Biosynthesis of 20,20,20-trifluoroleukotriene B4 from 20,20,20-trifluoroarachidonic acid: a metabolically stable analog of leukotriene B4 and its application to a study of stimulation of leukotriene B4 synthesis by immunoglobulin G1,2.

Leukotriene B4 is rapidly metabolized through omega-oxidation, preventing its detection when it is produced under certain biological conditions. To investigate leukotriene B4 production in various physiological conditions, analogs of arachidonic acid which are converted to metabolically stable analogs of leukotriene B4 would be useful. We have synthesized 20,20,20-trifluoroarachidonic acid by the cis-selective Wittig reaction of the C12-C20 fragment with phosphonium salt. 20,20,20-trifluoroarachidonic acid was transformed into 20,20,20-trifluoroleukotriene B4 when incubated with human neutrophils in the presence of the calcium ionophore A23187. The product was identified by uv absorption spectrophotometry, gas chromatography-mass spectrometry, and coelution on high-performance liquid chromatography with 20,20,20-trifluoroleukotriene B4, which was enantioselectively synthesized by the reaction of the fluorine-containing C11-C20 fragment with the C1-C10 phosphonate. The fluorinated leukotriene B4 demonstrated as much chemotactic activity on human neutrophils as natural leukotriene B4 and was metabolically stable when incubated with human neutrophils, probably by blocking omega-oxidation. Also, enzymes catalyzing the transformation of arachidonic acid (AA) into leukotriene B4 did not discriminate the fluorinated precursors from the natural, nonfluorinated AA, thus 20-F3-AA is a valid analog of AA to be used in the study of AA metabolism. When 50 microM of the fluorinated acid was incubated with neutrophils stimulated with heat-aggregated human immunoglobulin G, a significant amount of fluorinated leukotriene B4 (4.3 ng/10(6) cells/40 min, at most) was formed in a dose-dependent manner while little leukotriene B4 was detected with incubation with 50 microM arachidonic acid, probably due to omega-oxidation of the product, leukotriene B4. 20,20,20-Trifluoroarachidonic acid appears to be a useful tool for studying the capacity of leukotriene B4 synthesis in various biological systems while long-lasting 20,20,20-trifluoroleukotriene B4 would serve as an excellent analog of leukotriene B4 in pharmacological studies to understand functions of leukotrienes B4.