l-663536 and sodium-arsenite

Licofelone is a dual inhibitor of the cyclooxygenase and 5-lipoxygenase (5-LO) pathway, and has been developed for the treatment of inflammatory diseases. Here, we investigated the molecular mechanisms underlying the inhibition by licofelone of the formation of 5-LO products.. The efficacy of licofelone to inhibit the formation of 5-LO products was analysed in human isolated polymorphonuclear leukocytes (PMNL) or transfected HeLa cells, as well as in cell-free assays using respective cell homogenates or purified recombinant 5-LO. Moreover, the effects of licofelone on the subcellular redistribution of 5-LO were studied.. Licofelone potently blocked synthesis of 5-LO products in Ca(2+)-ionophore-activated PMNL (IC(50)=1.7 microM) but was a weak inhibitor of 5-LO activity in cell-free assays (IC(50)>>10 microM). The structures of licofelone and MK-886, an inhibitor of the 5-LO-activating protein (FLAP), were superimposable. The potencies of both licofelone and MK-886 in ionophore-activated PMNL were impaired upon increasing the concentration of arachidonic acid, or under conditions where 5-LO product formation was evoked by genotoxic, oxidative or hyperosmotic stress. Furthermore, licofelone prevented nuclear redistribution of 5-LO in ionophore-activated PMNL, as had been observed for FLAP inhibitors. Finally, licofelone as well as MK-886 caused only moderate inhibition of the synthesis of 5-LO products in HeLa cells, unless FLAP was co-transfected.. Our data suggest that the potent inhibition of the biosynthesis of 5-LO products by licofelone requires an intact cellular environment and appears to be due to interference with FLAP.

Topics: 5-Lipoxygenase-Activating Proteins; Acetates; Arachidonate 5-Lipoxygenase; Arachidonic Acid; Arsenites; Bridged Bicyclo Compounds; Calcimycin; Calcium; Carrier Proteins; Cell-Free System; Cells, Cultured; Dithiothreitol; Dose-Response Relationship, Drug; HeLa Cells; Humans; Indoles; Leukotriene Antagonists; Leukotrienes; Lipoxygenase Inhibitors; Membrane Proteins; Molecular Structure; Neutrophils; Nuclear Envelope; Pyrroles; Quinolines; Sodium Compounds; Transfection