The molecular mechanism of the inhibition by licofelone of the biosynthesis of 5-lipoxygenase products.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Fischer
L
L
Institute of Pharmaceutical Chemistry, University of Frankfurt, Frankfurt, Germany.
Hornig
M
M
Pergola
C
C
Meindl
N
N
Franke
L
L
Tanrikulu
Y
Y
Dodt
G
G
Schneider
G
G
Steinhilber
D
D
Werz
O
O
D058927:5-Lipoxygenase-Activating Proteins; D000085:Acetates / Q000737:chemistry / Q000494:pharmacology*; D001094:Arachidonate 5-Lipoxygenase / Q000235:genetics / Q000378:metabolism; D016718:Arachidonic Acid / Q000737:chemistry / Q000494:pharmacology; D018053:Arsenites / Q000494:pharmacology; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D002474:Cell-Free System; D002478:Cells, Cultured; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells; D006801:Humans; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology; D020024:Leukotriene Antagonists / Q000494:pharmacology; D015289:Leukotrienes / Q000096:biosynthesis / Q000737:chemistry; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D008565:Membrane Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D015394:Molecular Structure; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009685:Nuclear Envelope / Q000187:drug effects / Q000378:metabolism; D011758:Pyrroles / Q000737:chemistry / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology; D017670:Sodium Compounds / Q000494:pharmacology; D014162:Transfection; D002722:Chlorobenzenes
D058927:5-Lipoxygenase-Activating Proteins; D000085:Acetates; D001094:Arachidonate 5-Lipoxygenase; D016718:Arachidonic Acid; D018053:Arsenites; D001643:Bridged Bicyclo Compounds; D000001:Calcimycin; D002118:Calcium; D002352:Carrier Proteins; D004229:Dithiothreitol; D007211:Indoles; D020024:Leukotriene Antagonists; D015289:Leukotrienes; D016859:Lipoxygenase Inhibitors; D008565:Membrane Proteins; D011758:Pyrroles; D011804:Quinolines; D017670:Sodium Compounds; C548592:ALOX5AP protein, human; C100577:L 739010; C060893:MK-886; D002722:Chlorobenzenes; C017947:sodium arsenite; C088092:licofelone
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