Abstract
(−)-Epigallocatechin-3-gallate (EGCG), one of the main constituents of green tea, has been reported to function as an antioxidant with chemopreventive potential. In contrast, we have recently reported that EGCG enhanced pro-matrix metalloproteinase (MMP)-7 in HT-29 human colon cancer cells via spontaneous superoxide generation. In the present study, we examined the effects of dietary antioxidants on both spontaneous and EGCG-upregulated proMMP-7 production in HT-29 cells. Benzyl isothiocyanate (BITC), curcumin (CUR), gallic acid (GA), and N-acetyl-L-cysteine (NAC) reduced that production, while each alone did not have any effect on spontaneous production. None of the dietary factors suppressed EGCG-induced hydrogen peroxide generation in the media tested, whereas BITC, GA, and NAC inhibited the EGCG-enhanced activator protein (AP)-1 transcription activity by 126%, 77%, and 97%, respectively. Although CUR abolished the EGCG-upregulated MMP-7 mRNA expression, it unexpectedly enhanced the AP-1 activity by 502%, suggesting that this factor may disrupt the MMP-7 mRNA stabilization process. Together, our results indicate that dietary antioxidants modulate EGCG-induced MMP-7 production through different mechanisms.
