1. ¹INSERM U.352, Laboratoire de Biochimie et Pharmacologie INSA-Lyon, Villeurbanne, France
2. ²Centre de Recherche en Rhumatologie et Immunologie and the Department of Medicine, Université Laval, Québec, Canada
3. ³Faculty of Medicine, Sherbrooke University, Sherbrooke, Québec, Canada

Correspondence: Dr. Patrice E. Poubelle, Centre de Recherche du CHUL, 2705 boul Laurier, Ste-Foy, Qué, G1V 4G2, Canada. E-mail: Patrice.Poubelle@crchul.ulaval.ca

^†Deceased.

Received 18 November 2002.

Abstract

Neutrophils are physiologically associated with platelets in whole blood. Inflammatory reactions can be modulated by the presence of platelets. To investigate the influence of platelets on neutrophil activity, we studied the 5-lipoxygenase (5-LOX) metabolic pathway in normal human blood neutrophils stimulated with f-Met-Leu-Phe (fMLP) or monosodium urate monohydrate (MSUM) in the presence of autologous platelets. Platelets inhibited by more than 90% the synthesis of leukotriene B₄ and 5-HETE in neutrophils activated with fMLP or MSUM. The addition of exogenous arachidonic acid did not reverse the inhibitory effect of platelets on 5-LOX–generated metabolites in fMLP- or MSUM-activated neutrophils. Preincubation of neutrophils with adenosine deaminase reversed the inhibitory effect of platelets in fMLP-treated neutrophils, indicating that adenosine was responsible for the platelet inhibition of leukotriene B₄ and 5-HETE formation. In contrast, adenosine deaminase had no influence on the inhibitory effects of platelets in MSUM-stimulated cells. These results suggest that platelets can inhibit the synthesis of 5-LOX products (a) by acting mainly downstream to phospholipase A₂ in cells stimulated by fMLP or MSUM, (b) through adenosine when neutrophils are activated with fMLP, and (c) by an adenosine-independent mechanism in MSUM-activated neutrophils by an as-yet-unidentified mediator.