Proteome Analysis of Rheumatoid Arthritis Gut Mucosa

Protein Citrullination by Peptidyl Arginine Deiminase/Arginine Deiminase Homologs in Members of the Human Microbiota and Its Recognition by Anti-Citrullinated Protein Antibodies

The human microbiome exists throughout the body, and it is essential for maintaining various physiological processes, including immunity, and dysbiotic events, which are associated with autoimmunity. Peptidylarginine deiminase (PAD) enzymes can citrullinate self-proteins related to rheumatoid arthritis (RA) that induce the production of anti-citrullinated protein antibodies (ACPAs) and lead to inflammation and joint damage. The present investigation was carried out to demonstrate the expression of homologs of PADs or arginine deiminases (ADs) and citrullinated proteins in members of the human microbiota. To achieve the objective, we used 17 microbial strains and specific polyclonal antibodies (pAbs) of the synthetic peptide derived from residues 100-200 of human PAD2 (anti-PAD2 pAb), and the recombinant fragment of amino acids 326 and 611 of human PAD4 (anti-PAD4 pAb), a human anti-citrulline pAb, and affinity ACPAs of an RA patient. Western blot (WB), enzyme-linked immunosorbent assay (ELISA), elution, and a test with Griess reagent were used. This is a cross-sectional case-control study on patients diagnosed with RA and control subjects. Inferential statistics were applied using the non-parametric Kruskal-Wallis test and Mann-Whitney U test generated in the SPSS program. Some members of phyla Firmicutes and Proteobacteria harbor homologs of PADs/ADs and citrullinated antigens that are reactive to the ACPAs of RA patients. Microbial citrullinome and homolog enzymes of PADs/ADs are extensive in the human microbiome and are involved in the production of ACPAs. Our findings suggest a molecular link between microorganisms of a dysbiotic microbiota and RA pathogenesis.

Emerging role of gut microbiota in autoimmune diseases

Accumulating studies have indicated that the gut microbiota plays a pivotal role in the onset of autoimmune diseases by engaging in complex interactions with the host. This review aims to provide a comprehensive overview of the existing literatures concerning the relationship between the gut microbiota and autoimmune diseases, shedding light on the complex interplay between the gut microbiota, the host and the immune system. Furthermore, we aim to summarize the impacts and potential mechanisms that underlie the interactions between the gut microbiota and the host in autoimmune diseases, primarily focusing on systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, type 1 diabetes mellitus, ulcerative colitis and psoriasis. The present review will emphasize the clinical significance and potential applications of interventions based on the gut microbiota as innovative adjunctive therapies for autoimmune diseases.

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

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

Rheumatoid arthritis and the intestinal microbiome: probiotics as a potential therapy

Rheumatoid arthritis (RA) is a systemic autoimmune disorder characterized by swollen joints, discomfort, stiffness, osteoporosis, and reduced functionality. Genetics, smoking, dust inhalation, high BMI, and hormonal and gut microbiota dysbiosis are all likely causes of the onset or development of RA, but the underlying mechanism remains unknown. Compared to healthy controls, patients with RA have a significantly different composition of gut microbiota. It is well known that the human gut microbiota plays a key role in the initiation, maintenance, and operation of the host immune system. Gut microbiota dysbiosis has local or systematic adverse effects on the host immune system, resulting in host susceptibility to various diseases, including RA. Studies on the intestinal microbiota modulation and immunomodulatory properties of probiotics have been reported, in order to identify their potential possibility in prevention and disease activity control of RA. This review summarized current studies on the role and potential mechanisms of gut microbiota in the development and progression of RA, as well as the preventative and therapeutic effects and potential mechanisms of probiotics on RA. Additionally, we proposed the challenges and difficulties in the application of probiotics in RA, providing the direction for the research and application of probiotics in the prevention of RA.

Microbial Imbalance and Intestinal Permeability in the Pathogenesis of Rheumatoid Arthritis: A Mechanism Review with a Focus on Bacterial Translocation, Citrullination, and Probiotic Intervention

This review aims to investigate the role of intestinal permeability (IP) in rheumatoid arthritis (RA), following the hypotheses that leakage of intestinal microbes can influence increased citrullination of peptides leading to anti-citrullinated protein antibody (ACPA) production and inflammation in RA; and that leaked microbes can migrate to the peripheral joints, leading to immune responses and synovitis in peripheral joints. This review explored the evidence for the link between microbial dysbiosis and increased IP in the inflammatory state in RA, as well as the role of increased citrullination and bacterial translocation in the link between microbiota and immune responses in RA. Furthermore, this research aims to evaluate the potential effect of probiotics on RA symptoms and pathogenesis via proposed mechanisms, including the support of microbial balance and suppression of inflammatory factors in RA. A systematic literature search was conducted in three tranches (review, mechanism, intervention). 71 peer-reviewed papers met the inclusions criteria and are summarized in a narrative analysis. Primary studies were critically appraised, synthesized and their relevance to clinical practice evaluated. Evidence found in this mechanism review consistently supported intestinal dysbiosis and increased IP in arthritis. An altered intestinal microbiome was demonstrated in RA with specific microbes such as Collinsella and Eggerthella correlating with increased IP, mucosal inflammation, and immune responses. Hypercitrullination and ACPA production correlated with arthritic symptoms and intestinal microbes were shown to influence hypercitrullination. Some in vitro and animal studies demonstrated a link between leakage of microbes and bacterial translocation, but further research is needed to elucidate the link between IP and citrullination. Probiotic intervention studies evidenced reductions in inflammatory markers IL-6 and TNFα, associated with proliferation of synovial tissue and pain perception in RA joint inflammation. Despite some conflict in the literature, probiotics may present a promising nutritional intervention in the suppression of both, disease activity and inflammatory markers.Key teaching pointsThere is evidence for a dysbiotic profile of the RA gut with specific RA-associated microbes.Increased intestinal permeability and leakage of PAD enzyme facilitates citrullination of peptides.Hypercitrullination and ACPA production correlate to arthritic signs.Microbial leakage and translocation plays a role in the pathogenesis of RA.Probiotics (e.g. L. Casei 01) may reduce inflammation and ameliorate RA symptoms.

Prolonged administration of total glucosides of paeony improves intestinal immune imbalance and epithelial barrier damage in collagen-induced arthritis rats based on metabolomics-network pharmacology integrated analysis

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by synovial inflammation and joint damage with complex pathological mechanisms. In recent years, many studies have shown that the dysregulation of intestinal mucosal immunity and the damage of the epithelial barrier are closely related to the occurrence of RA. Total glucosides of paeony (TGP) have been used clinically for the treatment of RA in China for decades, while the pharmacological mechanism is still uncertain. The purpose of this study was to investigate the regulatory effect and mechanism of TGP on intestinal immunity and epithelial barrier in RA model rats. The results showed that TGP alleviated immune hyperfunction by regulating the ratio of CD3+, CD4+ and CD8+ in different lymphocyte synthesis sites of the small intestine, including Peyer's patches (PPs), intraepithelial lymphocytes (IELs), and lamina propria lymphocytes (LPLs). Specially, TGP first exhibited immunomodulatory effects on sites close to the intestinal lumen (IELs and LPLs), and then on PPs far away from the intestinal lumen as the administration time prolonged. Meanwhile, TGP restores the intestinal epithelial barrier by upregulating the ratio of villi height (V)/crypt depth (C) and expression of tight junction proteins (ZO-1, occludin). Finally, the integrated analysis of metabolomics-network pharmacology was also used to explore the possible regulation mechanism of TGP on the intestinal tract. Metabolomics analysis revealed that TGP reversed the intestinal metabolic profile disturbance in CIA rats, and identified 32 biomarkers and 163 corresponding targets; network pharmacology analysis identified 111 potential targets for TGP to treat RA. By intersecting the results of the two, three key targets such as ADA, PNP and TYR were determined. Pharmacological verification experiments showed that the levels of ADA and PNP in the small intestine of CIA rats were significantly increased, while TGP significantly decreased their ADA and PNP levels. In conclusion, purine metabolism may play an important role in the process of TGP improving RA-induced intestinal immune imbalance and impaired epithelial barrier.

The SYSCID map: a graphical and computational resource of molecular mechanisms across rheumatoid arthritis, systemic lupus erythematosus and inflammatory bowel disease

Chronic inflammatory diseases (CIDs), including inflammatory bowel disease (IBD), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are thought to emerge from an impaired complex network of inter- and intracellular biochemical interactions among several proteins and small chemical compounds under strong influence of genetic and environmental factors. CIDs are characterised by shared and disease-specific processes, which is reflected by partially overlapping genetic risk maps and pathogenic cells (e.g., T cells). Their pathogenesis involves a plethora of intracellular pathways. The translation of the research findings on CIDs molecular mechanisms into effective treatments is challenging and may explain the low remission rates despite modern targeted therapies. Modelling CID-related causal interactions as networks allows us to tackle the complexity at a systems level and improve our understanding of the interplay of key pathways. Here we report the construction, description, and initial applications of the SYSCID map (https://syscid.elixir-luxembourg.org/), a mechanistic causal interaction network covering the molecular crosstalk between IBD, RA and SLE. We demonstrate that the map serves as an interactive, graphical review of IBD, RA and SLE molecular mechanisms, and helps to understand the complexity of omics data. Examples of such application are illustrated using transcriptome data from time-series gene expression profiles following anti-TNF treatment and data from genome-wide associations studies that enable us to suggest potential effects to altered pathways and propose possible mechanistic biomarkers of treatment response.

Advances in proteomics: characterization of the innate immune system after birth and during inflammation

Proteomics is the characterization of the protein composition, the proteome, of a biological sample. It involves the large-scale identification and quantification of proteins, peptides, and post-translational modifications. This review focuses on recent developments in mass spectrometry-based proteomics and provides an overview of available methods for sample preparation to study the innate immune system. Recent advancements in the proteomics workflows, including sample preparation, have significantly improved the sensitivity and proteome coverage of biological samples including the technically difficult blood plasma. Proteomics is often applied in immunology and has been used to characterize the levels of innate immune system components after perturbations such as birth or during chronic inflammatory diseases like rheumatoid arthritis (RA) and inflammatory bowel disease (IBD). In cancers, the tumor microenvironment may generate chronic inflammation and release cytokines to the circulation. In these situations, the innate immune system undergoes profound and long-lasting changes, the large-scale characterization of which may increase our biological understanding and help identify components with translational potential for guiding diagnosis and treatment decisions. With the ongoing technical development, proteomics will likely continue to provide increasing insights into complex biological processes and their implications for health and disease. Integrating proteomics with other omics data and utilizing multi-omics approaches have been demonstrated to give additional valuable insights into biological systems.

Advances in the implications of the gut microbiota on the treatment efficacy of disease-modifying anti-rheumatic drugs in rheumatoid arthritis

Alterations in the composition or function of the gut microbiota are associated with the etiology of human diseases. Drug-microbiota interactions can affect drug bioavailability, effectiveness, and toxicity through various routes. For instance, the direct effect of microbial enzymes on drugs can either boost or diminish their efficacy. Thus, considering its wide range of metabolic capabilities, the gut microbiota is a promising target for pharmacological modulation. Furthermore, drugs can alter the microbiota and the mechanisms by which they interact with their host. Individual variances in microbial profiles can also contribute to the different host responses to various drugs. However, the influence of interactions between the gut microbiota and drugs on treatment efficacy remains poorly elucidated. In this review, we will discuss the impact of microbiota dysbiosis in the pathogenesis of rheumatoid arthritis (RA), and we will attempt to elucidate the crosstalk between the gut microbiota and disease-modifying anti-rheumatic drugs (DMARDs), with an emphasis on how drug-microbiota interactions affect the treatment efficacy in RA. We speculate that improved knowledge of these critical interactions will facilitate the development of novel therapeutic options that use microbial markers for predicting or optimizing treatment outcomes.

Impaired Abcb1a function and red meat in a translational colitis mouse model induces inflammation and alters microbiota composition

Inflammatory Bowel Disease (IBD) affects approximately 0.3% of the global population, with incidence rates rising dramatically worldwide. Emerging evidence points to an interplay between exposome factors such as diet and gut microbiota, host genetics, and the immune system as crucial elements in IBD development. ATP-binding cassette (ABC) transporters, including human p-glycoprotein encoded by the Abcb1 gene, influence intestinal inflammation, and their expression may interact with environmental factors such as diet and gut microbes. Our study aimed to examine the impact of protein sources on a genetic colitis mouse model.

Methods

Abcb1a-deficient colitis mice were fed either casein or red meat-supplemented diets to investigate potential colitis-aggravating components in red meat and their effects on host-microbiota interactions. We conducted deep label free quantitative proteomic inflammation profiling of gastrointestinal tissue (colon, ileum) and urine, and determined the overall microbiome in feces using 16S rRNA gene sequencing. Microbiota shifts by diet and protein transporter impairment were addressed by multivariate statistical analysis. Colon and systemic gut inflammation were validated through histology and immune assays, respectively.

Results

A quantitative discovery based proteomic analysis of intestinal tissue and urine revealed associations between ileum and urine proteomes in relation to Abcb1a deficiency. The absence of Abcb1a efflux pump function and diet-induced intestinal inflammation impacted multiple systemic immune processes, including extensive neutrophil extracellular trap (NET) components observed in relation to neutrophil degranulation throughout the gastrointestinal tract. The colitis model's microbiome differed significantly from that of wild-type mice, indicating the substantial influence of efflux transporter deficiency on microbiota.

Conclusion

The proteomic and microbiota analyzes of a well-established murine model enabled the correlation of gastrointestinal interactions not readily identifiable in human cohorts. Insights into dysregulated biological pathways in this disease model might offer translational biomarkers based on NETs and improved understanding of IBD pathogenesis in human patients. Our findings demonstrate that drug transporter deficiency induces substantial changes in the microbiota, leading to increased levels of IBD-associated strains and resulting in intestinal inflammation. GRAPHICAL ABSTRACT.

Using the Microbiome as a Regenerative Medicine Strategy for Autoimmune Diseases

Autoimmune (AI) diseases, which present in a multitude of systemic manifestations, have been connected to many underlying factors. These factors include the environment, genetics, individual microbiomes, and diet. An individual's gut microbiota is an integral aspect of human functioning, as it is intimately integrated into the metabolic, mechanical, immunological, and neurologic pathways of the body. The microbiota dynamically changes throughout our lifetimes and is individually unique. While the gut microbiome is ever-adaptive, gut dysbiosis can exert a significant influence on physical and mental health. Gut dysbiosis is a common factor in various AI, and diets with elevated fat and sugar content have been linked to gut microbiome alterations, contributing to increased systemic inflammation. Additionally, multiple AI's have increased levels of certain inflammatory markers such as TNF-a, IL-6, and IL-17 that have been shown to contribute to arthropathy and are also linked to increased levels of gut dysbiosis. While chronic inflammation has been shown to affect many physiologic systems, this review explores the connection between gut microbiota, bone metabolism, and the skeletal and joint destruction associated with various AI, including psoriatic arthritis, systemic lupus erythematosus, irritable bowel disease, and rheumatoid arthritis. This review aims to define the mechanisms of microbiome crosstalk between the cells of bone and cartilage, as well as to investigate the potential bidirectional connections between AI, bony and cartilaginous tissue, and the gut microbiome. By doing this, the review also introduces the concept of altering an individual's specific gut microbiota as a form of regenerative medicine and potential tailored therapy for joint destruction seen in AI. We hope to show multiple, specific ways to target the microbiome through diet changes, rebalancing microbial diversity, or decreasing specific microbes associated with increased gut permeability, leading to reduced systemic inflammation contributing to joint pathology. Additionally, we plan to show that diet alterations can promote beneficial changes in the gut microbiota, supporting the body's own endogenous processes to decrease inflammation and increase healing. This concept of microbial alteration falls under the definition of regenerative medicine and should be included accordingly. By implementing microbial alterations in regenerative medicine, this current study could lend increasing support to the current research on the associations of the gut microbiota, bone metabolism, and AI-related musculoskeletal pathology.

Antibodies against citrullinated proteins of IgA isotype are associated with progression to rheumatoid arthritis in individuals at-risk

OBJECTIVE

Events triggering disease outbreak in individuals at-risk for rheumatoid arthritis (RA at-risk) remain unclear, and the role of the various anticitrullinated protein antibody (ACPA) isotypes in this process is still to be established. We aimed to investigate the prevalence of IgA ACPA in RA at-risk individuals, their role in the transition from the RA at-risk status to RA and their dynamics during this transition.

METHODS

Cross-sectional measurement of serum IgA1 and IgA2 ACPA levels was conducted in healthy controls, RA at-risk individuals and patients with RA and compared with the frequency of RA development in at risk individuals during a follow-up of 14 months. In addition, longitudinal measurements of serum IgA1 and IgA2 ACPA levels prior to, at and after the onset of RA were performed.

RESULTS

Approximately two-thirds of RA at-risk individuals were positive for serum IgA1 and IgA2 ACPA in levels comparable to IgG ACPA positive patients with RA. IgA1, but not IgA2 ACPA positivity was associated with the transition from the RA at-risk state to RA within the following 14 months. Interestingly, during this transition process, IgA1 ACPA levels declined at RA onset and also thereafter during the early phase of RA. This decline was confirmed in a second, independent cohort.

CONCLUSION

Both IgA1 and IgA2 ACPA are present in RA at-risk individuals, but only IgA1 ACPA are associated with the progression to RA. The observed decline in serum IgA1 ACPA levels before the onset of RA might indicate starting barrier leakiness prior to disease outbreak.

Platelets derived citrullinated proteins and microparticles are potential autoantibodies ACPA targets in RA patients

Citrullinated neoepitopes have emerged as key triggers of autoantibodies anti-citrullinated protein antibodies (ACPA) synthesis in rheumatoid arthritis (RA) patients. Apart from their critical role in homeostasis and thrombosis, platelets have a significant contribution to inflammation as well. Although anuclear in nature, platelets have an intricate post-translational modification machinery. Till now, citrullination in platelets and its contribution to trigger autoantibodies ACPA production in RA is an unexplored research direction. Herein, we investigated the expression of peptidylarginine deiminase (PAD) enzymes and citrullinated proteins/peptides in the human platelets and platelet derived microparticles (PDP). Both PAD4 mRNA and protein, but not the other PAD isoforms, are detectable in the human platelets. With a strict filtering criterion,108 citrullination sites present on 76 proteins were identified in the human platelets, and 55 citrullinated modifications present on 37 different proteins were detected in the PDPs. Among them, some are well-known citrullinated autoantigens associated with RA. Citrullinated forms of thrombospondin-1, β-actin, and platelet factor-4 (also known as CXCL4) are highly immunogenic and bound by autoantibodies ACPA. Furthermore, ACPA from RA sera and synovial fluids recognized citrullinated proteins from platelets and significantly activated them as evidenced by P-selectin upregulation and sCD40 L secretion. These results clearly demonstrate the presence of citrullinated autoantigens in platelets and PDPs, thus could serve as potential targets of ACPA in RA.

PADs and NETs in digestive system: From physiology to pathology

Peptidylarginine deiminases (PADs) are the only enzyme class known to deiminate arginine residues into citrulline in proteins, a process known as citrullination. This is an important post-translational modification that functions in several physiological and pathological processes. Neutrophil extracellular traps (NETs) are generated by NETosis, a novel cell death in neutrophils and a double-edged sword in inflammation. Excessive activation of PADs and NETs is critically implicated in their transformation from a physiological to a pathological state. Herein, we review the physiological and pathological functions of PADs and NETs, in particular, the involvement of PAD2 and PAD4 in the digestive system, from inflammatory to oncological diseases, along with related therapeutic prospects.

Early-stage inflammation changes in supraspinatus muscle after rotator cuff tear

BACKGROUND

Rotator cuff (RC) tendon tear leads to impaired shoulder function and pain. The supraspinatus (SS) tendon is most often affected, but the biological response of the SS muscle to SS tendon tear is largely unknown. This study aimed to investigate time-dependent muscle inflammation, degeneration, fatty infiltration, and regeneration in experimental SS tear conditions.

METHODS

Forty-five C57BL/6 mice were subjected to SS tendon tear and allowed to recover for 1, 3, 5, 7, 14, or 28 days. The extent of muscle damage was examined using histologic, flow cytometric, proteomic, and chemiluminescence analyses.

RESULTS

We found that muscle inflammation peaked around day 5 with increased monocyte infiltration and increased cytokine levels in the ipsilateral compared to the contralateral SS muscle. Bioinformatics analysis of proteomics on mice that survived 5 days after RC tendon tear revealed upregulated proteins involved in "neutrophil activation involved in immune response" and "extracellular matrix organization," whereas "skeletal muscle tissue development and contraction" and "respiratory electron transport chain" were among the most downregulated. Histologic analysis of collagen showed increased collagen accumulation and fatty infiltration of the ipsilateral SS over time. Finally, we observed time- and lesion-dependent changes in satellite cell and fibro-adipogenic progenitor populations.

CONCLUSION

Altogether, we demonstrate that the SS muscle shows severe signs of acute inflammation, early degeneration, and fatty infiltration, as well as reduced regenerative potential following SS tendon tear.

Pros and cons of causative association between periodontitis and rheumatoid arthritis

Research in recent decades has brought significant advancements in understanding of the molecular basis of the etiology of autoimmune diseases, including rheumatoid arthritis, a common systemic disease in which an inappropriate or inadequate immune response to environmental challenges leads to joint destruction. Recent studies have indicated that the classical viewpoint of the immunological processes underpinning the pathobiology of rheumatoid arthritis is restricted and needs to be expanded to include a more holistic and interdisciplinary approach incorporating bacteria-induced inflammatory reactions as an important pathway in rheumatoid arthritis etiology. Here, we discuss in detail data showing the clinical and molecular association of rheumatoid arthritis development with periodontal diseases. We also describe the unique role of periopathogens, which have been proposed to be crucial in the initiation and progression of this autoimmune pathological disorder.

Low-Dose Interleukin-2 Altered Gut Microbiota and Ameliorated Collagen-Induced Arthritis

Purpose

Low-dose interleukin-2 (ld-IL-2) has been shown to regulate the balance between effector T and regulatory T (Treg) cells and has been used in several clinical trials to treat autoimmune diseases including rheumatoid arthritis (RA). In this study, we investigated the effects of ld-IL-2 on collagen-induced arthritis (CIA) in mice.

Methods

Arthritis severity in CIA mice was measured using the arthritis index (AI), radiographs, and hematoxylin and eosin staining. Cytokines were detected using enzyme-linked immunosorbent assay. Gut microbiota alterations and short-chain fatty acid production were analyzed through 16S rRNA sequencing and gas chromatography.

Results

The AI scores of CIA mice treated with ld-IL-2 were significantly lower compared to the model group, which significantly reduced the severity of arthritis. Ld-IL-2 also altered the gut microbiota in CIA mice. The diversity, composition, and dominant species of gut microbiota were altered by ld-IL-2 treatment. Ld-IL-2 also increased short-chain fatty acid levels. There was a strong correlation between ld-IL-2 treatment and improved gut microbiota.

Conclusion

Ld-IL-2 significantly ameliorated joint inflammation and bone damage and improved gut microbial dysbiosis in CIA, indicating that it may be a promising therapy for RA patients.

Crosstalk between immune cells and bone cells or chondrocytes

The term "osteoimmunology" was coined to denote the bridge between the immune system and the skeletal system. Osteoimmunology is interdisciplinary, and a full understanding and development of this "bridge" will provide an in-depth understanding of the switch between body health and disease development. B lymphocytes can promote the maturation and differentiation of osteoclasts, and osteoclasts have a negative feedback effect on B lymphocytes. Different subtypes of T lymphocytes regulate osteoclasts in different directions. T lymphocytes have a two-way regulatory effect on osteoblasts, while B lymphocytes have minimal regulatory effects on osteoblasts. In contrast, osteoblasts can promote the differentiation and maturation of T lymphocytes and B lymphocytes. Different immune cells have different effects on chondrocytes; some cooperate with each other, while some antagonize each other. In a healthy adult body, bone resorption and bone formation are in a dynamic balance under the action of multiple mechanisms. In this review, we summarize the interactions and key signaling molecular mechanisms between each type of cell in the immune system and the skeletal system.

Quinoline-based fluorescent probe for the detection and monitoring of hypochlorous acid in a rheumatoid arthritis model

The development of effective bioanalytical methods for the visualization of hypochlorous acid (HOCl) in situ in rheumatoid arthritis (RA) directly contributes to better understanding the roles of HOCl in this disease. In this work, a new quinoline-based fluorescence probe (HQ) has been developed for the detection and visualization of a HOCl-mediated inflammatory response in a RA model. HQ possesses a donor–π–acceptor (D–π–A) structure that was designed by conjugating p-hydroxybenzaldehyde (electron donor) and 1-ethyl-4-methylquinolinium iodide (electron acceptor) through a C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C double bond. In the presence of HOCl, oxidation of phenol to benzoquinone led to the red-shift (93 nm) of the adsorption and intense quenching of the fluorescence emission. The proposed response reaction mechanism was verified by high performance liquid chromatography (HPLC) and high-resolution mass spectroscopy (HRMS) titration analysis. The remarkable color changes of the HQ solution from pale yellow to pink enabled the application of HQ-stained chromatography plates for the “naked-eye” detection of HOCl in real-world water samples. HQ featured high selectivity and sensitivity (6.5 nM), fast response time (<25 s) to HOCl, reliability at different pH (3.0 to 11.5) and low cytotoxicity. HQ's application in biological systems was then demonstrated by the monitoring of HOCl-mediated treatment response to RA. This work thus provided a new tool for the detection and imaging of HOCl in inflammatory disorders.

A quinoline-based fluorescent probe (HQ) has been designed and synthesized for the monitoring of HOCl-mediated treatment response of a rheumatoid arthritis (RA) model and “naked-eye” detection of HOCl in real water samples.

Intestinal barrier dysfunction plays an integral role in arthritis pathology and can be targeted to ameliorate disease

Background

Evidence suggests an important role for gut-microbiota dysbiosis in the development of rheumatoid arthritis (RA). The link between changes in gut bacteria and the development of joint inflammation is missing. Here, we address whether there are changes to the gut environment and how they contribute to arthritis pathogenesis.

Methods

We analyzed changes in markers of gut permeability, damage, and inflammation in peripheral blood and serum of RA patients. Serum, intestines, and lymphoid organs isolated from K/BxN mice with spontaneous arthritis or from wild-type, genetically modified interleukin (IL)-10R^−/−or claudin-8^−/−mice with induced arthritis were analyzed by immunofluorescence/histology, ELISA, and flow cytometry.

Findings

RA patients display increased levels of serum markers of gut permeability and damage and cellular gut-homing markers, both parameters positively correlating with disease severity. Arthritic mice display increased gut permeability from early stages of disease, as well as bacterial translocation, inflammatory gut damage, increases in interferon γ (IFNγ)⁺and decreases in IL-10⁺intestinal-infiltrating leukocyte frequency, and reduced intestinal epithelial IL-10R expression. Mechanistically, both arthritogenic bacteria and leukocytes are required to disrupt gut-barrier integrity. We show that exposing intestinal organoids to IFNγ reduces IL-10R expression by epithelial cells and that mice lacking epithelial IL-10R display increased intestinal permeability and exacerbated arthritis. Claudin-8^−/−mice with constitutively increased gut permeability also develop worse joint disease. Treatment of mice with AT-1001, a molecule that prevents development of gut permeability, ameliorates arthritis.

Conclusions

We suggest that breakdown of gut-barrier integrity contributes to arthritis development and propose restoration of gut-barrier homeostasis as a new therapeutic approach for RA.

Funding

Funded by Versus Arthritis (21140 and 21257) and UKRI/MRC (MR/T000910/1).

Serum gut-permeability markers LPB, LPS, and I-FABP are increased in RA

Mice with arthritis have increased gut permeability and intestinal inflammation

Both bacteria and leukocytes are needed to disrupt gut-barrier integrity

Prevention of gut-barrier dysfunction in arthritis ameliorates joint inflammation

Rheumatoid arthritis is an autoimmune disorder characterized by chronic joint inflammation. Accumulating evidence suggests that changes in the composition of the bacteria residing in the gut could be responsible for joint inflammation. Currently, it is unclear how bacteria or their products instruct cells of the immune system to become harmful and induce arthritis. Researchers at University College London have shown that, in arthritis, there is profound damage to the gut lining, which fails to work properly as a barrier, as well as an accumulation in the gut of white blood cells that cause inflammation. The authors show that, in arthritis, bacteria cross the prohibited border of the intestinal lining and that repairing gut permeability defects with specific drugs inhibits joint inflammation.

Interplay of Microbiota and Citrullination in the Immunopathogenesis of Rheumatoid Arthritis

Microbiota is a balanced ecosystem that has important functions to the host health including development, defense, digestion, and absorption of dietary fibers and minerals, vitamin synthesizes, protection, and training the host immune system. On the other hand, its dysbiosis is linked to many human diseases such as rheumatoid arthritis (RA). The RA is an inflammatory autoimmune disorder caused by genetic and environmental factors; microbiota may be considered as a risk environmental factor for it. Citrullination is a post-translation modification (PMT) that converts the amino acid arginine to amino acid citrulline in certain proteins. These citrullinated proteins are recognized as a foreign antigen by the immune system resulting in the upregulation of inflammatory action such as in RA. The current work highlights the effect of both gut and oral microbiota dysbiosis on the development of RA, as well as discusses how the alteration in microbiota composition leads to the overgrowth of some bacterial species that entangled in RA pathogenicity. The evidence suggested that some oral and gut microbial species such as Porphyromonas gingivalis and Prevotella copri, respectively, contribute to RA pathogenesis. During dysbiosis, these bacteria can mediate the citrullination of either human or bacteria proteins to trigger an immune response that leads to the generation of autoantibodies.

Sample Preparation for High-Throughput Urine Proteomics Using 96-Well Polyvinylidene Fluoride (PVDF) Membranes

Proteomics analysis of urine samples allows for studying the impact of system perturbation. However, meaningful proteomics-based biomarker discovery projects often require the analysis of large patient cohorts with hundreds of samples to describe the biological variability. Thus, robust high-throughput sample processing methods are a prerequisite for clinical proteomics pipelines that minimize experimental bias due to individual sample processing methods. Herein we describe a high-throughput method for parallel 96-well plate-based processing of urine samples for subsequent LC/MS-based proteomic analyses. Protein digestion and subsequent sample processing steps are efficiently performed in 96-well polyvinylidene fluoride (PVDF) membrane plate allowing for the use of vacuum manifolds for rapid liquid transfer, and multichannel pipettes and/or liquid handing robots. In this chapter we make available a detailed step-by-step protocol for our 'MStern blotting' sample processing strategy applied to patient urine samples followed by mass spectrometry-based proteomics analysis. Subsequently, we provide an example application using minimal volume of urine samples (e.g. 150 μL) collected from children pre and post thoracotomy to identify the predominant sites of protein catabolism and aid in the design of therapies to ameliorate protein catabolism and breakdown during critical illness. Furthermore, we demonstrate how the systemic state is reflected in the urine as an easily obtainable, stable, and safe biofluid.

Oral Dysbiosis and Autoimmunity: From Local Periodontal Responses to an Imbalanced Systemic Immunity. A Review

The current paradigm of onset and progression of periodontitis includes oral dysbiosis directed by inflammophilic bacteria, leading to altered resolution of inflammation and lack of regulation of the inflammatory responses. In the construction of explanatory models of the etiopathogenesis of periodontal disease, autoimmune mechanisms were among the first to be explored and historically, for more than five decades, they have been described in an isolated manner as part of the tissue damage process observed in periodontitis, however direct participation of these mechanisms in the tissue damage is still controversial. Autoimmunity is affected by genetic and environmental factors, leading to an imbalance between the effector and regulatory responses, mostly associated with failed resolution mechanisms. However, dysbiosis/infection and chronic inflammation could trigger autoimmunity by several mechanisms including bystander activation, dysregulation of toll-like receptors, amplification of autoimmunity by cytokines, epitope spreading, autoantigens complementarity, autoantigens overproduction, microbial translocation, molecular mimicry, superantigens, and activation or inhibition of receptors related to autoimmunity by microorganisms. Even though autoreactivity in periodontitis is biologically plausible, the associated mechanisms could be related to non-pathologic responses which could even explain non-recognized physiological functions. In this review we shall discuss from a descriptive point of view, the autoimmune mechanisms related to periodontitis physio-pathogenesis and the participation of oral dysbiosis on local periodontal autoimmune responses as well as on different systemic inflammatory diseases.

DMARDs-Gut Microbiota Feedback: Implications in the Response to Therapy

Due to its immunomodulatory effects and the limitation in the radiological damage progression, disease-modifying antirheumatic drugs (DMARDs) work as first-line rheumatoid arthritis (RA) treatment. In recent years, numerous research projects have suggested that the metabolism of DMARDs could have a role in gut dysbiosis, which indicates that the microbiota variability could modify the employment of direct and indirect mechanisms in the response to treatment. The main objective of this review was to understand the gut microbiota bacterial variability in patients with RA, pre and post-treatment with DMARDs, and to identify the possible mechanisms through which microbiota can regulate the response to pharmacological therapy.

Interactions between Gut Microbiota and Immunomodulatory Cells in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases caused by abnormal immune activation and immune tolerance. Immunomodulatory cells (ICs) play a critical role in the maintenance and homeostasis of normal immune function and in the pathogenesis of RA. The human gastrointestinal tract is inhabited by trillions of commensal microbiota on the mucosal surface that play a fundamental role in the induction, maintenance, and function of the host immune system. Gut microbiota dysbiosis can impact both the local and systemic immune systems and further contribute to various diseases, such as RA. The neighbouring intestinal ICs located in distinct intestinal mucosa may be the most likely intermediary by which the gut microbiota can affect the occurrence and development of RA. However, the reciprocal interaction between the components of the gut microbiota and their microbial metabolites with distinct ICs and how this interaction may impact the development of RA are not well studied. Therefore, a better understanding of the gut microbiota, ICs, and their interactions might improve our knowledge of the mechanisms by which the gut microbiota contribute to RA and facilitate the further development of novel therapeutic approaches. In this review, we have summarized the roles of the gut microbiota in the immunopathogenesis of RA, especially the interactions between the gut microbiota and ICs, and further discussed the strategies for treating RA by targeting/regulating the gut microbiota.

Proteomic analysis of synovial fluid from rheumatic arthritis and spondyloarthritis patients

Background

The aetiologies and pathogeneses of the joint diseases rheumatoid arthritis (RA) and spondyloarthritis (SpA) are still not fully elucidated. To increase our understanding of the molecular pathogenesis, we analysed the protein composition of synovial fluid (SF) from rheumatoid arthritis (RA) and spondyloarthritis (SpA) patients.

Methods

Fifty-six synovial fluid samples (RA, n = 32; SpA, n = 24) were digested with trypsin, and the resulting peptides were separated by liquid chromatography and analysed by tandem mass spectrometry. Additionally, the concentration of cell-free DNA (cfDNA) in the synovial fluid was measured, and plasma C-reactive protein (CRP) was determined.

Results

Three hundred thirty five proteins were identified within the SF. The more abundant proteins seen in RA SF were inflammatory proteins, including proteins originating from neutrophil granulocytes, while SpA SF had less inflammatory proteins and a higher concentration of haptoglobin. The concentration of cell-free DNA in the SF increased together with proteins that may have originated from neutrophils. Plasma CRP levels in both RA and SpA, correlated to other acute phase reactants.

Conclusions

The proteomic results underline that neutrophils are central in the RA pathology but not in SpA, and even though inhibitors of neutrophils (migration, proteinase inhibitors) were present in the SF it was not sufficient to interrupt the disease process.

Troublesome friends within us: the role of gut microbiota on rheumatoid arthritis etiopathogenesis and its clinical and therapeutic relevance

The role of gut microbiota on immune regulation and the development of autoimmune diseases such as rheumatoid arthritis (RA) is an emerging research topic. Multiple studies have demonstrated alterations on gut microbiota composition and/or function (referred to as dysbiosis) both in early and established RA patients. Still, research delineating the molecular mechanisms by which gut microorganisms induce the loss of immune tolerance or contribute to disease progression is scarce. Available data indicate that gut microbiota alterations are involved in RA autoimmune response by several mechanisms including the post-translational modification of host proteins, molecular mimicry between bacterial and host epitopes, activation of immune system and polarization toward inflammatory phenotypes, as well as induction of intestinal permeability. Therefore, in this review we analyze recent clinical and molecular evidence linking gut microbiota with the etiopathogenesis of RA. The potential of the gut microbiota as a diagnostic or severity biomarker is discussed, as well as the opportunity areas for the development of complementary therapeutic strategies based on the modulation of gut microbiota in the rheumatic patient.

Infectious Triggers in Periodontitis and the Gut in Rheumatoid Arthritis (RA): A Complex Story About Association and Causality

Rheumatoid arthritis (RA) is a systemic immune mediated inflammatory disease of unknown origin, which is predominantly affecting the joints. Antibodies against citrullinated peptides are a rather specific immunological hallmark of this heterogeneous entity. Furthermore, certain sequences of the third hypervariable region of human leukocyte antigen (HLA)-DR class II major histocompatibility (MHC) molecules, the so called "shared epitope" sequences, appear to promote autoantibody positive types of RA. However, MHC-II molecule and other genetic associations with RA could not be linked to immune responses against specific citrullinated peptides, nor do genetic factors fully explain the origin of RA. Consequently, non-genetic factors must play an important role in the complex interaction of endogenous and exogenous disease factors. Tobacco smoking was the first environmental factor that was associated with onset and severity of RA. Notably, smoking is also an established risk factor for oral diseases. Furthermore, smoking is associated with extra-articular RA manifestations such as interstitial lung disease in anatomical proximity to the airway mucosa, but also with subcutaneous rheumatoid nodules. In the mouth, Porphyromonas gingivalis is a periodontal pathogen with unique citrullinating capacity of foreign microbial antigens as well as candidate RA autoantigens. Although the original hypothesis that this single pathogen is causative for RA remained unproven, epidemiological as well as experimental evidence linking periodontitis (PD) with RA is rapidly accumulating. Other periopathogens such as Aggregatibacter actinomycetemcomitans and Prevotella intermedia were also proposed to play a specific immunodominant role in context of RA. However, demonstration of T cell reactivity against citrullinated, MHC-II presented autoantigens from RA synovium coinciding with immunity against Prevotella copri (Pc.), a gut microbe attracted attention to another mucosal site, the intestine. Pc. was accumulated in the feces of clinically healthy subjects with citrulline directed immune responses and was correlated with RA onset. In conclusion, we retrieved more than one line of evidence for mucosal sites and different microbial taxa to be potentially involved in the development of RA. This review gives an overview of infectious agents and mucosal pathologies, and discusses the current evidence for causality between different exogenous or mucosal factors and systemic inflammation in RA.

Expansion of Rare and Harmful Lineages is Associated with Established Rheumatoid Arthritis

Objectives: To characterize the gut microbiota profile in rheumatoid arthritis (RA) patients and investigate its association with certain characteristics of RA. Patients and methods: A nested case–control cohort of 40 patients with RA and 40 sex-age matched controls was studied. Subjects with diabetes, with any other inflammatory disease, practicing extreme diets, taking antibiotics, probiotics or under any new treatment for at least three months prior to sampling were excluded. The microbiota composition was determined by 16S rRNA pyrosequencing and bioinformatics analysis by Quantitative Insights Into Microbial Ecology (QIIME). Other variables included clinical-laboratory variables and average Disease Activity Score 28 points during the follow-up period. Multiple linear regression models were constructed to investigate the possible risk factors for the microbiota. Results: β-diversity data showed that patients tend to differ from healthy subjects according to their microbiota (p = 0.07). The analysis showed an increase in Collinsella aerofaciens, Sedimentibacter and Enterococcus genera in patients compared to controls, as well as a decrease in Dorea formicigenerans. Likewise, an increase in the activity of arginine deiminase was observed, which was found in approximately 90% of the RA genes of the genus Collinsela. The sequence number of Collinsella aerofaciens was independently associated with age (B (95%CI), −0.347 (−21.6, −2.1)), high ACPA (0.323 (27.4–390.0)) and smoking (0.300 (8.8–256.4)) in RA patients. In addition, we observed decreases in Sarcina, 02d06 and Porphyromonas bacterial lineages. Conclusion: Patients with RA present dysbiosis, resulting from an abundance of certain bacterial lineages and a decrease in others. These alterations could influence the maintenance of autoimmunity to this disease.

Human Umbilical Mesenchymal Stem Cells Display Therapeutic Potential in Rheumatoid Arthritis by Regulating Interactions Between Immunity and Gut Microbiota via the Aryl Hydrocarbon Receptor

Background

Rheumatoid arthritis (RA) is an autoimmune disease that may be associated with gut microbiota via the aryl hydrocarbon receptor (AhR). Human umbilical mesenchymal stem cells (HUMSCs) have therapeutic potential against RA, but the underlying mechanism has not been fully elucidated. The purpose of this study was to explore the mechanism of action of HUMSCs in rats with collagen-induced arthritis (CIA).

Method

HUMSCs (1 × 10⁶) were transplanted into each rat with CIA. The tissue localization of HUMSCs and the therapeutic effects in the ankles were assessed. The immune status and expression of immune-related genes and proteins in related lymphoid tissues were subsequently tested. Furthermore, the levels of immune-related factors in serum and the changes in gut microbiota in the ileum were detected, and the levels of indole and their derivatives in plasma and the levels of AhR in the ileum were evaluated.

Results

HUMSCs homed to the popliteal lymph node (PLN), mesenteric lymph node (MLN), ankle cartilage, and ileum mucosa in rats with CIA. The transplantation of HUMSCs reduced the pathology scores and the degree of bone damage in the ankles. The immune status of T regulatory cells (Tregs) and T helper (Th)17 cells and the gene expression levels of interleukin (IL)-10, transforming growth factor (TGF)-β1, and IL-17A were altered in the PLN, which is the lymph tissue closest to the nidus, and the MLN, which is one of the gut-associated lymphoid tissues (GALTs). The proportion and function of B cells, Tregs, and Th17 cells were regulated in other GALTs, namely, Peyer’s patches and the lamina propria. The gene expression of TGF-β1 and IL-17A and protein expression of IL-10, TGF-β1, IL-17A, IL-22, and immunoglobulin A (IgA) were modulated in the ileum, and the serum levels of IL-10, TGF-β1, IL-17A, IL-1β, and tumor necrosis factor (TNF)-α were regulated in the rats with CIA. The relative abundances of the genera Bacteroides and Bacillus were increased in the HUMSCs-treated rat with CIA; in addition, the levels of indole, indoleacetic acid, and indole-3-lactic acid were consistently upregulated, and this upregulation was accompanied by increases in AhR gene and protein expression.

Conclusion

Our study demonstrates that HUMSCs play a therapeutic role in rats with CIA by regulating the interactions between host immunity and gut microbiota via the AhR.

Сandidate SNP-markers of rheumatoid arthritis that can significantly alter the affinity of the TATA-binding protein for human gene promoters

Rheumatoid polyarthritis (RA) is an autoimmune disease with autoantibodies, including antibodies to citrullant antigens and proinflammatory cytokines, such as TNF-α and IL-6, which are involved in the induction of chronic synovitis, bone erosion, followed by deformity. Immunopathogenesis is based on the mechanisms of the breakdown of immune tolerance to its own antigens, which is characterized by an increase in the activity of T-effector cells, causing RA symptomatology. At the same time, against the background of such increased activity of effector lymphocytes, a decrease in the activity of a number of regulatory cells, including regulatory T-cells (Treg) and myeloid suppressor cells, is recorded. There is reason to say that it is the change in the activity of suppressor cells that is the leading element in RA pathogenesis. That is why only periods of weakening (remission) of RA are spoken of. According to the more powerful female immune system compared to the male one, the risk of developing RA in women is thrice as high, this risk decreases during breastfeeding and grows during pregnancy as well as after menopause in proportion to the level of sex hormones. It is believed that 50 % of the risk of developing RA depends on the conditions and lifestyle, while the remaining 50 % is dependent on genetic predisposition. That is why, RA fits the main idea of postgenomic predictive-preventive personalized medicine that is to give a chance to those who would like to reduce his/her risk of diseases by bringing his/her conditions and lifestyle in line with the data on his/her genome sequenced. This is very important, since doctors consider RA as one of the most frequent causes of disability. Using the Web service SNP_TATA_Z-tester (http://beehive.bionet.nsc.ru/cgi-bin/mgs/tatascan_fox/start.pl), 227 variants of single nucleotide polymorphism (SNP) of the human gene promoters were studied. As a result, 43 candidate SNP markers for RA that can alter the affinity of the TATA-binding protein (TBP) for the promoters of these genes were predicted.

Insights into the study and origin of the citrullinome in rheumatoid arthritis

The presence of autoantibodies and autoreactive T cells to citrullinated proteins and citrullinating enzymes in patients with rheumatoid arthritis (RA), together with the accumulation of citrullinated proteins in rheumatoid joints, provides substantial evidence that dysregulated citrullination is a hallmark feature of RA. However, understanding mechanisms that dysregulate citrullination in RA has important challenges. Citrullination is a normal process in immune and non-immune cells, which is likely activated by different conditions (eg, inflammation) with no pathogenic consequences. In a complex inflammatory environment such as the RA joint, unique strategies are therefore required to dissect specific mechanisms involved in the abnormal production of citrullinated proteins. Here, we will review current models of citrullination in RA and discuss critical components that, in our view, are relevant to understanding the accumulation of citrullinated proteins in the RA joint, collectively referred to as the RA citrullinome. In particular, we will focus on potential caveats in the study of citrullination in RA and will highlight methods to precisely detect citrullinated proteins in complex biological samples, which is a confirmatory approach to mechanistically link the RA citrullinome with unique pathogenic pathways in RA.

Rheumatoid Arthritis-Associated Mechanisms of Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans

Rheumatoid arthritis (RA) is an autoimmune disease of unknown etiology characterized by immune-mediated damage of synovial joints and antibodies to citrullinated antigens. Periodontal disease, a bacterial-induced inflammatory disease of the periodontium, is commonly observed in RA and has implicated periodontal pathogens as potential triggers of the disease. In particular, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans have gained interest as microbial candidates involved in RA pathogenesis by inducing the production of citrullinated antigens. Here, we will discuss the clinical and mechanistic evidence surrounding the role of these periodontal bacteria in RA pathogenesis, which highlights a key area for the treatment and preventive interventions in RA.

Reconsidering the Use of Minocycline in the Preliminary Treatment Regime of Rheumatoid Arthritis

Strong epidemiologic, clinical, and basic science studies have identified a number of factors that may lead to rheumatoid arthritis (RA) onset and progression, particularly involving the complex interplay between genomics, environmental risk factors, the breakdown of immune self-tolerance, and microbiome dysbiosis. A chronic state of inflammation established by infectious agents has long been suspected to set the stage for the development of RA. The purpose of this article is to review the contribution of the gut, lung, and oral microbiomes to the pathogenesis of RA and consider the importance of supplementing the preliminary treatment regime of RA patients with antibiotics, in particular, minocycline. Minocycline has been used in the treatment of RA due to its bacteriostatic, as well as immunomodulatory and anti-inflammatory properties. Ultimately, a short course of antibiotic treatment with minocycline may eliminate pathogenic organisms contributing to the development and progression of RA. 

Mucosa-Environment Interactions in the Pathogenesis of Rheumatoid Arthritis

Mucosal surfaces play a central role in the pathogenesis of rheumatoid arthritis (RA). Several risk factors, such as cigarette smoking, environmental pollution, and periodontitis interact with the host at the mucosal level, triggering immune system activation. Moreover, the alteration of microbiota homeostasis is gaining increased attention for its involvement in the disease pathogenesis, modulating the immune cell response at a local and subsequently at a systemic level. Currently, the onset of the clinical manifest arthritis is thought to be the last step of a series of pathogenic events lasting years. The positivity for anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF), in absence of symptoms, characterizes a preclinical phase of RA-namely systemic autoimmune phase- which is at high risk for disease progression. Several immune abnormalities, such as local ACPA production, increased T cell polarization towards a pro-inflammatory phenotype, and innate immune cell activation can be documented in at-risk subjects. Many of these abnormalities are direct consequences of the interaction between the environment and the host, which takes place at the mucosal level. The purpose of this review is to describe the humoral and cellular immune abnormalities detected in subjects at risk of RA, highlighting their origin from the mucosa-environment interaction.

Release of active peptidylarginine deiminase into the circulation during acute inflammation induced by coronary artery bypass surgery

Purpose: Peptidylarginine deiminase (PAD) catalyzes citrullination, a post-translational modification that can alter structure, function and antigenicity of proteins. Citrullination in the lungs due to smoking is believed to initiate an anti-citrulline immune response in rheumatoid arthritis. Citrullination in other inflamed organs has also been demonstrated, but it is not known whether smoking or inflammatory processes in general result in release of relevant amounts of PAD into the circulation with potential to cause citrullination of proteins at various anatomical sites. Coronary artery bypass grafting (CABG) using cardiopulmonary bypass (CPB) induces an acute systemic inflammation response. In the present study, we investigate whether smoking or acute systemic inflammation causes release of PAD into the circulation.

Patients and methods: This study included 36 patients with coronary heart disease (16 smokers and 20 non-smokers) undergoing CABG surgery with CPB. Circulating levels of PAD2 and PAD4, PAD activity, the neutrophil activation markers MPO, MMP-9 and lipocalin-2, the cytokines IL-6 and IL-10, and the chemokine CXCL8 were measured 2 hrs preoperatively and 2 hrs postoperatively.

Results: At baseline, serum PAD2 and PAD4 concentration did not differ between smokers and non-smokers. However, serum from non-smokers contained higher PAD activity than serum from smokers. Circulating PAD2 levels and PAD activity increased markedly in both groups after surgery, as did all neutrophil activation markers, cytokines and chemokine. PAD2 levels correlated with neutrophil activation markers, but not with cytokine and chemokine levels.

Conclusion: Blood levels of PAD2 did not differ significantly between smokers and non-smokers, but smokers had decreased PAD activity in the circulation. PAD2 levels and PAD activity increased in blood during inflammation induced by CABG with CPB. This suggests that acute inflammation, ischemia or reperfusion, or a combination of these, leads to systemic spreading of enzymatically active PAD, which may affect protein function and induce generation of citrullinated self-antigens.

Anti-cyclic citrullinated peptide antibody titers decrease in rheumatoid arthritis patients treated with tocilizumab: A pilot study

Objectives: To analyze the effects of tocilizumab on peripheral B-cell subpopulation and its ability to produce anti-cyclic citrullinated peptide (CCP) antibody in patients with rheumatoid arthritis (RA).Methods: Thirteen consecutive RA patients initiated with tocilizumab were enrolled in our prospective study. Anti-CCP antibody titers and clinical parameters were evaluated during treatment. Peripheral blood B-cell subsets were analyzed using flow cytometry according to the Human Immunology Project.Results: Disease activity was significantly improved and anti-CCP antibody titers significantly decreased at week 24 compared to baseline. The percentages of post-switch memory B cells in CD19+ cells transiently increased at week 12, but there was no significant difference in any of the investigated B-cell subpopulations at week 24 compared to baseline. The ratios of post-switch memory to naïve B cells (post-switch/naïve) correlated negatively with anti-CCP antibody titers regardless of the time-points.Conclusion: Our study indicated that tocilizumab has a potential to reduce anti-CCP antibody production presumably by affecting post-switch/naïve ratio, and that anti-CCP antibody titers reflect B-cell distribution/subpopulation. As anti-CCP antibodies are produced in lymph nodes or ectopic lymphoid structures in synovial tissues, not in circulation, transient increment of post-switch memory B cells after tocilizumab treatment may reflect the altered balance of B-cell distribution between circulation and arthritic joints, resulting in suppressed production of anti-CCP antibody in situ.

Dynamic molecular changes during the first week of human life follow a robust developmental trajectory

Systems biology can unravel complex biology but has not been extensively applied to human newborns, a group highly vulnerable to a wide range of diseases. We optimized methods to extract transcriptomic, proteomic, metabolomic, cytokine/chemokine, and single cell immune phenotyping data from <1 ml of blood, a volume readily obtained from newborns. Indexing to baseline and applying innovative integrative computational methods reveals dramatic changes along a remarkably stable developmental trajectory over the first week of life. This is most evident in changes of interferon and complement pathways, as well as neutrophil-associated signaling. Validated across two independent cohorts of newborns from West Africa and Australasia, a robust and common trajectory emerges, suggesting a purposeful rather than random developmental path. Systems biology and innovative data integration can provide fresh insights into the molecular ontogeny of the first week of life, a dynamic developmental phase that is key for health and disease.

The first week of life impacts health for all of life, but the mechanisms are little-understood. Here the authors extract multi-omic data from small volumes of blood to study the dynamic molecular changes during the first week of life, revealing a robust developmental trajectory common to different populations.

A Study of Fecal Calprotectin in Obese Children and Adults

BACKGROUND

Obesity is a complex, medical condition causally contributing to many chronic diseases and a number of efforts have been made to find the associated markers for novel prevention and treatment of obesity. Our study was to evaluate the relationship between gut immune response and obesity and overweight with use of fecal calprotectin (FC) both in adult and children groups.

METHODS

Fecal samples were obtained from 74 subjects: 14 non-obese and overweight children (PN), 13 obese and overweight children (PO), 20 non-obese and overweight adults (AN), and 27 obese and overweight adults (AO). FC was measured using a commercial Legend Max quantitative enzyme-linked immunosorbent assay (BioLegend). Mann-Whitney U-test was used for statistical analysis.

RESULTS

Median FC concentration was 7.9 μg/g (range, 1.9-28.9 μg/g) for PN, 5.0 μg/g (range, 2.6-29.6 μg/g) for PO, 9.5 μg/g (range, 0.8-28.9 μg/g) for AN, and 10.0 μg/g (range, 1.6-25.6 μg/g) for AO, respectively. In both adults and children age groups, the FC showed no statistically significant difference between AO and AN or PO and PN. However, FC showed statistically significant difference (P<0.05) between AO and PO while not significant between AN and PN.

CONCLUSION

FC level in AO was significantly higher than that in PO, suggestive of different pathophysiologic mechanism between children obesity and adults obesity.

Identification of brain antigens recognized by autoantibodies in experimental autoimmune encephalomyelitis-induced animals treated with etomoxir or interferon-β

Multiple sclerosis (MS) is a neurodegenerative autoimmune disease, where chronic inflammation plays an essential role in its pathology. A feature of MS is the production of autoantibodies stimulated by an altered-peptide-ligand response and epitope spreading, resulting in loss of tolerance for self-proteins. The involvement of autoantibodies in MS pathogenesis has been suggested to initiate and drive progression of inflammation; however, the etiology of MS remains unknown. The effect of etomoxir and interferon-β (IFN-β) was examined in an experimental-autoimmune-encephalomyelitis (EAE) model of MS. Moreover, the impact of etomoxir and IFN-β on recognition of brain proteins in serum from EAE rats was examined with the purpose of identifying the autoantibody reactivities involved in MS. Animals treated with etomoxir on day 1 exhibited a statistically significantly lower disease score than animals treated with IFN-β (on day 1 or 5) or placebo. Etomoxir treatment on day 5 resulted in a significantly lower disease score than IFN-β treatment on day 1. After disease induction antibodies was induced to a broad pallet of antigens in the brain. Surprisingly, by blocking CPT1 and therewith lipid metabolism several alterations in the antibody response was observed suggesting that autoantibodies play a role in the EAE animal model.

A Cost-Effective High-Throughput Plasma and Serum Proteomics Workflow Enables Mapping of the Molecular Impact of Total Pancreatectomy with Islet Autotransplantation

Blood is an ideal body fluid for the discovery or monitoring of diagnostic and prognostic protein biomarkers. However, discovering robust biomarkers requires the analysis of large numbers of samples to appropriately represent interindividual variability. To address this analytical challenge, we established a high-throughput and cost-effective proteomics workflow for accurate and comprehensive proteomics at an analytical depth applicable for clinical studies. For validation, we processed 1 μL each from 62 plasma samples in 96-well plates and analyzed the product by quantitative data-independent acquisition liquid chromatography/mass spectrometry; the data were queried using feature quantification with Spectronaut. To show the applicability of our workflow to serum, we analyzed a unique set of samples from 48 chronic pancreatitis patients, pre and post total pancreatectomy with islet autotransplantation (TPIAT) surgery. We identified 16 serum proteins with statistically significant abundance alterations, which represent a molecular signature distinct from that of chronic pancreatitis. In summary, we established a cost-efficient high-throughput workflow for comprehensive proteomics using PVDF-membrane-based digestion that is robust, automatable, and applicable to small plasma and serum volumes, e.g., finger stick. Application of this plasma/serum proteomics workflow resulted in the first mapping of the molecular implications of TPIAT on the serum proteome.

Identification of new biomarkers to promote personalised treatment of patients with inflammatory rheumatic disease: protocol for an open cohort study

INTRODUCTION

The introduction of biological disease-modifying antirheumatic drugs (bDMARDs) has improved the treatment of inflammatory rheumatic diseases dramatically. However, bDMARD treatment failure occurs in 30%-40% of patients due to lack of effect or adverse events, and the tools to predict treatment outcomes in individual patients are currently limited. The objective of the present study is to identify diagnostic, prognostic and predictive biomarkers, which can be used to (1) diagnose inflammatory rheumatic diseases early in the disease course with high sensitivity and specificity, (2) improve prognostication or (3) predict and monitor treatment effectiveness and tolerability for the individual patient.

METHODS AND ANALYSIS

The present study is an observational and translational open cohort study with prospective collection of clinical data and biological materials (primarily blood) in patients with inflammatory rheumatic diseases treated in routine care. Patients contribute with one cross-sectional blood sample and/or are enrolled for longitudinal follow-up on initiation of a new DMARD (blood sampling after 0, 3, 6, 12, 24, 36, 48, 60 months of treatment). Other biological materials will be collected when accessible and relevant. Demographics, disease characteristics, comorbidities and lifestyle factors are registered at inclusion; DMARD treatment and outcomes are collected repeatedly during follow-up. Currently (July 2017), >5000 samples from approximately 3000 patients have been collected. Data will be analysed using appropriate statistical analyses.

ETHICS AND DISSEMINATION

The protocol is approved by the Danish Ethics Committee and the Danish Data Protection Agency. Participants give written and oral informed consent. Biomarkers will be evaluated and published according to the Reporting Recommendations for Tumour Marker (REMARK) prognostic studies, Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) and the Standards for Reporting of Diagnostic Accuracy (STARD) guidelines. Results will be published in peer-reviewed scientific journals and presented at international conferences.

TRIAL REGISTRATION NUMBER

NCT03214263.

Proteomics dataset: The colon mucosa from inflammatory bowel disease patients, gastrointestinal asymptomic rheumatoid arthritis patients, and controls

The datasets presented in this article are related to the research articles entitled “Neutrophil Extracellular Traps in Ulcerative Colitis: A Proteome Analysis of Intestinal Biopsies” (Bennike et al., 2015 [1]), and “Proteome Analysis of Rheumatoid Arthritis Gut Mucosa” (Bennike et al., 2017 [2]). The colon mucosa represents the main interacting surface of the gut microbiota and the immune system. Studies have found an altered composition of the gut microbiota in rheumatoid arthritis patients (Zhang et al., 2015; Vaahtovuo et al., 2008; Hazenberg et al., 1992) [5], [6], [7] and inflammatory bowel disease patients (Morgan et al., 2012; Abraham and Medzhitov, 2011; Bennike, 2014) [8], [9], [10]. Therefore, we characterized the proteome of colon mucosa biopsies from 10 inflammatory bowel disease ulcerative colitis (UC) patients, 11 gastrointestinal healthy rheumatoid arthritis (RA) patients, and 10 controls. We conducted the sample preparation and liquid chromatography mass spectrometry (LC-MS/MS) analysis of all samples in one batch, enabling label-free comparison between all biopsies. The datasets are made publicly available to enable critical or extended analyses. The proteomics data and search results, have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifiers PXD001608 for ulcerative colitis and control samples, and PXD003082 for rheumatoid arthritis samples.

Intestinal Dysbiosis and Rheumatoid Arthritis: A Link between Gut Microbiota and the Pathogenesis of Rheumatoid Arthritis

Characterization and understanding of gut microbiota has recently increased representing a wide research field, especially in autoimmune diseases. Gut microbiota is the major source of microbes which might exert beneficial as well as pathogenic effects on human health. Intestinal microbiome's role as mediator of inflammation has only recently emerged. Microbiota has been observed to differ in subjects with early rheumatoid arthritis compared to controls, and this finding has commanded this study as a possible autoimmune process. Studies with intestinal microbiota have shown that rheumatoid arthritis is characterized by an expansion and/or decrease of bacterial groups as compared to controls. In this review, we present evidence linking intestinal dysbiosis with the autoimmune mechanisms involved in the development of rheumatoid arthritis.

Defining the proteomic landscape of rheumatoid arthritis: progress and prospective clinical applications

INTRODUCTION

The heterogeneity of Rheumatoid Arthritis (RA) and the absence of clinical tests accurate enough to identify the early stages of this disease have hampered its management. Therefore, proteomics research is increasingly focused on the discovery of novel biological markers, which would not only be able make an early diagnosis, but also to gain insight into the different pathological mechanisms underlying the heterogeneity of RA and also to stratify patients, which is critical to enabling effective treatments. Areas covered: The proteomic approaches that have been utilised to provide knowledge about RA pathogenesis, and to identify biomarkers for RA diagnosis, prognosis, disease monitoring and prediction of response to therapy, are summarized. Expert commentary: Although each proteomic study is unique in its design, all of them have contributed to the understanding of RA pathogenesis and the discovery of promising biomarkers for patient stratification, which would improve clinical care of RA patients. Still, efforts need to be made to validate these findings and translate them into clinical practice.