Low-level ambient ozone exposure associated with neutrophil extracellular traps and pro-atherothrombotic biomarkers in healthy adults.

BACKGROUND AND AIMS

Uncertainty of the causality determinations for ambient ozone (O) on cardiovascular events is heightened by the limited understanding of the mechanisms involved in humans. We aimed to examine the pro-atherothrombotic impacts of O exposure and to explore the potential mediating roles of dysfunctional neutrophils, focusing on neutrophil extracellular traps (NETs).

METHODS

A longitudinal panel study of 152 healthy adults was conducted in the cool to cold months with relatively low levels of O between September 2019 and January 2020 in Beijing, China. Four repeated measurements of indicators reflecting atherothrombotic balance and NETs were performed for each participant.

RESULTS

Daily average exposure levels of ambient O were 16.6 μg/m throughout the study period. Per interquartile range increase in average concentrations of O exposure at prior up to 7 days, we observed elevations of 200.1-276.3% in D-dimer, 27.2-36.8% in thrombin-antithrombin complex, 10.8-60.3% in plasminogen activator inhibitor 1, 13.9-21.8% in soluble P-selectin, 16.5-45.1% in matrix metalloproteinase-8, and 2.4-12.4% in lipoprotein-associated phospholipase A2. These pro-atherothrombotic changes were accompanied by endothelial activation, lung injury, and immune inflammation. O exposure was also positively associated with circulating NETs indicators, including citrullinated histone H3, neutrophil elastase, myeloperoxidase, and double-stranded DNA. Mediation analyses indicated that NETs could mediate O-associated pro-atherothrombotic responses. The observational associations remained significant and robust after controlling for other pollutants, and were generally greater in participants with low levels of physical activity.

CONCLUSIONS

Ambient O exposure was associated with significant increases in NETs and pro-atherothrombotic potential, even at exposure levels well below current air quality guidelines of the World Health Organization.