Influence of NADPH oxidase on inflammatory response in primary intestinal epithelial cells in patients with ulcerative colitis

Low dose radiation upregulates Ras/p38 and NADPH oxidase in mouse colon two months after exposure

BACKGROUND

Exposure to ionizing is known to cause persistent cellular oxidative stress and NADPH oxidase (Nox) is a major source of cellular oxidant production. Chronic oxidative stress is associated with a myriad of human diseases including gastrointestinal cancer. However, the roles of NADPH oxidase in relation of long-term oxidative stress in colonic epithelial cells after radiation exposure are yet to be clearly established.

METHODS AND RESULTS

Mice were exposed either to sham or to 0.5 Gy γ radiation, and NADPH oxidase, oxidative stress, and related signaling pathways were assessed in colon samples 60 days after exposure. Radiation exposure led to increased expression of colon-specific NADPH oxidase isoform, Nox1, as well as upregulation of its modifiers such as Noxa1 and Noxo1 at the mRNA and protein level. Co-immunoprecipitation experiments showed enhanced binding of Rac1, an activator of NADPH oxidase, to Nox1. Increased 4-hydroxynonenal, 8-oxo-dG, and γH2AX along with higher protein carbonylation levels suggest increased oxidative stress after radiation exposure. Immunoblot analysis demonstrates upregulation of Ras/p38 pathway, and Gata6 and Hif1α after irradiation. Increased staining of β-catenin, cyclinD1, and Ki67 after radiation was also observed.

CONCLUSIONS

In summary, data show that exposure to a low dose of radiation was associated with upregulation of NADPH oxidase and its modifiers along with increased Ras/p38/Gata6 signaling in colon. When considered along with oxidative damage and proliferative markers, our observations suggest that the NADPH oxidase pathway could be playing a critical role in propagating long-term oxidative stress after radiation with implications for colon carcinogenesis.

Insights into diet-associated oxidative pathomechanisms in inflammatory bowel disease and protective effects of functional amino acids

There has been a substantial rise in the incidence and prevalence of clinical patients presenting with inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis. Accumulating evidence has corroborated the view that dietary factors (particularly diets with high levels of saturated fat or sugar) are involved in the development and progression of IBD, which is predominately associated with changes in the composition of the gut microbiota and an increase in the generation of reactive oxygen species. Notably, the ecological imbalance of the gut microbiome exacerbates oxidative stress and inflammatory responses, leading to perturbations of the intestinal redox balance and immunity, as well as mucosal integrity. Recent findings have revealed that functional amino acids, including L-glutamine, glycine, L-arginine, L-histidine, L-tryptophan, and hydroxyproline, are effectively implicated in the maintenance of intestinal redox and immune homeostasis. These amino acids and their metabolites have oxygen free-radical scavenging and inflammation-relieving properties, and they participate in modulation of the microbial community and the metabolites in the gut. The principal focus of this article is a review of recent advances in the oxidative pathomechanisms of IBD development and progression in relation to dietary factors, with a particular emphasis on the redox and signal transduction mechanisms of host cells in response to unbalanced diets and enterobacteria. In addition, an update on current understanding of the protective effects of functional amino acids against IBD, together with the underlying mechanisms for this protection, have been provided.

Zinc and Selenium in Inflammatory Bowel Disease: Trace Elements with Key Roles?

Inflammatory bowel disease (IBD) is a chronic inflammatory condition that may emerge at a young age and often lasts for life. It often goes through phases of recurrence and remission and has a devastating effect on quality of life. The exact etiology of the disease is still unclear, but it appears that an inappropriate immune response to intestinal flora bacteria in people with a genetic predisposition may cause the disease. Managing inflammatory bowel disease is still a serious challenge. Oxidative stress and free radicals appear to be involved in the pathogenesis of this disease, and a number of studies have suggested the use of antioxidants as a therapeutic approach. The antioxidant and anti-inflammatory properties of some trace elements have led some of the research to focus on studying these trace elements in inflammatory bowel disease. Zinc and selenium are among the most important trace elements that have significant anti-inflammatory and antioxidant properties. Some studies have shown the importance of these trace elements in inflammatory bowel disease. In this review, we have attempted to provide a comprehensive overview of the findings of these studies and to gather current knowledge about the association of these trace elements with the inflammatory process and inflammatory bowel disease.

Evaluation of Porcine Intestinal Epitheliocytes as an In vitro Immunoassay System for the Selection of Probiotic Bifidobacteria to Alleviate Inflammatory Bowel Disease

The use of in vitro systems that allow efficient selection of probiotic candidates with immunomodulatory properties could significantly minimize the use of experimental animals. In this work, we generated an in vitro immunoassay system based on porcine intestinal epithelial (PIE) cells and dextran sodium sulfate (DSS) administration that could be useful for the selection and characterization of potential probiotic strains to be used in inflammatory bowel disease (IBD) patients. Our strategy was based on two fundamental pillars: on the one hand, the capacity of PIE cells to create a monolayer by attaching to neighboring cells and efficiently mount inflammatory responses and, on the other hand, the use of two probiotic bifidobacteria strains that have been characterized in terms of their immunomodulatory capacities, particularly in mouse IBD models and patients. Our results demonstrated that DSS administration can alter the epithelial barrier created in vitro by PIE cells and induce a potent inflammatory response, characterized by increases in the expression levels of several inflammatory factors including TNF-α, IL-1α, CCL4, CCL8, CCL11, CXCL5, CXCL9, CXCL10, SELL, SELE, EPCAM, VCAM, NCF2, and SAA2. In addition, we demonstrated that Bifidobacterium breve M-16V and B. longum BB536 are able to regulate the C-jun N-terminal kinase (JNK) intracellular signalling pathway, reducing the DSS-induced alterations of the in vitro epithelial barrier and differentially regulating the inflammatory response in a strain-dependent fashion. The good correlation between our in vitro findings in PIE cells and previous studies in animal models and IBD patients shows the potential value of our system to select new probiotic candidates in an efficient way.

Anti-Inflammatory Effects of Hyperbaric Oxygenation during DSS-Induced Colitis in BALB/c Mice Include Changes in Gene Expression of HIF-1α, Proinflammatory Cytokines, and Antioxidative Enzymes

Reactive oxygen species (ROS) and nitrogen species have an indispensable role in regulating cell signalling pathways, including transcriptional control via hypoxia inducible factor-1α (HIF-1α). Hyperbaric oxygenation treatment (HBO₂) increases tissue oxygen content and leads to enhanced ROS production. In the present study DSS-induced colitis has been employed in BALB/c mice as an experimental model of gut mucosa inflammation to investigate the effects of HBO₂ on HIF-1α, antioxidative enzyme, and proinflammatory cytokine genes during the colonic inflammation. Here we report that HBO₂ significantly reduces severity of DSS-induced colitis, as evidenced by the clinical features, histological assessment, impaired immune cell expansion and mobilization, and reversal of IL-1β, IL-2, and IL-6 gene expression. Gene expression and antioxidative enzyme activity were changed by the HBO₂ and the inflammatory microenvironment in the gut mucosa. Strong correlation of HIF-1α mRNA level to GPx1, SOD1, and IL-6 mRNA expression suggests involvement of HIF-1α in transcriptional regulation of these genes during colonic inflammation and HBO₂. This is further confirmed by a strong correlation of HIF-1α with known target genes VEGF and PGK1. Results demonstrate that HBO₂ has an anti-inflammatory effect in DSS-induced colitis in mice, and this effect is at least partly dependent on expression of HIF-1α and antioxidative genes.

Hypothalamic paraventricular nucleus stimulation reduces intestinal injury in rats with ulcerative colitis

AIM: To investigate the effect and mechanism of stimulation of the hypothalamic paraventricular nucleus with glutamate acid in rats with ulcerative colitis (UC).

METHODS: The rats were anesthetized with 10% chloral hydrate via abdominal injection and treated with an equal volume of TNBS + 50% ethanol enema, injected into the upper section of the anus with the tail facing up. Colonic damage scores were calculated after injecting a certain dose of glutamic acid into the paraventricular nucleus (PVN), and the effect of the nucleus tractus solitarius (NTS) and vagus nerve in alleviating UC injury through chemical stimulation of the PVN was observed in rats. Expression changes of C-myc, Apaf-1, caspase-3, interleukin (IL)-6, and IL-17 during the protection against UC injury through chemical stimulation of the PVN in rats were detected by Western blot. Malondialdehyde (MDA) content and superoxide dismutase (SOD) activity in colon tissues of rats were measured by colorimetric methods.

RESULTS: Chemical stimulation of the PVN significantly reduced UC in rats in a dose-dependent manner. The protective effects of the chemical stimulation of the PVN on rats with UC were eliminated after chemical damage to the PVN. After glutamate receptor antagonist kynurenic acid was injected into the PVN, the protective effects of the chemical stimulation of the PVN were eliminated in rats with UC. After AVP-Vl receptor antagonist ([Deamino-penl, val4, D-Arg8]-vasopressin) was injected into NTS or bilateral chemical damage to NTS, the protective effect of the chemical stimulation of PVN on UC was also eliminated. After chemical stimulation of the PVN, SOD activity increased, MDA content decreased, C-myc protein expression significantly increased, caspase-3 and Apaf-1 protein expression significantly decreased, and IL-6 and IL-17 expression decreased in colon tissues in rats with UC.

CONCLUSION: Chemical stimulation of the hypothalamic PVN provides a protective effect against UC injury in rats. Hypothalamic PVN, NTS and vagus nerve play key roles in this process.

Oxidative Stress and DNA Damage: Implications in Inflammatory Bowel Disease

This review will focus on published human studies on oxidative stress and DNA damage in inflammatory bowel disease (IBD), both ulcerative colitis and Crohn's disease, assessing their role in the pathophysiology of these diseases. Search was performed over PubMed and ScienceDirect databases to identify relevant bibliography, using keywords including "oxidative stress," "DNA damage," "IBD," and "oxidative DNA damage." Whether as cause or effect, mechanisms underlying oxidative stress have the potential to condition the course of various pathologies, particularly those driven by inflammatory scenarios. IBDs are chronic inflammatory relapsing conditions. Oxidative stress has been associated with some of the characteristic clinical features exhibited in IBD, namely tissue injury and fibrosis, and also to the ulcerative colitis-associated colorectal cancer. The possible influence of oxidative stress over therapeutic behavior and response, as well as their contribution to the oxidative burden and consequences, is also addressed. Due to the high prevalence and incidence of IBD worldwide, and also to its associated morbidity, complications, and disease and treatment costs, it is of paramount importance to better understand the pathophysiology of these diseases.

Digital imaging of colon tissue: method for evaluation of inflammation severity by spatial frequency features of the histological images

BACKGROUND

The efficacy of histological analysis of colon sections used for evaluation of inflammation severity can be improved by means of digital imaging giving quantitative estimates of main diagnostic features. The aim of this study was to reveal most valuable diagnostic features reflecting inflammation severity in colon and elaborate the evaluation method for computer-aided diagnostics.

METHODS

Tissue specimens from 24 BALB/c mice and 15 patients were included in the study. Chronic and acute colon inflammation in mice was induced by oral administration of dextran sulphate sodium (DSS) solution, while mice in the control group did not get DSS. Human samples of inflamed colon tissue were obtained from patients with ulcerative colitis (n = 6). Non-inflamed colon tissue of control subjects (n = 9) was obtained from patients with irritable bowel syndrome or functional obstipation. Analysis of morphological changes in mice and human colon mucosa was performed using 4-μm haematoxylin-eosin (HE) sections. The features reflecting morphological changes in the images of colon mucosa were calculated by convolution of Gabor filter bank and array of pixel values. All features were generalized by calculating mean, histogram skewness and entropy of every image response. Principal component analysis was used to construct optimal representation of morphological changes.

RESULTS

First principal component (PC1) was representing the major part of features variation (97 % in mice and 71 % in human specimens) and was selected as a measure of inflammation severity. Validation of new measure was performed by means of custom-made software realizing double blind comparison of differences in PC1 with expert's opinion about inflammation severity presented in two compared pictures. Overall accuracy of 80 % for mice and 67 % for human was reached.

CONCLUSION

Principal component analysis of spatial frequency features of histological images may provide continuous scale estimation of inflammation severity of colon tissue.

Significance of NADPH oxidases Nox1 and Duox2 expression in mouse colitis

AIM: To investigate the significance of expression of NADPH oxidases Nox1 and Duox2 in the pathogenesis of mouse colitis.

METHODS: Six-to-eight-week-old C57BL/6 mice were randomly divided into a control group, a 1.5% dextran sulfate sodium (DSS) group and a 3% DSS group (n = 10 for each group). Colitis was induced in mice by giving 1.5% DSS or 3% DSS in drinking water for 6 d, and mice in the control group was given drinking water only. Disease activity index (DAI), colon length and inflammatory score of the colon were observed. Oxidative stress indicators, malondialdehyde (MDA) in serum and oxidized glutathione/glutathione (GSSG/GSH) ratio in colon tissue, were measured by biochemical methods. The protein and mRNA expression of Nox1 and Duox2 in colon tissue of mice was evaluated by immunohistochemistry and quantitative real-time PCR, respectively.

RESULTS: There was no colitis in the control group, while mild and severe enteritis was found in mice in the 1.5% DSS group and 3.0% DSS group, respectively. Oxidative stress (MDA and GSSG/GSH) was enhanced along with the increased concentration of DSS (P < 0.05 for both). The expression of Nox1 and Duox2 protein and mRNA was different with the severity of inflammation: Nox1 protein and mRNA was highly expressed in normal colon epithelial cells, but down-regulated in the 1.5% DSS group (P < 0.05), and further reduced in the 3% DSS group (P < 0.05); Duox2 protein and mRNA expression was increased (P < 0.05) in mice in the 1.5% DSS group compared to the control group, but returned to the control level in the 3% DSS group.

CONCLUSION: Nox1 is mainly involved in the functional and structural maintenance of normal colonic epithelium, while Duox2 may actively participate in the inflammatory pathogenesis besides the physiological process of the colon.

Chronic administration of Δ9-tetrahydrocannabinol induces intestinal anti-inflammatory microRNA expression during acute simian immunodeficiency virus infection of rhesus macaques

Recreational and medical use of cannabis among human immunodeficiency virus (HIV)-infected individuals has increased in recent years. In simian immunodeficiency virus (SIV)-infected macaques, chronic administration of Δ9-tetrahydrocannabinol (Δ9-THC) inhibited viral replication and intestinal inflammation and slowed disease progression. Persistent gastrointestinal disease/inflammation has been proposed to facilitate microbial translocation and systemic immune activation and promote disease progression. Cannabinoids including Δ9-THC attenuated intestinal inflammation in mouse colitis models and SIV-infected rhesus macaques. To determine if the anti-inflammatory effects of Δ9-THC involved differential microRNA (miRNA) modulation, we profiled miRNA expression at 14, 30, and 60 days postinfection (days p.i.) in the intestine of uninfected macaques receiving Δ9-THC (n=3) and SIV-infected macaques administered either vehicle (VEH/SIV; n=4) or THC (THC/SIV; n=4). Chronic Δ9-THC administration to uninfected macaques significantly and positively modulated intestinal miRNA expression by increasing the total number of differentially expressed miRNAs from 14 to 60 days p.i. At 60 days p.i., ∼28% of miRNAs showed decreased expression in the VEH/SIV group compared to none showing decrease in the THC/SIV group. Furthermore, compared to the VEH/SIV group, THC selectively upregulated the expression of miR-10a, miR-24, miR-99b, miR-145, miR-149, and miR-187, previously been shown to target proinflammatory molecules. NOX4, a potent reactive oxygen species generator, was confirmed as a direct miR-99b target. A significant increase in NOX4+ crypt epithelial cells was detected in VEH/SIV macaques compared to the THC/SIV group. We speculate that miR-99b-mediated NOX4 downregulation may protect the intestinal epithelium from oxidative stress-induced damage. These results support a role for differential miRNA induction in THC-mediated suppression of intestinal inflammation. Whether similar miRNA modulation occurs in other tissues requires further investigation.

IMPORTANCE

Gastrointestinal (GI) tract disease/inflammation is a hallmark of HIV/SIV infection. Previously, we showed that chronic treatment of SIV-infected macaques with Δ9-tetrahydrocannabinol (Δ9-THC) increased survival and decreased viral replication and infection-induced gastrointestinal inflammation. Here, we show that chronic THC administration to SIV-infected macaques induced an anti-inflammatory microRNA expression profile in the intestine at 60 days p.i. These included several miRNAs bioinformatically predicted to directly target CXCL12, a chemokine known to regulate lymphocyte and macrophage trafficking into the intestine. Specifically, miR-99b was significantly upregulated in THC-treated SIV-infected macaques and confirmed to directly target NADPH oxidase 4 (NOX4), a reactive oxygen species generator known to damage intestinal epithelial cells. Elevated miR-99b expression was associated with a significantly decreased number of NOX4+ epithelial cells in the intestines of THC-treated SIV-infected macaques. Overall, our results show that selective upregulation of anti-inflammatory miRNA expression contributes to THC-mediated suppression of gastrointestinal inflammation and maintenance of intestinal homeostasis.

Protective action of NADPH oxidase inhibitors and role of NADPH oxidase in pathogenesis of colon inflammation in mice

AIM: To investigate the role of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in colon epithelial cells in the pathogenesis of acute and chronic colon inflammation in a mouse model of dextran sulphate sodium (DSS)-induced colitis.

METHODS: Balb/c mice were divided into three groups: 8 mice with acute DSS-induced colitis (3.5% DSS solution; 7 d), 8 mice with chronic DSS-induced colitis (3.5% DSS solution for 5 d + water for 6 d; 4 cycles; total: 44 d) and 12 mice without DSS supplementation as a control group. Primary colonic epithelial cells were isolated using chelation method. The cells were cultivated in the presence of mediators (lipopolysaccharide (LPS), apocynin or diphenyleneiodonium). Viability of cells was assessed by fluorescent microscopy. Production of reactive oxygen species (ROS) by the cells was measured fluorometrically using Amplex Red. Production of tumour necrosis factor-alpha (TNF-α) by the colonic epithelial cells was analysed by ELISA. Nox1 gene expression was assessed by real-time PCR.

RESULTS: Our study showed that TNF-α level was increased in unstimulated primary colonic cells both in the acute and chronic colitis groups, whereas decreased viability, increased ROS production, and expression of Nox1 was characteristic only for chronic DSS colitis mice when compared to the controls. The stimulation by LPS increased ROS generation via NADPH oxidase and decreased cell viability in mice with acute colitis. Treatment with NADPH oxidase inhibitors increased cell viability and decreased the levels of ROS and TNF-α in the LPS-treated cells isolated from mice of both acute and chronic colitis groups.

CONCLUSION: Our study revealed the importance of NADPH oxidase in the pathogenesis of both acute and chronic inflammation of the colon.

PPARα-UGT axis activation represses intestinal FXR-FGF15 feedback signalling and exacerbates experimental colitis

Bile acids play a pivotal role in the pathological development of inflammatory bowel disease (IBD). However, the mechanism of bile acid dysregulation in IBD remains unanswered. Here we show that intestinal peroxisome proliferator-activated receptor α (PPARα)-UDP-glucuronosyltransferases (UGTs) signalling is an important determinant of bile acid homeostasis. Dextran sulphate sodium (DSS)-induced colitis leads to accumulation of bile acids in inflamed colon tissues via activation of the intestinal peroxisome PPARα-UGTs pathway. UGTs accelerate the metabolic elimination of bile acids, and thereby decrease their intracellular levels in the small intestine. Reduced intracellular bile acids results in repressed farnesoid X receptor (FXR)-FGF15 signalling, leading to upregulation of hepatic CYP7A1, thus promoting the de novo bile acid synthesis. Both knockout of PPARα and treatment with recombinant FGF19 markedly attenuate DSS-induced colitis. Thus, we propose that intestinal PPARα-UGTs and downstream FXR-FGF15 signalling play vital roles in control of bile acid homeostasis and the pathological development of colitis.

Bile acids have been linked to the development of inflammatory bowel diseases, such as colitis. Here the authors show that bile acid levels in mice are controlled by a circular feedback system involving the nuclear receptors PPARα and FXR, and that this system is dysregulated in colitis.