Dextran Sulfate Sodium Colitis Model Research Articles

Eosinophil Depletion as a Potential Therapeutic Strategy in Acute and Chronic Intestinal Inflammation Based on a Dextran Sulfate Sodium Colitis Model.

A role for eosinophils in intestinal inflammation and fibrosis in the context of inflammatory bowel disease has been suggested, yet the precise nature, whether causal or secondary remains debated. Hence, it remains unclear whether targeting eosinophils should be further explored as a treatment option in inflammatory bowel disease. Acute and chronic dextran sulfate sodium colitis was induced in wild-type C57BL/6 mice. Eosinophils were depleted by anti-CCR3 injections before colitis induction in a chronic model and after colitis onset in an acute model in order to investigate the impact of eosinophil depletion on pre-existing colitis. Inflammation was assessed using the disease activity index, macroscopic damage, and histological disease activity score. In the chronic model, fibrosis was assessed by examining colon weight/length ratio, collagen deposition through Martius Scarlet Blue staining, hydroxyproline assay, and COL1A1 expression. Protein and gene expression were assessed using the Meso Scale Discovery platform and real-time quantitative polymerase chain reaction. In the acute and chronic colitis model, eosinophil depletion resulted in reduced disease activity and faster recovery, as observed via the total area under the curve of the disease activity index (P = .004 and P = .02, respectively), macroscopic damage score (P = .009 and P = .08, respectively), and histological disease activity score (P = .09 and P = .002, respectively). In the acute model, the accelerated recovery was accompanied by an increase in interleukin (IL)-10 (P = .03) and a decrease in IL-4 (P = .03) and IL-6 (P = .009). Colon weight/length ratio and collagen deposition were not affected by eosinophil depletion. Eosinophil depletion prevents and decreases intestinal inflammation in a preclinical dextran sulfate sodium model without affecting fibrosis. These results pave the way for exploring eosinophil depletion as a novel treatment modality in addressing intestinal inflammation.

High cannabigerol hemp extract moderates colitis and modulates the microbiome in an inflammatory bowel disease model.

Cannabis sativa L. has a long history of medicinal use, particularly for gastrointestinal diseases. Patients with inflammatory bowel disease (IBD) report using cannabis to manage their symptoms, despite little data to support the use of cannabis or cannabis products to treat the disease. In this study, we utilize the well-described dextran sodium sulfate (DSS) model of colitis in mice to assess the impact of commercially available, non-euphorigenic, high cannabigerol (CBG) hemp extract (20 mg/mL cannabigerol, 20.7 mg/mL cannabidiol, 1 mg/mL cannabichromene) on IBD activity and the colonic microbiome. Mice were given 2% DSS in drinking water for 5 days, followed by 2 days of regular drinking water. Over the 7 days, mice were dosed daily with either high CBG hemp extract or matched vehicle control. Daily treatment with high CBG hemp extract dramatically reduces the severity of disease at the histological and organismal levels as measured by decreased disease activity index, increased colon length, and decreases in percent colon tissue damage. 16S rRNA gene sequencing of the fecal microbiota reveals high CBG hemp extract treatment results in alterations in the microbiota, that may be beneficial for colitis. Finally, using metabolomic analysis of fecal pellets, we find that mice treated with high CBG hemp extract have a normalization of several metabolic pathways, including those involved in inflammation. Taken together these data suggest that high CBG hemp extracts may offer a novel treatment option for patients. Significance Statement Using the DSS model of colitis, we show that treatment with high CBG hemp extract reduces the severity of symptoms associated with colitis. Additionally, we show that treatment modulates both the fecal microbiota and metabolome with potential functional significance.

A254 CANAGLIFLOZIN EXACERBATES CHEMICALLY INDUCED COLITIS WHEN COMBINED WITH A HIGH SUGAR DIET

Abstract Background Consumption of high-sugar diets exacerbates inflammation and hinders the healing process in animal models of acute colitis. Canagliflozin (CANA) is a sodium glucose cotransporter-2 (SGLT2) inhibitor primarily used for the management of type 2 diabetes and cardiovascular disease. CANA has demonstrated the ability to suppress human T cell and macrophage effector function and to improve inflammation in rat colitis models. Based on these findings, we hypothesized that CANA would mitigate the deleterious effects of a high sugar diet in a DSS colitis model through its effects on immune effector cells. Aims The aim of this study was to examine the effects of a high sugar diet and CANA administration on colonic inflammation in an animal model of acute colitis. Methods Adult wild-type male and female 129/SvEv mice were placed on standard chow or a high-sugar diet (HSD) containing 50% sucrose (AIN76A) ± CANA (10mg/kg) gavaged daily (n=4-6 for each group). Following three days on the respective diet, mice received 1.8-2% dextran sodium sulfate (DSS) in their drinking water for 5 days, followed by water alone for 4 days. Disease Activity Index (DAI) was computed daily based on changes in animal weight, stool consistency, and blood in stool. Colonic tissues were evaluated for histological changes, weight-to-length ratio, and cytokine levels using the MesoScale discovery platform. Results Mice on the HSD had increased severity of colitis compared with chow fed mice as evidenced by enhanced DAI, increased weight loss, and increased levels of colonic TNFα (pampersand:003C0.02). Response to CANA treatment was both sex and diet dependent. Contrary to our hypothesis, CANA treatment increased severity of colitis in male mice on the HSD as evidenced by increased DAI and delayed healing with increased enterocyte injury and increased levels of lamina propria neutrophils and lymphocytes. CANA treatment did not exacerbate disease severity in females on the HSD but did delay healing as evidenced by increased lamina propria neutrophils and lymphocytes and worse enterocyte injury. These effects were not observed in mice that were fed standard chow diets with CANA. Conclusions A high-sugar diet significantly exacerbates chemically induced colitis and delays healing. This effect is intensified when combined with CANA, especially in male mice. These findings indicate that effects of SGLT2 inhibitors on colonic inflammation can be modulated by both dietary intake and sex. Funding Agencies CCC

P077 The Immunometabolic Bimodal Mechanism of NLRX1 Agonist NX-13 in a Pig Model of Ulcerative Colitis

Abstract Background In mouse models, NX-13 is an orally active, gut-restricted NLRX1 agonist that has been shown to reduce severity of disease in multiple UC models through a novel immunometabolic, bimodal mechanism. Most preclinical UC studies rely upon rodent models, the human gastrointestinal physiology, microbiome, and immune system bear a greater similarity to that of pigs. Therefore, we sought to expand and validate our preclinical NX-13 results in mice using the dextran sulfate sodium (DSS) pig model of colitis. Here, we describe the disease severity, cellular, and biomarker results, and confirm the immunometabolic MOA observed in other species. Methods Pigs were randomized by weight (n=6 per group) and were administered tablets of excipient alone (placebo), NX-13 10 mg, NX-13 50 mg, or NX-13 100mg once daily. Pigs were challenged with 1% DSS in drinking water for 6 days and monitored daily for weight gain (loss). Composite disease activity score (0-12) was taken based on the sum of three subscores (0-4) for rectal bleeding, stool consistency and overall health/activity. Necropsy was conducted on day 7. Feces were collected for fecal calprotectin (FCP) quantification. Colonic tissue was macroscopically scored and collected for analysis by flow cytometry, histopathology and gene expression. Results Oral NX-13 treatment protected against weight loss and reduced colitis development with differences as early as day 2, becoming significant between days 4 and 6 as disease worsens in placebo treated pigs (Fig1A). NX-13 yielded a dose-dependent improvement in macroscopic lesion severity and microscopic immune cell infiltration (Fig1B). Specifically, Th1 cells (Fig1C) and TNF producing myeloid cells in the colonic lamina propria were reduced by NX-13, as well as FCP levels in stool (Fig1D) and mRNA expression in the colon (Fig1E). Oral NX-13 treatment reduced inflammatory markers including TNF, monocyte and neutrophil chemo attractants, IL-6, and IL-23 (Fig3F). Additionally, NX-13 treatment affected markers specific to the bimodal immunometabolic MOA of NLRX1 activation, namely upregulation of NLRX1 and mitochondrial metabolism gene COX3 (Fig1G), and reduction of NFkB and NLRP3 (Fig1H). Conclusion NX-13 demonstrated fast and clinically meaningful improvement in disease activity, and significantly impacted on key inflammatory markers in a DSS colitis model in pigs. These results align with previous murine results and observations in the phase 1b clinical program. Therefore, they can be used to generate additional mechanistic hypotheses for translational studies in the ongoing NEXUS phase 2 trial in moderate to severe UC.

P082 Downregulated apelin expression in T cells in the setting of Chronic Colitis

Abstract Background APJ is a G protein-coupled receptor and was originally found as an orphan receptor. Isolation of apelin (APL) from the alimentary tract was found to be the endogenous ligand for APJ. It has been reported that APL is upregulated in the colonic tissues of a murine model of acute colitis induced by dextran sodium sulfate (DSS), and thus it may be suggested to be associated with the pathogenesis of inflammatory bowel diseases (IBD) in humans. However, the mechanism and function of APL in the context of IBD are still not understood. Here, we analyzed APL expression in an animal model of chronic colitis to define its function in the pathogenesis of IBD. Methods Each cell type in the colonic tissue, including epithelial cells and lamina propria lymphocytes, were first isolated from wild type C57BL6 mice (WT) to assess APL expression. Next, naïve T cells isolated from WT were adoptively transferred into Rag deficient mice (Rag-/-) to induce chronic colitis, and then APL expression was measured either in the colonic tissue or in the isolated splenic and colonic CD4+ T cells from these T cell-reconstituted Rag-/- to compare with those of WT or Rag-/- without colitis. In addition, WT naïve T cells were differentiated into either Th1, Th2 or Th17 in vitro to analyze APL expression. Finally, the Rag-/- receiving naïve T cells were administered a synthetic APL peptide, APL-13, to assess the severity of colitis. Results Semi-quantitative PCR (qPCR) revealed that CD4+ T cells express relatively higher level of APL compared to other cell types including the epithelial cells in colonic tissue from WT. However, APL expression in the colonic tissues from the Rag-/- induced chronic colitis was unexpectedly downregulated compared to control groups without colitis; this is not consistent with the previous report using acute DSS colitis model. Subsequently, qPCR revealed significantly decreased APL expression in the splenic and colonic T cells from Rag-/- induced colitis compared to that of WT. APL expressions in the effecter T cells in vivo and all of the differentiated T cells in vitro were also significantly downregulated compared to naïve T cells and non-differentiated control T cells, respectively. Given these results, APL-13 was injected into the Rag-/- that underwent T cell reconstitution to antagonize the APL downregulation. This resulted in reduced severity of colitis compared to that of vehicle control-injected group. Conclusion These results suggest that T cells can be one of the major sources of APL in colonic tissues, and APL downregulation in effecter T cells may lead to the development of chronic colitis. In addition, this study also suggests that APL may be a novel therapeutic target for IBD.

Loss of NOD2 in macrophages improves colitis and tumorigenesis in a lysozyme-dependent manner.

Crohn's disease (CD) is a complex and poorly understood myeloid-mediated disorder. Genetic variants with loss of function in the NOD2 gene confer an increased susceptibility to ileal CD. While Nod2 in myeloid cells may confer protection against T-cell mediated ileopathy, it remains unclear whether it may promote resolution of the inflamed colon. In this study, we evaluated the function of Nod2 in myeloid cells in a model of acute colitis and colitis-associated colon cancer (CAC). To ablate Nod2 specifically within the myeloid compartment, we generated LysMCre/+;Nod2fl/fl mice. The role of NOD2 was studied in a setting of Dextran Sodium Sulfate (DSS)-induced colitis and in azoxymethane (AOM)/DSS model. Clinical parameters were quantified by colonoscopy, histological, flow cytometry, and qRT-PCR analysis. Upon DSS colitis model, LysMCre/+;Nod2fl/fl mice lost less weight than control littermates and had less severe damage to the colonic epithelium. In the AOM/DSS model, endoscopic monitoring of tumor progression revealed a lowered number of adenomas within the colon of LysMCre/+;Nod2fl/fl mice, associated with less expression of Tgfb. Mechanistically, lysozyme M was required for the improved disease severity in mice with a defect of NOD2 in myeloid cells. Our results indicate that loss of Nod2 signaling in myeloid cells aids in the tissue repair of the inflamed large intestine through lysozyme secretion by myeloid cells. These results may pave the way to design new therapeutics to limit the inflammatory and tumorigenic functions of NOD2.

Fundamental role for the creatine kinase pathway in protection from murine colitis

Inflammatory diseases of the digestive tract, including inflammatory bowel disease, cause metabolic stress within mucosal tissue. Creatine is a key energetic regulator. We previously reported a loss of creatine kinases (CKs) and the creatine transporter expression in inflammatory bowel disease patient intestinal biopsy samples and that creatine supplementation was protective in a dextran sulfate sodium (DSS) colitis mouse model. In the present studies, we evaluated the role of CK loss in active inflammation using the DSS colitis model. Mice lacking expression of CK brain type/CK mitochondrial form (CKdKO) showed increased susceptibility to DSS colitis (weight loss, disease activity, permeability, colon length, and histology). In a broad cytokine profiling, CKdKO mice expressed near absent interferon gamma (IFN-γ) levels. We identified losses in IFN-γ production from CD4+ and CD8+ T cells isolated from CKdKO mice. Addback of IFN-γ during DSS treatment resulted in partial protection for CKdKO mice. Extensions of these studies identified basal stabilization of the transcription factor hypoxia-inducible factor in CKdKO splenocytes and pharmacological stabilization of hypoxia-inducible factor resulted in reduced IFN-γ production by control splenocytes. Thus, the loss of IFN-γ production by CD4+ and CD8+ T cells in CKdKO mice resulted in increased colitis susceptibility and indicates that CK is protective in active mucosal inflammation.

Transgenic mice overexpressing human ALOX15 under the control of the aP2 promoter are partly protected in the complete Freund's adjuvant-induced paw inflammation model.

Arachidonic acid 15-lipoxygenase (ALOX15) has been implicated in the pathogenesis of inflammatory diseases but since pro- and anti-inflammatory roles have been suggested, the precise function of this enzyme is still a matter of discussion. To contribute to this discussion, we created transgenic mice, which express human ALOX15 under the control of the activating protein 2 promoter (aP2-ALOX15 mice) and compared the sensitivity of these gain-of-function animals in two independent mouse inflammation models with Alox15-deficient mice (loss-of-function animals) and wildtype control animals. Transgenic aP2-ALOX15 mice were tested in comparison with Alox15 knockout mice (Alox15-/-) and corresponding wildtype control animals (C57BL/6J) in the complete Freund's adjuvant induced hind-paw edema model and in the dextran sulfate sodium induced colitis (DSS-colitis) model. In the paw edema model, the degree of paw swelling and the sensitivity of the inflamed hind-paw for mechanic (von Frey test) and thermal (Hargreaves test) stimulation were quantified as clinical readout parameters. In the dextran sodium sulfate induced colitis model the loss of body weight, the colon lengths and the disease activity index were determined. In the hind-paw edema model, systemic inactivation of the endogenous Alox15 gene intensified the inflammatory symptoms, whereas overexpression of human ALOX15 reduced the degree of hind-paw inflammation. These data suggest anti-inflammatory roles for endogenous and transgenic ALOX15 in this particular inflammation model. As mechanistic reason for the protective effect downregulation of the pro-inflammatory ALOX5 pathways was suggested. However, in the dextran sodium sulfate colitis model, in which systemic inactivation of the Alox15 gene protected female mice from DSS-induced colitis, transgenic overexpression of human ALOX15 did hardly impact the intensity of the inflammatory symptoms. The biological role of ALOX15 in the pathogenesis of inflammation is variable and depends on the kind of the animal inflammation model.

Effect of aging on the formation and growth of colonic epithelial organoids by changes in cell cycle arrest through TGF-β-Smad3 signaling

BackgroundThis study aimed to investigate how aging alters the homeostasis of the colonic intestinal epithelium and regeneration after tissue injury using organoid models and to identify its underlying molecular mechanism.MethodsTo investigate aging-related changes in the colonic intestinal epithelium, we conducted organoid cultures from old (older than 80 weeks) and young (6–10 weeks) mice and compared the number and size of organoids at day 5 of passage 0 and the growth rate of organoids between the two groups.ResultsThe number and size of organoids from old mice was significantly lower than that from young mice (p < 0.0001) at day 5 of passage 0. The growth rate of old-mouse organoids from day 4 to 5 of passage 0 was significantly slower than that of young-mouse organoids (2.21 times vs. 1.16 times, p < 0.001). RNA sequencing showed that TGF-β- and cell cycle-associated genes were associated with the aging effect. With regard to mRNA and protein levels, Smad3 and p-Smad3 in the old-mouse organoids were markedly increased compared with those in the young-mouse organoids. Decreased expression of ID1, increased expression of p16INK4a, and increased cell cycle arrest were observed in the old mouse-organoids. Treatment with SB431542, a type I TGF-β receptor inhibitor, significantly increased the formation and growth of old-mouse organoids, and TGF-β1 treatment markedly suppressed the formation of young-mouse organoids. In the acute dextran sulfate sodium-colitis model and its organoid experiments, the colonic epithelial regeneration after tissue injury in old mice was significantly decreased compared with young mice.ConclusionsAging reduced the formation ability and growth rate of colonic epithelial organoids by increasing cell cycle arrest through TGF-β-Smad3-p16INK4a signaling.

P037 Enhancing the efficacy of cannabidiol using protein nanoparticles to treat inflammatory bowel disease

Abstract Background Inflammatory bowel disease (IBD) is a global health burden and approximately 30% of the patients with severe IBD require surgery following treatments, leaving an unmet need of new and safe therapies. Cannabidiol (CBD) is one of the major non-psychoactive and water-insoluble constituents of medicinal cannabis, known for its anti-inflammatory properties in epilepsy. The compound is safe at high doses and doesn’t have the psychotropic effects of delta-9-tetrahydrocannabinol. Therefore, this study investigated the therapeutic potential of CBD in controlling intestinal inflammation. Methods CBD was loaded in the protein nanoparticles (PNP-CBD) and tested for its water solubility. Primary intestinal epithelial cells (IECs; organoids) and bone marrow-derived macrophages (BMDM) were isolated from C57BL/6 mice and treated with IL-1β and LPS, respectively. Stimulated cells were treated with ±CBD and checked for downstream signalling through inflammatory gene expression using qRT PCR. Conditioned media from LPS-treated BMDM was also harvested to treat mIECs to check link between macrophage activation and intestinal inflammation. Accordingly, we assessed the efficacy of CBD in suppressing intestinal inflammation using dextran sulfate sodium (DSS)-induced acute experimental colitis in the C57BL/6J mice. At the end, blood samples were collected for hematology and serum analyses, mesenteric lymph nodes for immune cell signatures, colon samples for histological analysis and qRT PCR analysis for inflammatory genes. Results CBD loading in the protein nanoparticles (PNP-CBD) increased its water solubility up to 60 times. In the mIECs, CBD did not have any effects on cytokine-induced inflammation; however, it significantly dampened LPS-induced BMDM activation and inflammatory cytokine production. The results also showed that inhibition of CB2 but not CB1 receptor can completely abolish the anti-inflammatory potential of CBD in the BMDM. Transferring conditioned media from BMDM to mIECs showed macrophage-specific targeting alleviated inflammation in the mIECs. These have also been observed in the acute DSS colitis model where not CBD alone but PNP-CBD improved disease severity index including body weight loss, diarrhoea, shorter colon length, and inflammatory gene expression in the colon. PNP-CBD also reduced histological colitis and increased goblet cell mucin production in the DSS-treated colon. Conclusion Encapsulation of CBD increased water solubility and efficacy in alleviating intestinal inflammation in ulcerative colitis. These data also demonstrated that CB2 receptor targeting of macrophage activation is the primary mechanism of CBD’s effect.

DOP09 Eosinophils exert a pro-inflammatory role in a chronic DSS colitis model without an impact on fibrosis

Abstract Background Eosinophils might play a pro-inflammatory role in inflammatory bowel disease (IBD). However, the role of eosinophils in intestinal fibrosis remains poorly understood, although a pro-fibrotic function has been hypothesized based on data outside the gastrointestinal tract. Therefore, we aimed to unravel the role of eosinophils in chronic intestinal inflammation and fibrosis and to explore eosinophil depletion as a potential therapeutic target. Methods A 3-cycles chronic dextran sodium sulphate (DSS) model was induced in 6-8-week-old C57BL/6 wild type mice. Mice received 3 DSS cycles (1.5% - 2.00% - 2.00%) in which 1 DSS cycle consisted of 1 week of DSS administration followed by 2 weeks of recovery. During the 3 cycles, and starting 3 days prior to colitis induction, anti-CCR3 antibody or isotype injections were given twice weekly to study the effect of the eosinophil depletion (total of 18 injections). The disease activity index (DAI; weight loss, stool consistency and presence of blood) was determined twice weekly. At sacrifice, colonic damage was scored macroscopically (presence of hyperaemia, adhesions and length and degree of colon affected by inflammation) and colonic single cells were isolated and fluorescently stained for flow cytometry. Eosinophils were thereby identified as CD45+ CD11b+ Siglec-F+ CD117- cells. Lastly, a histological active disease score was determined comprising of the sum of neutrophil infiltration, mononuclear cell infiltration, changes in mucosal architecture, goblet cell loss and epithelial defects (Creyns et al., 2019). Intestinal fibrosis was assessed via colon weight/length ratio, COL1A1 gene expression and collagen deposition with a Martius Scarlet Blue (MSB) staining and a colorimetric hydroxyproline assay. Results Blood and colonic eosinophil depletion via anti-CCR3 injections was confirmed via flow cytometry (figure 1). The DAI in the eosinophil depleted group was decreased compared to the isotype injected group (area under the curve 115.4 ± 29 vs 160.6 ± 28; p=0.02). A similar trend was seen in the macroscopic damage score (2.0 ± 1.3 vs 3.9 ± 2.1; p=0.08). Furthermore, a lower histological active disease score was found in the mice in which the eosinophils were depleted compared to the isotype injected mice (8.8 ± 0.8 vs 12.8 ± 1.5; p=0.002) (figure 2). Lastly, no differences in the parameters for fibrosis between the anti-CCR3 injected and isotype injected groups were observed (figure 3). Conclusion Eosinophil depletion via intraperitoneal anti-CCR3 injections resulted in partial protection from intestinal inflammation in chronic DSS, and could therefore be further explored as a potential therapeutic agent. In contrast, eosinophil depletion does not seem to have any anti-fibrotic effect

D-amino Acids Ameliorate Experimental Colitis and Cholangitis by Inhibiting Growth of Proteobacteria: Potential Therapeutic Role in Inflammatory Bowel Disease

D-amino acids, the chiral counterparts of protein L-amino acids, were primarily produced and utilized by microbes, including those in the human gut. However, little was known about how orally administered or microbe-derived D-amino acids affected the gut microbial community or gut disease progression. The ratio of D- to L-amino acids was analyzed in feces and blood from patients with ulcerative colitis (UC) and healthy controls. Also, composition of microbe was analyzed from patients with UC. Mice were treated with D-amino acid in dextran sulfate sodium colitis model and liver cholangitis model. The ratio of D- to L-amino acids was lower in the feces of patients with UC than that of healthy controls. Supplementation of D-amino acids ameliorated UC-related experimental colitis and liver cholangitis by inhibiting growth of Proteobacteria. Addition of D-alanine, a major building block for bacterial cell wall formation, to culture medium inhibited expression of the ftsZ gene required for cell fission in the Proteobacteria Escherichia coli and Klebsiella pneumoniae, thereby inhibiting growth. Overexpression of ftsZ restored growth of E.coli even when D-alanine was present. We found that D-alanine not only inhibited invasion of pathological K.pneumoniae into the host via pore formation in intestinal epithelial cells but also inhibited growth of E.coli and generation of antibiotic-resistant strains. D-amino acids might have potential for use in novel therapeutic approaches targeting Proteobacteria-associated dysbiosis and antibiotic-resistant bacterial diseases by means of their effects on the intestinal microbiota community.

Tenascin-C is a driver of inflammation in the DSS model of colitis

Inflammatory Bowel Disease (IBD) is a grouping of chronic inflammatory disorders of the gut. Tenascin-C is a pro-inflammatory, extracellular matrix protein found upregulated in IBD patients and whilst a pathological driver of chronic inflammation, its precise role in the etiology of IBD is unknown. To study tenascin-C’s role in colitis pathology we investigated its expression in a murine model of IBD. Wild-type (WT) or tenascin-C knockout (KO) male mice were left untreated or treated with dextran sodium sulphate (DSS) in their drinking water. Tenascin-C was upregulated at the mRNA level in the colitic distal colon of day eight DSS treated mice, coinciding with significant increases in gross and histological pathology. Immunohistochemistry localized this increase in tenascin-C to areas of inflammation and ulceration in the mucosa. Tenascin-C KO mice exhibited reduced gross pathology in comparison. These differences also extended to the histopathological level where reduced colonic inflammation and tissue damage were found in KO compared to WT mice. Furthermore, the severity of the distal colon lesions were less in the KO mice after 17 days of recovery from DSS treatment. This study demonstrates a role for tenascin-C as a driver of inflammatory pathology in a murine model of IBD and thus suggests neutralizing its pro-inflammatory activity could be explored as a therapeutic strategy for treating IBD.

Pentosan Polysulfate Sodium augments the therapeutic effect of 5-Aminosalicylic Acid in DSS colitis model; the role of IL-35 expression

Ulcerative colitis (UC) primarily affects the mucosa of the distal colon. Dysregulated immune response in genetically-prone persons is claimed to be responsible for chronic intestinal inflammation. This study aimed to explore the efficacy and the hematological effects of pentosan polysulfate sodium (PPS) in a dextran sulfate sodium (DSS)-induced colitis model. Forty C57BL/6 female mice were equally divided into five groups: control group, DSS-colitis group, DSS-colitis treated with 5-aminosalicylic acid, DSS-colitis treated with PPS, and DSS-colitis treated with both drugs. Disease activity index (DAI) and colon length were calculated. Colonic IL-6 and IL-35 levels were assayed by ELISA. IL-35 gene expression was evaluated by qRT-PCR. Colon tissue samples were examined by H&E stain and immunohistochemistry (IHC) of Ki67. The colitis group subjected to combined treatment showed the best outcome with significant improvement of DAI and increased colon length. Colonic IL-6 was significantly lower in both PPS- and combination-treated groups accompanied by a significantly higher IL-35 level and its EBI3 subunit mRNA expression. However, the PPS-treated colitis group showed higher gene expression of IL-35 EBI3 subunit by 1.5-fold compared with the combined group. The colon mucosa and crypts were significantly preserved in mice treated with both drugs with the best Ki67 positive cell density. PPS is a safe and promising drug in the treatment of UC as it exerted the best positive effect on the anti-inflammatory IL-35 level and gene expression. However, superior improvement of DAI was seen when PPS was added to ASA with a greater mucosal proliferation and repair.

GPX3 IS REQUIRED TO MEDIATE PROTECTIVE EFFECTS OF GPX1 LOSS IN COLITIS

Abstract Reactive oxygen species (ROS) have long been known to contribute to the development and severity of Inflammatory Bowel Disease. However, more recent data indicates ROS may not always be pathogenic, and in fact ROS may be necessary for intestinal homeostasis. Thus, the role of ROS in the intestine, and antioxidant proteins which regulate ROS, may be contextual and dose-dependent. Members of the glutathione peroxidase (GPx) family are antioxidants that reduce hydrogen peroxide to water. Previously, we determined that loss of GPx1, the most widely expressed GPx, protected against dextran sodium sulfate (DSS)-induced colitis and augmented intestinal proliferation. To better understand how a stepwise increase in ROS may affect intestinal phenotypes, Gpx1-/- mice were next crossed with Gpx3 null mice to yield double-knockout (DKO) mice. First, we assessed baseline proliferation, apoptosis, and DNA damage in the colon. Interestingly, while Gpx1-/- mice displayed increased proliferation compared to WT mice, this was not observed in the DKO mice. Furthermore, Gpx1-/- mice had no change in apoptosis or DNA damage, yet both were increased in DKO mice. Together, these data suggest DKO mice lose the survival benefits of GPx1 loss upon greater reduction of antioxidant capabilities. Next, we assessed the effects of combined GPx1 and GPx3 loss in the context of inflammation and colitis. At baseline, multiplex cytokine profiling identified higher levels of colitis-associated cytokines, including IL-12, CCL4, and CCL5, in DKO mice as compared to either Gpx1-/- or WT cohorts. Pro-inflammatory changes were more pronounced upon aging, as one-year-old DKO mice showed higher levels of TNF-α and IL-17, as well as histologic evidence of chronic inflammation which was absent in similarly aged WT mice. Next, we tested the effects of experimental DSS colitis. Here, while Gpx1-/- mice had less severe injury in the DSS colitis model, DKO mice showed more pronounced weight loss and a trend towards shortened colons as compared to WT mice. Finally, altered ROS-mediated signaling is known to impact interactions with the microbiota, and increased microbial diversity is associated with protection from colitis. To establish whether loss of GPx1 and GPx3 impacted the gut microbiome, stool was harvested from WT, Gpx1-/-, and DKO mice and bacterial DNA was assessed by 16S RNA sequencing. Interestingly, and in line with less severe colitis, Gpx1-/- mice had increased diversity and evenness compared to WT mice, whereas there was no change between WT and DKO mice. Taken together, these data indicate that GPx3 is required to mediate the anti-inflammatory effects of GPx1 loss. Furthermore, combinatorial GPx loss induces greater colonic inflammation at baseline and during DSS-induced colitis, highlighting dose-dependent effects of ROS and antioxidant capacity in the intestine.

P073 Eosinophil depletion partially protects from colonic inflammation, but increases colonic collagen deposition in a DSS colitis model

Abstract Background The role of eosinophils in intestinal inflammation and fibrosis in inflammatory bowel disease (IBD) is largely unknown. Therefore, we assessed the functional role of eosinophils in a chronic murine model of colitis and associated fibrosis via anti-CCR3 mediated eosinophil depletion. Methods 6-8-week-old C57BL/6 RAG-/- mice received three cycles of dextran sodium sulphate (DSS) (1.75% - 2.25% - 2.25%) each interspersed with 14 days of recovery. Twice weekly, anti-CCR3 antibody (n=8), isotype (n=8) or saline injections (n=8) were given intraperitoneally. At the same timepoints, the disease activity index (DAI; mouse weight, stool consistency and presence of blood) was determined. At sacrifice, colonic damage was scored macroscopically (presence of hyperaemia, adhesions and length and degree of colon affected by inflammation). Colonic single cells were isolated and stained for flow cytometry, where eosinophils were characterized as CD45+ CD11b+ Siglec-F+ CD117- cells. Intestinal fibrosis was scored via colon weight/length, collagen deposition (using a colorimetric hydroxyproline assay) and COL1A1 expression by PCR. Results Anti-CCR3 mediated eosinophil depletion resulted in decreased disease activity compared to the other DSS treated groups injected with saline or isotype, determined by the area under the curve of the DAI (74.6±18.4 vs. 127.5±42.9 and 136.9±33.6, p=0.01 and p=0.0008 respectively) (figure 1). The macroscopic damage score also suggested eosinophil depleted mice to be partially protected from colonic inflammation compared to the saline and isotype injected mice that received DSS (1.1±1.0 vs. 2.1±1.2 and 3.0±0.7, p=0.09 and p=0.001 respectively) (figure 1). Colon weight/length and hydroxyproline assay showed a trend towards increased fibrosis in the anti-CCR3 injected group compared to saline (p=0.03 and 0.07, respectively) but not isotype (p=0.3 and 0.1, respectively) injected groups (figure 2). However, COL1A1 expression levels were significantly increased in the eosinophil depleted mice compared to the saline and isotype injected mice receiving DSS (43.2±11.4 vs. 23.3±8.7 and 30.1±11.0, p=0.002 and 0.04 respectively) (figure 2), indicating increased collagen deposition. Conclusion Eosinophil depletion via intraperitoneal anti-CCR3 injections resulted in partial protection against colonic inflammation, but was associated with increased collagen production. Caution is therefore needed when designing therapeutic interventions targeting eosinophils.

P070 Novel long-acting lipidated interleukin-22 normalises colonic inflammation in an acute DSS colitis model

Abstract Background Most current treatments and new agents in clinical development for Inflammatory Bowel Disease (IBD) focus on inhibition of excessive inflammation. However, clinical remission rates for IBD have reached a plateau. New approaches directly improving mucosal healing, a process associated with reduced hospitalizations and long-term remission, therefore have great potential for addressing the unmet need. The cytokine interleukin-22 (IL-22) plays a key role in epithelial healing and has shown early proof-of-concept as a potential drug class in a phase 1 trial in Ulcerative Colitis. Here we present results from a mouse model of colitis on the efficacy of lipidated IL-22 analogues, which maintain more native-like molecular properties than current IL-22 modalities in development. Methods Chow-fed female C57Bl/6JRj mice were randomized to 4 groups (n=8 per group) based on body weight. Three groups received 2.5% (w/v) Dextran Sulfate Sodium (DSS) in the drinking water for 7 days from the start of the study. Animals receiving water without DSS served as healthy controls. Mice in the DSS groups received vehicle or lipidated IL-22 intraperitoneally at two dose levels for the entire duration of the study (10 days). At termination, plasma was sampled for assessment of target engagement biomarkers and intestines were removed and measured for weight and length before stereological analysis. Results Mice subjected to DSS developed colitis characterized by sustained weight loss and bloody diarrhoea. Vehicle dosed DSS mice showed clear histological features of colitis, with significantly (P&amp;lt;0.05) increased weight/length ratio of the colon as well as colonic mucosal, submucosal and inflammation volumes compared to healthy controls. Treatment with lipidated IL-22 significantly (P&amp;lt;0.05) improved all these parameters except mucosal volume compared to vehicle dosed DSS mice; in particular colonic inflammation volume was normalized to healthy control levels. Dose-dependent biomarker responses (e.g. Peptide YY levels) confirmed target engagement of the lipidated IL-22. Conclusion Novel long-acting lipidated IL-22, which acts on epithelial repair mechanisms, demonstrated strong improvements in histological parameters with normalisation of colonic inflammation in a DSS model of colitis. These beneficial effects were accompanied by dose-dependent increases in target engagement biomarkers. The underlying lipidation technology used for engineering these compounds has validated best in class potential in marketed treatments due to its molecular properties (e.g. size and potency). Clinical trials to assess safety and efficacy of lipidated IL-22 are expected to commence early 2023.

P008 Modulation of Wnt signaling via a Wnt mimetic improved epithelial healing without causing hyperplasia in a mouse colitis model

Abstract Background Disruption of the colon epithelial barrier is a characteristic of ulcerative colitis (UC), allowing luminal microbes to come into contact with intestinal immune cells resulting in inflammation. All approved UC treatments are anti-inflammatory drugs and because they do not directly heal the epithelial barrier, the intestinal immune system continues to be exposed to gut microbes, resulting in low remission rates. Physiological Wnt signaling is fundamental to intestine epithelial homeostasis and renewal. Modulation of Wnt signaling might present an opportunity to achieve histological remission, which is associated with an improved clinical course, in UC. Previously, in vivo overexpression or administration of exogenous R-Spondin (RSPO), which amplifies Wnt signaling by increasing the amount of Wnt receptors on the cell surface, was reported to show effects on the intestine epithelium and helped regenerate intestine epithelium in various injury models. However, RSPO was also reported, to induce hyperplasia in normal intestine epithelium. Wnt signaling may also be modulated with recently developed Wnt mimetics which mimic endogenous Wnt proteins and activate downstream β-catenin signaling upon engaging with receptors of Wnts. The objective of the current study was to compare the effect of these two approaches in an acute DSS model. Methods Utilizing a mouse acute DSS colitis model, we compared the epithelial healing effects of a Surrozen proprietary Wnt mimetic, R2M3-26, RSPO2, and combination treatments of R2M3-26 and RSPO2. Animals received 4% (wt/vol) dextran sulfate sodium (DSS) in drinking water for 7 days followed by 1% DSS in drinking water from day 8. Protein treatments began on day 4. Disease activity, body weight (BW), fecal score, and occult blood were measured daily. Animals were terminated on day 10 for colon and small intestine histology as well as a serum cytokine panel. Results DSS damage to the colon epithelium was visible by H&amp;E stain at day 4 and day 7 and continued to progress. We observed reduced mRNA expression of Wnt target genes and Wnt ligands in the colon, suggesting compromised Wnt signaling in the tissue. R2M3-26, RSPO2, and the combination treatments were efficacious in improving Disease Activity Index (DAI) and reducing serum cytokine levels. However, both RSPO treatments and combination treatments caused hyperproliferation of epithelium in the small intestine and the colon, consistent with what was reported in normal mice. Conclusion The Surrozen Wnt mimetic, R2M3-26, repaired the DSS damaged colon epithelium without causing hyperproliferation of epithelial cells in the intestine, making it a potential therapeutic platform for IBD.

Formyl Peptide Receptors and Annexin A1: Complementary Mechanisms to Infliximab in Murine Experimental Colitis and Crohn's Disease.

Non-responsiveness to anti-TNF-α therapies presents relevant rates in inflammatory bowel disease patients, presenting the need to find biomarkers involved in therapeutic efficacy. Herein, we demonstrate that higher levels of colonic formyl peptide receptor 1 and annexin A1 correlate with histological recovery in Crohn’s disease patients under remission. Using the dextran sulfate sodium colitis model in mice, we suggest that infliximab induces annexin A1 expression and secretion in activated intestinal leukocytes. Conversely, this mechanism might stimulate epithelial formyl peptide receptors, inducing wound healing and consequent histological remission. Our data indicate that assessing intestinal expressions of formyl peptide receptors and annexin A1 might provide precious information on the disease activity and responsiveness to infliximab in inflammatory bowel disease patients.

Intestinal inflammation-associated hypersensitivity is attenuated in a DSS model of colitis in Sigma-1 knockout C57BL/6 mice

Sigma-1 receptors (σ1R) have been implicated in several pain pathways. We assessed the implication of σ1Rs in the development of intestinal inflammation and inflammation-associated referred hypersensitivity in a model of colitis in σ1R knockout (KO) mice. Colitis was induced with dextran sulfate sodium (DSS) in wild type (WT) and σ1R KO mice. The development of referred mechanical hypersensitivity (von Frey test) was assessed. Colonic and spinal changes in expression of immune- and sensory-related markers were also investigated (RT-qPCR/Western blot). Absence of σ1Rs had little impact in colitis generation and progression, although during the chronic phase a reduction in edema and a down-regulation of iNOS gene expression was observed. In σ1R KO mice, inflammation-associated hypersensitivity was significantly attenuated (paw) or completely prevented (abdomen). During colitis, in WT mice, changes in the colonic expression of nociceptive markers were observed during the acute and chronic phases of inflammation. Although σ1R KO mice showed similar regulation in the acute phase, an attenuated response was observed during the chronic phase of colitis. These differences were especially relevant for CB2 and TRPV1 receptors, which could play an important role in σ1-mediated regulation of sensitivity. No changes were detected on ERK phosphorylation at the level of the lumbosacral spinal cord. In summary, intestinal inflammation-associated referred hyperalgesia was reduced (paw) or absent (abdomen) in σ1R KO mice, thus confirming an important role for σ1R in the development of colitis-associated hypersensitivity. These results identify σ1Rs as a possible therapeutic target for the treatment of hypersensitivity associated to intestinal inflammation.