Ultrafine particles and platelet activation in patients with coronary heart disease--results from a prospective panel study

Abstract

Background: Epidemiological studies on health effects of air pollution have consistently shown adverse cardiovascular effects. Toxicological studies have provided evidence for thrombogenic effects of particles.A prospective panel study in a susceptible population was conducted in Erfurt, Germany, to study the effects of daily changes in ambient particles on various blood cells and soluble CD40ligand (sCD40L, also known as CD154), a marker for platelet activation that can cause increased coagulation and inflammation. Blood cells and plasma sCD40L levels were repeatedly measured in 57 male patients with coronary heart disease (CHD) during winter 2000/2001. Fixed effects linear regression models were applied, adjusting for trend, weekday and meteorological parameters.Hourly data on ultrafine particles (UFP, number concentration of particles from 0.01 to 0.1 microm), mass concentration of particles less than 10 and 2.5 microm in diameter (PM10, PM2.5), accumulation mode particle counts (AP, 0.1-1.0 microm), elemental and organic carbon, gaseous pollutants and meteorological data were collected at central monitoring sites.

Results: An immediate increase in plasma sCD40L was found in association with UFP and AP (% change from geometric mean: 7.1; CI: [0.1, 14.5] and 6.9; CI: [0.5, 13.8], respectively). Platelet counts decreased in association with UFP showing an immediate, a three days delayed (lag 3) and a 5-day average response (% change from the mean: -1.8; CI: [-3.4,-0.2]; -2.4; CI: [-4.5,-0.3] and -2.2; CI: [-4.0,-0.3] respectively).

Conclusion: The increased plasma sCD40L levels support the hypothesis that higher levels of ambient air pollution lead to an inflammatory response in patients with CHD thus providing a possible explanation for the observed association between air pollution and cardiovascular morbidity and mortality in susceptible parts of the population.

Figure 1

Time series of number concentrations of particles sized 0.01 to 0.1 μm (ultra fine particles, UFP) and mass concentrations of particles less than 2.5 μm in diameter (PM_2.5) together with air temperature in Erfurt, Germany between October 2000 and April 2001. UFP: ultrafine particles (number concentration of particles with a size range of 0.01 to 0.1 μm); PM_2.5: mass concentration of particles less than 2.5 μm in diameter.

Figure 2

Association between UFP and sCD40L, platelets and leukocytes, 6-hour periods and lag 0 (0–23 hours). sCD40L: soluble CD40Ligand. UFP: ultrafine particles (number concentration of particles with a size range of 0.01 to 0.1 μm).

Figure 3

Schematic representation of the hypothesised mechanisms involved in direct vascular effects of particles or their translocated components. * see Reference [12]. sCD40L: soluble CD40Ligand. vWF: von Willebrand factor.