The estrogenic status and the COMT genotype of female blood donors influence the protective ability of the Mediterranean plant extracts against the hydrogen peroxide-induced DNA damage in lymphocytes.

The extent of oxidative DNA damage in lymphocytes can be used as a biomarker of the level of oxidative stress in the body. The comet assay has been widely used to measure such damage. The aim of our study was to evaluate: i) the extent of the oxidative DNA damage in lymphocytes isolated from blood of female donors taken in early and late follicular phases [low (LE) and high (HE) concentration of 17beta-estradiol, respectively], ii) the susceptibility of these lymphocytes to hydrogen peroxide exposure, and iii) the protective ability of five plant extracts against the hydrogen peroxide-induced DNA damage. The effect of the catechol-O-methytransferase genotype (wild COMT H/H and mutated homozygote COMT L/L) of female donors was also analyzed. The amount of endogenous DNA damage was higher in HE lymphocytes as compared with LE ones, independently of the genotype. When lymphocytes were stratified by COMT genotype, the level of DNA damage was higher in L/L donors. The protective effect of pretreatment with plant extracts (1 and 10 micro g/ml for 1 h) against the H(2)O(2) (25 microM, 5 min. at 4 degrees C)-induced oxidative DNA damage was observed only in H/H HE lymphocytes. In contrary, the plant extract pre-incubation enhanced the DNA damage in L/L HE lymphocytes. The plant extracts alone did not induce the DNA damage. The results showed that concentration of the circulating 17beta-estradiol influenced the extent of endogenous oxidative DNA damage while the beneficial or hazardous effects of the plant extracts might depend on the COMT genotype and the estrogen level.