Regulation of murine intestinal inflammation by reactive metabolites of oxygen and nitrogen: divergent roles of superoxide and nitric oxide

Vimentin regulates mitochondrial ROS production and inflammatory responses of neutrophils

The intermediate filament vimentin is present in immune cells and is implicated in proinflammatory immune responses. Whether and how it supports antimicrobial activities of neutrophils is not well established. Here, we developed an immortalized neutrophil model to examine the requirement of vimentin. We demonstrate that vimentin restricts the production of proinflammatory cytokines and reactive oxygen species (ROS), but enhances phagocytosis and swarming. We observe that vimentin is dispensable for neutrophil extracellular trap (NET) formation, degranulation, and inflammasome activation. Moreover, gene expression analysis demonstrated that the presence of vimentin was associated with changes in expression of multiple genes required for mitochondrial function and ROS overproduction. Treatment of wild-type cells with rotenone, an inhibitor for complex I of the electron transport chain, increases the ROS levels. Likewise, treatment with mitoTEMPO, a SOD mimetic, rescues the ROS production in cells lacking vimentin. Together, these data show vimentin regulates neutrophil antimicrobial functions and alters ROS levels through regulation of mitochondrial activity.

From gut to brain: understanding the role of microbiota in inflammatory bowel disease

With the proposal of the "biological-psychological-social" model, clinical decision-makers and researchers have paid more attention to the bidirectional interactive effects between psychological factors and diseases. The brain-gut-microbiota axis, as an important pathway for communication between the brain and the gut, plays an important role in the occurrence and development of inflammatory bowel disease. This article reviews the mechanism by which psychological disorders mediate inflammatory bowel disease by affecting the brain-gut-microbiota axis. Research progress on inflammatory bowel disease causing "comorbidities of mind and body" through the microbiota-gut-brain axis is also described. In addition, to meet the needs of individualized treatment, this article describes some nontraditional and easily overlooked treatment strategies that have led to new ideas for "psychosomatic treatment".

Protective effects of topiramate on acetic acid-induced colitis in rats through the inhibition of oxidative stress

Ulcerative colitis is an intestinal inflammatory condition characterized by a rise in inflammatory mediator production and oxidative stress. Topiramate is an anticonvulsant agent with effectiveness on a wide range of seizures, which is anti-oxidative. This study aims to examine the protective effects of topiramate on acetic acid-induced ulcerative colitis in rats. Rats were randomly divided into four groups as follows: control, acetic acid, acetic acid + topiramate, and acetic acid + dexamethasone groups. Topiramate (100 mg/kg/day) or dexamethasone (2 mg/kg/day) was administered for six consecutive days, and ulcerative colitis was induced on the first day of the study by transrectal administration of 4% acetic acid. Four hours after the last dose of treatments, animals of each group were sacrificed, and colon tissues were removed for further macroscopic, histopathologic, and biochemical analyses. Treatment with topiramate markedly decreased colonic lesions and macroscopic scores as well as the improvement of histopathologic changes. Topiramate also effectively decreased the levels of malondialdehyde and upregulated the activity of anti-oxidative enzymes, including catalase, superoxide dismutase, and glutathione peroxidase. Our results reveal that the administration of topiramate ameliorates acetic acid-induced colitis in rats via anti-oxidative properties, and further studies may introduce it as an effective therapeutic candidate to decrease ulcerative colitis severity.

Transient gestational hypothyroxinemia accelerates and enhances ulcerative colitis-like disorder in the male offspring

Introduction

Gestational hypothyroxinemia (HTX) is a condition that occurs frequently at the beginning of pregnancy, and it correlates with cognitive impairment, autism, and attentional deficit in the offspring. Evidence in animal models suggests that gestational HTX can increase the susceptibility of the offspring to develop strong inflammation in immune-mediated inflammatory diseases. Ulcerative colitis (UC) is a frequent inflammatory bowel disease with unknown causes. Therefore, the intensity of ulcerative colitis-like disorder (UCLD) and the cellular and molecular factors involved in proinflammatory or anti-inflammatory responses were analyzed in the offspring gestated in HTX (HTX-offspring) and compared with the offspring gestated in euthyroidism (Control-offspring).

Methods

Gestational HTX was induced by the administration of 2-mercapto-1-methylimidazole in drinking water to pregnant mice during E10-E14. The HTX-offspring were induced with UCLD by the acute administration of dextran sodium sulfate (DSS). The score of UCLD symptomatology was registered every day, and colon histopathology, immune cells, and molecular factors involved in the inflammatory or anti-inflammatory response were analyzed on day 6 of DSS treatment.

Results

The HTX-offspring displayed earlier UCLD pathological symptoms compared with the Control-offspring. After 6 days of DSS treatment, the HTX-offspring almost doubled the score of the Control-offspring. The histopathological analyses of the colon samples showed signs of inflammation at the distal and medial colon for both the HTX-offspring and Control-offspring. However, significantly more inflammatory features were detected in the proximal colon of the HTX-offspring induced with UCLD compared with the Control-offspring induced with UCLD. Significantly reduced mRNA contents encoding for protective molecules like glutamate-cysteine ligase catalytic subunit (GCLC) and mucin-2 (MUC-2) were found in the colon of the HTX-offspring as compared with the Control-offspring. Higher percentages of Th17 lymphocytes were detected in the colon tissues of the HTX-offspring induced or not with UCLD as compared with the Control-offspring.

Discussion

Gestational HTX accelerates the onset and increases the intensity of UCLD in the offspring. The low expression of MUC-2 and GCLC together with high levels of Th17 Lymphocytes in the colon tissue suggests that the HTX-offspring has molecular and cellular features that favor inflammation and tissue damage. These results are important evidence to be aware of the impact of gestational HTX as a risk factor for UCLD development in offspring.

Oral Delivery of Bioactive Glass-Loaded Core-Shell Hydrogel Microspheres for Effective Treatment of Inflammatory Bowel Disease

Resolving inflammation and promoting intestinal tissue regeneration are critical for inflammatory bowel disease (IBD) treatment. Bioactive glass (BG) is a clinically approved bone graft material and has been shown to modulate inflammatory response, but it is unknown whether BG can be applied to treat IBD. Here, it is reported that BG attenuates pro-inflammatory response of lipopolysaccharide (LPS)-stimulated macrophages and hence reduces inflammatory damage to intestinal organoids in vitro. In addition, zein/sodium alginate-based core-shell microspheres (Zein/SA/BG) are developed for oral delivery of BG, which helps prevent premature dissolution of BG in the stomach. The results show that Zein/SA/BG protects BG from a gastric-simulated environment while dissolved in an intestinal-simulated environment. When administered to acute and chronic colitis mice model, Zein/SA/BG significantly reduces intestinal inflammation, promotes epithelial tissue regeneration, and partially restores microbiota homeostasis. These findings are the first to reveal the therapeutic efficacy of BG against IBD, which may provide a new therapeutic approach at low cost for effective IBD treatment.

Anti-inflammatory effect and signaling mechanism of 8-shogaol and 10-shogaol in a dextran sodium sulfate-induced colitis mouse model

Ethnopharmacological relevance

Ginger (Zingiber officinale Roscoe) has been used for food and applied in Ayurvedic medicine in India for thousands of years. With a reputation for strong anti-inflammatory properties, it has been used for to treat colds, migraines, nausea, arthritis, and high blood pressure in China and Southeast Asia. The physiological activity of ginger is attributed to its functional components, including gingerol and shogaol, and their derivatives.

Aim of the study

We aimed to investigate the effects of 8- and 10-shogaol and their bioactive signaling mechanisms in a dextran sodium sulfate (DSS)-induced colitis mouse model. The anti-colitis efficacy of 6-, 8-, and 10-derivatives of gingerol and shogaol was comparatively analyzed.

Materials and methods

Colitis was induced by providing mice with drinking water containing 5% DSS (w/v) for 8 days. The 6-, 8-, and 10-derivatives of gingerol and shogaol were orally administered for two weeks at a dose of 30 mg/kg. Changes in body weight and disease activity index were measured. The levels of pro-inflammatory cytokines, iNOS and COX-2, as well as the phosphorylation of NF-κB were analyzed using ELISA, PCR, or western blotting. Mucin expression and mRNA levels were measured using alcian blue staining and PCR, respectively. The tight-junction-associated proteins occludin and ZO-1 were assessed using immunohistological staining.

Results

The 6-, 8-, and 10-derivatives of gingerol and shogaol exhibited anti-inflammatory effects by regulating NF-κB signaling. Among the compounds administered, 10-shogaol was the most effective against DSS-induced inflammation. Comparative analysis of the chemical structure showed that shogaol, a dehydrated analog of gingerol, was more effective. 6- and 10-shogaol showed similar effects on DSS-induced morphological changes in the colonic mucus layer, mucin expression, and tight junction proteins.

Conclusions

6-, 8-, and 10-Gingerol and 6-, 8-, and 10-shogaol significantly improved the clinical symptoms and intestinal epithelial barrier damage in DSS-induced colitis in mice. The derivatives effectively inhibited DSS-induced inflammation through the regulation of NF-κB signaling. Moreover, 10-shogaol showed the most potent anti-inflammatory effect among the six compounds used in this study. The results indicate that 8- and 10-shogaol, both main ingredients in ginger, may serve as therapeutic candidates for the treatment of colitis.

The effect of montelukast, a leukotriene receptor antagonist, on the acetic acid-induced model of colitis in rats: Involvement of NO-cGMP-KATP channels pathway

Inflammatory bowel disease is a chronic autoimmune disorder that may involve entire gastrointestinal tract. The leukotrienes have a role as mediators in the pathophysiology of colitis. Here, we investigated the effect of a leukotriene receptor antagonist, montelukast, and also the role of the NO-cGMP-K_ATP channel pathway in acetic acid-induced colitis. Rectal administration of acetic acid (4%) was used for induction of colitis in rats. To investigate our hypothesis, the rats were intraperitoneally pre-treated with L-NAME (NOS inhibitor), L-arginine, sildenafil, methylene blue, glibenclamide, or diazoxide 15 min before treatment with montelukast (5-20 mg/kg, i. p.), for three consecutive days. Then, microscopic, macroscopic, and inflammatory parameters were evaluated. Montelukast reduced the microscopic and macroscopic damage induced by acetic acid. Montelukast also reduced the level of IL-1β and TNF-α. We also showed that the effects of montelukast were significantly attenuated by L-NAME, methylene blue (guanylate cyclase inhibitor), and an ATP-sensitive potassium channel blocker (glibenclamide). Also, the administration of L-arginine, sildenafil, and diazoxide before montelukast produced protective effect. In conclusion, the pathway of the NO-cGMP-KATP channel is involved in the protective effect of montelukast in acetic acid-induced colonic tissue damage.

Nitric-Oxide-Modulatory Materials for Biomedical Applications

Nitric oxide (NO) is an endogenous signaling molecule that participates in various physiological and biological pathways associated with vasodilation, immune response, and cell apoptosis. Interestingly, NO has versatile and distinct functions in vivo depending on its concentration and the duration of exposure; it aids cellular proliferation at nanomolar concentrations but causes cellular death at micromolar concentrations. Therefore, achieving the precise and on-demand modulation of microenvironmental NO concentrations has become a major research target in biomedical fields. To this end, many studies have investigated feasible means for developing functional moieties that can either exogenously donate or selectively scavenge NO. However, these advances are limited by poor stability and a lack of target specificity, which represent two significant obstacles regarding the spatiotemporal adjustment of NO in vivo. Our group has addressed this issue by contributing to the development of next-generation NO-modulatory materials over the past decade. Over this period, we utilized various polymeric, inorganic, and hybrid systems to enhance the bioavailability of traditional NO donors or scavengers in an attempt to maximize their clinical usage while also minimizing their unwanted side effects. In this Account, strategies regarding the rational design of NO-modulatory materials are first summarized and discussed, depending on their specific purposes. These strategies include chemical approaches for encapsulating traditional NO donors inside specific vehicles; this prevents spontaneous NO release and allows said donors to be exposed on-demand, under a certain stimulus. The current status of these approaches and the recent contributions of other groups are also comprehensively discussed here to ensure an objective understanding of the topic. Moreover, in this paper, we discuss strategies for the selective depletion of NO from local inflammatory sites, where the overproduction of NO is problematic. Finally, the major challenges for current NO-modulatory systems are discussed, and requirements are outlined that need to be tackled to achieve their future therapeutic development. Starting from this current, relatively early stage of development, we propose that, through continuous efforts to surmount existing challenges, it will be possible in the future to achieve clinical translations regarding NO-modulatory systems. This Account provides insightful guidelines regarding the rational design of NO-modulatory systems for various biomedical applications. Moreover, it can facilitate the achievement of previously unattainable goals while revolutionizing future therapeutics.

Lactobacillus salivarius UCC118™ Dampens Inflammation and Promotes Microbiota Recovery to Provide Therapeutic Benefit in a DSS-Induced Colitis Model

The use of probiotics such as Lactobacillus and Bifidobacterium spp. as a therapeutic against inflammatory bowel disease (IBD) is of significant interest. Lactobacillus salivarus strain UCC118^TM is a commensal that has been shown to possess probiotic properties in vitro and anti-infective properties in vivo. However, the usefulness of UCC118 ^TM as a therapeutic against colitis remains unclear. This study investigates the probiotic potential of Lactobacillus salivarius, UCC118™ in a mouse model of colitis. DSS-induced colitis was coupled with pre-treatment or post-treatment with UCC118^TM by daily oral gavage. In the pre-treatment model of colitis, UCC118^TM reduced the severity of the disease in the early stages. Improvement in disease severity was coupled with an upregulation of tissue IL-10 levels and increased expression of macrophage M2 markers. This anti-inflammatory activity of UCC118^TM was further confirmed in vitro, using a model of LPS-treated bone marrow-derived macrophages. Taken together, these results suggest that UCC118^TM may promote the resolution of inflammation. This was supported in a mouse model of established DSS-induced colitis whereby UCC118^TM treatment accelerated recovery, as evidenced by weight, stool, histological markers and the recovery of microbiome-associated dysbiosis with an increased abundance of beneficial commensal species. These results demonstrate the potential of Lactobacillus salivarius UCC118^TM as a probiotic-based therapeutic strategy to promote health through the upregulation of anti-inflammatory IL-10 and protect against dysbiosis during IBD.

Vimentin Suppresses Inflammation and Tumorigenesis in the Mouse Intestine

Vimentin has been implicated in wound healing, inflammation, and cancer, but its functional contribution to intestinal diseases is poorly understood. To study how vimentin is involved during tissue injury and repair of simple epithelium, we induced colonic epithelial cell damage in the vimentin null (Vim^−/−) mouse model. Vim^−/− mice challenged with dextran sodium sulfate (DSS) had worse colitis manifestations than wild-type (WT) mice. Vim^−/− colons also produced more reactive oxygen and nitrogen species, possibly contributing to the pathogenesis of gut inflammation and tumorigenesis than in WT mice. We subsequently describe that CD11b⁺ macrophages served as the mainly cellular source of reactive oxygen species (ROS) production via vimentin-ROS-pSTAT3–interleukin-6 inflammatory pathways. Further, we demonstrated that Vim^−/− mice did not develop colitis-associated cancer model upon DSS treatment spontaneously but increased tumor numbers and size in the distal colon in the azoxymethane/DSS model comparing with WT mice. Thus, vimentin has a crucial role in protection from colitis induction and tumorigenesis of the colon.

From inflammatory bowel disease to colorectal cancer: what's the role of miRNAs?

Inflammatory Bowel Disease (IBD) is a chronic inflammatory disease with relapse and remission periods. Ulcerative colitis and Crohn's disease are two major forms of the disease. IBD imposes a lot of sufferings on the patient and has many consequences; however, the most important is the increased risk of colorectal cancer, especially in patients with Ulcerative colitis. This risk is increased with increasing the duration of disease, thus preventing the progression of IBD to cancer is very important. Therefore, it is necessary to know the details of events contributed to the progression of IBD to cancer. In recent years, the importance of miRNAs as small molecules with 20-22 nucleotides has been recognized in pathophysiology of many diseases, in which IBD and colorectal cancer have not been excluded. As a result, the effectiveness of these small molecules as therapeutic target is hopefully confirmed. This paper has reviewed the related studies and findings about the role of miRNAs in the course of events that promote the progression of IBD to colorectal carcinoma, as well as a review about the effectiveness of some of these miRNAs as therapeutic targets.

Flavocoxid halts both intestinal and extraintestinal alterations in acetic acid-induced colitis in rats

Ulcerative colitis (UC) is an idiopathic chronic inflammatory disorder mainly affecting the colon and rectum. The present investigation was undertaken to evaluate the potential protective effect of flavocoxid, a dual COX and LOX inhibitor, in colitis model in rats. UC was induced by instillation of 2 ml of 4% acetic acid (AA) into the colon using a pediatric catheter in rats, and flavocoxid (10 and 20 mg·kg^-1) was given once daily for 7 days before induction of colitis. Rats were sacrificed; sera were collected; colons and livers were isolated and then analyzed by biochemical, macroscopic, and histopathological examination. Pretreatment with flavocoxid (10 and 20 mg·kg^-1) significantly reduced serum levels of alanine transaminase (ALT) (43.7 ± 7 and 76.2 ± 7.3 vs. 288.7 ± 31.4 in AA group) and aspartate transaminase (AST) (179.5 ± 22.2 and 200.5 ± 14 vs. 392.7 ± 35.6 in AA group) (p>0.05). Also, it decreased malondialdehyde (MDA) and nitric oxide (NOx) levels in both colonic and hepatic tissues. Moreover, flavocoxid effectively elevated colonic and hepatic reduced glutathione (GSH) level and superoxide dismutase (SOD) activity when compared to AA group (p>0.05). Additionally, flavocoxid significantly decreased levels of tumor necrosis factor-α (TNF-α) (878.2 ± 13.4 and 560.1 ± 2.9 vs. 1378.1 ± 31 in AA group) in colonic tissues and (701 ± 6.9 and 442.5 ± 8.2 vs. 1501 ± 9.4 in AA group) in hepatic tissues, nuclear factor kappa B (NF-κBp65) (493.8 ± 6.8 and 368.7 ± 3.1 vs. 659.2 ± 9.4 in AA group) in colonic tissues and (358 ± 5.1 and 163.5 ± 7.8 vs. 732.5 ± 4.5 in AA group) in hepatic tissues, myeloperoxidase (MPO) (15.7 ± 0.3 and 13 ± 0.2 vs. 20.9 ± 0.5 in AA group) in colonic tissues and (20.4 ± 0.3 and 16.3 ± 0.3 vs. 23.9 ± 1.2 in AA group) in hepatic tissues, and inducible nitric oxide synthase (iNOS) (12.5 ± 0.3 and 10 ± 0.2 vs. 16 ± 0.1 in AA group) in colonic tissues and (14.1 ± 0.04 and 11.5 ± 0.08 vs. 17.8 ± 0.1 in AA group) in hepatic tissues (p>0.05). Furthermore, it down-regulated Bax and caspase-3 expression in colonic and hepatic tissues upon comparison with AA group. Collectively, flavocoxid conferred a protective impact against acetic acid-induced colitis in rats via attenuating oxidative stress, inflammation, and apoptosis.

The preventive effect and underlying mechanism of Rhus chinensis Mill. fruits on dextran sulphate sodium-induced ulcerative colitis in mice

The purpose of this research was to explore the preventive effect of an 80% ethanol extract of Rhus chinensis Mill. fruits on dextran sulfate sodium (DSS)-induced colitis in mice and to elucidate the underlying molecular mechanisms of this effect. The results indicated that the extract, especially when administered at a high dose, could dramatically decrease the disease activity index, maintain normal spleen conditions, and improve colonic histopathology and length in the DSS-induced mice. In addition, extract administration could significantly suppress the levels of malondialdehyde, myeloperoxidase, tumor necrosis factor-α, interleukin-1β, and interleukin-6 and enhance superoxide dismutase and glutathione levels. The extract obviously protected intestinal barrier integrity by improving Occludin, ZO-1 and Claudin-1 expression levels. Western blot and immunohistochemistry analyses further indicated that the preventive effect of the phenol-rich extract on DSS-induced colitis might be achieved through the up-regulation of the expression of several pivotal oxidative stress-associated proteins, namely Nrf2, NQO1 and HO-1, and the down-regulation of the expression of several pivotal inflammation-associated proteins, namely p-NF-κB, p-IκB, COX-2, iNOS, p-P38, p-Erk1/2, and p-JNK. Therefore, R. chinensis fruits extract possesses the capability to prevent DSS-induced ulcerative colitis in mice and could be utilized as a natural substance in the exploitation of functional foods as an adjuvant dietary therapy for preventing and/or alleviating inflammatory bowel disease.

Chronic Toxoplasma gondii infection enhances susceptibility to colitis

Oral infection with Toxoplasma gondii results in dysbiosis and enteritis, both of which revert to normal during chronic infection. However, whether infection leaves a lasting impact on mucosal responses remains uncertain. Here we examined the effect of the chemical irritant dextran sodium sulfate (DSS) on intestinal damage and wound healing in chronically infected mice. Our findings indicate that prior infection with T. gondii exacerbates damage to the colon caused by DSS and impairs wound healing by suppressing stem cell regeneration of the epithelium. Enhanced tissue damage was attributable to inflammatory monocytes that emerge preactivated from bone marrow, migrate to the intestine, and release inflammatory mediators, including nitric oxide. Tissue damage was reversed by neutralization of inflammatory monocytes or nitric oxide, revealing a causal mechanism for tissue damage. Our findings suggest that chronic infection with T. gondii enhances monocyte activation to increase inflammation associated with a secondary environmental insult.

Thromboembolic and atherosclerotic cardiovascular events in inflammatory bowel disease: epidemiology, pathogenesis and clinical management

Inflammatory bowel disease (IBD) is associated with an increased risk of cardiovascular disease (CVD). The increased risk of CVD concerns an increased risk of venous thromboembolism (VTE), atherosclerotic cardiovascular disease (ASCVD) and heart failure (HF), at corresponding relative risks of 2.5, 1.2 and 2.0, respectively, as compared with the general population. Especially young patients under the age of 40 years run a relatively high risk of these complications when compared with the general population. Chronic systemic inflammation causes a hypercoagulable state leading to the prothrombotic tendency characteristic of VTE, and accelerates all stages involved during atherogenesis in ASCVD. Increased awareness of VTE risk is warranted in patients with extensive colonic disease in both ulcerative colitis and Crohn's disease, as well as during hospitalization, especially when patients are scheduled for surgery. Similarly, critical periods for ASCVD events are the 3 months prior to and 3 months after an IBD-related hospital admission. The increased ASCVD risk is not fully explained by an increased prevalence of traditional risk factors and includes pro-atherogenc lipid profiles with high levels of small dense low-density lipoprotein cholesterol particles and dysfunctional high-density lipoprotein cholesterol. Risk factors associated with HF are location and extent of inflammation, female sex, and age exceeding 40 years. A dose-dependent increase of overall CVD risk has been reported for corticosteroids. Immunomodulating maintenance therapy might reduce CVD risk in IBD, not only by a direct reduction of chronic systemic inflammation but possibly also by a direct effect of IBD medication on platelet aggregation, endothelial function and lipid and glucose metabolism. More data are needed to define these effects accurately. Despite accumulating evidence on the increased CVD risk in IBD, congruent recommendations to develop preventive strategies are lacking. This literature review provides an overview of current knowledge and identifies gaps in evidence regarding CVD risk in IBD, by discussing epidemiology, pathogenesis, and clinical management.

Role of p40phox in host defense against Citrobacter rodentium infection

NADPH oxidase (NOX) is a membrane-bound enzyme complex that generates reactive oxygen species (ROS). Mutations in NOX subunit genes have been implicated in the pathogenesis of inflammatory bowel disease (IBD), indicating a crucial role for ROS in regulating host immune responses. In this study, we utilize genetically deficient mice to investigate whether defects in p40phox , one subunit of NOX, impair host immune response in the intestine and aggravate disease in an infection-based (Citrobacter rodentium) model of colitis. We show that p40phox deficiency does not increase susceptibility of mice to C. rodentium infection, as no differences in body weight loss, bacterial clearance, colonic pathology, cytokine production, or immune cell recruitment were observed between p40phox-/- and wild-type mice. Interestingly, higher IL-10 levels were observed in the supernatants of MLN cells and splenocytes isolated from infected p40phox -deficient mice. Further, a higher expression level of inducible nitric oxide synthase (iNOS) was also noted in mice lacking p40phox . In contrast to wild-type mice, p40phox-/- mice exhibited greater NO production after LPS or bacterial antigen re-stimulation. These results suggest that p40phox-/- mice do not develop worsened colitis. While the precise mechanisms are unclear, it may involve the observed alteration in cytokine responses and enhancement in levels of iNOS and NO.

Dynamic role of macrophage CX3CR1 expression in inflammatory bowel disease

Inflammatory bowel disease (IBD), consisting of ulcerative colitis (UC) and Crohn's disease (CD), is featured by overactive immune response and enduring course of unrestrained colitis. Genetic predisposition and environmental factors are fundamental in disease progression. Notably, microbiota dysregulation and its interaction with host mucosal barrier perplex disease phenotype. Under experimental setting, distinct mouse models are established to mimic human colitis process, including infection induced dysbiosis, dextran sulfate sodium (DSS) etc. induced barrier destruction, anti-CD40 L induced innate immunity dominant colitis and T cell transfer colitis model. Thus, from a more detailed aspect, IBD is heterogeneous and can be further classified into different subtypes based on the specific etiological pathways. As a typical inflammatory disorder, various immune cell types are involved in IBD pathogenesis. Among them, macrophages are believed to play a pivotal role. CX3CR1⁺ macrophages, deriving from peripheral patrolling CD14⁺ Ly6C^hi monocytes, are specified cell population dwelling in the gut. Accumulating evidence suggests that CX3CR1⁺ macrophages are critical for mucosal homeostasis and IBD pathogenesis, while some conflicts exist in current studies with both protective and harmful effects being revealed. Herein, we reviewed published literatures and found that the observed discrepancies stem from many aspects: the expression level of CX3CR1, the confounding dendritic cell subsets and most importantly, the different colitis stages and subtypes. Overall, CX3CR1 targeting strategy could be powerful weapon in fighting against colitis, but at the same time, the precise etiological and pathological mechanisms should be cautiously examined concerning the appropriate usage of CX3CR1 targeted therapy.

The Impact of Oxidative Stress in Human Pathology: Focus on Gastrointestinal Disorders

Accumulating evidence shows that oxidative stress plays an essential role in the pathogenesis and progression of many diseases. The imbalance between the production of reactive oxygen species (ROS) and the antioxidant systems has been extensively studied in pulmonary, neurodegenerative cardiovascular disorders; however, its contribution is still debated in gastrointestinal disorders. Evidence suggests that oxidative stress affects gastrointestinal motility in obesity, and post-infectious disorders by favoring the smooth muscle phenotypic switch toward a synthetic phenotype. The aim of this review is to gain insight into the role played by oxidative stress in gastrointestinal pathologies (GIT), and the involvement of ROS in the signaling underlying the muscular alterations of the gastrointestinal tract (GIT). In addition, potential therapeutic strategies based on the use of antioxidants for the treatment of inflammatory gastrointestinal diseases are reviewed and discussed. Although substantial progress has been made in identifying new techniques capable of assessing the presence of oxidative stress in humans, the biochemical-molecular mechanisms underlying GIT mucosal disorders are not yet well defined. Therefore, further studies are needed to clarify the mechanisms through which oxidative stress-related signaling can contribute to the alteration of the GIT mucosa in order to devise effective preventive and curative therapeutic strategies

Dual Switch Mechanism of Erythropoietin as an Antiapoptotic and Pro-Angiogenic Determinant in the Retina

Constant or intense light degenerates the retina and retinal pigment epithelial cells. Light generates reactive oxygen species and nitric oxide leading to initial reactions of retinal degeneration. Apoptosis is the primary mechanism of abnormal death of photoreceptors, retinal ganglion cells, or retinal pigment epithelium (RPE) in degenerative retinal diseases, including diabetic retinopathy and age-related macular degeneration. The current study evaluated the function of erythropoietin (EPO) on angiogenesis and apoptosis in the retina and RPE under oxidative stress. We determined the pro-angiogenic and antiapoptotic mechanism of EPO under stress conditions using a conditional EPO knockdown model using siRNA, EPO addition, proteomics, immunocytochemistry, and bioinformatic analysis. Our studies verified that EPO protected retinal cells from light-, hypoxia-, hyperoxia-, and hydrogen peroxide-induced apoptosis through caspase inhibition, whereas up-regulated angiogenic reactions through vascular endothelial growth factor (VEGF) and angiotensin pathway. We demonstrated that the EPO expression in the retina and subsequent serine/threonine/tyrosine kinase phosphorylations might be linked to oxidative stress response tightly to determining angiogenesis and apoptosis. Neuroprotective roles of EPO may involve the balance between antiapoptotic and pro-angiogenic signaling molecules, including BCL-xL, c-FOS, caspase-3, nitric oxide, angiotensin, and VEGF receptor. Our data indicate a new therapeutic application of EPO toward retinal degeneration based on the dual roles in apoptosis and angiogenesis at the molecular level under oxidative stress.

Targeting gut barrier dysfunction with phytotherapies: Effective strategy against chronic diseases

The intestinal epithelial layer serves as a physical and functional barrier between the microbe-rich lumen and immunologically active submucosa; it prevents systemic translocation of microbial pyrogenic products (e.g. endotoxin) that elicits immune activation upon translocation to the systemic circulation. Loss of barrier function has been associated with chronic 'low-grade' systemic inflammation which underlies pathogenesis of numerous no-communicable chronic inflammatory disease. Thus, targeting gut barrier dysfunction is an effective strategy for the prevention and/or treatment of chronic disease. This review intends to emphasize on the beneficial effects of herbal formulations, phytochemicals and traditional phytomedicines in attenuating intestinal barrier dysfunction. It also aims to provide a comprehensive understanding of intestinal-level events leading to a 'leaky-gut' and systemic complications mediated by endotoxemia. Additionally, a variety of detectable markers and diagnostic criteria utilized to evaluate barrier improving capacities of experimental therapeutics has been discussed. Collectively, this review provides rationale for targeting gut barrier dysfunction by phytotherapies for treating chronic diseases that are associated with endotoxemia-induced systemic inflammation.

NOX1 Regulates Collective and Planktonic Cell Migration: Insights From Patients With Pediatric-Onset IBD and NOX1 Deficiency

BACKGROUND

Genetic defects of pediatric-onset inflammatory bowel disease (IBD) provide critical insights into molecular factors controlling intestinal homeostasis. NOX1 has been recently recognized as a major source of reactive oxygen species (ROS) in human colonic epithelial cells. Here we assessed the functional consequences of human NOX1 deficiency with respect to wound healing and epithelial migration by studying pediatric IBD patients presenting with a stop-gain mutation in NOX1.

METHODS

Functional characterization of the NOX1 variant included ROS generation, wound healing, 2-dimensional collective chemotactic migration, single-cell planktonic migration in heterologous cell lines, and RNA scope and immunohistochemistry of paraffin-embedded patient tissue samples.

RESULTS

Using exome sequencing, we identified a stop-gain mutation in NOX1 (c.160C>T, p.54R>*) in patients with pediatric-onset IBD. Our studies confirmed that loss-of-function of NOX1 causes abrogated ROS activity, but they also provided novel mechanistic insights into human NOX1 deficiency. Cells that were NOX1-mutant showed impaired wound healing and attenuated 2-dimensional collective chemotactic migration. High-resolution microscopy of the migrating cell edge revealed a reduced density of filopodial protrusions with altered focal adhesions in NOX1-deficient cells, accompanied by reduced phosphorylation of p190A. Assessment of single-cell planktonic migration toward an epidermal growth factor gradient showed that NOX1 deficiency is associated with altered migration dynamics with loss of directionality and altered cell-cell interactions.

CONCLUSIONS

Our studies on pediatric-onset IBD patients with a rare sequence variant in NOX1 highlight that human NOX1 is involved in regulating wound healing by altering epithelial cytoskeletal dynamics at the leading edge and directing cell migration.

Transient Receptor Potential Channels and Inflammatory Bowel Disease

The transient receptor potential (TRP) cation channels are present in abundance across the gastrointestinal (GI) tract, serving as detectors for a variety of stimuli and secondary transducers for G-protein coupled receptors. The activation of TRP channels triggers neurogenic inflammation with related neuropeptides and initiates immune reactions by extra-neuronally regulating immune cells, contributing to the GI homeostasis. However, under pathological conditions, such as inflammatory bowel disease (IBD), TRP channels are involved in intestinal inflammation. An increasing number of human and animal studies have indicated that TRP channels are correlated to the visceral hypersensitivity (VHS) and immune pathogenesis in IBD, leading to an exacerbation or amelioration of the VHS or intestinal inflammation. Thus, TRP channels are a promising target for novel therapeutic methods for IBD. In this review, we comprehensively summarize the functions of TRP channels, especially their potential roles in immunity and IBD. Additionally, we discuss the contradictory findings of prior studies and offer new insights with regard to future research.

Analysis of free radical production capacity in mouse faeces and its possible application in evaluating the intestinal environment: a pilot study

Complex interplay between the intestinal environment and the host has attracted considerable attention and has been well studied with respect to the gut microbiome and metabolome. Oxygen free radicals such as superoxide and the hydroxyl radical (^•OH) are generated during normal cellular metabolism. They are toxic to both eukaryotic and prokaryotic cells and might thus affect intestinal homeostasis. However, the effect of oxygen free radicals on the intestinal environment has not been widely studied. Herein, we applied electron spin resonance spectroscopy with spin trapping reagents to evaluate oxygen free radical production capacity in the intestinal lumen and the faeces of mice. ^•OH was generated in faeces and lumens of the small and large intestines. There were no remarkable differences in ^•OH levels between faeces and the large intestine, suggesting that faeces can be used as alternative samples to estimate the ^•OH production capacity in the colonic contents. We then compared free radical levels in faecal samples among five different mouse strains (ddY, ICR, C57BL/6, C3H/HeJ, and BALB/c) and found that strain ddY had considerably higher levels than the other four strains. In addition, strain ddY was more susceptible to dextran sulphate sodium-induced colitis. These differences were possibly related to the relative abundance of the gut bacterial group Candidatus Arthromitus, which is known to modulate the host immune response. From these results, we suggest that the production capacity of oxygen free radicals in mouse faeces is associated with intestinal homeostasis.

Correlations between the serum bilirubin level and ulcerative colitis: a case-control study

OBJECTIVE

To analyze whether the bilirubin level is a protective factor in ulcerative colitis (UC) and the predictive value of the bilirubin level.

PATIENTS AND METHODS

We compared the bilirubin levels of 100 UC patients and 140 healthy controls as well as those of the subgroups of patients with different UC severities and then analyzed the correlation between the bilirubin level and UC and the correlations among the erythrocyte sedimentation rate (ESR), high sensitivity C-reactive protein (hs-CRP) level, UC severity, and bilirubin level. The predictive value of the bilirubin level for UC was determined by constructing a receiver operating characteristic (ROC) curve.

RESULTS

The mean levels of the total bilirubin (TBIL) and indirect bilirubin (IBIL) in the UC were lower in comparison with the mean TBIL and IBIL levels in the control group, and the TBIL and IBIL levels were significantly higher in the mild activity subgroup than in the moderate and severe activity subgroups (P<0.05). TBIL (P<0.001, 95% confidence interval: 0.794-0.918) and especially IBIL (P<0.001, 95% confidence interval: 0.646-0.809) were independent protective factors for UC. There were also significant differences in the serum ESR and hs-CRP levels between the patients with different UC severities (ESR=χ: 23.975; hs-CRP=χ: 26.626, P<0.001), and there was a positive correlation between these two parameters (ESR=r: 0.472; hs-CRP=r: 0.495, P<0.001). However, the TBIL and IBIL levels were correlated negatively with the ESR (rtotal=-0.429, rindirect=-0.461, P<0.001) and hs-CRP (rtotal=-0.289, rindirect=-0.25, P<0.05) levels. The ROC curve showed that the threshold values of TBIL and IBIL were 8.87 and 6.735 µmol/l, the areas under the maximum ROC curve were 0.664 and 0.716, the sensitivities were 0.450 and 0.61, and the specificities were 0.800 and 0.786, respectively.

CONCLUSION

TBIL and especially IBIL may be independent protective factors for UC because of their antioxidant and anti-inflammatory effects. A low level of IBIL has a moderate predictive value for UC, and an IBIL level less than 6.735 µmol/l can be used as a defining index for predicting UC.

Loss of C/EBPδ enhances apoptosis of intestinal epithelial cells and exacerbates experimental colitis in mice

Inflammatory bowel diseases (IBDs) are characterized by chronic inflammation involving intestinal tissue damage, which include ulcerative colitis and Crohn's disease as major entities. Accumulating evidence suggests that excessive apoptosis of intestinal epithelial cells (IECs) contributes to the development of IBD. It was recently reported that the transcription factor CCAAT/enhancer-binding protein delta (C/EBPδ) is involved in inflammation; however, its role in colitis remains unclear. Here, we found that C/EBPδ knockout mice showed enhanced susceptibility to dextran sodium sulfate (DSS)-induced colitis, a mouse model of IBD, which was associated with severe colonic inflammation and mucosal damage with increased IEC apoptosis. Additionally, DSS stimulation induced increased expression of pro-apoptotic BH3-only protein Bim in the colon of C/EBPδ knockout mice. Collectively, our findings demonstrate that C/EBPδ plays an essential role in suppressing DSS-induced colitis, likely by attenuating IEC apoptosis.

Thioredoxin-1 confines T cell alloresponse and pathogenicity in graft-versus-host disease

Oxidative stress is elevated in the recipients of allogeneic hematopoietic transplantation (allo-HCT) and likely contributes to the development of graft-versus-host disease (GVHD). GVHD is characterized by activation, expansion, cytokine production and migration of alloreactive donor T cells, and remains a major cause of morbidity and mortality after allo-HCT. Hence, strategies to limit oxidative stress in GVHD are highly desirable. Thioredoxin1 (Trx1) counteracts oxidative stress by scavenging reactive oxygen species (ROS) and regulating other enzymes that metabolize H2O2. The present study sought to elucidate the role of Trx1 in the pathophysiology of GVHD. Using murine and xenograft models of allogeneic bone marrow transplantation (allo-BMT) and genetic (human Trx1-transgenic, Trx1-Tg) as well as pharmacologic (human recombinant Trx1, RTrx1) strategies; we found that Trx1-Tg donor T cells or administration of the recipients with RTrx1 significantly reduced GVHD severity. Mechanistically, we observed RTrx1 reduced ROS accumulation and cytokine production of mouse and human T cells in response to alloantigen stimulation in vitro. In allo-BMT settings, we found that Trx1-Tg or RTrx1 decreased downstream signaling molecules including NFκB activation and T-bet expression, and reduced proliferation, IFN-γ production and ROS accumulation in donor T cells within GVHD target organs. More importantly, administration of RTrx1 did not impair the graft-versus-leukemia (GVL) effect. Taken together, the current work provides a strong rationale and demonstrates feasibility to target the ROS pathway, which can be readily translated into clinic.

Elevated ER stress exacerbates dextran sulfate sodium-induced colitis in PRDX4-knockout mice

BACKGROUND AND AIMS

Peroxiredoxin 4 (PRDX4), a secretory protein that is preferentially retained in the endoplasmic reticulum (ER), is encoded by a gene located on the X chromosome and highly expressed in colonic tissue. In this study, we investigated the role of PRDX4 by means of male PRDX4-knockout (PRDX4^-/y) mice in the development of intestinal inflammation using a dextran sulfate sodium (DSS)-induced colitis model.

MATERIALS AND METHODS

Acute colitis was induced with DSS (2.5% in drinking water) in wild-type (WT) and PRDX4^-/y male C57BL/6 mice. Histological and biochemical analyses were performed on the colonic tissues.

RESULTS

PRDX4 was mainly localized in the colonic epithelial cells in WT mice. The disease activity index (DAI) scores of PRDX4^-/y mice were significantly higher compared to those of WT mice. Specifically, PRDX4^-/y mice showed marked body weight loss and shortening of colon length compared to WT mice, whereas the myeloperoxidase levels were increased in PRDX4^-/y compared to WT mice. In addition, the mRNA expression levels of TNF-α and IFN-γ were significantly higher in the colonic mucosa of PRDX4^-/y compared to WT mice. Moreover, the levels of CHOP and activated caspase 3 were higher in the colonic tissues of PRDX4^-/y compared to WT mice following treatment with DSS. The ER also showed greater expansion in PRDX4^-/y than WT mice, which was consistent with severe ER stress under PRDX4 deficiency.

CONCLUSION

Our results demonstrated that the lack of PRDX4 aggravated the colonic mucosal damage induced by DSS. Because PRDX4 functions as an ER thiol oxidase as well as an antioxidant, DSS induced oxidative damage and ER stress to a greater degree in PRDX4^-/y than WT mice. These findings suggest that PRDX4 may represent a novel therapeutic molecule in intestinal inflammation.

Dietary Arginine Regulates Severity of Experimental Colitis and Affects the Colonic Microbiome

There is great interest in safe and effective alternative therapies that could benefit patients with inflammatory bowel diseases (IBD). L-arginine (Arg) is a semi-essential amino acid with a variety of physiological effects. In this context, our aim was to investigate the role of dietary Arg in experimental colitis. We used two models of colitis in C57BL/6 mice, the dextran sulfate sodium (DSS) model of injury and repair, and Citrobacter rodentium infection. Animals were given diets containing (1) no Arg (Arg0), 6.4 g/kg (ArgNL), or 24.6 g/kg Arg (ArgHIGH); or (2) the amino acids downstream of Arg: 28 g/kg L-ornithine (OrnHIGH) or 72 g/kg L-proline (ProHIGH). Mice with DSS colitis receiving the ArgHIGH diet had increased levels of Arg, Orn, and Pro in the colon and improved body weight loss, colon length shortening, and histological injury compared to ArgNL and Arg0 diets. Histology was improved in the ArgNL vs. Arg0 group. OrnHIGH or ProHIGH diets did not provide protection. Reduction in colitis with ArgHIGH diet also occurred in C. rodentium-infected mice. Diversity of the intestinal microbiota was significantly enhanced in mice on the ArgHIGH diet compared to the ArgNL or Arg0 diets, with increased abundance of Bacteroidetes and decreased Verrucomicrobia. In conclusion, dietary supplementation of Arg is protective in colitis models. This may occur by restoring overall microbial diversity and Bacteroidetes prevalence. Our data provide a rationale for Arg as an adjunctive therapy in IBD.

The microbiome and immunodeficiencies: Lessons from rare diseases

Primary immunodeficiencies (PIDs) are inherited disorders of the immune system, associated with a considerable increase in susceptibility to infections. PIDs can also predispose to malignancy, inflammation and autoimmunity. There is increasing awareness that some aspects of the immune dysregulation in PIDs may be linked to intestinal microbiota. Indeed, the gut microbiota and its metabolites have been shown to influence immune functions and immune homeostasis both locally and systemically. Recent studies have indicated that genetic defects causing PIDs lead to perturbations in the conventional mechanisms underlying homeostasis in the gut, resulting in poor immune surveillance at the intestinal barrier, which associates with altered intestinal permeability and bacterial translocation. Consistently, a substantial proportion of PID patients presents with clinically challenging IBD-like pathology. Here, we describe the current body of literature reporting on dysbiosis of the gut microbiota in different PIDs and how this can be either the result or cause of immune dysregulation. Further, we report how infections in PIDs enhance pathobionts colonization and speculate how, in turn, pathobionts may be responsible for increased disease susceptibility and secondary infections in these patients. The potential relationship between the microbial composition in the intestine and other sites, such as the oral cavity and skin, is also highlighted. Finally, we provide evidence, in preclinical models of PIDs, for the efficacy of microbiota manipulation to ameliorate disease complications, and suggest that the potential use of dietary intervention to correct dysbiotic flora in PID patients may hold promise.

Gastrointestinal Complications in Chronic Granulomatous Disease

Almost half of patients with chronic granulomatous disease (CGD) suffer from gastrointestinal (GI) inflammation, the pathogenesis of which is complex and multifactorial. As a result, the management of CGD-associated GI inflammation remains challenging due to its chronicity and difficulty in managing the simultaneous need for immunomodulation with increased susceptibility to infection. In order to contextualize prospective treatment interventions for CGD-associated GI inflammation, we have reviewed the clinical presentation, pathogenesis and current management of this disease. Increased understanding of the role of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex 2 (NOX2)-derived reactive oxygen species (ROS) in inflammatory bowel disease (IBD) will likely reveal novel targets for therapeutic intervention.

Redox-Sensing Iron-Sulfur Cluster Regulators

SIGNIFICANCE

Iron-sulfur cluster proteins carry out multiple functions, including as regulators of gene transcription/translation in response to environmental stimuli. In all known cases, the cluster acts as the sensory module, where the inherent reactivity/fragility of iron-sulfur clusters with small/redox-active molecules is exploited to effect conformational changes that modulate binding to DNA regulatory sequences. This promotes an often substantial reprogramming of the cellular proteome that enables the organism or cell to adapt to, or counteract, its changing circumstances. Recent Advances: Significant progress has been made recently in the structural and mechanistic characterization of iron-sulfur cluster regulators and, in particular, the O₂ and NO sensor FNR, the NO sensor NsrR, and WhiB-like proteins of Actinobacteria. These are the main focus of this review.

CRITICAL ISSUES

Striking examples of how the local environment controls the cluster sensitivity and reactivity are now emerging, but the basis for this is not yet fully understood for any regulatory family.

FUTURE DIRECTIONS

Characterization of iron-sulfur cluster regulators has long been hampered by a lack of high-resolution structural data. Although this still presents a major future challenge, recent advances now provide a firm foundation for detailed understanding of how a signal is transduced to effect gene regulation. This requires the identification of often unstable intermediate species, which are difficult to detect and may be hard to distinguish using traditional techniques. Novel approaches will be required to solve these problems.

Mucus-penetrating budesonide nanosuspension enema for local treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory gastrointestinal disorder that affects more than 1 million individuals in the USA. Local therapy with enema formulations, such as micronized budesonide (Entocort®), is a common strategy for treating patients with distally active IBD. However, we hypothesize that micronized particulates are too large to effectively penetrate colorectal mucus, limiting the extent of drug delivery to affected tissues prior to clearance. Here, we describe the development of a budesonide nanosuspension (NS) with the appropriate surface coating and size to enhance penetration of colorectal mucus and ulcerated colorectal tissues. We demonstrate that model fluorescent polystyrene (PS) particles ∼200 nm in size with a muco-inert Pluronic F127 coating provide enhanced mucosal distribution and tissue penetration in mice with trinitrobenzenesulfonic acid (TNBS)-induced IBD compared to model 2 μm PS particles coated with polyvinylpyrollidone (PVP), the stabilizer used in the clinical micronized budesonide formulation. We then used a wet-milling process to develop a budesonide NS formulation with a muco-inert Pluronic F127 coating (particle size ∼230 nm), as well as a budesonide microsuspension (MS) stabilized with PVP (particle size ∼2 μm). Using an acute TNBS mouse model of IBD, we show that daily budesonide NS enema treatment resulted in a significant reduction in the macroscopic (decreased colon weight) and microscopic (histology score) symptoms of IBD compared to untreated controls or mice treated daily with the budesonide MS enema. Further, we show that the budesonide NS enema treated mice had a significantly reduced number of inflammatory macrophages and IL-β producing CD11b + cells in colon tissue compared to untreated controls or mice treated with the budesonide MS enema. We conclude that the nano-size and muco-inert coating allowed for enhanced local delivery of budesonide, and thus, a more significant impact on local colorectal tissue inflammation.

Effect of Milk Fermented with Lactobacillus fermentum on the Inflammatory Response in Mice

Currently, the effect of fermented milk on the T-helper 17 response in inflammatory bowel diseases (IBDs) is unknown. The aim of the present study was to evaluate the effect of milks fermented with Lactobacillus fermentum on the Th1/Th17 response in a murine model of mild IBD. Exopolysaccharide (EPS), lactic acid (LA), and total protein (TP) contents and bacterial concentration were determined. Male C57Bl/6 mice intragastrically received either raw (FM) or pasteurized (PFM) fermented milk before and during a dextran sulfate infusion protocol. Blood, spleen, and colon samples were collected at Weeks 6 and 10. IL-6, IL-10, and TNFα were determined in serum, and IL-17, IL-23, and IFNγ were determined in intestinal mucosa and serum. The FM groups did not differ in cell concentration, LA, or TP content (p > 0.05); FM-J28 had the highest EPS content. Spleen weight and colon length did not differ among the FM groups (p > 0.05). In the FM-J20 and PFM-J20 groups, IL-17 and IFNγ decreased, and the IL-10 concentration was enhanced (p < 0.05) at Week 6. IL-6, TNFα, IL-23, and IFNγ did not differ in serum and mucosa (p > 0.05), and IL-17 was lowest in FM-J28 and FM-J20. Therefore, FM appears to potentially play a role in decreasing the Th17 response. However, further studies are needed to elucidate the FM-mediated anti-inflammatory mechanisms in IBD.

NADPH oxidases and ROS signaling in the gastrointestinal tract

Reactive oxygen species (ROS), initially categorized as toxic by-products of aerobic metabolism, have often been called a double-edged sword. ROS are considered indispensable when host defense and redox signaling is concerned and a threat in inflammatory or degenerative diseases. This generalization does not take in account the diversity of oxygen metabolites being generated, their physicochemical characteristics and their production by distinct enzymes in space and time. NOX/DUOX NADPH oxidases are the only enzymes solely dedicated to ROS production and the prime ROS producer for intracellular and intercellular communication due to their widespread expression and intricate regulation. Here we discuss new insights of how NADPH oxidases act via ROS as multifaceted regulators of the intestinal barrier in homeostasis, infectious disease and intestinal inflammation. A closer look at monogenic VEOIBD and commensals as ROS source supports the view of H₂O₂ as key beneficial messenger in the barrier ecosystem.

Host-Derived Nitric Oxide and Its Antibacterial Effects in the Urinary Tract

Urinary tract infection (UTI) is one of the most common bacterial infections in humans, and the majority are caused by uropathogenic Escherichia coli (UPEC). The rising antibiotic resistance among UPEC and the frequent failure of antibiotics to effectively treat recurrent UTI and catheter-associated UTI motivate research on alternative ways of managing UTI. Abundant evidence indicates that the toxic radical nitric oxide (NO), formed by activation of the inducible nitric oxide synthase, plays an important role in host defence to bacterial infections, including UTI. The major source of NO production during UTI is from inflammatory cells, especially neutrophils, and from the uroepithelial cells that are known to orchestrate the innate immune response during UTI. NO and reactive nitrogen species have a wide range of antibacterial targets, including DNA, heme proteins, iron-sulfur clusters, and protein thiol groups. However, UPEC have acquired a variety of defence mechanisms for protection against NO, such as the NO-detoxifying enzyme flavohemoglobin and the NO-tolerant cytochrome bd-I respiratory oxidase. The cytotoxicity of NO-derived intermediates is nonspecific and may be detrimental to host cells, and a balanced NO production is crucial to maintain the tissue integrity of the urinary tract. In this review, we will give an overview of how NO production from host cells in the urinary tract is activated and regulated, the effect of NO on UPEC growth and colonization, and the ability of UPEC to protect themselves against NO. We also discuss the attempts that have been made to develop NO-based therapeutics for UTI treatment.

Cardiotrophin-1 attenuates experimental colitis in mice

Cardiotrophin-1 (CT-1) holds potent anti-inflammatory, cytoprotective, and anti-apoptotic effects in the liver, kidneys, and heart. In the present study, the role of endogenous CT-1 and the effect of exogenous CT-1 were evaluated in experimental ulcerative colitis. Colitis was induced in CT-1 knockout and wild-type (WT) mice by administration of dextran sulphate sodium (DSS) in the drinking water during 7 days. CT-1 knockout mice showed higher colon damage and disease severity than WT mice. In addition, CT-1 (200 µg/kg/day, iv) or vehicle (as control) was administered during 3 days to WT, colitic mice, starting on day 4 after initiation of DSS. Disease activity index (DAI), inflammatory markers (tumor necrosis factor α (TNF-α), INFγ, IL-17, IL-10, inducible nitric oxide synthase (iNOS)), colon damage, apoptosis (cleaved caspase 3), nuclear factor κB (NFκB) and STAT-3 activation, and bacterial translocation were measured. Compared with mice treated with DSS, mice also treated with exogenous CT-1 showed lower colon damage, DAI, plasma levels of TNFα, colon expression of TNF-α, INFγ, IL-17, iNOS and cleaved caspase 3, higher NFκB and signal transducer and activator of transcription 3 (STAT3) pathways activation, and absence of bacterial translocation. We conclude that endogenous CT-1 plays a role in the defense and repair response of the colon against ulcerative lesions through an anti-inflammatory and anti-apoptotic effect. Supplementation with exogenous CT-1 ameliorates disease symptoms, which opens a potentially new therapeutic strategy for ulcerative colitis.

Redox-sensing iron-sulfur cluster regulators

SIGNIFICANCE

Iron-sulfur cluster proteins carry out a wide range of functions, including as regulators of gene transcription/translation in response to environmental stimuli. In all known cases, the cluster acts as the sensory module, where the inherent reactivity/fragility of iron-sulfur clusters towards small/redox active molecules is exploited to effect conformational changes that modulate binding to DNA regulatory sequences. This promotes an often substantial re-programming of the cellular proteome that enables the organism or cell to adapt to, or counteract, its changing circumstances. Recent Advances. Significant progress has been made recently in the structural and mechanistic characterization of iron-sulfur cluster regulators and, in particular, the O2 and NO sensor FNR, the NO sensor NsrR, and WhiB-like proteins of Actinobacteria. These are the main focus of this review.

CRITICAL ISSUES

Striking examples of how the local environment controls the cluster sensitivity and reactivity are now emerging, but the basis for this is not yet fully understood for any regulatory family.

FUTURE DIRECTIONS

Characterization of iron-sulfur cluster regulators has long been hampered by a lack of high resolution structural data. Though this still presents a major future challenge, recent advances now provide a firm foundation for detailed understanding of how a signal is transduced to effect gene regulation. This requires the identification of often unstable intermediate species, which are difficult to detect and may be hard to distinguish using traditional techniques. Novel approaches will be required to solve these problems.

Equine Intestinal Mucosal Pathobiology

The equine intestinal mucosa is intimately involved in maintaining homeostasis both on a systemic level by controlling extracellular fluid movement and at the local level to maintain barrier function. Horses are particularly susceptible to the clinical syndrome of colic, with the most severe cases involving strangulating obstruction that induces ischemia. Because of the mucosal vascular architecture, the mucosal epithelium is particularly susceptible to ischemic injury. The potential for reperfusion injury has been investigated and found to play a minimal role. However, inflammation does affect mucosal repair. Mechanisms of repair, including villus contraction, epithelial restitution, and tight junction closure, are critical to reforming the mucosal barrier. Nonsteroidal anti-inflammatory drugs have an impact on this repair, particularly at the level of the tight junctions. Completion of mucosal regeneration requires proliferation, which is now being actively studied in equine enteroids. All of these aspects of equine mucosal pathobiology are reviewed in depth.

Reactivation of Intestinal Inflammation Is Suppressed by Catestatin in a Murine Model of Colitis via M1 Macrophages and Not the Gut Microbiota

While there is growing awareness of a relationship between chromogranin-A (CHGA) and susceptibility to inflammatory conditions, the role of human catestatin [(hCTS); CHGA_352–67] in the natural history of established inflammatory bowel disease is not known. Recently, using two different experimental models, we demonstrated that hCTS-treated mice develop less severe acute colitis. We have also shown the implication of the macrophages in this effect. The aims of this study were to determine (1) whether hCTS treatment could attenuate the reactivation of inflammation in adult mice with previously established chronic colitis; (2) whether this effect is mediated through macrophages or the gut microbiota. Quiescent colitis was induced in 7–8-week-old C57BL6 mice using four cycles (2–4%) of dextran sulfate sodium. hCTS (1.5 mg/kg/day) treatment or vehicle started 2 days before the last induction of colitis and continuing for 7 days. At sacrifice, macro- and microscopic scores were determined. Colonic pro-inflammatory cytokines [interleukin (IL)-6, IL-1β, and TNF- α], anti-inflammatory cytokines (IL-10, TGF- β), classically activated (M1) (iNOS, Mcp1), and alternatively activated (M2) (Ym1, Arg1) macrophages markers were studied using ELISA and/or RT-qPCR. In vitro, peritoneal macrophages isolated from naïve mice and treated with hCTS (10⁻⁵ M, 12 h) were exposed to either lipopolysaccharide (100 ng/ml, 12 h) to polarize M1 macrophages or to IL-4/IL-13 (20 ng/ml) to polarize M2 macrophages. M1/M2 macrophage markers along with cytokine gene expression were determined using RT-qPCR. Feces and mucosa-associated microbiota (MAM) samples were collected, and the V4 region of 16 s rRNA was sequenced. Micro- and macroscopic scores, colonic IL-6, IL-1β, TNF- α, and M1 macrophages markers were significantly decreased in the hCTS-treated group. Treatment did not have any effect on colonic IL-10, TGF-β, and M2 markers nor modified the bacterial richness, diversity, or the major phyla in colitic fecal and MAM samples. In vitro, pro-inflammatory cytokines levels, as well as their gene expression, were significantly reduced in hCTS-treated M1 macrophages. hCTS treatment did not affect M2 macrophage markers. These findings suggest that hCTS treatment attenuates the severity of inflammatory relapse through the modulation of the M1 macrophages and the release of pro-inflammatory cytokines.

Aronia Berry Extract Ameliorates the Severity of Dextran Sodium Sulfate-Induced Ulcerative Colitis in Mice

Inflammatory bowel disease, including Crohn's disease and ulcerative colitis (UC), is a group of inflammatory conditions of the colon and small intestine. UC is a chronic inflammatory disorder of the colon and rectum that includes intervals of acute exacerbation. Although recent studies have suggested that proinflammatory cytokines might have initiated the inflammatory responses in UC, its etiology remains unclear. Aronia berries are rich in dietary polyphenols such as phenolic acids, anthocyanins, flavonoids, and proanthocyanidins with various health benefits, including antioxidant, anti-inflammatory, and antiaging activities. The objective of this study was to determine whether Aronia berry can be an effective intervention for the treatment of UC. BALB/c mice were administered 5% dextran sulfate sodium (DSS) to induce UC. They were then given Aronia berry extracts at concentrations of 10 or 100 mg/kg. During the induction of UC, the expression levels of nuclear factor-kappa B were increased in colonic epithelial cells and immune cells, leading to increased proinflammatory cytokine levels. Aronia berry extract significantly improved the clinical signs of DSS-induced UC, including body weight loss, colon length shortening, and disease activity index increase, with histological markers of colon injury. Furthermore, oral administration of Aronia berry extract inhibited prostaglandin E₂ production in DSS-induced colitis and decreased the levels of nitric oxide, interleukin-6, and tumor necrosis factor-α in lipopolysaccharide-stimulated macrophages. These results suggest that Aronia berry extract could efficiently ameliorate clinical signs and inflammatory mediators of UC. Therefore, Aronia berry might be a promising natural treatment for UC.

ROS in gastrointestinal inflammation: Rescue Or Sabotage?

The intestine is composed of many distinct cell types that respond to commensal microbiota or pathogens with immune tolerance and proinflammatory signals respectively. ROS produced by mucosa-resident cells or by newly recruited innate immune cells are essential for antimicrobial responses and regulation of signalling pathways including processes involved in wound healing. Impaired ROS production due to inactivating patient variants in genes encoding NADPH oxidases as ROS source has been associated with Crohn's disease and pancolitis, whereas overproduction of ROS due to up-regulation of oxidases or altered mitochondrial function was linked to ileitis and ulcerative colitis. Here, we discuss recent advances in our understanding of how maintaining a redox balance is crucial to preserve gut homeostasis.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Determinants of hypoxia-inducible factor activity in the intestinal mucosa

The intestinal mucosa is exposed to fluctuations in oxygen levels due to constantly changing rates of oxygen demand and supply and its juxtaposition with the anoxic environment of the intestinal lumen. This frequently results in a state of hypoxia in the healthy mucosa even in the physiologic state. Furthermore, pathophysiologic hypoxia (which is more severe and extensive) is associated with chronic inflammatory diseases including inflammatory bowel disease (IBD). The hypoxia-inducible factor (HIF), a ubiquitously expressed regulator of cellular adaptation to hypoxia, is central to both the adaptive and the inflammatory responses of cells of the intestinal mucosa in IBD patients. In this review, we discuss the microenvironmental factors which influence the level of HIF activity in healthy and inflamed intestinal mucosae and the consequences that increased HIF activity has for tissue function and disease progression.

Electrochemical reverse engineering: A systems-level tool to probe the redox-based molecular communication of biology

The intestine is the site of digestion and forms a critical interface between the host and the outside world. This interface is composed of host epithelium and a complex microbiota which is "connected" through an extensive web of chemical and biological interactions that determine the balance between health and disease for the host. This biology and the associated chemical dialogues occur within a context of a steep oxygen gradient that provides the driving force for a variety of reduction and oxidation (redox) reactions. While some redox couples (e.g., catecholics) can spontaneously exchange electrons, many others are kinetically "insulated" (e.g., biothiols) allowing the biology to set and control their redox states far from equilibrium. It is well known that within cells, such non-equilibrated redox couples are poised to transfer electrons to perform reactions essential to immune defense (e.g., transfer from NADH to O₂ for reactive oxygen species, ROS, generation) and protection from such oxidative stresses (e.g., glutathione-based reduction of ROS). More recently, it has been recognized that some of these redox-active species (e.g., H₂O₂) cross membranes and diffuse into the extracellular environment including lumen to transmit redox information that is received by atomically-specific receptors (e.g., cysteine-based sulfur switches) that regulate biological functions. Thus, redox has emerged as an important modality in the chemical signaling that occurs in the intestine and there have been emerging efforts to develop the experimental tools needed to probe this modality. We suggest that electrochemistry provides a unique tool to experimentally probe redox interactions at a systems level. Importantly, electrochemistry offers the potential to enlist the extensive theories established in signal processing in an effort to "reverse engineer" the molecular communication occurring in this complex biological system. Here, we review our efforts to develop this electrochemical tool for in vitro redox-probing.

Anti-inflammatory effects of an ethanol extract of Aster glehni via inhibition of NF-κB activation in mice with DSS-induced colitis

Aster glehnihad a protective effect on colonic inflammation by inactivation of NF-κB and the modulation of pathophysiological activity during DSS-induced colitis.

Rocuronium Bromide Inhibits Inflammation and Pain by Suppressing Nitric Oxide Production and Enhancing Prostaglandin E2 Synthesis in Endothelial Cells

Purpose

Rocuronium bromide is a nondepolarizing neuromuscular blocking drug and has been used as an adjunct for relaxation or paralysis of the skeletal muscles, facilitation of endotracheal intubation, and improving surgical conditions during general anesthesia. However, intravenous injection of rocuronium bromide induces injection pain or withdrawal movement. The exact mechanism of rocuronium bromide-induced injection pain or withdrawal movement is not yet understood. We investigated whether rocuronium bromide treatment is involved in the induction of inflammation and pain in vascular endothelial cells.

Methods

For this study, calf pulmonary artery endothelial (CPAE) cells were used, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, Western blot, nitric oxide detection, and prostaglandin E₂ immunoassay were conducted.

Results

Rocuronium bromide treatment inhibited endothelial nitric oxide synthase and suppressed nitric oxide production in CPAE cells. Rocuronium bromide activated cyclooxygenase-2, inducible nitric oxide synthase and increased prostaglandin E₂ synthesis in CPAE cells.

Conclusions

Rocuronium bromide induced inflammation and pain in CPAE cells. Suppressing nitric oxide production and enhancing prostaglandin E₂ synthesis might be associated with rocuronium bromide-induced injection pain or withdrawal movement.

Role of glutamatergic neurotransmission in the enteric nervous system and brain-gut axis in health and disease

Several studies have been carried out in the last 30 years in the attempt to clarify the possible role of glutamate as a neurotransmitter/neuromodulator in the gastrointestinal tract. Such effort has provided immunohistochemical, biomolecular and functional data suggesting that the entire glutamatergic neurotransmitter machinery is present in the complex circuitries of the enteric nervous system (ENS), which participates to the local coordination of gastrointestinal functions. Glutamate is also involved in the regulation of the brain-gut axis, a bi-directional connection pathway between the central nervous system (CNS) and the gut. The neurotransmitter contributes to convey information, via afferent fibers, from the gut to the brain, and to send appropriate signals, via efferent fibers, from the brain to control gut secretion and motility. In analogy with the CNS, an increasing number of studies suggest that dysregulation of the enteric glutamatergic neurotransmitter machinery may lead to gastrointestinal dysfunctions. On the whole, this research field has opened the possibility to find new potential targets for development of drugs for the treatment of gastrointestinal diseases. The present review analyzes the more recent literature on enteric glutamatergic neurotransmission both in physiological and pathological conditions, such as gastroesophageal reflux, gastric acid hypersecretory diseases, inflammatory bowel disease, irritable bowel syndrome and intestinal ischemia/reperfusion injury.