Abstract
Background Inflammation may cause fever and trigger the Brugada syndrome (BrS) phenotype in some patients. Whether inflammation per se can exacerbate BrS and the underlying mechanism have not been fully clarified. This study was designed to investigate roles and mechanisms of inflammatory factors in BrS patients carrying different gene variants.
Methods Human induced pluripotent stem cell (hiPSC) lines generated from fibroblasts of three BrS patients harboring variants in SCN5A(c.3148G>A/p.Ala1050Thr, BrS1), SCN10A (c.3749G>A/p.Arg1250Gln, BrS2) and CACNB2 (c.425C > T/p.S142F, BrS3), and one healthy donor (WT) and a site-corrected (using CRISPR/Cas9) hiPSC line of each BrS patient (isogenic1, isogengic2 and isogenic3) were used for differentiation into cardiomyocytes (hiPSC-CMs). Cells were challenged by lipopolysaccharide (LPS, 2 µg/ml 24 h). Western blot, patch clamp and calcium transient analyses were carried out.
Results The BrS-hiPSC-CMs showed a significantly reduced peak sodium current (INa) and maximal velocity of depolarization (Vmax) of action potential compared with isogenic or WT hiPSC-CMs. hiPSC-CMs of BrS3 showed also a significant reduction in L-type calcium channel currents (ICa-L). Arrhythmia-like events were detected more frequently in hiPSC-CMs from all BrS patients, indicating the BrS phenotype in BrS-hiPSC-CMs. Treating the BrS1 and BrS2 cells with LPS showed a further reduction of peak INa and Vmax, and increased arrhythmic events. Treating hiPSC-CMs of BrS3 with LPS reduced ICa-L and APD50, increased arrhythmic events and interval variability. ROS-Blocker abolished the LPS effects in all the three BrS hiPSC-CMs, while an interleukin-6 receptor blocker abolished the proarrhythmic effect of LPS only in BrS1and BrS2 hiPSC-CMs but not in hiPSC-CMs of BrS3. In BrS-hiPSC-CMs, LPS increased IL-6 protein expression level detected by western blot and enhanced IL-6 production detected by ELISA analysis.
Conclusion LPS enhanced the BrS phenotype in hiPSC-CMs of all three BrS cell lines. ROS contributes to LPS effects in BrS cells with SCN5A, SCN10A and CACNB2 variants, while IL-6 signaling contributes to LPS effects on BrS only with SCN5A and SCN10A variants.
