Dapsone inhibits the generation of 5-lipoxygenase products in human polymorphonuclear leukocytes

Dapsone (4,4'-diaminodiphenylsulfone) is effective in treating inflammatory skin diseases. Several lines of evidence suggest that the anti-inflammatory properties of this sulfone are partially due to modulation of functions of polymorphonuclear leukocytes (PMN). The goal of the present investigation is therefore to ascertain possible inhibitory effects of dapsone upon human 5-lipoxygenase (5-LOX) pathway. PMN of healthy donors were pretreated with dapsone in different concentrations (1.6-100 microM) for 5 min following by adding Ca ionophore A 23187 (10 microM) and subsequent incubation for 10 min. Thereupon the eicosanoids were assessed by reversed-phase high-performance liquid chromatography (RP-HPLC). Dapsone exhibited dose-dependent inhibitory activity showing 50% inhibition at 15 microM for leukotriene B4 (LTB4) with 5 x 10(6) PMN. The IC50 (half maximum inhibition concentration) of dapsone for 5-hydroxyeicosatetraenoic acid (5-HETE) and omega-OH-LTB4 amounted to similar values (5-HETE: 9 microM; omega-OH-LTB4: 11 microM). The inhibition of the conversion of arachidonic acid to several eicosanoids mainly suggests an effect on the 5-LOX enzyme. The comparison of inhibition values between intact PMN and a cell-free system (by sonification) indicates an additional effect of dapsone upon enzymes other than 5-LOX. Since the concentrations used are comparable with therapeutic conditions, dapsone may exert part of its anti-inflammatory effect by prevention of the generation of 5-LOX metabolites.