Single Nucleotide Polymorphisms (SNPs) in the intracellular pattern recognition receptor gene NLRP3 are associated with susceptibility to Crohn’s disease, a form of inflammatory bowel disease (IBD). Following cell damage or infection, NLRP3 triggers the formation of inflammasomes, a multimolecular protein complex containing NLRP3, ASC and caspase-1, which mediate secretion of IL-1β and IL-18. NLRP3 inflammasome activation in macrophages has been implicated in protection against several pathogens, but whether NLRP3 activation in tissue cells contributes to protective immunity against bacterial pathogens is unknown. We show that upon infection with the attaching/effacing (A/E) intestinal pathogen Citrobacter rodentium, Nlrp3-/- and Asc-/- mice displayed higher bacterial colonization, more weight loss and exacerbated intestinal inflammation. We further show that Nlrp3 inflammasome activation in intestinal epithelial cells (IECs) acts rapidly after infection to limit bacterial replication and penetration, and inhibits the development of inflammatory pathology in the gut. We also show that epithelial Nlrp3-mediated protection is independent of the classical inflammasome cytokines IL-1β and IL-18. Thus an Nlrp3-Asc circuit in IECs regulates early defense against a mucosal pathogen and limits inflammation in the intestine. Nlrp3 inflammasome activation has also been implicated in protection in acute models of experimental colitis, but its role in chronic models of colitis is unknown. We found that Asc signaling is necessary for the development of innate chronic intestinal inflammation driven by Helicobacter hepaticus. Thus while deficient inflammasome signaling in tissue cells increases susceptibility towards enteric pathogens, excessive inflammasome activation can drive chronic intestinal inflammation.

Bioactive food components containing n-3 polyunsaturated fatty acids (PUFA) and curcumin modulate multiple determinants that link inflammation to cancer initiation and progression. In this dissertation, both transgenic and dietary mouse models were used to elucidate the effect of n-3 PUFA and curcumin treatment on murine intestinal inflammation. Specifically, fat-1 transgenic mice, which convert endogenous n-6 PUFA to n-3 PUFA in multiple tissues, exhibited a reduced number of colonic adenocarcinomas per mouse (1.05 plus/minus 0.29 versus 2.12 plus/minus 0.51, P = 0.033), elevated apoptosis (P = 0.03), and a decrease in n-6 PUFA–derived eicosanoids compared with wild-type (wt) mice in an azoxymethane (AOM) - dextran sodium sulfate (DSS) model. Following a 2-week recovery period after 5 days of DSS exposure, colonic inflammation and ulceration scores returned to pretreatment levels only in fat-1 mice. In addition, fat-1 vs wt mice exhibited decreased (P < 0.05) levels of CD3 , CD4 T helper, and macrophage cell numbers in the colon. The ability of n-3 PUFA to favorably modulate the resolution of intestinal inflammation in fat-1 mice was linked to an enhancement (P < 0.05) in the percentage of colonic lamina propria (cLP) CD4 FoxP3 cells and a decrease in both splenic and cLP Th17 cells (0.8 vs 1.2 percent in spleen, 1.4 vs 1.7 percent in colon) (P < 0.05) in fat-1 mice compared to wt. These results suggest that the antitumorigenic effect of n-3 PUFA may be mediated via its anti-inflammatory properties. The combined effect of n-3 PUFA and curcumin on DSS induced colitis was assessed in C57BL/6 mice. Addition of fish oil (FO) and/or curcumin to a corn oil (CO) based diet increased animal mortality compared to CO alone (P < 0.05). Consistently, following 1 or 2 cycles of DSS treatment, both dietary FO and curcumin promoted mucosal injury/ulceration compared to CO. However, compared to other diets, FO and curcumin combined feeding enhanced the resolution of chronic inflammation and suppressed (p < 0.05) a key inflammatory mediator, NF-kB, in colon mucosa. Mucosal microarray analysis revealed that dietary FO and curcumin differentially modulated the expression of genes induced by DSS treatment. These results suggest that dietary lipids and curcumin interact to regulate mucosal homeostasis and the resolution of chronic inflammation in the colon.

Introduction: Appetite is often impaired in patients with gastrointestinal inflammation. Up to 75% of hospitalised Crohn's disease (CD) patients are malnourished. Recent animal research has suggested that immune mediated upregulation of enteroendocrine cell (EEC) activity plays a mechanistic role in the appetite and feeding disturbance observed during gut inflammation. The role of EEC in producing factors regulating satiety and intestinal growth is well recognised but work on their use as therapeutic targets or agents in inflammatory bowel disease (IBD) is still in its infancy. EEC peptide dynamics are further controlled through dipeptidyl peptidase (DP4) protease metabolism but no data are yet available on its expression in IBD. My aim is to understand the roles of EEC in appetite control and the maintenance of gut mucosal integrity in intestinal inflammation. Methodology: Patients with CD and healthy controls were studied. Symptoms were assessed using visual analogue scores (VAS). Gut hormone responses to a test meal were studied using a multiplex-ELISA technique, and correlated to symptoms. At the tissue level, EEC markers and transcription factors were quantified using immunohistochemistry, quantitative polymerase chain reaction (qPCR) and western blotting techniques. The same techniques were used to study DP4 expression. The effects of glucagon-like peptide-2 (GLP-2) on a gut model of the epithelial barrier were studied by measuring the transepithelial electrical resistance (TEER) across GLP-2 exposed Caco-2 cell monolayers after cytokine exposure. Tight junction protein expression in naïve and GLP-2 exposed cells was quantified by western blotting. Main Results: CD patients with active inflammation displayed a significant reduction in appetite. At the tissue level, GLP-1 and chromogranin A (CgA) were significantly upregulated. At the mRNA level significant increased expression was noted for CgA, glucagon-like peptide-1 (GLP-1), ubiquitination factor 4a and neurogenin 3. At the plasma level, total polypeptide YY (PYY) was increased. A significant correlation was seen between postprandial PYY responses and symptoms of nausea and bloating. Ghrelin, was 3-fold higher in the CD group compared to controls, and showed a reversed postprandial response with a significant correlation with the CD activity index (CDAI). Protein DP4 expression was significantly decreased at the tissue and plasma level in CD. GLP-2 increased tight junction protein expression in Caco-2 cells and maintained stable TEER and tight junction protein expression after cytokine exposure. Conclusions: The data presented are compatible with a potential role of EEC in appetite dysregulation in intestinal inflammation. An enhanced EEC response to food intake may directly affect appetite in such patients through increased gut-brain signalling. These may present tractable therapeutic targets. The decrease in mucosal DP4 expression in CD may make bioactive GLP-2 more available in the affected gut, hence improving gut mucosal integrity in intestinal inflammation. This pilot work has shown that GLP-2 has a role in maintaining gut mucosal integrity in intestinal inflammation through a positive effect on tight junction protein expression.

Inflammatory bowel disease causes structural and functional alterations in the enteric nervous system (ENS). Since the onset of intestinal inflammation involves the activation of resident immune cells as well as rapid influx of infiltrating cells, we proposed that changes in the ENS are a result of the release of toxic inflammatory factors. We hypothesized that early damage to the ENS in inflammation is caused by harmful levels of nitric oxide (NO) generated by the enzyme inducible nitric oxide synthase (iNOS) found in immune cells. This was assessed in the 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)-model of colitis in rats. Large increases in infiltrating granulocytes, particularly neutrophils and blood-derived monocytes were found in the muscularis layers adjacent to the ENS. A rapid increase in iNOS immunoreactivity in the muscularis regions during early stages of inflammation (6 – 24 hr) was observed. Whether high NO levels generated by chemical donors could be toxic to neurons was tested in a co-culture model of myenteric neurons, smooth muscle and glia enzymatically isolated from neonatal rats. Exposure of co-cultures to NO for 48 hr resulted in significant, concentration dependent decrease in neuron survival. We then developed a model that permitted the direct study of immune cell interactions with myenteric neurons. Myenteric neurons were co-cultured with activated peritoneal immune cells that expressed iNOS and generated high NO levels (49 + 6.2µM) for 48 hr. This caused significant neuronal death, reducing neuron number by 19 + 5%, and disruption of axons. Pre-treatment of immune cells with a selective iNOS-inhibitor, L-NIL resulted in neuron numbers that were not significantly different from control (96 + 2%) suggesting that NO played a central role in mediating the damaging effects of immune cells. Lastly, when direct contact between immune cells and neurons was prevented in the previous experiment through use of trans-wells, unanticipated neurotrophic effects were observed. Increased axon outgrowth (282 + 57%) was detected in addition to loss of the neurotoxic effects in spite of similar experimental conditions. We concluded that proximity and contact plays an important role in determining the nature of immune cell mediated alterations in enteric neurons. / Thesis (Master, Physiology) -- Queen's University, 2009-11-30 10:09:38.384

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INTRODUCCIÓ: Hi ha molt poca informació a la literatura mèdica que suggereix que existeix una alta prevalença de la infecció pel virus hepatitis B (VHB) i C (VHC) en malalts amb malaltia inflamatòria intestinal (MII). El seu coneixement és important per la possibilitat de reactivació viral relacionada amb el tractament immunosupressor. HIPÒTESI: La infecció per VHB i C és més freqüent en la MII que en la població general de referència. El tractament immunosupressor pot reactivar la infecció per VHB i C. OBJECTIUS: Avaluar: 1) La prevalença d'infecció per VHB i C en pacients amb MII de diferents àrees geogràfiques d'Espanya. 2) L'efecte del tractament immunosupressor i els fàrmacs biològics sobre l'evolució de la infecció per VHB i C. METODOLOGIA: Estudi 1: inclusió de 2076 pacients amb MII, als quals s'avalua l'existència d'infecció per VHB i C mitjançant tècniques analítiques estàndard (ELISA i PCR). Es van registrar els factors relacionats amb la MII i la infecció. Estudi 2: Inclusió de 162 pacients amb MII i infecció per VHB i / o C i que van rebre tractament immunosupressor per la MII. Es van registrar variables clíniques i analítiques relacionades amb la reactivació. Tots dos són estudis multicèntrics amb registre electrònic (www.repentina.com). Per a l’anàlisi de resultats es van utilitzar tests univariants (2 i test de t Student) i multivariants (regressió logística i model de risc proporcional de Cox). RESULTATS: Estudi 1: El 9.7% de pacients amb colitis ulcerosa (CU) i malaltia de Crohn (MC) van presentar positivitat de marcadors d'infecció pel VHB i C actual o passada (CU: HBsAg 0.8 % , anti-HBc 8 % , anti-VHC 1.3 % ; MC: HBsAg 0.6 % , anti-HBc 7.1 % , anti-VHC 2.3 % ). El 12% de pacients amb MII van presentar marcadors de vacunació eficaç. En l’anàlisi multivariant, l'edat, la història familiar d'hepatitis i la MII moderada-greu, es van relacionar de manera significativa amb el VHB, mentre que les transfusions i l'ús d'antibiòtics ho van fer amb el VHC. Estudi 2: Un 36% de pacients van presentar disfunció hepàtica (DH) relacionada amb el VHB, un 66% dels quals van presentar insuficiència hepàtica. L’anàlisi multivariant va demostrar que l’únic factor relacionat amb la DH per VHB va ser l'ús simultani de 2 o més immunosupressors. En canvi només un 15.7% dels pacients amb VHC van presentar DH. CONCLUSIONS:Estudi 1: El pacients amb MII presenten una prevalença d’infecció pels VHB i VHC similar a la de la població general de referència, i aquesta és més baixa del que prèviament s’havia publicat. L’escassa relació de la infecció pel VHC i VHB amb els procediments invasius i ingressos hospitalaris suggereix que aquestes infeccions rarament s’adquireixen en l’àmbit hospitalari al nostre país. Es detecta un baix percentatge de vacunació eficaç pel VHB, el que obliga a intensificar els programes de vacunació en aquests pacients. Estudi 2: La DH en pacients amb MII tractats amb immunosupressors, és més freqüent i greu en els pacients amb infecció pel VHB que en el pacients amb infecció pel VHC. La immunosupressió combinada va ser l’únic factor predictiu independent de reactivació pel VHB. / Background: Limited information suggests the existence of a high prevalence of hepatitis B (HBV) and C virus (HCV) in inflammatory bowel disease (IBD). Hypothesis: HBV and HCV infection is more common in IBD than in the general population. Immunosuppressants can reactivate these infections.Objectives: To asses: 1) the prevalence of HBV and HCV in IBD, in a nationwide study, and to evaluate associated risk factors. 2) the influence of immunosuppressants on the course of HBV and HCV in IBD.Methods: Study 1: inclusion of 2076 IBD patients, which evaluates the existence of HBV and HCV using ELISA and PCR. Factors related to IBD and to infection were registered. Study 2: Inclusion of 162 IBD patients with HBV and HCV infection and immunosuppressants. Registration of clinical and laboratory variables related to reactivation. Both are multicentre studies with electronic data base (www.repentina.com). The results are analyzed by univariate and multivariate analysis. Results: Study 1: Present and / or past HBV and HCV infection was found in 9.7 % of IBD patients (HBsAg 0,6-0,8% / antiHBc 7-8% / anti-HCV 1.3-2.3%). Effective vaccination was present in 12 % of patients. In multivariate analysis, age, family history of hepatitis and moderate-to-severe IBD were significantly associated with HBV, whereas transfusions and antibiotics were significantly associated with HCV. Study 2: Liver dysfunction (LD) was observed in 36% HBsAg positive patients, 66% of whom developed hepatic failure. In contrast LD in HCV was observed in 15.7% of HCV-RNA positive patients. Treatment with ≥2 immunosuppressants was an independent predictor of HBV reactivation.Conclusions: Study 1: Prevalence of HBV and HCV infection in IBD is similar to that of the general population and lower than that in previously published series. This fact, in addition to the lack of association with invasive procedures, suggests the existence of adequate preventive measures in centres attending to these patients. The low percentage of effective vaccination makes it mandatory to intensify B virus vaccination in IBD. Study 2: LD in patients with IBD treated with immunosuppressants is more frequent and severe in those with HBV than in HCV carriers and is associated with combined immunosuppression.

β-Glucans have beneficial health effects due to their immune modulatory properties. Oral administration of β-glucans affects tumour growth, microbial infection, sepsis, and wound healing. We hypothesized that pre-treatment with orally delivered soluble and particulate β-glucans could ameliorate the development of aggravate dextran sulfate sodium (DSS) induced intestinal inflammation. To study this, mice were orally pre-treated with β-glucans for 14 days. We tested curdlan (a particulate β-(1,3)-glucan), glucan phosphate (a soluble β-(1,3)-glucan), and zymosan (a particle made from Saccharomyces cerevisiae, which contains around 55% β-glucans). Weight loss, colon weight, and feces score did not differ between β-glucan and vehicle treated groups. However, histology scores indicated that β-glucan-treated mice had increased inflammation at a microscopic level suggesting that β-glucan treatment worsened intestinal inflammation. Furthermore, curdlan and zymosan treatment led to increased colonic levels of inflammatory cytokines and chemokines, compared to vehicle. Glucan phosphate treatment did not significantly affect cytokine and chemokine levels. These data suggest that particulate and soluble β-glucans differentially affect the intestinal immune responses. However, no significant differences in other clinical colitis scores between soluble and particulate β-glucans were found in this study. In summary, β-glucans aggravate the course of dextran sulfate sodium (DSS)-induced intestinal inflammation at the level of the mucosa.

Normal intestinal functions are coordinated by enteric neurons within the enteric nervous system (ENS). In the embryonic and neonatal gut, enteric neuron survival is dependent on the expression of glial cell line-derived neurotrophic factor (GDNF) from its targets of innervation - the intestinal smooth muscle cells (ISMC). In the inflamed adult intestine, enteric neuron loss is immediately followed by ISMC proliferation, resulting in severe disruption of normal intestinal functions. Although GDNF can support the survival of postnatal enteric neurons, whether adult ISMC can secrete GDNF and support neuron survival is unclear. Results from qPCR analysis showed that freshly isolated adult ISMC have acquired the ability to express GDNF at the onset of proliferation, in vitro. Western blot analysis indicates that GDNF continues to be upregulated in ISMC at Passage 2 (P2), but its expression is decreased after long periods of proliferation at Passage 10 (P10). A neuron survival bioassay suggests that GDNF expression is correlated with enteric neuron survival. Results showed that P2 ISMC or conditioned media (CM) - but not P10 ISMC and CM, significantly increased enteric neuron survival. In subsequent experiments, the RET tyrosine kinase inhibitor vandetanib was used to block GDNF receptor-ligand interactions, and anti-GDNF neutralizing antibody was used to sequester soluble GDNF within the culture media. Both methods were successful at decreasing myenteric neuron survival. Furthermore, abolishing GDNF expression in P2 ISMC with GDNF siRNA also resulted in a decreased myenteric neuron survival. The above observations suggest that ISMC-derived GDNF is important in supporting myenteric neuron survival in vitro. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2012-09-28 09:43:23.968

Vitamin D may have immunomodulatory effects in the intestine. Our objective was to determine if exposure to vitamin D mitigates intestinal inflammation in IL-10 KO mice. Mice were randomized to a diet containing 25 IU (low) or 5000 IU (high) of vitamin D/kg of diet in utero and offspring were maintained on the same diet or switched to the other diet at weaning. Fecal samples were collected at 3 months of age. Vitamin D did not affect intestinal inflammation in male and female mice and did not affect KC cytokine concentration or regulate colonic gene expression in male mice. Vitamin D modulated the gut microbiota in a sex-specific manner and depending on timing of exposure. Females in the HH group had significantly higher fecal counts of C. coccoides than the other vitamin D interventions. Therefore, vitamin D may favourably modulate microbiota composition without attenuating inflammation.

Vitamin D may have immunomodulatory effects in the intestine. Our objective was to determine if exposure to vitamin D mitigates intestinal inflammation in IL-10 KO mice. Mice were randomized to a diet containing 25 IU (low) or 5000 IU (high) of vitamin D/kg of diet in utero and offspring were maintained on the same diet or switched to the other diet at weaning. Fecal samples were collected at 3 months of age. Vitamin D did not affect intestinal inflammation in male and female mice and did not affect KC cytokine concentration or regulate colonic gene expression in male mice. Vitamin D modulated the gut microbiota in a sex-specific manner and depending on timing of exposure. Females in the HH group had significantly higher fecal counts of C. coccoides than the other vitamin D interventions. Therefore, vitamin D may favourably modulate microbiota composition without attenuating inflammation.