The cardiotoxic impact of air pollution has been established in multiple epidemiological studies, with increasing levels positively correlating with increased risk of cardiovascular disorders. Through aquatic pollution studies surrounding environmental catastrophes, it was found that much of the cardiovascular dysfunction seen in affected fish species was attributable to lower molecular weight members of the polycyclic aromatic hydrocarbon (PAH) family. Phenanthrene, a 3-ringed PAH, was highlighted in single compound studies to be particularly malignant, impacting calcium cycling, ionic currents, and contractility. However, there is a clear paucity of knowledge on phenanthreneâs impact on cardiomyocyte function in more human-relevant species. This thesis investigated phenanthreneâs effect on cellular calcium cycling in 3 key models; the zebrafish, the sheep and the human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM), using a combination of epifluorescence microscopy and molecular biology. The initial zebrafish study indicated the detrimental impact of phenanthrene previously identified in marine species, may also be observed in other human-relevant models. In isolated adult sheep ventricular myocytes, 25 µM acute exposure phenanthrene induced significant shortening of the action potential duration (APD) as APD90 was reduced to 63.5 ± 9.7% (N = 6; n = 11). This was concurrent with a 55.8 +/- 5.3% (N = 3; n = 5) inhibition of the rapid delayed rectifier potassium channel current and a 39.3 ± 12.6% (N = 4; n = 10) reduction in calcium transient amplitude, alongside a 60.7 ± 12.6% (N = 4; n = 10) prolongation in the rate of decay. HiPSC-CMs allowed the study of both acute and prolonged phenanthrene exposure on human-specific currents and proteins. The outcome of acute exposure was comparable to sheep, with an additional 62.0 ± 3.7% (N = 5; n = 8) inhibition of the L-type calcium current by 25 µM phenanthrene. Calcium transient disruption may involve reactive oxygen species (ROS) signalling as a 137.3 ± 45.8% (N = 4; n = 16) increase was observed following 25 µM phenanthrene exposure. After 5-7 days of prolonged low-level exposure significantly smaller calcium transient amplitudes compared to DMSO controls were observed (ÎF/F0 DMSO 2.4 ± 0.2; 3 µM 1.6 ± 0.3; N = 3; n = 22 - 29), as well as longer rates of decay (tau DMSO 313.9 ± 19.9; 3 µM 568.5 ± 39.6; N = 3; n = 20-21). Investigation into key calcium genes found significant reduction in ryanodine receptor 2 mRNA expression. This research contributes to our understanding of air pollutantâs impact on vertebrate models.
The impact of the air pollutant phenanthrene, on cardiomyocyte function in three human relevant models
Marris, C. (Author). 1 Aug 2023
Student thesis: Phd