Expression of Toll-like receptors 2 and 4 is increased in peripheral blood and synovial fluid monocytes of patients with enthesitis-related arthritis subtype of juvenile idiopathic arthritis

Synovial monocytes contribute to chronic inflammation in childhood-onset arthritis via IL-6/STAT signalling and cell-cell interactions

Introduction

Monocytes are key effector cells in inflammatory processes. We and others have previously shown that synovial monocytes in childhood-onset arthritis are activated. However, very little is known about how they contribute to disease and attain their pathological features. Therefore, we set out to investigate the functional alterations of synovial monocytes in childhood-onset arthritis, how they acquire this phenotype, and whether these mechanisms could be used to tailorize treatment.

Methods

The function of synovial monocytes was analysed by assays believed to reflect key pathological events, such as T-cell activation-, efferocytosis- and cytokine production assays using flow cytometry in untreated oligoarticular juvenile idiopathic arthritis (oJIA) patients (n=33). The effect of synovial fluid on healthy monocytes was investigated through mass spectrometry and functional assays. To characterize pathways induced by synovial fluid, we utilized broad-spectrum phosphorylation assays and flow cytometry, as well as inhibitors to block specific pathways. Additional effects on monocytes were studied through co-cultures with fibroblast-like synoviocytes or migration in transwell systems.

Results

Synovial monocytes display functional alterations with inflammatory and regulatory features, e.g., increased ability to induce T-cell activation, resistance to cytokine production following activation with LPS and increased efferocytosis. In vitro, synovial fluid from patients induced the regulatory features in healthy monocytes, such as resistance to cytokine production and increased efferocytosis. IL-6/JAK/STAT signalling was identified as the main pathway induced by synovial fluid, which also was responsible for a majority of the induced features. The magnitude of synovial IL-6 driven activation in monocytes was reflected in circulating cytokine levels, reflecting two groups of low vs. high local and systemic inflammation. Remaining features, such as an increased ability to induce T-cell activation and markers of antigen presentation, could be induced by cell-cell interactions, specifically via co-culture with fibroblast-like synoviocytes.

Conclusions

Synovial monocytes in childhood-onset arthritis are functionally affected and contribute to chronic inflammation, e.g., via promoting adaptive immune responses. These data support a role of monocytes in the pathogenesis of oJIA and highlight a group of patients more likely to benefit from targeting the IL-6/JAK/STAT axis to restore synovial homeostasis.

Signals and Mechanisms Regulating Monocyte and Macrophage Activation in the Pathogenesis of Juvenile Idiopathic Arthritis

Monocytes (Mos) and macrophages (Mφs) are key players in the innate immune system and are critical in coordinating the initiation, expansion, and regression of many autoimmune diseases. In addition, they display immunoregulatory effects that impact inflammation and are essential in tissue repair and regeneration. Juvenile idiopathic arthritis (JIA) is an umbrella term describing inflammatory joint diseases in children. Accumulated evidence suggests a link between Mo and Mφ activation and JIA pathogenesis. Accordingly, topics regarding the signals and mechanisms regulating Mo and Mφ activation leading to pathologies in patients with JIA are of great interest. In this review, we critically summarize recent advances in the understanding of how Mo and Mφ activation is involved in JIA pathogenesis and focus on the signaling pathways and mechanisms participating in the related cell activation processes.

Type I Interferons in the Pathogenesis and Treatment of Autoimmune Diseases

Type I interferons (IFN-Is) are a very important group of cytokines that are produced by innate immune cells but also act on adaptive immune cells. IFN-Is possess antiviral, antitumor, and anti-proliferative effects, as well are associated with the initiation and maintenance of autoimmune disorders. Studies have shown that aberrantly expressed IFN-Is and/or type I IFN-inducible gene signatures in the serum or tissues of patients with autoimmune disorders are linked to their pathogenesis, clinical manifestations, and disease activity. Type I interferonopathies with mutations in genes impacting the type I IFN signaling pathway have shown symptoms and characteristics similar to those of systemic lupus erythematosus (SLE). Furthermore, both interventions in animal models and clinical trials of therapies targeting the type I IFN signaling pathway have shown efficacy in the treatment of autoimmune diseases. Our review aims to summarize the functions and targeted therapies (as well as clinical trials) of IFN-Is in both adult and pediatric autoimmune diseases, such as SLE, pediatric SLE (pSLE), rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), juvenile dermatomyositis (JDM), Sjögren syndrome (SjS), and systemic sclerosis (SSc), discussing the potential abnormal regulation of transcription factors and epigenetic modifications and providing a potential mechanism for pathogenesis and therapeutic strategies for future clinical use.

Similarities and Differences Between Juvenile and Adult Spondyloarthropathies

Spondyloarthritis (SpA) encompasses a broad spectrum of conditions occurring from childhood to middle age. Key features of SpA include axial and peripheral arthritis, enthesitis, extra-articular manifestations, and a strong association with HLA-B27. These features are common across the ages but there are important differences between juvenile and adult onset disease. Juvenile SpA predominantly affects the peripheral joints and the incidence of axial arthritis increases with age. Enthesitis is important in early disease. This review article highlights the similarities and differences between juvenile and adult SpA including classification, pathogenesis, clinical features, imaging, therapeutic strategies, and disease outcomes. In addition, the impact of the biological transition from childhood to adulthood is explored including the importance of musculoskeletal and immunological maturation. We discuss how the changes associated with adolescence may be important in explaining age-related differences in the clinical phenotype between juvenile and adult SpA and their implications for the treatment of juvenile SpA.

TLR expression profiles are a function of disease status in rheumatoid arthritis and experimental arthritis

The role of the innate immune system has been established in the initiation and perpetuation of inflammatory disease, but less attention has been paid to its role in the resolution of inflammation and return to homeostasis. Toll-like receptor (TLR) expression profiles were analysed in tissues with differing disease status in rheumatoid arthritis (RA), ankylosing spondylitis (AS), and in experimental arthritis. TLR gene expression was measured in whole blood and monocytes, before and after TNF blockade. In RA and osteoarthritis synovia, the expression of TLRs was quantified by standard curve qPCR. In addition, four distinct stages of disease were defined and validated in collagen-induced arthritis (CIA), the gold standard animal model for RA - pre-onset, early disease, late disease and immunised mice that were resistant to the development of disease. TLR expression was measured in spleens, lymph nodes, blood cells, liver and the paws (inflamed and unaffected). In RA whole blood, the expression of TLR1, 4 and 6 was significantly reduced by TNF blockade but the differences in TLR expression profiles between responders and non-responders were less pronounced than the differences between RA and AS patients. In RA non-responders, monocytes had greater TLR2 expression prior to therapy compared to responders. The expression of TLR1, 2, 4 and 8 was higher in RA synovium compared to control OA synovium. Circulating cytokine levels in CIA resistant mice were similar to naïve mice, but anti-collagen antibodies were similar to arthritic mice. Distinct profiles of inflammatory gene expression were mapped in paws and organs with differing disease status. TLR expression in arthritic paws tended to be similar in early and late disease, with TLR1 and 2 moderately higher in late disease. TLR expression in unaffected paws varied according to gene and disease status but was generally lower in resistant paws. Disease status-specific profiles of TLR expression were observed in spleens, lymph nodes, blood cells and the liver. Notably, TLR2 expression rose then fell in the transition from naïve to pre-onset to early arthritis. TLR gene expression profiles are strongly associated with disease status. In particular, increased expression in the blood precedes clinical manifestation.

Patients with enthesitis related arthritis show similar monocyte function pattern as seen in adult axial spondyloarthropathy

BACKGROUND

Axial SpA and Enthesitis related arthritis (ERA) patients show strong HLA-B27 association, gut dysbiosis, high toll like receptor (TLR)2 and 4 expression on monocytes, pro-inflammatory cytokine production and elevated levels of TLR4 endogenous ligands [tenascin-c (TNC) and myeloid related protein (MRP)8/14] in serum. Hence, we aimed to understand if these diseases have similar or different monocyte response.

METHODS

Fifty adult axial SpA, 52 ERA patients and 25 healthy controls (HC) were enrolled. Cytokine-producing monocyte frequency before and after stimulation with lipopolysaccharide (LPS), peptidoglycan (PG), TNC or MRP8 were measured in whole blood (WB) and synovial fluid mononuclear cells (SFMC) by flow cytometry. Also, IL-6, TNF, MMP3, TNC and MRP8/14 levels were measured in unstimulated and TLR ligand stimulated WB cultures supernatant by ELISA. Finally, the mRNA expression levels of TNF and IL-6 were measured post stimulation with LPS, TNC and MRP8.

RESULTS

At baseline, ERA and axial SpA patients showed similar TNF-α producing monocyte frequency which was higher than HC. MRP8 simulation led to increased TNF-α producing monocyte frequency in ERA than axial SpA. TNC and MRP8 stimulation led to similar IL-6 producing monocyte frequency in axial SpA and ERA patients. Baseline TNF and IL-6 producing monocyte frequency also modestly correlated with disease activity scores. TNF and IL-6 producing monocyte frequency increased in response to TLR stimulation in SFMC from both patients. In culture supernatants, axial SpA and ERA patients showed similar TNF production at baseline. MRP8 and TNC stimulation led to higher TNF production from ERA. Baseline IL-6 and MMP3 production was higher in ERA while TLR stimulation led to similar IL-6 and MMP3 production from axial SpA and ERA. TNC stimulation led to higher MMP3 production in ERA. mRNA expression in response to TLR stimulation was observed to be similar in axial SpA and ERA. TNC production was higher in ERA at baseline, while MRP8/14 production was higher in axial SpA than ERA post stimulation.

CONCLUSION

ERA patients have similar monocyte response to exogenous and endogenous TLR ligands as patients with axial SpA. This suggests that differences between pediatric and adult-onset SpA are minimal and they may have a common pathogenesis.

Role of Stem Cells in Pathophysiology and Therapy of Spondyloarthropathies-New Therapeutic Possibilities?

Considerable progress has been made recently in understanding the complex pathogenesis and treatment of spondyloarthropathies (SpA). Currently, along with traditional disease modifying anti-rheumatic drugs (DMARDs), TNF-α, IL-12/23 and IL-17 are available for treatment of such diseases as ankylosing spondylitis (AS) and psoriatic arthritis (PsA). Although they adequately control inflammatory symptoms, they do not affect the abnormal bone formation processes associated with SpA. However, the traditional therapeutic approach does not cover the regenerative treatment of damaged tissues. In this regards, stem cells may offer a promising, safe and effective therapeutic option. The aim of this paper is to present the role of mesenchymal stromal cells (MSC) in pathogenesis of SpA and to highlight the opportunities for using stem cells in regenerative processes and in the treatment of inflammatory changes in articular structures.

Gut microbiome in children with enthesitis-related arthritis in a developing country and the effect of probiotic administration

In Asia, enthesitis-related arthritis (ERA) is the most frequent category of juvenile idiopathic arthritis. ERA has a strong association with human leucocyte antigen (HLA)-B27 and subclinical gut inflammation. In an HLA-B27 transgenic rat model, the presence of Bacteroides bacteria in the gut appears to cause spondyloarthropathy (SpA). Thus, we studied gut microbiota in children with ERA. Stool specimens from 33 patients with ERA and 14 age-matched healthy controls were studied; none had any gastrointestinal symptom, or had received a drug known to affect gut motility or microbiota in the preceding 6 weeks. From each specimen, a cDNA library for the V3 region of bacterial 16S rRNA was subjected to high-throughput, massively parallel sequencing. Relationship of the specimens was studied using principal co-ordinate analysis (PCoA), and abundances of various bacterial taxa and alpha diversity were compared between groups. In eight patients, a repeat faecal specimen was studied after 12 weeks of probiotic therapy. The 55 specimens yielded a median (range) of 397 315 (102 093-1 502 380) high-quality reads each. In PCoA, gut microbiota from ERA showed a wider dispersion than those from controls. In patients, families Bacteroidaceae and Enterobacteriaceae were more abundant and Prevotellaceae were less abundant than in controls. Also, genera Bacteroides, Entercoccus and Klebsiella were over-represented and genus Prevotella was under-represented in ERA patients. Probiotic therapy led to a non-significant increase in Prevotellaceae. Patients with ERA have a dysbiosis in the gut, with increased abundance of Bacteroides and reduction of Prevotella. Probiotic supplementation in a subset of patients did not reverse these changes significantly.

Juvenile Idiopathic Arthritis: Diagnosis and Treatment

Juvenile idiopathic arthritis is a broad term that describes a clinically heterogeneous group of arthritides of unknown cause, which begin before 16 years of age. This term encompasses several disease categories, each of which has distinct presentation, clinical manifestations, and, presumably, genetic background and etiopathogenesis. Although none of the available drugs has curative potential, prognosis has greatly improved as a result of substantial progresses in disease management. The most important new development has been the introduction of the biologic medications, which constitute a valuable treatment option for patients who are resistant to conventional antirheumatic agents. Further insights into the disease pathogenesis and treatment will be provided by the continuous advances in understanding of the mechanisms related to the immune response and inflammatory process, and by the development of new drugs that are capable of selectively inhibiting single molecules or pathways.

Atopy in children with the enthesitis-related arthritis (ERA) subtype of juvenile idiopathic arthritis is associated with a worse outcome

We aimed to assess the influence of co-existing atopy on the prognosis of enthesitis-related arthritis (ERA). Patients diagnosed with ERA between March 2006 and August 2012 were enrolled in a prospective cohort study and followed for 2 years. Management of patients was evaluated using the American College of Rheumatology (ACR) pediatric (Pedi) 30/50/70 criteria and laboratory variables. A total of 151 ERA patients were enrolled at diagnosis and were divided into those with atopy (n = 62) and those without (n = 89). When compared with the non-atopic group, atopic patients had significantly more active joints at disease onset (4.72 vs. 3.75), more joints with limitation of motion (LOM) (1.45 vs. 0.87), more painful joints (3.61 vs. 2.80), and more swollen joints (1.02 vs. 0.69) (p < 0.05 for all comparisons). At 3, 6, 12, 18, and 24 months, fewer ERA patients with atopy reached the ACR Pedi 50 and 70 criteria (at 3 months, 25.8 vs. 60.7 % and 11.3 vs. 34.8 %, respectively; at 6 months, 50 vs. 77.5 % and 22.6 vs. 58.4 %, respectively; at 12 months, 53.2 vs. 70.8 % and 33.9 vs. 55.1 %, respectively; at 18 months, 62.9 vs. 86.5 % and 56.5 vs. 78.7 %, respectively; at 24 months, 66.1 vs. 89.9 % and 61.3 vs. 78.7 %, respectively; all p < 0.05). During the 2 years of follow-up, the number of flares was significantly higher in ERA patients with co-existing atopy (1.48 vs. 0.70, p < 0.05).

CONCLUSION

Co-existing atopy in children with ERA may exert an adverse influence on ERA, with atopic patients manifesting more active disease at diagnosis and poorer outcome. \

Enthesitis-related arthritis

Juvenile idiopathic arthritis (JIA) is the most common chronic arthritis of childhood. Currently, it is characterized by seven categories. The enthesitis-related arthritis (ERA) category usually affects boys older than 6 years and presents with lower limb asymmetrical arthritis associated with enthesitis. Later, these children can develop inflammatory lumbosacral pain (IBP). These children are at risk of developing acute anterior uveitis. A recently devised disease activity index, Juvenile Spondyloarthropathy Disease Activity Index (JSpADA), has been validated in retrospective cohorts. The corner stone of treatment is NSAIDs, local corticosteroid injections, and exercise. Methotrexate and sulfasalazine can be used for peripheral arthritis while anti-tumor necrosis factor (TNF) agents are sometimes used to treat refractory enthesitis and sacroiliitis. Almost two third of patients with ERA have persistent disease and often have impairments in their quality of life. The presence of hip or ankle arthritis and a family history of spondyloarthropathy or polyarticular joint involvement at onset are associated with poorer prognosis.

Tenascin-C Levels, A Toll-like Receptor 4 Ligand, in Enthesitis-related Arthritis Category of Juvenile Idiopathic Arthritis: A Cross-sectional and Longitudinal Study

OBJECTIVE

Monocytes of children with enthesitis-related arthritis (ERA) show Toll-like receptor 4 (TLR4) overexpression. Tenascin-C (TNC) is an extracellular matrix glycoprotein and acts as an endogenous TLR4 ligand. Thus, we studied the serum and synovial fluid (SF) levels of TNC in children with ERA.

METHODS

TNC was measured in the serum of 80 children with ERA satisfying the International League of Associations for Rheumatology criteria. Fifteen children were followed up while being treated with regular nonsteroidal antiinflammatory drug (NSAID) therapy and levels were reassessed at 3 months. Seventeen paired serum-SF samples and 25 healthy control serum samples were also analyzed. Disease activity was assessed by physician's global assessment (PGA), early morning stiffness (EMS), tender (TJC) and swollen joint counts (SJC), enthesitis score, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).

RESULTS

The mean serum TNC level in patients with active disease (67.1 ± 44.9 ng/ml) was significantly higher than in those with inactive disease (40.6 ± 36.7 ng/ml, p = 0.01) and healthy controls (21 ± 15.2 ng/ml, p < 0.001). Levels of TNC were higher in HLA-B27-positive (58.4 ng/ml) versus -negative disease (20.4 ng/ml, p = 0.01). TNC levels correlated moderately with disease activity: PGA r = 0.4, EMS r = 0.34, TJC r = 0.4, SJC r = 0.46, ESR r = 0.42, and CRP r = 0.32. In receiver-operation characteristic analysis for active versus inactive diseases, TNC [area under the curve (AUC) = 0.754] was equivalent to ESR (AUC = 0.787) and CRP (AUC = 0.789). Regular NSAID therapy led to a significant fall in serum TNC levels at 3 months (p = 0.0003). The SF TNC level was 17.39 ng/ml, significantly lower than the paired serum values (p = 0.01).

CONCLUSION

Serum TNC levels are significantly raised and correlate with various clinical and laboratory variables of disease activity in children with ERA. Regular NSAID therapy reduces the TNC levels, probably related to controlling disease activity.

Advances in biomarkers for paediatric rheumatic diseases

The search for biomarkers in paediatric rheumatic diseases, particularly juvenile idiopathic arthritis (JIA), childhood lupus nephritis (LN), and juvenile idiopathic inflammatory myopathies (JIIMs) is attracting increased interest. In JIA, a number of biomarkers have shown potential for predicting clinical phenotype, disease activity and severity, clinical remission and relapse, response to treatment, and disease course over time. In systemic JIA, measurement of biomarkers that reflect the degree of activation and expansion of T cells and macrophages might be helpful for detecting subclinical macrophage activation syndrome. Urine biomarkers for childhood LN hold promise for facilitating early diagnosis and improving disease monitoring and assessment of response to therapy. Myositis-specific autoantibodies define distinct serological subgroups of JIIMs, albeit with similar clinical features, responses to therapy, and prognoses. Use of biomarkers may potentially help to avoid invasive procedures, such as renal biopsy in systemic lupus erythematosus and muscle biopsy in juvenile dermatomyositis. Incorporation of effective and reliable biomarkers into routine practice might facilitate adoption of a stratified approach to investigation and management, foster the implementation of research into the design of personalized and targeted therapies, and ultimately lead to more rational and effective clinical care.

Aberrant expression of shared master-key genes contributes to the immunopathogenesis in patients with juvenile spondyloarthritis

Association of juvenile spondyloarthritis (jSpA) with the HLA-B27 genotype is well established, but there is little knowledge of other genetic factors with a role in the development of the disease. To date, only a few studies have tried to find those associated genes by obtaining expression profiles, but with inconsistent results due to various patient selection criteria and methodology. The aim of the present study was to identify and confirm gene signatures and novel biomarkers in highly homogeneous cohorts of untreated and treated patients diagnosed with jSpA and other forms of juvenile idiopathic arthritis (JIA) according to ILAR criteria. For the purposes of the research, total RNA was isolated from whole blood of 45 children with jSpA and known HLA genotype, 11 children with oligo- and polyarticular forms of JIA, as well as 12 age and sex matched control participants without diagnosis of inflammatory disease. DNA microarray gene expression was performed in 11 patients with jSpA and in four healthy controls, along with bioinformatical analysis of retrieved data. Carefully selected differentially expressed genes where analyzed by qRT-PCR in all participants of the study. Microarray results and bioinformatical analysis revealed 745 differentially expressed genes involved in various inflammatory processes, while qRT-PCR analysis of selected genes confirmed data universality and specificity of expression profiles in jSpA patients. The present study indicates that jSpA could be a polygenic disease with a possible malfunction in antigen recognition and activation of immunological response, migration of inflammatory cells and regulation of the immune system. Among genes involved in these processes TLR4, NLRP3, CXCR4 and PTPN12 showed almost consistent expression in study patients diagnosed with jSpA. Those genes and their products could therefore potentially be used as novel biomarkers, possibly predictive of disease prognosis and response to therapy, or even as a target for new therapeutic approaches.

ZAP-70 genotype disrupts the relationship between microbiota and host, leading to spondyloarthritis and ileitis in SKG mice

OBJECTIVE

The spondyloarthritides share genetic susceptibility, interleukin-23 (IL-23) dependence, and the involvement of microbiota. The aim of the current study was to elucidate how host genetics influence gut microbiota and the relationship between microbiota and organ inflammation in spondyloarthritides.

METHODS

BALB/c ZAP-70(W163C) -mutant (SKG) mice, Toll-like receptor 4 (TLR-4)-deficient SKG mice, and wild-type BALB/c mice were housed under specific pathogen-free conditions. SKG and wild-type BALB/c mice were maintained under germ-free conditions, and some of these mice were recolonized with altered Schaedler flora. All of the mice were injected intraperitoneally with microbial β-1,3-glucan (curdlan). Arthritis, spondylitis, and ileitis were assessed histologically. Microbiome composition was analyzed in serial fecal samples obtained from mice that were co-housed beginning at the time of weaning, using 454 pyrosequencing. Infiltrating cells and cytokines in the peritoneal cavity were measured by flow cytometry and enzyme-linked immunosorbent assay. Cytokine, endoplasmic reticulum (ER) stress marker, and tight junction protein transcription was measured by quantitative real-time polymerase chain reaction.

RESULTS

Microbiota content and response to curdlan varied according to whether T cell receptor signal strength was normal or was impaired due to the ZAP-70(W163C) mutation. Curdlan triggered acute inflammation regardless of the presence of the SKG allele or microbiota. However, no or limited microbiota content attenuated the severity of arthritis. In contrast, ileal IL-23 expression, ER stress, lymph node IL-17A production, goblet cell loss, and ileitis development were microbiota-dependent. Ileitis but not arthritis was suppressed by microbiota transfer upon co-housing SKG mice with wild-type BALB/c mice, as well as by TLR-4 deficiency.

CONCLUSION

The interaction between immunogenetic background and host microbiota leads to an IL-23-dependent loss of mucosal function, triggering ileitis in response to curdlan.

Expression of toll-like receptors 3, 7, and 9 in peripheral blood mononuclear cells from patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown aetiology. The results of experimental studies point to the involvement of innate immunity receptors-toll-like receptors (TLR)-in the pathogenesis of the disease. The aim of the study was to assess the expression of TLR3, 7, and 9 in the population of peripheral blood mononuclear cells (PBMC) and in B lymphocytes (CD19(+)), T lymphocytes (CD4(+) and CD8(+)) using flow cytometry. The study group included 35 patients with SLE and 15 healthy controls. The patient group presented a significantly higher percentage of TLR3- and TLR9-positive cells among all PBMCs and their subpopulations (CD3(+), CD4(+), CD8(+), and CD19(+) lymphocytes) as well as TLR7 in CD19(+) B-lymphocytes, compared to the control group. There was no correlation between the expression of all studied TLRs and the disease activity according to the SLAM scale, and the degree of organ damage according to the SLICC/ACR Damage Index. However, a correlation was observed between the percentage of various TLR-positive cells and some clinical (joint lesions) and laboratory (lymphopenia, hypogammaglobulinemia, anaemia, and higher ESR) features and menopause in women. The results of the study suggest that TLR3, 7, and 9 play a role in the pathogenesis of SLE and have an impact on organ involvement in SLE.

Do changing toll-like receptor profiles in different layers and grades of osteoarthritis cartilage reflect disease severity?

OBJECTIVE

Cartilage degeneration in osteoarthritis (OA) leads to release of potential danger signals. The aim of our study was to profile OA cartilage for the Toll-like receptor (TLR) danger signal receptors.

METHODS

Osteochondral cylinders from total knee replacements were graded using OA Research Society International score and stained for proteoglycans, collagenase-cleaved type II collagen, and TLR 1-10, which were analyzed histomorphometrically.

RESULTS

Grade 1 OA lesions contained 22%-55% TLR 1-9-positive cells in the surface zone, depending on the TLR type. In Grade 2 TLR, immunoreactivity was 60%-100% (p < 0.01) and it was even higher in Grades 3 and 4 (p < 0.01 vs Grade 1). TLR-positive cells in Grade 1 middle zone were low, 0-19.9%, but were 5.1%-32.7% in Grade 2 (p < 0.01) and 34%-83% in Grades 3-4 samples (p < 0.001). TLR values in Grade 5 were low (14.3%-28.7%; p < 0.001). In Grades 3-4 OA, cartilage matrix stained strongly for TLR. In Grade 1, COL2-3/4M was restricted to chondrocytes, but was increasingly seen in matrix upon progress of OA to Grade 4, and then declined.

CONCLUSION

Cells in the gliding surface zone are fully equipped with TLR in mild OA. Their proportion increases and extends to the middle or even the deep zone, reflecting OA progression. COL2A-3/4M staining suggests Endo180-mediated intake for intralysosomal degradation by cathepsins in Grade 1, but in higher grades this chondrocyte-mediated clearance fails and the matrix demonstrates extensive collagenase-induced damage. Detached and/or partially degraded matrix components can then act as endogenous danger signals (damage-associated molecular patterns or DAMP) and stimulate increasingly TLR-equipped chondrocytes to inflammation. At the peak inflammatory response, soluble TLR may exert negative feedback, explaining in part the low TLR levels in Grade 5 OA.

Membrane-bound toll-like receptors are overexpressed in peripheral blood and synovial fluid mononuclear cells of enthesitis-related arthritis category of juvenile idiopathic arthritis (JIA–ERA) patients and lead to secretion of inflammatory mediators

We examined expression and function of TLRs in enthesitis-related arthritis (ERA) patients. RNA levels of TLR1, TLR3, and TLRs 5–8 were measured in 24 ERA peripheral blood mononuclear cells (PBMC), 18 synovial fluid mononuclear cells (SFMC), and IRAK1, IRAK4, TRIF, TRAF3, and TRAF6 in 18 PBMC and 10 SFMC. IL-6 and IL-8 were measured in supernatants from ERA PBMC (n=7), SFMC (n=3), and healthy PBMC (n=5) cultured with ligands for TLR1/2 (Pam 3-cys), TLR3 (polyI:C), TLR5 (flagellin), and TLR2/6 (zymosan). TLRs 1, 3, 5, and 6 were measured in whole blood (n=20 ERA, seven healthy) and SFMC (n=2) by flow cytometry. ERA PBMC compared to healthy PBMC and SFMC compared to ERA PBMC had higher RNA expression of TLR1, TLR3, TLR5, TLR6, IRAK1, IRAK4, TRIF, TRAF3, and TRAF6. TLR7 and TLR8 RNA expression was similar in all study groups. IL-6 and IL-8 levels were higher in stimulated ERA SFMC compared to ERA PBMC and in ERA PBMC compared to control PBMC. TLRs 1, 3, and 6 were also overexpressed at the protein level.

Lack of association of single nucleotide polymorphisms in toll-like receptors 2 and 4 with enthesitis-related arthritis category of juvenile idiopathic arthritis in Indian population

Toll-like receptors 2 and 4 are over expressed in patients with enthesitis-related arthritis and cause increased production of pro-inflammatory cytokines. This aberrant functioning could be due to polymorphisms in TLR2 and TLR4. Hence, we genotyped ERA patients for Arg753Gln and Arg677Trp polymorphism in TLR2 gene and Asp299Gly and Thr399Ile polymorphism in TLR4 gene. DNA was extracted from blood from ERA patients and healthy controls. All four polymorphisms were studied by PCR-RFLP method. 200 healthy controls and 97 ERA patients were enrolled. All healthy controls and patients had wild-type allele for Arg753Gln and Arg677Trp TLR2 polymorphism. Regarding TLR4, Asp299Gly polymorphism A allele frequency was 90 % in controls and 96 % in patients (OR 2.7, 95 % CI 0.81-8.8). GG homozygous genotype was detected in one healthy control and was absent from patients. The TLR4 Thr399Ileu variant was not detected in patients. Out of 200 healthy controls, 10 were heterozygous (5 %) and only one was homozygous for rare variant (0.5 %). Polymorphisms in TLR2 and TLR4 are not associated with ERA.

The potential importance of Toll-like receptors in ankylosing spondylitis

Cells involved in innate immunity scan for pathogens via extracellular and intracellular (endosomal) pattern recognition receptors (PRRs). Engagement of PRRs by a specific ligand results in downstream activation of intracellular inflammatory cascades. There is emerging evidence indicating that one class of PRR, the Toll-like receptor (TLR) plays a potential role in the pathogenesis of spondyloarthropathies. Since certain Gram-negative bacteria are known to act as triggers for reactive arthritis, there has been much interest in studying the role of TLRs in spondyloarthropathies. In this article, we introduce the immunology of TLRs followed by a discussion of their potential role in ankylosing spondylitis.

Increased expression of Toll-like receptors by monocytes and natural killer cells in ANCA-associated vasculitis

Introduction

Toll-like receptors (TLRs) are a family of receptors that sense pathogen associated patterns such as bacterial cell wall proteins. Bacterial infections are associated with anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV). Here, we assessed the expression of TLRs 2, 4, and 9 by peripheral blood leukocytes from patients with AAV, and investigated TLR mediated responses ex vivo.

Methods

Expression of TLRs was determined in 38 AAV patients (32 remission, 6 active disease), and 20 healthy controls (HC). Membrane expression of TLRs 2, 4, and 9, and intracellular expression of TLR9 by B lymphocytes, T lymphocytes, NK cells, monocytes and granulocytes was assessed using 9-color flowcytometry. Whole blood from 13 patients and 7 HC was stimulated ex vivo with TLR 2, 4 and 9 ligands and production of cytokines was analyzed.

Results

In patients, we observed increased proportions of TLR expressing NK cells. Furthermore, patient monocytes expressed higher levels of TLR2 compared to HC, and in a subset of patients an increased proportion of TLR4⁺ monocytes was observed. Monocytes from nasal carriers of Staphylococcus aureus expressed increased levels of intracellular TLR9. Membrane expression of TLRs by B lymphocytes, T lymphocytes, and granulocytes was comparable between AAV patients and HC. Patients with active disease did not show differential TLR expression compared to patients in remission. Ex vivo responses to TLR ligands did not differ significantly between patients and HC.

Conclusions

In AAV, monocytes and NK cells display increased TLR expression. Increased TLR expression by these leukocytes, probably resulting from increased activation, could play a role in disease (re)activation.