Induction of apoptosis by epigallocatechin-3-gallate in human lymphoblastoid B cells

The Effects of Green Tea Catechins in Hematological Malignancies

Green tea catechins are bioactive polyphenol compounds which have attracted significant attention for their diverse biological activities and potential health benefits. Notably, epigallocatechin-3-gallate (EGCG) has emerged as a potent apoptosis inducer through mechanisms involving caspase activation, modulation of Bcl-2 family proteins, disruption of survival signaling pathways and by regulating the redox balance, inducing oxidative stress. Furthermore, emerging evidence suggests that green tea catechins can modulate epigenetic alterations, including DNA methylation and histone modifications. In addition to their apoptotic actions, ROS signaling effects and reversal of epigenetic alterations, green tea catechins have shown promising results in promoting the differentiation of leukemia cells. This review highlights the comprehensive actions of green tea catechins and provides valuable insights from clinical trials investigating the therapeutic potential of green tea catechins in leukemia treatment. Understanding these multifaceted mechanisms and the outcomes of clinical trials may pave the way for the development of innovative strategies and the integration of green tea catechins into clinical practice for improving leukemia patient outcomes.

The use of African medicinal plants in cancer management

Cancer is the third leading cause of premature death in sub-Saharan Africa. Cervical cancer has the highest number of incidences in sub-Saharan Africa due to high HIV prevalence (70% of global cases) in African countries which is linked to increasing the risk of developing cervical cancer, and the continuous high risk of being infected with Human papillomavirus In 2020, the risk of dying from cancer amongst women was higher in Eastern Africa (11%) than it was in Northern America (7.4%). Plants continue to provide unlimited pharmacological bioactive compounds that are used to manage various illnesses, including cancer. By reviewing the literature, we provide an inventory of African plants with reported anticancer activity and evidence supporting their use in cancer management. In this review, we report 23 plants that have been used for cancer management in Africa, where the anticancer extracts are usually prepared from barks, fruits, leaves, roots, and stems of these plants. Extensive information is reported about the bioactive compounds present in these plants as well as their potential activities against various forms of cancer. However, information on the anticancer properties of other African medicinal plants is insufficient. Therefore, there is a need to isolate and evaluate the anticancer potential of bioactive compounds from other African medicinal plants. Further studies on these plants will allow the elucidation of their anticancer mechanisms of action and allow the identification of phytochemicals that are responsible for their anticancer properties. Overall, this review provides consolidated and extensive information not only on diverse medicinal plants of Africa but on the different types of cancer that these plants are used to manage and the diverse mechanisms and pathways that are involved during cancer alleviation.

Pomegranate juice anthocyanidins induce cell death in human cancer cells by mobilizing intracellular copper ions and producing reactive oxygen species

Anthocyanidins are the most abundant polyphenols in pomegranate juice. This class of molecules includes Delphinidin (Del), Cyanidin (Cya), and Pelargonidin (Pel). Using prostate, breast and pancreatic cancer cell lines PC3, MDA-MB-231, BxPC-3 and MiaPaCa-2, we show that anthocyanidins inhibit cell proliferation (measured by MTT assay) and induce apoptosis like cell death (measured by DNA/Histone ELISA). Copper chelator neocuproine and reactive oxygen species scavengers (thiourea for hydroxyl radical and superoxide dismutase for superoxide anion) significantly inhibit this reaction thus demonstrating that intracellular copper reacts with anthocyanidins in cancer cells to cause DNA damage via ROS generation. We further show that copper-supplemented media sensitizes normal breast epithelial cells (MCF-10A) to Del-mediated growth inhibition as determined by decreased cell proliferation. Copper supplementation results in increased expression of copper transporters Ctr1 and ATP7A in MCF-10A cells, which is attenuated by the addition of Del in the medium. We propose that the copper mediated, ROS-induced mechanism of selective cell death of cancer cells may in part explain the anticancer effects of anthocyanidins.

Natural Polyphenols as Modulators of Etoposide Anti-Cancer Activity

Polyphenols are naturally occurring compounds found in abundance in fruits and vegetables. Their health-promoting properties and their use in the prevention and treatment of many human diseases, including cancer, have been known for years. Many anti-cancer drugs are derived from these natural compounds. Etoposide, which is a semi-synthetic derivative of podophyllotoxin, a non-alkaloid lignan isolated from the dried roots and rhizomes of Podophyllum peltatum or Podophyllum emodi (Berberidaceae), is an example of such a compound. In this review, we present data on the effects of polyphenols on the anti-cancer activity of etoposide in in vitro and in vivo studies.

Catechins-Modified Selenium-Doped Hydroxyapatite Nanomaterials for Improved Osteosarcoma Therapy Through Generation of Reactive Oxygen Species

Osteosarcoma is the most common bone cancer with limited therapeutic options. It can be treated by selenium-doped hydroxyapatite owing to its known antitumor potential. However, a high concentration of Se is toxic toward normal and stem cells whereas its low concentration cannot effectively remove cancer cells. Therefore, the current study was aimed to improve the anticancer activity of Se-HAp nanoparticles through catechins (CC) modification owing to their high cancer therapeutic value. The sequentially developed catechins modified Se-HAp nanocomposites (CC/Se-HAp) were characterized for various physico-chemical properties and antitumor activity. Structural analysis showed the synthesis of small rod-like single phase HAp nanoparticles (60 ± 15 nm), which effectively interacted with Se and catechins and formed agglomerated structures. TEM analysis showed the internalization and degradation of CC/Se-HAp nanomaterials within MNNG/HOS cells through a non-specific endocytosis process. Cell toxicity analysis showed that catechins modification improved the antitumor activity of Se-HAp nanocomposites by inducing apoptosis of human osteosarcoma MNNG/HOS cell lines, through generation of reactive oxygen species (ROS) which in turn activated the caspase-3 pathway, without significantly affecting the growth of human normal bone marrow stem cells (hBMSCs). qPCR and western blot analyses revealed that casp3, p53, and bax genes were significantly upregulated while cox-2 and PTK-2 were slightly downregulated as compared to control in CC/Se-HAp-treated MNNG/HOS cell lines. The current study of combining natural biomaterial (i.e., catechins) with Se and HAp, can prove to be an effective therapeutic approach for bone cancer therapy.

ROS-Mediated Cancer Cell Killing through Dietary Phytochemicals

Reactive oxygen species (ROS) promote carcinogenesis by inducing genetic mutations, activating oncogenes, and raising oxidative stress, which all influence cell proliferation, survival, and apoptosis. Cancer cells display redox imbalance due to increased ROS level compared to normal cells. This unique feature in cancer cells may, therefore, be exploited for targeted therapy. Over the past few decades, natural compounds have attracted attention as potential cancer therapies because of their ability to maintain cellular redox homeostasis with minimal toxicity. Preclinical studies show that bioactive dietary polyphenols exert antitumor effects by inducing ROS-mediated cytotoxicity in cancer cells. These bioactive compounds also regulate cell proliferation, survival, and apoptotic and antiapoptotic signalling pathways. In this review, we discuss (i) how ROS is generated and (ii) regulated and (iii) the cell signalling pathways affected by ROS. We also discuss (iv) the various dietary phytochemicals that have been implicated to have cancer therapeutic effects through their ROS-related functions.

New Perspectives in Iron Chelation Therapy for the Treatment of Neurodegenerative Diseases

Iron chelation has been introduced as a new therapeutic concept for the treatment of neurodegenerative diseases with features of iron overload. At difference with iron chelators used in systemic diseases, effective chelators for the treatment of neurodegenerative diseases must cross the blood–brain barrier. Given the promissory but still inconclusive results obtained in clinical trials of iron chelation therapy, it is reasonable to postulate that new compounds with properties that extend beyond chelation should significantly improve these results. Desirable properties of a new generation of chelators include mitochondrial destination, the center of iron-reactive oxygen species interaction, and the ability to quench free radicals produced by the Fenton reaction. In addition, these chelators should have moderate iron binding affinity, sufficient to chelate excessive increments of the labile iron pool, estimated in the micromolar range, but not high enough to disrupt physiological iron homeostasis. Moreover, candidate chelators should have selectivity for the targeted neuronal type, to lessen unwanted secondary effects during long-term treatment. Here, on the basis of a number of clinical trials, we discuss critically the current situation of iron chelation therapy for the treatment of neurodegenerative diseases with an iron accumulation component. The list includes Parkinson’s disease, Friedreich’s ataxia, pantothenate kinase-associated neurodegeneration, Huntington disease and Alzheimer’s disease. We also review the upsurge of new multifunctional iron chelators that in the future may replace the conventional types as therapeutic agents for the treatment of neurodegenerative diseases.

Structure-Based Classification and Anti-Cancer Effects of Plant Metabolites

A variety of malignant cancers affect the global human population. Although a wide variety of approaches to cancer treatment have been studied and used clinically (surgery, radiotherapy, chemotherapy, and immunotherapy), the toxic side effects of cancer therapies have a negative impact on patients and impede progress in conquering cancer. Plant metabolites are emerging as new leads for anti-cancer drug development. This review summarizes these plant metabolites with regard to their structures and the types of cancer against which they show activity, organized by the organ or tissues in which each cancer forms. This information will be helpful for understanding the current state of knowledge of the anti-cancer effects of various plant metabolites against major types of cancer for the further development of novel anti-cancer drugs.

Role of EGCG in Containing the Progression of Lung Tumorigenesis - A Multistage Targeting Approach

Lung cancer is a prominent form among various types of cancers, irrespective of the sex worldwide. Treatment of lung cancer involves the intensive phase of chemotherapy/radiotherapy which is associated with high rate of adverse events. There is a need of safe and reliable treatment/adjunctive therapy to apprehend the cancer by reducing the undesirable outcome of primary therapy. Epigallocatechin-3-gallate (EGCG), which is a potent antioxidant and anticancer compound extracted from the plant camellia sinensis has proved to be a novel agent to control or reduce lung tumorigenesis by affecting the signaling molecules of cell cycle regulation and apoptotic pathways. In vitro studies have revealed that EGCG can contain carcinogenesis by altering the molecules involved in multiple signal transduction pathways like ERK, VEGF, COX2, NEAT, Ras-GTPase, and kinases. The animal studies have also demonstrated effectiveness of EGCG by inhibiting various molecular pathways which include AKT, NFkB, MAPK, Bcl/Bax, DNMT1, and HIF-1α. Various attempts have been made to see the adjunctive role of EGCG in human lung cancer. Phase I/II clinical studies have recommended that EGCG is quite safe and effective in providing protection against cancer. In this review, we will discuss the role of EGCG and its molecular mechanisms in lung carcinogenesis.

Complementary and Integrative Medicine in Hematologic Malignancies: Questions and Challenges

Hematologic malignancies represent 9.7% of all cancers, making them the fourth most common type of cancer in the United States. The aggressive and complex treatments administered in hematologic malignancies result in a high burden of psychological needs. Complementary and integrative medicine (CIM) is becoming one of the options that patients use to address their distress during and after cancer treatments. It is not clear whether appropriate CIM can relieve distress in patients affected by these malignancies. This review covers the potential benefits of CIM as relates to nutrition, nutritional supplements, exercise, circadian rhythm, methods for reducing distress during bone marrow aspiration, massage therapy, and acupuncture, in treating patients with hematological malignancies. This review may provide a framework to enhance patient-doctor dialogue regarding CIM use in hematologic malignancies.

Green Tea and Bone Marrow Transplantation: From Antioxidant Activity to Enzymatic and Multidrug-resistance Modulation

Epigallocatechin-3-gallate (EGCG), the main flavonoid of green tea (GT), could play an active role in the prevention of oxidative-stress-related diseases, such as hematologic malignancies. Some effects of EGCG are not imputable to antioxidant activity, but involve modulation of antioxidant enzymes and uric acid (UA) levels. The latter is the major factor responsible of the plasma non-enzymatic antioxidant capacity (NEAC). However, hyperuricemia is a frequent clinical feature caused by tumor lysis syndrome or cyclosporine side effects, both before and after bone marrow transplantation (BMT). Besides this, food-drug interactions could be associated with GT consumption and could have clinical implications. The molecular mechanisms involved in the redox and drug metabolizing/transporting pathways were discussed, with particular reference to the potential role of GT and EGCG in BMT. Moreover, on reviewing data on NEAC, isoprostanes, uric acid, and various enzymes from human studies on GT, its extract, or EGCG, an increase in NEAC, without effect on isoprostanes, and contrasting results on UA and enzymes were observed. Currently, few and contrasting available evidences suggest caution for GT consumption in BMT patients and more studies are needed to better understand the potential impact of EGCG on oxidative stress and metabolizing/transporting systems.

Encapsulation of sesamol in phosphatidyl choline micelles: Enhanced bioavailability and anti-inflammatory activity

Sesamol, the phenolic degradation product of sesamolin, although recognised for its anti-inflammatory effects, has low bioavailability. In this manuscript, we attempted to improve its bioavailability by encapsulation in mixed phosphatidylcholine micelles. Sesamol could be solubilised and entrapped in phosphatidylcholine mixed micelles (PCS) with 96.8% efficiency (particle size 3.0±0.06nm). Fluorescence spectra of PCS revealed lower relative fluorescence intensity (RFI 112) compared to 'free' sesamol (FS) (RFI 271). The bioaccessibility, transport across a monolayer of cells and cellular uptake of PCS was 8.58%, 1.5-fold and 1.2-fold better, respectively, compared to FS. The anti-inflammatory effects of FS and PCS were compared using LPS treated RAW 264.7 cell line and lipoxygenase inhibition. PCS effected downregulation of iNOS protein expression (27%), NO production (20%), ROS (32%) and lipoxygenase inhibition (IC₅₀=31.24μM) compared to FS.

Shemamruthaa, a Herbal Formulation Induces Apoptosis in Breast Cancer Cells and Inhibits Tumor Progression in Rats

Phytochemicals present in plants are more effective than their individual constituents in preventing cancer through synergetic effects. From this perspective, Shemamruthaa, a herbal formulation was evaluated with a view to potentiate more intense anticancer property. This study investigates the anticancer activity of Shemamruthaa in breast cancer (MDA-MB 231) cell lines and its cancer therapeutic potential in 7,12-dimethylbenz[a]anthracene induced breast cancer rats. Results of MTT, trypan blue, and apoptotic marker assays suggested that Shemamruthaa can induce cytotoxicity in cancer cells, in a concentration- and time-dependent manner. Oral administration of Shemamruthaa effectively suppressed the tumor progression as evidenced by decrease in tumor volume and modulation of oxidant-antioxidant status and resulted in extended life span. Gas chromatography-mass spectrometry and high-performance liquid chromatography analysis of Shemamruthaa revealed the presence of pyrogallol, 5-hydrxoymethylfurfural, trilinolein, and flavonoids. Finally, we show that Shemamruthaa contains potential anticancer agents acting either singly or in combination against breast cancer cell proliferation.

Anticancer effects and molecular mechanisms of epigallocatechin-3-gallate

Epigallocatechin-3-gallate (EGCG) is a type of catechin found in green tea. EGCG exhibits a variety of activities, including anti-inflammatory, antidiabetes, antiobesity, and antitumor. In this review, we focus on the antitumor effects of EGCG. EGCG inhibits carcinogen activity, tumorigenesis, proliferation, and angiogenesis, and induces cell death. These effects are associated with modulation of reactive oxygen species (ROS) production. Although EGCG has a dual function of antioxidant and pro-oxidant potential, EGCG-mediated modulation of ROS production is reported to be responsible for its anticancer effects. The EGCG-mediated inhibition of nuclear factor-κB signaling is also associated with inhibition of migration, angiogenesis, and cell viability. Activation of mitogen-activated protein kinases activity upregulates the anticancer effect of EGCG on migration, invasion, and apoptosis. In addition, EGCG could also induce epigenetic modification by inhibition of DNA methyltransferase activity and regulation of acetylation on histone, leading to an upregulation of apoptosis. Although EGCG promotes strong anticancer effects by multiple mechanisms, further studies are needed to define the use of EGCG in clinical treatment.

(-)-Epigallocatechin-3-gallate induces non-apoptotic cell death in human cancer cells via ROS-mediated lysosomal membrane permeabilization

(−)-Epigallocatechin-3-gallate (EGCG) is the most extensive studied tea polyphenol for its anti-cancer function. In this study, we report a novel mechanism of action for EGCG-mediated cell death by identifying the critical role of lysosomal membrane permeabilization (LMP). First, EGCG-induced cell death in human cancer cells (both HepG2 and HeLa) was found to be caspase-independent and accompanied by evident cytosolic vacuolization, only observable when cells were treated in serum-free medium. The cytosolic vacuolization observed in EGCG-treated cells was most probably caused by lysosomal dilation. Interestingly, EGCG was able to disrupt autophagic flux at the degradation stage by impairment of lysosomal function, and EGCG-induced cell death was independent of Atg5 or autophagy. The key finding of this study is that EGCG is able to trigger LMP, as evidenced by Lyso-Tracker Red staining, cathepsin D cytosolic translocation and cytosolic acidification. Consistently, a lysosomotropic agent, chloroquine, effectively rescues the cell death via suppressing LMP-caused cytosolic acidification. Lastly, we found that EGCG promotes production of intracellular ROS upstream of LMP and cell death, as evidenced by increased level of ROS in cells treated with EGCG and the protective effects of antioxidant N-acetylcysteine (NAC) against EGCG-mediated LMP and cell death. Taken together, data from our study reveal a novel mechanism underlying EGCG-induced cell death involving ROS and LMP. Therefore, understanding this lysosome-associated cell death pathway shed new lights on the anti-cancer effects of EGCG.

Resveratrol-induced apoptosis is enhanced in low pH environments associated with cancer

Many critical factors such as hypoxia, nutrient deficiency, activation of glycolytic pathway/Warburg effect contribute to the observed low pH in tumors compared to normal tissue. Studies suggest that such tumor specific acidic environment can be exploited for the development of therapeutic strategies against cancer. Independent observations show reduction in pH of mammalian cells undergoing internucleosomal DNA fragmentation and apoptosis. As such, our group has extensively demonstrated that anticancer mechanisms of different plant polyphenols involve mobilization of endogenous copper and consequent internucleosomal DNA breakage. Copper is redox active metal, an essential component of chromatin and is sensitive to subtle pH changes in its microenvironment. Here we explored whether, acidic pH promotes growth inhibition, apoptosis, and DNA damaging capacity of chemopreventive agent resveratrol. Our results reveal that growth inhibition and internucleosomal DNA fragmentation induced apoptosis in Capan-2 and Panc-28 pancreatic cancer cell lines (and not in normal HPDE cells) by resveratrol is enhanced at lower pH. Using comet assay, we further demonstrate that DNA breakage by resveratrol is enhanced with acidification. Membrane permeable copper specific chelator neocuproine (and not iron chelator orthophenanthroline) abrogated growth inhibition and apoptosis by resveratrol. Western blot results show enhanced activation of DNA laddering marker H2.aX by resveratrol at acidic pH that was reversed by neocuproine and not by orthophenanthroline. Our findings provide irrevocable proof that low pH environment can be turned into tumor weakness and assist in eradication of cancer cells by resveratrol.

Role of nuclear factor (erythroid-derived 2)-like 2 in metabolic homeostasis and insulin action: A novel opportunity for diabetes treatment?

Redox balance is fundamentally important for physiological homeostasis. Pathological factors that disturb this dedicated balance may result in oxidative stress, leading to the development or aggravation of a variety of diseases, including diabetes mellitus, cardiovascular diseases, metabolic syndrome as well as inflammation, aging and cancer. Thus, the capacity of endogenous free radical clearance can be of patho-physiological importance; in this regard, the major reactive oxygen species defense machinery, the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) system needs to be precisely modulated in response to pathological alterations. While oxidative stress is among the early events that lead to the development of insulin resistance, the activation of Nrf2 scavenging capacity leads to insulin sensitization. Furthermore, Nrf2 is evidently involved in regulating lipid metabolism. Here we summarize recent findings that link the Nrf2 system to metabolic homeostasis and insulin action and present our view that Nrf2 may serve as a novel drug target for diabetes and its complications.

The role of antioxidant versus pro-oxidant effects of green tea polyphenols in cancer prevention

Consumption of green tea (Camellia sinensis) may provide protection against chronic diseases, including cancer. Green tea polyphenols are believed to be responsible for this cancer preventive effect, and the antioxidant activity of the green tea polyphenols has been implicated as a potential mechanism. This hypothesis has been difficult to study in vivo due to metabolism of these compounds and poor understanding of the redox environment in vivo. Green tea polyphenols can be direct antioxidants by scavenging reactive oxygen species or chelating transition metals as has been demonstrated in vitro. Alternatively, they may act indirectly by upregulating phase II antioxidant enzymes. Evidence of this latter effect has been observed in vivo, yet more work is required to determine under which conditions these mechanisms occur. Green tea polyphenols can also be potent pro-oxidants, both in vitro and in vivo, leading to the formation of hydrogen peroxide, the hydroxyl radical, and superoxide anion. The potential role of these pro-oxidant effects in the cancer preventive activity of green tea is not well understood. The evidence for not only the antioxidant, but also pro-oxidant, properties of green tea is discussed in the present review.

(-)-Epigallocatechin-3-O-gallate induces nonapoptotic cell death in leukemia cells independent of the 67 kDa laminin receptor

The 67 kDa laminin receptor (67 LR) mediates (-)-epigallocatechin-3-O-gallate (1; EGCG)-67 LR direct action only at physiological concentrations. The relevancy of biological effects of 1 at physiological concentrations to 67 LR was investigated in myeloid and lymphoid leukemia cells using flow cytometric analysis. It was shown that physiological concentrations of 1 suppressed the cell growth of HL60 myeloid leukemia cells and Raji lymphoid leukemic cells independent of 67 LR expression. Moreover, there was no discernible change in the levels of intracellular reactive oxygen species, characteristics of apoptosis such as phosphatidylserine translocation and activated caspase-3. The activity of 1 at physiological concentrations does not depend on direct 67 LR-mediated actions, and this compound induces necrosis-like death of promyelocytic leukemia and non-Hodgkin's lymphoma cells.

Caspase-independent apoptosis induction of quorum-sensing autoinducer analogs against chronic myeloid leukemia K562

Quorum sensing is defined as the ability of microorganisms to sense their population density via the release of signaling molecules called autoinducers (AIs). Various types of AI analogs were prepared and their antitumor properties against chronic myeloid leukemia (CML) K562 cells were investigated. Two AI analogs induced progressive apoptosis with JNK activation and p21 induction. In addition, this induction of apoptosis is not related to bcr-abl kinase, which sustains CML proliferation. However, the progression of apoptosis was not inhibited by a caspase family inhibitor. These results suggested that AI analogs could induce caspase-independent apoptosis in CML K562.

Molecular bases of thioredoxin and thioredoxin reductase-mediated prooxidant actions of (-)-epigallocatechin-3-gallate

Thioredoxin (Trx) and thioredoxin reductase (TrxR) function as antioxidant and anti-apoptotic proteins, which are often up-regulated in drug-resistant cancer cells. (-)-epigallocatechin-3-gallate (EGCG) is a naturally occurring antioxidant in green tea, but also exhibits prooxidant and apoptosis-inducing properties. We have previously showed a linkage between EGCG-induced inactivation of TrxR and decreased cell survival, revealing TrxR as a new target of EGCG. However, the molecular events underlying the importance of Trx/TrxR in EGCG-induced cytotoxicity remain unclear. Here, we show that the crosstalk between EGCG and Trx/TrxR occurred in a redox-dependent manner, and EGCG induced inactivation of Trx/TrxR in parallel with increased ROS levels in HeLa cells. Moreover, EGCG displayed great reactivity with Cys/Sec residues that have low pK(a) values. The structure of EGCG suggests that its quinone form would readily react with thiolate and selenolate nucleophiles. Using mass spectrometry, we have demonstrated the formation of EGCG-Trx1 (Cys(32)) and EGCG-TrxR (Cys/Sec) conjugates, confirming that EGCG quinone specifically conjugates with active-site Cys(32) in Trx or C-terminal Cys/Selenocysteine (Sec) couple in TrxR under conditions where Trx/TrxR are reduced. Non-reduced form of Trx/TrxR could escape from EGCG inhibition. These data reveal a potential mechanism for enhancing EGCG-induced cancer cell death by the NADPH-dependent reduction of Trx/TrxR.

Protective effect of catechin on apoptosis of the lens epithelium in rats with N-methyl-N-nitrosourea-induced cataracts

Purpose

To investigate the effect of catechin on apoptotic cell death in the lens epithelium of rats with cataract.

Methods

Cataract was induced by intraperitoneal injection of 100 mg/kg N-methyl-N-nitrosourea (MNU) to ten day-old Sprague-Dawley rats. The neonatal rats were randomly divided into five groups (n=15 in each group): a control group, and four cataract-induction groups, treated with either 0, 50, 100, 200 mg/kg catechin. We performed slit-lamp biomicroscopic analysis, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, Western-blot for Bcl-2 and Bax, and immunohistochemistry for caspase-3.

Results

Apoptotic cell death in lens epithelial cells that increased following cataract formation in rats was suppressed by cathechin.

Conclusions

Catechin inhibited cataract-induced apoptotic cell death in the lens epithelium and may prove useful for the prevention of cataract progression.

Potentiation of (-)-epigallocatechin-3-gallate-induced apoptosis by bortezomib in multiple myeloma cells

The green tea constituent, (-)-epigallocatechin-3-gallate (EGCG), has chemopreventive and anticancer effects. This is partially because of the selective ability of EGCG to induce apoptosis and death in cancer cells without affecting normal cells. In the present study, the activity of EGCG against the myeloma cell line, KM3, was examined. Our results demonstrated, for the first time, that the treatment of the KM3 cell line with EGCG inhibits cell proliferation and induces apoptosis, and there is a synergistic effect when EGCG and bortezomib are combined. Further experiments showed that this effect involves the NF-kappaB pathway. EGCG inhibits the expression of the P65 mRNA and P65/pP65 protein, meanwhile it downregulates pIkappaBalpha expression and upregulates IkappaBalpha expression. EGCG also activates caspase-3, -8, cleaved caspase-9, and poly-ADP-ribose polymerase (PARP) and subsequent apoptosis. These findings provided experimental evidence for efficacy of EGCG alone or in combination with bortezomib in multiple myeloma therapy.

Green tea consumption and hematologic malignancies in Japan: the Ohsaki study

Several biologic studies have reported that green tea constituents have antitumor effects on hematologic malignancies. However, the effects in humans are uncertain. The authors used data from the Ohsaki National Health Insurance Cohort Study in Japan to evaluate the association between green tea consumption and the risk of hematologic malignancies. Study participants were 41,761 Japanese adults aged 40-79 years without a history of cancer at baseline who answered a food frequency questionnaire survey in 1994. During 9 years of follow-up beginning in 1995, the authors documented 157 hematologic malignancies, including 119 cases of lymphoid neoplasms and 36 cases of myeloid neoplasms. Hazard ratios were calculated by using the Cox proportional hazards regression model. Risk of hematologic malignancies was inversely associated with green tea consumption. The multivariate-adjusted hazard ratio of hematologic malignancies for 5 cups/day or more compared with less than 1 cup/day of green tea was 0.58 (95% confidence interval: 0.37, 0.89). The corresponding risk estimate was 0.52 (95% confidence interval: 0.31, 0.87) for lymphoid neoplasms and 0.76 (95% confidence interval: 0.32, 1.78) for myeloid neoplasms. This inverse association was consistent across sex and body mass index strata. In conclusion, green tea consumption was associated with a lower risk of hematologic malignancies.

Preclinical development of the green tea catechin, epigallocatechin gallate, as an HIV-1 therapy

BACKGROUND

Previously, we presented evidence that at physiologic concentrations the green tea catechin, epigallocatechin gallate (EGCG), inhibited attachment of HIV-1 glycoprotein 120 to the CD4 molecule on T cells, but the downstream effects of EGCG on HIV-1 infectivity were not determined.

OBJECTIVE

To evaluate the inhibition of HIV-1 infectivity by EGCG and begin preclinical development of EGCG as a possible therapy.

METHODS

PBMCs, CD4(+) T cells, and macrophages were isolated from blood of HIV-1-uninfected donors. HIV-1 infectivity was assessed by an HIV-1 p24 ELISA. Cell survival was assessed by cell viability by Trypan blue exclusion assay, cell growth by thymidine incorporation, and apoptosis by flow-cytometric analysis of annexin-V binding.

RESULTS

Epigallocatechin gallate inhibited HIV-1 infectivity on human CD4(+) T cells and macrophages in a dose-dependent manner. At a physiologic concentration of 6 mumol/L, EGCG significantly inhibited HIV-1 p24 antigen production across a broad spectrum of both HIV-1 clinical isolates and laboratory-adapted subtypes (B [P < .001], C, D, and G [P < .01]). The specificity of the EGCG-induced inhibition was substantiated by the failure of EGCG derivatives lacking galloyl and/or pyrogallol side groups to alter HIV-1 p24 levels. EGCG-induced inhibition of HV-1 infectivity was not a result of cytotoxicity, cell growth inhibition, or apoptosis.

CONCLUSION

We conclude that by preventing the attachment of HIV-1-glycoprotein 120 to the CD4 molecule, EGCG inhibits HIV-1 infectivity. Because this inhibition can be achieved at physiologic concentrations, the natural anti-HIV agent EGCG is a candidate as an alternative therapy in HIV-1 therapy.

Antioxidants alleviate electric field-induced effects on lung tissue based on assays of heme oxygenase-1, protein carbonyl content, malondialdehyde, nitric oxide, and hydroxyproline

In order to test whether antioxidants have beneficiary effects on electric field induced damage, we determined the pulmonary levels of heme oxygenase-1 (HO-1), protein carbonyl content (PCO), malondialdehyde (MDA), nitric oxide (NO) and hydroxyproline (HP) under extremely low frequency (ELF) electric (E) field exposure (50 Hz, 12 kV/m, 7 days/for 8 h/day). While PCO levels significantly increased (p<0.05), insignificant changes (p>0.05) were observed in HO-1, MDA, NO and HP levels for electric field exposure groups compared to the control group. We have not observed any significant change in these parameters on the electric field group compared to the group where NAC and EGCG were separately applied along with electric field. However, during our previous studies, we have concluded that NAC and EGCG are potent antioxidants and we believe that new studies should be established by way of setting up different experimental conditions.

Dietary polyphenols as topoisomerase II poisons: B ring and C ring substituents determine the mechanism of enzyme-mediated DNA cleavage enhancement

Dietary polyphenols are a diverse and complex group of compounds that are linked to human health. Many of their effects have been attributed to the ability to poison (i.e., enhance DNA cleavage by) topoisomerase II. Polyphenols act against the enzyme by at least two different mechanisms. Some compounds are traditional, redox-independent topoisomerase II poisons, interacting with the enzyme in a noncovalent manner. Conversely, others enhance DNA cleavage in a redox-dependent manner that requires covalent adduction to topoisomerase II. Unfortunately, the structural elements that dictate the mechanism by which polyphenols poison topoisomerase II have not been identified. To resolve this issue, the activities of two classes of polyphenols against human topoisomerase IIalpha were examined. The first class was a catechin series, including (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC). The second was a flavonol series, including myricetin, quercetin, and kaempferol. Compounds were categorized into four distinct groups: EGCG and EGC were redox-dependent topoisomerase II poisons, kaempferol and quercetin were traditional poisons, myricetin utilized both mechanisms, and ECG and EC displayed no significant activity. On the basis of these findings, a set of rules is proposed that predicts the mechanism of bioflavonoid action against topoisomerase II. The first rule centers on the B ring. While the C4'-OH is critical for the compound to act as a traditional poison, the addition of -OH groups at C3' and C5' increases the redox activity of the B ring and allows the compound to act as a redox-dependent poison. The second rule centers on the C ring. The structure of the C ring in the flavonols is aromatic and planar and includes a C4-keto group that allows the formation of a proposed pseudo ring with the C5-OH. Disruption of these elements abrogates enzyme binding and precludes the ability to function as a traditional topoisomerase II poison.

(-)-Epigallocatechin gallate, a major constituent of green tea, poisons human type II topoisomerases

(-)-Epigallocatechin gallate (EGCG) is the most abundant and biologically active polyphenol in green tea, and many of the therapeutic benefits of the beverage have been attributed to this compound. High concentrations of EGCG are cytotoxic and trigger genotoxic events in mammalian cells. Although this catechin affects a number of cellular systems, the genotoxic effects of several bioflavonoid-based dietary polyphenols are believed to be mediated, at least in part, by their actions on topoisomerase II. Therefore, the effects of green tea extract and EGCG on DNA cleavage mediated by human topoisomerase IIalpha and beta were characterized. The extract and EGCG increased levels of DNA strand breaks generated by both enzyme isoforms. However, EGCG acted by a mechanism that was distinctly different from those of genistein, a dietary polyphenol, and etoposide, a widely prescribed anticancer drug. In contrast to these agents, EGCG exhibited all of the characteristics of a redox-dependent topoisomerase II poison that acts by covalently adducting to the enzyme. First, EGCG stimulated DNA scission mediated by both isoforms primarily at sites that were cleaved in the absence of compounds. Second, exposure of EGCG to the reducing agent dithiothreitol (DTT) prior to its addition to DNA cleavage assays abrogated the effects of the catechin on DNA scission. Third, once EGCG stimulated topoisomerase II-mediated DNA cleavage, exposure to DTT did not effect levels of DNA strand breaks. Finally, EGCG inhibited the DNA cleavage activities of topoisomerase IIalpha and beta when incubated with either enzyme prior to the addition of DNA. Taken together, these results provide strong evidence that EGCG is a redox-dependent topoisomerase II poison and utilizes a mechanism similar to that of 1,4-benzoquinone.