Lungs, joints and immunity against citrullinated proteins in rheumatoid arthritis

Prevention of rheumatoid arthritis using a familial predictive medicine approach

Most of the chronic-degenerative diseases deserve a very early recognition of symptoms and signs for the earliest secondary prevention, which could be also very useful in many cases for the most precocious clinical approach. The periodic monitoring of a subject at risk of a specific disease, because of genomic predisposition by predictive medicine approach, may help to earlier detection of onset and/or the progression of the pathology itself, through intra-individual monitoring. This is particularly the case of rheumatoid arthritis (RA) for which an early diagnosis is undoubtedly the first step to ensure the most proper therapy for the patient. Thus, the earlier identification of individuals at high risk of RA could lead to ultra-preventive strategies to start for the best lifestyle performances and/or for any other effective therapeutic interventions to contrast the onset, and/or the evolution of the putative RA. This will also optimize both costs and medical resources, according to the health care policies of many countries.

A citrullinated antigenic vaccine in treatment of autoimmune arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease triggered by antigenic peptides with environmental and genetic risk factors. It has been shown that antigen-specific targeting could be a promising therapeutical strategy for RA by restoring immune tolerance to self-antigens without compromising normal immunity. Citrullination of antigens enhances antigenic properties and induces autoimmune responses. Here, we showed that citrullinated antigenic (citAg) vaccine ameliorated collagen-induced arthritis with decreased T-helper 1 (Th1) and Th17 cells, downregulated proinflammatory cytokines including interlukin-6 and tumor necrosis factor-α, and inhibited antigen recall responses. B cell receptor sequencing further revealed that citAg vaccine could dampen the dysregulated V(D)J recombination, restoring the immune repertoire. Taken together, the results demonstrated that citAg vaccine might have a therapeutic effect on RA.

Associations of upper respiratory mucosa microbiota with Rheumatoid arthritis, autoantibodies, and disease activity

The lung is recognized as a site for initiating the formation of self-antigen and autoimmune responses in rheumatoid arthritis (RA). We aimed to investigate the association of upper respiratory microbiota with RA, autoantibody production, and disease activity. Forty-six patients with RA and 17 controls were examined. Nasopharyngeal swab samples were sequenced for microbiome profiling using the V3-V4 region of the 16S rRNA gene. The microbial diversity and relative abundance were compared between RA patients and controls. Correlation analyses were conducted to evaluate the relationship between microbial abundance and clinical markers such as autoantibodies and disease activity. Microbial diversity analysis revealed no major differences between RA patients and healthy controls. However, beta diversity analysis indicated a subtle distinction in microbial composition (unweighted UniFrac distance) between the two groups (P = 0.03), hinting at a minor subset of microbiota associated with disease status. Differential abundance analysis uncovered specific taxa at various taxonomic levels, including Saccharibacteria (TM7) [O-1] (PFDR = 2.53 × 10-2), TM7 [F-1] (PFDR = 5.20 × 10-3), Microbacterium (PFDR = 3.37 × 10-4), and Stenotrophomonas (PFDR = 2.57 × 10-3). The relative abundance of ten genera correlated significantly with anti-cyclic citrullinated peptide (anti-CCP) antibody levels (PFDR < 0.05) and 11 genera were significantly associated with disease activity markers, including ESR, CRP, DAS28-ESR, and DAS-CRP (PFDR < 0.05). In particular, Saccharibacteria TM7 [G-3] and Peptostreptococcaceae [XI] [G-1] were correlated with all disease activity biomarkers. Dysbiosis in the upper respiratory mucosa is associated with RA, anti-CCP antibody levels, and disease activity.

Mid1 promotes synovitis in rheumatoid arthritis via ubiquitin-dependent post-translational modification

INTRODUCTION

Current anti-rheumatic drugs are primarily modulating immune cell activation, yet their effectiveness remained suboptimal. Therefore, novel therapeutics targeting alternative mechanisms, such as synovial activation, is urgently needed.

OBJECTIVES

To explore the role of Midline-1 (Mid1) in synovial activation.

METHODS

NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice were used to establish a subcutaneous xenograft model. Wild-type C57BL/6, Mid1-/-, Dpp4-/-, and Mid1-/-Dpp4-/- mice were used to establish a collagen-induced arthritis model. Cell viability, cell cycle, qPCR and western blotting analysis were used to detect MH7A proliferation, dipeptidyl peptidase-4 (DPP4) and Mid1 levels. Co-immunoprecipitation and proteomic analysis identified the candidate protein of Mid1 substrates. Ubiquitination assays were used to determine DPP4 ubiquitination status.

RESULTS

An increase in Mid1, an E3 ubiquitin ligase, was observed in human RA synovial tissue by GEO dataset analysis, and this elevation was confirmed in a collagen-induced mouse arthritis model. Notably, deletion of Mid1 in a collagen-induced arthritis model completely protected mice from developing arthritis. Subsequent overexpression and knockdown experiments on MH7A, a human synoviocyte cell line, unveiled a previously unrecognized role of Mid1 in synoviocyte proliferation and migration, the key aspects of synovial activation. Co-immunoprecipitation and proteomic analysis identified DPP4 as the most significant candidate of Mid1 substrates. Mechanistically, Mid1 promoted synoviocyte proliferation and migration by inducing ubiquitin-mediated proteasomal degradation of DPP4. DPP4 deficiency led to increased proliferation, migration, and inflammatory cytokine production in MH7A, while reconstitution of DPP4 significantly abolished Mid1-induced augmentation of cell proliferation and activation. Additionally, double knockout model showed that DPP4 deficiency abolished the protective effect of Mid1 defect on arthritis.

CONCLUSION

Overall, our findings suggest that the ubiquitination of DPP4 by Mid1 promotes synovial cell proliferation and invasion, exacerbating synovitis in RA. These results reveal a novel mechanism that controls synovial activation, positioning Mid1 as a promising target for therapeutic intervention in RA.

Genetic evidence reveals a causal relationship between rheumatoid arthritis and interstitial lung disease

Background/purpose: Previous epidemiological studies have associated interstitial lung disease (ILD) with rheumatoid arthritis (RA), yet the causality of this relationship remains uncertain. This study aimed to investigate the genetic causal link between ILD and RA. Methods: Genome-wide association study (GWAS) statistics for ILD and RA were collected from public datasets. Relevant single-nucleotide polymorphisms (SNPs) were selected by executing quality control steps from the GWAS summary results. A two-sample bidirectional Mendelian randomization (MR) analysis was performed to assess the causal relationship between the two conditions. The MR analysis primarily used the inverse variance weighting (IVW), weighted median (WM), and MR-Egger regression methods. Sensitivity analyses, including MR-Egger, leave-one-out, and MR Pleiotropy RESidual Sum and Outlier (MR-PRESSO), were conducted to evaluate the heterogeneity and pleiotropy. Replication analyses using Asian datasets were also conducted to enhance the robustness of our findings. Results: In the European population, RA was found to increase the risk of ILD by 9.6% (OR: 1.096, 95% CI: 1.023-1.174, p = 0.009). Conversely, ILD was associated with a 12.8% increased risk of RA (OR: 1.128, 95% CI: 1.013-1.256, p = 0.029). Replication analyses from Asian GWAS further supported these findings, particularly the increased risk of ILD attributable to RA (OR: 1.33, 95% CI: 1.18-1.49, p-value <0.001). Conclusion: Our findings underscore the clinical importance of screening for ILD in RA patients and suggest that effective management of RA could significantly benefit ILD patients. The potential applicability of novel RA treatments to ILD warrants further exploration. Additionally, racial disparities in the manifestation of these diseases should not be overlooked, as they may offer new perspectives for targeted therapies in diverse populations.

Exhaled Nitric Oxide Reflects the Immune Reactions of the Airways in Early Rheumatoid Arthritis

Patients with rheumatoid arthritis (RA) have altered levels of exhaled nitric oxide (NO) compared with healthy controls. Here, we investigated whether the clinical features of and immunological factors in RA pathogenesis could be linked to the NO lung dynamics in early disease. A total of 44 patients with early RA and anti-citrullinated peptide antibodies (ACPAs), specified as cyclic citrullinated peptide 2 (CCP2), were included. Their exhaled NO levels were measured, and the alveolar concentration, the airway compartment diffusing capacity and the airway wall concentration of NO were estimated using the Högman-Meriläinen algorithm. The disease activity was measured using the Disease Activity Score for 28 joints. Serum samples were analysed for anti-CCP2, rheumatoid factor, free secretory component, secretory component containing ACPAs, antibodies against Porphyromonas gingivalis (Rgp) and total levels of IgA, IgA1 and IgA2. Significant negative correlations were found between the airway wall concentration of NO and the number of swollen joints (Rho -0.48, p = 0.004), between the airway wall concentration of NO and IgA rheumatoid factor (Rho -0.41, p = 0.017), between the alveolar concentration and free secretory component (Rho -0.35, p = 0.023) and between the alveolar concentration and C-reactive protein (Rho -0.36, p = 0.016), but none were found for anti-CCP2, IgM rheumatoid factor or the anti-Rgp levels. In conclusion, altered NO levels, particularly its production in the airway walls, may have a role in the pathogenesis of ACPA-positive RA.

Naïve Inflammatory Proteome Profiles of Glucocorticoid Responsive Polymyalgia Rheumatica and Rheumatic Arthritis Patients-Links to Triggers and Proteomic Manifestations

Polymyalgia rheumatica (PMR) is an inflammatory disorder of unknown etiology, sharing symptoms with giant cell arthritis (GCA) and rheumatoid arthritis (RA). The pathogenic inflammatory roots are still not well understood, and there is a lack of extensive biomarker studies to explain the disease debut and post-acute phase. This study aimed to deeply analyze the serum proteome and inflammatory response of PMR patients before and after glucocorticoid treatment. We included treatment-naïve PMR patients, collecting samples before and after 3 months of treatment. For comparison, disease-modifying antirheumatic drug (DMARD)-naïve RA patients were included and matched to healthy controls (CTL). The serum proteome was examined using label-free quantitative mass spectrometry, while inflammation levels were assessed using multiplex inflammatory cytokine and cell-free DNA assays. The serum proteomes of the four groups comprised acute phase reactants, coagulation factors, complement proteins, immunoglobulins, and apolipoproteins. Serum amyloid A (SAA1) was significantly reduced by active PMR treatment. Cell-free DNA levels in PMR and RA groups were significantly higher than in healthy controls due to acute inflammation. Complement factors had minimal changes post-treatment. The individual serum proteome in PMR patients showed over 100 abundantly variable proteins, emphasizing the systemic impact of PMR disease debut and the effect of treatment. Interleukin (IL)-6 and interferon-gamma (IFN-γ) were significantly impacted by glucocorticoid treatment. Our study defines the PMR serum proteome during glucocorticoid treatment and highlights the role of SAA1, IL-6, and IFN-γ in treatment responses. An involvement of PGLYRP2 in acute PMR could indicate a response to bacterial infection, highlighting its role in the acute phase of the immune response. The results suggest that PMR may be an aberrant response to a bacterial infection with an exacerbated IL-6 and acute phase inflammatory response and molecular attempts to limit the inflammation.

Vaccines for immune tolerance against autoimmune disease

The high prevalence and rising incidence of autoimmune diseases have become a prominent public health issue. Autoimmune disorders result from the immune system erroneously attacking the body's own healthy cells and tissues, causing persistent inflammation, tissue injury, and impaired organ function. Existing treatments primarily rely on broad immunosuppression, leaving patients vulnerable to infections and necessitating lifelong treatments. To address these unmet needs, an emerging frontier of vaccine development aims to restore immune equilibrium by inducing immune tolerance to autoantigens, offering a potential avenue for a cure rather than mere symptom management. We discuss this burgeoning field of vaccine development against inflammation and autoimmune diseases, with a focus on common autoimmune disorders, including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, inflammatory bowel disease, and systemic lupus erythematosus. Vaccine-based strategies provide a new pathway for the future of autoimmune disease therapeutics, heralding a new era in the battle against inflammation and autoimmunity.

Autoreactive B cells against malondialdehyde-induced protein cross-links are present in the joint, lung, and bone marrow of rheumatoid arthritis patients

Autoantibodies to malondialdehyde (MDA) proteins constitute a subset of anti-modified protein autoantibodies in rheumatoid arthritis (RA), which is distinct from citrulline reactivity. Serum anti-MDA IgG levels are commonly elevated in RA and correlate with disease activity, CRP, IL6, and TNF-α. MDA is an oxidation-associated reactive aldehyde that together with acetaldehyde mediates formation of various immunogenic amino acid adducts including linear MDA-lysine, fluorescent malondialdehyde acetaldehyde (MAA)-lysine, and intramolecular cross-linking. We used single-cell cloning, generation of recombinant antibodies (n = 356 from 25 donors), and antigen-screening to investigate the presence of class-switched MDA/MAA+ B cells in RA synovium, bone marrow, and bronchoalveolar lavage. Anti-MDA/MAA+ B cells were found in bone marrow plasma cells of late disease and in the lung of both early disease and risk-individuals and in different B cell subsets (memory, double negative B cells). These were compared with previously identified anti-MDA/MAA from synovial memory and plasma cells. Seven out of eight clones carried somatic hypermutations and all bound MDA/MAA-lysine independently of protein backbone. However, clones with somatic hypermutations targeted MAA cross-linked structures rather than MDA- or MAA-hapten, while the germline-encoded synovial clone instead bound linear MDA-lysine in proteins and peptides. Binding patterns were maintained in germline converted clones. Affinity purification of polyclonal anti-MDA/MAA from patient serum revealed higher proportion of anti-MAA versus anti-MDA compared to healthy controls. In conclusion, IgG anti-MDA/MAA show distinct targeting of different molecular structures. Anti-MAA IgG has been shown to promote bone loss and osteoclastogenesis in vivo and may contribute to RA pathogenesis.

Rheumatoid Arthritis-Specific Autoimmunity in the Lung Before and at the Onset of Disease

OBJECTIVE

The lung is implicated as a site for breach of tolerance prior to onset of seropositive rheumatoid arthritis (RA). To substantiate this, we investigated lung-resident B cells in bronchoalveolar lavage (BAL) samples from untreated early RA patients and anti-citrullinated protein antibody (ACPA)-positive individuals at risk for developing RA.

METHODS

Single B cells (n = 7,680) were phenotyped and isolated from BAL samples from individuals at risk of RA (n = 3) and at RA diagnosis (n = 9). The immunoglobulin variable region transcripts were sequenced and selected for expression as monoclonal antibodies (n = 141). Monoclonal ACPAs were tested for reactivity patterns and binding to neutrophils.

RESULTS

Using our single-cell approach, we found significantly increased proportions of B lymphocytes in ACPA+ compared to ACPA- individuals. Memory and double-negative B cells were prominent in all subgroups. Upon antibody re-expression, 7 highly mutated citrulline-autoreactive clones originating from different memory B cell subsets were identified, both in individuals at risk of RA and early RA patients. Lung IgG variable gene transcripts from ACPA+ individuals carried frequent mutation-induced N-linked Fab glycosylation sites (P < 0.001), often in the framework 3 of the variable region. Two of the lung ACPAs bound to activated neutrophils, 1 from an individual at risk of RA and 1 from an early RA patient.

CONCLUSION

T cell-driven B cell differentiation resulting in local class switching and somatic hypermutation are evident in lungs before as well as in early stages of ACPA+ RA. Our findings add to the notion of lung mucosa being a site for initiation of citrulline autoimmunity preceding seropositive RA.

Protein citrullination and NET formation do not contribute to the pathology of A20/TNFAIP3 mutant mice

A20 serves as a critical brake on NF-κB-dependent inflammation. In humans, polymorphisms in or near the TNFAIP3/A20 gene have been linked to various inflammatory disorders, including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Experimental gene knockout studies in mice have confirmed A20 as a susceptibility gene for SLE and RA. Here, we examine the significance of protein citrullination and NET formation in the autoimmune pathology of A20 mutant mice because autoimmunity directed against citrullinated antigens released by neutrophil extracellular traps (NETs) is central to the pathogenesis of RA and SLE. Furthermore, genetic variants impairing the deubiquitinase (DUB) function of A20 have been shown to contribute to autoimmune susceptibility. Our findings demonstrate that genetic disruption of A20 DUB function in A20 C103R knockin mice does not result in autoimmune pathology. Moreover, we show that PAD4 deficiency, which abolishes protein citrullination and NET formation, does not prevent the development of autoimmunity in A20 deficient mice. Collectively, these findings provide experimental confirmation that PAD4-dependent protein citrullination and NET formation do not serve as pathogenic mechanisms in the development of RA and SLE pathology in mice with A20 mutations.

Presence of anti-modified protein antibodies in idiopathic pulmonary fibrosis

BACKGROUND AND OBJECTIVE

Studies of autoimmunity and anti-citrullinated protein antibodies (ACPA) in idiopathic pulmonary fibrosis (IPF) have been confined to investigations of anti-cyclic citrullinated peptide (anti-CCP) antibodies which utilize synthetic peptides as surrogate markers for in vivo citrullinated antigens. We studied immune activation by analysing the prevalence of in vivo anti-modified protein antibodies (AMPA) in IPF.

METHODS

We included patients with incident and prevalent IPF (N = 120), sex and smoking-matched healthy controls (HC) (N = 120) and patients with RA (N = 104). Serum (median time: 11 months [Q1-Q3: 1-28 months] from diagnosis) was analysed for presence of antibodies towards native and posttranslational modified (citrullinated [Cit, N = 25]; acetylated [Acet, N = 4] and homocitrullinated [Carb, N = 1]) peptides derived from tenascin (TNC, N = 9), fibrinogen (Fib, N = 11), filaggrin (Fil, N = 5), histone (N = 8), cathelicidin (LL37, N = 4) and vimentin (N = 5) using a custom-made peptide microarray.

RESULTS

AMPA were more frequent and in increased levels in IPF than in HC (44% vs. 27%, p < 0.01), but less than in RA (44% vs. 79%, p < 0.01). We specifically observed AMPA in IPF towards certain citrullinated, acetylated and carbamylated peptides versus HC: tenascin (Cit(2033) -TNC2025-2040 ; Cit(2197) -TNC2177-2200 ; Cit(2198) -TNC2177-2200 ), fibrinogen (Cit(38,42) -Fibα36-50 ; Cit(72) -Fibβ60-74 ) and filaggrin (Acet-Fil307-324 , Carb-Fil307-324 ). No differences in survival (p = 0.13) or disease progression (p = 0.19) between individuals with or without AMPA was observed in IPF. However, patients with incident IPF had better survival if AMPA were present (p = 0.009).

CONCLUSION

A significant proportion of IPF patients present with specific AMPA in serum. Our results suggest autoimmunity as a possible characteristic for a subgroup of IPF that may affect disease outcome.

Effect of Chronic Rhinosinusitis on the Risk of Development of Rheumatoid Arthritis

PURPOSE

Several studies have reported a possible link between chronic rhinosinusitis (CRS) and rheumatoid arthritis (RA). However, it remains unclear whether CRS could influence the risk of developing RA. Therefore, in this study, we focused on examining the association between CRS and RA.

METHODS

A total of 14,867 individuals with CRS and 14,867 without CRS were enrolled after 1:1 propensity score match from a nationwide longitudinal cohort database in South Korea. RA incidence was assessed using person-years at risk, and the hazard ratio (HR) was examined using the Cox proportional hazards model.

RESULTS

The incidence of RA (per 1,000 person-years) was 6.51 for those with CRS, 6.55 for those with CRS without nasal polyps (CRSsNP), and 5.96 for those with CRS with nasal polyps (CRSwNP). We found that CRS individuals had a significantly increased risk of subsequent RA development with an adjusted HR of 1.41, regardless of the phenotype (adjusted HR was 1.42 in CRSsNP and 1.37 in CRSwNP patients). Moreover, the risk of developing RA over time was relatively higher within the first 4 years after the diagnosis of CRS.

CONCLUSIONS

Our nationwide population-based cohort study suggests that CRS may be associated with a subsequent increase in RA events, regardless of the phenotype. Therefore, physicians should consider RA risk when diagnosing and treating CRS patients.

Deep immunophenotyping reveals circulating activated lymphocytes in individuals at risk for rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease with currently no universally highly effective prevention strategies. Identifying pathogenic immune phenotypes in 'At-Risk' populations prior to clinical disease onset is crucial to establishing effective prevention strategies. Here, we applied mass cytometry to deeply characterize the immunophenotypes in blood from At-Risk individuals identified through the presence of serum antibodies to citrullinated protein antigens (ACPA) and/or first-degree relative (FDR) status (n=52), as compared to established RA (n=67), and healthy controls (n=48). We identified significant cell expansions in At-Risk individuals compared with controls, including CCR2+CD4+ T cells, T peripheral helper (Tph) cells, type 1 T helper cells, and CXCR5+CD8+ T cells. We also found that CD15+ classical monocytes were specifically expanded in ACPA-negative FDRs, and an activated PAX5 low naïve B cell population was expanded in ACPA-positive FDRs. Further, we developed an "RA immunophenotype score" classification method based on the degree of enrichment of cell states relevant to established RA patients. This score significantly distinguished At-Risk individuals from controls. In all, we systematically identified activated lymphocyte phenotypes in At-Risk individuals, along with immunophenotypic differences among both ACPA+ and ACPA-FDR At-Risk subpopulations. Our classification model provides a promising approach for understanding RA pathogenesis with the goal to further improve prevention strategies and identify novel therapeutic targets.

Antibodies against Porphyromonas gingivalis in serum and saliva and their association with rheumatoid arthritis and periodontitis. Data from two rheumatoid arthritis cohorts in Sweden

Background

Periodontitis and oral pathogenic bacteria can contribute to the development of rheumatoid arthritis (RA). A connection between serum antibodies to Porphyromonas gingivalis (P. gingivalis) and RA has been established, but data on saliva antibodies to P. gingivalis in RA are lacking. We evaluated antibodies to P. gingivalis in serum and saliva in two Swedish RA studies as well as their association with RA, periodontitis, antibodies to citrullinated proteins (ACPA), and RA disease activity.

Methods

The SARA (secretory antibodies in RA) study includes 196 patients with RA and 101 healthy controls. The Karlskrona RA study includes 132 patients with RA ≥ 61 years of age, who underwent dental examination. Serum Immunoglobulin G (IgG) and Immunoglobulin A (IgA) antibodies and saliva IgA antibodies to the P. gingivalis-specific Arg-specific gingipain B (RgpB) were measured in patients with RA and controls.

Results

The level of saliva IgA anti-RgpB antibodies was significantly higher among patients with RA than among healthy controls in multivariate analysis adjusted for age, gender, smoking, and IgG ACPA (p = 0.022). Saliva IgA anti-RgpB antibodies were associated with RA disease activity in multivariate analysis (p = 0.036). Anti-RgpB antibodies were not associated with periodontitis or serum IgG ACPA.

Conclusion

Patients with RA had higher levels of saliva IgA anti-RgpB antibodies than healthy controls. Saliva IgA anti-RgpB antibodies may be associated with RA disease activity but were not associated with periodontitis or serum IgG ACPA. Our results indicate a local production of IgA anti-RgpB in the salivary glands that is not accompanied by systemic antibody production.

Occupational inhalable agents constitute major risk factors for rheumatoid arthritis, particularly in the context of genetic predisposition and smoking

OBJECTIVES

To assess the effects of occupational inhalable exposures on rheumatoid arthritis (RA) development and their interactions with smoking and RA-risk genes, stratifying by presence of anticitrullinated protein antibodies (ACPA).

METHODS

Data came from the Swedish Epidemiological Investigation of RA, consisting of 4033 incident RA cases and 6485 matched controls. Occupational histories were retrieved, combining with a Swedish national job-exposure matrix, to estimate exposure to 32 inhalable agents. Genetic data were used to define Genetic Risk Score (GRS) or carrying any copy of human leucocyte antigen class II shared epitope (HLA-SE) alleles. Associations were identified with unconditional logistical regression models. Attributable proportion due to interaction was estimated to evaluate presence of interaction.

RESULTS

Exposure to any occupational inhalable agents was associated with increased risk for ACPA-positive RA (OR 1.25, 95% CI 1.12 to 1.38). The risk increased as number of exposed agents increased (P_trend<0.001) or duration of exposure elongated (P_trend<0.001). When jointly considering exposure to any occupational inhalable agents, smoking and high GRS, a markedly elevated risk for ACPA-positive RA was observed among the triple-exposed group compared with those not exposed to any (OR 18.22, 95% CI 11.77 to 28.19). Significant interactions were found between occupational inhalable agents and smoking/genetic factors (high GRS or HLA-SE) in ACPA-positive RA.

CONCLUSIONS

Occupational inhalable agents could act as important environmental triggers in RA development and interact with smoking and RA-risk genes leading to excessive risk for ACPA-positive RA. Future studies are warranted to assess preventive strategies aimed at reducing occupational hazards and smoking, especially among those who are genetically vulnerable.

Progression of pre-rheumatoid arthritis to clinical disease of joints: Potential role of mesenchymal stem cells

Rheumatoid arthritis (RA) related autoimmunity is developed at mucosal sites due to the interplay between genetic risk factors and environmental triggers. The pre-RA phase that leads to anti-citrullinated protein antibodies, rheumatoid factor, and other autoantibodies spread in the systemic circulation may not affect articular tissue for years until a mysterious second hit triggers the localization of RA-related autoimmunity in joints. Several players in the joint microenvironment mediate the synovial innate and adaptive immunological processes, eventually leading to clinical synovitis. There still exists a gap in the early phase of RA pathogenesis, i.e., the progression of diseases from the systemic circulation to joints. The lack of better understanding of these events results in the inability to answer questions about why only after a certain point of time the disease appears in joints and why in some cases, it simply remains latent and doesn't affect joints at all. In the current review, we focused on the immunomodulatory and regenerative role of mesenchymal stem cells and associated exosomes in RA pathology. We also highlighted the age-related dysregulations in activities of mesenchymal stem cells and how that might trigger homing of systemic autoimmunity to joints.

Effects of Microecological Regulators on Rheumatoid Arthritis: A Systematic Review and Meta-Analysis of Randomized, Controlled Trials

In this study, the available data from published randomized, controlled trials (RCTs) of the use of intestinal microecological regulators as adjuvant therapies to relieve the disease activity of rheumatoid arthritis (RA) are systematically compared. An English literature search was performed using PubMed, Embase, Scopus, Web of Science and the Cochrane Central Registry of Controlled Trials and supplemented by hand searching reference lists. Three independent reviewers screened and assessed the quality of the studies. Among the 2355 citations identified, 12 RCTs were included. All data were pooled using a mean difference (MD) with a 95% CI. The disease activity score (DAS) showed a significant improvement following microecological regulators treatment (MD (95% CI) of -1.01 (-1.81, -0.2)). A borderline significant reduction in the health assessment questionnaire (HAQ) scores was observed (MD (95% CI) of -0.11 (-0.21, -0.02)). We also confirmed the known effects of probiotics on inflammatory parameters such as the C-reactive protein (CRP) (MD -1.78 (95% CI -2.90, -0.66)) and L-1β (MD -7.26 (95% CI -13.03, -1.50)). No significant impact on visual analogue scale (VAS) of pain and erythrocyte sedimentation rate (ESR) reduction was observed. Intestinal microecological regulators supplementation could decrease RA activity with a significant effect on DAS28, HAQ and inflammatory cytokines. Nevertheless, these findings need further confirmation in large clinical studies with greater consideration of the confounding variables of age, disease duration, and individual medication regimens.

Added value of multiple autoantibody testing for predicting progression to inflammatory arthritis in at-risk individuals

BACKGROUND

Predicting progression to clinical arthritis in individuals at-risk of developing rheumatoid arthritis is a prerequisite to developing stratification groups for prevention strategies. Selecting accurate predictive criteria is the critical step to define the population at-risk. While positivity for anti-citrullinated protein antibodies (ACPA) remains the main recruitment biomarker, positivity for other autoantibodies (AutoAbs) identified before the onset of symptoms, may provide additional predictive accuracy for stratification.

OBJECTIVE

To perform a multiple AutoAbs analysis for both the prediction and the time of progression to inflammatory arthritis (IA).

METHODS

392 individuals were recruited based on a new musculoskeletal complaint and positivity for ACPA or rheumatoid factor (RF). ELISAs were performed for ACPA, RF, anti-nuclear Ab, anti-carbamylated protein (anti-CarP) and anti-collagen AutoAbs. Logistic and COX regression were used for analysis.

RESULTS

Progression to IA was observed in 125/392 (32%) of cases, of which 78 progressed within 12 months. The AutoAbs ACPA, RF, anti-CarP were individually associated with progression (p<0.0001) and improved prediction when combined with demographic/clinical data (Accuracy >77%; area under the curve (AUC) >0.789), compared with prediction using only demographic/clinical data (72.9%, AUC=0.760). Multiple AutoAbs testing provided added value, with +6.4% accuracy for number of positive AutoAbs (AUC=0.852); +5.4% accuracy for AutoAbs levels (ACPA/anti-CarP, AUC=0.832); and +6.2% accuracy for risk-groups based on high/low levels (ACPA/RF/anti-CarP, AUC=0.837). Time to imminent progression was best predicted using ACPA/anti-CarP levels (AUC=0.779), while the number of positive AutoAbs was/status/risk were as good (AUC=0.778).

CONCLUSION

We confirm added value of multiple AutoAbs testing for identifying progressors to clinical disease, allowing more specific stratification for intervention studies.

Thoracic Involvement in Systemic Autoimmune Rheumatic Diseases: Pathogenesis and Management

Thoracic involvement is one of the main determinants of morbidity and mortality in patients with autoimmune rheumatic diseases (ARDs), with different prevalence and manifestations according to the underlying disease. Interstitial lung disease (ILD) is the most common pulmonary complication, particularly in patients with systemic sclerosis (SSc), idiopathic inflammatory myopathies (IIMs) and rheumatoid arthritis (RA). Other thoracic manifestations include pulmonary arterial hypertension (PAH), mostly in patients with SSc, airway disease, mainly in RA, and pleural involvement, which is common in systemic lupus erythematosus and RA, but rare in other ARDs.In this review, we summarize and critically discuss the current knowledge on thoracic involvement in ARDs, with emphasis on disease pathogenesis and management. Immunosuppression is the mainstay of therapy, particularly for ARDs-ILD, but it should be reserved to patients with clinically significant disease or at risk of progressive disease. Therefore, a thorough, multidisciplinary assessment to determine disease activity and degree of impairment is required to optimize patient management. Nevertheless, the management of thoracic involvement-particularly ILD-is challenging due to the heterogeneity of disease pathogenesis, the variety of patterns of interstitial pneumonia and the paucity of randomized controlled clinical trials of pharmacological intervention. Further studies are needed to better understand the pathogenesis of these conditions, which in turn is instrumental to the development of more efficacious therapies.

Observational studies: Ambient air pollution and hospitalization for RA-ILD in a heavily polluted city in China

Little is known within the medical community about the impact of air pollution on hospital admissions due to rheumatoid arthritis associated with interstitial lung disease (RA-ILD). Our research aimed to explore whether there is a correlation and to estimate how the association was distributed across various lags in Jinan, China.The relationships between ambient air pollutant concentrations, including PM2.5, PM10, sulfur dioxide (SO2), ozone (O3), and nitrogen dioxide (NO2), and monthly hospitalizations for RA-ILD were studied by employing a general linear model with a Poisson distribution. This time-series study was performed from January 1st, 2015 to December 31st, 2019.In the 5-year study, there were 221 hospitalizations for RA-ILD in Jinan city. The levels of PM2.5, PM10, SO2, and NO2 were significantly related to the number of admissions for RA-ILD. PM2.5, PM10, and SO2 showed the most significant effect on the month (lag 0), and NO2 was most related to RA-ILD at a lag of two months (lag 2). The monthly admissions of RA-ILD increased by 0.875% (95% CI: 0.375-1.377%), 0.548% (95% CI: 0.148-0.949%), 1.968% (95% CI: 0.869-3.080%), and 1.534% (95% CI: 0.305-2.778%) for each 10 μg/m3 increase in PM2.5, PM10, SO2 and NO2, respectively.This study might add more detailed evidence that higher levels of PM2.5, PM10, SO2 and NO2 increase the risk of hospitalizations for RA-ILD. Further study of the role of air pollution in the pathogenesis of RA-ILD is warranted.

Exhaled nitric oxide in early rheumatoid arthritis and effects of methotrexate treatment

Patients with established rheumatoid arthritis (RA) and disease modifying treatments have lower nitric oxide (NO) levels in the alveolar compartment (C_ANO) and in the airway wall (C_awNO), but also higher diffusion capacities for NO in the airways (D_awNO) compared to matched controls. The aim of the present study was to investigate the NO lung dynamics in patients with recent onset RA before and after immune suppression with methotrexate therapy. Patients with early RA and antibodies against anticitrullinated peptides (ACPA) were recruited. Measurement of exhaled NO and inflammatory markers in serum were performed. Clinical disease activity was evaluated with Disease Activity Score for 28 joints. Healthy individuals were used as matched controls. Data are presented as median (lower quartile, upper quartile) values. RA patients (n = 44) had lower exhaled NO (F_ENO₅₀) 16 (10–24) ppb compared to controls 21 (15, 29) ppb, p = 0.013. In NO-dynamics, C_ANO was lower in RA patients 1.6 (1.0, 2.2) ppb compared to the control subjects 2.3 (1.3, 3.1) ppb, p = 0.007. C_awNO was also lower in the RA patients 55 (24, 106) ppb compared to control subjects 124 (110, 170) ppb, p < 0.001, but D_awNO was higher 17 (8, 30) mL/s and 9 (5, 11) mL/s respectively, p < 0.001. Methotrexate treatment for three months reduced disease activity, but did not change the NO dynamics. In conclusion, the altered NO dynamics of the lung in ACPA-positive RA patients are already present in the early stages of the disease before any treatments and do not change after methotrexate therapy suggesting a role in the pathogenesis.

Recent Advances in Basic and Clinical Aspects of Rheumatoid Arthritis-associated Interstitial Lung Diseases

Rheumatoid arthritis (RA) is a common autoimmune disease that mainly affects the joints and systemic organs, such as the skin, eyes, heart, gastrointestinal tract, and lungs. In particular, among various pulmonary involvements, interstitial lung disease (ILD) is closely related to the selection of anti-rheumatic drugs and the long-term prognosis of patients with RA. Although the exact pathogenesis of RA-ILD is not well defined, several mechanistic pathways, similar to those of idiopathic pulmonary fibrosis, have been elucidated recently. Conversely, RA-related autoantibodies, including anti-cyclic citrullinated peptide antibody, are detectable in circulation and in the lungs, even in the absence of articular symptoms. RA-ILD can also predate years before the occurrence of joint symptoms. This evidence supports the fact that local dysregulated mucosal immunity in the lung causes systemic autoimmunity, resulting in clinically evident polyarthritis of RA. Because the early diagnosis of RA-ILD is important, imaging tests, such as computed tomography and pulmonary function tests, are being used for early diagnosis, but there is no clear guideline for the early diagnosis of RA-ILD and selection of optimal disease-modifying anti-rheumatic drugs for the treatment of patients with RA with ILD. In addition, the efficacy of nintedanib, a new anti-fibrotic agent, for RA-ILD treatment, has been investigated recently. This review collectively discusses the basic and clinical aspects, such as pathogenesis, animal models, diagnosis, and treatment, of RA-ILD.

New Druggable Targets for Rheumatoid Arthritis Based on Insights From Synovial Biology

Rheumatoid arthritis (RA) is a multifactorial autoimmune disease characterized by chronic inflammation and destruction of multiple small joints which may lead to systemic complications. Altered immunity via pathogenic autoantibodies pre-date clinical symptom development by several years. Incompletely understood range of mechanisms trigger joint-homing, leading to clinically evident articular disease. Advances in therapeutic approaches and understanding pathogenesis have improved prognosis and likely remission. However, partial/non-response to conventional and biologic therapies witnessed in a subset of patients highlights the need for new therapeutics. It is now evident that joint disease chronicity stems from recalcitrant inflammatory synovial environment, majorly maintained by epigenetically and metabolically reprogrammed synoviocytes. Therefore, interference with effector functions of activated cell types seems a rational strategy to reinstate synovial homeostasis and complement existing anti-inflammatory interventions to mitigate chronic RA. Presenting this newer aspect of fibroblast-like synoviocytes and myeloid cells underlying the altered synovial biology in RA and its potential for identification of new druggable targets is attempted in this review. Major leads from i) molecular insights of pathogenic cell types from hypothesis free OMICS approaches; ii) hierarchy of their dysregulated signaling pathways; and iii) knowledge of druggability of molecular nodes in these pathways are highlighted. Development of such synovial biology-directed therapeutics hold promise for an enriched drug repertoire for RA.

Anti-citrullinated Protein Antibody Generation, Pathogenesis, Clinical Application, and Prospects

Anti-citrullinated protein antibodies (ACPAs) are autoantibodies commonly observed in patients with rheumatoid arthritis (RA). Currently, most of the mechanisms of ACPA formation and bone destruction are well-understood, however, some unknown mechanisms still exist. There have been many new advances in ACPA-related clinical applications and targeted therapies. However, the existence of different ACPA subtypes is a limitation of targeted therapy. Herein, we present an overview of the process of ACPA generation, the underlying pathogenesis, and relevant clinical application and prospects.

IABR Symposium 2021 meeting report: breath standardization, sampling, and testing in a time of COVID-19

Due to COVID-19 travel disruptions, the International Association of Breath Research hosted the planned 2021 Breath Summit virtually as a symposium with oral and poster presentations. The event was comprised of a week-long social media asynchronous online event for sharing research abstracts, posters and discussions. Subsequently, there were two days of real-time webinar platform interactions each featuring three technical presentations, open forum questions, answers, and commentary. The symposium was well attended and well received. It allowed the breath community to share new research and to reconnect with colleagues and friends. This report presents an overview of the topics presented and various salient discussion points.

Anti-alpha enolase multi-antibody specificity in human diseases. Clinical significance and molecular mechanisms

Alpha-enolase (Eno) is an ubiquitary glycolytic enzyme playing multiple functions that go well beyond its principal metabolic role of energy supplier during glycolysis. Eno is localized in the cytoplasm, but also expressed on the cell membrane, where it binds plasminogen allowing its activation. Its shorter form, in the nucleus, acts as transcription factor. In inflammatory conditions, Eno undergoes post-translational modifications, such as citrullination, oxidation and phosphorylation. Eno is also an autoantigen in different disorders. In fact, autoantibodies to Eno have been detected in rheumatoid arthritis, lupus nephritis, primary glomerulonephritis, cancer, infections and other disorders, and in many cases they represent specific markers to be utilized in clinical practice. Anti-Eno antibodies in the different clinical conditions are not equal: they differ in isotype and often recognize different epitopes on the enzyme. IgG1 and IgG3 are prevalent in Rheumatoid Arthritis, IgG2 in Lupus nephritis and IgG4 in primary autoimmune glomerulopathy. This review analyzes the characteristics of anti-Eno autoantibodies in autoimmune disorders and cancer, describing their fine specificity and isotype restriction. The post-translational modifications that are target of autoantibodies are also discussed, as they represent the basis for elucidating the molecular mechanisms responsible for epitope generation. Despite an impressive amount of experimental work on anti-Eno antibodies, it is still necessary to validate the use of anti-Eno antibodies as biomarkers of selected diseases and extend the knowledge on the mechanisms of anti-Eno autoantibody production. Strategies that downmodulate the immune response to Eno may represent in the future novel approaches in the treatment of autoimmune disorders.

Expression and Correlation of IgG4 and IL-21 in Collagen-Induced Arthritis Rats

Purpose

We explored the expression levels of IgG4 and interleukin (IL)-21 in the serum and ankle joints of collagen-induced arthritis (CIA) rats at different disease stages.

Materials and Methods

Wistar rats were randomly divided into normal and model groups, and the latter group was administered bovine type II collagen to induce arthritis. Enzyme-linked immunosorbent assay was performed at 21, 28, 35, and 42 days to detect IgG4 and IL-21 in the serum, followed by histological and immunohistochemical analyses of IgG4 and IL-21r in the ankle joint of rats.

Results

The contents of IgG4 and IL-21 in the serum of the CIA model group were positively correlated and increased with disease progression. The expression of IgG4 and IL-21 receptors in the ankle joint of the CIA model group was significantly higher than that in the control group. These proteins were closely related to the pathological score. The serum IL-21 level in the model group was closely related to the level of IL-21 receptor in the ankle joint.

Conclusion

IL-21 may promote the occurrence and development of rheumatoid arthritis by combining with IL-21r to regulate the content of IgG4.

Citrullinated fibrinogen is a target of auto-antibodies in interstitial lung disease in mice with collagen-induced arthritis

Interstitial lung disease (ILD) is a very common and lethal complication of rheumatoid arthritis (RA), yet its pathogenesis is not well understood, in part due to the lack of adequate animal models. Although collagen-induced arthritis (CIA) is the most widely used animal model for RA, the lung involvement occurring in this model has scarcely been studied. To evaluate the suitability of CIA as a model for RA-associated ILD (RA-ILD), we immunized DBA/1 mice with bovine type II collagen and characterized lung disease in this model. Histologic analyses revealed patchy interstitial infiltration of inflammatory cells in the peripheral regions of the lung, notably in the subpleural region, in mice with CIA. This pattern resembled usual interstitial pneumonia in humans, which is the most prevalent pattern in RA-ILD. Among infiltrates in the lung, CD11bhi macrophages of the M2 phenotype were most prominently increased. IgG and C3 were deposited in the subpleural region where inflammatory cells infiltrated. The sera from CIA mice contained auto-antibodies against citrullinated proteins, which are specific and predictive markers for RA. Protein citrullination was enhanced in the lung of CIA mice compared with naive mice, and citrullinated fibrinogen was primarily targeted by these auto-antibodies. The elevation of auto-antibodies against citrullinated proteins and their deposition in the lung with patchy subpleural preponderance suggest that CIA can serve as a model to study the pathogenesis of RA-ILD.

Specific Increase in Joint Neutrophil Extracellular Traps and Its Relation to Interleukin 6 in Autoimmune Arthritis

Neutrophils and their extracellular traps have been shown to play an important role in the pathogenesis of rheumatoid arthritis (RA), but the detailed mechanisms in joints are still unclear, and their regulation remains to be solved. Here, we explored neutrophil extracellular trap (NET)osis in experimental models of arthritis and further investigated the effects of interleukin-6 (IL-6) inhibition in neutrophils and NETosis. In skins of peptide GPI-induced arthritis (pGIA), citrullinated protein was detected as well as citrullinated histone expression in immunized skin but this was not specific to pGIA. Citrullinated histone expression in pGIA joints was specific to pGIA and was merged with neutrophil elastase, suggesting NETosis. Neutrophils in joints tend to upregulate IL-6 receptors when compared with bone marrow neutrophils. Administration of mouse anti-IL-6 receptor antibodies in pGIA suppressed arthritis in association with a decrease in neutrophil infiltration and NETosis in joints. In the plasma of RA patients, citrullinated protein was significantly reduced after tocilizumab treatment. Our results suggest that IL-6 enhances neutrophil chemotaxis and NETosis in inflammatory joints and could be the source of citrullinated proteins.

Association between number and type of different ACPA fine specificities with lung abnormalities in early, untreated rheumatoid arthritis

Background

Rheumatoid arthritis (RA)-associated anticitrullinated protein/peptide antibodies (ACPA) might originate at mucosal sites such as the lungs. We aimed to examine the relationship between the ACPA repertoire and lung abnormalities on high-resolution CT (HRCT) in patients with earlyuntreated RA.

Methods

106 patients with newly diagnosed untreated RA were examined with HRCT of the lungs. Blood samples were analysed for presence of rheumatoid factor (RF) and ACPA using either a CCP2 detection kit or an immunochip containing 10 different citrullinated peptides. Association between HRCT findings and the antibody repertoire was assessed by logistic regression analysis.

Results

The number (%) of patients with HRCT abnormalities was 58 (54.7%) for parenchymal abnormalities and 68 (64.2%) for airway abnormalities. CCP2 IgG, RF IgA and antibodies against citrullinated fibrinogen were associated with the presence of parenchymal lung abnormalities. Interestingly, a high number of ACPA fine specificities gave a high risk of having parenchymal lung abnormalities at the time of RA diagnosis. No significant signals were identified between ACPA specificities and risk for airway abnormalities.

Conclusions

The presence of RF and ACPAs (especially against citrullinated fibrinogen peptides) as well as high number of ACPAs fine specificities are associated with parenchymal lung abnormalities in patients with early, untreated RA. This provides further support for an important pathogenic link between the lung and systemic autoimmunity, contributing to RA development.

Unique autoantibody prevalence in long-term recovered SARS-CoV-2-infected individuals

The variability in resolution of SARS-CoV-2-infections between individuals neither is comprehended, nor are the long-term immunological consequences. To assess the long-term impact of a SARS-CoV-2-infection on the immune system, we conducted a prospective study of 80 acute and former SARS-CoV-2 infected individuals and 39 unexposed donors to evaluate autoantibody responses and immune composition. Autoantibody levels against cyclic citrullinated peptide (CCP), a specific predictor for rheumatoid arthritis (RA), were significantly (p = 0.035) elevated in convalescents only, whereas both acute COVID-19 patients and long-term convalescents showed critically increased levels of anti-tissue transglutaminase (TG), a specific predictor of celiac disease (CD) (p = 0.002). Both, anti-CCP and anti-TG antibody levels were still detectable after 4–8 months post infection. Anti-TG antibodies occurred predominantly in aged patients in a context of a post-SARS-CoV-2-specific immune composition (R² = 0.31; p = 0.044). This study shows that increased anti-CCP and anti-TG autoantibody levels can remain long-term after recovering even from mildly experienced COVID-19. The inter-relationship of the lung as viral entry side and RA- and CD-associated autoimmunity indicates that a SARS-CoV-2-infection could be a relevant environmental factor in their pathogenesis.

Human PD-1hiCD8+ T Cells Are a Cellular Source of IL-21 in Rheumatoid Arthritis

Background

Rheumatoid arthritis (RA) is a prototypical autoantibody-driven autoimmune disease in which T-B interactions play a critical role. Recent comprehensive analysis suggests that PD-1⁺CD8⁺ T cells as well as two distinct IL-21-producing PD-1⁺CD4⁺ T cell subsets, follicular helper T (Tfh) and peripheral helper T (Tph) cells, are involved in the pathogenesis of RA. Herein, we aimed to clarify a generation mechanism of IL-21-producing CD8⁺ T cells in humans, and to characterize this novel subset in patients with RA.

Methods

CD8⁺ T cells in the peripheral blood (PB) and synovial fluid (SF) of healthy control (HC) and patients with RA were subject to the analysis of IL-21 mRNA and protein. We evaluated the surface marker, cytokine and transcription profiles of IL-21-producing CD8⁺ T cells in HCPB, RAPB and RASF.

Results

IL-21-producing CD8⁺ T cells were enriched in the CD45RA^-(memory) PD-1⁺, especially PD-1^hi subpopulation, and IL-12 and IL-21 synergistically induced IL-21 production by naïve CD8⁺ T cells. Memory PD-1^hiCD8⁺ T cells in HCPB facilitated plasmablast differentiation and IgG production in an IL-21-dependent manner. In addition, PD-1^hiCD8⁺ T cells in RASF and RAPB produced large amounts of IL-21 and were characterized by high levels of CD28, ICOS, CD69, HLA-DR, and CCR2 but not CXCR5. Furthermore, PD-1^hiCD8⁺ T cells expressed high levels of transcripts of MAF and PRDM1, a feature observed in Tph cells.

Conclusions

Identification of IL-21-producing PD-1^hiCD8⁺ T cells expands our knowledge of T cell subsets with B helper functions in RA. Selective targeting of these subsets could pave an avenue for the development of novel treatment strategies for this disease.

The pre-clinical phase of rheumatoid arthritis: From risk factors to prevention of arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease considered as a multistep process spanning from the interaction of genetic (e.g., shared epitope or non-HLA loci), environmental and behavioral risk factors (e.g., smoking) leading to breaking immune tolerance and autoimmune processes such as the production of autoantibodies (e.g., antibodies against citrullinated proteins ACPA or rheumatoid factors, RF), development of the first symptoms without clinical arthritis, and, finally, the manifestation of arthritis. Despite the typical joint involvement in established RA, the pathogenesis of the disease likely begins far from joint structures: in the lungs or periodontium in association with citrullination, intestinal microbiome, or adipose tissue, which supports normal findings in synovial tissue in ACPA+ patients with arthralgia. The presence of ACPA is detectable even years before the first manifestation of RA. The pre-clinical phase of RA is the period preceding clinically apparent RA with ACPA contributing to the symptoms without subclinical inflammation. While the combination of ACPA and RF increases the risk of progression to RA by up to 10 times, increasing numbers of novel autoantibodies are to be investigated to contribute to the increased risk and pathogenesis of RA. With growing knowledge about the course of RA, new aspiration emerges to cure and even prevent RA, shifting the "window of opportunity" to the pre-clinical phases of RA. The clinical definition of individuals at risk of developing RA (clinically suspect arthralgia, CSA) makes it possible to unify these at-risk individuals' clinical characteristics for "preventive" treatment in ongoing clinical trials using mostly biological or conventional synthetic disease-modifying drugs. However, the combination of symptoms, laboratory, and imaging biomarkers may be the best approach to select the correct target at-risk population. The current review aims to explore different phases of RA and discuss the potential of (non)pharmacological intervention aiming to prevent RA.

Systematic Review and Meta-analysis on the Association of Occupational Exposure to Free Crystalline Silica and Rheumatoid Arthritis

• Occupational exposure to free crystalline silica and tobacco smoking are associated with an increased risk rheumatoid arthritis, with the evidence of an interaction in seropositive subjects.

• Further studies in the field are needed to support such association

We carried out a systematic search for all published epidemiological studies concerning the association between occupational exposure to free crystalline silica (FCS) and subsequent development of rheumatoid arthritis (RA). A meta-analysis was conducted on relevant studies. We searched PubMed and Embase, search engines, for original articles published (from 1960 to November 2019) in any language. In addition, we also searched reference lists of included studies manually for additional relevant articles. Finally, twelve studies were included in the meta-analysis (seven case-control cases and five cohort studies). The odds risks and 95% confidence interval (CI) were calculated using a random effect meta-analysis. A primary meta-analysis (using a random effect model)—regarding RA risk in subjects exposed to FCS—yelled to an overall OR of 1.94 (95% CI 1.46–2.58). We also conducted three further meta-analysis, taking into account the presence of autoantibodies (anti-RF or anti-ACPA) and smoking habits and found a significant association between FCS and RA in both seropositive and seronegative subjects (OR 1.74, 95% CI 1.35–2.25 and OR 1.23, 95% CI 1.06–1.4, respectively) and in seropositive subjects which were smokers (OR 3.30, 95% CI 2.40–4.54). The studies that have investigated the association between RA and occupatational exposure to FCS are still scarce and the heterogeneity between the studies remains high. Some critical limitations have been identified within studies, among which, the methods for assessing exposure stand out. Although with due caution, our results confirm the hypothesis of an association between occupational exposure to FCS and RA development. There was an interaction between FCS and tobacco smoking in RA seropositive workers.

Inhalants other than personal cigarette smoking and risk for developing rheumatoid arthritis

PURPOSE OF REVIEW

The current review summarizes the current evidence on inhalants other than personal cigarette smoking and risk for developing rheumatoid arthritis (RA).

RECENT FINDINGS

Personal cigarette smoking has been implicated as an environmental risk factor for seropositive RA, perhaps by inducing autoimmunity at pulmonary mucosa. Since many patients with RA are nonsmokers, other inhalants are being investigated as potential RA risk factors. Recent case-control and cohort studies have investigated passive cigarette smoking, air pollution, inhalant-related occupations, silica, pesticides, household environment, and allergic inhalants as inhalant exposures for RA risk. Inhalant-related occupations and silica inhalants have the most consistent evidence for associations with increased RA risk. However, most studies relied on retrospective designs and had limited ability to adjust for personal cigarette smoking or investigate associations among nonsmokers.

SUMMARY

Several inhalants other than personal cigarette smoking may be associated with increased risk for developing RA. These results support the hypothesis that inhalants, pulmonary mucosal inflammation, and RA pathogenesis may be linked. Future studies are needed to firmly establish the independence of these findings from personal cigarette smoking and to determine the specific inhalants and biologic mechanisms related to RA pathogenesis.

Contribution of Multiplex Immunoassays to Rheumatoid Arthritis Management: From Biomarker Discovery to Personalized Medicine

Rheumatoid arthritis (RA) is a multifactorial, inflammatory and progressive autoimmune disease that affects approximately 1% of the population worldwide. RA primarily involves the joints and causes local inflammation and cartilage destruction. Immediate and effective therapies are crucial to control inflammation and prevent deterioration, functional disability and unfavourable progression in RA patients. Thus, early diagnosis is critical to prevent joint damage and physical disability, increasing the chance of achieving remission. A large number of biomarkers have been investigated in RA, although only a few have made it through the discovery and validation phases and reached the clinic. The single biomarker approach mostly used in clinical laboratories is not sufficiently accurate due to its low sensitivity and specificity. Multiplex immunoassays could provide a more complete picture of the disease and the pathways involved. In this review, we discuss the latest proposed protein biomarkers and the advantages of using protein panels for the clinical management of RA. Simultaneous analysis of multiple proteins could yield biomarker signatures of RA subtypes to enable patients to benefit from personalized medicine.

Effect of Porphyromonas gingivalis infection on gut dysbiosis and resultant arthritis exacerbation in mouse model

BACKGROUND

Porphyromonas gingivalis (Pg) infection causes periodontal disease and exacerbates rheumatoid arthritis (RA). It is reported that inoculation of periodontopathogenic bacteria (i.e., Pg) can alter gut microbiota composition in the animal models. Gut microbiota dysbiosis in human has shown strong associations with systemic diseases, including RA, diabetes mellitus, and inflammatory bowel disease. Therefore, this study investigated dysbiosis-mediated arthritis by Pg oral inoculation in an experimental arthritis model mouse.

METHODS

Pg inoculation in the oral cavity twice a week for 6 weeks was performed to induce periodontitis in SKG mice. Concomitantly, a single intraperitoneal (i.p.) injection of laminarin (LA) was administered to induce experimental arthritis (Pg-LA mouse). Citrullinated protein (CP) and IL-6 levels in serum as well as periodontal, intestinal, and joint tissues were measured by ELISA. Gut microbiota composition was determined by pyrosequencing the 16 s ribosomal RNA genes after DNA purification of mouse feces. Fecal microbiota transplantation (FMT) was performed by transferring Pg-LA-derived feces to normal SKG mice. The effects of Pg peptidylarginine deiminase (PgPAD) on the level of citrullinated proteins and arthritis progression were determined using a PgPAD knockout mutant.

RESULTS

Periodontal alveolar bone loss and IL-6 in gingival tissue were induced by Pg oral infection, as well as severe joint destruction, increased arthritis scores (AS), and both IL-6 and CP productions in serum, joint, and intestinal tissues. Distribution of Deferribacteres and S24-7 was decreased, while CP was significantly increased in gingiva, joint, and intestinal tissues of Pg-inoculated experimental arthritis mice compared to experimental arthritis mice without Pg inoculation. Further, FMT from Pg-inoculated experimental arthritis mice reproduced donor gut microbiota and resulted in severe joint destruction with increased IL-6 and CP production in joint and intestinal tissues. The average AS of FMT from Pg-inoculated experimental arthritis was much higher than that of donor mouse. However, inoculation of the PgPAD knockout mutant inhibited the elevation of arthritis scores and ACPA level in serum and reduced CP amount in gingival, joint, and intestinal tissues compared to Pg wild-type inoculation.

CONCLUSION

Pg oral infection affected gut microbiota dysbiosis and joint destruction via increased CP generation.

Environment and Lifestyle: Their Influence on the Risk of RA

Background: Rheumatoid arthritis (RA) is a complex disease in which environmental agents are thought to interact with genetic factors that lead to triggering of autoimmunity. Methods: We reviewed environmental, hormonal, and dietary factors that have been suggested to be associated with the risk of RA. Results: Smoking is the most robust factor associated with the risk of RA, with a clear gene–environment interaction. Among other inhalants, silica may increase the risk of RA in men. There is less evidence for pesticides, pollution, and other occupational inhalants. Regarding female hormonal exposures, there is some epidemiological evidence, although not consistent in the literature, to suggest a link between hormonal factors and the risk of RA. Regarding dietary factors, available evidence is conflicting. A high consumption of coffee seems to be associated with an increased risk of RA, whereas a moderate consumption of alcohol is inversely associated with the risk of RA, and there is less evidence regarding other food groups. Dietary pattern analyses (Mediterranean diet, the inflammatory potential of the diet, or diet quality) suggested a potential benefit of dietary modifications for individuals at high risk of RA. Conclusion: To date, smoking and silica exposure have been reproducibly demonstrated to trigger the emergence of RA. However, many other environmental factors have been studied, mostly with a case-control design. Results were conflicting and studies rarely considered potential gene–environment interactions. There is a need for large scale prospective studies and studies in predisposed individuals to better understand and prevent the disease and its course.

Arthritis and the role of endogenous glucocorticoids

Rheumatoid arthritis and osteoarthritis, the most common forms of arthritis, are chronic, painful, and disabling conditions. Although both diseases differ in etiology, they manifest in progressive joint destruction characterized by pathological changes in the articular cartilage, bone, and synovium. While the potent anti-inflammatory properties of therapeutic (i.e., exogenous) glucocorticoids have been heavily researched and are widely used in clinical practice, the role of endogenous glucocorticoids in arthritis susceptibility and disease progression remains poorly understood. Current evidence from mouse models suggests that local endogenous glucocorticoid signaling is upregulated by the pro-inflammatory microenvironment in rheumatoid arthritis and by aging-related mechanisms in osteoarthritis. Furthermore, these models indicate that endogenous glucocorticoid signaling in macrophages, mast cells, and chondrocytes has anti-inflammatory effects, while signaling in fibroblast-like synoviocytes, myocytes, osteoblasts, and osteocytes has pro-inflammatory actions in rheumatoid arthritis. Conversely, in osteoarthritis, endogenous glucocorticoid signaling in both osteoblasts and chondrocytes has destructive actions. Together these studies provide insights into the role of endogenous glucocorticoids in the pathogenesis of both inflammatory and degenerative joint disease.

Recent advances in rheumatoid arthritis-associated interstitial lung disease

PURPOSE OF REVIEW

To provide an overview of recent studies that could be helpful in a better understanding of rheumatoid arthritis-associated interstitial lung disease (RA-ILD) and to facilitate the clinical management of this severe complication of RA.

RECENT FINDINGS

The advances in deciphering the genetic architecture of RA-ILD support the hypothesis of RA-ILD as a complex disease with a complex phenotype encompassing at least the usual interstitial pneumonia (UIP) high-resolution CT pattern and non-UIP. Genetics studies have provided evidence for a shared genetic background in idiopathic pulmonary fibrosis (IPF) and RA-ILD, and more specifically RA-UIP, a disease with high morbidity and mortality. These findings support the rationale for common pathogenic pathways opening new avenues for future intervention in RA-ILD, notably with - drugs that proved active in IPF. In agreement, a recent controlled trial suggests efficacy of nintedanib, an antifibrotic drug, in patients with progressive lung fibrosis, including RA-ILD. However, there is a substantial gap in RA-ILD treatment, notably evaluating the effect of the RA treatments on the ILD course because of no controlled trial yet.

SUMMARY

The phenotypical, environmental, and genetic similarities between IPF and RA-ILD have led to a better understanding of the underlying pathogenesis of RA-ILD. Despite the identification of several biomarkers and useful screening tools, several questions remain unanswered regarding the identification of patients with RA at increased risk of ILD and risk of progression. Other substantial gaps are the lack of recommendations for how high-risk patients should be screened and which specific therapeutic strategy should be initiated. International collaborative efforts are needed to address these issues and develop specific recommendations for RA-ILD.

Pentraxin 3: A promising therapeutic target for autoimmune diseases

Pentraxin 3 (PTX3) is a prototypic humoral soluble pattern recognition molecule that exerts a pivotal role in innate immune response and inflammation, as well as in tissue damage and remodeling. Recently, emerging evidence has revealed that PTX3 is involved in the occurrence and development of various autoimmune diseases, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), ankylosing spondylitis (AS), systemic sclerosis (SSc), inflammatory bowel disease (IBD), multiple sclerosis (MS) and psoriasis, etc. In this review, we have succinctly summarized the complex immunological functions of PTX3 and mostly focused on recent findings of the pleiotropic activities played by PTX3 in the pathogenesis of autoimmune diseases, aiming at hopefully offering possible future therapeutic alternatives.

Host-microbiota interactions in immune-mediated diseases

Host-microbiota interactions are fundamental for the development of the immune system. Drastic changes in modern environments and lifestyles have led to an imbalance of this evolutionarily ancient process, coinciding with a steep rise in immune-mediated diseases such as autoimmune, allergic and chronic inflammatory disorders. There is an urgent need to better understand these diseases in the context of mucosal and skin microbiota. This Review discusses the mechanisms of how the microbiota contributes to the predisposition, initiation and perpetuation of immune-mediated diseases in the context of a genetically prone host. It is timely owing to the wealth of new studies that recently contributed to this field, ranging from metagenomic studies in humans and mechanistic studies of host-microorganism interactions in gnotobiotic models and in vitro systems, to molecular mechanisms with broader implications across immune-mediated diseases. We focus on the general principles, such as breaches in immune tolerance and barriers, leading to the promotion of immune-mediated diseases by gut, oral and skin microbiota. Lastly, the therapeutic avenues that either target the microbiota, the barrier surfaces or the host immune system to restore tolerance and homeostasis will be explored.

The importance of differences; On environment and its interactions with genes and immunity in the causation of rheumatoid arthritis

The current review uses rheumatoid arthritis (RA) as a prominent example for how studies on the interplay between environmental and genetic factors in defined subsets of a disease can be used to formulate aetiological hypotheses that subsequently can be tested for causality using molecular and functional studies. Major discussed findings are that exposures to airways from many different noxious agents including cigarette smoke, silica dust and more interact with major susceptibility genes, mainly HLA-DR genetic variants in triggering antigen-specific immune reactions specific for RA. We also discuss how several other environmental and lifestyle factors, including microbial, neural and metabolic factors, can influence risk for RA in ways that are different in different subsets of RA.The description of these processes in RA provides the best example so far in any immune-mediated disease of how triggering of immunity at one anatomical site in the context of known environmental and genetic factors subsequently can lead to symptoms that precede the classical inflammatory disease symptoms and later contribute also to the classical RA joint inflammation. The findings referred to in the review have led to a change of paradigms for very early therapy and prevention of RA and to efforts towards what we have named 'personalized prevention'. We believe that the progress described here for RA will be of relevance for research and practice also in other immune-mediated diseases.

IL-4 controls activated neutrophil FcγR2b expression and migration into inflamed joints

Neutrophils are the most abundant immune cells found in actively inflamed joints of patients with rheumatoid arthritis (RA), and most animal models for RA depend on neutrophils for the induction of joint inflammation. Exogenous IL-4 and IL-13 protect mice from antibody-mediated joint inflammation, although the mechanism is not understood. Neutrophils display a very strong basal expression of STAT6, which is responsible for signaling following exposure to IL-4 and IL-13. Still, the role of IL-4 and IL-13 in neutrophil biology has not been well studied. This can be explained by the low neutrophil surface expression of the IL-4 receptor α-chain (IL-4Rα), essential for IL-4- and IL-13-induced STAT6 signaling. Here we identify that colony stimulating factor 3 (CSF3), released during acute inflammation, mediates potent STAT3-dependent neutrophil IL-4Rα up-regulation during sterile inflammatory conditions. We further demonstrate that IL-4 limits neutrophil migration to inflamed joints, and that CSF3 combined with IL-4 or IL-13 results in a prominent neutrophil up-regulation of the inhibitory Fcγ receptor (FcγR2b). Taking these data together, we demonstrate that the IL-4 and CSF3 pathways are linked and play important roles in regulating proinflammatory neutrophil behavior.

Obstructive lung diseases and risk of rheumatoid arthritis

Introduction: Smoking is an established risk factor for both lung diseases and rheumatoid arthritis (RA). Chronic mucosal airway inflammation may result in immune tolerance loss, neoantigen formation, and production of RA-related autoantibodies that increase the subsequent risk of RA. In this review, we aimed to summarize the current evidence supporting the role of obstructive lung diseases and subsequent risk of RA.Areas covered: We identified scientific articles discussing the biologic mechanisms linking mucosal airway inflammation and RA risk. We also identified studies investigating asthma, chronic obstructive pulmonary disease, bronchiectasis, cystic fibrosis, chronic tuberculous and nontuberculous mycobacterial infections, and interstitial lung disease with subsequent risk for RA.Expert opinion: The current evidence supports the hypothesis that mucosal airway inflammation may increase the risk of developing RA. However, most studies investigating this relationship have been retrospective and may not have adequately addressed the role of smoking. Larger prospective studies may provide stronger evidence for obstructive lung disease and RA risk. Determining the role of obstructive lung disease in RA pathogenesis may provide opportunity for RA prevention and screening strategies, while identifying novel biologic mechanisms that could offer targets to improve treatment and outcomes.