In vitro inhibition of leukotriene B4 formation by exogeneous 5-lipoxygenase inhibitors is associated with enhanced generation of 15-hydroxy-eicosatetraenoic acid (15-HETE) by human neutrophils.
Leukotrienes, products of the 5-lipoxygenase pathway of arachidonic acid metabolism, have been suggested to play a pathogenic role in psoriasis, because of their ability to induce skin inflammation and to stimulate epidermal proliferation. The 15-lipoxygenase product 15-hydroxy-eicosatetraenoic acid (15-HETE) has no proinflammatory capacity. In contrast, it can inhibit the activity of the 5-lipoxygenase. The purpose of the present study was to study the effect of 5-lipoxygenase inhibitors on the formation of 15-HETE by human neutrophils in vitro. Purified neutrophils were incubated with A 23187 (5 microM) and arachidonic acid (25 microM) with and without different inhibitors of 5-lipoxygenase activity (RS 43179, benoxaprofen, NDGA, and CP 66248). Methods for identifying eicosanoids included RP-HPLC and radioimmunoassay. Formation of leukotriene B4 was inhibited in a dose-dependent way, which was strongly correlated with a concomitant increase in the formation of 15-HETE (r = 0.97, p less than 0.01). The cyclooxygenase inhibitor indomethacin did not change 15-HETE formation. The stimulation of 15-HETE formation was not associated with cell damage as assessed by LDH release. Furthermore, identical incubations of T lymphocytes, characterized by a low 5-lipoxygenase activity, did not result in increased 15-HETE formation. These results show that inhibition of 5-lipoxygenase activity can lead to increased formation of 15-HETE. Because 15-HETE inhibits formation of 5-LO products, it may amplify the effect of 5-lipoxygenase inhibitors.
Fogh
K
K
Department of Dermatology, Marselisborg Hospital, University of Aarhus, Denmark.
Herlin
T
T
Kragballe
K
K
D001091:Arachidonate Lipoxygenases / Q000037:antagonists & inhibitors*; D000001:Calcimycin / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis*; D066298:In Vitro Techniques; D007975:Leukotriene B4 / Q000096:biosynthesis*; D016859:Lipoxygenase Inhibitors; D009281:Naphthalenes / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism*
D006893:Hydroxyeicosatetraenoic Acids; D016859:Lipoxygenase Inhibitors; D009281:Naphthalenes; D007975:Leukotriene B4; D000001:Calcimycin; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; C045954:RS 43179; D001091:Arachidonate Lipoxygenases