Novel insights in the pathomechanism of Brugada syndrome and fever-related type 1 ECG changes in a preclinical study using human induced pluripotent stem cell-derived cardiomyocytes

Background Brugada syndrome (BrS) is causing sudden cardiac death (SCD) mainly at young age. Studying the underlying mechanisms associated with BrS type I ECG changes in presence of fever and roles of autophagy for BrS remains lacking.

Objectives We sought to study the pathogenic role of a SCN5A gene variant for BrS with fever induced type 1 ECG phenotype. In addition, we studied the role of inflammation and autophagy in the pathomechanism of BrS.

Methods Human induced pluripotent stem cell (hiPSC) lines from a BrS patient harboring a pathogenic variant (c.3148G>A/p. Ala1050Thr) in SCN5A and two healthy donors (non-BrS) and a CRISPR/Cas9 site-corrected cell line (BrS-corr) were differentiated into cardiomyocytes (hiPSC-CMs) for the study.

Results A reduction of Na_v1.5 expression, peak sodium channel current (I_Na) and upstroke velocity (V_max) of action potentials, and an increase in arrhythmic events was detected in BrS compared to non-BrS and BrS-corr cells. Increasing the cell culture temperature from 37°C to 40°C (fever-like-state) exacerbated the phenotypic changes in BrS cells. The fever-effects were enhanced by protein kinase A (PKA) inhibitor but reversed by PKA activator. Lipopolysaccharides (LPS) but not increased temperature up to 40°C enhanced the autophagy level in BrS-hiPSC-CMs by increasing reactive oxidative species (ROS) and inhibiting PI3K/AKT signaling, and hence exacerbated the phenotypic changes. LPS enhanced high temperature related effect on peak I_Na shown in BrS hiPSC-CMs. Effects of LPS and high temperature were not detected in non-BrS cells.

Conclusions The study demonstrated that the SCN5A variant (c.3148G>A/p.Ala1050Thr) caused loss-of-function of sodium channels and increased the channel sensitivity to high temperature and LPS challenge in hiPSC-CMs from a BrS cell line with this variant but not in two non-BrS hiPSC-CM lines. The results suggest that LPS may exacerbate BrS phenotype via enhancing autophagy, whereas fever may exacerbate BrS phenotype via inhibiting PKA-signaling in BrS cardiomyocytes with but probably not limited to this variant.