Human Inflammatory Bowel Disease Research Articles

Unveiling the roles of dietary Tryptophan and Arginine metabolism in Lactobacillus rhamnosus GG-mediated barrier protection

Inflammatory bowel disease (IBD) is often characterized by increased intestinal paracellular permeability and abnormalities in tight junctions (TJ). IBD patients commonly exhibit reduced serum tryptophan (TRP) levels. Furthermore, animal models on low-TRP diets are more susceptible to chemically induced intestinal inflammation, while those on high-TRP diets show reduced inflammation. The interaction between TRP and gut microbiota in reinforcing the intestinal barrier warrants further investigation. To address this, we introduced Lactobacillus rhamnosus GG (LGG), known for enhancing the gut barrier, and PBS as a control into germ-free mice fed TRP-suffcient or -deficient diets. Our analysis of the mouse ileal transcriptome revealed dramatic upregulation of key genes in arginine metabolism only in LGG-TRP mice, particularly of argininosuccinate lyase ( Asl) that catabolizes argininosuccinate (ASA). Interestingly, our in-silico analysis of human IBD data GEO 179285 transcriptome showed marked dysregulation of similar genes, including inappropriate increases in ASA synthetase ( Ass1). Moreover, this unique expression pattern in the mouse ileum was TRP-dependent and specific to LGG, and not observed in mice monocolonized with pathobiont Ruminococcus gnavus or specific pathogen-free mice. LC-MS analysis of fecal and serum metabolites in LGG-TRP mice revealed elevated levels of fecal arginine, glutamine, and aspartate, suggesting their involvement in host arginine biosynthesis, along with significant reductions in serum ASA levels. ASA was highly negatively correlated with numerous TJ genes, suggesting its potential to compromise barrier function. Indeed, treating mouse enteroids with ASA enhanced dextran permeability, exacerbated LPS disruption of the gut barrier, and decreased expression of TJ genes Ocln and Tjp1. Furthermore, elevated serum ASA and decreased colonic ASL levels were observed in colitis-afflicted mice, perturbing gut homeostasis, as indicated by increased fecal lipocalin-2 and delayed colitis recovery after intraperitoneal ASA administration. We propose that LGG-TRP stimulates gut-mediated ASA turnover as evidenced by substantial increases in Asl levels. Interestingly, LGG alone reduced ASA concentration in the culture medium under anaerobic and aerobic conditions. Collectively, our study identifies ASA as a potential biomarker of gut inflammation and enhanced permeability. Moreover, we highlight the potential of LGG-TRP therapy for IBD-associated leaky gut conditions, offering novel insights for gut health interventions. NIHR01-AT010243 (NG,RF), R01DK119198 (NG), NSF 1754783 (RF). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Blimp-1 and c-Maf regulate immune gene networks to protect against distinct pathways of pathobiont-induced colitis

Intestinal immune responses to microbes are controlled by the cytokine IL-10 to avoid immune pathology. Here, we use single-cell RNA sequencing of colon lamina propria leukocytes (LPLs) along with RNA-seq and ATAC-seq of purified CD4+ T cells to show that the transcription factors Blimp-1 (encoded by Prdm1) and c-Maf co-dominantly regulate Il10 while negatively regulating proinflammatory cytokines in effector T cells. Double-deficient Prdm1fl/flMaffl/flCd4Cre mice infected with Helicobacter hepaticus developed severe colitis with an increase in TH1/NK/ILC1 effector genes in LPLs, while Prdm1fl/flCd4Cre and Maffl/flCd4Cre mice exhibited moderate pathology and a less-marked type 1 effector response. LPLs from infected Maffl/flCd4Cre mice had increased type 17 responses with increased Il17a and Il22 expression and an increase in granulocytes and myeloid cell numbers, resulting in increased T cell–myeloid–neutrophil interactions. Genes over-expressed in human inflammatory bowel disease showed differential expression in LPLs from infected mice in the absence of Prdm1 or Maf, revealing potential mechanisms of human disease.

Rab7-dependent regulation of goblet cell protein CLCA1 modulates gastrointestinal homeostasis

Inflammation in ulcerative colitis is typically restricted to the mucosal layer of distal gut. Disrupted mucus barrier, coupled with microbial dysbiosis, has been reported to occur prior to the onset of inflammation. Here, we show the involvement of vesicular trafficking protein Rab7 in regulating the colonic mucus system. We identified a lowered Rab7 expression in goblet cells of colon during human and murine colitis. In vivo Rab7 knocked down mice (Rab7KD) displayed a compromised mucus layer, increased microbial permeability, and depleted gut microbiota with enhanced susceptibility to dextran sodium-sulfate induced colitis. These abnormalities emerged owing to altered mucus composition, as revealed by mucus proteomics, with increased expression of mucin protease chloride channel accessory 1 (CLCA1). Mechanistically, Rab7 maintained optimal CLCA1 levels by controlling its lysosomal degradation, a process that was dysregulated during colitis. Overall, our work establishes a role for Rab7-dependent control of CLCA1 secretion required for maintaining mucosal homeostasis.

Rab7-dependent regulation of goblet cell protein CLCA1 modulates gastrointestinal homeostasis.

Inflammation in ulcerative colitis is typically restricted to the mucosal layer of distal gut. Disrupted mucus barrier, coupled with microbial dysbiosis, has been reported to occur prior to the onset of inflammation. Here, we show the involvement of vesicular trafficking protein Rab7 in regulating the colonic mucus system. We identified a lowered Rab7 expression in goblet cells of colon during human and murine colitis. In vivo Rab7 knocked down mice (Rab7KD) displayed a compromised mucus layer, increased microbial permeability, and depleted gut microbiota with enhanced susceptibility to dextran sodium-sulfate induced colitis. These abnormalities emerged owing to altered mucus composition, as revealed by mucus proteomics, with increased expression of mucin protease chloride channel accessory 1 (CLCA1). Mechanistically, Rab7 maintained optimal CLCA1 levels by controlling its lysosomal degradation, a process that was dysregulated during colitis. Overall, our work establishes a role for Rab7-dependent control of CLCA1 secretion required for maintaining mucosal homeostasis.

Abstract SY45-02: Engineering strategies based on receptors derived from gdT cells

Abstract SY45-02: Engineering strategies based on receptors derived from gdT cells

Profiling the colonic mucosal response to fecal microbiota transplantation identifies a role for GBP5 in colitis in humans and mice

Host molecular responses to fecal microbiota transplantation (FMT) in ulcerative colitis are not well understood. Here, we profile the human colonic mucosal transcriptome prior to and following FMT or placebo to identify molecules regulated during disease remission. FMT alters the transcriptome above the effect of placebo (n = 75 vs 3 genes, q < 0.05), including modulation of structural, metabolic and inflammatory pathways. This response is attributed to responders with no consistency observed in non-responders. Regulated pathways in responders include tight junctions, calcium signalling and xenobiotic metabolism. Genes significantly regulated longitudinally in responders post-FMT could discriminate them from responders and non-responders at baseline and non-responders post-FMT, with GBP5 and IRF4 downregulation being associated with remission. Female mice with a deletion of GBP5 are more resistant to developing colitis than their wild-type littermates, showing higher colonic IRF4 phosphorylation. The colonic mucosal response discriminates UC remission following FMT, with GBP5 playing a detrimental role in colitis.

A Comprehensive Exploration of Therapeutic Strategies in Inflammatory Bowel Diseases: Insights from Human and Animal Studies.

Inflammatory bowel disease (IBD) is a collective term for a group of chronic inflammatory enteropathies which are characterized by intestinal inflammation and persistent or frequent gastrointestinal signs. This disease affects more than 3.5 million humans worldwide and presents some similarities between animal species, in particular, dogs and cats. Although the underlying mechanism that triggers the disease is not yet well understood, the evidence suggests a multifactorial etiology implicating genetic causes, environmental factors, microbiota imbalance, and mucosa immune defects, both in humans and in dogs and cats. Conventional immunomodulatory drug therapies, such as glucocorticoids or immunosuppressants, are related with numerous adverse effects that limit its long-term use, creating the need to develop new therapeutic strategies. Mesenchymal stromal cells (MSCs) emerge as a promising alternative that attenuates intestinal inflammation by modulating inflammatory cytokines in inflamed tissues, and also due to their pro-angiogenic, anti-apoptotic, anti-fibrotic, regenerative, anti-tumor, and anti-microbial potential. However, this therapeutic approach may have important limitations regarding the lack of studies, namely in veterinary medicine, lack of standardized protocols, and high economic cost. This review summarizes the main differences and similarities between human, canine, and feline IBD, as well as the potential treatment and future prospects of MSCs.

Antioxidant and Anti-Inflammatory Phytochemicals for the Treatment of Inflammatory Bowel Disease: A Systematic Review

Inflammatory bowel disease (IBD) remains a burden for patients with increasing prevalence in industrialized countries. Phytochemicals are non-nutrient plant derived bioactive substances with antioxidant and anti-inflammatory effects that may prove beneficial to IBD patients. This review aims to overview current evidence on the application and impact of isolated phytochemicals or phytochemicals contained in plant extracts and essential oils on patients suffering from IBD. A systematic literature search was conducted for studies relating to the use of phytochemicals for the treatment of IBD. Ultimately, 37 human clinical trials and 3 systematic reviews providing human IBD patient data relevant to phytochemicals as therapeutic agents were included. Phytochemicals in the form of curcumin, Plantago ovata seeds, polyphenon E, silymarin, resveratrol supplements or an herbal preparation of myrrh, chamomile and coffee charcoal have evidence from human clinical trials supporting their safety and beneficial effects. Cannabinoids improve quality of life but not IBD outcomes. The addition of probiotics like B. longum to fructo-oligosaccharides promote healthy composition of the gut microbiome. Phytochemicals like mastiha, anthocyanins, berberine, tormentil, T2, ecabet sodium and Pycnogenol need more well-designed trials. Systematic research on phytochemicals can lead to the discovery of useful therapeutics. These secondary metabolites can be incorporated in current IBD treatment strategies to limit side effects, promote mucosal healing and provide higher quality of life to patients.

IL-10 constrains sphingolipid metabolism to limit inflammation

Interleukin-10 (IL-10) is a key anti-inflammatory cytokine that can limit immune cell activation and cytokine production in innate immune cell types1. Loss of IL-10 signalling results in life-threatening inflammatory bowel disease in humans and mice—however, the exact mechanism by which IL-10 signalling subdues inflammation remains unclear2–5. Here we find that increased saturated very long chain (VLC) ceramides are critical for the heightened inflammatory gene expression that is a hallmark of IL-10 deficiency. Accordingly, genetic deletion of ceramide synthase 2 (encoded by Cers2), the enzyme responsible for VLC ceramide production, limited the exacerbated inflammatory gene expression programme associated with IL-10 deficiency both in vitro and in vivo. The accumulation of saturated VLC ceramides was regulated by a decrease in metabolic flux through the de novo mono-unsaturated fatty acid synthesis pathway. Restoring mono-unsaturated fatty acid availability to cells deficient in IL-10 signalling limited saturated VLC ceramide production and the associated inflammation. Mechanistically, we find that persistent inflammation mediated by VLC ceramides is largely dependent on sustained activity of REL, an immuno-modulatory transcription factor. Together, these data indicate that an IL-10-driven fatty acid desaturation programme rewires VLC ceramide accumulation and aberrant activation of REL. These studies support the idea that fatty acid homeostasis in innate immune cells serves as a key regulatory node to control pathologic inflammation and suggests that ‘metabolic correction’ of VLC homeostasis could be an important strategy to normalize dysregulated inflammation caused by the absence of IL-10.

An in vitro model to study immune activation, epithelial disruption and stromal remodelling in inflammatory bowel disease and fistulising Crohn's disease.

At present, preclinical models of inflammatory bowel disease (IBD) are insufficient, limiting translation between research and new therapeutics. This is especially true for fistulising Crohn's disease (CD), as the severe lack of relevant models hinders research progression. To address this, we present in vitro human IBD mucosal models that recapitulate multiple pathological hallmarks of IBD simultaneously in one model system - immune cell infiltration, stromal remodelling and epithelial disruption. Stimulation of models induces epithelial aberrations common in IBD tissue including altered morphology, microvilli abnormalities, claudin gene expression changes and increased permeability. Inflammatory biomarkers are also significantly increased including cytokines and chemokines integral to IBD pathogenesis. Evidence of extracellular matrix remodelling, including upregulated matrix-metalloproteinases and altered basement membrane components, suggests the models simulate pathological stromal remodelling events that closely resemble fistulising CD. Importantly, MMP-9 is the most abundant MMP and mimics the unique localisation observed in IBD tissue. The inflamed models were subsequently used to elucidate the involvement of TNF-α and IFN- γ in intestinal stromal remodelling, in which TNF-α but not IFN- γ induced MMP upregulation, specifically of MMP-3 and MMP-9. Collectively, our results demonstrate the potential of the IBD models for use in preclinical research in IBD, particularly for fistulising CD.

Naturally occurring phytanic acid exerts anti‐inflammatory effects in a mouse model of dextran sulfate sodium‐induced colitis

AbstractPhytanic acid is one of the branched‐chain fatty acids in the human diet. Humans incorporate it into their bodies through the ingestion of ruminant meat and milk since these animal products contain the 3RS, 7R, 11R‐isomer, as naturally occurring phytanic acid (nPA). Although phytanic acid has been reported to have health‐promoting effects such as immunomodulatory effects, these findings were obtained mostly from in vitro cell‐based experiments. In this study, the in vivo anti‐inflammatory effects of nPA were investigated using a mouse model of dextran sulfate sodium (DSS)‐induced colitis. Mice were fed diets containing 0%, 0.05%, or 0.1% nPA for 4 weeks. During the fourth week, acute colitis was induced by administration of a 3% DSS solution. The intake of 0.05% and 0.1% nPA inhibited DSS‐induced body weight loss in mice, and showed improvement of histopathological changes in colon epithelium. nPA also inhibited the production of proinflammatory cytokines, especially macrophage‐related cytokines such as interleukin‐1β in the colon. These results suggest that nPA exerts anti‐inflammatory effects under in vivo physiological conditions.Practical application: There is a growing demand for fatty acids possessing distinct nutritional and physical characteristics in the realms of health, nutrition, and food‐related applications. The present study demonstrated that a branched‐chain fatty acid, phytanic acid, exerts anti‐inflammatory activity under not only in vitro but also in vivo conditions, using a commonly used mouse model of human inflammatory bowel disease. Our findings encourage further studies to determine whether phytanic acid elicits beneficial properties in humans, and suggest that phytanic acid enrichment can be a novel product strategy in the food market.

Polymorphisms in CLEC5A and CLEC7A genes modify risk for inflammatory bowel disease.

Inflammatory bowel disease (IBD) seems to arise from an interplay between genetic and environmental factors. CLEC5A and CLEC7A genes code for 2 members of the C-type lectin receptor superfamily, which participate in the immune response against various pathogens, mediating inflammatory signaling. CLEC5A polymorphisms have been linked to the risk of Crohn's disease (CD), whereas CLEC7A has been implicated in fungal dysbiosis, chemically induced colitis in mice and undertreated ulcerative colitis (UC) in humans. This study aimed to explore how specific CLEC5A and CLEC7A polymorphisms contribute to the development of CD and UC. One hundred twelve CD patients, 94 UC patients and 164 sex- and age- matched healthy individuals were genotyped for the single nucleotide polymorphisms rs2078178 and rs16910631 of the CLEC7A gene, and rs1285933 of the CLEC5A gene. The CLEC7A rs2078178 AA genotype was more frequent in UC patients compared to healthy individuals, The CLEC7A rs16910631 CT genotype was significantly associated with UC risk compared to healthy individuals, while there was no statistical correlation with CD. The CLEC5A rs1285933 GA genotype was found to be protective against UC and CD, and the AA genotype against CD. Carriers of the rs1285933 A allele appeared to have reduced susceptibility to CD, implying that the presence of the A allele could be protective against CD development. This is the first study to correlate the CLEC5A rs1285933 polymorphism with the risk for UC. The rs2078178 AA genotype and the CLEC7A rs16910631 CT could be promising biomarkers for UC susceptibility.

Intestinal Epithelia and Myeloid Immune Cells Shape Colitis Severity and Colorectal Carcinogenesis via High-mobility Group Box Protein 1.

High-mobility group box protein 1 [HMGB1] is a ubiquitous nucleoprotein with immune-regulatory properties following cellular secretion or release in sterile and in infectious inflammation. Stool and serum HMGB1 levels correlate with colitis severity and colorectal cancer [CRC] progression, yet recent reports indicate that HMGB1 mainly operates as an intracellular determinant of enterocyte fate during colitis, and investigations into the roles of HMGB1 in CRC are lacking. Using mice with conditional HMGB1-knockout in enterocytes [Hmgb1ΔIEC] and myeloid cells [Hmgb1ΔLysM], respectively, we explored functions of HMGB1 in pathogenetically diverse contexts of colitis and colitis-associated CRC. HMGB1 is overexpressed in human inflammatory bowel disease and gastrointestinal cancers, and HMGB1 protein localises in enterocytes and stromal cells in colitis and CRC specimens from humans and rodents. As previously described, enterocyte HMGB1 deficiency aggravates severe chemical-induced intestinal injury, but not Citrobacter rodentium or T cell transfer colitis in mice. HMGB1-deficient enterocytes and organoids do not exhibit deviant apoptotic or autophagic activity, altered proliferative or migratory capacity, abnormal intestinal permeability, or aberrant DSS-induced organoid inflammation in vitro. Instead, we observed altered in vivo reprogramming of both intestinal epithelia and infiltrating myeloid cells in Hmgb1ΔIEC early during colitis, suggesting HMGB1-mediated paracrine injury signalling. Hmgb1ΔIEC had higher CRC burden than wild types in the Apc+/min model, whereas inflammatory CRC was attenuated in Hmgb1ΔLysM. Cellular and molecular phenotyping of Hmgb1ΔIEC and Hmgb1ΔLysM cancers indicates context-dependent transcriptional modulation of immune signalling and extracellular matrix remodelling via HMGB1. Enterocytes and myeloid cells context-dependently regulate host responses to severe colitis and maladaptive intestinal wound healing via HMGB1.

Unveiling Colitis: A Journey through the Dextran Sodium Sulfate-induced Model.

Animal models of inflammatory bowel disease (IBD) are valuable tools for investigating the factors involved in IBD pathogenesis and evaluating new therapeutic options. The dextran sodium sulfate (DSS)-induced model of colitis is arguably the most widely used animal model for studying the pathogenesis of and potential treatments for ulcerative colitis (UC), which is a primary form of IBD. This model offers several advantages as a research tool: it is highly reproducible, relatively easy to generate and maintain, and mimics many critical features of human IBD. Recently, it has also been used to study the role of gut microbiota in the development and progression of IBD and to investigate the effects of other factors, such as diet and genetics, on colitis severity. However, although DSS-induced colitis is the most popular and flexible model for preclinical IBD research, it is not an exact replica of human colitis, and some results obtained from this model cannot be directly applied to humans. This review aims to comprehensively discuss different factors that may be involved in the pathogenesis of DSS-induced colitis and the issues that should be considered when using this model for translational purposes.

Bibliometric and visual analysis of intestinal flora and immunity.

The gut microbiota and its stability have important relationships with immunity. However, bibliometric analysis in this field is underdeveloped. This study aims to visualize publications related to the gut microbiota and immunity to identify research frontiers and hotspots, providing references and guidance for further research. Gut microbiota and immunity data were retrieved from the Web of Science Core Collection database, and Microsoft Excel, Scimago Graphica and VOSviewer software were used to analyze publication output trends, the most productive countries/regions, journals, authors, co-cited references, and keywords. This study analyzed 16,611 publications, including 10,865 articles and 5746 reviews, and found a continuous increase in publications related to gut microbiota and immunity since 2013. We identified 62,872 authors contributing to this field from 2144 journals and 9965 organizations/institutions in 145 countries/regions. The top publisher with the highest output is University of California System with 525 papers. Among these journals, the top 3 most prolific journals are Frontiers in Immunology, Frontiers in Microbiology, and PLOS ONE. The literature with the highest citation frequency is published in Science and has been cited 3006 times by Patrick M. Smith and others.Gut microbiota research hotspots include gut microbiota inflammation, immune response, inflammatory bowel diseases (IBDs), and microbiota tumors. The gut microbiota and its microbial homeostasis play critical roles in immune reactions, inflammation, and even tumors and IBDs.Current research on gut microbiota and immunity is a popular field. Previous studies have shown that the gut microbiota and its microbial species have important effects on maintaining human health, immune function, inflammation, tumorigenesis, and IBDs. Understanding the roles of microbial communities and specific bacterial species as well as their interactions with humans has led to numerous discoveries that provide unique opportunities for exploring human health and future research. This study used bibliometric and visualization analysis to identify the development trends and hotspots of publications related to the gut microbiota and immunity. The findings of this study provide valuable insights into the emerging trends and future directions in this field.

EVALUATION OF THE CLINICAL STAGE FXR AGONIST FXR314 IN HUMAN PRIMARY CELL 3D MODELS OF CROHN’S DISEASE AND ULCERATIVE COLITIS

Abstract There is a critical need for novel approaches to treat inflammatory bowel disease (IBD) that extend beyond modulating the immune response. These innovative strategies should also focus on enhancing the integrity of the intestinal barrier and addressing fibrotic tissue development throughout the course of the disease, both critical components of IBD, to improve long term outcomes. Targeting the ligand-activated nuclear Farnesoid X Receptor (FXR) represents such an emerging opportunity. Intestinal epithelial cells exhibit high expression of FXR which is pivotal for intestinal function by regulating the innate immune response, reducing bacterial translocation into the intestinal wall, preserving the integrity of the epithelial barrier, and potentially reducing fibrotic deposition. We have developed a human 3D co-culture model of multiple cell types derived from Crohn’s disease (CD) or ulcerative colitis patients (UC). These 3D-culture CD and UC models faithfully replicate various aspects of the IBD disease state, including differences in gene expression patterns relative to intestinal tissues from healthy donors, compromised epithelial barrier integrity (as measured by Fluorescein isothiocyanate-dextran and TEER assays) and disrupted fibrotic deposition (as determined via fibrosis biomarkers and quantitative collagen deposition). FXR314 is an orally administered non-bile acid FXR agonist that has completed a Phase 2a clinical trial in NASH and is being considered as a novel therapeutic approach for IBD. We assessed the capacity of FXR314 to improve disease biomarkers in 3D models of human IBD. Specifically, its effects were characterized in five CD donors and three UC donors. Target engagement was demonstrated in all CD and UC donors tested through activation of FGF19, a well-accepted target of FXR activation. In CD donors, FXR314 broadly improved measures of epithelial barrier function in a subset of donors, and fibrotic markers in all five donors. In UC donors, FXR314 improved epithelial barrier function and fibrotic activity in all three donors. As anticipated, the effects seen across the different metrics were concentration dependent. These primary multicellular 3D human IBD models (CD, UC) constitute a powerful tool to more accurately predict the relevance of specific targets and assess the efficacy of therapeutic candidates. Consequently, this could enhance the probability of success when conducting clinical trials. In this study, we demonstrated that the non-bile acid FXR agonist FXR314 improves multiple aspects of Crohn’s disease and ulcerative colitis in human donors, thereby strengthening its potential as a novel therapeutic approach for IBD.

GRANZYME A-PRODUCING CD4 T CELLS ARE DRIVERS OF IMMUNE CHECKPOINT BLOCKADE-INDUCED COLITIS

Abstract Immune checkpoint blockade (ICB) (i.e. anti-CTLA4 and/or anti-PD-1) is a type of cancer immunotherapy that is broadly and effectively used across multiple cancer types. Despite this efficacy, ~60% of individuals of ICB recipients develop autoimmune-like inflammation in the skin, lungs and intestines. Of these barrier sites, an inflamed intestine is the most common form of severe disease that requires cessation of immunotherapy and potential tumor rebound. ICB-induced colitis therefore represents a significant health concern in an increasing population of cancer patients receiving this otherwise effective immunotherapy. Previous work has shown evidence of a dysregulated intestinal CD4 T cell response in ICB colitis patients, however, how CD4 T cells might contribute to disease has remained unclear. Here, we identify a unique subset of T helper (Th) 1-like CD4 T cells that express the serine protease granzyme A (GZMA) that are specifically elevated in ICB-induced colitis patients, suggesting a pathogenic role for GZMA-expressing Th cells in disease. As mouse models for ICB-induced colitis are virtually non-existent, we have profiled existing mouse models of intestinal inflammation for the presence of colonic GZMA-expressing CD4 T cells for more in-depth functional studies. Using this approach, we have identified the T cell transfer model of colitis as a model that mimics the GZMA CD4 T cell phenotype observed in human ICB colitis patients. Within this model, GZMA-expressing CD4 T cells arise early in the intestines after transfer and only minimally express other CD4 T helper (Th) cell lineage cytokines (i.e. IFN-γ or IL-17) indicating that these cells may represent a unique Th cell subtype that are associated with intestinal disease. Indeed, transfer of GZMA-deficient CD4 T cells into colitis-prone mice resulted in reduced intestinal inflammation and damage, despite efficient trafficking of these cells to the intestines. Mechanistically, CD4 T cell-derived GZMA promoted an exaggerated intestinal epithelial cell response to the microbiota, but was not required for immune-editing of the microbiota in this setting. Taken together, our data indicate that GZMA-producing Th cells are likely major contributors to ICB-induced colitis and may represent a valuable therapeutic target for limiting intestinal disease during ICB therapy.

ENHANCED MITOCHONDRIAL BIOGENESIS INCREASES ANTI-OXIDANT ENZYMES AND IMPROVES TISSUE INFLAMMATION IN HUMAN IBD TISSUE

Abstract BACKGROUND In patients with inflammatory bowel disease (IBD), there exists a connection between mitochondrial dysfunction and two key issues: increased oxidative stress and attenuated ATP production. Previously we presented at this meeting the effect of a novel gold-based compound (AuPhos) on enhancing mitochondrial function in attenuating mice colitis (). In the present study we interrogate the effect of AuPhos on mitochondrial biogenesis in biopsies from control and active ulcerative colitis (UC) (Mayo 1-2) patients and normal human colonic epithelial cells (NCM460). We postulate that AuPhos-induced mitochondrial function enhances biogenesis and anti-oxidant levels and improves tissue inflammation in human IBD tissue. METHODS Effects of AuPhos on mitochondrial and anti-oxidant proteins were evaluated in NCM460 cells by western blot (WB) +/- low-dose TNF(1ng/ml). Human colonic biopsy samples (n=3) were collected and treated ex-vivo with vehicle or AuPhos (3h, 4oC), and processed for protein and mRNA analysis by WB and RT-qPCR, respectively. Flow cytometry of mitotracker green quantified mitochondrial mass in NCM460 and intestinal epithelial cells (IECs) from human control and UC tissues (n=3, Mayo 1-2). RESULTS AuPhos increased mitochondrial mass (mitotracker, Fig.1A,1B) and biogenesis protein levels PGC1α, NRF2 and TFAM (Fig.1C) in human intestinal epithelial cells (IECs), biopsies, and in NCM460 cells. Protein analysis in NCM460 cells show that AuPhos increases downstream antioxidant markers such as manganese superoxide dismutase (MnSOD), glutathione peroxidase 4 (GPX4), thioredoxin reductase2 (Trx2), and catalase expression when compared to the TNF or control samples. AuPhos substantially upregulates levels of mitochondria complex (mtCO1, mtCO2 Cox6A1, ATP5A1) and anti-oxidant enzyme (MnSOD, GPX, PRDX-2, -4, and -6) mRNA and protein levels in human colonic biopsies compared to vehicle and TNF treated samples (Fig. 1D). Furthermore, AuPhos reduces tissue cytokine and chemokine mRNA levels (IL1β, MCP1, RankL, and TNFα) in human UC tissues (Fig. 1E). CONCLUSIONS The current study reveals that AuPhos increases mitochondrial biogenesis, mitochondrial complex, and antioxidant enzyme levels in human IBD tissue. THE REDUCTION IN TISSUE CYTOKINES AND CHEMOKINES SUGGESTS THAT ENHANCED MITOCHONDRIAL FUNCTION IMPROVES TISSUE INFLAMMATION. This suggests the potential of AuPhos in treating IBD through the restoration of mitochondrial biogenesis.

P148 Longitudinal single-cell data informs deterministic modelling of inflammatory bowel disease

Abstract Background Crucial contributions to our understanding of the inflammatory process in inflammatory bowel disease (IBD) have been made using single cell level approaches. Extracting mechanistic details of cell and gene dynamics would be critical to understanding the mechanisms mediating mucosal healing and predicting response to specific therapies. However, this remains challenging. Therefore, our aim was to use ordinary differential equations (ODEs) for mathematical modelling of cell abundance and prediction of biological processes in IBD. Methods We used mathematical modelling of published longitudinal single-cell mRNA sequencing (scRNA-seq) data from DSS colitis in mice to simulate cellular dynamics during IBD. We validated our predictions using pseudo-bulk gene expression analysis and flow cytometry. We also analysed a published microarray dataset from colonic biopsies of 51 IBD patients prior to infliximab treatment. Results Based on the scRNA-seq data, we used our mathematical model to predict the immune dynamics of a different mouse colitis protocol. We validated these predictions experimentally using flow cytometry and found good agreement between model simulation and experimental data (predicted vs. observed, Pearson's rho=0.92). We found that the estimated turnover rates predicted the protein level of the proliferation marker KI-67 (rho=0.88) in DSS colitis. Finally, we wanted to investigate whether our mathematical model reflected processes in human IBD. We reasoned that genes correlated with epithelial cell dynamics might be indicative of mucosal healing after DSS retrieval. We found more highly correlated genes when using simulated epithelial abundance compared to experimentally measured epithelial abundance. Many genes associated with tight junctions (Cldn8, Cftr, Crb3, Jam2) were among the highly positively correlated genes and genes associated with inflammation (Il1b, Jak2, Il10ra) were among the negatively correlated genes with epithelial cell abundance. We then looked for differentially expressed (DE) genes in pre-treatment colon biopsies between responders and non-responders to infliximab. We found a significant overlap of 25 positively correlated genes with upregulated DE genes in responders, i.e. associated with tight junctions, and 73 negatively correlated genes with upregulated genes in non-responders, i.e. associated with inflammatory pathways. Conclusion We demonstrate that mathematical modelling of colonic cell dynamics provides insight into IBD progression and treatment response. Furthermore, our results suggest that pre-treatment barrier integrity may predict and influence response to infliximab treatment.

Interleukin 21 Drives a Hypermetabolic State and CD4+ T-Cell–Associated Pathogenicity in Chronic Intestinal Inflammation

Incapacitated regulatory T cells (Tregs) contribute to immune-mediated diseases. Inflammatory Tregs are evident during human inflammatory bowel disease; however, mechanisms driving the development of these cells and their function are not well understood. Therefore, we investigated the role of cellular metabolism in Tregs relevant to gut homeostasis. Using human Tregs, we performed mitochondrial ultrastructural studies via electron microscopy and confocal imaging, biochemical and protein analyses using proximity ligation assay, immunoblotting, mass cytometry and fluorescence-activated cell sorting, metabolomics, gene expression analysis, and real-time metabolic profiling utilizing the Seahorse XF analyzer. We used a Crohn's disease single-cell RNA sequencing dataset to infer the therapeutic relevance of targeting metabolic pathways in inflammatory Tregs. We examined the superior functionality of genetically modified Tregs in CD4+ T-cell-induced murine colitis models. Mitochondria-endoplasmic reticulum appositions, known to mediate pyruvate entry into mitochondria via voltage-dependent anion channel 1 (VDAC1), are abundant in Tregs. VDAC1 inhibition perturbed pyruvate metabolism, eliciting sensitization to other inflammatory signals reversible by membrane-permeable methyl pyruvate supplementation. Notably, interleukin (IL) 21 diminished mitochondria-endoplasmic reticulum appositions, resulting in enhanced enzymatic function of glycogen synthase kinase 3 β, a putative negative regulator of VDAC1, and a hypermetabolic state that amplified Treg inflammatory response. Methyl pyruvate and glycogen synthase kinase 3 β pharmacologic inhibitor (LY2090314) reversed IL21-induced metabolic rewiring and inflammatory state. Moreover, IL21-induced metabolic genes in Tregs invitro were enriched in human Crohn's disease intestinal Tregs. Adoptively transferred Il21r-/- Tregs efficiently rescued murine colitis in contrast to wild-type Tregs. IL21 triggers metabolic dysfunction associated with Treg inflammatory response. Inhibiting IL21-induced metabolism in Tregs may mitigate CD4+ T-cell-driven chronic intestinal inflammation.