Dextran Sulfate Sodium Colitis Model Research Articles

Angiotensin converting enzyme-inhibitor reduces colitis severity in an IL-10 knockout model.

We previously demonstrated angiotensin converting enzymes (ACE) over-expression in a dextran-sodium sulfate colitis model; ACE inhibitor (ACE-I) treatment reduced colitis severity in this model. However, ACE-I has not been tested in more immunologically relevant colitis models. We hypothesized that ACE-I would decrease disease severity in an IL-10 knockout (-/-) colitis model. Colitis was induced by giving 10-week old IL-10-/- mice piroxicam (P.O.) for 14 days. The ACE-I enalaprilat was given transanally at a dose of 6.25 mg/kg for 21 days. Prednisolone (PSL) with or without enalaprilat were used as therapeutic, comparative groups. All groups were compared to a placebo treated group. Outcome measures were clinical course, histology, abundance of pro-inflammatory cytokines/chemokines, and epithelial barrier function. Enalaprilat exhibited better survival (91 %) versus other treatment groups (PSL: 85.7 %, PSL + ACE-I: 71.4 %, placebo: 66.6 %). The ACE-I and PSL + ACE-I groups showed significantly better histological scores versus placebo mice. ACE-I and the PSL groups significantly reduced several pro-inflammatory cytokines versus placebo mice. FITC-dextran permeability was reduced in the ACE-I and PSL + ACE-I groups. Blood pressure was not affected in ACE-I treated mice compared to placebo mice. ACE-I was effective in reducing severity of colitis in an IL-10-/- model. The addition of prednisolone minimally augmented this effect. The findings suggest that appropriately dosed ACE-I with or without steroids may be a new therapeutic agent for colitis.

Novel Insights on the Effect of Nicotine in a Murine Colitis Model

Studies showed that nicotine has a positive influence on symptoms of ulcerative colitis. In the present study, we explored the effect of nicotine treatment using different routes of administration in the dextran sodium sulfate (DSS) colitis mouse model. We also investigated the effects of cotinine, a major metabolite of nicotine, in the model. C57BL6 adult male mice were given DSS solution freely in the drinking water for seven consecutive days, and tap water was given thereafter. Disease severity, length of the colon, colon tissue histology, and inflammatory markers, including colonic myeloperoxidase activity and colonic tumor necrosis factor-α levels, were evaluated. The effect of nicotine and cotinine treatments via various different routes of administration were examined the DSS model. In addition, we measured the plasma levels of nicotine and cotinine in our treatment protocols. Administration of low, but not high, doses of oral nicotine in DSS-treated mice resulted in a significant decrease in disease severity, histologic damage scores, as well as colonic level of tumor necrosis factor-α. However, the anti-inflammatory effect of nicotine was not seen after chronic s.c. or minipump infusion of the drug. Differences in plasma levels of nicotine and cotinine do not seem to account for this lack of effect. Finally, oral cotinine alone failed to show a significant effect in the DSS model of colitis. These results highlight that dose and route of administration play a critical role in the protective effect of nicotine in the DSS mouse colitis model.

Protective and Aggravating Effects of Nlrp3 Inflammasome Activation in IBD Models: Influence of Genetic and Environmental Factors

Background: Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation due to dysregulation of the mucosal immune system. The cytokines IL-1β and IL-18 appear early in intestinal inflammation and their pro-forms are processed via the caspase-1-activating multiprotein complex, the Nlrp3 inflammasome. Previously, we reported that the uptake of dextran sodium sulfate (DSS) by macrophages activates the Nlrp3 inflammasome and that Nlrp3^–/– mice are protected in the acute DSS colitis model. Of note, other groups have reported opposing effects in regards to DSS susceptibility in Nlrp3^–/– mice. Recently, mice lacking inflammasomes were found to develop a distinct intestinal microflora. Methods: To reconcile the contradicting observations, we investigated the role of Nlrp3 deficiency in two different IBD models: acute DSS colitis and TNBS (2,4,6-trinitrobenzene sulfonic acid)-induced colitis. In addition, we investigated the impact of the intestinal flora on disease severity by performing cohousing experiments of wild-type and Nlrp3^–/– mice, as well as by antibiotic treatment. Results: Nlrp3^–/– mice treated with either DSS or TNBS exhibited attenuated colitis and lower mortality. This protective effect correlated with an increased frequency of CD103+ lamina propria dendritic cells expressing a tolerogenic phenotype in Nlrp3^–/– mice in steady state conditions. Interestingly, after cohousing, Nlrp3^–/– mice were as susceptible as wild-type mice, indicating that transmission of endogenous bacterial flora between the two mouse strains might increase susceptibility of Nlrp3^–/– mice towards DSS-induced colitis. Accordingly, treatment with antibiotics almost completely prevented colitis in the DSS model. Conclusions: The composition of the intestinal microflora significantly influences disease severity in IBD models comparing wild-type and Nlrp3^–/– mice. This observation may – at least in part – explain contradictory results concerning the role of the inflammasome in different labs. Further studies are required to define the role of the Nlrp3 inflammasome in noninflamed mucosa under steady state conditions and in IBD.

Multifunctional role of dextran sulfate sodium for in vivo modeling of intestinal diseases

BackgroundInflammatory bowel diseases (IBDs) are chronic, relapsing disorders that affect the gastrointestinal tract of millions of people and continue to increase in incidence each year. While several factors have been associated with development of IBDs, the exact etiology is unknown. Research using animal models of IBDs is beginning to provide insights into how the different factors contribute to disease development. Oral administration of dextran sulfate sodium (DSS) to mice induces a reproducible experimental colitis that models several intestinal lesions associated with IBDs. The murine DSS colitis model can also be adapted to quantify intestinal repair following injury. Understanding the mechanistic basis behind intestinal repair is critical to development of new therapeutics for IBDs because of their chronic relapsing nature.ResultsThe murine DSS colitis model was adapted to provide a system enabling the quantification of severe intestinal injury with impaired wound healing or mild intestinal injury with rapid restoration of mucosal integrity, by altering DSS concentrations and including a recovery phase. We showed that through a novel format for presentation of the clinical disease data, the temporal progression of intestinal lesions can be quantified on an individual mouse basis. Additionally, parameters for quantification of DSS-induced alterations in epithelial cell populations are included to provide insights into mechanisms underlying the development of these lesions. For example, the use of the two different model systems showed that toll-like receptor 9, a nucleic acid-sensing pattern recognition receptor, is important for protection only following mild intestinal damage and suggests that this model is superior for identifying proteins necessary for intestinal repair.ConclusionsWe showed that using a murine DSS-induced experimental colitis model system, and presenting data in a longitudinal manner on a per mouse basis, enhanced the usefulness of this model, and provided novel insights into the role of an innate immune receptor in intestinal repair. By elucidating the mechanistic basis of intestinal injury and repair, we can begin to understand the etiology of IBDs, enabling development of novel therapeutics or prophylactics.

Phylotype-level 16S rRNA analysis reveals new bacterial indicators of health state in acute murine colitis

Human inflammatory bowel disease and experimental colitis models in mice are associated with shifts in intestinal microbiota composition, but it is unclear at what taxonomic/phylogenetic level such microbiota dynamics can be indicative for health or disease. Here, we report that dextran sodium sulfate (DSS)-induced colitis is accompanied by major shifts in the composition and function of the intestinal microbiota of STAT1(-/-) and wild-type mice, as determined by 454 pyrosequencing of bacterial 16S rRNA (gene) amplicons, metatranscriptomics and quantitative fluorescence in situ hybridization of selected phylotypes. The bacterial families Ruminococcaceae, Bacteroidaceae, Enterobacteriaceae, Deferribacteraceae and Verrucomicrobiaceae increased in relative abundance in DSS-treated mice. Comparative 16S rRNA sequence analysis at maximum possible phylogenetic resolution identified several indicator phylotypes for DSS treatment, including the putative mucin degraders Akkermansia and Mucispirillum. The analysis additionally revealed strongly contrasting abundance changes among phylotypes of the same family, particularly within the Lachnospiraceae. These extensive phylotype-level dynamics were hidden when reads were grouped at higher taxonomic levels. Metatranscriptomic analysis provided insights into functional shifts in the murine intestinal microbiota, with increased transcription of genes associated with regulation and cell signaling, carbohydrate metabolism and respiration and decreased transcription of flagellin genes during inflammation. These findings (i) establish the first in-depth inventory of the mouse gut microbiota and its metatranscriptome in the DSS colitis model, (ii) reveal that family-level microbial community analyses are insufficient to reveal important colitis-associated microbiota shifts and (iii) support a scenario of shifting intra-family structure and function in the phylotype-rich and phylogenetically diverse Lachnospiraceae in DSS-treated mice.

Tu1860 Inverse Expression of IL-33 in TH1 Versus TH2 Mediated Experimental Colitis

Background: Interleukin (IL)-33 is a pro-inflammatory cytokine that has been associated with induction of human T helper 2 (TH2)-type inflammatory responses through activation of the ST2 receptor. Recent research has shown that IL-33 is upregulated in active ulcerative colitis (UC), but the role of IL-33 in regulation of intestinal mucosal immunologic reactions is uncertain. Aim: The aim of the present study was to describe the regulation of IL-33 in a TH1 and a TH2 model of experimental colitis, to determine if IL-33 is also regulated according to the T helper cell profile in the inflamed intestinal mucosa. Methods: Expression of IL-33 was investigated in dextran sodium sulphate (DSS)-induced colitis (a TH2-type of inflammation) and in the T-cell transfer model of colitis (SCID colitis) (a TH1-type of inflammation). The colonic IL-33 mRNA expression was analyzed by a quantitative realtime polymerase chain reaction (qRT-PCR). IL-33 protein expression and its localization were investigated by immunoblotting and by standard immunohistochemical procedures. The association between IL-33 expression and clinical outcome measures including the disease activity index (DAI), colon length, and histological inflammation scores was determined. Results: The colonic IL-33 mRNA expression was significantly up-regulated in the experimental DSS colitis model (p<0.05), and significantly down-regulated in the SCID colitis (p<0.01). Our results showed an increased number of IL-33 positive cells in DSS colitis localized to lamina propria inflammatory cells, whereas IL-33 protein expression in SCID colitis was abolished. IL-33 expression correlated positively with the DAI-score (p<0.001), colon length (p<0.001), and the histological inflammation score (p<0.001) of the DSS model. Conclusions: The present study demonstrates that colonic IL-33 expression in mice is highly dependent on the type of mucosal inflammatory response induced, being high in TH2-type inflammatory conditions, and low in TH1-type inflammatory responses. IL-33 might be a key determinant of the nature of the colonic mucosal inflammation and thus be of importance for the development of inflammatory bowel disease. Inhibition of IL33 signalling could in this way be a potential therapeutic target in UC which is driven by a TH2-type inflammatory reaction.

Tu1861 The IBD Associated Gene, Protein Tyrosine Phosphate Non Receptor Type 22, Modulates Interferon-γ Induced Cytokine Responses in Human Monocytes

Background: Interleukin (IL)-33 is a pro-inflammatory cytokine that has been associated with induction of human T helper 2 (TH2)-type inflammatory responses through activation of the ST2 receptor. Recent research has shown that IL-33 is upregulated in active ulcerative colitis (UC), but the role of IL-33 in regulation of intestinal mucosal immunologic reactions is uncertain. Aim: The aim of the present study was to describe the regulation of IL-33 in a TH1 and a TH2 model of experimental colitis, to determine if IL-33 is also regulated according to the T helper cell profile in the inflamed intestinal mucosa. Methods: Expression of IL-33 was investigated in dextran sodium sulphate (DSS)-induced colitis (a TH2-type of inflammation) and in the T-cell transfer model of colitis (SCID colitis) (a TH1-type of inflammation). The colonic IL-33 mRNA expression was analyzed by a quantitative realtime polymerase chain reaction (qRT-PCR). IL-33 protein expression and its localization were investigated by immunoblotting and by standard immunohistochemical procedures. The association between IL-33 expression and clinical outcome measures including the disease activity index (DAI), colon length, and histological inflammation scores was determined. Results: The colonic IL-33 mRNA expression was significantly up-regulated in the experimental DSS colitis model (p<0.05), and significantly down-regulated in the SCID colitis (p<0.01). Our results showed an increased number of IL-33 positive cells in DSS colitis localized to lamina propria inflammatory cells, whereas IL-33 protein expression in SCID colitis was abolished. IL-33 expression correlated positively with the DAI-score (p<0.001), colon length (p<0.001), and the histological inflammation score (p<0.001) of the DSS model. Conclusions: The present study demonstrates that colonic IL-33 expression in mice is highly dependent on the type of mucosal inflammatory response induced, being high in TH2-type inflammatory conditions, and low in TH1-type inflammatory responses. IL-33 might be a key determinant of the nature of the colonic mucosal inflammation and thus be of importance for the development of inflammatory bowel disease. Inhibition of IL33 signalling could in this way be a potential therapeutic target in UC which is driven by a TH2-type inflammatory reaction.

Chitosan oligosaccharide as potential therapy of inflammatory bowel disease: Therapeutic efficacy and possible mechanisms of action

Inflammatory bowel disease (IBD) results from intestinal epithelial barrier defect and dysregulated mucosal immune response. This study aimed to evaluate the therapeutic potential of chitosan oligosaccharide (COS), a biodegradation product of dietary fiber chitosan, in the treatment of IBD and to elucidate its possible mechanisms of action. Oral administration of COS protected against mortality and intestinal inflammation in a mouse model of acute colitis induced by 5% dextran sulfate sodium (DSS). The most effective dose range of COS was 10–20mg/kg/day. In addition, nuclear factor kappa B (NF-κB) activation, and levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in colonic tissues were suppressed in mice receiving COS. Similar protective effect of COS against mortality and intestinal inflammation was observed in another mouse model of acute colitis induced by rectal instillation of 4% acetic acid. Importantly, COS administration after colitis induction was effective in ameliorating intestinal inflammation in both acute colitis models induced by 5% DSS and chronic colitis models induced by cycles of 2.5% DSS. In human colonic epithelial cells (T84 cells), COS treatment prevented NF-κB activation, production of TNF-α and IL-6, and loss of epithelial barrier integrity under both lipopolysaccharide (LPS) and TNF-α-stimulated conditions. Furthermore, binding of LPS to T84 cells, and TNF-α and oxidative stress-induced apoptosis of T84 cells were prevented by treatment with COS. These results suggest that COS may be effective in the treatment of IBD through inhibition of NF-κB signaling and apoptosis of intestinal epithelial cells.

Therapeutic Potential of Carbon Monoxide (CO) for Intestinal Inflammation

The pathogenesis of inflammatory bowel disease (IBD) is complicated and even several therapeutic strategies have been developed, they are not adequate for achieving mucosal remission in all IBD patients. Several reports have described the role of carbon monoxide (CO) in protection against chronic intestinal inflammation. CO has recently emerged as a potent immunomodulatory entity, anti-inflammatory agent, and homeostasis of physiological condition. CO reduces lipopolysaccharide-induced proinflammatory cytokines in macrophages via the effect of MAPK pathways. Interleukin-6, one of the important cytokines in the pathogenesis of IBD is also regulated by CO. Epithelial cell restitution is reported to be important factor to control IBD and CO has been reported to enhance colonic epithelial restitution through FGF15/19 expression in colonic myofibroblasts. CO also reduced mucosal damage and inflammation in several experimental animal colitis models such as interleukin-10(-/-) mouse model, TCRα(-/-) mouse model, dextran sodium sulfate colitis model, and trinitrobennzen sulfonic acid colitis model. Taken together, CO has anti-inflammatory and enhancement of restitution examined in vitro model and in vivo experimental colitis model. These results indicate that CO may have a potential to be one of the therapeutic strategies in IBD patients.

Modeling IBD in the mouse through random germline mutagenesis

Inflammatory bowel diseases (IBD), including both ulcerative colitis and Crohn's disease, have strong genetic components. In mice, several mutations are known to favor IBD or to inhibit intestinal inflammation. But a comprehensive picture of the pathogenesis of IBD cannot be assembled based on the limited information so far available from genetic analyses. To unveil new genes important for the pathogenesis of IBD, we took an unbiased, hypothesis-free view of IBD, using germline mutagenesis to analyze the phenomenon in mice. We screen for mutations that cause susceptibility to IBD on a defined genetic background using the Dextran sodium sulfate (DSS) colitis model, positionally clone these mutations, and form hypotheses concerning the participation of each validated gene in the disease pathogenesis. A total of 5846 mice have been screened by placing them on 1% DSS in drinking water for a period of 7 days. During this time period all animals are weighed daily, and extreme outliers are retrieved for further study. A total of 16 transmissible mutations causing hypersensitivity to DSS have been detected. Of these, 6 have been identified, and fall into 5 genes. Failure of epithelial integrity is sensed by Toll-like receptors (TLR) on epithelial cells. Wound closure also additionally requires water transport via aquaporin 3, signaling via the EGF receptor pathway, and an intact unfolded protein response, which depends on Mbtps1, also known as the site-1 protease. Relatively common mutations affecting the structure of Mucin-2 also enhance susceptibility to colitis, evidently by increasing ER stress. In addition, genes with unknown functions have been identified causing increased susceptibility to DSS colitis. One of the mutant mice identified in this screen was homozygous for a mutation in an uncharacterized gene. The gene is predicted to encode a protein with an unstructured cytoplasmic N-terminal domain and a C-terminal domain containing five transmembrane α helices connected by short loops. The mutation lies in the splice acceptor site of intron 3 of the seven exon gene, and affects a thymine base five nucleotides from the next exon. cDNA sequencing revealed that the mutation results in skipping of exon 4. Splicing of exon 3 to exon 5 creates a frameshift and a premature stop codon. The Klein-Zschocher mouse showed severe weight loss after administration of 1% DSS in the drinking water. Periodic acid-Schiff stain staining of small intestines and colons of Klein-Zschocher mice revealed reduced numbers of Paneth and goblet cells in naïve mutant mice. Furthermore, electron microscopy of the small intestine and colon of naive Klein-Zschocher mice showed abnormal vesicles in Paneth and goblet cells of the mutant mice. Defective Paneth cells of Klein-Zschocher mutant mice show enhanced autophagy as demonstrated by LC3 Western blotting. In addition, the intestinal permeability was increased 85% in Klein-Zschocher mice demonstrating epithelial barrier dysfunction in these mice. Disturbed epithelial integrity together with abnormal Paneth and goblet cells explain the increased susceptibility in the DSS colitis model. Taken together, using random mutagenesis and the DSS mouse model we found new genes and new functions of known genes that might play a role in IBD. A coherent picture of the essential events required for homeostasis has begun to emerge.

Targeted delivery of vitamin D to the colon using β-glucuronides of vitamin D: therapeutic effects in a murine model of inflammatory bowel disease

1,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D] has been shown to inhibit development of dextran sodium sulfate (DSS)-induced colitis in mice but can also cause hypercalcemia. The aim of this study was to evaluate whether β-glucuronides of vitamin D could deliver 1,25(OH)(2)D to the colon to ameliorate colitis while reducing the risk of hypercalcemia. Initial studies demonstrated that bacteria residing in the lower intestinal tract were capable of liberating 1,25(OH)(2)D from 1,25-dihydroxyvitamin D(3)-25-β-glucuronide [β-gluc-1,25(OH)(2)D]. We also determined that a much greater upregulation of the vitamin D-dependent 24-hydroxylase gene (Cyp24) was induced in the colon by treatment of mice with an oral dose of β-gluc-1,25(OH)(2)D than 1,25(OH)(2)D, demonstrating targeted delivery of 1,25(OH)(2)D to the colon. We then tested β-glucuronides of vitamin D in the mouse DSS colitis model in two studies. In mice receiving DSS dissolved in distilled water and treated with 1,25(OH)(2)D or β-gluc-1,25(OH)(2)D, severity of colitis was reduced. Combination of β-gluc-1,25(OH)(2)D with 25-hydroxyvitamin D(3)-25-β-glucuronide [β-gluc-25(OH)D] resulted in the greatest reduction of colitis lesions and symptoms in DSS-treated mice. Plasma calcium concentrations were lower in mice treated with β-gluc-1,25(OH)(2)D alone or in combination with β-gluc-25(OH)D than in mice treated with 1,25(OH)(2)D, which were hypercalcemic at the time of death. β-Glucuronides of vitamin D compounds can deliver 1,25(OH)(2)D to the lower intestine and can reduce symptoms and lesions of acute colitis in this model.

Use of Enterally Delivered Angiotensin II Type Ia Receptor Antagonists to Reduce the Severity of Colitis

Renin-angiotensin system blockade reduces inflammation in several organ systems. Having found a fourfold increase in angiotensin II type Ia receptor expression in a dextran sodium sulfate colitis model, we targeted blockade with angiotensin II type Ia receptor antagonists to prevent colitis development. Because hypotension is a major complication of angiotensin II type Ia receptor antagonists use, we hypothesized that use of angiotensin II type Ia receptor antagonists compounds which lack cell membrane permeability, and thus enteric absorption, would allow for direct enteral delivery at far higher concentrations than would be tolerated systemically, yet retain efficacy. Based on the structure of the angiotensin II type Ia receptor antagonist losartan, deschloro-losartan was synthesized, which has extremely poor cell membrane permeability. Angiotensin II type Ia receptor antagonist efficacy was evaluated by determining the ability to block NF-κB activation in vitro. Dextran sodium sulfate colitis was induced in mice and angiotensin II type Ia receptor antagonist efficacy delivered transanally was assessed. In vitro, deschloro-losartan demonstrated near equal angiotensin II type Ia receptor blockade compared to losartan as well as another angiotensin II type Ia receptor antagonist, candesartan. In the dextran sodium sulfate model, each compound significantly improved clinical and histologic scores and epithelial cell apoptosis. Abundance of TNF-α, IL-1β, and IL6 mRNA were significantly decreased with each compound. In vitro and in vivo intestinal drug absorption, as well as measures of blood pressure and mucosal and colonic blood flow, showed significantly lower uptake of deschloro-losartan compared to losartan and candesartan. This study demonstrated efficacy of high-dose angiotensin II type Ia receptor antagonists in this colitis model. We postulate that a specially designed angiotensin II type Ia receptor antagonist with poor oral absorption may have great potential as a new therapeutic agent for inflammatory bowel disease in the future.

Colitis induced in mice with dextran sulfate sodium (DSS) is mediated by the NLRP3 inflammasome

Aims: The proinflammatory cytokines IL-1β and IL-18 are central players in the pathogenesis of inflammatory bowel disease (IBD). In response to a variety of microbial components and crystalline substances, both cytokines are processed via the caspase-1 activating multi-protein complex, the NLRP3 inflammasome. Here, we examined the role of the NLRP3 inflammasome in experimental colitis induced by dextran sulfate sodium (DSS). Methods: IL-1β production in response to dextran sulfate sodium (DSS) was studied in macrophages of wild-type (WT), caspase-1–/–, NLRP3–/–, ASC–/–, cathepsin B–/– or cathepsin L–/– mice. Colitis was induced in C57BL/6 and NLRP3–/– mice by oral DSS administration. A clinical disease activity score was evaluated daily. Histological colitis severity and expression of cytokines were determined in colonic tissue. Results: Macrophages incubated with DSS in vitro secreted high levels of IL-1β in a caspase-1-dependent manner. IL-1β secretion was abrogated in macrophages lacking NLRP3, ASC or caspase-1, indicating that DSS activates caspase-1 via the NLRP3 inflammasome. Moreover, IL-1β secretion was dependent on phagocytosis, lysosomal maturation, cathepsin B and L, and reactive oxygen species (ROS). After oral administration of DSS, NLRP3–/– mice developed a less severe colitis than WT mice and produced lower levels of proinflammatory cytokines in colonic tissue. Pharmacological inhibition of caspase-1 with pralnacasan achieved a comparable level of mucosal protection as NLRP3 deficiency. Conclusions: We identified the NLRP3 inflammasome as a critical check-point of intestinal inflammation in the DSS colitis model. The NLRP3 inflammasome may serve as a novel target for the development of therapeutics for patients with IBD.

Colitis induced in mice with dextran sulfate sodium (DSS) is mediated by the NLRP3 inflammasome

BackgroundThe proinflammatory cytokines interleukin 1β (IL-1β) and IL-18 are central players in the pathogenesis of inflammatory bowel disease (IBD). In response to a variety of microbial components and crystalline substances,...

Naturally Occurring Glycoalkaloids in Potatoes Aggravate Intestinal Inflammation in Two Mouse Models of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) may be initiated following disruption of the intestinal epithelial barrier. This disruption, in turn, permits luminal antigens unfettered access to the mucosal immune system and leads to an uncontrolled inflammatory response. Glycoalkaloids, which are found in potatoes, disrupt cholesterol-containing membranes such as those of the intestinal epithelium. Glycoalkaloid ingestion through potatoes may play a role in the initiation and/or perpetuation of IBD. To determine if commercial and high glycoalkaloids containing fried potato skins aggravate intestinal inflammation using two different animal models of IBD. Fried potato skins from commercial potatoes containing low/medium glycoalkaloid levels and high glycoalkaloids potatoes were fed for 20 days to interleukin 10 gene-deficient mice and dextran sodium sulfate-induced colitic mice. Intestinal permeability, mucosal cytokine and myeloperoxidase levels and body weight were determined to assess intestinal injury. Deep frying potato skins markedly increased glycoalkaloid content. Interleukin 10 gene-deficient mice fed fried commercial potato skins with medium glycoalkaloid content exhibited significantly elevated levels of ileal IFN-γ relative to controls. Mice in the dextran sodium sulfate colitis model that were fed the same strain of potatoes demonstrated significantly elevated levels of pro-inflammatory cytokines IFN-γ, TNF-α, and IL-17 in the colon in addition to an enhanced colonic permeability. Inflammatory response was intensified when the mice were fed potatoes with higher glycoalkaloid contents. Our results demonstrate that consumption of potato skins containing glycoalkaloids can significantly aggravate intestinal inflammation in predisposed individuals.

Epigenetic maturation in colonic mucosa continues beyond infancy in mice

Monozygotic twin and other epidemiologic studies indicate that epigenetic processes may play an important role in the pathogenesis of inflammatory bowel diseases that commonly affect the colonic mucosa. The peak onset of these disorders in young adulthood suggests that epigenetic changes normally occurring in the colonic mucosa shortly before adulthood could be important etiologic factors. We assessed developmental changes in colitis susceptibility during the physiologically relevant period of childhood in mice [postnatal day 30 (P30) to P90] and concurrent changes in DNA methylation and gene expression in murine colonic mucosa. Susceptibility to colitis was tested in C57BL/6J mice with the dextran sulfate sodium colitis model. Methylation specific amplification microarray (MSAM) was used to screen for changes in DNA methylation, with validation by bisulfite pyrosequencing. Gene expression changes were analyzed by microarray expression profiling and real time RT-PCR. Mice were more susceptible to chemically induced colitis at P90 than at P30. DNA methylation changes, however, were not extensive; of 23 743 genomic intervals interrogated, only 271 underwent significant methylation alteration during this developmental period. We found an excellent correlation between the MSAM and bisulfite pyrosequencing at 11 gene associated intervals validated (R(2) = 0.89). Importantly, at the genes encoding galectin-1 (Lgals1), and mothers against decapentaplegic homolog 3 or Smad3, both previously implicated in murine colitis, developmental changes in DNA methylation from P30 to P90 were inversely correlated with expression. Colonic mucosal epigenetic maturation continues through early adulthood in the mouse, and may contribute to the age-associated increase in colitis susceptibility. Transcript Profiling: Gene Expression Omnibus (http://www.ncbi.nlm.nih.gov/geo/), accession numbers: GSE18031 (DNA methylation arrays), GSE19506 (gene expression arrays).

Transanal delivery of angiotensin converting enzyme inhibitor prevents colonic fibrosis in a mouse colitis model: development of a unique mode of treatment

We have previously shown that angiotensin converting enzyme-inhibitor (ACE-I) improved colonic inflammation and apoptosis in a dextran sodium sulfate (DSS)-induced colitis model. This study attempted to determine whether ACE-I could prevent the development of colonic fibrosis. Colitis was induced in C57BL/6 mice with 2.5% DSS water for 7 days, followed by 7 days without DSS (fibrosis development). Study groups: Control (naive or non-treated), DSS+Placebo (polyethylene glycol (PEG), and DSS+ACE-I (using enalaprilat and PEG which are not absorbed through intact mucosa). Placebo and ACE-I were delivered daily via transanal route. Colonic mucosal fibrosis and inflammation were evaluated based on histological findings and cytokine expression. Transanal administration of ACE-I/PEG dose-dependently decreased the severity of fibrosis and pro-inflammatory cytokine expression. We next investigated if ACE-I acted on the TGF-beta/Smad signaling pathway as a mechanism of this anti-fibrosis action. Results showed a significant down-regulation of TGF-beta1 expression; as well, downstream signaling of the Smad family, known to mediate fibrosis, showed a decline in Smad 3 and 4 expression with ACE-I/PEG. ACE-I/PEG is effective in preventing colonic fibrosis and pro-inflammatory cytokine expression in a DSS colitis model, most likely by down-regulating the TGF-beta signaling pathway. ACE-I/PEG may be a potential new option for treating inflammatory bowel disease.

Disease modifying effect of statins in dextran sulfate sodium model of mouse colitis

We evaluated the disease modifying effect of simvastatin and atorvastatin in Dextran Sulfate Sodium (DSS) model of colitis. Thirty, 8-week old female Swiss-Webster mice were separated into 5 groups (n = 6/group). Colitis was induced by feeding 4 % DSS solution for 7 days. Following discontinuation of DSS, over the next 7 days, the groups orally received simvastatin (20 mg/kg/day), atorvastatin (60 mg/kg/day), vehicle only (0.75 % methylcellulose), subcutaneous 30 mug injections of anti-TNFalpha monoclonal antibody or intraperitoneal anti-mouse apolipoprotein A-I antibody respectively. Disease activity Index (DAI) was determined daily by a blinded investigator. The mean reduction in DAI scores from day 7 to day 14 for anti-TNFalpha group, simvastatin and atorvastatin group were 74 %, 76 % and 64 %, respectively as compared to 41 % reduction in vehicle and anti-apolipoprotein A-I antibody-treated groups. This finding suggests that statins may have the ability to modify the disease activity in the DSS model of colitis and the disease modifying effect is comparable to anti-mouse TNFalpha treatment in this model.

Prostaglandins and epithelial response to injury

This review will highlight recent studies in the role of prostaglandins in regulating the epithelial response to injury in the gastrointestinal tract. Prostaglandins, particularly PGE2, regulate intestinal epithelial apoptosis and proliferation in the face of injury. In the dextran sodium sulphate colitis model, PGE2, produced through cyclooxygenase-2, supports epithelial proliferation. Two studies demonstrated that PGE2 is an important mediator of the protective effects of toll-like receptor signaling in the dextran sulphate sodium model. One study suggested that toll-like receptor signaling induced cyclooxygenase-2 expression whereas the other suggested that toll-like receptor signaling induces the repositioning of cyclooxygenase-2 expressing stromal cells. PGE2 is also protective of small intestinal epithelial cells in the radiation injury model. In this model PGE2 decreases radiation-induced apoptosis and increases crypt survival. PGE2 binds to EP receptors; EP2 appears to be especially important in mediating the protective effects of PGE2 on epithelial cells. The intracellular signaling pathways by which PGE2 mediates its pro-proliferative and antiapoptotic effects include the PI3 kinase/Akt pathway, the MAP kinase pathway and the beta-catenin pathway. Endogenous PGE2 has pro-proliferative and antiapoptotic effects on epithelial cells in gastrointestinal injury.

The specific JNK inhibitor SP600125 targets tumour necrosis factor‐α production and epithelial cell apoptosis in acute murine colitis

Stress-activated protein kinases (SAPKs) are activated in human inflammatory bowel disease (IBD). Recently it has been demonstrated that p38MAPK (mitogen-activated protein kinase) inhibition using SB203580 is effective in reducing disease in both dextran sulphate sodium (DSS)-induced and 2,4,6-trinitrobenzenesulphonic acid (TNBS)-induced murine colitides, underscoring the importance of this pathway in gastrointestinal inflammation. However, the contribution of c-Jun N-terminal kinase (JNK) in intestinal inflammation is unknown. Based on the known involvement of JNK in tumour necrosis factor-alpha (TNF-alpha) expression and in mediating the effects of oxidant stress, we hypothesized that JNK inhibition would also affect colitis. Our studies in mice with DSS-induced colitis treated with the JNK inhibitor SP600125, indicate that there is a significant reduction in wasting as well as a significant reduction in histological damage scores. Both total colonic and mesenteric lymphocyte CD3/CD28-stimulated TNF-alpha levels were dramatically reduced under the same circumstances. This was associated with a reduction in JNK protein expression and activity, as well as a reduction in AP-1 DNA binding with SP600125. Interestingly, there were no apparent changes in either p38MAPK or p42/44ERKs. Immunofluorescence of the colon for the active form of JNK revealed a prominent signal arising from the infiltrating inflammatory cells. SP600125 reduced this as well as, specifically, macrophage infiltration. Strikingly, we also demonstrate reduced epithelial cell apoptosis in response to treatment with SP600125. We conclude that specific inhibition of JNK is beneficial in the DSS model of colitis, and may be of value in human IBD.