The development of clinical signs of rheumatoid synovial inflammation is associated with increased synthesis of the chemokine CXCL8 (interleukin-8)

A remotely controlled nanotherapeutic with immunomodulatory property for MRSA-induced bone infection

Osteomyelitis is a deep bone tissue infection caused by pathogenic microorganisms, with the primary pathogen being methicillin-resistant Staphylococcus aureus (MRSA). Due to the tendency of the infection site to form biofilms that shield drugs and immune cells to kill bacteria, combined with the severe local inflammatory response causing bone tissue destruction, the treatment of osteomyelitis poses a significant challenge. Herein, we developed a remotely controlled nanotherapeutic (TLBA) with immunomodulatory to treat MRSA-induced osteomyelitis. TLBA, combined with baicalin and gold nanorods, is positively charged to actively target and penetrate biofilms. Near-infrared light (808 nm) triggers spatiotemporal, controllable drug release, while bacteria are eliminated through synergistic interaction of non-antibiotic drugs and photothermal therapy, enhancing bactericidal efficiency and minimizing drug resistance. TLBA eliminated nearly 100 % of planktonic bacteria and dispersed 90 % of biofilms under NIR light stimulation. In MRSA-induced osteomyelitis rat models, laser irradiation raised the infection site temperature to 50 °C, effectively eradicating bacteria, promoting M2 macrophage transformation, inhibiting bone inflammation, curbing bone destruction, and fostering bone tissue repair. In summary, TLBA proposes a more comprehensive treatment strategy for the two characteristic pathological changes of bacterial infection and bone tissue damage in osteomyelitis.

Targeting cyclin-dependent kinases in rheumatoid arthritis and psoriasis - a review of current evidence

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory disease associated with synovial proliferation and bone erosion, which leads to the structural and functional impairment of the joints. Immune cells, together with synoviocytes, induce a pro-inflammatory environment and novel treatment agents target inflammatory cytokines. Psoriasis is a chronic immune-mediated skin disease, and several cytokines are considered as typical mediators in the progression of the disease, including IL-23, IL-22, and IL-17, among others.

AREA COVERED

In this review, we try to evaluate whether cyclin-dependent kinases (CDK), enzymes that regulate cell cycle and transcription of various genes, could become novel therapeutic targets in RA and psoriasis. We present the main results of in vitro and in vivo studies, as well as scarce clinical reports.

EXPERT OPINION

CDK inhibitors seem promising for treating RA and psoriasis because of their multidirectional effects. CDK inhibitors may affect not only the process of osteoclastogenesis, thereby reducing joint destruction in RA, but also the process of apoptosis of neutrophils and macrophages responsible for the development of inflammation in both RA and psoriasis. However, assessing the efficacy of these drugs in clinical practice requires multi-center, long-term clinical trials evaluating the effectiveness and safety of CDK-blocking therapy in RA and psoriasis.

The chemokine landscape: one system multiple shades

Leukocyte trafficking is mainly governed by chemokines, chemotactic cytokines, which can be concomitantly produced in tissues during homeostatic conditions or inflammation. After the discovery and characterization of the individual chemokines, we and others have shown that they present additional properties. The first discoveries demonstrated that some chemokines act as natural antagonists on chemokine receptors, and prevent infiltration of leukocyte subsets in tissues. Later on it was shown that they can exert a repulsive effect on selective cell types, or synergize with other chemokines and inflammatory mediators to enhance chemokine receptors activities. The relevance of the fine-tuning modulation has been demonstrated in vivo in a multitude of processes, spanning from chronic inflammation to tissue regeneration, while its role in the tumor microenvironment needs further investigation. Moreover, naturally occurring autoantibodies targeting chemokines were found in tumors and autoimmune diseases. More recently in SARS-CoV-2 infection, the presence of several autoantibodies neutralizing chemokine activities distinguished disease severity, and they were shown to be beneficial, protecting from long-term sequelae. Here, we review the additional properties of chemokines that influence cell recruitment and activities. We believe these features need to be taken into account when designing novel therapeutic strategies targeting immunological disorders.

The forgotten key players in rheumatoid arthritis: IL-8 and IL-17 - Unmet needs and therapeutic perspectives

Despite the relevant advances in our understanding of the pathogenetic mechanisms regulating inflammation in rheumatoid arthritis (RA) and the development of effective therapeutics, to date, there is still a proportion of patients with RA who do not respond to treatment and end up progressing toward the development of joint damage, extra-articular complications, and disability. This is mainly due to the inter-individual heterogeneity of the molecular and cellular taxonomy of the synovial membrane, which represents the target tissue of RA inflammation. Tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) are crucial key players in RA pathogenesis fueling the inflammatory cascade, as supported by experimental evidence derived from in vivo animal models and the effectiveness of biologic-Disease Modifying Anti-Rheumatic Drugs (b-DMARDs) in patients with RA. However, additional inflammatory soluble mediators such as IL-8 and IL-17 exert their pathogenetic actions promoting the detrimental activation of immune and stromal cells in RA synovial membrane, tendons, and extra-articular sites, as well as blood vessels and lungs, causing extra-articular complications, which might be excluded by the action of anti-TNFα and anti-IL6R targeted therapies. In this narrative review, we will discuss the role of IL-8 and IL-17 in promoting inflammation in multiple biological compartments (i.e., synovial membrane, blood vessels, and lung, respectively) in animal models of arthritis and patients with RA and how their selective targeting could improve the management of treatment resistance in patients.

Chemokines and chemokine receptors as promising targets in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that commonly causes inflammation and bone destruction in multiple joints. Inflammatory cytokines, such as IL-6 and TNF-α, play important roles in RA development and pathogenesis. Biological therapies targeting these cytokines have revolutionized RA therapy. However, approximately 50% of the patients are non-responders to these therapies. Therefore, there is an ongoing need to identify new therapeutic targets and therapies for patients with RA. In this review, we focus on the pathogenic roles of chemokines and their G-protein-coupled receptors (GPCRs) in RA. Inflamed tissues in RA, such as the synovium, highly express various chemokines to promote leukocyte migration, tightly controlled by chemokine ligand-receptor interactions. Because the inhibition of these signaling pathways results in inflammatory response regulation, chemokines and their receptors could be promising targets for RA therapy. The blockade of various chemokines and/or their receptors has yielded prospective results in preclinical trials using animal models of inflammatory arthritis. However, some of these strategies have failed in clinical trials. Nonetheless, some blockades showed promising results in early-phase clinical trials, suggesting that chemokine ligand-receptor interactions remain a promising therapeutic target for RA and other autoimmune diseases.

[Effect of chemokines CXCL9 and CXCL10 on bone erosion in patients with rheumatoid arthritis]

OBJECTIVE

To detect the serum level of soluble chemokines CXCL9 and CXCL10 in patients with rheumatoid arthritis (RA), and to analyze their correlation with bone erosion, as well as the clinical significance in RA.

METHODS

In the study, 105 cases of RA patients, 90 osteoarthritis (OA) patients and 25 healthy controls in Peking University People's Hospital were included. All the clinical information of the patients was collected, and the serum CXCL9 and CXCL10 levels of both patients and healthy controls were measured by enzyme-linked immune sorbent assay (ELISA). CXCL9 and CXCL10 levels among different groups were compared. The correlation between serum levels with clinical/laboratory parameters and the occurrence of bone erosion in RA were analyzed. Independent sample t test, Chi square test, Mann-Whitney U test, Spearman's rank correlation and Logistic regression were used for statistical analysis.

RESULTS

The levels of CXCL9 and CXCL10 were significantly higher in the RA patients [250.02 (126.98, 484.29) ng/L, 108.43 (55.16, 197.17) ng/L] than in the OA patients [165.05 (75.89, 266.37) ng/L, 69.00 (33.25, 104.74) ng/L] and the health controls [79.47 (38.22, 140.63) ng/L, 55.44 (18.76, 95.86) ng/L] (all P < 0.01). Spearman's correlation analysis showed that the level of serum CXCL9 was positively correlated with swollen joints (SJC), rheumatoid factor (RF) and disease activity score 28 (DAS28) (r=0.302, 0.285, 0.289; P=0.009, 0.015, 0.013). The level of serum CXCL10 was positively correlated with tender joints (TJC), SJC, C-reactive protein (CRP), immunoglobulin (Ig) A, IgM, RF, anti-cyclic citrullinated peptide antibody (ACPA), and DAS28 (r=0.339, 0.402, 0.269, 0.266, 0.345, 0.570, 0.540, 0.364; P=0.010, 0.002, 0.043, 0.045, 0.009, < 0.001, < 0.001, 0.006). Serum CXCL9 and CXCL10 levels in the RA patients with bone erosion were extremely higher than those without bone erosion [306.84 (234.02, 460.55) ng/L vs. 149.90 (75.88, 257.72) ng/L, 153.74 (89.50, 209.59) ng/L vs. 54.53 (26.30, 83.69) ng/L, respectively] (all P < 0.01). Logistic regression analysis showed that disease duration, DAS28 and serum level of CXCL9 were correlated with bone erosion in the RA patients (P < 0.05).

CONCLUSION

Serum levels of CXCL9 and CXCL10 were remarkably elevated in patients with RA, and correlated with disease activities and occurrence of bone erosion. Chemokines CXCL9 and CXCL10 might be involved in the pathogenesis and bone destruction in RA.

Recombinant Adiponectin Induces the Production of Pro-Inflammatory Chemokines and Cytokines in Circulating Mononuclear Cells and Fibroblast-Like Synoviocytes From Non-Inflamed Subjects

Adiponectin is an adipokine with a modulatory role in metabolism and exerting both anti- and pro-inflammatory effects. Levels of adiponectin are increased in serum and synovial fluid from patients with rheumatoid arthritis (RA). Adiponectin is able to stimulate the production of different pro-inflammatory factors from peripheral blood mononuclear cells (PBMCs) and fibroblast-like synoviocytes (FLS) from subjects with established RA. As increased circulating adiponectin levels are a risk factor for future development of RA in subjects with obesity, we hypothesize that adiponectin is implicated in the development of RA at an early stage by initiating the pro-inflammatory processes associated with the disease pathogenesis. Therefore, we aimed to determine if adiponectin is able to induce pro-inflammatory responses in cells involved in the pathogenesis of RA, but collected from subjects without any known inflammatory disease. PBMCs and FLS were obtained from non-inflamed subjects and stimulated with 5 μg/ml human recombinant adiponectin. Supernatants collected after 48 h were analyzed for the production of 13 chemokines and 12 cytokines using multiplex assay and ELISA. Adiponectin significantly stimulated the production of CXCL1, CXCL5, and interleukin (IL)-6 in both PBMCs and FLS, whereas it induced CCL20, CCL4, CCL3, CCL17, tumor necrosis factor (TNF), granulocyte-macrophage colony-stimulating factor and IL-10 only in PBMCs, and CXCL8, CXCL10, CCL5, CCL11, and CCL2 only in FLS. Pre-stimulation with TNF of FLS from non-inflamed subjects did not significantly enhance the release of most pro-inflammatory factors compared to adiponectin alone. Our findings indicate that PBMCs and FLS from non-inflamed subjects react to adiponectin stimulation with the secretion of several pro-inflammatory chemokines and cytokines. These results suggest that adiponectin is able to initiate pro-inflammatory responses in cells from non-inflamed subjects and support the hypothesis that adiponectin is implicated in the early phases of RA pathogenesis.

Intracellular Staphylococcus aureus in bone and joint infections: A mechanism of disease recurrence, inflammation, and bone and cartilage destruction

Bone and joint infections are devastating afflictions. Although medical interventions and advents have improved their care, bone and joint infections still portend dismal outcomes. Indeed, bone and joint infections are associated with extremely high mortality and morbidity rates and, generally, occur secondary to the aggressive pathogen Staphylococcus aureus. The consequences of bone and joint infections are further compounded by the fact that although they are aggressively treated, they frequently recur and result in massive bone and articular cartilage loss. Here, we review the literature and chronicle the fact that the fundamental cellular components of the musculoskeletal system can be internally infected with Staphylococcus aureus, which explains the ready recurrence of bone and joint infections even after extensive administration of antibiotic therapy and debridement and offer potential treatment solutions for further study. Moreover, we review the ramifications of intracellular infection and expound that the massive bone and articular cartilage loss is caused by the sustained proinflammatory state induced by infection and offer potential combination therapies for further study to protect bone and cartilage.

Evaluation of serum MMP-2 and MMP-3, synovial fluid IL-8, MCP-1, and KC concentrations as biomarkers of stifle osteoarthritis associated with naturally occurring cranial cruciate ligament rupture in dogs

The purpose of this study was to evaluate matrix metalloproteinases (MMP) -2 and MMP-3 in serum, and keratinocyte-derived chemoattractant (KC), interleukin 8 (IL-8) and monocyte chemoattractant 1 (MCP-1) in synovial fluid (SF) as stifle osteoarthritis (OA) biomarkers in dogs. Dogs with naturally occurring cranial cruciate ligament (CrCL) rupture (OA group) and healthy controls were recruited. Stifles with CrCL deficiency were surgically stabilized. Serum, SF, and synovial biopsy samples were collected from the OA group preoperatively, whereas samples were collected once from control dogs. A blinded veterinary pathologist graded synovial biopsies. Serum and SF analyses were performed using xMAP technology. General linear regression was used for statistical comparisons of serum biomarkers, and mixed linear regression for SF biomarkers and temporal concentration changes. The overall discriminative ability was quantified using area under curve (AUC). Spearman's correlation coefficient was used to assess correlations between synovial histology grades and the biomarkers. Samples from 62 dogs in the OA group and 50 controls were included. The MMP-2 and MMP-3 concentrations between the OA and control groups were not significantly different, and both with an AUC indicating a poor discriminative ability. All three SF biomarker concentrations were significantly different between the OA group and controls (P <0.05). The MCP-1 was the only biomarker showing an acceptable discriminative performance with an AUC of 0.91 (95% confidence interval: 0.83-0.98). The sum of the inflammatory infiltrate score was significantly correlated with all three SF biomarkers (P <0.01). Summed synovial stroma, and all scores combined were significantly correlated with IL-8 and MCP-1 concentrations (P <0.003), and the summed synoviocyte scores were significantly correlated with MCP-1 concentrations (P <0.001). Correlations between MCP-1 concentrations and synovial histopathologic grading and its discriminative ability suggest its potential as a synovitis biomarker in canine stifle OA associated with CrCL rupture.

D-Lactate Increases Cytokine Production in Bovine Fibroblast-Like Synoviocytes via MCT1 Uptake and the MAPK, PI3K/Akt, and NFκB Pathways

Acute ruminal acidosis (ARA) is caused by the excessive intake of highly fermentable carbohydrates, followed by the massive production of D-lactate and the appearance of neutrophilic aseptic polysynovitis. Bovines with ARA develop different lesions, such as ruminitis, polioencephalomalacia (calves), liver abscess and lameness. Lameness in cattle with ARA is closely associated with the presence of laminitis and polysynovitis. However, despite decades of research in bovine lameness as consequence of ruminal acidosis, the aetiology and pathogenesis remain unclear. Fibroblast-like synoviocytes (FLSs) are components of synovial tissue, and under pathological conditions, FLSs increase cytokine production, aggravating inflammatory responses. We hypothesized that D-lactate could induce cytokine production in bovine FLSs. Analysis by qRT-PCR and ELISA revealed that D-lactate, but not L-lactate, increased the expression of IL-6 and IL-8 in a monocarboxylate transporter-1-dependent manner. In addition, we observed that the inhibition of the p38, ERK1/2, PI3K/Akt, and NF-κB pathways reduced the production of IL-8 and IL-6. In conclusion, our results suggest that D-lactate induces an inflammatory response; this study contributes to the literature by revealing a potential key role of D-lactate in the polysynovitis of cattle with ARA.

Comprehensive Bioinformatics Analysis Reveals Hub Genes and Inflammation State of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by erosive arthritis, which has not been thoroughly cured yet, and standardized treatment is helpful for alleviating clinical symptoms. Here, various bioinformatics analysis tools were comprehensively utilized, aiming to identify critical biomarkers and possible pathogenesis of RA. Three gene expression datasets profiled by microarray were obtained from GEO database. Dataset GSE55235 and GSE55457 were merged for subsequent analyses. We identified differentially expressed genes (DEGs) in RStudio with limma package, performing functional enrichment analysis based on GSEA software and clusterProfiler package. Next, protein-protein interaction (PPI) network was set up through STRING database and Cytoscape. Moreover, CIBERSORT website was used to assess the inflammatory state of RA. Finally, we validated the candidate hub genes with dataset GSE77298. As a result, we identified 106 DEGs (72 upregulated and 34 downregulated genes). Through GO, KEGG, and GSEA analysis, we found that DEGs were mainly involved in immune response and inflammatory signaling pathway. With the help of Cytoscape software and MCODE plug-in, the most prominent subnetwork was screened out, containing 14 genes and 45 edges. For ROC curve analysis, eight genes with AUC >0.80 were considered as hub genes of RA. In conclusion, compared with healthy controls, the DEGs and their closely related biological functions were analyzed, and we held that chemokines and immune cells infiltration promote the progression of rheumatoid arthritis. Targeting the eight biomarkers we identified may be useful for the diagnosis and treatment of rheumatoid arthritis.

Data describing expression of formyl peptide receptor 2 in human articular chondrocytes

The formyl peptide receptor 2 (FPR2) belongs to the family of seven-transmembrane G protein-coupled receptors (GPCR) and are expressed by many different cells but mainly studied in immune cells. FPR2 is involved in host defense against bacterial infections and clearance of damaged cells through the oxidative burst and chemotaxis of neutrophils. In addition, FPR2 has also been implicated as an immunomodulator in sterile inflammations, e.g. inflammatory joint diseases. Here we present data regarding FPR2 expression in human articular chondrocytes, isolated from healthy individuals and osteoarthritic patients, on both mRNA and protein level using qPCR and Imagestream flow cytometry. We also present data after receptor stimulation and monitoring of production of nitric oxide, reactive oxygen species, IL-6, IL-8 and MMP-3. The presented data show that human articular chondrocytes from patients with osteoarthritis as well as from healthy individuals express FPR2 both at mRNA and protein level. The biological relevance of FPR2 expression in chondrocytes needs to be further investigated.

Functional Deficits in Mice Expressing Human Interleukin 8

We showed previously that inflammatory mediators, including IL8, in intervertebral disc tissues from patients with discogenic back pain may play a key role in back pain. To investigate the molecular mechanism of IL8 signaling in back pain, we generated a mouse model that conditionally expresses human (h) IL8. We hypothesized that hIL8 levels affect mouse activity and function. Briefly, hIL8 cDNA was inserted into the pCALL2 plasmid, linearized, and injected into mouse embryos. Resulting pCALL2-hIL8 mice were then bred with GDF5-Cre mice to express the transgene in cartilage and intervertebral disc (IVD) tissues. Functional capacities including nest-making and other natural behaviors were measured. Both male and female mice expressing hIL8 showed lower nesting scores than did littermates that did not express hIL8 (n = 14 to 16 per group). At 28 wk of age, mice expressing hIL8 (n = 35) spent more time immobile and eating during each night than littermate controls (n = 33). Furthermore, hIL8-expressing mice traveled shorter distances and at a lower average speed than littermate controls. Thus, in an initial effort to investigate the relationship between this chemokine and mouse behavior, we have documented changes in normal activities in mice conditionally expressing hIL8.

Chemokines in rheumatic diseases: pathogenic role and therapeutic implications

Chemokines, a family of small secreted chemotactic cytokines, and their G protein-coupled seven transmembrane spanning receptors control the migratory patterns, positioning and cellular interactions of immune cells. The levels of chemokines and their receptors are increased in the blood and within inflamed tissue of patients with rheumatic diseases, such as rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, vasculitis or idiopathic inflammatory myopathies. Chemokine ligand-receptor interactions control the recruitment of leukocytes into tissue, which are central to the pathogenesis of these rheumatic diseases. Although the blockade of various chemokines and chemokine receptors has yielded promising results in preclinical animal models of rheumatic diseases, human clinical trials have, in general, been disappointing. However, there have been glimmers of hope from several early-phase clinical trials that suggest that sufficiently blocking the relevant chemokine pathway might in fact have clinical benefits in rheumatic diseases. Hence, the chemokine system remains a promising therapeutic target for rheumatic diseases and requires further study.

Immunoexpression of canonical Wnt and NF-κB signaling pathways in the temporomandibular joint of arthritic rats

OBJECTIVE

To investigate the participation of canonical Wnt and NF-κB signaling pathways in an experimental model of chronic arthritis induced by methylated bovine serum albumin (mBSA) in rat temporomandibular joint (TMJ).

MATERIALS AND METHODS

Wistar rats were sensitized by mBSA+Complete Freund Adjuvant (CFA)/Incomplete Freund Adjuvant (IFA) on the first 14 days (1 ×/week). Subsequently, they received 1, 2 or 3 mBSA or saline solution injections into the TMJ (1 ×/week). Hypernociceptive threshold was assessed during the whole experimental period. 24 h after the mBSA injections, the TMJs were removed for histopathological and immunohistochemical analyses for TNF-α, IL-1β, NF-κB, RANKL, Wnt-10b, β-catenin and DKK1.

RESULTS

The nociceptive threshold was significantly reduced after mBSA injections. An inflammatory infiltrate and thickening of the synovial membrane were observed only after mBSA booster injections. Immunolabeling of TNF-α, IL-1β and Wnt-10b was increased in the synovial membrane in arthritic groups. The immunoexpression of nuclear β-catenin was significantly higher only in the group that received 2 booster TMJ injections. However, NF-κB, RANKL and DKK1 immunoexpression were increased only in animals with 3 mBSA intra-articular injections.

CONCLUSION

Our results suggest that canonical Wnt and NF-κB signaling pathways participate in the hypernociception and inflammatory response in TMJ synovial membrane during the development of rheumatoid arthritis in rats.

Analysis of gene expression in rheumatoid arthritis and related conditions offers insights into sex-bias, gene biotypes and co-expression patterns

The era of next-generation sequencing has mounted the foundation of many gene expression studies. In rheumatoid arthritis research, this has led to the discovery of important candidate genes which offered novel insights into mechanisms and their possible roles in the cure of the disease. In the last years, data generation has outstripped data analysis and while many studies focused on specific aspects of the disease, a global picture of the disease is not yet accomplished. Here, we analyzed and compared a collection of gene expression information from healthy individuals and from patients suffering under different arthritis conditions from published studies containing the following clinical conditions: early and established rheumatoid arthritis, osteoarthritis and arthralgia. We show comprehensive overviews of this data collection and give new insights specifically on gene expression in the early stage, into sex-dependent gene expression, and we describe general differences in expression of different biotypes of genes. Many genes that are related to cytoskeleton changes (actin filament related genes) are differently expressed in early rheumatoid arthritis in comparison to healthy subjects; interestingly, eight of these genes reverse their expression ratio significantly between men and women compared early rheumatoid arthritis and healthy subjects. There are some slighter changes between men and woman between the conditions early and established rheumatoid arthritis. Another aspect are miRNAs and other gene biotypes which are not only promising candidates for diagnoses but also change their expression grossly in average at rheumatoid arthritis and arthralgia compared to the healthy condition. With a selection of intersecting genes, we were able to generate simple classification models to distinguish between healthy and rheumatoid arthritis as well as between early rheumatoid arthritis to other arthritides based on gene expression.

The many facets of macrophages in rheumatoid arthritis

Macrophages are central to the pathophysiology of rheumatoid arthritis (RA). They constitute the main source of pro-inflammatory cytokines and chemokines such as TNF and IL-1β, they activate a wide range of immune and non-immune cells, and they secrete diverse tissue degrading enzymes driving chronic pro-inflammatory, tissue destructive and pain responses in RA. However, they can also produce anti-inflammatory cytokines such as IL-10, secrete inhibitors of tissue degrading enzymes and promote immunoregulatory and protective responses, suggesting the existence of macrophages with distinct and diverse functional activities. Although the underlying basis of this phenomenon has remained obscure for years, emerging evidence has now provided insight into the mechanisms and molecular processes involved. Here, we review current knowledge on the biology of macrophages in RA, and highlight recent literature on the heterogeneity, origins and ontogeny of macrophages as part of the mononuclear phagocyte system. We also discuss their plasticity in the context of the M1/M2 paradigm, and the emerging theme of metabolic rewiring as a major mechanism for programming macrophage functions and pro-inflammatory activities. This sheds light into the many facets of macrophages in RA, their molecular regulation and their translational potential for developing novel protective and therapeutic strategies in the clinic.

RHAMM induces progression of rheumatoid arthritis by enhancing the functions of fibroblast-like synoviocytes

Background

Rheumatoid arthritis (RA) is a chronic and refractory autoimmune joint disease. Fibroblast-like synoviocytes (FLS) produce inflammatory cytokines and are involved in the migration and invasion of panuus tissue, which leads to the destruction of joints in RA. Receptor for hyaluronan mediated motility (RHAMM), is known to be one of the important receptors for hyaluronic acid. It has the ability to regulate migration of fibrocytes and infiltration of inflammatory cells. Here,we explored the mechanisms of RHAMM in RAFs.

Methods

Quantitative PCR and western blot were performed to test the expression of RHAMM in synoviocytes of RA patients and osteoarthritis (OA) controls. Collagen antibody-induced arthritis (CAIA) was used to investigate the RHAMM expression in mouse synovial issues. RHAMM siRNA was used to detect the function of RHAMM in FLS.

Results

RA-FLS has a significantly higher expression of RHAMM than OA-FLS. Expression of RHAMM in joint synovial tissue was markedly increased in the CAIA mice compared with the controls. RHAMM silencing using SiRNA was not only decreased the production of IL-6 and IL-8, but also inhibited the migration and invasion of RA-FLS.

Conclusions

RHAMM has an important role in the FLS induced modulation of inflammation and destruction of joints in RA.

Immunomodulatory drug methotrexate used to treat patients with chronic inflammatory rheumatisms post-chikungunya does not impair the synovial antiviral and bone repair responses

Chikungunya virus (CHIKV) is a mosquito-transmitted RNA alphavirus causing major outbreaks of infectious chronic inflammatory rheumatisms (CIR). Recently, methotrexate (MTX), a disease modifying anti-rheumatic drug has been used successfully to treat patients suffering from rheumatoid-like arthritis post-CHIK but its immunomodulatory activity in the context of viral persistence has been a matter of concerns. We herein used a model of primary human synovial fibroblasts (HSF) and the synthetic molecule polyriboinosinic:polyribocytidylic acid (PIC) to mimic chronic infectious settings in the joints of CHIKV infected patients. The innate antiviral immune and inflammatory responses were investigated in response to MTX used at the therapeutic concentration of 1 μM. We found that MTX did not affect cellular viability as indicated by the LDH release assay. By quantitative RT-PCR, we observed that HSF responded robustly to PIC by increasing ISG15 and IFNβ mRNA levels. Furthermore, PIC upregulated the mRNA expression of two of the major pattern recognition receptors, RIG-I and MDA5 involved in the innate immune detection of viral RNA. MTX did not impact the antiviral response of PIC on ISG15, IFNβ, RIG-I and MDA5 mRNA expressions. MTX alone or combined with PIC did not affect the expression of proinflammatory CCL2 and CXCL8 chemokines. PIC strongly upregulated the mRNA and protein expression of osteoclastogenic factors (IL-6, GM-CSF but not RANKL). Critically, MTX treatment alone or combined with PIC did not affect the expression of all three tested osteoclastogenic cytokines. We found that MTX alone did not increase the capacity of CHIKV to infect and replicate in HSF. In conclusion, our study argues for a beneficial effect of MTX to treat CIR post-CHIKV given that it does not critically impact the antiviral, the proinflammatory and the bone tissue remodeling responses of synovial cells.

Chikungunya is a mosquito-borne virus (CHIKV) and has been incriminated in the development of arthralgia (pain of the joint) and arthritis particularly in elderly patients. Methotrexate (MTX) has been used widely to effectively treat these chronic rheumatic symptoms. Using a model of primary human joint fibroblasts (HSF), we investigated the capacity of the MTX immunosuppressive drug to affect the immune antiviral and inflammatory responses essential to clear the virus while allowing bone tissue repair. This study is important given that CHIKV and its RNA were shown to persist in the joint for months to years post infection and leading to injuries through ill-characterized mechanisms. The molecule PIC was used to mimic the effect of viral RNA. Interestingly, we found that MTX did not affect the expression of several proinflammatory and bone repair factors by HSF. Remarkably, MTX did not also impair the antiviral response of synovial fibroblasts. Our study revealed for the first time that MTX treatment should be considered as safe even in the context of viral persistence associated with chronic inflammation. MTX will not affect the capacity of the synovial tissue to maintain antiviral mechanism, to control inflammation and to promote bone tissue repair.

Association between levels of synovial anti-citrullinated peptide antibodies and neutrophil response in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by the presence of anti-citrullinated peptide antibodies (ACPAs) and neutrophils infiltrating the synovial fluid (SF) of the affected joints. The aim of this work was to analyze whether the presence of ACPAs in SF is associated with neutrophil infiltration and with their phenotype in the inflamed joints of RA patients. We found that in the presence of ACPAs, the number of synovial neutrophils correlated with severe disease activity. The SF were divided according to synovial ACPA levels in negative- (<25 U/mL), low- (25-200 U/mL) and high level (˃200 U/mL; ACPA^high ). We observed that IL-6, IL-17, and IL-8 were significantly elevated in ACPA^high SF and that IL-8 levels correlated positively with neutrophil counts and with worse clinical manifestations. Additionally, in vitro incubation of neutrophils with ACPA^high SF resulted in an increased ROS production and extracellular DNA release compared to neutrophils incubated with ACPA-negative SF. These exacerbated effector functions were associated with a fraction of ICAM-1-positive neutrophils, which were induced by ACPA^high SF. Likewise, in in vivo, we could also detect this subset among neutrophils present in ACPA^high SF. In conclusion, the data presented here shed light on the role of SF-ACPAs as inductors of a proinflammatory profile in neutrophils.

Caffeine inhibits STAT1 signaling and downregulates inflammatory pathways involved in autoimmunity

Caffeine is a widely consumed pharmacologically active product. We focused on characterizing immunomodulatory effects of caffeine on peripheral blood mononuclear cells. Caffeine at high doses showed a robust downregulatory effect on cytokine activity and genes related to several autoimmune diseases including lupus and rheumatoid arthritis. Dose-dependent validation experiments showed downregulation at the mRNA levels of key inflammation-related genes including STAT1, TNF, IFNG, and PPARG. TNF and PPARG were suppressed even with the lowest caffeine dose tested, which corresponds to the serum concentration of caffeine after administration of one cup of coffee. Cytokine levels of IL-8, MIP-1β, IL-6, IFN-γ, GM-CSF, TNF, IL-2, IL-4, MCP-1, and IL-10 were decreased significantly with caffeine treatment. Upstream regulator analysis suggests that caffeine inhibits STAT1 signaling, which was confirmed by showing reduced phosphorylated STAT1 after caffeine treatment. Further studies exploring disease-modulating potential of caffeine in autoimmune diseases and further exploring the mechanisms involved are warranted.

Resistin upregulates chemokine production by fibroblast-like synoviocytes from patients with rheumatoid arthritis

Background

Adipokines are bioactive hormones secreted by adipose tissues. Resistin, an adipokine, plays important roles in the regulation of insulin resistance and inflammation. Resistin levels are known to be increased in the serum and synovial fluid of rheumatoid arthritis (RA) patients. However, the pathogenic role of resistin in RA has not yet been elucidated.

Methods

The expression of resistin and adenylate cyclase-associated protein 1 (CAP1), a receptor for resistin, was examined immunohistochemically in synovial tissue. CAP1 expression in in vitro cultured fibroblast-like synoviocytes (FLSs) was assessed with a reverse transcription-polymerase chain reaction (PCR) and western blotting. The gene expression of resistin-stimulated FLSs was evaluated by RNA sequencing (RNA-Seq) and quantitative real-time PCR. Concentrations of chemokine (C-X-C motif) ligand (CXCL) 8, chemokine (C-C motif) ligand (CCL) 2, interleukin (IL)-1β, IL-6 and IL-32 in culture supernatants were measured by enzyme-linked immunosorbent assay. Small interfering RNA (siRNA) for CAP1 was transfected into FLSs in order to examine inhibitory effects.

Results

The expression of resistin and CAP1 in synovial tissue was stronger in RA than in osteoarthritis (OA). Resistin was expressed by macrophages in the RA synovium, while CAP1 was expressed by macrophages, FLSs and endothelial cells. In vitro cultured RA FLSs also expressed CAP1. RNA-Seq revealed that the expression levels of 18 molecules were more than twofold higher in resistin-stimulated FLSs than in unstimulated FLSs. Seven chemokines, CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL8, and CCL2, were included among the 18 molecules. Increases induced in the expression of CXCL1, CXCL8, and CCL2 by the resistin stimulation were confirmed by real-time PCR. The stimulation with resistin increased the protein levels of CXCL8 and CCL2 produced by RA FLSs, and the upregulated expression of CXCL8 was inhibited by the abrogation of CAP1 by siRNA for CAP1. Production of IL-6 by FLSs was also increased by resistin. Expression of IL-1β and IL-32 was not detected by ELISA.

Conclusions

Resistin contributes to the pathogenesis of RA by increasing chemokine production by FLSs via CAP1 in synovial tissue.

Anti-interleukin-6 signalling therapy rebalances the disrupted cytokine production of B cells from patients with active rheumatoid arthritis

Rheumatoid arthritis (RA) is associated with abnormal B cell-functions implicating antibody-dependent and -independent mechanisms. B cells have emerged as important cytokine-producing cells, and cytokines are well-known drivers of RA pathogenesis. To identify novel cytokine-mediated B-cell functions in RA, we comprehensively analysed the capacity of B cells from RA patients with an inadequate response to disease modifying anti-rheumatic drugs to produce cytokines in comparison with healthy donors (HD). RA B cells displayed a constitutively higher production of the pathogenic factors interleukin (IL)-8 and Gro-α, while their production of several cytokines upon activation via the B cell receptor for antigen (BCR) was broadly suppressed, including a loss of the expression of the protective factor TRAIL, compared to HD B cells. These defects were partly erased after treatment with the IL-6-signalling inhibitor tocilizumab, indicating that abnormal IL-6 signalling contributed to these abnormalities. Noteworthy, the clinical response of individual patients to tocilizumab therapy could be predicted using the amounts of MIP-1β and β-NGF produced by these patients' B cells before treatment. Taken together, our study highlights hitherto unknown abnormal B-cell functions in RA patients, which are related to the unbalanced cytokine network, and are potentially relevant for RA pathogenesis and treatment.

TIARP attenuates autoantibody-mediated arthritis via the suppression of neutrophil migration by reducing CXCL2/CXCR2 and IL-6 expression

TNFα-induced adipose-related protein (TIARP) is a six-transmembrane protein expressed on macrophages, neutrophils and synoviocytes. We reported recently that mice deficient in TIARP (TIARP^−/−) spontaneously develop arthritis and are highly susceptible to collagen-induced arthritis (CIA) with enhanced interleukin (IL)-6 production. However, the effects of TIARP on neutrophils and fibroblast-like synoviocytes (FLS) have not been elucidated. We analyzed the roles of TIARP in K/BxN serum transfer model using TIARP^−/− mice. Arthritis in TIARP^−/− mice transferred with K/BxN serum was significantly exacerbated compared with WT mice. We characterized the differences in neutrophils between wild-type (WT) and TIARP^−/− mice by DNA microarray. Overexpression of CXCR1 and CXCR2 was noted in TIARP^−/− neutrophils. Neutrophils of TIARP^−/− mice showed strong migration activity, which was markedly facilitated by CXCL2 in vitro and in vivo. Moreover, enhanced production of CXCL2 and IL-6 and cell proliferation was noted in TIARP^−/− TNFα-stimulated FLS. Blockade of IL-6R significantly attenuated serum-transferred TIARP^−/− arthritis with diminished neutrophil recruitment in joints. Our findings suggested that TIARP independently down-regulated CXCL2 and IL-6 production by FLS, and the expression of chemokine receptors (CXCR1 and CXCR2) in neutrophils, with resultant reduction of neutrophil migration into arthritic joints.

Urinary interleukin-6 as a predictor of radiographic progression in rheumatoid arthritis: A 3-year evaluation

Previously, we demonstrated that the urine proteome signature of patients with rheumatoid arthritis (RA) reflects inflammation-related cellular processes. Here, we measured interleukin (IL)-6, IL-8, and chemokine ligand 2 (CCL2) concentrations in the urine of RA patients and prospectively investigated their role in predicting RA activity and prognosis. One hundred seventy-three RA patients and 62 non-RA controls were recruited. Urinary IL-6, CCL2, and IL-8 levels were elevated in RA patients and correlated well with disease activity. Urinary IL-6 level at presentation was an independent risk factor of radiographic progression at 1 and 3 years. High urinary IL-6 level increased the risk ratio of radiographic progression by 2.9-fold, which was comparable to high serum CRP. Moreover, combination of urinary IL-6 and serum CRP measures synergistically increased the predictability of radiographic progression. In a subgroup with normal ESR, patients with the highest tertile of urinary IL-6 were at 6.4-fold greater risk of radiographic progression. Conclusively, high urinary IL-6 level at presentation is an independent risk factor for radiographic progression of RA, reflecting disease activity. Urinary IL-6 in combination with serum CRP may be a useful parameter for estimating RA prognosis.

Granulocyte-augmented chemokine production induced by type II collagen containing immune complexes is mediated via TLR4 in rheumatoid arthritis patients

Rheumatoid arthritis (RA) patients with early elevations of antibodies against collagen type II (CII) have a distinct acute onset phenotype, associated with cytokine induction by surface‐bound anti‐CII‐containing immune complexes (ICs) and high C‐reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Polymorphonuclear granulocytes (PMNs) and peripheral blood mononuclear cells (PBMCs) are abundant in the vicinity of CII in RA joints, and both PMN and PBMC reactivity against anti‐CII IC individually relate to early joint destruction and early elevation of CRP and ESR in RA. We searched for CII‐dependent mechanisms that might attract PMNs and PBMCs to RA joints. Human PBMCs and PMNs were stimulated with anti‐CII ICs and control ICs, either individually or in cocultures. Cocultured PMNs and PBMCs stimulated with anti‐CII ICs synergistically augmented production of the chemokines CXCL8, RANTES and MCP‐1, whereas downregulation was seen with control IC. This upregulation was unique to chemokines, as TNF‐α, IL‐1β, and GM‐CSF were downregulated in anti‐CII IC‐stimulated cocultures. The coculture‐associated chemokine upregulation depended on endogenous TLR4 ligand(s) and functionally active PMN enzymes, and was partially mediated by GM‐CSF. As anti‐CII levels peak around the time of RA diagnosis, this mechanism can attract inflammatory cells to joints in early RA and intensify the anti‐CII‐associated acute onset RA phenotype.

Paired Ig-Like Type 2 Receptor-Derived Agonist Ligands Ameliorate Inflammatory Reactions by Downregulating β1 Integrin Activity

The paired immunoglobulin-like type 2 receptor (PILR) family consists of two functionally opposite members, inhibitory PILRα and activating PILRβ receptors. PILRs are widely expressed in various immune cells and interact with their ligands, especially CD99 expressed on activated T cells, to participate in immune responses. Here we investigated whether PILR-derived agonists inhibit β1 integrin activity as ligands for CD99. PILR-derived peptides as well as PILR-Fc fusion proteins prevented cell adhesion to fibronectin through the regulation of β1 integrin activity. Especially, PILRpep3, a representative 3-mer peptide covering the conserved motifs of the PILR extracellular domain, prevented the clustering and activation of β1 integrin by dephosphorylating FAK and vinculin, which are major components of focal adhesion. In addition, PILRpep3 inhibited transendothelial migration of monocytes as well as endothelial cell tube formation. Furthermore, upon intraperitoneal injection of PILRpep3 into mice with collagen-induced arthritis, the inflammatory response of rheumatoid arthritis was strongly suppressed. Taken together, these results suggest that PILR-derived agonist ligands may prevent the inflammatory reactions of rheumatoid arthritis by activating CD99.

Identification of a novel chemokine-dependent molecular mechanism underlying rheumatoid arthritis-associated autoantibody-mediated bone loss

OBJECTIVES

Rheumatoid arthritis (RA)-specific anti-citrullinated protein/peptide antibodies (ACPAs) appear before disease onset and are associated with bone destruction. We aimed to dissect the role of ACPAs in osteoclast (OC) activation and to identify key cellular mediators in this process.

METHODS

Polyclonal ACPA were isolated from the synovial fluid (SF) and peripheral blood of patients with RA. Monoclonal ACPAs were isolated from single SF B-cells of patients with RA. OCs were developed from blood cell precursors with or without ACPAs. We analysed expression of citrullinated targets and peptidylarginine deiminases (PAD) enzymes by immunohistochemistry and cell supernatants by cytometric bead array. The effect of an anti-interleukin (IL)-8 neutralising antibody and a pan-PAD inhibitor was tested in the OC cultures. Monoclonal ACPAs were injected into mice and bone structure was analysed by micro-CT before and after CXCR1/2 blocking with reparixin.

RESULTS

Protein citrullination by PADs is essential for OC differentiation. Polyclonal ACPAs enhance OC differentiation through a PAD-dependent IL-8-mediated autocrine loop that is completely abolished by IL-8 neutralisation. Some, but not all, human monoclonal ACPAs derived from single SF B-cells of patients with RA and exhibiting distinct epitope specificities promote OC differentiation in cell cultures. Transfer of the monoclonal ACPAs into mice induced bone loss that was completely reversed by the IL-8 antagonist reparixin.

CONCLUSIONS

We provide novel insights into the key role of citrullination and PAD enzymes during OC differentiation and ACPA-induced OC activation. Our findings suggest that IL8-dependent OC activation may constitute an early event in the initiation of the joint specific inflammation in ACPA-positive RA.

CXCL8 and CCL20 Enhance Osteoclastogenesis via Modulation of Cytokine Production by Human Primary Osteoblasts

Generalized osteoporosis is common in patients with inflammatory diseases, possibly because of circulating inflammatory factors that affect osteoblast and osteoclast formation and activity. Serum levels of the inflammatory factors CXCL8 and CCL20 are elevated in rheumatoid arthritis, but whether these factors affect bone metabolism is unknown. We hypothesized that CXCL8 and CCL20 decrease osteoblast proliferation and differentiation, and enhance osteoblast-mediated osteoclast formation and activity. Human primary osteoblasts were cultured with or without CXCL8 (2–200 pg/ml) or CCL20 (5–500 pg/ml) for 14 days. Osteoblast proliferation and gene expression of matrix proteins and cytokines were analyzed. Osteoclast precursors were cultured with CXCL8 (200 pg/ml) and CCL20 (500 pg/ml), or with conditioned medium (CM) from CXCL8 and CCL20-treated osteoblasts with or without IL-6 inhibitor. After 3 weeks osteoclast formation and activity were determined. CXCL8 (200 pg/ml) and CCL20 (500 pg/ml) enhanced mRNA expression of KI67 (2.5–2.7-fold), ALP (1.6–1.7-fold), and IL-6 protein production (1.3–1.6-fold) by osteoblasts. CXCL8-CM enhanced the number of osteoclasts with 3–5 nuclei (1.7-fold), and with >5 nuclei (3-fold). CCL20-CM enhanced the number of osteoclasts with 3–5 nuclei (1.3-fold), and with >5 nuclei (2.8-fold). IL-6 inhibition reduced the stimulatory effect of CXCL8-CM and CCL20-CM on formation of osteoclasts. In conclusion, CXCL8 and CCL20 did not decrease osteoblast proliferation or gene expression of matrix proteins. CXCL8 and CCL20 did not directly affect osteoclastogenesis. However, CXCL8 and CCL20 enhanced osteoblast-mediated osteoclastogenesis, partly via IL-6 production, suggesting that CXCL8 and CCL20 may contribute to osteoporosis in rheumatoid arthritis by affecting bone cell communication.

Rational design of a peptide capture agent for CXCL8 based on a model of the CXCL8:CXCR1 complex

A CXCL8-binding peptide designed from the interaction sites of CXCR1 with CXCL8 serves as a capture agent and inhibits neutrophil migration.

Neutrophil migration towards C5a and CXCL8 is prevented by non-steroidal anti-inflammatory drugs via inhibition of different pathways

BACKGROUND AND PURPOSE

Non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to induce PG-independent anti-inflammatory actions. Here, we investigated the role of three different NSAIDs (naproxen, ibuprofen and oxaprozin) on neutrophil responses to CXCL8 and C5a.

EXPERIMENTAL APPROACH

Human neutrophils were isolated from healthy volunteers by dextran and Ficoll-Hypaque density gradients. Neutrophils were pre-incubated with different concentrations (1-100 µM) of NSAIDs or kinase inhibitors. Neutrophil degranulation into supernatants was tested by elisa and zymography. Neutrophil chemotaxis was determined using Boyden chambers. F-actin polymerization was determined by Alexa-Fluor 488-conjugated phalloidin fluorescent assay. Integrin expression was assessed by flow cytometry. The phosphorylation of intracellular kinases was studied by Western blot.

KEY RESULTS

Pretreatment with NSAIDs did not affect neutrophil degranulation, but inhibited neutrophil migration and polymerization of F-actin, in response to CXCL8 and C5a. Pretreatment with different NSAIDs prevented C5a-induced integrin (CD11b) up-regulation, while only ibuprofen reduced CXCL8-induced CD11b up-regulation. Pre-incubation with naproxen or oxaprozin, but not ibuprofen, inhibited the PI3K/Akt-dependent chemotactic pathways. Both endogenous (released in cell supernatants) or exogenous (added to cell cultures) PGE2 did not affect C5a- or CXCL8-induced activities. Short-term incubation with NSAIDs did not affect neutrophil PGE2 release.

CONCLUSION AND IMPLICATIONS

Treatment with NSAIDs reduced C5a- and CXCL8-induced neutrophil migration and F-actin polymerization via different mechanisms. Inhibition by ibuprofen was associated with integrin down-regulation, while naproxen and oxaprozin blocked the PI3K/Akt pathway. Both NSAID actions were independent of COX inhibition and PGE2 release.

Lysophosphatidic acid-induced IL-8 secretion involves MSK1 and MSK2 mediated activation of CREB1 in human fibroblast-like synoviocytes

Lysophosphatidic acid (LPA) is a pleiotropic lipid mediator that promotes motility, survival, and the synthesis of chemokines/cytokines such as interleukin-8 (IL-8) and interleukin-6 by human fibroblast-like synoviocytes from patients with rheumatoid arthritis (RAFLS). In those cells LPA was reported to induce IL-8 secretion through activation of various signaling pathways including p38 mitogen-activated protein kinase (p38 MAPK), p42/44 MAPK, and Rho kinase. In addition to those pathways we report that mitogen- and stress-activated protein kinases (MSKs) known to be activated downstream of the ERK1/2 and p38 MAPK cascades and CREB are phosphorylated in response to LPA. The silencing of MSKs with small-interfering RNAs and the pharmacological inhibitor of MSKs SB747651A shows a role for both MSK1 and MSK2 in LPA-mediated phosphorylation of CREB at Ser-133 and secretion of IL-8 and MCP-1. Whereas CREB inhibitors have off target effects and increased LPA-mediated IL-8 secretion, the silencing of CREB1 with short hairpin RNA significantly reduced LPA-induced chemokine production in RAFLS. Taken together the data clearly suggest that MSK1 and MSK2 are the major CREB kinases in RAFLS stimulated with LPA and that phosphorylation of CREB1 at Ser-133 downstream of MSKs plays a significant role in chemokine production.

Lipopolysaccharide accelerates collagen-induced arthritis in association with rapid and continuous production of inflammatory mediators and anti-type II collagen antibody

Collagen-induced arthritis (CIA) is an animal model for rheumatoid arthritis (RA). Lipopolysaccharide (LPS) is known to accelerate CIA; however, the pathogenetic mechanisms are not yet fully understood. In this study, type II collagen (CII)-immunized mice were found to have marked increases in degree of expression of mRNA of inflammatory mediators such as tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and macrophage inflammatory protein-2 (MIP-2) in their arthritic paws and of serum anti-CII antibody concentration before the onset of arthritis induced by LPS injection. The gene expression was rapid and continuous after direct activation of nuclear factor κB. The amounts of mRNA of TNF-α, IL-1β, and MIP-2, as well as of matrix metalloproteinases and the receptor activator of nuclear factor κB ligand, increased with the development of arthritis, correlated positively with clinical severity and corresponded with histopathological changes. Moreover, anti-TNF-α neutralizing antibody inhibited the development of LPS-accelerated CIA and a single injection of recombinant mouse TNF-α induced increases in anti-CII antibody concentrations, suggesting TNF-α may contribute to the development of arthritis by both initiation of inflammation and production of autoantibodies. These data suggest that exacerbation of RA by LPS is associated with rapid and continuous production of inflammatory mediators and autoantibodies.

Role of inflammatory factors and adipose tissue in pathogenesis of rheumatoid arthritis and osteoarthritis. Part II: Inflammatory background of osteoarthritis

Osteoarthritis is the most common rheumatoid disease. It may develop as a primary disease of the motor organ or as a secondary one in the course of other inflammatory joint diseases. Similarly to the majority of rheumatoid conditions, the pathogenesis of osteoarthritis has not been fully explained. The fact that its development is determined by adipocytokines, which are inflammatory mediators produced in the adipose tissue, has been known for several years. Additionally, inflammatory processes taking place in the adipose tissue that lead to degenerative changes are the main subject of studies conducted by various immunological laboratories. Degenerative changes in patients with osteoarthritis are frequently accompanied by secondary inflammation with cellular infiltrations in the synovial membrane. In numerous cases, the intensification of inflammatory lesions resembles changes seen in arthritis, particularly in rheumatoid arthritis, which inhibits the differential diagnosis by means of imaging examinations. This may have significant clinical implications, e.g. with respect to sonography, which is the basic imaging examination in diagnosing rheumatoid arthritis, monitoring the efficacy of implemented treatment or confirming remission. This article discusses the pathogenesis of three elements of osteoarthritis, i.e. synovitis (due to the difficulties in differentiation of synovitis in the course of osteoarthritis and in rheumatoid arthritis) as well as osteophytes and subchondral sclerosis (due to the significance of the inflammatory factor in their development).

Towards a role of ultrasound in children with juvenile idiopathic arthritis

US is a powerful tool for the assessment of joint synovitis in children with JIA and has been shown to be more accurate than clinical examination in detecting synovial disease. Recent studies have documented the presence of US-detected synovial pathology in children with JIA in clinical remission. US assessment enables the differentiation of joint synovitis from tenosynovitis, may help detect enthesitis and is valuable for capturing cartilage damage and early bone erosions. Guidance to local injection therapy represents an important application of US in routine care. Although US has a great potential for diffusion among paediatric rheumatologists, several issues need to be addressed. In particular, a thorough knowledge of US anatomy of joints in growing children is necessary to interpret US findings in JIA patients. The present review examines the potential role of US in the assessment of joint disease in children with JIA.

Extracellular ATP-stimulated macrophages produce macrophage inflammatory protein-2 which is important for neutrophil migration

Macrophages are the major source of the chemokines macrophage inflammatory protein-2 (MIP-2) and keratinocyte-derived chemokine (KC), which play a major role in neutrophil migration to sites of inflammation. Although extracellular ATP from inflammatory tissues induces several immune responses in macrophages, it is unclear whether ATP-stimulated macrophages affect neutrophil migration. Therefore, the aim of the present study was to investigate the role of ATP-induced MIP-2 production by macrophages. When ATP was injected intraperitoneally into mice, the number of neutrophils within the peritoneal cavity markedly increased, along with the levels of MIP-2 and KC in the peritoneal lavage fluid. Consistent with this, ATP induced MIP-2 production, but not that of KC, by peritoneal exudate macrophages (PEMs) in vitro. This occurred via interactions with the P2X(7) receptor and P2Y(2) receptor. Furthermore, treatment of PEMs with ATP led to the production of reactive oxygen species. The ATP-induced MIP-2 production was inhibited by treatment with the antioxidant N-acetyl-l-cysteine. Also, MIP-2 production was inhibited by pre-incubating PEMs with inhibitors of extracellular signal-regulated kinase 1/2 or p38 mitogen-activated protein kinase. The MIP-2 neutralization reduced the increase in neutrophil numbers observed in ATP-treated mice. Taken together, these results suggest that increased production of reactive oxygen species by ATP-stimulated macrophages activates the signalling pathways that promote MIP-2 production which, in turn, induces neutrophil migration.

What did we learn on host's genetics by studying large cohorts of HIV-1-infected patients in the genome-wide association era?

PURPOSE OF REVIEW

Genome-wide association studies (GWASs) performed in large cohorts of HIV-1-infected patients have shown that high throughput genomics can add valuable information in understanding disease progression. We report recent information gathered in the international field during the last few years and revisit the importance of well documented cohorts for genotype-phenotype association studies.

RECENT FINDINGS

The majority of GWASs in the HIV-1 field found that viral loads and disease progression are under the control of variants located in the major histocompatibility complex (MHC) in untreated patients. Although these experiments brought a new and more objective vision of genotype-phenotype correlations in HIV-1 disease, they also pointed out that less than 15% of the observed phenotypic variability can be explained as common genetic variants. Most of the studies have included mainly white patients and the few studies performed in Africans are underpowered but suggest that MHC is probably not the only genetic determinant influencing disease progression in this population.

SUMMARY

Although the first results of the GWASs in HIV disease look as a confirmation of previous findings, high throughput agnostic genomics entered the field of chronic infectious diseases and will probably unveil new genotype-phenotype associations in the future. Networks between existing cohorts leading to 'virtual mega-cohorts' will be necessary to increase the probability to discover new genetic pathways important for HIV disease. Finally, predictive models including genetic information for clinical usage is another challenge in HIV disease genetics.

Targeting chemokine receptors in chronic inflammatory diseases: an extensive review

The traffic of the different types of immune cells is an important aspect in the immune response. Chemokines are soluble peptides that are able to attract cells by interaction with chemokine receptors on their target cells. Several different chemokines and receptors exist enabling the specific trafficking of different immune cells. In chronic inflammatory disorders there is abundance of immune cells present at the inflammatory site. This review focuses on the role of chemokine receptors in chronic inflammatory disorders of the lungs, intestine, joints, skin and nervous system and the potential of targeting these receptors as therapeutic intervention in these disorders.

CXCL8 and CCL5 expression in synovial fluid and blood serum in patients with osteoarthritis of the knee

Chemokines proved able to induce release of enzymes relevant in cartilage damage. The present study addressed the levels of CXCL8 and CCL5 and the potential role of these chemokines in predicting the morphological changes in the course of osteoarthritis (OA). Synovial fluid (SF) and blood serum were obtained from 20 patients undergoing knee replacement surgery because of OA. For comparison, samples were also obtained from another 20 patients during diagnostic or therapeutic arthroscopy performed because of knee injury. The samples were analyzed for CXCL8 and CCL5 using enzyme-linked immunosorbent assay. SF from the group with OA showed significantly (p = 0.024) increased levels of CXCL8 when compared with the group after knee injury. We have not demonstrated any significant correlation between chemokine expression and clinical or radiological signs of OA. Mediators of inflammation are the potential predicting factors of OA, however, with respect to examined chemokines development of a diagnostic test can be limited by the low serum concentration and lack of correlation with clinical and radiological signs of the disease.

The chemokine receptor CXCR2 ligand KC (CXCL1) mediates neutrophil recruitment and is critical for development of experimental Lyme arthritis and carditis

Deletion of the chemokine receptor CXCR2 prevents the recruitment of neutrophils into tissues and subsequent development of experimental Lyme arthritis. Following footpad inoculation of Borrelia burgdorferi, the agent of Lyme disease, expression of the CXCR2 ligand KC (CXCL1) is highly upregulated in the joints of arthritis-susceptible mice and is likely to play an important role in the recruitment of neutrophils to the site of infection. To test this hypothesis, we infected C3H KC(-/-) mice with B. burgdorferi and followed the development of arthritis and carditis. Ankle swelling was significantly attenuated during the peak of arthritis in the KC(-/-) mice. Arthritis severity scores were significantly lower in the KC(-/-) mice on days 11 and 21 postinfection, with fewer neutrophils present in the inflammatory lesions. Cardiac lesions were also significantly decreased in KC(-/-) mice at day 21 postinfection. There were, however, no differences between C3H wild-type and KC(-/-) mice in spirochete clearance from tissues. Two other CXCR2 ligands, LIX (CXCL5) and MIP-2 (CXCL2), were not increased to compensate for the loss of KC, and the production of several innate cytokines was unaltered. These results demonstrate that KC plays a critical nonredundant role in the development of experimental Lyme arthritis and carditis via CXCR2-mediated recruitment of neutrophils into the site of infection.