Lipoxin A(4) stable analogs are potent mimetics that stimulate human monocytes and THP-1 cells via a G-protein-linked lipoxin A(4) receptor

Lipoxins (LX) are bioactive eicosanoids that activate human monocytes and inhibit neutrophils. LXA(4) is rap idly converted by monocytes to inactive products, and to resist metabolism, synthetic analogs of LXA(4) were designed, Here, we examined the bioactivity of several LXA(4),analogs in monocytes and found, for chemotaxis, 15(R/S)-methyl-LXA(4) and 15-epi-LXA(4) were equal in activity, and 16-phenoxy-LXA(4) was more potent than native LXA(4). Both 15(R/S)-methyl-LXA(4) and 16-phenoxy-LXA(4) were similar to 1 log molar more potent than LXA(4) in stimulating THP-1 cell adherence (EC(50) approximate to 1 x 10(-10) M), Dimethylamide derivatives of the LXA(4) analogs also possessed agonist rather than antagonist properties for monocytes. Neither LXA(4) nor 16-phenoxy-LXA(4) affected monocyte-mediated cytotoxicity. We cloned an LXA(4) receptor from THP-1 cells identical to that found in PMN. Evidence of receptor-mediated function of LXA(4) and the stable analogs in monocytes included desensitization of intracellular calcium mobilization to a second challenge by equimolar concentrations of these analogs, but not to LTB(4). Increases in [Ca2+](i) by LXA(4) and the analogs were specifically inhibited by an antipeptide antibody to the LXA(4) receptor; and both LXA(4-) and analog-induced adherence and increments in Ca2+ were sensitive to pertussis toxin. Together, these results indicate that the LXA(4) stable analogs are potent monocyte chemoattractants and are more potent than native LXA(4) in stimulating THP-1 cell adherence, at subnanomolar concentrations, Moreover, they provide additional evidence that the LXA(4) stable analogs retain selective bioactivity in monocytes and are valuable instruments for examining the functions and modes of action of LXA(4).