Prevention of oxidative DNA damage in inner organs and lymphocytes of rats by green tea extract.
BACKGROUND
Consumption of green tea (GT) is associated with decreased incidences of specific forms of cancer in humans and it was postulated that its antioxidant (AO) properties may account for these effects. The evidence for AO effects of GT is mainly based on the results from in vitro experiments and on animal studies in which protection against chemically induced damage was monitored.


OBJECTIVE
The goal of the study was the investigation of the prevention of strand breaks and DNA migration attributable to endogenous oxidation of bases by GT extract (GTE) in inner organs and lymphocytes of untreated rats. In addition, immunological parameters and biochemical markers were monitored.


METHODS
DNA migration was measured in hepatocytes, colonocytes and lymphocytes after consumption of a low (1.3 mg/kg bw per day, 5 days) and a high dose (6.5 mg/kg bw per day, 5 days) of GTE in COMET assays (n = 5 animals per group). In addition, immunological parameters (TNF-alpha, IFN-gamma, IL-4 and IL-10), the total AO capacity and oxidized low-density lipoproteins were determined in plasma.


RESULTS
No evidence for reduction in DNA damage was found with a lower dose, whereas with the higher dose, reduction in DNA migration attributable to formamidopyrimidine-DNA-glycosylase sensitive lesions (oxidized purines) and endonuclease III-sensitive sites (oxidized pyrimidines) (58 and 73%) was observed in lymphocytes; also, in colonocytes (reduction in FPG-sensitive sites by 46%) and hepatocytes (decrease in Endo III-sensitive sites by 74%) protective effects were found, while none of the other parameters was altered.


CONCLUSIONS
Our results show that a dose of GTE, which is equivalent to consumption of 500 ml GT/p/day in humans protects lymphocytes and to a lesser extent inner organs against oxidative DNA damage, while no effect was seen with a lower dose corresponding to an uptake of 100 ml/p/day.
Department of Medicine I, Institute of Cancer Research, Medical University of Vienna, Borschkegasse 8a, 1090, Vienna, Austria.
Nina
N
Kager
Franziska
F
Ferk
Michael
M
Kundi
Karl-Heinz
KH
Wagner
Miroslav
M
Misík
Siegfried
S
Knasmüller
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001628:Beverages; D003106:Colon / Q000166:cytology; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000097:blood; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D013662:Tea / Q000737:chemistry*; D014409:Tumor Necrosis Factor-alpha / Q000097:blood
D000975:Antioxidants; D010936:Plant Extracts; D013662:Tea; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma