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Role of interleukin-6 in beta2-microglobulin-induced bone mineral dissolution
E Balint1, C F Marshall, S M Sprague
1Department of Medicine and Research Institute, Evanston-Northwestern Healthcare, Northwestern University Medical School, Evanston, IL 60201, USA.
Background:
beta2-microglobulin (beta2m) amyloidosis is commonly seen in patients undergoing long-term dialysis. beta2m has been shown to induce in vitro bone mineral dissolution. The present study was designed to investigate the effect of beta2m on osteoblast function and the role of interleukin-6 (IL-6) on beta2m-induced bone resorption.
Methods:
Using neonatal mouse calvariae as well as primary osteoblasts and MC 3T3 osteoblast-like cells, IL-6 production, release, and gene expression were investigated with enzyme-linked immunosorbent assay (ELISA) and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) techniques, respectively.
Results:
In calvariae, beta2m induced a time- and dose-dependent calcium release, which was maximum following a 48-hour incubation at a concentration of 10-5 mol/L. beta2m (10-6 mol/L) also induced a significant release of IL-6 from calvarial and primary osteoblastic cultures. Using 10-6 mol/L beta2m, the amount of IL-6 mRNA in MC 3T3 cells increased in a time-dependent fashion, which peaked at 3 hours and declined to baseline by 12 hours. In primary osteoblast cells, beta2m maximally increased IL-6 mRNA levels at 6 hours; however, they remained elevated up to 24 hours. Compared with control, the presence of beta2m significantly increased cell proliferation of both primary osteoblasts and MC 3T3 cells. To investigate osteoblastic function further, osteocalcin mRNA was quantitated. Incubation with beta2m for 3 to 24 hours did not alter the amount of osteocalcin mRNA in the MC 3T3 osteoblast cells.
Conclusion:
beta2m affects bone metabolism by mechanisms that include increasing IL-6 gene expression and release, and enhancing osteoblast proliferation without affecting osteocalcin gene expression.
Insights
Beta-2-microglobulin (beta2m) increases interleukin-6 (IL-6) gene expression and release, impacting bone metabolism. This study shows beta2m enhances osteoblast proliferation without altering osteocalcin gene expression.
Area of Science:
- Biochemistry
- Cell Biology
- Bone Metabolism
Background:
- Beta-2-microglobulin (beta2m) amyloidosis is prevalent in dialysis patients.
- Beta2m can induce bone mineral dissolution in vitro.
- The study investigates beta2m's effect on osteoblast function and IL-6's role in beta2m-induced bone resorption.
Purpose of the Study:
- To determine the impact of beta2m on osteoblast function.
- To elucidate the role of interleukin-6 (IL-6) in beta2m-induced bone resorption.
Main Methods:
- Utilized neonatal mouse calvariae, primary osteoblasts, and MC 3T3 osteoblast-like cells.
- Measured IL-6 production, release, and gene expression via ELISA and RT-PCR.
- Quantitated osteocalcin mRNA to assess osteoblast function.
Main Results:
- Beta2m induced dose- and time-dependent calcium release from calvariae.
- Beta2m significantly increased IL-6 release and mRNA expression in osteoblasts.
- Osteoblast proliferation was enhanced by beta2m, but osteocalcin mRNA levels remained unchanged.
Conclusions:
- Beta2m influences bone metabolism through increased IL-6 gene expression and release.
- Beta2m promotes osteoblast proliferation.
- Osteocalcin gene expression is not affected by beta2m, suggesting specific mechanisms of bone metabolism alteration.