Rachael Rigby - Academia.edu (original) (raw)

Papers by Rachael Rigby

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2011

Background-Surgical resection of the ileum, cecum and proximal right colon (ICR) is common in the... more Background-Surgical resection of the ileum, cecum and proximal right colon (ICR) is common in the management of Crohn's disease, yet little is known about the effect of active inflammation on the adaptive response following intestinal loss. We recently developed a surgical model of ICR in germ-free (GF) IL-10 null mice that develop small intestinal inflammation only when mice undergo conventionalization with normal fecal microflora (CONV) before surgical intervention. In this study, we examined the effects of post-surgical small bowel inflammation on adaptive growth after ICR. Methods-8-10 week old GF 129SvEv IL-10 null mice were allocated to GF or CONV groups. Non-operated GF and CONV mice provided baseline controls. Two weeks later GF and CONV mice were further allocated to ICR or sham operation. Small intestine and colon were harvested 7d after surgery for histological analysis. Results-All mice within the gnotobiotic facility maintained GF status and did not develop small intestinal or colonic inflammation. CONV resulted in colitis in all groups, whereas small intestinal inflammation was only observed following ICR. Resection-induced small intestinal inflammation in CONV mice was associated with increases in proliferation, crypt depth and villus height when compared to GF mice after ICR. Resection-induced increases in crypt fission only occurred in CONV mice. Conclusion-ICR-dependent small intestinal inflammation in CONV IL-10 null mice dramatically enhances early adaptive growth of the small intestine. Additional studies utilizing our model may provide clinical insight leading to optimal therapies in managing IBD patients after surgical resection.

Medical Hypotheses, Mar 1, 2020

Hypothesis: bacterial induced inflammation disrupts the orderly progression of the stem cell hier... more Hypothesis: bacterial induced inflammation disrupts the orderly progression of the stem cell hierarchy and has a role in the pathogenesis of breast cancer, Medical

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2008

Background-Bile acid reclamation following ileo-cecal resection (ICR) may prevent colonic mucosa ... more Background-Bile acid reclamation following ileo-cecal resection (ICR) may prevent colonic mucosa from chronic injury. In this study, we hypothesized that in a murine model of ICR the remnant colon would upregulate the cellular machinery necessary for BA reclamation and would do so in an FXR-and bacteria-dependent manner. Methods-Conventional (WT), conventional FXR knockout (FXR null) and germ free (GF) mice were randomized to undergo either ICR or sham operation. The ascending colon was harvested for histology & immunohistochemistry and changes in bile acid homeostatic gene expression determined by RT-PCR 7d following surgery. Results-Following ICR WT mice showed significant increases in the expression of genes regulating bile acid transport including IBABP, Asbt, Ostβ and FGF 15. Increased expression of IBABP and Asbt was confirmed by immunohistochemistry. Induction of bile acid transport genes was absent or attenuated in FXR null and GF mice. Conclusion-Bacterial dependent up regulation of IBABP is FXR mediated in the colon following ICR. Mice lacking microbiota (GF) or FXR are unable to increase the expression of IBABP or FGF 15.

Gut microbes, Jul 26, 2016

Doxorubicin (DOXO) induces significant, but transient, increases in apoptosis in the stem cell zo... more Doxorubicin (DOXO) induces significant, but transient, increases in apoptosis in the stem cell zone of the jejunum, followed by mucosal damage involving a decrease in crypt proliferation, crypt number, and villus height. The gastrointestinal tract is home to a vast population of commensal bacteria and numerous studies have demonstrated a symbiotic relationship between intestinal bacteria and intestinal epithelial cells (IEC) in maintaining homeostatic functions of the intestine. However, whether enteric bacteria play a role in DOXO-induced damage is not well understood. We hypothesized that enteric bacteria are necessary for induction of apoptosis and damage associated with DOXO treatment. Conventionally raised (CONV) and germ free (GF) mice were given a single injection of DOXO, and intestinal tissue was collected at 6, 72, and 120 h after treatment and from no treatment (0 h) controls. Histology and morphometric analyses quantified apoptosis, mitosis, crypt depth, villus height, and crypt density. Immunostaining for muc2 and lysozyme evaluated Paneth cells, goblet cells or dual stained intermediate cells. DOXO administration induced significant increases in apoptosis in jejunal epithelium regardless of the presence of enteric bacteria; however, the resulting injury, as demonstrated by statistically significant changes in crypt depth, crypt number, and proliferative cell number, was dependent upon the presence of enteric bacteria. Furthermore, we observed expansion of Paneth and goblet cells and presence of intermediate cells only in CONV and not GF mice. These findings provide evidence that manipulation and/or depletion of the enteric microbiota may have clinical significance in limiting chemotherapy-induced mucositis.

The FASEB Journal, Apr 1, 2009

The FASEB Journal, Apr 1, 2015

Gastroenterology, Jul 1, 2006

Immunity, inflammation and disease, May 15, 2017

Introduction: Suppressor of cytokine signaling 3 (SOCS3) is a tumour suppressor, limiting intesti... more Introduction: Suppressor of cytokine signaling 3 (SOCS3) is a tumour suppressor, limiting intestinal epithelial cell (IEC) proliferation in acute inflammation, and tumour growth, but little is known regarding its role in mucosal homeostasis. Resistance to the intestinal helminth Trichuris muris relies on an ''epithelial escalator'' to expel the parasite. IEC turnover is restricted by parasite-induced indoleamine 2,3-dioxygenase (IDO). Methods: Mice with or without conditional knockout of SOCS3 were infected with T. muris. Crypt depth, worm burden, and proliferating cells and IDO were quantified. SOCS3 knockdown was also performed in human IEC cell lines. Results: Chronic T. muris infection increased expression of SOCS3 in wild-type mice. Lack of IEC SOCS3 led to a modest increase in epithelial turnover. This translated to a lower worm burden, but not complete elimination of the parasite suggesting a compensatory mechanism, possibly IDO, as seen in SOCS3 knockdown. Conclusions: We report that SOCS3 impacts on IEC turnover following T. muris infection, potentially through enhancement of IDO. IDO may dampen the immune response which can drive IEC hyperproliferation in the absence of SOCS3, demonstrating the intricate interplay of immune signals regulating mucosal homeostasis, and suggesting a novel tumour suppressor role of SOCS3.

Statistical Applications in Genetics and Molecular Biology, Oct 1, 2021

The human gut microbiome has been shown to be associated with a variety of human diseases, includ... more The human gut microbiome has been shown to be associated with a variety of human diseases, including cancer, metabolic conditions and inflammatory bowel disease. Current approaches for detecting microbiome associations are limited by relying on specific measures of ecological distance, or only allowing for the detection of associations with individual bacterial species, rather than the whole microbiome. In this work, we develop a novel hierarchical Bayesian model for detecting global microbiome associations. Our method is not dependent on a choice of distance measure, and is able to incorporate phylogenetic information about microbial species. We perform extensive simulation studies and show that our method allows for consistent estimation of global microbiome effects. Additionally, we investigate the performance of the model on two real-world microbiome studies: a study of microbiome-metabolome associations in inflammatory bowel disease, and a study of associations between diet and the gut microbiome in mice. We show that we can use the method to reliably detect associations in real-world datasets with varying numbers of samples and covariates.

Gastroenterology, May 1, 2010

Background: Inflammatory bowel diseases (IBD) are marked by increased levels of inflammatory cyto... more Background: Inflammatory bowel diseases (IBD) are marked by increased levels of inflammatory cytokines, such as tumor necrosis factor (TNF), and enhanced epithelial cell apoptosis. We have recently shown that expression of ErbB4, a member of the epidermal growth factor receptor family of receptor tyrosine kinases, is induced and phosphorylated in response to TNF and is also elevated in IBD. In this study, we tested the hypothesis that TNF transactivates ErbB4 through TNF alpha converting enzyme (TACE)-mediated ligand release, and that this transactivation protects colonic epithelial cells from inflammation-induced apoptosis. Methods: Conditionally immortalized TACE-/mouse colon epithelial (MCE) cells expressing either wild type TACE or vector were treated with 100 ng/mL TNF; subsequently, ErbB4 phosphorylation was assessed by Western blot analysis of whole cell lysates using an antibody directed towards phospho-ErbB4 (pY-1284). ErbB4-expressing young adult mouse colon epithelial (YAMC) cells were pretreated with an ErbB4 blocking antibody (10 μg/mL) for 1 hr before the addition of TNF (100 ng/mL, 30 min) to determine whether extracellular ligands were required for ErbB4 transactivation. For survival studies, YAMC cells were pretreated with either the ErbB4 blocking antibody or with 10 μM TAPI-1 (a TACE specific inhibitor) for 1 hr before the addition of TNF and cycloheximide (1 μg/mL) for 5 hours. Apoptosis was then measured by Western blot analysis of cell lysates using anti-active caspase 3 and cleaved PARP antibodies, or by counting TUNEL stained cells. Results: ErbB4 was not phosphorylated in response to TNF in TACE-/-MCE cells; re-expression of wild type TACE restored TNF transactivation of ErbB4. TNF-induced phosphorylation of ErbB4 was also completely inhibited by pretreatment of cells with an ErbB4 blocking antibody, supporting our hypothesis that ligand release mediates ErbB4 transactivation by TNF. Both TACE activity and ErbB4 ligand binding were required for ErbB4-mediated anti-apoptotic effects in the presence of inflammatory cytokines. During TNF exposure, YAMC cells overexpressing ErbB4 exhibited decreased TUNEL staining compared to cells expressing vector only. However, pretreatment with an ErbB4 blocking antibody or TACE inhibitor reversed the ability of ErbB4 to protect from apoptosis. These results were corroborated by immunoblotting with antibodies against the apoptotic markers cleaved PARP and active caspase 3. Conclusions: TNF transactivates ErbB4 through TACE-dependent ligand cleavage, which is required for ErbB4 protection against inflammatory cytokine-induced apoptosis in colon epithelial cells.

Journal of Surgical Research, Jun 1, 2011

Gut microbes, Apr 13, 2023

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2010

Background: Obesity induced by high fat (HF) diet is associated with inflammation which contribut... more Background: Obesity induced by high fat (HF) diet is associated with inflammation which contributes to development of insulin resistance. Most prior studies have focused on adipose tissue as the source of obesity-associated inflammation. Increasing evidence links intestinal bacteria to development of diet-induced obesity (DIO). This study tested the hypothesis that HF western diet and gut bacteria interact to promote intestinal inflammation, which contributes to the progression of obesity and insulin resistance. Methodology/Principal Findings: Conventionally raised specific-pathogen free (CONV) and germ-free (GF) mice were given HF or low fat (LF) diet for 2-16 weeks. Body weight and adiposity were measured. Intestinal inflammation was assessed by evaluation of TNF-a mRNA and activation of a NF-kB EGFP reporter gene. In CONV but not GF mice, HF diet induced increases in body weight and adiposity. HF diet induced ileal TNF-a mRNA in CONV but not GF mice and this increase preceded obesity and strongly and significantly correlated with diet induced weight gain, adiposity, plasma insulin and glucose. In CONV mice HF diet also resulted in activation of NF-kB EGFP in epithelial cells, immune cells and endothelial cells of small intestine. Further experiments demonstrated that fecal slurries from CONV mice fed HF diet are sufficient to activate NF-kB EGFP in GF NF-kB EGFP mice. Conclusions/Significance: Bacteria and HF diet interact to promote proinflammatory changes in the small intestine, which precede weight gain and obesity and show strong and significant associations with progression of obesity and development of insulin resistance. To our knowledge, this is the first evidence that intestinal inflammation is an early consequence of HF diet which may contribute to obesity and associated insulin resistance. Interventions which limit intestinal inflammation induced by HF diet and bacteria may protect against obesity and insulin resistance.

Oncogene, Feb 12, 2007

Intestinal injury or chronic inflammation induce cytokines that promote crypt regeneration and mu... more Intestinal injury or chronic inflammation induce cytokines that promote crypt regeneration and mucosal repair. If excessive or prolonged, such mechanisms may increase colon cancer risk. Factors that terminate or limit cytokine action in intestinal epithelial cells (IEC) may protect against crypt hyperplasia and neoplasia. We hypothesized that suppressor of cytokine signaling-3 (SOCS3) is such a factor. Mice with Vilin-promoter/Cre-recombinase (VC)mediated IEC-specific SOCS3 gene disruption (VC/HO), WT/HO littermates with floxed but intact SOCS3 genes and VC/WT mice were studied. Colon was examined after acute dextran sodium sulfate (DSS)-induced mucosal injury or after azoxymethane (AOM) and chronic DSS. Signaling pathways were examined in colon, cultured IEC or colon cancer cell lines. VC/HO mice showed no basal phenotype. After acute DSS, VC/HO exhibited enhanced crypt proliferation and crypt hyperplasia and reduced transforming growth factor (TGF) b expression in colon. Inflammation and mucosal damage were similar across genotypes. Following AOM/DSS, VC/HO mice had increased size, number and load of colonic tumors and increased STAT3 and nuclear factor-kappa B (NF-jB) activation in colon. In vitro, SOCS3 overexpression reduced proliferation, IL-6-mediated STAT3 activation and tumor necrosis factor (TNF) a-mediated NF-jB activation. We conclude that cytokine induction of SOCS3 normally provides an intrinsic mechanism to limit injury-induced crypt hyperproliferation and inflammationassociated colon cancer by regulating both STAT3 and NF-jB pathways.

Inflammatory Bowel Diseases, Apr 1, 2006

Inflammatory Bowel Diseases, Oct 1, 2008

F ibrosis in inflammatory bowel disease (IBD) is a consequence of chronic inflammation, and can o... more F ibrosis in inflammatory bowel disease (IBD) is a consequence of chronic inflammation, and can occur in both Crohn's disease (CD) and ulcerative colitis (UC), but is much more prevalent in CD. In UC, fibrosis is limited to the mucosal layer. In CD, fibrosis is variable in presentation but typically involves transmural increases of multiple extracellular matrix (ECM) components and overgrowth of the smooth muscle and serosal layers. Resultant thickening of the bowel wall and lumen narrowing can cause dysmotility or partial obstruction contributing to pain, early satiety, anorexia, diarrhea or constipation, and bacterial overgrowth. Severe fibrosis can result in critical narrowing of the lumen, stenosis, or stricture, commonly leading to obstruction that requires surgical or mechanical intervention. 1 Current antiinflammatory therapies do not prevent fibrosis nor do they reverse established strictures, which may present years after remission of active inflammation.

The FASEB Journal, Apr 1, 2012

A single layer of IEC, expressing TLR, line the intestine. TLR‐induced inflammatory pathways are ... more A single layer of IEC, expressing TLR, line the intestine. TLR‐induced inflammatory pathways are vital for mucosal homeostasis and dysregulated repair may predispose to inflammatory bowel disease (IBD). In IBD, the expression of SOCS3, a negative feedback inhibitor of the JAK/STAT pathway, is enhanced. The aim of this study was to establish the function of SOCS3 in TLR‐mediated epithelial homeostasis. We developed SW480 IEC cell lines to over‐express SOCS3 (SOCS3hi), to study gene expression, vs. SOCS3norm IEC in response to microbial stimulation. IEC production of pro‐inflammatory TNFα mRNA was upregulated following stimulation with flagellin (TLR5), but not LPS (TLR4) or Poly I:C (TLR3), at varying concentrations. This response was significantly enhanced in SOCS3hi vs. SOCS3normIEC: 31.9 ± 10 vs. 8.7 ± 1.8 fold increase at 1ug/ml (p≤0.05), 20.3 ± 4.4 vs. 6.4 ± 1.6 fold‐increase at 0.1ug/ml (p≤0.03) and 15.1 ± 5.1 vs. 4 ± 1.1 fold‐increase at 0.01ug/ml (p≤0.05), compared with no‐treatment control mRNA levels. Our studies indicate that SOCS3 is not only an inhibitor of epithelial repair, but may help to perpetuate the inflammatory response by promoting the production of pro‐inflammatory TNFα.

Journal of Surgical Research, Feb 1, 2009

Introduction: Neoadjuvant therapy followed by surgical resection has been shown to reduce recurre... more Introduction: Neoadjuvant therapy followed by surgical resection has been shown to reduce recurrence of stage II and III rectal cancer. Chemoradiation therapy carries significant morbidity, however, and identification of early stage patients with increased risk of recurrence could possibly individualize treatment plans. Down-regulated expression of carcinoembryonic antigen cellular adhesion molecule-7 (CEACAM-7), a regulator of apoptosis, has been shown to predict disease recurrence in patients with primary breast cancer. The predictive relationship of CEACAM-7 to rectal cancer has not been described. This study evaluates CEACAM-7 expression in rectal adenocarcinoma and its ability to predict disease recurrence. Methods: An IRB-approved colorectal cancer clinical database and biobank were quarried for patients with rectal cancers and available frozen tumor tissue. Clinical endpoints of distant recurrence or disease-free survival with at least 3-year follow-up were used as inclusion criteria. Demographics, tumor characteristics, and clinical follow-up were recorded. mRNA from frozen tumor tissue as well as normal rectal mucosa was isolated and CEACAM-7 expression was analyzed using quantitative real-time PCR. Relative expression was measured between normal tissue and that from patients with nonrecurrent disease and those that subsequently developed disease recurrence. Statistical significance was defined as pϽ0.05. Results: There were 86 patients included in the study. Thirty-seven patients had non-recurrent disease at a median follow up of 72 months (36-261), 31 patients who subsequently developed recurrent rectal cancer and 18 patients who presented with stage IV disease. Patient demographics and stage distribution were statistically similar between non-recurrent and recurrent disease patients. Non-malignant rectal mucosa samples from 7 patients were used as controls. CEACAM-7 expression was decreased in rectal cancers compared to normal rectal mucosa (pϭ0.001) and stage IV rectal cancers had the greatest loss of expression at 58-fold compared to normal rectal mucosa (pϽ0.0001). CEACAM-7 expression was not statistically different for stage I or stage III patients with non-recurrent versus recurrent disease. However, there was a large difference in CEACAM-7 expression for stage II patients with a 10-fold decrease in patients with recurrent disease compared to non-recurrent disease (pϭ0.004) and decreased 115-fold compared to normal rectal mucosa (pϽ0.0003). Conclusions: Decreased expression of CEACAM-7 is observed in rectal cancer compared to normal rectal mucosa. The loss of CEACAM-7 expression occurs as an early event in development of rectal cancer as seen by the early loss of expression in stage I disease. Differences seen in stage II non-recurrent versus recurrent rectal cancer creates potential for its use as a tumor marker to define a subset of stage II patients that might benefit from neoadjuvant therapy.