To investigate the role of genetic and environmental factors in the development of anticitrullinated protein antibodies (ACPA) and ACPA-positive rheumatoid arthritis (RA) in a twin cohort.
A total of ...12 590 twins were analysed for the presence of ACPAs (CCP2 ELISA), HLA-DRB1 shared epitope (SE) gene alleles, and exposure to smoking. Twins with established RA were identified in national public care registers. Antibody reactivities against citrullinated and native forms of α-enolase, vimentin, fibrinogen and type II collagen peptides were tested by ELISA in anti-CCP2-positive subjects and their cotwins. Structural equation models and ORs for the development of ACPA and ACPA-positive RA were computed for smokers and SE carriers.
A total of 2.8% (350/12 590) of the twins were ACPA positive, and 1.0% (124/12 590) had ACPA-positive RA. Most of the variability in the ACPA status was accounted for by non-shared environmental or stochastic factors (78%, 95% CI 55% to 100%) rather than shared environmental and genetic factors. Analysis of specific risk factors revealed an association between smoking and SE and the presence of ACPAs. Twins with ACPA-positive RA were more frequently SE positive than twins with ACPAs without RA. Reactivities against multiple citrullinated peptides were present in most twins with ACPA-positive RA but in fewer twins with ACPAs without RA.
Environment, lifestyle and stochastic factors may be more important than genetics in determining which individuals develop ACPAs. Genetic factors (particularly SE) may have a relatively larger role in determining which ACPA-positive individuals will ultimately develop arthritis.
Abstract
Objectives
Advances in immunotherapy by blocking TNF have remarkably improved treatment outcomes for Rheumatoid arthritis (RA) patients. Although treatment specifically targets TNF, the ...downstream mechanisms of immune suppression are not completely understood. The aim of this study was to detect biomarkers and expression signatures of treatment response to TNF inhibition.
Methods
Peripheral blood mononuclear cells (PBMCs) from 39 female patients were collected before anti-TNF treatment initiation (day 0) and after 3 months. The study cohort included patients previously treated with MTX who failed to respond adequately. Response to treatment was defined based on the EULAR criteria and classified 23 patients as responders and 16 as non-responders. We investigated differences in gene expression in PBMCs, the proportion of cell types and cell phenotypes in peripheral blood using flow cytometry and the level of proteins in plasma. Finally, we used machine learning models to predict non-response to anti-TNF treatment.
Results
The gene expression analysis in baseline samples revealed notably higher expression of the gene EPPK1 in future responders. We detected the suppression of genes and proteins following treatment, including suppressed expression of the T cell inhibitor gene CHI3L1 and its protein YKL-40. The gene expression results were replicated in an independent cohort. Finally, machine learning models mainly based on transcriptomic data showed high predictive utility in classifying non-response to anti-TNF treatment in RA.
Conclusions
Our integrative multi-omics analyses identified new biomarkers for the prediction of response, found pathways influenced by treatment and suggested new predictive models of anti-TNF treatment in RA patients.
Rheumatoid arthritis (RA)-specific anti-citrullinated protein/peptide antibodies (ACPAs) might contribute to bone loss and arthralgia before the onset of joint inflammation. We aimed to dissect ...additional mechanisms by which ACPAs might contribute to development of joint pathology.
Fibroblast-like synoviocytes (FLS) were isolated from the synovial membrane of patients with RA. The FLS cultures were stimulated with polyclonal ACPAs (anti-CCP-2 antibodies) purified from the peripheral blood of patients with RA or with monoclonal ACPAs derived from single synovial fluid B cells. We analysed how ACPAs modulate FLS by measuring cell adhesion and mobility as well as cytokine production. Expression of protein arginine deiminase (PAD) enzymes and protein citrullination were analysed by immunofluorescence, and signal transduction was studied using immunoblotting.
Challenge of FLS by starvation-induced stress or by exposure to the chemokine interleukin-8 was essential to sensitise the cells to ACPAs. These challenges led to an increased PAD expression and protein citrullination and an ACPA-mediated induction of FLS migration through a mechanism involving phosphoinositide 3-kinase activation. Inhibition of the PAD enzymes or competition with soluble citrullinated proteins or peptides completely abolished the ACPA-induced FLS migration. Different monoclonal ACPAs triggered distinct cellular effects in either fibroblasts or osteoclasts, suggesting unique roles for individual ACPA clones in disease pathogenesis.
We propose that transient synovial insults in the presence of a certain pre-existing ACPA repertoire might result in an ACPA-mediated increase of FLS migration.
Antibodies targeting citrullinated proteins (ACPAs anticitrullinated protein antibodies) are commonly found in patients with rheumatoid arthritis (RA), strongly associate with distinct HLA-DR ...alleles, and predict a more aggressive disease course as compared with seronegative patients. Still, many features of these antibodies, including their site of production and the extent of MHC class II-driven T cell help, remain unclarified. To address these questions, we have used a single B cell-based cloning technology to isolate and express immunoglobulin (Ig) genes from joint-derived B cells of active RA patients. We found ∼25% of synovial IgG-expressing B cells to be specific for citrullinated autoantigens in the investigated ACPA(+) RA patients, whereas such antibodies were not found in ACPA(-) patients. The citrulline-reactive monoclonal antibodies did not react with the unmodified arginine peptides, yet several reacted with more than one citrullinated antigen. A role for active antigen selection of the citrulline-reactive synovial B cells was supported by the strong bias toward amino acid replacement mutations in ACPA(+) antibodies and by their loss of reactivity to citrullinated autoantigens when somatic mutations were reverted to the corresponding germline sequences.
Environmental factors may play a role in the development of rheumatoid arthritis (RA). We examined whether long-term exposures to air pollution were associated with the risk of RA in the Swedish ...Epidemiological Investigation of Rheumatoid Arthritis Study.
We studied 1497 incident RA cases and 2536 controls. Local levels of particulate matter (PM10) and gaseous pollutants (sulphur dioxide (SO2) and nitrogen dioxide (NO2)) from traffic and home heating were predicted for all residential addresses. We examined the association of an IQR increase (2 µg/m3 for PM10, 8 µg/m3 for SO2 and 9 µg/m3 for NO2) in each pollutant at different time points before symptom onset and average exposure with the risk of all RA and the risk of the rheumatoid factor and anti-citrullinated protein antibody (ACPA) RA phenotypes.
There was no evidence of an increased risk of RA with PM10. Total RA risks were modestly elevated for the gaseous pollutants, but were not statistically significant after adjustment for smoking and education (OR 1.18, 95% CI 0.97 to 1.43 and OR 1.09, 95% CI 0.99 to 1.19 for SO2 and NO2 in the 10th year before onset). Stronger elevated risks were observed for individuals with less than a university education and with the ACPA-negative RA phenotype.
No consistent overall associations between air pollution in the Stockholm area and the risk of RA were observed. However, there was a suggestion of increased risks of RA incidence with increases in NO2 from local traffic and SO2 from home heating sources with stronger associations for the ACPA-negative phenotype.
Abstract
Objectives
To investigate the association between psychosocial vulnerability, defined as either low social support or low decision latitude at work, and disease remission at 3, 12, and 60 ...months in patients with rheumatoid arthritis (RA).
Methods
This cohort study included all patients enrolled in both the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA) 1996–2015 and the Swedish Rheumatology Quality Register (SRQ,
n
= 2820). Information on social support and decision latitude at work at RA diagnosis were identified from the EIRA questionnaire. Indexes for levels of social support and decision latitude at work, respectively, were calculated based on the questionnaire. Low social support and low decision latitude at work, respectively, were identified by a score in the lowest quartile and compared with the three other quartiles (not low). Disease-activity parameters were retrieved from SRQ at 3, 12, and 60 months. The associations between social support or decision latitude at work, respectively, and Disease Activity Score 28 joint count with C-reactive protein (DAS28-CRP) remission were analysed using logistic regression models adjusted for age, sex, smoking habits, alcohol habits, symptom duration, and educational level.
Results
Having low social support (
n
= 591) was not associated with DAS28-CRP remission at 3 (OR 0.93, 95% CI 0.74–1.16), 12 (OR 0.96, 95%CI 0.75–1.23), or 60 (OR 0.89, 95%CI 0.72–1.10) months compared to not low social support (
n
= 2209). No association was observed for low (
n
= 212) versus not low (
n
= 635) decision latitude at work and DAS28-CRP remission at 3 (OR 0.84, 95%CI 0.54–1.31), 12 (OR 0.81, 95%CI 0.56–1.16), or 60 (OR 1.37, 95%CI 0.94–2.01) months.
Conclusion
In a country with general access to healthcare, psychosocial vulnerability does not influence the likelihood of achieving remission in early RA.
Abstract
Background
Our study aims to investigate an intrinsic link underlying sex hormone-binding globulin (SHBG) and rheumatoid arthritis (RA), which remains inconclusive in observational settings.
...Methods
Summary statistics were collected from the largest GWAS(s) on SHBG adjusted for BMI (SHBG
adj
BMI;
N
overall
= 368,929;
N
men
= 180,094;
N
women
= 188,908), crude SHBG (
N
overall
= 370,125;
N
men
= 180,726;
N
women
= 189,473), and RA (
N
case
= 22,350;
N
control
= 74,823). A genome-wide cross-trait design was performed to quantify global and local genetic correlation, identify pleiotropic loci, and infer a causal relationship.
Results
Among the overall population, a significant global genetic correlation was observed for SHBG
adj
BMI and RA (
$$r_{{\text{g}}}$$
r
g
= 0.11,
P
= 1.0 × 10
−4
) which was further supported by local signal (1q25.2). A total of 18 independent pleiotropic SNPs were identified, of which three were highly likely causal variants and four were found to have effects on both traits through gene expression mediation. A putative causal association of SHBG
adj
BMI on RA was demonstrated (OR = 1.20, 95% CI = 1.01–1.43) without evidence of reverse causality (OR = 0.999, 95% CI = 0.997–1.000). Sex-specific analyses revealed distinct shared genetic regions (men: 1q32.1-q32.2 and 5p13.1; women: 1q25.2 and 22q11.21-q11.22) and diverse pleiotropic SNPs (16 in men and 18 in women, nearly half were sex-specific) underlying SHBG
adj
BMI and RA, demonstrating biological disparities between sexes. Replacing SHBG
adj
BMI with crude SHBG, a largely similar yet less significant pattern of results was observed.
Conclusion
Our cross-trait analysis suggests an intrinsic, as well as a sex-specific, link underlying SHBG and RA, providing novel insights into disease etiology.
A relationship between rheumatoid arthritis (RA) and periodontitis has been suggested from findings that individuals with RA are prone to have advanced periodontitis and vice versa. In search of ...possible common pathogenetic features of these two diseases, we investigated the presence of citrullinated proteins and expression of endogenous peptidylarginine deiminases (PAD2 and PAD4), in periodontal tissue of individuals with periodontitis and healthy controls, in relation to the periodontal pathogens Porphyromonas gingivalis (P. gingivalis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), producing leukotoxin as virulence factor. These two oral bacteria have been suggested to be linked to anti-citrullinated protein antibodies in patients with RA.
Gingival tissue biopsies were obtained from 15 patients with periodontitis and 15 individuals without periodontal disease. Presence of CD3-positive lymphocytes, citrullinated proteins, PAD2, PAD4, P. gingivalis as well as A. actinomycetemcomitans and Mannheimia haemolytica produced leukotoxins were analysed by immunohistochemistry, followed by triple-blind semi-quantitative analysis. Mann-Whitney and Fisher's exact tests were used to analyse differences between groups. PADI2 and PADI4 mRNA levels were assessed by RT-qPCR and analysed using Wilcoxon signed rank test.
Increased staining of citrullinated proteins was observed in gingival connective tissue from subjects with periodontitis (80%, 12/15) compared to healthy gingival tissue (27%, 4/15), whereas no differences were observed in gingival epithelium. There was also an increased staining of the citrullinating enzymes PAD2 and PAD4 in gingival connective tissue of patients with periodontitis whereas similar levels of PAD2 and PAD4 were observed in the gingival epithelium of the two groups. Similarly, the mRNA levels of PADI2 and PADI4 were also increased in the gingival tissue of patients with periodontitis compared to healthy controls. Furthermore, presence of P. gingivalis and leukotoxins was comparable in both epithelium and connective tissue, from the different investigated individuals with and without periodontitis, and there were no correlations between the presence of periodontal pathogens and the expression of citrullinated proteins or PAD enzymes.
Chronic gingival inflammation is associated with increased local citrullination and PAD2 and PAD4 expression in periodontitis. The increased citrullination and PAD2 and PAD4 expression in periodontitis were, however, independent of the presence of periodontal pathogen P. gingivalis and A. actinomycetemcomitans leukotoxin.
Current guidelines rank abatacept, rituximab, tocilizumab and TNF-inhibitors (TNFi) as having equal effectiveness for the treatment of RA, at least as second line therapies. These recommendations are ...mainly based on meta-analysis of randomized controlled trials, with few direct drug-drug comparisons. Our objective was to compare the real-world absolute and relative effectiveness among RA patients starting any of the available biologic DMARDs (bDMARDs).
We used the Swedish Rheumatology Register to identify patients with RA initiating TNFi, rituximab, abatacept or tocilizumab in 2010-2016 as first bDMARD (n = 9333), or after switch from TNFi as first bDMARD (n = 3941). National Swedish registers provided additional covariates and censoring events. Effectiveness was assessed 3 and 12 months after treatment start, as the proportion remaining on therapy and with EULAR Good Response, HAQ improvement >0.2, zero swollen/tender joints and CDAI remission. Adjusted differences were estimated with multivariable linear regression.
Patients starting non-TNFi (vs TNFi) as first bDMARD had a higher proportion remaining on drug and reaching most response outcomes as first bDMARD (1-year EULAR Good Response/HAQ improvement: TNFi 24.9/25.4%, rituximab 28.6/37.2%, abatacept 31.9/33.7%, tocilizumab 50.9/43.1%). After switch from a first TNFi, rituximab and tocilizumab, but not abatacept, were associated with significantly better response measures than TNFi (1-year EULAR Good Response/HAQ improvement: TNFi 11.6/16.1%, rituximab 24.8/33.2%, abatacept 13.1/17.5%, tocilizumab 34.1/29.4%). Differences remained significant after adjusting for potential confounders.
Treatment outcomes among RA patients treated in Swedish clinical practice are in line with a superior effectiveness of non-TNFi bDMARDs, in particular tocilizumab and rituximab, compared with TNFi.
Objective
To investigate potential associations between dietary intake of polyunsaturated fatty acids (FAs) and pain patterns in early rheumatoid arthritis (RA) patients after 3 months of ...methotrexate (MTX) treatment.
Methods
We included 591 early RA patients with MTX monotherapy from a population‐based prospective case–control study, the Epidemiological Investigation of Rheumatoid Arthritis. Dietary data on polyunsaturated FAs (food frequency questionnaires) were linked with data on unacceptable pain (visual analog scale VAS >40 mm), noninflammatory/refractory pain (VAS >40 mm and C‐reactive protein CRP level <10 mg/liter), and inflammatory pain (VAS >40 mm and CRP level >10 mg/liter) after 3 months. Statistical analysis included logistic regression.
Results
After 3 months of MTX treatment, 125 patients (21.2%) had unacceptable pain, of which 92 patients had refractory pain, and 33 patients had inflammatory pain. Omega‐3 FA intake was inversely associated with unacceptable pain and refractory pain (odds ratio OR 0.57 95% confidence interval (95% CI) 0.35–0.95 and OR 0.47 95% CI 0.26–0.84, respectively). The omega‐6:omega‐3 FA ratio, but not omega‐6 FA alone, was directly associated with unacceptable pain and refractory pain (OR 1.70 95% CI 1.03–2.82 and OR 2.33 95% CI 1.28–4.24, respectively). Furthermore, polyunsaturated FAs were not associated with either inflammatory pain or CRP level and erythrocyte sedimentation rate at followup. Omega‐3 FA supplementation was not associated with any pain patterns.
Conclusion
Omega‐3 FA was inversely associated with, and the omega‐6:omega‐3 FA ratio was directly associated with, unacceptable and refractory pain, but not with inflammatory pain or systemic inflammation. The inverse association between omega‐3 FA and refractory pain may have a role in pain suppression in RA.
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