Karlijn Debusschere

Elevated calprotectin levels reveal bowel inflammation in spondyloarthritis

Introduction Microscopic bowel inflammation is present in up to 50% of patients with spondyloarthritis (SpA) and is associated with more severe disease. Currently no reliable biomarkers exist to identify patients at risk. Calprotectin is a sensitive marker of neutrophilic inflammation, measurable in serum and stool. Objectives To assess whether serum and faecal calprotectin in addition to C-reactive protein (CRP) can be used to identify patients with SpA at risk of microscopic bowel inflammation. Methods Serum calprotectin and CRP were measured in 125 patients with SpA. In 44 of these patients, faecal samples were available for calprotectin measurement. All 125 patients underwent an ileocolonoscopy to assess the presence of microscopic bowel inflammation. Results Microscopic bowel inflammation was present in 53 (42.4%) patients with SpA. Elevated serum calprotectin and CRP were independently associated with microscopic bowel inflammation. Faecal calprotectin was also significantly higher in patients with microscopic bowel inflammation. Patients with CRP and serum calprotectin elevated had a frequency of bowel inflammation of 64% vs 25% in patients with low levels of both. When either CRP or serum calprotectin was elevated, the risk was intermediate (40%) and measuring faecal calprotectin provided further differentiation. Hence we suggest a screening approach where initially serum calprotectin and CRP are assessed and, if necessary, faecal calprotectin. The model using this scenario provided an area under the ROC curve of 74.4% for detection of bowel inflammation. Conclusions Calprotectin measurements in stool and serum, in addition to CRP, may provide a promising strategy to identify patients with SpA at risk of bowel inflammation and could play a role in overall patient stratification.

Integrating the pathogenesis of spondyloarthritis: gut and joint united?

Purpose of reviewThe association between spondyloarthritis (SpA) and inflammatory bowel disease (IBD) is well known. Additionally, about half of SpA patients show microscopic gut inflammation. Substantial progress has been made in understanding the pathogenesis of SpA and IBD, with new therapeutic targets for either of them in clinical development. Recent findingsMicroscopic gut inflammation was found in early forms of SpA in about 50% of cases and is associated with age, sex, disease activity and degree of MRI inflammation on sacroiliac joints. Although prospective follow-up data in men and murine animal studies show a parallelism between gut and joint evolution in SpA, therapeutic outcomes are not always the same in SpA and IBD. These differences can be ascribed to differences in not only the cytokine pathways and cells involved in disease, tissue localization and environmental factors but also in pharmacokinetics and biodistribution. SummaryA significant amount of data all point in the direction of arthritis and gut inflammation being pathogenetically closely linked in the SpA concept. However, when it comes to therapeutic effectiveness, the gut and the joints do not always react in the same way. These differences in therapeutic effect could be attributed to the different ways in which cytokine pathways are involved in SpA and IBD.

A20 inhibition of STAT1 expression in myeloid cells: a novel endogenous regulatory mechanism preventing development of enthesitis.

Objectives A20 is an important endogenous regulator of inflammation. Single nucleotide polymorphisms in A20 have been associated with various immune-mediated inflammatory diseases, and cell-specific deletion of A20 results in diverse inflammatory phenotypes. Our goal was to delineate the underlying mechanisms of joint inflammation in myeloid-specific A20-deficient mice (A20myelKO mice). Methods Inflammation in A20myelKO mice was assessed in a time-dependent manner. Western blot analysis and quantitative PCR analysis were performed on bone marrow-derived macrophages from A20myelKO and littermate control mice to study the effect of A20 on STAT1/STAT3 expression and STAT1/STAT3-dependent gene transcription in myeloid cells. The in vivo role of Janus kinase-Signal Transducer and Activator of Transcription (JAK-STAT) signalling in the development of enthesitis in A20myelKO mice was assessed following administration of a JAK inhibitor versus placebo control. Results Enthesitis was found to be an early inflammatory lesion in A20myelKO mice. A20 negatively modulated STAT1-dependent, but generally not STAT3-dependent gene transcription in myeloid cells by suppressing STAT1 but not STAT3 expression, both in unstimulated conditions and after interferon-γ or interleukin-6 stimulation. The increase in STAT1 gene transcription in the absence of A20 was shown to be JAK-STAT-dependent. Moreover, JAK inhibition in vivo resulted in significant reduction of enthesitis, both clinically and histopathologically. Conclusions Our data reveal an important and novel interplay between myeloid cells and tissue resident cells at entheseal sites that is regulated by A20. In the absence of A20, STAT1 but not STAT3 expression is enhanced leading to STAT1-dependent inflammation. Therefore, A20 acts as a novel endogenous regulator of STAT1 that prevents onset of enthesitis.

MAIT cells: not just another brick in the wall

The link between gut and joint inflammation in spondyloarthritis (SpA) is well established, in particular in ankylosing spondylitis (AS) and peripheral SpA. In 1995, Mielants et al 1 discovered that almost 50% of patients with SpA have subclinical gut inflammation, of which a fraction develops Crohns disease over time. Recent studies clearly showed that the onset of disease and disease severity are linked to the presence of subclinical gut inflammation.2 However, the mechanism behind this phenomenon is hitherto not fully elucidated. Over the past decade, the interleukin (IL)-23/IL-17-axis has been put forward as a key player in the pathogenesis of SpA. Polymorphisms in the IL23R gene were found both in SpA and in inflammatory bowel disease (IBD),3 linking pathology in these physically distant sites. Cells that are typically responsive to IL-23 are IL-23R+RORγt+ IL-17A-producing cells, such as TH17 cells. In multiple inflammatory diseases, such as multiple sclerosis (MS), IBD and SpA, it is assumed that there is an overall distortion of the cytokine profile towards IL-17A, contributing to disease.4 However, it should be noted that in IBD IL-17A might also exert tissue-protective functions and that mechanisms driving gut inflammation in SpA do not necessarily represent those contributing to the development of full-blown IBD.3 Intriguingly, Sherlock et al 5 showed that systemic IL-23 overexpression is able to drive the development of enthesitis via enthesis-resident CD3+CD4−CD8−RORγt+IL23R+ T cells, independently of TH17 cells. The concept that not TH17 cells but innate-like T cells such as γδ T cells, invariant natural killer T cells (iNKT) and mucosal-associated invariant T (MAIT) cells are the main source of IL-17A recently gained support.6 Interestingly, innate-like T cells such as MAIT cells act at the …

The Effect of Cigarette Smoke Exposure on the Development of Inflammation in Lungs, Gut and Joints of TNFΔARE Mice

The inflammatory cytokine TNF-α is a central mediator in many immune-mediated diseases, such as Crohn’s disease (CD), spondyloarthritis (SpA) and chronic obstructive pulmonary disease (COPD). Epidemiologic studies have shown that cigarette smoking (CS) is a prominent common risk factor in these TNF-dependent diseases. We exposed TNFΔARE mice; in which a systemic TNF-α overexpression leads to the development of inflammation; to 2 or 4 weeks of air or CS. We investigated the effect of deregulated TNF expression on CS-induced pulmonary inflammation and the effect of CS exposure on the initiation and progression of gut and joint inflammation. Upon 2 weeks of CS exposure, inflammation in lungs of TNFΔARE mice was significantly aggravated. However, upon 4 weeks of CS-exposure, this aggravation was no longer observed. TNFΔARE mice have no increases in CD4+ and CD8+ T cells and a diminished neutrophil response in the lungs after 4 weeks of CS exposure. In the gut and joints of TNFΔARE mice, 2 or 4 weeks of CS exposure did not modulate the development of inflammation. In conclusion, CS exposure does not modulate gut and joint inflammation in TNFΔARE mice. The lung responses towards CS in TNFΔARE mice however depend on the duration of CS exposure.

The Role of the Microbiome in Gut and Joint Inflammation in Psoriatic Arthritis and Spondyloarthritis

Spondyloarthritis (SpA) encompasses a group of diseases characterized by an inflammatory arthritis involving both joints and entheses. However, extraarticular symptoms constitute a large element of the pathology and should not be underestimated. Microscopic gut inflammation is observed in 50% of patients with SpA and has been linked to disease activity, underscoring the effect of gut inflammation in SpA. In this review, we discuss the influence of gut microbiota on SpA pathogenesis. A change in microbiota composition has been linked to the development of various inflammatory arthritides, and dysbiosis is a potential factor in the pathogenesis of multiple inflammatory diseases. In this context, several groups have reported the modulatory effects of gut microbiota-derived metabolites on the effect of immune cells. The gut mucosa is populated by several types of regulatory T cells, but also some specialized unconventional innate-like T cells. These cells are predominantly found at mucosal and epithelial barrier sites, where they serve an essential role in modulating host-microbial interplay. Apart from the close association between the composition of the microbiota and inflammatory diseases, the therapeutic value of dysbiosis needs further investigation, and the identification of a causal inflammatory pathway between gut dysbiosis and musculoskeletal inflammation could revolutionize the therapeutic approach in SpA.

Born to run: The paradox of biomechanical force in spondyloarthritis from an evolutionary perspective

Spondyloarthritis (SpA) refers to a group of chronic inflammatory arthritic diseases that can be severely debilitating. The most common form of SpA affecting the peripheral skeleton is psoriatic arthritis, while that affecting the axial skeleton is ankylosing spondylitis. SpA has a multifactorial nature, with both genetic and environmental factors initiating and maintaining the disease. Recently, the role of biomechanical stress as an initiator of disease has gained much attention, with efforts focusing on the underlying cellular and molecular mechanisms. In this review, we provide a different view, with emphasis on the apparently contradictory role of physical therapy in SpA owing to the impact of biomechanical stress and put this in an evolutionary context due to changes in environment and lifestyle across time.

02.50 Intestinal overexpression of human tnf triggers sacro-iliitis

An intriguing link exists between gut and joint inflammation in spondyloarthritis (SpA). About 50% of patients has subclinical (eg, microscopic) gut inflammation, which represents a risk factor for development of Crohn’s disease, sacroiliac inflammation and evolution in to ankylosing spondylitis. However, the underlying mechanisms are still relatively poorly understood. Our goal was to examine the relationship between TNF, microscopic gut inflammation and axial inflammation. Therefore, we examined in situ expression of TNF, TNFR1 and TNFR2 using triple in situ hybridisation in gut biopsies of human SpA patients and found marked upregulation of TNF in inflamed versus non-inflamed biopsies. We also noted a predominant upregulation of TNFR1 on intestinal epithelium and TNFR2 in lamina propria respectively. Of interest, IL-17 and IL-23 were also markedly increased while IL-22 was most abundant in chronically inflamed samples. In line with this, we found that patients with gut inflammation had a higher need for anti-TNF therapy and their degree of clinical response after anti-TNF was also markedly higher. We speculated that TNF in the gut represents an important risk factor for disease severity and progression in SpA. To investigate this further we generated intestinal specific human TNF transgenic mice, in which hTNF is under control of a rat iFABP (fatty acid binding protein) promoter, generating a mouse-model over-expressing human TNF in the ileum. These mice, together with wild type littermates, were evaluated for the development of arthritis up until the age of 13 weeks after which they were euthanized and ankle and sacroiliac joints as well as ileum were processed for histology. Transgenic mice exhibit a runt phenotype and hallmarks of inflammatory bowel disease, including increased intestinal permeability and inflammation compared to their wild-type littermates. While in peripheral joints no clear signs of arthritis were observed, the sacroiliac joints in transgenic mice, by contrast, showed marked signs of inflammation as well as bone erosion and destruction. These data propose a new paradigm that gut-derived TNF is sufficient to trigger sacroiliitis and provide an alternate explanation on the relationship between gut inflammation, evolution to inflammatory bowel disease and axial inflammation in SpA.

SAT0248 Calgranulins are Elevated in Spondyloarthritis and Reflect the Presence of Acute Microscopic Bowel Inflammation

Background Microscopic bowel inflammation is present in about 50% of spondyloarthritis (SpA) patients. Although subclinical, it appears to be a prognostic factor in SpA, linked with more extensive disease and a less favorable outcome. At this moment, however, reliable biomarkers are missing. The calgranulins S100A8/S100A9 and S100A12 are very sensitive markers of innate immune activation. They are released from monocytes and granulocytes in the early phase of the immune response and exert prominent pro-inflammatory effects via Toll-like receptor 4 dependent mechanisms. Calgranulins can be measured in serum and stool. Moreover, the S100A8/S100A9 heterodimer, also called calprotectin, has been established for a long time as a fecal marker of disease activity in inflammatory bowel disease. Objectives To assess whether calgranulins can be used as biomarkers for microscopic bowel inflammation in SpA. Methods Serum calgranulin levels were measured in 122 newly diagnosed SpA patients and 39 healthy controls. SpA patients underwent an ileocolonoscopy to assess the presence of microscopic bowel inflammation. Bowel biopsies were histologically scored and subsequently immuno-stained for S100A8 and S100A9. Results Serum levels of S100A8/S100A9 and S100A12 were significantly higher in SpA patients versus healthy controls (p<0.001). Levels correlated moderately with CRP, but not with ASDAS, BASDAI or swollen joint count. SpA patients with the acute type of microscopic gut inflammation (N=23) had significantly higher calgranulin levels compared to those with normal gut histology (N=62) (p=0.025 for S100A8/S100A9 and p=0.040 for S100A12). Furthermore, immunohistology showed high staining of S100A8 and S100A9 on acutely inflamed bowel biopsies, compared to absent/minimal staining on normal biopsies. Importantly, NSAID intake had neither influence on immunohistology nor on serum measurements. Additionally, we found that having both an elevated CRP together with an elevated S100A8/S100A9 increased the odds of having microscopic bowel inflammation with a factor of 5.4. Conclusions Calgranulin levels, both systemically and locally, reflected the presence of acute microscopic bowel inflammation in SpA. These results also illustrate the high sensitivity of calgranulins, as they detected inflammation present only on a subclinical level. Their measurements can provide a way to identify those patients in whom further invasive checkup might be useful, as endoscopic screening of all SpA patients is not feasible in daily clinical practice. Calgranulins are therefore the first surrogate markers for subclinical bowel inflammation in SpA, allowing for more individually tailored diagnostic and therapeutic decision making. Acknowledgements The research leading to these results has received funding from the European Unions 7th Framework Program under EC-GA No. 305266 “MIAMI”. Disclosure of Interest None declared