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Limonoid 7-Deacetoxy-7-oxogedunin (CG-1) Attenuates RANKL-Induced Osteoclastogenesis via Inhibiting PI3K/Akt-NFATc1
1Department of Pathobiochemistry, Faculty of Pharmacy, Osaka Medical and Pharmaceutical University, 4-20-1 Nasahara, Takatsuki 569-1094, Osaka, Japan.
Abstract:
Excessive bone resorption by osteoclasts causes pathological bone loss in diseases such as osteoporosis. 7-Deacetoxy-7-oxogedunin (CG-1), a limonoid isolated from Carapa guianensis (Meliaceae), exhibits various biological activities. Here, we examined the anti-osteoclastogenic effect of CG-1 and its underlying mechanism in receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation of RAW264.7 cells. CG-1 inhibited the formation of tartrate-resistant acid phosphatase-positive multinucleated cells and decreased the expression of osteoclastogenesis-related genes. When CG-1 was added to the culture during the first 3 days of the 5-day-osteoclastogenesis period, the expression levels of the osteoclastogenesis-related genes (Nfatc1, Acp5, Src, Ctsk, and Mmp9) were decreased, as was observed when CG-1 was added continuously for 5 days. Furthermore, CG-1 lowered RANKL-induced Akt phosphorylation, which is similar to the results seen with the PI3K inhibitor, LY294002. Moreover, CG-1 and LY294002 suppressed the RANKL-induced expression of NFATc1, the master transcription factor for regulating terminal differentiation into osteoclasts. These results suggest that CG-1 attenuated RANKL-induced osteoclastogenesis by inhibiting the PI3K/Akt-NFATc1 axis during the early stage of osteoclast differentiation. Thus, CG-1 has the potential to suppress osteoclast-mediated bone resorption.
Insights
7-Deacetoxy-7-oxogedunin (CG-1) inhibits osteoclast formation, a key process in bone loss diseases like osteoporosis. This compound may offer a new therapeutic strategy for suppressing excessive bone resorption.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Osteoclasts are crucial for bone remodeling, but their excessive activity leads to pathological bone loss in conditions like osteoporosis.
- Receptor activator of NF-κB ligand (RANKL) signaling is a primary driver of osteoclast differentiation and bone resorption.
- 7-Deacetoxy-7-oxogedunin (CG-1), a limonoid from *Carapa guianensis*, possesses diverse biological activities, prompting investigation into its effects on bone metabolism.
Purpose of the Study:
- To investigate the anti-osteoclastogenic effects of CG-1.
- To elucidate the underlying molecular mechanisms of CG-1's action on osteoclast differentiation.
- To assess CG-1's potential therapeutic role in mitigating excessive bone resorption.
Main Methods:
- Utilized RAW264.7 cells induced to differentiate into osteoclasts by RANKL.
- Assessed osteoclast formation by counting tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells.
- Quantified the expression of key osteoclastogenesis-related genes, including *Nfatc1*, *Acp5*, *Src*, *Ctsk*, and *Mmp9*.
- Examined the impact of CG-1 on the PI3K/Akt signaling pathway and NFATc1 expression.
Main Results:
- CG-1 significantly inhibited osteoclast differentiation and the formation of TRAP-positive multinucleated cells.
- CG-1 treatment decreased the expression of critical osteoclastogenesis genes, irrespective of whether administered early or throughout the differentiation period.
- CG-1 suppressed RANKL-induced Akt phosphorylation and subsequently inhibited the expression of NFATc1, the master regulator of osteoclast differentiation.
- CG-1's inhibitory effects on osteoclastogenesis were comparable to those of the PI3K inhibitor LY294002.
Conclusions:
- CG-1 effectively attenuates RANKL-induced osteoclastogenesis by inhibiting the PI3K/Akt-NFATc1 signaling axis.
- The compound demonstrates potential as a therapeutic agent for conditions characterized by excessive osteoclast-mediated bone resorption, such as osteoporosis.
- Targeting the early stages of osteoclast differentiation with CG-1 offers a promising strategy for bone protective therapies.
