No abstract

Osteolytic bone diseases, for example postmenopausal osteoporosis, arise from the imbalances between osteoclasts and osteoblasts in the bone remodeling process, whereby osteoclastic bone resorption greatly exceeds osteoblastic bone formation resulting in severe bone loss and deterioration in bone structure and microarchitecture. Therefore, the identification of agents that can inhibit osteoclast formation and/or function for the treatment of osteolytic bone disease has been the focus of bone and orthopedic research. Vindoline (Vin), an indole alkaloid extracted from the medicinal plant Catharanthus roseus, has been shown to possess extensive biological and pharmacological benefits, but its effects on bone metabolism remains to be documented. Our study demonstrated for the first time, that Vin could inhibit osteoclast differentiation from bone marrow macrophages (BMMs) precursor cells as well as mature osteoclastic bone resorption. We further determined that the underlying molecular mechanism of action of Vin is in part due to its inhibitory effect against the activation of MAPK including p38, JNK, and ERK and intracellular reactive oxygen species (ROS) production. This effect ultimately suppressed the induction of c-Fos and NFATc1, which consequently downregulated the expression of the genes required for osteoclast formation and bone resorption. Consistent with our in vitro findings, in vivo administration of Vin protected mice against ovariectomy (OVX)-induced bone loss and trabecular bone deterioration. These results provided promising evidence for the potential therapeutic application of Vin as a novel treatment option against osteolytic diseases.

This article was submitted to Experimental Pharmacology and Drug Discovery, a section of the journal Frontiers in Pharmacology. Postmenopausal osteoporosis (PMOP), which increases the risk of fracture, is the most common bone disease in women. PMOP not only increases the risk of death but also imposes a financial burden on countless families. At present, most of the drugs used to treat osteoporosis have significant side effects, so it is important to find effective anti-osteoporosis medications without major side effects. Sesamolin (Ses) is a kind of natural lignan extracted from sesame oil. Many researches have shown that Ses has anti-inflammatory, antioxidative, and anticancer effects, however it is still unknown whether it has any effect on osteoporosis. In this research, we explored the therapeutic effect of Ses in the process of osteoclast formation and bone resorption and found that Ses effectively inhibited osteoclast formation in vitro through TRAcP staining and hydroxyapatite resorption assays. Through Western blot analysis of the NF-κB pathway, MAPK pathway, c-Fos and NFATc1, it was found that Ses not only effectively inhibited the activation of NF-κB and MAPK signaling pathways induced by RANKL but also significantly reduced the protein expression of c-Fos and NFATc1. Several genes specifically expressed in osteoclasts were determined by qPCR, and Ses was also found to play a significant inhibitory role on the expression of these genes. Besides, an osteoporosis model induced in ovariectomized (OVX) mice was employed to verify that Ses could effectively reduce bone loss caused by estrogen deficiency in vivo. In conclusion, Ses showed promise as a new treatment for postmenopausal osteoporosis.

Revision operations have become a new issue after successful artificial joint replacements, and periprosthetic osteolysis leading to prosthetic loosening is the main cause of why the overactivation of osteoclasts (OCs) plays an important role. The effect of biochanin A (BCA) has been examined in osteoporosis, but no study on the role of BCA in prosthetic loosening osteolysis has been conducted yet. In this study, we utilised enzyme-linked immunosorbent assay, computed tomography imaging, and histological analysis. Results showed that BCA downregulated the secretion levels of tumor necrosis factor-α, interleukin-1α (IL-1α), and IL-1β to suppress inflammatory responses. The secretion levels of receptor-activated nuclear factor-κB ligand, CTX-1, and osteoclast-associated receptor as well as Ti-induced osteolysis were also reduced. BCA effectively inhibited osteoclastogenesis and suppressed hydroxyapatite resorption by downregulating OC-related genes in vitro. Analysis of mechanisms indicated that BCA inhibited the signalling pathways of mitogenactivated protein kinase (P38, extracellular signal-regulated kinase, and c-JUN N-terminal kinase) and nuclear factor-κB (inhibitor κB-α and P65), thereby downregulating the expression of nuclear factor of activated T cell 1 and c-Fos. In conclusion, BCA may be an alternative choice for the prevention of prosthetic loosening caused by OCs.

Aseptic prosthetic loosening and periprosthetic infection resulting in inflammatory osteolysis is a leading complication of total joint arthroplasty (TJA). Excessive bone destruction around the bone and prosthesis interface plays a key role in the loosening prostheses leading to revision surgery. The bacterial endotoxins or implant‐derived wear particles‐induced inflammatory response is the major cause of the elevated osteoclast formation and activity. Thus, agents or compounds that can attenuate the inflammatory response and/or inhibit the elevated osteoclastogenesis and excessive bone resorption would provide a promising therapeutic avenue to prevent aseptic prosthetic loosening in TJA. Daphnetin (DAP), a natural coumarin derivative, is clinically used in Traditional Chinese Medicine for the treatment of rheumatoid arthritis due to its anti‐inflammatory properties. In this study, we report for the first time that DAP could protect against lipopolysaccharide‐induced inflammatory bone destruction in a murine calvarial osteolysis model in vivo. This protective effect of DAP can in part be attributed to its direct inhibitory effect on RANKL‐induced osteoclast differentiation, fusion, and bone resorption in vitro. Biochemical analysis found that DAP inhibited the activation of the ERK and NFATc1 signaling cascades. Collectively, our findings suggest that DAP as a natural compound has potential for the treatment of inflammatory osteolysis.