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Patient-derived Enterococcus mundtii and its capsular polysaccharides cause depression through the downregulation of

Min-Kyung Joo1, Xiaoyang Ma1, Jong-Wook Yoo1

  • 1Neurobiota Research Center and Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, Kyung Hee University, Seoul 02447, South Korea.

Microbes and Infection
|February 9, 2023
PubMed

Insights

Certain Enterococcus strains, particularly Enterococcus mundtii, may contribute to depression. Research found E. mundtii induced depression-like behaviors and altered brain chemicals in mice, suggesting it could be a depression risk factor.

Area of Science:

  • Microbiology
  • Neuroscience
  • Immunology

Background:

  • Enterococcus bacteria are often found in higher numbers in the gut of individuals with depression.
  • Comorbidities like inflammatory bowel disease (IBD) can be present alongside depression.

Purpose of the Study:

  • To investigate the potential role of specific Enterococcus species, isolated from IBD and depression patients, in the development of depression.
  • To identify specific bacterial components responsible for depression-inducing effects.

Main Methods:

  • Isolation and identification of Enterococcus species from patient fecal samples.
  • In vitro assessment of bacterial effects on microglial cells (NF-κB, TNF-α, IL-6).
  • In vivo studies in mice to evaluate depression-like behaviors, neuroinflammation, brain-derived neurotrophic factor (BDNF), and serotonin levels.
  • Analysis of bacterial capsular polysaccharide (CP) effects and genetic comparison.

Main Results:

  • Enterococcus mundtii NK1516 most significantly induced inflammatory markers (TNF-α, IL-6) in microglia.
  • E. mundtii NK1516 caused depression-like behaviors in mice without sickness behaviors or neuroinflammation.
  • NK1516 reduced hippocampal BDNF and serotonin levels and altered Htr1a mRNA expression.
  • The capsular polysaccharide (CP) of NK1516, but not cytoplasmic components or E. mundtii ATCC882 CP, induced these effects.
  • Unique CP biosynthesis genes were identified in NK1516 compared to ATCC882.

Conclusions:

  • Enterococcus mundtii, specifically strain NK1516, may act as a risk factor for depression.
  • The capsular polysaccharide of E. mundtii NK1516 appears to be a key factor in its depression-inducing effects.
  • Further research into E. mundtii's role in gut-brain axis disorders is warranted.
Keywords:
Brain-derived neurotrophic factorCapsular polysaccharideDepressionEnterococcus mundtiiGut–brain axisSerotonin

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