Deficiency in Duox2 activity alleviates ileitis in GPx1- and GPx2-knockout mice without affecting apoptosis incidence in the crypt epithelium

Novel mRNA Signature for Anti-TNF-α Therapy Primary Response in Patients With Ulcerative Colitis

BACKGROUND

Ulcerative colitis (UC), an idiopathic, chronic inflammatory disorder of the colonic mucosa, is commonly treated with antitumor necrosis factor α (anti-TNF-α) agents. However, only approximately two-thirds have an initial response to these therapies.

METHODS

We integrated gene expression profiling from 3 independent data sets of 79 UC patients before they began anti-TNF-α therapy and calculated the differentially expressed genes between patient response and nonresponse to anti-TNF-α therapy and developed a de novo response-associated transcription signature score (logOR_Score) to demonstrate the predictive capability of anti-TNF-α therapy for therapeutic efficacy. Furthermore, we performed association analysis of the logOR_Score and clinical features, such as disease activity and immune microenvironment.

RESULTS

A total of 2522 responsive and 1824 nonresponsive genes were identified from the integrated data set. Responsive genes were significantly enriched in metabolism-related pathways, whereas nonresponsive ones were associated with immune response-related pathways. The logOR_Score enabled the accurate prediction of the therapeutic efficacy of anti-TNF-α in 4 independent patient cohorts and outperformed the predictions made based on 6 transcriptome-based signatures. In terms of clinical features, the logOR_Score correlated highly with the activity of UC. From an immune microenvironment perspective, logOR_Scores of CD8+IL-17+ T cells, follicular B cells, and innate lymphoid cells significantly decreased in inflamed UC tissue.

CONCLUSIONS

The de novo response-associated transcription signature may provide novel insights into the personalized treatment of patients with UC. Comprehensive analyses of the response-related subtypes and the association between logOR_Score and clinical features and immune microenvironment may provide insights into the underlying UC pathogenesis.

Increased NOX1 and DUOX2 expression in the colonic mucosa of patients with chronic functional constipation

To determine whether oxidative stress and inflammation are associated with constipation by examining the expression of the main producers of reactive oxygen species, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, and pro-inflammatory cytokines in the colon of patients with chronic functional constipation. The colonic biopsies were collected from 32 patients with chronic functional constipation and 30 healthy subjects who underwent colonoscopy. Colonic mucosal histology was observed. Interleukin (IL)-1β, IL-6, IL-8 messenger RNA (mRNA), and 4 members of NADPH oxidase (NOX1, NOX2, DUOX2, and NOX4) protein and mRNA were assessed by immunohistochemistry, western blotting, and reverse transcription polymerase chain reaction. The tissues from both patients and healthy subjects showed normal histological structure without increase of inflammatory cells. NOX1 protein and mRNA levels were significantly increased compared to controls (P < .05). DUOX2 protein, but not mRNA, was increased by 2-fold compared to controls (P < .05). The levels of NOX2 and NOX4 protein and mRNA demonstrated no significant difference between patients and control subjects. The levels of IL-1β and IL-6 mRNA were significantly higher in constipation patients (P < .05), while IL-8 mRNA level was no different between the 2 groups. NADPH oxidase and pro-inflammatory cytokine might be involved in the pathogeneses of chronic functional constipation.

The beginning of GPX2 and 30 years later

We published the first paper to characterize GPX2 (aka GSHPx-GI) as a selenoenzyme with glutathione peroxidase activity in 1993. Among the four Se-GPX isozymes, GPX1-4, GPX1 and GPX2 are closely related in terms of structure, substrate specificities, and subcellular localization. What sets them apart are distinct patterns of gene regulation, tissue distribution and response to selenium. While we identified the digestive tract epithelium as the main site of GPX2 expression, later work has shown GPX2 is found more widely in epithelial tissues with concentration of expression in stem cell and proliferative compartments. GPX2 expression is regulated over a wide range of levels by many pathways, including NRF2, WNT, p53, RARE and this often results in attaching undue significance to GPX2 as GPX2 is only a part of a system of hydroperoxidase activities, including GPX1, peroxiredoxins and catalase. These other activities may play equal or greater roles, particularly in cell lines cultured without selenium supplementation and often with very low GPX2 levels. This could be assessed by examining levels of mRNA and protein among these various peroxidases at the outset of studies. As an example, it was found that GPX1 responds to the absence of GPX2 in mouse ileum and colon epithelium with higher expression. As such, both Gpx1 and Gpx2 had to be knocked out in mice to produce ileocolitis. However, we note that the actual role of GPX1 and GPX2 in relation to peroxiredoxin function is unclear. There may be an interdependence that requires only low amounts of GPX1 and/or GPX2 in a supporting role to maintain proper peroxiredoxin function. GPX2 levels may be prognostic for cancer progression in colon, breast, prostate and liver, however, there is no consistent trend for higher or lower levels to be favorable.

Roscovitine Worsens Mycobacterium abscessus Infection by Reducing DUOX2-mediated Neutrophil Response

Persistent neutrophilic inflammation associated with chronic pulmonary infection causes progressive lung injury and, eventually, death in individuals with cystic fibrosis (CF), a genetic disease caused by biallelic mutations in the CF transmembrane conductance regulator (CFTR) gene. Therefore, we examined whether roscovitine, a cyclin-dependent kinase inhibitor that (in other conditions) reduces inflammation while promoting host defense, might provide a beneficial effect in the context of CF. Herein, using CFTR-depleted zebrafish larvae as an innovative vertebrate model of CF immunopathophysiology, combined with murine and human approaches, we sought to determine the effects of roscovitine on innate immune responses to tissue injury and pathogens in the CF condition. We show that roscovitine exerts antiinflammatory and proresolution effects in neutrophilic inflammation induced by infection or tail amputation in zebrafish. Roscovitine reduces overactive epithelial reactive oxygen species (ROS)-mediated neutrophil trafficking by reducing DUOX2/NADPH-oxidase activity and accelerates inflammation resolution by inducing neutrophil apoptosis and reverse migration. It is important to note that, although roscovitine efficiently enhances intracellular bacterial killing of Mycobacterium abscessus in human CF macrophages ex vivo, we found that treatment with roscovitine results in worse infection in mouse and zebrafish models. By interfering with DUOX2/NADPH oxidase-dependent ROS production, roscovitine reduces the number of neutrophils at infection sites and, consequently, compromises granuloma formation and maintenance, favoring extracellular multiplication of M. abscessus and more severe infection. Our findings bring important new understanding of the immune-targeted action of roscovitine and have significant therapeutic implications for safely targeting inflammation in CF.

Implication of Intestinal Barrier Dysfunction in Gut Dysbiosis and Diseases

The intestinal mucosal barrier, also referred to as intestinal barrier, is widely recognized as a critical player in gut homeostasis maintenance as it ensures the complex crosstalk between gut microbes (both commensals and pathogens) and the host immune system. Highly specialized epithelial cells constantly cope with several protective and harmful agents to maintain the multiple physiological functions of the barrier as well as its integrity. However, both genetic defects and environmental factors can break such equilibrium, thus promoting gut dysbiosis, dysregulated immune-inflammatory responses, and even the development of chronic pathological conditions. Here, we review and discuss the molecular and cellular pathways underlying intestinal barrier structural and functional homeostasis, focusing on potential alterations that may undermine this fine balance.

Telomere dysfunction instigates inflammation in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory condition driven by diverse genetic and nongenetic programs that converge to disrupt immune homeostasis in the intestine. We have reported that, in murine intestinal epithelium with telomere dysfunction, DNA damage-induced activation of ataxia-telangiectasia mutated (ATM) results in ATM-mediated phosphorylation and activation of the YAP1 transcriptional coactivator, which in turn up-regulates pro-IL-18, a pivotal immune regulator in IBD pathogenesis. Moreover, individuals with germline defects in telomere maintenance genes experience increased occurrence of intestinal inflammation and show activation of the ATM/YAP1/pro-IL-18 pathway in the intestinal epithelium. Here, we sought to determine the relevance of the ATM/YAP1/pro-IL-18 pathway as a potential driver of IBD, particularly older-onset IBD. Analysis of intestinal biopsy specimens and organoids from older-onset IBD patients documented the presence of telomere dysfunction and activation of the ATM/YAP1/precursor of interleukin 18 (pro-IL-18) pathway in the intestinal epithelium. Employing intestinal organoids from healthy individuals, we demonstrated that experimental induction of telomere dysfunction activates this inflammatory pathway. In organoid models from ulcerative colitis and Crohn's disease patients, pharmacological interventions of telomerase reactivation, suppression of DNA damage signaling, or YAP1 inhibition reduced pro-IL-18 production. Together, these findings support a model wherein telomere dysfunction in the intestinal epithelium can initiate the inflammatory process in IBD, pointing to therapeutic interventions for this disease.

Targeting Mitochondrial Damage as a Therapeutic for Ileal Crohn's Disease

Paneth cell defects in Crohn's disease (CD) patients (called the Type I phenotype) are associated with worse clinical outcomes. Recent studies have implicated mitochondrial dysfunction in Paneth cells as a mediator of ileitis in mice. We hypothesized that CD Paneth cells exhibit impaired mitochondrial health and that mitochondrial-targeted therapeutics may provide a novel strategy for ileal CD. Terminal ileal mucosal biopsies from adult CD and non-IBD patients were characterized for Paneth cell phenotyping and mitochondrial damage. To demonstrate the response of mitochondrial-targeted therapeutics in CD, biopsies were treated with vehicle or Mito-Tempo, a mitochondrial-targeted antioxidant, and RNA transcriptome was analyzed. During active CD inflammation, the epithelium exhibited mitochondrial damage evident in Paneth cells, goblet cells, and enterocytes. Independent of inflammation, Paneth cells in Type I CD patients exhibited mitochondrial damage. Mito-Tempo normalized the expression of interleukin (IL)-17/IL-23, lipid metabolism, and apoptotic gene signatures in CD patients to non-IBD levels. When stratified by Paneth cell phenotype, the global tissue response to Mito-Tempo in Type I patients was associated with innate immune, lipid metabolism, and G protein-coupled receptor (GPCR) gene signatures. Targeting impaired mitochondria as an underlying contributor to inflammation provides a novel treatment approach for CD.

DUOX2 promotes the progression of colorectal cancer cells by regulating the AKT pathway and interacting with RPL3

Dual oxidase 2 (DUOX2) is an important regulatory protein in the organic process of thyroid hormone iodine. Mounting evidence suggests that DUOX2 plays a crucial role in the occurrence and development of cancers. However, the function and mechanism of DUOX2 in colorectal cancer (CRC) have not been fully clarified. In the present study, the relationship between the expression of DUOX2 and the clinicopathological features and prognosis of CRC patients was analyzed. Furthermore, the effects of DUOX2 on proliferation and invasion in vitro and in vivo were examined. DUOX2-associated proteins were identified by immunoprecipitation (IP). Next-generation sequencing detection was performed to illustrate the mechanism of DUOX2 in CRC cells. It was found that the expression levels of DUOX2 in metastatic sites were significantly higher than those in primary tumor tissues, and this was demonstrated to be associated with poor prognosis. The knockdown of DUOX2 inhibited the invasion and migration of CRC cells. Furthermore, DUOX2 regulated the stability of ribosomal protein uL3 (RPL3) by affecting the ubiquitination status of RPL3, and the invasion and migration ability of DUOX2 can be reversed by the overexpression of RPL3. The downregulation of DUOX2 can affect the expression level of a large number of genes, and a number of these are enriched in the PI3K-AKT pathway. Some of the changes caused by DUOX2 can be reversed by RPL3. In summary, DUOX2 exhibits a significantly higher expression in CRC tumor samples, and facilitates the invasion and metastasis ability of CRC cells by interacting with RPL3.

Preventing Colitis-Associated Colon Cancer With Antioxidants: A Systematic Review

Inflammatory bowel disease (IBD) patients have an increased risk of developing colitis-associated colon cancer (CAC); however, the basis for inflammation-induced genetic damage requisite for neoplasia is unclear. Several studies have shown that IBD patients have signs of increased oxidative damage, which could be a result of genetic and environmental factors such as an excess in oxidant molecules released during chronic inflammation, mitochondrial dysfunction, a failure in antioxidant capacity, or oxidant promoting diets. It has been suggested that chronic oxidative environment in the intestine leads to the DNA lesions that precipitate colon carcinogenesis in IBD patients. Indeed, several preclinical and clinical studies show that different endogenous and exogenous antioxidant molecules are effective at reducing oxidation in the intestine. However, most clinical studies have focused on the short-term effects of antioxidants in IBD patients but not in CAC. This review article examines the role of oxidative DNA damage as a possible precipitating event in CAC in the context of chronic intestinal inflammation and the potential role of exogenous antioxidants to prevent these cancers.

Mini review: immunologic functions of dual oxidases in mucosal systems of vertebrates

Abstract Mucosal epithelial cells act as the first immunologic barrier of organisms, and contact directly with pathogens. Therefore, hosts must have differential strategies to combat pathogens efficiently. Reactive oxygen species (ROS), as a kind of oxidizing agents, participates in the early stage of killing pathogens quickly. Recent reports have revealed that dual oxidase (DUOX) plays a key role in mucosal immunity. And the DUOX is a transmembrane protein which produces ROS as their primary enzymatic products. This process is an important pattern for eliminating pathogens. In this review, we highlight the DUOX immunologic functions in the respiratory and digestive tract of vertebrates.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Role of the microbiota in ileitis of a mouse model of inflammatory bowel disease-Glutathione peroxide isoenzymes 1 and 2-double knockout mice on a C57BL background

C57Bl6 (B6) mice devoid of glutathione peroxidases 1 and 2 (Gpx1/2-DKO) develop ileitis after weaning. We previously showed germ-free Gpx1/2-DKO mice of mixed B6.129 background did not develop ileocolitis. Here, we examine the composition of the ileitis provoking microbiota in B6 Gpx1/2-DKO mice. DNA was isolated from the ileum fecal stream and subjected to high-throughput sequencing of the V3 and V4 regions of the 16S rRNA gene to determine the abundance of operational taxonomic units (OTUs). We analyzed the role of bacteria by comparing the microbiomes of the DKO and pathology-free non-DKO mice. Mice were treated with metronidazole, streptomycin, and vancomycin to alter pathology and correlate the OTU abundances with pathology levels. Principal component analysis based on Jaccard distance of abundance showed 3 distinct outcomes relative to the source Gpx1/2-DKO microbiome. Association analyses of pathology and abundance of OTUs served to rule out 7-11 of 24 OTUs for involvement in the ileitis. Collections of OTUs were identified that appeared to be linked to ileitis in this animal model and would be classified as commensals. In Gpx1/2-DKO mice, host oxidant generation from NOX1 and DUOX2 in response to commensals may compromise the ileum epithelial barrier, a role generally ascribed to oxidants generated from mitochondria, NOX2 and endoplasmic reticulum stress in response to presumptive pathogens in IBD. Elevated oxidant levels may contribute to epithelial cell shedding, which is strongly associated with progress toward inflammation in Gpx1/2-DKO mice and predictive of relapse in IBD by allowing leakage of microbial components into the submucosa.

The Dual Role of Reactive Oxygen Species-Generating Nicotinamide Adenine Dinucleotide Phosphate Oxidases in Gastrointestinal Inflammation and Therapeutic Perspectives

Significance: Despite their intrinsic cytotoxic properties, mounting evidence indicates that reactive oxygen species (ROS) physiologically produced by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) of epithelial cells (NOX1, dual oxidase [DUOX]2) and phagocytes (NOX2) are critical for innate immune response and homeostasis of the intestinal mucosa. However, dysregulated ROS production could be a driving factor in inflammatory bowel diseases (IBDs). Recent Advances: In addition to NOX2, recent studies have demonstrated that NOX1- and DUOX2-derived ROS can regulate intestinal innate immune defense and homeostasis by impacting many processes, including bacterial virulence, expression of bacteriostatic proteins, epithelial renewal and restitution, and microbiota composition. Moreover, the antibacterial role of DUOX2 is a function conserved in evolution as it has been described in invertebrates, and lower and higher vertebrates. In humans, variants of the NOX2, NOX1, and DUOX2 genes, which are associated with impaired ROS production, have been identified in very early onset IBD, but overexpression of NOX/DUOX, especially DUOX2, has also been described in IBD, suggesting that loss-of-function or excessive activity of the ROS-generating enzymes could contribute to disease progression. Critical Issues: Therapeutic perspectives aiming at targeting NOX/DUOX in IBD should take into account the two sides of NOX/DUOX-derived ROS in intestinal inflammation. Hence, NOX/DUOX inhibitors or ROS inducers should be considered as a function of the disease context. Future Directions: A thorough understanding of the physiological and pathological regulation of NOX/DUOX in the gastrointestinal tract is an absolute pre-requisite for the development of therapeutic strategies that can modulate ROS levels in space and time.

Gut bacteria signaling to mitochondria in intestinal inflammation and cancer

The gastrointestinal microbiome plays a pivotal role in physiological homeostasis of the intestine as well as in the pathophysiology of diseases including inflammatory bowel diseases (IBD) and colorectal cancer (CRC). Emerging evidence suggests that gut microbiota signal to the mitochondria of mucosal cells, including epithelial cells and immune cells. Gut microbiota signaling to mitochondria has been shown to alter mitochondrial metabolism, activate immune cells, induce inflammasome signaling, and alter epithelial barrier function. Both dysbiosis of the gut microbiota and mitochondrial dysfunction are associated with chronic intestinal inflammation and CRC. This review discusses mitochondrial metabolism of gut mucosal cells, mitochondrial dysfunction, and known gut microbiota-mediated mitochondrial alterations during IBD and CRC.

Dexamethasone and Tofacitinib suppress NADPH oxidase expression and alleviate very-early-onset ileocolitis in mice deficient in GSH peroxidase 1 and 2

C57BL6/J (B6) mice lacking Se-dependent GSH peroxidase 1 and 2 (GPx1/2-DKO) develop mild to moderate ileocolitis around weaning. These DKO mice have a disease resembling human very-early-onset inflammatory bowel disease (VEOIBD), which is associated with mutations in NADPH oxidase genes. Drugs including dexamethasone (Dex), Tofacitinib (Tofa; a Janus kinase/JAK inhibitor) and anti-TNF antibody are effective to treat adult, but not pediatric IBD.

AIMS

To test the efficacy of hydrophobic Dex and hydrophilic Dex phosphate (Dex phos), Tofa, anti-Tnf Ab, Noxa1ds-TAT and gp91ds-TAT peptides (inhibiting NOX1 and NOX2 assembly respectively), antioxidant MJ33 and ML090, and pifithrin-α (p53 inhibitor) on alleviation of gut inflammation in DKO weanlings.

MAIN METHODS

All treatments began on 22-day-old GPx1/2-DKO mice. The mouse intestine pathology was compared between the drug- and vehicle-treated groups after six or thirteen days of treatment.

KEY FINDINGS

Among all drugs tested, Dex, Dex phos and Tofa were the strongest to suppress ileocolitis in the DKO weanlings. Dex, Dex phos and Tofa inhibited crypt apoptosis and increased crypt density. Dex or Dex phos alone also inhibited cell proliferation, exfoliation and crypt abscess in the ileum. Dex, but not Tofa, retarded mouse growth. Both Dex and Tofa inhibited ileum Nox1, Nox4 and Duox2, but not Nox2 gene expression. Noxa1ds-TAT and gp91ds-TAT peptides as well as MJ33 had subtle effect on suppressing pathology, while others had negligible effect.

SIGNIFICANCE

These findings suggest that NADPH oxidases can be novel drug targets for pediatric IBD therapy, and Tofa may be considered for treating VEOIBD.

Intestinal Epithelial Cells Respond to Chronic Inflammation and Dysbiosis by Synthesizing H2O2

The microbes in the gastrointestinal tract are separated from the host by a single layer of intestinal epithelial cells (IECs) that plays pivotal roles in maintaining homeostasis by absorbing nutrients and providing a physical and immunological barrier to potential pathogens. Preservation of homeostasis requires the crosstalk between the epithelium and the microbial environment. One epithelial-driven innate immune mechanism that participates in host-microbe communication involves the release of reactive oxygen species (ROS), such as hydrogen peroxide (H₂O₂), toward the lumen. Phagocytes produce high amounts of ROS which is critical for microbicidal functions; the functional contribution of epithelial ROS, however, has been hindered by the lack of methodologies to reliably quantify extracellular release of ROS. Here, we used a modified Amplex Red assay to investigate the inflammatory and microbial regulation of IEC-generated H₂O₂ and the potential role of Duox2, a NADPH oxidase that is an important source of H₂O₂. We found that colonoids respond to interferon-γ and flagellin by enhancing production of H₂O₂ in a Duox2-mediated fashion. To extend these findings, we analyzed ex vivo production of H₂O₂ by IECs after acute and chronic inflammation, as well as after exposure to dysbiotic microbiota. While acute inflammation did not induce a significant increase in epithelial-driven H₂O₂, chronic inflammation caused IECs to release higher levels of H₂O₂. Furthermore, colonization of germ-free mice with dysbiotic microbiota from mice or patients with IBD resulted in increased H₂O₂ production compared with healthy controls. Collectively, these data suggest that IECs are capable of H₂O₂ production during chronic inflammation and dysbiotic states. Our results provide insight into luminal production of H₂O₂ by IECs as a read-out of innate defense by the mucosa.

Distinct and overlapping functions of glutathione peroxidases 1 and 2 in limiting NF-κB-driven inflammation through redox-active mechanisms

Glutathione peroxidase 2 (GPx2) is one of the five selenoprotein GPxs having a selenocysteine in the active center. GPx2 is strongly expressed in the gastrointestinal epithelium, as is another isoform, GPx1, though with a different localization pattern. Both GPxs are redox-active enzymes that are important for the reduction of hydroperoxides.

Studies on GPx2-deficient mice and human HT-29 cells with a stable knockdown (kd) of GPx2 revealed higher basal and IL-1β-induced expression of NF-κB target genes in vivo and in vitro. The activation of the IKK–IκBα–NF-κB pathway was increased in cultured GPx2 kd cells. Basal signaling was only restored by re-expressing active GPx2 in GPx2 kd cells but not by redox-inactive GPx2. As it is still not clear if the two isoforms GPx1 and GPx2 have different functions, kd cell lines for either GPx1 or GPx2 were studied in parallel. The inhibitory effect of GPx2 on NF-κB signaling and its target gene expression was stronger than that of GPx1, whereas cyclooxygenase (COX)- and lipoxygenase (LOX)-derived lipid mediator levels increased more strongly in GPx1 kd than in GPx2 kd cells. Under unstimulated conditions, the levels of the COX-derived prostaglandins PGE₂ and PGD₂ were enhanced in GPx2 as well as in GPx1 kd compared to control cells. Specifically, in GPx1 kd cells IL-1β stimulation led to a dramatic shift of the PGE₂/PGD₂ ratio towards pro-inflammatory PGE₂.

Taken together, GPx2 and GPx1 have overlapping functions in controlling inflammatory lipid mediator synthesis and, most probably, exert their anti-inflammatory effects by preventing excessive PGE₂ production. In view of the high activity of COX and LOX pathways during inflammatory bowel disease our data therefore provide new insights into the mechanisms of the protective function of GPx1 and GPx2 during colitis as well as inflammation-driven carcinogenesis.

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Loss of GPx2 results in higher basal and IL-1β-induced NF-κB activation.

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Suppressive effects of GPx2 on NF-κB are mediated in a redox-dependent manner.

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Both GPx isoforms modulate the lipid mediator profile in response to IL-1β.

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COX-derived prostaglandins increase more strongly in GPx1 than in GPx2 kd cells.

Colitis susceptibility in mice with reactive oxygen species deficiency is mediated by mucus barrier and immune defense defects

Reactive oxygen species (ROS) generated by NADPH oxidases (NOX/DUOX) provide antimicrobial defense, redox signaling, and gut barrier maintenance. Inactivating NOX variants are associated with comorbid intestinal inflammation in chronic granulomatous disease (CGD; NOX2) and pediatric inflammatory bowel disease (IBD; NOX1); however Nox-deficient mice do not reflect human disease susceptibility. Here we assessed if a hypomorphic patient-relevant CGD mutation will increase the risk for intestinal inflammation in mice. Cyba (p22^phox) mutant mice generated low intestinal ROS, while maintaining Nox4 function. The Cyba variant caused profound mucus layer disruption with bacterial penetration into crypts, dysbiosis, and a compromised innate immune response to invading microbes, leading to mortality. Approaches used in treatment-resistant CGD or pediatric IBD such as bone marrow transplantation or oral antibiotic treatment ameliorated or prevented disease in mice. The Cyba mutant mouse phenotype implicates loss of both mucus barrier and efficient innate immune defense in the pathogenesis of intestinal inflammation due to ROS deficiency, supporting a combined-hit model where a single disease variant compromises different cellular functions in interdependent compartments.

IL-4 and IL-17A Cooperatively Promote Hydrogen Peroxide Production, Oxidative DNA Damage, and Upregulation of Dual Oxidase 2 in Human Colon and Pancreatic Cancer Cells

Dual oxidase 2 (DUOX2) generates H₂O₂ that plays a critical role in both host defense and chronic inflammation. Previously, we demonstrated that the proinflammatory mediators IFN-γ and LPS enhance expression of DUOX2 and its maturation factor DUOXA2 through STAT1- and NF-κB‒mediated signaling in human pancreatic cancer cells. Using a panel of colon and pancreatic cancer cell lines, we now report the induction of DUOX2/DUOXA2 mRNA and protein expression by the T_H2 cytokine IL-4. IL-4 activated STAT6 signaling that, when silenced, significantly decreased induction of DUOX2. Furthermore, the T_H17 cytokine IL-17A combined synergistically with IL-4 to increase DUOX2 expression in both colon and pancreatic cancer cells mediated, at least in part, by signaling through NF-κB. The upregulation of DUOX2 was associated with a significant increase in the production of extracellular H₂O₂ and DNA damage-as indicated by the accumulation of 8-oxo-dG and γH2AX-which was suppressed by the NADPH oxidase inhibitor diphenylene iodonium and a DUOX2-specific small interfering RNA. The clinical relevance of these experiments is suggested by immunohistochemical, microarray, and quantitative RT-PCR studies of human colon and pancreatic tumors demonstrating significantly higher DUOX2, IL-4R, and IL-17RA expression in tumors than in adjacent normal tissues; in pancreatic adenocarcinoma, increased DUOX2 expression is adversely associated with overall patient survival. These data suggest a functional association between DUOX2-mediated H₂O₂ production and induced DNA damage in gastrointestinal malignancies.

Selenoproteins in colon cancer

Selenocysteine-containing proteins (selenoproteins) have been implicated in the regulation of various cell signaling pathways, many of which are linked to colorectal malignancies. In this in-depth excurse into the selenoprotein literature, we review possible roles for human selenoproteins in colorectal cancer, focusing on the typical hallmarks of cancer cells and their tumor-enabling characteristics. Human genome studies of single nucleotide polymorphisms in various genes coding for selenoproteins have revealed potential involvement of glutathione peroxidases, thioredoxin reductases, and other proteins. Cell culture studies with targeted down-regulation of selenoproteins and studies utilizing knockout/transgenic animal models have helped elucidate the potential roles of individual selenoproteins in this malignancy. Those selenoproteins, for which strong links to development or progression of colorectal cancer have been described, may be potential future targets for clinical interventions.

Microbiota-sensitive epigenetic signature predicts inflammation in Crohn's disease

Altered response to the intestinal microbiota strongly associates with inflammatory bowel disease (IBD); however, how commensal microbial cues are integrated by the host during the pathogenesis of IBD is not understood. Epigenetics represents a potential mechanism that could enable intestinal microbes to modulate transcriptional output during the development of IBD. Here, we reveal a histone methylation signature of intestinal epithelial cells isolated from the terminal ilea of newly diagnosed pediatric IBD patients. Genes characterized by significant alterations in histone H3-lysine 4 trimethylation (H3K4me3) showed differential enrichment in pathways involving immunoregulation, cell survival and signaling, and metabolism. Interestingly, a large subset of these genes was epigenetically regulated by microbiota in mice and several microbiota-sensitive epigenetic targets demonstrated altered expression in IBD patients. Remarkably though, a substantial proportion of these genes exhibited H3K4me3 levels that correlated with the severity of intestinal inflammation in IBD, despite lacking significant differential expression. Collectively, these data uncover a previously unrecognized epigenetic profile of IBD that can be primed by commensal microbes and indicate sensitive targets in the epithelium that may underlie how microbiota predispose to subsequent intestinal inflammation and disease.

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.

NOX1 loss-of-function genetic variants in patients with inflammatory bowel disease

Genetic defects that affect intestinal epithelial barrier function can present with very early-onset inflammatory bowel disease (VEOIBD). Using whole-genome sequencing, a novel hemizygous defect in NOX1 encoding NAPDH oxidase 1 was identified in a patient with ulcerative colitis-like VEOIBD. Exome screening of 1,878 pediatric patients identified further seven male inflammatory bowel disease (IBD) patients with rare NOX1 mutations. Loss-of-function was validated in p.N122H and p.T497A, and to a lesser degree in p.Y470H, p.R287Q, p.I67M, p.Q293R as well as the previously described p.P330S, and the common NOX1 SNP p.D360N (rs34688635) variant. The missense mutation p.N122H abrogated reactive oxygen species (ROS) production in cell lines, ex vivo colonic explants, and patient-derived colonic organoid cultures. Within colonic crypts, NOX1 constitutively generates a high level of ROS in the crypt lumen. Analysis of 9,513 controls and 11,140 IBD patients of non-Jewish European ancestry did not reveal an association between p.D360N and IBD. Our data suggest that loss-of-function variants in NOX1 do not cause a Mendelian disorder of high penetrance but are a context-specific modifier. Our results implicate that variants in NOX1 change brush border ROS within colonic crypts at the interface between the epithelium and luminal microbes.

Chicoric acid prevents PDGF-BB-induced VSMC dedifferentiation, proliferation and migration by suppressing ROS/NFκB/mTOR/P70S6K signaling cascade

Phenotypic switch of vascular smooth muscle cells (VSMCs) is characterized by increased expressions of VSMC synthetic markers and decreased levels of VSMC contractile markers, which is an important step for VSMC proliferation and migration during the development and progression of cardiovascular diseases including atherosclerosis. Chicoric acid (CA) is identified to exert powerful cardiovascular protective effects. However, little is known about the effects of CA on VSMC biology. Herein, in cultured VSMCs, we showed that pretreatment with CA dose-dependently suppressed platelet-derived growth factor type BB (PDGF-BB)-induced VSMC phenotypic alteration, proliferation and migration. Mechanistically, PDGF-BB-treated VSMCs exhibited higher mammalian target of rapamycin (mTOR) and P70S6K phosphorylation, which was attenuated by CA pretreatment, diphenyleneiodonium chloride (DPI), reactive oxygen species (ROS) scavenger N-acetyl-l-cysteine (NAC) and nuclear factor-κB (NFκB) inhibitor Bay117082. PDGF-BB-triggered ROS production and p65-NFκB activation were inhibited by CA. In addition, both NAC and DPI abolished PDGF-BB-evoked p65-NFκB nuclear translocation, phosphorylation and degradation of Inhibitor κBα (IκBα). Of note, blockade of ROS/NFκB/mTOR/P70S6K signaling cascade prevented PDGF-BB-evoked VSMC phenotypic transformation, proliferation and migration. CA treatment prevented intimal hyperplasia and vascular remodeling in rat models of carotid artery ligation in vivo. These results suggest that CA impedes PDGF-BB-induced VSMC phenotypic switching, proliferation, migration and neointima formation via inhibition of ROS/NFκB/mTOR/P70S6K signaling cascade.

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Chicoric acid attenuated PDGF-BB-evoked VSMC phenotypic transformation, proliferation and migration.

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Chicoric acid antagonized the activated ROS/NFκB/mTOR/P70S6K signaling pathway in VSMCs.

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Chicoric acid treatment prevented intimal hyperplasia in rat models of carotid artery ligation.

Selenium-Dependent Glutathione Peroxidases During Tumor Development

Five out of eight human glutathione peroxidases (GPxes) are selenoproteins and thus their expression depends on the selenium (Se) supply. Most Se-dependent GPxes are downregulated in tumor cells, while only GPx2 is considerably upregulated. Whether expression profiles of GPxes predict tumor development and patient survival is controversially discussed. Also, results from in vitro and in vivo studies modulating the expression of GPx isoforms provide evidence for both anti- and procarcinogenic mechanisms. GPxes are able to reduce hydroperoxides, which otherwise would damage DNA, possibly resulting in DNA mutations, modulate redox-sensitive signaling pathways affecting proliferation, differentiation, and cellular metabolism or initiate cell death. Considering these different processes, the role and functions of individual Se-dependent GPx isoforms will be discussed herein in the context of tumorigenesis.

High Immunoreactivity of DUOX2 Is Associated With Poor Response to Preoperative Chemoradiation Therapy and Worse Prognosis in Rectal Cancers

Purpose: Colorectal cancer is the third most common cancer and also the fourth most common cause of cancer mortality worldwide. For rectal cancer, neoadjuvant concurrent chemoradiotherapy (CCRT) followed by radical proctectomy is gold standard treatment for patients with stage II/III rectal cancer. By data mining a documented database of rectal cancer transcriptome (GSE35452) from Gene Expression Omnibus, National Center of Biotechnology Information, we recognized that DUOX2 was the most significantly up-regulated transcript among those related to cytokine and chemokine mediated signaling pathway (GO:0019221). Hence, the aim of this study was to assess the DUOX2 expression level and its clinicopathological correlation and prognostic significance in patients of rectal cancer.

Materials and Methods: DUOX2 immunostain was performed in 172 rectal adenocarcinomas treated with preoperative CCRT followed by radical proctectomy, which were divided into high- and low-expression subgroups. Furthermore, statistical analyses were examined to correlate the relationship between DUOX2 immunoreactivity and important clinical and pathological characteristics, as well as three survival indices: disease-specific survival (DSS), local recurrence-free survival (LRFS) and metastasis-free survival (MeFS).

Results: DUOX2 overexpression was linked to post-CCRT tumor advancement, pre- and post-CCRT nodal metastasis and poor response to CCRT (all P ≤ 0.021). Furthermore, DUOX2 high expression was significantly associated with inferior DSS, LRFS and MeFS in univariate analysis (P ≤ 0.0097) and also served as an independent prognosticator indicating shorter DSS and LRFS interval in multivariate analysis (hazard ratio (HR) = 3.413, 95% confidence interval (CI): 1.349-8.633; HR = 4.533, 95% CI: 1.499-13.708, respectively).

Conclusion: DUOX2 may play a pivotal role in carcinogenesis, tumor progression and response to neoadjuvant CCRT in rectal cancers, and serve as a novel prognostic biomarker. Additional researches to clarify the molecular and biochemical pathways are essential for developing promising DUOX2-targeted therapies for patients with rectal cancers.

N-Acetylcysteine supplementation alleviates intestinal injury in piglets infected by porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) infects the intestine of young pigs, but effective measures for prevention and treatment are lacking. N-Acetylcysteine (NAC) has been shown to reduce endotoxin-induced intestinal dysfunction. This study was conducted with the PEDV-infected neonatal piglet model to determine the effect of NAC supplementation on intestinal function. Thirty-two 7-day-old piglets were randomly allocated to one of four treatments in a 2 × 2 factorial design consisting of two liquid diets (0 or 50 mg/kg BW NAC supplementation) and oral administration of 0 or 10^4.5 TCID₅₀ (50% tissue culture infectious dose) PEDV. On day 7 of the trial, half of the pigs (n = 8) in each dietary treatment received either sterile saline or PEDV (Yunnan province strain) solution at 10^4.5 TCID₅₀ per pig. On day 10 of the trial, D-xylose (0.1 g/kg BW) was orally administrated to all pigs. One hour later, jugular vein blood samples were collected, and then all pigs were killed to obtain the small intestine. PEDV infection increased diarrhea incidence, while reducing ADG. PEDV infection also decreased plasma D-xylose concentration, small intestinal villus height, mucosal I-FABP and villin mRNA levels but increased mucosal MX1 and GCNT3 mRNA levels (P < 0.05). Dietary NAC supplementation ameliorated the PEDV-induced abnormal changes in all the measured variables. Moreover, NAC reduced oxidative stress, as indicated by decreases in plasma and mucosal H₂O₂ levels. Collectively, these novel results indicate that dietary supplementation with NAC alleviates intestinal mucosal damage and improves the absorptive function of the small intestine in PEDV-infected piglets.