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RANKL enhances macrophage paracrine pro-calcific activity in high phosphate-treated smooth muscle cells: dependence
Kate Ann Deuell1, Andrea Callegari, Cecilia M Giachelli
1Department of Bioengineering, University of Washington, Seattle, WA 98195, USA.
Insights
Receptor activator of NF-κB ligand (RANKL) promotes vascular calcification by increasing pro-inflammatory cytokines in macrophages. This study reveals RANKL’s role in smooth muscle cell calcification, a key factor in cardiovascular disease.
Area of Science:
- Cardiovascular Biology
- Immunology
- Cell Biology
Background:
- Vascular calcification is a significant risk factor for cardiovascular disease (CVD) morbidity and mortality.
- Inflammation is closely linked to vascular calcification.
- Receptor activator of NF-κB ligand (RANKL) inhibition reduces vascular calcification in atherosclerosis models.
Purpose of the Study:
- To investigate the hypothesis that RANKL regulates smooth muscle cell (SMC) calcification.
- To determine if RANKL modulates macrophage-derived pro-calcific cytokines.
Main Methods:
- Utilized a co-culture system of bone marrow-derived macrophages (BMDM) and SMCs.
- Examined the effects of RANKL on BMDM activation and SMC matrix calcification.
- Assessed the expression of cytokines IL-6 and TNF-α in BMDMs treated with RANKL.
Main Results:
- RANKL alone did not induce SMC calcification; however, it enhanced phosphate-induced calcification in BMDM/SMC co-cultures.
- RANKL treatment increased IL-6 and TNF-α expression in BMDMs.
- Neutralizing antibodies against IL-6 and TNF-α significantly reduced RANKL-induced SMC calcification.
Conclusions:
- RANKL activation of pro-inflammatory and pro-calcific pathways in macrophages contributes to vascular calcification.
- Macrophage-derived cytokines, IL-6 and TNF-α, mediate RANKL's effect on SMC calcification.
- Targeting RANKL-mediated inflammatory pathways may offer therapeutic strategies for vascular calcification.
Background:
Vascular calcification is highly correlated with cardiovascular disease (CVD) morbidity and mortality, and it is associated with inflammation. Receptor activator of NF-ĸB ligand (RANKL) inhibition in vivo has been shown to reduce vascular calcification in a mouse model of atherosclerosis. Therefore, we tested the hypothesis that RANKL regulates smooth muscle cell (SMC) calcification by modulating macrophage production of pro-calcific cytokines.
Methods:
We used a bone marrow-derived macrophage (BMDM)/SMC co-culture system and examined the effects of RANKL on BMDM activation and SMC matrix calcification.
Results:
Treatment with RANKL alone did not stimulate SMC calcification induced by elevated phosphate. BMDMs differentiated with macrophage colony-stimulating factor and placed in co-culture with SMCs increased phosphate-induced SMC calcification. RANKL added to the BMDM/SMC co-cultures further enhanced SMC calcification. Treatment of BMDMs with RANKL resulted in increased expression of IL-6 and TNF-α. Thus, increased expression of these pro-calcific cytokines in macrophages may mediate RANKL-induced SMC calcification in a paracrine fashion. Addition of neutralizing IL-6 and TNF-α antibodies together with RANKL treatment significantly reduced the RANKL induction of SMC calcification.
Conclusion:
RANKL activation of pro-inflammatory and pro-calcific pathways in macrophages may contribute to vascular calcification and inflammation.
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