Autoreactive T cells to citrullinated HSP90 are associated with interstitial lung disease in rheumatoid arthritis

Etiology and Pathogenesis of Rheumatoid Arthritis-Interstitial Lung Disease

Interstitial lung disease (ILD) is one of the most serious extra-articular complications of rheumatoid arthritis (RA), which increases the mortality of RA. Because the pathogenesis of RA-ILD remains poorly understood, appropriate therapeutic strategies and biomarkers have not yet been identified. Thus, the goal of this review was to summarize and analyze the reported data on the etiology and pathogenesis of RA-ILD. The incidence of RA-ILD increases with age, and is also generally higher in men than in women and in patients with specific genetic variations and ethnicity. Lifestyle factors associated with an increased risk of RA-ILD include smoking and exposure to pollutants. The presence of an anti-cyclic citrullinated peptide antibody, high RA disease activity, and rheumatoid factor positivity also increase the risk of RA-ILD. We also explored the roles of biological processes (e.g., fibroblast-myofibroblast transition, epithelial-mesenchymal transition, and immunological processes), signaling pathways (e.g., JAK/STAT and PI3K/Akt), and the histopathology of RA involved in RA-ILD pathogenesis based on published preclinical and clinical models of RA-ILD in animal and human studies.

Anti-citrullinated protein antibodies as biomarkers in rheumatoid arthritis

INTRODUCTION

The serological biomarker anti-citrullinated protein antibodies (ACPAs) may have several functions but is especially important for the diagnosis of rheumatoid arthritis (RA) along with clinical symptoms.

AREAS COVERED

This review provides an overview of ACPAs, which are useful in RA diagnostics and may improve our understanding of disease etiology. PubMed was searched with combinations of words related to antibodies recognizing epitopes containing the post-translationally modified amino acid citrulline in combination with rheumatoid arthritis; cyclic citrullinated peptide, CCP, anti-CCP, anti-citrullinated protein antibodies, ACPA, citrullination, peptide/protein arginine deiminase, PAD, filaggrin, vimentin, keratin, collagen, perinuclear factor, EBNA1, EBNA2, and others. From this search, we made a qualitative extract of publications relevant to the discovery, characterization, and clinical use of these antibodies in relation to RA. We highlight significant findings and identify areas for improvement.

EXPERT OPINION

ACPAs have high diagnostic sensitivity and specificity for RA and recognize citrullinated epitopes from several proteins. The best-performing single epitope originates from Epstein-Barr Virus nuclear antigen 2 and contains a central Cit-Gly motif, which is recognized by ACPAS when located in a flexible peptide structure. In addition, ACPAs may also have prognostic value, especially in relation to early treatment, although ACPAs' main function is to aid in the diagnosis of RA.

Potential of resveratrol in the treatment of interstitial lung disease

Interstitial lung disease (ILD) is a heterogeneous group of diseases characterized by lung injury caused by lung fibroblast proliferation, interstitial inflammation, and fibrosis. Different cell signal transduction pathways are activated in response to various proinflammatory or fibrotic cytokines, such as IL-6, and these cytokines are increased in different ILDs. The overexpressed cytokines and growth factors in ILD can activate TGF-β/Smad2/3/4, NF-κB, and JAK/STAT signal transduction pathways, promote the activation of immune cells, increase the release of pro-inflammatory and pro-fibrotic factors, differentiate fibroblasts into myofibroblasts, and promote the occurrence and development of ILD. This finding suggests the importance of signal transduction pathways in patients with ILD. Recent evidence suggests that resveratrol (RSV) attenuates excessive inflammation and pulmonary fibrosis by inhibiting the TGF-β/Smad2/3/4, NF-κB, and JAK/STAT signal transduction pathways and overactivation of immune cells. In this review, advances in lung protection and the underlying mechanisms of RSV are summarized, and the potential efficacy of RSV as a promising treatment option for ILD is highlighted.

Unmet needs and perspectives in rheumatoid arthritis-associated interstitial lung disease: A critical review

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by synovitis as the most common clinical manifestation, and interstitial lung disease (RA-ILD) represents one of the most common and potentially severe extra-articular features. Our current understanding of the mechanisms and predictors of RA-ILD is limited despite the demonstration that an early identification of progressive fibrosing forms is crucial to provide timely treatment with antifibrotic therapies. While high resolution computed tomography is the gold standard technique for the diagnosis and follow-up of RA-ILD, it has been hypothesized that serum biomarkers (including novel and rare autoantibodies), new imaging techniques such as ultrasound of the lung, or the application of innovative radiologic algorithms may help towards predicting and detecting early forms of diseases. Further, while new treatments are becoming available for idiopathic and connective tissue disease-associated forms of lung fibrosis, the treatment of RA-ILD remains anecdotal and largely unexplored. We are convinced that a better understanding of the mechanisms connecting RA with ILD in a subgroup of patients as well as the creation of adequate diagnostic pathways will be mandatory steps for a more effective management of this clinically challenging entity.

Host cell stress response as a predictor of COVID-19 infectivity and disease progression

The coronavirus disease (COVID-19) caused by a coronavirus identified in December 2019 has caused a global pandemic. COVID-19 was declared a pandemic in March 2020 and has led to more than 6.3 million deaths. The pandemic has disrupted world travel, economies, and lifestyles worldwide. Although vaccination has been an effective tool to reduce the severity and spread of the disease there is a need for more concerted approaches to fighting the disease. COVID-19 is characterised as a severe acute respiratory syndrome . The severity of the disease is associated with a battery of comorbidities such as cardiovascular diseases, cancer, chronic lung disease, and renal disease. These underlying diseases are associated with general cellular stress. Thus, COVID-19 exacerbates outcomes of the underlying conditions. Consequently, coronavirus infection and the various underlying conditions converge to present a combined strain on the cellular response. While the host response to the stress is primarily intended to be of benefit, the outcomes are occasionally unpredictable because the cellular stress response is a function of complex factors. This review discusses the role of the host stress response as a convergent point for COVID-19 and several non-communicable diseases. We further discuss the merits of targeting the host stress response to manage the clinical outcomes of COVID-19.

Alarmins in autoimmune diseases

Alarmins are endogenous, constitutively expressed, chemotacting and immune activating proteins or peptides released because of non-programmed cell death (i.e. infections, trauma, etc). They are considered endogenous damage-associated molecular patterns (DAMPs), able to induce a sterile inflammation. In the last years, several studies highlighted a possible role of different alarmins in the pathogenesis of various autoimmune and immune-mediated diseases. We reviewed the relevant literature about this topic, for about 160 articles. Particularly, we focused on systemic autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, idiopathic inflammatory myopathies, ANCA-associated vasculitides, Behçet's disease) and cutaneous organ-specific autoimmune diseases (vitiligo, psoriasis, alopecia, pemphigo). Finally, we discussed about future perspectives and potential therapeutic implications of alarmins in autoimmune diseases. In fact, identification of receptors and downstream signal transducers of alarmins may lead to the identification of antagonistic inhibitors and agonists, with the capacity to modulate alarmins-related pathways and potential therapeutic applicability.

Extracellular Heat Shock Proteins as Therapeutic Targets and Biomarkers in Fibrosing Interstitial Lung Diseases

Interstitial lung diseases (ILDs) include a large number of diseases and causes with variable outcomes often associated with progressive fibrosis. Although each of the individual fibrosing ILDs are rare, collectively, they affect a considerable number of patients, representing a significant burden of disease. Idiopathic pulmonary fibrosis (IPF) is the typical chronic fibrosing ILD associated with progressive decline in lung. Other fibrosing ILDs are often associated with connective tissues diseases, including rheumatoid arthritis-ILD (RA-ILD) and systemic sclerosis-associated ILD (SSc-ILD), or environmental/drug exposure. Given the vast number of progressive fibrosing ILDs and the disparities in clinical patterns and disease features, the course of these diseases is heterogeneous and cannot accurately be predicted for an individual patient. As a consequence, the discovery of novel biomarkers for these types of diseases is a major clinical challenge. Heat shock proteins (HSPs) are molecular chaperons that have been extensively described to be involved in fibrogenesis. Their extracellular forms (eHSPs) have been recently and successfully used as therapeutic targets or circulating biomarkers in cancer. The current review will describe the role of eHSPs in fibrosing ILDs, highlighting the importance of these particular stress proteins to develop new therapeutic strategies and discover potential biomarkers in these diseases.

Protective Role of Genetic Variants in HSP90 Genes-Complex in COPD Secondary to Biomass-Burning Smoke Exposure and Non-Severe COPD Forms in Tobacco Smoking Subjects

Background: Chronic Obstructive Pulmonary Disease (COPD) is an inflammatory disease characterized by airflow obstruction, commonly present in smokers and subjects exposed to noxious particles product of biomass-burning smoke (BBS). Several association studies have identified single-nucleotide polymorphisms (SNP) in coding genes related to the heat shock proteins family-genes that codify the heat shock proteins (Hsp). Hsp accomplishes critical roles in regulating immune response, antigen-processing, eliminating protein aggregates and co-activating receptors. The presence of SNPs in these genes can lead to alterations in immune responses. We aimed to evaluate the association of SNPs in the HSP90 gene complex and COPD. Methods: We enrolled 1549 participants, divided into two comparison groups; 919 tobacco-smoking subjects (cases COPD-TS n = 294 and, controls SWOC n = 625) and 630 chronic exposed to BBS (cases COPD-BBS n = 186 and controls BBES n = 444). We genotyped 2 SNPs: the rs13296 in HSP90AB1 and rs2070908 in HSP90B1. Results: Through the dominant model (GC + CC), the rs2070908 is associated with decreased risk (p < 0.01, OR = 0.6) to suffer COPD among chronic exposed BBS subjects. We found an association between rs13296 GG genotype and lower risk (p = 0.01, OR = 0.22) to suffer severe COPD-TS forms in the severity analysis. Conclusions: single-nucleotide variants in the HSP90AB1 and HSP90B1 genes are associated with decreased COPD risk in subjects exposed to BBS and the most severe forms of COPD in tobacco-smoking subjects.

Lifestyle and Clinical Risk Factors for Incident Rheumatoid Arthritis-associated Interstitial Lung Disease

OBJECTIVE

To determine the association between novel lifestyle factors on risk of rheumatoid arthritis (RA)-associated interstitial lung disease (ILD), define the threshold at which smoking increases RA-ILD risk, and calculate the degree to which known lifestyle and clinical factors predict RA-ILD.

METHODS

This nested case-control study matched incident RA-ILD cases to RA non-ILD controls on age, sex, RA duration, rheumatoid factor, and time from exposure assessment to RA-ILD. Exposures included education, BMI, smoking, anticyclic citrullinated peptide antibodies, race, joint erosions, rheumatoid nodules, C-reactive protein (CRP), disease activity score, functional status, disease-modifying antirheumatic drug use, and glucocorticoid use. OR for each exposure on risk of RA-ILD were obtained from logistic regression models. Area under the curve (AUC) was calculated based on all lifestyle and clinical exposures.

RESULTS

We identified 84 incident RA-ILD cases and 233 matched controls. After adjustment, obesity, high-positive CRP (≥ 10 mg/L), and poor functional status (multidimensional Health Assessment Questionnaire [MDHAQ] ≥ 1) were associated with increased risk of RA-ILD (OR 2.42, 95% CI 1.11-5.24 vs normal BMI; OR 2.61, 95% CI 1.21-5.64 vs CRP < 3 mg/L; OR 3.10, 95% CI 1.32-7.26 vs MDHAQ < 0.2). Smoking 30 pack-years or more was strongly associated with risk of RA-ILD compared to never smokers (OR 6.06, 95% CI 2.72-13.5). Together, lifestyle and clinical risk factors for RA-ILD had an AUC of 0.79 (95% CI 0.73-0.85).

CONCLUSION

Obesity, CRP, functional status, and extensive smoking may be novel risk factors for RA-ILD that may be useful for RA-ILD risk assessment and prevention. The overall ability to predict RA-ILD remains modest.

Bacterial citrullinated epitopes generated by Porphyromonas gingivalis infection-a missing link for ACPA production

OBJECTIVES

Porphyromonas gingivalis (P.g.) is discussed to be involved in triggering self-reactive immune responses. The aim of this study was to investigate the autocitrullinated prokaryotic peptidylarginine deiminase (PPAD) from P.g. CH2007 (RACH2007-PPAD) from a rheumatoid arthritis (RA) patient and a synthetic citrullinated PPAD peptide (CPP) containing the main autocitrullination site as potential targets for antibody reactivity in RA and to analyse the possibility of citrullinating native human proteins by PPAD in the context of RA.

METHODS

Recombinant RACH2007-PPAD was cloned and expressed in Escherichia coli. Purified RACH2007-PPAD and its enzymatic activity was analysed using two-dimensional electrophoresis, mass spectrometry, immunoblot and ELISA. Autoantibody response to different modified proteins and peptides was recorded and bioinformatically evaluated.

RESULTS

RACH2007-PPAD was capable to citrullinate major RA autoantigens, such as fibrinogen, vimentin, hnRNP-A2/B1, histone H1 and multiple peptides, which identify a common RG/RGG consensus motif. 33% of RA patients (n=30) revealed increased reactivity for α-cit-RACH2007-PPAD before RA onset. 77% of RA patients (n=99) presented α-cit-specific signals to CPP amino acids 57-71 which were positively correlated to α-CCP2 antibody levels. Interestingly, 48% of the α-CPP-positives were rheumatoidfactor IgM/anti-citrullinated peptide/protein antibodies (ACPA)-negative. Anti-CPP and α-RACH2007-PPAD antibody levels increase with age. Protein macroarrays that were citrullinated by RACH2007-PPAD and screened with RA patient sera (n=6) and controls (n=4) uncovered 16 RACH2007-PPAD citrullinated RA autoantigens and 9 autoantigens associated with lung diseases. We showed that the α-CPP response could be an important determinant in parenchymal changes in the lung at the time of RA diagnosis (n=106; p=0.018).

CONCLUSIONS

RACH2007-PPAD induced internal citrullination of major RA autoantigens. Anti-RACH2007-PPAD correlates with ACPA levels and interstitial lung disease autoantigen reactivity, supporting an infection-based concept for induction of ACPAs via enzymatic mimicry.

Rheumatoid arthritis-associated interstitial lung disease: Current update on prevalence, risk factors, and pharmacologic treatment

Purpose of review

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is one of the most serious extra-articular RA manifestations. RA-ILD is associated with worse physical function, lower quality of life, and increased mortality. RA-ILD is comprised of heterogeneous subtypes characterized by inflammation and fibrosis. Diagnosis can be difficult since the presentation of RA-ILD is characterized by non-specific symptoms and imaging findings. Management of RA-ILD is also challenging due to difficulty in precisely measuring pulmonary disease activity and response to treatment in patients who may also have articular inflammation. We provide a current overview of RA-ILD focusing on prevalence, risk factors, and treatment.

Recent findings

Research interest in RA-ILD has increased in recent years. Some studies suggest that RA-ILD prevalence may be increasing; this may be due to underlying biologic drivers or increases in imaging and recognition. Novel RA-ILD risk factors include the MUC5B promotor variant, articular disease activity, autoantibodies, and biomarkers of damaged pulmonary parenchyma. Treatment should focus on controlling RA disease activity, which emerging data suggest may reduce RA-ILD risk. Immunomodulatory and antifibrotic drugs may also treat RA-ILD.

Summary

RA-ILD is an underrecognized and serious manifestation of RA, but important progress is being made in identifying risk factors and treatment.

Inhibitory Effect of Tetramerized Single-Chain Variable Fragment of Anti-Cyclic Citrullinated Peptide Antibodies on the Proliferation, Activation, and Secretion of Cytokines of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis In Vitro Co-Culture System

Tetramerized single-chain variable fragment (ScFv) of anti-cyclic citrullinated peptide (TeAb-CCP) is a constructed tetramerized ScFv of anti-cyclic citrullinated peptide (CCP) antibodies with p53 tetrameric domain, aim to investigate its effect on fibroblast-like synoviocytes (FLSs) proliferation, migration, invasion, and production of inflammatory mediators in the in vitro co-culture system of peripheral mononuclear cells (PBMCs) and FLSs. TeAb-CCP was constructed by modifying a monovalent ScFv antibody to CCP with p53 tetrameric domain to improve its affinity. FLSs were isolated and cultured from rheumatoid arthritis (RA) patients and control subjects. A co-culture system of peripheral mononuclear cells (PBMCs) and FLSs was used. FLSs proliferation, migration, and invasion were measured by MTT, scratch test, and Transwell chamber. Supernatants were measured for cytokines, chemokines, metalloproteinases, and anti-CCP antibodies by Luminex liquid phase protein chip and ELISA. TeAb-CCP significantly inhibited FLSs proliferation in a dose-dependent mode, with maximal action at concentration of 100 μg/ml on the 7th day in the co-culture system with PBMCs and FLSs, but not the same with only FLSs. TeAb-CCP significantly suppressed FLSs migration and invasive ability compared with the controls. Significantly lower levels of interleukin (IL)-6, IL-8, RANKL, protein arginine deiminase (PAD)-2, PAD4, metalloproteinase (MMP)-1 and MMP-3 and anti-CCP antibodies were found in co-culture supernatant of TeAb-CCP group. In contrast, transforming growth factor-β (TGF-β) and tissue inhibitor of metalloproteinases-2 (TIMP-2) was significantly increased in the TeAb-CCP group. No significant difference of IL-1a, IL-10, IL-17, TNFα, VEGF, and FGF was found between two groups. As a blocking antibody, TeAb-CCP can significantly inhibit PBMCs of RA to produce pro-inflammatory mediators, and furthermore, inhibit the proliferation, activation, migration, and invasion of FLSs in vitro. In turn, it is suggested that citrullinated modified self-epitopes may be a new target for RA therapy.

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.