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Cajaninstilbene Acid targets TNF-α-mediated mitochondrial translocation to restore osteogenic-osteoclastic coupling
Benlu Chen1, Hongduo Lu2, Jiayu Gan3
1State Key Laboratory of Traditional Chinese Medicine Syndromes, The First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou, 510405, China; The Laboratory of Orthopaedics and Traumatology of Lingnan Medical Research Center, Guangzhou University of Chinese Medicine, Guangzhou, 510405, China.
Background:
Oestrogen-deficient osteoporosis features an imbalanced bone formation-resorption coupling with excessive osteoclast activation and impaired osteoblast function. Compounds that bidirectionally regulate bone metabolism remain rare among natural small molecules. Cajaninstilbene acid (CSA) from Cajanus cajan leaves exerts regulatory effects on bone metabolism and anti-inflammatory activity, but its mechanism in restoring bone homeostasis via intercellular mitochondrial transfer remains unclear.
Purpose:
To investigate the therapeutic effect of CSA on oestrogen-deficient osteoporosis and reveal its molecular mechanism by targeting TNF-α-mediated mitochondrial transfer to rebalance osteogenesis and osteoclastogenesis.
Materials:
Ovariectomised (OVX) mice were used as the estrogen-deficient osteoporosis model and treated with CSA for 6 weeks. Bone microstructure and metabolism were evaluated by micro-computed tomography (micro-CT), histological staining and immunohistochemistry (IHC). Primary bone marrow macrophages (BMMs) and bone marrow mesenchymal stem cells (BMSCs) were cultured for osteoclastic and osteogenic differentiation. Differentiation was assessed by tartrate-resistant acid phosphatase (TRAcP), alkaline phosphatase (ALP) and alizarin red staining (ARS). Key targets were screened by transcriptomic analysis and validated by molecular docking and surface plasmon resonance (SPR). Mitochondrial transfer and activity were observed by co-culture, fluorescence labelling and JC-1 staining. Protein and gene expression were determined by Western blot (WB) and quantitative real-time polymerase chain reaction (qPCR).
Results:
CSA significantly increased bone mineral density and improved trabecular microarchitecture in OVX mice without obvious hepatorenal toxicity. In vitro, CSA dose-dependently suppressed RANKL-induced osteoclastogenesis by downregulating NFATc1 and CTSK, while enhancing osteoblast differentiation by upregulating RUNX2, OCN and OPG. Mechanistically, CSA directly bound and inhibited TNF-α, upregulated the mitochondrial transporter MIRO1, and restored mitochondrial transfer from osteoblasts to osteoclasts, reversing the disrupted bone coupling balance.
Conclusion:
CSA bidirectionally inhibits bone resorption and promotes bone formation by blocking TNF-α signalling and restoring MIRO1-mediated mitochondrial transfer, effectively ameliorating oestrogen-deficient osteoporosis. This study provides pharmacological support and novel mechanistic insights for CSA as a promising natural candidate for osteoporosis treatment.
Insights
Cajaninstilbene acid (CSA) effectively treats osteoporosis by blocking TNF-α and restoring mitochondrial transfer, promoting bone formation and inhibiting resorption. This natural compound offers a promising therapeutic approach for bone health.
Area of Science:
- Biochemistry and Molecular Biology
- Cell Biology
- Pharmacology
Background:
- Oestrogen-deficient osteoporosis is characterized by imbalanced bone metabolism, with excessive osteoclast activity and reduced osteoblast function.
- Natural small molecules that can bidirectionally regulate bone metabolism are scarce.
- Cajaninstilbene acid (CSA) shows potential but its mechanism in restoring bone homeostasis via intercellular mitochondrial transfer is unclear.
Purpose of the Study:
- To investigate the therapeutic effect of CSA on oestrogen-deficient osteoporosis.
- To elucidate the molecular mechanism of CSA, focusing on TNF-α-mediated mitochondrial transfer in rebalancing osteogenesis and osteoclastogenesis.
Main Methods:
- Ovariectomized (OVX) mice were treated with CSA to assess bone microstructure and metabolism.
- In vitro studies utilized primary bone marrow macrophages (BMMs) and mesenchymal stem cells (BMSCs) to evaluate osteoclast and osteoblast differentiation.
- Transcriptomic analysis, molecular docking, surface plasmon resonance, and mitochondrial activity assays were employed to identify and validate key molecular targets and mechanisms.
Main Results:
- CSA treatment significantly improved bone mineral density and trabecular microarchitecture in OVX mice without toxicity.
- In vitro, CSA suppressed osteoclastogenesis and enhanced osteoblast differentiation by regulating key transcription factors and enzymes.
- CSA was found to directly inhibit TNF-α, upregulate the mitochondrial transporter MIRO1, and restore mitochondrial transfer between osteoblasts and osteoclasts.
Conclusions:
- CSA effectively ameliorates oestrogen-deficient osteoporosis by inhibiting bone resorption and promoting bone formation.
- The mechanism involves blocking TNF-α signaling and restoring MIRO1-mediated mitochondrial transfer, rebalancing bone metabolism.
- CSA presents a promising natural therapeutic candidate for osteoporosis with novel mechanistic insights.
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