J Bacon

Dual action of sulforaphane in the regulation of thioredoxin reductase and thioredoxin in human HepG2 and Caco-2 cells.

We have previously demonstrated that sulforaphane is a potent inducer for thioredoxin reductase in HepG2 and MCF-7 cells (Zhang et al. Carcinogenesis 2003, 24, 497-503; Wang et al. J. Agric. Food Chem. 2005, 53, 1417-1421). In this study, we have shown that sulforaphane is not only an inducer for thioredoxin reductase but also an inducer for its substrate, thioredoxin in HepG2, and undifferentiated Caco-2 cells. Sulforaphane acts at two levels in the regulation of thioredoxin reductase/thioredoxin system by the upregulation of the expression of both the enzyme and the substrate. In human hepatoma HepG2 cells, sulforaphane induced thioredoxin reductase mRNA and protein by 4- and 2-fold, respectively, whereas thioredoxin mRNA was induced 2.9-fold and thioredoxin protein was unchanged in whole cell extracts, but an increase in nuclear accumulation (1.8-fold) was observed. Moreover, the induction of thioredoxin reductase was found faster than that of thioredoxin. The effects of PI3K and MAPK kinase inhibitors, LY294002, PD98059, SP600125, and SB202190, have been investigated on the sulforaphane-induced expression of thioredoxin reductase and thioredoxin. PD98059 abrogates the sulforaphane-induced thioredoxin reductase at both mRNA and protein levels in HepG2 cells, although other inhibitors were found less effective. However, both PD98059 and LY294002 significantly decrease thioredoxin mRNA expression in HepG2 cells. None of the inhibitors tested were able to modulate the level of expression of either thioredoxin reductase mRNA or protein in Caco-2 cells suggesting that there are cell-specific responses to sulforaphane. In summary, the dietary isothiocyanate, sulforaphane, is important in the regulation of thioredoxin reductase/thioredoxin redox system in cells.

Anticancer activity of olive oil hydroxytyrosyl acetate in human adenocarcinoma Caco-2 cells.

The anticancer activity of hydroxytyrosyl acetate (HTy-Ac) has been studied in human colon adenocarcinoma cells. Gene expression of proteins involved in cell cycle (p21, p53, cyclin B1, and cyclin G2) and programmed cell death (BNIP3, BNIP3L, PDCD4, and ATF3), as well as phase I and phase II detoxifying enzymes CYPA1 and UGT1A10, were evaluated by reverse transcription polymerase chain reaction after 24 h of exposure of Caco-2/TC7 cells to 5, 10, and 50 μM of HTy-Ac. The results show that HTy-Ac inhibited cell proliferation and arrested cell cycle by enhancing p21 and CCNG2 and lowering CCNB1 protein expression. HTy-Ac also affected the transcription of genes involved in apoptosis up-regulating of BNIP3, BNIP3L, PDCD4, and ATF3 and activating caspase-3. In addition, HTy-Ac also up-regulated xenobiotic metabolizing enzymes CYP1A1 and UGT1A10, thus enhancing carcinogen detoxification. In conclusion, these results highlight that HTy-Ac has the potential to modulate biomarkers involved in colon cancer.