Indole-3-lactic acid associated with Bifidobacterium-dominated microbiota significantly decreases inflammation in intestinal epithelial cells

Abstract

Background Bifidobacterium longum subsp. infantis (B. infantis) is a commensal bacterium that colonizes the gastrointestinal tract of breast-fed infants. B. infantis can efficiently utilize the abundant supply of oligosaccharides found in human milk (HMO) to help establish residence. We hypothesized that metabolites from B. infantis grown on HMO produce a beneficial effect on the host. Results In a previous study, we demonstrated that B. infantis routinely dominated the fecal microbiota of a breast fed Bangladeshi infant cohort (1). Characterization of the fecal metabolome of binned samples representing high and low B. infantis populations from this cohort revealed higher amounts of the tryptophan metabolite indole-3-lactic acid (ILA) in feces with high levels of B. infantis. Further in vitro analysis confirmed that B. infantis produced significantly greater quantities of the ILA when grown on HMO versus lactose, suggesting a growth substrate relationship to ILA production. The direct effects of ILA were assessed in a macrophage cell line and intestinal epithelial cell lines. ILA (1-10 mM) significantly attenuated lipopolysaccharide (LPS)-induced activation of NF-kB in macrophages. ILA significantly attenuated TNF-α- and LPS-induced increase in the pro-inflammatory cytokine IL-8 in intestinal epithelial cells. ILA increased mRNA expression of the aryl hydrogen receptor (AhR)-target gene CYP1A1 and nuclear factor erythroid 2–related factor 2 (Nrf2)-targeted genes glutathione reductase 2 (GPX2), superoxide dismutase 2 (SOD2), and NAD(P) H dehydrogenase (NQO1). Pretreatment with either the AhR antagonist or Nrf-2 antagonist inhibited the response of ILA on downstream effectors. Conclusions These findings suggest that ILA, a predominant metabolite from B. infantis grown on HMO and elevated in infant stool high in B. infantis, and protects gut epithelial cells in culture via activation of the AhR and Nrf2 pathway.

Bifidobacteria-mediated immune system imprinting early in life

“…HMO metabolism influences immune system development Various organic molecules produced by bacteria, including organic acids, phenylalanine, and tryptophan derivatives, have been shown to broadly influence host health (Ehrlich et al, 2020;Fukuda et al, 2011;Laursen et al, 2020). Specifically, Bifidobacterium-derived metabolites have been shown to modulate pathogen-induced inflammation via the aryl hydrocarbon receptor (AhR) and NRF-2 pathway (Ehrlich et al, 2020;Meng et al, 2020).…”

“…HMO metabolism influences immune system development Various organic molecules produced by bacteria, including organic acids, phenylalanine, and tryptophan derivatives, have been shown to broadly influence host health (Ehrlich et al, 2020;Fukuda et al, 2011;Laursen et al, 2020). Specifically, Bifidobacterium-derived metabolites have been shown to modulate pathogen-induced inflammation via the aryl hydrocarbon receptor (AhR) and NRF-2 pathway (Ehrlich et al, 2020;Meng et al, 2020). To test whether the presence of HMO-utilization genes could explain the immune perturbations in children lacking gut Bifidobacteriaceae, we used the Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology (KO) database and identified 57 representative key functions necessary to metabolize HMOs (Nguyen et al, 2021;Sela et al, 2008).…”

“…Metabolites within the tryptophan metabolism pathway were particularly enriched. The most overrepresented tryptophan metabolite in EVC001-fed infant feces compared to controls was ILA (Figure 6E; p = 5.89 3 10 À8 ; FDR) (Ehrlich et al, 2020;Meng et al, 2020). Importantly, bifidobacteria-derived ILA has recently been shown to bind both the AhR and hydrocarboxylic acid receptor 3 (HCAR3) and modulates monocyte responses to lipopolysaccharide (LPS) (Laursen et al, 2020).…”

Bifidobacterium Longum: Protection against Inflammatory Bowel Disease

“…It interacts with the transcription factor aryl hydrocarbon receptor (AHR) and prevents transcription of the inflammatory cytokine IL-8 [82]. In addition, it could significantly attenuate lipopolysaccharide-(LPS-) induced activation of NF-κB in macrophages and significantly attenuate TNF-alpha and IL-8 in intestinal epithelial cells to protects gut epithelial cells [82,83]. ILA increased the mRNA expression of the aryl hydrogen receptor-(AhR-) target gene CYP1A1 and nuclear factor erythroid 2-related factor 2-(Nrf2-) targeted genes glutathione reductase 2 (GPX2), superoxide dismutase 2 (SOD2), and NADPH dehydrogenase (NQO1) and protects gut epithelial cells in culture via activation of the AhR and Nrf2 pathway [83].…”

“…In addition, it could significantly attenuate lipopolysaccharide-(LPS-) induced activation of NF-κB in macrophages and significantly attenuate TNF-alpha and IL-8 in intestinal epithelial cells to protects gut epithelial cells [82,83]. ILA increased the mRNA expression of the aryl hydrogen receptor-(AhR-) target gene CYP1A1 and nuclear factor erythroid 2-related factor 2-(Nrf2-) targeted genes glutathione reductase 2 (GPX2), superoxide dismutase 2 (SOD2), and NADPH dehydrogenase (NQO1) and protects gut epithelial cells in culture via activation of the AhR and Nrf2 pathway [83]. Therefore, Bifidobacterium longum can reduce the production of proinflammatory cytokines, inhibit the activation of NF-κB induced by TNF-α, and improve the symptoms of IBD (Figure 1).…”