Air pollution-associated procoagulant changes: the role of circulating microvesicles

. Background: Epidemiological studies suggest an association between exposure to particulate matter (PM) in air pollution and the risk of venous thromboembolism (VTE). Objectives: To investigate the underlying pathophysiological pathways linking PM exposure and VTE. Patients and methods: We assessed potential associations between PM exposure and coagulation and inflammation parameters, including circulating microvesicles, in a group of 233 patients with diabetes. Results: The numbers of circulating blood platelet-derived and annexin V-binding microvesicles were inversely associated with the current levels of PM2.5 or PM10, measured on the day of sampling. Recent past exposure to PM10, up to 1 week prior to blood sampling, estimated at the patients residential addresses, was associated with elevated high-sensitivity C-reactive protein (CRP), leukocytes and fibrinogen, as well as with tissue factor (TF)-dependent procoagulant changes in thrombin generation assays. When longer windows of past exposure were considered, up to 1 year preceding blood sampling, procoagulant changes were evident from the strongly increased numbers of red blood cell-derived circulating microvesicles and annexin V-binding microvesicles, but they no longer associated with TF. Past PM exposure was never associated with activated partial thromboplastin time (aPTT), prothrombin time (PT), or factor (F) VII, FVIII, FXII or D-dimers. Residential distance to a major road was only marginally correlated with procoagulant changes in FVIII and thrombin generation. Conclusions: Increases in the number of microvesicles and in their procoagulant properties, rather than increases in coagulation factors per se, seem to contribute to the risk of VTE, developing during prolonged exposure to air pollutants.