MK886, a potent and specific leukotriene biosynthesis inhibitor blocks and reverses the membrane association of 5-lipoxygenase in ionophore-challenged leukocytes.
Recently, we have shown that ionophore activation of human leukocytes results in leukotriene synthesis and a translocation of 5-lipoxygenase from the cytosol to cellular membrane. This membrane translocation was postulated to be an important early activation step for the enzyme. 3-[1-(p-Chlorobenzyl)-5-(isopropyl)-3-tert-butylthioindol-2-yl]-2, 2- dimethylpropanoic acid (MK886) is a potent and specific inhibitor of leukotriene biosynthesis in vivo and in intact cells, but has no direct effect on 5-lipoxygenase activity in cell-free systems. In this report, we show that MK886 can both prevent and reverse the membrane translocation of 5-lipoxygenase, in conjunction with the inhibition of leukotriene synthesis. Similar compounds of the indole class could also inhibit the membrane translocation of 5-lipoxygenase in a rank order of potency that correlated with their potencies for leukotriene synthesis inhibition. In contrast L-656,224, a direct 5-lipoxygenase inhibitor, had no effect on the translocation of the enzyme. Attempts to demonstrate the effects of MK886 on the association of 5-lipoxygenase with membrane in cell-free preparations failed due to a nonspecific Ca2+-dependent sedimentation of the enzyme. The mechanism of action of MK-886 is therefore to block translocation, prevent subsequent activation of 5-lipoxygenase, and hence block cellular leukotriene biosynthesis.
Rouzer
C A
CA
Department of Pharmacology, Merck Frosst Centre for Therapeutic Research, Pointe Claire-Dorval, Québec, Canada.
Ford-Hutchinson
A W
AW
Morton
H E
HE
Gillard
J W
JW
D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D001091:Arachidonate Lipoxygenases / Q000378:metabolism*; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002451:Cell Compartmentation / Q000187:drug effects; D002462:Cell Membrane / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D007962:Leukocytes / Q000201:enzymology; D015289:Leukotrienes / Q000096:biosynthesis*; D013329:Structure-Activity Relationship; D002722:Chlorobenzenes
D001094:Arachidonate 5-Lipoxygenase; D001091:Arachidonate Lipoxygenases; D016718:Arachidonic Acid; D001095:Arachidonic Acids; D000001:Calcimycin; D002118:Calcium; D007211:Indoles; D015289:Leukotrienes; C060893:MK-886; D002722:Chlorobenzenes