The Journal of Experimental Medicine
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© The Rockefeller University Press, 0022-1007/1997/10/1401/ $5.00
The Journal of Experimental Medicine, Volume 186, Number 8, October 20, 1997 1401-1406

Brief Definitive Reports

Suppression of Leukotriene B4 Biosynthesis by Endogenous Adenosine in Ligand-activated Human Neutrophils

Eric Krump*, Serge Picard*, Joseph Mancini{ddagger}, and Pierre Borgeat*

From the * Centre de Recherche en Rhumatologie et Immunologie, Centre de recherche du CHUL et Université Laval, Québec, Canada; and {ddagger} Merck Frosst Center for Therapeutic Research, Pointe-Claire, Québec, Canada

Adenosine (Ado) has been shown to suppress several functional responses of human polymorphonuclear leukocytes (PMNs). The current study investigated whether endogenous Ado regulates the biosynthesis of leukotriene (LT)B4 in ligand-stimulated PMNs. Measurements of Ado in PMN resuspended in Hanks' buffered salt solution (HBSS) or plasma showed a cell concentration– and time–dependent accumulation of the nucleoside. The removal of endogenous Ado with either Ado deaminase or the blockade of its action by the Ado A2a receptor antagonist, 8-(3-chlorostyryl) caffeine, markedly increased LTB4 biosynthesis upon ligand stimulation in HBSS. Similarly, LTB4 synthesis by ligand-stimulated PMNs in plasma (containing recombinant LTA4 hydrolase to allow the conversion of protein-bound LTA4) was strongly enhanced by addition of Ado deaminase. Addition of red blood cells to suspensions of PMNs in plasma mimicked the effect of adding Ado deaminase and LTA4 hydrolase in enhancing LTB4 biosynthesis upon ligand stimulation. This effect of red blood cells on LTB4 biosynthesis was blocked by dipyridamole, an inhibitor of Ado transport, or captopril, an inhibitor of LTA4 hydrolase. These results demonstrate that endogenous Ado efficiently downregulates ligand-stimulated LTB4 biosynthesis in PMN suspensions, pointing out a potentially important regulatory function of Ado in inflammatory exudates. These results also unveil a dual role for red blood cells in upregulating LTB4 biosynthesis, namely, the removal of endogenous Ado and the conversion of LTA4 released by activated PMNs.

Address correspondence to Dr. Pierre Borgeat, Centre de Recherche en Rhumatologie et Immunologie, 2705 Blvd. Laurier, Rm T 1-49, Sainte-Foy, Québec G1V 4G2 Canada. Phone: 418-654-2772; FAX: 418-654-2765.


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