Parkin Inhibits RANKL-Induced Osteoclastogenesis and Ovariectomy-Induced Bone Loss

Corynoline Suppresses Osteoclastogenesis and Attenuates ROS Activities by Regulating NF-κB/MAPKs and Nrf2 Signaling Pathways

Declining estrogen production in postmenopausal females causes osteoporosis in which the resorption of bone exceeds the increase in bone formation. Although clinical drugs are currently available for the treatment of osteoporosis, sustained medication use is accompanied by serious side effects. Corydalis bungeana Herba, a famous traditional Chinese herb listed in the Chinese Pharmacopoeia Commission, constitutes various traditional Chinese Medicine prescriptions, which date back to thousands of years. One of the primary active components of C. bungeana Turcz. is Corynoline (Cor), a plant isoquinoline alkaloid derived from the Corydalis species, which possesses bone metabolism disease therapeutic potential. The study aimed at exploring the effects as well as mechanisms of Cor on osteoclast formation and bone resorption. TRAcP staining, F-actin belt formation, and pit formation were employed for assessing the osteoclast function. Western blot, qPCR, network pharmacology, and docking analyses were used for analyzing the expression of osteoclast-associated genes and related signaling pathways. The study focused on investigating how Cor affected OVX-induced trabecular bone loss by using a mouse model. Cor could weaken osteoclast formation and function by affecting the biological receptor activators of NF-κB and its ligand at various concentrations. Mechanistically, Cor inhibited the NF-κB activation, and the MAPKs pathway stimulated by RANKL. Besides, Cor enhanced the protein stability of the Nrf2, which effectively abolished the RANKL-stimulated ROS generation. According to an OVX mouse model, Cor functions in restoring bone mass, improving microarchitecture, and reducing the ROS levels in the distal femurs, which corroborated with its in vitro antiosteoclastogenic effect. The present study indicates that Cor may restrain osteoclast formation and bone loss by modulating NF-κB/MAPKs and Nrf2 signaling pathways. Cor was shown to be a potential drug candidate that can be utilized for the treatment of osteoporosis.

Guizhi Shaoyao Zhimu granules attenuate bone destruction in mice with collagen-induced arthritis by promoting mitophagy of osteoclast precursors to inhibit osteoclastogenesis

BACKGROUND

Guizhi Shaoyao Zhimu decoction, a traditional Chinese medicine formula used empirically for the treatment of rheumatoid arthritis (RA), has been shown to alleviate bone destruction in rats with collagen-induced arthritis (CIA).

PURPOSE

The aim of this study is to characterize the effects of Guizhi Shaoyao Zhimu granules (GSZGs) on bone destruction in RA and the underlying mechanism.

STUDY DESIGN

A CIA arthritis model using DBA/1 mice. The animals were divided into a normal group; CIA model group; low, medium, and high-dose GSZG groups (3, 6, and 9 g/kg/day); and a methotrexate group (1.14 mg/kg/w). In vitro, a cytokine induced osteoclastogenesis model was established.

METHODS

After 28 days of treatment, the paw volume was measured, bone destruction was examined by micro-CT, and the generation of osteoclasts in bone tissue was evaluated via tartrate-resistant acid phosphatase (TRAP) staining. Furthermore, the inhibitory effect and underlying mechanism of action of GSZG on RANKL-induced osteoclastogenesis were investigated in vitro.

RESULTS

The in vivo analyses demonstrated that the paw volume and degree of bone erosion of mice in the medium- and high-dose GSZG groups were significantly decreased compared to the CIA model group. In addition, GSZG treatment suppressed the excessive generation of osteoclasts in the bone tissue of CIA mice. In vitro, GSZG inhibited RANKL-induced osteoclastogenesis and osteoclast-mediated bone resorption. Specifically, it only inhibited the generation of osteoclast precursors (OCPs); it had no significant effect on the fusion of OCPs or maturation of osteoclasts. Finally, we showed that the inhibitory effect of GSZG on osteoclastogenesis was related to the promotion of PTEN-induced kinase protein 1 (PINK1)/Parkin pathway-mediated mitophagy of osteoclast precursors, which was verified using a PINK1 knockdown small interfering RNA in OCPs.

CONCLUSION

These findings indicate that GSZG is a candidate for the treatment of bone destruction in RA and provide a more detailed elucidation of the mechanism of GSZG anti-RA bone erosion, i.e., inhibition of the ROS/NF-κB axis through the PINK1/Parkin-mediated mitochondrial autophagic pathway to inhibit osteoclast precursor production, compared to the published literature.