Crossover Subsets of CD4+ T Lymphocytes in the Intestinal Lamina Propria of Patients with Crohn's Disease and Ulcerative Colitis

BACKGROUND

Hovhannisyan et al. first showed evidence of plasticity between Treg and Th17 in the inflamed intestine of Crohn's disease (CD) patients. Our previous report suggests that the inflammatory cytokine milieu generates IL-17⁺ Foxp3⁺ CD4⁺ T lymphocytes which is a crossover population converting Treg subset to Th17 in the peripheral blood of IBD patients. This is considered as an evidence of Treg/Th17 plasticity.

AIM

The aim of this study was to characterize a variety of helper T cell crossover population, not limited to IL-17⁺ Foxp3⁺ CD4⁺ T lymphocytes, in the lamina propria (LP) of IBD patients.

METHODS

Fresh colonoscopic biopsies were obtained from patients with CD (n = 50) and ulcerative colitis (UC, n = 32) and from healthy controls (HC, n = 25). LP mononuclear cells were assessed for intracellular cytokines and transcription factors such as IFNγ, IL-13, IL-17, IL-22, T-bet, Gata-3, RORγt, and Foxp3 using multicolor flow cytometry to detect subsets of LP CD4⁺ T lymphocytes.

RESULTS

Patients with IBD demonstrated increased crossover populations in IL-17⁺ Foxp3⁺, T-bet⁺ Foxp3⁺, Gata3⁺ Foxp3⁺, RORγt⁺ Foxp3⁺ populations compared to HC. There was an inverse correlation of Harvey-Bradshaw index with Gata3⁺ Foxp3⁺ population in CD patients, while IL-13⁺ Foxp3⁺ population was directly correlated with Mayo clinical scores in UC patients. Furthermore, total IL-22 expressing cells as well as Th22 and IL-22⁺ Th1 populations were decreased in UC compared to CD and HC.

CONCLUSION

IBD patients exhibit the increased crossover populations in LP Treg cells toward Th2 and Th17 compared to HC. The prevalence of Treg/Th2 crossover populations is associated with clinical disease score of IBD.

The NOD2-Smoking Interaction in Crohn's Disease is likely Specific to the 1007fs Mutation and may be Explained by Age at Diagnosis: A Meta-Analysis and Case-Only Study

Background

NOD2 and smoking are risk factors for Crohn's disease. We meta-analyzed NOD2-smoking interactions in Crohn's disease (Phase 1), then explored the effect of age at diagnosis on NOD2-smoking interactions (Phase 2).

Methods

Phase 1: MEDLINE and EMBASE were searched for studies (n = 18) providing data on NOD2 and smoking in Crohn's disease. NOD2-smoking interactions were estimated using odds ratios (ORs) and 95% confidence intervals (CIs) calculated using random effects models. Phase 2: A case-only study compared the proportion of smokers and carriers of the 1007 fs variant across ages at diagnosis (≤ 16, 17–40, > 40 years).

Findings

Phase 1: Having ever smoked was less common among carriers of the 1007 fs variant of NOD2 (OR 0.74, 95%CI:0.66–0.83). There was no interaction between smoking and the G908R (OR 0.96, 95%CI:0.82–1.13) or the R702W variant (OR 0.89, 95%CI:0.76–1.05). Phase 2: The proportion of patients (n = 627) carrying the 1007 fs variant decreased with age at diagnosis (≤ 16 years: 15%; 17–40: 12%; > 40: 3%; p = 0.003). Smoking was more common in older patients (≤ 16 years: 4%; 17–40: 48%; > 40: 71%; p < 0.001).

Interpretation

The negative NOD2-smoking interaction in Crohn's disease is specific to the 1007 fs variant. However, opposing rates of this variant and smoking across age at diagnosis may explain this negative interaction.

•

There is a negative interaction between NOD2 smoking in Crohn's disease and it is specific to the 1007fs variant.

•

With increasing age, the prevalence of the 1007fs variant decreases and exposure to cigarette smoke increases.

•

Contrasting trends in the 1007fs variant and cigarette smoking may explain the negative NOD2-smoking interaction.

We reviewed 18 studies evaluating NOD2-smoking interactions in Crohn's disease. Only the 1007fs variant interacted with smoking. Smokers with this mutation were less likely to develop Crohn's disease. We then conducted a study of 627 patients with Crohn's disease, which showed that the 1007fs variant was common in young patients and rare in older patients, whereas smoking was more common among older patients. The decreasing prevalence of 1007fs mutation and increasing exposure to smoking as age of diagnosis advances may explain the negative interaction between NOD2 and smoking observed in our meta-analysis. Our study highlights the challenges of identifying gene-environment interactions.

Career and research outcomes of the physician-scientist training program at the University of Calgary: a retrospective cohort study

BACKGROUND

Physician-scientists are integral to medical research, with medical programs throughout Canada invested in training hybrid physician-scientists. Few data exist as to whether these programs are generating the diversity, gender equity and numbers of trainees essential for the future of medical research and teaching. We aimed to identify factors that contribute to research productivity, diversity and retention of individuals as physician-scientists.

METHODS

We completed a retrospective cohort study, for the period 1973 to 2015, of the University of Calgary Leaders in Medicine Program in Calgary, Alberta. Participants were coregistered in graduate (master's or PhD) and medical degree programs. Primary outcomes included number of publications and the eventual career paths of graduates, with individuals characterized as physicians or physician-scientists on the basis of these metrics.

RESULTS

Of the 307 individuals who were coregistered in or had completed a joint graduate and medical degree, 125 (40.7%) were PhD students/graduates, and 182 (59.3%) were master's trainees/graduates. While in the joint program, male PhD students consistently published more frequently than female PhD students. There was no significant difference in publication records between male and female master's students. Of the 172 individuals who were 5 years or more beyond graduation, 47 (27.3%) were classified as physician-scientists; these individuals consisted of 28 (40.6%) of the 69 PhD graduates and 19 (18.4%) of the 103 master's graduates.

INTERPRETATION

Overall, our study shows that graduates receiving both clinical and research training, through master's or PhD programs, continue to be involved in research in their subsequent careers.

The effects of pregnancy on the pharmacokinetics of infliximab and adalimumab in inflammatory bowel disease

BACKGROUND

Transplacental transfer of infliximab and adalimumab results in detectable drug levels in the cord blood and infant.

AIM

To determine if pregnancy influenced the pharmacokinetics of anti-TNF agents in women with inflammatory bowel disease.

METHODS

Twenty-five women from the University of Calgary inflammatory bowel disease(IBD) pregnancy clinic on maintenance infliximab or adalimumab were recruited prospectively with serum bio-banking performed each trimester. Infliximab trough and adalimumab steady-state levels were the outcomes of interest and were analysed using the ANSER infliximab and adalimumab assays. Multivariate linear mixed-effects models were constructed to assess infliximab and adalimumab drug levels during pregnancy adjusting for the clinical covariates of albumin, BMI and CRP.

RESULTS

Fifteen women (eight Crohn's disease, seven ulcerative colitis) received infliximab and 10 women with 11 pregnancies were treated with adalimumab. Median age was 29.6 years (IQR: 27.6-31.2 years). Median disease duration was 9.2 years (IQR: 3.16-15.0 years). Median trough infliximab concentrations were 8.50 μg/mL (IQR: 7.23-10.07 μg/mL), 10.31 μg/mL (IQR: 7.66-15.63 μg/mL) and 21.02 μg/mL (IQR: 16.01-26.70 μg/mL) at trimesters 1, 2 and 3 respectively. Significant changes in albumin and BMI (P < 0.05) but not CRP (P > 0.05) were documented throughout pregnancy. After adjusting for albumin, BMI and CRP, infliximab trough levels increased during pregnancy, by 4.2 μg/mL per trimester (P = 0.02), while adalimumab drug levels remained stable (P > 0.05).

CONCLUSIONS

Infliximab levels rise during pregnancy, whereas adalimumab levels remain stable after accounting for changes in albumin, BMI and CRP. Therapeutic drug monitoring in the second trimester may be useful in guiding dosing in the third trimester.

Giardia duodenalis induces pathogenic dysbiosis of human intestinal microbiota biofilms

Giardia duodenalis is a prevalent cause of acute diarrheal disease worldwide. However, recent outbreaks in Italy and Norway have revealed a link between giardiasis and the subsequent development of chronic post-infectious irritable bowel syndrome. While the mechanisms underlying the causation of post-infectious irritable bowel syndrome remain obscure, recent findings suggest that alterations in gut microbiota communities are linked to the pathophysiology of irritable bowel syndrome. In the present study, we use a laboratory biofilm system to culture and enrich mucosal microbiota from human intestinal biopsies. Subsequently, we show that co-culture with Giardia induces disturbances in biofilm species composition and biofilm structure resulting in microbiota communities that are intrinsically dysbiotic - even after the clearance of Giardia. These microbiota abnormalities were mediated in part by secretory-excretory Giardia cysteine proteases. Using in vitro cell culture and germ-free murine infection models, we show that Giardia-induced disruptions of microbiota promote bacterial invasion, resulting in epithelial apoptosis, tight junctional disruption, and bacterial translocation across an intestinal epithelial barrier. Additionally, these dysbiotic microbiota communities resulted in increased activation of the Toll-like receptor 4 signalling pathway, and overproduction of the pro-inflammatory cytokine IL-1beta in humanized germ-free mice. Previous studies that have sought explanations and risk factors for the development of post-infectious irritable bowel syndrome have focused on features of enteropathogens and attributes of the infected host. We propose that polymicrobial interactions involving Giardia and gut microbiota may cause persistent dysbiosis, offering a new interpretation of the reasons why those afflicted with giardiasis are predisposed to gastrointestinal disorders post-infection.

Multiple Lymphomatous Diverticulosis and Comorbid Chronic Lymphocytic Leukemia: Novel Manifestations of Ileocolic Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) has tropism for the gastrointestinal tract (GIT) identifiable as multiple polyps and mass lesions throughout the GIT. We describe 2 novel manifestations of MCL. A 60-year-old woman with known chronic lymphocytic leukemia (CLL) had an exophytic mass of the appendiceal orifice. Multiple polypoid masses of the distal ileum were identified in the right hemicolectomy specimen (multiple lymphomatous polyposis). Ancillary studies confirmed the coexistence of the 2 independent lymphoproliferative disorders. A 69-year-old man had recurrent urinary tract infections and pneumatouria caused by a colovesicular fistula complicating diverticulosis coli. Segmental resections of the sigmoid and ileocecum confirmed diverticulosis of the left and right colon. Histology identified infiltrates of MCL confined to the penetrating aspects of colonic diverticula. MCL has not been documented to coexist with CLL. An invaginating morphology of lymphoma, multiple lymphomatous diverticulosis is also a novel presentation. These 2 scenarios expand MCL's known manifestations within the GIT.

NLRP3 regulates a non-canonical platform for caspase-8 activation during epithelial cell apoptosis

Nod-like receptor, pyrin containing 3 (NLRP3) is characterized primarily as a canonical caspase-1 activating inflammasome in macrophages. NLRP3 is also expressed in the epithelium of the kidney and gut; however, its function remains largely undefined. Primary mouse tubular epithelial cells (TEC) lacking Nlrp3 displayed reduced apoptosis downstream of the tumor necrosis factor (TNF) receptor and CD95. TECs were identified as type II apoptotic cells that activated caspase-8, tBid and mitochondrial apoptosis via caspase-9, responses that were reduced in Nlrp3-/- cells. The activation of caspase-8 during extrinsic apoptosis induced by TNFα/cycloheximide (TNFα/CHX) was dependent on adaptor protein apoptosis-associated speck-like protein containing a CARD (ASC) and completely independent of caspase-1 or caspase-11. TECs and primary human proximal tubular epithelial cells (HPTC) did not activate a canonical inflammasome, caspase-1, or IL-1β secretion in response to TNFα/CHX or NLRP3-dependent triggers, such as ATP or nigericin. In cell fractionation studies and by confocal microscopy, NLRP3 colocalized with ASC and caspase-8 in speck-like complexes at the mitochondria during apoptosis. The formation of NLRP3/ASC/caspase-8 specks in response to TNFα/CHX was downstream of TNFR signaling and dependent on potassium efflux. Epithelial ASC specks were present in enteroids undergoing apoptosis and in the injured tubules of wild-type but not Nlrp3-/- or ASC-/- mice following ureteric unilateral obstruction in vivo. These data show that NLRP3 and ASC form a conserved non-canonical platform for caspase-8 activation, independent of the inflammasome that regulates apoptosis within epithelial cells.

Vitamin D₃ metabolites enhance the NLRP3-dependent secretion of IL-1β from human THP-1 monocytic cells

Vitamin D3 has emerged as an important regulator of the immune system. With metabolic enzymes for vitamin D3 activation and vitamin D receptors (VDR) now identified in a variety of immune cells, the active vitamin D3 metabolite 1,25(OH)2D3, is thought to possess immunomodulatory properties. We examined whether 1,25(OH)2D3 might also enhance the NLRP3-dependent release of mature IL-1β from macrophages. PMA-differentiated THP-1 cells were stimulated with vitamin D3 metabolites and assessed for CYP27, CYP24, NLRP3, ASC, pro-caspase-1 expression by western blot and real-time qPCR as well as inflammasome activation with pro-inflammatory cytokine IL-1β release measured by ELISA. Exposure to 1,25(OH)2D3 had no effect on the basal expression levels of VDR; however, CYP27A1 transcript was suppressed and CYP24A1 transcript was substantively elevated. Both 1,25(OH)2D3 - and 25(OH)D3 induced IL-1β release from THP-1 cells, and these effects were blocked with application of the caspase-1 inhibitor YVAD and the NLRP3 inhibitors glyburide and Bay 11-7082. Interestingly, 1,25 (OH)2D3 exposure reduced NLRP3 protein expression but had no effect on ASC or pro-caspase-1 protein levels. The increase in mature IL-1β elicited by 1,25(OH)2D3 was modest compared to that found for ATP or C. difficile toxins. However, co-treatment of THP-1 cells with ATP and 1,25(OH)2D3 resulted in more IL-1β secretion than ATP or 1,25(OH)2D3 alone.

Proceedings from the 6th Annual University of Calgary Leaders in Medicine Research Symposium

On November 14, 2014, the Leaders in Medicine (LIM) program at the Cumming School of Medicine, University of Calgary hosted its 6th Annual Research Symposium. Dr. Danuta Skowronski, Epidemiology Lead for Influenza and Emerging Respiratory Pathogens at the British Columbia Centre for Disease Control (BCCDC), was the keynote speaker and presented a lecture entitled "Rapid response research during emerging public health crises: influenza and reflections from the five year anniversary of the 2009 pandemic". The LIM symposium provides a forum for both LIM and non-LIM medical students to present their research work, either as an oral or poster presentation. There were a total of six oral presentations and 77 posters presented. 
The oral presentations included: Swathi Damaraju, "The role of cell communication and 3D Cell-Matrix environment in a stem cell-based tissue engineering strategy for bone repair"; Menglin Yang, "The proteolytic activity of Nepenthes pitcher fluid as a therapeutic for the treatment of celiac disease"; Amelia Kellar, "Monitoring pediatric inflammatory bowel disease - a retrospective analysis of transabdominal ultrasound"; Monica M. Faria-Crowder, "The design and application of a molecular profiling strategy to identify polymicrobial acute sepsis infections"; Waleed Rahmani, "Hair follicle dermal stem cells regenerate the dermal sheath, repopulate the dermal papilla and modulate hair type"; and, Laura Palmer, "A novel role for amyloid beta protein during hypoxia/ischemia". 
The article on the University of Calgary Leaders in Medicine Program, "A Prescription that Addresses the Decline of Basic Science Education in Medical School," in a previous issue of CIM (2014 37(5):E292) provides more details on the program. Briefly, the LIM Research Symposium has the following objectives: (1) to showcase the impressive variety of projects undertaken by students in the LIM Program as well as University of Calgary medical students; (2) to encourage medical student participation in research and special projects; and, (3) to inform students and faculty about the diversity of opportunities available for research and special projects during medical school and beyond.

The following abstracts were submitted for publication.

Highlights from the 6th Annual University of Calgary Leaders in Medicine Research Symposium and the Keynote Address by Dr. Danuta Skowronski

The Leaders in Medicine (LIM) Program at the University of Calgary hosted its 6th Annual Research Symposium on November 14, 2014, showcasing the quality and breadth of work performed by students at the Cumming School of Medicine. Participation at this year's event was our most successful to date, with a total of six oral and 77 poster presentations during the afternoon symposium. For a detailed description of the work presented at the symposium, please see the Proceedings from the 6th Annual University of Calgary Leaders in Medicine Research Symposium published in this issue of Clinical and Investigative Medicine.

Gastrointestinal dysbiosis and the use of fecal microbial transplantation in Clostridium difficile infection

The impact of antibiotics on the human gut microbiota is a significant concern. Antibiotic-associated diarrhea has been on the rise for the past few decades with the increasing usage of antibiotics. Clostridium difficile infections (CDI) have become one of the most prominent types of infectious diarrheal disease, with dramatically increased incidence in both the hospital and community setting worldwide. Studies show that variability in the innate host response may in part impact upon CDI severity in patients. That being said, CDI is a disease that shows the most prominent links to alterations to the gut microbiota, in both cause and treatment. With recurrence rates still relatively high, it is important to explore alternative therapies to CDI. Fecal microbiota transplantation (FMT) and other types of bacteriotherapy have become exciting avenues of treatment for CDI. Recent clinical trials have generated excitement for the use of FMT as a therapeutic option for CDI; however, the exact components of the human gut microbiota needed for protection against CDI have remained elusive. Additional investigations on the effects of antibiotics on the human gut microbiota and subsequent CDI will help reduce the socioeconomic burden of CDI and potentially lead to new therapeutic modalities.

Helicobacter pylori Eradication in Patients with Immune Thrombocytopenic Purpura: A Review and the Role of Biogeography

Idiopathic thrombocytopenic purpura (ITP) is typically a diagnosis of exclusion, assigned by clinicians after ruling out other identifiable etiologies. Since a report by Gasbarrini et al. in 1998, an accumulating body of evidence has proposed a pathophysiological link between ITP and chronic Helicobacter pylori (H. pylori) infection. Clinical reports have described a spontaneous resolution of ITP symptoms in about 50% of chronic ITP patients following empirical treatment of H. pylori infection, but response appears to be geography dependent. Studies have also documented that ITP patients in East Asian countries are more likely to express positive antibody titers against H. pylori-specific cytotoxic-associated gene A (CagA), a virulence factor that is associated with an increased risk for gastric diseases including carcinoma. While a definitive mechanism by which H. pylori may induce thrombocytopenia remains elusive, proposed pathways include molecular mimicry of CagA by host autoantibodies against platelet surface glycoproteins, as well as perturbations in the phagocytic activity of monocytes. Traditional treatments of ITP have been largely empirical, involving the use of immunosuppressive agents and immunoglobulin therapy. However, based on the findings of clinical reports emerging over the past 20 years, health organizations around the world increasingly suggest the detection and eradication of H. pylori as a treatment for ITP. Elucidating the exact molecular mechanisms of platelet activation in H. pylori-positive ITP patients, while considering biogeographical differences in response rates, could offer insight into how best to use clinical H. pylori eradication to treat ITP, but will require well-designed studies to confirm the suggested causative relationship between bacterial infection and an autoimmune disease state.

Inhibiting Inducible Nitric Oxide Synthase in Enteric Glia Restores Electrogenic Ion Transport in Mice With Colitis

BACKGROUND & AIMS

Disturbances in the control of ion transport lead to epithelial barrier dysfunction in patients with colitis. Enteric glia regulate intestinal barrier function and colonic ion transport. However, it is not clear whether enteric glia are involved in epithelial hyporesponsiveness. We investigated enteric glial regulation of ion transport in mice with trinitrobenzene sulfonic acid- or dextran sodium sulfate-induced colitis and in Il10(-/-) mice.

METHODS

Electrically evoked ion transport was measured in full-thickness segments of colon from CD1 and Il10(-/-) mice with or without colitis in Ussing chambers. Nitric oxide (NO) production was assessed using amperometry. Bacterial translocation was investigated in the liver, spleen, and blood of mice.

RESULTS

Electrical stimulation of the colon evoked a tetrodotoxin-sensitive chloride secretion. In mice with colitis, ion transport almost completely disappeared. Inhibiting inducible NO synthase (NOS2), but not neuronal NOS (NOS1), partially restored the evoked secretory response. Blocking glial function with fluoroacetate, which is not a NOS2 inhibitor, also partially restored ion transport. Combined NOS2 inhibition and fluoroacetate administration fully restored secretion. Epithelial responsiveness to vasoactive intestinal peptide was increased after enteric glial function was blocked in mice with colitis. In colons of mice without colitis, NO was produced in the myenteric plexus almost completely via NOS1. NO production was increased in mice with colitis, compared with mice without colitis; a substantial proportion of NOS2 was blocked by fluoroacetate administration. Inhibition of enteric glial function in vivo reduced the severity of trinitrobenzene sulfonic acid-induced colitis and associated bacterial translocation.

CONCLUSIONS

Increased production of NOS2 in enteric glia contributes to the dysregulation of intestinal ion transport in mice with colitis. Blocking enteric glial function in these mice restores epithelial barrier function and reduces bacterial translocation.

Giardia duodenalis infection reduces granulocyte infiltration in an in vivo model of bacterial toxin-induced colitis and attenuates inflammation in human intestinal tissue

Giardia duodenalis (syn. G. intestinalis, G. lamblia) is a predominant cause of waterborne diarrheal disease that may lead to post-infectious functional gastrointestinal disorders. Although Giardia-infected individuals could carry as much as 10⁶ trophozoites per centimetre of gut, their intestinal mucosa is devoid of overt signs of inflammation. Recent studies have shown that in endemic countries where bacterial infectious diseases are common, Giardia infections can protect against the development of diarrheal disease and fever. Conversely, separate observations have indicated Giardia infections may enhance the severity of diarrheal disease from a co-infecting pathogen. Polymorphonuclear leukocytes or neutrophils (PMNs) are granulocytic, innate immune cells characteristic of acute intestinal inflammatory responses against bacterial pathogens that contribute to the development of diarrheal disease following recruitment into intestinal tissues. Giardia cathepsin B cysteine proteases have been shown to attenuate PMN chemotaxis towards IL-8/CXCL8, suggesting Giardia targets PMN accumulation. However, the ability of Giardia infections to attenuate PMN accumulation in vivo and how in turn this effect may alter the host inflammatory response in the intestine has yet to be demonstrated. Herein, we report that Giardia infection attenuates granulocyte tissue infiltration induced by intra-rectal instillation of Clostridium difficile toxin A and B in an isolate-dependent manner. This attenuation of granulocyte infiltration into colonic tissues paralled decreased expression of several cytokines associated with the recruitment of PMNs. Giardia trophozoite isolates that attenuated granulocyte infiltration in vivo also decreased protein expression of cytokines released from inflamed mucosal biopsy tissues collected from patients with active Crohn’s disease, including several cytokines associated with PMN recruitment. These results demonstrate for the first time that certain Giardia infections may attenuate PMN accumulation by decreasing the expression of the mediators responsible for their recruitment.

A Prescription that Addresses the Decline of Basic Science Education in Medical School

Over 30 years ago a cry rang out through the proverbial halls of academia; “The clinician scientist is an endangered species.” These prophetic words have been reverberated in the ears of every specialty and every general medical organization in deafening tones. Why is the role of the clinician scientist or clinician investigator so important that this phrase has been repeated subsequently in medical and educational journals? Simply put, the clinician scientist bridges the ravine between the ever-growing mountain of scientific knowledge and the demanding patient centered clinical care. Here, we describe the current educational model established by the University of Calgary, Leaders in Medicine Program. Our program seeks to train future physicians and clinician scientists by incorporating training in basic science, translational and clinical research with clinical and medical education in a longitudinal program to students of traditional MD/PhD, MD/MSc or MD/MBA stream as well as interested Doctor of Medicine students.

Proceedings from the 5th Annual University of Calgary Leaders in Medicine Research Symposium

On November 8, 2013, the Leaders in Medicine (LIM) program hosted the 5th Annual Research Symposium. Dr. Jerrold Ellner, Chief of the Infectious Diseases section at Boston Medical Centre and Professor of Medicine at Boston University School of Medicine, was the keynote speaker and presented his lecture entitled “Tuberculosis – Past, Present and Future”. The LIM symposium gives a forum for LIM as well as non-LIM medical students to present their research work as either an oral or poster presentation. There were a total of 53 abstracts presented and five oral presentations. The symposium was attended by over 100 students and more than 30 staff members. The oral presentations included • Amrita Roy, Aboriginal identity, ethnic minority status, and prenatal depressive symptoms in a longitudinal pregnancy cohort study in Alberta. • David Nicholl, Obstructive sleep apnea treatment with continuous positive airway pressure decreases intraglomerular pressure and alters renal sensitivity to angiotensin. • James Cotton, An assemblage A Giardia cathepsin B protease degrades interleukin-8 and attenuates neutrophil chemotaxis. • Krystyna Ediger, Alexander Arnold and Emily Shelton, Rebuilding the Calgary Student Run Clinic: A Model for Sustainability. • Sarah MacEachern, Inhibiting inducible nitric oxide synthase restores electrogenic ion transport in experimental IBD: a novel role for enteric glia. See the article on the University of Calgary Leaders in Medicine Program, “A Prescription that Addresses the Decline of Basic Science Education in Medical School” in this same issue of CIM for more details on the program. In short, the LIM Research Symposium has the following objectives: (1) to showcase the impressive variety of projects undertaken by students in the LIM Program as well as U of C medical students; (2) to encourage medical student participation in research and special projects; and, (3) to inform students and faculty about the diversity of opportunities available for research and special projects during medical school and beyond. The following abstracts are those that were put forward for publication.

Targeting mitochondria-derived reactive oxygen species to reduce epithelial barrier dysfunction and colitis

Epithelial permeability is often increased in inflammatory bowel diseases. We hypothesized that perturbed mitochondrial function would cause barrier dysfunction and hence epithelial mitochondria could be targeted to treat intestinal inflammation. Mitochondrial dysfunction was induced in human colon-derived epithelial cell lines or colonic biopsy specimens using dinitrophenol, and barrier function was assessed by transepithelial flux of Escherichia coli with or without mitochondria-targeted antioxidant (MTA) cotreatment. The impact of mitochondria-targeted antioxidants on gut permeability and dextran sodium sulfate (DSS)-induced colitis in mice was tested. Mitochondrial superoxide evoked by dinitrophenol elicited significant internalization and translocation of E. coli across epithelia and control colonic biopsy specimens, which was more striking in Crohn's disease biopsy specimens; the mitochondria-targeted antioxidant, MitoTEMPO, inhibited these barrier defects. Increased gut permeability and reduced epithelial mitochondrial voltage-dependent anion channel expression were observed 3 days after DSS. These changes and the severity of DSS-colitis were reduced by MitoTEMPO treatment. In vitro DSS-stimulated IL-8 production by epithelia was reduced by MitoTEMPO. Metabolic stress evokes significant penetration of commensal bacteria across the epithelium, which is mediated by mitochondria-derived superoxide acting as a signaling, not a cytotoxic, molecule. MitoTEMPO inhibited this barrier dysfunction and suppressed colitis in DSS-colitis, likely via enhancing barrier function and inhibiting proinflammatory cytokine production. These novel findings support consideration of MTAs in the maintenance of epithelial barrier function and the management of inflammatory bowel diseases.

Clostridium difficile infection worsens the prognosis of ulcerative colitis

BACKGROUND

The impact of Clostridium difficile infections among ulcerative colitis (UC) patients is well characterized. However, there is little knowledge regarding the association between C difficile infections and postoperative complications among UC patients.

OBJECTIVE

To determine whether C difficile infection is associated with undergoing an emergent colectomy and experiencing postoperative complications.

METHODS

The present population-based case-control study identified UC patients admitted to Calgary Health Zone hospitals for a flare between 2000 and 2009. C difficile toxin tests ordered in hospital or 90 days before hospital admission were provided by Calgary Laboratory Services (Calgary, Alberta). Hospital records were reviewed to confirm diagnoses and to extract clinical data. Multivariate logistic regression analyses were performed among individuals tested for C difficile to examine the association between C difficile infection and emergent colectomy and diagnosis of any postoperative complications and, secondarily, an infectious postoperative complication. Estimates were presented as adjusted ORs with 95% CIs.

RESULTS

C difficile was tested in 278 (58%) UC patients and 6.1% were positive. C difficile infection was associated with an increased risk for emergent colectomy (adjusted OR 3.39 [95% CI 1.02 to 11.23]). Additionally, a preoperative diagnosis of C difficile was significantly associated with the development of postoperative infectious complications (OR 4.76 [95% CI 1.10 to 20.63]).

CONCLUSION

C difficile diagnosis worsened the prognosis of UC by increasing the risk of colectomy and postoperative infectious complications following colectomy. Future studies are needed to explore whether early detection and aggressive management of C difficile infection will improve UC outcomes.

Mitochondrial NLRP3 protein induces reactive oxygen species to promote Smad protein signaling and fibrosis independent from the inflammasome

Nucleotide-binding domain and leucine-rich repeat containing PYD-3 (NLRP3) is a pattern recognition receptor that is implicated in the pathogenesis of inflammation and chronic diseases. Although much is known regarding the NLRP3 inflammasome that regulates proinflammatory cytokine production in innate immune cells, the role of NLRP3 in non-professional immune cells is unclear. Here we report that NLRP3 is expressed in cardiac fibroblasts and increased during TGFβ stimulation. NLRP3-deficient cardiac fibroblasts displayed impaired differentiation and R-Smad activation in response to TGFβ. Only the central nucleotide binding domain of NLRP3 was required to augment R-Smad signaling because the N-terminal Pyrin or C-terminal leucine-rich repeat domains were dispensable. Interestingly, NLRP3 regulation of myofibroblast differentiation proceeded independently from the inflammasome, IL-1β/IL-18, or caspase 1. Instead, mitochondrially localized NLRP3 potentiated reactive oxygen species to augment R-Smad activation. In vivo, NLRP3-deficient mice were protected against angiotensin II-induced cardiac fibrosis with preserved cardiac architecture and reduced collagen 1. Together, these results support a distinct role for NLRP3 in non-professional immune cells independent from the inflammasome to regulate differential aspects of wound healing and chronic disease.

Effects of nitric oxide and reactive oxygen species on HIF-1α stabilization following clostridium difficile toxin exposure of the Caco-2 epithelial cell line

BACKGROUND/AIMS

Stabilization of the hypoxia-inducible factor (HIF-1α) is proposed to provide a protective host-response to C. difficile intoxication. Here, we aimed to elucidate whether nitric oxide and/or reactive oxygen species produced during C. difficile toxin exposure could influence HIF-1α stability and initiate protection against epithelial cell damage.

METHODS/RESULTS

HIF-1α and inducible nitric oxide synthase (iNOS) proteins were up-regulated whereas factor-inhibiting HIF-1 (FIH-1) protein was down-regulated in Caco-2 epithelial cell monolayers with in vitro toxin exposure. We demonstrate using the biotin-switch assay that the stabilization of HIF-1α protein occurred via iNOS-dependent nitrosylation. Inhibition of iNOS activity by selective inhibitor (1400W) attenuated HIF-1α stabilization and exacerbated toxin-dependent disruptions in Caco-2 monolayer morphology and tight junctional integrity in vitro. Treatment of Caco-2 cell monolayers with N-actylcysteine (NAC), a scavenger of reactive oxygen species (ROS), attenuated toxin-dependent increases in iNOS and HIF-1α protein levels but had no effect on FIH-1 responses. In addition, mice that were exposed to C. difficile toxin in vivo also demonstrated a significant increase in HIF-1α protein and nitrosylation levels.

CONCLUSION

Taken together, these data suggest that important synergistic actions exist between nitric oxide and ROS to stabilize HIF-1α and its innate, protective actions in the context of C. difficile toxin-mediated epithelial injury.

The association between celiac disease and eosinophilic esophagitis in children and adults

Background

An association between eosinophilic esophagitis (EoE) and celiac disease (CD) has been suggested in the literature. Our aim was to confirm and quantify the association between these two diseases.

Methods

All patients in a large Canadian city diagnosed with EoE or CD over a five-year period were identified. Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) were calculated.

Results

Over the five-year study EoE was diagnosed in 421 patients and CD was diagnosed in 763 patients. The incidence of EoE ranged from 2.1 to 10.7 cases per 100,000 population. The incidence of CD ranged from 10.4 to 15.7 cases per 100,000 population. Among the EoE cohort, 83 (20%) cases of EoE and 245 (32%) cases of CD were diagnosed in pediatric patients. The incidence of EoE in the pediatric subpopulation ranged from 3.7 to 6.9 cases per 100,000 population. The incidence of CD in the pediatric subpopulation ranged from 9.5 to 22.7 cases per 100,000 population. The concomitant diagnosis of both EoE and CD was made in three patients, all of whom were pediatric males. The SIR for EoE in the CD cohort was 48.4 (95% CI = 9.73, 141.41) with a SIR for CD within the paediatric EoE cohort of 75.05 (95% CI = 15.08, 219.28).

Conclusions

This study confirms the association between EoE and CD. However, this association may be limited to pediatrics where the risk of each condition is increased 50 to 75-fold in patients diagnosed with the alternative condition. The concomitant diagnosis of these conditions should be considered in pediatric patients with upper gastrointestinal symptoms.

Lymphocytic colitis is associated with increased pro-inflammatory cytokine profile and up regulation of prostaglandin receptor EP4

Microscopic colitis (MC) is comprised of two entities, lymphocytic (LC) and collagenous colitis. Up to 20% of patients with chronic diarrhea that have a normal appearing colonoscopy will be diagnosed with MC. Since MC was first described less than 40 years ago, little is known about the mechanisms involved in disease pathogenesis. Nonsteroidal anti-inflammatory drugs are associated with an increased risk of MC and some reports suggest a dysregulation in prostaglandin production. Recent genome wide screens have found an association between prostaglandin receptor EP4 expression and inflammatory bowel disease; however, EP4 expression has never been studied in MC. The aim of this study was to assess colonic mucosal inflammatory cytokine profiles in patients with LC and to assess expression of the prostaglandin receptor EP4. Colonic mucosal biopsies were obtained from patients undergoing colonoscopy for investigation of diarrhea and in those undergoing colon cancer screening. Following histological assessment, expression of cytokines and the prostaglandin receptor EP4 was analyzed using real-time reverse transcriptase-PCR and immunohistochemistry. Patients with LC had markedly increased mRNA expression for TNF-α, IFN-γ and IL-8 compared to normal controls (p<0.001). No significant differences were noted for IL-1β, IL-4, IL-10 or IL-12/23. Interestingly, those with LC had increased EP4 receptor expression, which positively correlated with increased TNF-α expression. This is the first report to demonstrate that LC is associated with increased TNF-α, INF-γ and IL-8 concurrent with a marked up-regulation of EP4. These findings add to our knowledge on the pathogenesis of LC and may give rise to possible new therapeutic and/or diagnostic tools in the management of MC.

Drug-induced inflammatory bowel disease and IBD-like conditions

The pathogenesis of inflammatory bowel disease (IBD) is multifactorial and results from an interaction between genetic, immunologic, microbial, and environmental factors. Certain drugs could act as a trigger for the disease and have been implicated in the development of new onset IBD in a number a studies. These relationships are based on case reports and cohort studies, as proving this in the context of randomized controlled trials would be difficult. Drugs that have been linked to causing or worsening IBD include isotretinoin, antibiotics, nonsteroidal antiinflammatory drugs, oral contraceptives, mycophenolate mofetil, etanercept, ipilimumab, and rituximab. Bowel preparation for colonoscopy has also been associated with aphthoid lesions that may be confused with IBD. However, given the source of these reports we have to be cautious in the interpretation of the data before concluding that these drugs trigger IBD and what is being observed is not related to other confounding factors. Different pathogenic mechanisms have been suggested for the different drugs listed above. In order to clarify the confusion a comprehensive literature review was performed with the goal of advancing the knowledge on this subject.