heart-health

Green tea and the metabolism of 2-amino-3-methylimidazo[4,5-f]quinoline in F344 rats

Author: C.W Embola and M.C Weisburger and J.H Weisburger

The effects of green tea intake on the metabolism of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in the rat was studied. IQ belongs to a new class of mutagens and carcinogens, heterocyclic arylamines, formed during cooking through browning meats and fish, thus, in the food chain of most non-vegetarians. Ten adult male and female Fischer 344 rats were placed on a 2% solution of green tea and 10 control rats were on water for 6 weeks. Then, animals were administered a single dose of 40 mg/kg body weight of [2-14C]IQ by oral gavage. Twenty-four hour urine samples were collected and metabolites were separated by HPLC and quantitated by scintillation counting. Two minor and three major metabolites were isolated, including, small quantities of IQ itself. The rats on tea showed significant differences (P < 0.05) in the recovery of the three major metabolites, namely, IQ-sulfamate, IQ-5-O-sulfate, and IQ-5-O-glucuronide, respectively. Green tea, therefore, influences the manner in which the food carcinogen IQ is metabolized and excreted in urine. Formation of glucuronides, increased by green tea, represent a key means of detoxification of the heterocyclic amine, IQ.

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Author: Sosamma J. Berger and Sanjay Gupta and Charles A. Belfi and David M. Gosky and Hasan Mukhtar

DNA topoisomerases I and II are essential for cell survival and play critical roles in DNA metabolism and structure. Inhibitors of topoisomerase constitute a novel family of antitumor agents with demonstrated clinical activity in human malignancies. The clinical use of these agents is limited due to severe toxic effects on normal cells. Therefore, there is a need to develop novel, nontoxic topoisomerase inhibitors that have the ability to spare normal cells. Recent studies have shown that green tea and its major polyphenolic constituent, epigallocatechin-3-gallate (EGCG), impart growth inhibitory responses to cancer cells but not to normal cells. Based on the knowledge that EGCG induces DNA damage, cell cycle arrest, and apoptosis, we considered the possibility of the involvement of topoisomerase in the antiproliferative response of EGCG. Here, for the first time, we show that EGCG inhibits topoisomerase I, but not topoisomerase II in several human colon carcinoma cell lines. Based on this study it is tempting to suggest that combination of EGCG with other conventional topoisomerase inhibitors could be an improved strategy for treatment of colon cancer. The possible role of EGCG as a chemotherapeutic agent needs to be investigated.

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Author: Tao Jiang and Barry W. Glickman and Johan G. de Boer

Author: Reiko Hirano and Yukihiko Momiyama and Rie Takahashi and Hiroaki Taniguchi and Kazuo Kondo and Haruo Nakamura and Fumitaka Ohsuzu

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GREEN TEA POLYPHENOL BLOCKS H2O2-INDUCED INTERLEUKIN-8 PRODUCTION FROM HUMAN ALVEOLAR EPITHELIAL CELLS

Author: Katsunari Matsuoka and Noritaka Isowa and Takashi Yoshimura and Mingyao Liu and Hiromi Wada 

Reactive oxygen species (ROS) play crucial roles in ischemia-reperfusion (IR) injury of lung transplants. Reactive oxygen species may stimulate the production of neutrophil chemotactic factors such as interleukin-8 (IL-8), from alveolar epithelial cells, causing recruitment and activation of neutrophils in the reperfused tissue. Green tea polyphenol has potent anti-oxidative activities and anti-inflammatory effects by decreasing cytokine production. In the present study, we found that green tea polyphenol significantly inhibited IL-8 production induced by hydrogen peroxide (H2O2) in human lung alveolar epithelial cells (A549 line). It has been shown that mitogen activated protein kinases, such as Jun N-terminal kinase (JNK), p38 and p44/42, could mediate IL-8 production from a variety of cell types. We further investigated the effect of green tea polyphenol on these protein kinases, and demonstrated that H2O2-induced phosphorylation of JNK and p38 but not p44/42 was inhibited by green tea polyphenol in A549 cells. We speculate that green tea polyphenol may inhibit H2O2-induced IL-8 production from A549 cells through inactivation of JNK and p38.

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Author: E.I Korotkova and Y.A Karbainov and A.V Shevchuk

A highly attractive, convenient and especially sensitive voltammetric approach for the study of antioxidant properties and determination of their activity is suggested in this work, where antioxidants are substances, which interrupt radical-chain oxidation processes in organic and inorganic molecules. The comparative analysis of the activity of well-known antioxidants such as ascorbic and citric acids, glucose, their compound solutions, some food products (green tea extract, apple vinegar) and pharmaceuticals (haemodesum, polyglucinum, Ringer solution) has been carried out. The character of the antioxidant influence on the oxygen electrochemical reduction has been investigated. Finally the use of these substances for prophylactic purposes has been recommended.

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Author: Helaine M Alessio and Ann E Hagerman and Mary Romanello and Stephane Carando and Melinda S Threlkeld and J Rogers and Yoana Dimitrova and Subiquah Muhammed and Ronald L Wiley

The effects of green tea on biomarkers of exercise-induced oxidative status were measured in young male Sprague-Dawley rats. Rats (n = 12) drank green tea or water ad lib for 6.5 weeks. Half of each group was sacrificed at rest, and the other half ran 25 m/min at 0% grade for approximately 30 min immediately before sacrifice. Green tea had no effect on resting heart rate, blood pressure, body weight, cholesterol, or triglycerides. Tea consumption had a mild influence on total plasma antioxidants, heart glutathione, and plasma ascorbic acid. Exercise had a major impact on malonaldehyde (MDA) equivalents in kidney (+290%, p = 0.0001), and to a lesser extent, liver (+81%, p = 0.18) in rats that drank water. In contrast, kidney MDA equivalents were unchanged by exercise in rats that drank green tea. Green tea may have selective protective effects within the body, especially on the kidney.

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Author: J.H Weisburger and Fung-Lung Chung

The beverage tea, from the top leaves of the plant Camellia sinensis is one of the most widely used beverages in the world, second only to water. Black and green tea have mostly similar actions. The active components are polyphenols, mainly epigallocatechin gallate in green tea, and the tea leaf polyphenol oxidase mediated oxidation to oolong and black tea, yielding other polyphenols, theaflavin and thearubigins. There is 40−50 mg caffeine in a 160-ml cup of tea. The chemopreventive effects of tea depend on: (1) its action as an antioxidant; (2) the specific induction of detoxifying enzymes; (3) its molecular regulatory functions on cellular growth, development and apoptosis; and (4) a selective improvement in the function of the intestinal bacterial flora. The oxidation of LDL cholesterol, associated with a risk for atherosclerosis and heart disease, is inhibited by tea. Many of cancers are caused by lifestyle elements. One is cigarette and tobacco use, leading to cancer in the oral cavity, esophagus and lung, inhibited by tea. Mice administered a tobacco nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), developed significantly fewer lung tumors than controls when given green tea or its major polyphenol, epigallocatechin gallate (EGCG). Tea suppressed the formation of 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative DNA damage, in the lung DNA of mice given NNK. Gastric cancer, caused by a combination of Helicobacter pylori and salted foods, is lower in tea drinkers. Western nutritionally-linked cancers of the breast, colon, prostate and pancreas can be inhibited by tea. The formation of genotoxic carcinogens for these target organs during the cooking of meats, heterocyclic amines, and their effects were decreased by tea. Tea inhibited the formation of reactive oxygen species and radicals and induced cytochromes P450 1A1, 1A2 and 2B1, and glucuronosyl transferase. The higher formation of glucuronides represents an important mechanism in detoxification. The developmental aspects and growth of cancers through promotion are decreased by tea. The regular use of a widely available, tasty, inexpensive beverage, tea, has displayed valuable preventive properties in chronic human diseases.

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Author: Anoop K Singh and Pankaj Seth and Peter Anthony and Mirza M Husain and Subhashree Madhavan and Hasan Mukhtar and Radha K Maheshwari

Several independent research studies have shown that consumption of green tea reduces the development of cancer in many animal models. Epidemiological observations, though inconclusive, are suggesting that green tea consumption may also reduce the risk of some cancers in humans. These anti-carcinogenic effects of green tea have been attributed to its constituent polyphenols. Angiogenesis is a crucial step in the growth and metastasis of cancers. We have investigated the effect of the major polyphenolic constituent of green tea, epigallocatechin-3-gallate (EGCG), on the tube formation of human umbilical vein endothelial cells (HUVEC) on matrigel. Tube formation was inhibited by treatment both prior to plating and after plating endothelial cells on matrigel. EGCG treatment also was found to reduce the migration of endothelial cells in matrigel plug model. The role of matrix metalloproteinases (MMP) has been shown to play an important role during angiogenesis. Zymography was performed to determine if EGCG had any effect on MMPs. Zymographs of EGCG-treated culture supernatants modulated the gelatinolytic activities of secreted proteinases indicating that EGCG may be exerting its inhibitory effect by regulating proteinases. These findings suggest that EGCG acts as an angiogenesis inhibitor by modulating protease activity during endothelial morphogenesis.

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Author: Alessandra Bordoni and Silvana Hrelia and Cristina Angeloni and Emanuele Giordano and Carlo Guarnieri and Claudio M Caldarera and Pier L Biagi

Antioxidant-rich diets exert a protective effect in diseases involving oxidative damage. Among dietary components, green tea is an excellent source of antioxidants. In this study, cultured neonatal rat cardiomyocytes were used to clarify the protective effect of a green tea extract on cell damage and lipid peroxidation induced by different periods of hypoxia followed by reoxigenation. Cultures of neonatal rat cardiomyocytes were exposed to 2–8 hr hypoxia, eventually followed by reoxygenation, in the absence or presence of α-tocopherol or green tea. LDH release and the production of conjugated diene lipids were measured, and appeared linearly related to the duration of hypoxia. During hypoxia, both LDH release and conjugated diene production were reduced by α-tocopherol and, in a dose dependent manner, by green tea, the 50 μg/ml being the most effective dose. Reoxygenation caused no further increase in LDH leakage, while it caused a significant increase in conjugate dienes, which absolute value was lower in antioxidant supplemented cells. Anyway, the ratio between conjugated diene production after hypoxia and after reoxygenation was similar in all groups, indicating that the severity of free radical-induced reoxygenation injury is proportional to the severity of previous hypoxic injury. Since hypoxic damage is reduced by α-tocopherol and green tea, our data suggest that any nutritional intervention to attenuate reoxygenation injury must be directed toward the attenuation of the hypoxic injury. Therefore, recommendations about a high dietary intake of antioxidants may be useful not only in the prevention, but also in the reduction of cardiac injury following ischemia.

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