CGRP, PACAP, and VIP Modulate Langerhans Cell Function by Inhibiting NF-κB Activation

The neuropeptides calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP), and vasoactive intestinal peptide (VIP) suppress Langerhans cell (LC) antigen presentation and modulate cytokine production. We have tested the hypothesis that these neuropeptides (NP) inhibit LC function by modulating activation of NF-κB. Lipopolysaccharide (LPS) activates NF-κB in both a LC-like cell line (XS52) and epidermal LC enriched to ∼95% and this effect is inhibited by each of the NP. Furthermore, CGRP, PACAP, and VIP suppress phosphorylation of IκB kinase β (P-IKKβ), prevent degradation of the IκBα, and inhibit activation of NF-κB. Thus, these NP modulate LC function by reducing NF-κB activation. Bay 11-7085, an inhibitor of IKK, reduced tumor necrosis factor-α (TNFα) production from LPS-stimulated XS52 cells and inhibited the ability of LC to present antigen to a T-cell clone in vitro. Each NP also inhibited LPS-induced secretion of TNFα by XS52 cells and LC enriched to ∼95% homogeneity. We suggest that the inhibitory activities of CGRP, PACAP, and VIP on LC function are mediated, at least in part, by inhibition of P-IKKβ, which prevents IκBα degradation and activation of NF-κB. Modulation of this signaling pathway may be useful for therapeutic modulation of immunity in the skin.