New series of lipoxins isolated from human eosinophils

Granulocytes from human eosinophilic donors were incubated with arachidonic acid or 15-hydroxyeicosatetraenoic acid (15-HETE) and stimulated with the ionophore A23187. The eicosanoids were extracted with reversed-phase cartridges and subjected to RP-HPLC analysis. When extracts from eosinophil-enriched populations were analysed and compared with extracts from human neutrophils, three additional peaks were detected which coeluted with 15-hydroxy-delta 13-trans-15H derivatives of leukotriene C4, D4 and E4 in different HPLC systems. The recorded absorbance spectra of the eluted compounds and the standards were identical and showed a maximum at 307 nm which is characteristic for a conjugated tetraene system with a bathochromic shift by the sulfur moiety in alpha-position to the tetraene system. The compound which coeluted with the 15-hydroxy-LTC4 standard was treated with gamma-glutamyltransferase and converted to the corresponding leukotriene D4 derivative. The results indicate that interaction between the 5- and 15-lipoxygenase pathways leads to the formation of a new series of arachidonic acid metabolites in human eosinophils. Since the biosynthetic route is similar to that of lipoxin A4 and lipoxin B4, we suggest the trivial names lipoxin C4, D4 and E4.