Nonredox 5-lipoxygenase inhibitors require glutathione peroxidase for efficient inhibition of 5-lipoxygenase activity.
Nonredox type 5-lipoxygenase (5-LO) inhibitors, such as ZM 230487, its methyl analogue ZD 2138, or the Merck compound L-739,010, suppress cellular leukotriene synthesis of ionophore stimulated granulocytes with IC50 values of about 50 nM. However, in cell homogenates or in preparations of purified enzyme, up to 150-fold higher concentrations are required for similar inhibition of 5-LO activity. This loss of 5-LO inhibition in cell homogenates was reversed by addition of glutathione or dithiothreitol, which increased the inhibitory potency of ZM 230487 or L-739,010 by about 100 to 150-fold so that 5-LO inhibition was comparable with that of intact cells. In the presence of thiols, addition of hydroperoxide [13(S)-HpODE], glutathione-peroxidase inhibition by iodacetate or selenium-deficiency lead to impaired 5-LO inhibition by ZM 230487 in cell homogenates. Moreover, addition of glutathione peroxidase was required for efficient inhibition of purified human 5-LO by ZM 230487. The data suggest that low hydroperoxide concentrations are important for efficient 5-LO inhibition by ZM 230487. The kinetic analysis revealed a noncompetitive inhibition of 5-LO by ZM 230487 at low hydroperoxide levels, whereas it acted as a competitive inhibitor with low affinity under nonreducing conditions in granulocyte homogenates. No such redox-dependent effects were observed with the 5-LO inhibitor BWA4C, the 5-LO activating protein-inhibitor MK-886 or the pentacyclic triterpene acetyl-11-keto-beta-boswellic acid. These data suggest that physiological conditions associated with oxidative stress and increased peroxide levels lead to impaired efficacy of nonredox type 5-LO inhibitors like ZM 230487 or L-739,010. This could explain the reported lack of activity of this class of 5-LO inhibitors in chronic inflammatory processes.
Werz
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Institute of Pharmaceutical Chemistry, University of Frankfurt, D-60439 Frankfurt, Germany.
Szellas
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Henseler
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Steinhilber
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D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D002478:Cells, Cultured / Q000187:drug effects; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics; D005979:Glutathione Peroxidase / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D009195:Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism; D011714:Pyrans / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology; D015363:Quinolones / Q000494:pharmacology*; D012643:Selenium / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism / Q000494:pharmacology
D001643:Bridged Bicyclo Compounds; C100577:L 739010; D016859:Lipoxygenase Inhibitors; D011714:Pyrans; D011804:Quinolines; D015363:Quinolones; D013438:Sulfhydryl Compounds; C088450:ZM 230487; D006861:Hydrogen Peroxide; D009195:Peroxidase; D005979:Glutathione Peroxidase; D001094:Arachidonate 5-Lipoxygenase; D012643:Selenium