Piperlongumine Inhibits Titanium Particles-Induced Osteolysis, Osteoclast Formation, and RANKL-Induced Signaling Pathways

Inhibitory effects of norcantharidin on titanium particle-induced osteolysis, osteoclast activation and bone resorption via MAPK pathways

Wear particles generated from the surface of implanted prostheses can lead to peri-implant osteolysis and subsequent aseptic loosening. In the inflammatory environment, extensive formation and activation of osteoclasts are considered the underlying cause of peri-implant osteolysis. Current medications targeting osteoclasts for the treatment of particle-induced bone resorption are not ideal due to significant side effects. Therefore, there is an urgent need to develop more effective drugs with fewer side effects. Norcantharidin (NCTD), a derivative of cantharidin extracted from blister beetles, is currently primarily used for the treatment of solid tumors in clinical settings. However, the potential role of NCTD in treating aseptic loosening of the prosthesis has not been reported. In this study, the in vitro results demonstrated that NCTD could effectively inhibit the formation of osteoclasts and bone resorption induced by the RANKL. Consistently, NCTD strongly inhibited RANKL-induced mRNA and protein levels of c-Fos and NFATc1, concomitant with reduced expression of osteoclast specific genes including TRAP, CTR and CTSK. The in vivo data showed that NCTD exerted significant protective actions against titanium particle-induced inflammation and subsequent osteolysis. The molecular mechanism investigation revealed that NCTD could suppress the activations of RANKL-induced MAPK (p38, ERK). Overall, these findings support the potential use of NCTD for the treatment of aseptic loosening following total joint arthroplasty.

Piperlongumine, a Piper longum-derived amide alkaloid, protects mice from ovariectomy-induced osteoporosis by inhibiting osteoclastogenesis via suppression of p38 and JNK signaling

Postmenopausal osteoporosis (PMOP) is a metabolic bone disease that results from overproduction and hyperactivation of osteoclasts caused by insufficient estrogen in women after menopause. Current therapeutic strategies are mainly focused on treating PMOP patients who have already developed severe bone loss or even osteoporotic fractures. Obviously, a better strategy is to prevent PMOP from occurring in the first place. However, such reagents are largely lacking. Piperlongumine (PLM), an amide alkaloid extracted from long pepper Piper longum, exhibits the anti-osteoclastogenic effect in normal bone marrow macrophages (BMMs) and the protective effect against osteolysis induced by titanium particles in mice. This study examined the preventive effect of PLM on PMOP and explored the potential mechanism of this effect using both ovariectomized mice and their primary cells. The result showed that PLM (5 and 10 mg kg-1) administered daily for 6 weeks ameliorated ovariectomy-induced bone loss and osteoclast formation in mice. Further cell experiments showed that PLM directly suppressed osteoclast formation, F-actin ring formation, and osteoclastic resorption pit formation in BMMs derived from osteoporotic mice, but did not obviously affect osteogenic differentiation of bone marrow stromal cells (BMSCs) from these mice. Western blot analysis revealed that PLM attenuated maximal activation of p38 and JNK pathways by RANKL stimulation without affecting acute activation of NF-κB, AKT, and ERK signaling. Furthermore, PLM inhibited expression of key osteoclastogenic transcription factors NFATc1/c-Fos and their target genes (Dcstamp, Atp6v0d2, Acp5, and Oscar). Taken together, our findings suggest that PLM inhibits osteoclast formation and function by suppressing RANKL-induced activation of the p38/JNK-cFos/NFATc1 signaling cascade, thereby preventing ovariectomy-induced osteoporosis in mice. Thus, PLM can potentially be used as an anti-resorption drug or dietary supplement for the prevention of PMOP.

Protective effects of piperlongumine against adjuvant-induced arthritis in rats through modulating OPG/RANKL/NF-κB signaling pathway

OBJECTIVES

We examined the antirheumatoid effects of piperlongumine (PLM) on rat adjuvant-induced arthritis (AIA) and explored the underlying mechanisms involved.

METHODS

PLM (2.5, 5, and 10 mg/kg) was administered intraperitoneally to AIA rats to assess its effectiveness. Blood, thymus, spleen, ankle joint, and synovial tissue samples were gathered for subsequent analyses, like enzyme-linked immunosorbent assay, thymus/spleen index measurement, ankle joint pathological examination, immunohistochemistry assay, polymerase chain reaction, and western blot assay. Moreover, the involvement of osteoprotegerin (OPG)/receptor activators of nuclear factor κB ligand (RANKL)/nuclear factor-κB (NF-κB) signaling was investigated.

KEY FINDINGS

PLM effectively relieved inflammation and joint destruction in AIA rats, as indicated by reductions in hind paw swelling, arthritis index, thymus/spleen index, ankle joint pathological damage, production of TNF-α, IL-1β, and IL-6 in both serum and synovium, and osteoclast formation. Also, PLM treatment raised OPG production, reduced RANKL expression, and elevated the OPG/RANKL ratio in synovial tissues. Furthermore, PLM prevented IκBα degradation and phosphorylation, resulting in a reduced expression of the nuclear NF-κB p65 protein in AIA rat synovial tissues.

CONCLUSIONS

PLM demonstrated strong antiarthritic effects in rats with AIA by influencing the OPG/RANKL/NF-κB signaling pathway, highlighting its potential clinical relevance in treating rheumatoid arthritis.

CB2 regulates oxidative stress and osteoclastogenesis through NOX1-dependent signaling pathway in titanium particle-induced osteolysis

Periprosthetic osteolysis (PPO) induced by wear particles at the interface between the prosthesis and bone is a crucial issue of periprosthetic bone loss and implant failure. After wear and tear, granular material accumulates around the joint prosthesis, causing a chronic inflammatory response, progressive osteoclast activation and eventual loosening of the prosthesis. Although many studies have been conducted to address bone loss after joint replacement surgeries, they have not fully addressed these issues. Focusing on osteoclast activation induced by particles has important theoretical implications. Cannabinoid type II receptor (CB2) is a seven-transmembrane receptor that is predominantly distributed in the human immune system and has been revealed to be highly expressed in bone-associated cells. Previous studies have shown that modulation of CB2 has a positive effect on bone metabolism. However, the exact mechanism has not yet been elucidated. In our experiments, we found that NOX1-mediated ROS accumulation was involved in titanium particle-stimulated osteoclast differentiation. Furthermore, we confirmed that CB2 blockade alleviated titanium particle-stimulated osteoclast activation by inhibiting the NOX1-mediated oxidative stress pathway. In animal experiments, downregulation of CB2 alleviated the occurrence of titanium particle-induced cranial osteolysis by inhibiting osteoclasts and scavenging intracellular ROS. Collectively, our results suggest that CB2 blockade may be an attractive and promising therapeutic scheme for particle-stimulated osteoclast differentiation and preventing PPO.

Mechanism of regulating macrophages/osteoclasts in attenuating wear particle-induced aseptic osteolysis

Joint replacement surgery is the most effective treatment for end-stage arthritis. Aseptic loosening caused by periprosthetic osteolysis is a common complication after joint replacement. Inflammation induced by wear particles derived from prosthetic biomaterials is a major cause of osteolysis. We emphasize that bone marrow-derived macrophages and their fusion-derived osteoclasts play a key role in this pathological process. Researchers have developed multiple intervention approaches to regulate macrophage/osteoclast activation. Aiming at wear particle-induced periprosthetic aseptic osteolysis, this review separately discusses the molecular mechanism of regulation of ROS formation and inflammatory response through intervention of macrophage/osteoclast RANKL-MAPKs-NF-κB pathway. These molecular mechanisms regulate osteoclast activation in different ways, but they are not isolated from each other. There is also a lot of crosstalk among the different mechanisms. In addition, other bone and joint diseases related to osteoclast activation are also briefly introduced. Therefore, we discuss these new findings in the context of existing work with a view to developing new strategies for wear particle-associated osteolysis based on the regulation of macrophages/osteoclasts.

Corylifol A protects against ovariectomized-induced bone loss and attenuates RANKL-induced osteoclastogenesis via ROS reduction, ERK inhibition, and NFATc1 activation

Osteoclast differentiation and function are critical targets for anti-osteoporosis treatment. Oxidative stress also plays an important regulatory role in the differentiation of osteoclasts. Corylifol A (CA) is a flavonoid extracted from the Psoralea fruit. It has anti-inflammatory and antioxidant properties despite its unknown effect on osteoporosis. This study found that CA prevented estrogen-deficiency-induced bone loss and suppressed osteoclastogenesis in ovariectomized (OVX) mice by inhibiting intracellular reactive oxygen species (ROS) levels. In vivo, CA effectively prevented trabecular bone loss and reduced osteoclasts' number on the bone surface in OVX mice, as demonstrated in micro-CT, osteometry, and immunohistochemical data. However, CA did not affect cortical bone. In vitro, CA inhibited RANKL-induced podosome belt formation, osteoclastogenesis, and bone resorption functions. CA suppressed RANKL-induced ROS by boosting antioxidant enzymes (Catalase and NQO1) and NFATc1 signaling pathway related protein expression, including integrin αvβ3, NFATc1 and CTSK. Moreover, CA inhibited osteoclast-specific genes, including Ctsk, Acp5, and Mmp9. CA also attenuated the MAPK/ERK pathway, but did not affect the NF-κB signaling pathway. In terms of osteogenesis, CA did not inhibit or promote osteogenic differentiation and mineralization in vitro. These results reveal that CA could be a new replacement therapy for treating estrogen-deficiency osteoporosis via suppressing osteoclastogenesis and intracellular ROS.

Phosphatidyl Inositol 3-Kinase (PI3K)-Inhibitor CDZ173 protects against LPS-induced osteolysis

A major complication of a joint replacement is prosthesis loosening caused by inflammatory osteolysis, leading to the revision of the operation. This is due to the abnormal activation of osteoclast differentiation and function caused by periprosthetic infection. Therefore, targeting abnormally activated osteoclasts is still effective for treating osteolytic inflammatory diseases. CDZ173 is a selective PI3K inhibitor widely used in autoimmune-related diseases and inflammatory diseases and is currently under clinical development. However, the role and mechanism of CDZ173 in osteoclast-related bone metabolism remain unclear. The possibility for treating aseptic prosthesis loosening brought on by inflammatory osteolysis illness can be assessed using an LPS-induced mouse cranial calcium osteolysis model. In this study, we report for the first time that CDZ173 has a protective effect on LPS-induced osteolysis. The data show that this protective effect is due to CDZ173 inhibiting the activation of osteoclasts in vivo. Meanwhile, our result demonstrated that CDZ173 had a significant inhibitory effect on RANKL-induced osteoclasts. Furthermore, using the hydroxyapatite resorption pit assay and podosol actin belt staining, respectively, the inhibitory impact of CDZ173 on bone resorption and osteoclast fusion of pre-OC was determined. In addition, staining with alkaline phosphatase (ALP) and alizarin red (AR) revealed that CDZ173 had no effect on osteoblast development in vitro. Lastly, CDZ173 inhibited the differentiation and function of osteoclasts by weakening the signal axis of PI3K-AKT/MAPK-NFATc1 in osteoclasts. In conclusion, our results highlight the potential pharmacological role of CDZ173 in preventing osteoclast-mediated inflammatory osteolysis and its potential clinical application.