Dendritic cells (DCs), representative antigen-presenting cells, effectively induce antigen-specific immune responses through activation of CD4+T and CD8+T cells. In tumor microenvironments, DCs uptake tumor-derived antigens, and generate helper T cells and cytotoxic T lymphocytes (CTLs), which recognize and kill the target tumor cells in response to the antigens. Thus, proper regulation of DC function is important for tumor immunology.

Substance P (SP) and Neurokinin A (NKA), neurotransmitters, are widely distributed in both central and peripheral nervous system. Recently, we demonstrated that IFN-γ remarkably induced neurokinin-2 receptor (NK2R) expression human monocyte-derived dendritic cells. These findings strongly suggested that neuropeptide-signaling cascade might be closely related with regulation of DC-mediated immune responses. To elucidate the precise role of such neuro-immune crosstalk, we further investigated the effect of neuropeptide signaling on function of human DCs.

At first, we found that both neurokinin-1 receptor (NK2R) and NK2R mRNA expressions were significantly enhanced by IFN-β, IFN-γ, LPS, or poly I:C stimulation with human DCs generated from peripheral blood mononuclear cells (PBMCs). In addition, we confirmed that the upregulation of NK1R and NK2R mRNA expressions was induced in a STAT-1-dependent manner. Surface expression levels of HLA-DR and costimulatory molecules on DCs, augmented by poly I:C, were modulated in the presence of specific inhibitors against NK1R or NK2R. On the other hand, we confirmed that blockade of NK1R- and NK2R-mediated signaling cascade significantly suppressed cytokine productions by antigen-specific CD4+ T cells after the antigen stimulation with DCs. Finally, we found that human DCs also enhanced expression level of TAC-1 gene, which encodes SP and NKA, after the IFN-γ stimulation.

Thus, these findings indicate that NK1R- and NK2R-dependent neuropeptide signaling regulate Type-1 immunity through the activation of DC function, suggesting that such neuro-immune cross-talk through SP-NK1R and NKA-NK2R cascade might be involved in various diseases caused by excessive Type-1-dominant immunity including cancer and infection with chronic inflammation.

Citation Format: Hidemitsu Kitamura, Junya Ohtake, Shun Kaneumi, Kazutaka Masuko, Kentaro Sumida, Satoshi Terada, Takuto Kishikawa, Yosuke Ono, Toshiyuki Kita, Hiroya Kobayashi. Neuropeptide signaling activates Type-1 immunity through the NK1 and NK2 receptors on human dendritic cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3620. doi:10.1158/1538-7445.AM2014-3620