Dextran sodium sulfate colitis murine model: An indispensable tool for advancing our understanding of inflammatory bowel diseases pathogenesis

Inflammatory bowel diseases (IBD), including Crohn's disease and ulcerative colitis, are complex diseases that result from the chronic dysregulated immune response in the gastrointestinal tract. The exact etiology is not fully understood, but it is accepted that it occurs when an inappropriate aggressive inflammatory response in a genetically susceptible host due to inciting environmental factors occurs. To investigate the pathogenesis and etiology of human IBD, various animal models of IBD have been developed that provided indispensable insights into the histopathological and morphological changes as well as factors associated with the pathogenesis of IBD and evaluation of therapeutic options in the last few decades. The most widely used experimental model employs dextran sodium sulfate (DSS) to induce epithelial damage. The DSS colitis model in IBD research has advantages over other various chemically induced experimental models due to its rapidity, simplicity, reproducibility and controllability. In this manuscript, we review the newer publicized advances of research in murine colitis models that focus upon the disruption of the barrier function of the intestine, effects of mucin on the development of colitis, alterations found in microbial balance and resultant changes in the metabolome specifically in the DSS colitis murine model and its relation to the pathogenesis of IBD.

Gut microbiota modulation and anti-inflammatory properties of anthocyanins from the fruits of Lycium ruthenicum Murray in dextran sodium sulfate-induced colitis in mice

In the present study, the therapeutic effects of crude anthocyanins (ACN) from the fruits of Lycium ruthenicum Murray and the main monomer of ACN, petunidin 3-O-[rhamnopyranosyl-(trans-p-coumaroyl)]-5-O-[β-d-glucopyranoside] (P3G), on the dextran sodium sulfate (DSS)-induced colitis in mice were investigated. Both ACN and P3G showed intestinal anti-inflammatory effects, evidenced by restoration of various physical signs (body weight, feed quantity, solid fecal weight and colon length were increased, and DAI score was decreased), reduction of the expression of proinflammatory cytokines and related mRNA (such as TNF-α, IL-6, IL-1β and IFN-γ), and promotion of the intestinal barrier function by histological and immunofluorescence analysis (proteins such as ZO-1, occludin and claudin-1 were increased). Furthermore, the effects on gut microbiota community of DSS-induced colitis in mice have been investigated. It was found that Porphyromonadaceae, Helicobacter, Parasutterella, Parabacteroides, Oscillibacter and Lachnospiraceae were the key bacteria associated with inflammatory bowel disease. Taken together, P3G and ACN ameliorated DSS-induced colitis in mice through three aspects including blocking proinflammatory cytokines, increasing tight junction protein and modulating gut microbiota. What's more, P3G showed better anti-inflammatory effects than ACN.

Dietary tryptophan alleviates dextran sodium sulfate-induced colitis through aryl hydrocarbon receptor in mice

Ulcerative colitis is the typical progression of chronic inflammatory bowel disease. Amino acids, particularly tryptophan, have been reported to exert a protective effect against colitis induced by dextran sodium sulfate (DSS), but the precise underlying mechanisms remain incompletely clarified. Tryptophan metabolites are recognized to function as endogenous ligands for aryl hydrocarbon receptor (Ahr), which is a critical regulator of inflammation and immunity. Thus, we conducted this study to investigate whether dietary tryptophan supplementation protects against DSS-induced colitis by acting through Ahr. Female wild-type (WT) and Ahr-deficient (knockout; KO) mice (10-12 weeks old) were divided into four groups and fed either a control or 0.5% tryptophan diet. The tryptophan diet ameliorated DSS-induced colitis symptoms and severity in WT mice but not in KO mice, and the diet reduced the mRNA expression of Il-6, Tnfα, Il-1β and the chemokines Ccl2, Cxcl1 and Cxcl2 in the WT groups. Furthermore, Il-22 and Stat3 mRNA expression in the colon was elevated in WT mice fed with the tryptophan diet, which mainly protected epithelial layer integrity, and Ahr also modulated immune homeostasis by regulating Foxp3 and Il-17 mRNA expression. These data suggest that tryptophan-containing diet might ameliorate DSS-induced acute colitis and regulate epithelial homeostasis through Ahr. Thus, tryptophan could serve as a promising preventive agent in the treatment of ulcerative colitis.

Insights from advances in research of chemically induced experimental models of human inflammatory bowel disease

Inflammatory bowel disease (IBD), the most important being Crohn's disease and ulcerative colitis, results from chronic dysregulation of the mucosal immune system in the gastrointestinal tract. Although the pathogenesis of IBD remains unclear, it is widely accepted that genetic, environmental, and immunological factors are involved. Recent studies suggest that intestinal epithelial defenses are important to prevent inflammation by protecting against microbial pathogens and oxidative stresses. To investigate the etiology of IBD, animal models of experimental colitis have been developed and are frequently used to evaluate new anti-inflammatory treatments for IBD. Several models of experimental colitis that demonstrate various pathophysiological aspects of the human disease have been described. In this manuscript, we review the characteristic features of IBD through a discussion of the various chemically induced experimental models of colitis (e.g., dextran sodium sulfate-, 2,4,6-trinitrobenzene sulfonic acid-, oxazolone-, acetic acid-, and indomethacin-induced models). We also summarize some regulatory and pathogenic factors demonstrated by these models that can, hopefully, be exploited to develop future therapeutic strategies against IBD.

Short-chain fatty acids administration is protective in colitis-associated colorectal cancer development

Reduced short-chain fatty acids (SCFAs) have been reported in patients with ulcerative colitis, and increased intake of dietary fiber has shown to be clinically beneficial for colitis. Whether SCFAs suppress tumorigenesis in colitis-associated colorectal cancer remains unknown. The chemopreventive effect of SCFAs in colitis-associated colorectal cancer was evaluated in this study. Model of colitis-associated colorectal cancer in male BALB/c mice was induced by azoxymethane (AOM) and dextran sodium sulfate (DSS). SCFAs mix (67.5 mM acetate, 40 mM butyrate, 25.9 mM propionate) was administered in drink water during the study period. Macroscopic and histological studies were performed to examine the colorectal inflammation and tumorigenesis in AOM/DSS-induced mice treated with or without SCFA mix. The effects of SCFAs mix on colonic epithelial cellular proliferation were also assessed using Ki67 immunohistochemistry and TUNEL staining. The administration of SCFAs mix significantly reduced the tumor incidence and size in mice with AOM/DSS-induced colitis associated colorectal cancer. SCFAs mix protected from AOM/DSS-induced colorectal cancer by improving colon inflammation and disease activity index score as well as suppressing the expression of proinflammatory cytokines including IL-6, TNF-α and IL-17. A decrease in cell proliferation markers and an increase in TUNEL-positive tumor epithelial cells were also demonstrated in AOM/DSS mice treated with SCFAs mix. SCFAs mix administration prevented development of tumor and attenuated the colonic inflammation in a mouse model of colitis-associated colorectal cancer. SCFAs mix may be a potential agent in the prevention and treatment of colitis-associated colorectal cancer.

Ulcerative colitis: Gut microbiota, immunopathogenesis and application of natural products in animal models

Ulcerative colitis (UC) is an inflammatory bowel disease with increasing incidence in the world, especially in developing countries. Although knowledge of its pathogenesis has progressed over the last years, some details require clarification. Studies have highlighted the role of microbial dysbiosis and immune dysfunction as essential factors that may initiate the typical high-grade inflammatory outcome. In order to better understand the immunopathophysiological aspects of UC, experimental murine models are valuable tools. Some of the most commonly used chemicals to induce colitis are trinitrobenzene sulfonic acid, oxazolone and dextran sodium sulfate. These may also be used to investigate new ways of preventing or treating UC and therefore improving targeting in human studies. The use of functional foods or bioactive compounds from plants may constitute an innovative direction towards the future of alternative medicine. Considering the above, this review focused on updated information regarding the 1. gut microbiota and immunopathogenesis of UC; 2. the most utilized animal models of the disease and their relevance; and 3. experimental application of natural products, not yet tested in clinical trials.

Patchouli alcohol ameliorates dextran sodium sulfate-induced experimental colitis and suppresses tryptophan catabolism

Despite the increased morbidity of ulcerative colitis (UC) in recent years, available treatments remain unsatisfactory. Pogostemon cablin has been widely applied to treat a variety of gastrointestinal disorders in clinic for centuries, in which patchouli alcohol (PA, C₁₅H₂₆O) has been identified as the major active component. This study attempted to determine the bioactivity of PA on dextran sulfate sodium (DSS)-induced mice colitis and clarify the mechanism of action. Acute colitis was induced in mice by 3% DSS for 7 days. The mice were then given PA (10, 20 and 40mg/kg) or sulfasalazine (SASP, 200mg/kg) as positive control via oral administration for 7 days. At the end of study, animals were sacrificed and samples were collected for pathological and other analysis. In addition, a metabolite profiling and a targeted metabolite analysis, based on the Ultra-Performance Liquid Chromatography coupled with mass spectrometry (UPLC-MS) approach, were performed to characterize the metabolic changes in plasma. The results revealed that PA significantly reduced the disease activity index (DAI) and ameliorated the colonic injury of DSS mice. The levels of colonic MPO and cytokines involving TNF-α, IFN-γ, IL-1β, IL-6, IL-4 and IL-10 also declined. Furthermore, PA improved the intestinal epithelial barrier by enhancing the level of colonic expression of the tight junction (TJ) proteins, for instance ZO-1, ZO-2, claudin-1 and occludin, and by elevating the levels of mucin-1 and mucin-2 mRNA. The study also demonstrated that PA inhibited the DSS-induced cell death signaling by modulating the apoptosis related Bax and Bcl-2 proteins and down-regulating the necroptosis related RIP3 and MLKL proteins. By comparison, up-regulation of IDO-1 and TPH-1 protein expression in DSS group was suppressed by PA, which was in line with the declined levels of kynurenine (Kyn) and 5-hydroxytryptophan (5-HTP) in plasma. The therapeutic effect of PA was evidently reduced when Kyn was given to mice. In summary, the study successfully demonstrated that PA ameliorated DSS-induced mice acute colitis by suppressing inflammation, maintaining the integrity of intestinal epithelial barrier, inhibiting cell death signaling, and suppressing tryptophan catabolism. The results provided valuable information and guidance for using PA in treatment of UC.

Anti-inflammatory properties of fermented soy milk with Lactococcus lactis subsp. lactis S-SU2 in murine macrophage RAW264.7 cells and DSS-induced IBD model mice

Six lactic acid bacteria strains (four Lactobacillus plantarum strains and one each of Lactococcus lactis subsp. lactis and Pediococcus pentosaceus) have been isolated and shown to possess anti-oxidant activity. In this study, we determined their acid, bile, salt resistance, and adhesion activity on human enterocyte-like HT-29-Luc and Caco-2 cells. An isolate Lc. lactis S-SU2 showed highest bile resistance and adhesion activity compared to type strains. S-SU2 could ferment both 10% skimmed milk and soy milk while the type strain could not ferment soy milk. Soy milk fermented with S-SU2 showed an increased nitric oxide (NO) secretion in the mouse macrophage RAW264.7 cells without bacterial lipopolysaccharide (LPS). Furthermore, the inhibitory effects of the fermented soy milk on Escherichia coli O111 LPS-induced NO secretion were higher than those of fresh soy milk. Inflammatory bowel disease (IBD) was induced in mice fed either 5% (w/v) dextran sodium sulfate (DSS) in drinking water or 50% soy milk in drinking water. Shortening of colon length, breaking of epithelial cells, lowering liver and thymus weights, and enlargement of spleen are some of the characteristics observed in the IBD, which were prevented by the use of soy milk fermented with Lc. lactis S-SU2.

Cortical Inflammation is Increased in a DSS-Induced Colitis Mouse Model

While inflammatory bowel disease (IBD) might be a risk factor in the development of brain dysfunctions, the underlying mechanisms are largely unknown. Here, mice were treated with 5% dextran sodium sulfate (DSS) in drinking water and sacrificed on day 7. The serum level of IL-6 increased, accompanied by elevation of the IL-6 and TNF-α levels in cortical tissue. However, the endotoxin concentration in plasma and brain of mice with DSS-induced colitis showed a rising trend, but with no significant difference. We also found significant activation of microglial cells and reduction in occludin and claudin-5 expression in the brain tissue after DSS-induced colitis. These results suggested that DSS-induced colitis increases systemic inflammation which then results in cortical inflammation via up-regulation of serum cytokines. Here, we provide new information on the impact of colitis on the outcomes of cortical inflammation.

Carvacrol exhibits anti-oxidant and anti-inflammatory effects against 1, 2-dimethyl hydrazine plus dextran sodium sulfate induced inflammation associated carcinogenicity in the colon of Fischer 344 rats

Chronic inflammation is one of the remarkable etiologic factors for various human ailments including cancer. The well known hypothesis is that persistent inflammation in colon can increase the risk of colorectal cancer (CRC). In this study, a pharmacological evaluation of carvacrol, a phenolic monoterpene constituent of essential oils produced from aromatic plant Oreganum vulgarea sp. on colitis associated colon cancer (CACC) induced by 1,2 Dimethylhydrazine (DMH) and dextran sodium sulfate (DSS) in male Fischer 344 rat model was studied. F344 rats were given three subcutaneous injections of DMH (40 mg/kg body wt) in the first week and were given free access to drinking water containing 1% DSS for the next one week followed by 7-14 days of water as three cycles. Carvacrol was administrated before and after tumor induction at a concentration of 50 mg/kg body weight (o.p). Carvacrol treated groups promotes the endogenous antioxidant system and suppress the inflammation in DMH/DSS induced animals. An increased antioxidant status and restoration of histological lesions in the inflamed colonic mucosa was observed in carvacrol treated rats. This effect was confirmed biochemically by reducing free-radical accumulation and suppressing expression of pro-inflammatory mediators. In this study, Carvacrol significantly increased the anti-oxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) glutathione (GSH) levels and reduced lipid peroxides (LPO), myeloperoxidase (MPO) and nitric oxide (NO) as compared to DMH/DSS induced rats. These dramatic changes facilitate the suppression of pro-inflammatory mediators such as inducible nitric oxide synthase (iNOS), and interleukin-1 beta (IL-1β) in CACC induced rats. Taken together, these findings suggest that Carvacrol may play a beneficial role in DMH/DSS induced experimental rat model and serve as an excellent dietary antioxidant as well as anti-inflammatory agent. It may represent novel therapeutic interventions against colon cancer triggered by chronic inflammation.

From Gut to Brain: Alteration in Inflammation Markers in the Brain of Dextran Sodium Sulfate-induced Colitis Model Mice

Objective

Neuropsychiatric manifestations like depression and cognitive dysfunction commonly occur in inflammatory bowel disease (IBD). In the context of the brain-gut axis model, colitis can lead to alteration of brain function in a bottom-up manner. Here, the changes in the response of the hypothalamic-pituitary-adrenal axis and inflammation-related markers in the brain in colitis were studied.

Methods

Dextran sodium sulfate (DSS) was used to generate a mouse model of colitis. Mice were treated with DSS for 3 or 7 days and sacrificed. We analyzed the gene expression of brain-derived neurotrophic factor (BDNF), cyclo-oxygenase 2 (COX-2), and glial fibrillary acidic protein (GFAP), and the expression of GFAP, in the hippocampus, hypothalamus, and amygdala. Additionally, the levels of C-reactive protein (CRP) and serum cortisol/corticosterone were measured.

Results

Alteration of inflammatory-related markers varied depending on the brain region and exposure time. In the hippocampus, COX-2 mRNA, GFAP mRNA, and GFAP expression were upregulated during exposure to DSS. However, in the hypothalamus, COX-2 mRNA was upregulated only 3 days after treatment. In the amygdala, BDNF and COX-2 mRNAs were downregulated. CRP and corticosterone expression increased with DSS treatment at day 7.

Conclusion

IBD could lead to neuroinflammation in a bottom-up manner, and this effect varied according to brain region. Stress-related hormones and serum inflammatory markers, such as CRP, were upregulated from the third day of DSS treatment. Therefore, early and active intervention is required to prevent psychological and behavioral changes caused by IBD, and region-specific studies can help understand the precise mechanisms by which IBD affects the brain.

BBG enhances OLT1177-induced NLRP3 inflammasome inactivation by targeting P2X7R/NLRP3 and MyD88/NF-κB signaling in DSS-induced colitis in rats

Chronic ulceration of the colon is associated with the activation of TLR4/NF-κB and P2X7R/NLRP3 signaling pathways. We investigated the effect of individual or combined administration of BBG, a P2X7R blocker, and OLT1177, a selective NLRP3 inhibitor, in the dextran sodium sulfate-induced ulcerative colitis (UC) rat model. The ulcerative rats were treated orally with brilliant blue G (BBG) (50 mg/kg/day) or OLT1177 (200 mg/kg/day) or a combination of both. Myd88 and NF-κB levels were measured by ELISA, qRT-PCR, and immunohistochemical staining. Cytokines known to be associated with TLR4/NF-κB or P2X7R/NLRP3 signaling were measured by ELISA. P2X7R and NLRP3 expression were measured by ELISA and qRT-PCR. The administration of BBG or OLT1177 ameliorated the toxic effects of DSS on the colon as they restored normal colonic macroscopic and microscopic morphology. BBG administration, but not OLT1177, reduced the expression of Myd88, NF-κB, IL-6, and TNF-α in addition to lowering P2X7R and oxidative stress levels. Individual BBG or OLT1177 administration decreased NLRP3 inflammasome recruitment and subsequent activation of caspase-1, IL-1β, and IL-18. However, the combined administration of OLT1177 with BBG potentiated its inhibitory effect on the NLRP3, which was reflected by the additional suppressive effect on caspase-1, IL-1β, IL-18 levels. In conclusion, BBG/OLT1177 exhibited complementary effects and effectively ameliorated UC. This novel approach provides a basis for the clinical application of this combination for the treatment of IBDs and might also be promising for the pharmacological intervention of other NLRP3 inflammasome-dependent inflammatory conditions.

White and dark kidney beans reduce colonic mucosal damage and inflammation in response to dextran sodium sulfate

Common beans are a rich source of nondigestible fermentable components and phenolic compounds that have anti-inflammatory effects. We assessed the gut-health-promoting potential of kidney beans in healthy mice and their ability to attenuate colonic inflammation following dextran sodium sulphate (DSS) exposure (via drinking water, 2% DSS w/v, 7 days). C57BL/6 mice were fed one of three isocaloric diets: basal diet control (BD), or BD supplemented with 20% cooked white (WK) or dark red kidney (DK) bean flour for 3 weeks. In healthy mice, anti-inflammatory microbial-derived cecal short chain fatty acid (SCFA) levels (acetate, butyrate and propionate), colon crypt height and colonic Mucin 1 (MUC1) and Resistin-like Molecule beta (Relmβ) mRNA expression all increased in WK- and DK-fed mice compared to BD, indicative of enhanced microbial activity, gut barrier integrity and antimicrobial defense response. During colitis, both bean diets reduced (a) disease severity, (b) colonic histological damage and (c) increased mRNA expression of antimicrobial and barrier integrity-promoting genes (Toll-like Receptor 4 (TLR4), MUC1-3, Relmβ and Trefoil Factor 3 (TFF3)) and reduced proinflammatory mediator expression [interleukin (IL)-1β, IL-6, interferon (IFN)γ, tumor necrosis factor (TNF)α and monocyte chemoattractant protein-1], which correlated with reduced colon tissue protein levels. Further, bean diets exerted a systemic anti-inflammatory effect during colitis by reducing serum levels of IL-17A, IFNγ, TNFα, IL-1β and IL-6. In conclusion, both WK and DK bean-supplemented diets enhanced microbial-derived SCFA metabolite production, gut barrier integrity and the microbial defensive response in the healthy colon, which supported an anti-inflammatory phenotype during colitis. Collectively, these data demonstrate a beneficial colon-function priming effect of bean consumption that mitigates colitis severity.

Jianpi Qingchang decoction alleviates ulcerative colitis by inhibiting nuclear factor-κB activation

AIM

To investigate the therapeutic effect of Jianpi Qingchang decoction (JPQCD) on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) in mice.

METHODS

C57BL/c mice were injected intragastrically with 5% DSS instead of drinking water for 7 d, and their body weight, diarrhea severity and fecal bleeding were monitored, while the mice in the control group were treated with standard drinking water, without DSS. After 7 d, the DSS drinking water was changed to normal water and the DSS group continued with DSS water. The control and DSS groups were given normal saline by intragastric injection. The 5-aminosalicylic acid (5-ASA) group was treated orally with 5-ASA at a dose of 100 mg/kg daily. The JPQCD group was treated orally with JPQCD at a dose of 17.1 g/kg daily. On day 14, the colon length was measured, the colorectal histopathological damage score was assessed, and protein levels of interleukin (IL)-1β, IL-8 and tumor necrosis factor-alpha (TNF-α) in colon supernatants were measured by enzyme-linked immunosorbent assay. mRNA expression of IL-1β, IL-8, TNF-α and nuclear factor-kappa B (NF-κB) was detected by real-time quantitative polymerase chain reaction. Western blotting was used to detect the protein expression of NF-κB and inhibitor of kappa B.

RESULTS

Acute inflammation occurred in the mice administered DSS, including the symptoms of losing body weight, loose feces/watery diarrhea and presence of fecal blood; all these symptoms worsened at 7 d. The colons of mice treated with DSS were assessed by histological examination, and the results confirmed that acute inflammation had occurred, as evidenced by loss of colonic mucosa and chronic inflammatory cell infiltration, and these features extended into the deeper layer of the colon walls. The expression levels of IL-1β, IL-8 and TNF-α in the DSS group were higher than those in the control group (P < 0.05), and the expression levels of IL-1β, IL-8 and TNF-α in the JPQCD and 5-ASA groups were lower than those in the DSS group after treating with JPQCD and 5-ASA. Comparing with the DSS group, the mRNA level of IL-1β, IL-8, TNF-α and NF-κB was significantly reduced by 5-ASA and JPQCD. The difference between JPQCD and 5-ASA groups was not statistically significant (P > 0.05). Comparing with the DSS group, due to using JPQCD and 5-ASA, significant suppression of activation in DSS-induced NF-κB and increased phosphorylation of IκB in mice with experimental colitis occurred (P < 0.05). The difference between the JPQCD group and the 5-ASA group was not statistically significant (P > 0.05).

CONCLUSION

Activation of the NF-κB signaling pathway is inhibited by JPQCD, which shows the potential mechanism by which JPQCD treats UC.

Dextran Sulfate Sodium (DSS)-Induced Acute Colitis in the Rat

Inflammatory bowel diseases (IBDs) are complex multifactorial disease thought to result from inappropriate immune responses to the gut microbiota, in genetically susceptible individuals, under the influence of environmental factors. Among the different animal models developed to help in understanding IBDs pathophysiological mechanisms as well as to achieve pharmacological preclinical studies, the dextran sulfate sodium (DSS)-induced colitis model is the most widely used because of its simplicity, cost-effectiveness, and similarity with human IBDs. This section provides with a detailed protocol that we validated in our laboratory to perform DSS-induced acute colitis in the Sprague-Dawley (SPD) rat.

Dandelion root extract protects NCM460 colonic cells and relieves experimental mouse colitis

The protective potential of dandelion on acute hepatitis, lung injury and colorectal cancer has recently been revealed. Importantly, ulcerative colitis (UC), a clinically defined inflammatory bowel disease, accelerates the risk of colorectal cancer. However, studies focusing on the activity of dandelion on UC are extremely limited. In the present study, we found that an aqueous extract of dandelion root increases cell viability and decreases apoptosis in dextran sodium sulfate (DSS)-incubated NCM460 human colonic epithelial cells, probably through removing the production of reaction oxygen species and blocking nuclear factor-kappaB signaling. We then examined the anti-colitis efficacy of this extract in an in vivo study. We detected that dandelion root extract efficiently ameliorates progressive acute injury as demonstrated by a reduction in body weight loss, severity scores of disease index and shortened colon length during DSS treatment, as well as reducing the inflammatory conditions and oxidative stress in the colon of DSS-induced mice. Our study clearly demonstrates that dandelion has a strong cytoprotective effect on NCM460 colonocytes and shows powerful defense on an established experimental mouse model of DSS-induced UC. Therefore, dandelion root extract can be an effective anti-colitis complex mixture and can provide a complementary alternative to currently available therapeutic intervention in UC.

Dextran sodium sulfate potentiates NLRP3 inflammasome activation by modulating the KCa3.1 potassium channel in a mouse model of colitis

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, has increased in incidence and prevalence in recent decades. Both clinical and animal studies are critical for understanding the pathogenesis of this disease. Dextran sodium sulfate (DSS)-induced colitis is a frequently used animal model of IBD, but the underlying mechanism of the model remains incompletely understood. In this study, we found that NOD-like receptor family pyrin containing 3 (NLRP3) depletion markedly mitigated DSS-induced colitis and was accompanied by decreased activation of the inflammasome in the colons of mice. However, in vitro assays showed that DSS did not directly trigger but instead potentiated NLRP3 inflammasome assembly in macrophages in response to suboptimal ATP or nigericin stimulation. Mechanistically, DSS potentiated NLRP3 inflammasome activation in macrophages by augmenting KCa3.1-mediated potassium ion (K+) efflux. Furthermore, we found that pharmacologic blockade of the K+ channel KCa3.1 with TRAM-34 or genetic depletion of the Kcnn4 gene (encoding KCa3.1) not only ameliorated the severity of DSS-induced colitis but also attenuated in vivo inflammasome assembly in the colonic tissues of mice, suggesting a causal link between KCa3.1-mediated augmentation of the NLRP3 inflammasome and DSS-induced inflammatory injuries. Collectively, these results indicate that KCa3.1 plays a critical role in mediating DSS-induced colitis in mice by potentiating NLRP3 inflammasome activation. Our data provide a previously unknown mechanism by which DSS induces colitis in mice and suggests that KCa3.1 is an alternative therapeutic target for treating IBD.

The effect of algal polysaccharides laminarin and fucoidan on colonic pathology, cytokine gene expression and Enterobacteriaceae in a dextran sodium sulfate-challenged porcine model

The algal polysaccharides laminarin (LAM) and fucoidan (FUC) have potent anti-inflammatory activities in the gastrointestinal tract. Our objective was to examine the impact of prior consumption of LAM and/or FUC on pathology and inflammation following a dextran sodium sulfate (DSS) challenge in pigs. Pigs (n 7/group) were assigned to one of five experimental groups for 56 d. From 49-55 d, distilled water or DSS was administered intragastrically. The experimental groups were: (1) basal diet + distilled water (control); (2) basal diet + DSS (DSS); (3) basal diet + FUC + DSS (FUC + DSS); (4) basal diet + LAM + DSS (LAM + DSS); and (5) basal diet + LAM + FUC + DSS (LAMFUC + DSS). The DSS group had decreased body-weight gain (P < 0·05) and serum xylose (P < 0·05), and increased proximal colon pathology score (P < 0·05), diarrhoeal score (P < 0·001) and colonic Enterobacteriaceae (P < 0·05) relative to the control group. The FUC + DSS (P < 0·01), LAM + DSS (P < 0·05) and LAMFUC + DSS (P < 0·05) groups had improved diarrhoeal score, and the LAMFUC + DSS (P < 0·05) group had improved body weight relative to the DSS group. The FUC + DSS group (P < 0·001), LAM + DSS group (P < 0·05) and LAMFUC + DSS group (P < 0·001) had lower IL-6 mRNA abundance relative to the DSS group. The LAM + DSS group had reduced Enterobacteriaceae in proximal colon digesta relative to the DSS group (P < 0·05). In conclusion, FUC or a combination of FUC and LAM improved body-weight loss, diarrhoeal scores and clinical variables associated with a DSS challenge in pigs, in tandem with a reduction in colonic IL-6 mRNA abundance.

Colitis susceptibility in p47(phox-/-) mice is mediated by the microbiome

BACKGROUND

Chronic granulomatous disease (CGD) is caused by defects in nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) complex subunits (gp91(phox) (a.k.a. Nox2), p47(phox), p67(phox), p22(phox), p40(phox)) leading to reduced phagocyte-derived reactive oxygen species production. Almost half of patients with CGD develop inflammatory bowel disease, and the involvement of the intestinal microbiome in relation to this predisposing immunodeficiency has not been explored.

RESULTS

Although CGD mice do not spontaneously develop colitis, we demonstrate that p47(phox-/-) mice have increased susceptibility to dextran sodium sulfate colitis in association with a distinct colonic transcript and microbiome signature. Neither restoring NOX2 reactive oxygen species production nor normalizing the microbiome using cohoused adult p47(phox-/-) with B6Tac (wild type) mice reversed this phenotype. However, breeding p47(phox+/-) mice and standardizing the microflora between littermate p47(phox-/-) and B6Tac mice from birth significantly reduced dextran sodium sulfate colitis susceptibility in p47(phox-/-) mice. We found similarly decreased colitis susceptibility in littermate p47(phox-/-) and B6Tac mice treated with Citrobacter rodentium.

CONCLUSIONS

Our findings suggest that the microbiome signature established at birth may play a bigger role than phagocyte-derived reactive oxygen species in mediating colitis susceptibility in CGD mice. These data further support bacteria-related disease in CGD colitis.

Paeoniflorin ameliorates experimental colitis by inhibiting gram-positive bacteria-dependent MDP-NOD2 pathway

Previous studies reported that antibiotics inhibit the growth of Gram-positive bacteria and alleviate ulcerative colitis (UC). But how Gram-positive bacteria are involved in the occurrence of inflammatory bowel disease (IBD) and which component of it causes inflammation remain unclear. This work aims to demonstrate that Gram-positive bacteria may be an underlying cause of experimental colitis in mice through the muramyl dipeptide (MDP)-nucleotide-binding oligomerization domain-containing protein-2 (NOD2) pathway and paeoniflorin inhibits the pathway above to alleviate experimental colitis. In this study, colitis mice were established by oral administration of 3% dextran sulfate sodium (DSS) and paeoniflorin (25, 50,100 mg/kg per day, ig) was administered to the mice for 10 days. Results shown that the abundance and the infiltration of Gram-positive bacteria in intestinal tissues increased in UC mice. Paeoniflorin treatment significantly alleviated DSS-induced experimental colitis mice, reduced the abundance of Gram-positive bacteria in feces and the infiltration of Gram-positive bacteria in intestinal tissues. Paeoniflorin also inhibited mRNA and protein expression of MDP-NOD2 pathway components and decreased the levels of related inflammatory cytokines. In vitro experiments showed that MDP strongly stimulated RAW264.7 cells to secrete tumor necrosis factor α (TNF-α), and induced translocation of nuclear factor-kappa B (NF-κB p65) from the cytoplasm to nucleus using immunofluorescence co-localization experiments. Overall, the results indicated that Gram-positive bacteria promote the occurrence of colitis via up-regulation of MDP-NOD2 pathway, and paeoniflorin is able to decrease the infiltration of Gram-positive bacteria in intestine and inhibit Gram-positive bacteria-dependent MDP-NOD2 pathway to alleviate mice colitis.

Aryl hydrocarbon receptor activation alleviates dextran sodium sulfate-induced colitis through enhancing the differentiation of goblet cells

BACKGROUND

The intestinal inflammation induces disruption of the intestinal barrier function and leads to bacteria invasion. Accumulating evidences revealed that the aryl hydrocarbon receptor (AhR) plays a vital role in maintaining the intestinal barrier function. However, the precise mechanism remains to be unclear.

METHODS

Adult C57BL/6J mice were randomly divided into three groups: Sham, DSS and DSS + 6-formylindolo (3, 2-b) carbazole (FICZ)group. The colons and epithelial cell were harvested for histological examination, pro-inflammatory cytokines detection, bacterial load analysis, immunohistochemistry and Muc2 protein analysis. Under physiological condition, AhRKO model and FICZ treatment were used to evaluate the roles of AhR in the differentiation of goblet cells and the expression of Muc2 in mice. In vitro, we used HT29 mol to research the signaling pathway.

RESULTS

AhR activation by FICZ could increase the Muc2 expression and the number of goblet cells and reduce bacterial infiltration to ameliorate DSS-induced Colitis. Under physiological conditions, the treatment of FICZ promote the differentiation of goblet cell and the expression of Muc2 and inhibit the notch-signaling. Genetic deletion of AhR led to the loss of goblet cells and the decrease of Muc2 expression and enhance the notch-signaling. In HT29 cells, the differentiation of goblet cell meditated by AhR can be abolished by the inhibitor of AhR, pErk1/2 and knocking-down AhR.

CONCLUSION

FICZ promoted the differentiation of goblet cell through AhR-pErk1/2 signaling pathway and ameliorate DSS-induced Colitis.

Purification of Total RNA from DSS-treated Murine Tissue via Lithium Chloride Precipitation

We have developed a protocol to purify RNA from DSS (Dextran Sulfate Sodium)-treated mouse tissues. This method, which prevents downstream inhibition of q-RT-PCR observed in DSS-treated tissues, relies on successive precipitations with lithium chloride.

Cyclosporine A-loaded lipid nanoparticles in inflammatory bowel disease

Cyclosporine A (CsA) is a well-known immunosuppressive agent used as rescue therapy in severe steroid-refractory ulcerative colitis (UC). However, toxicity issues associated with CsA when administered in its commercially available formulations have been reported in clinical practice. Since nanotechnology has been proposed as a promising strategy to improve safety and efficacy in the treatment of inflammatory bowel disease (IBD), the main purpose of this study was to evaluate the effect of oral administration of CsA-loaded lipid nanoparticles (LN) in the dextran sodium sulfate (DSS)-induced colitis mouse model using Sandimmune Neoral(®) as reference. The results showed that the formulations used did not decrease colon inflammation in terms of myeloperoxidase activity (MPO), tumor necrosis factor (TNF)-α expression, or histological scoring in the acute stage of the disease. However, further studies are needed in order to corroborate the efficacy of these formulations in the chronic phase of the disease.

Topical application of glycyrrhizin preparation ameliorates experimentally induced colitis in rats

AIM: To examine the efficacy of glycyrrhizin preparation (GL-p) in the treatment of a rat model of ulcerative colitis (UC).

METHODS: Experimental colitis was induced by oral administration of dextran sodium sulfate. Rats with colitis were intrarectally administered GL-p or saline. The extent of colitis was evaluated based on body weight gain, colon wet weight, and macroscopic damage score. The expression levels of pro-inflammatory cytokines and chemokines in the inflamed mucosa were measured by cytokine antibody array analysis. The effect of GL-p on myeloperoxidase (MPO) activity in the inflamed mucosa and purified enzyme was assayed.

RESULTS: GL-p treatment significantly ameliorated the extent of colitis compared to sham treatment with saline. Cytokine antibody array analysis showed that GL-p treatment significantly decreased the expression levels of pro-inflammatory cytokines and chemokines, including interleukin (IL)-1β, IL-6, tumor necrosis factor-α, cytokine-induced neutrophil chemoattractant-2, and monocyte chemoattractant protein-1 in the inflamed mucosa. Furthermore, GL-p inhibited the oxidative activity of mucosal and purified MPO.

CONCLUSION: GL-p enema has a therapeutic effect on experimental colitis in rats and may be useful in the treatment of UC.

Treatment with butyrate alleviates dextran sulfate sodium and Clostridium difficile-induced colitis by preventing activity of Th17 cells via regulation of SIRT1/mTOR in mice

Inflammatory bowel disease (IBD) patients are particularly vulnerable to infection with Clostridium difficile infection (CDI).Available treatments of IBD with CDI have not effective. Butyrate, the metabolites of microbiota, plays a vital role in maintaining immune homeostasis and potential drugs for treatment of IBD with CDI. The aim of this study was to investigate the effect of butyrate on IBD with CDI. Mice were given dextran sulfate sodium (DSS) and were infected with C. difficile (CD). Butyrate was treated during the study period. Butyrate protected from DSS+CD induced colitis by improving weight loss, survival, colon shorten, activity index score, and suppressing the expression of proinflammatory cytokines including IL-6, IL-17, TNF-α, IL-1β as well as regulating Th17/Treg balance through activation of SIRT1/mTOR. Besides, SR1001, an inhitor of the orphan nuclear receptors retinoic acid-related receptor γt, which is a transcription factor specific to the formation of Th17 cells can suppress the Th17 development and alleviate the DSS+CD induced colitis in mice. Notably, the therapeutic effect of butyrate was revered when disease mice treated with butyrate and Ex-527, a SIRT1 inhibitor. Taken together, we demonstrate that butyrate alleviates dextran sulfate sodium and clostridium difficile induced colitis by preventing Th17 through activation of SIRT1/mTOR.