br The apoptotic mechanism involved
The apoptotic mechanism involved in the decrease of tumor growth in mice fed with chickpea with high selenium concentrations differed due to the presence of isoflavonoids. In contrast to previous reports, isoflavones in this study increased expression of Bcl2 (Han et al., 2015). Isoflavonoids extracted from chickpea sprouts decreased the expression of antiapoptotic gene BCL2 and increased the expression the CASP9, inducing the apoptosis of human breast cancer cells (Chen et al., 2015). In this study, isoflavonoids-enriched diets, with low or high selenium content, increased the expression of casp9 compared to diet not en-riched with isoflavonoids. Other flavonoids such as tectochrysin also lead to apoptotic cell death in colon cancer cells through activation of death receptors expression (Park et al., 2015).
Based on these results, we have proposed that isoflavonoids and selenium contained in the diets did not exert synergistic effects in the induction of the intrinsic apoptotic pathway in colon cancer. On the contrary, when isoflavonoids and selenium were present in the diets separately, they induced the apoptosis of cancer cells through the in-trinsic pathway, mainly due to the inhibition of Bcl2 protein expression (Fig. 6A). The effect of dietary selenium in the inhibition of BCL2 and induction of apoptosis has been previously observed in colon and breast cancer cells (Li, et al., 2013; Hui et al., 2014; Yuan et al., 2016).
The increase in the expression of Fas protein, due to the effect of a diet with a high content of selenium and isoflavonoids (GSe1), induced apoptosis of colon cancer cells through the activation of the extrinsic pathway (Fig. 6B). HIF1a mediates the AR-13324 of cells and tissues to low oxygen concentrations and its gene translation was favored when high doses of isoflavonoids and selenium were consumed (GSe1). HIF1a
Fig. 5. Effects of sprouted chickpea diets containing different amounts of selenium and isoflavonoids on expression profiles of apoptotic genes and protein in HT-29 RFP cells xenografted in immune suppressed male mice at day 21 post-inoculation. (A) Heat map display showing relative expression levels of 92 genes. (B) Relative expression plot showing fold change of the expression levels. (C) Protein expression profile in western analysis. GAPDH and HPRT1 were used as selected controls for data normalization. In the upper scale, moderate expression level (as determined by Delta CT plus value) is shown as black, while lower expression is indicated by the increasing shade of green and higher expression e increasing shade of red. GC: Germinated control; GSe1: High content of selenium and isoflavonoids; GSe2: High content of selenium without presence of isoflavonoids.
overexpresion has been positively correlated to anticancer effects (Lim et al., 2006).
We showed that glutathione peroxidase and thioredoxin reductase activities increased with high selenium intake with or without iso-flavonoids. In a previous study, rats fed Se-enriched diet fortified with selenized mushroom (1µg Se/g diet) increased GPx activity by 1.77-fold compared to the control diet, but TrxR activity was not affected (Maseko, Howell, Dunshea, & Ng, 2014). Moreover, mice fed with a Kaiware radish sprouts-based diet containing 2.0 Se µg/g, increased GPx activity by 127% and decreased the formation of aberrant crypt loci in the colon of mice compared to control (Yoshida et al., 2007).
We observed that TRIGL, LDL-C, HDL-C and CHOL levels were dif-ferent in mice xenografted with colon cancer cells fed with diets en-riched with selenium. High intake of dietary selenium increased TRIGL, LDL-C and CHOL to levels closer to the basal as an indicator of the reduction of lipid consumption by cancer cells. Interestingly, it has been shown that compounds that regulate cholesterol levels could induce cancer cell apoptosis and exhibit important antitumor activity (Huang,
& Freter, 2015). Previous studies showed that high selenium con-centrations have been positively associated with elevated levels of CHOL, TRIGL, and LDL-C (Bleys et al., 2008; Stranges et al., 2010; Stranges et al., 2011; Yu, Zhang, Lu, & Zhang, 2014; Ju et al., 2017). In this study, we hypothesized that selenium decreased lipid oxidation mediated by glutathione peroxidase and in turn decreased the cellular
redox state (Fig. 6C). In a previous study, it has been observed, that selenium enhanced glutathione peroxidase activity and inhibited lipid peroxidation in human hepatocellular carcinoma cell lines (HCC); it also increased glutathione peroxidase expression and reduced nodule growth in a rat hepatocarcinogenesis model (Rohr-Udilova et al., 2012).