Generation of eicosanoids from 15(S)-hydroxyeicosatetraenoic acid in blood monocytes from steroid-dependent asthmatic patients

Abstract

The aim of this study was to investigate eicosanoid metabolism by human peripheral blood monocytes (PBM) from steroid-dependent asthmatic patients as compared to control subjects and untreated asthmatic patients. Eicosanoid biosynthesis by PBM isolated from venous blood using Percoll gradient centrifugation was evaluated following stimulation of 5 × 10 6 cells with calcium ionophore A23187, with or without exogenous 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE), and analyzed by reverse phase high performance liquid chromatography (RP-HPLC). Without 15(S)-HETE, PBM synthesized leukotriene B 4 (LTB 4) only (40 ± 12 ng and 59 ± 11 ng for untreated and steroid-dependent asthmatics, respectively). In the presence of 15(S)-HETE, PBM produced six-fold smaller amounts of leukotriene B 4 ( P < 0.0001). They also released 5(S),15(S)-dihydroxyeicosatetraenoic acid (5(S),15(S)-diHETE) in similar amounts for all the populations, whereas low amounts of lipoxins (LXs) were produced by PBM from asthmatics only (2.7 ± 0.7 ng and 4.6 ± 2.8 ng for untreated and steroid-dependent asthmatics, respectively). Moreover, PBM were also able to release an unknown compound containing conjugated triene chromophore. Cells from steroid-dependent asthmatic patients synthesized this unknown metabolite in higher amounts than controls and untreated asthmatics (133 ± 18 ng vs 52 ± 19 ng and 68 ± 15 ng, respectively, P < 0.02).This work shows for the first time that human PBM are able to metabolize 15(S)-HETE and lead to lipoxins and to an unknown metabolite, with the amounts of the latter being enhanced by long-term corticosteroid treatment.