Project description:Purpose: Among the diverse cytokines involved in osteoclast differentiation, IL-3 has been shown to inhibit RANKL-induced osteoclastogenesis. However, the mechanism underlying IL-3-mediated inhibition of osteoclast differentiation is not fully understood. In the present study, we demonstrate that IL-3 activation of STAT5 inhibits RANKL-induced osteoclastogenesis through the induction of Id genes. Methods: To investigate the effect of STAT5 on osteoclast differentiation and IL-3-mediated inhibition of osteoclast differentiation, bone marrow derived macrophages isolated from STAT5 wild-type (Stat5fl/fl) or STAT5 cKO (STAT5;MX1-Cre) were differentiated to osteoclast in the presence of M-CSF and RANKL with or without IL-3; and bone marrow derived macrophges from STAT5 wild-type and STAT5 cKO were overexpressed with PMX-FIG (control) or STAT5A1*6 (constitutively active form of STAT5A) and differentiated to osteoclast. To analyze bone phenotype, femurs and tibiae of 16 week-old STAT5 wild-type and STAT5 cKO were subjected to micro CT analysis and histomorphometry, respectively. Results: Overexpression of STAT5 inhibited RANKL-induced osteoclastogenesis. However, RANKL did not regulate either expression or activation of STAT5 during osteoclast differentiation. STAT5 deficiency prevented IL-3-mediated inhibition of osteoclastogenesis, suggesting that STAT5 plays an important role in IL-3-mediated inhibition of osteoclast differentiation. In addition, IL-3-induced STAT5 activation upregulated expression of the Id1 and Id2 genes, which are negative regulators of osteoclastogenesis. Overexpression of ID1 or ID2 in STAT5-deficient cells reversed osteoclast development recovered from IL-3-mediated inhibition. Moreover, micro-computed tomography and histomorphometric analysis revealed that STAT5 conditional knockout mice showed reduced bone mass, with an increased number of osteoclasts. Furthermore, IL-3 inhibited RANKL-induced osteoclast differentiation less effectively in STAT5 conditional knockout mice than in wild-type mice in a RANKL injection model. Conclusion: Taken together, our results suggest that STAT5 is a key transcription factor for IL-3-mediated inhibition of RANKL-induced osteoclastogenesis through Id gene expression. Examination of 4 different combination of osteoclast differentiation condition of bone marrow derived macrophages.

Project description:Purpose: Among the diverse cytokines involved in osteoclast differentiation, IL-3 has been shown to inhibit RANKL-induced osteoclastogenesis. However, the mechanism underlying IL-3-mediated inhibition of osteoclast differentiation is not fully understood. In the present study, we demonstrate that IL-3 activation of STAT5 inhibits RANKL-induced osteoclastogenesis through the induction of Id genes. Methods: To investigate the effect of STAT5 on osteoclast differentiation and IL-3-mediated inhibition of osteoclast differentiation, bone marrow derived macrophages isolated from STAT5 wild-type (Stat5fl/fl) or STAT5 cKO (STAT5;MX1-Cre) were differentiated to osteoclast in the presence of M-CSF and RANKL with or without IL-3; and bone marrow derived macrophges from STAT5 wild-type and STAT5 cKO were overexpressed with PMX-FIG (control) or STAT5A1*6 (constitutively active form of STAT5A) and differentiated to osteoclast. To analyze bone phenotype, femurs and tibiae of 16 week-old STAT5 wild-type and STAT5 cKO were subjected to micro CT analysis and histomorphometry, respectively. Results: Overexpression of STAT5 inhibited RANKL-induced osteoclastogenesis. However, RANKL did not regulate either expression or activation of STAT5 during osteoclast differentiation. STAT5 deficiency prevented IL-3-mediated inhibition of osteoclastogenesis, suggesting that STAT5 plays an important role in IL-3-mediated inhibition of osteoclast differentiation. In addition, IL-3-induced STAT5 activation upregulated expression of the Id1 and Id2 genes, which are negative regulators of osteoclastogenesis. Overexpression of ID1 or ID2 in STAT5-deficient cells reversed osteoclast development recovered from IL-3-mediated inhibition. Moreover, micro-computed tomography and histomorphometric analysis revealed that STAT5 conditional knockout mice showed reduced bone mass, with an increased number of osteoclasts. Furthermore, IL-3 inhibited RANKL-induced osteoclast differentiation less effectively in STAT5 conditional knockout mice than in wild-type mice in a RANKL injection model. Conclusion: Taken together, our results suggest that STAT5 is a key transcription factor for IL-3-mediated inhibition of RANKL-induced osteoclastogenesis through Id gene expression.

Project description:The pathogenesis of rheumatoid arthritis (RA) is complicated and involves both innate and adaptive immunity [5]. The innate immunity such as macrophages or fibroblast-like synoviocytes (FLS) in the synovium can generate inflammatory mediators, including TNF-α, IL-1, IL-6, IL-17, IFN-γ, and chemo kines that lead to synovial inflammation, bone erosion, and cartilage damage [6-8]. The IL-17 signaling mediates the autoantibody production in collagen-induced arthritis (CIA) model [9]. However, the treatment response with an anti-IL17 monoclonal antibody in RA patients shows a high degree of heterogeneity [10]. The inhibitors of the Janus kinase (JAK) pathway are approved for RA patients [11]. These data suggest that the targeted multiple cytokines through the JAK pathway are useful for RA treatment. Disturbance of type I IFNs (IFNs-I) signaling and production drive autoimmune development [12]. The presymptomatic RA patients display an increase of IFNs-I before the onset of symptoms [13]. The RA patients also show the elevation of IFN- α in the synovial fluid and high expression of IFNs-I regulated gene in peripheral blood mononuclear cells (PBMC) [14]. However, the role of IFNs-I in arthritis and bone homeostasis has suggested the accelerating effect of arthritis and bone damage. The interferon-alpha receptor knockout mice develop arthritis severity higher than wild-type mice in the model of antigen-induced arthritis [15]. IFNs-I also affects the bone homeostasis by inhibiting osteoclastogenesis via receptor activator of nuclear factor-kappa B (RANK) pathway, and reduction of c-FOS expression [16-18]. Therefore, the goal of RA treatment with antagonizing the IFNs-I pathway has to be optimized between efficacy and potentially adverse effect. STING is a cytosolic DNA sensor that initiates the production of IFNs-I. STING functions have been reported as both pro-inflammatory signaling and negative regulator against inflammation [19-21]. The mutation in exon 5 of the STING gene results in gain function leading to initiate inflammation and cause the Sting associated vasculopathy with onset in infancy (SAVI) [22]. Loss of STING function rescues DNaseII-deficient mice from lethality and polyarthritis [23]. However, Sting-deficient lupus mice (MRL/Lpr mice) show higher and earlier mortality than Sting-sufficient MRL/Lpr mice [24]. The pathology also shows lymphoid hypertrophy with a higher amount of macrophages and granulocytes infiltration, autoantibodies, and cytokine [24]. The objective of this study was to identify the role of STING in the pathogenesis of rheumatoid arthritis using collagen-induced arthritis (CIA) model as a representative model of the human RA.

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Bub1 negatively regulates osteoclast activation through NF-κB suppression in inflammatory arthritis

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