A 4-trifluoromethyl derivative of salicylate, triflusal, stimulates nitric oxide production by human neutrophils: role in platelet function

Background: The thrombotic process is a multicellular phenomenon in which not only platelets but also neutrophils are involved. Recent in vitro studies performed in our laboratory have demonstrated that triflusal, a 4-trifluoromethyl derivative of salicylate, reduced platelet aggregation not only by inhibiting thromboxane A2 production but also by stimulating nitric oxide (NO) generation by neutrophils. The aim of the present study was to evaluate whether oral treatment of healthy volunteers with triflusal could modify the ability of their neutrophils to produce NO and to test the role of the NO released by neutrophils in the modulation of ADP-induced platelet aggregation and alpha-granule secretion.

Methods: The study was performed in 12 healthy volunteers who were orally treated with triflusal (600 mg day-1) for 5 days. Flow cytometric detection of platelet surface expression of P-selectin was used as a measure of the ability of platelets to release the contents of their alpha-granules.

Results: After treatment with triflusal, there was an increase in NO production by neutrophils and an increase in endothelial nitric oxide synthase (eNOS) protein expression in neutrophils. A potentiation of the inhibition of platelet aggregation by neutrophils was reversed by incubating neutrophils with both an L-arginine antagonist, NG-nitro-L-arginine methyl ester (L-NAME) and an NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5 tetramethylimidazoline 1-oxyl 3-oxide (C-PTIO). A slight decrease in P-selectin surface expression on platelets was found which was not modified by the presence of neutrophils and therefore by the neutrophil-derived NO. Exogenous NO released by sodium nitroprusside dose-dependently inhibited both ADP-stimulated alpha-granule secretion and platelet aggregation. Therefore, platelet aggregation showed a greater sensitivity to be inhibited by exogenous NO than P-selectin expression.

Conclusion: Oral treatment of healthy volunteers with triflusal stimulated NO production and eNOS protein expression in their neutrophils. After triflusal treatment, the neutrophils demonstrated a higher ability to prevent ADP-induced platelet aggregation. However, the neutrophils and the endogenous NO generated by them failed to modify P-selectin expression in ADP-activated platelets.