Drug-Herb Interaction Between Selective Estrogen Receptor Modulators and Estrogenic Herbal Medicine Er-Xian Decoction in Bone in Vivo and in Vitro

Abstract 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.