Elucidating the Effects of the Environmental Pollutant Benzo[a]pyrene [BaP] on Cardiac Arrhythmogenicity

Benzo[a]pyrene (BaP) is a product of combustion and is an abundant constituent of wildfire derived smoke and particulate matter 2.5 (PM2.5). Although arrythmias are associated with wildfire, the mechanism remains unclear. We hypothesized that BaP might predispose individuals to arrhythmias and possibly sudden cardiac death. Human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from healthy donors (n=3) were used to investigate the cardiovascular toxicity of BaP. Across a broad concentration range, BaP did not affect iPSC-CM viability, and a 4-day exposure of BaP at 50 M did not affect contractility. After exposure to BaP at 50 M for 5 days, iPSC-CMs were subjected to bulk RNA sequencing, and analysis revealed markers of inflammation were upregulated, and ion channel expression was modulated. Because inflammation is associated with reactive oxygen species (ROS) production, iPSC-CMs exposed to BaP had a concentration-dependent increase in ROS production. Mitotracker fluorescent imaging revealed decreased mitochondrial membrane potentials after iPSC-CMs treatment with 50 μM BaP. Seahorse assays revealed that BaP exposure decreased oxygen consumption rate, basal respiration, and maximal respiration in a dose-dependent manner. Using multiple electrode array (MEA) assays, iPSC-CMs exposed to 50 M BaP for 3 days, had prolonged field potential duration (FPD) and increased beat period (BP). However, co-treatment with N-acetyl cysteine (NAC), a nucleophile that scavenges ROS and preserves glutathione, attenuated the effect of BaP on FPD and BP (p<0.001). In summary, BaP exposure upregulated inflammatory cytokines and increased ROS production by impairing mitochondrial function. BaP had proarrhythmic effects of increased BP and FPD and was abrogated by NAC. Thus, BaP inhalation from wildfire smoke may predispose individuals to QT prolongation, arrhythmia, and sudden cardiac death.