Modulatory effects of black tea polyphenols on rat forestomach carcinogenesis.
ABSTRACT ABSTRACT The present study was designed to evaluate the chemopreventive effects of black tea polyphenols (Polyphenon-B) on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in Wistar rats. Intragastric administration of MNNG induced well-differentiated squamous cell carcinomas that showed diminished mitochondrial lipid and protein oxidation and an increase in antioxidants. In contrast to tumor tissue, the liver mitochondria of tumor-bearing animals showed elevated lipid and protein oxidation with compromised antioxidant defenses. Dietary administration of Polyphenon-B effectively suppressed MNNG-induced stomach tumors, modulated mitochondrial lipid and protein oxidation, and enhanced antioxidant enzyme activities in the stomach and liver. Our results suggest that Polyphenon-B may exert its chemopreventive effects by modulating mitochondrial cellular redox status in the tumor as well as in the host liver.
- SourceAvailable from: Garry R Buettner[Show abstract] [Hide abstract]
ABSTRACT: It has been hypothesized that exposure of cells to hyperthermia results in an increased flux of reactive oxygen species (ROS), primarily superoxide anion radicals, and that increasing antioxidant enzyme levels will result in protection of cells from the toxicity of these ROS. In this study, the prostate cancer cell line, PC-3, and its manganese superoxide dismutase (MnSOD)-overexpressing clones were subjected to hyperthermia (43 degrees C, 1 h). Increased expression of MnSOD increased the mitochondrial membrane potential (MMP). Hyperthermic exposure of PC-3 cells resulted in increased ROS production, as determined by aconitase inactivation, lipid peroxidation, and H2O2 formation with a reduction in cell survival. In contrast, PC-3 cells overexpressing MnSOD had less ROS production, less lipid peroxidation, and greater cell survival compared to PC-3 Wt cells. Since MnSOD removes superoxide, these results suggest that superoxide free radical or its reaction products are responsible for part of the cytotoxicity associated with hyperthermia and that MnSOD can reduce cellular injury and thereby enhance heat tolerance.Free Radical Research 10/2004; 38(10):1119-32. · 3.28 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Chronic diseases such as cancer, and other non-communicable diseases are fast replacing comm-unicable diseases in India and other developing countries. We deal here with the epidemiology of cancer, its control and prevention measures as applicable to Indian situation. Tobacco is the most important identified cause of cancer followed by dietary practices, inadequate physical activity, alcohol consumption, infections due to viruses and sexual behaviour. Cancer prevention includes primary and secondary prevention measures. Public education on 'tobacco and its health hazards', recommended dietary guidelines, safe sexual practices, and lifestyle modifications form the main features of primary prevention of cancer. Incorporating screening for cancer of cervix, breast and oral cancers into peripheral health infrastructure can have a significant effect on reducing mortal-ity from these diseases. THE burden of cancer is still increasing worldwide des-pite advances for diagnosis and treatment. Epidemiologi-cal studies have shown that many cancers may be avoidable. It is widely held that 80–90% of human can-cers may be attributable to environmental and lifestyle factors such as tobacco, alcohol and dietary habits 1 . Can-cer prevention includes primary, secondary and preven-tion methods. Primary prevention refers to avoiding cancer-causing substances in the environment or dietary elements associated with increased risk; dietary supple-mentation with putative protective agents. Secondary prevention aims at early detection and removal of benign tumours of oral, cervical and breast cancers 2 . It was esti-mated that in the year 2000, worldwide over 10 million new cases of cancer occurred (approximately 5.3 million men and 4.7 million women) and over 6 million people died from cancers 3 . The most frequently affected organs are lung, breast, colon, rectum, stomach and liver. Epide-miology of cancer, its control and prevention measures as applicable to Indian population have been discussed here.
- [Show abstract] [Hide abstract]
ABSTRACT: Tea shows many health promoting activities including chemopreventive action during carcinogenesis due to the presence of antioxidative polyphenolic constituents. The present experiment evaluated the anticarcinogenic role of black tea infusion on azoxymethane induced colonic preneoplastic lesions, the aberrant crypt foci in Sprague-Dawley rats. Rats were injected with azoxymethane (15 mg/kg b.w.) and received oral administration of 1% and 2% (w/v) tea infusions from first day of carcinogen application. This treatment was continued for twelve weeks and assessed for aberrant crypt foci and compared with untreated carcinogen control group. Levels of lipid peroxidation were determined in liver as well as in colon tissue. During initiation phase of carcinogenesis, glutathione-S-transferase (GST) and glutathione peroxidase (GPx) activities were also evaluated. Significant reduction in the number of aberrant crypt foci and levels of lipid peroxidation among the tea-treated groups were observed. Induction of GST and GPx activities was noted during the initiation phase of carcinogenesis. Results of the present study indicate that the protective effect of black tea infusions may be due to an outcome of antioxidative influence of tea components on azoxymethane induced carcinogenesis.Journal of experimental & clinical cancer research: CR 07/2003; 22(2):185-91. · 1.50 Impact Factor