Transcriptomic and proteomic analysis of iris tissue and aqueous humor in juvenile idiopathic arthritis-associated uveitis

Uveitis Associated with Juvenile Idiopathic Arthritis

Juvenile idiopathic arthritis (JIA) is the most common cause of uveitis in children. While symptoms are usually mild, persistent eye inflammation could lead to severe complications and impaired vision. It is essential that JIA patients at risk are diagnosed with uveitis early, receive adequate treatment, and avoid developing complications, such as cataract, glaucoma, and amblyopia. The purpose of this mini-review is to summarize the screening strategies and clinical management for JIA-associated uveitis (JIA-U) as well as the current state of molecular markers linked to this condition. Because glaucoma is one of the most common causes of visual loss in JIA-U, special focus will be put on this serious complication. We conclude by describing the current evidence regarding the long-standing question of whether chronic anterior uveitis without arthritis may be the same disease entity as JIA-U.

Peptidylarginine deiminase 2 citrullinates MZB1 and promotes the secretion of IgM and IgA

Introduction

MZB1 is an endoplasmic reticulum residential protein preferentially expressed in plasma cells, marginal zone and B1 B cells. Recent studies on murine B cells show that it interacts with the tail piece of IgM and IgA heavy chain and promotes the secretion of these two classes of immunoglobulin. However, its role in primary human B cells has yet to be determined and how its function is regulated is still unknown. The conversion of peptidylarginine to peptidylcitrulline, also known as citrullination, by peptidylarginine deiminases (PADs) can critically influence the function of proteins in immune cells, such as neutrophils and T cells; however, the role of PADs in B cells remains to be elucidated.

Method

An unbiased analysis of human lung citrullinome was conducted to identify citrullinated proteins that are enriched in several chronic lung diseases, including rheumatoid arthritis-associated interstitial lung disease (RA-ILD), chronic obstructive pulmonary disease, and idiopathic pulmonary fibrosis, compared to healthy controls. Mass spectrometry, site-specific mutagenesis, and western blotting were used to confirm the citrullination of candidate proteins. Their citrullination was suppressed by pharmacological inhibition or genetic ablation of PAD2 and the impact of their citrullination on the function and differentiation of human B cells was examined with enzyme-linked immunosorbent assay, flow cytometry, and co-immunoprecipitation.

Results

Citrullinated MZB1 was preferentially enriched in RA-ILD but not in other chronic lung diseases. MZB1 was a substrate of PAD2 and was citrullinated during the differentiation of human plasmablasts. Ablation or pharmacological inhibition of PAD2 in primary human B cells attenuated the secretion of IgM and IgA but not IgG or the differentiation of IgM or IgA-expressing plasmablasts, recapitulating the effect of ablating MZB1. Furthermore, the physical interaction between endogenous MZB1 and IgM/IgA was attenuated by pharmacological inhibition of PAD2.

Discussion

Our data confirm the function of MZB1 in primary human plasmablasts and suggest that PAD2 promotes IgM/IgA secretion by citrullinating MZB1, thereby contributing to the pathogenesis of rheumatoid arthritis and RA-ILD.

Challenges and management of childhood non-infectious chronic uveitis

INTRODUCTION

Childhood uveitis is a sight-threatening condition, because if not properly recognized and treated can lead to several ocular complications and blindness. It represents a real challenge not only from an etiologic/diagnostic point of view, but also for management and therapy.

AREAS COVERED

In this review we will discuss the main etiologies, the diagnostic approach, risk factors associated to childhood non-infectious uveitis (cNIU), and the difficulties in eye examination in childhood. Moreover, we will discuss the treatment of cNIU in term of therapeutic choice, timing of initiation and withdrawal.

EXPERT OPINION

Identification of specific diagnosis is mandatory to prevent severe complications, thus a thorough differential diagnosis is essential. Pediatric eye examination may be extremely challenging due to the scarce collaboration, but novel techniques and biomarkers will help in identify low grade of inflammation, eventually modify long-term outcomes. Once identified the appropriate diagnosis, recognition of children who may benefit of a systemic treatment is crucial. What, When and how long are the key questions to address in this field. Current evidence and future results of ongoing clinical trials will help in driving treatment. A proper ocular screening, not only in the context of systemic disease, should be discussed by experts.

Tocilizumab in Juvenile Idiopathic Arthritis Associated Uveitis, a Narrative Review

Juvenile idiopathic arthritis (JIA) associated uveitis (JIA-U) is the most common extra-articular manifestation of JIA, affecting 10–15% of patients, especially in oligoarticular JIA where its course may be faint. Therefore, JIA-U is one of the most challenging pediatric uveitis, associated with major ocular morbidity and possibly leading to irreversible structural ocular damage and to vision-threatening complications. Adequate management is crucial for avoiding visual impairment complications. Since the introduction of biologic disease modifying anti-rheumatic drugs (bDMARDS), the visual prognosis of JIA-U has dramatically improved over the decades. Tumor necrosis factor-α (TNF-α) blockers are the most used bDMARDs in treating JIA-U with large evidence of efficacy. However, inadequate response to these agents, either due to intolerance or inefficacy, may be observed, requiring a swap to other classes of immunosuppressive agents, including anti-IL-6, anti-CD20, and, more recently, JAK inhibitors. Tocilizumab is a humanized monoclonal antibody to the interelukin-6 receptor preventing IL-6 from binding to its soluble and membrane-bound receptors. A growing body of literature provides promising results about the efficacy of intravenous and subcutaneous tocilizumab in the treatment of JIA-U. A narrative review of the literature on this topic will improve our knowledge on the potential use of tocilizumab in JIA-U.

Proteomic profiling of extracellular vesicles in synovial fluid and plasma from Oligoarticular Juvenile Idiopathic Arthritis patients reveals novel immunopathogenic biomarkers

Introduction

New early low-invasive biomarkers are demanded for the management of Oligoarticular Juvenile Idiopathic Arthritis (OJIA), the most common chronic pediatric rheumatic disease in Western countries and a leading cause of disability. A deeper understanding of the molecular basis of OJIA pathophysiology is essential for identifying new biomarkers for earlier disease diagnosis and patient stratification and to guide targeted therapeutic intervention. Proteomic profiling of extracellular vesicles (EVs) released in biological fluids has recently emerged as a minimally invasive approach to elucidate adult arthritis pathogenic mechanisms and identify new biomarkers. However, EV-prot expression and potential as biomarkers in OJIA have not been explored. This study represents the first detailed longitudinal characterization of the EV-proteome in OJIA patients.

Methods

Fourty-five OJIA patients were recruited at disease onset and followed up for 24 months, and protein expression profiling was carried out by liquid chromatography-tandem mass spectrometry in EVs isolated from plasma (PL) and synovial fluid (SF) samples.

Results

We first compared the EV-proteome of SF vs paired PL and identified a panel of EV-prots whose expression was significantly deregulated in SF. Interaction network and GO enrichment analyses performed on deregulated EV-prots through STRING database and ShinyGO webserver revealed enrichment in processes related to cartilage/bone metabolism and inflammation, suggesting their role in OJIA pathogenesis and potential value as early molecular indicators of OJIA development. Comparative analysis of the EV-proteome in PL and SF from OJIA patients vs PL from age/gender-matched control children was then carried out. We detected altered expression of a panel of EV-prots able to differentiate new-onset OJIA patients from control children, potentially representing a disease-associated signature measurable at both the systemic and local levels with diagnostic potential. Deregulated EV-prots were significantly associated with biological processes related to innate immunity, antigen processing and presentation, and cytoskeleton organization. Finally, we ran WGCNA on the SF- and PL-derived EV-prot datasets and identified a few EV-prot modules associated with different clinical parameters stratifying OJIA patients in distinct subgroups.

Discussion

These data provide novel mechanistic insights into OJIA pathophysiology and an important contribution in the search of new candidate molecular biomarkers for the disease.

Transcriptomic profiling of iris tissue highlights LCK signaling and T cell-mediated immunity in Behcet's uveitis

Uveitis is the most common form of ocular lesions in Behcet's disease, severely affecting visual function. Molecular pathological changes of ocular lesions in patients with Behcet's uveitis (BU) are largely unknown. In this study, we performed the first comprehensive transcriptomic profiling of iris specimens from BU patients and healthy donors to provide an insight into intraocular immunopathogenesis. The mRNA sequencing identified 1633 differentially expressed genes (DEGs) between the BU group and healthy controls. GO functional enrichment analysis on DEGs showed that T cell activation was the most significantly enriched biological process. KEGG analysis of DEGs also revealed several prominently enriched T cell-related pathways, including the T cell receptor signaling pathway, Th17 cell differentiation, and Th1 and Th2 cell differentiation. The lymphocyte-specific protein tyrosine kinase (LCK) was identified as the key hub gene in the protein interaction network of DEGs. Western blot analysis further showed increased expression of active LCK in the BU group, suggesting activation of LCK signaling. Using publicly accessible single-cell RNA-sequencing data of the healthy iris, LCK was found to be expressed in clusters of activated T cells but not in other iris cell clusters, suggesting an overt association between LCK upregulation and T cell-mediated immune dysregulation. Additionally, 16 drugs were predicted to be potential inhibitors of LCK. Overall, these findings not only highlighted the central role of T cell-mediated immunity and previously unreported LCK signaling in intraocular immunopathogenesis but also revealed the potential value of LCK as a new therapeutic target for BU patients.

Circulatory cytokeratin 17, marginal zone B1 protein and leucine-rich α2-glycoprotein-1 as biomarkers for disease severity and fibrosis in systemic sclerosis patients

Introduction

Systemic sclerosis (Ssc) is a multiorgan debilitating autoimmune disease that associates the triad: vascular involvement, tissue fibrosis and profound immune response alterations. Numerous previous studies focused on identification of candidate proteomic Ssc biomarkers using mass-spectrometry techniques and a large number of candidate Ssc biomarkers emerged. These biomarkers must firstly be confirmed in independent patient groups. The aim of the present study was to investigate the association of cytokeratin 17 (CK17), marginal zone B1 protein (MZB1) and leucine-rich α2-glycoprotein-1 (LRG1) with clinical and biological Ssc characteristics.

Material and methods

Serum CK17, MZB1 and LRG1 were assessed in samples of the available Ssc biobank comprising of samples from 53 Ssc patients and 26 matched age and gender controls.

Results

Circulatory CK17, LRG1 and MZB1 concentrations were increased in Ssc patients. Cytokeratin 17 is independently associated with Ssc disease activity. Patients with pulmonary fibrosis expressed higher LRG1 and MZB1 concentrations. Serum MZB1 concentrations were also associated with extensive skin fibrosis.

Conclusions

Serum CK17, MZB1 and LRG1 were confirmed biomarkers for Ssc. LRG1 seems a good biomarker for pulmonary fibrosis, while MZB1 is a good biomarker for extensive skin fibrosis. CK17 proved to be independently associated with Ssc disease severity, higher CK17 values being protective for a more active disease.

How does age determine the development of human immune-mediated arthritis?

Does age substantially affect the emergence of human immune-mediated arthritis? Children do not usually develop immune-mediated articular inflammation during their first year of life. In patients with juvenile idiopathic arthritis, this apparent ‘immune privilege’ disintegrates, and chronic inflammation is associated with variable autoantibody signatures and patterns of disease that resemble adult arthritis phenotypes. Numerous mechanisms might be involved in this shift, including genetic and epigenetic predisposing factors, maturation of the immune system with a progressive modulation of putative tolerogenic controls, parallel development of microbial dysbiosis, accumulation of a pro-inflammatory burden driven by environmental exposures (the exposome) and comorbidity-related drivers. By exploring these mechanisms, we expand the discussion of three (not mutually exclusive) hypotheses on how these factors can contribute to the differences and similarities between the loss of immune tolerance in children and the development of established immune-mediated arthritis in adults. These three hypotheses relate to a critical window in genetics and epigenetics, immune maturation, and the accumulation of burden. The varied manifestation of the underlying mechanisms among individuals is only beginning to be clarified, but the establishment of a framework can facilitate the development of an integrated understanding of the pathogenesis of arthritis across all ages.

In this Review, the authors discuss age-related arthropathy and the similarities and differences between childhood loss of immune tolerance and adult development of immune-mediated arthritis, and develop three hypotheses describing age-related mechanisms that contribute to the onset of arthritis.

The arthritis-free ‘immune privilege’ of early childhood is overridden by multiple mechanisms, progressively and age-dependently, generating recognizable patterns of chronic inflammatory arthritis.

The emergence of arthritis involves interconnected mechanisms related to immune priming, to a situational susceptibility and to the accumulation of an inflammatory burden.

The accumulation of epigenetic drift may contribute to differences across ages.

The exposome is expected to contribute to arthritis emergence in adults as well as in children.

MZB1 targeted by miR-185-5p inhibits the migration of human periodontal ligament cells through NF-κB signaling and promotes alveolar bone loss

OBJECTIVE

To explore the role of Marginal Zone B and B-1 Cell-Specific Protein (MZB1), a novel molecule associated with periodontitis, in migration of human periodontal ligament cells (hPDLCs) and alveolar bone orchestration.

BACKGROUND

MZB1 is an ER-localized protein and its upregulation has been found to be associated with a variety of human diseases. However, few studies have investigated the effect and mechanism of MZB1 on hPDLCs in periodontitis.

METHODS

Gene expression profiles in human gingival tissues were acquired from the Gene Expression Omnibus (GEO) database, and candidate molecules were then selected through bioinformatic analysis. Subsequently, we identified the localization and expression of MZB1 in human gingival tissues, mice, and hPDLCs by immunofluorescence, RT-qPCR, and Western blot. Dual-luciferase reporter assay was applied to assess the binding of miR-185-5p to MZB1. Furthermore, the effects of MZB1 on cell migration, proliferation, and apoptosis in vitro were investigated by wound-healing assay, transwell assay, CCK-8 assay, and flow cytometry analysis. Finally, Micro-CT analysis and H&E staining were performed to examine the effects of MZB1 on alveolar bone loss in vivo.

RESULTS

Bioinformatic analysis discovered that MZB1 was one of the most significantly increased genes in periodontitis patients. MZB1 was markedly increased in the gingival tissues of periodontitis patients, in the mouse models, and in the hPDLCs treated with lipopolysaccharide of Porphyromonas gingivalis (LPS-PG). Furthermore, in vitro experiments showed that MZB1, as a target gene of miR-185-5p, inhibited migration of hPDLCs. Overexpression of MZB1 specifically upregulated the phosphorylation of p65, while pretreatment of MZB1-overexpressed hPDLCs with PDTC (NF-κB inhibitor) notably reduced the p-p65 level and promoted cell migration. In addition, the mRNA expression levels of alkaline phosphatase (ALP) and Runt-related transcription factor 2 (Runx2) were inhibited in MZB1-overexpressed hPDLCs and miR-185-5p inhibitor treated hPDLCs, respectively. In vivo experiments showed that knockdown of MZB1 alleviated the loss of alveolar bone.

CONCLUSION

As a target gene of miR-185-5p, MZB1 plays a crucial role in inhibiting the migration of hPDLCs through NF-κB signaling pathway and deteriorating alveolar bone loss.

B Cells on the Stage of Inflammation in Juvenile Idiopathic Arthritis: Leading or Supporting Actors in Disease Pathogenesis?

Juvenile idiopathic arthritis (JIA) is a term that collectively refers to a group of chronic childhood arthritides, which together constitute the most common rheumatic condition in children. The International League of Associations for Rheumatology (ILAR) criteria define seven categories of JIA: oligoarticular, polyarticular rheumatoid factor (RF) negative (RF-), polyarticular RF positive (RF+), systemic, enthesitis-related arthritis, psoriatic arthritis, and undifferentiated arthritis. The ILAR classification includes persistent and extended oligoarthritis as subcategories of oligoarticular JIA, but not as distinct categories. JIA is characterized by a chronic inflammatory process affecting the synovia that begins before the age of 16 and persists at least 6 weeks. If not treated, JIA can cause significant disability and loss of quality of life. Treatment of JIA is adjusted according to the severity of the disease as combinations of non-steroidal anti-inflammatory drugs (NSAIDs), synthetic and/ or biological disease modifying anti-rheumatic drugs (DMARDs). Although the disease etiology is unknown, disturbances in innate and adaptive immune responses have been implicated in JIA development. B cells may have important roles in JIA pathogenesis through autoantibody production, antigen presentation, cytokine release and/ or T cell activation. The study of B cells has not been extensively explored in JIA, but evidence from the literature suggests that B cells might have indeed a relevant role in JIA pathophysiology. The detection of autoantibodies such as antinuclear antibodies (ANA), RF and anti-citrullinated protein antibodies (ACPA) in JIA patients supports a breakdown in B cell tolerance. Furthermore, alterations in B cell subpopulations have been documented in peripheral blood and synovial fluid from JIA patients. In fact, altered B cell homeostasis, B cell differentiation and B cell hyperactivity have been described in JIA. Of note, B cell depletion therapy with rituximab has been shown to be an effective and well-tolerated treatment in children with JIA, which further supports B cell intervention in disease development.

Assessment of angiogenesis-related parameters in juvenile idiopathic arthritis-associated uveitis

PURPOSE

Juvenile idiopathic arthritis-associated uveitis (JIAU) may run a chronic and treatment-resistant course, and occasionally, alterations of the iris vasculature may be observed clinically.

METHODS

Iris tissue (IT), aqueous humor (AH) and serum samples from patients with clinically inactive JIAU (n = 30), acute anterior uveitis (AAU; n = 18), and primary open angle glaucoma (POAG; n = 20) were obtained during trabeculectomy or cataract surgery. Samples were analyzed by RNA-Seq, qRT-PCR, LC-IMS, Western-Blot, and LEGENDplex™ analysis. Pattern of iris vasculature in JIAU patients was assessed qualitatively via fluorescein and indocyanine green angiography (FLA/ICGA).

RESULTS

RNA-Seq of IT showed significantly differential expression (DE) of 136 genes between JIAU and POAG, of which 15 were associated with angiogenesis. qRT-PCR, performed to validate RNA-Seq results, showed upregulation of the angiogenesis-related genes Kdr, Angpt-1, Tie-1, Tie-2 and Mmrn2 in IT (JIAU vs POAG, p > 0.05). LC-IMS of IT revealed a total number of 56 DE proteins (JIAU vs POAG), of which Angiopoetin, Lumican and Decorin were associated with angiogenesis and showed increased (p > 0.05) expression on Western-Blot analysis. LEGENDplex™ analysis showed upregulation of ANGPT-2 in AH from JIAU compared to AAU and POAG, whereas VEGF was upregulated in AAU. Iris vascular leakage, hypoperfusion and neovascularization were observed by FLA/ICGA in JIA patients with treatment-refractory complicated course of uveitis.

CONCLUSION

Angiogenesis-related factors could play a role in long-standing complicated JIAU, leading to clinically visible alterations in selected cases.

A Blood Protein Signature Stratifies Clinical Response to csDMARD Therapy in Pediatric Uveitis

Purpose

To identify a serum biomarker signature that can help predict response to conventional synthetic disease-modifying antirheumatic drug (csDMARD) therapy in pediatric noninfectious uveitis.

Methods

In this case-control cohort study, we performed a 368-plex proteomic analysis of serum samples of 72 treatment-free patients with active uveitis (new onset or relapse) and 15 healthy controls. Among these, 37 patients were sampled at diagnosis before commencing csDMARD therapy. After 6 months, csDMARD response was evaluated and cases were categorized as “responder” or “nonresponder.” Patients were considered “nonresponders” if remission was not achieved under csDMARD therapy. Serum protein profiles were used to train random forest models to predict csDMARD failure and compared to a model based on eight clinical parameters at diagnosis (e.g., maximum cell grade).

Results

In total, 19 of 37 (51%) cases were categorized as csDMARD nonresponders. We identified a 10-protein signature that could predict csDMARD failure with an overall accuracy of 84%, which was higher compared to a model based on eight clinical parameters (73% accuracy). Adjusting for age, sex, anatomic location of uveitis, and cell grade, cases stratified by the 10-protein signature at diagnosis showed a large difference in risk for csDMARD failure (hazard ratio, 12.8; 95% confidence interval, 2.5–64.6; P = 0.002).

Conclusions

Machine learning models based on the serum proteome can stratify pediatric patients with uveitis at high risk for csDMARD failure.

Translational Relevance

The identified protein signature has implications for the development of clinical decision tools that integrate clinical parameters with biological data to better predict the best treatment option.

Intraocular dendritic cells characterize HLA-B27-associated acute anterior uveitis

Uveitis describes a heterogeneous group of inflammatory eye diseases characterized by infiltration of leukocytes into the uveal tissues. Uveitis associated with the HLA haplotype B27 (HLA-B27) is a common subtype of uveitis and a prototypical ocular immune-mediated disease. Local immune mechanisms driving human uveitis are poorly characterized mainly due to the limited available biomaterial and subsequent technical limitations. Here, we provide the first high-resolution characterization of intraocular leukocytes in HLA-B27-positive (n = 4) and -negative (n = 2) anterior uveitis and an infectious endophthalmitis control (n = 1) by combining single-cell RNA-sequencing with flow cytometry and protein analysis. Ocular cell infiltrates consisted primarily of lymphocytes in both subtypes of uveitis and of myeloid cells in infectious endophthalmitis. HLA-B27-positive uveitis exclusively featured a plasmacytoid and classical dendritic cell (cDC) infiltrate. Moreover, cDCs were central in predicted local cell-cell communication. This suggests a unique pattern of ocular leukocyte infiltration in HLA-B27-positive uveitis with relevance to DCs.

Assessment of systemic and ocular inflammation in juvenile idiopathic arthritis via choroidal vascularity index

We aimed to evaluate the retina and the choroid in children with juvenile idiopathic arthritis (JIA) employing optical coherence tomography (OCT). This cross-sectional study, carried out between June 2017-December 2019, included JIA patients with (JIAU; n = 28) and without (JIAN; n = 65) uveitis and age-matched healthy controls (HC) (n = 102). Laboratory and demographic information of the children were obtained from hospital records. Activity of the disease was evaluated by the Juvenile Arthritis Disease Activity Score-71 (JADAS-71). Choroidal scans were obtained with spectral domain-OCT in enhanced-depth imaging (EDI)-OCT mode to assess choroidal thickness (ChT) at five locations (under the fovea, at 750 and 1500 μm nasal and temporal sections), luminal area (LA), stromal area (SA), total subfoveal choroidal area (TCA) and CVI (choroidal vascularity index). Central foveal thickness (CFT) and 1-mm diameter foveal thickness (FT) were calculated automatically through macular volume scan analysis. The choroid was significantly thicker in JIAU and JIAN patients than in HC at the subfoveal and at the 750N, 750T, 1500T points (p < 0.001, p = 0.009, p < 0.001, and p < 0.001, respectively). The CVI was lower in JIAU patients than in JIAN patients and HC (p = 0.02). Conversely, CFT was greater in JIAU patients as compared to the JIAN patients and HC (p = 0.02). Changes in chorioretinal OCT parameters in the absence of uveitis in JIA patients may reflect subclinical choroidal inflammation in these patients. Ophthalmologic examination, including choroidal imaging in a larger cohort, may clarify this aspect.

Juvenile Idiopathic Arthritis Associated Uveitis

Juvenile idiopathic arthritis (JIA) is the most common childhood rheumatic disease. The development of associated uveitis represents a significant risk for serious complications, including permanent loss of vision. Initiation of early treatment is important for controlling JIA-uveitis, but the disease can appear asymptomatically, making frequent screening procedures necessary for patients at risk. As our understanding of pathogenic drivers is currently incomplete, it is difficult to assess which JIA patients are at risk of developing uveitis. Identification of specific risk factors for JIA-associated uveitis is an important field of research, and in this review, we highlight the genomic, transcriptomic, and proteomic factors identified as potential uveitis risk factors in JIA, and discuss therapeutic strategies.

Novel biomarkers for prediction of outcome and therapeutic response in juvenile idiopathic arthritis

INTRODUCTION

The search for biomarkers in juvenile idiopathic arthritis (JIA) is a promising and rapidly expanding field of investigation. The biomarkers identified so far may help to dissect the clinical heterogeneity of the illness, measure the level of disease activity, predict clinical remission, relapse, response to medications, course over time, complications, and forestall disease flares.

AREAS COVERED

We provide a summary of the most recent advances in the development and application of biomarkers in JIA. We performed a PubMed search for significant articles combining predetermined keywords related to biomarkers in non-systemic and systemic JIA, chronic uveitis, and macrophage activation syndrome (MAS). The biomarkers available or under study are presented and discussed separately for non-systemic and systemic subtypes and for the two main disease complications, uveitis and MAS.

EXPERT OPINION

The incorporation of valid and reliable biomarkers in standard clinical care may help to design better patient-tailored treatment regimens and to improve the therapeutic strategies based on the treat-to-target approach. The establishment of biomarkers that predict the risk of disease flare may lead to define the optimal modalities for treatment discontinuation after the achievement of clinical remission.

A Review of the Various Roles and Participation Levels of B-Cells in Non-Infectious Uveitis

Non-infectious uveitis is an inflammatory disorder of the eye that accounts for severe visual loss without evident infectious agents. While T cells are supposed to dominate the induction of inflammation in non-infectious uveitis, the role of B cells in the pathogenesis of this disease is obscure. Therefore, this review aimed to discuss diverse B-cell participation in different non-infectious uveitides and their roles in the pathogenesis of this disease as well as the mechanism of action of rituximab. Increasing evidence from experimental models and human non-infectious uveitis has suggested the participation of B cells in non-infectious uveitis. The participation levels vary in different uveitides. Furthermore, B cells play multiple roles in the pathogenic mechanisms. B cells produce autoantibodies, regulate T cell responses via antibody-independent functions, and constitute ectopic lymphoid structures. Regulatory B cells perform pivotal anti-inflammatory functions in non-infectious uveitis. Rituximab may work by depleting pro-inflammatory B cells and restoring the quantity and function of regulatory B cells in this disease. Identifying the levels of B-cell participation and the associated roles is beneficial for optimizing therapy. Diversified experimental model choices and emerging tools and/or methods are conducive for future studies on this topic.

Update on noninfectious uveitis in children and its treatment

PURPOSE OF REVIEW

To give an overview of recently published articles covering risk factors, novel biomarkers and treatment for noninfectious uveitis in children.

RECENT FINDINGS

In the last few years, several genetic markers, serum biomarkers, aqueous humor markers, tear biomarkers and clinical factors have been identified, which are associated with childhood noninfectious uveitis. We describe the most important reports in this field that may help to tailor the screening and monitoring of this population in the future and might become the target of novel therapies. The advances in the biologic therapy of paediatric uveitis, thanks to evidence provided by the SYCAMORE, ADJUVITE and APTITUDE trials, offer new possibilities for the treatment of patients who fail methotrexate with adalimumab and tocilizumab. We discuss the importance of comprehensive outcome measures as proposed by the Multinational Interdisciplinary Working Group for Uveitis in Childhood (MIWGUC).

SUMMARY

Paediatric noninfectious uveitis is a sight-threatening condition and the identification of risk factors and novel biomarkers is critical for tailored management. Biologic therapies are revolutionizing the outcomes of patients resistant to conventional therapy. Increasing our knowledge of disease pathogenesis is crucial to improve targeting of screening to those at highest risk and stratification of treatments.

High CO2 levels drive the TCA cycle backwards towards autotrophy

It has recently been shown that in anaerobic microorganisms the tricarboxylic acid (TCA) cycle, including the seemingly irreversible citrate synthase reaction, can be reversed and used for autotrophic fixation of carbon^1,2. This reversed oxidative TCA cycle requires ferredoxin-dependent 2-oxoglutarate synthase instead of the NAD-dependent dehydrogenase as well as extremely high levels of citrate synthase (more than 7% of the proteins in the cell). In this pathway, citrate synthase replaces ATP-citrate lyase of the reductive TCA cycle, which leads to the spending of one ATP-equivalent less per one turn of the cycle. Here we show, using the thermophilic sulfur-reducing deltaproteobacterium Hippea maritima, that this route is driven by high partial pressures of CO₂. These high partial pressures are especially important for the removal of the product acetyl coenzyme A (acetyl-CoA) through reductive carboxylation to pyruvate, which is catalysed by pyruvate synthase. The reversed oxidative TCA cycle may have been functioning in autotrophic CO₂ fixation in a primordial atmosphere that is assumed to have been rich in CO₂.

Clinicomolecular Identification of Conserved and Individualized Features of Granulomatous Uveitis

Objective

To identify molecular features that distinguish individuals with shared clinical features of granulomatous uveitis.

Design

Cross-sectional, observational study.

Participants

Four eyes from patients with active granulomatous uveitis.

Methods

We performed single-cell RNA-sequencing with antigen-receptor sequence analysis to obtain an unbiased gene expression survey of ocular immune cells and identify clonally expanded lymphocytes.

Main Outcomes Measures

For each inflamed eye, we measured the proportion of distinct immune cell types, the amount of B or T cell clonal expansion, and the transcriptional profile of T and B cells.

Results

Each individual had robust clonal expansion arising from a single T or B cell lineage, suggesting distinct, antigen-driven pathogenic processes in each patient. This variability in clonal expansion was mirrored by individual variability in CD4 T cell populations, whereas ocular CD8 T cells and B cells were more transcriptionally similar between patients. Finally, ocular B cells displayed evidence of class-switching and plasmablast differentiation within the ocular microenvironment, providing additional support for antigen-driven immune responses in granulomatous uveitis.

Conclusions

Collectively, our study identified both conserved and individualized features of granulomatous uveitis, illuminating parallel pathophysiologic mechanisms, and suggesting that future personalized therapeutic approaches may be warranted.

A proteomic approach towards understanding the pathogenesis of Mooren's ulcer

Mooren's ulcer (MU) is a refractory autoimmune corneal ulcer with a high recurrence rate. So far, its molecular profiles and pathomechanisms remain largely unknown. Therefore, we aim to characterize the protein profiles of MU specimens by data-independent-acquisition (DIA) mass spectrometry (MS), and to define the functions of differentially-expressed proteins (DEPs). Through LC-MS/MS, 550 DEPs were identified between MU biopsies and age-matched controls (Ctrl). KEGG analysis revealed that the significantly enriched pathways of the up-regulated proteins mainly covered lysosomes, antigen processing and presentation, and phagosomes. We subsequently validated the expressions of the selected candidates using parallel-reaction-monitoring (PRM)-based MS and immunohistochemistry (IHC), including cathepsins, TIMP3, MMP-10, MYOC, PIGR, CD74, CAT, SOD2, and SOD3. Moreover, immunoglobulin (Ig) components and B lymphocytes associated proteins MZB1, HSPA5, and LAP3 in MU were significantly increased and validated by PRM-based MS and IHC. The remarkable enrichment of neutrophil extracellular traps (NETs) components in MU samples was also identified and determined. The up-regulated Ig components and NETs components suggested that B lymphocytes and neutrophils participated in the immunopathology of MU. Importantly, we also identified and validated much more expression of peptidyl arginine deiminase 4 (PADI4) in MU samples. The double-immunofluorescence staining showed the co-localization of citrulline residues with MPO, NE, and IgG in MU samples. These results indicated the presences of PADI4-mediated citrullination modification and anti-citrullinated protein antibodies (ACPAs) in MU samples. Our findings, for the first time, provide a global proteomic signature of MU, which may open a new avenue towards disease pathology and therapeutics.

Role of Polymeric Immunoglobulin Receptor in IgA and IgM Transcytosis

Transcytosis of polymeric IgA and IgM from the basolateral surface to the apical side of the epithelium and subsequent secretion into mucosal fluids are mediated by the polymeric immunoglobulin receptor (pIgR). Secreted IgA and IgM have vital roles in mucosal immunity in response to pathogenic infections. Binding and recognition of polymeric IgA and IgM by pIgR require the joining chain (J chain), a small protein essential in the formation and stabilization of polymeric Ig structures. Recent studies have identified marginal zone B and B1 cell-specific protein (MZB1) as a novel regulator of polymeric IgA and IgM formation. MZB1 might facilitate IgA and IgM transcytosis by promoting the binding of J chain to Ig. In this review, we discuss the roles of pIgR in transcytosis of IgA and IgM, the roles of J chain in the formation of polymeric IgA and IgM and recognition by pIgR, and focus particularly on recent progress in understanding the roles of MZB1, a molecular chaperone protein.

Redox proteomics reveals an interdependence of redox modification and location of adhesome proteins in NGF-treated PC12 cells

Proteomics studies have revealed that adhesomes are assembled from a plethora of proteins at integrin-mediated cellular contact sites with the extracellular matrix. By combining dimedone-trapping of sulfenylated proteins with the purification of the adhesome complex, we extended previous proteomics approaches on adhesomes to a redox proteomic analysis. This added a new aspect of adhesome complexity as individual adhesome proteins change their redox state in response to environmental signals. As model system, rat pheochromocytoma PC12 cells were studied in contact with type IV collagen and in response to nerve growth factor (NGF). NGF stimulates the endogenous production of reactive oxygen species (ROS) and the formation of neurite-like cell protrusions, which are anchored to the substratum via adhesomes. Dimedone detects the reversible oxidation of cysteine thiol groups into sulfenic acid groups which was used in proteomic analysis of adhesome proteins revealing that sulfenylation and location of proteins mutually influence each other. For some proteins, identified by the redox proteomics approach, among them Nck-associated protein-1 (Nap-1), proximity ligation analysis and co-immunoprecipitation assays proved that protein sulfenylation sites colocalize with adhesomes of protrusions. In conclusion, the suprastructural composition and function of adhesomes is redox-regulated by ROS. Of interest in this respect, isoform-selective pharmacological inhibition of NADPH-oxidases (Noxs) reduced the adhesomal location of the collagen-binding α1β1 integrin and the length of the outgrowing neurites, indicative of a role of Nox isoforms in the redox-regulation of adhesomes. Thus, our novel redox proteomics approach not only revealed redox-modifications and the potential redox-regulation of adhesomes and their constituents but it may also provide a tool to analyze the ROS-stimulated neurite repair of peripheral neurons.

High-resolution Crystal Structure of Human pERp1, A Saposin-like Protein Involved in IgA, IgM and Integrin Maturation in the Endoplasmic Reticulum

The folding of disulfide bond containing proteins in the endoplasmic reticulum (ER) is a complex process that requires protein folding factors, some of which are protein-specific. The ER resident saposin-like protein pERp1 (MZB1, CNPY5) is crucial for the correct folding of IgA, IgM and integrins. pERp1 also plays a role in ER calcium homeostasis and plasma cell mobility. As an important factor for proper IgM maturation and hence immune function, pERp1 is upregulated in many auto-immune diseases. This makes it a potential therapeutic target. pERp1 belongs to the CNPY family of ER resident saposin-like proteins. To date, five of these proteins have been identified. All are implicated in protein folding and all contain a saposin-like domain. All previously structurally characterized saposins are involved in lipid binding. However, there are no reports of CNPY family members interacting with lipids, suggesting a novel function for the saposin fold. However, the molecular mechanisms of their function remain elusive. To date, no structure of any CNPY protein has been reported. Here, we present the high-resolution (1.4 Å) crystal structure of human pERp1 and confirm that it has a saposin-fold with unique structural elements not present in other saposin-fold structures. The implications for the role of CNPY proteins in protein folding in the ER are discussed.

CD21lo/-CD27-IgM- Double-Negative B Cells Accumulate in the Joints of Patients With Antinuclear Antibody-Positive Juvenile Idiopathic Arthritis

Juvenile idiopathic arthritis (JIA) encompasses a heterogeneous group of diseases. The appearance of antinuclear antibodies (ANAs) in almost half of the patients suggests B cell dysregulation as a distinct pathomechanism in these patients. Additionally, ANAs were considered potential biomarkers encompassing a clinically homogenous subgroup of JIA patients. However, in ANA+ JIA patients, the site of dysregulated B cell activation as well as the B cell subsets involved in this process is still unknown. Hence, in this cross-sectional study, we aimed in an explorative approach at characterizing potential divergences in B cell differentiation in ANA+ JIA patients by assessing the distribution of peripheral blood (PB) and synovial fluid (SF) B cell subpopulations using flow cytometry. The frequency of transitional as well as switched-memory B cells was higher in PB of JIA patients than in healthy controls. There were no differences in the distribution of B cell subsets between ANA- and ANA+ patients in PB. However, the composition of SF B cells was different between ANA- and ANA+ patients with increased frequencies of CD21^lo/-CD27^-IgM^- "double negative" (DN) B cells in the latter. DN B cells might be a characteristic subset expanding in the joints of ANA+ JIA patients and are potentially involved in the antinuclear immune response in these patients. The results of our explorative study might foster further research dissecting the pathogenesis of ANA+ JIA patients.

Proteomic analysis of aqueous humor in patients with pathologic myopia

Complications from pathologic myopia (PM) are a major cause of visual impairment and blindness. However, an efficient clinical therapeutic strategy for PM is still lacking. The aim of this study was to quantitatively compare the proteomic profiles of aqueous humor between PM and non-PM cataract patients. Twenty aqueous humor samples from each group were analyzed with label-free quantitative proteomic analysis to identify the differentially expressed proteins for function enrichment analyses and protein-protein interaction network construction. Hub protein was validated with ELISA using an independent cohort consisting of 20 samples from each group and its receiver operating characteristic (ROC) curve analysis was conducted. A total of 583 proteins were identified and 101 proteins were found to be differentially expressed, including 63 up-regulated proteins and 38 down-regulated proteins. The bioinformatics analysis suggested that PM is closely associated with immunity and inflammation interactions, and remodeling of extracellular matrix. Apolipoprotein A-I (ApoA1) was enriched as the hub protein of the network with the highest score, degree and centrality. ROC analysis showed that ApoA1 could distinguish PM from controls with an area under the curve of 0.963 (p < 0.001). The findings could provide potential clues for further study on the molecular mechanisms and developing new treatments for PM, especially related to immunity and inflammation interactions. ApoA1 may be a potential key protein and therapeutic target in human PM. SIGNIFICANCE: It is important and urgent to discover the mechanisms of pathologic myopia (PM) to inhibit its progression. This study applied the quantitative proteomic analysis to study aqueous humor from patients with or without PM, aiming to discover dysregulated proteins related to PM. Our results suggested that those dysregulated proteins are closely associated with immunity and inflammation interactions, and remodeling of extracellular matrix. The findings from this study could provide potential clues for further research on the molecular mechanisms and developing new treatments for PM, especially related to immunity and inflammation. ApoA1 may be a potential key protein and therapeutic target in human PM.

Insights into the molecular pathogenesis of ocular tuberculosis

Unclear pathogenic mechanisms underlying the ocular tuberculosis (OTB) has resulted in perplexity related to the diagnosis and management of the disease. Developments in experimental research and innovations in molecular diagnostics have recently provided a new understanding of disease pathogenesis and natural history. The current review focuses on the new insights into OTB pathogenesis, derived from in vivo and in vitro studies on Mycobacterium tuberculosis dissemination and localization into the eye, in combination with histopathological studies on chorioretinal tissue and vascular network. Advances in the knowledge of OTB have influenced disease management in the clinical setting and lead to reconsideration of the role of existing treatments and suggesting potential new therapeutic approaches.

Whole Transcriptome Analysis Reveals Heterogeneity in B Cell Memory Populations in Patients With Juvenile Idiopathic Arthritis-Associated Uveitis

Purpose

Patients with juvenile idiopathic arthritis (JIA) are prone to developing chronic anterior uveitis (JIA-U+). Although several risk factors for JIA-U+ have been identified, the underlying etiology is poorly understood. Histopathological studies demonstrate B cell infiltrates in eye tissues of patients with JIA-U+.

Methods

We performed transcriptome profiling of peripheral blood CD19-positive B cells taken from 14 cases with JIA-U+, 13 JIA cases without uveitis (JIA-U-), and five healthy controls. Deconvolution-based estimation was used to determine the immune cell fractions for each sample.

Results

Deconvolution results revealed that naive B cells made up on average 71% of the CD19-positive cell fractions analyzed. Differential expression analysis identified 614 differentially expressed genes (DEGs) between the groups at nominal significance and six genes at a false discovery rate of 5% (FDR < 0.05). Head-to-head comparison of all JIA-U- versus JIA-U+ revealed no DEGs in the CD19+ B cell pool (FDR < 0.05). However, principal component analysis based on a panel of key genes for B cell subsets revealed that JIA-U+ cases bifurcate into distinct clusters, characterized by markedly disparate expression for genes associated with specific memory B cell populations. CIBERSORT analysis of the overall transcriptome of the new uveitis cluster identified an increased proportion of memory B cells.

Conclusion

These data show that JIA-U- and JIA-U+ have a globally similar transcriptome considering the global peripheral CD19-positive B cell pool. However, heterogeneity in B cell memory genes among cases with uveitis suggests a role for specific memory B cell subsets in the etiology of JIA-U+.

Are formalin-fixed and paraffin-embedded tissues fit for proteomic analysis?

Formalin-fixed and paraffin-embedded (FFPE)-tissue archives are potential treasure troves in the search for clinically interesting specimens. However, while the FFPE-treatment provides excellent conservation of the three-dimensional structure of the tissue and prevents degradation over decades, it also introduces numerous nonspecific and irreversible protein modifications. In this study, we have evaluated several published workflows for FFPE-tissue by fit-for-purpose proteomics technologies. We demonstrate that many protein modifications and cross-links remain after treatment and conclude that the proteomics of FFPE-tissue is of value, but clear-cut limitations must be kept in mind. The analysis of abundant proteins in FFPE is straightforward, but confident identification of low-level proteins and/or biologically relevant modifications is seriously hampered by the FFPE-treatment. Peptide assignment should only be performed on high-quality spectra, even if this is at the cost of lower numbers of protein IDs. As Yergey and Coorssen stated in 2015: "Data quality is considered the primary criterion, and we thus emphasize that the standards of Analytical Chemistry must apply throughout any proteomic analysis."

Improving quick and accurate diagnosis of childhood JIA-uveitis from a pediatric rheumatology perspective

INTRODUCTION

Juvenile idiopathic arthritis (JIA) is the most common pediatric rheumatic disease associated with uveitis. JIA-associated uveitis (JIA-U) is typically asymptomatic, chronic, and can lead to sight-threatening complications. This review will provide approaches to improve the diagnosis and outcomes of children with JIA-U.

AREAS COVERED

We will provide updates on risk factors for uveitis onset and ocular complications, improvements in the ophthalmic screening schedule for uveitis detection, and potential strategies to advance the diagnosis and monitoring of JIA-U using advanced ophthalmic imaging and diagnostic equipment and laboratory biomarkers.

EXPERT OPINION

There is a lack of high-quality research in JIA-U and few randomized controlled trials, underscoring the urgent need for further studies in this population. Early uveitis diagnosis combined with timely and appropriate treatment can improve visual outcomes. Improved knowledge of uveitis pathogenesis, risk factors for uveitis onset, measurement of uveitis outcomes, and optimal treatment are crucial.

Juvenile idiopathic arthritis-associated uveitis

Juvenile idiopathic arthritis (JIA) is the commonest rheumatic disease in children and JIA-associated uveitis its most frequent extra-articular manifestation. The uveitis is potentially sight-threatening and so carries a considerable risk of morbidity. The commonest form of uveitis seen in JIA is chronic anterior uveitis which is almost always asymptomatic in the initial stages. Therefore, screening for JIA-associated uveitis in at-risk patients is essential. The aim of early detection and treatment is to minimise intra-ocular inflammation and avoid complications leading to visual loss, resulting from both disease activity and medications. There is increasing evidence for the early introduction of systemic immunosuppressive therapies in order to reduce topical and systemic glucocorticoid use. Two randomised controlled trials of adalimumab in JIA-associated uveitis provide convincing evidence for the use of this biologic in patients who fail to respond adequately to methotrexate. Tocilizumab and baricitinib are being investigated as alternatives to anti-tumour necrosis factor drugs.

Identification of Ocular Autoantigens Associated With Juvenile Idiopathic Arthritis-Associated Uveitis

The purpose of the current study was to analyze the binding patterns of serum autoantibodies from juvenile idiopathic arthritis (JIA) and JIA-associated uveitis (JIAU) patients to proteomes from different ocular tissues and to identify potential ocular autoantigens in JIAU. Proteomes from porcine iris, ciliary body, or retina tissue were isolated, separated using 2D-gel electrophoresis, and transferred to a blotting membrane. The binding pattern of serum antibodies from JIA or JIAU patients or healthy controls to ocular proteins was visualized by using anti-human IgG secondary antibodies and chemiluminescence reaction. Selected protein spots were excised from silver-stained 2D gels and subjected to mass spectrometry. Serum antibodies binding to ocular proteins were detected in all patient groups and healthy controls. Irrespective of the patient groups, serum antibodies bound to 49 different protein spots of the retina proteome, to 53 of the ciliary body proteome, and to 44 of the iris proteome. The relative binding frequency of sera to these iris protein spots was significantly higher in JIAU than in JIA patients or healthy controls. Particularly in JIAU patients, cluster analyses indicated a broad range of serum antibodies directed against ocular antigens, mostly in the iris proteome. Iris proteins frequently bound by serum antibodies in all groups were identified as tubulin beta chain, vimentin, ATP synthase subunit beta, actin, and L-lactate dehydrogenase B chain. Iris proteins exclusively bound by JIAU serum antibodies were heat shock cognate 71 kDa protein and keratin. Although serum autoantibody binding to ocular antigens was not disease-specific, a significant diversity of autoantibodies against a broad range of antigens, particularly from the iris tissue, was detected in JIAU patients. As the iris is a major site of inflammation in JIAU, the present data give further evidence that autoantibodies may be involved in JIAU immunopathology.