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The inhibitory effect of interleukin-10 on mouse osteoclast formation involves novel tyrosine-phosphorylated proteins
M H Hong1, H Williams, C H Jin
1Department of Endocrine Research, Ligand Pharmaceuticals, Inc., San Diego, California 92121, USA.
Abstract:
Interleukin-10 (IL-10) inhibits osteoclast (OC) formation in rat and mouse systems. However, little is known concerning the mechanism of this inhibitory effect. Using a coculture system of mouse bone marrow cells and primary osteoblastic cells (POB), we evaluated the potential target cells for IL-10 and components of the IL-10 activating pathway. In the coculture system, IL-10 treatment abolished OC differentiation in a dose-dependent manner. This inhibitory effect occurred regardless of the stage of cellular proliferation and differentiation, suggesting that IL-10 may act on a variety of genes participating in OC formation. IL-10 specifically abrogated the production of IL-6 by enriched bone marrow-derived mononuclear cells (BMM) but not by osteoblastic cells. IL-10 treatment also stimulated the binding of a protein in the BMM to an IL-10 response element, whereas no such activation was induced in osteoblastic cells. In contrast, interferon gamma (IFN-gamma), another inhibitory factor, stimulated tyrosine-phosphorylated proteins to bind to an IL-10 response element in both monocytes and osteoblastic cells. These data suggest that the BMM are the direct target of IL-10 action. Importantly, oligonucleotide-specific precipitation confirmed that IL-10 treatment strongly augmented 88, 85, and 70 kDa tyrosine-phosphorylated proteins in BMM. Taken together, these data show that IL-10 inhibits mouse OC formation by acting directly on hemopoietic OC precursor, through a novel signal transduction and activation pathway.
Insights
Interleukin-10 (IL-10) inhibits osteoclast (OC) formation by targeting bone marrow cells. This study reveals IL-10 acts on hemopoietic OC precursors via a novel signaling pathway, blocking IL-6 production and activating specific proteins.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Interleukin-10 (IL-10) is known to inhibit osteoclast (OC) formation in rodent models.
- The precise mechanism underlying IL-10's inhibitory effect on OC differentiation remains largely unelucidated.
- Understanding this mechanism is crucial for developing therapeutic strategies targeting bone resorption.
Purpose of the Study:
- To investigate the cellular targets of IL-10 action in OC formation.
- To identify the components of the IL-10 signaling pathway involved in OC inhibition.
- To elucidate the molecular mechanism by which IL-10 suppresses osteoclastogenesis.
Main Methods:
- Coculture system using mouse bone marrow cells and primary osteoblastic cells (POB).
- Dose-dependent assessment of IL-10's effect on OC differentiation.
- Analysis of IL-6 production by different cell types.
- Electrophoretic mobility shift assays (EMSA) to study protein-DNA interactions.
- Oligonucleotide-specific precipitation to identify tyrosine-phosphorylated proteins.
Main Results:
- IL-10 treatment dose-dependently abolished OC differentiation, irrespective of cellular proliferation or differentiation stage.
- IL-10 specifically abrogated Interleukin-6 (IL-6) production by bone marrow-derived mononuclear cells (BMM), but not by osteoblastic cells.
- IL-10 stimulated the binding of proteins in BMM to an IL-10 response element, indicating BMM as the direct target.
- Oligonucleotide precipitation confirmed IL-10 augmented specific tyrosine-phosphorylated proteins (88, 85, and 70 kDa) in BMM.
Conclusions:
- IL-10 directly inhibits mouse osteoclast formation by acting on hemopoietic OC precursors.
- The mechanism involves a novel signal transduction and activation pathway.
- IL-10's action is mediated through the suppression of IL-6 production and the activation of specific tyrosine-phosphorylated proteins in BMM.