Selectivity of Recombinant Human Leukotriene D₄, Leukotriene B₄, and Lipoxin A₄ Receptors with Aspirin-Triggered 15-epi-LXA₄ and Regulation of Vascular and Inflammatory Responses

Aspirin-triggered lipoxin A₄ (ATL, 15-epi-LXA₄) and leukotriene D₄(LTD₄) possess opposing vascular actions mediated via receptors distinct from the LXA₄ receptor (ALX) that is involved in leukocyte trafficking. Here, we identified these receptors by nucleotide sequencing and demonstrate that LTD₄ receptor (CysLT₁) is induced in human vascular endothelia by interleukin-1β. Recombinant CysLT₁receptor gave stereospecific binding with both [³H]-LTD₄ and a novel labeled mimetic of ATL ([³H]-ATLa) that was displaced with LTD₄ and ATLa (∼IC₅₀ 0.2 to 0.9 nmol/L), but not with a bioinactive ATL isomer. The clinically used CysLT₁ receptor antagonist, Singulair, showed a lower rank order for competition with [³H]-ATLa (IC₅₀ ≈ 8.3 nmol/L). In contrast, LTD₄ was an ineffective competitive ligand for recombinant ALX receptor with [³H]-ATLa, and ATLa did not compete for [³H]-LTB₄ binding with recombinant LTB₄ receptor. Endogenous murine CysLT₁receptors also gave specific [³H]-ATLa binding that was displaced with essentially equal affinity by LTD₄ or ATLa. Systemic ATLa proved to be a potent inhibitor (>50%) of CysLT₁-mediated vascular leakage in murine skin (200 μg/kg) in addition to its ability to block polymorphonuclear leukocyte recruitment to dorsal air pouch (4 μg/kg). These results indicate that ATL and LTD₄ bind and compete with equal affinity at CysLT₁, providing a molecular basis for aspirin-triggered LXs serving as a local damper of both vascular CysLT₁ signals as well as ALX receptor-regulated polymorphonuclear leukocyte traffic.