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.