664 The neurokinin A/NK2R axis controls IL-10 levels to inhibit activation of cutaneous MCs in vitro and in vivo

Abstract

Untoward IgE-initiated mast cell (MC) activation is associated with cutaneous allergy. In the skin, MCs reside near peripheral sensory nerve fibers and are affected by local release of neuropeptides. The tachykinin family member, neurokinin A is highly expressed in the skin, but few studies have addressed its impact on cutaneous immune cells. In this study, we investigated the effects of NKA on IgE-activated bone marrow (BM)MCs and in the murine model of passive cutaneous anaphylaxis (PCA). The addition of NKA to IgE-loaded BMMCS did not affect MC degranulation, but reduced IL-4, IL-6 and IL-13 transcription. In parallel, STAT5 activation was inhibited by NKA. Mechanistically NKA maintained IL-10R expression, increased IL-10 transcription, and decreased release of an IL-10-degrading protease. Neutralizing IL-10 reversed the inhibitory effects of NKA on STAT5 phosphorylation and on transcription. In vivo, NKA dampened MC activation in PCA, reducing Evan’s blue extravasation, myeloperoxidase activity and the percentages of neutrophils recruited to the skin. In PCA, MC-derived IL-10 was needed for NKA to inhibit PCA. Administration of NKA in tandem with the NK2R antagonist, GR159897 reversed the effects of NKA, causing an increase in the percentage of neutrophils recruited to the skin, even in absence of IgE cross-linking. IgE-independent neutrophil recruitment was abrogated when NKA and GR159897 were co-administered in mice lacking cutaneous MCs, suggesting that this is a MC-specific pathway. While NK2R antagonism reversed the effects of NKA in PCA, co-administration of NKA with a dual NK1R/Mrg family inhibitor did not affect NKA-mediated inhibition, demonstrating receptor specificity. In conclusion, NKA diminishes MC function through a mechanism involving IL-10 and the NK2R. Herein, we have uniquely identified a multi-tiered neuroimmune regulatory pathway that tempers cutaneous MC activation and may have broad impact for understanding the cutaneous manifestations of IgE-initiated allergy.