Oxidative stress-mediated platelet CD40 ligand upregulation in patients with hypercholesterolemia: Effect of atorvastatin

OBJECTIVES: We speculated that in patients with hypercholesterolemia CD40L overexpression could depend on low-density lipoprotein (LDL)-induced enhanced intraplatelet formation of O(2)*(-) and statin could reduce platelet CD40L via interference with platelet O(2)*(-) production. BACKGROUND: CD40L is a protein with inflammatory and thrombotic properties. CD40L is upregulated in platelets from hypercholesterolemic (HC) patients but the underlying mechanism is unclear. METHODS: Collagen-induced platelet CD40L and platelet O(2)*(-) expression were investigated in 40 HC patients and 40 healthy subjects. HC patients were then randomized to either a diet (n = 20) (group A) or atorvastatin 10 mg day (n = 20) (group B); the above variables were measured at baseline and after 3 and 30 days of treatment. O(2)*(-) and CD40L were also measured in vitro in LDL-treated platelets with or without nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor or atorvastatin added. RESULTS: Compared with controls, HC patients showed higher values of platelet CD40L (P < 0.001) and O(2)*(-) (P < 0.001). Platelet CD40L was significantly correlated with O(2)*(-) (P < 0.001). The interventional trial showed no changes in group A and a significant and parallel decrease in platelet CD40L (P < 0.001) and O(2)*(-) (P < 0.001) in group B. In vitro studies demonstrated that LDL-induced platelet CD40L and GP IIb/IIIa (PAC1 binding) activation via the NADPH oxidase pathway. CD40L upregulation was counteracted by atorvastatin in a dose-dependent fashion. CONCLUSIONS: This study suggests that in patients with hypercholesterolemia platelet CD40L is upregulated via NADPH oxidase-dependent O(2)*(-) generation. Atorvastatin downregulated CD40L with an oxidative stress-mediated mechanism likely involving platelet NADPH oxidase, an effect that seemed to be independent of its cholesterol-lowering action.