Dexamethasone Promotes Expression of Membrane-Bound Macrophage Colony-Stimulating Factor in Murine Osteoblast-Like Cells¹

Abstract

The mechanisms by which glucocorticosteroids promote osteoclastogenesis in vitro are uncertain. As macrophage colony-stimulating factor (MCSF) is critical for osteoclastogenesis, we hypothesized that glucocorticosteroids might regulate membrane-bound MCSF (mMCSF) and soluble MCSF (sMCSF) production by stromal cells or osteoblasts. ST2 cells or murine calvarial osteoblasts (MOBs) were treated with dexamethasone (Dex; 100 nM) and/or 1,25-dihydroxyvitamin D [1,25(OH)2D; 10 nM] for 3 days. Control values for mMCSF and sMCSF as units per 100,000 cells were 9 +/- 1.4 and 511 +/- 56 in ST2 cells and 5.9 +/- 0.8 and 379 +/- 47 in MOB cells, respectively. Dex increased mMCSF to 156 +/- 16% and 143 +/- 26% compared with the control value in ST2 and MOB cells, respectively, whereas 1,25-(OH)2D caused increases of 195 +/- 16% and 164 +/- 21%. In the presence of both Dex and 1,25-(OH)2D, mMCSF increased to 209 +/- 24% and 216 +/- 26% in the two cell types, respectively. 1,25-(OH)2D caused modest increases in sMCSF, as expected, in both cell types (153 +/- 6% and 122 +/- 4%). Dex inhibited 1,25-(OH)2D-stimulated sMCSF (115 +/- 7% of control) in ST2 cells. Analysis of mMCSF transcript levels by semiquantitative RT-PCR revealed Dex-stimulated increases of 170 +/- 11% in ST2 cells and 126 +/- 16% in MOB cells compared with the control level. The increased expression of the transcript for sMCSF in the presence of Dex and 1,25-(OH)2D, measured by both RT-PCR and Northern analysis (219 +/- 53% and 242%, respectively), despite inhibition of sMCSF protein, indicated that the inhibitory effect of Dex in ST2 cells was posttranscriptional. Half-life studies showed that Dex prolonged MCSF messenger RNA from 2.8 to 7.5 h. These results suggest that Dex influences osteoclastogenesis by increasing the expression of mMCSF by accessory cells in culture.

Dexamethasone Enhances Osteoclast Formation Synergistically with Transforming Growth Factor-β by Stimulating the Priming of Osteoclast Progenitors for Differentiation into Osteoclasts

“…In our culture system, however, the stimulation occurred even in the absence of the osteoclast-supporting cells such as osteoblasts. In addition, Dex has been demonstrated in cultures of human and murine osteoblasts to increase the expression of RANKL and M-CSF, which are essential for osteoclastogenesis, and to decrease the production of osteoprotegerin, which is a decoy receptor of RANK that interferes with RANKL/RANK signalings (34,35,50,51). This indirect action of GC via osteoblastic cells is one of the mechanisms for GCinduced osteoclastogenesis.…”

“…On the other hand, many in vitro studies have indicated the direct action of GCs on osteoblasts (31)(32)(33). Recent studies (34,35) show that GC acts directly on osteoblasts to up-regulate the expression of RANKL and M-CSF and that the steroid oppositely down-regulates osteoprotegerin, a decoy receptor of RANKL that prevents the transmission of the RANKL signal into cells of the osteoclast lineage. This regulation is likely to be a mechanism for induction of bone resorption by GCs.…”

Comparative Serum Analyses Identify Cytokines and Hormones Commonly Dysregulated as Well as Implicated in Promoting Osteolysis in MMP-2-Deficient Mice and Children

“…Glucocorticoids including cortisol inhibit calcium absorption, an increase of urinary calcium excretion (Canalis and Delany, 2002), inhibit bone formation as well as increase bone resorption, which lead to osteoporosis after continued exposure to elevated cortisol (Hahn et al, 1979;Canalis, 1996;Dalle Carbonare et al, 2001). Cortisol increases the expression of the crucial osteoclastogenesis factor M-CSF (Rubin et al, 1998) while decreasing the production of the anti-resorptive RANK-L decoy receptor osteoprotegrin (downregulated in MONA patients; Figure 3C; Hofbauer et al, 1999), therefore promoting bone resorption and osteoclastogenesis while disrupting the coupled osteoblast-osteoclast interaction (Canalis and Delany, 2002). Cortisol can decrease osteoblasts replication and slow their differentiation into mature osteoblasts (Pereira et al, 2001;Canalis and Delany, 2002).…”

Biological Characterization of Uncleavable Plasma Membrane-Anchored Human Macrophage Colony-Stimulating Factor

“…The cellsurface form of CSF-1 is expressed in bone marrow stromal cells (45), osteoblasts (46,47) and cells of endometrial glands (48). Furthermore, the expression of membrane-anchored CSF-1 in osteoblast-like cells can be regulated by parathyroid hormone, tumor necrosis factor, and dexamethone treatment (49,50). CSF-1R is expressed in monocytes, macrophages, osteoclasts, and their precursors (13,14).…”