Validation of a new optical diagnosis training module to improve dysplasia characterization in inflammatory bowel disease: a multicenter international study.

BACKGROUND AND AIMS: Inflammatory bowel disease (IBD) increases risk of dysplasia and colorectal cancer. Advanced endoscopic techniques allow for the detection and characterization of IBD dysplastic lesions, but specialized training is not widely available. We aimed to develop and validate an online training platform to improve the detection and characterization of colonic lesions in IBD: OPtical diagnosis Training to Improve dysplasia Characterization in Inflammatory Bowel Disease (OPTIC-IBD). METHODS: We designed a web-based learning module that includes surveillance principles, optical diagnostic methods, approach to characterization, and classifications of colonic lesions using still images and videos. We invited gastroenterologists from Canada, Italy, and the United Kingdom with a wide range of experience. Participants reviewed 24 educational videos of IBD colonic lesions, predicted histology, and rated their confidence. The primary endpoint was to improve accuracy in detecting dysplastic lesions after training on the platform. Furthermore, participants were randomized 1:1 to get additional training or not, with a final assessment occurring after 60 days. Diagnostic performance for dysplasia and rater confidence were measured. RESULTS: A total of 117 participants completed the study and were assessed for the primary endpoint. Diagnostic accuracy improved from 70.8% to 75.0% (P = .002) after training, with the greatest improvements seen in less experienced endoscopists. Improvements in both accuracy and confidence were sustained after 2 months of assessment, although the group randomized to receive additional training did not improve further. Similarly, participants' confidence in characterizing lesions significantly improved between before and after the course (P < .001), and it was sustained after 2 months of assessment. CONCLUSIONS: The OPTIC-IBD training module demonstrated that an online platform could improve participants' accuracy and confidence in the optical diagnosis of dysplasia in patients with IBD. The training platform can be widely available and improve endoscopic care for people with IBD. (Clinical trial registration number: NCT04924543.).

Artificial Intelligence Enabled Histological Prediction of Remission or Activity and Clinical Outcomes in Ulcerative Colitis.

BACKGROUND & AIMS: Microscopic inflammation has significant prognostic value in ulcerative colitis (UC); however, its assessment is complex with high interobserver variability. We aimed to develop and validate an artificial intelligence (AI) computer-aided diagnosis system to evaluate UC biopsies and predict prognosis. METHODS: A total of 535 digitalized biopsies (273 patients) were graded according to the PICaSSO Histologic Remission Index (PHRI), Robarts, and Nancy Histological Index. A convolutional neural network classifier was trained to distinguish remission from activity on a subset of 118 biopsies, calibrated on 42 and tested on 375. The model was additionally tested to predict the corresponding endoscopic assessment and occurrence of flares at 12 months. The system output was compared with human assessment. Diagnostic performance was reported as sensitivity, specificity, prognostic prediction through Kaplan-Meier, and hazard ratios of flares between active and remission groups. We externally validated the model in 154 biopsies (58 patients) with similar characteristics but more histologically active patients. RESULTS: The system distinguished histological activity/remission with sensitivity and specificity of 89% and 85% (PHRI), 94% and 76% (Robarts Histological Index), and 89% and 79% (Nancy Histological Index). The model predicted the corresponding endoscopic remission/activity with 79% and 82% accuracy for UC endoscopic index of severity and Paddington International virtual ChromoendoScopy ScOre, respectively. The hazard ratio for disease flare-up between histological activity/remission groups according to pathologist-assessed PHRI was 3.56, and 4.64 for AI-assessed PHRI. Both histology and outcome prediction were confirmed in the external validation cohort. CONCLUSION: We developed and validated an AI model that distinguishes histologic remission/activity in biopsies of UC and predicts flare-ups. This can expedite, standardize, and enhance histologic assessment in practice and trials.

Constrained multiple instance learning for ulcerative colitis prediction using histological images.

BACKGROUND AND OBJECTIVE: Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) affecting the colon and the rectum characterized by a remitting-relapsing course. To detect mucosal inflammation associated with UC, histology is considered the most stringent criteria. In turn, histologic remission (HR) correlates with improved clinical outcomes and has been recently recognized as a desirable treatment target. The leading biomarker for assessing histologic remission is the presence or absence of neutrophils. Therefore, the finding of this cell in specific colon structures indicates that the patient has UC activity. However, no previous studies based on deep learning have been developed to identify UC based on neutrophils detection using whole-slide images (WSI). METHODS: The methodological core of this work is a novel multiple instance learning (MIL) framework with location constraints able to determine the presence of UC activity using WSI. In particular, we put forward an effective way to introduce constraints about positive instances to effectively explore additional weakly supervised information that is easy to obtain and enjoy a significant boost to the learning process. In addition, we propose a new weighted embedding to enlarge the relevance of the positive instances. RESULTS: Extensive experiments on a multi-center dataset of colon and rectum WSIs, PICASSO-MIL, demonstrate that using the location information we can improve considerably the results at WSI-level. In comparison with prior MIL settings, our method allows for 10% improvements in bag-level accuracy. CONCLUSION: Our model, which introduces a new form of constraints, surpass the results achieved from current state-of-the-art methods that focus on the MIL paradigm. Our method can be applied to other histological concerns where the morphological features determining a positive WSI are tiny and similar to others in the image.

PICaSSO Histologic Remission Index (PHRI) in ulcerative colitis: development of a novel simplified histological score for monitoring mucosal healing and predicting clinical outcomes and its applicability in an artificial intelligence system.

Histological remission is evolving as an important treatment target in UC. We aimed to develop a simple histological index, aligned to endoscopy, correlated with clinical outcomes, and suited to apply to an artificial intelligence (AI) system to evaluate inflammatory activity. METHODS: Using a set of 614 biopsies from 307 patients with UC enrolled into a prospective multicentre study, we developed the Paddington International virtual ChromoendoScopy ScOre (PICaSSO) Histologic Remission Index (PHRI). Agreement with multiple other histological indices and validation for inter-reader reproducibility were assessed. Finally, to implement PHRI into a computer-aided diagnosis system, we trained and tested a novel deep learning strategy based on a CNN architecture to detect neutrophils, calculate PHRI and identify active from quiescent UC using a subset of 138 biopsies. RESULTS: PHRI is strongly correlated with endoscopic scores (Mayo Endoscopic Score and UC Endoscopic Index of Severity and PICaSSO) and with clinical outcomes (hospitalisation, colectomy and initiation or changes in medical therapy due to UC flare-up). A PHRI score of 1 could accurately stratify patients' risk of adverse outcomes (hospitalisation, colectomy and treatment optimisation due to flare-up) within 12 months. Our inter-reader agreement was high (intraclass correlation 0.84). Our preliminary AI algorithm differentiated active from quiescent UC with 78% sensitivity, 91.7% specificity and 86% accuracy. CONCLUSIONS: PHRI is a simple histological index in UC, and it exhibits the highest correlation with endoscopic activity and clinical outcomes. A PHRI-based AI system was accurate in predicting histological remission.

Revisiting the distinct histomorphologic features of inflammatory bowel disease-associated neoplastic precursor lesions in the SCENIC and post-DALM Era.

Distinct histomorphologic features of colitis-associated dysplasia (CAD) or neoplastic precursors in inflammatory bowel disease (IBD) have never been clearly identified. In this study, we tried to further explore the differentiating morphologic features of CAD by retrospectively reviewing the lesions that were clearly associated with carcinomas (carcinoma-related lesions) and by comparing between endoscopically nonpolypoid (non-adenoma-like) lesions and polypoid (adenoma-like) lesions and sporadic conventional adenomas found in the noncolitic mucosa and in patients without IBD. Our study results have revealed that (1) precursor lesions related to IBD-associated colorectal carcinomas were almost always nonpolypoid in macroscopic/endoscopic appearance; (2) nearly half of the carcinoma-related lesions and nonpolypoid lesions were similarly nonadenomatous (nonconventional) lesions, largely serrated type, with no or only mild/focal adenomatous dysplasia, and commonly had mixed adenomatous and nonadenomatous features; (3) carcinoma-related and nonpolypoid adenomatous dysplastic lesions frequently showed some peculiar histocytologic features that we observed and described for the first time, including mixed features of inflammatory pseudopolyps or granulation tissue, pleomorphic and disarrayed nuclei, micropapillary or hobnailing surface epithelial cells, and microvesicular or bubbling cytoplasm of dysplastic cells; and (4) polypoid lesions in the colitic mucosa were identical to sporadic adenomas in the noninflamed mucosa and in patients without IBD, and they lacked the aforementioned features. The seemingly distinctive morphologic characteristics that we proposed here, although still not absolutely specific or unique, can be used as the features of inclusion for identifying CAD on endoscopic biopsies when the endoscopy images are not readily available to pathologists and thus to alert clinicians for a closer follow-up.

Perturbed Mitochondrial Dynamics Is a Novel Feature of Colitis That Can Be Targeted to Lessen Disease.

BACKGROUND & AIMS: Mitochondria exist in a constantly remodelling network, and excessive fragmentation can be pathophysiological. Mitochondrial dysfunction can accompany enteric inflammation, but any contribution of altered mitochondrial dynamics (ie, fission/fusion) to gut inflammation is unknown. We hypothesized that perturbed mitochondrial dynamics would contribute to colitis. METHODS: Quantitative polymerase chain reaction for markers of mitochondrial fission and fusion was applied to tissue from dextran sodium sulfate (DSS)-treated mice. An inhibitor of mitochondrial fission, P110 (prevents dynamin related protein [Drp]-1 binding to mitochondrial fission 1 protein [Fis1]) was tested in the DSS and di-nitrobenzene sulfonic acid (DNBS) models of murine colitis, and the impact of DSS ± P110 on intestinal epithelial and macrophage mitochondria was assessed in vitro. RESULTS: Analysis of colonic tissue from mice with DSS-colitis revealed increased mRNA for molecules associated with mitochondrial fission (ie, Drp1, Fis1) and fusion (optic atrophy factor 1) and increased phospho-Drp1 compared with control. Systemic delivery of P110 in prophylactic or treatment regimens reduced the severity of DSS- or DNBS-colitis and the subsequent hyperalgesia in DNBS-mice. Application of DSS to epithelial cells or macrophages caused mitochondrial fragmentation. DSS-evoked perturbation of epithelial cell energetics and mitochondrial fragmentation, but not cell death, were ameliorated by in vitro co-treatment with P110. CONCLUSIONS: We speculate that the anti-colitic effect of systemic delivery of the anti-fission drug, P110, works at least partially by maintaining enterocyte and macrophage mitochondrial networks. Perturbed mitochondrial dynamics can be a feature of intestinal inflammation, the suppression of which is a potential novel therapeutic direction in inflammatory bowel disease.

Newly recognized non-adenomatous lesions associated with enteric carcinomas in inflammatory bowel disease - Report of six rare and unique cases.

It is the current view that the inflammatory bowel disease (IBD)-associated precancerous lesions may be adenomatous (with classic cytologic dysplasia) and non-adenomatous (without frank cytologic dysplasia), and the latter ones are in various histomorphologies including serrated, mucinous, eosinophilic (goblet cell deficient), and differentiated (dysplasia with terminal epithelial differentiation) types. By retrospectively reviewing the surgically resected IBD-associated colorectal and ileal carcinomas (×53), analyzing the background epithelial changes/lesions in the mucosa surrounding and adjacent to invasive carcinomas, and testing the key molecular profile (KRAS, BRAF, PIK3CA, NRAS, p53, mismatch repair proteins, and SAT-B2) known to be involved in colorectal carcinogenesis, we identified 6 representative, rare and unique cases, in which non-adenomatous lesions were clearly in vicinity and in transition to invasive carcinomas. Furthermore, we identified certain colonic carcinoma-related molecular alterations, and thus further confirmed the neoplastic nature of various non-adenomatous lesions. It was also revealed that non-adenomatous lesions are heterogeneous in both morphology and molecular alterations, and that it is common to have more than one type of lesions be associated with a carcinoma. Moreover, mixed focal adenomatous dysplasia was common, which may be the necessary step in the malignant transformation of the non-adenomatous lesions.

Another Whipple's triad? Pericardial, myocardial and valvular disease in an unusual case presentation from a Canadian perspective.

BACKGROUND: Whipple's disease is a clinically relevant multi-system disorder that is often undiagnosed given its elusive nature. We present an atypical case of Whipple's disease involving pan-valvular endocarditis and constrictive pericarditis, requiring cardiac intervention. A literature review was also performed assessing the prevalence of atypical cases of Whipple's disease. CASE PRESENTATION: A previously healthy 56-year-old male presented with a four-year history of congestive heart failure with weight loss and fatigue. Notably, he had absent gastrointestinal symptoms. He went on to develop pan-valvular endocarditis and constrictive pericarditis requiring urgent cardiac surgery. A clinical diagnosis of Whipple's disease was suspected, prompting duodenal biopsy sampling which was unremarkable, Subsequently, Tropheryma whipplei was identified by 16S rDNA PCR on the cardiac valvular tissue. He underwent prolonged antibiotic therapy with recovery of symptoms. CONCLUSIONS: Our study reports the first known case of Whipple's disease involving pan-valvular endocarditis and constrictive pericarditis. A literature review also highlights this presentation of atypical Whipple's with limited gastrointestinal manifestations. Duodenal involvement was limited and the gold standard of biopsy was not contributory. We also highlight the Canadian epidemiology of the disease from 2012 to 2016 with an approximate 4% prevalence rate amongst submitted samples. Routine investigations for Whipple's disease, including duodenal biopsy, in this case may have missed the diagnosis. A high degree of suspicion was critical for diagnosis of unusual manifestations of Whipple's disease.

Crohn's-like disease in a patient exposed to anti-Interleukin-17 blockade (Ixekizumab) for the treatment of chronic plaque psoriasis: a case report.

BACKGROUND: Plaque psoriasis and inflammatory bowel disease (IBD) are both chronic immune-mediated inflammatory diseases with an overlapping genetic profile and have been linked in epidemiological studies. Psoriasis and IBD share similar components in their inflammatory pathways and animal and human studies have suggested a potential role for targeting interleukin (IL)-17 with novel antibody therapies in the treatment of these diseases. These studies, while promising for psoriasis, have been associated with deterioration in patients with IBD. Post-hoc analyses of clinical trials involving Ixekizumab revealed adverse outcomes in a small cluster of patients with IBD, prompting recommendations to monitor this population with the use of this drug. CASE PRESENTATION: Forty-two year old Caucasian male with treatment-refractory chronic plaque psoriasis who developed new onset diarrheal illness and rectal bleeding following a 12 week induction period with Ixekizumab (anti-IL-17 neutralizing antibody). Colonoscopy revealed severe ulceration throughout the ascending and transcending colon. Histopathology, combined with endoscopic findings, led to a diagnosis of Crohn's-like colitis. The patient's anti-IL-17 medication was discontinued and endoscopic remission was induced with the use of corticosteroids, escalated anti-TNF therapy and eventually anti IL-12/23 neutralizing antibody (ustekinumab). CONCLUSION: Murine studies implicate IL-17 and the downstream effects of its inhibition, in the breakdown of the gut epithelial layer, the disruption of normal host immune responses and the propagation of intestinal inflammation. The increasing use of IL-17 inhibitors has led to reports of exacerbation and potential development of inflammatory bowel disease. While clinical trials have revealed clusters of new inflammatory bowel disease cases amongst psoriasis patients using an IL-17 inhibitor, there remains a lack of evidence to suggest a causal relationship. This is the first case report of de-novo severe Crohn's-like IBD in association with the use of Ixekizumab requiring rescue with escalated dosing of anti-TNF therapy and highlights the importance of close monitoring in patients being treated with IL-17 inhibitors, especially in those patients with known risk factors for inflammatory bowel disease.

Real-world clinical, endoscopic and radiographic efficacy of vedolizumab for the treatment of inflammatory bowel disease.

BACKGROUND: Vedolizumab is an α4ß7 integrin antagonist with proven efficacy for inducing and maintaining clinical response and remission in Crohn's disease (CD) and ulcerative colitis (UC). AIM: To evaluate clinical and objective response and remission rates with vedolizumab in a large, real world cohort. METHODS: A retrospective cohort study of adult CD and UC patients receiving vedolizumab between 2012 and 2017 was conducted. PRIMARY OUTCOME: clinical or objective response and remission at 3, 6 and 12 months after induction. Clinical remission was defined by complete, steroid-free absence of symptoms. Objective remission was defined by endoscopic mucosal healing or normalisation of radiographic appearance on contrast-enhanced ultrasound or CT/MR enterography. RESULTS: The study included 222 vedolizumab patients (122 CD, 100 UC). In CD, clinical remission at 3, 6 and 12 months was achieved in 19.8% (22/111), 22.1% (21/95) and 22.1% (15/68) of patients, respectively. Objective remission occurred in 11.5% (6/52), 21.2% (14/66), and 18.9% (7/37) of patients at 3, 6 and 12 months, respectively. In UC, clinical remission at 3, 6, and 12 months was 51.0% (51/100), 61.8% (55/89) and 61.9% (39/63), respectively. Endoscopic remission occurred in 27.5% (11/40), 41.0% (16/39) and 47.8% (22/46) of patients at 3, 6 and 12 months, respectively. In multivariable analysis, patients with UC as compared to CD, and those with milder disease activity were more likely to achieve objectively defined remission at both 6 and 12 months. CONCLUSIONS: Vedolizumab was effective for induction and maintenance of clinical and objective remission, both in Crohn's disease and ulcerative colitis.

Targeted Biopsies Identify Larger Proportions of Patients With Colonic Neoplasia Undergoing High-Definition Colonoscopy, Dye Chromoendoscopy, or Electronic Virtual Chromoendoscopy.

BACKGROUND & AIMS: It is unclear what are the best and most appropriate endoscopic procedures for detecting colonic neoplasia in patients with long-term colonic inflammatory bowel disease (IBD). Dye chromoendoscopy (DCE) is the standard used in IBD surveillance colonoscopies. However, studies are needed to determine the optimal endoscopic technique for detecting dysplastic lesions. We investigated current practices used in surveillance colonoscopies by IBD gastroenterologists at a single tertiary center. We also determined the rate of neoplasia detection among different surveillance endoscopic techniques in an analysis of random or targeted biopsies. METHODS: We collected data on 454 patients with IBD (54.5% male; mean age, 50 y; mean disease duration, 14.5 y; 55.9% with ulcerative colitis, 42.7% with Crohn's disease, and 1.3% with indeterminate colitis) who underwent surveillance colonoscopy from April 2011 through March 2014 at the University of Calgary in Canada. Subjects were examined using white-light standard-definition endoscopy (WLE), high-definition (HD) colonoscopy, virtual electronic chromoendoscopy (VCE), or DCE; random or targeted biopsy specimens were collected. Endoscopic and histologic descriptions with suspected neoplasia were recorded. Rates of neoplasia detection by the different endoscopic procedures were compared using chi-square analysis. RESULTS: Of the patients analyzed, 27.7% had WLE endoscopy with random collection of biopsy specimens, 27.3% had HD colonoscopy with random collection of biopsy specimens, 14.1% had VCE with random collection of biopsy specimens, 0.9% had DCE with random collection of biopsy specimens, 12.8% had HD colonoscopy with collection of targeted biopsy specimens, 11.9% had VCE with collection of targeted biopsy specimens, and 5.3% had DCE with collection of targeted biopsy specimens. Neoplastic lesions were detected in 8.2% of the procedures performed in the random biopsy group (95% confidence interval, 5.6-11.7) and 19.1% of procedures in the targeted biopsy group (95% confidence interval, 13.4-26.5) (P < .001). Neoplasias were detected in similar proportions of patients by HD colonoscopy, VCE, or DCE, with targeted biopsy collection. CONCLUSIONS: In a large cohort of IBD patients undergoing surveillance colonoscopy, targeted biopsies identified greater proportions of subjects with neoplasia than random biopsies. Targeted collection of biopsy specimens appears to be sufficient for detecting colonic neoplasia in patients undergoing HD colonoscopy, DCE, or VCE, but not WLE.

Proresolution effects of hydrogen sulfide during colitis are mediated through hypoxia-inducible factor-1α.

During a course of colitis, production of the gaseous mediator hydrogen sulfide (H2S) is markedly up-regulated at sites of mucosal damage and contributes significantly to healing and resolution of inflammation. The signaling mechanisms through which H2S promotes resolution of colitis are unknown. We hypothesized that the beneficial effects of H2S in experimental colitis are mediated via stabilization of hypoxia-inducible factor (HIF)-1α. The hapten dinitrobenzene sulfonic acid was used to induce colitis in rats and mice. This resulted in an elevated expression of the H2S-producing enzyme, cystathionine γ-lyase (CSE), and HIF-1α at sites of mucosal ulceration, and the expression of these 2 enzymes followed a similar pattern throughout the course of colitis. This represented a functionally important relationship because the loss of CSE-derived H2S production led to decreased HIF-1α stabilization and exacerbation of colitis. Furthermore, application of an H2S-releasing molecule, diallyl disulfide (DADS), stabilized colonic HIF-1α expression, up-regulated hypoxia-responsive genes, and reduced the severity of disease during peak inflammation. Importantly, the ability of DADS to promote the resolution of colitis was abolished when coadministered with an inhibitor of HIF-1α in vivo (PX-478). DADS was also able to maintain HIF-1α expression at a later point in colitis, when HIF-1α levels would have normally returned to control levels, and to enhance resolution. Finally, we found that HIF-1α stabilization inhibited colonic H2S production and may represent a negative feedback mechanism to prevent prolonged HIF-1α stabilization. Our findings demonstrate an important link between H2S and HIF-1α in the resolution of inflammation and injury during colitis and provide mechanistic insights into the therapeutic value of H2S donors.

Impaired hydrogen sulfide synthesis and IL-10 signaling underlie hyperhomocysteinemia-associated exacerbation of colitis.

Vitamin B deficiencies, which can lead to hyperhomocysteinemia (Hhcy), are commonly reported in patients with inflammatory bowel disease (IBD) and may be a causative underlying factor. However, the mechanism for this effect is not known. Hydrogen sulfide (H2S) is a gaseous mediator that promotes tissue repair and resolution of inflammation. In experimental colitis, a marked increase in colonic H2S synthesis drives ulcer healing and resolution of inflammation. Because H2S synthesis is in part dependent upon enzymes that require vitamin B6 as a cofactor, we tested the hypothesis that Hhcy in rodent models would increase the susceptibility to colitis. In all three models tested, diet-induced Hhcy significantly exacerbated colitis. The usual elevation of colonic H2S synthesis after induction of colitis was absent in all three models of colitis. Administration of an H2S donor to Hhcy rats significantly decreased the severity of colitis. Compared with wild-type mice, interleukin (IL) 10-deficient mice on a normal diet had decreased levels of colonic H2S synthesis, a 40% increase in serum homocysteine, and a phenotype similar to wild-type mice with Hhcy. IL-10-deficient mice fed the vitamin B-deficient diet exhibited more severe colonic inflammation, but the normal elevation of colonic H2S synthesis was absent. Administration of IL-10 to the IL-10-deficient mice restored colonic H2S synthesis and significantly decreased serum homocysteine levels. These results suggest that the exacerbation of colitis in Hhcy is due in part to impaired colonic H2S synthesis. Moreover, IL-10 plays a novel role in promoting H2S production and homocysteine metabolism, which may have therapeutic value in conditions characterized by Hhcy.

Giardia duodenalis cathepsin B proteases degrade intestinal epithelial interleukin-8 and attenuate interleukin-8-induced neutrophil chemotaxis.

Giardia duodenalis (syn. G. intestinalis, G. lamblia) infections are a leading cause of waterborne diarrheal disease that can also result in the development of postinfectious functional gastrointestinal disorders via mechanisms that remain unclear. Parasite numbers exceed 10(6) trophozoites per centimeter of gut at the height of an infection. Yet the intestinal mucosa of G. duodenalis-infected individuals is devoid of signs of overt inflammation. G. duodenalis infections can also occur concurrently with infections with other proinflammatory gastrointestinal pathogens. Little is known of whether and how this parasite can attenuate host inflammatory responses induced by other proinflammatory stimuli, such as a gastrointestinal pathogen. Identifying hitherto-unrecognized parasitic immunomodulatory pathways, the present studies demonstrated that G. duodenalis trophozoites attenuate secretion of the potent neutrophil chemoattractant interleukin-8 (CXCL8); these effects were observed in human small intestinal mucosal tissues and from intestinal epithelial monolayers, activated through administration of proinflammatory interleukin-1ß or Salmonella enterica serovar Typhimurium. This attenuation is caused by the secretion of G. duodenalis cathepsin B cysteine proteases that degrade CXCL8 posttranscriptionally. Furthermore, the degradation of CXCL8 via G. duodenalis cathepsin B cysteine proteases attenuates CXCL8-induced chemotaxis of human neutrophils. Taken together, these data demonstrate for the first time that G. duodenalis trophozoite cathepsins are capable of attenuating a component of their host's proinflammatory response induced by a separate proinflammatory stimulus.

Enhanced synthesis and diminished degradation of hydrogen sulfide in experimental colitis: a site-specific, pro-resolution mechanism.

Hydrogen sulfide (H2S) is produced throughout the gastrointestinal tract, and it contributes to maintenance of mucosal integrity, resolution of inflammation, and repair of damaged tissue. H2S synthesis is elevated in inflamed and damaged colonic tissue, but the enzymatic sources of that synthesis are not completely understood. In the present study, the contributions of three enzymatic pathways to colonic H2S synthesis were determined, with tissues taken from healthy rats and rats with colitis. The ability of the colonic tissue to inactivate H2S was also determined. Colonic tissue from rats with hapten-induced colitis produced significantly more H2S than tissue from healthy controls. The largest source of the H2S synthesis was the pathway involving cysteine amino transferase and 3-mercaptopyruvate sulfurtransferase (an α-ketoglutarate-dependent pathway). Elevated H2S synthesis occurred specifically at sites of mucosal ulceration, and was not related to the extent of granulocyte infiltration into the tissue. Inactivation of H2S by colonic tissue occurred rapidly, and was significantly reduced at sites of mucosal ulceration. This correlated with a marked decrease in the expression of sulfide quinone reductase in these regions. Together, the increased production and decreased inactivation of H2S at sites of mucosal ulceration would result in higher H2S levels at these sites, which promotes of resolution of inflammation and repair of damaged tissue.

Up-regulation of Annexin-A1 and lipoxin A(4) in individuals with ulcerative colitis may promote mucosal homeostasis.

BACKGROUND: One of the characteristics of an active episode of ulcerative colitis (UC) is the intense mucosal infiltration of leukocytes. The pro-resolution mediators Annexin-A1 (AnxA1) and lipoxin A(4) (LXA(4)) exert counter-regulatory effects on leukocyte recruitment, however to date, the dual/cumulative effects of these formyl peptide receptor-2 (FPR2/ALX) agonists in the context of human intestinal diseases are unclear. To define the contribution of these mediators, we measured their expression in biopsies from individuals with UC. METHODS: Colonic mucosal biopsies were collected from two broad patient groups: healthy volunteers without ('Ctrl' n  = 20) or with a prior history of UC ('hx of UC' n = 5); individuals with UC experiencing active disease ('active' n = 8), or in medically-induced remission ('remission' n = 16). We assessed the mucosal expression of LXA(4), AnxA1, and the FPR2/ALX receptor in each patient group using a combination of fluorescence microscopy, biochemical and molecular analyses. RESULTS: Mucosal expression of LXA(4) was elevated exclusively in biopsies from individuals in remission (3-fold, P<0.05 vs. Ctrl). Moreover, in this same group we observed an upregulation of AnxA1 protein expression (2.5-fold increase vs. Ctrl, P<.01), concurrent with an increased level of macrophage infiltration, and an elevation in FPR2/ALX mRNA (7-fold increase vs. Ctrl, P<.05). Importantly, AnxA1 expression was not limited to cells infiltrating the lamina propria but was also detected in epithelial cells lining the intestinal crypts. CONCLUSIONS: Our results demonstrate a specific up-regulation of this pro-resolution circuit in individuals in remission from UC, and suggest a significant role for LXA(4) and AnxA1 in promoting mucosal homeostasis.

Hydrogen sulfide: an endogenous mediator of resolution of inflammation and injury.

SIGNIFICANCE: Hydrogen sulfide is emerging as an important mediator of many aspects of inflammation, and perhaps most importantly as a factor promoting the resolution of inflammation and repair of injury. RECENT ADVANCES: In the gastrointestinal tract, H(2)S has been shown to promote healing of ulcers and the resolution of mucosal inflammation. On the other hand, suppression of endogenous H(2)S synthesis impairs mucosal defense and leads to increased granulocyte infiltration. H(2)S has been exploited in the design of more effective and safe anti-inflammatory drugs. CRITICAL ISSUES: Enteric bacteria can be a significant source of H(2)S, which could affect mucosal integrity; indeed, luminal H(2)S can serve as an alternative to oxygen as a metabolic substrate for mitochondrial respiration in epithelial cells. Enterocytes and colonocytes thereby represent a "metabolic barrier" to the diffusion of bacteria-derived H(2)S into the subepithelial space. A compromise of this barrier could result in modulation of mucosal function and integrity by bacterial H(2)S. FUTURE DIRECTIONS: Improvements in methods for measurement of H(2)S and development of more selective inhibitors are crucial for gaining a better understanding of the pathophysiological importance of this mediator. Results from animal studies suggest that H(2)S-releasing agents are promising therapeutic agents for many indications, but these compounds need to be assessed in a clinical setting.

New pharmacologic therapies in gastrointestinal disease.

Many gastrointestinal diseases remain poorly responsive to therapies, and even in the cases of conditions for which there are many effective drugs, there is still considerable room for improvement. This article is focused on drugs for digestive disorders that have entered the marketplace recently, or are expected to reach the marketplace within the next 1 to 2 years. Although advances have been made in understanding gastrointestinal motility, visceral pain, mucosal inflammation, and tissue repair, the major gastrointestinal diseases remain as significant therapeutic challenges.

A pro-resolution mediator, prostaglandin D(2), is specifically up-regulated in individuals in long-term remission from ulcerative colitis.

Patients with ulcerative colitis (UC) experience unpredictable bouts of active inflammation and ulceration. Relatively little attention has been paid to the role of antiinflammatory mediators in the pathogenesis of UC, although rodent studies suggest an important role of prostaglandin (PG) D(2) in the resolution of tissue injury and inflammation. The present study was performed to determine if colonic PGD(2) synthesis was altered in patients in remission from UC and if expression of the key enzymes and receptors related to PGD(2) was altered. During routine colon-cancer screening, colonic biopsies were obtained from healthy individuals, some of whom had been in remission from UC, without treatment, for >4 y. UC patients with active disease or in medically induced remission were also biopsied. Only patients with active UC exhibited elevated expression of several proinflammatory cytokines (TNFalpha and IFNgamma) and colonic PGE(2) synthesis. In contrast, colonic PGD(2) synthesis was only elevated ( approximately 3-fold) in the healthy individuals with a prior history of UC. This group also exhibited significantly elevated expression of DP1, the key receptor mediating the antiinflammatory actions of PGD(2). Expression of the synthetic enzymes cyclooxygenase-1, cyclooxygenase-2, and hematopoietic PGD synthase was not altered in the healthy individuals with a prior history of UC. These results show a marked up-regulation of synthesis of an antiinflammatory prostanoid and expression of its receptor, specifically in individuals in long-term remission from UC. This is consistent with animal studies showing the importance of PGD(2) in the induction and maintenance of remission from colitis.

Hydrogen sulphide synthesis in the rat and mouse gastrointestinal tract.

AIMS: Hydrogen sulphide (H2S) exerts several anti-inflammatory effects, accelerates the healing of experimental gastric ulcers, and can stimulate intestinal secretion. Little is known about H2S synthesis in the gastrointestinal tract. The aim of this study was to characterize H2S synthesis throughout the gastrointestinal tract. METHODS: H2S synthesis in various gastrointestinal tissues of rats and mice was determined. The effects and selectivity of inhibitors of two key enzymes for H2S synthesis, cystathionine-gamma-lyase and cystathionine-beta-synthase, were examined. Cystathionine-gamma-lyase and cystathionine-beta-synthase expression was evaluated by Western blotting and immunohistochemistry. Cystathionine-gamma-lyase and cystathionine-beta-synthase expression in biopsies of human colon was also examined. RESULTS: H2S synthesis was variable throughout the gastrointestinal tract in parallel with variations in cystathionine-gamma-lyase and cystathionine-beta-synthase expression. The efficacy of cystathionine-beta-synthase and cystathionine-gamma-lyase inhibitors to reduce H2S synthesis in these tissues was also variable. Cystathionine-beta-synthase is the predominant source of H2S synthesis in the colon of rodents. Cystathionine-gamma-lyase and cystathionine-beta-synthase were also expressed in healthy human colon biopsies. CONCLUSIONS: The capacity for H2S synthesis varies throughout the rodent gastrointestinal tract, as does the distribution and contribution of the two key enzymes. Investigation of additional enzymatic sources of H2S and the development of more selective inhibitors are suggested.