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Nur77 Prevents Osteoporosis by Inhibiting the NF-κB Signalling Pathway and Osteoclast Differentiation
Huanlian Tian1,2, Feng Chen1, Yingfang Wang3
1Department of Gerontology and Geriatrics, Shengjing Hospital of China Medical University, Shenyang, Liaoning, China.
Abstract:
Inflammation is a major risk factor for osteoporosis, and reducing inflammatory levels is important for the prevention of osteoporosis. Although nuclear receptor 77 (Nur77) protects against inflammation in a variety of diseases, its role in osteoporosis is unknown. Therefore, the main purpose of this study was to investigate the osteoprotective and anti-inflammatory effects of Nur77. The microCT and haematoxylin and eosin staining results indicated that knockout of Nur77 accelerated femoral bone loss in mice. The enzyme-linked immunosorbent assay (ELISA) results showed that knockout of Nur77 increased the serum levels of hsCRP and IL-6. The expression levels of NF-κB, IL-6, TNF-α and osteoclastogenesis factors (TRAP, NFATC1, Car2, Ctsk) in the femurs of Nur77 knockout mice were increased significantly. Furthermore, in vitro, shNur77 promoted the differentiation of RAW264.7 cells into osteoclasts by activating NF-κB, which was confirmed by PDTC treatment. Mechanistically, Nur77 inhibited osteoclast differentiation by inducing IκB-α and suppressing IKK-β. In RAW264.7 cells, overexpression of Nur77 alleviated inflammation induced by siIκB-α, while siIKK-β alleviated inflammation induced by shNur77. Consistent with the in vivo studies, we found that compared with control group, older adults with high serum hsCRP levels were more likely to suffer from osteoporosis (OR = 1.76, p < 0.001). Our data suggest that Nur77 suppresses osteoclast differentiation by inhibiting the NF-κB signalling pathway, strongly supporting the notion that Nur77 has the potential to prevent and treat osteoporosis.
Insights
Nuclear receptor 77 (Nur77) inhibits osteoclast differentiation and bone loss by suppressing the NF-κB pathway. Nur77 shows potential for preventing and treating osteoporosis by reducing inflammation.
Area of Science:
- Molecular Biology
- Immunology
- Bone Biology
Background:
- Inflammation is a key risk factor for osteoporosis.
- Nuclear receptor 77 (Nur77) has known anti-inflammatory roles, but its function in osteoporosis is uncharacterized.
Purpose of the Study:
- To investigate the osteoprotective and anti-inflammatory effects of Nur77 in osteoporosis.
- To elucidate the molecular mechanisms underlying Nur77's role in bone metabolism.
Main Methods:
- Utilized a knockout mouse model (Nur77 knockout) for in vivo studies.
- Employed microCT, H&E staining, ELISA, and Western blotting for molecular analysis.
- Conducted in vitro experiments using RAW264.7 cells to study osteoclast differentiation and inflammatory pathways.
Main Results:
- Nur77 knockout accelerated femoral bone loss and increased serum levels of hsCRP and IL-6.
- Knockout mice exhibited elevated expression of NF-κB, IL-6, TNF-α, and osteoclastogenesis factors.
- Nur77 inhibited osteoclast differentiation by inducing IκB-α and suppressing IKK-β, thereby dampening the NF-κB signaling pathway.
Conclusions:
- Nur77 suppresses osteoclast differentiation and bone loss by inhibiting the NF-κB signaling pathway.
- Nur77 demonstrates significant potential as a therapeutic target for preventing and treating osteoporosis.
- Elevated hsCRP levels are associated with an increased likelihood of osteoporosis in older adults.
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