Abstract

Upon stimulation with agonists, platelets express CD40 ligand (CD40L), a transmembrane protein implicated in the initiation and progression of atherosclerotic disease. We have recently discovered that oxidative stress plays a major role in platelet CD40L expression. In this study, we sought to determine whether vitamin C, a known antioxidant, is able to influence platelet CD40L expression. In vitro experiments were done by stimulating platelets with collagen in the presence or absence of vitamin C (50–100 μM) or vehicle as control. An in vivo study was done in 10 healthy subjects who were randomized to intravenous infusion of placebo or 1 g vitamin C for 45 min in a crossover design. At the end of infusion platelet CD40L and O_2- were measured. The in vitro study demonstrated that vitamin C dose dependently inhibited platelet CD40L expression without affecting agonist-induced platelet aggregation. In subjects treated with placebo no changes of platelet CD40L and O_2- were observed; conversely, vitamin C infusion caused a significant and parallel decrease of platelet O_2- (−70%, P < 0.001) and CD40L (−68%, P < 0.001). Platelet aggregation was not modified by either treatment. This study suggests that water-soluble antioxidants, which scavenge superoxide radicals, may reduce platelet CD40L expression.

Keywords: Vitamin C; Platelets; Free radicals/free-radical scavengers; Reactive oxygen species

Abbreviations: CD40L, CD40 ligand; sCD40L, soluble CD40L; PRP, platelet-rich plasma; FITC, fluorescein isothiocyanate; Mab, monoclonal antibodies; PBS, phosphate-buffered saline; BSA, bovine serum albumin; AU, arbitrary unit

Article Outline

Introduction

Methods

Platelet preparation and activation

O₂^– detection

CD40L and CD62P expression

Analysis of sCD40L

In vitro study

In vivo study

Statistical analysis

Results

Discussion

References