Lack of activity of 15‐epi‐lipoxin A 4 on FPR 2/ ALX and CysLT1 receptors in interleukin‐8‐driven human neutrophil function

Summary Neutrophil recruitment and survival are important control points in the development and resolution of inflammatory processes. 15‐epi‐lipoxin ( LX ) A 4 interaction with formyl peptide receptor 2 ( FPR 2)/ ALX receptor is suggested to enhance anti‐inflammatory neutrophil functions and mediate resolution of airway inflammation. However, it has been reported that 15‐epi‐ LXA 4 analogues can also bind to cysteinyl leukotriene receptor 1 ( C ys LT 1) and that the C ys LT 1 antagonist MK ‐571 binds to FPR 2/ ALX , so cross‐reactivity between FPR 2/ ALX and C ys LT 1 ligands cannot be discarded. It is not well established whether the resolution properties reported for 15‐epi‐ LXA 4 are mediated through FPR 2/ ALX , or if other receptors such as C ys LT 1 may also be involved. Evaluation of specific FPR 2/ ALX ligands and C ys LT 1 antagonists in functional biochemical and cellular assays were performed to establish a role for both receptors in 15‐epi‐ LXA 4 ‐mediated signalling and function. In our study, a FPR 2/ ALX synthetic peptide ( WKYMV m) and a small molecule FPR 2/ ALX agonist (compound 43) induced FPR 2/ ALX ‐mediated signalling, enhancing guanosine triphosphate‐gamma ( GTP γ) binding and decreasing cyclic adenosine monophosphate (c AMP) levels, whereas 15‐epi‐ LXA 4 was inactive. Furthermore, 15‐epi‐ LXA 4 showed neither binding affinity nor signalling towards C ys LT 1. In neutrophils, 15‐epi‐ LXA 4 showed a moderate reduction of interleukin ( IL) ‐8‐mediated neutrophil chemotaxis but no effect on neutrophil survival was observed. In addition, C ys LT 1 antagonists were inactive in FPR 2/ ALX signalling or neutrophil assays. In conclusion, 15‐epi‐ LXA 4 is not a functional agonist or an antagonist of FPR 2/ ALX or C ys LT 1, shows no effect on IL ‐8‐induced neutrophil survival and produces only moderate inhibition in IL ‐8‐mediated neutrophil migration. Our data do not support an anti‐inflammatory role of 15‐epi‐ LXA 4 ‐ FPR 2/ ALX interaction in IL ‐8‐induced neutrophil inflammation.