The effect of green tea on oxidative damage and tumour formation in Lobund–Wistar rats

Abstract

A number of epidemiological studies suggest that the consumption of green tea reduces the incidence of prostate cancer. Since the major catechins present in green tea are potent anti-oxidants, we hypothesized that genetic and cellular damage induced by oxygen free radicals could be significantly reduced by potent anti-oxidants in green tea, thus reducing the cumulative genetic and cellular damage with age, and slowing or preventing tumour formation. Long-term administration of a decaffeinated green tea extract to Lobund-Wistar rats for periods up to 26 months almost halved the incidence of primary tumours in the genitourinary tract when compared to an aged-matched cohort receiving just water. We observed no inhibition of DNA adduct formation or lipid peroxidation in animals consuming green tea compared to animals consuming de-ionized water. The decrease in tumour formation was associated with an increase in 8-hydroxy-2’deoxyguanosine (8-OH-dG) and 4-hydroxynonenal (4-HNE) content (markers of DNA adduct formation and lipid peroxidation respectively) in the epithelium of the ventral prostate in aging animals. There was also an increase in 8-OH-dG expression, but no change in 4-HNE expression in the seminal vesicles of older animals. There was an age associated increase in expression of the anti-oxidant enzymes MnSOD and catalase in the epithelium of the ventral prostate of aging animals. There was also an increase in MnSOD expression, but no change in catalase expression in the seminal vesicles of older animals. These data demonstrate that consumption of green tea decreases the incidence of genitourinary tract tumours in the Lobund-Wistar rat, but has no effect on age associated DNA adduct formation and lipid peroxidation in the aging rat ventral prostate and seminal vesicles.

Dietary soy and tea mitigate chronic inflammation and prostate cancer via NFκB pathway in the Noble rat model

“…The current study shows a lack of chemopreventive effects with dietary soy or tea alone, which is in contrast to prior studies that showed high concentrations of soy isoflavone or green tea extracts induced protective effects in other models [56–59]. However, similar to our findings, Cohen et al utilized lower concentrations of soy protein isolate (≤20% by weight) in the diet and showed a lack of preventative effects against hormone refractory prostate tumor growth in rats [60].…”

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

“…Inhibition was characterized by cancer cell apoptosis and induction of oxidative damage to tumor cell DNA (8‐OHdG), but not in normal tissues 76. Decaffeinated green tea (0.6% in water) reduced genitourinary tumor load in rats, concurrent with formation of 8‐OHdG and 4‐hydroxynonenal, both indicators of oxidative damage 91.…”

“…Green tea polyphenols have also been shown to increase levels of phase II antioxidant enzymes in the small intestine, lungs, and skin of mice 93, the prostate of rats 91, and the oral cavity of hamsters 94. This may be mediated through activation of MAPKs by green tea polyphenols 95.…”

Chemopreventive effects of tea in prostate cancer: Green tea versus black tea

“…One study by O'Sullivan et al showed a decrease in tumor progression of 50% compared with water control but no decrease in tissue oxidative DNA damage marker, 8‐hydroxydeoxy‐guanosine (8‐OHdG). However, manganese superoxide dismutase (MnSOD) protein expression was increased by the tea treatment 21.…”