Background:

Brugada syndrome (BrS) is associated with sudden cardiac death (SCD) and ventricular tachyarrhythmias at fever situations. However, the underlying mechanism in human cardiomyocytes is not yet studied.

Methods:

Human induced pluripotent stem cell (hiPSC) lines generated from fibroblasts of two BrS patients harboring variants in SCN10A and CACNB2, and one healthy donor and a site-corrected (using CRISPR/CAS9) cell line of each BrS patient were used for differentiation of cardiomyocytes cells (hiPSC-CMs). Western blot, patch clamp and calcium transient analyses were carried out.

Results:

The hiPSC-CMs of BrS in presence of SCN10A variant showed a significantly reduced peak I_Na and increased arrhythmic events compared to isogenic or healthy control at baseline. HiPSC-CMs of CACNB2 patients showed a significantly reduced Ica-L and increased arrhythmic events compared to the healthy donor or the isogenic control at baseline. These data confirmed the BrS phenotype. Temperature of hiPSC-CMs was increased from 37°C to 40°C for 24 hours to mimic fever. A significantly reduced peak sodium channel current (I_Na) was detected in hiPSC-CMs of the BrS patient with SCN10A mutation but not in the CACNB2 patients after increasing the temperature. No changes of ICa-L in hiPSC-CMs were detected after increasing the temperature in the CACNB2 patient. Arrhythmic events and an increased interval variability as a sign of high arrhythmogenicity was recorded in hiPSC-CMs with SCN10A variant but not in CACNB2 variant after increasing the temperature from 37°C to 40°C. Due to increased temperature the Protein kinase A (PKA) level was reduced in hiPSC-CMs with SCN10A variant. A PKA activator abolished and a PKA inhibitor enhanced the high temperature (40°C) effects in BrS-cells.

Conclusions

Fever effect of BrS phenotype is gene variant-dependent. Fever can aggravate the phenotype of BrS by reducing PKA activity. PKA activator might be used as a treatment target in these patients.