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Melatonin at pharmacological concentrations suppresses osteoclastogenesis via the attenuation of intracellular ROS
Abstract:
Osteoporosis is linked to age-related decline of melatonin production; however, the direct effects of melatonin on osteoclastogenesis remain unknown. Our study demonstrates that melatonin at pharmacological concentrations, rather than at physiological concentrations, significantly inhibits osteoclastogenesis. Melatonin-mediated anti-osteoclastogenesis involves a reactive oxygen species (ROS)-mediated but not a silent information regulator type 1 (SIRT1)-independent pathway.
Introduction:
Osteoporosis is a bone disorder linked to impaired bone formation and excessive bone resorption. Melatonin has been suggested to treat osteoporosis due to its beneficial actions on osteoblast differentiation. However, the direct effects of melatonin on osteoclastogenesis in bone marrow monocytes (BMMs) remain unknown. This study was to investigate whether melatonin at either physiological or pharmacological concentrations could affect osteoclast differentiation.
Methods:
Primary BMMs were isolated from the femurs and tibias of C57BL/6 mice and were induced toward multinucleated osteoclasts, in the presence of melatonin at either physiological (0.01 to 10 nM) or pharmacological (1 to 100 μM) concentrations. Tartrate-resistant acid phosphatase (TRAP) staining was used to label multinucleated osteoclasts and the levels of osteoclast-specific genes were evaluated. To further explore the underlying mechanisms, the roles of silent information regulator type 1 (SIRT1) and reactive oxygen species (ROS) were evaluated.
Results:
We found that melatonin at pharmacological concentrations, rather than at physiological concentrations, significantly inhibited osteoclast formation in a dose-dependent manner. The number of TRAP-positive cells and the gene expression of osteoclast-specific markers were significantly downregulated in melatonin-treated BMMs. The melatonin-mediated repression of osteoclast differentiation involved the inhibition of the nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. The treatment with SIRT1 inhibitors did not affect osteoclast differentiation but, when supplemented with exogenous hydrogen peroxide, a partial rescue of melatonin-suppressed osteoclastogenesis was observed.
Conclusion:
Melatonin at pharmacological doses directly inhibited osteoclastogenesis of BMMs by a ROS-mediated but not a SIRT1-independent pathway.
Insights
Pharmacological doses of melatonin significantly inhibit osteoclastogenesis, the process of bone breakdown. This effect is mediated by reactive oxygen species (ROS), not SIRT1, offering new insights into osteoporosis treatment.
Area of Science:
- Endocrinology and Bone Biology
- Cellular and Molecular Biology
Background:
- Osteoporosis is characterized by imbalanced bone remodeling, with excessive bone resorption.
- Melatonin, known for its role in circadian rhythms, has shown potential in treating osteoporosis.
- The direct impact of melatonin on osteoclastogenesis, the formation of bone-resorbing cells, requires clarification.
Purpose of the Study:
- To investigate the direct effects of melatonin on osteoclast differentiation.
- To determine if melatonin affects osteoclastogenesis at physiological or pharmacological concentrations.
- To elucidate the underlying molecular mechanisms, including the roles of SIRT1 and ROS.
Main Methods:
- Primary bone marrow monocytes (BMMs) from mice were cultured and induced to form osteoclasts.
- Melatonin was administered at physiological (0.01–10 nM) and pharmacological (1–100 μM) concentrations.
- Osteoclast formation was assessed by TRAP staining, gene expression analysis, and evaluation of SIRT1 and ROS pathways.
Main Results:
- Melatonin significantly inhibited osteoclast formation in a dose-dependent manner at pharmacological concentrations.
- Melatonin treatment downregulated TRAP-positive cells and osteoclast-specific gene expression.
- The inhibitory effect involved reactive oxygen species (ROS) and the NF-κB pathway, independent of SIRT1.
Conclusions:
- Pharmacological doses of melatonin directly inhibit osteoclastogenesis in BMMs.
- Melatonin exerts its anti-osteoclastogenic effect through a ROS-mediated pathway.
- Melatonin's action is independent of SIRT1, suggesting a distinct mechanism for its bone-protective effects.
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