Background: A major cause of enteric infection, Gram-negative pathogenic bacteria activate mucosal inflammation through lipopolysaccharide (LPS) binding to intestinal toll-like receptor 4 (TLR4). Breast feeding lowers risk of disease, and human milk modulates inflammation.
Objective and methods: This study tested whether human milk oligosaccharides (HMOs) influence pathogenic Escherichia coli-induced interleukin (IL)-8 release by intestinal epithelial cells (IECs), identified specific proinflammatory signalling molecules modulated by HMOs, specified the active HMOs and determined its mechanism of action. Models of inflammation were IECs invaded by type 1 pili enterotoxigenic E. coli (ETEC) in vitro: T84 modelled mature, and H4 modelled immature IECs. LPS-induced signalling molecules co-varying with IL-8 release in the presence or absence of HMOs were identified. Knockdown and overexpression verified signalling mediators. The oligosaccharide responsible for altered signalling was identified.
Results: HMOs attenuated LPS-dependent induction of IL-8 caused by ETEC, uropathogenic E. coli, and adherent-invasive E. coli (AIEC) infection, and suppressed CD14 transcription and translation. CD14 knockdown recapitulated HMO-induced attenuation. Overexpression of CD14 increased the inflammatory response to ETEC and sensitivity to inhibition by HMOSs. 2’fucosyllactose (2’FL), at milk concentrations, displayed equivalent ability as total HMOs to suppress CD14 expression, and protected AIEC-infected mice.Conclusions: HMOs and 2’FL directly inhibit LPS-mediated inflammation during ETEC invasion of T84 and H4 IECs through attenuation of CD14 induction. CD14 expression mediates LPS-TLR4 stimulation of portions of the ‘macrophage migration inhibitory factors’ inflammatory pathway via suppressors of cytokine signalling 2/signal transducer and activator of transcription 3/NF-κB. HMOs direct inhibition of inflammation supports its functioning as an innate immune system whereby the mother protects her vulnerable neonate through her milk. 2’FL, a principal HMO, quenches inflammatory signaling Read More
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