Involvement of ERK and protein tyrosine phosphatase signaling pathways in EGCG-induced cyclooxygenase-2 expression in Raw 264.7 cells

The potential of EGCG in modulating the oral-gut axis microbiota for treating inflammatory bowel disease

Inflammatory bowel disease (IBD) is a recurrent chronic intestinal disorder that includes ulcerative colitis (UC) and Crohn's disease (CD). Its pathogenesis involves intricate interactions between pathogenic microorganisms, native intestinal microorganisms, and the intestinal immune system via the oral-gut axis. The strong correlation observed between oral diseases and IBD indicates the potential involvement of oral pathogenic microorganisms in IBD development. Consequently, therapeutic strategies targeting the proliferation, translocation, intestinal colonization and exacerbated intestinal inflammation of oral microorganisms within the oral-gut axis may partially alleviate IBD. Tea consumption has been identified as a contributing factor in reducing IBD, with epigallocatechin gallate (EGCG) being the primary bioactive compound used for IBD treatment. However, the precise mechanism by which EGCG mediates microbial crosstalk within the oral-gut axis remains unclear. In this review, we provide a comprehensive overview of the diverse oral microorganisms implicated in the pathogenesis of IBD and elucidate their colonization pathways and mechanisms. Subsequently, we investigated the antibacterial properties of EGCG and its potential to attenuate microbial translocation and colonization in the gut, emphasizing its role in attenuating exacerbations of IBD. We also elucidated the toxic and side effects of EGCG. Finally, we discuss current strategies for enhancing EGCG bioavailability and propose novel multi-targeted nano-delivery systems for the more efficacious management of IBD. This review elucidates the role and feasibility of EGCG-mediated modulation of the oral-gut axis microbiota in the management of IBD, contributing to a better understanding of the mechanism of action of EGCG in the treatment of IBD and the development of prospective treatment strategies.

Nutritional Modulation of Immune Function: Analysis of Evidence, Mechanisms, and Clinical Relevance

It is well-established that the nutritional deficiency or inadequacy can impair immune functions. Growing evidence suggests that for certain nutrients increased intake above currently recommended levels may help optimize immune functions including improving defense function and thus resistance to infection, while maintaining tolerance. This review will examine the data representing the research on prominent intervention agents n-3 polyunsaturated fatty acids (PUFA), micronutrients (zinc, vitamins D and E), and functional foods including probiotics and tea components for their immunological effects, working mechanisms, and clinical relevance. Many of these nutritive and non-nutritive food components are related in their functions to maintain or improve immune function including inhibition of pro-inflammatory mediators, promotion of anti-inflammatory functions, modulation of cell-mediated immunity, alteration of antigen-presenting cell functions, and communication between the innate and adaptive immune systems. Both animal and human studies present promising findings suggesting a clinical benefit of vitamin D, n-3 PUFA, and green tea catechin EGCG in autoimmune and inflammatory disorders, and vitamin D, vitamin E, zinc, and probiotics in reduction of infection. However, many studies report divergent and discrepant results/conclusions due to various factors. Chief among them, and thus call for attention, includes more standardized trial designs, better characterized populations, greater consideration for the intervention doses used, and more meaningful outcome measurements chosen.

Antinociceptive effects of dezocine on complete Freund's adjuvant-induced inflammatory pain in rats

Inflammatory pain is known to severely impact the life quality of patients. Notably, dezocine is widely used for the treatment of pain. Therefore, the current study aimed to examine the effects of dezocine on a complete Freund's adjuvant (CFA)-induced inflammatory pain model in rats and to investigate the possible underlying molecular mechanisms. Rats were randomly divided into three groups, including the control, CFA and dezocine+CFA groups, and then subcutaneously injected with 100 µl saline, subcutaneously injected with 100 µl CFA or pretreated with 1 ml dezocine (0.4 µg/kg) at 30 min before CFA injection in the plantar surface of right hind paw, respectively. The paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were measured with a dynamic plantar esthesiometer at 1 day before and 6 h after CFA injection. The ipsilateral lumbar spinal cords of all the rats were harvested for detecting the expression profiles of phosphorylated (p)-p65, p-extracellular signal-regulated kinase 1/2 (p-ERK1/2), cyclooxygenase-2 (COX-2), interleukin (IL)-1β and tumor necrosis factor (TNF)-α by western blot analysis and/or reverse transcription-quantitative polymerase chain reaction. In addition, prostaglandin E2 (PGE2) expression was determined by enzyme-linked immunosorbent assay. Compared with the control group, CFA-induced peripheral inflammation downregulated the PWT and PWL values of rats, which were significantly alleviated by dezocine treatment. Furthermore, the protein levels of p-p65, p-ERK1/2, COX-2, PGE2, IL-1β and TNF-α were significantly upregulated following CFA injection, while they were suppressed by dezocine pretreatment. In conclusion, the analgesic effect of dezocine on inflammatory pain induced by CFA may be associated with the inhibition of the spinal ERK1/2-COX-2 pathway.

Anti-inflammatory activity of a sulfated polysaccharide isolated from an enzymatic digest of brown seaweed Sargassum horneri in RAW 264.7 cells

BACKGROUND/OBJECTIVES

Sargassum horneri is an edible brown alga that grows in the subtidal zone as an annual species along the coasts of South Korea, China, and Japan. Recently, an extreme amount of S. horneri moved into the coasts of Jeju Island from the east coast of China, which made huge economic and environmental loss to the Jeju Island. Thus, utilization of this biomass becomes a big issue with the local authorities. Therefore, the present study was performed to evaluate the anti-inflammatory potential of crude polysaccharides (CPs) extracted from S. horneri China strain in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells.

MATERIALS/METHODS

CPs were precipitated from S. horneri digests prepared by enzyme assistant extraction using four food-grade enzymes (AMG, Celluclast, Viscozyme, and Alcalase). The production levels of nitric oxide (NO) and pro-inflammatory cytokines, including tumor necrosis factor (TNF)-α and interleukin (IL)-1β were measured by Griess assay and enzyme-linked immunosorbent assay, respectively. The levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), nuclear factor (NF)-κB, and mitogen-activated protein kinases (MAPKs) were measured by using western blot. The IR spectrums of the CPs were recorded using a fourier transform infrared spectroscopy (FT-IR) spectrometer.

RESULTS

The polysaccharides from the Celluclast enzyme digest (CCP) showed the highest inhibition of NO production in LPS-stimulated RAW 264.7 cells (IC₅₀ value: 95.7 µg/mL). Also, CCP dose-dependently down-regulated the protein expression levels of iNOS and COX-2 as well as the production of inflammatory cytokines, including TNF-α and IL-1β, compared to the only LPS-treated cells. In addition, CCP inhibited the activation of NF-κB p50 and p65 and the phosphorylation of MAPKs, including p38 and extracellular signal-regulated kinase, in LPS-stimulated RAW 264.7 cells. Furthermore, FT-IR analysis showed that the FT-IR spectrum of CCP is similar to that of commercial fucoidan.

CONCLUSIONS

Our results suggest that CCP has anti-inflammatory activities and is a potential candidate for the formulation of a functional food ingredient or/and drug to treat inflammatory diseases.

In vitro immunomodulatory activity and in vivo anti-inflammatory and analgesic potential with gastroprotective effect of the Mediterranean red alga Laurencia obtusa

CONTEXT

Red algae have been recognized as a rich natural source of compounds possessing interesting biological and pharmacological activities.

OBJECTIVE

This work investigates anti-inflammatory, analgesic and gastroprotective activities of MeOH/CH₂Cl₂ crude extract and its fractions F1 (50% MeOH) and F2 (80% MeOH) from the whole alga plant Laurencia obtusa Hudson (Rhodomelaceae).

MATERIALS AND METHODS

Anti-inflammatory activity was evaluated in vitro using cytometric bead array (CBA) technology to follow up the secretion of tumour necrosis factor alpha (TNF-α) in lipopolysaccharide activated THP-1 monocytic cells at doses of 10-250 μg/mL and in vivo using carrageenan-induced paw oedema in Wistar rats at doses of 25, 50, 100 and 200 mg/kg. Crude extract and fractions were tested at the doses of 25, 50, 100 and 200 mg/kg for peripheral and central analgesic activity by acetic acid-induced writhing test and hot-plate method, respectively, in Swiss albino mice. Gastroprotective activity was evaluated using HCl/ethanol-induced gastric ulcer test in rats at doses of 25, 50, 100 and 200 mg/kg.

RESULTS

Crude extract, F1 and F2 showed an interesting inhibition of TNF-α secretion with IC₅₀ values of 25, 52 and 24 μg/mL, respectively, and a significant anti-inflammatory activity in vivo (p <  0.01), 3 h after carrageenan injection, the oedema inhibition was 55.37%, 52.18% and 62.86%, respectively, at the dose of 100 mg/kg. Furthermore, they showed a significant peripheral analgesic activity with 53.79%, 55.92% and 57.37% (p <  0.01) of writhing inhibition, respectively. However, no significant activity was found in the hot-plate test. An interesting gastroprotective effect was observed with crude extract and its fractions F1 and F2 with a gastric ulcer inhibition of 65.48%, 77.42% and 81.29%, respectively, at the dose of 50 mg/kg.

DISCUSSION AND CONCLUSION

These results suggest that L. obtusa might be used as a potential source of natural anti-inflammatory and analgesic agents with gastroprotective effect.

Vitamin A or E and a catechin synergize as vaccine adjuvant to enhance immune responses in mice by induction of early interleukin-15 but not interleukin-1β responses

Vitamins A and E and select flavonoids in the family of catechins are well-defined small molecules that, if proven to possess immunomodulatory properties, hold promise as vaccine adjuvants and various therapies. In an effort to determine the in vivo immunomodulatory properties of these molecules, we found that although mucosal and systemic vaccinations with a recombinant HIV-1BaL gp120 with either a catechin, epigallo catechin gallate (EGCG) or pro-vitamin A (retinyl palmitate) alone in a vegetable-oil-in-water emulsion (OWE) suppressed antigen-specific responses, the combination of EGCG and vitamin A or E in OWE (Nutritive Immune-enhancing Delivery System, NIDS) synergistically enhanced adaptive B-cell, and CD4(+) and CD8(+) T-cell responses, following induction of relatively low local and systemic innate tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) and IL-17, but relatively high levels of early systemic IL-15 responses. For induction of adaptive interferon-γ and TNF-α responses by CD4(+) and CD8(+) T cells, the adjuvant effect of NIDS was dependent on both IL-15 and its receptor. In addition, the anti-oxidant activity of NIDS correlated positively with higher expression of the superoxide dismutase 1, an enzyme involved in reactive oxygen species elimination but negatively with secretion of IL-1β. This suggests that the mechanism of action of NIDS is dependent on anti-oxidant activity and IL-15, but independent of IL-1β and inflammasome formation. These data show that this approach in nutritive vaccine adjuvant design holds promise for the development of potentially safer effective vaccines.

Is phytoestrogen intake associated with decreased risk of prostate cancer? A systematic review of epidemiological studies based on 17,546 cases

This study uses current epidemiological data to evaluate whether phytoestrogen intake is associated with a reduced risk of prostate cancer. We performed a random-effect meta-analysis of published data retrieved from PubMed, Web of Science, ProQuest, and CNKI, which was supplemented by a manual search of relevant references. Study quality was assessed using the Newcastle-Ottawa Scale (NOS). Subgroup analysis and meta-regression were performed to explore the source of heterogeneity. Sensitivity analysis was evaluated to assess the stability of the results. Egger's test and funnel plots were used to detect the existence of publication bias. We retrieved 507 papers, and 29 studies were ultimately confirmed as eligible. The meta-analysis showed that phytoestrogen intake was significantly associated with a reduced risk of prostate cancer, with an odds ratio (OR) of 0.77 (95% CI 0.66-0.88; I(2)  = 77.6%). The food/nutritional sources that were significantly associated with a reduced risk of prostate cancer included soy and soy products, tofu, legumes, daidzein, and genistein. Subgroup analysis indicated that the associations were significant among Asians and Caucasians, but not among Africans. Meta-regression revealed that the pooled OR increased with the number of cases in the studies. The results might be affected by publication bias based on the Eggers' test (p = 0.011) and the asymmetry of the funnel plot. Phytoestrogen intake may reduce the risk of prostate cancer in Asians and Caucasians. Regular intake of food that is rich in phytoestrogens, such as soy/soy products or legumes, should be recommended.

Prostate cancer in East Asia: evolving trend over the last decade

Prostate cancer is now becoming an emerging health priority in East Asia. Most of our current knowledge on Prostate cancer has been generated from studies conducted in Western population; however, there is considerable heterogeneity of Prostate cancer between East and West. In this article, we reviewed epidemiologic trends, risk factors, disease characteristics and management of Prostate cancer in East Asian population over the last decade. Growing evidence from East Asia suggests an important role of genetic and environmental risk factors interactions in the carcinogenesis of Prostate cancer. Exposure to westernized diet and life style and improvement in health care in combination contribute substantially to the increasing epidemic in this region. Diagnostic and treatment guidelines in East Asia are largely based on Western knowledge. Although there is a remarkable improvement in the outcome over the last decade, ample evidence suggests an inneglectable difference in diagnostic accuracy, treatment efficacy and adverse events between different populations. The knowledge from western countries should be calibrated in the Asian setting to provide a better race-based treatment approach. In this review, we intend to reveal the evolving trend of Prostate cancer in the last decade, in order to gain evidence to improve Prostate cancer prevention and control in East Asia.

Induction of cellular and molecular immunomodulatory pathways by vitamin A and flavonoids

INTRODUCTION

A detailed study of reports on the immunomodulatory properties of vitamin A and select flavonoids may pave the way for using these natural compounds or compounds with similar structures in novel drug and vaccine designs against infectious and autoimmune diseases and cancers.

AREAS COVERED

Intracellular transduction pathways, cellular differentiation and functional immunomodulatory responses have been reviewed. The reported studies encompass in vitro, in vivo preclinical and clinical studies that address the role of vitamin A and select flavonoids in induction of innate and adaptive B- and T-cell responses, including TH1, TH2 and regulatory T cells (Treg).

EXPERT OPINION

While the immunomodulatory role of vitamin A, and related compounds, is well-established in many preclinical studies, its role in humans has begun to gain wider acceptance. In contrast, the role of flavonoids is mostly controversial in clinical trials, due to the diversity of the various classes of these compounds, and possibly due to the purity and the selected doses of the compounds. However, current preclinical and clinical studies warrant further detailed studies of these promising immunomodulatory compounds.

Immunomodulating effects of epigallocatechin-3-gallate from green tea: mechanisms and applications

Consuming green tea or its active ingredient, epigallocatechin-3-gallate (EGCG), has been shown consistently to benefit the healthy functioning of several body systems. In the immune system specifically, accumulating evidence has revealed an immunomodulating effect of green tea/EGCG. Several types of immune cells in both the innate and adaptive immune systems are known to be affected in varying degrees by green tea/EGCG. Among them, the dramatic effect on T cell functions has been repeatedly demonstrated, including T cell activation, proliferation, differentiation, and production of cytokines. In particular, dysregulated T cell function with respect to different subsets of CD4(+) T cells is a critical pathogenic factor in the development of autoimmune inflammatory diseases. Recent studies have shown that EGCG affects the differentiation of naïve CD4(+) T cells into different effector subsets in a way that would be expected to favorably impact autoimmunity. Consistent with these findings, studies using animal models of autoimmune diseases have reported disease improvement in animals treated with green tea/EGCG. Altogether, these studies identify and support the use of EGCG as a potential therapeutic agent in preventing and ameliorating T cell-mediated autoimmune diseases. Given the paucity of information in human studies, the translational value of these findings needs to be verified in future research.

Association between Gαi2 and ELMO1/Dock180 connects chemokine signalling with Rac activation and metastasis

The chemokine CXCL12 and its G-protein-coupled receptor CXCR4 control the migration, invasiveness and metastasis of breast cancer cells. Binding of CXCL12 to CXCR4 triggers activation of heterotrimeric Gi proteins that regulate actin polymerization and migration. However, the pathways linking chemokine G-protein-coupled receptor/Gi signalling to actin polymerization and cancer cell migration are not known. Here we show that CXCL12 stimulation promotes interaction between Gαi2 and ELMO1. Gi signalling and ELMO1 are both required for CXCL12-mediated actin polymerization, migration and invasion of breast cancer cells. CXCL12 triggers a Gαi2-dependent membrane translocation of ELMO1, which associates with Dock180 to activate small G-proteins Rac1 and Rac2. In vivo, ELMO1 expression is associated with lymph node and distant metastasis, and knocking down ELMO1 impairs metastasis to the lung. Our findings indicate that a chemokine-controlled pathway, consisting of Gαi2, ELMO1/Dock180, Rac1 and Rac2, regulates the actin cytoskeleton during breast cancer metastasis.

Transcutaneous electrical nerve stimulation attenuates CFA-induced hyperalgesia and inhibits spinal ERK1/2-COX-2 pathway activation in rats

BACKGROUND

Transcutaneous electrical nerve stimulation (TENS) is a non-pharmacologic treatment for pain relief. In previous animal studies, TENS effectively alleviated Complete Freund's Adjuvant (CFA)- or carrageenan-induced inflammatory pain. Although TENS is known to produce analgesia via opioid activation in the brain and at the spinal level, few reports have investigated the signal transduction pathways mediated by TENS. Prior studies have verified the importance of the activation of extracellular signal-regulated kinase (ERK) signal transduction pathway in the spinal cord dorsal horn (SCDH) in acute and persistent inflammatory pains. Here, by using CFA rat model, we tested the efficacy of TENS on inhibiting the expressions of p-ERK1/2 and of its downstream cyclooxygenase-2 (COX-2) and the level of prostaglandin E2 (PGE2) at spinal level.

METHODS

Rats were randomly divided into control, model and TENS groups, and injected subcutaneously with 100 μl CFA or saline in the plantar surface of right hind paw. Rats in the TENS group were treated with TENS (constant aquare wave, 2 Hz and 100 Hz alternating frequencies, intensities ranging from 1 to 2 mA, lasting for 30 min each time) at 5 h and 24 h after injection. Paw withdrawal thresholds (PWTs) were measured with dynamic plantar aesthesiometer at 3d before modeling and 5 h, 6 h, and 25 h after CFA injection. The ipsilateral sides of the lumbar spinal cord dosral horns were harvested for detecting the expressions of p-ERK1/2 and COX-2 by western blot analysis and qPCR, and PGE2 by ELISA.

RESULTS

CFA-induced periphery inflammation decreased PWTs and increased paw volume of rats. TENS treatment significantly alleviated mechanical hyperalgesia caused by CFA. However, no anti-inflammatory effect of TENS was observed. Expression of p-ERK1/2 protein and COX-2 mRNA was significantly up-regualted at 5 h and 6 h after CFA injection, while COX-2 and PGE2 protein level only increased at 6 h after modeling. Furthermore, the high expression of p-ERK1/2 and COX-2, and over-production of PGE2 induced by CFA, were suppressed by TENS administration.

CONCLUSIONS

TENS may be an effective therapy in controlling inflammatory pain induced by CFA. Its analgesic effect may be associated with the inhibition of activation of the spinal ERK1/2-COX-2 pathway.

Chemoprevention of prostate cancer: soy isoflavones and curcumin

The burden of increasing morbidity and mortality due to prostate cancer imposes a need for new, effective measures of prevention in daily life. The influence of lifestyle on carcinogenesis in Asian men who migrate to Western cultures supports a causal role for dietary, environmental, and genetic factors in the epidemiology of prostate cancer. Chemoprevention, a prophylactic approach that uses nontoxic natural or synthetic compounds to reverse, inhibit, or prevent cancer by targeting specific steps in the carcinogenic pathway, is gaining traction among health care practitioners. Soy isoflavones and curcumin, staples of the Asian diet, have shown promise as functional factors for the chemoprevention of prostate cancer because of their ability to modulate multiple intracellular signaling pathways, including cellular proliferation, apoptosis, inflammation, and androgen receptor signaling. Recent evidence has revealed the DNA damage response (DDR) to be one of the earliest events in the multistep progression of human epithelial carcinomas to invasive malignancy. Soy isoflavones and curcumin activate the DDR, providing an opportunity and rationale for the clinical application of these nutraceuticals in the chemoprevention of prostate cancer.

(-)-Epigallocatechin-3-gallate, a green tea-derived catechin, synergizes with celecoxib to inhibit IL-1-induced tumorigenic mediators by human pancreatic adenocarcinoma cells Colo357

Despite their toxic side effects prostaglandin H(2) synthase-2 (PGHS-2) inhibitors hold promise for cancer chemoprevention. In order to overcome adverse effects lower doses of PGHS-2 inhibitors could be applied in combination with other agents exhibiting complementary effects. Herein, the effects of the PGHS-2-specific inhibitor celecoxib either alone or in combination with the green tea-derived catechin (-)-epigallocatechin-3-gallate (EGCG) were studied on the expression of interleukin (IL)-1-induced tumorigenic factors in Colo357 human pancreatic adenocarcinoma cells. This approach mimics tumor-associated pancreatic inflammation which is considered as a key player in pancreatic malignancy. We found that co-incubation of Colo357 with celecoxib and EGCG synergistically diminished metabolic activity via apoptosis induction and down-regulated release of pro-angiogenic vascular endothelial growth factor (VEGF) and invasiveness-promoting matrix metalloproteinase (MMP)-2 to a maximum of 30%. Celecoxib and EGCG synergistically reduced IL-1-induced production of pro-inflammatory IL-6 and pro-angiogenic IL-8 to 23-50%. Celecoxib dose-dependently increased PGHS-2 levels. Whereas EGCG was able to compensate for celecoxib-mediated increase of PGHS-2, it failed to potentiate celecoxib-mediated suppression of prostaglandin E(2) (PGE(2)) release. Thus, in Colo357, EGCG synergistically boosts celecoxib-mediated effects and reduces the levels of celecoxib required to elicit beneficial effects on tumorigenic mediators by a factor of ten.

Oolong tea theasinensins attenuate cyclooxygenase-2 expression in lipopolysaccharide (LPS)-activated mouse macrophages: structure-activity relationship and molecular mechanisms

Oolong tea theasinensins are a group of tea polyphenols different from green tea catechins and black tea theaflavins. The present study reports the inhibitory effects of oolong tea theasinensins on the expression of cyclooxygenase-2 (COX-2) and underlying molecular mechanisms in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. The structure-activity data revealed that the galloyl moiety of theasinensins played an important role in the inhibitory actions. Theasinensin A, a more potent inhibitor, caused a dose-dependent inhibition of mRNA, protein, and promoter activity of COX-2. An electrophoretic mobility shift assay (EMSA) revealed that theasinensin A reduced the complex of NF-κB- and AP-1-DNA in the promoter of COX-2. Signaling analysis demonstrated that theasinensin A attenuated IκB-α degradation, nuclear p65 accumulation, and c-Jun phosphorylation. Furthermore, theasinensin A suppressed the phosphorylation of MAPKs, IκB kinase α/β (IKKα/β), and TGF-β activated kinase (TAK1). These data demonstrated that the down-regulation of TAK1-mediated MAPKs and NF-κB signaling pathways might be involved in the inhibition of COX-2 expression by theasinensin A. These findings provide the first molecular basis for the anti-inflammatory properties of oolong tea theasinensins.

EGCG functions through estrogen receptor-mediated activation of ADAM10 in the promotion of non-amyloidogenic processing of APP

Estrogen depletion following menopause has been correlated with an increased risk of developing Alzheimer's disease (AD). We previously explored the beneficial effect of (-)-epigallocatechin-3-gallate (EGCG) on AD mice and found increased non-amyloidogenic processing of amyloid precursor protein (APP) through the α-secretase a disintegrin and metallopeptidase domain 10 (ADAM10). Our results in this study suggest that EGCG-mediated enhancement of non-amyloidogenic processing of APP is mediated by the maturation of ADAM10 via an estrogen receptor-α (ERα)/phosphoinositide 3-kinase/Ak-transforming dependent mechanism, independent of furin-mediated ADAM10 activation. These data support prior assertions that central selective ER modulation could be a therapeutic target for AD and support the use of EGCG as a well-tolerated alternative to estrogen therapy in the prophylaxis and treatment of this disease.

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-kappaB) pathway has been implicated as an important mediator between chronic inflammation, cell proliferation and prostate cancer. Dietary factors that inhibit inflammation and NF-kappaB 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-kappaB, 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.

COX-2 and PGE2 signaling is essential for the regulation of IDO expression by curcumin in murine bone marrow-derived dendritic cells

Indoleamine 2,3-dioxygenase (IDO), a key enzyme that catalyzes the initial, rate-limiting step in tryptophan degradation, is expressed in dendritic cells (DCs) which are stimulated by lipopolysaccharide (LPS) or interferons. In this study we show that curcumin inhibits IDO expression in vitro and in vivo in DCs, leading to the suppression of LPS-induced DC maturation. The effect of curcumin relative to LPS is not limited to the above, as it also enhances LPS-induced expression of cyclooxygenase (COX)-2 and production of prostaglandin E2 (PGE2). Additionally, PGE2 diminished the LPS-induced IDO expression in DCs, thereby contributing to the inhibition of expression of the surface molecules (CD80, CD86 and MHC class I) and the production of the proinflammatory cytokines (IL-12 p70 and TNF-alpha) by LPS stimulation. Under our experimental conditions, curcumin plays an immunomodulatory role by downregulating IDO expression via a COX-2/PGE2-dependant pathway, thus impacting DC maturation in vitro and in vivo.

The modifying effects of green tea polyphenols on acute colitis and inflammation-associated colon carcinogenesis in male ICR mice

Reactive oxygen species (ROS) have been implicated as mediators of intestinal inflammation and carcinogenesis. Although green tea polyphenols (GTP) have anticancer property as antioxidants they also generate ROS in vitro. In this study, we investigated the modifying effects of GTP on dextran sulfate sodium (DSS)-induced acute colitis and on 1,2-dimethylhydrazine (DMH) and DSS-induced colon carcinogenesis in male ICR mice. At sacrifice after 6 days, the colon shortening induced by 2% DSS was unchanged by 0.1% and 0.25% GTP, but increased by 0.5% and 1% GTP-containing diet. The expression of interleukin-1beta and macrophage-migration inhibitory factor in the DSS + 0.1% GTP group were lower than the DSS alone group, whereas the expression levels were increased in the DSS + 0.5% GTP and DSS + 1% GTP groups when compared with the DSS alone group. In a subsequent experiment to determine the effects of 0.01-1% GTP on inflammation-associated colon carcinogenesis induced by DMH/DSS, 0.5 and 1% doses of GTP failed to prevent the development of multiple colon tumors, rather, they tended to increase it. Our results thus indicate that the modifying effects of GTP on DSS-induced acute colitis and DMH/DSS-induced colon carcinogenesis depends upon its dosage and the expression of proinflammatory cytokines.

Comparative examination of anti-proliferative activities of (-)-epigallocatechin gallate and (--)-epigallocatechin against HCT116 colorectal carcinoma cells

We compared anti-proliferative activities of (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin (EGC) against HCT116 colorectal carcinoma cells. These catechins inhibited cell growth to nearly the same extent at low cell confluency in plates. However, their inhibitory effect grew weaker as cell confluence increased, and this tendency was more conspicuous for EGC than for EGCG. Both EGCG and EGC activated the phosphorylation of the major MAPKs, ERK, JNK, and p38, in the HCT116 cells as in many other established human cancer cells though to different extents. Cell cycle analyses, DNA fragmentation assays, and TUNEL assays as well as Western blot assays suggested that these catechins inhibited cell growth through mitogen-activated protein kinase (MAPK)-mediated apoptosis rather than cell cycle regulation.

Grape polyphenols affect mRNA expression of PGHS-2, TIS11b and FOXO3 in endometrium of heifers under ACTH-induced stress

Stress activates the hypothalamo-pituitary-adrenal axis leading to enhanced glucocorticoid secretion and concurrently disrupts ovarian cycle. Plant polyphenols are known to posses antioxidant and anti-inflammatory proprieties. This could be of interest for ovarian cycle when stressing conditions lead to progesterone enhancement and hamper normal reproduction activity. The present study examined whether ovarian follicular development and progesterone secretory pattern are affected by exogenous ACTH administration in heifers. Moreover, the effect of grape polyphenols in endometrium of heifers, under adrenocorticotropic hormone challenge, is evaluated in terms of transcriptional patterns of genes related to inflammation, oxidative stress and endometrial functions. At day 14 of synchronized estrous cycle, Holstein Friesian heifers received injections of either saline (CTR group) or adrenocorticotropic hormone (ACT group) agonist every 12 h for 7 days. Another group (POL group) of animals received the same treatment plus an oral supplementation of 15 g/day of grape skin extract. Cortisol and progesterone were analysed in the blood samples collected at days 0, 3, 6, 9, 12, 14, 17, 21, 24 of the estrous cycle. Endometrial biopsies were collected at diestrus (day 18) and at estrus and a panel of gene expressions were quantified by real-time PCR. ACTH administration increased both cortisol (P<0.001) and progesterone concentrations (P<0.01) compared to CTR group. PGHS-2 was significantly (P<0.01) up-regulated in the POL group compared to ACT and CTR groups at diestrus and at estrus. FOXO3 and TIS11b were down-regulated in the CTR group compared to ACT and POL groups. The PGHS-2, SOD2 (P<0.05), FOXO3 and TIS11b (P<0.10) genes were down-regulated at estrus in all groups compared to diestrus. An interesting role of polyphenols in modulating the expression levels of PGHS-2 in endometrial tissue and on the activation of TIS11b and SOD2 through c-AMP-dependent signalling was suggested.

Epigallocatechin-3-gallate suppresses NF-kappaB activation and phosphorylation of p38 MAPK and JNK in human astrocytoma U373MG cells

Epigallocatechin-3-gallate (EGCG) is the major polyphenol component of green tea and is primarily responsible for the green tea effect. EGCG possesses two triphenolic groups in its structure. These groups are reported to be important with respect to anticarcinogenic and antioxidant effects. However, the anti-inflammatory effect of EGCG on Alzheimer's disease (AD) is still not fully understood. In this study, we investigated the effects of EGCG in attenuating the inflammatory response induced by interleukin (IL)-1beta+beta-amyloid (25-35) fragment (Abeta) in human astrocytoma, U373MG cells. EGCG significantly inhibited the IL-1beta+Abeta (25-35)-induced IL-6, IL-8, vascular endothelial growth factor (VEGF) and prostaglandin (PG)E(2) production at 24 h (P<.01). The maximal inhibition rate of IL-6, IL-8, VEGF and PGE(2) production by EGCG was approximately 54.40%, 56.01%, 69.06% and 47.03%, respectively. EGCG also attenuated the expression of cyclooxygenase-2 and activation of nuclear factor-kappaB induced by IL-1beta+Abeta (25-35). We demonstrated that EGCG suppresses IL-1beta+Abeta (25-35)-induced phosphorylation of the mitogen-activated protein kinase p38 and the c-Jun N-terminal kinase. In addition, EGCG induced the expression of mitogen-activated protein kinase phosphatase-1. These results provide new insight into the pharmacological actions of EGCG and its potential therapeutic application to various neurodegenerative diseases such as AD.

Suppression of MyD88- and TRIF-dependent signaling pathways of Toll-like receptor by (-)-epigallocatechin-3-gallate, a polyphenol component of green tea

Toll-like receptors (TLRs) play an important role in recognition of microbial components and induction of innate immunity. The microbial components trigger the activation of two downstream signaling pathways of TLRs; MyD88- and/or TRIF-dependent pathways leading to activation of NF-kappaB. (-)-Epigallocatechin-3-gallate (EGCG), a flavonoid found in green tea, is known to inhibit NF-kappaB activation induced by many pro-inflammatory stimuli. EGCG was shown to inhibit the activity of IKKbeta which is the key kinase in the canonical pathway for NF-kappaB activation in MyD88-dependent pathway of TLRs. However, it is not known whether EGCG inhibits TRIF-dependent pathway through which more than 70% of lipopolysaccharide (LPS)-induced genes are regulated. Therefore, we attempted to identify the molecular target of EGCG in TRIF-dependent pathways of TLR3 and TLR4. EGCG inhibited the activation of IFN regulatory factor 3 (IRF3) induced by LPS, poly[I:C], or the overexpression of TRIF. The inhibition of IRF3 activation by EGCG was mediated through the suppression of the kinase activity of TBK1. However, EGCG did not inhibit activation of IRF3 induced by overexpression of constitutively active IRF3. These results suggest that the molecular target of EGCG is TBK1 in TRIF-dependent signaling pathways of TLR3 and TLR4. Therefore, our results suggest that green tea flavonoids can modulate both MyD88- and TRIF-dependent signaling pathways of TLRs and subsequent inflammatory target gene expression.

Involvement of early growth response gene 1 in the modulation of microsomal prostaglandin E synthase 1 by epigallocatechin gallate in A549 human pulmonary epithelial cells

The prostaglandin E(2) (PGE(2)) can play critical roles in the pulmonary inflammation or carcinogenesis. It is the first investigation of the effect of a green tea polyphenol, (-)-epigallocatechin gallate (EGCG), on the PGE(2)-producing microsomal prostaglandin E synthase 1 (mPGES-1) expression in the lung alveolar type II pneumocytes, A549 cells as an epithelial model. EGCG enhanced cyclooxygenase (COX)-2 and mPGES-1 gene expression as well as PGE(2). Among several tea catechins, EGCG was most effective in inducing mPGES-1 expression. Moreover, even in the cytokine-stimulated cells, mPGES-1 protein was super-induced by EGCG treatment. As signaling mediators in mPGES-1 induction by EGCG, active ERK1/2 MAP kinases and early growth response gene 1 (EGR-1) were increased after exposure to EGCG. Moreover, EGCG stimulated the nuclear translocation of the EGR-1 protein in A549 cells through ERK signaling pathway. Recent studies demonstrate that EGR-1 is a key transcription factor in mPGES-1 gene expression. When blocking the gene expression of EGR-1 with EGR-1 siRNA or ERK inhibitor, EGCG-induced mPGES-1 was suppressed in both cases. mPGES-1 promoter with deleted or point-mutated EGR-1 binding sites showed significantly less response to the EGCG stimulation, which also implicated the importance of EGR-1 binding in promoting mPGES-1 gene expression. Taken all, EGCG was strong inducer of EGR-1 expression and mediated EGR-1 nuclear translocation via ERK signaling pathway in A549 pulmonary epithelial cells. Induced EGR-1 then stimulated the induction of mPGES-1 gene expression and this effect mechanistically can be linked to the pharmacological or toxicological actions after human exposure to green tea catechins.

Molecular and cellular targets

Carcinogenesis is a multistage process consisting of initiation, promotion, and progression stages and each stage may be a possible target for chemopreventive agents. A significant outcome of these investigations on the elucidation of molecular and cellular mechanisms is the explication of signal transduction pathways induced by tumor promoters in cancer development. The current belief today is that cancer may be prevented or treated by targeting specific cancer genes, signaling proteins, and transcription factors. The molecular mechanisms explaining how normal cells undergo neoplastic transformation induced by tumor promoters are rapidly being clarified. Accumulating research evidence suggests that many of dietary factors, including tea compounds, may be used alone or in combination with traditional chemotherapeutic agents to prevent or treat cancer. The potential advantage of many natural or dietary compounds seems to focus on their potent anticancer activity combined with low toxicity and very few adverse side effects. This review summarizes some of our recent work regarding the effects of the various tea components on signal transduction pathways involved in neoplastic cell transformation and carcinogenesis.

Green tea polyphenol (-)-epigallocatechin-3-gallate inhibits cyclooxygenase-2 expression in colon carcinogenesis

Tea, one of the most widely consumed beverages worldwide, has been shown to have anti-cancer activity in various cancers including colon cancer. It has been demonstrated that overexpression of the inducible isoform of cyclooxygenase (COX-2) occurs during colon tumorigenesis and inhibition of COX-2 by non-steroidal anti-inflammatory drugs (NSAIDs) is chemopreventive. To determine whether the anti-cancer effect associated with green tea impacted COX-2 expression levels, human colorectal cancer cell lines HT-29 and HCA-7, were treated with (-)-epigallocatechin-3-gallate (EGCG), the most abundant and effective polyphenol of green tea. EGCG significantly inhibited constitutive COX-2 mRNA and protein overexpression. The inhibitory effects of EGCG on signaling pathways controlling COX-2 expression were examined. We observed that EGCG down regulated the ERK1/2 and Akt pathways in colon cancer cells. The effect of EGCG on COX-2 expression resulted in decreased COX-2 promoter activity via inhibition of nuclear factor kappaB (NF-kappaB) activation. EGCG also promoted rapid mRNA decay mediated through the COX-2 3'untranslated region (3'UTR). In conclusion, these data suggest that inhibition of COX-2 is a mechanism for the anti-proliferative effect of green tea and emphasizes the role that dietary factors have as anti-cancer agents.

ADAM10 Activation Is Required for Green Tea (–)-Epigallocatechin-3-gallate-induced α-Secretase Cleavage of Amyloid Precursor Protein

Recently, we have shown that green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) exerts a beneficial role on reducing brain Abeta levels, resulting in mitigation of cerebral amyloidosis in a mouse model of Alzheimer disease. EGCG seems to accomplish this by modulating amyloid precursor protein (APP) processing, resulting in enhanced cleavage of the alpha-COOH-terminal fragment (alpha-CTF) of APP and corresponding elevation of the NH(2)-terminal APP product, soluble APP-alpha (sAPP-alpha). These beneficial effects were associated with increased alpha-secretase cleavage activity, but no significant alteration in beta-or gamma-secretase activities. To gain insight into the molecular mechanism whereby EGCG modulates APP processing, we evaluated the involvement of three candidate alpha-secretase enzymes, a-disintegrin and metalloprotease (ADAM) 9, 10, or 17, in EGCG-induced non-amyloidogenic APP metabolism. Results show that EGCG treatment of N2a cells stably transfected with "Swedish" mutant human APP (SweAPP N2a cells) leads to markedly elevated active ( approximately 60 kDa mature form) ADAM10 protein. Elevation of active ADAM10 correlates with increased alpha-CTF cleavage, and elevated sAPP-alpha. To specifically test the contribution of ADAM10 to non-amyloidogenic APP metabolism, small interfering RNA knockdown of ADAM9, -10, or -17 mRNA was employed. Results show that ADAM10 (but not ADAM9 or -17) is critical for EGCG-mediated alpha-secretase cleavage activity. In summary, ADAM10 activation is necessary for EGCG promotion of non-amyloidogenic (alpha-secretase cleavage) APP processing. Thus, ADAM10 represents an important pharmacotherapeutic target for the treatment of cerebral amyloidosis in Alzheimer disease.

(-)-Epigallocatechin-3-gallate promotes pro-matrix metalloproteinase-7 production via activation of the JNK1/2 pathway in HT-29 human colorectal cancer cells

Matrix metalloproteinase (MMP)-7 (matrilysin-1) plays significant roles in the growth, invasion, and metastasis of colorectal tumors, while (-)-epigallocatechin-3-gallate (EGCG), a green tea polyphenol with chemopreventive properties, has been shown to be an inhibitor of MMP-2 and MMP-9. In the present study, HT-29 human colorectal cancer cells were treated with EGCG to examine its effects on pro-MMP-7 induction and production using RT-PCR and western blot analyses. Surprisingly, EGCG (10-100 microM) treatment increased both intracellular and extracellular pro-MMP-7 protein levels (2.6-8.4-fold and 1.9-6.4-fold, respectively) in dose- and time-dependent manner, with a significant upregulation of its mRNA expression. EGCG also activated extracellular signal-regulated protein kinase (ERK)1/2, c-JUN NH2-terminal kinase (JNK)1/2 and p38 mitogen-activated protein kinase (MAPK), as previously reported. In addition, the polyphenol triggered the phosphorylation of c-JUN (Ser63 and Ser73) and induced c-JUN/c-FOS, thereby increasing the DNA binding activity of activator protein-1 (AP-1), as shown by an AP-1 luciferase reporter assay. Pharmacological blockade of MAPK activities suggested that pro-MMP-7 expression was induced via JNK1/2 activation, but not in the case of ERK1/2 or p38 MAPK. N-Acetyl-L-cysteine, superoxide (O2-) dismutase and catalase attenuated the EGCG-induced pro-MMP-7 production, suggesting an involvement of oxidative stress in these events. Conversely, EGCG spontaneously generated O2- in a cell-free system that utilized a cytochrome C reduction method. Further, (-)-epicatechin-3-gallate (25 and 100 microM) and green tea polyphenols (33 and 132 microg/ml) induced pro-MMP-7 expression, whereas (-)-epicatechin and (-)-epigallocatechin (100 microM each) did not. Induction of pro-MMP-7 expression by EGCG was also shown in another human colorectal adenocarcinoma cell line, Caco-2. Our results suggest that some green tea catechins induce pro-MMP-7 production via O2- production and the activation of JNK1/2, c-JUN, c-FOS and AP-1 in HT-29 cells.

Cyclooxygenase-2 Inhibits Novel Ginseng Metabolite-Mediated Apoptosis

Recently, a novel intestinal bacterial metabolite of ginseng protopanaxadiol saponins, i.e., 20-O-(beta-D-glucopyranosyl)-20(S)-protopanaxadiol (IH-901), has been reported to induce apoptosis in a variety of cancer cells. Here we show a differential effect of IH-901 on several cell types. Exposure to IH-901 for 48 hours at a supposedly subapoptotic concentration of 40 mumol/L led to both apoptotic cell death and G1 arrest in Hep3B cells, but only resulted in G1 arrest in MDA-MB-231, Hs578T, and MKN28 cells. Additionally, the treatment of MDA-MB-231, but not of Hep3B, with IH-901 up-regulated cyclooxygenase-2 (COX-2) mRNA (2 hours) and protein (6 hours), and enhanced the production of prostaglandin E2. In MDA-MB-231 cells, IH-901 induced the sustained activation of extracellular signal-regulated kinase (ERK), whereas inhibition of mitogen-activated protein/ERK kinase blocked IH-901-mediated COX-2 induction and resulted in apoptosis, suggesting the involvement of an ERK-COX-2 pathway. Combined treatment with IH-901 and nonsteroidal anti-inflammatory drugs inhibited COX-2 enzyme and induced apoptosis in MDA-MB-231 and Hs578T cells. Adenovirus-mediated COX-2 small interfering RNAs also effectively inhibited COX-2 protein expression and enhanced IH-901-mediated apoptosis without inhibiting ERK 1/2 phosphorylation, thus providing direct evidence that COX-2 is an antiapoptotic molecule. Moreover, IH-901-mediated G1 arrest resulted from an increase in p27Kip1 mRNA and protein expression followed by a decrease in CDK2 kinase activity that was concurrent with the hypophosphorylation of Rb and p130. In conclusion, IH-901 induced both G1 arrest and apoptosis, and this apoptosis could be inhibited by COX-2 induction.

Signal transduction network leading to COX-2 Induction: a road map in search of cancer chemopreventives

Cancer is still a major global health concern even after an everlasting strive in conquering this dread disease. Emphasis is now given to chemoprevention to reduce the risk of cancer and also to improve the quality of life among cancer afflicted individuals. Recent progress in molecular biology of cancer has identified key components of the cellular signaling network, whose functional abnormality results in undesired alterations in cellular homeostasis, creating a cellular microenvironment that favors premalignant and malignant transformation. Multiple lines of evidence suggest an elevated expression of cyclooxygenase-2 (COX-2) is causally linked to cancer. In response to oxidative/pro-inflammatory stimuli, turning on unusual signaling arrays mediated through diverse classes of kinases and transcription factors results in aberrant expression of COX-2. Population-based as well as laboratory studies have explored a broad spectrum of chemopreventive agents including selective COX-2 inhibitors and a wide variety of anti-inflammatory phytochemicals, which have been shown to target cellular signaling molecules as underlying mechanisms of chemoprevention. Thus, unraveling signaling pathways regulating aberrant COX-2 expression and targeted blocking of one or more components of those signal cascades may be exploited in searching chemopreventive agents in the future.

beta-Carotene downregulates the steady-state and heregulin-alpha-induced COX-2 pathways in colon cancer cells

Experimental studies have shown that beta-carotene inhibited the growth of colon cancer cells, and human trials have demonstrated that the carotenoid reduces colon cell proliferation of adenomatous polyps; however, molecular mechanisms underlying this chemopreventive activity remain unclear. Because COX-2 has been implicated as a causative factor in colon carcinogenesis, the present study was designed to investigate the relation between the growth-inhibitory effect of the carotenoid and COX-2 expression in colon cancer cells. We evaluated the effects of beta-carotene on the growth of human colon adenocarcinoma cells overexpressing (LS-174, HT-29, WiDr) or not expressing (HCT116) COX-2. We also studied COX-2 expression induced by heregulin-alpha, apoptosis induction, reactive oxygen species (ROS) production, and extracellular signal-regulated kinase 1/2 (ERK1/2) activation. beta-Carotene (0.5-2.0 micromol/L) decreased COX-2 expression (P < 0.05) and prostaglandin E(2) (PGE(2)) production (P < 0.05) in colon cancer cells. This effect was not observed in cells treated with retinoic acid or retinol. The downregulation of COX-2 by the carotenoid occurred in both untreated and heregulin-treated cells. It was accompanied by an increased ability of cells to undergo apoptosis and by a decrease in intracellular ROS production and in the activation of ERK1/2. Moreover, cells not expressing COX-2 were insensitive to the growth-inhibitory and proapoptotic effects of the carotenoid. Here, we report that the suppression of COX-2 by beta-carotene may represent a molecular mechanism by which this compound acts as an antitumor agent in colon carcinogenesis.

In vitro Assessment of Renal Toxicity and Inflammatory Events of Two Protein Phosphatase Inhibitors Cantharidin and Nor-Cantharidin*

In China, cantharidin has been reported to be active against various human cancers, but with severe side effects such as nephrotoxicity. In order to reduce this toxicity, its demethylated analogue nor-cantharidin has been synthesized and used in cancer therapy, but with only few data regarding safety assessment. The aim of this study was to compare the in vitro effects of cantharidin and nor-cantharidin on renal toxicity and on inflammatory events associated with tumoural process where protein phosphatases could be involved (energy status, prostanoid production, glutathione and nitrite contents) on RAW 264.7 and LLC-PK1 cells. In macrophages, both cantharidin and nor-cantharidin decreased cell viability, in a concentration- and time-dependent manner. However, IC50 was lower with cantharidin than with nor-cantharidin. These two drugs significantly decreased the ATP level after 24 hr incubation. However, ATP decreased much more with cantharidin (up to 4 times) than with nor-cantharidin. When control macrophages were activated with lipopolysaccharide+interferon-gamma for 24 hr a significant increase in nitrite content and in prostanoids were observed. Addition of either drug decreased nitrite generation and prostanoids, however these decreases were greater with cantharidin than with nor-cantharidin. In LLC-PK1 cells, incubated with either cantharidin or nor-cantharidin, our results show significant differences between the two drugs, similar to those observed in peritoneal macrophages, except for GSH content with opposite variations in both cells. We provide a better understanding of the various mechanisms of cantharidin side effects, allowing an easier comparison with nor-cantharidin which could be an attractive therapeutic potential in cancer chemotherapy in western countries.

Targeting signal transduction pathways by chemopreventive agents

Cancer is a dynamic process that involves many complex factors, which may explain why a "magic bullet" cure for cancer has not been found. Death rates are still rising for many types of cancers, which possibly contributes to the increased interest in chemoprevention as an alternative approach to the control of cancer. This strategy for cancer control is based on the presumption that because cancer develops through a multi-step process, each step may be a prospective target for reversing or suppressing the process. Thus, the design and development of chemopreventive agents that act on specific and/or multiple molecular and cellular targets is gaining support as a rational approach to control cancer. Nutritional or dietary factors have attracted a great deal of interest because of their perceived ability to act as highly effective chemopreventive agents. They are professed as being generally safe and may have efficacy as chemopreventive agents by preventing or reversing premalignant lesions and/or reducing second primary tumor incidence. Many of these dietary compounds appear to act on multiple target signaling pathways. Some of the most interesting and well documented are resveratrol and components of tea, including EGCG, theaflavins and caffeine. This review will focus on recent work regarding three well-accepted cellular/molecular mechanisms that may at least partially explain the effectiveness of selected food factors, including those indicated above, as chemopreventive anti-promotion agents. These food compounds may act by: (1) inducing apoptosis in cancer cells; (2) inhibiting neoplastic transformation through the inhibition of AP-1 and/or NF-kappaB activation; and/or (3) suppressing COX-2 overexpression in cancer cells.

Effects of tea polyphenols on signal transduction pathways related to cancer chemoprevention

The inhibition of carcinogenesis by tea and tea polyphenols has been demonstrated in different animal models by many investigators. The mechanisms of this inhibitory activity have also been investigated extensively, mostly in cell culture systems, but no clear conclusion can be reached concerning the cancer preventive mechanisms in vivo. In this article, we reviewed the possible mechanisms, which include the inhibition of specific protein kinase activities, blocking receptor-mediated functions, and inhibition of proteases. These events may lead to cell cycle regulation, growth inhibition, enhanced apoptosis, inhibition of angiogenesis, and inhibition of invasion and metastases. The possible complications of translating results obtained in cell culture studies to animals and humans are discussed. It is likely that multiple signal transduction pathways are involved in the inhibition of carcinogenesis by tea constituents. The relative importance of these pathways needs to be determined in vivo.

Phospholipase D Isozymes Mediate Epigallocatechin Gallate-induced Cyclooxygenase-2 Expression in Astrocyte Cells

Little is known about the effect of epigallocatechin-3 gallate (EGCG), a major constituent of green tea, on the expression of cyclooxygenase (COX)-2. Here, we studied the role of phospholipase D (PLD) isozymes in EGCG-induced COX-2 expression. Stimulation of human astrocytoma cells (U87) with EGCG induced formation of phosphatidylbutanol, a specific product of PLD activity, and synthesis of COX-2 protein and its product, prostaglandin E(2) (PGE(2)). Pretreatment of cells with 1-butanol, but not 3-butanol, suppressed EGCG-induced COX-2 expression and PGE synthesis. Furthermore, evidence that PLD was involved in EGCG-induced COX-2 expression was provided by the observations that COX-2 expression was stimulated by overexpression of PLD1 or PLD2 isozymes and treatment with phosphatidic acid (PA), and that prevention of PA dephosphorylation by 1-propranolol significantly potentiated COX-2 expression induced by EGCG. EGCG induced activation of p38 mitogen-activated protein kinase (p38 MAPK), and specific inhibition of p38 MAPK dramatically abolished EGCG-induced PLD activation, COX-2 expression, and PGE(2) formation. Moreover, protein kinase C (PKC) inhibition suppressed EGCG-induced p38 MAPK activation, COX-2 expression, and PGE(2) accumulation. The same pathways as those obtained (2)in the astrocytoma cells were active in primary rat astrocytes, suggesting the relevance of the findings. Collectively, our results demonstrate for the first time that PLD isozymes mediate EGCG-induced COX-2 expression through PKC and p38 in immortalized astroglial line and normal astrocyte cells.

Chemopreventive potential of epigallocatechin gallate and genistein: evidence from epidemiological and laboratory studies

A wide array of antioxidative and anti-inflammatory substances derived from edible plants have been reported to possess chemopreventive and chemoprotective activities. Among the most extensively investigated and well-defined dietary chemopreventives are epigallocatechin gallate (EGCG), a principal antioxidant derived from green tea and genistein, a major pharmacologically active isoflavone widely present in soy products. Multiple lines evidence from epidemiologic studies indicate that frequent consumption of green tea is inversely associated with the risk of several types of human cancer, and studies with animal and in vitro cell culture models have revealed EGCG as a major chemopreventive ingredient of green tea. The lower frequencies of breast and prostate cancer in Asian population in general, compared to those in Western societies have been attributed to their consumption of relatively large amounts of soy products. Genistein, as a principal chemopreventive components of soy, exerts a wide array of chemopreventive activities in each stage of multistep carcinogenesis. The purpose of this review is to provide perspectives on the molecular basis of chemopreventive activities of EGCG and geneistein as representative functional food phytochemicals with emphasis on their ability to control intracellular signaling cascades responsible for regulating cell growth and differentiation.

Involvement of EGF receptor activation in the induction of cyclooxygenase-2 in HaCaT keratinocytes after UVB

Because selective inhibition of cyclooxygenase-2 (COX-2) suppressed the induction of skin tumors in mice by UV and as UV has been shown to induce expression of COX-2 in skin and cells, COX-2 may be crucial for photocarcinogenesis of the skin. We studied the mechanism of UVB-induced expression of COX-2 focusing on the signal transduction pathway involved. Hydrogen peroxide (H2O2) treatment of HaCaT cells induced expression of COX-2 and pretreatment with the antioxidant N-acetylcysteine (NAC) partly inhibited the UVB-induced expression of COX-2 protein in HaCaT cells, suggesting that oxidative stress contributes to COX-2 induction. To examine the signaling pathways involved in the UVB-induced expression of COX-2 in HaCaT cells, we analysed the expression of COX-2 protein after treatment with various inhibitors of signaling molecules. Inhibition of EGFR by a specific inhibitor and by a neutralizing antibody suppressed the induction of COX-2 expression by UV. Although a neutralizing antibody to transforming growth factor-alpha (TGF-alpha) suppressed COX-2 expression induced by TGF-alpha, it did not suppress COX-2 expression by UV, indicating that a direct activation of EGFR is involved. Treatment of cells at low temperature (4 degrees C) inhibited UVB-induced JNK activation, but it did not inhibit COX-2 expression by UV. Inhibitors of MEK, p38 MAP kinase and PI3-kinase, suppressed the induction of COX-2 expression by UV. In contrast, an erbB-2 inhibitor augmented the UVB-induced increase of COX-2 protein. These data indicate that oxidative stress in association with activation of EGFR, ERK, p38 MAP kinase, and PI3-kinase plays crucial roles in the UVB induction of expression of COX-2.

Epigallocatechin-3-gallate-induced stress signals in HT-29 human colon adenocarcinoma cells

Epigallocatechin-3-gallate (EGCG), a major component in green tea polyphenols, has been proven to suppress colonic tumorigenesis in animal models and epidemiological studies. As EGCG is retained in the gastrointestinal tract after oral administration, this pharmacokinetics property gives it the potential to function as a chemopreventive agent against colon cancer. In this study, human colorectal carcinoma HT-29 cells were treated with EGCG to examine the anti-proliferative and pro-apoptotic effects of EGCG, as well as the molecular mechanism underlying these effects. Cell viability assay, nuclear staining, DNA fragmentation, caspase assay, cytochrome c release, DiOC6(3) staining, mitogen-activated protein kinases (MAPK) phosphorylation and trypan blue exclusion assays, were utilized to dissect the signaling pathways induced by EGCG. After 36 h treatment, EGCG inhibited HT-29 cell growth with an IC50 of approximately 100 microM. HT-29 cells treated with doses higher than 100 microM showed apparent nuclear condensation and fragmentation, which was confirmed by DNA laddering. Caspase-3 and -9 activation was detected after 12 h treatment, accompanied by mitochondrial transmembrane potential transition and cytochrome c release. Activation of MAPKs was detected as early signaling event elicited by EGCG. Inhibition of c-Jun N-terminal kinase (JNK) pathway showed the involvement of JNK in EGCG-induced cytochrome c release and cell death. EGCG-induced JNK activation was blocked by the antioxidants glutathione and N-acetyl-l-cysteine, suggesting that the cell death signaling was potentially triggered by oxidative stress. In summary, our results from this study suggest that in HT-29 human colon cancer cells (i) EGCG treatment causes damage to mitochondria, and (ii) JNK mediates EGCG-induced apoptotic cell death.

Combinatorial effects of nonsteroidal anti-inflammatory drugs and food constituents on production of prostaglandin E2 and tumor necrosis factor-alpha in RAW264.7 murine macrophages

Combinatorial chemopreventive strategies, in contrast to those with individual agents, show potential in terms of potentially lower toxicity and higher efficacy. In this study, we combined several agents and examined their suppressive effects on the combined lipopolysaccharide (LPS)- and interferon(IFN)-gamma-induced formation of proinflammatory mediators, including prostaglandin (PG) E2 and tumor necrosis factor (TNF)-alpha, in RAW264.7 murine macrophages. The combinatorial effects of indomethacin/genistein (GEN) and aspirin/GEN were found to be synergistic for PGE2 suppression, while the nimesulide/GEN combination was antagonistic. Further, while (-)-epigallocatechin gallate (EGCG) alone increased LPS/IFM-gamma-induced production of PGE2 and TNF-alpha as well as cyclooxygenase-2 expression, the EGCG/GEN combination markedly suppressed these parameters. Our results suggest that certain chemopreventive agents act complexly and that, when used in combination, they affect the intracellular signaling pathways of the paired agents to exert additive, synergistic, or antagonistic effects.

Green tea polyphenol epigallocatechin-3 gallate induces apoptosis of proliferating vascular smooth muscle cells via activation of p53

Green tea polyphenols (GTPs), which possess antioxidant properties, have been shown to inhibit the development of atherosclerotic lesions. Epigallocatechin-3-gallate (EGCG), the most abundant GTP, displays antiproliferative effects in a variety of cell types. Here, we examined the effects of GTPs on aortic smooth muscle cell (SMC) proliferation. Treatment with a GTP mixture or EGCG at a dose of 40 to 50 microg/ml slowed SMC growth, while at a higher dose of 80 microg/ml EGCG also induced cell death as judged by TUNEL assay. Apoptosis was mainly observed in proliferating SMCs in subconfluent cultures; whereas at higher confluency, cell viability was largely unaffected. Treatment with 80 microg/ml EGCG induced the tumor suppressor p53, which was functional as judged by activation of the target cyclin-dependent kinase inhibitor p21CIP1. Inhibition of p53 activity with a dominant negative mutant reduced cell death. The increase in p53 protein was due to increased stability. EGCG also induced functional nuclear factor-kappaB (NF-kappaB) complexes, and inhibition of this activity reduced the extent of cell death. Thus, EGCG inhibits growth and induces death of SMCs in a p53- and NF-kappaB-dependent manner. These results provide evidence for a new molecular mechanism whereby green tea polyphenols inhibit SMC proliferation and function to prevent the development of atherosclerosis.

Redox-sensitive mechanisms of phytochemical-mediated inhibition of cancer cell proliferation (review)

Phytochemicals are potential cancer chemopreventive agents, based partly on cellular research establishing that phytochemicals inhibit the proliferation of cancer cells. To elucidate the mechanism of phytochemicals, a basic understanding is needed of what stimulates cancer cell proliferation. Cancer cells, particularly those that are highly invasive or metastatic, may require a certain level of oxidative stress to maintain a balance between undergoing either proliferation or apoptosis. They constitutively generate large but tolerable amounts of H2O2 that apparently function as signaling molecules in the mitogen-activated protein kinase pathway to constantly activate redox-sensitive transcription factors and responsive genes that are involved in the survival of cancer cells as well as their proliferation. With such a reliance of cancer cells on H2O2 it follows that if the excess H2O2 can be scavenged by phenolic phytochemicals having antioxidant activity, the oxidative stress-responsive genes can be suppressed and consequently cancer cell proliferation inhibited. On the other hand, phenolic phytochemicals and another group of phytochemicals known as isothiocyanates can induce the formation of H2O2 to achieve an intolerable level of high oxidative stress in cancer cells. As an early response, the stress genes are activated. However, when the critical threshold for cancer cells to cope with the induced oxidative stress has been reached, key cellular components such as DNA are damaged irreparably. In conjunction, genes involved in initiating cell cycle arrest and/or apoptosis are activated. Therefore, phytochemicals can either scavenge the constitutive H2O2 or paradoxically generate additional amounts of H2O2 to inhibit the proliferation of cancer cells.

RECOMBINANT GLUCOCORTICOID INDUCED TUMOUR NECROSIS FACTOR RECEPTOR (rGITR) INDUCED COX-2 ACTIVITY IN MURINE MACROPHAGE Raw 264.7 CELLS

Stimulation of murine macrophages with recombinant soluble glucocorticoid induced tumour necrosis factor receptor (GITR) induced cyclooxygenase (COX)-2 protein and generated significant amounts of PGE(2). Previous result demonstrated that macrophages express GITR and GITR ligand constitutively. Induction of COX-2 was synergistic with interferon (INF)-gamma. GITR/ligand system could deliver an activation signal to macrophages in inflammatory processes.