Danggui Buxue Tang (DBT), a traditional Chinese Medicine decoction containing Astragali Radix (AR) and Angelicae Sinensis Radix (ASR), is commonly prescribed for women in China as a remedy for menopausal symptoms. Previous study indicated that DBT stimulated cell growth and differentiation of human osteosarcoma MG-63 cells and exhibited estrogenic properties via estrogen receptors (ERs). The present study aimed to study the bone protective effects of DBT and its potential interactions with selective estrogen receptor modulators (SERMs, tamoxifen and raloxifene) in both in vivo and in vitro models as they act via similar ERs. Six-month-old Sprague-Dawley rats were randomly assigned to the following treatments for 12 weeks: (1) sham-operated control group with vehicle (sham), (2) ovariectomized group with vehicle (OVX), (3) OVX with 17β-estradiol (E2, 2.0 mg/kg day), (4) OVX with tamoxifen (Tamo, 1.0 mg/kg day), (5) OVX with raloxifene (Ralo, 3.0 mg/kg day), (6) OVX with DBT (DBT, 3.0 g/kg day), (7) OVX with DBT+Tamoxifen (DBT+Tamo), and (8) OVX with DBT+Raloxifene (DBT+Ralo). Effects of DBT and potential interactions between DBT and SERMs were also evaluated in MG-63 cells. DBT, tamoxifen, raloxifene, and their combinations significantly increased bone mineral density (BMD) and improved trabecular bone properties, including bone surface (BS), trabecular bone number (Tb.N), and trabecular bone separation (Tb.Sp), as well as restored changes in bone turnover biomarkers and mRNA expression of genes involved in bone metabolism in OVX rats. Furthermore, DBT, SERMs, and their combinations significantly increased serum estradiol and suppressed follicle stimulating hormone and luteinizing hormone in OVX rats, suggesting the possible involvement of the hypothalamus–pituitary–gonadal axis in mediating their bone protective effects. However, SERMs, but not DBT, significantly increased uterus index in OVX rats. DBT significantly induced ALP activity and estrogen response element-dependent transcription in MG-63 cells. Our study demonstrated that DBT alone and in combinations with SERMs could exert bone protective effects in vitro and in vivo.

Our previous study demonstrated that the bone protective actions of herbal medicine Rhizoma Drynariae (Gusuibu, RD) were mainly mediated by flavonoid phytoestrogens via estrogen receptors, raising concerns about the safety of using RD as it may induce estrogen-like risk-benefit profile and interact with other ER ligands, such as selective estrogen receptor modulators (SERMs), when coadministered. The present study evaluated the estrogenic activities of RD and its potential interaction with tamoxifen, a SERM, in estrogen-sensitive tissues by using mature ovariectomized (OVX) rats and ER-positive cells. Similar to but weaker than tamoxifen, RD at its clinical dose dramatically ameliorated OVX-induced changes in bone and dopamine metabolism-related markers in OVX rats. However, tamoxifen, but not RD, induced uterotrophic effects. No significant alteration in mammary gland was observed in OVX rats treated with RD, which was different from the inhibitory actions of tamoxifen. The two-way ANOVA results indicated the interactions between RD and tamoxifen in the bone, brain, and uterus of OVX rats while RD did not alter their responses to tamoxifen. Our results demonstrate that RD selectively exerts estrogenic actions in a different manner from tamoxifen. Moreover, RD interacts with tamoxifen without altering its effects in OVX rats.

Background: Er-Xian decoction (EXD), a traditional Chinese Medicine for managing menopausal syndrome and osteoporosis in China, could exert osteoprotective action via activation of estrogen receptor (ERs) and regulation of serum estradiol without causing severe side effects. However, no fundamental studies have explored its potential interaction in the combined use of prescription drugs, Selective Estrogen Receptor Modulators (SERMs), regarding the osteogenic and uterotrophic effects. The present study evaluated the estrogenic effects of EXD and its potential interactions with tamoxifen and raloxifene in bone and uterus using a mature ovariectomized (OVX) Sprague-Dawley (SD) rat model and human osteoblastic MG-63 cells. Methods: Six-month-old female SD rats were randomly assigned to Sham-operated group or seven OVX groups: vehicle, 17ß-estradiol (E2, 1.0 mg/kg.day), Tamoxifen (Tamo, 1.0 mg/kg.day), Raloxifene (Ralo, 3.0 mg/kg.day), EXD (EXD, 1.6 g/kg.day), EXD+Tamoxifen (EXD+Tamo) and EXD+Raloxifene (EXD+Ralo). The effect of EXD on bodyweight, bone mineral density (BMD), bone microarchitecture, biochemical analysis of serum and urine, and uterus were evaluated. In addition, Alkaline phosphatase assay and activation of estrogen-responsive element mediated by EXD and in its combination with SERMs were investigated in MG-63 cells. Results: In vivo, EXD could interact with SERMs to modulate the serum estradiol, follicle-stimulating hormone, osteocalcin level as well as BMD and bone properties in OVX rats. Moreover, EXD could relieve the uterotrophic effect of SERMs. In vitro, EXD crude extract and EXD-treated serum could promote ALP activity. In particular, EXD-treated serum could interact with SERMs on regulating ALP activity in MG-63 cells. Conclusion: Our study demonstrated that EXD in vivo and EXD-treated serum in vitro did not weaken the osteogenic effect of SERMs. Interestingly, EXD seems to ameliorate the uterotrophic effects of SERMs. Therefore, the combined use of EXD and SERMs may be considered safe and effective in managing postmenopausal osteoporosis.