Arachidonic acid regulates the translocation of 5-lipoxygenase to the nuclear membranes in human neutrophils.
Elevation of the intracellular cAMP concentration in agonist-activated human neutrophils (PMN) leads to the concomitant inhibitions of arachidonic acid (AA) release, 5-lipoxygenase (5-LO) translocation, and leukotriene (LT) biosynthesis. We report herein that exogenous AA completely prevents cAMP-dependent inhibition of 5-LO translocation and LT biosynthesis in agonist-activated PMN. Moreover, the group IVA phospholipase A2 inhibitor pyrrophenone and the MEK inhibitor U-0126 inhibited AA release and 5-LO translocation in activated PMN, and these effects were also prevented by exogenous AA, demonstrating a functional link between AA release and 5-LO translocation. Polyunsaturated fatty acids of the C18 and C20 series containing at least three double bonds located from carbon 9 (or closer to the carboxyl group) were equally effective as AA in restoring 5-LO translocation in pyrrophenone-treated agonist-activated PMN. Importantly, experiments with the 5-LO-activating protein inhibitor MK-0591 and the intracellular Ca2+ chelator BAPTA-AM demonstrated that the AA-regulated 5-LO translocation is FLAP- and Ca2+-dependent. Finally, the redox and competitive 5-LO inhibitors L-685,015, L-739,010, and L-702,539 (but not cyclooxygenase inhibitors) efficiently substituted for AA to reverse the pyrrophenone inhibition of 5-LO translocation, indicating that the site of regulation of 5-LO translocation by AA is at or in the vicinity of the catalytic site. This report demonstrates that AA regulates the translocation of 5-LO in human PMN and unravels a novel mechanism of the cAMP-mediated inhibition of LT biosynthesis.
Flamand
Nicolas
N
Centre de Recherche en Rhumatologie et Immunologie, Université Laval, Québec, Canada G1V 4G2.
Lefebvre
Julie
J
Surette
Marc E
ME
Picard
Serge
S
Borgeat
Pierre
P
D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D016718:Arachidonic Acid / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D015289:Leukotrienes / Q000096:biosynthesis; D016859:Lipoxygenase Inhibitors; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism*; D009685:Nuclear Envelope / Q000201:enzymology*
D002614:Chelating Agents; D015289:Leukotrienes; D016859:Lipoxygenase Inhibitors; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D016718:Arachidonic Acid; D004533:Egtazic Acid; D000242:Cyclic AMP; D001094:Arachidonate 5-Lipoxygenase; D002118:Calcium