DSS-induced Chronic Colitis Research Articles

A20 Restores Impaired Intestinal Permeability and Inhibits Th2 Response in Mice with Colitis.

The etiology of inflammatory bowel disease is multifactorial and still obscure. The protective role of ubiquitin E3 ligase A20 (A20) in colitis needs to be further elucidated. This study aimed to investigate whether A20 exogenous administration restored impaired intestinal permeability and inhibited T helper (Th)2 response in mice with colitis. The effect of A20 overexpression in colonic mucosa on epithelial barrier function and T cell differentiation was evaluated in mice with dextran sulfate sodium (DSS)-induced chronic colitis. A20 rectal treatment alleviated DSS-induced chronic colitis and restored impaired intestinal permeability. Oral challenge with 2% DSS elicited a Th2-type response in mice with colitis, and A20 rectal treatment inhibited CD4+ interleukin (IL)-4+ T cell differentiation and proliferation. In addition, the RNA expressions of Th2-related costimulatory molecular T-cell immunoglobulin and mucin domain (TIM)-1 and IL-4 were suppressed, while thrombospondin (TSP)-1 and interferon (IFN)-γ expressions were upregulated, after A20 rectal administration. A20 rectal treatment restores impaired intestinal permeability and inhibits activated Th2 cell response in mice with colitis.

Effect of Long-Term Intake of Dietary Titanium Dioxide Nanoparticles on Intestine Inflammation in Mice.

Early stage exposure of foodborne substances, such as brightening agent titanium dioxide nanoparticles (TiO2 NPs), can cause long-term effects in adulthood. We aimed to explore the potential adverse effect of long-term dietary intake of TiO2 NPs. After feeding for 2-3 months from weaning, TiO2 NPs-exposed mice showed lower body weight and induced intestinal inflammation. However, this phenomenon was not observed in gut microbiota-removed mice. TiO2 NPs exposure rarely affected the diversity of microbial communities, but significantly decreased the abundance of several probiotic taxa including Bifidobacterium and Lactobacillus. Additionally, TiO2 NPs aggravated DSS-induced chronic colitis and immune response in vivo, and reduced the population of CD4+T cells, regulatory T cells, and macrophages in mesenteric lymph nodes. Therefore, dietary TiO2 NPs could interfere with the balance of immune system and dynamic of gut microbiome, which may result in low-grade intestinal inflammation and aggravated immunological response to external stimulus, thus introducing potential health risk.

Autotaxin-Lysophosphatidic Acid Axis Blockade Improves Inflammation by Regulating Th17 Cell Differentiation in DSS-Induced Chronic Colitis Mice.

Autotaxin-lysophosphatidic acid (ATX-LPA) axis is closely associated with several inflammation-related diseases. In the colonic mucosa of patients with chronic ulcerative colitis (UC), the expression of ATX and the percentage of Th17 cells are found to increase. However, it is unclear whether ATX-LPA axis affects the differentiation of Th17 cells in chronic UC. To investigate whether ATX-LPA axis contributes to Th17 cell differentiation, a mouse model of chronic UC was established by drinking water with DSS at intervals. ATX inhibitor was used as an intervention. The disease active index (DAI), colonic weight to length ratio, colon length, colon histopathology, and MAdCAM-1 were observed. Additionally, the expression of ATX, LPA receptor, CD34, IL-17A, IL-21, IL-6, ROR-γt, STAT3 in colonic tissue, and the percentage of Th17 cells in spleens and mesenteric lymph nodes (MLNs) were measured using different methods. ATX blockade was able to relieve symptoms and inflammatory response of DSS-induced chronic colitis. The DAI and colonic weight to length ratio were apparently decreased, while the colon length was increased. The pathological damage and colitis severity were lighter in the inhibitor group than that in the DSS group. Inhibiting ATX reduced the expression of ATX, LPA receptor, and CD34 and also decreased the percentages of Th17 cells in spleens and MLNs and the expressions of IL-17A and IL-21, as well as the factors in Th17 cell signaling pathway including IL-6, ROR-γt, and STAT3 in colonic tissue. ATX-LPA axis blockade could alleviate inflammation by suppressing Th17 cell differentiation in chronic UC.

Tu1765 – Histone 3 Lysine 27 Acetylation Profiling Reveals Its Role in the Chronic Dss-Induced Colitis Mouse Model

Tu1765 – Histone 3 Lysine 27 Acetylation Profiling Reveals Its Role in the Chronic Dss-Induced Colitis Mouse Model

3375 Chronic inflammation promotes intestinal macrophages to become modulators of the Notch pathway

OBJECTIVES/SPECIFIC AIMS: The purpose of this research was to investigate how chronic inflammation promotes the generation of proinflammatory intestinal macrophages and if macrophages contribute to intestinal inflammation through Notch activation. METHODS/STUDY POPULATION: We utilized two animal models of chronic colitis, the chronic DSS-induced colitis mouse model and the spontaneous enterocolitis development in IL-10-deficient mice to investigate the role of chronic inflammation in the generation of proinflammatory intestinal macrophages and its influence in notch signaling. Bone marrow-derived monocytes were collected from each group and differentiated into macrophages (BMM) for gene and protein analysis. Ex vivo phenotypical and functional analysis of colonic macrophages was assessed as was the presence of goblet cells and mucosal T cells. In addition, we analyzed the development of goblet cell differentiation in colonoids in a co-culture system with proinflammatory macrophages. RESULTS/ANTICIPATED RESULTS: Our chronic inflammation models revealed an increase in proinflammatory macrophages present in the lamina propria and that these cells expressed significantly higher levels of notch ligand, Jagged1. Jagged 1 has been shown to enhance TH1 differentiation and T cells isolated from the mucosa of both chronic colitis models display strong TH1 skewing compared to controls. Chronic inflammation also contributes to intestinal barrier defects, enhanced permeability and bacterial translocation. We believe this enhanced intestinal permeability and subsequent bacterial translocation promote Jagged1 expression in intestinal macrophages. To support this concept, we show TLR stimulation induces the upregulation of Jagged1 in BMM. Additionally, the generation of BMM from our chronic DSS-induced colitis mice or age matched controls, revealed BMM derived from a host of chronic inflammation were skewed to a proinflammatory state prior to stimulation showing increased gene expression of several proinflammatory molecules including IL-1α, IL-1β, IL-12 and TNF-α. This would suggest monocytes migrating to the intestinal mucosa have more potential to become proinflammatory instead of traditional anti-inflammatory macrophages. Furthermore, proinflammatory notch ligand-positive macrophages co-cultured with colonoids, derived from unperturbed mice, significantly decreased the number of mucus producing goblet cells. In support of this observation, notch activation in intestinal stem cells promote absorptive (i.e. colonocytes) cell differentiation and prevents secretory cell (i.e. goblet cells) differentiation. DISCUSSION/SIGNIFICANCE OF IMPACT: Taken together, our results strongly suggest chronic inflammation modulates macrophages role in maintaining intestinal homeostasis through possible notch activation in both T cells and the intestinal epithelial barrier.

Disease Development Is Accompanied by Changes in Bacterial Protein Abundance and Functions in a Refined Model of Dextran Sulfate Sodium (DSS)-Induced Colitis

Using the acute dextran sulfate sodium (DSS)-induced colitis model, studies have demonstrated that intestinal inflammation is accompanied by major changes in the composition of the intestinal microbiota. Only little is known about the microbial changes and more importantly their functional impact in the chronic DSS colitis model. We used a refined model of chronic DSS-induced colitis that reflects typical symptoms of the human disease without detrimental weight loss usually observed in DSS models. We sampled cecum and colon content as well as colon mucus from healthy and diseased mouse cohorts ( n = 12) and applied 16S rRNA gene sequencing and metaproteomics. An increase of Prevotella sp. in both colon content and mucus was observed. Functional differences were observed between sample types demonstrating the importance of separately sampling lumen content and mucus. The abundance of Desulfovibrio, a sulfate-reducing bacterium, was positively associated with the carbon metabolism. Lachnoclostridium was positively correlated to both vitamin B6 and tryptophan metabolism. In summary, functional changes in the distal colon caused by DSS treatment were more pronounced in the mucus-associated microbiota than in the microbiota present in the distal colon content.

Profiling of histone 3 lysine 27 acetylation reveals its role in a chronic DSS-induced colitis mouse model.

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the gastrointestinal tract. In current dogma, pathogenesis of IBD is attributed to the dysregulated mucosal immune response to gut flora in genetically susceptible individuals, but the genetics evidence from GWAS studies so far is insufficient to explain the observed heritability in IBD. For this discordance, epigenetics has emerged to be one of the important causes. Recent studies have reported that histone acetylation is correlated with the development of IBD, whereas its role and underlying molecular mechanism in the disease still remain elusive. Here, we established a dextran sulfate sodium (DSS)-induced chronic colitis model and performed RNA-sequencing (RNA-seq) and Chromatin Immunoprecipitation followed by NGS sequencing (ChIP-seq) for H3K27ac in the mice colon tissues to investigate whether H3K27ac is involved in the development of intestinal inflammation. We found that the global H3K27ac level and distribution in colon tissue had no significant difference after DSS treatment, while H3K27ac signals were significantly enriched in the typical-enhancers of the DSS group compared with the control. By combining with RNA-seq data (fold change >2), we identified 56 candidate genes as potential target genes for H3K27ac change upon DSS treatment. We further predicted transcription factors (TFs) involved in DSS-induced colitis according to the enhancers with increased H3K27ac. H3K27ac increase in special typical-enhancers in the DSS group is possibly related to the development of intestinal inflammation by up-regulating adjacent gene expression and shifting TF networks, which will provide new insight into the pathogenesis and therapy of IBD.

Changes of intestinal mucosal barrier in mice with chronic ulcerative colitis

Objective: To study the damage and mechanism of intestinal mucosal barrier function in mice with ulcerative colitis induced by Dextran sulphate sodium (DSS). Methods: Mice models of chronic ulcerative colitis induced by DSS were established. The mice were completely randomized into normal control group and DSS group, 25 mice in each group. The body weight and colon length of the mice were monitored. The pathological examination of colon tissue was confirmed the success of the model and assessed the integrity of the colonic mucosal barrier; Evan's Blue's intestinal permeability analysis assessed the function of colon mucosal barrier; immunofluorescence staining and Western blot were used to evaluate the expression of intestinal mucosal barrier integrity-related proteins. Results: Compared with the normal control group, the DSS group had lower body weight [(25.6±0.7)g vs (23.5±0.7)g, t=2.14, P<0.05], and the colon length was shorter [(7.3±0.4)cm vs (5.6±0.2)cm, t=3.975, P<0.001]; colonic pathological results showed that the intestinal mucosa became thinner and part of the intestinal mucosa was defective; Evan's Blue instilled into the intestinal lumen was more abundant into the intestinal mucosa, and the optical density at 620 nm (OD(620))/colon tissue weight (g) was higher [(0.11±0.01) vs (0.15±0.01), t=4.174, P<0.05]; immunofluorescence and Western blot results showed lower expression of ZO-1, Claudin-1, and F-actin in colonic mucosa. Conclusion: The structure and function of intestinal mucosal barrier in DSS-induced chronic ulcerative colitis mice is impaired.

IL-33 Protects Mice against DSS-Induced Chronic Colitis by Increasing Both Regulatory B Cell and Regulatory T Cell Responses as Well as Decreasing Th17 Cell Response.

Background Previously, we have reported that IL-33 functioned as a protective modulator in dextran sulfate sodium- (DSS-) induced chronic colitis by suppressing Th17 cell response in colon lamina propria and IL-33 induced both regulatory B cells (Bregs) and regulatory T cells (Tregs) in mesenteric lymph nodes (MLNs) of mice with DSS-induced acute colitis. Moreover, we speculated that IL-33 would promote the Treg or Breg responses leading to the attenuation of DSS-induced chronic colitis. So, we investigated the role of IL-33 on Bregs and Tregs in the MLN of DSS-induced chronic colitis mice. Methods IL-33 was administered by intraperitoneal injection to mice with DSS-induced chronic colitis. Clinical symptoms, colon length, and histological changes were determined. The production of cytokines was measured by ELISA. The T and B cell subsets were measured by flow cytometry. The expression of mRNA of transcription factors was measured by quantitative real-time PCR. Results We show that IL-33 treatment increases both Breg and Treg responses in the MLN of mice with DSS-induced chronic colitis. Moreover, IL-33 treatment also decreases Th17 cell response in the MLN of mice with DSS-induced chronic colitis. Conclusion Our data provide clear evidence that IL-33 plays a protective role in DSS-induced chronic colitis, which is closely related to increasing Breg and Treg responses in the MLN of mice as well as suppressing Th17 cell responses.

Severity of local inflammation does not impact development of fibrosis in mouse models of intestinal fibrosis

Intestinal fibrosis is thought to be a consequence of excessive tissue repair, and constitutes a common problem in patients with Crohn’s disease (CD). While fibrosis seems to require inflammation as a prerequisite it is unclear whether the severity or persistence of inflammation influences the degree of fibrosis. Our aim was to investigate the role of sustained inflammation in fibrogenesis. For the initiation of fibrosis in vivo the models of Il10−/− spontaneous colitis, dextran sodium sulfate (DSS)-induced chronic colitis and heterotopic transplantation were used. In Il10−/− mice, we determined a positive correlation between expression of pro-inflammatory factors (Il1β, Tnf, Ifnγ, Mcp1 and Il6). We also found a positive correlation between the expression of pro-fibrotic factors (Col3a1 Col1a1, Tgfβ and αSma). In contrast, no significant correlation was determined between the expression of pro-inflammatory Tnf and pro-fibrotic αSma, Col1a1, Col3a1, collagen layer thickness and the hydroxyproline (HYP) content. Results from the DSS-induced chronic colitis model confirmed this finding. In the transplantation model for intestinal fibrosis a pronounced increase in Mcp1, inos and Il6 in Il10−/− as compared to WT grafts was observed, indicating more severe inflammation in Il10−/− grafts. However, the increase of collagen over time was virtually identical in both Il10−/− and WT grafts. Severity of inflammation during onset of fibrogenesis did not correlate with collagen deposition. Although inflammation might be a pre-requisite for the initiation of fibrosis our data suggest that it has a minor impact on the progression of fibrosis. Our results suggest that development of fibrosis and inflammation may be disconnected. This may be important for explaining the inefficacy of anti-inflammatory treatments agents in most cases of fibrotic inflammatory bowel diseases (IBD).

Mesenchymal stem cell transplantation improves chronic colitis-associated complications through inhibiting the activity of toll-like receptor-4 in mice

BackgroundA variety of extra-intestinal manifestations (EIMs), including hepatobiliary complications, are associated with inflammatory bowel disease (IBD). Mesenchymal stem cells (MSCs) have been shown to play a potential role in the therapy of IBD. This study was designed to investigate the effect and mechanism of MSCs on chronic colitis-associated hepatobiliary complications using mouse chronic colitis models induced by dextran sulfate sodium (DSS).MethodsDSS-induced mouse chronic colitis models were established and treated with MSCs. Severity of colitis was evaluated by disease activity index (DAI), body weight (BW), colon length and histopathology. Serum lipopolysaccharide (LPS) levels were detected by limulus amebocyte lysate test (LAL-test). Histology and liver function of the mice were checked correspondingly. Serum LPS levels and bacterial translocation of mesenteric lymph nodes (MLN) were detected. Pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-17A (IL-17A), Toll receptor 4 (TLR4), TNF receptor-associated factor 6 (TRAF6) and nuclear factor kappa B (NF-κB) were detected by immunohistochemical staining, western blot analysis and real-time PCR, respectively.ResultsThe DSS-induced chronic colitis model was characterized by reduced BW, high DAI, worsened histologic inflammation, and high levels of LPS and E. coli. Liver histopathological lesions, impaired liver function, enhanced proteins and mRNA levels of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB were observed after DSS administration. MSCs transplantation markedly ameliorated the pathology of colon and liver by reduction of LPS levels and proteins and mRNA expressions of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB.ConclusionsMSCs can improve chronic colitis-associated hepatobiliary complications, probably by inhibition of enterogenous endotoxemia and hepatic inflammation through LPS/TLR4 pathway. MSCs may represent a novel therapeutic approach for chronic colitis-associated hepatobiliary complications.

Interaction between sphingosine kinase/sphingosine 1 phosphate and transforming growth factor-β/Smads pathways in experimental intestinal fibrosis. An in vivo immunohistochemical study.

A concomitant action of multiple profibrotic mediators appears crucial in the development and progression of fibrosis. Sphingosine kinase/sphingosine 1 phosphate and transforming growth factor- β/Smads pathways are both involved in pathogenesis of fibrosis in several organs by controlling differentiation of fibroblasts to myofibroblasts and the epithelial-to-mesenchymal transition. However, their direct involvement in chronic colitis-associated fibrosis it is not yet known. In this study we evaluated the immunohistochemical expression of some proteins implicated in sphingosine kinase/sphingosine 1 phosphate and transforming growth factor-β/Smads pathways in Dextrane Sodium Sulphate (DSS)- induced colorectal fibrosis in mice. Compared to control mice, DSS-induced chronic colitis mice developed a marked intestinal fibrosis associated with a concomitant overexpression of TGF-β, p-Smad3, α-SMA, collagen I-III, SPHK1, RhoA, PI3K, Akt, p-Akt, p-mTOR. This study highlights the relationship between the two pathways and the possible role of SPHK1 in the intestinal fibrosis. These results, if confirmed by in vitro studies, may have important clinical implications in the development of new therapeutical approaches in inflammatory bowel disease.

Restoration of mucosal integrity and epithelial transport function by concomitant anti-TNFα treatment in chronic DSS-induced colitis.

Chronic DSS treatment caused a loss of NHE3 and PDZK1 in the brush border region of the absorptive enterocyte and decreases colonic fluid absorption. In DSS-induced colitis, anti-TNFα treatment reduced mucosal immune cell infiltration and expression of the pro-inflammatory cytokines IL-1β and TNFα. In DSS-induced colitis, anti-TNFα treatment normalized NHE3-mediated fluid absorption and restored NHE3 and PDZK1 location in the enterocytes. In DSS-induced colitis, anti-TNFα treatment decreased inflammatory activity, improved mucosal integrity, and restored transport function.

Dro1/Ccdc80 inactivation promotes AOM/DSS-induced colorectal carcinogenesis and aggravates colitis by DSS in mice.

Colorectal carcinogenesis is a progressive multistep process involving the sequential accumulation of genetic alterations in tumor suppressor genes and oncogenes. Downregulated by oncogenes 1 (Dro1/Ccdc80) has been shown to be a potent tumor suppressor of colorectal carcinogenesis in the genetic ApcMin/+ mouse model. In ApcMin/+ mice, loss of DRO1 strongly increases colonic tumor multiplicity and leads to the regular formation of adenocarcinoma in the colon. To investigate DRO1's role in chemically induced as well as inflammation-associated colorectal carcinogenesis, the effect of Dro1 inactivation was studied in mice subjected to the carcinogen azoxymethane (AOM) and upon combined treatment with AOM and the proinflammatory agent dextran sodium sulfate (DSS), respectively. Loss of DRO1 increases multiplicity of preneoplastic aberrant crypt foci and colonic tumors upon administration of AOM. Combined treatment with AOM and DSS leads to increased colonic tumor number and promotes formation of adenocarcinoma in the colon. Moreover, Dro1 inactivation aggravates histological signs of acute and chronic DSS-induced colitis, strongly enlarges the size of ulcerative lesions in the intestinal lining, and exacerbates clinical signs and morbidity by DSS. Our results demonstrate DRO1 to be a strong tumor suppressor in the chemically induced colon carcinogenic mouse model. Additionally, we demonstrate DRO1 to inhibit colitis-associated colon cancer formation and uncover a novel putative role for DRO1 in inflammatory bowel disease.

Effect of Eucommia ulmoides Leaf Extract on Chronic Dextran Sodium Sulfate-Induced Colitis in Mice.

Ulcerative colitis (UC) is a refractory disease that causes chronic inflammation or ulceration in the mucosa of the large intestine with multiple relapses. Although several drugs, including 5-aminosalicylic acid, steroids, immunosuppressants, and infliximab, are used for UC therapy, patients suffer from side effects of these drugs, and a new safer therapeutic agent is desired. Eucommia ulmoides OLIV. leaf extract (ELE) has an anti-inflammatory effect. Therefore, we examined the effect of ELE on UC using a chronic dextran sulfate sodium (DSS)-induced colitis model in mice. Chronic DSS-induced colitis was triggered by alternately repeating 5 days' DSS and 7 days' water administration in mice for 29 d. The severity of DSS-induced colitis was evaluated by daily body weight and bloody stool score, and colon length and myeloperoxidase (MPO) activity in colon tissue on day 29. ELE (3 or 9%) was administered in combination by feeding for 29 d, and the effect on colitis was evaluated. The mice given DSS exhibited chronic colitis symptoms with body weight loss, increased bloody stool score and MPO activity, and shortened colon length. Administration of 3 or 9% ELE suppressed the body weight loss, bloody stool score, colon shortening, and MPO activity in a dose-dependent manner. Histological analysis showed that the ELE-treated mice had less damages and leukocyte infiltration in the mucosal layer of the large intestine compared to DSS alone group. These results suggested that ELE has the potential to prevent the development of DSS-induced colitis and a therapeutic effect on UC in a safe manner.

BCL2 Regulates Differentiation of Intestinal Fibroblasts.

Fibrosis in patients with Crohn's disease (CD) results from an imbalance toward excessive fibrous tissue formation driven by fibroblasts. Activation of fibroblasts is linked to the B-cell lymphoma 2 (BCL2) family, which is involved in the induction of apoptosis. We investigated the impact of BCL2 repression on fibrogenesis. The model of dextran sodium sulfate (DSS)-induced chronic colitis and the heterotopic transplantation model of fibrosis were used. Following the administration of the BCL2 antagonist (ABT-737, 50 mg/kg/d), collagen layer thickness and hydroxyproline (HYP) content were determined. Fibroblasts were stimulated with the BCL2 antagonist (0.01-100 µM). BCL2, alpha smooth muscle actin (αSMA), and collagen I (COL1A1) were determined by quantitative polymerase chain reaction (qPCR), immunofluorescence microscopy (IF), and western blot (WB). mRNA expression pattern was determined by next-generation sequencing (NGS). Collagen layer thickness was significantly decreased in both DSS-induced chronic colitis and the transplantation model of fibrosis upon BCL2 antagonist administration compared with vehicle. Decreased HYP content confirmed the preventive effects of the BCL2 antagonist on fibrosis. In vitro, a significant increase in PI+/annexin V+ human colonic fibroblasts was determined by fluorescence-activated cell sorting upon treatment with high-dose BCL2 antagonist; at a lower dose, αSMA, COL1A1, and TGF were decreased. NGS, IF, and qPCR revealed decreased expression and nuclear translocation of GATA6 and SOX9, known for reprogramming fibroblasts. BCL2 antagonist administration partially prevented fibrogenesis in both fibrosis models. The BCL2 antagonist reduced the expression of TGFβ-induced factors involved in differentiation of myofibroblasts, and therefore might represent a potential treatment option against CD-associated fibrosis.

Helicobacter pylori Colonization Protects Against Chronic Experimental Colitis by Regulating Th17/Treg Balance.

Epidemiological studies have demonstrated an inverse association between Helicobacter pylori infection and the risk of developing inflammatory bowel disease (IBD). The mechanisms by which H. pylori infection protects against IBD are unclear. Here, we explored the possible protective effects and mechanisms of gastric H. pylori colonization on a chronic colitis model, with focus on whether H. pylori exerted its effects through regulating Th17/Treg immune responses. Chronic colitis was induced by dextran sulfate sodium (DSS) treatment. Flow cytometry analysis was performed to determine Th17 cells, Treg cells, and M1/M2 macrophages in the spleen, mesenteric lymph nodes, and colonic lamina propria. The levels of Th17- and Treg-associated cytokines were measured by quantitative polymerase chain reaction. The direct effect of H. pylori extract on the polarization status of macrophages was determined in vitro. Gastric H. pylori colonization significantly ameliorated the severity of chronic DSS-induced colitis. H. pylori colonization decreased Th17 cells and mRNA levels of IL-17A, IL-17F, and IL-21 in the colon. Simultaneously, H. pylori colonization increased Treg cells and IL-10 expression. As to cytokines driving Th17 and Treg differentiation, H. pylori colonization increased TGFβ and decreased IL-6 and IL-23. Moreover, H. pylori colonization significantly increased M2 macrophages in the colon. In vitro, H. pylori extract promotion of M2 macrophage polarization was dependent on the presence of CagA. H. pylori colonization protects against chronic DSS-induced colitis via balancing Th17/Treg responses and shifting macrophages toward anti-inflammatory M2 phenotype. Our results strengthen the rationale for gastric H. pylori colonization affecting the immune homeostasis of the colon.

A characterization of pro-inflammatory cytokines in dextran sulfate sodium-induced chronic relapsing colitis mice model

Repeated cycles of dextran sulfate sodium (DSS) administration in mice, inducing chronic relapsing colitis, have been used to mimic human ulcerative colitis (UC). However, no systematic characterization of pro-inflammatory cytokines in these DSS mice has been reported. In this study, the development of colitis was examined by assessment of the disease severity and inflammation in the colon of C57BL/6 mice that received DSS. ELISA was used to analyze the levels of pro-inflammatory cytokines in serum, colon, spleen and supernatant of cultured splenocytes. mRNA levels of the above cytokines in colon and mesenteric lymph node (MLN) were measured with RT-PCR. The mice receiving three cycles of 2% DSS over a 43-day period showed a fluctuating appearance of diarrhea and bloody feces, and a significant reduction in body weight and colon length. When compared with normal control mice, an increase in TNF-α level in serum was detected in the DSS mice, along with a decrease in the amounts of TNF-α, IL-17, IL-1β and IL-6 in the colonic tissue. However, mRNA levels of these cytokines were found to be significantly increased in the colon while decreased in the MLN of the colitis mice. Further, the ELISA assay suggested a pronounced increase of TNF-α production by cultured splenocytes with PMA/ionomycin re-stimulation but no increase in its presence in spleen tissue upon DSS challenge. In conclusion, we have systematically demonstrated the dysregulation of pro-inflammatory cytokines in the DSS-induced chronic relapsing colitis model, which will provide markers to test emerging therapeutic strategies by this model.

Adipose-derived stem cells ameliorate colitis by suppression of inflammasome formation and regulation of M1-macrophage population through prostaglandin E2

Inflammatory bowel disease (IBD) is an idiopathic disease caused by a dysregulated immune response to intestinal microbes in an individual with a genetic predisposition. Therefore, alleviation of inflammation is very important to treat IBD. Mesenchymal stem cells (MSCs) have been highlighted as new candidates for treating autoimmune disease based on their immunomodulatory properties. In this study, we investigated the anti-inflammatory mechanism and therapeutic effects of adipose tissue-derived MSCs (ASCs) using THP-1 macrophages and dextran sodium sulfate (DSS)-induced mice with chronic colitis. LPS-treated THP-1 cells expressed mRNA of CD11b, an M1 macrophage marker, at day 2. However, THP-1 co-cultured with ASCs expressed mRNA of CD206, CD68, CCL18, legumain, and IL-10, markers of M2 macrophages. In THP-1 cells co-cultured with ASCs, precursor (pro)-IL-1β, Cox-2, and NLRP3 increased dramatically compared to LPS-treated THP-1 cells. Secretion of IL-1β and IL-18 was significantly inhibited by ASCs, but PGE2 production was highly increased in co-culture conditions of THP-1 and ASCs. IL-18 secretion was inhibited by PGE2 treatment, and PGE2 inhibited inflammasome complex (ASC/Cas-1/NLRP3) formation in THP-1 cells. In the DSS-induced chronic colitis model, ASCs ameliorated colitis by decreasing the total number of macrophages and the M1 macrophage population. Our results suggest that ASCs can suppress the inflammatory response by controlling the macrophage population, and ASCs may be therapeutically useful for the treatment of IBD.

Implementation of an automated inclusion system for the histological analysis of murine tissue samples: A feasibility study in DSS-induced chronic colitis

Animal models are powerful tools to expand our understanding of human diseases. Histopathological evaluation of murine experimental models is often required to support further research; thus, a more rigorous evaluation of murine histological samples is strongly advocated. Indeed, the overall quality of tissue sections is critical to draw reliable and accurate conclusions. As several methodological variables may reduce the reliability of the pathological analysis, a standardization of the procedural steps required for the processing of histological murine tissues is advisable. Here, we describe a method to standardize the technical procedure from the initial preparation to the paraffin embedding of murine samples. Specifically, we have implemented an automated inclusion system, that is, the SAKURA Tissue-Tek inclusion instrument, which is routinely used for paraffin inclusion of human samples, to process murine specimens of intestinal inflammation. Colitis severity was assessed in chronically Dextran Sodium Sulphate (DSS)–treated mice by cytofluorimetric analysis of colonic cellular infiltrates, expression of inflammatory genes and histopathological analysis of tissue samples, comparing manual and automated tissue preparation systems. We here conclude that implementation of this technique can significantly increase the quality and the reliability of histopathological examination of murine tissues.