The arthritis connection to inflammatory bowel disease (IBD): why has it taken so long to understand it?

The intestinal mucosa-associated microbiota in IBD-associated arthritis displays lower relative abundance of Roseburia intestinalis

The most common extra-intestinal manifestation (EIM) of inflammatory bowel disease (IBD), IBD-associated arthritis (IAA), occurs in 25-40% of patients and can be debilitating. In IBD, mucosal and stool microbiota richness is decreased, and compositional changes can precede or accompany disease onset. Likewise, spondyloarthritides are associated with altered gut microbiota, with overlapping bacterial signatures observed in IBD, suggesting key shared microbial factors are involved in both conditions. Much has been learned about the role of the intestinal microbiome in IBD, but less is known regarding its role in IAA. To address this knowledge gap, we analyzed the mucosa-associated intestinal microbiota of participants enrolled in the LOCATION-IBD cohort. Microbiota composition was established using 16S rRNA gene amplicon sequencing of intestinal biopsy samples taken from participants with IBD, with or without arthropathy. Microbiota samples clustered predominantly by participant, and similar taxa were present across the colon. The mucosal intestinal microbiota of females with IAA displayed a lower relative abundance of R. intestinalis, while males with IAA had a higher relative abundance of Corynebacterium, even when controlling for IBD-type, whether samples were taken from a site of inflammation and intestinal location. These findings indicate the mucosa-associated intestinal microbiota is associated with IAA in a sex-specific manner.

Frequency of Spondyloarthritis Symptoms Among US Patients With Inflammatory Bowel Disease: A Cross-Sectional Multi-Center Study

OBJECTIVE

Spondyloarthritis (SpA) is the most common extraintestinal manifestation of inflammatory bowel disease (IBD). The application of screening tools to detect SpA in patients with IBD may lead to earlier recognition of SpA and affect treatment decisions.

METHODS

A combination of two previously described SpA screening questionnaires, the Detection of Arthritis in Inflammatory Bowel Disease (DETAIL) and IBD Identification of Spondyloarthritis Questionnaire (IBIS-Q), was administered to consecutive patients with IBD attending IBD specialty clinics in six US academic medical centers. Demographic data, IBD, and rheumatology history were extracted by chart review.

RESULTS

A total of 669 patients were analyzed. The median age was 40 years (interquartile range [IQR] 30-54) with a median disease duration of 12 years (IQR 6-22) and moderate to severe IBD based on medication exposure and history of bowel surgery. A total of 81 patients (12%) carried a diagnosis of an inflammatory rheumatic disease, whereas 75 (11%) had consulted a rheumatologist during the previous year. Using published cutoffs, 180 out of 669 patients (27%) screened positive with DETAIL, 266 (40%) with IBIS-Q, and 275 (41%) with either questionnaire. Axial symptoms were more frequently reported than peripheral musculoskeletal complaints. Notably, 189 out of 275 (69%) screen-positive patients had neither a documented inflammatory rheumatic disease diagnosis nor a visit with a rheumatologist within the past year.

CONCLUSION

A substantial proportion of patients with IBD have symptoms suggestive of SpA, and many of these may have undiagnosed SpA. The IBIS-Q questionnaire appears to identify more potential SpA cases than DETAIL. Strategies are needed to prioritize rheumatology consultations for those patients with IBD who are most likely to benefit.

Inflammatory Bowel Disease and Joint Surgery: A 20-Year Cohort Study of Arthroplasty and Arthritis Risks

Background Patients with inflammatory bowel disease (IBD) have a higher risk of adverse outcomes after total hip arthroplasty (THA) and total knee arthroplasty (TKA) compared to the general population. However, existing literature has not fully elucidated the risk of IBD patients to undergo arthroplasty for treatment of arthritis. Therefore, the purpose of this study is to understand the incidence of arthroplasty and osteoarthritis, enteropathic arthritis, or inflammatory polyarthropathies in patients with IBD compared to the general population. Methods A retrospective cohort analysis was conducted using the TriNetX research database to identify all patients who experienced the primary outcomes between 2004 and 2024. Two cohorts were stratified by a diagnosis of IBD and propensity score matched (1:1) to mitigate baseline differences in demographics and comorbidities. Results After propensity matching, each cohort contained 531,263 patients who were included for analysis. Patients with IBD were significantly less likely to undergo THA (OR 0.853, 95% CI 0.804-0.906) and TKA (OR 0.830, 95% CI 0.788-0.874) and less likely to incur a diagnosis of hip osteoarthritis (OR 0.943, 95% CI 0.922-0.965) or knee osteoarthritis (OR 0.794, 95% CI 0.780-0.808). Conversely, IBD patients were significantly more likely to incur a diagnosis of enteropathic arthropathy (OR 287.9, 95% CI 181.3-457.5) or inflammatory polyarthropathies (OR 1.390, 95% CI 1.365-1.414). Conclusions Patients with IBD are less likely to undergo THA and TKA despite the association between IBD and arthritis. These findings underscore the importance of tailored treatment strategies for joint-related complications in IBD patients and highlight the need for further research to optimize surgical outcomes in this population.

Joint Manifestations in Inflammatory Bowel Diseases, "Red Flags" for the Early Recognition and Management of Related Arthropathies: A Narrative Review

Inflammatory bowel diseases (IBDs), including Crohn's disease and ulcerative colitis, frequently present with extra-intestinal manifestations. Virtually all patients with IBD could be at risk for developing inflammatory arthropathies within the spectrum of spondyloarthritis (SpA). In this context, prompt recognition of musculoskeletal "red flags" (lower back pain, dactylitis, enthesitis, swelling of peripheral joints, musculoskeletal chest pain, family history of SpA, psoriasis, and anterior uveitis) is crucial for early referral and multidisciplinary management by gastroenterologists and rheumatologists. Recent advances have refined diagnostic tools including questionnaires, alongside imaging modalities and laboratory markers, enhancing the detection of SpA in IBD patients. Effective treatment strategies targeting both gastrointestinal and musculoskeletal symptoms may significantly reduce long-term morbidity in these patients. In this narrative review, we aimed to underscore the importance of integrating clinical, diagnostic, and therapeutic approaches for optimal patient management and outcome over time.

Arthritis complicating inflammatory bowel disease- the future is now

Fundamental advances are occurring across immune-mediated inflammatory diseases. Recent therapeutic developments include strategies to prevent rheumatoid arthritis in high-risk individuals, using baseline cellular immunophenotypes to predict response to biologics in psoriatic arthritis, and using biologics in a top-down approach for Crohn's disease. However, meaningful progress has not occurred in the management of patients with spondyloarthropathy complicating inflammatory bowel disease (IBD). Currently, the pathophysiology of IBD-related spondyloarthropathy is poorly understood; moreover, there are no accepted or disease-specific screening tools, diagnostic criteria, or licenced treatments. Current approaches to clinical care from rheumatologists and gastroenterologists largely involve the extrapolation of spondyloarthropathy and IBD clinical guidelines, respectively, despite increasing recognition of IBD-related spondyloarthropathy being its own entity, with a unique phenotype. There is an obvious contrast between spondyloarthropathy complicating IBD and the management of arthropathy complicating psoriasis, a disease area where defined diagnostic criteria and dedicated clinical trials allow clear management guidelines. We argue that the time has come for a parallel approach and dedicated focus on IBD-related spondyloarthropathy.

Inflammatory Bowel Disease-Associated Arthritis Is Associated with Concomitant Autoimmune and Inflammatory Disorders

BACKGROUND

Extraintestinal Manifestations (EIMs) are a common and potentially debilitating complication of Inflammatory Bowel Diseases (IBD), sometimes requiring additional treatment beyond those used to control intestinal disease. IBD-associated arthritis (IAA), a form of spondyloarthritis, is associated with several factors including disease location, sex, and IBD type. However, much remains unknown about other clinical factors predicting development of EIMs. Our goal was to identify additional factors associated with IAA.

METHODS

Participants in the LOCATION-IBD cohort were included in this analysis. We performed univariate and multivariate analysis of demographics, clinical data, and patient-reported outcomes data.

RESULTS

The LOCATION-IBD cohort included 182 participants with (n = 53) and without (n = 110) joint EIMs and with joint pain of unclear etiology (n = 19). In a multivariate analysis comparing those with and without joint EIMs, female sex (OR = 2.5, p = 0.014), the presence of concomitant autoimmune and inflammatory disorders (OR = 2.5, p = 0.038), and Crohn's disease (OR = 2.9, p = 0.026) were associated with the presence of joint EIMs.

CONCLUSION

This analysis reveals patients with IAA are more likely to have concomitant autoimmune disorders. Further studies are needed to confirm this association, understand the mechanisms underlying the common pathogenesis of these concurrent disorders, and evaluate their impact on the treatment of IAA.

Cholestyramine alleviates bone and muscle loss in irritable bowel syndrome via regulating bile acid metabolism

Irritable bowel syndrome (IBS) is a widespread gastrointestinal disorder known for its multifaceted pathogenesis and varied extraintestinal manifestations, yet its implications for bone and muscle health are underexplored. Recent studies suggest a link between IBS and musculoskeletal disorders, but a comprehensive understanding remains elusive, especially concerning the role of bile acids (BAs) in this context. This study aimed to elucidate the potential contribution of IBS to bone and muscle deterioration via alterations in gut microbiota and BA profiles, hypothesizing that cholestyramine could counteract these adverse effects. We employed a mouse model to characterize IBS and analysed its impact on bone and muscle health. Our results revealed that IBS promotes bone and muscle loss, accompanied by microbial dysbiosis and elevated BAs. Administering cholestyramine significantly mitigated these effects, highlighting its therapeutic potential. This research not only confirms the critical role of BAs and gut microbiota in IBS-associated bone and muscle loss but also demonstrates the efficacy of cholestyramine in ameliorating these conditions, thereby contributing significantly to the field's understanding and offering a promising avenue for treatment.

Leaky gut, circulating immune complexes, arthralgia, and arthritis in IBD: coincidence or inevitability?

Most host-microbiota interactions occur within the intestinal barrier, which is essential for separating the intestinal epithelium from toxins, microorganisms, and antigens in the gut lumen. Gut inflammation allows pathogenic bacteria to enter the blood stream, forming immune complexes which may deposit on organs. Despite increased circulating immune complexes (CICs) in patients with inflammatory bowel disease (IBD) and discussions among IBD experts regarding their potential pathogenic role in extra-intestinal manifestations, this phenomenon is overlooked because definitive evidence demonstrating CIC-induced extra-intestinal manifestations in IBD animal models is lacking. However, clinical observations of elevated CICs in newly diagnosed, untreated patients with IBD have reignited research into their potential pathogenic implications. Musculoskeletal symptoms are the most prevalent extra-intestinal IBD manifestations. CICs are pivotal in various arthritis forms, including reactive, rheumatoid, and Lyme arthritis and systemic lupus erythematosus. Research indicates that intestinal barrier restoration during the pre-phase of arthritis could inhibit arthritis development. In the absence of animal models supporting extra-intestinal IBD manifestations, this paper aims to comprehensively explore the relationship between CICs and arthritis onset via a multifaceted analysis to offer a fresh perspective for further investigation and provide novel insights into the interplay between CICs and arthritis development in IBD.

Causal association of gut microbiota on spondyloarthritis and its subtypes: a Mendelian randomization analysis

Background

Despite establishing an association between gut microbiota and spondyloarthritis (SpA) subtypes, the causal relationship between them remains unclear.

Methods

Gut microbiota data were obtained from the MiBioGen collaboration, and SpA genome-wide association study (GWAS) summary data were obtained from the FinnGen collaboration. We conducted a two-sample Mendelian randomization (MR) analysis using the inverse-variance-weighted method supplemented with four additional MR methods (MR-Egger, weighted median, simple mode, and weighted mode). Pleiotropy and heterogeneity were also assessed. Reverse MR analysis was used to detect reverse causal relationships.

Results

We identified 23 causal links between specific gut microbiota taxa and SpA levels. Of these, 22 displayed nominal causal associations, and only one demonstrated a robust causal connection. Actinobacteria id.419 increased the risk of ankylosing spondylitis (AS) (odds ratio (OR) = 1.86 (95% confidence interval (CI): 1.29-2.69); p = 8.63E-04). The family Rikenellaceae id.967 was associated with a reduced risk of both AS (OR = 0.66 (95% CI: 0.47-0.93); p = 1.81E-02) and psoriatic arthritis (OR = 0.70 (95% CI: 0.50-0.97); p = 3.00E-02). Bacillales id.1674 increased the risk of AS (OR = 1.23 (95% CI: 1.00-1.51); p = 4.94E-02) and decreased the risk of enteropathic arthritis (OR = 0.56 (95% CI: 0.35-0.88); p = 1.14E-02). Directional pleiotropy, or heterogeneity, was not observed. No reverse causal associations were observed between the diseases and the gut microbiota.

Conclusion

Our MR analysis suggested a genetic-level causal relationship between specific gut microbiota and SpA, providing insights into the underlying mechanisms behind SpA development mediated by gut microbiota.

Role of MicroRNAs in Inflammatory Joint Diseases: A Review

Inflammatory arthritis commonly initiates in the soft tissues lining the joint. This lining swells, as do the cells in it and inside the joint fluid, producing chemicals that induce inflammation signs such as heat, redness, and swelling. MicroRNA (miRNA), a subset of non-coding small RNA molecules, post-transcriptionally controls gene expression by targeting their messenger RNA. MiRNAs modulate approximately 1/3 of the human genome with their multiple targets. Recently, they have been extensively studied as key modulators of the innate and adaptive immune systems in diseases such as allergic disorders, types of cancer, and cardiovascular diseases. However, research on the different inflammatory joint diseases, such as rheumatoid arthritis, gout, Lyme disease, ankylosing spondylitis, and psoriatic arthritis, remains in its infancy. This review presents a deeper understanding of miRNA biogenesis and the functions of miRNAs in modulating the immune and inflammatory responses in the above-mentioned inflammatory joint diseases. According to the literature, it has been demonstrated that the development of inflammatory joint disorders is closely related to different miRNAs and their specific regulatory mechanisms. Furthermore, they may present as possible prognostic and diagnostic biomarkers for all diseases and may help in developing a therapeutic response. However, further studies are needed to determine whether manipulating miRNAs can influence the development and progression of inflammatory joint disorders.

SpA plus IBD or IBD plus SpA: Does commutative property apply?

The term spondyloarthritis (SpA) encompasses a group of interrelated disorders characterised by the involvement of the musculoskeletal system as well as extra-articular manifestations like acute anterior uveitis, psoriasis and inflammatory bowel diseases (IBD). Likewise, IBD may present with various extra-intestinal manifestations among which those involving the musculoskeletal system, namely peripheral and axial SpA are the most common. The identification of patients with both SpA and IBD is of paramount importance in clinical practice since the coexistence of these two entities has been associated with great disability and decreased quality of life. In order to achieve an early diagnosis of IBD-SpA it is instrumental that rheumatologists seek for gastrointestinal symptoms in SpA patients and likewise that gastroenterologists seek for inflammatory musculoskeletal symptoms in patients with IBD. This narrative review aims at critically appraising the available evidence about SpA occurring in IBD patients versus IBD occurring in patients with SpA and at highlighting similarities and differences between the two scenarios.

Pivotal Role of Intestinal Microbiota and Intraluminal Metabolites for the Maintenance of Gut-Bone Physiology

Intestinal microbiota, and their mutual interactions with host tissues, are pivotal for the maintenance of organ physiology. Indeed, intraluminal signals influence adjacent and even distal tissues. Consequently, disruptions in the composition or functions of microbiota and subsequent altered host-microbiota interactions disturb the homeostasis of multiple organ systems, including the bone. Thus, gut microbiota can influence bone mass and physiology, as well as postnatal skeletal evolution. Alterations in nutrient or electrolyte absorption, metabolism, or immune functions, due to the translocation of microbial antigens or metabolites across intestinal barriers, affect bone tissues, as well. Intestinal microbiota can directly and indirectly alter bone density and bone remodeling. Intestinal dysbiosis and a subsequently disturbed gut-bone axis are characteristic for patients with inflammatory bowel disease (IBD) who suffer from various intestinal symptoms and multiple bone-related complications, such as arthritis or osteoporosis. Immune cells affecting the joints are presumably even primed in the gut. Furthermore, intestinal dysbiosis impairs hormone metabolism and electrolyte balance. On the other hand, less is known about the impact of bone metabolism on gut physiology. In this review, we summarized current knowledge of gut microbiota, metabolites and microbiota-primed immune cells in IBD and bone-related complications.

Epidemiological and clinicopathological findings in 15 fatal outbreaks of salmonellosis in dairy calves and virulence genes in the causative Salmonella enterica Typhimurium and Dublin strains

Salmonella enterica is a major food-borne pathogen that affects cattle-rearing systems worldwide. Little information is available on the epidemiology and pathology of salmonellosis and the virulence genes (VGs) carried by Salmonella in spontaneous outbreaks in cattle. We describe epidemiological findings in 15 fatal outbreaks of salmonellosis in Uruguayan dairy farms and the age, clinical signs, and pathology in 20 affected calves. We also describe the serotypes and frequencies of 17 VGs in the causative Salmonella strains and explore their associations with epidemiological, clinical, and pathological findings. Salmonella Typhimurium and Dublin were identified in 11/15 and 4/15 outbreaks, respectively. The most frequent reason for consultation was digestive disease (8 outbreaks caused by S. Typhimurium), followed by sudden death (4 outbreaks, 3 caused by S. Dublin). Morbidity, mortality, and lethality ranged 4.8-100%, 3.8-78.9%, and 10-100%, without significant differences between serotypes. Diarrhea, the most common clinical sign (14 cases), was associated with the Typhimurium serotype (OR = 26.95), especially in ≤ 30-day-old calves with fibrinous enteritis as the main autopsy finding. The Dublin serotype affected ≥ 50-day-old calves and was associated with fibrinosuppurative splenitis (p = 0.01) and tubulointerstitial nephritis (OR = 48.95). The chances of the Dublin serotype increased significantly with age. There was low variability of VG across serotypes. The pefA gene was associated with the Typhimurium serotype (OR = 21.95), macroscopic enteritis (p = 0.03), and microscopic fibrinosuppurative splenitis (p = 0.04). Understanding the epidemiology, pathology, and virulence of S. enterica at the farm level is key to delineating prevention and control strategies to mitigate its impact on animal and human health.

Contrasting Autoimmune Comorbidities in Microscopic Colitis and Inflammatory Bowel Diseases

BACKGROUND

Inflammatory bowel diseases (Crohn's disease and ulcerative colitis) and microscopic colitis (lymphocytic and collagenous colitis) are immune-mediated diseases of the gastrointestinal tract, with distinct pathophysiology.

OBJECTIVE

We sought to compare the prevalence of autoimmune diseases between microscopic colitis (MC) and inflammatory bowel diseases (IBDs) in our patient cohorts in their medical history.

METHODS

We collected data from 611 patients (508 with IBD, 103 with MC). We recorded cases of other autoimmune diseases. The screened documentation was written in the period between 2008 and 2022. We sought to determine whether colonic involvement had an impact on the prevalence of autoimmune diseases.

RESULTS

Ulcerative colitis patients and patients with colonic-predominant Crohn's disease had a greater propensity for autoimmune conditions across the disease course than patients with ileal-predominant Crohn's disease. Gluten-related disorders were more common in Crohn's disease than in ulcerative colitis, and slightly more common than in microscopic colitis. In ulcerative colitis, 10 patients had non-differentiated collagenosis registered, which can later develop into a definite autoimmune disease.

CONCLUSIONS

Predominantly colonic involvement can be a predisposing factor for developing additional autoimmune disorders in IBD. Ulcerative colitis patients may have laboratory markers of autoimmunity, without fulfilling the diagnostic criteria for definitive autoimmune disorders (non-differentiated collagenosis).

Effects of intestinal microbes on rheumatic diseases: A bibliometric analysis

Background

Rheumatic diseases (RD) are a group of multi-system inflammatory autoimmune diseases whose causes are still under study. In the past few decades, researchers have found traces of the association between rheumatic diseases and intestinal microbiota, which can partially explain the pathogenesis of rheumatic diseases. We aimed to describe the research trend and main divisions on how gut flora interreacts with rheumatic diseases, and discussed about the possible clinical applications.

Methods

We analyzed bibliometric data from the Web of Science core collection (dated 15th May 2022). Biblioshiny R language software packages (bibliometrix) were used to obtain the annual publication and citations, core sources according to Bradford's law, and country collaboration map. We designed and verified the keyword co-occurrence network and strategic diagram with the help of VOSviewer and CiteSpace, subdivided the research topic into several themes and identified research dimensions. The tables of most local cited documents and core sources were processed manually. Furthermore, the Altmetric Attention Score and the annual Altmetric Top 100 were applied to analyze the annual publication and citation.

Results

From a total of 541 documents, we found that the overall trend of annual publication and citation is increasing. The major research method is to compare the intestinal microbial composition of patients with certain rheumatic disease and that of the control group to determine microbial alterations related to the disease's occurrence and development. According to Bradford's law, the core sources are Arthritis and Rheumatology, Annals of the Rheumatic Diseases, Current Opinion in Rheumatology, Nutrients, Rheumatology, and Journal of Rheumatology. Since 1976, 101 countries or regions have participated in studies of rheumatology and intestinal microbes. The United States ranks at the top and has the broadest academic association with other countries. Five themes were identified, including the pivotal role of inflammation caused by intestinal bacteria in the rheumatic pathogenesis, the close relationship between rheumatic diseases and inflammatory bowel disease, immunoregulation mechanism as a mediator of the interaction between rheumatic diseases and gut flora, dysbiosis and decreased diversity in intestine of patients with rheumatic diseases, and the influence of oral flora on rheumatic diseases. Additionally, four research dimensions were identified, including pathology, treatment, disease, and experiments.

Conclusion

Studies on rheumatic diseases and the intestinal microbiota are growing. Attention should be paid to the mechanism of their interaction, such as the microbe-immune-RD crosstalk. Hopefully, the research achievements can be applied to diseases' prevention, diagnosis, and treatment, and our work can contribute to the readers' future research.

Peptidomics analysis of plasma in patients with ankylosing spondylitis

Background

This study aimed to explore the differential expression of peptides associated with ankylosing spondylitis (AS) patients, enabling identification of potential functional peptides to provide the basis for the novel intervention targets for AS.

Material and Methods

3 AS patients and 3 healthy volunteers were enrolled in this study. The expression profiles for peptides present in the plasma of AS patients and the healthy individual were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The physicochemical properties and biological functions of identified peptides were further analyzed by bioinformatics. The results of peptide identification were verified by cell viability analysis, using CCK8 and Edu staining assay, and the differential peptides relevant to the disease were screened.

Results

52 differential peptides were successfully identified using mass spectrometry. 44 peptides were up-regulated, while eight were down-regulated. FGA-peptide (sequences: DSGEGDFLAEGGGVRGPR), C4A-peptide (sequences: NGFKSHAL), and TUBB-peptide (sequences: ISEQFTAMFR) were screened out that could significantly promote the proliferation of fibroblasts in AS patients. Bioinformatics analysis showed these differentially expressed peptides might be associated with "MHC class I protein binding" and "pathogenic Escherichia coli infection" pathways, which might further affect the progression of AS.

Conclusion

This pilot study shows 3 differentially expressed peptides may have the potential function for the occurrence and development of AS, may provide novel insights into the underlying molecular mechanisms of AS based on peptide omics.

In Silico Study and Effects of BDMC33 on TNBS-Induced BMP Gene Expressions in Zebrafish Gut Inflammation-Associated Arthritis

The bone morphogenic protein (BMP) family is a member of the TGF-beta superfamily and plays a crucial role during the onset of gut inflammation and arthritis diseases. Recent studies have reported a connection with the gut-joint axis; however, the genetic players are still less explored. Meanwhile, BDMC33 is a newly synthesized anti-inflammatory drug candidate. Therefore, in our present study, we analysed the genome-wide features of the BMP family as well as the role of BMP members in gut-associated arthritis in an inflammatory state and the ability of BDMC33 to attenuate this inflammation. Firstly, genome-wide analyses were performed on the BMP family in the zebrafish genome, employing several in silico techniques. Afterwards, the effects of curcumin analogues on BMP gene expression in zebrafish larvae induced with TNBS (0.78 mg/mL) were determined using real time-qPCR. A total of 38 identified BMP proteins were revealed to be clustered in five major clades and contain TGF beta and TGF beta pro peptide domains. Furthermore, BDMC33 suppressed the expression of four selected BMP genes in the TNBS-induced larvae, where the highest gene suppression was in the BMP2a gene (an eight-fold decrement), followed by BMP7b (four-fold decrement), BMP4 (four-fold decrement), and BMP6 (three-fold decrement). Therefore, this study reveals the role of BMPs in gut-associated arthritis and proves the ability of BDMC33 to act as a potential anti-inflammatory drug for suppressing TNBS-induced BMP genes in zebrafish larvae.

Cytokine competent gut-joint migratory T Cells contribute to inflammation in the joint

Although studies have identified the presence of gut-associated cells in the enthesis of joints affected by spondylarthritis (SpA), a direct link through cellular transit between the gut and joint has yet to be formally demonstrated. Using KikGR transgenic mice to label in situ and track cellular trafficking from the distal colon to the joint under inflammatory conditions of both the gut and joint, we demonstrate bona-fide gut-joint trafficking of T cells from the colon epithelium, also called intraepithelial lymphocytes (IELs), to distal sites including joint enthesis, the pathogenic site of SpA. Similar to patients with SpA, colon IELs from the TNF^ΔARE/+ mouse model of inflammatory bowel disease and SpA display heightened TNF production upon stimulation. Using ex vivo stimulation of photo-labeled gut-joint trafficked T cells from the popliteal lymph nodes of KikGR and KikGR TNF^ΔARE/+ we saw that the CD4+ photo-labeled population was highly enriched for IL-17 competence in healthy as well as arthritic mice, however in the TNF^ΔARE/+ mice these cells were additionally enriched for TNF. Using transfer of magnetically isolated IELs from TNF^+/+ and TNF^ΔARE/+ donors into Rag1 ^-/- hosts, we confirmed that IELs can exacerbate inflammatory processes in the joint. Finally, we blocked IEL recruitment to the colon epithelium using broad spectrum antibiotics in TNF^ΔARE/+ mice. Antibiotic-treated mice had reduced gut-joint IEL migration, contained fewer Il-17A and TNF competent CD4+ T cells, and lessened joint pathology compared to untreated littermate controls. Together these results demonstrate that pro-inflammatory colon-derived IELs can exacerbate inflammatory responses in the joint through systemic trafficking, and that interference with this process through gut-targeted approaches has therapeutic potential in SpA.

Spondyloarthropathy in Inflammatory Bowel Disease: From Pathophysiology to Pharmacological Targets

Spondyloarthritis (SpA) represents one of the most frequent extraintestinal manifestations of inflammatory bowel disease (IBD). Evidence of shared genetic and molecular pathways underlying both diseases is emerging, which has led to rational approaches when treating patients with concomitant diseases. Clinical efficacy of tumor necrosis factor (TNF) antagonists has been ascertained over the years, and they currently represent the cornerstone of treatment in patients with IBD and SpA, but the therapeutic armamentarium in these cases has been recently expanded. Evidence for vedolizumab is controversial, as it was associated both with improvement and development of arthralgias, while ustekinumab, the first anti-interleukin 12/23 (IL-12/23) approved for IBD, has demonstrated good efficacy, especially in peripheral arthritis, and more IL-23 inhibitors are being developed in IBD. Tofacitinib was the first Janus kinase (JAK) inhibitor to be approved in IBD, and as it demonstrated efficacy in treating ankylosing spondylitis, it may represent a good choice in axial arthritis, while more selective JAK inhibitors are yet to be approved. Unexpectedly, the first anti-IL17 that was studied in IBD (secukinumab) has shown not to be effective in treating IBD, and the role of anti-IL17 drugs in these diseases needs further investigation. Therefore, as availability of biologics and small molecules is increasing, their positioning in clinical practice is becoming more and more challenging, and multidisciplinary management needs to be implemented in both research and clinical settings in order to enhance early recognition of SpA in IBD patients, optimize treatment and ultimately improve the patients' quality of life.

Inflammatory Bowel Disease: Focus on Enteropathic Arthritis and Therapy

Inflammatory bowel disease (IBD) is a chronic inflammatory disease primarily affecting the gastrointestinal (GI) tract and other organs. In this article, we provide a comprehensive review of IBD, particularly in the context of enteropathic arthritis and its therapeutic advances. Patients with IBD present with intestinal and extraintestinal manifestations (EIMs). Enteropathic arthritis or arthritis associated with IBD (Crohn's disease [CD] and ulcerative colitis [UC]) is the most common EIM and can involve both peripheral and axial joints with some overlaps. Furthermore, peripheral arthritis can be divided into two subcategories. Due to its varied inflammatory presentations and association with NOD2 mutations, CD can mimic other autoimmune and autoinflammatory diseases. Differential diagnosis should be extended to include another NOD2-associated disease, Yao syndrome. Therapy for IBD entails a myriad of medications and procedures, including various biologics targeting different pathways and Janus kinase (JAK) inhibitors. A better understanding of the therapeutic efficacy and mechanism of each drug aids in proper selection of more effective treatment for IBD and its associated inflammatory arthritis.

Reflecting on the immunopathology of arthritis associated with inflammatory bowel disease: what do we know and what should we know?

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is clinically closely associated with arthritis. Three major arthritis clinical subtypes have been described, peripheral arthritis type 1 (PeA1), peripheral arthritis type 2 (PeA2), and axial spondyloarthritis (axSpA). While genetic overlaps between IBD and arthritis have been defined, detailed pathophysiology for these three major subtypes of arthritis in patients with IBD has only recently begun to be established. The genetic and molecular mechanisms distinguishing axial and peripheral arthropathies in patients with UC and CD need to be better described. Understanding the pathophysiology for PeA1, PeA2, and axSpA in the settings of both UC and CD is necessary to provide the fundamental biology underlying the clinical phenotypes in IBD arthritis. This has been attempted for CD-associated spondyloarthritis, differentiating this from both CD and axSpA, while observing unique peripheral blood mononuclear cells linking gut inflammation to joint disease. We should know more about the processes by which immune cells are perturbed in these disorders, how they translocate to joints, how they are activated, what other molecules and mediators are involved, and how gut microbes and microbial products damage joints. Information from such studies are needed to elucidate whether distinctions between IBD-related peripheral and axSpA are clinically meaningful. IBD-related peripheral and axSpA studies are needed to elucidate whether distinctions between peripheral and axSpA are clinically meaningful, to better understand immunopathogenesis, and to develop novel targeted therapies.

The gut barrier and chronic diseases

PURPOSE OF REVIEW

The purpose of this review is to provide an update regarding the gut barrier and its involvement with chronic diseases, as well as to review biomarkers for identification of gut barrier integrity. This review is timely and relevant as our knowledge is increasing regarding the role of the gut microbiome and the gut barrier in health and disease.

RECENT FINDINGS

This review provides an overview of: the gut barrier, which is complex and comprised of the mucus layer and the intestinal apical junctional protein complex; the gut microbiome in its relation to regulating the integrity of the gut barrier; select acute and chronic conditions that are known to be associated with gut dysbiosis and impaired gut integrity or 'leaky gut'; and current means for identifying loss in gut barrier integrity.

SUMMARY

Many chronic conditions are associated with gut dysbiosis and systemic inflammation. Identifying whether the gut barrier is compromised in these conditions could help to inform potential therapeutics as a means to correct losses in gut barrier integrity and mitigate associated medical conditions.

Microplastic consumption induces inflammatory signatures in the colon and prolongs a viral arthritis

Global microplastic (MP) contamination and the effects on the environment are well described. However, the potential for MP consumption to affect human health remains controversial. Mice consuming ≈80 μg/kg/day of 1 μm polystyrene MPs via their drinking water showed no weight loss, nor were MPs detected in internal organs. The microbiome was also not significantly changed. MP consumption did lead to small transcriptional changes in the colon suggesting plasma membrane perturbations and mild inflammation. Mice were challenged with the arthritogenic chikungunya virus, with MP consumption leading to a significantly prolonged arthritic foot swelling that was associated with elevated Th1, NK cell and neutrophil signatures. Immunohistochemistry also showed a significant increase in the ratio of neutrophils to monocyte/macrophages. The picture that emerges is reminiscent of enteropathic arthritis, whereby perturbations in the colon are thought to activate innate lymphoid cells that can inter alia migrate to joint tissues to promote inflammation.