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From The William Harvey Research Institute, London, United Kingdom
We tested here the hypothesis that calcitonin and glucocorticoids, known to modulate bone metabolism, could have opposite actions on bone cells regulating expression of cytokine receptor activator of nuclear factor-
B ligand (RANKL) and osteoprotegerin (OPG). In the U2OS osteosarcoma cell line, calcitonin (1011 to 109 mol/L) reduced RANKL and augmented OPG both at the mRNA and protein levels. Cell incubation with prednisolone (108 to 106 mol/L), the glucocorticoid chosen for this study, produced opposite results. These molecular studies prompted more functional analyses whereby osteoclast bone resorptive activity was determined. Calcitonin (1010 mol/L) abrogated the stimulating effect of 10 ng/ml RANKL or 109 mol/L prednisolone; similar results were obtained with OPG. Assessment of calcitonin and prednisolone effects in an in vivo model of rheumatoid arthritis revealed partially surprising results. In fact, calcitonin not only preserved bone morphology (as assessed on day 18) in rats subjected to arthritis and treated with prednisolone (0.8 to 4 mg/kg daily from day 13) but also synergized with the steroid to elicit its antiarthritic effects. These results suggest that calcitonin could be used as a novel cotreatment to augment efficacy and reduce side effects associated with the prolonged use of steroids.
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