Vitamin A differentially regulates RANKL and OPG expression in human osteoblasts.
All-trans-retinoic acid (ATRA) induces bone resorption, but the molecular mechanisms are unknown. We have studied the effect of ATRA on osteoprotegerin (OPG) and receptor activator of NF-kappaB ligand (RANKL) expression in human MG-63 osteosarcoma cells and primary osteoblast-like cultures. ATRA dose-dependently down-regulated protein levels of OPG in MG-63 cells, with a maximum (-56%) observed at a dose of 10(-6)M. This effect was confirmed with quantitative real-time PCR, where OPG mRNA was decreased after 4h (-68%) in primary cultures and after 8h (-87%) in MG-63 cells. The reduction in OPG expression was inhibited by a retinoic acid receptor (RAR)-antagonist and was mimicked by a RARbeta,gamma-agonist, indicating that the ATRA effect is mediated by these receptors. In primary cultures we found a threefold induction of RANKL mRNA expression. Thus, the RANKL/OPG ratio was markedly increased, suggesting a potential mechanism of ATRA-induced bone resorption.
Department of Medical Sciences, Uppsala University Hospital, Uppsala, Sweden. annica.Jacobson@medsci.uu.se
A
A
Jacobson
S
S
Johansson
M
M
Branting
H
H
Melhus
D002352:Carrier Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D053244:Osteoprotegerin; D012516:Osteosarcoma / Q000378:metabolism*; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor; D014212:Tretinoin / Q000494:pharmacology*
D002352:Carrier Proteins; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D018124:Receptors, Tumor Necrosis Factor; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; D014212:Tretinoin