Protective Effects of Prunasin A against the Differentiation of Osteoclasts and Destruction of Cartilage via the Receptor Activator of Nuclear Factor-Kappa-Β Ligand/Mitogen-Activated Protein Kinase/Osteoprotegerin Pathway in a Rat Model of Arthritis.

The present study evaluated the protective effects of pseurotin A against inflammation and the destruction of cartilage in a rat model of rheumatoid arthritis (RA). RA was induced by intradermal injections of Freund's complete adjuvant (1 mg/mL), and the treatment with pseurotin A (50 and 100 mg/kg, p.o.) was administered over 1 week. The effects of pseurotin A were assessed by estimating hind paw volume (HPV) and determining the levels of inflammatory mediators in the serum and synovial fluid of collagen-induced arthritis (CIA)-induced RA rats. Western blot and histopathological assays were performed to assess changes in synovial tissues. Additionally, in vitro analyses of receptor activator of nuclear factor-kappa-Β ligand (RANKL)-stimulated RAW264.7 cells treated with pseurotin A at different concentrations (1, 10, and 100 µg/mL) were conducted to assess the effects of pseurotin A on apoptosis ratio, real-time polymerase chain reaction data, and tartrate-resistant acid phosphatase staining. Compared to the RA group, treatment with pseurotin A significantly decreased HPV and reduced the levels of inflammatory mediators in the synovial fluid and blood. Additionally, pseurotin A ameliorated the protein expressions of osteoprotegerin, nuclear factor of activated T-cells, nuclear factor-kappa beta (NF-κB), IκBα, extracellular signal regulated kinase, and P38 as well as histopathological changes in the synovial tissue of CIA-induced RA rats. The in vitro findings revealed that pseurotin A treatment did not alter the apoptosis ratio in RANKL-stimulated RAW264.7 cells but significantly reduced the mRNA expressions of calcitonin receptor, NF-κB, and matrix metallopeptidase-9. The present findings suggest that pseurotin A ameliorated the differentiation of osteoclasts and the destruction of cartilage in RA rats via regulation of the mitogen-activated protein kinase/RANKL/NF-kB pathway.

Altered Bone Remodeling in Psoriatic Disease: New Insights and Future Directions.

Psoriatic arthritis (PsA) is an inflammatory rheumatic disorder that occurs in patients with psoriasis and predominantly affects musculoskeletal structures, skin, and nails. The etiology of PsA is not well understood but evidence supports an interplay of genetic, immunologic, and environmental factors which promote pathological bone remodeling and joint damage in PsA. Localized and systemic bone loss due to increased activity of osteoclasts is well established in PsA based on animal models and translational studies. In contrast, the mechanisms responsible for pathological bone remodeling in PsA remain enigmatic although new candidate molecules and pathways have been identified. Recent reports have revealed novel findings related to bone erosion and pathologic bone formation in PsA. Many associated risk factors and contributing molecular mechanisms have also been identified. In this review, we discuss new developments in the field, point out unresolved questions regarding the pathogenetic origins of the wide array of bone phenotypes in PsA, and discuss new directions for investigation.

RANKL/RANK/OPG Axis Is Deregulated in the Cerebrospinal Fluid of Multiple Sclerosis Patients at Clinical Onset.

OBJECTIVES: Our study focused on the RANKL (receptor activator of nuclear factor-κB ligand)/RANK/OPG (osteoprotegerin) axis and selected proinflammatory/immunoregulatory upstream mediators in the peripheral blood (PBL) and cerebrospinal fluid (CSF) of multiple sclerosis (MS) patients. METHODS: PBL and CSF were collected from healthy controls (n = 35) and MS patients at the clinical onset of the disease (n = 33). In addition, PBL samples were obtained from relapse-remitting (RR)-MS patients (n = 30). Patients were assessed by means of the expanded disability status scale (EDSS) and routine laboratory parameters. Soluble (s)RANKL and OPG were measured in the CSF and plasma; gene expression was detected for RANKL, RANK, OPG, and selected cytokines/chemokines (interleukin [IL]-4, IL-10, IL-17, CCL2, and CXCL12) in PBL mononuclear cells. RESULTS: The OPG level in the CSF was lower in MS patients at clinical onset than in controls. Moreover, the sRANKL/OPG ratio was higher in the CSF of MS patients at clinical onset and in the plasma of RR-MS patients than in controls. Gene expression of RANKL/RANK/OPG in PBL mononuclear cells was higher only in RR-MS patients. IL-4, CCL2, and CXCL12 were positively correlated and IL-10 was negatively correlated with RANKL/RANK expression. OPG was negatively correlated with EDSS and alkaline phosphatase level. CONCLUSION: Our study revealed that changes of RANKL/RANK/OPG axis are associated with MS, particularly the decreased OPG level in the CSF at disease onset. Therefore, these factors may serve as disease biomarkers and molecular targets of novel therapeutic approaches.

Plaque Accumulation and Inflammation Adjacent to Restorations of Amorphous Calcium Phosphate-containing Composite in Early Childhood Caries.

PURPOSE: To evaluate the clinical, biochemical, and microbiological reactions to nanocomposite containing amorphous calcium phosphate (ACP) in comparison to a traditional composite restorative material in early childhood caries. MATERIALS AND METHODS: Eighteen teeth were restored with the test material (ACP-containing resin) and 18 teeth were restored with the control material (traditional composite, TC) in fourteen paediatric patients using a split-mouth design. One caries- and restoration-free intact tooth in each patient was selected as the healthy control. Gingival crevicular fluid (GCF) and supragingival plaque samples were collected at baseline before the treatment and also on days 1, 7, 14 and 30 after treatment. Unstimulated whole saliva samples were obtained from each patient at baseline, and 1 and 6 months after restoration. GCF and saliva samples were assayed for IL-17A, IL-17F IL-17A/F, IL-17E, OPG and RANKL levels by ELISA, and plaque composition was assessed using RT-PCR. RESULTS: Clinical evaluation indicated no statistically significant differences between the two restorative materials according to the FDI criteria surface lustre, material retention and marginal adaptation properties. Pro-inflammatory IL-17 levels decreased statistically significantly at 6 months compared to baseline and 1-month values (p < 0.05). The baseline pro-inflammatory IL-17 cytokine levels in GCF samples around the carious teeth were higher than those obtained around the healthy teeth (p < 0.05), but similar in GCF from the ACP-test and TC teeth. Microbiological findings were similar in the ACP and T groups. CONCLUSION: It may be suggested that both ACP-containing and traditional resin composites show similar antimicrobial and biochemical effects in early childhood caries.

Autoantibodies to Osteoprotegerin are Associated with Low Hip Bone Mineral Density and History of Fractures in Axial Spondyloarthritis: A Cross-Sectional Observational Study.

Osteoporosis is a recognised complication of axial spondyloarthritis (axSpA) and is thought to be due to functional impairment and the osteoclast-activating effects of proinflammatory cytokines. The development of autoantibodies to OPG (OPG-Ab) has been associated with severe osteoporosis and increased bone resorption in rheumatoid arthritis. In this study, we screened for the presence of OPG-Ab in axSpA and reviewed their clinical significance. We studied 134 patients, recruited from two centres in the United Kingdom. Their mean age was 47.5 years and 75% were male. Concentrations of OPG-Ab were related to bone mineral density (BMD) and fracture history using linear and logistic regression models adjusting for age, gender, disease duration and activity, body mass index and bisphosphonate use. We detected OPG-Ab in 11/134 patients (8.2%). Femoral neck and total hip BMD were significantly reduced in OPG-Ab positive patients (0.827 vs. 0.967 g/cm2, p = 0.008 and 0.868 vs. 1.028 g/cm2, p = 0.002, respectively). Regression analysis showed that the presence of OPG-Ab was independently associated with total hip osteopenia (ORadj 24.2; 95% CI 2.57, 228) and history of fractures (ORadj 10.5; 95% CI 2.07, 53.3). OPG-Ab concentration was associated with total hip BMD in g/cm2 (ß = -1.15; 95% CI -0.25, -0.04). There were no associations between OPG-Ab concentration and bone turnover markers, but free sRANKL concentrations were lower in OPG-Ab-positive patients (median 0.04 vs. 0.11 pmol/L, p = 0.050). We conclude that OPG-Ab are associated with hip BMD and fractures in axSpA suggesting that they may contribute to the pathogenesis of bone loss in some patients with this condition.

Osteoprotegerin-Mediated Homeostasis of Rank+ Thymic Epithelial Cells Does Not Limit Foxp3+ Regulatory T Cell Development.

In the thymus, medullary thymic epithelial cells (mTEC) regulate T cell tolerance via negative selection and Foxp3(+) regulatory T cell (Treg) development, and alterations in the mTEC compartment can lead to tolerance breakdown and autoimmunity. Both the receptor activator for NF-κB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) axis and expression of the transcriptional regulator Aire are involved in the regulation of thymus medullary microenvironments. However, their impact on the mechanisms controlling mTEC homeostasis is poorly understood, as are the processes that enable the thymus medulla to support the balanced production of mTEC-dependent Foxp3(+) Treg. In this study, we have investigated the control of mTEC homeostasis and examined how this process impacts the efficacy of Foxp3(+) Treg development. Using newly generated RANK Venus reporter mice, we identify distinct RANK(+) subsets that reside within both the mTEC(hi) and mTEC(lo) compartments and that represent direct targets of OPG-mediated control. Moreover, by mapping OPG expression to a subset of Aire(+) mTEC, our data show how cis- and trans-acting mechanisms are able to control the thymus medulla by operating on multiple mTEC targets. Finally, we show that whereas the increase in mTEC availability in OPG-deficient (Tnfrsf11b(-/-)) mice impacts the intrathymic Foxp3(+) Treg pool by enhancing peripheral Treg recirculation back to the thymus, it does not alter the number of de novo Rag2pGFP(+)Foxp3(+) Treg that are generated. Collectively, our study defines patterns of RANK expression within the thymus medulla, and it shows that mTEC homeostasis is not a rate-limiting step in intrathymic Foxp3(+) Treg production.

Parathyroid Diseases and T Cells.

PURPOSE OF REVIEW: This review summarizes studies into the permissive role of T cells in the bone catabolic effects of hyperparathyroidism and parathyroid hormone (PTH). RECENT FINDINGS: Work in animals combined with recent translational studies in humans now highlight the potent amplificatory action of T cells on PTH-induced bone resorption. Mechanistic animal studies reveal a complex pathway by which PTH exploits natural self-renewal functions of CD4+ T cells, to drive TNFα production that promotes formation of IL-17A secreting Th17 T cells. TNFα and IL-17 further amplify osteoblastic receptor activator of NF-κB ligand (RANKL) production and down-modulate osteoprotegerin (OPG), establishing conditions propitious for osteoclastic bone resorption. These findings are consistent with, and add to, the traditional view of PTH-induced bone loss involving only osteoblast-lineage cells. T cells potently amplify traditional pathways and provide permissive costimulatory signals to bone marrow stromal cells, facilitating the development of an increased RANKL/OPG ratio favourable to bone resorption and bone loss.

OPG/RANKL/RANK axis is a critical inflammatory signaling system in ischemic brain in mice.

Osteoprotegerin (OPG) is a soluble secreted protein and a decoy receptor, which inhibits a receptor activator of nuclear factor κB (NF-κB) ligand (RANKL)/the receptor activator of NF-κB (RANK) signaling. Recent clinical studies have shown that a high-serum-OPG level is associated with unfavorable outcome in ischemic stroke, but it is unclear whether OPG is a culprit or an innocent bystander. Here we demonstrate that enhanced RANKL/RANK signaling in OPG(-/-) mice or recombinant RANKL-treated mice contributed to the reduction of infarct volume and brain edema via reduced postischemic inflammation. On the contrary, infarct volume was increased by reduced RANKL/RANK signaling in OPG(-/-) mice and WT mice treated with anti-RANKL neutralizing antibody. OPG, RANKL, and RANK mRNA were increased in the acute stage and were expressed in activated microglia and macrophages. Although enhanced RANKL/RANK signaling had no effects in glutamate, CoCl2, or H2O2-stimulated neuronal culture, enhanced RANKL/RANK signaling showed neuroprotective effects with reduced expression in inflammatory cytokines in LPS-stimulated neuron-glia mixed culture, suggesting that RANKL/RANK signaling can attenuate inflammation through a Toll-like receptor signaling pathway in microglia. Our findings propose that increased OPG could be a causal factor of reducing RANKL/RANK signaling and increasing postischemic inflammation. Thus, the OPG/RANKL/RANK axis plays critical roles in controlling inflammation in ischemic brains.

Associations of Osteocalcin, Osteoprotegerin, and Calcitonin with Inflammation Biomarkers in Atherosclerotic Plaques of Coronary Arteries.

We studied associations of osteocalcin, osteoprotegerin, and calcitonin with markers of inflammation in atherosclerotic plaques in coronary arteries and assessed the influence of these biomolecules on calcification of atherosclerotic plaques. The initial stage of calcification of atherosclerotic plaques is characterized by activation of inflammatory processes, which is seen from increased levels of proinflammatory biomarkers (IL-6, IL 8, TNF-α, and IL-1ß). Progressive calcification of atherosclerotic plaques is accompanied by insignificant accumulation of calcitonin and osteoprotegerin. The exception is osteocalcin, its concentration significantly increased during calcification. The results suggest that severe vascular calcification can be regarded as non-specific marker of atherosclerosis. Instability of atherosclerotic plaques is associated with higher level of calcification.

Brucella abortus Invasion of Osteocytes Modulates Connexin 43 and Integrin Expression and Induces Osteoclastogenesis via Receptor Activator of NF-κB Ligand and Tumor Necrosis Factor Alpha Secretion.

Osteoarticular brucellosis is the most common localization of human active disease. Osteocytes are the most abundant cells of bone. They secrete factors that regulate the differentiation of both osteoblasts and osteoclasts during bone remodeling. The aim of this study is to determine if Brucella abortus infection modifies osteocyte function. Our results indicate that B. abortus infection induced matrix metalloproteinase 2 (MMP-2), receptor activator for NF-κB ligand (RANKL), proinflammatory cytokines, and keratinocyte chemoattractant (KC) secretion by osteocytes. In addition, supernatants from B. abortus-infected osteocytes induced bone marrow-derived monocytes (BMM) to undergo osteoclastogenesis. Using neutralizing antibodies against tumor necrosis factor alpha (TNF-α) or osteoprotegerin (OPG), RANKL's decoy receptor, we determined that TNF-α and RANKL are involved in osteoclastogenesis induced by supernatants from B. abortus-infected osteocytes. Connexin 43 (Cx43) and the integrins E11/gp38, integrin-α, integrin-ß, and CD44 are involved in cell-cell interactions necessary for osteocyte survival. B. abortus infection inhibited the expression of Cx43 but did not modify the expression of integrins. Yet the expression of both Cx43 and integrins was inhibited by supernatants from B. abortus-infected macrophages. B. abortus infection was not capable of inducing osteocyte apoptosis. However, supernatants from B. abortus-infected macrophages induced osteocyte apoptosis in a dose-dependent manner. Taken together, our results indicate that B. abortus infection could alter osteocyte function, contributing to bone damage.

Immunology of Osteoporosis: A Mini-Review.

Osteoporosis is a major cause of fractures and associated morbidity in the aged population. The pathogenesis of osteoporosis is multifactorial; whereas traditional pathophysiological concepts emphasize endocrine mechanisms, it has been recognized that also components of the immune system have a significant impact on bone. Since 2000, when the term 'osteoimmunology' was coined, novel insights into the role of inflammatory cytokines by influencing the fine-tuned balance between bone resorption and bone formation have helped to explain the occurrence of osteoporosis in conjunction with chronic inflammatory reactions. Moreover, the phenomenon of a low-grade, chronic, systemic inflammatory state associated with aging has been defined as 'inflamm-aging' by Claudio Franceschi and has been linked to age-related diseases such as osteoporosis. Given the tight anatomical and physiological coexistence of B cells and the bone-forming units in the bone marrow, a role of B cells in osteoimmunological interactions has long been suspected. Recent findings of B cells as active regulators of the RANK/RANKL/OPG axis, of altered RANKL/OPG production by B cells in HIV-associated bone loss or of a modulated expression of genes linked to B-cell biology in response to estrogen deficiency support this assumption. Furthermore, oxidative stress and the generation of advanced glycation end products have emerged as links between inflammation and bone destruction.

OPG-Fc inhibits ovariectomy-induced growth of disseminated breast cancer cells in bone.

Dormant disseminated tumour cells can be detected in the bone marrow of breast cancer patients several years after resection of the primary tumour. The majority of these patients will remain asymptomatic, however, ∼ 15% will go on to develop overt bone metastases and this condition is currently incurable. The reason why these dormant cells are stimulated to proliferate and form bone tumours in some patients and not others remains to be elucidated. We have recently shown that in an in vivo model, increasing bone turnover by ovariectomy stimulated proliferation of disseminated tumour cells, resulting in formation of bone metastasis. We now show for the first time that osteoclast mediated mechanisms induce growth of tumours from dormant MDA-MB-231 cells disseminated in the bone. We also show that disruption of RANK-RANKL interactions following administration of OPG-Fc inhibits growth of these dormant tumour cells in vivo. Our data support early intervention with anti-resorptive therapy in a low-oestrogen environment to prevent development of bone metastases.

Characterisation of osteoprotegerin autoantibodies in coeliac disease.

Autoantibodies neutralising the effect of the bone regulatory cytokine osteoprotegerin (OPG) have been described in a patient with severe osteoporosis and coeliac disease. This study aimed to determine the prevalence and epitope specificity of autoantibodies to OPG in patients with coeliac disease, and correlate their presence with bone mineral density. A direct enzyme-linked immunosorbent assay was developed and used to screen patients with coeliac disease for autoantibodies to OPG. Recombinant fragments of OPG were made to evaluate the epitope specificity and affinity of these antibodies. Phenotype information of the patients was obtained by case note review. Raised titres of antibodies to OPG were found in 7/71 (9.8 %) patients with coeliac disease, compared with 1/72 (1.4 %) non-coeliac osteoporosis clinic control patients (p < 0.05). Our results suggest that a polyclonal antibody response to OPG is raised in these patients capable of recognising different epitopes of OPG with varying affinity. The titre of OPG antibodies was associated with lower bone mineral density Z-score of the hip in coeliac patients on univariate (p < 0.05) and multivariate analysis including age, sex height and weight as covariates (p < 0.01). Polyclonal antibodies to OPG are more common in patients with coeliac disease and are independently associated with lower bone mineral density Z-scores of the hip. Further work is required to establish the clinical utility of testing for OPG antibodies.

Ginsenoside metabolite compound K attenuates inflammatory responses of adjuvant-induced arthritis rats.

OBJECTIVE: To investigate the effects of ginsenoside metabolite compound K (CK) on adjuvant-induced arthritis (AA) rats and the partial mechanisms focused on the function of immunocyte (B cell and macrophage) and effectors' cell (fibroblast-like synoviocyte, FLS). METHODS: Animals were divided randomly into nine groups including control, AA, CK (5, 10, 20, 40, 80, and 160 mg/kg, i.g.), and MTX (0.5 mg/kg, i.g.). The effects of CK on AA rats are evaluated by swelling of the paw, histopathology of joint, and inflammatory cytokine production in serum. To further investigate the effects of CK on the function of B cell, peritoneal macrophage, and FLS from AA rats, we examined the proliferation of B cell and FLS by [3H] thymidine incorporation, and the phagocytic function of peritoneal macrophage was measured by neutral red uptake. Cytokines and antibodies in serum and the supernatant from peritoneal macrophage and FLS were measured by ELISA kit. RESULTS: CK suppressed the severity of AA rats by attenuating the paw swelling and histopathology of joint. CK can inhibit the proliferation of B cell and autoantibody levels, and suppressed the phagocytic function of peritoneal macrophage and secreted pro-inflammatory cytokines TNF-α, IFN-γ, and IL-17 and up-regulated the level of protective cytokines IL-10. CK attenuated the proliferation of FLS, and balanced the ratio of RANKL to OPG in AA rats. CONCLUSION: Our results suggest that CK may attenuate the severity of AA rats, partially by influencing the function of immunocyte (B cell and macrophage) and effectors' cells (FLS) in AA.

Kinetics and interplay of mediators of inflammation-induced bone damage in the course of adjuvant arthritis.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation, bone erosion, and cartilage destruction in the joints. It is increasingly being realized that inflammation might play an important role in inducing bone damage in arthritis. However, there is limited validation of this concept in vivo in well-controlled experimental conditions. We addressed this issue using the adjuvant arthritis (AA) model of RA. In AA, the draining lymph nodes are the main sites of activation of pathogenic leukocytes, which then migrate into the joints leading to the induction of arthritis. We tested the temporal kinetics of mediators of bone damage [e.g., receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG) and osteopontin (OPN)] and inflammation (pro-inflammatory cytokines and chemokines) in the draining lymph node cells (LNC) at different phases of AA, and then examined their inter-relationships. Our study revealed that, together with cytokines/chemokines, some of the mediators of bone remodeling are also produced in LNC. Various cytokines/chemokines showed distinct kinetics of expression as well as patterns of correlation with mediators of bone remodeling at different phases of the disease. Pro-inflammatory cytokines such as TNF-alpha are known to play an important role in bone damage. Interestingly, there was a positive correlation between TNF-alpha and RANKL, between RANKL and each of the 3 chemokines tested (RANTES, MIP-1alpha, and GRO/KC), and between TNF-alpha and RANTES. Our results in the AA model lend support to the concept of osteo-immune crosstalk during the course of autoimmune arthritis.

[Osteoimmunologic regulation of aging].

In bones, aging manifests itself as a shift towards production of myeloid cells in bone marrow, a condition associated with increased chronic inflammation by macrophages and decreased bone mass due to excess bone resorption by osteoclasts. An increase in the ratio of RANKL, a cytokine promoting osteoclast differentiation, to osteoprotegerin (OPG) , which acts as a decoy RANKL receptor, cannot explain the observed increase in osteoclast production, as serum OPG levels increase with age in humans, apparently to levels insufficient to counteract bone loss and prevent fracture. Age-related increases in osteoclastogenesis, decreases in lymphopoiesis, and inflammation including arthritis are likely best explained by a vicious cycle of myeloid skewing and inflammation occurring in bone marrow. These activities are due to aging of both hematopoietic stem cells themselves and the bone marrow microenvironment (niche cells) , which supports hematopoiesis. Impaired osteoblastogenesis and niche cell function are most likely pathologies emerging from increased oxidative stress, peroxisome proliferator-activated receptorγ (PPARγ) activity, and adipogenesis in the aging bone marrow. Currently, administration of either OPG or an anti-RANKL antibody has proved beneficial to prevent block bone dysfunction and osteoporosis in the elderly. However, anti-aging interventions targeting mesenchymal stem cell differentiation in the bone marrow may also help counteract inflammation and osteoclastic bone loss and enhance osteoblastic bone formation.

Osteoporosis associated with neutralizing autoantibodies against osteoprotegerin.

Autoantibodies against osteoprotegerin, which block the inhibitory effect of osteoprotegerin on signaling by the receptor activator of nuclear factor (NF)-kappaB (RANK), were identified in a man with celiac disease who presented with severe osteoporosis and high bone turnover. The osteoporosis did not respond to the treatment of his celiac disease but was completely reversed by bisphosphonate therapy. Autoantibodies against osteoprotegerin were detected in three additional patients with celiac disease. Such autoantibodies may be associated with the development of high-turnover osteoporosis, but whether autoantibodies against osteoprotegerin commonly contribute to the pathogenesis of osteoporosis in patients with celiac disease remains to be determined.

Proteasome inhibition aggravates tumor necrosis factor-mediated bone resorption in a mouse model of inflammatory arthritis.

OBJECTIVE: The proteasome inhibitor bortezomib has potent anti-myeloma and bone-protective activity. Recently, bortezomib was shown to directly inhibit osteoclastogenesis. The aim of this study was to analyze the influence and therapeutic effect of bortezomib in a mouse model of inflammatory arthritis. METHODS: Heterozygous human tumor necrosis factor α (hTNFα)-transgenic mice and their wild-type (WT) littermates were intravenously injected with 0.75 mg/kg of bortezomib or phosphate buffered saline twice weekly. The mice were assessed for clinical signs of arthritis. After 6 weeks of treatment, mice were analyzed for synovial inflammation, cartilage damage, bone erosions, and systemic bone changes. Osteoclast precursors from WT and hTNF-transgenic mice were isolated from bone marrow, treated with bortezomib, and analyzed for osteoclast differentiation, bone resorption, and expression of osteoclast-specific genes as well as apoptosis and ubiquitination. RESULTS: Bortezomib-treated hTNF-transgenic mice showed moderately increased inflammatory activity and dramatically enhanced bone erosions associated with a significant increase in the number of synovial osteoclasts. Interestingly, bortezomib did not alter systemic bone turnover in either hTNF-transgenic mice or WT mice. In vitro, treatment with therapeutically relevant concentrations of bortezomib resulted in increased differentiation of monocytes into osteoclasts and more resorption pits. Molecularly, bortezomib increased the expression of TNF receptor-associated factor 6, c-Fos, and nuclear factor of activated T cells c1 in osteoclast precursors. CONCLUSION: In TNF-mediated bone destruction, bortezomib treatment increased synovial osteoclastogenesis and bone destruction. Hence, proteasome inhibition may have a direct bone-resorptive effect via stimulation of osteoclastogenesis during chronic arthritis.

Human single-chain variable fragment that specifically targets arthritic cartilage.

OBJECTIVE: To demonstrate that posttranslational modification of type II collagen (CII) by reactive oxygen species (ROS), which are known to be present in inflamed arthritic joints, can give rise to epitopes specific to damaged cartilage in rheumatoid arthritis (RA) and osteoarthritis (OA) and to establish a proof of concept that antibodies specific to ROS-modified CII can be used to target therapeutics specifically to inflamed arthritic joints. METHODS: We used a semisynthetic phage display human antibody library to raise single-chain variable fragments (scFv) specific to ROS-modified CII. The specificity of anti-ROS-modified CII scFv to damaged arthritic cartilage was assessed in vitro by immunostaining articular cartilage from RA and OA patients and from normal controls. The in vivo targeting potential was tested using mice with antigen-induced arthritis, in which localization of anti-ROS-modified CII scFv in the joints was determined. The therapeutic effect of anti-ROS-modified CII scFv fused to soluble murine tumor necrosis factor receptor II-Fc fusion protein (mTNFRII-Fc) was also investigated. RESULTS: The anti-ROS-modified CII scFv bound to damaged arthritic cartilage from patients with RA and OA but not to normal preserved cartilage. When systemically administered to arthritic mice, the anti-ROS-modified CII accumulated selectively at the inflamed joints. Importantly, when fused to mTNFRII-Fc, it significantly reduced inflammation in arthritic mice, as compared with the effects of mTNFRII-Fc alone or of mTNFRII-Fc fused to an irrelevant scFv. CONCLUSION: Our findings indicate that biologic therapeutics can be targeted specifically to arthritic joints and suggest a new approach for the development of novel treatments of arthritis.

How has research into cytokine interactions and their role in driving immune responses impacted our understanding of periodontitis?

OBJECTIVE: To review current knowledge on cytokine interactions and the cytokine-mediated links between innate and adaptive immunity that are relevant to the pathophysiology of periodontitis. MATERIALS AND METHODS: A structured review of the literature was undertaken to identify relevant research publications using a Medline search from 1950 to September 2010. The focus of the search was on the functional role of cytokines, i.e. their actions and responses relevant to the pathogenesis of periodontal disease rather than more descriptive studies of their expression in tissues and body fluids. It was not possible to conduct a traditional systematic review with a focussed question due to the heterogeneity of published research. RESULTS: There is enormous heterogeneity in the periodontal literature in terms of experimental approaches. We have the deepest understanding of the role of the pro-inflammatory cytokines [e.g. interleukin (IL)-1ß, tumour necrosis factor-α, IL-6] with accumulating data on T-cell regulatory cytokines (e.g. IL-12, IL-18), chemokines and cytokines which mediate bone cell development and function (e.g. receptor activator of NF-κB ligand, osteoprotegerin). It is clear that there are multiple, overlapping and complex functional links between cytokines with regulatory control exerted at a number of levels and involving numerous cell types (both immune cells and resident cells in the periodontium). CONCLUSION: Cytokines appear to interact functionally in networks in the periodontium and integrate aspects of innate and adaptive immunity. However, our understanding is far from complete, particularly how molecular and cellular pathways relate to disease pathogenesis. We should adopt consistent experimental approaches to gain better insight into the totality of cytokine networks and how they drive immune responses in the periodontium.