Environmental factors such as diet contribute to the pathogenesis of inflammatory bowel disease (IBD). Epidemiological evidence suggests a robust linkage between IBD and the Western diet, which is often characterized by a high intake of food additives. These additives, including synthetic colourants, are widely used, leading to significant human exposure. Allura Red AC (AR) is one of the most popular synthetic colourants, yet little is known about its impact on human health and the role of AR in the pathogenesis of colitis remains elusive. Serotonin (5-hydroxytryptamine; 5-HT), which regulates various gut physiological processes, has been shown to modulate the gut microbiota and enhance susceptibility to colitis. In this thesis, it was discovered that chronic exposure to AR, at a dose found in commonly consumed dietary products, exacerbated dextran sulfate sodium (DSS)-induced colitis and triggered early onset of disease in the CD4+CD45RBhigh T cell-induced colitis model. AR also induced low grade colonic inflammation in naïve C57BL/6 mice. Exposure to AR was associated with increased colonic 5-HT levels and impaired intestinal barrier function via activation of the myosin light chain kinase (MLCK) pathway. However, AR did not promote colitis in mice lacking tryptophan hydroxylase 1 (Tph1), the rate-limiting enzyme responsible for colonic 5-HT synthesis. Further, AR increased colonic 5-HT levels in germ-free (GF) mice and perturbed the gut microbiota composition in specific pathogen-free (SPF) mice. Transfer of this altered microbiota from the dye-exposed SPF mice to GF mice conferred enhanced susceptibility to DSS-induced colitis. Mechanistically, AR induced reactive oxygen species (ROS) generation and promoted 5-HT secretion via the NF-κB pathway in BON cells. Data in this thesis indicate that the widely used synthetic colourant, AR, promotes colitis via colonic 5-HT in microbiota-dependent and -independent pathways. Collectively, these findings provide important information on enhancing public awareness of its detrimental effects on human health. / Thesis / Candidate in Philosophy / Epidemiological and experimental studies suggest a potential link between inflammatory bowel disease (IBD) and diet. The Western diet, often characterized by a high intake of processed foods, is associated with the growing incidence of IBD. Allura Red AC (AR) is a popular artificial food dye found in highly common processed foods, yet little is known about its impact on human health and disease. Serotonin, a key molecule in the gut, has been implicated in large bowel inflammation. Herein, the potential role of AR in the development of colitis was examined. Across multiple models, AR exposure heightened vulnerability to colitis in mice, an effect attenuated by reduced serotonin production in the gut. The effect of AR in enhancing colitis vulnerability occurred via gut microbiota-dependent and -independent pathways. These studies have identified how AR promotes colitis, findings that may advance public health awareness and impact the health of patients with IBD.

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<p>Stress is known to play an important role in the natural history of gastrointestinal diseases, and functional disorders in particular. In health, activation of the stress response serves to maintain homeostasis in response to harmful stimuli. However, prolonged activation of the stress response can become maladaptive and contribute to the initiation and maintenance of symptoms in disorders such as irritable bowel syndrome (IBS). The mechanisms underlying this detrimental effect are unclear. This thesis investigates this relationship by examining the influence of 10 days of water avoidance stress on a murine model of acute bacterial gastroenteritis; a known trigger in a subset of IBS patients. Results indicate that stress can increase the level of the stress hormone norepinephrine in the gut. However, the overall influence of host stress during infection proves to be beneficial in this model, with decreased colonic inflammation and earlier clearance of the pathogen. Next, we utilized the olfactory bulbectomy (OBx) model of depression comorbid anxiety, which shows a heightened stress response, to examine mechanism underlying stress-mediated susceptibility in a more chronic setting. OBx resulted in increased neural activity and motility in the gut, and a change in composition of gut microbiota. These responses were not accompanied by changes in gut permeability or immune activation. Thus stress alters the habitat of commensal bacteria via a neurally mediated change in colonic motility. These results have bearing on the ability of stress to alter the microbiota: a feature of functional GI disorders.</p> / Doctor of Philosophy (Medical Science)

<p>Increased visceral pain is often seen in patients with gastrointestinal (GI) inflammation. Some studies, however, have suggested that such pain may persist after resolution of damage or inflammation. Despite the debilitating pain associated with GI inflammation, and its significant impact on affected individuals, few studies have addressed this issue. We hypothesized that altered visceral pain responses would persist after resolution of a bout of colitis in an animal model of colitis. We studied the pain responses to colorectal distention in Wistar rats with dinitrobenzene sulfonic acid (DNBS)-induced colitis, using changes in heart rate as an index of pain. Colonic inflammation had resolved by day 15 after DNBS administration. The assessment of colonic inflammation was based on histological scores, colonic tissue pro-inflammatory cytokine levels and myleoperoxidase activity. Rats examined at 15 days post-DNBS administration exhibited diminished pain responses to colorectal distention as compared to healthy rats. This was associated with significant increases in colonic tissue levels of IL-4 and IL-10 as compared to healthy rats, indicating a possible role for these anti-inflammatory cytokines in counteracting the generation of pain and hyperalgesia. We also studied the effects of hydrogen sulfide (H2S) in our animal model, by administering inhibitors of two of the key enzymes involved in the production of H2S. Our results demonstrated that inhibition of H2S production did not significantly alter the pain responses observed in rats at 15 days post-DNBS administration. In summary, our results demonstrate altered autonomic responses to colorectal distension following resolution of colitis. Further research on the role of anti-inflammatory cytokines and H2S may help to determine the mechanism underlying this effect.</p> / Master of Science (MSc)

Mucosal inflammation in conditions ranging from infective acute enteritis or colitis to inflammatory bowel disease (IBD) is accompanied by alteration in enterochromaffin (EC) cell numbers and serotonin (5-hydroxytryptamine; 5-HT) content in the gut. Previously we had shown that CD4+ T cells, via production of T helper (Th)2 cytokines, regulate EC cell biology in the Trichuris muris-infectious colitis model. I further examined the mechanisms of immuno-endocrine interactions in the context of intestinal inflammation. In chapter 3, utilizing human EC cell line and Trichuris muris-mouse model of infectious colitis we identified a critical role of interleukin (IL)-13, a key Th2 cytokine, in increasing EC cell numbers, tryptophan hydroxylase (TPH)1 expression (rate-limiting enzyme of mucosal 5-HT bio-synthesis), and 5-HT production. In chapter 4, we show that IL-13 driven intestinal inflammation is critically dependent on increased 5-HT production using dextran sulfate sodium (DSS) and dinitrobenzene sulphonic acid (DNBS) models of colitis. In DSS-induced colitis, we were the first to identify the increased production of IL-13 and its pathogenic role as IL-13 knockout (IL-13-KO) mice had less severe inflammation compared to wild-type, which was exacerbated following replenishment of 5-HT in IL-13-KO mice. In chapter 5, biopsy examination revealed, higher mucosal IL-13 expression accompanied inflammation in Crohn's disease (CD), which was additionally associated with increased TPH1, 5-HT receptor (5-HTR)3A, 5-HTR7 and decreased 5-HT transporter (5-HTT) expressions. Moreover, CD patients had elevated plasma and platelet-poor plasma 5-HT levels compared to healthy controls (HCs). Furthermore, 5-HTT polymorphism associated genotypes causing inefficiency in 5-HT re-uptake were more common in our patient cohort than HCs. The findings included in this thesis further emphasize the role of immuno-endocrine interactions in intestinal inflammation, which may be a step toward a better diagnosis or management or even a cure for a disease that is of growing concern, and in understanding IBD pathogenesis. / Dissertation / Doctor of Philosophy (PhD) / The gut produces most of the serotonin found in our body, where it regulates many normal functions. A group of special cells, named enterochromaffin cells, produces nearly all of the serotonin in the gut. In diseases of the gut, especially ones that involve inflammation resulting in symptoms like abdominal pain, diarrhea and bleeding, the number of these cells and serotonin concentration are different from that in the normal gut. I found that these changes are controlled by a particular protein produced by immune cells, called interleukin-13, and alteration in serotonin levels, in turn, contributes to the inflammatory process. Our laboratory experiments with cells and animals establish this connection between interleukin-13 and serotonin in gut inflammation. We further confirm this association between interleukin-13 and serotonin in human inflammatory bowel disease. Moreover, we identify a potential genetic cause of these changes in serotonin concentrations which may ultimately result in inflammatory bowel disease.

Commercial and homemade diets are currently used to treat many canine patients with acquired disorders of the colon. Clinically, the efficacy of diets has been found to be unpredictable. Only one study to date has evaluated the effect of diet on the colonic mucosa. This study showed that diet did not observably alter the colonic mucosa of normal dogs, when biopsy samples were evaluated by light microscopy. The effect of diet on colonic ultrastructure in the dog, using transmission electron microscopy, has not previously been investigated. To determine the effect of diet on colonic ultrastructure, cell height, cell area, microvillus height, number of microvilli/apex width and basement membrane width were measured. Ten cells per animal were evaluated. Six dogs were assigned to the control group and fed the control diet for the duration of the study. Six dogs were fed each of the three test diets at four week intervals. The test diets used included a high fiber diet, a hypoallergenic diet and a highly digestible diet. These diets were selected because they are the diets most often recommended for the canine patient with colonic disorders. The value for cell height for the highly digestible group was significantly greater than the other groups, as measured by ANOV A and Duncan's multiple comparison test. No other significant differences were found. The biological relevance of a significantly different value for cell height alone is difficult to evaluate, as other parameters that would indicate an alteration in maturation or proliferation of the colonic epithelial cells did not change. value for cell height alone is difficult to evaluate, as other parameters that would indicate an alteration in maturation or proliferation of the colonic epithelial cells did not change. Therefore, we conclude that commercial diets do not have an effect on the colonic ultrastructure of normal dogs. Although no effect of diet was found, this study does provide morphologic measurements that can be used as a basis for future ultrastructural studies of the colonic mucosa. / Master of Science

BACKGROUND: Genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) associated with diseases of the colon including inflammatory bowel diseases (IBD) and colorectal cancer (CRC). However, the functional role of many of these SNPs is largely unknown and tissue-specific resources are lacking. Expression quantitative trait loci (eQTL) mapping identifies target genes of disease-associated SNPs. This study provides a comprehensive eQTL map of distal colonic samples obtained from 40 healthy African Americans and demonstrates their relevance for GWAS of colonic diseases. RESULTS: 8.4 million imputed SNPs were tested for their associations with 16,252 expression probes representing 12,363 unique genes. 1,941 significant cis-eQTL, corresponding to 122 independent signals, were identified at a false discovery rate (FDR) of 0.01. Overall, among colon cis-eQTL, there was significant enrichment for GWAS variants for IBD (Crohn's disease [CD] and ulcerative colitis [UC]) and CRC as well as type 2 diabetes and body mass index. ERAP2, ADCY3, INPP5E, UBA7, SFMBT1, NXPE1 and REXO2 were identified as target genes for IBD-associated variants. The CRC-associated eQTL rs3802842 was associated with the expression of C11orf93 (COLCA2). Enrichment of colon eQTL near transcription start sites and for active histone marks was demonstrated, and eQTL with high population differentiation were identified. CONCLUSIONS: Through the comprehensive study of eQTL in the human colon, this study identified novel target genes for IBD- and CRC-associated genetic variants. Moreover, bioinformatic characterization of colon eQTL provides a tissue-specific tool to improve understanding of biological differences in diseases between different ethnic groups.

In the present investigation peripheral blood lymphocytes from patients with inflammatory bowel disease (IBD) and different cancer states were treated with various agents and compared with lymphocytes from healthy control individuals (HCI) treated in the same way and measured in the Comet assay. For inflammatory bowel disease, patient's responses in IBD patients treated with H2O2 were higher than in HCI and Crohn's patients (CD) were found to have higher responses than Ulcerative colitis (UC) patients. The responses for all IBD and HCI were all reduced in the presence of chaga mushroom extract which behaved in an antioxidant manner. A second group of IBD patients were treated with the heterocyclic amine (food mutagen), IQ and H2O2 and responses were reduced in the presence of the flavonoids, quercetin and epicatechin and compared with HCI similarity treated. In all cells responses were reduced with flavonoids and again CD had higher responses than the UC patients and IBD patients higher than HCI. The responses with CD and UC were that confirmed in two independent studies with IBD, one with chaga mushroom extract and the other with flavonoids. Peripheral lymphocytes from malignant melanoma and suspected melanoma patients and colon cancer and polyposis patients were compared to the lymphocytes from HCI and treated with UVA. There were differential sensitivities when measured in the micronucleus and Comet assays. The cancer patients had higher responses than those in the precancerous states and they in turn were higher than responses in HCI. In all the studies, untreated baseline DNA damage values were also higher in IBD and cancer patients and pre-cancerous patients than HCIs. This would suggest that baseline frequencies of different diseases compared to controls could be an important biomarker in the diagnosis of pre-cancers and early stage cancers. Also peripheral lymphocytes are a useful surrogate for cancers and pre-cancerous disease states since, blood is present in all organs and tissues and DNA is basically the same in all cells.

Quorum sensing enables bacteria to communicate with bacteria of the same or different species, and to modulate their behavior in a cell-density dependent manner. Communication occurs by means of small quorum sensing signaling molecules (QSMs) whose concentration is proportional to the population size. When a QSM threshold concentration is reached, certain genes are expressed, thus allowing control of several processes, such as, virulence factor production, antibiotic production, and biofilm formation. Not only many pathogenic bacteria are known to produce QSMs, but also QSMs have been identified in some bacteria-related disorders. Therefore, quantitative detection of QSMs present in clinical samples may be a useful tool in the investigation and monitoring of bacteria-related diseases, thus prompting the use of QSMs as biomarkers of disease. Herein, we have developed and utilized whole-cell biosensing systems and protein based biosensing systems to detect QSMs in clinical samples, such as, saliva, stool, and bowel secretions. Additionally, since bacteria are responsible for food spoilage, we employed the developed biosensing systems to detect QSMs in food samples and demonstrated their applicability for early identification of food contamination. Furthermore, we have utilized these biosensing systems to screen antibacterial compounds employed for food preservation, namely, generally regarded as safe (GRAS) compounds, for their effect on quorum sensing.