) to establish an endotoxin-induced inflammatory model. Immunostaining, real-time PCR, and patch-clamp techniques were used for the study.

Results: ECRG4 was detected in hiPSC-CMs at different differentiation time. LPS treatment increased ECRG4 expression in hiPSC-CMs. Knockdown of ECRG4 decreased the expression level of Toll-Like-Receptor 4 (TLR4, a LPS receptor) and its associated genes and inflammatory cytokines. Furthermore, ECRG4 knockdown shortened the action potential duration (APD) and intercepted LPS-induced APD prolongation by enhancing I_SK (small conductance calcium-activated K channel current) and attenuating I_NCX (Na/Ca exchanger current). Overexpression of ECRG4 mimicked LPS effects on I_SK and I_NCX, which could be prevented by NFκB signaling blockers.

Conclusion: This study demonstrated that LPS effects on cardiac ion channel function were mediated by the upregulation of ECRG4, which affects NFκB signaling. Our findings support the roles of ECRG4 in inflammatory responses and the ion channel dysfunctions induced by LPS challenge.