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Interleukin-18 (interferon-gamma-inducing factor) is produced by osteoblasts and acts via granulocyte/macrophage colony-stimulating factor and not via interferon-gamma to inhibit osteoclast formation.

Udagawa N, Horwood NJ, Elliott J, Mackay A, Owens J, Okamura H, Kurimoto M, Chambers TJ, Martin TJ, Gillespie MT - J. Exp. Med. (1997)

Bottom Line: The stromal cell populations used for comparison differed in their ability to promote osteoclast-like multinucleated cell (OCL) formation. mRNA for IL-18 was found to be expressed in greater abundance in lines that were unable to support OCL formation than in supportive cells.Neutralizing antibodies to GM-CSF were able to rescue IL-18 inhibition of OCL formation, whereas neutralizing antibodies to IFN-gamma did not.The work provides evidence that IL-18 is expressed by osteoblasts and inhibits OCL formation via GM-CSF production and not via IFN-gamma production.

View Article: PubMed Central - PubMed

Affiliation: St. Vincent's Institute of Medical Research and The University of Melbourne, Department of Medicine, Victoria, Australia.

ABSTRACT
We have established by differential display polymerase chain reaction of mRNA that interleukin (IL)-18 is expressed by osteoblastic stromal cells. The stromal cell populations used for comparison differed in their ability to promote osteoclast-like multinucleated cell (OCL) formation. mRNA for IL-18 was found to be expressed in greater abundance in lines that were unable to support OCL formation than in supportive cells. Recombinant IL-18 was found to inhibit OCL formation in cocultures of osteoblasts and hemopoietic cells of spleen or bone marrow origin. IL-18 inhibited OCL formation in the presence of osteoclastogenic agents including 1alpha,25-dihydroxyvitamin D3, prostaglandin E2, parathyroid hormone, IL-1, and IL-11. The inhibitory effect of IL-18 was limited to the early phase of the cocultures, which coincides with proliferation of hemopoietic precursors. IL-18 has been reported to induce interferon-gamma (IFN-gamma) and granulocyte/macrophage colony-stimulating factor (GM-CSF) production in T cells, and both agents also inhibit OCL formation in vitro. Neutralizing antibodies to GM-CSF were able to rescue IL-18 inhibition of OCL formation, whereas neutralizing antibodies to IFN-gamma did not. In cocultures with osteoblasts and spleen cells from IFN-gamma receptor type II-deficient mice, IL-18 was found to inhibit OCL formation, indicating that IL-18 acted independently of IFN-gamma production: IFN-gamma had no effect in these cocultures. Additionally, in cocultures in which spleen cells were derived from receptor-deficient mice and osteoblasts were from wild-type mice and vice versa, we identified that the target cells for IFN-gamma inhibition of OCL formation were the hemopoietic cells. The work provides evidence that IL-18 is expressed by osteoblasts and inhibits OCL formation via GM-CSF production and not via IFN-gamma production.

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OCL formation in cocultures of mouse bone marrow and  osteoblastic cells in the presence of IL-18 (A) or IFN-γ (B). Mouse bone  marrow and primary osteoblastic cells were cocultured with 1α,25(OH)2  D3 (10−8 M) and PGE2 (10−7 M) in the presence of increasing concentrations of IL-18 (A) or IFN-γ (B). For negative and positive controls, cocultures were performed in the absence and presence of 1α,25(OH)2 D3  and PGE2, respectively. After culture for 7 d, TRAP-positive OCLs were  counted. Data are expressed as the means ± SEM of quadruplicate cultures, and are representative of three similar experiments.
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Figure 2: OCL formation in cocultures of mouse bone marrow and osteoblastic cells in the presence of IL-18 (A) or IFN-γ (B). Mouse bone marrow and primary osteoblastic cells were cocultured with 1α,25(OH)2 D3 (10−8 M) and PGE2 (10−7 M) in the presence of increasing concentrations of IL-18 (A) or IFN-γ (B). For negative and positive controls, cocultures were performed in the absence and presence of 1α,25(OH)2 D3 and PGE2, respectively. After culture for 7 d, TRAP-positive OCLs were counted. Data are expressed as the means ± SEM of quadruplicate cultures, and are representative of three similar experiments.

Mentions: IL-18 was originally identified because of its effect on IFN-γ production, and hence it was originally called interferon-γ–inducing factor (IGIF) (22). The name was subsequently changed to IL-18 (23). Because IFN-γ is a potent inhibitor of osteoclastogenesis (10, 13, 14, 31), and IL-18 mRNA levels were elevated in cells with an OCL-noninductive phenotype, we sought to identify whether IL-18 affects osteoclastogenesis via IFN-γ production. We examined TRAP-positive OCL formation in cocultures of mouse bone marrow and osteoblastic cells. OCLs were formed in cocultures where PGE2 and 1α,25(OH)2 D3 were added; without at least one of these agents, no OCLs were formed (Fig. 2 A). Autoradiographic study using labeled calcitonin revealed that TRAP-positive multinucleated and mononuclear cells formed in these cocultures possessed calcitonin receptors (data not shown). Recombinant mouse IL-18 dose-dependently inhibited OCL formation, giving maximal inhibition at 8 ng/ml (Fig. 2 A); this dose response to IL-18 is very similar to that in other biological systems (22). Recombinant mouse IFN-γ dosedependently inhibited OCL formation with maximal inhibition at 50 U/ml (Fig. 2 B), confirming previous observations in mouse bone marrow cultures (10). In subsequent experiments, IL-18 was used at 10 ng/ml and IFN-γ at 50 U/ml. OCL formation can be enhanced by a number of agents that act through different second messenger systems (e.g., vitamin D receptor, cAMP, and gp130) (1). To examine whether the inhibitory actions of IL-18 on OCL formation was stimulator specific or whether it acted as a general inhibitor, IL-18 was added to cocultures with the osteoclastogenic agents 1α,25(OH)2 D3, PGE2, PTH, or IL-11. IL-18 or IFN-γ inhibited OCL formation induced by each of these agents of osteoclastogenesis (Fig. 3).


Interleukin-18 (interferon-gamma-inducing factor) is produced by osteoblasts and acts via granulocyte/macrophage colony-stimulating factor and not via interferon-gamma to inhibit osteoclast formation.

Udagawa N, Horwood NJ, Elliott J, Mackay A, Owens J, Okamura H, Kurimoto M, Chambers TJ, Martin TJ, Gillespie MT - J. Exp. Med. (1997)

OCL formation in cocultures of mouse bone marrow and  osteoblastic cells in the presence of IL-18 (A) or IFN-γ (B). Mouse bone  marrow and primary osteoblastic cells were cocultured with 1α,25(OH)2  D3 (10−8 M) and PGE2 (10−7 M) in the presence of increasing concentrations of IL-18 (A) or IFN-γ (B). For negative and positive controls, cocultures were performed in the absence and presence of 1α,25(OH)2 D3  and PGE2, respectively. After culture for 7 d, TRAP-positive OCLs were  counted. Data are expressed as the means ± SEM of quadruplicate cultures, and are representative of three similar experiments.
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Related In: Results  -  Collection

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Figure 2: OCL formation in cocultures of mouse bone marrow and osteoblastic cells in the presence of IL-18 (A) or IFN-γ (B). Mouse bone marrow and primary osteoblastic cells were cocultured with 1α,25(OH)2 D3 (10−8 M) and PGE2 (10−7 M) in the presence of increasing concentrations of IL-18 (A) or IFN-γ (B). For negative and positive controls, cocultures were performed in the absence and presence of 1α,25(OH)2 D3 and PGE2, respectively. After culture for 7 d, TRAP-positive OCLs were counted. Data are expressed as the means ± SEM of quadruplicate cultures, and are representative of three similar experiments.
Mentions: IL-18 was originally identified because of its effect on IFN-γ production, and hence it was originally called interferon-γ–inducing factor (IGIF) (22). The name was subsequently changed to IL-18 (23). Because IFN-γ is a potent inhibitor of osteoclastogenesis (10, 13, 14, 31), and IL-18 mRNA levels were elevated in cells with an OCL-noninductive phenotype, we sought to identify whether IL-18 affects osteoclastogenesis via IFN-γ production. We examined TRAP-positive OCL formation in cocultures of mouse bone marrow and osteoblastic cells. OCLs were formed in cocultures where PGE2 and 1α,25(OH)2 D3 were added; without at least one of these agents, no OCLs were formed (Fig. 2 A). Autoradiographic study using labeled calcitonin revealed that TRAP-positive multinucleated and mononuclear cells formed in these cocultures possessed calcitonin receptors (data not shown). Recombinant mouse IL-18 dose-dependently inhibited OCL formation, giving maximal inhibition at 8 ng/ml (Fig. 2 A); this dose response to IL-18 is very similar to that in other biological systems (22). Recombinant mouse IFN-γ dosedependently inhibited OCL formation with maximal inhibition at 50 U/ml (Fig. 2 B), confirming previous observations in mouse bone marrow cultures (10). In subsequent experiments, IL-18 was used at 10 ng/ml and IFN-γ at 50 U/ml. OCL formation can be enhanced by a number of agents that act through different second messenger systems (e.g., vitamin D receptor, cAMP, and gp130) (1). To examine whether the inhibitory actions of IL-18 on OCL formation was stimulator specific or whether it acted as a general inhibitor, IL-18 was added to cocultures with the osteoclastogenic agents 1α,25(OH)2 D3, PGE2, PTH, or IL-11. IL-18 or IFN-γ inhibited OCL formation induced by each of these agents of osteoclastogenesis (Fig. 3).

Bottom Line: The stromal cell populations used for comparison differed in their ability to promote osteoclast-like multinucleated cell (OCL) formation. mRNA for IL-18 was found to be expressed in greater abundance in lines that were unable to support OCL formation than in supportive cells.Neutralizing antibodies to GM-CSF were able to rescue IL-18 inhibition of OCL formation, whereas neutralizing antibodies to IFN-gamma did not.The work provides evidence that IL-18 is expressed by osteoblasts and inhibits OCL formation via GM-CSF production and not via IFN-gamma production.

View Article: PubMed Central - PubMed

Affiliation: St. Vincent's Institute of Medical Research and The University of Melbourne, Department of Medicine, Victoria, Australia.

ABSTRACT
We have established by differential display polymerase chain reaction of mRNA that interleukin (IL)-18 is expressed by osteoblastic stromal cells. The stromal cell populations used for comparison differed in their ability to promote osteoclast-like multinucleated cell (OCL) formation. mRNA for IL-18 was found to be expressed in greater abundance in lines that were unable to support OCL formation than in supportive cells. Recombinant IL-18 was found to inhibit OCL formation in cocultures of osteoblasts and hemopoietic cells of spleen or bone marrow origin. IL-18 inhibited OCL formation in the presence of osteoclastogenic agents including 1alpha,25-dihydroxyvitamin D3, prostaglandin E2, parathyroid hormone, IL-1, and IL-11. The inhibitory effect of IL-18 was limited to the early phase of the cocultures, which coincides with proliferation of hemopoietic precursors. IL-18 has been reported to induce interferon-gamma (IFN-gamma) and granulocyte/macrophage colony-stimulating factor (GM-CSF) production in T cells, and both agents also inhibit OCL formation in vitro. Neutralizing antibodies to GM-CSF were able to rescue IL-18 inhibition of OCL formation, whereas neutralizing antibodies to IFN-gamma did not. In cocultures with osteoblasts and spleen cells from IFN-gamma receptor type II-deficient mice, IL-18 was found to inhibit OCL formation, indicating that IL-18 acted independently of IFN-gamma production: IFN-gamma had no effect in these cocultures. Additionally, in cocultures in which spleen cells were derived from receptor-deficient mice and osteoblasts were from wild-type mice and vice versa, we identified that the target cells for IFN-gamma inhibition of OCL formation were the hemopoietic cells. The work provides evidence that IL-18 is expressed by osteoblasts and inhibits OCL formation via GM-CSF production and not via IFN-gamma production.

Show MeSH
Related in: MedlinePlus