Cyclic AMP-mediated inhibition of 5-lipoxygenase translocation and leukotriene biosynthesis in human neutrophils.
5-Lipoxygenase (5-LO) catalyzes the transformation of arachidonic acid to leukotrienes (LT). In stimulated human PMN, activation of 5-LO involves calcium, p38 MAP kinase (p38) phosphorylation, and translocation of 5-LO from the cytosol to nuclear membranes containing the 5-LO activating protein (FLAP). In this study, cAMP-elevating agents such as isoproterenol, prostaglandin E(2), CGS-21680 (an adenosine A(2a) receptor agonist), the type IV phosphodiesterase inhibitor RO 20-1724, the adenylate cyclase activator forskolin, and the Gs-protein activator cholera toxin all inhibited LT biosynthesis and 5-LO translocation to the nucleus in cytokine-primed human PMN stimulated with platelet-activating factor and in human PMN stimulated with the endomembrane Ca(2+)-ATPase blocker thapsigargin. Furthermore, monophosphorothioate analogs of cAMP, which activate protein kinase A (PKA), also inhibited LT biosynthesis and 5-LO translocation in stimulated cells. Treatment of PMN with CGS-21680 also prevented the phosphorylation of p38 by thapsigargin. Treatment of PMN with the PKA inhibitors H-89 and KT-5720 prevented the inhibitory effect of cAMP-elevating agents on LT biosynthesis, 5-LO translocation, and p38 phosphorylation, whereas the p38 inhibitor SB 203,580 dose-dependently inhibited arachidonic acid-induced LT biosynthesis. The 5-LO translocation was also inhibitable by the FLAP antagonist MK-0591 and correlated with LT biosynthesis in all experimental conditions tested. These results indicate that cAMP-mediated PKA activation in PMN results in the concomitant inhibition of 5-LO translocation and LT biosynthesis and support a role of p38 in the signaling pathway involved. This represents the first physiological down-regulation mechanism of 5-LO translocation in human PMN.
Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, and Faculté de Médecine, Université Laval, Québec, Canada.
Nicolas
N
Flamand
Marc E
ME
Surette
Serge
S
Picard
Sylvain
S
Bourgoin
Pierre
P
Borgeat
D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D001692:Biological Transport; D000242:Cyclic AMP / Q000378:metabolism*; D006801:Humans; D015289:Leukotrienes / Q000096:biosynthesis*; D009504:Neutrophils / Q000201:enzymology* / Q000378:metabolism
D015289:Leukotrienes; D000242:Cyclic AMP; D001094:Arachidonate 5-Lipoxygenase