GENERATION OF EICOSANOIDS FROM 15(S)-HYDROXYEICOSATETRAENOIC ACID IN BLOOD MONOCYTES FROM STEROID-DEPENDENT ASTHMATIC-PATIENTS

The aim of this study was to investigate eicosanoid metabolism by huma n peripheral blood monocytes (PBM) from steroid-dependent asthmatic pa tients as compared to control subjects and untreated asthmatic patient s. Eicosanoid biosynthesis by PBM isolated from venous blood using Per coll gradient centrifugation was evaluated following stimulation of 5 x 10(6) cells with calcium ionophore A23187, with or without exogenous 15(S)-hydroxpeicosatetraenoic acid (15(S) HETE), and analyzed by reve rse phase high performance liquid chromatography (RP-HPLC). Without 15 (S)-HETE, PBM synthesized leukotriene B-4 (LTB4) only (40 +/- 12 ng an d 59 +/- 11 ng for untreated and steroid-dependent asthmatics, respect ively). In the presence of 15(S) HETE, PBM produced six-fold smaller a mounts 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 pr oduced by PBM from asthmatics only (2.7 +/- 0.7 ng and 4.6 +/- 2.8 ng for untreated and steroid dependent asthmatics, respectively). Moreove r, PBM were also able to release an unknown compound containing conjug ated triene chromophore. Cells from steroid dependent asthmatic patien ts 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 t o an unknown metabolite, with the amounts of the latter being enhanced by long-term corticosteroid treatment, BIOCHEM PHARMACOL 56;4:535-541 , 1998. (C) 1998 Elsevier Science Inc.