ABSTRACT
Objective: To evaluate the immunomodulatory effects of rice bran hydrolysates on cultured immune cells and their underlying mechanism. Methods: Rice bran hydrolysates were prepared from pigmented rice (Oryza sativa L.) by hydrothermolysis and protease digestion. Rice bran hydrolysates were assayed for phenolic content and antioxidant activity. Cell proliferation of Jurkat, THP-1 and peripheral blood mononuclear cells (PBMC) was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Chemotaxis was evaluated by transwell chamber methods. Immunoadherence of THP-1 was performed on cultured human umbilical vein endothelial cells (HUVEC). Cytokine released from PBMC was measured by ELISA assay kits. Lymphocyte-mediated cytotoxicity was carried out on KKU-452 cells. Proteins associated with immunomodulation were analyzed by Western immunoblotting assay. Results: Rice bran hydrolysates were rich in phenolic compounds, such as ferulic acid, catechin, quercetin, and quercetin glycosides. Rice bran hydrolysates suppressed phytohemagglutinin (PHA)-stimulated proliferation of PBMC and Jurkat cells, chemotaxis of Jurkat and THP-1 cells, and immunoadherence of THP-1 on HUVEC cultured cells. The cellular mechanism of rice bran hydrolysates involved the activation of AMPK as well as suppression of mTOR, NF-κB and VCAM-1. Rice bran hydrolysates potentiated PBMC on the PHA-stimulated release of IL-2, TNF-α, and IL-4, and enhanced PHA-induced non-MHC-restricted cytotoxicity on KKU-452 cancer cells. Conclusions: The immunomodulatory effect of phytochemicals derived from rice bran hydrolysates suggests its therapeutic potential for further investigation.
ABSTRACT
Aim of Study: Cholangiocarcinoma (CCA) is an aggressive cancer with considerable metastatic potential. Various cytokines secreted by tumor cells or cells in the tumor environment can promote the metastasis of CCA. The aim of the present study was to investigate the effect of myricetin on the inhibition of cytokine-induced migration and invasion and the associated cellular mechanisms in human CCA cells. Materials and Methods: CCA KKU-100 cells were treated with a pro-inflammatory cytokine mixture consisting of interleukin-6, interferon-γ, and tumor necrosis factor-α. The migratory and invasive ability of KKU-100 cells were determined using a wound-healing assay and transwell invasion assay. The effect of myricetin on cytokine-induced STAT3 activation in CCA cells was determined using Western blot analysis. The real-time polymerase chain reaction was performed to determine messenger RNA expression. Results: Myricetin significantly inhibited cytokine-induced migration and invasion of KKU-100 cells. Detailed molecular analyses revealed that myricetin suppressed the activation of the STAT3 pathway, evidently by a decrease of the active phospho-STAT3 protein expression after myricetin treatment. The cytokine-mediated upregulation of metastasis- and inflammatory-associated genes, which are downstream genes of STAT3 including the intercellular adhesion molecule-1, matrix metalloproteinase-9, inducible nitric oxide synthase, and cyclo-oxygenase 2 (COX-2), were also significantly abolished by myricetin treatment. Moreover, the anti-migratory and anti-invasive activities of a widely prescribed COX inhibitor, indomethacin, were also revealed. Conclusion: This finding reveals the anti-metastatic effect of myricetin against CCA cells which is mediated partly through suppression of the STAT3 pathway. This compound could be potentially useful as a therapeutic agent against CCA