Disruption of intestinal barrier function associated with experimental colitis: possible role of mast cells

Present and Future Therapeutic Approaches to Barrier Dysfunction

There is converging and increasing evidence, but also uncertainty, for the role of abnormal intestinal epithelial barrier function in the origin and development of a growing number of human gastrointestinal and extraintestinal inflammatory disorders, and their related complaints. Despite a vast literature addressing factors and mechanisms underlying changes in intestinal permeability in humans, and its connection to the appearance and severity of clinical symptoms, the ultimate link remains to be established in many cases. Accordingly, there are no directives or clinical guidelines related to the therapeutic management of intestinal permeability disorders that allow health professionals involved in the management of these patients to carry out a consensus treatment based on clinical evidence. Instead, there are multiple pseudoscientific approaches and commercial propaganda scattered on the internet that confuse those affected and health professionals and that often lack scientific rigor. Therefore, in this review we aim to shed light on the different therapeutic options, which include, among others, dietary management, nutraceuticals and medical devices, microbiota and drugs, and epigenetic and exosomes-manipulation, through an objective evaluation of the scientific publications in this field. Advances in the knowledge and management of intestinal permeability will sure enable better options of dealing with this group of common disorders to enhance quality of life of those affected.

Experimental Modeling of Eosinophil-Associated Diseases

Eosinophils are an important subtype of leukocytes derived from bone marrow multipotent hematopoietic stem cells and represent about 1% of leukocytes in circulating blood. In homeostatic conditions, eosinophils reside in the intestine to maintain the balance of immune responses by communicating with gut microbes without causing inflammation. However, under the stressed or diseased condition, eosinophils degranulate, releasing their granule-derived cytotoxic proteins that are involved in inflammatory responses. Various eosinophil-associated inflammatory diseases are eosinophilic esophagitis (EoE), eosinophilic gastroenteritis (EG), and eosinophilic colitis (EC), together called EGID, asthma, hypereosinophilic syndrome, and eosinophilic pneumonia (EP). Eosinophil degranulation results in the release of their four toxic proteins [major basic protein (MBP), eosinophil cationic protein (ECP), eosinophil peroxidase (EPO), and eosinophil-derived neurotoxin (EDN)] which promote disease pathogenesis. Pancreatitis is the inflammatory disease of the pancreas that arises due to blockage of the pancreatic duct, trypsinogen mutation, alcohol consumption, and repeated occurrence of pancreatitis leading to chronic pancreatitis (CP); subsequently some CP patients may also develop pancreatic cancer. The presence of eosinophils is now shown in various case reports with acute, recurrent acute, and chronic pancreatitis and pancreatic cancer indicating the role of eosinophils in the pathogenesis of various pancreatic inflammatory disorders. However, the details of eosinophil accumulation during pancreatic diseases are not well explored and need further attention. Overall, the chapter provides the current understanding of reported eosinophils associated with inflammatory diseases like EGID diseases, asthma, and pancreatic disorders, i.e., acute, chronic pancreatitis, and pancreatic cancer. This knowledge will be helpful for future studies to develop novel treatment options for the eosinophils associated diseases. Therefore, more efforts are needed to perform preclinical and clinical studies in this field for the successful development of eosinophil-targeting treatments for a variety of eosinophil-associated diseases.

Effects of experimental colitis in rats on incretin levels, inflammatory markers, and enteric neuronal function

INTRODUCTION

The aim of the study was to assess the effects of chronic inflammation on incretin levels, inflammatory markers, and enteric neuronal function measured in isolated preparations of smooth muscle of rat.

MATERIAL AND METHODS

We induced experimental colitis using 2,4-dinitrobenzenesulfonic acid (DNBS) in 17 Albino male Sprague-Dawley rats, while 16 rats were used as a control. They were housed in temperature-controlled rooms in a 12-h light/dark cycle at 22-24°C and 50 to 60% humidity. We evaluated in both inflamed and healthy rats: fasting plasma glucose concentration, fasting plasma insulin, myeloperoxidase, active glucose-dependent insulinotropic peptide (GIP), glucagon-like peptide-1 (GLP-1), and GLP-2 levels, adiponectin, and C-reactive protein (CRP). We also evaluated colonic longitudinal smooth muscle contractile activity.

RESULTS

Intrarectal administration of DNBS reduced body weight gain in inflamed rats. We recorded higher levels of fasting plasma glucose, and insulin in inflamed rats. We observed higher levels of myeloperoxidase and CRP, and lower levels of ADN in inflamed rats. We recorded higher levels of GIP, GLP-1, and GLP-2 in inflamed rats compared to the healthy ones. Regarding functional response of colon intestinal smooth muscle after electrical stimulation, we recorded a lower functional response of colon intestinal smooth muscle after electrical stimulation in inflamed rats.

CONCLUSIONS

We can conclude that chronic inflammation leads to an increase of incretin levels and to a decrease of functional response of colon intestinal smooth muscle after electrical stimulation.

NDRG2 regulates adherens junction integrity to restrict colitis and tumourigenesis

BACKGROUND

Paracellular barriers play an important role in the pathogenesis of Inflammatory bowel disease (IBD) and maintain gut homeostasis. N-myc downstream-regulated gene 2 (NDRG2) has been reported to be a tumour suppressor gene and to inhibit colorectal cancer metastasis. However, whether NDRG2 affects colitis initiation and colitis-associated colorectal cancer is unclear.

METHODS

Intestine-specific Ndrg2 deficiency mice (Ndrg2^ΔIEC) were subjected to DSS- or TNBS-induced colitis, and AOM-DSS-induced colitis-associated tumour. HT29 cells, Caco2 cells, primary intestinal epithelial cells (IECs) from Ndrg2^ΔIEC mice, mouse embryo fibroblasts (MEFs) from systemic Ndrg2 knockout mice, HEK293 cells and human UC and DC specimens were used to investigate NDRG2 function in colitis and colitis-associated tumour.

FINDINGS

Ndrg2 loss led to adherens junction (AJ) structure destruction via E-cadherin expression attenuation, resulting in diminished epithelial barrier function and increased intestinal epithelial permeability. Mechanistically, NDRG2 enhanced the interaction of E3 ligase FBXO11 with Snail, the repressor of E-cadherin, to promote Snail degradation by ubiquitination and maintained E-cadherin expression. In human ulcerative colitis patients, reduced NDRG2 expression is positively correlated with severe inflammation.

INTERPRETATION

These findings demonstrate that NDRG2 is an essential colonic epithelial barrier regulator and plays an important role in gut homeostasis maintenance and colitis-associated tumour development.

FUNDING

National Natural Science Foundation of China (No. 81770523, 31571437, 81672751), Creative Research Groups of China (No. 81421003), State Key Laboratory of Cancer Biology Project (CBSKL2019ZZ11, CBSKL201406, CBSKL2017Z08 and CBSKL2017Z11), Fund for Distinguished Young Scholars of ShaanXi province (2019JC-22).

Sodium selenite ameliorates both intestinal and extra-intestinal changes in acetic acid-induced colitis in rats

Selenium and its derivatives including sodium selenite (sod sel) belong to the group of essential trace elements needed for proper health and nutrition. They are fairly safe and possess antioxidant and anti-inflammatory properties. The aim of present investigation was to elucidate the effect of sod sel on experimental colitis model in rats. Colitis was induced by intrarectal instillation of 4% (v/v) acetic acid. Two hours later, sod sel was given to rats on a daily basis for 15 consecutive days. Clinical symptoms, colon mass index, spleen weight inflammatory markers, hematological, biochemical, macroscopic, and histological changes were determined. Sod sel markedly ameliorated colitis as evidenced by a significant decrease in macroscopic and microscopic score, disease activity index, colon mass index, and spleen weight. Treatment with sod sel attenuated oxidative stress in the colon by normalizing the colonic content of nitric oxide, malondialdehyde, and reduced glutathione, as well as the activities of catalase, superoxide dismutase, and junctional adhesion molecule (JAM-a). In addition, it significantly reduced colonic myeloperoxidase content, the intercellular adhesion molecule (ICAM-1), and the proinflammatory cytokines; TNF-α, IL-1β. Moreover, sod sel normalized hematological parameters, serum transaminases, and kidney and liver function enzymes. The current study indicates that sod sel was effective in ameliorating the intestinal and extra-intestinal manifestation in acetic acid-induced colitis through its antioxidant, anti-inflammatory, and immunomodulatory effects.

A functional IL1RL1 variant regulates corticosteroid-induced sST2 expression in ulcerative colitis

The ST2/IL33 signalling pathway has been associated with ulcerative colitis (UC). ST2, encoded by the IL1RL1 gene, is expressed as both a membrane-anchored receptor (ST2L) activated by IL33 and as a soluble receptor (sST2) with anti-inflammatory properties. In UC patients, sST2 is further increased by corticosteroid treatment; however, the glucocorticoid-mediated molecular regulation remains unknown. We therefore tested whether genetic variants in the IL1RL1 distal promoter are involved in UC and affect glucocorticoid-mediated ST2 expression. Serum ST2 levels and genetic variants in the IL1RL1 distal promoter were examined by ELISA and PCR sequencing in UC patients receiving corticosteroids. Glucocorticoid-mediated ST2 production was evaluated in intestinal mucosa cultures. Molecular regulation of glucocorticoid-mediated ST2 was assessed by RT-qPCR, ChIP assay and luciferase reporter assay. Dexamethasone effect on ST2 transcript expression was analyzed in leukocytes and related to IL1RL1 variants. Sequencing of a distal IL1RL1 promoter region demonstrated that SNPs rs6543115(C) and rs6543116(A) are associated with increased sST2 in UC patients on corticosteroids. Dexamethasone up-regulated sST2 transcription through interaction with the glucocorticoid-response element (GRE) carrying rs6543115(C) variant. Our data indicate that IL1RL1 SNPs rs6543115(C) confer susceptibility to UC and is contained in the GRE, which may modulate glucocorticoid-induced sST2 expression.

Visceral Hypersensitivity Is Provoked by 2,4,6-Trinitrobenzene Sulfonic Acid-Induced Ileitis in Rats

BACKGROUND AND AIMS

Crohn's Disease (CD), a chronic Inflammatory Bowel Disease, can occur in any part of the gastrointestinal tract, but most frequently in the ileum. Visceral hypersensitivity contributes for development of chronic abdominal pain in this disease. Currently, the understanding of the mechanism underlying hypersensitivity of Crohn's ileitis has been hindered by a lack of specific animal model. The present study is undertaken to investigate the visceral hypersensitivity provoked by 2,4,6-trinitrobenzene sulfonic (TNBS)-induced ileitis rats.

METHODS

Male Sprague-Dawley rats were anaesthetized and laparotomized for intraileal injection of TNBS (0.6 ml, 80 mg/kg body weight in 30% ethanol, n = 48), an equal volume of 30% Ethanol (n = 24), and Saline (n = 24), respectively. Visceral hypersensitivity was assessed by visceromotor responses (VMR) to 20, 40, 60, 80, and 100 mmHg colorectal distension pressure (CRD) at day 1, 3, 7, 14, 21, and 28. Immediately after CRD test, the rats were euthanized for collecting the terminal ileal segment for histopathological examinations and ELISA of myleoperoxidase and cytokines (TNF-α, IL-1β, IL-6), and dorsal root ganglia (T11) for determination of calcitonin gene-related peptide by immunohistochemistry, respectively.

RESULTS

Among all groups, TNBS-treatment showed transmural inflammation initially at 3 days, reached maximum at 7 days and persisted up to 21 days. The rats with ileitis exhibited (P < 0.05) VMR to CRD at day 7 to day 21. The calcitonin gene-related peptide-immunoreactive positive cells increased (P < 0.05) in dorsal root ganglia at day 7 to 21, which was persistently consistent with visceral hypersensitivity in TNBS-treated rats.

CONCLUSION

TNBS injection into the ileum induced transmural ileitis including granuloma and visceral hypersensitivity. As this model mimics clinical manifestations of CD, it may provide a road map to probe the pathogenesis of gut inflammation and visceral hypersensitivity, as well as for establishing the therapeutic protocol for Crohn's ileitis.

Microparticles as controlled drug delivery carrier for the treatment of ulcerative colitis: A brief review

Ulcerative colitis is the chronic relapsing multifactorial gastrointestinal inflammatory bowel disease, which is characterized by bloody or mucus diarrhea, tenesmus, bowel dystension, anemia. The annual incidence of ulcerative colitis in Asia, North America and Europe was found to be 6.3, 19.2 and 24.3 per 100,000 person-years. The major challenge in the treatment of ulcerative colitis is appropriate local targeting and drug related side-effects. To overcome these challenges, microparticulate systems seem to be a promising approach for controlled and sustained drug release after oral administration. The main goal of this article is to explore the role of microparticles in ulcerative colitis for the appropriate targeting of drugs to colon. There are different approaches which have been studied over the last decade, including prodrugs, polymeric approach, time released system, pH sensitive system, which show the site specific drug delivery to colon. Among these approaches, microparticulate drug delivery system has been gaining an immense importance for local targeting of drug to colon at a controlled and sustained rate. Combined approaches such as pH dependent and time dependent system provide the maximum release of drug into colon via oral route. This article embraces briefly about pathophysiology, challenges and polymeric approaches mainly multiparticulate systems for site specific drug delivery to colon in sustained and controlled manner so that drug related side-effects by reducing dosage frequency can be minimized.

Herbal prescription Chang'an II repairs intestinal mucosal barrier in rats with post-inflammation irritable bowel syndrome

AIM

The herbal prescription Chang'an II is derived from a classical TCM formula Tong-Xie-Yao-Fang for the treatment of liver-qi stagnation and spleen deficiency syndrome of irritable bowel syndrome (IBS). In this study we investigated the effects of Chang'an II on the intestinal mucosal immune barrier in a rat post-inflammation IBS (PI-IBS) model.

METHODS

A rat model of PI-IBS was established using a multi-stimulation paradigm including early postnatal sibling deprivation, bondage and intrarectal administration of TNBS. Four weeks after TNBS administration, the rats were treated with Chang'an II (2.85, 5.71 and 11.42 g · kg(-1) · d(-1), ig) for 14 d. Intestinal sensitivity was assessed based on the abdominal withdrawal reflex (AWR) scores and fecal water content. Open field test and two-bottle sucrose intake test were used to evaluate the behavioral changes. CD4(+) and CD8(+) cells were counted and IL-1β and IL-4 levels were measured in intestinal mucosa. Transmission electron microscopy was used to evaluate ultrastructural changes of the intestinal mucosal barrier.

RESULTS

PI-IBS model rats showed significantly increased AWR reactivity and fecal water content, and decreased locomotor activity and sucrose intake. Chang'an II treatment not only reduced AWR reactivity and fecal water content, but also suppressed the anxiety and depressive behaviors. Ultrastructural study revealed that the gut mucosal barrier function was severely damaged in PI-IBS model rats, whereas Chang'an II treatment relieved intestinal mucosal inflammation and repaired the gut mucosal barrier. Furthermore, PI-IBS model rats showed a significantly reduced CD4(+)/CD8(+) cell ratio in lamina propria and submucosa, and increased IL-1β and reduced IL-4 expression in intestinal mucosa, whereas Chang'an II treatment reversed PI-IBS-induced changes in CD4(+)/CD8(+) cell ratio and expression of IL-1β and IL-4.

CONCLUSION

Chang'an II treatment protects the intestinal mucosa against PI-IBS through anti-inflammatory, immunomodulatory and anti-anxiety effects.

Nanotechnology in the treatment of inflammatory bowel diseases

BACKGROUND AND AIMS

Treatment of inflammatory bowel diseases (IBD) is only aimed to block or inhibit the pathogenetic steps of the inflammatory cascade. Side effects of systemic therapies, poor targeting of orally administered topical drug and low adherence to prescription represent frequent therapeutic challenges. Recent observations suggest that nanotechnology could provide amazing advantage in this field since particles having dimension in the nanometer scale (nanoparticles) can modify pharmacokinetic step of biologic and conventional therapeutic agents with a better delivery of drugs within the intestinal inflammatory cells. The aim of this review was to provide the clinician with an insight into the potential role of nanotechnology in the treatment of IBD.

METHODS

A systematic search (PubMed) for experimental studies on the treatment of intestinal inflammation using nanotechnology for the delivery of drugs.

RESULTS AND CONCLUSIONS

The size of the pharmaceutical formulation is inversely related to specificity for inflammation. Nanoparticles can penetrate epithelial and inflammatory cells resulting in much higher, effective and long-acting concentrations than can be obtained using conventional delivery systems. From a practical point of view, this should lead to improvements in both efficacy and adherence to treatment, providing patients with the prospect of stable and prolonged remissions with reduced drug loadings. Reduced systemic side effects could also be expected.

Protective effects of Aegle marmelos fruit pulp on 2,4,6-trinitrobenzene sulfonic acid-induced experimental colitis

Background:

Aegle marmelos (AM) fruit has been advocated in indigenous system of medicine for the treatment of various gastrointestinal disorders, fever, asthma, inflammations, febrile delirium, acute bronchitis, snakebite, epilepsy, leprosy, myalgia, smallpox, leucoderma, mental illnesses, sores, swelling, thirst, thyroid disorders, tumours and upper respiratory tract infections.

Objective:

The objective of this study was to study the curative effect of 50% ethanol extract of dried fruit pulp of AM (AME) against 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced experimental colitis.

Materials and Methods:

AME (200 mg/kg) was administered orally, once daily for 14 days after TNBS-induced colitis. Rats were given intracolonic normal saline or TNBS alone or TNBS plus oral AME. AME was studied for its in vitro antibacterial activity against Gram-negative intestinal bacteria and on TNBS-induced changes in colonic damage, weight and adhesions (macroscopic and microscopic), diarrhea, body weight and colonic levels of free radicals (nitric oxide and lipid peroxidation), antioxidants (superoxide dismutase, catalase and reduced glutathione) and pro-inflammatory marker (myeloperoxidase [MPO]) in rats.

Results:

AME showed antibacterial activity against intestinal pathogens and decreased colonic mucosal damage and inflammation, diarrhea, colonic free radicals and MPO and enhanced body weight and colonic antioxidants level affected by TNBS. The effects of AME on the above parameters were comparable with sulfasalazine, a known colitis protective drug (100 mg/kg, oral).

Conclusion:

AME shows curative effects against TNBS-induced colitis by its antibacterial activity and promoting colonic antioxidants and reducing free radicals and MPO-induced colonic damage.

Propionyl-L-Carnitine is Efficacious in Ulcerative Colitis Through its Action on the Immune Function and Microvasculature

Objectives:

Microvascular endothelial dysfunction characterizes ulcerative colitis (UC), the most widespread form of inflammatory bowel disease. Intestinal mucosal microvessels in UC display aberrant expression of cell adhesion molecules (CAMs) and increased inflammatory cell recruitment. Propionyl-L-carnitine (PLC), an ester of L-carnitine required for the mitochondrial transport of fatty acids, ameliorates propionyl-CoA bioavailability and reduces oxidative stress in ischemic tissues. The present study aimed to document the efficacy of anti-oxidative stress properties of PLC in counteracting intestinal microvascular endothelial dysfunction and inflammation.

Methods:

To evaluate the efficacy in vivo, we analyzed the effects in intestinal biopsies of patients with mild-to-moderate UC receiving oral PLC co-treatment and in rat TNBS-induced colitis; in addition, we investigated antioxidant PLC action in TNF-α-stimulated human intestinal microvascular endothelial cells (HIMECs) in vitro.

Results:

Four-week PLC co-treatment reduced intestinal mucosal polymorph infiltration and CD4⁺ lymphocytes, ICAM-1⁺ and iNOS⁺ microvessels compared with placebo-treated patients with UC. Oral and intrarectal administration of PLC but not L-carnitine or propionate reduced intestinal damage and microvascular dysfunction in rat TNBS-induced acute and reactivated colitis. In cultured TNF-α-stimulated HIMECs, PLC restored β-oxidation and counteracted NADPH oxidase 4-generated oxidative stress-induced CAM expression and leukocyte adhesion. Inhibition of β-oxidation by L-aminocarnitine increased reactive oxygen species production and PLC beneficial effects on endothelial dysfunction and leukocyte adhesion. Finally, PLC reduced iNOS activity and nitric oxide accumulation in rat TNBS-induced colitis and in HIMEC cultures.

Conclusions:

Our results show that the beneficial antioxidant effect of PLC targeting intestinal microvasculature restores endothelial β-oxidation and function, and reduces mucosal inflammation in UC patients.

Intraluminal acid activates esophageal nodose C fibers after mast cell activation

Acid reflux in the esophagus can induce esophageal painful sensations such as heartburn and noncardiac chest pain. The mechanisms underlying acid-induced esophageal nociception are not clearly understood. In our previous studies, we characterized esophageal vagal nociceptive afferents and defined their responses to noxious mechanical and chemical stimulation. In the present study, we aim to determine their responses to intraluminal acid infusion. Extracellular single-unit recordings were performed in nodose ganglion neurons with intact nerve endings in the esophagus using ex vivo esophageal-vagal preparations. Action potentials evoked by esophageal intraluminal acid perfusion were compared in naive and ovalbumin (OVA)-challenged animals, followed by measurements of transepithelial electrical resistance (TEER) and the expression of tight junction proteins (zona occludens-1 and occludin). In naive guinea pigs, intraluminal infusion with either acid (pH = 2-3) or capsaicin did not evoke an action potential discharge in esophageal nodose C fibers. In OVA-sensitized animals, following esophageal mast cell activation by in vivo OVA inhalation, intraluminal acid infusion for about 20 min started to evoke action potential discharges. This effect is further confirmed by selective mast cell activation using in vitro tissue OVA challenge in esophageal-vagal preparations. OVA inhalation leads to decreased TEER and zona occludens-1 expression, suggesting an impaired esophageal epithelial barrier function after mast cell activation. These data for the first time provide direct evidence of intraluminal acid-induced activation of esophageal nociceptive C fibers and suggest that mast cell activation may make esophageal epithelium more permeable to acid, which subsequently may increase esophageal vagal nociceptive C fiber activation.

Establishment of a novel extracorporeal bowel model to study luminal approaches to treat inflammatory bowel disease

We have established an extracorporeal bowel model system for the analysis of early events in inflammatory bowel disease (IBD) and therapeutic applications. This model consists of an intestinal segment that is cannulated and perfused in situ, allowing the investigation of cellular responses of apical mucosa cells on luminal applied substances. Short-term treatment with iodoacetamide mimicked experimental intestinal inflammation in IBD, as indicated by histological alterations such as hemorrhage, hyperemia and loss of regular crypt architecture, as well as enhanced expression of cytokines (e.g. IL-6, IL-10 and MCP-1) compared with control segments perfused with media. Perfusion of therapeutic agents (e.g. dexamethasone or Mutaflor) in the small intestine segment significantly reduced the features of early inflammation that are induced by iodoacetamide. Moreover, similar data were obtained for Resormin(®), a montmorillonite-illite mixed-layer mineral (smectite), indicating that smectites might be a newly identified therapeutic option for IBD. In summary, this model could provide novel insights into epithelial injury as well as genesis of IBD and, therefore, be useful in testing the therapeutic potential of compounds for IBD therapy.

Alteration of neuromuscular transmissions in the hamster colon following the resolution of TNBS-induced colitis

The aim of this study was to determine whether trinitrobenzene sulfonic acid-induced colitis leads to alterations in enteric neuronal transmission in hamsters. We assessed the mechanical responses induced by the application of electrical field stimulation (EFS) in isolated segments of the distal colon. The EFS-induced relaxation and contraction were blocked by a nitric oxide synthase inhibitor and by the combination of antagonists for tachykinin NK1 and NK2 receptors and muscarinic acetylcholine receptors, respectively. The mechanical responses to EFS were attenuated in the inflamed colon at 7 days and were recovered by 30 days after inflammation treatment. In addition, we found that purinergic and opioidergic excitatory neural components are expressed following the resolution of colitis. These results suggest that colonic inflammation causes indiscriminate damage to enteric neurons but that neuronal components are restored and that new excitatory neural components, compensating for the contractile responses in smooth muscle after colitis, are expressed.

Mast cells and inflammation-associated colorectal carcinogenesis

Close association between chronic inflammation and cancer has been recently highlighted. Indeed, inflammatory bowel disease (IBD) has been strongly linked with an increased risk of development of colorectal cancer (CRC). Inflammatory cell-produced inflammatory mediators, such as proinflammatory cytokines and inducible enzymes, contribute to this association. In an inflammatory microenvironment, infiltrating macrophages and mast cells mediate production of these inflammatory mediators to promote growth of tumors in target tissues. In contrast to macrophages, contribution of mast cells to CRC development in inflamed colon is not well understood. This study aimed to determine the role of mast cells in inflammation-associated colorectal carcinogenesis. CRC was induced by administration of the colonic carcinogen, azoxymethane (AOM), and the tumor promoter dextran sodium sulfate (DSS) in male mast cell-deficient WBBF(1)-kit (W/W-v) (W/W(v)) and mast cell-normal WBB6F(1)-+/+(WT) mice. At week 12, the W/W(v) mice had markedly lower inflammation scores in the colon when compared with WT mice. The mRNA levels of colonic proinflammatory cytokines and inducible enzymes were also decreased in W/W(V) mice at weeks 12 and 20, when compared with WT counterparts. Colorectal tumors, including CRC, were identified by histopathological analysis performed 20 weeks thereafter. Importantly, there were less neoplastic and preneoplastic colonic lesions in the W/W(v) mice compared with the WT mice. Thus, for the first time, our study shows that mice lacking mast cells are less susceptible to inflammation-associated colorectal carcinogenesis. Our findings also suggest that mast cells and their selected cytokines could play an important role in inflammation-mediated tumorigenesis through regulation of proinflammatory cytokines and inducible inflammatory enzymes.

Curative effect of Terminalia chebula extract on acetic acid-induced experimental colitis: role of antioxidants, free radicals and acute inflammatory marker

The present study has evaluated the healing effects of extract of dried fruit pulp of Terminalia chebula (TCE) on acetic acid (AA)-induced colitis in rats. TCE (600 mg/kg) showed healing effects against AA-induced colonic damage score and weight when administered orally daily for 14 days. TCE was further studied for its effects on various physical (mucus/blood in stool and stool frequency, food and water intake and body weight changes), histology, antibacterial activity and free radicals (NO and LPO), antioxidants (SOD, CAT and GSH) and myeloperoxidase in colonic tissue. Intra-colonic AA administration increased colonic mucosal damage and inflammation, mucus/bloody diarrhoea, stool frequency, but decreased body weight which were reversed by TCE and sulfasalazine (SS, positive control) treatments. TCE showed antibacterial activity and both TCE and SS enhanced the antioxidants, but decreased free radicals and myeloperoxidase activities affected in acetic acid-induced colitis. TCE indicated the presence of active principles with proven antioxidants, anti-inflammatory, immunomodulatory, and free radical scavenging and healing properties. Thus, TCE seemed to be safe and effective in healing experimental colitis.

Kynurenines and intestinal neurotransmission: the role of N-methyl-D-aspartate receptors

Gastrointestinal neuroprotection involves the net effect of many mechanisms which protect the enteral nervous system and its cells from death, dysfunction or degeneration. Neuroprotection is also a therapeutic strategy, aimed at slowing or halting the progression of primary neuronal loss following acute or chronic diseases. The neuroprotective properties of a compound clearly have implications for an understanding of the mechanism of dysfunctions and for therapeutic approaches in a number of gastrointestinal diseases.This paper focused on the roles of glutamate and N-methyl-D-aspartate (NMDA) receptors in the intrinsic neuronal control of gastrointestinal motility; the consequences of inflammation on gastrointestinal motility changes; and the involvement of tryptophan metabolites (especially kynurenic acid) in the regulatory function of the enteral nervous system and the modulation of the inflammatory response. Common features in the mechanisms of action, illustrative evidence from animal models, and experimental neuroprotective therapies making use of the currently available possibilities are also discussed.Overall, the evidence suggests that gastrointestinal neuroprotection against inflammation and glutamate-induced neurotoxicity may be mediated synergistically through the blockade of NMDA receptors and the inhibition of neuronal nitric oxide synthase activity and xanthine oxidoreductase-dependent superoxide production. These components are likewise significant factors in the pathomechanism of gastrointestinal inflammatory diseases and inflammation-linked motility alterations. Inhibition of the enteric NMDA receptors by kynurenic acid or its analogues may provide a novel option via which to influence intestinal hypermotility and inflammatory processes simultaneously.

Down-regulation of interleukin-16 in human mast cells HMC-1 by Clostridium difficile toxins A and B

Toxin A (TcdA) and toxin B (TcdB) are the major virulence factors of Clostridium difficile and are the causative agents for clinical symptoms, such as secretory diarrhoea and pseudomembranous colitis. Mast cells are essentially involved in the toxin-induced colonic inflammatory processes. To study the direct effects of these toxins on the expression of inflammatory genes, a DNA microarray containing evaluated probes of 90 selected inflammatory genes was applied to the immature mast cell line HMC-1. TcdA and TcdB induced up-regulation of only a limited number of genes within the early phase of cell treatment. Interleukin-8 (IL-8), transcription factor c-jun and heme oxygenase-1 messenger RNA (mRNA) increased more than 2-fold. In contrast, IL-16, known as a CD4(+) T-cell chemoattractant factor and the chemokine receptor cKit were down-regulated. Stimulation of HMC-1 cells with IL-8 had no effect on IL-16 mRNA level, indicating that both cytokines were independently affected by the toxins. Regulation of both cytokines, however, depended on glucosylation of Rho GTPases as tested by application of enzyme-deficient TcdA or TcdB. Down-regulation of total and secreted IL-16 protein was checked by enzyme-linked immunosorbent assay. The data implicate that TcdA and TcdB affect lymphocyte migration by modulating release of the chemoattractant factor IL-16 from mast cells. In addition, this is the first report showing that Rho GTPases are involved in the regulation of IL-16 expression.

Infection with Hymenolepis diminuta is more effective than daily corticosteroids in blocking chemically induced colitis in mice

Purpose. To compare infection with the tapeworm, Hymenolepis diminuta, with steroid (dexamethasone) administration in the inhibition of dinitrobenzene sulfonic acid- (DNBS-) induced colitis in mice. Procedures. Mice were treated with DNBS ± infected with H. diminuta or treated with daily dexamethasone (2 mg/Kg, ip.) and were assessed 72 hours post-DNBS by the calculation of disease activity and histological damage scores, and spleen cell cytokine production. Results. H. diminuta-infected mice showed increased IL-4 and IL-10 production by spleen cells compared to other groups and were protected from DNBS-induced colitis. In contrast, there was little benefit of dexamethasone in the treatment of colitis. Collagen deposition in the colon was not different between the groups. Conclusions. H. diminuta was superior to dexamethasone in the prevention of DNBS-induced colitis and did not result in additional side effects (i.e., collagen deposition). Comparisons with current therapeutics and long-term followup to studies are essential if “helminth therapy” is to become a viable treatment for specific inflammatory diseases in the gut or other tissues.

N-Methyl-D-aspartate receptor antagonism decreases motility and inflammatory activation in the early phase of acute experimental colitis in the rat

BACKGROUND

Inflammatory bowel diseases are accompanied by severe motility disorders. The aim of our study was to investigate whether the blockade of peripheral N-methyl-D-aspartate (NMDA)-sensitive glutamate receptors (NMDA-Rs) alters motility changes in chemically induced acute colitis and how this modulation is accomplished.

METHODS

The inflammatory and motility changes in 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis were studied in anaesthetized Wistar rats following treatment with the natural NMDA-R antagonist kynurenic acid (KynA) or SZR-72, a blood-brain barrier-permeable synthetic KynA analogue. The macrohaemodynamics, serosal microcirculation (visualized by intravital videomicroscopy), plasma levels of tumour necrosis factor alpha (TNF-alpha), inflammatory enzyme activities (xanthine oxidoreductase (XOR), myeloperoxidase (MPO) and nitric oxide synthase (NOS)), and colonic motility (with a strain-gauge technique) were evaluated 17 h after colitis induction and compared with the control conditions.

KEY RESULTS

The TNBS enema induced a systemic hyperdynamic circulatory reaction, increased the serosal capillary blood flow, significantly elevated the mucosal XOR, MPO and NOS activities and augmented the colonic motility relative to the controls. The NMDA-R antagonist treatment with KynA or SZR-72 significantly reduced the XOR, NOS and MPO activities, decreased the motility and increased the tone of the colon.

CONCLUSIONS & INFERENCES

These data demonstrate a potential modulatory mechanism of NMDA-R in altered colonic motility in TNBS colitis. Inhibition of the enteric NMDA-Rs may provide a therapeutic option via which to influence intestinal hypermotility, microcirculatory changes and inflammatory activation simultaneously.

Targeted drug-delivery approaches by nanoparticulate carriers in the therapy of inflammatory diseases

Limitations in therapy induced by adverse effects due to unselective drug availability and therefore the use of potentially too high doses are a common problem. One prominent example for this dilemma are inflammatory diseases. Colloidal carriers allow one to improve delivery of drugs to the site of action and appear promising to overcome this general therapeutic drawback. Specific uptake of nanoparticles by immune-related cells in inflamed barriers offers selective drug targeting to the inflamed tissue. Here we focus on nanocarrier-based drug delivery strategies for the treatment of common inflammatory disorders like rheumatoid arthritis, multiple sclerosis, uveitis or inflammatory bowel disease.

Balsalazine decreases intestinal mucosal permeability of dextran sulfate sodium-induced colitis in mice

AIM

To investigate the effect of balsalazine treatment on intestinal mucosal permeability in dextran sulfate sodium (DSS)-induced colitis and to determine the mechanism of the balsalazine-induced changes.

METHODS

Experimental colitis was induced in C57BL/6J mice by the administration of 5% DSS. Balsalazine was administered intragastrically at doses of 42, 141, and 423 mg/kg. The disease activity index (DAI) score was evaluated and colon tissue was collected for the assessment of histological changes. The amount of malondialdehyde (MDA) in the colon was determined, along with the activity of myeloperoxidase (MPO), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Mucosa from the small intestine was collected to determine the levels of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma. The mucosa was ultrastructurally examined with transmission electron microscopy and intestinal permeability was assayed using Evans blue.

RESULTS

Balsalazine was found to reduce the DAI score and the histological index (HI) score, decrease the MDA content and the activity of MPO, and increase the activity of SOD and GSH-Px in colitis mice. At the same time, balsalazine ameliorated microvillus and tight junction structure, resulting in a decrease in the amount of Evans blue permeating into the intestinal wall and the levels of TNF-alpha and IFN-gamma in colitis mice.

CONCLUSION

In colitis mice, the anti-colitis effect of balsalazine results in a decrease in intestinal mucosal permeability. The mechanism of this effect is partly associated with balsalazine's antioxidative and anti-inflammatory effects.Acta Pharmacologica Sinica (2009) 30: 987-993; doi: 10.1038/aps.2009.77.

Lineage-specific T-cell responses to cancer mucosa antigen oppose systemic metastases without mucosal inflammatory disease

Cancer mucosa antigens are emerging as a new category of self-antigens expressed normally in immunologically privileged mucosal compartments and universally by their derivative tumors. These antigens leverage the established immunologic partitioning of systemic and mucosal compartments, limiting tolerance opposing systemic antitumor efficacy. An unresolved issue surrounding self-antigens as immunotherapeutic targets is autoimmunity following systemic immunization. In the context of cancer mucosa antigens, immune effectors to self-antigens risk amplifying mucosal inflammatory disease promoting carcinogenesis. Here, we examined the relationship between immunotherapy for systemic colon cancer metastases targeting the intestinal cancer mucosa antigen guanylyl cyclase C (GCC) and its effect on inflammatory bowel disease and carcinogenesis in mice. Immunization with GCC-expressing viral vectors opposed nascent tumor growth in mouse models of pulmonary metastasis, reflecting systemic lineage-specific tolerance characterized by CD8(+), but not CD4(+), T-cell or antibody responses. Responses protecting against systemic metastases spared intestinal epithelium from autoimmunity, and systemic GCC immunity did not amplify chemically induced inflammatory bowel disease. Moreover, GCC immunization failed to promote intestinal carcinogenesis induced by germ-line mutations or chronic inflammation. The established role of CD8(+) T cells in antitumor efficacy, but CD4(+) T cells in autoimmunity, suggests that lineage-specific responses to GCC are particularly advantageous to protect against systemic metastases without mucosal inflammation. These observations support the utility of GCC-targeted immunotherapy in patients at risk for systemic metastases, including those with inflammatory bowel disease, hereditary colorectal cancer syndromes, and sporadic colorectal cancer.

Glycosyltransferase function in core 2-type protein O glycosylation

Three glycosyltransferases have been identified in mammals that can initiate core 2 protein O glycosylation. Core 2 O-glycans are abundant among glycoproteins but, to date, few functions for these structures have been identified. To investigate the biological roles of core 2 O-glycans, we produced and characterized mice deficient in one or more of the three known glycosyltransferases that generate core 2 O-glycans (C2GnT1, C2GnT2, and C2GnT3). A role for C2GnT1 in selectin ligand formation has been described. We now report that C2GnT2 deficiency impaired the mucosal barrier and increased susceptibility to colitis. C2GnT2 deficiency also reduced immunoglobulin abundance and resulted in the loss of all core 4 O-glycan biosynthetic activity. In contrast, the absence of C2GnT3 altered behavior linked to reduced thyroxine levels in circulation. Remarkably, elimination of all three C2GnTs was permissive of viability and fertility. Core 2 O-glycan structures were reduced among tissues from individual C2GnT deficiencies and completely absent from triply deficient mice. C2GnT deficiency also induced alterations in I-branching, core 1 O-glycan formation, and O mannosylation. Although the absence of C2GnT and C4GnT activities is tolerable in vivo, core 2 O glycosylation exerts a significant influence on O-glycan biosynthesis and is important in multiple physiological processes.

Anti-Inflammatory mechanisms of enteric Heligmosomoides polygyrus infection against trinitrobenzene sulfonic acid-induced colitis in a murine model

Recent studies showed that enteric helminth infection improved symptoms in patients with inflammatory bowel disease as well as in experimental models of colitis. The aim of this study was to determine the mechanism of the protective effect of helminth infection on colitis-induced changes in immune and epithelial cell function. BALB/c mice received an oral infection of Heligmosomoides polygyrus third-stage larvae, were given intrarectal saline or trinitrobenzene sulfonic acid (TNBS) on day 10 postinfection, and were studied 4 days later. Separate groups of mice received intrarectal saline or TNBS on day 10 and were studied on day 14. Muscle-free colonic mucosae were mounted in Ussing chambers to measure mucosal permeability and secretion. Expression of cytokines was assessed by quantitative real-time PCR, and mast cells were visualized by immunohistochemistry. TNBS-induced colitis induced mucosal damage, upregulated Th1 cytokines, and depressed secretory responses. Heligmosomoides polygyrus elevated Th2 cytokine expression, increased mast cell infiltration and mucosal resistance, and also reduced some secretory responses. Prior H. polygyrus infection prevented TNBS-induced upregulation of Th1 cytokines and normalized secretory responses to specific agonists. TNBS-induced colitis did not alter H. polygyrus-induced mast cell infiltration or upregulation of Th2 cytokine expression. The results indicate that the protective mechanism of enteric nematode infection against TNBS-induced colitis involves prevention of Th1 cytokine expression and improved colonic function by a mechanism that may involve mast cell-mediated protection of neural control of secretory function. Similar response patterns could account for the clinical improvement seen in inflammatory bowel disease with helminthic therapy.

Impairment and restoration of spontaneous contractile activity of longitudinal smooth muscles in the TNBS-inflamed hamster distal colon

In the present study, we aimed to determine how inflammation affects spontaneous motility in the longitudinal direction of a hamster colon preparation. Trinitrobenzene sulfonic acid (TNBS) injected into the distal colon caused diarrhea 4-7 days after the treatment, but diarrhea was not observed in hamsters kept for 4 weeks. At 1 week after induction of colitis, spontaneous motility in the longitudinal direction was strongly suppressed. Contraction of longitudinal smooth muscles induced by electrical field stimulation was impaired, but not that induced by exogenously applied acetylcholine, indicating that acute inflammation preferentially impairs neurotransmissions with a minor effect on contractility of the longitudinal smooth muscle itself. The spontaneous motility reappeared in the colonic preparation isolated from the hamster maintained for 4 weeks after induction of colitis. The reappearance of the motility accompanied cholinergic and nitrergic regulations of contractile activity. These results demonstrated that impairment and following restoration of spontaneous contractile activity of longitudinal smooth muscles in the TNBS-inflamed distal colon of the hamster may depend on the damage and recovery of neural factors, rather than alteration of muscle contractility.

Neuroimmune interactions: potential target for mitigating or treating intestinal radiation injury

Intestinal radiation injury is characterized by breakdown of the epithelial barrier and mucosal inflammation. In addition to replicative and apoptotic cell death, radiation also induces changes in cellular function, as well as alterations secondary to tissue injury. The recognition of these "non-cytocidal" radiation effects has enhanced the understanding of normal tissue radiation toxicity, thus allowing an integrated systems biology-based approach to modulating radiation responses and providing a mechanistic rationale for interventions to mitigate or treat radiation injuries. The enteric nervous system regulates intestinal motility, blood flow and enterocyte function. The enteric nervous system also plays a central role in maintaining the physiological state of the intestinal mucosa and in coordinating inflammatory and fibroproliferative processes. The afferent component of the enteric nervous system, in addition to relaying sensory information, also exerts important effector functions and contributes critically to preserving mucosal integrity. Interactions between afferent nerves, mast cells as well as other cells of the resident mucosal immune system serve to maintain mucosal homeostasis and to ensure an appropriate response to injury. Notably, enteric sensory neurons regulate the activation threshold of mast cells by secreting substance P, calcitonin gene-related peptide and other neuropeptides, whereas mast cells signal to enteric nerves by the release of histamine, nerve growth factor and other mediators. This article reviews how enteric neurons interact with mast cells and other immune cells to regulate the intestinal radiation response and how these interactions may be modified to mitigate intestinal radiation toxicity. These data are not only applicable to radiation therapy, but also to intestinal injury in a radiological terrorism scenario.

Predisposition to colorectal cancer in rats with resolved colitis: role of cyclooxygenase-2-derived prostaglandin d2

Colitis markedly increases the risk of developing colon cancer, but the underlying mechanisms are not fully understood. In a rat model of colitis, alterations in epithelial secretion, proliferation, and barrier function persist long after healing has occurred. In the present study, we examined whether rats that have recovered from a bout of colitis are more susceptible to preneoplastic lesions and whether this susceptibility is mediated by cyclooxygenase (COX)-2-derived prostaglandin (PG) D2. Colitis was induced by intracolonic administration of trinitrobenzenesulfonic acid. Six weeks later, weekly treatment with the carcinogen azoxymethane was initiated. Postcolitis rats exhibited significantly more aberrant crypt foci after azoxymethane treatment than controls. The postcolitis rats also exhibited markedly increased colonic PGD2 synthesis and elevated COX-2, H-PGD synthase, and beta-catenin expression. Treatment for 1 week with a selective COX-2 inhibitor or with a selective PGD2 receptor (DP1) antagonist significantly reduced susceptibility of postcolitis rats to aberrant crypt foci development, beta-catenin expression, and mucosal thickness. The results from this animal model suggest that prolonged elevation of COX-2-derived PGD2 synthesis after resolution of colitis may contribute significantly to colitis-associated increases in colon cancer incidence. PGD2 may therefore represent a rational target for therapies directed at reducing the incidence of colitis-associated colorectal cancer.

Animal models of inflammatory bowel disease

In inflammatory bowel disease (IBD), experimental models have proven to be important tools for detecting potential therapeutic agents and for investigating the mechanisms of pathogenesis. This review is intended to cover recent advances in basic IBD model applications. The use of more than 20 animal models has allowed the detection of numerous protective pharmacological agents, including a number of immunomodulatory agents that have entered the therapeutic armamentarium. The models have been classified into five main categories based on the methods of induction: gene knockout (KO), transgenic, chemical, adoptive transfer, and spontaneous (each with subcategories).

Beneficial effects of estrogen treatment in the HLA-B27 transgenic rat model of inflammatory bowel disease

A well-established model of bowel inflammation is the HLA-B27 transgenic rat that exhibits a spontaneous disease phenotype resulting in chronic diarrhea caused by immune cell activation. Estrogens have previously been shown to modulate the immune system, and both estrogen receptors (ERalpha and ERbeta) are present in the intestine and cells of the immune system. Therefore, the ability of estrogen to ameliorate disease progression in the HLA-B27 transgenic rat was determined. HLA-B27 transgenic rats with chronic diarrhea were treated with 17alpha-ethynyl-17beta-estradiol (EE) for 5 days. EE treatment dramatically improved stool scores after only 3 days. Histological scores of the degree of ulceration, inflammatory cell infiltration, fibrosis, and lesion depth of the colon were also improved by EE treatment. Because neutrophil infiltration into the colon is involved in the development and propagation of disease, myeloperoxidase (MPO) activity was measured. MPO levels were reduced by 80% by EE treatment. Cotreatment with the pure ER antagonist ICI-182780 (ICI) blocked the effects of EE on stool character, MPO activity, and histology scores, strongly suggesting that the activity of EE is mediated through ER. Mast cell proteases can promote neutrophil infiltration, and gene expression analysis demonstrated that mast cell protease 1, 3, and 4 mRNA were all decreased in colons from estrogen-treated rats. In addition, a direct effect of estrogen on bone marrow-derived mast cell activity was demonstrated, suggesting that ER-mediated inactivation of mast cells may contribute to the improvement in the clinical sign and histological scores in this model.

Morphological and functional alterations of the myenteric plexus in rats with TNBS-induced colitis

The 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced model of experimental colitis was used to investigate the time-course of alterations in enteric neurotransmission and/or smooth muscle function that occur in chronic inflammation. Myenteric plexus morphology (immunocytochemical markers), functional integrity of cholinergic neurons (3H-choline uptake, acetylcholine release and contractile response to electrical field stimulation) and smooth muscle integrity (contractile response to exogenous acetylcholine) were determined 2, 7, 15, and 30 days after TNBS treatment. In TNBS-treated rats extensive ulcerations of the mucosa and/or the submucosa and increase in colonic weights were accompanied by significant reduction in 3H-choline uptake, acetylcholine release and contractile response to stimulation of enteric nerves. These changes were maximal 7 and 15 days after TNBS treatment. Immunocytochemical marker (PGP 9.5, SNAP 25, synaptophysin and S100 protein) expression was absent in necrotic areas of colons removed 7 days post-injury and partially reduced in colons removed 15 days after TNBS treatment. By contrast, the contractile response to exogenous acetylcholine was significantly increased after 7 days in both inflamed and uninflamed regions and returned to control values by day 30. Likewise, an almost complete recovery of neural cholinergic function and of myenteric plexus morphology was observed 30 days after TNBS treatment. These data suggest that TNBS-induced colitis is associated with progressive and selective alterations in myenteric plexus structure and function, with consequent reduction of cholinergic neurotransmission and abnormality in colonic contractility. The reversibility of myenteric plexus disruption is a clear indication of neuronal plasticity within enteric nervous system as an adaptative mechanism against inflammatory challenges.

Size-dependent bioadhesion of micro- and nanoparticulate carriers to the inflamed colonic mucosa

PURPOSE

The size-dependent deposition of microparticles and nanoparticles after oral administration to rats using an experimental model colitis was examined. Local delivery of an entrapped drug could reduce side effects and would be a distinct improvement compared with existing colon delivery devices.

METHODS

Ulcerative colitis was induced in Lewis rats with trinitrobenzenesulfonic acid. Fluorescent polystyrene particles with a size of 0.1, 1, or 10 microm were administered for 3 days. The animals then were sacrificed and their guts resected. Particle distribution in the colon was imaged by confocal laser scanning microscopy and quantified by fluorescence spectrophotometry.

RESULTS

In the inflamed tissue, an increased adherence of particles was observed at the thicker mucus layer and in the ulcerated regions. A size dependency of the deposition was found, and an increased number of attached particles to the colon was determined compared with the control group. For 10-micorm particles, only fair deposition was observed (control group: 1.4 +/- 0.6%; colitis: 5.2 +/- 3.8% of administered particle mass). One-micrometer particles showed higher binding (control group: 2.0 +/- 0.8%; colitis: 9.1 +/- 4.2%). Highest binding was found for 0.1-microm particles (control group: 2.2 +/- 1.6%; colitis: 14.5 +/- 6.3%). The ratio of colitis/control deposition increased with smaller particle sizes.

CONCLUSIONS

The use of submicron-sized carriers holds promise for the targeted delivery of drugs to the inflamed colonic mucosal areas in inflammatory bowel disease.