Enhanced serum antigen-specific IgG1 and proinflammatory cytokine production in nicotinic acetylcholine receptor α7 subunit gene knockout mice

Human and murine immune cells such as mononuclear leukocytes consisting of mainly T and B cells, bone marrow derived dendritic cells (DCs) and macrophages all express various nicotinic acetylcholine (ACh) receptor (nAChR) subunits. Activated T cells and DCs have the ability to synthesize ACh by choline acetyltransferase, suggesting the role of non-neuronal cholinergic system expressed in immune cells in the regulation of immune cell function. Stimulation of human leukemic T and B cell lines with nicotine causes a transient Ca2+-signaling that is antagonized by a-bungarotoxin, suggesting the involvement of alpha 7 subunit. Furthermore, alpha 7 nAChRs have been shown to negatively regulate synthesis and release of tumor necrosis factor (TNF)-alpha in macrophages. These findings suggest that immune cell function is regulated by its own non-neuronal cholinergic system, at least in part, via alpha 7 nAChR-mediated pathways. In the present study, we tested the role of alpha 7 nAChRs in the regulation of immune function by measuring total serum and antigen-specific IgG(1) and IgM, and production of TNF-alpha, gamma interferon (IFN-gamma) and interleukin (IL)-6 in activated spleen cells of nAChR alpha 7 subunit gene knockout (alpha 7 KO) and wild-type C57BL/6J mice immunized with ovalbumin (OVA). We found that serum levels of total and anti-OVA-specific IgG(1) were significantly elevated in U7 KO mice, though there were no significant differences in serum levels of total and anti-OVA-specific IgM between the two genotypes. Production of TNF-alpha, IFN-gamma and IL-6 in spleen cells was significantly facilitated in alpha 7 KO mice. Expression of AChE mRNA was not different between the two genotypes. These results suggest that alpha 7 nAChRs are involved in the regulation of cytokine production, through which modulates TNF-alpha, IFN-gamma and IL-6 productions, leading to modification of antibody production, but are not involved in expression of cholinergic components in immune cells. (C) 2007 Elsevier B.V. All rights reserved.