Type 3 Muscarinic Receptors Contribute to Clearance of Citrobacter rodentium

Abstract

Background The role of muscarinic receptors in mucosal homeostasis, response to enteric pathogens, and modulation of immune cell function is undefined. Methods The contribution of type 3 muscarinic receptors (M3R) to mucosal homeostasis within the colon and host defense against Citrobacter rodentium was determined in uninfected and C. rodentium-infected WT and M3R-deficient (Chrm3−/−) mice. In addition, WT and Chrm3−/− bone marrow-derived macrophages (BMDM) were studied to determine the ability of M3R to modulate macrophage phenotype and function. Results In Chrm3−/− mice clearance of C. rodentium was delayed despite an amplified TH1/TH17 response. Delayed clearance of C. rodentium from Chrm3−/− mice was associated with prolonged adherence of bacteria to colonic mucosa, decreased goblet cell number, and decreased mucin 2 gene expression. Treatment of BMDM with bethanechol, a muscarinic-selective agonist, induced a classically activated macrophage phenotype, which was dependent on M3R expression. Chrm3−/− BMDM retained their ability to attain a classically activated macrophage phenotype when treated with the TH1 cytokine IFN-γ. Conclusions In Chrm3−/− mice mucin production is attenuated and is associated with prolonged adherence of C. rodentium to colonic mucosa. The immune response, as characterized by production of TH1/TH17 cytokines, in C. rodentium-infected Chrm3−/− mice is intact. In addition, M3R activity promotes the development of classically activated macrophages. Our data establish a role for M3R in host defense against C. rodentium through effects on goblet cell mucus production and in the modulation of macrophage phenotype and function.

Bidirectional brain-gut interactions and chronic pathological changes after traumatic brain injury in mice

“…Two hours prior to euthanasia, mice were injected intraperitoneally with 10mg/kg of 5-bromo-2′-deoxyuridine (BrdU) (Sigma-Aldrich) diluted in warm PBS. Samples were collected, fixed, and processed, as described previously 35 . BrdU-positive cells were counted in 8-10 well-oriented crypts per section in images acquired with a 10× objective.…”

Modulation of the Immune Response by Nematode Secreted Acetylcholinesterase Revealed by Heterologous Expression in Trypanosoma musculi

“…Somewhat different results were obtained in a recent study which examined the response to Citrobacter rodentium in m3R-/- mice. Contrasting effects of cholinergic signalling through the nα7R and the m3R on macrophage function were described, with macrophages polarised to either an M1 or an M2 phenotype depending on the cytokine environment [35]. Nevertheless, in our current system, the net effect of over-expressing nematode AChE during systemic infection of mice with our vehicle is polarisation to a Th1 environment and skewing of macrophages to an M1 phenotype.…”

Enteric nematodes and the path to up-regulation of type 2 cytokines IL-4 and IL-13

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