Selectivity of recombinant human leukotriene D-4, leukotriene B-4, and lipoxin A(4) receptors with aspirin-triggered 15-epi-LXA(4) and regulation of vascular and inflammatory responses

Aspirin-triggered Lipoxin A(4) (ATL, 15-epi-LXA(4)) and leukotriene D-4 (LT D4) possess opposing vascular actions mediated via receptors distinct from the LXA(4) receptor (ALX) that is involved in leukocyte trafficking. Here, we identified these receptors by nucleotide sequencing and demonstrate that LTD4 receptor (CysLT(1)) is induced in human vascular endothelia by interk ukin-1 beta. Recombinant CysLT(1) receptor gave stereospecific binding with both [H-3]-LTD4 and a novel labeled mimetic of ATL ([H-3]-ATLa) that was d isplaced with LTD4 and ATLa (similar to IC50 0.2 to 0.9 nmol/ L), but not w ith a bioinactive ATL isomer. The clinically used CysLT(1) receptor antagon ist, Singulair, showed a lower rank order for competition with [H-3]-ATLa ( IC50 approximate to 8.3 nmol/L). In contrast, LTD4 was an ineffective compe titive ligand for recombinant ALX receptor with [H-3]-ATLa, and ATLa did no t compete for [H-3]-LTB4 binding with recombinant LTB4 receptor. Endogenous murine CysLT(1) receptors also gave specific [H-3]-ATLa binding that was d isplaced with essentially equal affinity by LTD, or ATLa, Systemic ATLa pro ved to be a potent inhibitor (>50%) of CysLT(1)-mediated vascular leakage i n murine skin (200 mug/kg) in addition to its ability to block polymorphonu clear leukocyte recruitment to dorsal air pouch (4 mug/kg). These results i ndicate that ATL and LTD, bind and compete with equal affinity at CysLT(1), providing a molecular basis for aspirin-triggered LXs serving as a local d amper of both vascular CysLT(1) signals as well as ALX receptor-regulated p olymorphonuclear leukocyte traffic.