Upregulation of the CD40/CD40 ligand dyad and platelet-monocyte aggregation in cigarette smokers

Background-Smoking is a potent cardiovascular risk factor and is associated with proinflammatory and prothrombotic responses. The CD40/CD40 ligand (CD40L) dyad and platelet-monocyte aggregation mediate a range of proinflammatory and prothrombotic processes thought to be important in atherothrombosis. We investigated whether expression of the CD40/CD40L dyad and platelet-monocyte aggregation are altered in cigarette smokers. Methods and Results-C-reactive protein (CRP), soluble (s) CD40L, and surface expression of CD40L on platelets and T cells and of CD40 on monocytes and platelet-monocyte aggregates were compared in 25 cigarette smokers and 25 age- and gender-matched nonsmokers. Cigarette smokers had increased serum CRP (2.47 +/- 2.60 versus 0.94 +/- 0.96 mg/L, P = 0.008) and appeared to have elevated plasma sCD40L (0.8 +/- 1.09 versus 0.37 +/- 0.21 ng/mL, P = 0.07) concentrations. Smokers also had increased surface expression of CD40 on monocytes (45.9 +/- 7.7% versus 39.9 +/- 6.5%, P = 0.006), of CD40L on platelets (2.9 +/- 1.0% versus 2.3 +/- 0.6%, P = 0.03), and of platelet-monocyte aggregates (26.6 +/- 10.9% versus 19.7 +/- 8.6%, P = 0.02). Plasma cotinine concentrations correlated with monocyte CD40 expression, platelet CD40L expression, and platelet-monocyte aggregates. Conclusions-Cigarette smokers have upregulation of the CD40/CD40L dyad and platelet-monocyte aggregation that may account for the atherothrombotic consequences of this major cardiovascular risk factor.