title: MK-886, an inhibitor of the 5-lipoxygenase-activating protein, inhibits cyclooxygenase-1 activity and suppresses platelet aggregation.
abstract: MK-886, an inhibitor of the 5-lipoxygenase-activating protein (FLAP), potently suppresses leukotriene biosynthesis in intact cells and is frequently used to define a role of the 5-lipoxygenase (EC 1.13.11.34) pathway in cellular or animal models of inflammation, allergy, cancer, and cardiovascular disease. Here we show that MK-886 also interferes with the activities of cyclooxygenases (COX, EC 1.14.99.1). MK-886 inhibited isolated COX-1 (IC(50)=8 microM) and blocked the formation of the COX-1-derived products 12(S)-hydroxy-5-cis-8,10-trans-heptadecatrienoic acid (12-HHT) and thromboxane B(2) in washed human platelets in response to collagen as well as from exogenous arachidonic acid (IC(50)=13-15 microM). Isolated COX-2 was less affected (IC(50)=58 microM), and in A549 cells, MK-886 (33 microM) failed to suppress COX-2-dependent 6-keto-prostaglandin (PG)F(1alpha) formation. The distinct susceptibility of MK-886 towards COX-1 and -2 is apparent in automated molecular docking studies that indicate a preferred binding of MK-886 to COX-1 into the active site. MK-886 (10 microM) inhibited COX-1-mediated platelet aggregation induced by collagen or arachidonic acid whereas thrombin- or U-46619-induced (COX-independent) aggregation was not affected. Since leukotrienes and prostaglandins share (patho)physiological properties in the development and regulation of carcinogenesis, inflammation, and vascular functions, caution should be used when interpreting data where MK-886 is used as tool to determine the involvement of FLAP and/or the 5-lipoxygenase pathway in respective experimental models.
authors.affiliation: Department of Pharmaceutical Analytics, Pharmaceutical Institute, University of Tuebingen, Tuebingen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Koeberle
authors.forename: Ulf
authors.initials: U
authors.lastname: Siemoneit
authors.forename: Hinnak
authors.initials: H
authors.lastname: Northoff
authors.forename: Bettina
authors.initials: B
authors.lastname: Hofmann
authors.forename: Gisbert
authors.initials: G
authors.lastname: Schneider
authors.forename: Oliver
authors.initials: O
authors.lastname: Werz
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D051545:Cyclooxygenase 1 / Q000302:isolation & purification / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006860:Hydrogen Bonding; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D016859:Lipoxygenase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000473:pathology; D008956:Models, Chemical; D015394:Molecular Structure; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012756:Sheep; D002722:Chlorobenzenes
chemical_list: D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D007211:Indoles; D016859:Lipoxygenase Inhibitors; D010975:Platelet Aggregation Inhibitors; D011994:Recombinant Proteins; C060893:MK-886; D002722:Chlorobenzenes