OPN promotes pro-inflammatory cytokine expression via ERK/JNK pathway and M1 macrophage polarization in Rosacea

Rosacea is a chronic inflammatory dermatosis that involves dysregulation of innate and adaptive immune systems. Osteopontin (OPN) is a phosphorylated glycoprotein produced by a broad range of immune cells such as macrophages, keratinocytes, and T cells. However, the role of OPN in rosacea remains to be elucidated. In this study, it was found that OPN expression was significantly upregulated in rosacea patients and LL37-induced rosacea-like skin inflammation. Transcriptome sequencing results indicated that OPN regulated pro-inflammatory cytokines and promoted macrophage polarization towards M1 phenotype in rosacea-like skin inflammation. In vitro, it was demonstrated that intracellular OPN (iOPN) promoted LL37-induced IL1B production through ERK1/2 and JNK pathways in keratinocytes. Moreover, secreted OPN (sOPN) played an important role in keratinocyte-macrophage crosstalk. In conclusion, sOPN and iOPN were identified as key regulators of the innate immune system and played different roles in the pathogenesis of rosacea.

Osteopontin: A Bone-Derived Protein Involved in Rheumatoid Arthritis and Osteoarthritis Immunopathology

Osteopontin (OPN) is a bone-derived phosphoglycoprotein related to physiological and pathological mechanisms that nowadays has gained relevance due to its role in the immune system response to chronic degenerative diseases, including rheumatoid arthritis (RA) and osteoarthritis (OA). OPN is an extracellular matrix (ECM) glycoprotein that plays a critical role in bone remodeling. Therefore, it is an effector molecule that promotes joint and cartilage destruction observed in clinical studies, in vitro assays, and animal models of RA and OA. Since OPN undergoes multiple modifications, including posttranslational changes, proteolytic cleavage, and binding to a wide range of receptors, the mechanisms by which it produces its effects, in some cases, remain unclear. Although there is strong evidence that OPN contributes significantly to the immunopathology of RA and OA when considering it as a common denominator molecule, some experimental trial results argue for its protective role in rheumatic diseases. Elucidating in detail OPN involvement in bone and cartilage degeneration is of interest to the field of rheumatology. This review aims to provide evidence of the OPN’s multifaceted role in promoting joint and cartilage destruction and propose it as a common denominator of AR and OA immunopathology.

Vascular health in subjects with rheumatoid arthritis: assessment of endothelial function indices and serum biomarkers of vascular damage

BACKGROUND

The cardiovascular risk (CVD) in patients with rheumatoid arthritis (RA) is 1.5-2 times higher than that in individuals of the same age and sex.

AIMS

To analyse the degree of endothelial dysfunction, the atherogenic immunoinflammatory serum background and the relationships among some vascular indices, cardiovascular comorbidities, and cognitive performance in subjects with RA.

PATIENTS AND METHODS

All consecutive patients with a rheumatoid arthritis diagnosis admitted to the Rheumatology Ward of "Policlinico Paolo Giaccone" Hospital of Palermo were enrolled from July 2019 to September 2020. We evaluated our patients' cognitive functions by administering the Mini-Mental State Examination (MMSE). Reactive Hyperaemia Index (RHI) was evaluated for assessment of endothelial function. Serum levels of angiopoietin 2, osteopontin and pentraxin 3 were assessed by blood collection.

RESULTS

Fifty-eight consecutive patients with RA and 40 control subjects were analysed. RA patients showed significantly lower mean RHI values, significantly higher mean Augmentation Index (AIX) values and significantly lower mean Mini-Mental State Examination (MMSE) score values than the control group. Patients with rheumatoid arthritis also showed higher mean serum values of pentraxin 3 and angiopoietin 2 than healthy controls. Multivariate logistic regression analysis showed a significant association between pentraxin 3 and angiopoietin 2 and the presence of RA.

DISCUSSION

Angiopoietin 2 and pentraxin 3 could be considered surrogate biomarkers of endothelial activation and vascular disease, as they could play an essential role in the regulation of endothelial integrity and inflammation.

A Decreased Absolute Number of Treg Cells in Patients with Active Rheumatoid Arthritis is Associated with Elevated Serum Osteopontin Levels with Disease Progression

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic and refractory autoimmune disease characterized by synovial inflammation with unknown aetiology. Immune system dysfunction mediated by CD4⁺ T lymphocytes, which is regulated by the cytokine osteopontin (OPN), plays an important role in the pathogenesis of RA.

METHODS

In this study, the levels of peripheral CD4⁺ T subsets and serum OPN in patients with active RA were measured and analysed to determine the possible pathogenesis of RA and to provide potential therapeutic targets.

RESULTS

Serum OPN levels in both patients with active RA and patients with refractory RA were higher than those in healthy controls (HCs). Compared with HCs, the absolute numbers of Th2 cells increased in patients with active RA, while the absolute counts of Th1 and T_reg cells decreased. There was no significant difference in CD4⁺ T subset levels between new-onset and refractory patients. As the condition persisted or deteriorated, a gradual increase in the levels of OPN and gradual declines in the absolute counts of Th1 and T_reg cells were observed in patients with active RA. The fewest Th1 and T_reg cells and the highest OPN levels were observed in patients with high disease activity. The serum OPN level was only significantly negatively correlated with the absolute counts of T_reg cells in the CD4⁺ T lymphocyte subsets.

CONCLUSIONS

Fewer T_reg cells with the increase in disease activity may be related to the increased OPN concentration, which may provide new ideas and directions for the targeted immunoregulatory treatment of RA.

Osteopontin in autoimmune disorders: current knowledge and future perspective

Osteopontin (OPN) is a multifunctional cytokine and adhesion molecule, as well as an unusual regulator for both innate and adaptive immune responses. Several immune cells can produce OPN, including dendritic cells (DCs), macrophages, and T lymphocytes. OPN expression is reported to be increased in a wide range of disorders, including autoimmunity, cancer, and allergy. The overexpression of OPN in several autoimmune disorders, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), Type 1 diabetes (T1D), inflammatory bowel disease (IBD), Sjögren's, and myasthenia gravis, have been shown to be correlated with disease severity. Regarding the important regulatory roles of OPN in the immune system, this study aimed to review the role of this molecule in autoimmune disorders and to provide a complete view of the current knowledge in this field.

Curcumin: A Dietary Phytochemical for Targeting the Phenotype and Function of Dendritic Cells

Dendritic cells (DCs) are the most powerful antigen-presenting cells which link the innate and adaptive immune responses. Depending on the context, DCs initiate the immune responses or contribute to immune tolerance. Any disturbance in their phenotypes and functions may initiate inflammatory or autoimmune diseases. Hence, dysregulated DCs are the most attractive pharmacological target for the development of new therapies aiming at reducing their immunogenicity and at enhancing their tolerogenicity. Curcumin is the polyphenolic phytochemical component of the spice turmeric with a wide range of pharmacological activities. It acts in several ways as a modulator of DCs and converts them into tolerogenic DCs. Tolerogenic DCs possess anti-inflammatory and immunomodulatory activities that regulate the immune responses in health and disease. Curcumin by blocking maturation markers, cytokines and chemokines expression, and disrupting the antigen-presenting machinery of DCs render them non- or hypo-responsive to immunostimulants. It also reduces the expression of co-stimulatory and adhesion molecules on DCs and prevents them from both migration and antigen presentation but enhances their endocytosis capacity. Hence, curcumin causes DCs-inducing regulatory T cells and dampens CD4+ T helper 1 (Th1), Th2, and Th17 polarization. Inhibition of transcription factors such as NF-κB, AP-1, MAPKs (p38, JNK, ERK) and other intracellular signaling molecules such as JAK/STAT/SOCS provide a plausible explanation for most of these observations. In this review, we summarize the potential effects of curcumin on the phenotypes and functions of DCs as the key players in orchestration, stimulation, and modulation of the immune responses.

Osteopontin's relationship with malnutrition and oxidative stress in adolescents. A pilot study

Osteopontin (OPN) is a protein involved in inflammatory illnesses such as fibrosis and cancer; its overexpression in cardiovascular diseases promotes the biomineralization of blood vessels and other soft tissues. Moreover, there is an active component of oxidative stress related with those diseases. The present study relates serum OPN levels with nutritional condition and oxidative stress in a group of adolescents. Anthropometric measurements were performed, and fasting blood samples were analyzed to determine OPN concentrations, blood chemistry parameters (glucose, triglycerides, total cholesterol, urea, uric acid, and creatinine) and oxidative stress biomarkers (Paraoxonase-1, Glutathione S-Transferase, Catalase, NAD(P)H Quinone Oxidoreductase, free carbonyl groups and malondialdehyde). Adolescents were categorized according to body mass index (BMI) and metabolic syndrome (MetS) criteria. We found increased OPN serum concentrations in overweight and obese adolescents, as well as in adolescents with MetS. Rises in OPN correlated with arm circumference and biomarkers of lipid peroxidation; with regard to serum glucose there was a trend to positive correlation. Our results suggest that serum OPN is associated to nutritional status and could be considered as an early biomarker of low-grade inflammation and probably the early biomineralization of soft tissues in adolescence.

Osteopontin in the host response to Leishmania amazonensis

BACKGROUND

Leishmania (L.) spp are intracellular eukaryotic parasites responsible for cutaneous or visceral leishmaniasis, replicating predominantly in macrophages (MF). In C57BL/6 mice virulence with L. amazonensis has been associated with inhibition of Th1 immune responses and an uncontrolled lesion development, whereas DBA/2 mice control any lesion. Parasitic clearance by the MFs requires the activation of proper immune responses. One of the immune related genes expressed in immune cells including MF, codes for osteopontin (OPN). OPN is a secreted glycoprotein, acting as an immune regulator. Its implication in promoting Th1 immunity in response to infectious microorganisms and its known protective effect against viral and bacterial infections via activation of the immune response, render OPN a molecule of interest in the study of the host response to L. amazonensis.

RESULTS

We examined the host response to L. amazonensis of opn mutant and wild type C57BL/6 mice. Bone marrow derived MFs were infected with the parasites in vitro, and opn mutant and wild type mice were inoculated in vivo by intradermal injection in the ears. The DBA/2 strain known to control L. amazonensis infection was also used for comparison. Our data indicate that the parasites increased opn gene expression and OPN protein while parasitic proliferation was contained in the presence of OPN. In the presence of parasites the expression of inflammation-related transcripts was inhibited. Interleukin-1-beta (IL-1β), and transcripts of the NLR-family (NLRC4, NLRP3) were down regulated after L. amazonensis infection. In the absence of OPN, the inhibition by the parasites of IL-1β transcripts was less efficient and a pyroptosis-like cell phenotype was detected in vitro, suggesting a central role of OPN in the host-response to L. amazonensis. Similarly, in vivo, in the absence of OPN, while the clinical inflammatory phenotype is more severe, an increase of these transcripts was observed.

CONCLUSIONS

L. amazonensis infection induces opn gene expression and protein, which in turn participates in shaping the host response to the parasites, seemingly by decreasing the activation of inflammation. OPN, further evaluated as a target for Leishmaniasis control represents an additional interest in improving vaccination strategies against the parasites.

Raw cow's milk consumption and allergic diseases - The potential role of bioactive whey proteins

The prevalence of allergic diseases has increased significantly in Western countries in the last decades. This increase is often explained by the loss of rural living conditions and associated changes in diet and lifestyle. In line with this 'hygiene hypothesis', several epidemiological studies have shown that growing up on a farm lowers the risk of developing allergic diseases. The consumption of raw, unprocessed, cow's milk seems to be one of the factors contributing to this protective effect. Recent evidence indeed shows an inverse relation between raw cow's milk consumption and the development of asthma and allergies. However, the consumption of raw milk is not recommended due to the possible contamination with pathogens. Cow's milk used for commercial purposes is therefore processed, but this milk processing is shown to abolish the allergy-protective effects of raw milk. This emphasizes the importance of understanding the components and mechanisms underlying the allergy-protective capacity of raw cow's milk. Only then, ways to produce a safe and protective milk can be developed. Since mainly heat treatment is shown to abolish the allergy-protective effects of raw cow's milk, the heat-sensitive whey protein fraction of raw milk is an often-mentioned source of the protective components. In this review, several of these whey proteins, their potential contribution to the allergy-protective effects of raw cow's milk and the consequences of heat treatment will be discussed. A better understanding of these bioactive whey proteins might eventually contribute to the development of new nutritional approaches for allergy management.

Regulatory Roles of Osteopontin in Production of Monocyte-Origin MCP-1

Osteopontin (OPN), expressed by various immune cells, plays a critical role in leukocyte migration. Although OPN was found to selectively induce the expression of proinflammatory chemokines, the molecular mechanisms that control OPN gene expression and its underlying mechanism for migration and recruitment of inflammatory cells remain largely unknown. In this study, real-time polymerase chain reaction and enzyme-linked immunosorbent assay were used to determine OPN and monocyte chemoattractant protein 1 (MCP-1) expression. Signaling and molecular events between OPN and MCP-1 were analyzed by Western blot. Leukocyte migration in the presence of OPN was measured by chemotaxis assay. Our data indicated that phosphoinositide 3-kinase (PI3K), c-Jun NH2-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) that are activated upon stimulation with lipopolysaccharide were shown to upregulate OPN expression. Endogenous production of OPN was attributable to increased production of MCP-1, and this effect could be blocked by an anti-β1 integrin antibody and JNK and p38 kinase inhibitors. Furthermore, we found that the effect of OPN on inflammatory cell migration was mediated through inducing the expression of MCP-1 in monocytes. These results support a role of OPN in monocyte migration via MCP-1, which may represent an additional mechanism for innate and adaptive immune responses.

Integrin, alpha9 subunit blockade suppresses collagen-induced arthritis with minimal systemic immunomodulation

Integrin, alpha9 subunit (hereinafter, alpha9) has been identified as a novel putative therapeutic target for rheumatoid arthritis (RA). Support for this target comes from the observations that alpha9 is overexpressed both in the joints of RA patients and in animal models of arthritis. In the experimental models, the increase in alpha9 expression precedes the onset of arthritic symptoms. The current study presents data on the pharmacological profile of an anti-alpha9 antibody in a collagen-induced arthritis (CIA) mouse model. Administration of an alpha9-blocking antibody in CIA mice suppressed the development of arthritis and significantly decreased plasma level of activated fibroblast-like synoviocyte (FLS)-derived biomarkers without reducing the formation of anti-type II collagen antibodies. While anti-alpha9 antibody administration significantly suppress the accumulation of immune cells in arthritic joints it had no effect on immune cell number in the spleen. Furthermore, in non-arthritic mice, alpha9 had no inhibitory effect in either a mixed lymphocyte reaction (MLR) or in a delayed type hypersensitivity (DTH) reaction. These results suggest that blocking alpha9 exerts its anti-arthritic effect through suppression of FLS-activation via a non-immune mediated mechanism. Finally, therapeutic administration of anti-alpha9 antibody alleviated established arthritis in CIA mice. Our data provide evidence that alpha9 blockade is a promising therapy for joint inflammation with minimal systemic immunomodulation.

Osteopontin inhibits osteoblast responsiveness through the down-regulation of focal adhesion kinase mediated by the induction of low-molecular weight protein tyrosine phosphatase

Osteopontin (OPN), a major marker of osteogenic differentiation, suppresses osteoblast responses to mechanical stress and cytokines, including HGF and PDGF. These OPN-induced effects are mediated through focal adhesion kinase inactivation by the induction of low–molecular weight protein tyrosine phosphatase.

Osteopontin (OPN) is an osteogenic marker protein. Osteoblast functions are affected by inflammatory cytokines and pathological conditions. OPN is highly expressed in bone lesions such as those in rheumatoid arthritis. However, local regulatory effects of OPN on osteoblasts remain ambiguous. Here we examined how OPN influences osteoblast responses to mechanical stress and growth factors. Expression of NO synthase 1 (Nos1) and Nos2 was increased by low-intensity pulsed ultrasound (LIPUS) in MC3T3-E1 cells and primary osteoblasts. The increase of Nos1/2 expression was abrogated by both exogenous OPN overexpression and recombinant OPN treatment, whereas it was promoted by OPN-specific siRNA and OPN antibody. Moreover, LIPUS-induced phosphorylation of focal adhesion kinase (FAK), a crucial regulator of mechanoresponses, was down-regulated by OPN treatments. OPN also attenuated hepatocyte growth factor–induced vitamin D receptor (Vdr) expression and platelet-derived growth factor–induced cell mobility through the repression of FAK activity. Of note, the expression of low–molecular weight protein tyrosine phosphatase (LMW-PTP), a FAK phosphatase, was increased in both OPN-treated and differentiated osteoblasts. CD44 was a specific OPN receptor for LWW-PTP induction. Consistently, the suppressive influence of OPN on osteoblast responsiveness was abrogated by LMW-PTP knockdown. Taken together, these results reveal novel functions of OPN in osteoblast physiology.

Early detection of rheumatoid arthritis in rats and humans with 99mTc-3PRGD2 scintigraphy: imaging synovial neoangiogenesis

OBJECTIVES

To validate 99mTc-labeled arginylglycylaspartic acid (99mTc-3PRGD2) scintigraphy as a means to image synovial neoangiogenesis in joints afflicted by rheumatoid arthritis and to investigate its potential in the early detection and management of rheumatoid arthritis.

METHODS

Rheumatoid arthritis and osteoarthritis were generated in Sprague Dawley rats by type II collagen immunization and papain injection, respectively. Rats were imaged with 99mTc-3PRGD2 and 99mTc- methyl diphosphonate (99mTc MDP). X-ray images were also obtained and assessed by a radiologist. Immunohistochemistry of αvβ3 and CD31confirmed the onset of synovial neoangiogenesis. The effect of bevacizumab on rheumatoid arthritis was followed with 99mTc-3PRGD2 scintigraphy. A patient with rheumatoid arthritis and a healthy volunteer were scanned with 99mTc-3PRGD2.

RESULTS

Two weeks after immunization, a significant increase in 99mTc-3PRGD2 was observed in the joints of the rheumatoid arthritis model though uptake in osteoarthritis model and untreated controls was low. 99mTc-MDP whole body scans failed to distinguish early rheumatoid arthritis joints from healthy controls. The expression of αvβ3 and CD31was significantly higher in the joints of rheumatoid arthritis rats compared to normal controls. In serial 99mTc-3PRGD2 scintigraphy studies, 99mTc-3PRGD2 uptake increased in parallel with disease progression. Bevacizumab anti-angiogenetic therapy both improved the symptoms of the rheumatoid arthritis rats and significantly decreased 99mTc-3PRGD2 uptake. Significantly higher 99mTc-3PRGD2 accumulation was also observed in rheumatoid arthritis joints in the patient.

CONCLUSIONS

Our findings indicate that 99mTc-3PRGD2 scintigraphy could detect early rheumatoid arthritis by imaging the associated synovial neoangiogenesis, and may be useful in disease management.

Osteopontin inhibition of miR-129-3p enhances IL-17 expression and monocyte migration in rheumatoid arthritis

BACKGROUND

Osteopontin (OPN) is an important proinflammatory cytokine in rheumatoid arthritis (RA). Levels of OPN have been shown to be significantly correlated with interleukin-17 (IL-17) production and expression of Th17 cells in the synovial fluid of RA patients. Here, we investigated the role of OPN in monocyte migration, IL-17 production and osteoblasts.

METHODS

OPN and IL-17 expression profiles in osteoarthritis (OA) and RA synovial fluid were determined by enzyme-linked immunosorbent assay (ELISA). The expression of the microRNA, miR-129-3p, in osteoblasts was analyzed by real-time quantitative polymerase chain reaction (qPCR). Immunoreactive proteins were spotted by Western blotting. We used the collagen-induced arthritis (CIA) mouse model to investigate the role of OPN in monocyte migration during RA.

RESULTS

OPN and IL-17 expression were higher in RA synovial fluid as compared to OA samples. We also found that OPN promotes IL-17 expression in osteoblasts and thereby enhances monocyte migration via the Syk/PI3K/Akt signaling pathway. miR-129-3p expression was found to be negatively regulated by OPN via the Syk/PI3K/Akt signal cascade. In contrast, lentiviral vectors expressing short hairpin RNA inhibited OPN expression and ameliorated articular swelling, cartilage erosion and monocyte infiltration in the ankle joints of CIA mice.

CONCLUSION

To our knowledge, our study is the first to describe how OPN promotes monocyte migration by upregulating IL-17 expression in osteoblasts in RA disease.

SIGNIFICANCE

These findings indicate that OPN could serve as a potential therapeutic target for the treatment of RA.

Correlation between Serum Osteopontin and miR-181a Levels in Allergic Rhinitis Children

Background. Osteopontin (OPN) has been proved to be associated with allergic airway inflammation. However, the roles of OPN and its regulation in childhood allergic rhinitis (AR) are poorly understood. Objective. This study aims to evaluate the expression of OPN and miR-181a in children with AR and their association with Th1/Th2 immune response. Methods. Children who suffered from AR were included along with control subjects. Serum was collected to examine the level of OPN and Th1/Th2 cytokines by enzyme-linked immunosorbent assay (ELISA) and the level of miR-181a by quantitative polymerase chain reaction (qPCR). Results. Children with AR had significantly higher serum levels of OPN and lower serum levels of miR-181a than healthy controls. Furthermore, serum levels of OPN were positively correlated with Th2 cytokine and negatively correlated with Th1 cytokine. On the contrary, miR-181a level had a negative correlation with IL-4/IL-5 and positive correlation with IFN-γ/IL-12. More importantly, there was also significant negative correlation between OPN and miR-181a. Conclusion. The OPN protein and miR-181a levels may serve as predictors of disease severity in childhood AR and appear to be promising targets for modulating AR.

Decreased level of osteopontin in children with allergic rhinitis during sublingual immunotherapy

OBJECTIVE

Sublingual immunotherapy (SLIT) is proven to be very effective in the treatment of allergic rhinitis (AR), but its regulatory mechanism and biomarkers for predicting efficacy are still unknown. Osteopontin (OPN), as a recently described Th2 inflammation related protein, plays key role in the pathogenesis of AR. The aim of this study was to identify the expression and role of OPN during SLIT in children.

METHODS

Fifty house dust mite (HDM)-sensitized children with AR were enrolled in this study. AR children received HDM allergen extract or placebo for SLIT. Serum of different time points during treatment was collected and used for enzyme-linked immuno sorbent assay (ELISA) of OPN and related cytokines, respectively. Peripheral blood mononuclear cells from children after SLIT or placebo treatment were collected and stimulated with HDM with or without OPN/anti-OPN after one year's treatment.

RESULTS

Our results showed that expression of OPN protein was decreased after one year's therapy. The decreased OPN expression was positively related to decreased Th2 cytokines and negatively related to enhanced IL-10 and TGF-β expression. In vitro experiments confirmed that children received SLIT treatment showed decreased production of Th2 cytokines by PBMCs after HDM stimulation.

CONCLUSION

During SLIT, decreased OPN expression was related to low Th2 cytokine expression and enhanced IL-10 and TGF-β expression. High serum OPN expression predicts poor treatment efficacy. OPN may be used as a biomarker for SLIT treatment.

Osteopontin That Is Elevated in the Airways during COPD Impairs the Antibacterial Activity of Common Innate Antibiotics

Bacterial infections of the respiratory tract contribute to exacerbations and disease progression in chronic obstructive pulmonary disease (COPD). There is also an increased risk of invasive pneumococcal disease in COPD. The underlying mechanisms are not fully understood but include impaired mucociliary clearance and structural remodeling of the airways. In addition, antimicrobial proteins that are constitutively expressed or induced during inflammatory conditions are an important part of the airway innate host defense. In the present study, we show that osteopontin (OPN), a multifunctional glycoprotein that is highly upregulated in the airways of COPD patients co-localizes with several antimicrobial proteins expressed in the airways. In vitro, OPN bound lactoferrin, secretory leukocyte peptidase inhibitor (SLPI), midkine, human beta defensin-3 (hBD-3), and thymic stromal lymphopoietin (TSLP) but showed low or no affinity for lysozyme and LL-37. Binding of OPN impaired the antibacterial activity against the important bacterial pathogens Streptococcus pneumoniae and Pseudomonas aeruginosa. Interestingly, OPN reduced lysozyme-induced killing of S. pneumoniae, a finding that could be explained by binding of OPN to the bacterial surface, thereby shielding the bacteria. A fragment of OPN generated by elastase of P. aeruginosa retained some inhibitory effect. Some antimicrobial proteins have additional functions. However, the muramidase-activity of lysozyme and the protease inhibitory function of SLPI were not affected by OPN. Taken together, OPN can contribute to the impairment of innate host defense by interfering with the function of antimicrobial proteins, thus increasing the vulnerability to acquire infections during COPD.

An update on dietary phenolic compounds in the prevention and management of rheumatoid arthritis

Certain nutritional components influence the cellular metabolism and interfere in the pathological inflammatory process, so that they may act as a coadjuvant in the treatment of many chronic inflammatory diseases, including rheumatoid arthritis (RA).

Baseline Serum Osteopontin Levels Predict the Clinical Effectiveness of Tocilizumab but Not Infliximab in Biologic-Naïve Patients with Rheumatoid Arthritis: A Single-Center Prospective Study at 1 Year (the Keio First-Bio Cohort Study)

Objective

To explore the baseline predictors of clinical effectiveness after tocilizumab or infliximab treatment in biologic-naïve rheumatoid arthritis patients.

Methods

Consecutive biologic-naïve patients with rheumatoid arthritis initiating infliximab (n = 57) or tocilizumab (n = 70) treatment were included in our prospective cohort study. Our cohort started in February 2010, and the patients observed for at least 1 year as of April 2013 were analysed. We assessed baseline variables including patients' characteristics (age, sex, disease duration, prednisolone dose, methotrexate dose, other disease-modifying antirheumatic drug use, Clinical Disease Activity Index [CDAI]) and serum biomarker levels (C-reactive protein, immunoglobulin M-rheumatoid factor, anti-cyclic citrullinated protein/peptide antibodies, interferon-γ, interleukin (IL)-1β, IL-2, IL-6, IL-8, IL-10, IL-17, tumor necrosis factor-α, soluble intercellular adhesion molecule-1, bone alkaline phosphatase, osteonectin, osteopontin) to extract factors associated with clinical remission (CDAI≤2.8) at 1 year using univariate analyses, and the extracted factors were entered into a multivariate logistic regression model. Similar analyses were also performed for Simplified Disease Activity Index (SDAI) remission (≤3.3) and Disease Activity Score with 28 joint counts, erythrocyte sedimentation rate (DAS28-ESR) remission (<2.6).

Results

There were no significant differences in the baseline characteristics except for methotrexate use between the groups. In the multivariate analyses, the low baseline osteopontin levels (OR 0.9145, 95% CI 0.8399–0.9857) were identified as predictors of CDAI remission in the tocilizumab group, whereas no predictors of CDAI remission were found in the infliximab group. Similar results were obtained when using SDAI and DAS28-ESR remission criteria.

Conclusion

Baseline low serum osteopontin levels predict clinical remission 1 year after tocilizumab treatment and not infliximab treatment in biologic-naïve patients with rheumatoid arthritis. Our prediction model provided insights into how to optimize the choice of biologics and warrants external validation in other cohorts.

Intranasal Delivery of RGD Motif-Containing Osteopontin Icosamer Confers Neuroprotection in the Postischemic Brain via αvβ3 Integrin Binding

Osteopontin (OPN) is a phosphorylated glycoprotein possessing an arginine-glycine-aspartate (RGD)-motif, which binds to several cell surface integrins and mediates a wide range of cellular processes. Inductions of OPN have been reported in the postischemic brain, and the neuroprotective effects of OPN have been demonstrated in animal models of stroke. In the present study, we showed a robust neuroprotective effect of RGD-containing icosamer OPN peptide (OPNpt20) in a rat model of focal cerebral ischemia (middle cerebral artery occlusion, MCAO). Intranasally administered OPNpt20 reduced mean infarct volume by 79.7 % compared to the treatment-naïve MCAO control animals and markedly ameliorated neurological deficits. In addition, OPNpt20 significantly suppressed the inductions of iNOS and of inflammatory markers in postischemic brains and in primary microglial cultures, demonstrating anti-inflammatory effects. Administration of a mutant peptide, in which RGD was replaced by arginine-alanine-alanine (RAA), failed to suppress infarct volumes in MCAO animals and co-administration of OPNpt20 with anti-αvβ3 integrin antibody failed to suppress iNOS induction in primary microglia culture, indicating that the RGD motif in OPNpt20 and endogenous αvβ3 integrin play critical roles. Furthermore, pull-down assay revealed a direct binding between OPNpt20 and αvβ3 integrin in primary microglia culture. Together, these results indicate that RGD-containing OPN icosamer has therapeutic potential in the postischemic brain and αvβ3 integrin-mediated anti-inflammatory effect might be an underlying mechanism.

Increased chemokine (C-C motif) ligand 21 expression and its correlation with osteopontin in Graves' disease

Graves' disease (GD) is a chronic autoimmune process characterized by the production of auto-antibodies that presumably consequent to the lymphocytic infiltrates in the thyroid. Chemokine (C-C motif) ligand 21 (CCL21) is important for the circulation of CC-chemokine receptor 7 (CCR7)-expressing cells. Meanwhile, osteopontin (OPN) enhances the production of proinflammatory cytokines and chemokines through NF-κB and MAPK signaling pathways in GD. Although CCL21 has been reported to play a vital role in several autoimmune diseases, little is known about the relationship between CCL21 and GD development. This study aimed to detect the CCL21 level in GD and to examine the role of OPN in regulating CCL21 production. 40 initial GD patients, 15 euthyroid GD patients, 12 TRAb-negative GD patients, and 25 healthy control donors were recruited. CCL21 levels in plasma and culture supernatants were quantified by enzyme-linked immunosorbent assay (ELISA). CD4+ T cells were isolated from peripheral blood mononuclear cells using antibody-coated magnetic beads. Quantitative polymerase chain reaction was used to determine CCL21 expression levels in CD4+ T cells. We demonstrated for the first time that plasma CCL21 levels were overexpressed in GD patients and recovered in TRAb-negative GD patients. Moreover, CCL21 levels correlated with TRAb levels and plasma OPN concentrations. Furthermore, we demonstrated that recombinant OPN increased the expression of CCL21 in a dose- and time-dependent manner. These data indicated a clinical correlation between plasma CCL21 levels and GD. CCL21 could serve as a novel biomarker for GD as well as a potential target for TRAb-positive GD treatment.

Osteopontin Promotes Oncostatin M Production in Human Osteoblasts: Implication of Rheumatoid Arthritis Therapy

Accumulating evidence indicates that subchondral bone might play an essential role in rheumatoid arthritis (RA). Osteopontin (OPN) induces the production of an important proinflammatory cytokine involved in the pathogenesis of RA. This study evaluated the activation of oncostatin M (OSM) by OPN in human primary osteoblasts to understand RA pathogenesis and characterized the intracellular signaling pathways involved in this activation. Quantitative PCR, ELISA, and Western blot results indicated that stimulation of human primary osteoblasts with OPN induces OSM expression through αvβ3 integrin/c-Src/platelet-derived growth factor receptor transactivation/MEK/ERK. Treatment of osteoblasts with OPN also increased c-Jun phosphorylation, AP-1 luciferase activity, and c-Jun binding to the AP-1 element on the OSM promoter, as demonstrated using chromatin immunoprecipitation assay. Moreover, inhibition of OPN expression using lentiviral-OPN short hairpin RNA resulted in the amelioration of articular swelling, cartilage erosion, and OSM expression in the ankle joint of mice with collagen-induced arthritis as shown using microcomputed tomography and immunohistochemistry staining. Our results imply that OSM expression in osteoblasts increases in response to OPN-induced inflammation in vitro. Finally, lentiviral-OPN short hairpin RNA ameliorates the inflammatory response and bone destruction in mice with collagen-induced arthritis. Therefore, OPN may be a potential therapeutic target for RA.

GSK3β negatively regulates LPS-induced osteopontin expression via inhibiting its transcription

Osteopontin (OPN) is expressed by a variety of immune cells and is critical for both innate and adaptive immune responses. The expression status of OPN might be tightly regulated to maintain immune homeostasis. However, the mechanisms by which OPN is negatively regulated in LPS-stimulated macrophages remain largely unknown. In this study, we showed that glycogen synthase kinase 3β (GSK3β) inhibitors - SB216763, LiCl and azakenpaullone - enhanced LPS-induced OPN expression in mouse peritoneal macrophages. GSK3β knock-down had the similar effects. Furthermore, we found that GSK3β inhibitors and GSK3β knock-down both increased the activity of OPN promoter in LPS-stimulated macrophages. GSK3β inhibitor-mediated enhancement of LPS-induced OPN promoter activity was abrogated in GSK3β siRNA-treated macrophages. Therefore, we identified GSK3β as a negative regulator of OPN expression and suggest GSK3β as a potential therapeutic target for the intervention of diseases with uncontrolled OPN production.

Association of SPP1 promoter variants with hip osteoarthritis susceptibility in Chinese population

Three genetic variants in the promoter of SPP1 (secreted phosphoprotein 1) gene have been reported to affect transcriptional activity of SPP1, thus conferring an increased risk for some diseases. To testify if these variants are associated with risk of hip osteoarthritis (OA) as well, we performed a case-control study including 389 hip OA patients and 315 healthy controls. Genotypes of SPP1 were determined by DNA sequencing, and differential expressions of SPP1 in relation with genotypes were evaluated by RT-PCR and ELISA. The results showed that rs17524488 (delG>insG) increased the risk of hip OA, with the adjusted OR 1.48 (95% CI 1.18-1.85, P<0.01) for risk allele insG, 1.90 (95% CI 1.35-2.66, P<0.01) for delG/insG and 2.04 (95% CI 1.20-3.49, P<0.01) for insG/insG respectively. However, as for rs11730582 (T>C), the adjusted ORs were 1.18 (95% CI 0.94-1.49, P=0.148) for allele C, 1.26 (95% CI 0.90-1.75, P=0.158) for TC, and 1.31 (95% CI 0.77-2.24, P=0.293) for CC, indicating no association of rs11730582 with hip OA risk. The variant rs28357094 was not observed in the tested subjects. Furthermore, the delG/insG and insG/insG genotypes of rs17524488 both correlated with higher levels of SPP1 expression in articular cartilage (P<0.01 for all comparisons) as well as in in synovial fluid (P<0.01 for all comparisons) compared with delG/delG, while rs11730582 had no effect on the SPP1 expression (P>0.05 for all comparisons). These results collectively indicate that the genetic variant rs17524488 in SPP1 promoter confers high risk for hip OA in a Chinese population, possibly through enhancing SPP1 expression.

Effect of osteopontin on the mRNA expression of ADAMTS4 and ADAMTS5 in chondrocytes from patients with knee osteoarthritis

Previous studies have demonstrated that osteopontin (OPN) levels are elevated in the synovial fluid and articular cartilage, and are associated with the severity of knee osteoarthritis (OA). However, the role of OPN in the pathogenesis of OA has yet to be elucidated. The present study aimed to investigate the effects of OPN on the expression of the aggrecanases, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)4 and ADAMTS5, in human OA chondrocytes, as they serve a key function in aggrecan degradation. Human OA chondrocytes were obtained from the knees of 16 patients with OA, and subsequently cultured in a monolayer. The chondrocytes were divided into three groups, which included the control (no treatment), N-OPN (treated with 100 ng/ml OPN, the normal circulating OPN concentration) and the H-OPN groups (treated with 1 µg/ml OPN, a high OPN concentration). Reverse transcription-quantitative polymerase chain reaction was performed to quantify the relative mRNA expression levels of ADAMTS4, ADAMTS5 and aggrecan in the chondrocytes. The mRNA expression levels of ADAMTS4 were significantly reduced in the N-OPN and H-OPN groups when compared with the control group (P<0.0001). In addition, the mRNA expression levels of ADAMTS4 were lower in the H-OPN group when compared with the N-OPN group (P<0.001). However, no statistically significant difference was observed in the relative mRNA expression levels of ADAMTS5 among the three groups (P>0.05). Furthermore, the mRNA expression levels of aggrecan were higher in the N-OPN and H-OPN groups when compared with the control group (P<0.0001), and a statistically significant difference was observed between the N-OPN and H-OPN groups with regard to the mRNA expression of aggrecan (P<0.0001). These results demonstrated that OPN may exert a protective effect in human OA chondrocytes against aggrecan degradation by suppressing the expression of ADAMTS4.

The osteopontin transgenic mouse is a new model for Sjögren's syndrome

Osteopontin (Opn) is a cytokine involved in both physiological and pathological processes, and is elevated in many autoimmune diseases. Sjögren's syndrome (SS) is an autoimmune disease with a strong female predilection characterized by lymphocytic infiltration of exocrine glands. We hypothesized that Opn contributes to SS pathogenesis. We examined an established SS model and found increased Opn locally and systemically. Next, we examined Opn transgenic (Opn Tg) mice for evidence of SS. Opn Tg animals exhibited lymphocytic infiltration of salivary and lacrimal glands, and Opn co-localized with the infiltrates. Moreover, saliva production was reduced, and SS autoantibodies were observed in the serum of these mice. Finally, female Opn Tg mice showed more severe disease compared to males. Taken together, these data support a role for Opn in SS pathogenesis. We identify a new model of spontaneous SS that recapitulates the human disease in terms of sex predilection, histopathology, salivary deficits, and autoantibodies.

Role of osteopontin in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by joint swelling, joint tenderness, and destruction of synovial joints, leading to severe disability and premature mortality. RA is a multifactorial disease with genetic, environmental, and stochastic components related to its susceptibility. It has been demonstrated that the expression of osteopontin (OPN) is upregulated in the RA patients. Numerous studies have indicated that the full-length OPN or even OPN fragments, such as thrombin-cleaved OPN and its receptors, play the key roles in RA pathogenesis. Therapeutic application of siRNA to target OPN or neutralizing antibodies related to OPN epitopes in RA animal models are in progress, and some results are encouraging. However, there is a long way to go along with the clinical trials. This review focuses on the recent development in research associated with the OPN role in the pathogenesis of RA and provides insights concerning the OPN targeting as therapeutic approaches for patients with RA.

Cord blood levels of osteopontin as a phenotype marker of gestational age and neonatal morbidities

OBJECTIVES

Osteopontin (OPN) is a proinflammatory cytokine associated with metabolic syndrome. Extreme birth weight categories including small for gestational age (SGA), and large for gestational age (LGA) are risk factors for metabolic syndrome. However normal levels of plasma OPN in neonates and the relationship of OPN to fetal growth remain unknown. We evaluated the association of umbilical cord blood OPN with gestational age, birth weight, and neonatal outcomes.

METHODS

A cross-sectional study of 261 newborns of all gestational ages beginning at week 26, and 26 adults for comparison was performed. Umbilical cord blood from newborns and analyzed plasma for OPN by ELISA was collected.

RESULTS

Plasma OPN was significantly higher in neonates (414.65 ± 136.72 ng/mL) compared to adults (33.37 ± 14.66 ng/mL, P < 0.001). There was an inverse correlation between OPN and gestational age (r = -0.48, P < 0.0001). LGA infants had lower OPN than appropriate for gestational age (AGA) infants, but LGA was not an independent predictor of OPN in multivariate analysis. Among preterm infants, patent ductus arteriosus (PDA) was independently associated with higher OPN (OR = 2.49, P = 0.02).

CONCLUSION

Our results raise the possibility that OPN has a physiologic role in fetal growth and development, and may be a useful biomarker for PDA.

The role of osteopontin in the induction of the CD40 ligand in Graves' disease

OBJECTIVE

Graves' disease (GD) is a common autoimmune disease involved autoantibody production. Although we previously reported that osteopontin (OPN), a proinflammatory protein, affected development of GD through NF-κB activation, little is known about the role of OPN in regulating immunoglobulin production in GD. CD40 Ligand (CD40L) is expressed on the surface of activated CD4+T cells and costimulates CD40 on B cells, stimulating production of immunoglobulins, a process which has been reported to play a vital role in immunological signalling transduction in several autoimmune diseases. This study sought to characterize the relationship between CD40L and GD development, as well as investigating the role of OPN in modulating immunoglobulin production in GD via CD40L.

METHODS

Forty incident patients with GD, twenty-one patients with GD in remission and twenty-seven healthy controls were recruited. Both membrane-bound and soluble forms of CD40L were measured, and their correlations with clinical parameters were studied. In addition, correlation between OPN and CD40L level was also examined. Furthermore, we studied the regulatory effect of OPN on CD40L in CD4+T cells.

RESULTS

We demonstrated that the CD40L levels were enhanced in patients with GD and recovered in patients with GD in remission. CD40L levels correlated with clinical GD diagnostic parameters and OPN concentration. Moreover, human recombinant OPN and plasma samples from patients with GD increased CD40L expression, which could be significantly suppressed by OPN monoclonal antibody. In addition, CD40L antibody blocked the immunoglobulin production augmented by OPN in cultured peripheral blood mononuclear cells (PBMCs), isolated from patients with GD and healthy subjects.

CONCLUSION

These results indicate that CD40L is induced by OPN and serves as the downstream effector of OPN for immunoglobulin production in GD development.

Suppression of osteopontin functions by levocetirizine, a histamine H1 receptor antagonist, in vitro

OBJECTIVES

Osteopontin (OPN), a multifunctional glycoprotein secreted from a wide variety of cells after inflammatory stimulation, is well accepted to contribute to the development of allergic diseases. However, the influence of histamine H1 receptor antagonists (antihistamines) on OPN functions is not well understood. The present study was undertaken to examine the influence of antihistamines on OPN functions in vitro.

METHODS

Human nasal epithelial cells (5 × 10(5) cells) were stimulated with 250 ng/mL OPN in the presence of either desloratadine (DL), fexofenadine (FEX), or levocetirizine (LCT). The levels of OPN, GM-CSF, Eotaxin, and RANTES in 24 h culture supernatants were examined by ELISA. The influence of LCT on mRNA expression and transcription factor activation in cells were also examined by real-time RT-PCR and ELISA, respectively.

KEY FINDINGS

The antihistamines examined significantly suppressed the production of GM-CSF, Eotaxin, and RANTES from cells after OPN stimulation. LCT also exhibited the suppression of mRNA expression for chemokines and transcription factor, NF- κ B and AP-1, activation, which were increased by the stimulation of cells with OPN.

CONCLUSIONS

The suppressive activity of LCT on OPN functions on nasal epithelial cells may be responsible for the attenuating effect of the agent on allergic diseases.

The rs3768777-G allele of ITGAV gene is associated with rheumatoid arthritis

Integrin αvβ3 (vitronectin receptor) plays a prominent role in angiogenesis, a key pathogenic feature of rheumatoid arthritis (RA). Moreover, integrin αV (ITGAV) subunit gene has been associated with a susceptibility to RA. The aim of the present study was to detect the potential association between ITGAV gene polymorphisms and a susceptibility to RA in a Turkish cohort. DNA samples were harvested from 160 patients with RA and 144 healthy controls (HC). Three single-nucleotide polymorphisms of ITGAV gene (rs3738919, rs3768777, and rs10174098) were genotyped using real-time PCR. Serum vitronectin levels were analyzed in 30 RA patients, 28 Behçet's disease (BD) patients, and 30 HC subjects. There was no significant difference between the RA and HC groups in terms of the genotypic and allelic distributions of rs3738919 and rs10174098 polymorphisms. However, the prevalence of rs3768777-G allele was higher in the RA group than in the HC group (OR 2.3, 95 % CI 1.6-3.2, p < 0.0001). Moreover, there was a significant association between RA and the genotypic distribution of rs3768777 (GG + AG vs. AA: OR 2.1, 95 % CI 1.3-3.4; GG vs. AG + AA: OR 4.1, 95 % CI 2.1-7.8). Serum vitronectin levels were lower in the RA and BD groups than in the HC group (p ANOVA = 0.002). The rs3738919 and rs10174098 polymorphisms of the ITGAV gene seem not to be associated with susceptibility to RA in Turkish patients. However, rs3768777 increases the risk of RA in this group. These results suggest that the ITGAV gene may be a candidate gene for the etiopathogenesis of RA.

α9β1 integrin acts as a critical intrinsic regulator of human rheumatoid arthritis

OBJECTIVE

The role of the joint tissue microenvironment in the pathogenesis of human RA has recently attracted much attention. The present study investigated the roles of α9β1 integrin and its ligands in synovial specimens of human RA patients in generating the unique human arthritic tissue microenvironment.

METHODS

Synovial fibroblasts and macrophages were isolated from the synovial tissue of patients with RA or OA. The expression of α9β1 integrin was analysed using FACS with multicolour staining. The production of MMPs and proinflammatory cytokines was analysed in cultures of synovial fibroblasts and macrophages with α9β1 integrin ligands.

RESULTS

Synovial fibroblasts and macrophages derived from arthritic joints spontaneously secreted tenascin-C and osteopontin. Synovial fibroblasts and macrophages obtained from patients with RA expressed α9β1 integrins, a common receptor for osteopontin and tenascin-C. In the synovial fibroblasts of RA, the amount of tenascin-C protein produced was much greater than that of osteopontin in synovial fibroblasts of RA. Importantly, autocrine and paracrine interactions of α9β1 integrin and tenascin-C induced the expression of MMPs and IL-6 in synovial fibroblasts, as well as TNF-α and IL-1β in synovial macrophages.

CONCLUSION

These findings indicate that autocrine and paracrine interaction of α9β1 integrin and tenascin-C in the joint tissue microenvironment contributes to the pathogenesis of RA. Therefore α9β1 integrin may become a potential therapeutic target for RA.

APL-1, an altered peptide ligand derived from human heat-shock protein 60, selectively induces apoptosis in activated CD4+ CD25+ T cells from peripheral blood of rheumatoid arthritis patients

Rheumatoid arthritis (RA) is a chronic T-cell mediated autoimmune disease that affects primarily the joints. The induction of immune tolerance through antigen-specific therapies for the blockade of pathogenic CD4+ T cells constitutes a current focus of research. In this focus it is attempted to simultaneously activate multiple regulatory mechanisms, such as: apoptosis and regulatory T cells (Tregs). APL-1 is an altered peptide ligand derived from a novel CD4+ T-cell epitope of human heat-shock protein of 60kDa, an autoantigen involved in the pathogenesis of RA. Previously, we have reported that APL-1 induces CD4+ CD25(high)Foxp3+ Tregs in several systems. Here, we investigated the ability of APL-1 in inducing apoptosis in PBMCs from RA patients, who were classified as active or inactive according to their DAS28 score. APL-1 decreased the viability of PBMCs from active but not from inactive patients. DNA fragmentation assays and typical morphological features clearly demonstrated that APL-1 induced apoptosis in these cells. Activated CD4+ CD25+ T cells but not resting CD4+ CD25- T cells were identified as targets of APL-1. Furthermore, CD4+ T-cell responses to APL-1 were found to be dependent on antigen presentation via the HLA-DR molecule. Thus, APL-1 is a regulatory CD4+ T cell epitope which might modulate inflammatory immune responses in PBMCs from RA patients by inducing CD4+ CD25(high)Foxp3+ Tregs and apoptosis in activated CD4+ T cells. These results support further investigation of this candidate drug for the treatment of RA.

Chemokine (C-C motif) ligand 20, a potential biomarker for Graves' disease, is regulated by osteopontin

Context

Graves’ disease (GD) is a common autoimmune disease involving the thyroid gland. The altered balance of pro- and anti-inflammatory cytokines plays an important role in the pathogenesis of GD. Chemokine (C-C motif) ligand 20 (CCL20) is important for interleukin-17 (IL-17) signal activation and a potent chemoattractant for Th17 cells. Meanwhile, Osteopontin (OPN), a broadly expressed pleiotropic cytokine, has been implicated in GD through inducing Th1-involved response to enhance the production of proinflammatory cytokines and chemokines, but little is known about the role of OPN in regulating CCL20 and IL-17 signaling.

Objective

This study sought to explore the possibility of CCL20 level as a biomarker for GD, as well as investigate the role of OPN in regulating CCL20 production.

Methods

Fifty untreated GD patients, fifteen euthyroid GD patients, twelve TRAb-negative GD patients and thirty-five healthy control donors were recruited. OPN, CCL20 and other clinical GD diagnosis parameters were measured. CD4+T cells were isolated from peripheral blood mononuclear cells (PBMCs) using antibody-coated magnetic beads. Enzyme-linked immune-sorbent assay and quantitative polymerase chain reaction were used to determine CCL20 expression level.

Results

We found that the plasma CCL20 level was enhanced in GD patients and decreased in euthyroid and TRAb-negative GD patients. In addition, CCL20 level correlated with GD clinical diagnostic parameters and plasma OPN level. Moreover, we demonstrated that recombinant OPN and plasma from untreated GD patients increased the expression of CCL20 in CD4+T cells, which could be blocked by OPN antibody. Furthermore, we found that the effect of OPN on CCL20 expression was mediated by β3 integrin receptor, IL-17, NF-κB and MAPK pathways.

Conclusions

These results demonstrated that CCL20 might serve as a biomarker for GD and suggested the possible role of OPN in induction of CCL20 expression.

Chronic hypoxia reprograms human immature dendritic cells by inducing a proinflammatory phenotype and TREM-1 expression

DCs are powerful antigen-presenting cells central in the orchestration of innate and acquired immunity. DC development, migration, and activities are intrinsically linked to the microenvironment. DCs migrate through pathologic tissues before reaching their final destination in the lymph nodes. Hypoxia, a condition of low partial oxygen pressure, is a common feature of many pathologic situations, capable of modifying DC phenotype and functional behavior. We studied human monocyte-derived immature DCs generated under chronic hypoxic conditions (H-iDCs). We demonstrate by gene expression profiling the upregulation of a cluster of genes coding for antigen-presentation, immunoregulatory, and pattern recognition receptors, suggesting a stimulatory role for hypoxia on iDC immunoregulatory functions. In particular, we show that H-iDCs express triggering receptor expressed on myeloid cells(TREM-1), a member of the Ig superfamily of immunoreceptors and an amplifier of inflammation. This effect is reversible because H-iDC reoxygenation results in TREM-1 down-modulation. TREM-1 engagement promotes upregulation of T-cell costimulatory molecules and homing chemokine receptors, typical of mature DCs, and increases the production of proinflammatory, Th1/Th17-priming cytokines/chemokines, resulting in increased T-cell responses. These results suggest that TREM-1 induction by the hypoxic microenvironment represents a mechanism of regulation of Th1-cell trafficking and activation by iDCs differentiated at pathologic sites.

A study of the link between bone turnover markers and bone mineral density with inflammation and body mass in postmenopausal women with active rheumatoid arthritis

In this study, the levels of bone turnover markers (BTMs) and bone mineral density (BMD) were studied in relation to body mass and several inflammatory markers, in postmenopausal patients with rheumatoid arthritis (RA). Fifty-nine postmenopausal women with active RA (lean, overweight, obese) were studied. The femoral BMD and serum levels of BTMs: osteocalcin (OC) and collagen type I cross-linked C-telopeptide fragments (CTX), and osteopontin (OPN), resistin, high sensitivity C-reactive protein, interleukin-6, tumor necrosis factor (TNF)-α in these patients were measured. It has been noticed that obese women had significantly higher total femoral BMD and total T-score compared to the lean subjects (p ≤ 0.01). The significant associations of BMD measures and CTX levels with body mass parameters (p ≤ 0.01 and p < 0.05, respectively) were found. Values of neck BMD adjusted for BMI were inversely associated with concentrations of TNF-α (p < 0.05). Osteocalcin levels inversely correlated with resistin (p ≤ 0.01) and CTX levels positively correlated with OPN (p ≤ 0.01). There were found no associations between BTMs and BMD with other inflammatory indices. Inverse correlations between OPN levels and body mass (p < 0.05), waist circumference (p < 0.05), and duration of postmenopausal period (p ≤ 0.01) were observed. Findings of the present study suggest that body mass and inflammatory markers, most of all OPN, resistin and TNF-α, play an important role in bone metabolism in postmenopausal women with active RA.

Usefulness of specific OA biomarkers, thrombin-cleaved osteopontin, in the posterior cruciate ligament OA rabbit model

OBJECTIVE

We undertook this study to determine whether thrombin-cleaved osteopontin (OPN) in synovial fluid (SF) represents a useful marker of osteoarthritis (OA) progression in the posterior cruciate ligament transection (PCLT) OA rabbit model.

METHOD

PCLT was performed on the right knee joints of 48 rabbits. The rabbits were then sacrificed separately at 4, 8, 16, and 24 weeks post-surgery, when the joint was harvested and macroscopic and histological assessments of articular cartilage were performed. Thrombin-cleaved OPN product in SF was determined using Western blotting and the levels were measured using an enzyme-linked immunoassay.

RESULTS

The macroscopic and histological scores for PCLT knees were already elevated 4 weeks after surgery and increased with time. Western blotting showed the presence of thrombin-cleaved OPN in SF from PCLT knees. Thrombin-cleaved OPN levels in SF were elevated at 4 weeks (P < 0.001) and were elevated peaking at 24 weeks (P < 0.00001) after PCLT compared to baseline. A positive significant correlation was found between thrombin-cleaved OPN levels and the macroscopic scores (8 weeks: ρ = 0.695, P = 0.012; 16 weeks: ρ = 0.751, P = 0.005; 24 weeks: ρ = 0.660, P = 0.020). Furthermore, the same correlation was noted between thrombin-cleaved OPN levels and the histological scores (4 weeks: ρ = 0.609, P = 0.036; 8 weeks: ρ = 0.662, P = 0.019; 16 weeks: ρ = 0.827, P = 0.001; 24 weeks: ρ = 0.813, P = 0.001).

CONCLUSION

In this rabbit model of PCLT, thrombin-cleaved OPN levels in SF appear to provide a useful marker of OA disease severity and progression.

Loss of MMP-2 in murine osteoblasts upregulates osteopontin and bone sialoprotein expression in a circuit regulating bone homeostasis

Multicentric osteolysis with arthropathy (MOA; MIM 605156) is an inherited osteolyses and arthritis syndrome resulting from loss of matrix metalloproteinase 2 (MMP-2). We recently demonstrated that Mmp2^–/– mice represent a unique model for the study of the human disease, sharing many features of the human syndrome including skeletal dysplasia and defects in osteoblast behavior. We therefore sought to explore the secondary molecular effects of MMP-2 loss, which coexist with the underlying skeletal and osteoblast phenotypes. We used quantitative real-time RT-PCR (qRT-PCR) to measure osteoblast-related gene expression through ex vivo osteoblast differentiation of bone marrow stromal cells (BMSC) from Mmp2^−/− and Mmp2^+/+ mice. We used western blot to measure osteopontin (OPN) serum levels and immunohistochemical staining to examine bone expression. MMP-2 expression was inhibited in SaOS2 cells using siRNA, and decreased MMP-2 expression at both RNA and protein levels was confirmed by qRT-PCR and western blot, respectively. Mmp2^−/− BMSC induced to differentiate into osteoblasts were shown to significantly upregulate OPN and bone sialoprotein (BSP) expression levels compared with controls. Transcriptional upregulation was maintained in vivo, as demonstrated by increased levels of OPN in serum and bone in Mmp2^−/− mice. These effects are generalizable because siRNA-mediated inhibition in cultured cells also upregulated OPN and BSP. OPN and BSP are known to affect MMP-2 expression and activity but have not previously been shown to be regulated by MMP-2. Identification of this newly defined circuitry provides insight into the potential molecular landscape underlying the MOA phenotype and highlights a pathway that might play a role in normal bone homeostasis.

Osteopontin regulates interleukin-17 production in hepatitis

The overexpression of osteopontin is associated with various inflammatory liver diseases. Interestingly, each of these diseases is also associated with IL-17 expression. Therefore, we sought to determine whether there is any mechanistic link between osteopontin and IL-17. Herein we show that IL-17 and osteopontin levels were significantly increased in patients with chronic hepatitis B. We found that IL-17 and osteopontin levels increased similarly in mice with concanavalin A-induced hepatitis. Both osteopontin- and IL-17-deficient mice were resistant to concanavalin A-induced hepatic injury. In addition, osteopontin markedly induced IL-17 expression by leukocytes (from humans and mice). This effect could be blocked by a specific antibody against osteopontin. β3 integrin (one of the osteopontin receptors) was critically involved in the induction of IL-17 production by osteopontin. Osteopontin-induced IL-17 expression was mediated through the p38, JNK, and NF-κB pathways. These findings suggest that osteopontin regulates IL-17 production during the pathogenesis of hepatitis and provide new evidence for the critical roles of osteopontin and IL-17 in hepatitis.

The hypoxic environment reprograms the cytokine/chemokine expression profile of human mature dendritic cells

Myeloid dendritic cells (DCs) are professional antigen-presenting cells critical for the orchestration of immunity and maintenance of self-tolerance. DC development and functions are tightly regulated by a complex network of inhibitory and activating signals present in the tissue microenvironment, and dysregulated DC responses may result in amplification of inflammation, loss of tolerance, or establishment of immune escape mechanisms. Generation of mature (m)DCs from monocytic precursors recruited at pathological sites occurs under condition of low partial oxygen pressure (pO(2)). However, the way in which the hypoxic microenvironment modulates the functions of these cells is still not clear. We demonstrate that chronic hypoxia (4 days, 1% O(2)) promotes the onset of a highly proinflammatory gene expression profile in mDCs generated from primary human monocytes, characterized by the modulation of a significant cluster of genes coding for proinflammatory chemokines/cytokines and/or their receptors. Within the chemokine system, strong upregulation of genes encoding proteins chemotactic for neutrophils, such as CXCL2, CXCL3, CXCL5, CXCL6, and CXCL8, and for activated/memory T lymphocytes, monocytes, and immature (i) DCs, e.g. CCL20, CCL3 and CCL5, was observed, concomitant with decreased expression of genes coding for naive/resting T cells chemoattractants, CCL18 and CCL23. Other hypoxia-inducible genes coded for cytokines with a primary role in inflammation and angiogenesis, including osteopontin, vascular endothelial growth factor, and IL-1β. mRNA modulation was paralleled by protein secretion. These results suggest that conditions of reduced O(2) availability reprograms mDCs toward a proinflammatory direction by tuning the cytokine/chemokine repertoire, thus affecting their ability to regulate leukocyte trafficking and activation at pathological sites, with potential implications for the pathogenesis of chronic inflammatory diseases.

Osteopontin levels are elevated in patients with asthma

Osteopontin (OPN) plays a role in T cell-mediated immunity, but its involvement in Th2-associated allergic responses, especially asthma, has not been investigated. This cross-sectional case-control study was designed to determine whether serum OPN levels are elevated in asthma patients and whether these correlated with disease severity. Serum samples were obtained from patients with mild (n = 42), moderate (n = 48) and severe (n = 39) asthma, and 41 healthy control subjects. OPN protein concentrations were measured by enzyme-linked immuno sorbent assay and were found to be significantly higher in all three asthma patient groups compared with healthy controls. There was no significant association between OPN concentration and disease severity. The data suggest a role for OPN in the pathogenesis of asthma. Further studies are needed to clarify the involvement of OPN in various aspects of asthma.