Incompatibility mechanism between Radix paeoniae alba and Veratrum nigrum focusing on estrogen-estrogen receptor pathway in immature/ovariectomized mice.

Radix paeoniae alba (RPA) and Veratrum nigrum (VN) L. belong to the 18 incompatible medicaments and have been prohibited for thousands of years in China. Previous studies focused on the chemical constituents that induced the toxicological response of the two agents, but this study offers preliminary insight into the pharmacodynamics and mechanism on estrogenic activity, which is responsible for their incompatibility. We undertook a characterization of the interaction on estrogenic activity of RPA and VN using in vivo models of immature and ovariectomized (OVX) mice and in vitro studies focused on estrogen receptor (ER) pathway for further mechanism. VN disturbed the estrogenic efficacy of RPA in promoting development of uterus and vagina in immature mice, and reversing the atrophy of reproductive tissues in OVX mice by decreasing the increase of serum estrogen level and upregulation of ER expression in reproductive tissues by treatment with RPA. Besides, VN antagonized the estrogenic efficacy of RPA in stimulating the binding with ER alpha and ER beta, increasing ER alpha/beta-estrogen response element (ERE) luciferase reporter gene expression and promoting MCF-7 cell viability. This study provided evidence that VN antagonized the estrogenic efficacy of RPA by decreasing the up-regulations of estrogen biosynthesis in circulation and ERs in target tissues caused by RPA, and through ER-ERE-dependent pathway.