cancer-prevention

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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Author: Sabu M.C and Smitha K and Ramadasan Kuttan

An aqueous solution of green tea polyphenols (GTP) was found to inhibit lipid peroxidation (LP), scavenge hydroxyl and superoxide radicals in vitro. Concentration needed for 50% inhibition of superoxide, hydroxyl and LP radicals were 10, 52.5 and 136 μg/ml, respectively. Administration of GTP (500 mg/kg b.wt.) to normal rats increased glucose tolerance significantly (P<0.005) at 60 min. GTP was also found to reduce serum glucose level in alloxan diabetic rats significantly at a dose level of 100 mg/kg b.wt. Continued daily administration (15 days) of the extract 50, 100 mg/kg b.wt. produced 29 and 44% reduction in the elevated serum glucose level produced by alloxan administration. Elevated hepatic and renal enzymes produced by alloxan were found to be reduced (P<0.001) by GTP. The serum LP levels which was increased by alloxan and was reduced by significantly (P<0.001) by the administration of 100 mg/kg b.wt. of GTP. Decreased liver glycogen, after alloxan administration showed a significant (P<0.001) increase after GTP treatment. GTP treated group showed increased antioxidant potential as seen from improvements in superoxide dismutase and glutathione levels. However catalase, LP and glutathione peroxidase levels were unchanged. These results indicate that alterations in the glucose utilizing system and oxidation status in rats increased by alloxan were partially reversed by the administration of the glutamate pyruvate transaminase.

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Author: M. Pelillo and B. Biguzzi and A. Bendini and T. Gallina Toschi and M. Vanzini and G. Lercker

There is an increasing interest in the biological and technological role of natural antioxidants present in green tea extracts. This is due to the inhibition of the oxidative process showed by tea catechins, which is higher than those of synthetic antioxidants (such as BHT) and other vegetal extracts (rosemary, oregano, grape seeds). In a first step of the work a rapid reversed phase HPLC method for the determination of catechins in green tea extracts, using a binary gradient system, was developed. Commercial green tea extracts were analyzed and the different catechins quantified. EGCG ((−)-epigallocatechin-3-gallate) and EGC ((−)-epigallocatechin) were proposed as index of the antioxidant quality of tea extracts. Subsequentely, the previous chromatographic method was applied on a HPLC–MS system in order to verify the accuracy of some HPLC-DAD results and compare the two detection modes, on such a polyphenolic mixture. The use of mass spectrometry detection in quantification of catechins ensured an higher specificity of the method and a constant qualitative control of the identity of chromatographic peaks thanks to the concurrent acquisition of more than one mass signal (as M+1 and M+Na pseudomolecular peaks).

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Author: Sanjay Gupta and Hasan Mukhtar

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Author: Rudolf Locher and Luca Emmanuele and Paolo M Suter and Wilhelm Vetter and Matthias Barton

This study investigated whether human vascular smooth muscle cell proliferation induced by native low-density lipoprotein (LDL) is affected by green tea catechins. Furthermore, the effects of native LDL on extracellular signal-regulated kinase (ERK) 1/2 activity were determined. Cell proliferation stimulated by native LDL was concentration-dependently inhibited by epigallocatechin, epigallocatechin-3-gallate, green tea polyphenon, and the nonspecific antioxidant N-acetylcysteine (P<0.05). Combined treatment of green tea polyphenon and N-acetylcysteine markedly potentiated the effect of each drug on vascular smooth muscle cell proliferation. ERK1/2 activity was only partly inhibited by green tea catechins alone or in combination with N-acetylcysteine (P<0.05). These data suggest that green tea constituents inhibit proliferation of human vascular smooth muscle cells exposed to high levels of native LDL. Green tea constituents and antioxidants may exert vascular protection by inhibiting human vascular smooth muscle cell growth associated with hypercholesterolemia.

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Author: E. Skrzydlewska and J. Ostrowska and R. Farbiszewski and K. Michalak

Summary This paper reports data on the effect of green tea on the lipid peroxidation products formation and parameters of antioxidative system of the liver, blood serum and central nervous tissue of healthy young rats drinking green tea for five weeks. The rats were permitted free access to solubilized extract of green tea. Bioactive ingredients of green tea extract caused in the liver an increase in the activity of glutathione peroxidase and glutathione reductase and in the content of reduced glutathione as well as marked decrease in lipid hydroperoxides (LOOH), 4-hydroksynonenal (4-HNE) and malondialdehyde (MDA). The concentration of vitamin A increased by about 40%. Minor changes in the measured parameters were observed in the blood serum. GSH content increased slightly, whereas the index of the total antioxidant status increased significantly. In contrast, the lipid peroxidation products, particularly MDA was significantly diminished. In the central nervous tissue the activity of superoxide dismutase and glutathione peroxidase decreased while the activity od glutathione reductase and catalase increased after drinking green tea. Moreover the level of LOOH, 4-HNE and MDA significantly decreased. The use of green tea extract appeared to be beneficial to rats in reducing lipid peroxidation products. These results support and substantiate traditional consumption of green tea as protection against lipid peroxidation in the liver, blood serum, and central nervous tissue.

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Author: S Gupta and B Saha and A.K Giri

Tea is the most popular beverage next to water, consumed by over two-thirds of the world’s population. It is processed in different ways in different parts of the world to give green, black or oolong tea. Experimental studies have demonstrated the significant antimutagenic and anticlastogenic effects of both green and black tea and its polyphenols in multiple mutational assays. In the present review, we have attempted to evaluate and update the comparative antimutagenic and anticlastogenic effects of green tea, black tea and their polyphenols in different test systems, based on available literature. Existing reports have suggested that the protective effects of black tea is as good as green tea, however, more studies on black tea and its polyphenols are needed before a final conclusion can be made.

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Author: Tushar Kanti Maiti and Juin Chatterjee and Swagata Dasgupta

Angiogenesis is a fundamental process by which new blood vessels are formed. The angiogenesis process is induced by several growth factors. Among them angiogenin is the most potent blood vessel inducer known. In this paper, we have investigated the effect of green tea polyphenols, mainly the catechins, on an angiogenin-like protein induced angiogenesis process. The angiogenin-like protein was isolated from goat serum and the effect of green tea components was tested by the chicken chorioallantoic membrane (CAM) assay. The results show that green tea components are capable of reducing the vascularization on CAM that is induced by the angiogenin-like protein.

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