Upregulation of platelet CD40, CD40 ligand (CD40L) and P-Selectin expression in cigarette smokers: a flow cytometry study.

Cigarette smoking is a well known risk factor for cardiovascular disease with a great impact on mortality. Studies have linked smoking to inflammation, platelet activation and enhanced atherosclerosis. The present study investigated the activation and expression of proinflammatory markers on platelets obtained from smokers. The expression of P-selectin (CD62P) (as a marker of activation) and CD40/CD40L (as a marker for proinflammatory processes) were quantified in platelets by flow cytometry. Platelet-rich plasma was obtained from 34 apparent healthy volunteers (19 cigarette smokers, 15 age-matched control persons). Basal measurements and the response to stimulation with ADP and TRAP (10, 30, 100 micromol/l) were evaluated. Values given (mean fluorescence index, MFI) are mean +/- standard deviation. The basal values of platelet bound CD40 (3.20 +/- 0.50 vs. 2.71 +/- 0.28; P = 0.002), CD40L (1.10 +/- 0.12 vs. 0.95 +/- 0.12; P = 0.005) and P-selectin (0.70 +/- 0.21 vs. 0.55 +/- 0.11; P = 0.012) were significantly elevated in smokers as compared to controls. In addition, higher values were noted on stimulation with ADP or TRAP in smokers, although these different values were without statistical significance. According to our data cigarette smoking activates platelets (P-selectin expression) and stimulates the CD40-CD40L-pathway in otherwise healthy volunteers. These findings emphasize that cigarette smoking leads to a proinflammatory and prothrombotic state thus contributing to accelerated atherosclerosis.