On the role of ischemia in the pathogenesis of IBD: a review

Regulation of pathologic fibroblast functions in digestive diseases: a role for hypoxia?

The recent uncovering of fibroblast heterogeneity has given great insight into the versatility of the stroma. Among other cellular processes, fibroblasts are now thought to contribute to the coordination of immune responses in a range of chronic inflammatory diseases and cancer. Although the pathologic roles of myofibroblasts, inflammatory fibroblasts, and cancer-associated fibroblasts in disease are reasonably well understood, the mechanisms behind their activation remain to be uncovered. In the gastrointestinal (GI) tract, several interleukins and tumor necrosis factor superfamily members have been identified as possible mediators driving the acquisition of inflammatory and fibrotic properties in fibroblasts. In addition to cytokines, other microenvironmental factors such as nutrient and oxygen availability are likely contributors to this process. In this respect, the phenomenon of low cellular oxygen levels known as hypoxia is common in a plethora of GI diseases. Indeed, the cross talk between hypoxia and inflammation is well-documented, with an abundance of studies suggesting that oxygen-sensing enzymes may have regulatory effects on inflammatory signaling pathways such as NF-κB. However, the impact that this has in GI fibroblasts in the context of chronic diseases has not been fully uncovered. Here we discuss the role of fibroblasts in GI diseases, the mediators that have emerged as regulators of their functions and the potential impact of hypoxia in this process, highlighting areas that require further investigation.

Hypoxia-Mediated Upregulation of Xanthine Oxidoreductase Causes DNA Damage of Colonic Epithelial Cells in Colitis

Xanthine oxidoreductase (XOR) serves as the primary source of hydrogen peroxide and superoxide anions in the intestinal mucosa. However, its specific contribution to the progression of colonic disease remains unclear. In this study, we investigated the role of XOR in ulcerative colitis (UC) and attempted to identify the underlying mechanisms. We used the dextran sulfate sodium (DSS)-induced mouse model to mimic UC and observed that XOR inhibitors, allopurinol and diphenyleneiodonium sulfate (DPI), significantly alleviated UC in mice. In addition, treatment with cobalt chloride (CoCl2) and 1% O2 increased the expression of XOR and induced DNA oxidative damage in colonic epithelial cells. Furthermore, we identified that XOR accumulation in the nucleus may directly cause DNA oxidative damage and regulates HIF1α protein levels. In addition, allopurinol effectively protected colon epithelial cells from CoCl2-induced DNA damage. Altogether, our data provided evidence that XOR could induce DNA damage under hypoxic conditions, indicating a significant role of XOR in the initiation and early development of colitis-associated colorectal cancer (CAC).

Unveiling the molecular complexity of intestinal ischemia-reperfusion injury through omics technologies

Intestinal ischemia-reperfusion injury (IR) is implicated in various clinical conditions and causes damage to the intestinal epithelium resulting in intestinal barrier loss. This presents a substantial clinical challenge, emphasizing the importance of gaining a comprehensive understanding of molecular events to aid in the identification of novel therapeutic targets. This review systematically explores the extent to which omics technologies-transcriptomics, proteomics, metabolomics, and metagenomics-have already contributed to deciphering the molecular mechanisms contributing to intestinal IR injury, in in vivo and in vitro animal and human models, and in clinical samples. Recent breakthroughs involve applying omics methodologies on exosomes, organoids, and single cells, shedding light on promising avenues and valuable targets to reduce intestinal IR injury. Future directions aimed at expediting clinical translation are discussed as well and include multi-omics data integration to facilitate the identification of key regulatory nodes driving intestinal IR injury and advancing human organoid models based on the novel insights by single-cell omics technologies, offering hope for clinical application of therapeutic strategies in the years to come.

Old targets, new strategy: Apigenin-7-O-β-d-(-6″-p-coumaroyl)-glucopyranoside prevents endothelial ferroptosis and alleviates intestinal ischemia-reperfusion injury through HO-1 and MAO-B inhibition

With the increasing morbidity and mortality, intestinal ischemia/reperfusion injury (IIRI) has attracted more and more attention, but there is no efficient therapeutics at present. Apigenin-7-O-β-D-(-6″-p-coumaroyl)-glucopyranoside (APG) is a new flavonoid glycoside isolated from Clematis tangutica that has strong antioxidant abilities in previous studies. However, the pharmacodynamic function and mechanism of APG on IIRI remain unknown. This study aimed to investigate the effects of APG on IIRI both in vivo and in vitro and identify the potential molecular mechanism. We found that APG could significantly improve intestinal edema and increase Chiu's score. MST analysis suggested that APG could specifically bind to heme oxygenase 1 (HO-1) and monoamine oxidase b (MAO-B). Simultaneously, APG could attenuate ROS generation and Fe²⁺ accumulation, maintain mitochondria function thus inhibit ferroptosis with a dose-dependent manner. Moreover, we used siRNA silencing technology to confirm that knocking down both HO-1 and MAO-B had a positive effect on intestine. In addition, we found the HO-1 and MAO-B inhibitors also could reduce endothelial cell loss and protect vascular endothelial after reperfusion. We demonstrate that APG plays a protective role on decreasing activation of HO-1 and MAO-B, attenuating IIRI-induced ROS generation and Fe²⁺ accumulation, maintaining mitochondria function thus inhibiting ferroptosis.

Use of contraceptives and risk of inflammatory bowel disease: a nested case-control study

BACKGROUND

How contraceptive formulation, dose, duration of therapy and mode of delivery affects the risk of inflammatory bowel disease (IBD) is poorly described.

AIM

To examine associations between types of hormonal contraception and development of IBD.

METHODS

This was a nested case-control study using IQVIA Medical Research Data. Women aged 15-49 years with a new diagnosis of IBD were matched with up to six controls by age, practice and year. Odds ratios (OR) and 95% confidence intervals (95% CI) for incident IBD and use of contraception were calculated.

RESULTS

4932 incident cases of IBD were matched to 29 340 controls. Use of combined oral contraceptive pills (COCPs) was associated with the development of Crohn's disease and ulcerative colitis (OR 1.60 [1.41-1.82] and 1.30 [1.15-1.45], respectively). Each additional month of COCP exposure per year of follow-up increased risk of Crohn's disease by 6.4% (5.1%-7.7%) and ulcerative colitis by 3.3% (2.1%-4.4%). Progestogen-only pills had no effect on Crohn's disease risk (OR 1.09 [0.84-1.40]) but there was a modest association with ulcerative colitis (OR 1.35 [1.12-1.64]). Parenteral contraception was not associated with the development of Crohn's disease or ulcerative colitis (OR 1.15 [0.99-1.47] and 1.17 [0.98-1.39], respectively).

CONCLUSIONS

We observed an increase in the risk of IBD with increasing duration of exposure to COCPs. Progestogen-only pills were not associated with Crohn's disease but there was a modest association with ulcerative colitis. There was no association between parenteral progestogen-only contraception and IBD. These findings are broadly consistent with a hypothesis that the oestrogen component of contraception may drive IBD pathogenesis.

Temporal Transcript Profiling Identifies a Role for Unfolded Protein Stress in Human Gut Ischemia-Reperfusion Injury

BACKGROUND & AIMS

Intestinal ischemia-reperfusion injury is a serious and life-threatening condition. A better understanding of molecular mechanisms related to intestinal ischemia-reperfusion injury in human beings is imperative to find therapeutic targets and improve patient outcome.

METHODS

First, the in vivo dynamic modulation of mucosal gene expression of the ischemia-reperfusion-injured human small intestine was studied. Based on functional enrichment analysis of the changing transcriptome, one of the predominantly regulated pathways was selected for further investigation in an in vitro human intestinal organoid model.

RESULTS

Ischemia-reperfusion massively changed the transcriptional landscape of the human small intestine. Functional enrichment analysis based on gene ontology and pathways pointed to the response to unfolded protein as a predominantly regulated process. In addition, regulatory network analysis identified hypoxia-inducing factor 1A as one of the key mediators of ischemia-reperfusion-induced changes, including the unfolded protein response (UPR). Differential expression of genes involved in the UPR was confirmed using quantitative polymerase chain reaction analysis. Electron microscopy showed signs of endoplasmic reticulum stress. Collectively, these findings point to a critical role for unfolded protein stress in intestinal ischemia-reperfusion injury in human beings. In a human intestinal organoid model exposed to hypoxia-reoxygenation, attenuation of UPR activation with integrated stress response inhibitor strongly reduced pro-apoptotic activating transcription factor 4 (ATF4)-CCAAT/enhancer-binding protein homologous protein (CHOP) signaling.

CONCLUSIONS

Transcriptome analysis showed a crucial role for unfolded protein stress in the response to ischemia-reperfusion in human small intestine. UPR inhibition during hypoxia-reoxygenation in an intestinal organoid model suggests that downstream protein kinase R-like ER kinase (PERK) signaling may be a promising target to reduce intestinal ischemia-reperfusion injury. Microarray data are available in GEO (https://www.ncbi.nlm.nih.gov/gds, accession number GSE37013).

Analysis of hypoxia-associated dendritic cells in colitic mice and effects of probiotics on IL-10 production in inflammatory dendritic-cells under hypoxia

The aim of this study was to analyse hypoxia-associated dendritic cells (DCs) in colitic mice and the effects of probiotics on interleukin (IL)-10 production in inflammatory DCs under hypoxic conditions. Extensive hypoxia was observed in the colonic mucosa of dextran sodium sulphate-induced colitic mice. Flow cytometric analysis demonstrated that hypoxia-inducible factor-1α+ DCs in colonic lamina propria (CLP) lymphocytes and mesenteric lymph nodes (MLN) were more abundant in colitic mice than those in controls. Among three subsets of DCs, i.e. plasmacytoid DCs, conventional DCs (cDCs), and monocyte-derived DCs (mDCs), cDCs and mDCs were more abundant in CLP of colitic mice. Bone marrow-derived Flt-3L-induced DCs (Flt-DCs) but not bone marrow-derived GM-CSF-induced DCs (GM-DCs), incubated with 1% O2 exhibited an inflammatory phenotype, with higher CD86, IL-6, and tumour necrosis factor-α expression, and lower IL-10 levels than those in Flt-DCs incubated with 21% O2. The hypoxia-induced decrease in IL-10 expression in Flt-DCs was restored by Bifidobacterium bifidum JCM 1255T promoted IL-10 expression through the p38 pathway under normoxic conditions. The anti-inflammatory effects of B. bifidum JCM 1255T in Flt-DCs were mediated through different cellular mechanisms under hypoxic and normoxic conditions. B. bifidum JCM 1255T could be used therapeutically for its anti-inflammatory effects.

Chromogranin-A and its derived peptides and their pharmacological effects during intestinal inflammation

The gastrointestinal tract is the largest endocrine organ that produces a broad range of active peptides. Mucosal changes during inflammation alter the distribution and products of enteroendocrine cells (EECs) that play a role in immune activation and regulation of gut homeostasis by mediating communication between the nervous, endocrine and immune systems. Patients with inflammatory bowel disease (IBD) typically have altered expression of chromogranin (CHG)-A (CHGA), a major soluble protein secreted by EECs that functions as a pro-hormone. CHGA gives rise to several bioactive peptides that have direct or indirect effects on intestinal inflammation. In IBD, CHGA and its derived peptides are correlated with the disease activity. In this review we describe the potential immunomodulatory roles of CHGA and its derived peptides and their clinical relevance during the progression of intestinal inflammation. Targeting CHGA and its derived peptides could be of benefit for the diagnosis and clinical management of IBD patients.

Human small intestine is capable of restoring barrier function after short ischemic periods

AIM

To assess intestinal barrier function during human intestinal ischemia and reperfusion (IR).

METHODS

In a human experimental model, 6 cm of jejunum was selectively exposed to 30 min of ischemia (I) followed by 30 and 120 min of reperfusion (R). A sham procedure was also performed. Blood and tissue was sampled at all-time points. Functional barrier function was assessed using dual-sugar absorption tests with lactulose (L) and rhamnose (R). Plasma concentrations of citrulline, an amino acid described as marker for enterocyte function were measured as marker of metabolic enterocytes restoration. Damage to the epithelial lining was assessed by immunohistochemistry for tight junctions (TJs), by plasma marker for enterocytes damage (I-FABP) and analyzed by electron microscopy (EM) using lanthanum nitrate as an electrondense marker.

RESULTS

Plasma L/R ratio’s were significantly increased after 30 min of ischemia (30I) followed by 30 min of reperfusion (30R) compared to control (0.75 ± 0.10 vs 0.20 ± 0.09, P < 0.05). At 120 min of reperfusion (120R), ratio’s normalized (0.17 ± 0.06) and were not significantly different from control. Plasma levels of I-FABP correlated with plasma L/R ratios measured at the same time points (correlation: 0.467, P < 0.01). TJs staining shows distortion of staining at 30I. An intact lining of TJs was again observed at 30I120R. Electron microscopy analysis revealed disrupted TJs after 30I with paracellular leakage of lanthanum nitrate, which restored after 30I120R. Furthermore, citrulline concentrations closely paralleled the histological perturbations during intestinal IR.

CONCLUSION

This study directly correlates histological data with intestinal permeability tests, revealing that the human gut has the ability of to withstand short episodes of ischemia, with morphological and functional recovery of the intestinal barrier within 120 min of reperfusion.

Misbalance in type III collagen formation/degradation as a novel serological biomarker for penetrating (Montreal B3) Crohn's disease

BACKGROUND

Misbalances in extracellular matrix turnover are key factors in the development of stricturing (Montreal B2) and penetrating (Montreal B3) Crohn's disease.

AIM

To determine whether serological markers for collagen formation and degradation could serve as biomarkers for complications of Crohn's disease.

METHODS

Serum biomarkers for type I, III, V and VI collagen formation (P1NP, Pro-C3, Pro-C5, Pro-C6) and matrix metalloproteinase mediated degradation (C1M, C3M, C5M and C6M) were measured in a retrospective, single centre cohort of 112 patients with Crohn's disease in the terminal ileum (nonstricturing/nonpenetrating: n=40, stricturing: n=55, penetrating: n=17) and 24 healthy controls. Active inflammation was defined as CRP >5 mg/L.

RESULTS

C3M and Pro-C5 levels were higher in penetrating vs nonpenetrating/nonstricturing and stricturing disease (33.6±5 vs 25.8±2.2 [P=.004] and 27.2±2.3 [P=.018] nmol/L C3M, 1262.7±259.4 vs 902.9±109.9 [P=.005] and 953.0±106.4 [P=.015] nmol/L Pro-C5). C1M (71.2±26.1 vs 46.2±6.2 nmol/L [P<.001]), C3M (31.6±3.9 vs 26.1±1.6 nmol/L [P=.002] and Pro-C5 levels (1171.7±171.5 vs 909.6±80.4 nmol/L [P=.002]) were higher in patients with active inflammation vs without active inflammation. Pro-C3/C3M-ratios were best to differentiate between penetrating vs nonstricturing/nonpenetrating and stricturing disease with area under the curves of 0.815±0.109 (P<.001) and 0.746±0.114 (P=.002) respectively.

CONCLUSIONS

Serological biomarkers show that penetrating Crohn's disease is characterised by increased matrix metalloproteinase-9 degraded type III collagen and formation of type V collagen. Active inflammation in Crohn's disease is characterised by increased formation of type V collagen and increased matrix metalloproteinase mediated breakdown of type I, III collagen. Pro-C3/C3M ratios are superior in differentiating between penetrating Crohn's disease vs inflammatory and stricturing Crohn's disease.

Protectin D1n-3 DPA and resolvin D5n-3 DPA are effectors of intestinal protection

The resolution of inflammation is an active process orchestrated by specialized proresolving lipid mediators (SPM) that limit the host response within the affected tissue; failure of effective resolution may lead to tissue injury. Because persistence of inflammatory signals is a main feature of chronic inflammatory conditions, including inflammatory bowel diseases (IBDs), herein we investigate expression and functions of SPM in intestinal inflammation. Targeted liquid chromatography-tandem mass spectrometry-based metabololipidomics was used to identify SPMs from n-3 polyunsaturated fatty acids in human IBD colon biopsies, quantifying a significant up-regulation of the resolvin and protectin pathway compared with normal gut tissue. Systemic treatment with protectin (PD)1n-3 DPA or resolvin (Rv)D5n-3 DPA protected against colitis and intestinal ischemia/reperfusion-induced inflammation in mice. Inhibition of 15-lipoxygenase activity reduced PD1n-3 DPA and augmented intestinal inflammation in experimental colitis. Intravital microscopy of mouse mesenteric venules demonstrated that PD1n-3 DPA and RvD5n-3 DPA decreased the extent of leukocyte adhesion and emigration following ischemia-reperfusion. These data were translated by assessing human neutrophil-endothelial interactions under flow: PD1n-3 DPA and RvD5n-3 DPA reduced cell adhesion onto TNF-α-activated human endothelial monolayers. In conclusion, we propose that innovative therapies based on n-3 DPA-derived mediators could be developed to enable antiinflammatory and tissue protective effects in inflammatory pathologies of the gut.

Statins Associated With Decreased Risk of New Onset Inflammatory Bowel Disease

OBJECTIVES

Prior studies suggest that medication exposures may be associated with new onset inflammatory bowel disease (IBD). The aim of this study was to determine the effect of statins on the risk of new onset IBD in a large United States health claims database.

METHODS

We conducted a retrospective matched case-control study with a national medical claims and pharmacy database from Source Healthcare Analytics LLC. We included any patient aged 18 or older with ICD-9 code 555.x for Crohn's disease (CD) or 556.x for ulcerative colitis (UC) between January 2008 and December 2012. IBD patients diagnosed in 2012 were compared with the age group, gender, race, and geographically matched controls. Controls had no ICD-9 codes for CD, UC, or IBD-associated diseases and no prescriptions for IBD-related medications. New onset IBD patients were defined as having at least three separate CD or UC ICD-9 codes and no IBD-related ICD-9 or prescription before first IBD ICD-9. Statin exposure was assessed by Uniform System of Classification level 5 code. To account for diagnostic delay, exposures within 6 months of first ICD-9 were excluded. Exposures within 12 and 24 months were excluded in sensitivity analyses. Conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for new onset IBD, CD, and UC.

RESULTS

A total of 9,617 cases and 46,665 controls were included in the analysis. Any statin exposure was associated with a significantly decreased risk of IBD (OR 0.68, 95% CI 0.64-0.72), CD (0.64, 95% CI 0.59-0.71), and UC (OR 0.70, 95% CI 0.65-0.76). This effect was similar for most specific statins and regardless of intensity of therapy. The protective effect against new onset CD was strongest among older patients. Statins' association with a lower risk of IBD was similar after adjusting for antibiotics, hormone replacement therapy, oral contraceptives, comorbidities, and cardiovascular medications.

CONCLUSIONS

Statins may have a protective effect against new onset IBD, CD, and UC. This decreased risk is similar across most statins and appears to be stronger among older patients, particularly in CD.

The Gastrointestinal Circulation: Physiology and Pathophysiology

The gastrointestinal (GI) circulation receives a large fraction of cardiac output and this increases following ingestion of a meal. While blood flow regulation is not the intense phenomenon noted in other vascular beds, the combined responses of blood flow, and capillary oxygen exchange help ensure a level of tissue oxygenation that is commensurate with organ metabolism and function. This is evidenced in the vascular responses of the stomach to increased acid production and in intestine during periods of enhanced nutrient absorption. Complimenting the metabolic vasoregulation is a strong myogenic response that contributes to basal vascular tone and to the responses elicited by changes in intravascular pressure. The GI circulation also contributes to a mucosal defense mechanism that protects against excessive damage to the epithelial lining following ingestion of toxins and/or noxious agents. Profound reductions in GI blood flow are evidenced in certain physiological (strenuous exercise) and pathological (hemorrhage) conditions, while some disease states (e.g., chronic portal hypertension) are associated with a hyperdynamic circulation. The sacrificial nature of GI blood flow is essential for ensuring adequate perfusion of vital organs during periods of whole body stress. The restoration of blood flow (reperfusion) to GI organs following ischemia elicits an exaggerated tissue injury response that reflects the potential of this organ system to generate reactive oxygen species and to mount an inflammatory response. Human and animal studies of inflammatory bowel disease have also revealed a contribution of the vasculature to the initiation and perpetuation of the tissue inflammation and associated injury response.

Risk of Inflammatory Bowel Disease with Oral Contraceptives and Menopausal Hormone Therapy: Current Evidence and Future Directions

Crohn's disease (CD) and ulcerative colitis (UC), collectively known as inflammatory bowel diseases, are archetypical inflammatory disorders of the gastrointestinal tract with rising incidence worldwide. Although the role of genetic factors in disease development has been highlighted by genome-wide association studies, environmental risk factors likely play a pivotal role in development of CD and UC. Prior observational studies have suggested a link between exogenous hormone use and risk of CD and UC. Specifically, studies have shown an association between oral contraceptive use and risk of CD and menopausal hormone therapy and risk of UC. Although the exact mechanism of these associations is largely unknown, a number of hypotheses have been proposed. First, oral estrogen has been shown to modify intestinal permeability, a critical step in the pathophysiology of inflammatory bowel disease. Second, exogenous hormone use through its effect on endogenous levels of hormones may enhance the development of Th1- and Th2-mediated inflammatory diseases. Lastly, recent data have linked modification in the gut microbiome to endogenous levels of androgens, which are also known to be altered with exogenous hormone use and influence the development of autoimmune diseases. This supports the intriguing hypothesis that the gut microbiome lies at the crossroads of pathways linking exogenous hormone use with innate and adaptive immunity. Future studies should therefore focus on bridging these epidemiologic findings to disease pathogenesis through comprehensive understanding of the complex interaction between exogenous hormone use, sex steroid biomarkers, genetic risk loci, and alterations in the intestinal microbial environment in the etiology of CD and UC.

Update on Colon Ischemia: Recent Insights and Advances

Colon ischemia (CI) is the most common manifestation of ischemic injury to the gastrointestinal (GI) tract. This usually self-limited disease is being diagnosed more frequently, and the list of known causes is increasing. Local hypoperfusion and reperfusion injury are both thought to contribute to the disease process, which manifests with a wide spectrum of injury including reversible colopathy (subepithelial hemorrhage and edema), transient colitis, chronic colitis, stricture, gangrene, and fulminant universal colitis. The distribution is usually segmental with left-sided disease (e.g., inferior mesenteric artery distribution) being more frequently observed than right-sided involvement (e.g., superior mesenteric artery distribution). Any portion of the colon can be affected, but the anatomic distribution of CI recently has been shown to be associated with outcome. Patients with isolated-right colon ischemia (IRCI) have a different presentation and worse outcomes than other distributions of disease. Although somewhat variable depending on disease location, CI presents with cramping abdominal pains over the segment of colon involved followed by a short course of bloody diarrhea. Diagnosis is usually made clinically and is supported with serologic, radiologic, and colonoscopic findings. Colonoscopy is the most accurate diagnostic study. Most patients respond to conservative supportive therapy although some with more severe disease require antimicrobials and/or surgical intervention.

Inflammatory bowel disease and thromboembolism

Patients with inflammatory bowel disease (IBD) have an increased risk of vascular complications. Thromboembolic complications, both venous and arterial, are serious extraintestinal manifestations complicating the course of IBD and can lead to significant morbidity and mortality. Patients with IBD are more prone to thromboembolic complications and IBD per se is a risk factor for thromboembolic disease. Data suggest that thrombosis is a specific feature of IBD that can be involved in both the occurrence of thromboembolic events and the pathogenesis of the disease. The exact etiology for this special association between IBD and thromboembolism is as yet unknown, but it is thought that multiple acquired and inherited factors are interacting and producing the increased tendency for thrombosis in the local intestinal microvasculature, as well as in the systemic circulation. Clinicians' awareness of the risks, and their ability to promptly diagnose and manage tromboembolic complications are of vital importance. In this review we discuss how thromboembolic disease is related to IBD, specifically focusing on: (1) the epidemiology and clinical features of thromboembolic complications in IBD; (2) the pathophysiology of thrombosis in IBD; and (3) strategies for the prevention and management of thromboembolic complications in IBD patients.

Oxidative stress: an essential factor in the pathogenesis of gastrointestinal mucosal diseases

Reactive oxygen species (ROS) are generated as by-products of normal cellular metabolic activities. Superoxide dismutase, glutathione peroxidase, and catalase are the enzymes involved in protecting cells from the damaging effects of ROS. ROS are produced in response to ultraviolet radiation, cigarette smoking, alcohol, nonsteroidal anti-inflammatory drugs, ischemia-reperfusion injury, chronic infections, and inflammatory disorders. Disruption of normal cellular homeostasis by redox signaling may result in cardiovascular, neurodegenerative diseases and cancer. ROS are produced within the gastrointestinal (GI) tract, but their roles in pathophysiology and disease pathogenesis have not been well studied. Despite the protective barrier provided by the mucosa, ingested materials and microbial pathogens can induce oxidative injury and GI inflammatory responses involving the epithelium and immune/inflammatory cells. The pathogenesis of various GI diseases including peptic ulcers, gastrointestinal cancers, and inflammatory bowel disease is in part due to oxidative stress. Unraveling the signaling events initiated at the cellular level by oxidative free radicals as well as the physiological responses to such stress is important to better understand disease pathogenesis and to develop new therapies to manage a variety of conditions for which current therapies are not always sufficient.

Preventive Effect of TU-100 on a Type-2 Model of Colitis in Mice: Possible Involvement of Enhancing Adrenomedullin in Intestinal Epithelial Cells

Purpose. Crohn's disease (CD) and ulcerative colitis (UC), the two major forms of inflammatory bowel disease (IBD), have histopathologically and immunologically different characteristics. We previously reported that a traditional Japanese medicine, daikenchuto (TU-100), ameliorated a trinitrobenzenesulfonic acid- (TNBS-) induced type-1 model colitis exhibiting histopathological features of CD through adrenomedullin (ADM) enhancement. Our current aims were to examine whether TU-100 ameliorates a type-2 model colitis that histologically resembles UC and identify the active ingredients. Methods. TU-100 was administered orally to mice with oxazolone- (OXN-) induced type-2 model colitis. The morbidity was evaluated by body weight loss and the macroscopic score of colonic lesions. ADM was quantified using an EIA kit. Results. TU-100 prevented weight loss and colon ulceration. ADM production by intestinal epithelial cells was increased by TU-100 addition. Screening to identify active ingredients showed that [6]-shogaol and hydroxy α -sanshool enhanced ADM production. Conclusions. TU-100 exerted a protective effect in OXN-induced type-2 model colitis, indicating that TU-100 may be a beneficial agent for treatment of UC.

Hyperbaric oxygen therapy does not improve the effects of standardized treatment in a severe attack of ulcerative colitis: a prospective randomized study

BACKGROUND AND AIMS

Complementary therapy options are needed in the treatment of active ulcerative colitis (UC). Hyperbaric oxygen therapy (HBOT) has been shown to have positive effects in experimental models of colitis and perianal Crohn's disease.

METHODS

In the present prospective randomized open-label study, HBOT in addition to conventional medical treatment was compared with conventional treatment alone. The primary objective in this study was improved clinical outcome evaluated by Mayo score, laboratory tests and fecal weight. The secondary objectives were improvement in health-related quality of life, avoidance of colectomy and evaluation of HBOT safety.

RESULTS

The authors found no statistically significant differences between the treatment groups in any of the assessed variables.

CONCLUSION

The study results do not support the use of HBOT as a treatment option in a severe attack of UC.

Ultrasonographic evaluation of bowel wall thickness and intramural blood flow in ulcerative colitis

Aim. This study aimed at assessing Doppler ultrasonographic findings of gut wall vessels and thickness in active and quiescent ulcerative colitis. Methods. Fifty patients with ulcerative colitis were studied using transabdominal grayscale and Doppler sonography of sigmoid, distal and middle parts of descending colon in different stages of the disease. Thickness of colon wall in the most involved site, number of color signals in each box, resistive index (RI), and pulsatility index (PI) were evaluated. Results. The median thickness of the colon wall in the most involved sites was 4.3 mm in acute phase and 4.4 mm in the inactive phase (P = 0.47). The median number of the color signals in the active phase at the most involved site, distal part of descending colon and sigmoid was higher than that of the color signals in the inactive phase (P = 0.0001). In the most involved site, the PI and RI were undetectable in the inactive phase. The median PI was 1.4 in the mild phase, 1.3 in the moderate phase, and 1.1 in the severe phase (P = 0.002). Conclusion. In contrast to the colon wall thickness, increased intramural blood flow reflected the clinical severity in ulcerative colitis patients.

Dimethyloxalyglycine stimulates the early stages of gastrointestinal repair processes through VEGF-dependent mechanisms

Dimethyloxalylglycine (DMOG) is an inhibitor of prolyl-4-hydroxylase domain enzymes. Its potential value and mechanism of actions in preventing/treating gastrointestinal injury are, however, poorly understood. We, therefore, examined the effect of DMOG on influencing gut injury and repair using a variety of in vitro and in vivo models. We performed in vitro studies utilising pro-migratory (wounded monolayer) and proliferation (using DNA quantitation) assays of human stomach (AGS) and colonic (HT29) carcinoma cells. Time course studies examined changes in hypoxia-inducible factor (HIF) and vascular endothelial growth factor (VEGF) levels, a growth factor known to be regulated via HIF. In vivo studies utilised a rat gastric (indomethacin, 20 mg/kg and 3 h restraint) damage model. DMOG stimulated migration in a dose-dependent manner, increasing migration twofold when added at 25μM (P<0.01). Additive effects were seen when DMOG was added to cells in hypoxic conditions. DMOG stimulated proliferation dose dependently, increasing proliferation threefold when added at 70 μM (P<0.01). DMOG caused upregulation of both HIF and VEGF within 4 h of administration. Addition of VEGF neutralising antibody truncated migratory and proliferative activity of DMOG by about 70%. Both oral and subcutaneous administration of DMOG decreased gastric injury without influencing intragastric pH (50% reduction in injury when 1 ml gavaged at 0.57 mM, P < 0.01). Indomethacin reduced tissue HIF and VEGF levels but this was prevented if DMOG was present. In conclusion, DMOG stimulates the early phases of gut repair and VEGF-dependent processes appear relevant. Non-peptide factors such as this may be useful to stabilise or repair gut mucosa.

Vascular contribution of adrenomedullin to microcirculatory improvement in experimental colitis

The effect of adrenomedullin (AM), a peptide that has demonstrated vasodilatory activity, was studied in the colon and small mesenteric arteries of rats in a chronic model of inflammatory bowel disease. AM (50 ng/kg/day) was administered i.p. daily, starting 24h after trinitrobenzensulfonic acid (TNBS, 30 mg) instillation. After 14 days, rats were sacrificed, colons were macroscopically analyzed and biochemical parameters (myeloperoxidase activity, cytokines, cyclooxygenase-2 (COX-2) as well as inducible nitric oxide synthase (iNOS) expression) were determined. Vascular function of small mesenteric arteries was assessed by addition of phenylephrine (10⁻⁸ to 10⁻⁴ mol/L) and participation of COX and NOS pathways was also evaluated by using different inhibitors: indomethacin, NS-398, L-NNA, and 1400 w. Chronic AM treatment significantly reduced colonic macroscopic damage and inflammation markers. TNBS instillation induced COX-2 and iNOS expressions in colon and small mesenteric arteries; AM treatment decreased COX-2 expression only in microvessels from rats with colitis. An attenuation of phenylephrine-induced contraction was detected in small mesenteric arteries from both TNBS and AM-treated rats. COX and NOS inhibitors altered the contractile ability of phenylephrine in small mesenteric arteries from TNBS rats, suggesting the involvement of COX-2 and iNOS derived factors in the deleterious effect of TNBS on vascular reactivity; AM administration was able to reduce such alteration. Finally, treatment with the peptide significantly reduced colonic nitric oxide (NO) levels, without affecting plasma concentration. In conclusion, AM showed beneficial effects in the restoration of vascular function through the regulation of vasoactive products derived from COX-2 and iNOS.

Intrarectal administration of oxygenated perfluorodecalin promotes healing of murine colitis by targeting inflammatory hypoxia

Intestinal inflammation is associated with enhanced mucosal hypoxia, which contributes to the ongoing inflammatory process and hampers appropriate mucosal healing. We questioned whether local treatment with an oxygen (O(2))-carrying and -releasing molecule (oxygenated perfluorodecalin, O(2)-PFD) could positively influence the course of experimental colitis. The impact of intrarectal (IR) treatment with O(2)-PFD was tested using the murine dextran sodium sulfate (DSS)-induced model of distal colitis, both in preventive and therapeutic settings. Colonic mucosal hypoxia was visualized by pimonidazole staining. Colonic permeability was evaluated with FITC-dextran. In the preventive study, mice treated with O(2)-PFD were protected against DSS colitis compared with saline-treated mice, as demonstrated by reduced shortening of colon length, reduced colonic tumor necrosis factor-alpha levels and a lower histological inflammation score (P<0.05 for all parameters). In the therapeutic study, administration of O(2)-PFD resulted in accelerated recovery of colitis compared with saline-treated littermates, and this was reflected by a better weight evolution, lower myeloperoxidase activity and a lower histological inflammation score (P<0.05 for all parameters). It was found that O(2)-PFD established its therapeutic effects through (1) intrinsic anti-inflammatory effects of the PFD molecule and (2) O(2)-induced preservation and healing of the intestinal epithelial surface. Further in vitro and in vivo studies showed that the barrier-protective activity of O(2)-PFD was obtained through prevention of colonocyte apoptosis and stimulation of colonocyte proliferation during inflammatory hypoxia. These data show that IR treatment with O(2)-PFD promotes colitis healing by the combined actions of direct anti-inflammatory effects and O(2)-induced restitution of the epithelial barrier. As such, O(2)-PFD enemas could be an attractive treatment option for patients with distal inflammatory bowel disease.

Mast cells drive mesenteric afferent signalling during acute intestinal ischaemia

Acute intestinal ischaemia stimulates visceral afferent nerves but the mechanisms responsible for this excitation are not fully understood. Mast cells may participate in this process as they are known to signal to mesenteric afferents during intestinal anaphylaxis and contribute to early inflammation and neuronal damage in response to cerebral ischaemia. We therefore hypothesised that mast cells are early responders to acute intestinal ischaemia and their activation initiates rapid signalling to the CNS via the excitation of mesenteric afferents. Primary afferent firing was recorded from a mesenteric nerve bundle supplying a segment of jejunum in anaesthetized adult rats. Acute focal ischaemia was produced by clamping theme senteric vessels for 8 min, and reperfusion followed removal of the vessel clip. Two episodes of ischaemia–reperfusion (I–R) separated by a 30 min interval were performed. Drugs or their vehicles were administered 10 min before the 2nd I–R episode. Ischaemia caused a reproducible, intense and biphasic afferent firing that was temporally dissociated from the concomitantly triggered complex pattern of intestinal motor activity. The L-type calcium channel blocker, nifedipine, significantly attenuated this afferent firing by a mechanism independent of its action on intestinal tone. Ischaemia-induced afferent firing was also abrogated by the mast cell stabilizer, doxantrazole, and the H1 histamine receptor antagonist, pyrilamine. In contrast, the nicotinic receptor antagonist, hexamethonium, and the N-type calcium channel toxin, ω-conotoxin GVIA, each reduced the ischaemia-evoked motor inhibition but not the concurrent afferent discharge. Similarly, the cyclooxygenase inhibitor, naproxen, had no effect on the ischaemic afferent response but reduced the intestinal tone shortly from the onset of ischaemia to the early period of reperfusion. These data support a critical role for mast cell-derived histamine in the direct chemoexcitation of mesenteric afferents during acute intestinal ischaemia, whereas enteric reflex mechanisms and cyclooxygenase products contribute primarily to ischaemia-induced changes in intestinal motility. Therefore, targeting mast cells may provide benefits in patients with abdominal pain resulting from an ischaemic insult to the gastrointestinal tract.

Colon ischemia: recent insights and advances

Ischemic colitis is the most common manifestation of ischemic injury to the gastrointestinal tract, and the variety of defined causes is increasing. Local hypoperfusion and reperfusion injury are both thought to contribute to the disease process, which manifests with a wide spectrum of injury including reversible colopathy (subepithelial hemorrhage and edema), transient colitis, chronic colitis, stricture, gangrene, and fulminant universal colitis. The distribution is typically segmental. Older studies showed that any portion of the colon can be involved; recently, it was established that the site of involvement and prognosis can be correlated. In particular, isolated involvement of the right side of the colon was shown to have a different presentation and worse outcome than ischemic colitis involving other segments. Diagnosis is usually made clinically and supported by radiologic imaging and colonoscopic evaluation. Most patients respond to conservative supportive therapy, although some with severe disease require surgical intervention.