Limits...
Exposure to receptor-activator of NFkappaB ligand renders pre-osteoclasts resistant to IFN-gamma by inducing terminal differentiation.

Huang W, O'Keefe RJ, Schwarz EM - Arthritis Res. Ther. (2002)

Bottom Line: These cells were also resistant to IFN-gamma-induced nitric oxide production, morphological change, and surface upregulation of CD11b and receptor-activator of NFkappaB, suggesting that early exposure of osteoclast precursors to RANKL induces a broad resistance to the cellular effects of IFN-gamma.Changes in STAT1 activation did not correlate with this resistance, as IFN-gamma activated STAT1 equally in both early-stage and late-stage pre-osteoclasts.Furthermore, we failed to observe changes in TRAF6 expression following IFN-gamma treatment in pre-osteoclasts.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, NY, USA. edward_schwarz@urmc.rochester.edu

ABSTRACT
While it has been established that IFN-gamma is a strong activator of macrophages and a potent inhibitor of osteoclastogenesis in vitro, it is also known that this cytokine is produced in particular settings of inflammatory bone loss, such as infection and psoriatic arthritis. Because of the different kinetics between rapid IFN-gamma macrophage activation (<24 hours) and the slower receptor-activator of NFkappaB ligand (RANKL) osteoclast differentiation (7 days), we postulated that IFN-gamma would have different effects on early-stage and late-stage osteoclast precursors. In RAW264.7 cells and primary splenocyte cultures, pretreatment with RANKL rendered these cells resistant to maximally anti-osteoclastogenic doses of IFN-gamma. These cells were also resistant to IFN-gamma-induced nitric oxide production, morphological change, and surface upregulation of CD11b and receptor-activator of NFkappaB, suggesting that early exposure of osteoclast precursors to RANKL induces a broad resistance to the cellular effects of IFN-gamma. Changes in STAT1 activation did not correlate with this resistance, as IFN-gamma activated STAT1 equally in both early-stage and late-stage pre-osteoclasts. Furthermore, we failed to observe changes in TRAF6 expression following IFN-gamma treatment in pre-osteoclasts. Together these data support a model of inflammatory bone loss in which early exposure to RANKL can prime osteoclast precursors to form in the presence of high levels of IFN-gamma using mechanisms independent of the signal molecules STAT1 and TRAF6.

Show MeSH

Related in: MedlinePlus

Receptor-activator of NFκB ligand (RANKL) pretreatment impairs IFN-γ-induced nitric oxide (NO) production in a dose-dependent manner. (a) RAW cells were treated as in Figure 2a, and supernatants assayed for NO production on day 4. NO production was significantly inhibited by pretreatment with RANKL (*P < 0.01 versus the IFN-γ only group). (b) RAW cells were grown in the presence of various doses of RANKL, then supplemented with various doses of IFN-γ and maximal GST-RANKL (200 ng/ml) on day 2. NO was assayed on day4. Black bars indicate cells treated on day 2 with 100 ng/ml IFN-γ. (c) This group (indicated by black bars) with statistics. Inhibition of NO production by RANKL pretreatment is dose dependent, with more inhibition with higher doses of RANKL (*P < 0.05 versus 0 ng/ml RANKL).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC154432&req=5

Figure 6: Receptor-activator of NFκB ligand (RANKL) pretreatment impairs IFN-γ-induced nitric oxide (NO) production in a dose-dependent manner. (a) RAW cells were treated as in Figure 2a, and supernatants assayed for NO production on day 4. NO production was significantly inhibited by pretreatment with RANKL (*P < 0.01 versus the IFN-γ only group). (b) RAW cells were grown in the presence of various doses of RANKL, then supplemented with various doses of IFN-γ and maximal GST-RANKL (200 ng/ml) on day 2. NO was assayed on day4. Black bars indicate cells treated on day 2 with 100 ng/ml IFN-γ. (c) This group (indicated by black bars) with statistics. Inhibition of NO production by RANKL pretreatment is dose dependent, with more inhibition with higher doses of RANKL (*P < 0.05 versus 0 ng/ml RANKL).

Mentions: We next investigated whether other IFN-γ effects besides osteoclast inhibition were blunted in RANKL-pretreated cells. IFN-γ-induced NO production in macrophages was blunted in osteoclasts, probably due to specialization for bone resorption in the latter differentiated cell (Fig. 6). Pretreatment with RANKL inhibited IFN-γ-induced NO production in a dose-dependent and time-dependent manner (Fig. 6b,6c).


Exposure to receptor-activator of NFkappaB ligand renders pre-osteoclasts resistant to IFN-gamma by inducing terminal differentiation.

Huang W, O'Keefe RJ, Schwarz EM - Arthritis Res. Ther. (2002)

Receptor-activator of NFκB ligand (RANKL) pretreatment impairs IFN-γ-induced nitric oxide (NO) production in a dose-dependent manner. (a) RAW cells were treated as in Figure 2a, and supernatants assayed for NO production on day 4. NO production was significantly inhibited by pretreatment with RANKL (*P < 0.01 versus the IFN-γ only group). (b) RAW cells were grown in the presence of various doses of RANKL, then supplemented with various doses of IFN-γ and maximal GST-RANKL (200 ng/ml) on day 2. NO was assayed on day4. Black bars indicate cells treated on day 2 with 100 ng/ml IFN-γ. (c) This group (indicated by black bars) with statistics. Inhibition of NO production by RANKL pretreatment is dose dependent, with more inhibition with higher doses of RANKL (*P < 0.05 versus 0 ng/ml RANKL).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC154432&req=5

Figure 6: Receptor-activator of NFκB ligand (RANKL) pretreatment impairs IFN-γ-induced nitric oxide (NO) production in a dose-dependent manner. (a) RAW cells were treated as in Figure 2a, and supernatants assayed for NO production on day 4. NO production was significantly inhibited by pretreatment with RANKL (*P < 0.01 versus the IFN-γ only group). (b) RAW cells were grown in the presence of various doses of RANKL, then supplemented with various doses of IFN-γ and maximal GST-RANKL (200 ng/ml) on day 2. NO was assayed on day4. Black bars indicate cells treated on day 2 with 100 ng/ml IFN-γ. (c) This group (indicated by black bars) with statistics. Inhibition of NO production by RANKL pretreatment is dose dependent, with more inhibition with higher doses of RANKL (*P < 0.05 versus 0 ng/ml RANKL).
Mentions: We next investigated whether other IFN-γ effects besides osteoclast inhibition were blunted in RANKL-pretreated cells. IFN-γ-induced NO production in macrophages was blunted in osteoclasts, probably due to specialization for bone resorption in the latter differentiated cell (Fig. 6). Pretreatment with RANKL inhibited IFN-γ-induced NO production in a dose-dependent and time-dependent manner (Fig. 6b,6c).

Bottom Line: These cells were also resistant to IFN-gamma-induced nitric oxide production, morphological change, and surface upregulation of CD11b and receptor-activator of NFkappaB, suggesting that early exposure of osteoclast precursors to RANKL induces a broad resistance to the cellular effects of IFN-gamma.Changes in STAT1 activation did not correlate with this resistance, as IFN-gamma activated STAT1 equally in both early-stage and late-stage pre-osteoclasts.Furthermore, we failed to observe changes in TRAF6 expression following IFN-gamma treatment in pre-osteoclasts.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, NY, USA. edward_schwarz@urmc.rochester.edu

ABSTRACT
While it has been established that IFN-gamma is a strong activator of macrophages and a potent inhibitor of osteoclastogenesis in vitro, it is also known that this cytokine is produced in particular settings of inflammatory bone loss, such as infection and psoriatic arthritis. Because of the different kinetics between rapid IFN-gamma macrophage activation (<24 hours) and the slower receptor-activator of NFkappaB ligand (RANKL) osteoclast differentiation (7 days), we postulated that IFN-gamma would have different effects on early-stage and late-stage osteoclast precursors. In RAW264.7 cells and primary splenocyte cultures, pretreatment with RANKL rendered these cells resistant to maximally anti-osteoclastogenic doses of IFN-gamma. These cells were also resistant to IFN-gamma-induced nitric oxide production, morphological change, and surface upregulation of CD11b and receptor-activator of NFkappaB, suggesting that early exposure of osteoclast precursors to RANKL induces a broad resistance to the cellular effects of IFN-gamma. Changes in STAT1 activation did not correlate with this resistance, as IFN-gamma activated STAT1 equally in both early-stage and late-stage pre-osteoclasts. Furthermore, we failed to observe changes in TRAF6 expression following IFN-gamma treatment in pre-osteoclasts. Together these data support a model of inflammatory bone loss in which early exposure to RANKL can prime osteoclast precursors to form in the presence of high levels of IFN-gamma using mechanisms independent of the signal molecules STAT1 and TRAF6.

Show MeSH
Related in: MedlinePlus