Interactions Between Commensal Bacteria and Enteric Neurons, via FPR1 Induction of ROS, Increase Gastrointestinal Motility in Mice

Abstract Background & Aims Reduced gastrointestinal (GI) motility is a feature of disorders associated with intestinal dysbiosis and loss of beneficial microbes. It is not clear how consumption of beneficial commensal microbes, marketed as probiotics, affects the enteric nervous system (ENS). We studied the effects of the widely used probiotic and the commensal Lactobacillus rhamnosus GG (LGG) on ENS and GI motility in mice. Methods Conventional and germ-free C57B6 mice were gavaged with LGG and intestinal tissues were collected; changes in the enteric neuronal subtypes were assessed by real-time PCR, immunoblots and immunostaining. Production of reactive oxygen species (ROS) in the jejunal myenteric plexi and phosphorylation (p) of mitogen-activated protein kinase 1 (MAPK1) in the enteric ganglia were assessed by immunoblots and immunostaining. Fluorescence in situ hybridization was performed on jejunal cryosections with probes to detect formyl peptide receptor 1 (FPR1). GI motility in conventional mice was assessed after daily gavage of LGG for 1 week. Results Feeding of LGG to mice stimulated myenteric production of ROS, increased levels of phosphorylated MAPK1, and increased expression of choline acetyl transferase by neurons (P Conclusions Using mouse models, we found that LGG-mediated signaling in the ENS requires bacterial adhesion, redox mechanisms, and FPR1. This pathway might be activated to increase GI motility in patients.