Human milk affects TLR4 activation and LPS-induced cytokine expression in Caco-2 intestinal epithelial cells

Background: Human milk (HM) components affect immune cell toll-like receptor 4 (TLR4) signaling. However, studies examining the immunomodulatory impacts of HM on TLR4 signaling in intestinal epithelial cells (IECs) are limited. Methods: : This study utilized both a TLR4 reporter cell line and a Caco-2 IEC model to examine the effects of HM on lipopolysaccharide (LPS)-induced TLR4 activation and cytokine responses, respectively. Additionally, we performed fast protein liquid chromatography and mass spectrometry to identify a HM component that contributes to the effect of HM on TLR4 signaling. Results: : HM enhances LPS-induced TLR4 signaling as well as IEC gene expression of pro-inflammatory cytokines and negative regulators of NF-κB. Human serum albumin (HSA) present in HM contributes to this effect. Conclusion: HSA within HM synergizes with LPS to induce TLR4 signaling as well as IEC gene expression of pro-inflammatory cytokines and negative regulators of NF-κB. Altogether, this study provides mechanistic evidence behind the immunomodulatory function of HM on IECs, which may contribute to an enhanced immune response in breast-fed neonates.