Tammy M. Bray

Induction of regulatory T cells by green tea polyphenol EGCG

Regulatory T cells (Treg) are critical in maintaining immune tolerance and suppressing autoimmunity. The transcription factor Foxp3 serves as a master switch that controls the development and function of Treg. Foxp3 expression is epigenetically regulated by DNA methylation, and DNA methyltransferase (DNMT) inhibitors can induce Foxp3 expression in naive CD4(+) T cells. We showed that EGCG, a major green tea polyphenol, could act as a dietary DNMT inhibitor, and induced Foxp3 and IL-10 expression in CD4(+) Jurkat T cells at physiologically relevant concentrations in vitro. We further showed that mice treated with EGCG in vivo had significantly increased Treg frequencies and numbers in spleen and lymph nodes and had inhibited T cell response. Induction of Foxp3 expression correlated with a concomitant reduction in DNMT expression and a decrease in global DNA methylation. Our data suggested that EGCG can induce Foxp3 expression and increase Treg frequency via a novel epigenetic mechanism. While the DNMT inhibitory effects of EGCG was not as potent as pharmacologic agents such as 5-aza-2-deoxycytidine, the ability of dietary agents to target similar mechanisms offers opportunities for potentially sustained and longer-term exposures with lower toxicity. Our work provides the foundation for future studies to further examine and evaluate dietary strategies to modulate immune function.

Differential effects of whole soy extract and soy isoflavones on apoptosis in prostate cancer cells.

Previous studies have suggested that soy isoflavones exert anticarcinogenic effects against prostate cancer. We propose that soy extracts, containing a mixture of soy isoflavones and other bioactive components, would be a more potent chemo-preventive agent than individual soy isoflavones. We compared the apoptotic effects of whole soy extracts and individual soy isoflavones, genistein and daidzein, on prostate cancer cells. The soy extract contained 50% w/w of total isoflavones with approximately 1:5.5:3.5 ratios of genistin, daidzin and glycitin, respectively. Benign prostate hyperplasia (BPH-1), LnCap and PC3 cells were treated with varying concentrations of soy extract, genistein or daidzein and analyzed for cell cycle alterations and induction of apoptosis. At equal concentrations (25 μmol/L), soy extract induced a significantly higher percentage of cells undergoing apoptosis than genistein or daidzein (P < 0.001). No significant changes in cell cycle arrest or apoptosis were observed in non-cancerous BPH-1 cells treated with soy extract, suggesting that the effects of soy extract may be tumor cell specific. On the contrary, both genistein and daidzein induced apoptosis in BPH-1 cells, suggesting that individual isoflavones may have cytotoxicity in non-cancerous cells. Soy extracts also increased Bax expression in PC3 cells, but no significant changes in nuclear factor κB (NFκB) activation were detected, suggesting that the induction of apoptosis was independent of the NFκB pathway. Food products that bear a combination of active compounds may be more efficacious and safer as chemo-preventive agents than individual compounds. This ‘whole-food’-based approach is significant for the development of public health recommendations for prostate cancer prevention.

Induction of proinflammatory response in prostate cancer epithelial cells by activated macrophages

Emerging evidence indicates that chronic inflammation plays an important role in prostate carcinogenesis. Yet to date the precise molecular and cellular mechanisms linking inflammation to carcinogenesis remains unclear. The purpose of this study was to determine the local contribution of prostate epithelial cells to the inflammatory process. We characterized the inflammatory response elicited directly by prostate epithelial cells using an in vitro culture system in which androgen-dependent LNCaP prostate cancer epithelial cells were exposed to conditioned media from LPS-activated THP-1 macrophages. Upon exposure to activated macrophage conditioned media, LNCaP cells elicited a local proinflammatory response, as evidenced by NFkappaB activation, and the production of proinflammatory cytokines TNFalpha, IL-1beta, and IL-6. Furthermore, we observed a significant upregulation of the adhesion molecule VCAM-1 and nuclear estrogen receptor alpha (ERalpha) two biomarkers that correlate with tumor immune evasion and tumor progression. Our results suggest that prostate epithelial cells may play a significant role in sustaining and amplifying the inflammation process through NFkappaB activation and local production of proinflammatory cytokines that results in the recruitment and activation of additional immune cells in the prostate. At the same time, increased expression of VCAM-1 and ERalpha in prostate epithelial cells upon exposure to inflammatory conditions highlights the potential link between chronic inflammation and its involvement in promoting prostate cancer carcinogenesis.

Dietary soy and tea mitigate chronic inflammation and prostate cancer via NFκB pathway in the Noble rat model

Chronic inflammation and nuclear factor-kappa B (NFκB) have been implicated in prostate cancer development; thus, dietary factors that inhibit NFκB may serve as effective chemo-preventative agents. Prostate cancer risk is significantly lower in Asian countries compared to the United States, which has prompted interest in the potential chemopreventative action of Asian dietary components such as soy and green tea. This study examined the effects of dietary soy and tea on NFκB activation and inflammation in vivo using a hormone-induced rat model for prostate cancer. Male Noble rats implanted with estradiol and testosterone were divided into 4 dietary groups: control, soy, tea, or soy+tea. NFκB activation and inflammatory cytokines were measured post implantation. The combination of soy and tea suppressed NFκB p50 binding activity and protein levels via induction of IκBα. Soy and tea also decreased prostate inflammatory infiltration, increased Bax/BcL2 ratio and decreased protein expression of tumor necrosis factor-alpha, interleukin (IL)-6 and IL-1β compared to control. Soy and tea attenuated prostate malignancy by decreasing prostate hyperplasia. These effects were not apparent in groups treated with soy or tea alone. The ongoing in vivo studies thus far suggest that combination of foods, such as soy and tea, may inhibit hormone-induced proinflammatory NFκB signals that contribute to prostate cancer development.

Anti-inflammatory activity of soy and tea in prostate cancer prevention

Prostate cancer is the leading cancer-related cause of death for men in the USA. Prostate cancer risk is significantly lower in Asian countries compared with the USA, which has prompted interest in the potential chemo-preventive action of soy and green tea that are more predominant in Asian diets. It has been proposed that chronic inflammation is a major risk factor of prostate cancer, acting as both an initiator and promoter. Specifically, the nuclear factor-kappa B (NF-κB) pathway has been implicated as an important mediator between chronic inflammation, cell proliferation and prostate cancer. Dietary factors that inhibit inflammation and NF-κB may serve as effective chemo-preventive agents. Recent studies have demonstrated that soy and green tea have anti-inflammatory properties, and may have the potential to block the inflammatory response during cancer progression. This minireview discusses the relationship between chronic inflammation and prostate cancer, emphasizing on the significance of NF-κB, and further explores the anti-inflammatory effects of soy and green tea. Finally, we propose that dietary strategies that incorporate these bioactive food components as whole foods may be a more effective means to target pathways that contribute to prostate cancer development.

Effect of conjugated linoleic acid on Delta-5 desaturase activity in yeast transformed with fungal Delta-5 desaturase gene

Conjugated linoleic acid (CLA), a mixture of positional and geometric isomers derived from linoleic acid (LA:Δ9, 12-18:2), has been shown to exhibit various biological functions based on studies using cell culture and animal models. It was postulated that the beneficial effects of CLA were exerted through suppression of production of arachidonic acid (AA;Δ5,8,11,14-20:4) and consequently, production of pro-inflammatory eicosanoids. In this study, we used the bakers yeast, Saccharomyces cerevisiae, transformed with fungal Δ5-desaturase gene as a model, to study whether CLA affects the activity of Δ5-desaturase, a rate-limiting step which converts dihomo-γ-linolenic acid (DGLA;Δ8,11, 14-20:3) to AA. The activity of Δ5-desaturase was examined in the transformed yeast incubated in a medium supplemented with DGLA and one of four different CLA isomers (c9, t11−, t10, c12−, c9, c11− and t9, t11). Results show that all four isomers were taken up readily by the yeast, and all of them suppressed the conversion of DGLA to AA. The degree of suppression, which varied significantly among four isomers was modulated by the level of CLA isomers added in the medium. Since portions of these CLA isomers could be converted to form Δ5-CLA metabolites (Δ5, c9, t11−, Δ5, t10, c12−, Δ5, c9, c11− and Δ5, t9, t11-18:3), it is suggested that CLA suppressed the Δ5-desaturation of DGLA to AA through substrate competition between DGLA and CLA isomers. (Mol Cell Biochem 265: 11–18, 2004)

Cigarette Smoking Increases Human Vitamin E Requirements as Estimated by Plasma Deuterium-Labeled CEHC

Abstract: Cigarette smoking (CS) is a well‐described oxidant burden in humans. We hypothesized that CS would accelerate α‐tocopherol (α‐T) utilization leaving less for metabolite (CEHC) production. After labeled α‐T consumption (75 mg each of d3‐RRR‐α‐TAc and d6‐all‐rac‐α‐TAc) by smokers and nonsmokers (n= 10/group), CS increased α‐T disappearance and decreased plasma and urinary CEHCs. Plasma d3/d6‐α‐T ratios were approximately 1.4 during supplementation and approximately 2 from days 5 to 17. d3/d6‐α‐CEHC ratios were on average 0.29 ± 0.05, confirming that all‐rac‐α‐tocopherol is metabolized more efficiently. CEHC may be a good marker of vitamin E status, and smokers may have an increased vitamin E requirement.

Antioxidants, NFκB Activation, and Diabetogenesis (44445)

Although many risk factors can trigger the development of insulin-dependent diabetes (IDDM), it is likely that reactive oxygen species (ROS) play a central role in β-cell death and disease progression. This review will focus on the role of antioxidant defense systems in the susceptibility to IDDM and on ROS as cellular messengers that regulate the expression of genes leading to β-cell death. Accumulating evidence indicates that increased antioxidant defense systems reduce the susceptibility to IDDM in animal models or in human study. It is suggested that pancreas-specific ROS productions play a critical role in signaling the cellular autoimmune/inflammatory response by activating the transcription factor, NFκB. Various diabetogenic factors may lead to an increase in ROS production, which activates the redox-sensltive NFκB. This may be the initial event for the expression of cytokines and chemotactlc agents involved in the autoimmune/inflammatory response. It is believed that this cascade results in a cyclic amplification of ROS and eventually leads to apoptosls and/or necrosis of β cells. The specificity of antioxidants to inhibit NFκB activation and the hyperglycemic response emphasizes the importance of selectivity in antioxidant therapy. Research in this area will contribute significantly to our understanding of the cellular and mechanistic role of ROS in the etiology of IDDM and will lead to the development of better prevention strategies.