Circulating mature granzyme B+ T cells distinguish Crohn's disease-associated axial spondyloarthritis from axial spondyloarthritis and Crohn's disease

BACKGROUND

Axial spondyloarthritis (axSpA) has strong connections with intestinal inflammation as occurs in Crohn's disease (CD). However, the immunologic mechanisms that distinguish axSpA, CD, and those with features of both diseases (CD-axSpA) are unknown. This study aimed to address this question by initial unbiased single cell RNA-sequencing (scRNAseq) on a pilot cohort followed by validating findings using flow cytometry and ELISA in a larger cohort.

METHODS

Two individuals each with CD, axSpA, CD-axSpA, and healthy controls (HC) were recruited for a pilot discovery scRNAseq cohort, and the validation cohort consisted of 18 axSpA, 24 CD, 13 CD-axSpA, and 17 HC that was evaluated by flow cytometry on PBMCs and ELISAs for plasma cytokines.

RESULTS

Uniquely, PBMCs from subjects with CD-axSpA demonstrated a significant increase in granzyme B+ T cells of both CD4+ and CD8+ lineages by both scRNAseq and flow cytometry. T cell maturation was also greater in those with CD-axSpA, particularly the CD4+ granzyme B+ population. Pathway analysis suggested increased interferon response genes in all immune cell populations within CD-axSpA. Although IFN-γ was elevated in the plasma of a subset of subjects with CD-axSpA, IL-6 was also significantly elevated.

CONCLUSIONS

Our findings support the presence of a chronic interferonopathy in subjects with CD-axSpA characterized by interferon signaling by pathway analysis and an expansion of mature, cytotoxic T cells. These data indicate fundamental immunological differences between CD-axSpA and both of the putative "parent" conditions, suggesting that it is a distinct disease with unique natural history and treatment needs.

Multi 'Omics Analysis of Intestinal Tissue in Ankylosing Spondylitis Identifies Alterations in the Tryptophan Metabolism Pathway

Intestinal microbial dysbiosis, intestinal inflammation, and Th17 immunity are all linked to the pathophysiology of spondyloarthritis (SpA); however, the mechanisms linking them remain unknown. One potential hypothesis suggests that the dysbiotic gut microbiome as a whole produces metabolites that influence human immune cells. To identify potential disease-relevant, microbiome-produced metabolites, we performed metabolomics screening and shotgun metagenomics on paired colon biopsies and fecal samples, respectively, from subjects with axial SpA (axSpA, N=21), Crohn's disease (CD, N=27), and Crohn's-axSpA overlap (CD-axSpA, N=12), as well as controls (HC, N=24). Using LC-MS based metabolomics of 4 non-inflamed pinch biopsies of the distal colon from subjects, we identified significant alterations in tryptophan pathway metabolites, including an expansion of indole-3-acetate (IAA) in axSpA and CD-axSpA compared to HC and CD and indole-3-acetaldehyde (I3Ald) in axSpA and CD-axSpA but not CD compared to HC, suggesting possible specificity to the development of axSpA. We then performed shotgun metagenomics of fecal samples to characterize gut microbial dysbiosis across these disease states. In spite of no significant differences in alpha-diversity among the 4 groups, our results confirmed differences in gene abundances of numerous enzymes involved in tryptophan metabolism. Specifically, gene abundance of indolepyruvate decarboxylase, which generates IAA and I3Ald, was significantly elevated in individuals with axSpA while gene abundances in HC demonstrated a propensity towards tryptophan synthesis. Such genetic changes were not observed in CD, again suggesting disease specificity for axSpA. Given the emerging role of tryptophan and its metabolites in immune function, altogether these data indicate that tryptophan metabolism into I3Ald and then IAA is one mechanism by which the gut microbiome potentially influences the development of axSpA.

Bile acids modulate colonic MAdCAM-1 expression in a murine model of combined cholestasis and colitis

Primary sclerosing cholangitis (PSC) is a progressive fibrosing cholestatic liver disease that is strongly associated with inflammatory bowel disease (IBD). PSC-associated IBD (PSC-IBD) displays a unique phenotype characterized by right-side predominant colon inflammation and increased risk of colorectal cancer compared to non-PSC-IBD. The frequent association and unique phenotype of PSC-IBD suggest distinctive underlying disease mechanisms from other chronic liver diseases or IBD alone. Multidrug resistance protein 2 knockout (Mdr2-/-) mice develop spontaneous cholestatic liver injury and fibrosis mirroring human PSC. As a novel model of PSC-IBD, we treated Mdr2-/- mice with dextran sulfate sodium (DSS) to chemically induce colitis (Mdr2-/-/DSS). Mdr2-/- mice demonstrate alterations in fecal bile acid composition and enhanced colitis susceptibility with increased colonic adhesion molecule expression, particularly mucosal addressin-cell adhesion molecule 1 (MAdCAM-1). In vitro, ursodeoxycholic acid (UDCA) co-treatment resulted in a dose dependent attenuation of TNF-α-induced endothelial MAdCAM-1 expression. In the combined Mdr2-/-/DSS model, UDCA supplementation attenuated colitis severity and downregulated intestinal MAdCAM-1 expression. These findings suggest a potential mechanistic role for alterations in bile acid signaling in modulating MAdCAM-1 expression and colitis susceptibility in cholestasis-associated colitis. Together, our findings provide a novel model and new insight into the pathogenesis and potential treatment of PSC-IBD.

Markers of Hypoxia Correlate with Histologic and Endoscopic Severity of Colitis in Inflammatory Bowel Disease

BACKGROUND

Inflammation results in significant shifts in tissue metabolism. Recent studies indicate that inflammation and hypoxia occur concomitantly. We examined whether circulating and tissue markers of hypoxia could serve as surrogate indicators of disease severity in adult and pediatric patients with inflammatory bowel disease (IBD).

METHODS

Serum and colonic biopsies were obtained from pediatric subjects with active IBD colitis and adult subjects with active and inactive ulcerative colitis, along with healthy non-colitis controls of all ages. Disease activity was evaluated by endoscopy and histopathology. Levels of serum hypoxia markers (macrophage inflammatory protein-3α [MIP-3α], vascular endothelial growth factor [VEGF], and erythropoietin [EPO]) were measured.

RESULTS

Children with active IBD colitis had higher levels of serum MIP-3α and VEGF compared to non-colitis controls (p<0.01 and p<0.05, respectively). In adult subjects with endoscopically active ulcerative colitis, serum MIP-3α and EPO were significantly elevated compared to non-colitis controls (both p<0.01). In parallel, analysis of colon tissue MIP-3α mRNA and protein in pediatric subjects revealed increased expression in those with IBD colitis compared to controls (p<0.05 and p<0.01 for mRNA and protein, respectively). Serum MIP-3α and VEGF significantly increased with histology grade.

CONCLUSION

Peripheral blood hypoxia markers may be useful indicators of disease activity for pediatric and adult IBD patients.

Functional intraepithelial lymphocyte changes in inflammatory bowel disease and spondyloarthritis have disease specific correlations with intestinal microbiota

Background

Dysbiosis occurs in spondyloarthritis (SpA) and inflammatory bowel disease (IBD), which is subdivided into Crohn’s disease (CD) and ulcerative colitis (UC). The immunologic consequences of alterations in microbiota, however, have not been defined. Intraepithelial lymphocytes (IELs) are T cells within the intestinal epithelium that are in close contact with bacteria and are likely to be modulated by changes in microbiota. We examined differences in human gut-associated bacteria and tested correlation with functional changes in IELs in patients with axial SpA (axSpA), CD, or UC, and in controls.

Methods

We conducted a case-control study to evaluate IELs from pinch biopsies of grossly normal colonic tissue from subjects with biopsy-proven CD or UC, axSpA fulfilling Assessment of SpondyloArthritis International Society (ASAS) criteria and from controls during endoscopy. IELs were harvested and characterized by flow cytometry for cell surface markers. Secreted cytokines were measured by ELISA. Microbiome analysis was by 16S rRNA gene sequencing from rectal swabs. Statistical analyses were performed with the Kruskal-Wallis and Spearman’s rank tests.

Results

The total number of IELs was significantly decreased in subjects with axSpA compared to those with IBD and controls, likely due to a decrease in TCRβ+ IELs. We found strong, significant negative correlation between peripheral lymphocyte count and IEL number. IELs secreted significantly increased IL-1β in patients with UC, significantly increased IL-17A and IFN-γ in patients with CD, and significantly increased TNF-α in patients with CD and axSpA as compared to other cohorts. For each disease subtype, IELs and IEL-produced cytokines were positively and negatively correlated with the relative abundance of multiple bacterial taxa.

Conclusions

Our data indicate differences in IEL function among subjects with axSpA, CD, and UC compared to healthy controls. We propose that the observed correlation between altered microbiota and IEL function in these populations are relevant to the pathogenesis of axSpA and IBD, and discuss possible mechanisms.

Trial registration

ClinicalTrials.gov, NCT02389075. Registered on 17 March 2015.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1639-3) contains supplementary material, which is available to authorized users.

Bacterial Dysbiosis Associates with Functional Intraepithelial Lymphocyte Changes in Inflammatory Bowel Disease and Spondyloarthritis

Dysbiosis occurs in spondyloarthritis (SpA) and inflammatory bowel disease (IBD), subdivided into Crohn’s Disease (CD) and Ulcerative Colitis (UC). The immunologic consequences of dysbiosis have not been defined. Intraepithelial lymphocytes (IELs) are T cells within the intestinal epithelium that are in close contact with bacteria, and as such, are likely to be modulated by dysbiosis. We correlated IELs with resident bacteria in SpA, IBD, and controls. Subjects with biopsy-proven IBD (N=10 with CD and 7 with UC), SpA fulfilling ASAS criteria (N=5), and healthy controls (N=15) were evaluated for fecal microbiome by 16S rRNA sequencing and IELs from colon biopsies analyzed by flow cytometry and ELSIA. Subjects with SpA had significantly lower numbers of IELs compared to controls (p=0.03). Subjects with CD had significantly increased IL-17A, (p=0.03) and IFN-γ (p&lt;0.01) whereas those with UC had higher IL-1β (p=0.01) compared to controls. Both subjects with CD and SpA had significantly increased secretion of TNF-α (p=0.04). Correlating cytokines to bacteria revealed an association between TNF-α and the Simpson Diversity Index in subjects with UC (Spearman’s r=0.943, p&lt;0.01); in subjects with CD, Fusobacterium had a negative correlation with TNFα+IFNγ+IL-1β (Spearman’s r=−0.786, p=0.02). Sequencing results from subjects with SpA are pending. Our data indicate differences in IEL function among subjects with SpA, CD, and UC compared to healthy controls. We hypothesize that the correlations between dysbiosis and IEL function are relevant to the pathogenesis of SpA and IBD. Future studies will be aimed at further understanding mucosal T cell and microbial interactions and may offer new therapeutic targets in these diseases.

Altered colonic intraepithelial lymphocyte composition and function in Crohn’s Disease

Inflammatory bowel disease (IBD), which is subdivided into Ulcerative Colitis (UC) and Crohn’s Disease (CD), is a chronic inflammatory disease of the intestine with an incompletely understood pathogenesis. Studies to date have indicated that gender, microbiome, epithelial biology, and host immune responses contribute to disease. Intraepithelial lymphocytes (IELs) are T cells within the intestinal epithelium that are in close contact with bacterial populations; they are prime candidates to study the interaction between intestinal microbiota and host immunity. Thus, we evaluated IELs in pinch biopsies of uninflamed colon tissue from subjects with biopsy-proven IBD and controls that were undergoing routine colonoscopies. Using flow cytometry, we observed a significantly increased percentage of TCRγδ+ CD8αα and CD44+ IELs in CD compared to controls, suggesting an increase in activated IELs in individuals with CD. Mitogen-stimulated IELs from subjects with CD showed significantly increased TNF-α secretion. Furthermore, while none of our controls secreted IL-17, a subset of CD patients, all premenopausal women, had IELs that produced large amounts of this cytokine. Thus, our data indicate differences in IEL populations between CD, UC, and controls, which support the pathophysiologic differences between CD and UC. The different phenotypes suggest a role for these cells in the diagnosis of IBD. Additionally, given the inflammatory cytokine profile of IELs in subjects with CD, especially women, we propose that IL-17+ IELs are an interesting population of effector T cells that deserve further study to increase our understanding of this complex disease.