Antiallergic Cromones Inhibit Neutrophil Recruitment Onto Vascular Endothelium via Annexin-A1 Mobilization

Abstract

Objective— To determine whether the inhibitory action of the antiallergic cromone “mast cell stabilizing” drugs on polymorphonuclear leukocyte (PMN) trafficking is mediated through an annexin-A1 (Anx-A1) dependent mechanism. Methods and Results— Intravital microscopy was used to monitor the actions of cromones in the inflamed microcirculation. Reperfusion injury provoked a dramatic increase in adherent and emigrated leukocytes in the mesenteric vascular bed, associated with augmented tissue levels of myeloperoxidase. Nedocromil, 2 to 20 mg/kg, significantly ( P <0.05) inhibited cell adhesion and emigration, as well as myeloperoxidase release, in wild-type but not Anx-A1 −/− mice. Short pretreatment of human PMNs with nedocromil, 10 nmol/L, inhibited cell adhesion ( P <0.05) in the flow chamber assay, and this effect was reversed by specific anti-AnxA1 or a combination of antiformyl peptide receptors 1 and 2, but not irrelevant control, antibodies. Western blotting experiments revealed that cromones stimulate protein kinase C–dependent phosphorylation and release Anx-A1 in human PMNs. Conclusion— We propose a novel mechanism to explain the antiinflammatory actions of cromones on PMN trafficking, an effect that has long puzzled investigators.