Effects of Tea Catechins on the ERE-Regulated Estrogenic Activity

Abstract

Tea catechins exert many biological effects, including anticancer and antibacterial activities. Also, it is reported that some plant flavonoids exhibit estrogenic activity. In this study, we investigated estrogenic or antiestrogenic activities of catechins in HeLa cells transiently transfected with an estrogen response element (ERE)-regulated luciferase reporter and an estrogen receptor (ER) alpha or ERbeta expression vector. Catechins alone did not induce luciferase (luc) activity in either of the ERs. Addition of 17beta-estradiol (E2) plus epicatechin gallate (ECG) or epigallocatechin gallate (EGCG) at 5 x 10(-6) M resulted in significant decreases in the ERalpha-mediated luc activity compared with that of E2 alone. On the contrary, lower concentrations significantly increased the E2-induced luc activity. Similar effects were observed with tamoxifen. The ERbeta-mediated estrogenic activities were stimulated by catechins. In conclusion, some catechins, particularly EGCG, were antiestrogenic for ERalpha at higher doses, and co-estrogenic for ERalpha at lower doses and for ERbeta. The lower doses were found in human plasma after tea-drinking. In addition, some catechins may be antiendocrine disruptors because they suppressed bisphenol A-induced luc activities.

Coffee and black tea consumption and risk of breast cancer by estrogen and progesterone receptor status in a Swedish cohort

“…A study in postmenopausal Chinese women found that plasma estrone levels were significantly 19% higher in regular black tea drinkers than in nondrinkers of tea [15]. An in vitro study showed that in the presence of estrogen, tea catechins in high concentrations had antiestrogenic activities through ERa but estrogenic activities at lower concentrations [16]. This may suggest that high intakes of tea catechins may decrease the risk of breast cancer, whereas lower intakes may increase the risk.…”

Adverse Effects of Dietary Habits on Menstrual Disorders in Young Women

“…Recent studies showed that catechins, which are abundant in green teas, have cancer preventing effects [106,107]. These polyphenols were also demonstrated to modulate estrogen action through molecular mechanisms at the serum concentration after tea-drinking [108,109].…”

Tea consumption and risk of gallbladder cancer: A meta-analysis of epidemiological studies

“…Previous studies demonstrated that high levels of estrogens were consistently associated with a high risk of gallbladder cancer in women (43)(44)(45). Experimental data from animal and cell models suggested that tea may affect estrogen metabolism, although the detailed mechanisms underlying this effect remain unknown (46,47).…”