1. Tryptophan from Human Milk Induces Oxidative Stress and Upregulates the Nrf-2-Mediated Stress Response in Human Intestinal Cell Lines.
- Author
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Elisia, Ingrid, Tsopmo, Apollinaire, Friel, James K., Diehl-Jones, William, and Kitts, David D.
- Subjects
BREAST milk ,MILK proteins ,ANTIOXIDANTS ,PEPTIDES ,TRYPTOPHAN ,CELL lines - Abstract
Chemical screening of digested human milk protein using the oxygen radical absorbance capacity (ORAC
FL ) antioxidant assay confirmed the presence of a peptide fraction (PF23) with high antioxidant activity [5.53 mmol Trolox equivalents (TE)/g] that contained tryptophan as a main component. We evaluated the effects of both PF23 and tryptophan alone on the modulation of oxidative stress in cultured intestinal cells using a dichlorofluorescein diacetate probe. Despite the high ORACFL value, PF23 enhanced (P< 0.05)2, 2′-azobis (2-amidinopropane) dihydrochloride (peroxyl radical generator)-induced intracellular oxidation in the Caco-2 human adenocarcinoma cell line, suggesting prooxidant activity. Compared to selected peptide fractions with relatively lower ORACFL values, PF23 induced oxidative stress more than all other peptide fractions tested (P < 0.05) and contained more tryptophan than the others (P < 0.05). Similar prooxidant activity was observed for tryptophan when it was added to culture medium for both the Caco-2 cells and FHs 74 Int primary fetal enterocytes, while also exhibiting a high ORACFL value (9.69 mmol TE/g). The effect of tryptophan that involves activation of the Nrf-2 pathway and transcription of antioxidant enzymes was therefore investigated in FHs 74 Int cells. Exposure of infant intestinal cells to tryptophan resulted in Nrf-2 activation and an increase in the gene transcript level of glutathione peroxidase 2. We conclude that tryptophan-induced oxidative stress associated with tryptophan-containing milk peptides induces an adaptive response that involves the activation of the antioxidant responsive signaling pathway in intestinal cells. [ABSTRACT FROM AUTHOR]- Published
- 2011
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