title: Oral treatment with Lactobacillus rhamnosus attenuates behavioural deficits and immune changes in chronic social stress.
abstract: BACKGROUND
  Stress-related disorders involve systemic alterations, including disruption of the intestinal microbial community. Given the putative connections between the microbiota, immunity, neural function, and behaviour, we investigated the potential for microbe-induced gut-to-brain signalling to modulate the impact of stress on host behaviour and immunoregulation.
  
  
  METHODS
  Male C57BL/6 mice treated orally over 28 days with either Lactobacillus rhamnosus (JB-1) ™ or vehicle were subjected to chronic social defeat and assessed for alterations in behaviour and immune cell phenotype. 16S rRNA sequencing and mass spectrometry were employed to analyse the faecal microbial community and metabolite profile.
  
  
  RESULTS
  Treatment with JB-1 decreased stress-induced anxiety-like behaviour and prevented deficits in social interaction with conspecifics. However, JB-1 did not alter development of aggressor avoidance following social defeat. Microbial treatment attenuated stress-related activation of dendritic cells while increasing IL-10+ regulatory T cells. Furthermore, JB-1 modulated the effect of stress on faecal metabolites with neuroactive and immunomodulatory properties. Exposure to social defeat altered faecal microbial community composition and reduced species richness and diversity, none of which was prevented by JB-1. Stress-related microbiota disruptions persisted in vehicle-treated mice for 3 weeks following stressor cessation.
  
  
  CONCLUSIONS
  These data demonstrate that despite the complexity of the gut microbiota, exposure to a single microbial strain can protect against certain stress-induced behaviours and systemic immune alterations without preventing dysbiosis. This work supports microbe-based interventions for stress-related disorders.
authors.affiliation: Department of Pathology & Molecular Medicine, McMaster University, Hamilton, Canada.|McMaster Brain-Body Institute, The Research Institute of St. Joseph's Hamilton, Hamilton, Canada.|Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Canada.
authors.forename: Aadil
authors.initials: A
authors.lastname: Bharwani
authors.affiliation: McMaster Brain-Body Institute, The Research Institute of St. Joseph's Hamilton, Hamilton, Canada.
authors.forename: M Firoz
authors.initials: MF
authors.lastname: Mian
authors.affiliation: Department of Medicine, McMaster University, The Brain-Body Institute, 50 Charlton Avenue East, T3302, Hamilton, Ontario, L8N 4A6, Canada.|Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Canada.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Surette
authors.affiliation: Department of Pathology & Molecular Medicine, McMaster University, Hamilton, Canada.|McMaster Brain-Body Institute, The Research Institute of St. Joseph's Hamilton, Hamilton, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Bienenstock
authors.affiliation: McMaster Brain-Body Institute, The Research Institute of St. Joseph's Hamilton, Hamilton, Canada. forsytp@mcmaster.ca.|Department of Medicine, McMaster University, The Brain-Body Institute, 50 Charlton Avenue East, T3302, Hamilton, Ontario, L8N 4A6, Canada. forsytp@mcmaster.ca.|Firestone Institute for Respiratory Health, St. Joseph's Healthcare Hamilton, Hamilton, Canada. forsytp@mcmaster.ca.
authors.forename: Paul
authors.initials: P
authors.lastname: Forsythe
mesh_terms: D000818:Animals; D001007:Anxiety / Q000517:prevention & control; D001522:Behavior, Animal / Q000187:drug effects; D001921:Brain / Q000378:metabolism; D000069196:Gastrointestinal Microbiome / Q000187:drug effects*; D016753:Interleukin-10 / Q000378:metabolism; D052201:Lacticaseibacillus rhamnosus; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019936:Probiotics / Q000008:administration & dosage* / Q000494:pharmacology; D012336:RNA, Ribosomal, 16S / Q000187:drug effects*; D013315:Stress, Psychological / Q000235:genetics / Q000517:prevention & control*
chemical_list: D012336:RNA, Ribosomal, 16S; D016753:Interleukin-10
keywords: Behaviour; Chronic social defeat; Gut-brain axis; Immune system; Microbiota; Psychiatric disease