Induction and activation of adaptive immune populations during acute and chronic phases of a murine model of experimental colitis

Epithelial-specific loss of Smad4 alleviates the fibrotic response in an acute colitis mouse model

Mucosal healing is associated with better clinical outcomes in patients with inflammatory bowel disease. But the epithelial-specific contribution to mucosal healing in vivo is poorly understood. We evaluated mucosal healing in an acute dextran sulfate sodium mouse model that shows an alleviated colitis response after epithelial-specific loss of Smad4. We find that enhanced epithelial wound healing alleviates the fibrotic response. Dextran sulfate sodium caused increased mesenchymal collagen deposition-indicative of fibrosis-within a week in the WT but not in the Smad4 KO colon. The fibrotic response correlated with decreased epithelial proliferation in the WT, whereas uninterrupted proliferation and an expanded zone of proliferation were observed in the Smad4 KO colon epithelium. Furthermore, the Smad4 KO colon showed epithelial extracellular matrix alterations that promote epithelial regeneration. Our data suggest that epithelium is a key determinant of the mucosal healing response in vivo, implicating mucosal healing as a strategy against fibrosis in inflammatory bowel disease patients.

Aryl hydrocarbon receptor activity in intestinal epithelial cells in the formation of colonic tertiary lymphoid tissues

After birth, the development of secondary lymphoid tissues (SLTs) in the colon is dependent on the expression of the aryl hydrocarbon receptor (AhR) in immune cells as a response to the availability of AhR ligands. However, little is known about how AhR activity from intestinal epithelial cells (IECs) may influence the development of tertiary lymphoid tissues (TLTs). As organized structures that develop at sites of inflammation or infection during adulthood, TLTs serve as localized centers of adaptive immune responses, and their presence has been associated with the resolution of inflammation and tumorigenesis in the colon. Here, we investigated the effect of the conditional loss of AhR activity in IECs in the formation and immune cell composition of TLTs in a model of acute inflammation. In females, loss of AhR activity in IECs reduced the formation of TLTs without significantly changing disease outcomes or immune cell composition within TLTs. In males lacking AhR expression in IECs, increased disease activity index, lower expression of functional-IEC genes, increased number of TLTs, increased T-cell density, and lower B- to T-cell ratio were observed. These findings may represent an unfavorable prognosis when exposed to dextran sodium sulfate (DSS)-induced epithelial damage compared with females. Sex and loss of IEC AhR also resulted in changes in microbial populations in the gut. Collectively, these data suggest that the formation of TLTs in the colon is influenced by sex and AhR expression in IECs.NEW & NOTEWORTHY This is the first research of its kind to demonstrate a clear connection between biological sex and the development of tertiary lymphoid tissues (TLT) in the colon. In addition, the research finds that in a preclinical model of inflammatory bowel disease, the expression of the aryl hydrocarbon receptor (AhR) influences the development of these structures in a sex-specific manner.

Peptide-Based Hydrogel for Nanosystems Encapsulation: the Next Generation of Localized Delivery Systems for the Treatment of Intestinal Inflammations

Conventional therapies for inflammatory bowel diseases are mainly based on systemic treatments which cause side effects and toxicity over long-term administration. Nanoparticles appear as a valid alternative to allow a preferential accumulation in inflamed tissues following oral administration while reducing systemic drug exposure. To increase their residence time in the inflamed intestine, the nanoparticles are here associated with a hydrogel matrix. A bioadhesive peptide-based hydrogel is mixed with nanoemulsions, creating a hybrid lipid-polymer nanocomposite. Mucopenetrating nanoemulsions of 100 nm are embedded in a scaffold constituted of the self-assembling peptide hydrogel product PuraStat. The nanocomposite is fully characterized to study the impact of lipid particles in the hydrogel structure. Rheological measurements and circular dichroism analyses are performed to investigate the system's microstructure and physical properties. Biodistribution studies demonstrate that the nanocomposite acts as a depot in the stomach and facilitates the slow release of the nanoemulsions in the intestine. Efficacy studies upon oral administration of the drug-loaded system show the improvement of the disease score in a mouse model of intestinal inflammation.

Lacticaseibacillusparacasei BNCC345679 revolutionizes DSS-induced colitis and modulates gut microbiota

The gut microbiota plays an important role in the disease progression of inflammatory bowel disease. Although probiotics are effective against IBD, not many studies have investigated their effects on gut microbiota composition and immunomodulation in mouse colitis models. Our study aimed at the therapeutic effects of Lacticaseibacillus paracasei BNCC345679 for the first time and explored its impact on gut microbiome dysbiosis, inflammatory cytokines, related miRNAs, VCAM-1, oxidative stress, intestinal integrity, and mucus barrier. We found that oral intervention of L. paracasei BNCC345679 affects recovering beneficial microbial taxa, including lactobacillus spp. and akkermansia spp., followed by improved body weight, DAI score, and inflammatory cytokines. L. paracasei BNCC345679 mitigated oxidative stress and increased the expression of intestinal integrity proteins MUC2 and ZO-1. These results suggested that L. paracasei BNCC345679 has the capacity to reduce DSS-induced colitis and has the potential as a supplement for the mitigation of IBD.

The microglial innate immune receptors TREM-1 and TREM-2 in the anterior cingulate cortex (ACC) drive visceral hypersensitivity and depressive-like behaviors following DSS-induced colitis

Inflammatory bowel disease (IBD) is a chronic condition with a high recurrence rate. To date, the clinical treatment of IBD mainly focuses on inflammation and gastrointestinal symptoms while ignoring the accompanying visceral pain, anxiety, depression, and other emotional symptoms. Evidence is accumulating that bi-directional communication between the gut and the brain is indispensable in the pathophysiology of IBD and its comorbidities. Increasing efforts have been focused on elucidating the central immune mechanisms in visceral hypersensitivity and depression following colitis. The triggering receptors expressed on myeloid cells-1/2 (TREM-1/2) are newly identified receptors that can be expressed on microglia. In particular, TREM-1 acts as an immune and inflammatory response amplifier, while TREM-2 may function as a molecule with a putative antagonist role to TREM-1. In the present study, using the dextran sulfate sodium (DSS)-induced colitis model, we found that peripheral inflammation induced microglial and glutamatergic neuronal activation in the anterior cingulate cortex (ACC). Microglial ablation mitigated visceral hypersensitivity in the inflammation phase rather than in the remission phase, subsequently preventing the emergence of depressive-like behaviors in the remission phase. Moreover, a further mechanistic study revealed that overexpression of TREM-1 and TREM-2 remarkably aggravated DSS-induced neuropathology. The improved outcome was achieved by modifying the balance of TREM-1 and TREM-2 via genetic and pharmacological means. Specifically, a deficiency of TREM-1 attenuated visceral hyperpathia in the inflammatory phase, and a TREM-2 deficiency improved depression-like symptoms in the remission phase. Taken together, our findings provide insights into mechanism-based therapy for inflammatory disorders and establish that microglial innate immune receptors TREM-1 and TREM-2 may represent a therapeutic target for the treatment of pain and psychological comorbidities associated with chronic inflammatory diseases by modulating neuroinflammatory responses.

ABX464 (Obefazimod) Upregulates miR-124 to Reduce Proinflammatory Markers in Inflammatory Bowel Diseases

Advanced therapies have transformed the treatment of inflammatory bowel disease; however, many patients fail to respond, highlighting the need for therapies tailored to the underlying cell and molecular disease drivers. The first-in-class oral molecule ABX464 (obefazimod), which selectively upregulates miR-124, has demonstrated its ability to be a well-tolerated treatment with rapid and sustained efficacy in patients with ulcerative colitis (UC). Here, we provide evidence that ABX464 affects the immune system in vitro , in the murine model of inflammatory bowel disease, and in patients with UC. In vitro , ABX464 treatment upregulated miR-124 and led to decreases in proinflammatory cytokines including interleukin (IL) 17 and IL6, and in the chemokine CCL2. Consistently, miR-124 expression was upregulated in the rectal biopsies and blood samples of patients with UC, and a parallel reduction in Th17 cells and IL17a levels was observed in serum samples. In a mouse model of induced intestinal inflammation with dextran sulfate sodium, ABX464 reversed the increases in multiple proinflammatory cytokines in the colon and the upregulation of IL17a secretion in the mesenteric lymph nodes. By upregulating miR-124, ABX464 acts as "a physiological brake" of inflammation, which may explain the efficacy of ABX464 with a favorable tolerability and safety profile in patients with UC.

Development of Spleen Targeting H2S Donor Loaded Liposome for the Effective Systemic Immunomodulation and Treatment of Inflammatory Bowel Disease

Nanoparticles are primarily taken up by immune cells after systemic administration. Thus, they are considered an ideal drug delivery vehicle for immunomodulation. Because the spleen is the largest lymphatic organ and regulates the systemic immune system, there have been studies to develop spleen targeting nanoparticles for immunomodulation of cancer and immunological disorders. Inflammatory bowel disease (IBD) includes disorders involving chronic inflammation in the gastrointestinal tract and is considered incurable despite a variety of treatment options. Hydrogen sulfide (H₂S) is one of the gasotransmitters that carries out anti-inflammatory functions and has shown promising immunomodulatory effects in various inflammatory diseases including IBD. Herein, we developed a delicately tuned H₂S donor delivering liposome for spleen targeting (ST-H₂S lipo) and studied its therapeutic effects in a dextran sulfate sodium (DSS) induced colitis model. We identified the ideal PEG type and ratio of liposome for a high stability, loading efficiency, and spleen targeting effect. In the treatment of the DSS-induced colitis model, we found that ST-H₂S lipo and conventional long-circulating liposomes loaded with H₂S donors (LC-H₂S lipo) reduced the severity of colitis, whereas unloaded H₂S donors did not. Furthermore, the therapeutic effect of ST-H₂S lipo was superior to that of LC-H₂S lipo due to its better systemic immunomodulatory effect than that of LC-H₂S lipo. Our findings demonstrate that spleen targeting H₂S lipo may have therapeutic potential for IBD.

Dietary-Induced Bacterial Metabolites Reduce Inflammation and Inflammation-Associated Cancer via Vitamin D Pathway

Environmental factors, including westernised diets and alterations to the gut microbiota, are considered risk factors for inflammatory bowel diseases (IBD). The mechanisms underpinning diet-microbiota-host interactions are poorly understood in IBD. We present evidence that feeding a lard-based high-fat (HF) diet can protect mice from developing DSS-induced acute and chronic colitis and colitis-associated cancer (CAC) by significantly reducing tumour burden/incidence, immune cell infiltration, cytokine profile, and cell proliferation. We show that HF protection was associated with increased gut microbial diversity and a significant reduction in Proteobacteria and an increase in Firmicutes and Clostridium cluster XIVa abundance. Microbial functionality was modulated in terms of signalling fatty acids and bile acids (BA). Faecal secondary BAs were significantly induced to include moieties that can activate the vitamin D receptor (VDR), a nuclear receptor richly represented in the intestine and colon. Indeed, colonic VDR downstream target genes were upregulated in HF-fed mice and in combinatorial lipid-BAs-treated intestinal HT29 epithelial cells. Collectively, our data indicate that HF diet protects against colitis and CAC risk through gut microbiota and BA metabolites modulating vitamin D targeting pathways. Our data highlights the complex relationship between dietary fat-induced alterations of microbiota-host interactions in IBD/CAC pathophysiology.

An IBD-associated pathobiont synergises with NSAID to promote colitis which is blocked by NLRP3 inflammasome and Caspase-8 inhibitors

Conflicting evidence exists on the association between consumption of non-steroidal anti-inflammatory drugs (NSAIDs) and symptomatic worsening of inflammatory bowel disease (IBD). We hypothesized that the heterogeneous prevalence of pathobionts [e.g., adherent-invasive Escherichia coli (AIEC)], might explain this inconsistent NSAIDs/IBD correlation. Using IL10^-/- mice, we found that NSAID aggravated colitis in AIEC-colonized animals. This was accompanied by activation of the NLRP3 inflammasome, Caspase-8, apoptosis, and pyroptosis, features not seen in mice exposed to AIEC or NSAID alone, revealing an AIEC/NSAID synergistic effect. Inhibition of NLRP3 or Caspase-8 activity ameliorated colitis, with reduction in NLRP3 inflammasome activation, cell death markers, activated T-cells and macrophages, improved histology, and increased abundance of Clostridium cluster XIVa species. Our findings provide new insights into how NSAIDs and an opportunistic gut-pathobiont can synergize to worsen IBD symptoms. Targeting the NLRP3 inflammasome or Caspase-8 could be a potential therapeutic strategy in IBD patients with gut inflammation, which is worsened by NSAIDs.

Lycium barbarum polysaccharides and capsaicin modulate inflammatory cytokines and colonic microbiota in colitis rats induced by dextran sulfate sodium

Active ingredients in the natural products have been considered to be used for alleviating the symptoms of ulcerative colitis, hence the effects of Lycium barbarum polysaccharides (LP) and capsaicin on dextran sulfate sodium (DSS)-induced colitis in rats were investigated. Rats were grouped into normal, DSS induced colitis, and colitis treated with 100 mg LP/kg body weight, 12 mg capsaicin/kg body weight, or combined 50 mg LP/kg body weight and 6 mg capsaicin/kg body weight. Treatment with LP or capsaicin was orally fed by gavage for 4 weeks, and 5% DSS was fed via drinking water for 6 days during week 3. Colon tissue and cecum content were collected for analysis. Treatments with LP and/or capsaicin ameliorated disease activity index scores, severity of colon distortion, and shrinkage of colon length. LP and capsaicin decreased colonic pro-inflammatory cytokine (IFN-γ, IL-17A, and IL-22) levels. Cecal microbiota in colitis rats were enriched with the genus Turicibacter and Lachnospira. The relative abundance of genus Ruminiclostridium_9 and Ruminoclostridium_1 was increased by LP and capsaicin treatment, respectively. Pretreatment with LP or capsaicin inhibits the severity of colonic damage in rats with DSS-induced colitis via anti-inflammation and modulation of colonic microbiota.

Cytochrome P450 1A1 is essential for the microbial metabolite, Urolithin A-mediated protection against colitis

Background

Cytochrome P450 Family 1 Subfamily A Member 1 (CYP1A1) pathway, which is regulated by aryl hydrocarbon receptor (AhR) plays an important role in chemical carcinogenesis and xenobiotic metabolism. Recently, we demonstrated that the microbial metabolite Urolithin A (UroA) mitigates colitis through its gut barrier protective and anti-inflammatory activities in an AhR-dependent manner. Here, we explored role of CYP1A1 in UroA-mediated gut barrier and immune functions in regulation of inflammatory bowel disease (IBD).

Methods

To determine the role of CYP1A1 in UroA-mediated protectives activities against colitis, we subjected C57BL/6 mice and Cyp1a1^-/- mice to dextran sodium sulphate (DSS)-induced acute colitis model. The phenotypes of the mice were characterized by determining loss of body weight, intestinal permeability, systemic and colonic inflammation. Further, we evaluated the impact of UroA on regulation of immune cell populations by flow cytometry and confocal imaging using both in vivo and ex vivo model systems.

Results

UroA treatment mitigated DSS-induced acute colitis in the wildtype mice. However, UroA-failed to protect Cyp1a1^-/- mice against colitis, as evident from non-recovery of body weight loss, shortened colon lengths and colon weight/length ratios. Further, UroA failed to reduce DSS-induced inflammation, intestinal permeability and upregulate tight junction proteins in Cyp1a1^-/- mice. Interestingly, UroA induced the expansion of T-reg cells in a CYP1A1-dependent manner both in vivo and ex vivo models.

Conclusion

Our results suggest that CYP1A1 expression is essential for UroA-mediated enhanced gut barrier functions and protective activities against colitis. We postulate that CYP1A1 plays critical and yet unknown functions beyond xenobiotic metabolism in the regulation of gut epithelial integrity and immune systems to maintain gut homeostasis in IBD pathogenesis.

Fibromodulin Ablation Exacerbates the Severity of Acute Colitis

Introduction

Epidemiological studies have associated pigment production with protection against certain human diseases. In contrast to African Americans, European descendants are more likely to suffer from angiogenesis-dependent and inflammatory diseases, such as wet age-related macular degeneration (ARMD) and ulcerative colitis (UC), respectively.

Methods

In a mouse model of dextran sulfate sodium (DSS)-induced acute colitis, the effect of fibromodulin (FMOD) depletion was examined on colitis severity.

Results

In this study, albino mice that produce high levels of FMOD developed less severe acute colitis compared with mice lacking in FMOD as assessed by clinical symptoms and histopathological changes. FMOD depletion affected the expression of tight junction proteins, contributing to the destruction of the epithelial barrier. Furthermore, this study revealed a stronger inflammatory response after DSS treatment in the absence of FMOD, where FMOD depletion led to an increase in activated T cells, plasmacytoid dendritic cells (pDCs), and type I interferon (IFN) production.

Discussion

These findings point to FMOD as a potential biomarker of disease severity in UC among light-skinned individuals of European descent.

Characterization of Maladaptive Processes in Acute, Chronic and Remission Phases of Experimental Colitis in C57BL/6 Mice

Inflammatory bowel disease (IBD) is a chronic recurrent inflammatory disease with unknown etiology. Dextran sulfate sodium (DSS) induced colitis is a widely used mouse model in IBD research. DSS colitis involves activation of the submucosal immune system and can be used to study IBD-like disease characteristics in acute, chronic, remission and transition phases. Insight into colon inflammatory parameters is needed to understand potentially irreversible adaptations to the chronification of colitis, determining the baseline and impact of further inflammatory episodes. We performed analyses of non-invasive and invasive colitis parameters in acute, chronic and remission phases of the DSS colitis in C57BL/6 mice. Non-invasive colitis parameters poorly reflected inflammatory aspects of colitis in chronic remission phase. We found invasive inflammatory parameters, positively linked to repeated DSS-episodes, such as specific colon weight, inflamed colon area, spleen weight, absolute cell numbers of CD4+ and CD8+ T cells as well as B cells, blood IFN-γ level, colonic chemokines BLC and MDC as well as the prevalence of Turicibacter species in feces. Moreover, microbial Lactobacillus species decreased with chronification of disease. Our data point out indicative parameters of recurrent gut inflammation in context of DSS colitis.

Bifidobacterium infantis regulates the programmed cell death 1 pathway and immune response in mice with inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) is caused by an abnormal immune response. Programmed cell death 1 (PD-1) is an immunostimulatory molecule, which interacts with PD ligand (PD-L1) playing a prime important role among autoimmune diseases. Bifidobacterium infantis (B. infantis) can promote the differentiation of CD (cluster of differentiation) 4⁺ T cells into regulatory T cells (Tregs). Tregs participate in the development of IBD and may be related to disease activity. B. infantis amplify the expression level of PD-1, PD-L1 and Tregs’ nuclear transcription factor forkhead box protein 3 (Foxp3). But the mechanism of B. infantis on PD-1/PD-L1 signaling remains unclear.

AIM

To explore the mechanism of B. infantis regulating the immune response in IBD.

METHODS

Forty-eight-week-old BALB/c mice were randomly divided into five groups: The control group, dextran sulphate sodium (DSS) model group, DSS + B. infantis group, DSS + B. infantis + anti-PD-L1 group, and DSS + anti-PD-L1 group. The control group mice were given drinking water freely, the other four groups were given drinking water containing 5% DSS freely. The control group, DSS model group, and DSS + anti-PD-L1 group were given normal saline (NS) 400 μL daily by gastric lavage, and the DSS + B. infantis group and DSS + B. infantis + anti-PD-L1 group were given NS and 1 × 10⁹ colony-forming unit of B. infantis daily by gastric lavage. The DSS + B. infantis + anti-PD-L1 group and DSS + anti-PD-L1 group were given 200 μg of PD-L1 blocker intraperitoneally at days 0, 3, 5, and 7; the control group, DSS + anti-PD-L1 group, and DSS + B. infantis group were given an intraperitoneal injection of an equal volume of phosphate buffered saline (PBS). Changes in PD-L1, PD-1, Foxp3, interleukin (IL)-10, and transforming growth factor β (TGF-β) 1 protein and gene expression were observed. Flow cytometry was used to observe changes in CD4⁺, CD25⁺, Foxp3⁺ cell numbers in the blood and spleen.

RESULTS

Compared to the control group, the expression of PD-1, Foxp3, IL-10, and TGF-β1 was significantly decreased in the intestinal tract of the DSS mice (P < 0.05). Compared to the control group, the proportion of CD4⁺, CD25⁺, Foxp3⁺ cells in spleen and blood of DSS group was visibly katabatic (P < 0.05). B. infantis upgraded the express of PD-L1, PD-1, Foxp3, IL-10, and TGF-β1 (P < 0.05) and increased the proportion of CD4⁺, CD25⁺, Foxp3⁺ cells both in spleen and blood (P < 0.05). After blocking PD-L1, the increase in Foxp3, IL-10, and TGF-β1 protein and gene by B. infantis was inhibited (P < 0.05), and the proliferation of CD4⁺, CD25⁺, Foxp3⁺ cells in the spleen and blood was also inhibited (P < 0.05). After blocking PD-L1, the messenger ribonucleic acid and protein expression of PD-1 were invariant.

CONCLUSION

It is potential that B. infantis boost the proliferation of CD4⁺, CD25⁺, Foxp3⁺ T cells in both spleen and blood, as well as the expression of Foxp3 in the intestinal tract by activating the PD-1/PD-L1 pathway.

l-Ergothioneine Exhibits Protective Effects against Dextran Sulfate Sodium-Induced Colitis in Mice

Background: Ulcerative colitis (UC) is a chronic disease of the intestinal tract in which excessive activation of inflammatory response is correlated. l-Ergothioneine (EGT) widely existing in mushrooms has various physiological activities. In this study, the protective effects of EGT on dextran sulfate sodium (DSS)-induced colitis mice were investigated. Results: It was observed that EGT administration, especially at the high dose level, prevented the body weight loss, the colon shortening, and the increase in disease activity index and spleen index caused by DSS. Moreover, EGT supplementation attenuated DSS-induced gut barrier damage by enhancing the expression of tight-junction protein and recovering the loss of gut mucus layer. Furthermore, EGT considerably decreased the colonic myeloperoxidase (MPO) activity induced by DSS, but no significant differences were observed in the concentrations of IL-6 and TNF-α in colon tissues. Additionally, EGT downregulated the populations of CD4⁺ T cells and macrophages, indicating that EGT stabilized the immune response caused by DSS. Conclusion: Together these results suggest that EGT can alleviate DSS-induced colitis and provide important insights concerning the potential anticolitis activity of such food products.

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

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Increased tenascin-C staining appeared to predominantly occur in damaged ulcerated areas.

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Tenascin-C knock-out mice were partly protected from DSS induced colitis.

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Mice deficient in tenascin-C had areas of + ve EpCAM staining indicating that crypt and epithelial integrity was maintained.

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.

Gut-innervating TRPV1+ Neurons Drive Chronic Visceral Pain via Microglial P2Y12 Receptor

BACKGROUND & AIMS

Chronic abdominal pain is a common symptom of inflammatory bowel diseases (IBDs). Peripheral and central mechanisms contribute to the transition from acute to chronic pain during active disease and clinical remission. Lower mechanical threshold and hyperexcitability of visceral afferents induce gliosis in central pain circuits, leading to persistent visceral hypersensitivity (VHS). In the spinal cord, microglia, the immune sentinels of the central nervous system, undergo activation in multiple models of VHS. Here, we investigated the mechanisms of microglia activation to identify centrally acting analgesics for chronic IBD pain.

METHODS

Using Designer Receptors Exclusively Activated by Designer Drugs (DREADD) expressed in transient receptor potential vanilloid member 1-expressing visceral neurons that sense colonic inflammation, we tested whether neuronal activity was indispensable to control microglia activation and VHS. We then investigated the neuron-microglia signaling system involved in visceral pain chronification.

RESULTS

We found that chemogenetic inhibition of transient receptor potential vanilloid member 1⁺ visceral afferents prevents microglial activation in the spinal cord and subsequent VHS in colitis mice. In contrast, chemogenetic activation, in the absence of colitis, enhanced microglial activation associated with VHS. We identified a purinergic signaling mechanism mediated by neuronal adenosine triphosphate (ATP) and microglial P2Y12 receptor, triggering VHS in colitis. Inhibition of P2RY12 prevented microglial reactivity and chronic VHS post-colitis.

CONCLUSIONS

Overall, these data provide novel insights into the central mechanisms of chronic visceral pain and suggest that targeting microglial P2RY12 signaling could be harnessed to relieve pain in patients with IBD who are in remission.

Clophosome alleviate dextran sulphate sodium-induced colitis by regulating gut immune responses and maintaining intestinal integrity in mice

Inflammatory bowel disease (IBD) is a chronic progressive disorder characterized by complicated gastrointestinal inflammation. Research on therapeutic agents is still urgent due to the lack of satisfactory treatments. Gut macrophages are considered to be predominant in excessive inflammatory responses. Thus, we aimed to investigate whether depletion of macrophages would have a beneficial effect on IBD and could be a potential therapeutic strategy. In this study, we established a 12-day Dextran sodium sulphate (DSS)-induced colitis mouse model and determined the effect of the macrophage depletion agent Clophosome (neutral clodronate liposomes; CNC). The results showed that CNC significantly alleviated the symptoms of colitis, as demonstrated by greater weight gain, decreased disease activity index (DAI) scores, and lower histopathological damage scores, as well was reduced levels of the proinflammatory cytokines interleukin (IL)-6 and tumour necrosis factor (TNF)-α. To investigate T cell subsets, cells were isolated from the lamina propria and cultured to analyse the expression of IL-17A, interferon (IFN)-γ and Foxp3 in CD4+ cells by flow cytometry. The data showed that during the process of colitis, the frequencies of CD4+ IL-17A+ T cells were significantly increased. Notably, CNC treatment markedly reduced the population of CD4+ IL-17A+ T cells, especially CD4+ IL-17A+ IFN-γ+ T cells. Furthermore, intestinal barrier integrity, as assessed by immunostaining of mucin and tight junction proteins, was severely disrupted in colitis. CNC improved the intestinal barrier by enhancing the expression of muc-2 and occludin. In summary, our findings demonstrated that CNC successfully ameliorated DSS-induced colitis and that its effect may be associated with inhibiting inflammatory responses and maintaining intestinal integrity.

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

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

Enteric Glia Modulate Macrophage Phenotype and Visceral Sensitivity following Inflammation

Mechanisms resulting in abdominal pain include altered neuro-immune interactions in the gastrointestinal tract, but the signaling processes that link immune activation with visceral hypersensitivity are unresolved. We hypothesized that enteric glia link the neural and immune systems of the gut and that communication between enteric glia and immune cells modulates the development of visceral hypersensitivity. To this end, we manipulated a major mechanism of glial intercellular communication that requires connexin-43 and assessed the effects on acute and chronic inflammation, visceral hypersensitivity, and immune responses. Deleting connexin-43 in glia protected against the development of visceral hypersensitivity following chronic colitis. Mechanistically, the protective effects of glial manipulation were mediated by disrupting the glial-mediated activation of macrophages through the macrophage colony-stimulating factor. Collectively, our data identified enteric glia as a critical link between gastrointestinal neural and immune systems that could be harnessed by therapies to ameliorate abdominal pain.

Prescription Opioids induce Gut Dysbiosis and Exacerbate Colitis in a Murine Model of Inflammatory Bowel Disease

BACKGROUND AND AIMS

Opioids are the most prescribed analgesics for pain in inflammatory bowel diseases [IBD]; however, the consequences of opioid use on IBD severity are not well defined. This is the first study investigating consequences of hydromorphone in both dextran sodium sulphate [DSS]-induced colitis and spontaneous colitis (IL-10 knockout [IL-10-/-]) mouse models of IBD.

METHODS

To determine the consequences of opioids on IBD pathogenesis, wild-type [WT] mice were treated with clinically relevant doses of hydromorphone and colitis was induced via 3% DSS in drinking water for 5 days. In parallel we also determined the consequences of opioids in a spontaneous colitis model.

RESULTS

Hydromorphone and DSS independently induced barrier dysfunction, bacterial translocation, disruption of tight junction organisation and increased intestinal and systemic inflammation, which were exacerbated in mice receiving hydromorphone in combination with DSS. Hydromorphone + DSS-treated mice exhibited significant microbial dysbiosis. Predictive metagenomic analysis of the gut microbiota revealed high abundance in the bacterial communities associated with virulence, antibiotic resistance, toxin production, and inflammatory properties. Hydromorphone modulates tight junction organisation in a myosin light chain kinase [MLCK]-dependent manner. Treatment with MLCK inhibitor ML-7 ameliorates the detrimental effects of hydromorphone on DSS-induced colitis and thus decreases severity of IBD. Similarly, we demonstrated that hydromorphone treatment in IL-10-/- mice resulted in accelerated clinical manifestations of colitis compared with control mice.

CONCLUSIONS

Opioids used for pain management in IBD accelerate IBD progression by dysregulation of the gut microbiota, leading to expansion of pathogenic bacteria, translocation of bacteria, immune deregulation and sustained inflammation.

The anti-inflammatory and immune-modulatory effects of OEA limit DSS-induced colitis in mice

Fatty acid ethanolamides acting on proliferator-activated receptor (PPAR)-α are among the endogenous lipid molecules that attenuate inflammatory processes and pain sensitivity. Whereas these properties are well-known for palmitoylethanolamide (PEA), the efficacy of oleoylethanolamide (OEA, first described as a satiety hormone synthesized in the jejunum) has been overlooked. In this study, we aimed to evaluate the effect of OEA administration in a mouse model of colitis. C57BL/6J mice were exposed to 2.5% dextran sodium sulphate (DSS) in drinking water for 5 days. Daily i.p. administration of 10 mg/kg OEA started 3 days before DSS and lasted for 12 days. The DSS-untreated control group received only ultrapure water. DSS mice treated with OEA had a significant improvement of disease score. OEA restored mRNA transcription of PPAR-α, of tight junctions and protective factors of colon integrity disrupted by DSS. The improvement correlated with significant decrease of colonic and systemic levels of pro-inflammatory cytokines compared to the DSS group. OEA antiinflammatory effects were mediated by the selective targeting of the TLR4 axis causing a downstream inhibition of nuclear factor kappa B (NF-κB)- MyD88-dependent and NLRP3 inflammation pathways. OEA treatment also inhibited DSS-induced increase of inflammatory cytokines levels in the mesenteric lymph nodes. CONCLUSIONS AND IMPLICATIONS: These results underscore the validity of OEA as a potent protective and anti-inflammatory agent in ulcerative colitis that may be exploited to broaden the pharmacological strategies against inflammatory bowel disease.

c-FLIP is crucial for IL-7/IL-15-dependent NKp46+ ILC development and protection from intestinal inflammation in mice

NKp46⁺ innate lymphoid cells (ILC) modulate tissue homeostasis and anti-microbial immune responses. ILC development and function are regulated by cytokines such as Interleukin (IL)-7 and IL-15. However, the ILC-intrinsic pathways translating cytokine signals into developmental programs are largely unknown. Here we show that the anti-apoptotic molecule cellular FLICE-like inhibitory protein (c-FLIP) is crucial for the generation of IL-7/IL-15-dependent NKp46⁺ ILC1, including conventional natural killer (cNK) cells, and ILC3. Cytokine-induced phosphorylation of signal transducer and activator of transcription 5 (STAT5) precedes up-regulation of c-FLIP, which protects developing NKp46⁺ ILC from TNF-induced apoptosis. NKp46⁺ ILC-specific inactivation of c-FLIP leads to the loss of all IL-7/IL-15-dependent NKp46⁺ ILC, thereby inducing early-onset chronic colitis and subsequently microbial dysbiosis; meanwhile, the depletion of cNK, but not NKp46⁺ ILC1/3, aggravates experimental colitis. In summary, our data demonstrate a non-redundant function of c-FLIP for the generation of NKp46⁺ ILC, which protect T/B lymphocyte-sufficient mice from intestinal inflammation.

Unexpected mechanism of colitis amelioration by artesunate, a natural product from Artemisia annua L

BACKGROUND

Artemisinin and its derivatives are known to exert immunosuppressive effects through modulating adaptive immunity. We investigated a novel role of artesunate in regulating innate immunity, including both macrophages (MΦ) and dendritic cells (DCs), which are known to involve in DSS-induced colitis.

METHODS

Effects of artesunate on innate immunity were extensively evaluated, both in vivo using DSS-colitis model with WT and T cell-deficient RAG mice (RAG^-/-) and in vitro using cell culture models, including in-depth analyses of MΦ/DC apoptosis and cytokine expression by flow cytometry, Western blot, or immunohistology.

RESULTS

Unexpectedly, artesunate significantly ameliorated the DSS colitis of both WT and RAG1^-/- mice with similar potency, suggesting a mechanism that involves primarily innate rather than adaptive immunity. In vivo mechanistic studies revealed that artesunate markedly induced apoptosis of lamina propria MΦs and DCs and suppressed mucosal TNF-α and IL-12p70 in DSS-colitis. In vitro, artesunate potently induced a dose- and time-dependent apoptosis of murine bone marrow-derived DCs and human THP-1 MΦs, through the caspases-9-mediated intrinsic pathway. Artesunate significantly decreased the secretion of IL-12p40/70 by DCs and TNF-α by MΦs. Furthermore, a combination of artesunate with an immunomodulator (methotrexate/triptolide/azathioprine) exhibited superior potency in promoting apoptosis of MΦs than any individual drug alone.

CONCLUSIONS

The immunomodulatory mechanism of artesunate in colitis involves a novel and potent induction of the intrinsic apoptosis pathway of proliferating MΦs and DCs and suppression of IL-12 and TNF-α. Artemisinin and its derivatives are promising new therapeutic alternatives for IBD, either alone or in combination with other immunomodulators.

Dietary exposure to chlorpyrifos inhibits the polarization of regulatory T cells in C57BL/6 mice with dextran sulfate sodium-induced colitis

Inflammatory bowel disease (IBD) is associated with loss of immune tolerance to antigens originating from the diet and from the gut microflora. T cells play crucial roles in the pathogenesis of IBD. Chlorpyrifos (CPF) is one of the most ubiquitous organophosphate pesticides in the world. The aim of the study was to investigate the effects of dietary exposure to CPF on T-cell populations in C57BL/6 mice with dextran sulfate sodium (DSS)-induced colitis. Mice received distilled water containing 3% DSS for 6 days to induce acute colitis, which was then replaced with distilled water for 21 days, allowing progression to chronic inflammation. During the experimental period, mice were given either an AIN-93-based control diet or a CPF diet-containing 7, 17.5, or 35 ppm of CPF. Results showed that dietary exposure to CPF significantly increased circulating neutrophils in colitic mice. CPF-exposed groups had lower percentages of blood and spleen T cells without altering the proportions of CD4⁺ and CD8⁺ T-cell subsets. The percentage of blood regulatory T (Treg) cells, as well as splenic expressions of Treg-related genes, were suppressed in CPF-exposed mice. CPF upregulated the colonic gene expression of tumor necrosis factor-α. Meanwhile, plasma haptoglobin, colon weights, and luminal immunoglobulin G levels were higher in CPF-exposed groups. Histopathological analyses also observed that colon injury was more severe in all CPF-exposed mice. These results suggest that dietary exposure to CPF aggravated tissue injuries in mice with DSS-induced chronic colitis by suppressing T-cell populations and Treg polarization.

β7 Integrin Inhibition Can Increase Intestinal Inflammation by Impairing Homing of CD25hiFoxP3+ Regulatory T Cells

BACKGROUND & AIMS

Integrin α4β7 mediates lymphocyte trafficking to the gut and gut-associated lymphoid tissues, a process critical for recruitment of effector lymphocytes from the circulation to the gut mucosa in inflammatory bowel disease (IBD) and murine models of intestinal inflammation. Antibody blockade of β7 integrins generally is efficacious in IBD; however, some patients fail to respond, and a few patients can experience exacerbations. This study examined the effects of loss of β7 integrin function in murine models of IBD.

METHODS

In a mouse IBD model caused by lack of interleukin 10, a cytokine important in CD25hiFoxP3+ regulatory T cell (Treg) function, genetic deletion of β7 integrin or antibody blockade of α4β7-mucosal addressin cell adhesion molecule-1 interaction paradoxically exacerbated colitis.

RESULTS

Loss of β7 impaired the capacity of Tregs homing to the gut and therefore suppress intestinal inflammation in an adoptive T-cell transfer model; however, the intrinsic suppressive function of β7-deficient Tregs remained intact, indicating that the β7 deficiency selectively impacts gut homing. Deletion of β7 integrin did not worsen colitis in an acute dextran sodium sulfate model in which Treg number and function were normal.

CONCLUSIONS

In Integrin subunit beta (Itgb)7-/-Il10-/- mice, loss of β7-dependent Treg homing to gut-associated lymphoid tissues combined with loss of intrinsic Treg function exacerbated intestinal inflammation. These results suggest that IBD patients with reduced CD25hiFoxP3+ Treg numbers or function or lack of interleukin 10 could be at risk for failure of α4β7 blocking therapy.

Persistent central inflammation and region specific cellular activation accompany depression- and anxiety-like behaviours during the resolution phase of experimental colitis

Depression and anxiety-related psychological symptoms are increasingly recognised as important co-morbidities in patients with inflammatory bowel disease (IBD). Dextran sulfate sodium (DSS) -induced colitis is an animal model of IBD in which afferent activation of the gut-brain axis can be assessed and explored as a source of behavioural change. Exposure of adult male Wistar rats to DSS (5%) in drinking water induced distal colitis. In parallel to local inflammatory responses in the gut wall, increased expression of IL-6 and iNOS was found in the cerebral cortex and an increase in ventricular volume. Immunoreactivity of immediate early gene FosB/ΔFosB activation was measured as an index of cellular activation and was increased in the nucleus accumbens and dorsal raphe nucleus in acutely colitic animals. Following resolution of the acute colitic response, sustained anhedonia in the saccharin preference test, immobility in the forced swim test, reduced burying behaviour in the marble burying test, and mild signs of anxiety in the elevated plus maze and light/dark box were observed. Central increases in iNOS expression persisted during the recovery phase and mapped to reactive microglia, particularly those found in the parenchyma surrounding circumventricular regions. Evidence of associated nitration was also found. Sustained increases in ventricular volume and reduced T2 magnetic resonance relaxometry time in cortical regions were observed during the recovery period. FosB/ΔFosB activation was evident in the dorsal raphe during recovery. Persistent central inflammation and cellular activation may underpin the emergence of symptoms of depression and anxiety in experimental colitis.

Therapeutic effects of a single injection of human umbilical mesenchymal stem cells on acute and chronic colitis in mice

Multiple injections of bone marrow mesenchymal stem cells (BMMSCs) have been used for treatment of chronic colitis in mice. We aimed to report the therapeutic effects of a single injection of human umbilical cord mesenchymal stem cells (hUCMSCs) on acute and chronic colitis. Male C57BL/6JNarl mice were divided into control, phosphate-buffered saline (PBS), and hUCMSCs treated groups, respectively. Acute and chronic colitis were induced in the mice (except controls) using 3% dextran sulfate sodium (DSS). The mice in the hUCMSCs group underwent a single injection of hUCMSCs. The disease activity index (DAI), colon length, histology, colon inflammation score, in vivo stem cells images, and blood cytokine levels were recorded. The DAI was significantly higher in the hUCMSCs group than in the control group and lower than in the PBS group on all days. The colon length was significantly longer and the colon inflammation score was significantly lower in the hUCMSCs group than in the PBS group on days 8 and 25. IL17A, Gro-α, MIP-1α, MIP-2, and eotaxin were significantly lower in the hUCMSCs group than in the PBS group on days 8 and 25. Single-injection hUCMSCs improved DSS–induced acute colitis and decreased progression of acute colitis to chronic colitis.

Lactobacillus fermentum species ameliorate dextran sulfate sodium-induced colitis by regulating the immune response and altering gut microbiota

We evaluated immunometabolic functions of novel Lactobacillus fermentum strains (KBL374 and KBL375) isolated from feces of healthy Koreans. The levels of inflammatory cytokines, such as interleukin (IL)-2, interferon-γ, IL-4, IL-13, and IL-17A, were decreased, and that of the anti-inflammatory cytokine IL-10 was increased, in human peripheral blood mononuclear cells (PBMCs) treated with the L. fermentum KBL374 or KBL375 strain. When these strains were orally administered to mice with dextran sulfate sodium (DSS)-induced colitis, both L. fermentum KBL374 and KBL375 showed beneficial effects on body weight, disease activity index score, colon length, cecal weight, and histological scores. Furthermore, both L. fermentum KBL374 and KBL375 modulated the innate immune response by improving gut barrier function and reducing leukocyte infiltration. Consistent with the PBMC data, both L. fermentum KBL374- and KBL375-treated DSS mice demonstrated decreased Th1-, Th2-, and Th17-related cytokine levels and increased IL-10 in the colon compared with the DSS control mice. Administration of L. fermentum KBL374 or KBL375 to mice increased the CD4+CD25+Foxp3+Treg cell population in mesenteric lymph nodes. Additionally, L. fermentum KBL374 or KBL375 administration reshaped and increased the diversity of the gut microbiota. In particular, L. fermentum KBL375 increased the abundance of beneficial microorganisms, such as Lactobacillus spp. and Akkermansia spp. Both L. fermentum KBL374 and KBL375 may alleviate inflammatory diseases, such as inflammatory bowel disease, in the gut by regulating immune responses and altering the composition of gut microbiota.

Mobilization of CD4+ T lymphocytes in inflamed mucosa reduces pain in colitis mice: toward a vaccinal strategy to alleviate inflammatory visceral pain

T lymphocytes play a pivotal role in endogenous regulation of inflammatory visceral pain. The analgesic activity of T lymphocytes is dependent on their production of opioids, a property acquired on antigen activation. Accordingly, we investigated whether an active recruitment of T lymphocytes within inflamed colon mucosa via a local vaccinal strategy may counteract inflammation-induced visceral pain in mice. Mice were immunized against ovalbumin (OVA). One month after immunization, colitis was induced by adding 3% (wt/vol) dextran sulfate sodium into drinking water containing either cognate antigen OVA or control antigen bovine serum albumin for 5 days. Noncolitis OVA-primed mice were used as controls. Visceral sensitivity was then determined by colorectal distension. Oral administration of OVA but not bovine serum albumin significantly reduced dextran sulfate sodium-induced abdominal pain without increasing colitis severity in OVA-primed mice. Analgesia was dependent on local release of enkephalins by effector anti-OVA T lymphocytes infiltrating the inflamed mucosa. The experiments were reproduced with the bacillus Calmette-Guerin vaccine as antigen. Similarly, inflammatory visceral pain was dramatically alleviated in mice vaccinated against bacillus Calmette-Guerin and then locally administered with live Mycobacterium bovis. Together, these results show that the induction of a secondary adaptive immune response against vaccine antigens in inflamed mucosa may constitute a safe noninvasive strategy to relieve from visceral inflammatory pain.

Therapeutic effects of lentinan on inflammatory bowel disease and colitis-associated cancer

In this study, we investigated the therapeutic potential of lentinan in mouse models of inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). Lentinan decreased the disease activity index and macroscopic and microscopic colon tissue damage in dextran sulphate sodium (DSS)-induced or TNBS-induced models of colitis. High-dose lentinan was more effective than salicylazosulfapyridine in the mouse models of colitis. Lentinan decreased the number of tumours, inflammatory cell infiltration, atypical hyperplasia and nuclear atypia in azoxymethane/DSS-induced CAC model. It also decreased the expression of pro-inflammatory cytokines, such as IL-13 and CD30L, in IBD and CAC model mice possibly by inhibiting Toll-like receptor 4 (TLR4)/NF-κB signalling and the expression of colon cancer markers, such as carcinoembryonic antigen, cytokeratin 8, CK18 and p53, in CAC model mice. In addition, lentinan restored the intestinal bacterial microbiotal community structure in IBD model mice. Thus, it shows therapeutic potential in IBD and CAC model mice possibly by inhibiting TLR4/NF-κB signalling-mediated inflammatory responses and disruption of the intestinal microbiotal structure.

Deciphering the immune microenvironment of a tissue by digital imaging and cognition network

Evidence has highlighted the importance of immune cells in various gut disorders. Both the quantification and localization of these cells are essential to the understanding of the complex mechanisms implicated in these pathologies. Even if quantification can be assessed (e.g., by flow cytometry), simultaneous cell localization and quantification of whole tissues remains technically challenging. Here, we describe the use of a computer learning-based algorithm created in the Tissue Studio interface that allows for a semi-automated, robust and rapid quantitative analysis of immunofluorescence staining on whole colon sections according to their distribution in different tissue areas. Indeed, this algorithm was validated to characterize gut immune microenvironment. Its application to the preclinical colon cancer APC^Min/+ mouse model is illustrated by the simultaneous counting of total leucocytes and T cell subpopulations, in the colonic mucosa, lymphoid follicles and tumors. Moreover, we quantify T cells in lymphoid follicles for which quantification is not possible with classical methods. Thus, this algorithm is a new and robust preclinical research tool, for investigating immune contexture exemplified by T cells but it is also applicable to other immune cells such as other myeloid and lymphoid populations or other cellular phenomenon along mouse gut.

Temporal clinical, proteomic, histological and cellular immune responses of dextran sulfate sodium-induced acute colitis

AIM

To investigate the temporal clinical, proteomic, histological and cellular immune profiles of dextran sulfate sodium (DSS)-induced acute colitis.

METHODS

Acute colitis was induced in C57Bl/6 female mice by administration of 1%, 2% or 3% DSS in drinking water for 7 d. Animals were monitored daily for weight loss, stool consistency and blood in the stool, while spleens and colons were harvested on day 8. A time course analysis was performed in mice ingesting 3% DSS, which included colon proteomics through multiplex assay, colon histological scoring by a blinded investigator, and immune response through flow cytometry or immunohistochemistry of the spleen, mesenteric lymph node and colon.

RESULTS

Progressive worsening of clinical colitis was observed with increasing DSS from 1% to 3%. In mice ingesting 3% DSS, colon shortening and increase in pro-inflammatory factors starting at day 3 was observed, with increased spleen weights at day 6 and day 8. This coincided with cellular infiltration in the colon from day 2 to day 8, with progressive accumulation of macrophages F4/80⁺, T helper CD4⁺ (Th), T cytotoxic CD8⁺ (Tcyt) and T regulatory CD25⁺ (Treg) cells, and progressive changes in colonic pathology including destruction of crypts, loss of goblet cells and depletion of the epithelial barrier. Starting on day 4, mesenteric lymph node and/or spleen presented with lower levels of Treg, Th and Tcyt cells, suggesting an immune cell tropism to the gut.

CONCLUSION

These results demonstrate that the severity of experimental colitis is dependent on DSS concentration, correlated with clinical, proteomic, histological and cellular immune response on 3% DSS.

Clostridium butyricum protects the epithelial barrier by maintaining tight junction protein expression and regulating microflora in a murine model of dextran sodium sulfate-induced colitis

OBJECTIVE

To investigate the protective effects of Clostridium butyricum on the epithelial barrier in dextran sodium sulfate (DSS)-induced colitis.

METHODS

Eight-week-old BALB/c mice were divided into a healthy control group and DSS-induced groups, including negative control (normal saline), 5-aminosalicylic acid (5-ASA), C. butyricum group, and 5-ASA + C. butyricum groups. Colitis was induced by 5% DSS ad libitum for 7 d. We assessed the disease activity index (DAI), histological grading, and ultrastructural changes by transmission electron microscopy. Stools were collected for bacterial microflora analysis. Tight junction (TJ) proteins, including claudin-1, claudin-2, occluding, and zonula occludens-1, were detected by immunohistochemical staining and western blot. We also assessed NF-κB and cytokines, including IL-1β, IL-13, and IL-10, by western blot.

RESULTS

C. butyricum decreased DAI and histological injury scores in DSS-induced mice, and repaired the damaged structure of TJs. Moreover, C. butyricum exerted its regulatory effect on fecal microflora by increasing and decreasing the growth of Lactobacillus spp. and Enterococcus spp., respectively, in the colon lumen. Expression levels of claudin-1, occludin and zonula occludens-1 were also elevated by the administration of C. butyricum. In addition, C. butyricum increased the expression of the anti-inflammatory cytokine, IL-10, and decreased levels of pro-inflammatory cytokines, including IL-1β, TNF, and IL-13, as well as NF-κB. Moreover, the beneficial effects of C. butyricum combined with 5-ASA were superior to treatment with C. butyricum only.

CONCLUSION

In a mouse model of ulcerative colitis (UC), C. butyricum exerted a protective effect on the epithelial barrier by regulating microflora, maintaining the expression of TJ proteins and exerting immunoregulatory effects.

Indoleamine 2,3-dioxygenase-dependent expansion of T-regulatory cells maintains mucosal healing in ulcerative colitis

BACKGROUND

Dendritic cell (DC)-derived indolamine 2,3-dioxygenase (IDO) degrades tryptophan to kynurenine, which promotes conversion of inflammatory T cells in immunosuppressive regulatory T cells (Tregs). We analyzed the significance of the IDO:Treg axis for inducing and maintaining mucosal healing in ulcerative colitis (UC).

METHODS

Dextran sodium sulphate (DSS)-induced colitis in BALB/c mice (model for mucosal healing) and C57BL/6 mice (model for persistent disease) was used. Serum, fecal samples and colon-infiltrating immune cells of 65 patients with UC with mucosal healing or persistent colitis were analyzed.

RESULTS

Significantly higher serum levels of kynurenine and downregulated inflammatory cytokines were noticed in DSS-treated BALB/c mice compared with C57BL/6 mice. Increased IDO activity and attenuated capacity for antigen presentation and production of inflammatory cytokines, observed in BALB/c DCs, was followed by a significantly lower number of inflammatory T helper 1 (Th1) and Th17 cells and a notably increased number of Tregs in the colons of DSS-treated BALB/c mice. DCs and Tregs were crucially important for the maintenance of mucosal healing since their depletion aggravated colitis. Mucosal healing, followed by an increase in kynurenine and intestinal Tregs, was re-established when BALB/c DCs were transferred into DC-depleted or Treg-depleted DSS-treated BALB/c mice. This phenomenon was completely abrogated by the IDO inhibitor. Significantly higher serum and fecal levels of kynurenine, accompanied by an increased presence of intestinal Tregs, were noticed in patients with UC with mucosal healing and negatively correlated with disease severity, fecal calprotectin, colon-infiltrating interferon γ and interleukin-17-producing cells, serum and fecal levels of inflammatory cytokines.

CONCLUSION

IDO-dependent expansion of endogenous Tregs should be further explored as a new approach for the induction and maintenance of mucosal healing in patients with UC.

T Cell-Specific Knockout of STAT3 Ameliorates Dextran Sulfate Sodium-Induced Colitis by Reducing the Inflammatory Response

Signal transducer and activator of transcription 3 (STAT3) has a crucial role in various autoimmune disorders including, inflammatory bowel disease (IBD). Our previous study demonstrated that STAT3 activation by IL-6 in colonic epithelial cells exacerbates experimental ulcerative colitis. Activated T lymphocytes are also found in ulcerative colitis patients with intestinal inflammation, but the role of STAT3 in T cells remains elusive. To determine the STAT3 function of T cells in intestinal inflammation, we generated T cell-specific STAT3 knockout (KO) mice and used dextran sulfate sodium (DSS) to induce colitis. In this study, we demonstrated that T cell-specific STAT3 deletion alleviated DSS-induced colitis in mice, resulting in reduced histological scores and myeloperoxidase (MPO) activity. Importantly, the population of T cells in the spleen and lymph nodes was significantly decreased in the control and DSS-induced groups of STAT3 KO mice. In addition, STAT3 deficiency in T cells markedly reduced the production of interferon (IFN)-γ, IL-6, and IL-17A, whereas IL-10 secretion was increased. Collectively, the results suggest that STAT3 in T cells may be a therapeutic target in ulcerative colitis by balancing the immune response through T cell homeostasis.

N-Methylcytisine Ameliorates Dextran-Sulfate-Sodium-Induced Colitis in Mice by Inhibiting the Inflammatory Response

This study aimed to investigate the anti-inflammatory effects of N-methylcytisine (NMC) in a dextran sulfate sodium (DSS)-induced colitis model and explore its possible mechanisms. Experimental colitis was induced by administering the mice with 5% DSS for 7 days. Different doses of NMC (1, 4 and 16 mg/kg) and 5-aminosalicylic acid (100 mg/kg) were given orally once every day for 7 days. The protective effect of NMC was evaluated using the disease activity index, colon length and results of histopathological examination. The possible mechanisms of NMC were explored by evaluating the expression levels of tumour necrosis factor-α, interleukin-1β and interleukin-6 (IL-6) using ELISA and analysing the protein expression levels of nuclear factor (NF)-κB p65, p-NF-κB p65, p-IκB, IκB, IκB kinase (IKK) and p-IKK using western blots. Results demonstrated that the oral administration of NMC attenuated the DSS-induced clinical symptoms and pathological damage. In addition, NMC treatment significantly reduced myeloperoxidase activity and level of pro-inflammatory cytokines. Further studies revealed that NMC blocked the activation of NF-κB by inhibiting IκB and IKK phosphorylation. These findings suggested that NMC exerts anti-inflammatory effects on DSS-induced colitis, and its mechanism may be related to the suppression of NF-κB activation. Thus, NMC may have potential therapeutic value in the treatment of colitis.

Ceramide Synthase 6 Deficiency Enhances Inflammation in the DSS model of Colitis

Colitis, an inflammatory disease of the digestive tract, is increasing in incidence and prevalence. Intestinal inflammation can occur as a consequence of dysfunctions in sphingolipid metabolism. In this study we used ceramide synthase 6 (CerS6) deficient mice, which have a reduced ability to generate long chain C₁₆-ceramide, to investigate the role of this enzyme in dextran sodium salt (DSS)-induced colitis. While CerS6-deficient mice are protected from T cell mediated colitis, in the T cell independent DSS model lack of CerS6 resulted in a more rapid onset of disease symptoms. CerS6-deficient mice maintained low levels of C₁₆-ceramide after DSS treatment, but the inflammatory lipid sphingosine-1-phosphate was significantly increased in colon tissue. In the absence of CerS6, DSS induced more severe pathology in the colon including enhanced neutrophil infiltration. In vivo analysis of myeloperoxidase activity, an enzyme released from neutrophils, was approximately 2.5-fold higher in CerS6-deficient mice compared to wild type. Differences in intestinal permeability did not account for the increase in neutrophils. Our study suggests that lack of CerS6 expression differentially impacts the development of colitis, depending on the model used.

Immuno-PET in Inflammatory Bowel Disease: Imaging CD4-Positive T Cells in a Murine Model of Colitis

Inflammatory bowel diseases (IBDs) in humans are characterized in part by aberrant CD4-positive (CD4+) T-cell responses. Currently, identification of foci of inflammation within the gut requires invasive procedures such as colonoscopy and biopsy. Molecular imaging with antibody fragment probes could be used to noninvasively monitor cell subsets causing intestinal inflammation. Here, GK1.5 cys-diabody (cDb), an antimouse CD4 antibody fragment derived from the GK1.5 hybridoma, was used as a PET probe for CD4+ T cells in the dextran sulfate sodium (DSS) mouse model of IBD. Methods: The DSS mouse model of IBD was validated by assessing changes in CD4+ T cells in the spleen and mesenteric lymph nodes (MLNs) using flow cytometry. Furthermore, CD4+ T cell infiltration in the colons of colitic mice was evaluated using immunohistochemistry. ⁸⁹Zr-labeled GK1.5 cDb was used to image distribution of CD4+ T cells in the abdominal region and lymphoid organs of mice with DSS-induced colitis. Region-of-interest analysis was performed on specific regions of the gut to quantify probe uptake. Colons, ceca, and MLNs were removed and imaged ex vivo by PET. Imaging results were confirmed by ex vivo biodistribution analysis. Results: An increased number of CD4+ T cells in the colons of colitic mice was confirmed by anti-CD4 immunohistochemistry. Increased uptake of ⁸⁹Zr-maleimide-deferoxamine (malDFO)-GK1.5 cDb in the distal colon of colitic mice was visible in vivo in PET scans, and region-of-interest analysis of the distal colon confirmed increased activity in DSS mice. MLNs from colitic mice were enlarged and visible in PET images. Ex vivo scans and biodistribution confirmed higher uptake in DSS-treated colons (DSS, 1.8 ± 0.40; control, 0.45 ± 0.12 percentage injected dose [%ID] per organ, respectively), ceca (DSS, 1.1 ± 0.38; control, 0.35 ± 0.09 %ID per organ), and MLNs (DSS, 1.1 ± 0.58; control, 0.37 ± 0.25 %ID per organ). Conclusion:⁸⁹Zr-malDFO-GK1.5 cDb detected CD4+ T cells in the colons, ceca, and MLNs of colitic mice and may prove useful for further investigations of CD4+ T cells in preclinical models of IBD, with potential to guide development of antibody-based imaging in human IBD.

Immunological effects of reduced mucosal integrity in the early life of BALB/c mice

Certain stimuli at the gut barrier may be necessary in early life to establish a proper balance of immune tolerance. We evaluated a compromised barrier in juvenile mice in relation to microbiota and local and systemic immunity. BALB/c mice were treated with a low dose of dextran sulfate sodium (DSS) with or without ampicillin and lipopolysaccharide (LPS) to clarify the importance of microbial antigens and interaction between microbial-associated patterns and toll-like receptors. The barrier breach resulted in increased plasma LPS, which was highest in mice treated simultaneously with ampicillin. Adding LPS in the food reduced its levels in plasma. Regulatory T cells were acutely increased in mesenteric lymph nodes (MLN) and spleen during DSS treatment regardless of simultaneous ampicillin treatment. In contrast, NK T and NK cells decreased in MLN and in spleen. This acute DSS effect was reflected in fold changes of haptoglobin and Il1a in colon, and this was also more pronounced in mice simultaneously treated with ampicillin. On day 1 post-treatment, major upregulations of Ifng, Foxp3, Il1b, Il2, and Il6 genes in colon were only observed in the mice simultaneously treated with ampicillin. A two-fold upregulation of colonic Foxp3 and Il1a was evident 25 days post-treatment. DSS skewed the microbiota in favor of Gram negative phyla. Therefore, increased permeability induced tolerogenic immunity independent of microbiota, and this was enhanced by LPS stimulation.

Quantitative analysis of mucosal oxygenation using ex vivo imaging of healthy and inflamed mammalian colon tissue

Colonic inflammation is associated with decreased tissue oxygenation, significantly affecting gut homeostasis. However, the crosstalk between O2 consumption and supply in the inflamed tissue are not fully understood. Using a murine model of colitis, we analysed O2 in freshly prepared samples of healthy and inflamed colon tissue. We developed protocols for efficient ex vivo staining of mouse distal colon mucosa with a cell-penetrating O2 sensitive probe Pt-Glc and high-resolution imaging of O2 concentration in live tissue by confocal phosphorescence lifetime-imaging microscopy (PLIM). Microscopy analysis revealed that Pt-Glc stained mostly the top 50-60 μm layer of the mucosa, with high phosphorescence intensity in epithelial cells. Measured O2 values in normal mouse tissue ranged between 5 and 35 μM (4-28 Torr), tending to decrease in the deeper tissue areas. Four-day treatment with dextran sulphate sodium (DSS) triggered colon inflammation, as evidenced by an increase in local IL6 and mKC mRNA levels, but did not affect the gross architecture of colonic epithelium. We further observed an increase in oxygenation, partial activation of hypoxia inducible factor (HIF) 1 signalling, and negative trends in pyruvate dehydrogenase activity and O2 consumption rate in the colitis mucosa, suggesting a decrease in mitochondrial respiration, which is known to be regulated via HIF-1 signalling and pyruvate oxidation rate. These results along with efficient staining with Pt-Glc of rat and human colonic mucosa reveal high potential of PLIM platform as a powerful tool for the high-resolution analysis of the intestinal tissue oxygenation in patients with inflammatory bowel disease and other pathologies, affecting tissue respiration.

Anti-Inflammatory Effects of Hyperbaric Oxygenation during DSS-Induced Colitis in BALB/c Mice Include Changes in Gene Expression of HIF-1α, Proinflammatory Cytokines, and Antioxidative Enzymes

Reactive oxygen species (ROS) and nitrogen species have an indispensable role in regulating cell signalling pathways, including transcriptional control via hypoxia inducible factor-1α (HIF-1α). Hyperbaric oxygenation treatment (HBO₂) increases tissue oxygen content and leads to enhanced ROS production. In the present study DSS-induced colitis has been employed in BALB/c mice as an experimental model of gut mucosa inflammation to investigate the effects of HBO₂ on HIF-1α, antioxidative enzyme, and proinflammatory cytokine genes during the colonic inflammation. Here we report that HBO₂ significantly reduces severity of DSS-induced colitis, as evidenced by the clinical features, histological assessment, impaired immune cell expansion and mobilization, and reversal of IL-1β, IL-2, and IL-6 gene expression. Gene expression and antioxidative enzyme activity were changed by the HBO₂ and the inflammatory microenvironment in the gut mucosa. Strong correlation of HIF-1α mRNA level to GPx1, SOD1, and IL-6 mRNA expression suggests involvement of HIF-1α in transcriptional regulation of these genes during colonic inflammation and HBO₂. This is further confirmed by a strong correlation of HIF-1α with known target genes VEGF and PGK1. Results demonstrate that HBO₂ has an anti-inflammatory effect in DSS-induced colitis in mice, and this effect is at least partly dependent on expression of HIF-1α and antioxidative genes.

New insights into salvianolic acid A action: Regulation of the TXNIP/NLRP3 and TXNIP/ChREBP pathways ameliorates HFD-induced NAFLD in rats

Salvianolic acid A (SalA), one of the most efficacious polyphenol compounds extracted from Radix Salvia miltiorrhiza (Danshen), has been shown to possess many potential pharmacological activities. This study aimed to investigate whether SalA has hepatoprotective effects against high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) and to further explore the mechanism underlying this process. SalA treatment significantly attenuated HFD-induced obesity and liver injury, and markedly decreased lipid accumulation in HFD-fed rat livers. Moreover, SalA treatment ameliorated HFD-induced hepatic inflammation and oxidative stress by decreasing hepatotoxic levels of cytokines, suppressing the overproduction of reactive oxygen species (ROS) and methane dicarboxylic aldehyde (MDA) and preventing the decreased expression of superoxide dismutase (SOD). Importantly, SalA reversed the HFD- or palmitic acid (PA)-induced activation of the NLRP3 inflammasome, the nuclear translocation of ChREBP and the up-regulation of FAS, and these effects were accompanied by TXNIP down-regulation. However, TXNIP siRNA treatment partially abrogated the above-mentioned effects of SalA in PA-treated HepG2 cells. Together, our results demonstrated, for the first time, that SalA protects against HFD-induced NAFLD by ameliorating hepatic lipid accumulation and inflammation, and these protective effects may partially due to regulation of the TXNIP/NLRP3 and TXNIP/ChREBP pathways.

Noninvasive Longitudinal Study of a Magnetic Resonance Imaging Biomarker for the Quantification of Colon Inflammation in a Mouse Model of Colitis

BACKGROUND

Colonoscopy is the gold standard to diagnose and follow up the evolution of inflammatory bowel diseases. However, this technique can still present a risk of severe complications, a general discomfort in patients, and its diagnostic value is limited to the visualization of the colon mucosal changes. Magnetic resonance imaging (MRI) is emerging as a noninvasive imaging technique of choice to overcome these limitations. The aim of this work was to evaluate the potential of colon wall thickness measured using MRI as an in vivo imaging biomarker of inflammation for inflammatory bowel disease in an animal model of this disease.

METHODS

On day 0, 2% or 3% Dextran sodium sulfate was added to the drinking water of mice (n = 10/group) for 5 days. Six mice were left as controls. Animals were imaged with colonoscopy and MRI on days 7, 11, and 21 to study the colitis progression. Histology was performed at the end of the protocol.

RESULTS

The colon wall thickness measured in Dextran sodium sulfate-treated animals was shown to be significantly and dose dependently increased compared to controls. Colonoscopy showed similar results and excellently correlated with MRI measurements and histology. The proposed protocol showed high robustness, with negligible interoperator and intraoperator variability.

CONCLUSIONS

The findings of this investigation suggest the feasibility of using MRI for the noninvasive assessment of colon wall thickness as a robust surrogate biomarker for colon inflammation detection and follow-up. The data presented show the potential of MRI in in vivo preclinical longitudinal studies, including testing of new drugs or investigation of inflammatory bowel disease development mechanisms.

Decreased Frequency of Intestinal Regulatory CD5+ B Cells in Colonic Inflammation

Background

CD5⁺ B cells are a type of regulatory immune cells, though the involvement of this B cell subset in intestinal inflammation and immune regulation is not fully understood.

Methods

We examined the distribution of CD5⁺ B cells in various mouse organs. Expression levels of CD11b, IgM, and toll-like receptor (TLR)-4 and -9 in B cells were evaluated. In vitro, TLR-stimulated IL-10 production by colonic lamina propria (LP) CD5⁺ and CD5^- B cells was measured. In vivo, mice with acute or chronic dextran sulfate sodium (DSS)-induced colonic injury were examined, and the frequency of colonic LP CD5⁺ B cells in those was assessed by flow cytometry.

Results

The expression level of TLR9 was higher in colonic LP CD5⁺ B cells as compared to CD5^- B cells. Colonic LP CD5⁺ B cells produced greater amounts of IL-10 following stimulation with TLR ligands, especially TLR9, as compared with the LP CD5^- B cells. Acute intestinal inflammation transiently decreased the frequency of colonic LP CD5⁺ B cells, while chronic inflammation induced a persistent decrease in colonic LP CD5⁺ B cells and led to a CD5^- B cell-dominant condition.

Conclusion

A persistent altered mucosal B cell population caused by chronic gut inflammation may be involved in the pathogenesis of inflammatory bowel diseases.

Intestinal Inflammation Leads to a Long-lasting Increase in Resistance to Systemic Salmonellosis that Requires Macrophages But Not B or T Lymphocytes at the Time of Pathogen Challenge

BACKGROUND

Intestinal inflammation is associated with systemic translocation of commensal antigens and the consequent activation of B and T lymphocytes. The long-term consequences of such immune activation are not completely understood.

METHODS

C57BL/6 mice were subjected to 2 courses of treatment with dextran sulfate sodium (DSS) to induce colitis. Two to 7 weeks after the DSS treatment, the mice were infected intraperitoneally with Salmonella enterica serovar Typhimurium. The outcome of infection was evaluated based on survival and tissue pathogen burden.

RESULTS

Mice that had recovered from DSS colitis displayed a significant increase in resistance to S. Typhimurium infection as indicated by improved survival and decreased tissue pathogen numbers. The colitis-induced increase in resistance to systemic salmonellosis lasted for as long as 7 weeks after discontinuing DSS and was dependent on T lymphocytes but not on B cells. Interestingly, depletion of CD4 and CD8 T cells just before the Salmonella infection did not alter the colitis-induced increase in resistance. Mice that had recovered from colitis had evidence of persistent activation of resident peritoneal macrophages and enhanced Salmonella-induced neutrophil recruitment to the peritoneum. Macrophage depletion with clodronate liposomes abrogated the colitis-induced increase in resistance to Salmonella.

CONCLUSIONS

Taken together, our results indicate that DSS colitis leads to a long-lasting increase in resistance to Salmonella infection that is initiated in a T cell-dependent manner but is ultimately mediated independently of B and T cells as a result of persistent changes in innate immune cell function.

T regulatory cells and B cells cooperate to form a regulatory loop that maintains gut homeostasis and suppresses dextran sulfate sodium-induced colitis

Regulatory T cells (Tregs) and B cells present in gut-associated lymphoid tissues (GALT) are both implicated in the resolution of colitis. However, how the functions of these cells are coordinated remains elusive. We used the dextran sulfate sodium (DSS)-induced colitis model combined with gene-modified mice to monitor the progression of colitis, and simultaneously examine the number of Tregs and B cells, and the production of IgA antibodies. We found that DSS-treated mice exhibited more severe colitis in the absence of B cells, and that the adoptive transfer of B cells attenuated the disease. Moreover, the transfer of IL-10(-/-) B cells also attenuated colitis, suggesting that B cells inhibited colitis through an interleukin-10 (IL-10)-independent pathway. Furthermore, antibody depletion of Tregs resulted in exacerbated colitis. Intriguingly, the number of GALT Tregs in B cell-deficient mice was significantly decreased during colitis and the adoptive transfer of B cells into these mice restored the Treg numbers, indicating that B cells contribute to Treg homeostasis. We also found that B cells induced the proliferation of Tregs that in turn promoted B-cell differentiation into IgA-producing plasma cells. These results demonstrate that B cells and Tregs interact and cooperate to prevent excessive immune responses that can lead to colitis.