Nicotine Improves Symptoms in Murine Oxazolone-Induced Ulcerative Colitis by Inhibiting Migration of Plasmacytoid Dendritic Cells Through Alpha7 Nicotinic Acetylcholine Receptors

Abstract

Some clinical trials and epidemiologic studies revealed improvements in symptoms of ulcerative colitis after smoking and nicotine patch treatment. However, mechanisms underlying the ameliorating effect of nicotine remain poorly understood. We have previously reported that nicotine administration ameliorates murine oxazolone (OXZ)-induced colitis through alpha7 nicotine acetylcholine receptors (α7nAChRs). In addition, we have shown that mRNA of α7nAChRs was expressed in plasmacytoid dendritic cells (pDCs) of OXZ colitis mouse colon. The aim of this study was to investigate a pathophysiological role of pDCs and immunological effects of nicotine on pDCs in ulcerative colitis. Method: OXZ-induced colitis was developed in BALB/c mice. Lamina propria mononuclear cells (LPMCs) of the colon and mesenteric lymph node (MLN) were collected in OXZ colitis mice. pDCs were isolated from LPMCs by using magnetic cell separation system (BD biosciences). In addition, mouse bone marrow (BM) cells were differentiated to pDC-like cells (BMpDC) by Flt3 ligand. Furthermore, immunological effects of nicotine on BMpDCwere examined by flow cytometry and BMpDC migration was examined by chemotaxis assay using EZ-TAXIScan. Moreover, the effect of nicotine administration on pDC subset proportion was investigated in the MLN of OXZ colitis mice. Result: α7nAChRs mRNA was expressed in pDC of OXZ colitis mouse colon and BMpDC, but not BM conventional dendritic cells (cDC). Flow cytometry analysis revealed that neither CD80, CD86 nor MHC class II expression in BMpDC was affected with nicotine in the induction of pDC maturation by CpG-DNA. On the other hand, CCL21induced migration of mature BMpDC was inhibited by nicotine and α7nAChRs selective agonist GTS-21, and α7nAChRs selective antagonist methyllycaconitine (MLA) blocked the inhibitory effect of nicotine and GTS-21. Furthermore, nicotine administration downregulated pDC subset proportion in the MLN of OXZ colitis mice. Conclusion: These data suggest that the activation of α7nAChRs reduces pDC-mediated antigen presentation to naive CD4 T cells by inhibiting pDC migration from colon to MLN, thereby alleviating the symptoms in OXZ colitis. Our results may contribute to the development of therapeutic medicines for ulcerative colitis by activating the cholinergic anti-inflammatory pathway.