Joint Bone Destruction Research Articles

KW2449 ameliorates collagen-induced arthritis by inhibiting RIPK1-dependent necroptosis.

Necroptosis has recently been found to be associated with the pathogenesis of many autoimmune diseases, including rheumatoid arthritis (RA). This study was undertaken to explore the role of RIPK1-dependent necroptosis in the pathogenesis of RA and the potential new treatment options. The plasma levels of receptor-interacting protein kinase 1 (RIPK1) and mixed lineage kinase domain-like pseudokinase (MLKL) in 23 controls and 42 RA patients were detected by ELISA. Collagen-induced arthritis (CIA) rats were treated with KW2449 by gavage for 28 days. Arthritis index score, H&E staining, and Micro-CT analysis were used to evaluate joint inflammation. The levels of RIPK1-dependent necroptosis related proteins and inflammatory cytokines were detected by qRT-PCR, ELISA and Western blot, and the cell death morphology was detected by flow cytometry analysis and high-content imaging analysis. The plasma levels of RIPK1 and MLKL in RA patients were higher than those in healthy people, and were positively correlated with the severity of RA. KW2449 could reduce joint swelling, joint bone destruction, tissue damage, and the plasma levels of inflammatory cytokines in CIA rats. Lipopolysaccharide combined with zVAD (LZ) could induce necroptosis in RAW 264.7 cells, which could be reduced by KW2449. RIPK1-dependent necroptosis related proteins and inflammatory factors increased after LZ induction and decreased after KW2449 treatment or knockdown of RIPK1. These findings suggest that the overexpression of RIPK1 is positively correlated with the severity of RA. KW2449, as a small molecule inhibitor targeting RIPK1, has the potential to be a therapeutic strategy for RA treatment by inhibiting RIPK1-dependent necroptosis.

TGF-β-activated kinase-1 inhibitor LL-Z1640-2 reduces joint inflammation and bone destruction in mouse models of rheumatoid arthritis by inhibiting NLRP3 inflammasome, TACE, TNF-α and RANKL expression.

ObjectivesAberrant NLRP3 inflammasome activation has been demonstrated in rheumatoid arthritis (RA), which may contribute to debilitating inflammation and bone destruction. Here, we explored the efficacy of the potent TGF‐β‐activated kinase‐1 (TAK1) inhibitor LL‐Z1640‐2 (LLZ) on joint inflammation and bone destruction in collagen‐induced arthritis (CIA).MethodsLL‐Z1640‐2 was administered every other day in CIA mice. Clinical and histological evaluation was performed. Priming and activation of NLRP3 inflammasome and osteoclastogenic activity were assessed.ResultsNLRP3 inflammasome formation was observed in synovial macrophages and osteoclasts (OCs) in CIA mice. TACE and RANKL were also overexpressed in synovial macrophages and fibroblasts, respectively, in the CIA joints. Treatment with LLZ mitigated all the above changes. As a result, LLZ markedly suppressed synovial hypertrophy and pannus formation to alleviate pain and inflammation in CIA mice. LLZ could block the priming and activation of NLRP3 inflammasome in RAW264.7 macrophage cell line, primary bone marrow macrophages and OCs upon treatment with LPS followed by ATP, thereby suppressing their IL‐1β production. LLZ also suppressed LPS‐induced production of TACE and TNF‐α in bone marrow macrophages and abolished IL‐1β‐induced production of MMP‐3, IL‐6 and RANKL in synovial fibroblasts. In addition, LLZ directly inhibits RANKL‐mediated OC formation and activation.ConclusionTAK1 inhibition with LLZ may become a novel treatment strategy to effectively alleviate inflammasome‐mediated inflammation and RANKL‐induced osteoclastic bone destruction in joints alongside its potent suppression of TNF‐α and IL‐6 production and proteinase‐mediated pathological processes in RA.

Interrupting oral infection of Porphyromonas gingivalis with anti-FimA antibody attenuates bacterial dissemination to the arthritic joint and improves experimental arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that typically results in strong inflammation and bone destruction in the joints. It is generally known that the pathogenesis of RA is linked to cardiovascular and periodontal diseases. Though rheumatoid arthritis and periodontitis share many pathologic features such as a perpetual inflammation and bone destruction, the precise mechanism underlying a link between these two diseases has not been fully elucidated. Collagen-induced arthritis (CIA) mice were orally infected with Porphyromonas gingivalis (Pg) or Pg preincubated with an anti-FimA antibody (FimA Ab) specific for fimbriae that are flexible appendages on the cell surface. Pg-infected CIA mice showed oral microbiota disruption and increased alveolar bone loss and had synovitis and joint bone destruction. However, preincubation with FimA Ab led to a significant reduction in the severity of both oral disease and arthritis. Moreover, FimA Ab attenuated bacterial attachment and aggregation on human gingival and rheumatoid arthritis synovial fibroblasts. In addition, we discovered bacteria may utilize dendritic cells, macrophages and neutrophils to migrate into the joints of CIA mice. These results suggest that disrupting Pg fimbriae function by FimA Ab ameliorates RA.

Recombinant Human Endostatin Suppresses Mouse Osteoclast Formation by Inhibiting the NF-κB and MAPKs Signaling Pathways.

Rheumatoid arthritis is an autoimmune disease characterized by synovial hyperplasia and progressive joint destruction. As reported previously, recombinant human endostatin (rhEndostatin) is associated with inhibition of joint bone destruction present in rat adjuvant-induced arthritis; however, the effect of rhEndostatin on bone destruction is not known. This study was designed to assess the inhibitory effect and mechanisms of rhEndostatin on formation and function of osteoclasts in vitro, and to gain insight into the mechanism underlying the inhibitory effect of bone destruction. Bone marrow-derived macrophages isolated from BALB/c mice were stimulated with receptor activator of NF-κB ligand (RANKL) and macrophage colony-stimulating factor to establish osteoclast formation. Osteoclast formation was determined by TRAP staining. Cell viability of BMMs affected by rhEndostatin was determined using a MTT assay. Bone resorption was examined with a bone resorption pits assay. The expression of osteoclast-specific markers was analyzed using quantitative real-time PCR. The related signaling pathways were examined using a Luciferase reporter assay and western blot analysis. Indeed, rhEndostatin showed a significant reduction in the number of osteoclast-like cells and early-stage bone resorption. Moreover, molecular analysis demonstrated that rhEndostatin attenuated RANKL-induced NF-κB signaling by inhibiting the phosphorylation of IκBα and NF-κB p65 nuclear translocation. Furthermore, rhEndostatin significantly inhibited the activation of RANKL-dependent mitogen-activated protein kinases, such as ERK1/2, JNK, and p38. Hence, we demonstrated for the first time that preventing the formation and function of osteoclasts is an important anti-bone destruction mechanism of rhEndostatin, which might be useful in the prevention and treatment of bone destruction in RA.

Vía de señalización Wnt en artritis reumatoide

Rheumatoid arthritis (RA) is a chronic systemic inflammatory joint disease characterized by the formation of a pannus and joint bone destruction. This leads to deformity, discapacity and a diminished quality of life and life expectancy. The Wnt signaling pathway plays an important role in a great number of physiological processes, and recently has been implicated in the regulation of key cells in bone homeostasis. Recent studies suggest that this pathway plays a role in the pathophysiology of RA by the overexpression of inhibitors like the Dickkopf1 protein (DKK1) that negatively affects the differentiation and activity of osteoblasts. High circulating levels of this protein have been associated with higher rates of radiological progression and greater disease activity in RA. Not much has been published about this subject in patients with RA, so the role of this pathway and DKK1 in RA it is not entirely clear. More studies in this area could improve our understanding about the differences in RA clinical presentation and prognosis, and even more they could provide new possible therapeutic targets for RA.

Arthritogenic T cells in autoimmune arthritis

Autoimmune diseases, including arthritis, often result from an imbalance between regulatory T (Treg) cells and IL-17-producing (Th17) cells. Dozens of studies in mice and humans have shed light on the pathological significance of T cells in RA. Since Th17 cells play an important role in the exacerbation of inflammation and bone destruction in joints, it has been an important issue how arthritic Th17 cells arise. Th17 cells are generated in the local inflammatory milieu via cytokines produced by macrophages or synovial fibroblasts, while it is reported that Th17 cells are generated in the gut in the presence of specific commensal bacteria. A recent report showed a pathogenic Th17 cell subset with a distinct pattern of gene expression and a potent osteoclastogenic ability are converted from Foxp3+ T cells in arthritic joints. Since Foxp3+ Treg cells contain T cells which recognize self-antigens, the fate of plastic Foxp3+ T cells can be a critical determinant of autoimmunity or self-tolerance. Further analysis on the molecular basis and antigen-specificity of arthritogenic Th17 cell subsets will be helpful to establish novel therapeutic approaches and clarify how self-tolerance breaks down in autoimmune arthritis.

THU0085 Effect of CSF-1R Kinase Inhibitor on FDG PET, MMP Optical, and Microct Imaging in a Rat SCW Model of Rheumatoid Arthritis: Use of Functional and Structural Imaging as Translation Tools

BackgroundTissue macrophage recruitment and osteoclastogenesis is dependent on the activation of colony stimulating factor-1 (CSF-1) receptor (R). To target macrophages and block osteoclastogenesis a JNJ compound was identified as a...

Norisoboldine Suppresses Osteoclast Differentiation through Preventing the Accumulation of TRAF6-TAK1 Complexes and Activation of MAPKs/NF-κB/c-Fos/NFATc1 Pathways

Norisoboldine (NOR) is the main alkaloid constituent in the dry root of Lindera aggregata (Sims) Kosterm. (L. strychnifolia Vill.). As reported previously, orally administered NOR displayed a robust inhibition of joint bone destruction present in both mouse collagen-induced arthritis and rat adjuvant-induced arthritis with lower efficacious doses than that required for ameliorating systemic inflammation. This attracted us to assess the effects of NOR on differentiation and function of osteoclasts, primary effector cells for inflammatory bone destruction, to get insight into its anti-rheumatoid arthritis mechanisms.Both RAW264.7 cells and mouse bone marrow-derived macrophages (BMMs) were stimulated with RANKL (100 ng/mL) to establish osteoclast differentiation models. ELISA, RT-PCR, gelatin zymography, western blotting, immunoprecipitation and EMSA were used to reveal related signalling pathways. NOR (10 and 30 µM), without significant cytotoxicity, showed significant reduction of the number of osteoclasts and the resorption pit areas, and it targeted osteoclast differentiation at the early stage. In conjunction with the anti-resorption effect of NOR, mRNA levels of cathepsin K and MMP-9 were decreased, and the activity of MMP-9 was attenuated. Furthermore, our mechanistic studies indicated that NOR obviously suppressed the ubiquitination of TRAF6, the accumulation of TRAF6-TAK1 complexes and the activation of ERK and p38 MAPK, and reduced the nuclear translocation of NF-κB-p65 and DNA-binding activity of NF-κB. However, NOR had little effect on expressions of TRAF6 or the phosphorylation and degradation of IκBα. Moreover, NOR markedly inhibited expressions of transcription factor NFATc1, but not c-Fos. Intriguingly, the subsequent nuclear translocations of c-Fos and NFATc1 were substantially down-regulated. Hence, we demonstrated for the first time that preventing the differentiation and function of osteoclasts at the early stage was an important anti-bone destruction mechanism of NOR, which might be attributed to inhibition of ubiquitination of TRAF6, the accumulation of TRAF6-TAK1 complexes and the activation of MAPKs/NF-κB/c-Fos/NFATc1 pathways.

Synovitis - an inflammation of joints destroying the bone.

This article is to share some of the key scientific insights made by Dr Barry Bresnihan in rheumatoid arthritis. Dr Bresnihan elaborated new and visionary concepts in arthritis research, which still influence current thinking. He had been particularly dedicated to investigate the inflammatory tissue (synovitis) in RA, which he considered as a clue to understand the pathogenesis of this disease. He thereby pioneered the concept of synovial biopsy as a technique, which allows to directly analyse synovitis and has stimulated many other rheumatologists in joining his efforts. He was also dedicated to understand why synovitis triggers bone destruction in joints and started to work on defining the molecular interactions between inflammation and the bone. This article picks up some of the major insights achieved by Dr Bresnihan's work and how these findings influenced today's understanding of arthritis.

Signal Transduction of Inflammatory Synoviocytes in Rheumatoid Arthritis

Recent advances in post-genomic technology enable us to analyze gene expression and protein modification comprehensively in tissues and cells, resulting in new developments in the analysis of molecular events of diseases. We have been studying the pathogenic and progressive mechanisms of diseases from the aspect of signalling pathways of cells. Inflammatory cytokines such as TNF-alpha and IL-1 produced from activated macrophages stimulate the overgrowth of synoviocytes and induce osteoclast differentiation in rheumatoid arthritis (RA). As a consequence, cartilage and bone destruction in joints is observed in RA patients. Recently, the pathogenic mechanisms are beginning to be discussed at the molecular level. For example, up-regulation of synoviolin, an ER-localizing E3 ubiquitin ligase, in synoviocytes is involved in RA because rheumatoid synoviocytes produce synoviolin and overexpression of human synoviolin in mice causes arthropathy. So far little is known about ligands inducing arthropathy and their receptors in the disease. We characterized rheumatoid synoviocytes by profiling gene expression with genome-wide DNA chips, and found that a cluster antigen is involved in the proteins up-regulated in rheumatoid synoviocytes. We have been analyzing the relationship between synoviolin expression and the activation of cluster antigen. The cluster antigen and its signal pathways could become a novel therapeutic target for RA. We discuss the possibility of direct induction of synoviolin expression via activation of signal pathways directed by the cluster antigen in RA synoviocytes.

Enhanced osteoclast development in collagen-induced arthritis in interferon-γ receptor knock-out mice as related to increased splenic CD11b+ myelopoiesis

Collagen-induced arthritis (CIA) in mice is accompanied by splenomegaly due to the selective expansion of immature CD11b+ myeloblasts. Both disease manifestations are more pronounced in interferon-γ receptor knock-out (IFN-γR KO) mice. We have taken advantage of this difference to test the hypothesis that the expanding CD11b+ splenic cell population constitutes a source from which osteoclast precursors are recruited to the joint synovia. We found larger numbers of osteoclasts and more severe bone destruction in joints of IFN-γR KO mice than in joints of wild-type mice. Osteoclast-like multinucleated cells appeared in splenocyte cultures established in the presence of macrophage colony-stimulating factor (M-CSF) and stimulated with the osteoclast-differentiating factor receptor activator of NF-κB ligand (RANKL) or with tumour necrosis factor-α (TNF-α). Significantly larger numbers of such cells could be generated from splenocytes of IFN-γR KO mice than from those of wild-type mice. This was not accompanied, as might have been expected, by increased concentrations of the intracellular adaptor protein TRAF6, known to be involved in signalling of RANKL- and TNF-α-induced osteoclast formation. Splenocyte cultures of IFN-γR KO mice also produced more TNF-α and more RANKL than those of wild-type mice. Finally, splenocytes isolated from immunised IFN-γR KO mice contained comparatively low levels of pro-interleukin-1β (pro-IL-1β) and pro-caspase-1, indicating more extensive conversion of pro-IL-1β into secreted active IL-1β. These observations provide evidence that all conditions are fulfilled for the expanding CD11b+ splenocytes to act as a source of osteoclasts and to be indirectly responsible for bone destruction in CIA. They also provide a plausible explanation for the higher susceptibility of IFN-γR KO mice to CIA.

Inflammatory mediators and radiographic changes in temporomandibular joints of patients with rheumatoid arthritis

The aim of this study was to investigate the relation between the inflammatory mediators tumor necrosis factor alpha (TNF ! ) and serotonin (5-HT), the inflammatory markers erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), as well as rheumatoid factor (RF) and thrombocyte particle concentration (TPC) in blood versus temporomandibular joint (TMJ) radiographic changes in patients with clinical TMJ involvement by rheumatoid arthritis (RA). Twenty patients were included. Venous blood was collected for quantification of the mediators, markers, and TPC. The radiographic signs of erosion, flattening, sclerosis, subchondral pseudocyst, and osteophyte as well as radiographic grade were investigated with computed tomography. The median (IQR) plasma levels of TNF ! and 5-HT were 0 (13) r pg/mL and 13 (22) r nmol/L, respectively, while serum level of 5-HT was 1360 (874) nmol/L. ESR, CRP, and TPC were abnormally high in 53%, 25%, and 15% of the patients, respectively. The most frequent radiographic signs were sclerosis (75%), erosion (50%), and flattening (30%). Erosion was found to be associated with high TPC and flattening with high plasma level of TNF ! . In conclusion, patients with clinical TMJ involvement by RA show an association between high level of TPC and TNF ! in plasma versus radiographic signs of joint bone destruction.

Revisión de tema

a b s t r a c t Rheumatoid arthritis (RA) is a chronic systemic inflammatory joint disease characterized by the formation of a pannus and joint bone destruction. This leads to deformity, discapacity and a diminished quality of life and life expectancy. The Wnt signaling pathway plays an important role in a great number of physiological processes, and recently has been implicated in the regulation of key cells in bone homeostasis. Recent studies suggest that this pathway plays a role in the pathophysiology of RA by the overexpression of inhibitors like the Dickkopf 1 protein (DKK1) that negatively affects the differentiation and activity of osteoblasts. High circulating levels of this protein have been associated with higher rates of radiological progression and greater disease activity in RA. Not much has been published