Formation of lipoxins and leukotrienes by human alveolar macrophages incubated with 15(S)-HETE: a model for cellular cooperation between macrophages and airway epithelial cells.

Human alveolar macrophages (AM) from bronchoalveolar lavage of asthmatic patients (AP) and healthy volunteers (HS) were compared for their respective capacities to produce lipoxins and leukotrienes when stimulated by calcium ionophore A23187 with or without 15(S)-HETE. The metabolites were analyzed using an isocratic RP-HPLC system and their formation profiles evaluated on the basis of chromatographic behaviour, UV spectral characteristics and co-elution with synthetic standards. Without 15-HETE, AM from AP produced more LTB4 and 5-HETE than those from HS. In the presence of 15-HETE, human AM were able to produce 5,15-diHETE and lipoxins. Moreover, the total amount of lipoxins synthesized by AM from AP was 2 fold higher than that synthesized by AM from HS, thus showing an enhanced cell activation via the 5-lipoxygenase (5-LO) pathway. These results presented AM as in vitro 15-HETE metabolizing cells and suggested some hypothesis about human AM 5-LO regulation mechanism. The enhanced 5-LO activity in AM from AP suggested that in vivo they could participate in cell to cell interaction mechanisms involved in inflammatory lung diseases and might also take up and transform 15-HETE predominantly released by airway epithelial cells.