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A Novel in vivo Gene Transfer Technique and in vitro Cell Based Assays for the Study of Bone Loss in Musculoskeletal Disorders
Published on: June 8, 2014
Okanin attenuates ovariectomy-induced bone loss in mice model through inhibition of IKKβ-mediated NF-κB p65
Kai Shi1, Ying-Jian Wang2, Shaoming Wang3
1State Key Laboratory for Diagnosis and Treatment of Severe Zoonotic Infectious Diseases, Key Laboratory for Zoonosis Research of the Ministry of Education, Institute of Zoonosis, and College of Veterinary Medicine, Department of Gynaecology and Obstetrics, China-Japan Union Hospital Jilin University, Changchun 130062, China; School of Life Sciences, Fudan University, Shanghai 200032, China.
Background:
Excessive activation of osteoclasts can lead to excessive bone resorption, thereby causing bone loss diseases. Okanin, a flavonoid derived from Coreopsis tinctoria, has been reported to possess antibacterial, anti-inflammatory and antioxidant activities, and has therapeutic effects on cerebral ischemia. Although okanin is known for other biological activities, its role in bone metabolism has not been clearly elucidated before.
Purpose:
In the present study, we evaluated the effects of okanin on osteoclast formation and function through in vitro assays, and further assessed its capacity to mitigate bone loss in a murine model of ovariectomy (OVX)-induced osteoporosis in vivo.
Study Design:
We employed a combination of in vitro cell-based assays and an in vivo ovariectomy (OVX)-induced osteoporosis mouse model to systematically assess okanin's bone-protective effects and underlying mechanisms.
Methods:
In vitro, bone marrow macrophages (BMMs) were treated with okanin (1.25-20 μM) during RANKL-induced osteoclast differentiation. Key endpoints included TRAP-positive multinucleated cell formation, F-actin ring integrity, resorption pit activity, and expression of osteoclastogenic markers (c-Fos, NFATc1) and signaling molecules (IKKβ, NF-κB p65). In silico molecular docking analyzed okanin's interaction with IKKα/β. In vivo, OVX mice were administered okanin (2 or 10 mg/kg, i.p.) for 8 weeks, followed by micro-CT, histological, and TRAP staining analyses of femurs to assess bone microarchitecture and osteoclast activity.
Results:
In vitro, okanin dose-dependently inhibited RANKL-induced osteoclast differentiation and disrupted F-actin ring formation without cytotoxicity. It downregulated c-Fos, NFATc1, and their target genes (TRAP, MMP-9, Atp6v0d2), while selectively suppressing IKKβ phosphorylation and NF-κB p65 activation (without affecting MAPK pathways or IKKα). Okanin also blunted RANKL-induced Blimp1 upregulation and preserved NFATc1 inhibitors (Bcl6, MafB, IRF8). In vivo, okanin dose-dependently preserved trabecular bone architecture in OVX mice, improving bone volume fraction (BV/TV), trabecular number (Tb.N), and thickness (Tb.Th), while reducing osteoclast numbers.
Conclusion:
In conclusion, these findings establish okanin as a novel bone-protective agent that inhibits osteoclastogenesis through a distinct mechanism involving selective IKKβ/NF-κB inhibition, thereby attenuating OVX-induced bone loss. This specificity distinguishes it from other compounds and highlights its promise as a lead candidate for development as a functional food supplement or therapeutic agent for osteoporosis.
Insights
Okanin, a flavonoid, effectively inhibits osteoclast formation and function, thereby preventing bone loss in osteoporosis. This compound shows promise as a natural therapeutic agent for bone health.
Area of Science:
- Biochemistry
- Pharmacology
- Bone Biology
Background:
- Excessive osteoclast activation leads to bone loss diseases like osteoporosis.
- Okanin, a flavonoid from Coreopsis tinctoria, has known anti-inflammatory and antioxidant properties but its role in bone metabolism was unclear.
Purpose of the Study:
- To evaluate okanin's effects on osteoclast formation and function in vitro.
- To assess okanin's efficacy in mitigating bone loss in an in vivo model of osteoporosis.
Main Methods:
- In vitro assays using bone marrow macrophages (BMMs) treated with okanin during RANKL-induced osteoclast differentiation.
- In vivo study using ovariectomy (OVX)-induced osteoporosis mouse model treated with okanin.
- Analysis of osteoclast markers, signaling pathways (IKKβ/NF-κB), bone microarchitecture, and osteoclast activity.
Main Results:
- Okanin dose-dependently inhibited osteoclast differentiation and function without cytotoxicity.
- It selectively suppressed IKKβ phosphorylation and NF-κB p65 activation, downregulating key osteoclastogenic markers.
- In vivo, okanin preserved bone microarchitecture and reduced osteoclast numbers in OVX mice.
Conclusions:
- Okanin is a novel bone-protective agent that inhibits osteoclastogenesis via selective IKKβ/NF-κB inhibition.
- This mechanism attenuates ovariectomy-induced bone loss, suggesting okanin's potential for osteoporosis treatment or functional food development.
