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Published on: March 18, 2019
Sulforaphane inhibits multiple myeloma cell-induced osteoclast differentiation and macrophage proliferation by
Weichu Sun1, Jingqi Sun2,3, Wei Hu2,3
1Department of Orthopedics, Xiangya Hospital, Central South University, Changsha, Hunan, China.
Purpose:
Osteolysis is a common complication in patients with multiple myeloma (MM). Our previous studies have demonstrated that MM cells can promote osteoclast differentiation of macrophages. In this study, we explored the effect of sulforaphane (SFN), a natural NRF2 activator found in broccoli, on MM cell-induced osteoclast differentiation.
Methods:
Conditional medium (CM) derived from MM cells was used to induce osteoclast differentiation, and TRAP staining was performed to examine osteoclast. Gene expression was detected by western blotting or real-time PCR. Cell counting and EdU staining were performed to test macrophage proliferation.
Results:
We showed that the CM of MM cells downregulated the expression of ferroportin1 (Fpn1), the only known iron exporter in vertebrate cells, thereby increasing cellular iron levels in murine macrophage cells RAW264.7. Deferoxamine (DFO), an iron chelator, effectively blocked MM cell CM-induced osteoclast differentiation and macrophage proliferation, suggesting that iron overload played a key role in these cellular events. Subsequent mechanistic investigations revealed that MM cell CM induced osteoclast differentiation and macrophage proliferation by activating the JNK/AP-1/NFATC1 pathway and PI3K/AKT pathway. SFN was found to increase Fpn1 expression, leading to decreased cellular iron levels in RAW264.7 cells activated by MM cell CM. Importantly, the osteoclast differentiation and macrophage proliferation induced by MM cell CM were significantly inhibited by SFN.
Conclusion:
Altogether, our findings indicated that SFN inhibits MM cell-induced osteoclast differentiation and macrophage proliferation by elevating FPN1 levels. SFN could be a promising therapeutic strategy for MM-associated osteolysis.
Insights
Sulforaphane (SFN) reduces iron overload in macrophages, inhibiting multiple myeloma (MM) cell-driven osteoclast differentiation and proliferation. This suggests SFN as a potential treatment for MM-related bone loss (osteolysis).
Area of Science:
- Biochemistry
- Cell Biology
- Oncology
Background:
- Osteolysis is a frequent complication in multiple myeloma (MM).
- MM cells are known to promote osteoclast differentiation from macrophages.
- Investigating therapeutic agents for MM-associated osteolysis is crucial.
Purpose of the Study:
- To explore the effect of sulforaphane (SFN), a natural NRF2 activator, on MM cell-induced osteoclast differentiation.
- To understand the role of iron metabolism in MM-induced osteoclastogenesis.
- To evaluate SFN's potential as a therapeutic strategy for MM-associated osteolysis.
Main Methods:
- Utilized conditional medium (CM) from MM cells to induce osteoclast differentiation in RAW264.7 macrophages.
- Assessed osteoclast formation via TRAP staining.
- Quantified gene expression using western blotting and real-time PCR.
- Evaluated macrophage proliferation using cell counting and EdU staining.
- Investigated the effects of iron chelator deferoxamine (DFO) and SFN.
Main Results:
- MM cell CM downregulated ferroportin1 (Fpn1) expression, increasing cellular iron levels in macrophages.
- Iron overload was identified as a key factor in MM-induced osteoclast differentiation and macrophage proliferation.
- MM cell CM activated the JNK/AP-1/NFATC1 and PI3K/AKT pathways.
- SFN treatment increased Fpn1 expression, reduced cellular iron, and significantly inhibited MM-induced osteoclast differentiation and macrophage proliferation.
Conclusions:
- SFN inhibits MM cell-induced osteoclast differentiation and macrophage proliferation by upregulating FPN1 levels and reducing cellular iron.
- These findings highlight SFN as a potential therapeutic agent for mitigating MM-associated osteolysis.
