Curcumin (CUR), a major bioactive polyphenolic component from turmeric curry, Curcuma longa, has been shown to be a potent anti-cancer phytochemical with well-established anti-inflammatory and anti-oxidative stress effects. Chromatin remodeling-related epigenetic regulation has emerged as an important mechanism of carcinogenesis, chemoprevention, and chemotherapy. CUR has been found to inhibit histone acetyltransferase activity, and it was also postulated to be a potential DNA methyltransferase (DNMT) and histone deacetylase (HDAC) inhibitor. In this study, we show that when human prostate LNCaP cells were treated with CUR, it led to demethylation of the first 14 CpG sites of the CpG island of the Neurog1 gene and restored the expression of this cancer-related CpG-methylation epigenome marker gene. At the protein level, CUR treatment had limited effects on the expression of epigenetic modifying proteins MBD2, MeCP2, DNMT1, and DNMT3a. Using ChIP assay, CUR decreased MeCP2 binding to the promoter of Neurog1 dramatically. CUR treatment showed different effects on the protein expression of HDACs, increasing the expression of HDAC1, 4, 5, and 8 but decreasing HDAC3. However, the total HDAC activity was decreased upon CUR treatment. Further analysis of the tri-methylation of histone 3 at lysine 27 (H3K27me3) showed that CUR decreased the enrichment of H3K27me3 at the Neurog1 promoter region as well as at the global level. Taken together, our present study provides evidence on the CpG demethylation ability of CUR on Neurog1 while activating its expression, suggesting a potential epigenetic modifying role for this phytochemical compound in human prostate cancer cells.

Curcumin (diferuloylmethane), a polyphenolic compound, is a component of Curcuma longa, commonly known as turmeric. It is a well-known anti-inflammatory, anti-oxidative, and anti-lipidemic agent and has recently been shown to modulate several diseases via epigenetic regulation. Many recent studies have demonstrated the role of epigenetic inactivation of pivotal genes that regulate human pathologies, such as neurocognitive disorders, inflammation, obesity, and cancers. Epigenetic changes involve changes in DNA methylation, histone modifications, or altered microRNA expression patterns which are known to be interconnected and play a key role in tumor progression and failure of conventional chemotherapy. The majority of epigenetic changes are influenced by lifestyle and diets. In this regard, dietary phytochemicals as dietary supplements have emerged as a promising source that are able to reverse these epigenetic alterations, to actively regulate gene expression and molecular targets that are known to promote tumorigenesis, and also to prevent age-related diseases through epigenetic modifications. There have been several studies which reported the role of curcumin as an epigenetic regulator in neurological disorders, inflammation, and in diabetes apart from cancers. The epigenetic regulatory roles of curcumin include (1) inhibition of DNA methyltransferases (DNMTs), which has been well defined from the recent studies on its function as a DNA hypomethylating agent; (2) regulation of histone modifications via regulation of histone acetyltransferases (HATs) and histone deacetylases (HDACs); and (3) regulation of micro RNAs (miRNA). This review summarizes the current knowledge on the effect of curcumin in the treatment and/or prevention of inflammation, neurodegenerative diseases, and cancers by regulating histone deacetylases, histone acetyltransferases, and DNA methyltransferases.

The role of phytochemicals in preventive and therapeutic medicine is a major area of scientific research. Several studies have illustrated the mechanistic roles of phytochemicals in Nrf2 transcriptional activation. The present study aims to examine the importance of the transcription factor Nrf2 by treating peritoneal macrophages from Nrf2+/+ and Nrf2–/– mice ex vivo with phenethyl isothiocyanate (PEITC) and curcumin (CUR). The peritoneal macrophages were pretreated with the drugs and challenged with lipopolysaccharides (LPSs) alone and in combination with PEITC or CUR to assess their anti-inflammatory and antioxidative effects based on gene and protein expression in the treated cells. LPS treatment resulted in an increase in the expression of inflammatory markers such as cycloxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in both Nrf2+/+ and Nrf2–/– macrophages, detected by quantitative polymerase chain reaction (qPCR). Nrf2+/+ macrophages treated with PEITC and CUR exhibited a significant decrease in the expression of these anti-inflammatory genes along with an increase in the expression of hemeoxygenase-1 (HO-1), which is an antioxidative stress gene downstream of the Nrf2 transcription factor battery. Although there was no significant decrease in the expression of the anti-inflammatory genes or an increase in HO-1 expression in Nrf2–/– macrophages treated with either PEITC or CUR, there was a significant decrease in the protein expression of COX-2 and an increase in the expression of HO-1 in Nrf2+/+ macrophages treated with PEITC compared to that with CUR treatment. No significant changes were observed in the macrophages from knockout animals. Additionally, there was a significant decrease in LPS-induced IL-6 and TNF-α production following PEITC treatment compared with that following CUR in Nrf2+/+ macrophages, whereas no change was observed in the macrophages from knockout animals. The results from qPCR, western blot, and ELISA analyses in macrophages from Nrf2+/+ and Nrf2 –/– mice indicate that Nrf2 plays an important role in the anti-inflammatory and antioxidative effects of PEITC and CUR, as observed by their decreased activities in Nrf2–/– macrophages.

Ginseng has long been used in the Asian Countries for more than 2,000 years. Currently, in the “Western World or Western Medicines”, many reports have indicated that they have used herbal medicines, and Ginseng is one of the most popular herbs. Several recent reports have indicated that the antioxidant / anti-oxidative stress activities of ginseng play a role in the benefits of ginseng, however the precise mechanism is lacking. The antioxidant response element (ARE) is a critical regulatory element for the expression of many anti-oxidant enzymes and phase II/III drug metabolizing/transporter genes, mediated by the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). The aim of this study was to examine the potential activation and synergism of Nrf2-ARE-mediated transcriptional activity between three common ginsenosides present in ginseng, ginsenoside Rb1 (Rb1), ginsenoside Rg1 (Rg1) and ginsenoside 20(S)-protopanaxytriol (20S). We tested whether these ginsenosides and their combinations, could induce Nrf2-ARE activities in HepG2-C8 cells with stably transfected ARE luciferase reporter gene. Cell proliferation, antioxidant and ARE activities, western blotting of Nrf2 protein and qPCR of mRNA of Nrf2 were conducted for Rb1, Rg1 and 20S as well as the combinations of 20S with Rb1 or Rg1. To determine the combination effects, the combination index (CI) was calculated. Rb1 and Rg1 are relatively non-toxic to the cells, while 20S at 50 μM or above significantly inhibited the cell proliferation. Rb1, Rg1 or 20S induced total antioxidant activity and ARE activity in a concentration-dependent manner. Furthermore, combinations of 20S with either Rb1 or Rg1 induced total antioxidant and ARE activity synergistically. Induction of Nrf2 protein and mRNA were also found to be synergistic with the combination treatments. In summary, in this study, we show that ginsenosides Rb1, Rg1 and 20S possess antioxidant activity, transcriptionally activating ARE as well as potential of synergistic activities. The Nrf2-ARE-mediated antioxidant pathway could play a role for the overall anti-oxidative stress activities, which could be important for ginseng's health beneficial effects such as cancer chemopreventive activities.

Indole-3-carbinol (I3C) found abundantly in crucifers has been shown to possess anti-cancer effects. The present study aims to examine the chemopreventive effects and the molecular mechanism of I3C, particularly the anti-oxidative stress pathway regulated by nuclear erythroid related factor 2 (Nrf2). HepG2-C8-ARE-luciferase cells were used for Nrf2-ARE activity. TRAMP C1 cells were used to investigate the effects of I3C on Nrf2-mediated genes. To test the chemopreventive efficacy of I3C, transgenic adenocarcinoma of mouse prostate (TRAMP) mice were fed with 1% I3C supplemented diet for 12 or 16 wk. The expression of Nrf2 and its downstream target genes, cell cycle and apoptosis genes were investigated using quantitative real-time polymerase chain reaction (qPCR). The protein expressions of these biomarkers were also investigated using Western blotting. I3C induced antioxidant response element (ARE)-luciferase activity in a dose-dependent manner. Treatments of TRAMP C1 cells with I3C also resulted in the induction of Nrf2-mediated genes. I3C significantly suppressed the incidence of palpable tumor and reduced the genitourinary weight in TRAMP mice. Western blots and qPCR analyses of prostate tissues showed that I3C induced the expression of Nrf2, NAD(P)H quinine oxidoreductase 1 (NQO-1) as well as cell cycle and apoptosis related biomarkers in I3C-fed TRAMP mice. This study demonstrated that the effectiveness of I3C as prostate cancer chemoprevention agent via up-regulation of a novel Nrf2-mediated anti-oxidative stress pathway.