Human intervention trials have provided evidence for protective effects of various (poly)phenol-rich foods against chronic disease, including cardiovascular disease, neurodegeneration, and cancer. While there are considerable data suggesting benefits of (poly)phenol intake, conclusions regarding their preventive potential remain unresolved due to several limitations in existing studies. Bioactivity investigations using cell lines have made an extensive use of both (poly)phenolic aglycones and sugar conjugates, these being the typical forms that exist in planta, at concentrations in the low-lM-to-mM range. However, after ingestion, dietary (poly)phenolics appear in the circulatory system not as the parent compounds, but as phase II metabolites, and their presence in plasma after dietary intake rarely exceeds nM concentrations. Substantial quantities of both the parent compounds and their metabolites pass to the colon where they are degraded by the action of the local microbiota, giving rise principally to small phenolic acid and aromatic catabolites that are absorbed into the circulatory system. This comprehensive review describes the different groups of compounds that have been reported to be involved in human nutrition, their fate in the body as they pass through the gastrointestinal tract and are absorbed into the circulatory system, the evidence of their impact on human chronic diseases, and the possible mechanisms of action through which (poly)phenol metabolites and catabolites may exert these protective actions. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes. Antioxid. Redox Signal. 18, 1818-1892.
Eph-ephrin system plays a central role in a large variety of human cancers. In
fact, alterated expression and/or de-regulated function of Eph-ephrin system
promotes tumorigenesis and development of a more aggressive and metastatic
tumour phenotype. In particular EphA2 upregulation is correlated with tumour
stage and progression and the expression of EphA2 in non-trasformed cells
induces malignant transformation and confers tumorigenic potential. Based on
these evidences our aim was to identify small molecules able to modulate
EphA2-ephrinA1 activity through an ELISA-based binding screening. We identified
lithocholic acid (LCA) as a competitive and reversible ligand inhibiting
EphA2-ephrinA1 interaction (Ki = 49 µM). Since each
ephrin binds many Eph receptors, also LCA does not discriminate between
different Eph-ephrin binding suggesting an interaction with a highly conserved
region of Eph receptor family. Structurally related bile acids neither inhibited
Eph-ephrin binding nor affected Eph phosphorylation. Conversely, LCA inhibited
EphA2 phosphorylation induced by ephrinA1-Fc in PC3 and HT29 human prostate and
colon adenocarcinoma cell lines (IC50 = 48 and
66 µM, respectively) without affecting cell viability or other receptor
tyrosine-kinase (EGFR, VEGFR, IGFR1β, IRKβ) activity. LCA did not
inhibit the enzymatic kinase activity of EphA2 at 100 µM (LANCE method)
confirming to target the Eph-ephrin protein-protein interaction. Finally, LCA
inhibited cell rounding and retraction induced by EphA2 activation in PC3 cells.
In conclusion, our findings identified a hit compound useful for the development
of molecules targeting ephrin system. Moreover, as ephrin signalling is a key
player in the intestinal cell renewal, our work could provide an interesting
starting point for further investigations about the role of LCA in the
intestinal homeostasis.
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