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Background: Osteoarthritis (OA) is widely recognized as the most common chronic joint disease accompanied by progressive cartilage and subchondral bone damage. Toddalolactone (TOD), a natural compound extracted from Toddalia asiatica (L.) Lam., has been widely used in the treatment of stroke, rheumatoid arthritis, and oedema. Nevertheless, what TOD acts as in the pathogenesis and progression of OA hasn't been reported. In this investigation, we have aimed to determine how TOD affects OA in vitro and in vivo. Methods: LPS (10 µg/ml) and IL-1β (10 ng/ml) were employed to induce chondrocyte inflammation or RANKL to induce osteoclast differentiation in bone marrow derived macrophages (BMMs). The effects of TOD on chondrocyte inflammation and osteoclast differentiation were evaluated. Anterior cruciate ligament transection (ACLT) was performed to develop an OA animal model and study the effects of TOD. Results: We found that TOD inhibited the expression of inflammatory and catabolic mediators (IL-6, IL-8, TNF-α, MMP2, MMP9, and MMP13) in inflammatory chondrocytes in vitro. Furthermore, TOD was proven to inhibit RANKL-induced-osteoclastogenesis and inhibit the expression of osteoclast marker genes. Our data also confirmed that TOD suppressed the destruction of articular cartilage and osteoclastogenesis via inhibiting the activation of NF-κB and MAPK signalling pathways. In the ACLT mouse model, we found that TOD attenuated cartilage erosion and inhibited bone resorption. Conclusions: These results showed that TOD can be adopted as a potential therapeutic agent for OA. [ABSTRACT FROM AUTHOR]

Objectives: Aseptic loosening (AL) is the most common reason of total hip arthroplasty (THA) failure and revision surgery. Osteolysis, caused by wear particles released from implant surfaces, has a vital role in AL. Although previous studies suggest that wear particles always lead to osteoblast programmed death in the process of AL, the specific mechanism remains incompletely understood and osteoblast ferroptosis maybe a new mechanism of AL. Materials and Methods: CoCrMo nanoparticles (CoNPs) were prepared to investigate the influence of ferroptosis in osteoblasts and calvaria resorption animal models. Periprosthetic osteolytic bone tissue was collected from patients who underwent AL after THA to verify osteoblast ferroptosis. Results: Our study demonstrated that CoNPs induced significant ferroptosis in osteoblasts and particles induced osteolysis (PIO) animal models. Blocking ferroptosis with specific inhibitor Ferrostatin‐1 dramatically reduced particle‐induced ferroptosis in vitro. Moreover, in osteoblasts, CoNPs significantly downregulated the expression of Nrf2 (nuclear factor erythroid 2‐related factor 2), a core element in the antioxidant response. The overexpression of Nrf2 by siKeap1 or Nrf2 activator Oltipraz obviously upregulated antioxidant response elements (AREs) and suppressed ferroptosis in osteoblasts. Furthermore, in PIO animal models, the combined utilization of Ferrostatin‐1 and Oltipraz dramatically ameliorated ferroptosis and the severity of osteolysis. Conclusions: These results indicate that CoNPs promote osteoblast ferroptosis by regulating the Nrf2‐ARE signalling pathway, which suggests a new mechanism underlying PIO and represents a potential therapeutic approach for AL. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoP-challenged macrophages can accelerate osteoclastogenesis. • CoPs result in macrophages pyroptosis and release of inflammatory cytokines. • CoPs stimulation promotes ROS accumulation and subsequently activates NLRP3. • High-concentration CoPs suppress mitophagy, further enhancing macrophages pyroptosis. • By promoting mitophagy and inhibiting NLRP3, CoP-induced osteolysis can be delayed. Wear particles derived from implant surfaces are the important factors causing periprosthetic osteolysis (PPO), which is the main reason for total joint revision. To date, the specific pathogenesis of PPO remains largely unknown, and developing new therapeutic strategies is urgently necessary. Our study indicated the most clinically common cobalt- chromium-molybdenum (CoCrMo) wear particles (CoPs) activated macrophages and further accelerated osteoclastogenesis. Subsequently, we put emphasis on the pathologic change in macrophages after CoPs stimulation. Meaningfully, high-concentration CoPs induced reactive oxygen species (ROS) accumulation in macrophages and activated NOD-like receptor pyrin domain-containing 3 (NLRP3)-dependent pyroptosis, promoting the release of cytokines such as IL-18, IL-1β and HMGB1, and subsequent formation of extracellular inflammatory microenvironment, which is crucial for osteoclastogenesis. More interestingly, transmission electron microscopy and flow cytometry results revealed that there were accumulation of endamaged mitochondria in high-concentration CoP-challenged macrophages, which accelerated intracellular ROS accumulation and mediated NLRP3-dependent pyroptosis. Mechanismly, high-concentration CoPs induced macrophage mitophagy impairment and the loss of mitochondrial membrane potential via inhibiting PINK1/Parkin signalling pathway. Furthermore, by subcutaneous injection of salidroside and/or CY-09 in situ significantly delayed CoP-induced mice calvaria osteolysis. Collectively, this study demonstrates a novel mechanism underlying the pathogenesis of PPO and provides a potential therapy avenue. [ABSTRACT FROM AUTHOR]