Microbiota-dependent indole production stimulates the development of collagen-induced arthritis in mice.

Altered tryptophan catabolism has been identified in inflammatory diseases like rheumatoid arthritis (RA) and spondyloarthritis (SpA), but the causal mechanisms linking tryptophan metabolites to disease are unknown. Using the collagen-induced arthritis (CIA) model, we identified alterations in tryptophan metabolism, and specifically indole, that correlated with disease. We demonstrated that both bacteria and dietary tryptophan were required for disease and that indole supplementation was sufficient to induce disease in their absence. When mice with CIA on a low-tryptophan diet were supplemented with indole, we observed significant increases in serum IL-6, TNF, and IL-1ß; splenic RORγt+CD4+ T cells and ex vivo collagen-stimulated IL-17 production; and a pattern of anti-collagen antibody isotype switching and glycosylation that corresponded with increased complement fixation. IL-23 neutralization reduced disease severity in indole-induced CIA. Finally, exposure of human colonic lymphocytes to indole increased the expression of genes involved in IL-17 signaling and plasma cell activation. Altogether, we propose a mechanism by which intestinal dysbiosis during inflammatory arthritis results in altered tryptophan catabolism, leading to indole stimulation of arthritis development. Blockade of indole generation may present a unique therapeutic pathway for RA and SpA.

Microbiota-dependent indole production is required for the development of collagen-induced arthritis.

Altered tryptophan catabolism has been identified in inflammatory diseases like rheumatoid arthritis (RA) and spondyloarthritis (SpA), but the causal mechanisms linking tryptophan metabolites to disease are unknown. Using the collagen-induced arthritis (CIA) model we identify alterations in tryptophan metabolism, and specifically indole, that correlate with disease. We demonstrate that both bacteria and dietary tryptophan are required for disease, and indole supplementation is sufficient to induce disease in their absence. When mice with CIA on a low-tryptophan diet were supplemented with indole, we observed significant increases in serum IL-6, TNF, and IL-1ß; splenic RORγt+CD4+ T cells and ex vivo collagen-stimulated IL-17 production; and a pattern of anti-collagen antibody isotype switching and glycosylation that corresponded with increased complement fixation. IL-23 neutralization reduced disease severity in indole-induced CIA. Finally, exposure of human colon lymphocytes to indole increased expression of genes involved in IL-17 signaling and plasma cell activation. Altogether, we propose a mechanism by which intestinal dysbiosis during inflammatory arthritis results in altered tryptophan catabolism, leading to indole stimulation of arthritis development. Blockade of indole generation may present a novel therapeutic pathway for RA and SpA.

A Novel Approach toward Less Invasive Multiomics Gut Analyses: a Pilot Study.

Newer 'omics approaches, such as metatranscriptomics and metabolomics, allow functional assessments of the interaction(s) between the gut microbiome and the human host. However, in order to generate meaningful data with these approaches, the method of sample collection is critical. Prior studies have relied on expensive and invasive means toward sample acquisition, such as intestinal biopsy, while other studies have relied on easier methods of collection, such as fecal samples that do not necessarily represent those microbes in contact with the host. In this pilot study, we attempt to characterize a novel, minimally invasive method toward sampling the human microbiome using mucosal cytology brush sampling compared to intestinal gut biopsy samples on 5 healthy participants undergoing routine screening colonoscopy. We compared metatranscriptomic analyses between the two collection methods and identified increased taxonomic evenness and beta diversity in the cytology brush samples and similar community transcriptional profiles between the two methods. Metabolomics assessment demonstrated striking differences between the two methods, implying a difference in bacterial-derived versus human-absorbed metabolites. Put together, this study supports the use of microbiome sampling with cytology brushes, but caution must be exercised when performing metabolomics assessment, as this represents differential metabolite production but not absorption by the host. IMPORTANCE In order to generate meaningful metabolomic and microbiome data, the method of sample collection is critical. This study utilizes and compares two methods for intestinal tissue collection for evaluation of metabolites and microbiomes, finding that using a brush to sample the microbiome provides valuable data. However, for metabolomics assessment, biopsy samples may still be required.

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.

Barrier lymphocytes in spondyloarthritis.

PURPOSE OF REVIEW: The clinical overlap between spondyloarthritis (SpA) and inflammation of barrier tissues such as the intestine and skin indicates a role of barrier tissue immunity in the development of SpA. Herein, we review the recent advances in understanding lymphocyte populations and functions within the intestine and skin implicated in the pathophysiology of SpA. RECENT FINDINGS: A number of unique lymphocyte populations have been identified to be expanded within the gut and skin of patients with SpA, including γδ T cells, mucosa-associated invariant T (MAIT) cells, innate lymphoid cells (ILCs) and T resident memory (TRM) cells. These cells respond to microbial cues at their barrier surface causing cellular activation and generation of interleukin (IL)-17, which is hypothesized to be the mechanism by which they contribute to SpA pathogenesis. SUMMARY: Understanding how unique lymphocyte populations expand and produce IL-17 in the development of SpA provides insights into the pathophysiology of this disease as well as potential future therapeutic avenues.

Molecular Biology Approaches to Understanding Spondyloarthritis.

New and emerging molecular techniques are expanding understanding of the pathophysiology of spondyloarthritis (SpA). Genome-wide association studies identified novel pathways in antigen processing and presentation as well as helper T cell type 17 (TH17) immunity associated with SpA. Immune cell profiling techniques have supported TH17 immune responses and increasingly are revealing intestinal mucosal immune cells as associated with disease. Emerging technologies in epigenetics, transcriptomics, microbiome, and proteomics/metabolomics are adding to these, refining disease pathways and potentially identifying biomarkers for diagnosis and treatment responses. This review describes many of the new molecular techniques that are being utilized to investigate SpA.

The Influence of Depression on Health Care Expenditures Among Adults with Spondylosis, Intervertebral Disc Disorders, and Other Back Problems in the United States.

BACKGROUND: Back pain is a very prevalent complaint, affecting two-thirds of the US population, and it accounts for $100 billion annually in health care expenditures. The occurrence of depression has been reported in existing literature among patients with back pain, but there is limited information regarding health care expenditures among patients with back pain and concurrent depression. OBJECTIVE: To assess excess total and subtypes of health care expenditures among adults with spondylosis, intervertebral disc disorders, and other back problems who reported having depression compared with those without depression in the United States. METHODS: We utilized a cross-sectional design, pooling Medical Expenditure Panel Survey data from 2010-2012. The eligible study sample included adults (age ≥18 years) who reported positive health care expenditure. Total and subtypes of health care expenditures constituted the dependent variable. Ordinary least squares (OLS) regressions on logged expenditures were performed. Four models were developed to assess influence of demographics, functional ability, and concurrent diagnoses on health care expenditures. RESULTS: A total of 6,739 adults with spondylosis, intervertebral disc disorders, and other back problems were assessed, 20.2% (N = 1,316) of whom had concurrent depression. Adults with concurrent depression had significantly higher total health care expenditures ($13,153) compared with the nondepression group ($7,477, P < 0.001). Outpatient and prescription expenditures showed similar findings. After adjusting for demographics, functional disabilities, and comorbidities, excess cost remained higher in the group reporting concurrent depression (46%). CONCLUSIONS: This study demonstrates that the presence of depression in adults with spondylosis, intervertebral disc disorders, and other back problems is associated with greater economic burden. These findings remained consistent after adjusting for all independent sets of variables. The study's findings suggest that interventions resulting in better management of depression have the potential to significantly reduce the economic burden in this population.

Risk of Infections and Cancer in Patients With Rheumatologic Diseases Receiving Interleukin Inhibitors: A Systematic Review and Meta-analysis.

Importance: The safety profile of interleukin (IL) inhibitors is not well established. Objective: To assess the risk of serious infections, opportunistic infections, and cancer in patients with rheumatologic diseases treated with IL inhibitors. Data Sources: Ovid MEDLINE and Epub Ahead of Print, In-Process & Other Non-Indexed Citations; Ovid MEDLINE Daily; Ovid Embase; Ovid Cochrane Central Register of Controlled Trials; Ovid Cochrane Database of Systematic Reviews; and Scopus were searched (inception to November 30, 2018). Study Selection: Randomized, placebo-controlled trials that evaluated IL inhibitor therapies in rheumatic diseases and reported safety data were included in the analyses. Data Extraction and Synthesis: This systematic review is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Two investigators independently extracted study data and assessed risk of bias and certainty in the evidence. Fixed-effects meta-analysis was conducted to pool odds ratios (ORs) for serious infections, opportunistic infections, and cancers for IL inhibitors vs placebo. Main Outcomes and Measures: The outcomes of interest were the number of serious infections, opportunistic infections, and cancers in individuals receiving IL inhibitor therapies compared with placebo. Results: In this meta-analysis, 74 studies comprising 29 214 patients (24 236 patients for serious infections, 9998 for opportunistic infections, and 21 065 for cancer [number of patients overlaps for each outcome]) were included. Patients receiving IL inhibitors had a higher risk of serious infections (OR, 1.97; 95% CI, 1.58-2.44; P < .001, I2 = 0%; high certainty), opportunistic infections (OR, 2.35; 95% CI, 1.09-5.05; P = .03, I2 = 0%; moderate certainty), and cancer (OR, 1.52; 95% CI, 1.05-2.19; P = .03, I2 = 11%; moderate certainty). Conclusions and Relevance: The risk of serious infections, opportunistic infections, and cancer appears to be increased in patients with rheumatologic diseases who are treated with IL inhibitors compared with placebo.

The 100 top-cited publications in psoriatic arthritis: a bibliometric analysis.

BACKGROUND: Citation analysis is a quantitative, bibliometric method that analyzes the frequency and pattern of citations in any given scientific discipline. Over the last two decades, the study of psoriatic arthritis has undergone substantial progress, which has enhanced our ability to assess and treat the disease, and yet an updated citation analysis that reflects these advances is lacking. OBJECTIVE: To highlight the scientific progress in psoriatic arthritis by identifying and analyzing the 100 top-cited psoriatic arthritis articles from the last 40 years. METHODS: Publications on psoriatic arthritis were identified using the Scopus citation database and Web of Science. No date range limits were applied. Data on the 100 top-cited publications were extracted and analyzed. RESULTS: Of the 100 top-cited publications, the median number of citations per publication was 265.9. Articles originated from 29 different countries. Publication dates ranged from 1973 to 2014. The majority (n = 88) were published after 1994, and the greatest number of highly cited psoriatic arthritis publications were reported between 2001 and 2007 (n = 36). Journals with the highest number of top-cited articles included Arthritis and Rheumatology (formerly Arthritis and Rheumatism) (n = 26), followed by Annals of Rheumatic Diseases (n = 21) and Journal of Rheumatology (n = 11). The top six journals with the most highly cited psoriatic arthritis articles were rheumatology journals, with the exception of the Journal of American Academy of Dermatology, a dermatology-based periodical. General medical journals published only nine of the 100 top citations. Impact factors ranged from 2.133 to 44.002, with a mean impact factor of 9.103. There were five authors with 10 or more highly cited psoriatic arthritis publications and 30 authors with five or more of the top publications. Subgroup analysis of the top 25 articles included nine randomized clinical trials, nine observational studies, five reviews, and two guideline statements. Additional subgroup analysis identified the top five hallmark trials in the field. Key publications provided data on classification criteria, disease prevalence, patterns of clinical and radiographic presentation, disease outcomes, associated cardiovascular disease risk, immunologic features and HLA associations, and efficacy and therapeutic benefit of TNFα inihbitors, interleukin-12/23 antagonists, and sulfasalazine. CONCLUSIONS: The study of psoriatic arthritis is rapidly evolving. This bibliometric analysis delineates the landmark publications in psoriatic arthritis that have defined innovative therapeutic modalities and provided critical reviews, guidelines, and other key studies, which highlight the important progress made in the field.

A systematic review and meta-analysis of the efficacy and safety of the interleukin (IL)-12/23 and IL-17 inhibitors ustekinumab, secukinumab, ixekizumab, brodalumab, guselkumab and tildrakizumab for the treatment of moderate to severe plaque psoriasis.

OBJECTIVE: To systematically analyze the efficacy and safety of interleukin (IL)-12/23, IL-17, and selective IL-23 inhibitors in moderate to severe plaque psoriasis. METHODS AND RESULTS: Twenty-four randomized placebo-controlled trials were included. Compared to placebo, risk ratios (RR) of achieving PASI-75 and PGA/IGA 0/1 respectively were 20.20 (95% CI 13.82-29.54, p < .00001) and 14.55 (10.42-20.31, p < .00001) for ustekinumab 90 mg, 13.75 (8.49-22.28, p < .00001) and 9.81 (5.70-16.89, p < .00001) for ustekinumab 45 mg, 17.65 (12.38-25.17, p < .00001) and 26.13 (16.05-42.53, p < .00001) for secukinumab 300 mg, 15.36 (10.76-21.94, p < .00001) and 20.91 (12.82-34.13, p < .00001) for secukinumab 150 mg, 18.22 (10.63-31.23, p < .000001) and 18.82 (10.36-34.16, p < .00001) for ixekizumab 80 mg every 4 weeks, 19.83 (11.07-35.52, p < .00001) and 20.41 (11.01-37.81, p < .00001) for ixekizumab 80 mg every 2 weeks, 14.79 (9.86-22.16, p < .00001) and 21.93 (15.52-31.01, p < .00001) for brodalumab 210 mg, 11.55 (7.77-17.18, p < .00001) and 16.59 (11.72-23.49, p < .00001) for brodalumab 140 mg, 12.40 (8.87-17.34, p < .00001) and 10.84 (7.91-14.85, p < .00001) for guselkumab 100 mg, 11.45 (7.45-17.58, p < .00001) and 10.97 (6.44-18.69, p < .00001) for tildrakizumab 200 mg, 11.02 (7.17-16.93, p < .00001) and 10.03 (6.45-15.59, p < .00001) for tildrakizumab 100 mg. Similar outcomes were seen for PASI-90. Safety was satisfactory for each therapy at any dose, but a slightly increased risk of withdrawal due to toxicity was observed in individuals receiving ixekizumab compared to placebo. CONCLUSION: Ustekinumab, secukinumab, ixekizumab, brodalumab, guselkumab, and tildrakizumab were highly efficacious and generally well-tolerated when used as treatments for moderate to severe plaque psoriasis.

Targeting the NF-κB Pathway as a Combination Therapy for Advanced Thyroid Cancer.

NF-κB signaling plays an important role in tumor cell proliferation, cell survival, angiogenesis, invasion, metastasis and drug/radiation resistance. Combination therapy involving NF-κB pathway inhibition is an attractive strategy for the treatment of advanced forms of thyroid cancer. This study was designed to test the efficacy of NF-κB pathway inhibition in combination with cytotoxic chemotherapy, using docetaxel and ionizing radiation in in vitro models of thyroid cancer. We found that while both docetaxel and ionizing radiation activated NF-κB signaling in thyroid cancer cells, there was no synergistic effect on cell proliferation and/or programmed cell death with either genetic (transduction of a dominant negative mutant form of IκBα) or pharmacologic (proteasome inhibitor bortezomib and IKKß inhibitor GO-Y030) inhibition of the NF-κB pathway in thyroid cancer cell lines BCPAP, 8505C, THJ16T and SW1736. Docetaxel plus bortezomib synergistically decreased in vitro invasion of 8505C cells, but not in the other cell lines. Screening of a panel of clinically relevant targeted therapies for synergy with genetic NF-κB inhibition in a proliferation/cytotoxicity assay identified the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) as a potential candidate. However, the synergistic effect was confirmed only in the BCPAP cells. These results indicate that NF-κB inhibitors are unlikely to be beneficial as combination therapy with taxane cytotoxic chemotherapy, external radiation therapy or radioiodine therapy. There may be unique circumstances where NF-κB inhibitors may be considered in combination with docetaxel to reduce tumor invasion or in combination with HDAC inhibitors to reduce tumor growth, but this does not appear to be a combination therapy that could be broadly applied to patients with advanced thyroid cancer. Further research may identify which subsets of patients/tumors may respond to this therapeutic approach.

OS-FRET: a new one-sample method for improved FRET measurements.

Fluorescence resonance energy transfer (FRET) is a powerful tool for studying macromolecular assemblies in vitro under near-physiological conditions. Here we present a new type of one-sample FRET (OS-FRET) method employing a novel, nonfluorescent methanethiosulfonate-linked acceptor that can be reversibly coupled to a target sulfhydryl residue via a disulfide bond. After the quenched donor emission is quantitated, the acceptor is removed by reduction, allowing measurement of unquenched donor emission in the same sample. Previous one-sample methods provide distinct advantages in specific FRET applications. The new OS-FRET method is a generalizable spectrochemical approach that can be applied to macromolecular systems lacking essential disulfide bonds and eliminates the potential systematic errors of some earlier one-sample methods. In addition, OS-FRET enables quantitative FRET measurements in virtually any fluorescence spectrometer or detection device. Compared to conventional multisample FRET methods, OS-FRET conserves sample, increases the precision of data, and shortens the time per measurement. The utility of the method is illustrated by its application to a protein complex of known structure formed by CheW and the P4-P5 fragment of CheA, both from Thermotoga maritima. The findings confirm the practicality and advantages of OS-FRET. Anticipated applications of OS-FRET include analysis of macromolecular structure, binding and conformational dynamics, and high-throughput screening for interactions and inhibitors.