The 5-lipoxygenase-activating protein (FLAP) inhibitor, MK886, induces apoptosis independently of FLAP.
The ability of various inhibitors of lipoxygenase (LOX) enzymes and 5-lipoxygenase-activating protein (FLAP) to induce apoptosis has implicated these pathways in the mechanism(s) of this form of cell death. Although FLAP plays an important role in 5-LOX activity, this protein is found at high levels in some cells lacking LOX, suggesting it might mediate other effects. Furthermore, the concentration of MK886, a FLAP inhibitor, required to induce apoptosis is approximately 100-fold more than that required to inhibit LOX, and this compound remains effective in cells lacking LOX. The present study examines the role of FLAP in MK886-induced apoptosis. MK886 induced apoptosis in WSU cells, a human chronic lymphocytic leukaemia cell line that lacks FLAP protein and mRNA, suggesting that this agent is acting independently of FLAP. This conclusion was further supported by the fact that a more specific FLAP inhibitor, MK591, induced only minimal apoptosis in FL5.12 cells, a murine prolymphoid cell line containing FLAP. The role of FLAP was examined more directly by decreasing its expression by more than 50% in FL5.12 cells treated with 10 microM of an antisense oligonucleotide for 48h. This change in FLAP was not accompanied by any increase in apoptosis. Furthermore, FLAP-depleted cells exhibited the same level of apoptosis 8 h after treatment with 10 microM MK886, as did control cells. The increased fluorescence seen in MK886-treated cells loaded with carboxydichlorofluorescein indicates that oxidative reactions are stimulated by this compound, possibly via the release of fatty acids from fatty acid-binding proteins and their subsequent oxidation.
Datta
K
K
Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712-1074, USA.
Biswal
S S
SS
Kehrer
J P
JP
D058927:5-Lipoxygenase-Activating Proteins; D000111:Acetylcysteine / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001483:Base Sequence; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D002722:Chlorobenzenes
D058927:5-Lipoxygenase-Activating Proteins; D000111:Acetylcysteine; D002352:Carrier Proteins; D007211:Indoles; D016859:Lipoxygenase Inhibitors; D008565:Membrane Proteins; D016376:Oligonucleotides, Antisense; D011804:Quinolines; C548592:ALOX5AP protein, human; C060893:MK-886; D002722:Chlorobenzenes; C078266:MK 0591