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.