Cimicifuga foetida and C. racemosa prevent postmenopausal osteoporosis by inhibiting autophagy of osteoclasts via CB2R and ERα.

BACKGROUND

Cannabinoid receptor type 2 (CB2R) and estrogen receptor alpha (ERα) activators have been shown to possess remarkable regulatory effects on bone metabolism. Cimicifuga foetida l. (CF), the same genus plant as Cimicifuga racemosa (l.) Nutt. (CR), is commonly used to alleviate menopausal syndrome and postmenopausal osteoporosis (PMOP) in Europe and North America. Both CF and CR possess agonistic activities on CB2R and ERα. However, whether CF and CR regulate bone metabolism based on CB2R and ERα remains unclear.

PURPOSE: This study aimed to investigate the potential effects of CF and CR on bone metabolism in PMOP, and explore their underlying mechanisms in osteoclasts (OCs) in vitro and an OVX rat model in vivo based on CB2R and ERα.

METHODS

The agonistic effects of the medicated serum of CF and CR on CB2R and ERα were investigated by relative luminescence value assay, cellular thermal shift assay (CETSA), cyclic adenosine monophosphate (cAMP) and ERα assay. Compounds with agonistic activities on CB2R and ERα in medicated serum of CF and CR were identified using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS), molecular docking and molecular dynamics simulation. Finally, the anti-OP effects and mechanisms of CF and CR upon CB2R and ERα activation were investigated in OCs derived from RAW264.7 cells and the OVX rat model, and the results were further validated using CB2R and ERα inhibitors.

RESULTS

Both CF and CR showed significant agonistic effects on CB2R and ERα as evidenced by relative luminescence value assay, CETSA, cAMP and ERα assay. Sixteen compounds were identified in the medicated serum of CR and CF, among which some compounds exhibited good binding affinities with CB2R and ERα. Treatment with either CF- or CR-medicated serum significantly inhibited the formation, differentiation and autophagy of the OCs derived from RAW264.7 cells, and the use of CB2R inverse agonist and ERα inhibitor reversed the effects of the medicated serum of CR and CF. Administration of CF and CR regulated bone metabolism, improved the bone microstructure, and inhibited OC differentiation and autophagy in OVX rats, while CB2R inverse agonist and ERα inhibitor mitigated the effect of CF on OVX rats.

CONCLUSIONS

Like CR, CF attenuated bone loss in PMOP by inhibiting OC differentiation and autophagy via CB2R and ERα activation.