Estrogenic Effects of Cimicifuga racemosa (Black Cohosh) in Mice and on Estrogen Receptors in MCF-7 Cells

Abstract

The estrogenic effects of Cimicifuga racemosa or Actacea racemosa (black cohosh, CR) extracts were tested in mice, and their effects on estrogen receptor (ER) levels in human breast cancer MCF-7 cells were also investigated. Four groups of weanling female Kunming mice were given 0 (control), 75, 150, or 300 mg/kg body weight CR extracts orally for 14 days. The estrus cycle and the weights of the uterus and ovary of mice, as well as serum estradiol (E₂) were measured. The proliferation patterns of MCF-7 cells exposed to CR extracts or 17β-estradiol were studied by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Subsequently, growth of MCF-7 cells in 0 (control) or 4.75 μg/L of CR extracts or 0.3 nmol/L of 17β-estradiol groups were observed for 5 days. ER levels in MCF-7 cells were analyzed by indirect immunofluorescence assay using flow cytometry. The uterine weights of mice increased with the increase in dosage of CR extracts, and the estrus duration was significantly prolonged in the group receiving 300 mg/kg body weight (P < .05). However, CR extracts did not increase the serum E₂ concentration significantly. In the in vitro study, a dose-response relationship was demonstrated when cells were treated with low doses of CR extracts, and the optimal enhancement concentration of CR extracts was 4.75 μg/L on MCF-7 cells. The doubling times (T_D) of cell growth in the CR extracts group and the 17β-estradiol group were 32.1 and 31.7 hours, respectively, both shorter than that of the negative control group (T_D = 35.3 hours). Additionally, 4.75 μg/L of CR extracts resulted in significantly increased ER levels compared with the control group (P <.01). In conclusion, CR extracts produced an estrogenic action. The effect of increasing ER levels by CR extracts may be one of the potential mechanisms of its phytotherapeutic effects for postmenopausal symptoms.