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

摘要

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 CysLT1 receptor 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 CysLT₁ receptors 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.