Introduction:
Air particulate matter (PM) represents one of the most critical environmental issues worldwide, causing more than 3 million deaths a year. In the US, hospital admissions due to heart failure (HF) increase by 0.8% for every 10 μg/m3 elevation in PM. However, the biological mechanisms behind the effects of PM on cardiovascular disease (CVD) remain poorly defined. Recent studies showed that PM
2.5
can translocate into the circulation, causing cumulative toxicity. With air pollution increasing due to human activity and the growing prevalence of HF, there is a critical need to understand PM's contributions to CVD to develop preventive treatments and novel therapeutic approaches.
Hypothesis:
We hypothesize that PM can exert its toxic effect by increasing oxidative stress and apoptosis and affecting cardiac electrophysiology.
Methods:
Three independent induced pluripotent stem cell lines (IPSC) were differentiated into cardiomyocytes (iCMs) and cultured for 30 days before treatment with 100 μg/ml of PM
2.5
for 48h. Experiments including immunostaining, qPCR, RNAseq and Multielectrode Array (MEA) were performed in control (CT) and PM-treated iCMs (PM).
Results:
Treatment with PM increased ROS and decreased ATP production (CT 9.9±1.2pmol vs PM 6.6±0.8pmol, p<0.01, n=20). Immunostaining showed mitochondrial fragmentation and increased expression of cleaved caspase3 without structural changes. Moreover, PM caused upregulation of the apoptotic markers
P53
,
PARP1
and
CASP3,
oxidative stress markers
CYP1A1, CYP1B1
and
MT2A,
and cardiac markers
CACNA1C
together with downregulation of
GJA1
. RNAseq analysis showed upregulation of Gene Ontology terms related to detoxification, response to toxic substances and oxidative stress. Upregulated KEGG pathways included oxidative phosphorylation, hypertrophic cardiomyopathy and dilated cardiomyopathy. MEA experiments revealed a decrease in the spike amplitude and conduction velocity, along with shortening of the action potential (APD90: CT 577±20ms vs. PM 489±16ms, p<0.05, n=20) and increased beat period irregularity (CT 3.2±0.7% vs. PM 13.1±1.6%, p<0.001, n=20). These electrophysiological changes were reversed by treatment with the antioxidant N-acetylcysteine.
Conclusions:
We conclude that PM plays a direct role in the development of CVD, causing an increase in oxidative stress and affecting the electrophysiology of the heart. Further functional studies in iCMs from HF patients will provide evidence of the effects of these changes on the phenotype of the disease.
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