Lactobacilli ‐induced Generation of Reactive Oxygen Species via Formyl Peptide Receptor‐1 (FPR1) Regulates Intestinal Motility in Mice

Abstract

RationaleVarious clinical conditions like diabetes and inflammatory diseases of the gut are associated with gastrointestinal (GI) motility disorders. Despite the increased consumption of beneficial commensal microbes marketed as ‘probiotics’, their mechanism of action on the enteric nervous system (ENS) is still unclear.AimWe studied the effects of the widely used probiotic and normal commensal Lactobacillus rhamnosus GG (LGG) on ENS and GI motility.MethodsConventional (Conv), formyl peptide receptor‐1 (FPR1 KO) and formyl peptide receptor‐2 (FPR2 KO) knockout mice were gavaged with hanks buffered salt solution (HBSS, negative control) or LGG. Mice were sacrificed after 2 h, and the jejunum was cryofixed and immunostained for phospho‐Erk (p44/42 MAPK, mitogen activated protein kinase). In a separate experiment, mice were intra peritoneally injected with a fluorescent hydro‐cy3 dye prior to HBSS/LGG gavage, and production of reactive oxygen species (ROS) was assessed in the longitudinal muscle myenteric plexus (LMMP) by confocal imaging after 2h. Ileum was assayed for gene expression of neuropeptides and Hand‐2 (transcription factor promoting enteric neuronal differentiation) by real time polymerase chain reaction (qRT‐PCR). Fluorescence in situ hybridization (FISH) was done on ileal cryosections from conventional mice using FPR1 and peripherin (pan neuronal marker) RNA probes. Conv mice were gavaged daily with HBSS or LGG for 2 weeks, and motility was assessed from stool frequency, total gastrointestinal transit time and ex vivo studies on isolated circular muscle strips by isometric muscle recording.ResultsLGG stimulated myenteric ROS production, enhanced Erk 1/2 phosphorylation and upregulated choline acetyl transferase (ChAT) neurons (P < 0.001) in Conv and FPR2 KO mice. These effects were abrogated in FPR1 KO mice, suggesting that LGG‐mediated signaling in the ENS is redox‐dependent and requires FPR1(P < 0.001), localized on enteric neurons by FISH assay. Functionally, LGG gavage for 2 weeks significantly improved stool frequency, reduced total GI transit time and enhanced ileal circular muscle strip contractions (P < 0.05).ConclusionsOur study demonstrates for the first time, the presence of FPR1 on enteric neurons, and the LGG‐FPR1‐dependent redox‐signaling pathway that could be exploited to improve GI motility.Support or Funding InformationWe acknowledge support from the U.S. National Institutes of Health grant AI64462 (A.S.N.) and DK089763 (A.N. and A.S.N.)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.