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

Several lines of antioxidant defense against oxidative stress: antioxidant enzymes, nanomaterials with multiple enzyme-mimicking activities, and low-molecular-weight antioxidants

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are well recognized for playing a dual role, since they can be either deleterious or beneficial to biological systems. An imbalance between ROS production and elimination is termed oxidative stress, a critical factor and common denominator of many chronic diseases such as cancer, cardiovascular diseases, metabolic diseases, neurological disorders (Alzheimer's and Parkinson's diseases), and other disorders. To counteract the harmful effects of ROS, organisms have evolved a complex, three-line antioxidant defense system. The first-line defense mechanism is the most efficient and involves antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). This line of defense plays an irreplaceable role in the dismutation of superoxide radicals (O2•-) and hydrogen peroxide (H2O2). The removal of superoxide radicals by SOD prevents the formation of the much more damaging peroxynitrite ONOO- (O2•-  + NO• → ONOO-) and maintains the physiologically relevant level of nitric oxide (NO•), an important molecule in neurotransmission, inflammation, and vasodilation. The second-line antioxidant defense pathway involves exogenous diet-derived small-molecule antioxidants. The third-line antioxidant defense is ensured by the repair or removal of oxidized proteins and other biomolecules by a variety of enzyme systems. This review briefly discusses the endogenous (mitochondria, NADPH, xanthine oxidase (XO), Fenton reaction) and exogenous (e.g., smoking, radiation, drugs, pollution) sources of ROS (superoxide radical, hydrogen peroxide, hydroxyl radical, peroxyl radical, hypochlorous acid, peroxynitrite). Attention has been given to the first-line antioxidant defense system provided by SOD, CAT, and GPx. The chemical and molecular mechanisms of antioxidant enzymes, enzyme-related diseases (cancer, cardiovascular, lung, metabolic, and neurological diseases), and the role of enzymes (e.g., GPx4) in cellular processes such as ferroptosis are discussed. Potential therapeutic applications of enzyme mimics and recent progress in metal-based (copper, iron, cobalt, molybdenum, cerium) and nonmetal (carbon)-based nanomaterials with enzyme-like activities (nanozymes) are also discussed. Moreover, attention has been given to the mechanisms of action of low-molecular-weight antioxidants (vitamin C (ascorbate), vitamin E (alpha-tocopherol), carotenoids (e.g., β-carotene, lycopene, lutein), flavonoids (e.g., quercetin, anthocyanins, epicatechin), and glutathione (GSH)), the activation of transcription factors such as Nrf2, and the protection against chronic diseases. Given that there is a discrepancy between preclinical and clinical studies, approaches that may result in greater pharmacological and clinical success of low-molecular-weight antioxidant therapies are also subject to discussion.

Dermatological Management of Aged Skin

The subject of the work concerns the dermatological management of patients mainly with aged skin. The purpose of the work was to present the basic techniques and preparations which are performed by dermatologists in the treatment of aged skin. There are dermatological treatments related to the treatment of skin diseases and cosmetic treatments which are mainly related to skin care. In this work, the method of literature research was applied. On the basis of books and journal articles on dermatological and cosmetic procedures for aged skin, an analysis of treatment types was made. Then, the results of this analysis were presented in the paper under discussion. The paper presents information on the skin and its properties. The structure and functions of the skin, aging processes and characteristics of aged skin were discussed. Then, the possibilities of reducing the visible signs of skin aging through the use of invasive and non-invasive dermatological and cosmetological treatments were given, and the most important components of preparations used supportively in combating skin aging processes were discussed.

Green Tea Polyphenol (-)-Epigallocatechin-3-Gallate (EGCG): A Time for a New Player in the Treatment of Respiratory Diseases?

(-)-Epigallocatechin-3-gallate (EGCG) is a major polyphenol of green tea that possesses a wide variety of actions. EGCG acts as a strong antioxidant which effectively scavenges reactive oxygen species (ROS), inhibits pro-oxidant enzymes including NADPH oxidase, activates antioxidant systems including superoxide dismutase, catalase, or glutathione, and reduces abundant production of nitric oxide metabolites by inducible nitric oxide synthase. ECGC also exerts potent anti-inflammatory, anti-fibrotic, pro-apoptotic, anti-tumorous, and metabolic effects via modulation of a variety of intracellular signaling cascades. Based on this knowledge, the use of EGCG could be of benefit in respiratory diseases with acute or chronic inflammatory, oxidative, and fibrotizing processes in their pathogenesis. This article reviews current information on the biological effects of EGCG in those respiratory diseases or animal models in which EGCG has been administered, i.e., acute respiratory distress syndrome, respiratory infections, COVID-19, bronchial asthma, chronic obstructive pulmonary disease, lung fibrosis, silicosis, lung cancer, pulmonary hypertension, and lung embolism, and critically discusses effectiveness of EGCG administration in these respiratory disorders. For this review, articles in English language from the PubMed database were used.

Evidence for Oxidative Pathways in the Pathogenesis of PD: Are Antioxidants Candidate Drugs to Ameliorate Disease Progression?

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that arises due to a complex and variable interplay between elements including age, genetic, and environmental risk factors that manifest as the loss of dopaminergic neurons. Contemporary treatments for PD do not prevent or reverse the extent of neurodegeneration that is characteristic of this disorder and accordingly, there is a strong need to develop new approaches which address the underlying disease process and provide benefit to patients with this debilitating disorder. Mitochondrial dysfunction, oxidative damage, and inflammation have been implicated as pathophysiological mechanisms underlying the selective loss of dopaminergic neurons seen in PD. However, results of studies aiming to inhibit these pathways have shown variable success, and outcomes from large-scale clinical trials are not available or report varying success for the interventions studied. Overall, the available data suggest that further development and testing of novel therapies are required to identify new potential therapies for combating PD. Herein, this review reports on the most recent development of antioxidant and anti-inflammatory approaches that have shown positive benefit in cell and animal models of disease with a focus on supplementation with natural product therapies and selected synthetic drugs.

TRK inhibitors block NFKB and induce NRF2 in TRK fusion-positive colon cancer

Tropomyosin receptor kinase (TRK) fusion is one of the oncogenic driver causes of colon cancer, and tropomyosin 3-neurotrophic receptor tyrosine kinase 1 (TPM3-NTRK1) fusion has been detected in the KM12SM cell line. In the present study, we investigated anticancer mechanisms in the KM12SM cell line using three different form of dovitinib (dovitinib (free base), dovitinib lactate (mono acid), and dovitinib dilactic acid (diacid)) and four TRK inhibitors (LOXO-101, entrectinib, regorafenib, and crizotinib). Exposure of TRK inhibitors at concentrations of 10 nM resulted in the apoptosis of KM12SM cells, whereas regorafenib had no effect. Treatment with all inhibitors except regorafenib also significantly increased the expression levels of the genes nuclear factor-erythroid 2-related factor 2 (NRF2) and glutamyl cysteine ligase catalytic subunit (GCLC) in KM12SM. These drugs significantly reduced expression of the phosphorylated proteins NFκB and COX-2 in the KM12SM cell line, and significantly attenuated KM12SM cell migration, according to a Transwell migration assay. Together, these results suggest that TRK inhibitors block products of carcinogenesis by negatively regulating the NFκB signaling pathway and positively regulating the antioxidant NRF2 signaling pathway.

Catechins as Model Bioactive Compounds for Biomedical Applications

Research regarding polyphenols has gained prominence over the years because of their potential as pharmacological nutrients. Most polyphenols are flavanols, commonly known as catechins, which are present in high amounts in green tea. Catechins are promising candidates in the field of biomedicine. The health benefits of catechins, notably their antioxidant effects, are related to their chemical structure and the total number of hydroxyl groups. In addition, catechins possess strong activities against several pathogens, including bacteria, viruses, parasites, and fungi. One major limitation of these compounds is low bioavailability. Catechins are poorly absorbed by intestinal barriers. Some protective mechanisms may be required to maintain or even increase the stability and bioavailability of these molecules within living organisms. Moreover, novel delivery systems, such as scaffolds, fibers, sponges, and capsules, have been proposed. This review focuses on the unique structures and bioactive properties of catechins and their role in inflammatory responses as well as provides a perspective on their use in future human health applications.

From tea to treatment; epigallocatechin gallate and its potential involvement in minimizing the metabolic changes in cancer

As the most abundant bioactive polyphenol in green tea, epigallocatechin gallate (EGCG) is a promising natural product that should be used in the discovery and development of potential drug leads. Due to its association with chemoprevention, EGCG may find a role in the development of therapeutics for prostate cancer. Natural products have long been used as a scaffold for drug design, as their already noted bioactivity can help accelerate the development of novel treatments. Green tea and the EGCG contained within have become associated with chemoprevention, and both in vitro and in vivo studies have correlated EGCG to inhibiting cell growth and increasing the metabolic stress of cancer cells, possibly giving merit to its long utilized therapeutic use in traditional therapies. There is accumulating evidence to suggest EGCG's role as an inhibitor of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin signaling cascade, acting upon major axis points within cancer survival pathways. The purpose of this review is to examine the research conducted on tea along with EGCG in the areas of the treatment of and/or prevention of cancer. This review discusses Camellia sinensis as well as the bioactive phytochemical compounds contained within. Clinical uses of tea are explored, and possible pathways for activity are discussed before examining the evidence for EGCG's potential for acting on these processes. EGCG is identified as being a possible lead phytochemical for future drug design investigations.

Advances on Natural Polyphenols as Anticancer Agents for Skin Cancer

Polyphenols are one of most important phytochemicals distributing in herb plants, vegetables and fruits, which known as important anticancer agents. Given the high incidence and mortality of skin cancer, this study aimed to uncover the chemopreventive effects of polyphenols against skin cancer metastasis. Electronic databases including Scopus, PubMed, and Cochrane library were used to compile the literature from 2000 to August 2019. Only in vivo mechanistic studies with English full-texts were chosen for this review. Polyphenols were included in this study if they were administered in purified form; while total extract and fractions were excluded. Among the 8254 primarily selected papers, only a final number of 34 studies were included. The chemopreventive effects of polyphenols as anthocyanins, ellagitanins, EGCG, oleuropeindihydroxy phenyl, punicalagin, quercetin, resveratrol and theaflavin, were mainly examined in treatment of melanoma as the highly metastatic form of this cutaneous cancer. Those properties are mediated by modulation of angiogenesis, apoptosis, inflammation, metastasis, proliferation, pathways such as EGFR/MAPK, mTOR/PI3K/Akt, JAK/STAT, FAK/RTK2, PGE-2/VEGF, PGE-1/ERK/HIIF-1α, and modulation of related signals including NF-κB, P21^WAF/CIP1, Bim, Bax, Bcl2, Bclx, Bim, Puma, Noxa, ILs and MMPs. Chemopreventive effects of polyphenols are mediated by several signaling pathways against skin carcinogenesis and metastasis, implying the importance of polyphenols to open up new horizons in development of anti-skin cancer therapeutic strategies.

Anti-gastric cancer effect of Salidroside through elevating miR-99a expression

Salidroside is an active ingredient extracted from Rhodiola rosea that has anti-tumor activities. The current paper attempted to assess the impact of Salidroside on gastric cancer (GC) and explore the potential mechanism. GC cell lines (SNU-216 and MGC803) and gastric epithelial cell line GES-1 were treated with Salidroside. CCK-8 assay, colony formation assay, flow cytometry and Transwell assay were respectively performed to evaluate GC cells phenotype. qRT-PCR and western blot were conducted to reveal the downstream genes and signaling of Salidroside. We found that 800 μM Salidroside was capable of reducing GC cells viability, while has no such impacts on GES-1 cells. Salidroside inhibited GC cells proliferation, migration, invasion and promoted apoptosis, which coupled with the down-regulation of p21, Bcl-2, MMP2, RhoA, p-ROCK1, Vimentin and the up-regulations of CyclinD1, Bax, cleaved caspases. miR-99a was found to be highly expressed in response to Salidroside treatment. Besides, the inhibition of MAPK/ERK and PI3K/AKT signaling induced by Salidroside was attenuated by miR-99a silence and in this process, IGF1R worked as a target of miR-99a. The anti-GC effect of Salidroside was also confirmed in a mouse model of GC. The promoting effect of Salidroside on miR-99a expression was also verified in vivo. Furthermore, Salidroside promoted the cisplatin-sensitivity of SGC7901/DDP cells. In conclusion, this study demonstrated that Salidroside possessed anti-GC effects through regulating miR-99a/IGF1R axis and inhibiting MAPK/ERK and PI3K/AKT pathways.

Changes in the Biotransformation of Green Tea Catechins Induced by Different Carbon and Nitrogen Sources in Aspergillus niger RAF106

Biotransformation of green tea catechins mediated by microbes and/or enzymes could increase their bioavailability and improve their health benefits, but the regulatory mechanism remains unclear. Here, Aspergillus niger RAF106 isolated from Pu-erh tea was proved to be capable of degrading gradually ester-catechins into non-ester-catechins with higher bioavailability and gallic acid (GA) in aqueous solution only containing green tea catechins, and the products displayed similar radical-scavenging activity in vitro with the control. Meanwhile, the degradation was mediated by inducible enzymes as the extracellular form, and tannase might be an important enzyme among the extracellular enzymes. Moreover, it was found for the first time that the biotransformation was accelerated significantly by the addition of different nitrogen sources (i.e., yeast extract, peptone, NaNO3, and NH4Cl) and lactose through stimulating the hyphal growth and the tannase activities but was inhibited by glucose effect. Furthermore, nitrogen sources continued to promote the degradation of GA and/or non-ester-catechins by up-regulating the transcriptional expression of two dioxygenases and 10 monooxygenases. Besides, the addition of different nutrient sources except yeast extract did not alter the radical-scavenging activity of green tea catechins during the whole fermentation. These results provide a global insight into the roles of A. niger RAF106 and different nutrient sources in mediating the biotransformation of green tea catechins and modifying the radical-scavenging activity of biotransformed catechins.

Polyphenol supplementation alters intramuscular apoptotic signaling following acute resistance exercise

The purpose of this study was to examine the effects of 28‐days of supplementation with an aqueous proprietary polyphenol blend (PPB) sourced from Camellia sinensis on intramuscular apoptotic signaling following an acute lower‐body resistance exercise protocol and subsequent recovery. Untrained males (n = 38, 21.8 ± 2.7 years, 173.4 ± 7.9 cm, 77.6 ± 14.6 kg) were randomized to PPB (n = 14), placebo (PL; n = 14) or control (CON; n = 10). Participants completed a lower‐body resistance exercise protocol comprised of the squat, leg press, and leg extension exercises. Skeletal muscle microbiopsies were obtained from the vastus lateralis preexercise (PRE), 1‐h (1HR), 5‐h (5HR), and 48‐h (48HR) post‐resistance exercise. Apoptotic signaling pathways were quantified using multiplex signaling assay kits to quantify total proteins (Caspase 3, 8, 9) and markers of phosphorylation status (JNK, FADD, p53, BAD, Bcl‐2). Changes in markers of muscle damage and intramuscular signaling were analyzed via separate repeated measures analysis of variance (ANOVA). Change in Bcl‐2 phosphorylation at 1H was significantly greater in PL compared to CON (P = 0.001). BAD phosphorylation was significantly elevated at 5H in PL compared to PPB (P = 0.015) and CON (P = 0.006). The change in JNK phosphorylation was significantly greater in PPB (P = 0.009), and PL (P = 0.017) compared to CON at 1H, while the change for PL was elevated compared to CON at 5H (P = 0.002). A main effect was observed (P < 0.05) at 1H, 5H, and 48H for p53 and Caspase 8, with Caspase 3 and Caspase 9 elevated at 48H. These data indicate that chronic supplementation with PPB alters apoptotic signaling in skeletal muscle following acute muscle‐damaging resistance exercise.

Effect of Genistein in Comparison with Trichostatin A on Reactivation of DNMTs Genes in Hepatocellular Carcinoma

Background and Aims: DNA methylation and histone modification are epigenetic modifications essential for normal function of mammalian cells. The processes are mediated by biochemical interactions between DNA methyltransferases (DNMTs) and histone deacetylases. Promoter hypermethylation and deacetylation of tumor suppressor genes play major roles in cancer induction, through transcriptional silencing of these genes. DNA hypermethylation is carried out by a family of DNMTs including DNMT1, DNMT3a and DNMT3b. In hepatocellular carcinoma, a significant positive correlation between over-expression of these genes and cancer induction has been reported. The DNA demethylating agent genistein (GE) has been demonstrated to reduce different cancers. Previously, we reported that GE can induce apoptosis and inhibit proliferation in hepatocellular carcinoma PLC/PRF5 and HepG2 cell lines. Besides, histone deacetylase inhibitors, such as trichostatin A (TSA), were successfully used to inhibit cancer cell growth. The present study was designed to assess the effect of GE in comparison with TSA on DNMT1, DNMT3a and DNMT3b gene expression, cell growth inhibition and apoptosis induction in the HepG2 cell line. Methods: Cells were seeded and treated with various doses of GE and TSA. The MTT assay, flow cytometry assay, and real-time RT-PCR were used to determine viability, apoptosis, and DNMT1, DNMT3a and DNMT3b gene expression respectively. Results: Both agents inhibited cell growth, induced apoptosis and reactivated DNMT1, DNMT3a and DNMT3b gene expression. Furthermore, TSA demonstrated a significantly greater apoptotic effect than the other agent, whereas GE improved gene expression more significantly than TSA. Conclusions: Our findings suggest that GE and TSA can significantly inhibit cell growth, induce apoptosis and restore DNMT1, DNMT3a and DNMT3b gene reactivation.

Resveratrol as an active ingredient for cosmetic and dermatological applications: a review

Resveratrol is now being increasingly used in cosmetology and dermatology. This polyphenolic phytoalexin present in large amounts in red grapes and berries has a number of scientifically proven health-promoting properties associated with a positive effect on the cardiovascular system, lowering the concentration of low-density lipoprotein, and the ability to inhibit the cyclooxygenases activity. Additionally, it has antiproliferative, anti-angiogenic, anti-inflammatory, antioxidant, and antimicrobial properties. Its popularity in cosmetology and dermatology is primarily associated with proven ability to penetrate the skin barrier and antiaging activity. It has been shown that formulations with resveratrol can stimulate the proliferation of fibroblasts and contributing to the increase in the concentration of collagen III. Resveratrol has an affinity for the estrogen protein receptors (both ERα and ERβ), thereby contributing to the stimulation of collagen types I and II production. Moreover, resveratrol also has the antioxidant properties, thus can protect cells against oxidative damage associated with the effects of free radicals and UV radiation on the skin by reducing the expression of AP-1 and NF-kB factors and it slows down the process of photoaging of the skin. This study reviews literature on the skin care properties of resveratrol and its dermal bioavailability, metabolism, and dermal safety of application.

Bioinformatics Analysis on Molecular Mechanism of Green Tea Compound Epigallocatechin-3-Gallate Against Ovarian Cancer

Epigallocatechin‐3‐gallate (EGCG) is the most abundant and biologically active catechin in green tea, and it exerts multiple effects in humans through mechanisms that remain to be clarified. The present study used bioinformatics to identify possible mechanisms by which EGCG reduces the risk of ovarian cancer. Possible human protein targets of EGCG were identified in the PubChem database, possible human gene targets were identified in the National Center for Biotechnology Information database, and then both sets of targets were analyzed using Ingenuity Pathway Analysis (IPA). The results suggest that signaling proteins affected by EGCG in ovarian cancer, which include JUN, FADD, NFKB1, Bcl‐2, HIF1α, and MMP, are involved primarily in cell cycle, cellular assembly and organization, DNA replication, etc. These results identify several specific proteins and pathways that may be affected by EGCG in ovarian cancer, and they illustrate the power of integrative informatics and chemical fragment analysis for focusing mechanistic studies.

Interaction between Pin1 and its natural product inhibitor epigallocatechin-3-gallate by spectroscopy and molecular dynamics simulations

The binding of epigallocatechin-3-gallate (EGCG) to wild type Pin1 in solution was studied by spectroscopic methods and molecular dynamics simulations in this research to explore the binding mode and inhibition mechanism. The binding constants and number of binding sites per Pin1 for EGCG were calculated through the Stern-Volmer equation. The values of binding free energy and thermodynamic parameters were calculated and indicated that hydrogen bonds, electrostatic interaction and Van der Waals interaction played the major role in the binding process. The alterations of Pin1 secondary structure in the presence of EGCG were confirmed by far-UV circular dichroism spectra. The binding model at atomic-level revealed that EGCG was bound to the Glu12, Lys13, Arg14, Met15 and Arg17 in WW domain. Furthermore, EGCG could also interact with Arg69, Asp112, Cys113 and Ser114 in PPIase domain.

Anti-cancer effect of (-)-epigallocatechin-3-gallate (EGCG) in head and neck cancer through repression of transactivation and enhanced degradation of β-catenin

BACKGROUND AND PURPOSE

Aberrant expression of β-catenin is highly associated with progression of various cancers including head and neck cancer (HNC). Green tea is most commonly used beverage in the world and one of the more bioactive compounds is the antioxidant epigallocatechin gallate (EGCG). This study was performed to investigate the mechanism by which EGCG inhibits the growth of HNC, focusing on the modulation of the expression and activity of β-catenin.

METHODS

In vitro effects of EGCG on the transcription, translation, or degradation of β-catenin were investigated. Antitumor effects of EGCG in vivo were evaluated in a syngeneic mouse model and β-catenin expression was checked in HNC patients' samples.

RESULTS

β-catenin expression was elevated in tumor samples of HNC patients. EGCG induced apoptosis in KB and FaDu cells through the suppression of β-catenin signaling. Knockdown of β-catenin using siRNA enhanced the proapoptotic activities of EGCG. EGCG decreased mRNA and transcriptional activity of β-catenin in p53 wild-type KB cells. EGCG also enhanced the ubiquitination and proteasomal degradation of β-catenin. The suppression of β-catenin and consequent apoptosis were observed in response to EGCG treatment in a syngeneic mouse model. In conclusion, we report that EGCG inhibits β-catenin expression through multiple mechanisms including decreased transcription and increased ubiquitin-mediated 26S proteasomal degradation.

CONCLUSION

This study proposes a novel molecular rationale for antitumor activities of green tea in HNCs.

Functional testing of topical skin formulations using an optimised ex vivo skin organ culture model

A number of equivalent-skin models are available for investigation of the ex vivo effect of topical application of drugs and cosmaceuticals onto skin, however many have their drawbacks. With the March 2013 ban on animal models for cosmetic testing of products or ingredients for sale in the EU, their utility for testing toxicity and effect on skin becomes more relevant. The aim of this study was to demonstrate proof of principle that altered expression of key gene and protein markers could be quantified in an optimised whole tissue biopsy culture model. Topical formulations containing green tea catechins (GTC) were investigated in a skin biopsy culture model (n = 11). Punch biopsies were harvested at 3, 7 and 10 days, and analysed using qRT-PCR, histology and HPLC to determine gene and protein expression, and transdermal delivery of compounds of interest. Reduced gene expression of α-SMA, fibronectin, mast cell tryptase, mast cell chymase, TGF-β1, CTGF and PAI-1 was observed after 7 and 10 days compared with treated controls (p < 0.05). Histological analysis indicated a reduction in mast cell tryptase and chymase positive cell numbers in treated biopsies compared with untreated controls at day 7 and day 10 (p < 0.05). Determination of transdermal uptake indicated that GTCs were detected in the biopsies. This model could be adapted to study a range of different topical formulations in both normal and diseased skin, negating the requirement for animal models in this context, prior to study in a clinical trial environment.

Green tea polyphenol EGCG suppresses Wnt/β-catenin signaling by promoting GSK-3β- and PP2A-independent β-catenin phosphorylation/degradation

(-)-Epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, has been reported to inhibit the Wnt/β-catenin pathway, which is aberrantly up-regulated in colorectal cancers, but its precise mechanism of action remains unclear. Here, we used a sensitive cell-based system to demonstrate that EGCG suppresses β-catenin response transcription (CRT), activated by Wnt3a-conditioned medium (Wnt3a-CM), by promoting the degradation of intracellular β-catenin. EGCG induced β-catenin N-terminal phosphorylation at the Ser33/37 residues and subsequently promoted its degradation; however, this effect was not observed for oncogenic forms of β-catenin. Pharmacological inhibition or depletion of glycogen synthase kinase-3β (GSK-3β) did not abrogate the EGCG-mediated β-catenin degradation. EGCG did not affect the activity and expression of protein phosphatase 2A (PP2A). Consistently, the phosphorylation and degradation of β-catenin was found in adenomatous polyposis coli (APC) mutated colon cancer cells after EGCG treatment. EGCG repressed the expression of cyclin D1 and c-myc, which are β-catenin/T-cell factor-dependent genes, and inhibited the proliferation of colon cancer cells. Our findings suggest that EGCG exerts its cancer-preventive or anticancer activity against colon cancer cells by promoting the phosphorylation and proteasomal degradation of β-catenin through a mechanism independent of the GSK-3β and PP2A.

Kinetics and Mechanistic Studies on the Reaction between Cytochrome c and Tea Catechins

Green tea is characterized by the presence of an abundance of polyphenolic compounds, also known as catechins, including epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (EGC) and epigallocatechin gallate (EGCG). In addition to being a popular beverage, tea consumption has been suggested as a mean of chemoprevention. However, its mode of action is unclear. It was discovered that tea catechins can react with cytochrome c. When oxidized cytochrome c was mixed with catechins commonly found in green tea under non-steady-state conditions, a reduction of cytochrome c was observed. The reaction rate of the catechins was dependent on the pH and the nature of the catechin. The pseudo-first order rate constant obtained increased in the order of EC < ECG < EGC < EGCG, which is consistent with previously reported superoxide reduction activities and Cu²⁺ reduction activities of tea catechins.

Chemoprevention of skin melanoma: facts and myths

Melanoma is the most dangerous type of skin cancer. Despite the rise of public awareness, the incidence rate among the white population has been rising constantly for several decades. Systematic improvement in knowledge about the biology of pigment cells and molecular mechanisms of their neoplastic transformation has enhanced the possibility of melanoma chemoprevention. Hence, chemopreventive agents that prevent, inhibit, or reverse melanoma development are being investigated intensively. Among synthetic compounds, especially well studied are lipid-lowering drugs and cyclooxygenase inhibitors. Substances found in everyday diet, such as genistein, apigenin, quercetin, resveratrol, and curcumin may also have potential chemopreventive qualities. However, studies examining the chemopreventive activity of these compounds have shown widely varying results. Early reports on the possible chemopreventive activity of statins and fibrates were not proved by the results of randomized clinical trials. Similarly, case-control studies examining the influence of NSAIDs on the risk of melanoma do not confirm the antitumor activity of cyclooxygenase inhibitors. Further clinical trials involving carefully selected target populations as well as the identification of specific biomarkers of prognostic and predictive value seem to be essential for the evaluation of the chemopreventive activity of the studied substances.

Chemoprevention of skin cancer with 1,1-Bis (3'-indolyl)-1-(aromatic) methane analog through induction of the orphan nuclear receptor, NR4A2 (Nurr1)

Background

The objective of this study was to demonstrate the anti-skin cancer and chemopreventive potential of 1,1-bis(3′-indolyl)-1-(p-chlorophenyl methane) (DIM-D) using an in vitro model.

Methods

In vitro cell cytotoxicity and viability assays were carried out in A431 human epidermoid carcinoma cell line and normal human epidermal keratinocytes (NHEK) respectively by crystal violet staining. Apoptosis induction in A431 cells (DIM-D treated) and NHEK cells pretreated with DIM-D (2 hr) prior to UVB irradiation, were assessed. The accumulation of reactive oxygen species (ROS) in DIM-D pretreated NHEK cells (2 hr) prior to UVB exposure was also determined. Immunocytochemistry and western blot analysis was performed to determine cleaved caspase 3 and DNA damage markers in DIM-D treated A431 cells and in DIM-D pretreated NHEK cells prior to UVB irradiation.

Results

The IC50 values of DIM-D were 68.7±7.3, 48.3±10.1 and 11.5±3.1 μM whilst for Epigallocatechin gallate (EGCG) were 419.1±8.3, 186.1±5.2 and 56.7±3.1 μM for 24, 48 and 72 hr treatments respectively. DIM-D exhibited a significantly (p<0.05) greater induction of DNA fragmentation in A431 cells compared to EGCG with percent cell death of 38.9. In addition, DIM-D induced higher expression in A431 cells compared to EGCG of cleaved caspase 3 (3.0-fold vs. 2.4-fold changes), Nurr1 (2.7-fold vs. 1.7-fold changes) and NFκB (1.3-fold vs. 1.1-fold changes). DIM-D also exhibited chemopreventive activity in UVB-irradiated NHEK cells by significantly (p<0.05) reducing UVB-induced ROS formation and apoptosis compared to EGCG. Additionally, DIM-D induced expression of Nurr1 but reduced expression of 8-OHdG significantly in UVB-irradiated NHEK cells compared to EGCG and UV only.

Conclusion

Our results suggest that DIM-D exhibits Nurr1-dependent transactivation in the induction of apoptosis in A431 cells and it protects NHEK cells against UVB-induced ROS formation and DNA damage.

Potential role of green tea catechins in various disease therapies: progress and promise

Green tea (from the plant Camellia sinensis), a beverage whose consumption started 5000 years ago in China, has important biological and pharmacological properties. The beneficial effects of green tea have been attributed to the presence of phenolic compounds that are powerful anti-oxidants and free iron scavengers. Of all the catechins found in green tea, namely (-)-epicatechin-3-gallate, (-)-epigallocatechin, (-)-epicatechin and (-)-epigallocatechin-3-gallate (EGCG), EGCG is the most abundant and powerful. It is widely believed that green tea may protect against death from all causes, especially cardiovascular diseases (coronary heart disease and stroke) owing to the presence of catechins associated with green tea consumption. Other health benefits include various types of cancer chemoprevention, weight loss and protective effects against neurodegenerative diseases (Alzheimer's disease and Parkinson's disease). Thus far, numerous pharmacological activities regulating disease-specific molecular targets have been reported in vitro for EGCG concentrations in the micromolar range, which are physiologically irrelevant. Although most of the studies have shown benefits with two to three cups of green tea per day, the optimal dose has not yet been established to enable any solid conclusions to be drawn regarding the various health benefits of green tea or its constituents in humans. With Phase I trials providing information on the safety profile and pharmacokinetics of EGCG, the window of opportunity is wider to undertake well-controlled long-term human studies to enable a full understanding of the protective effects of green tea catechins on various parameters in different settings.

Comparison of catechin profiles in human plasma and urine after single dosing and regular intake of green tea (Camellia sinensis)

Green tea (Camellia sinensis) catechin profiles in plasma and urine following single dosing and regular ingestion of green tea are not clear. We performed a placebo-controlled intervention study with sixteen healthy volunteers to determine changes in total and free catechins after a single dose and following 1 week of twice-daily green tea. Blood and urine samples were collected before (fasting) and after (60 and 120 min for blood; 90 and 180 min for urine) drinking 200 ml of 1.5% (w/v) green tea or water (n 8 each), and fasting samples were again collected after 7 d of 150 ml of 1% (w/v) supplemental green tea or water twice daily. After a 4-week washout, subjects were crossed onto the other treatment and procedures repeated. Plasma results at 1 h post-ingestion showed elevated (P < 0.05) mean epigallocatechin gallate (EGCG; 310 (SD 117) nmol/l; all in free form), epigallocatechin (EGC; 192 (SD 67) nmol/l; 30% free) and epicatechin gallate (ECG; 134 (SD 51) nmol/l; 75% free). Fasting plasma after 7 d of regular intake showed increased (P < 0.05) EGCG (80 v. 15 nmol/l at baseline) and ECG (120 v. 40 nmol/l), with > or =90% of both in their conjugated forms. Total EGC was < 10 nmol/l. Post-ingestion conjugation and renal loss of EGC and epicatechin were rapid and high, but were negligible for EGCG and ECG. In the green tea consumed, the content was EGCG > EGC > ECG, and the acute plasma response mirrored this. However, after chronic consumption there was almost no EGC found in fasting plasma, some EGCG was present, but a rather high level of ECG was maintained.

Inhibitory effect and mechanisms of an anthocyanins- and anthocyanidins-rich extract from purple-shoot tea on colorectal carcinoma cell proliferation

One newly bred variety of tea cultivar, purple-shoot tea, was selected to evaluate its antiproliferative effects on colorectal carcinoma cells, as well as normal colon cells. The phytochemicals and identified catechins of purple-shoot tea extract (PTE) were significantly higher than that of ordinary tea, especially the anthocyanins (surpassed by 135-fold) and anthocyanidins (surpassed by 3.5-fold). PTE inhibited the proliferation of COLO 320DM (IC(50) = 64.9 μg/mL) and HT-29 (IC(50) = 55.2 μg/mL) by blocking cell cycle progression during the G(0)/G(1) phase and inducing apoptotic death. Western blotting indicated that PTE induced cell cycle arrest by reducing the expression of cyclin E and cyclin D1 in COLO 320DM and the upregulation of p21 and p27 cyclin-dependent kinase inhibitors in HT-29. Two cells treated with PTE also indicated the cleavage of PARP, activation of caspase 3, and an increased Bax/Bcl-2 ratio. Our results showed that PTE is a potential novel dietary agent for colorectal cancer chemoprevention.

Green tea gets molecular

Green tea and its major polyphenolic flavonoid, epigallocatechin gallate (EGCG), have been credited with cancer chemopreventive activity for many years; the mechanism for this activity, however, has remained obscure. Now, as reported in this issue of the journal (beginning on page 1366), Urusova and colleagues showed direct binding of EGCG to the peptidyl prolyl cis/trans isomerase Pin1, which inhibited Pin1 enzymatic activity. They showed that Pin1 expression is required for EGCG effects on cell growth, c-Jun activation, and transcription regulation mediated by NF-κB and activator protein-1. The data provide a glimpse of the mechanism of action of EGCG and set a new bar for the future study of natural products with chemopreventive activity.

Identification and characterization of low molecular weight polyphenols in berry leaf extracts by HPLC-DAD and LC-ESI/MS

This paper reports the results of qualitative and quantitative analyses of low molecular weight phenolics from five berry leaf extract using HPLC-DAD and LC-ESI/MS. The identification of the black currant, raspberry, bilberry, honeysuckle, and strawberry leaf phytochemicals was based on the comparison of UV-vis absorption maxima (λ(max)) and mass spectral analysis. The peak identification in samples was also based on comparisons of the retention times (t(R)) of the isolated phytochemical standards. Knowledge of the precise phenolic profile of berry leaves may offer a scientific basis to put the underutilized berry leaves to good use as very cheap raw materials for polyphenol extract production. These studies indicated that these leaves can be used as a good and cheap source of bioactive constituents. These results suggest that berry leaves are a potential source of phenolics and have potential pro-healthy properties to contribute to human health.

Modulating effects of rooibos and honeybush herbal teas on the development of esophageal papillomas in rats

Widespread consumption of herbal teas has stimulated interest in their role as cancer preventive agents. The present investigation monitored the modulation of methylbenzylnitrosamine (MBN)-induced esophageal squamous cell carcinogenesis by rooibos (Aspalathus linearis) and honeybush (Cyclopia intermedia) herbal and Camellia sinensis teas in male F344 rats. The tumor multiplicity was significantly (P < 0.05) inhibited by unfermented honeybush (45.5%), green (50%), and black (36%) teas, while the other teas exhibited weaker effects (<30% inhibition). The mean total papilloma size was reduced by unfermented rooibos (87%), unfermented honeybush (94%), and fermented honeybush (74%) due to the absence of large papillomas (>10 mm(3)). Reduction of the mean total papilloma number correlated with the total polyphenol (TPP) (r = 0.79; P < 0.02) and flavanol/proanthocyanidin (FLAVA) (r = 0.89; P < 0.008) intake (mg/100 g body weight) of the teas and the FLAVA (r = 0.89; P < 0.04) and flavonol/flavones/xanthones (r = 0.99; P < 0.002) intake when considering only the herbal teas. A daily TPP intake threshold of 7 mg/100 g body weight existed below where no inhibition of papilloma development was observed. Fermentation of herbal teas reduced the inhibitory effects on papilloma development associated with a reduction in the polyphenolic constituents. The inhibitory effect of herbal teas on papilloma development is associated with different flavonoid subgroups and/or combination thereof.

Evaluation of renal protective effects of the green-tea (EGCG) and red grape resveratrol: role of oxidative stress and inflammatory cytokines

Epigallocatechin-gallate (EGCG) and resveratrol (RSVL) are two of the most promising natural medicines. We verified their capacity to ameliorate cisplatin (CP)-induced disruption of renal glomerular filtration rate (GFR) in rats, and sought the mediatory involvement of lipid peroxidation (malondialdehyde [MDA]-level) and inflammatory cytokine (TNF-α) therein. CP (10 mg kg⁻¹), a single i.p. dose, disrupted GFR (11-fold-rise in proteinuria, 2-5-fold rise in serum creatinine/urea levels) after 7 days, and killed all animals after 10 days. Kidney-homogenates from CP-treated rats displayed higher MDA and TNF-α, but lower reduced-glutathione (GSH) levels. Rats treated with EGCG (50 mg kg⁻¹, but not 25 mg kg⁻¹) had no fatalities and showed significantly-recovered GFR; while their kidney-homogenates had markedly reduced MDA, TNF-α and enhanced GSH levels at 7 days. Conversely, RSVL or quercetin (25, 50 mg kg⁻¹) neither improved GFR nor reduced (MDA)/TNF-α levels after 7 days. Resuming treatment with 50 mg kg⁻¹ for 10 days rescued only 25% of animals (p > 0.05). Correlation studies showed a significant association between creatinine level, and each of MDA (r = 0.91), GSH (r = -0.87), and TNF-α (0.91). The study showed for the first time that EGCG, unlike RSVL, can protect against CP-induced nephrotoxicity. At the molecular level, CP triggers a high level of oxidative stress and systemic inflammation, events that were all abrogated with EGCG; better than RSVL or quercetin.

EGCG-meditated cyto- and genotoxicity in HaCat keratinocytes is impaired by cell-mediated clearance of auto-oxidation-derived H2O2: an algorithm for experimental setting correction

Several lines of evidence suggest that besides antioxidant also prooxidant properties are crucially involved in cytotoxic and protective activities of the major green tea catechin epigallocatechin-3-gallate (EGCG) in vitro (Elbling et al., 2011). Furthermore recent data suggest that EGCG induces oxidative stress also in vivo (Li et al., 2010). Here we set out to identify factors modulating cellular effects of EGCG in vitro. Using the HaCat keratinocytes model, we demonstrate that the cytotoxic, genotoxic and signal-activating effects of EGCG are significantly dependent on the ratio of cell number to working volume. Treatment with identical EGCG concentrations at altered experimental settings resulted in IC(50) values differing up to orders of magnitude and could even exert contradictory effects. This effect was based on cell-mediated clearance of autooxidation-derived H(2)O(2) from the supernatant. In order to estimate EGCG/H(2)O(2) concentrations equally effective under different settings, we have rationally derived and experimentally verified a simple algorithm relating concentration, working volume, cell number and - indirectly - exposure time. Algorithm application resulted in similar H(2)O(2) clearance curves from cell supernatants as well as comparable EGCG/H(2)O(2) effects at different settings. Our results demonstrate the importance of standardized experimental settings when investigating cytotoxic and/or beneficial effects of autooxidizing compounds.

Implantation of green tea catechin α-tricalcium phosphate combination enhances bone repair in rat skull defects

The purpose of the present study is to investigate effects of the combination of epigallocatechin-3-gallate (EGCG) and α-tricalcium phosphate (α-TCP) on bone regenerative capacity in a bilateral rat calvarial bone defect model.

MATERIALS AND METHODS

Bilateral 5-mm-diameter calvarial defects were created in adult male Wistar rats and filled with preparations of EGCG (0, 0.1, 0.2, 0.4 mg) combined with α-TCP particles. This was done by dissolving EGCG in 100% ethanol (50 μL/14 mg) and dropping under sterile condition. The control group was left unfilled (n = 8). The animals were sacrificed at 2 and 4 weeks. Radiological images were taken, and histological analysis was done. Six animals from control (0 mg EGCG + α-TCP) group and (0.2 mg EGCG+ α-TCP) group were labeled with fluorescent dyes and histomorphometrically analyzed (n = 6) at 2 and 4 weeks.

RESULTS

Histomorphometric analysis revealed that the combination of EGCG and α-TCP at doses of 0.1 and 0.2 mg yielded significantly more new bone formation than untreated control group at 2 and 4 weeks (p > 0.05). Mineral apposition rate at 0.2-TCP group was enhanced compared with the one of the positive control α-TCP group at 4 weeks (p > 0.05).

CONCLUSION

The combination of α-TCP particles and 0.2 mg EGCG stimulates maximum bone regeneration in rat calvarial defects, and this combination would be potentially effective as bone graft material.

Extracts of Maqui ( Aristotelia chilensis ) and Murta ( Ugni molinae Turcz.): sources of antioxidant compounds and α-Glucosidase/α-Amylase inhibitors

The objective of this work was to evaluate the antioxidant and antihemolytic activities of crude, aqueous, and organic-aqueous extracts of maqui ( Aristotelia chilensis ) and murta ( Ugni molinae Turcz.), together with their inhibiting effect on enzymes involved in the metabolism of carbohydrates. Radical scavenging activity, inhibition of linoleic acid oxidation in a micellar system, antihemolytic activity, and inhibition of α-amylases and α-glucosidases were analyzed. Crude extracts of maqui leaves and fruits were found to be important sources of polyphenolic compounds, showing 69.0 ± 0.9 and 45.7 ± 1.1 mg GAE/g dm, respectively. Polyphenols from maqui leaves were active as antioxidants and antihemolytic compounds (p < 0.05), showing a noncompetitive inhibiting effect on α-glucosidase. Flavan-3-ol polymers and glycosylated flavonols, such as quercetin glucoside and kaempferol glucoside, were tentatively identified in extracts. This preliminary observation provides the basis for further examination of the suitability of polyphenol-enriched extracts from maqui and murta as nutritional or medicinal supplements with potential human health benefits.

Radiation-Induced Testicular Injury and Its Amelioration by Tinospora cordifolia (An Indian Medicinal Plant) Extract

The primary objective of this investigation is to determine the deleterious effects of sub lethal gamma radiation on testes and their possible inhibition by Tinospora cordifolia extract (TCE). For this purpose, one group of male Swiss albino mice was exposed to 7.5 Gy gamma radiation to serve as the irradiated control, while the other group received TCE (75 mg/kg b. wt./day) orally for 5 consecutive days half an hr before irradiation to serve as experimental. Exposure of animals to 7.5 Gy gamma radiation resulted into significant decrease in body weight, tissue weight, testes- body weight ratio and tubular diameter up to 15 days of irradiation. Cent percent mortality was recorded by day 17th in irradiated control, whereas all animals survived in experimental group. TCE pretreatment rendered significant increase in body weight, tissue weight, testes- body weight ratio and tubular diameter at various intervals as compared to irradiated group. Radiation induced histological lesions in testicular architecture were observed more severe in irradiated control then the experimental. TCE administration before irradiation significantly ameliorated radiation induced elevation in lipid peroxidation and decline in glutathione concentration in testes. These observations indicate the radio- protective potential of Tinospora cordifolia root extract in testicular constituents against gamma irradiation in mice.

Green tea (-)-epigallocatechin-3-gallate inhibits HGF-induced progression in oral cavity cancer through suppression of HGF/c-Met

Hepatocyte growth factor (HGF) and c-Met have recently attracted a great deal of attention as prognostic indicators of patient outcome, and they are important in the control of tumor growth and invasion. Epigallocatechin-3-gallate (EGCG) has been shown to modulate multiple signal pathways in a manner that controls the unwanted proliferation and invasion of cells, thereby imparting cancer chemopreventive and therapeutic effects. In this study, we investigated the effects of EGCG in inhibiting HGF-induced tumor growth and invasion of oral cancer in vitro and in vivo. We examined the effects of EGCG on HGF-induced cell proliferation, migration, invasion, induction of apoptosis and modulation of HGF/c-Met signaling pathway in the KB oral cancer cell line. We investigated the antitumor effect and inhibition of c-Met expression by EGCG in a syngeneic mouse model (C3H/HeJ mice, SCC VII/SF cell line). HGF promoted cell proliferation, migration, invasion and induction of MMP (matrix metalloproteinase)-2 and MMP-9 in KB cells. EGCG significantly inhibited HGF-induced phosphorylation of Met and cell growth, invasion and expression of MMP-2 and MMP-9. EGCG blocked HGF-induced phosphorylation of c-Met and that of the downstream kinases AKT and ERK, and inhibition of p-AKT and p-ERK by EGCG was associated with marked increases in the phosphorylation of p38, JNK, cleaved caspase-3 and poly-ADP-ribose polymerase. In C3H/HeJ syngeneic mice, as an in vivo model, tumor growth was suppressed and apoptosis was increased by EGCG. Our results suggest that EGCG may be a potential therapeutic agent to inhibit HGF-induced tumor growth and invasion in oral cancer.

Green tea and cancer prevention

Extracts of green tea and green tea polyphenols have exhibited inhibitory effects against the formation and development of tumors at different organ sites in animals. These include animal models for skin, lung, oral cavity, esophagus, stomach, intestine, colon, liver, pancreas, bladder, mammary gland, and prostate cancers. In addition to suppressing cell proliferation, promoting apoptosis, and modulating signaling transduction, green tea polyphenols, especially (-)-epigallocatechin-3-gallate, also inhibit cell invasion, angiogenesis, and metastasis. This article reviews data on the cancer preventive activities of green tea polyphenols, possible mechanisms involved, and the relationship between green tea consumption and human cancer risk.