Oligomer formation of a tea polyphenol, EGCG, on its sensing molecule 67 kDa laminin receptor.

Green tea polyphenol (-)-epigallocatechin-3-O-gallate (EGCG) has been attributed to the activation of its cell surface sensing receptor 67 kDa laminin receptor (67LR). However, the action of EGCG to activate 67LR remains unknown. Here we show that EGCG undergoes oligomer formation on its surface receptor 67LR.

Green tea polyphenol EGCG sensing motif on the 67-kDa laminin receptor.

BACKGROUND: We previously identified the 67-kDa laminin receptor (67LR) as the cell-surface receptor conferring the major green tea polyphenol (-)-epigallocatechin-3-O-gallate (EGCG) responsiveness to cancer cells. However, the underlying mechanism for interaction between EGCG and 67LR remains unclear. In this study, we investigated the possible role of EGCG-67LR interaction responsible for its bioactivities. METHODOLOGY/PRINCIPAL FINDINGS: We synthesized various peptides deduced from the extracellular domain corresponding to the 102-295 region of human 67LR encoding a 295-amino acid. The neutralizing activity of these peptides toward EGCG cell-surface binding and inhibition of cancer cell growth were assayed. Both activities were inhibited by a peptide containing the 10-amino acid residues, IPCNNKGAHS, corresponding to residues 161-170. Furthermore, mass spectrometric analysis revealed the formation of a EGCG-LR161-170 peptide complex. A study of the amino acid deletion/replacement of the peptide LR161-170 indicated that the 10-amino acid length and two basic amino acids, K(166) and H(169), have a critical role in neutralizing EGCG's activities. Moreover, neutralizing activity against the anti-proliferation action of EGCG was observed in a recombinant protein of the extracellular domain of 67LR, and this effect was abrogated by a deletion of residues 161-170. These findings support that the 10 amino-acid sequence, IPCNNKGAHS, might be the functional domain responsible for the anti-cancer activity of EGCG. CONCLUSIONS/SIGNIFICANCE: Overall, our results highlight the nature of the EGCG-67LR interaction and provide novel structural insights into the understanding of 67LR-mediated functions of EGCG, and could aid in the development of potential anti-cancer compounds for chemopreventive or therapeutic uses that can mimic EGCG-67LR interactions.

Anti-Allergic Effects of Kakrol (Momordica dioica Roxb.) Flesh Extract.

We examined the inhibitory effect of the extract of kakrol extracted by 3 types of solvent (water, 50% and 100% ethanol) on histamine release in human basophilic KU812 cells. The water extract of kakrol flesh showed the strongest inhibitory effect on histamine release as compared with the other extracts. Therefore, we evaluated whether water extract of kakrol flesh had a suppressive effect on development of atopic dermatitis-like lesions in picryl chloride-treated NC/Nga mice. The dietary kakrol flesh water extract alleviated the development of skin lesions in ears accompanied by lower IgE levels and inflammatory cytokines levels in serum. These results indicate that the water extract of kakrol flesh might have therapeutic potential for allergic responses in vitro and in vivo.

Dietary flavones suppresses IgE and Th2 cytokines in OVA-immunized BALB/c mice.

BACKGROUND: The flavonoids are a diverse family of chemicals commonly found in fruits and vegetables. Previously, we have shown that the two flavones, chrysin and apigenin could suppress the expression of the high affinity IgE receptor FcepsilonRI in human basophilic KU812 cells. We also demonstrated that dietary apigenin decreased IgE level in C57BL/6N mice sera. AIM OF THE STUDY: To evaluate the anti-allergic effect of the two flavones in vivo, we evaluated the effect of the two flavones, chrysin and apigenin, on the immune system in BALB/c mice sensitized with ovalbumin (OVA). METHODS: Mice were fed experimental diets containing either of the flavones for 3 weeks and immunized with OVA. After the experimental feeding period, measurement of Igs concentration in the mice sera was performed using a sandwich ELISA. Cytokines expression in mice sera was assessed using a cytokine array. Furthermore, cytokines mRNA levels in spleen lymphocytes from mice sensitized with OVA were measured by RT-PCR. RESULTS: The total IgE level in mice fed one of the two flavones were suppressed, whereas levels of IgG, IgM, and IgA were not affected. The production of interleukin (IL)-4, which is known as one of Th2 cytokines and regulates the production of IgE, was down-regulated by the chrysin or the apigenin diet. Moreover, OVA-induced mRNA expression of Th2 cytokines in spleen lymphocytes from mice sensitized with OVA, such as IL-4 and IL-13 were down-regulated by the chrysin or the apigenin diet. CONCLUSIONS: The results suggest that the diet containing one of the two flavones might suppress the up-regulation of serum IgE induced by OVA-immunization through the suppression of Th2-type immune response.