Genetic disorders coupled to ROS deficiency

Comparison of Candesartan and Angiotensin-(1-7) Combination to Mito-TEMPO Treatment for Normalizing Blood Pressure and Sympathovagal Balance in (mREN2)27 Rats

Hypertensive transgenic (mRen2)27 rats exhibit impaired baroreflex sensitivity (BRS) for control of heart rate (HR). Intracerebroventricular infusion of Ang-(1-7) improves indices of vagal BRS independent of lowering mean arterial pressure (MAP), whereas AT1 receptor blockade normalizes MAP and indices of sympathetic tone without correcting the vagal BRS. Scavenging cellular reactive oxygen species (ROS) with tempol in brain fails to correct either hypertension or sympathovagal balance in these animals, despite reports that mitochondrial ROS contributes to Ang II-infusion hypertension. To examine effects of a putative preferential mitochondrial ROS scavenger in the brain of (mRen2)27 rats, ICV infusions of Mito-TEMPO (3.2 μg/2.5 μL/h) were compared with artificial cerebrospinal fluid (aCSF; 2.5 μL/h) and combination AT1 receptor antagonist candesartan (CAN: 4 μg/2.5 μL/h) plus Ang-(1-7) (0.1 μg/2.5 μL/h) treatment. MAP was lower after CAN + Ang-(1-7) treatment, and both vagal and sympathetic components of BRS and sympathovagal balance were improved. By contrast, Mito-TEMPO improved sympathetic components of BRS and tended to improve overall sympathovagal balance but failed to alter MAP in this model of hypertension. Although further studies are required to determine whether Mito-TEMPO or CAN + Ang-(1-7) treatment at the doses used altered mitochondrial ROS, optimal therapeutic benefits are achieved by shifting the balance from Ang II toward Ang-(1-7) in this model of chronic RAS-dependent hypertension.

The innate immune perspective of autoimmune and autoinflammatory conditions

Innate immunity is one of two immune defence system arms. It is present at birth and does not require ‘learning’ through exposure to foreign organisms. It activates various mechanisms collectively to eliminate pathogens and hold an infection until the adaptive response are mounted. The innate immune system consists of four elements: the epithelial barrier, cells (e.g. macrophages, NK cells), plasma proteins (e.g. complement) and cytokines. These components act in concert to induce complex processes, as well as recruitment, activation and differentiation of adaptive responses. The innate response is more than just the ‘first line of defence’, as it essentially withholds the vast majority of any intruder, has a complex interplay with the adaptive arm and is crucial for survival of the host. Finally, yet importantly, a myriad of diseases has been linked with innate immune dysregulation. In this mini-review we will shed some light on these conditions, particularly regarding autoinflammatory ones.

Therapeutic benefits of apocynin in mice with lipopolysaccharide/D-galactosamine-induced acute liver injury via suppression of the late stage pro-apoptotic AMPK/JNK pathway

The excessive generation of reactive oxygen species (ROS) plays crucial roles in the development of acute liver injury. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) is responsible for the robust production of ROS under inflammatory circumstance, but the pathological roles of NOX and the pharmacological significance of NOX inhibitor in acute liver injury remains unclear. In the present study, the potential roles of NOX in acute liver injury were investigated in a mouse model with lipopolysaccharide (LPS)/D-galactosamine (D-Gal)-induced acute liver injury. The results indicated that LPS/D-Gal exposure time-dependently increased the level of ROS in liver tissue. Pretreatment with the NOX inhibitor apocynin suppressed LPS/D-Gal induced upregulation of ROS, 8-hydroxy-2-deoxyguanosine (8-OH-dG), protein carbonyl content and thiobarbituric acid reactive substances (TBARS). Pretreatment with apocynin also suppressed LPS/D-Gal-induced elevation of aminotransferase, alleviated histological abnormalities, inhibited the production of pro-inflammatory cytokine tumor necrosis factor α (TNF-α), blocked the activation of caspase cascade, reduced the count of TUNEL-positive cells and prevented LPS/D-Gal-induced mortality. Interestingly, post insult treatment with apocynin also suppressed LPS/D-Gal-induced oxidative stress, hepatocyte apoptosis, liver damage but improved the survival rate. Mechanistically, posttreatment with apocynin prohibited LPS/D-Gal-induced activation of the late stage pro-apoptotic AMP-activated protein kinase (AMPK)/c-Jun N-terminal kinase (JNK) pathway. Post-insult treatment with the antioxidant N-acetylcysteine also resulted in suppressed activation of AMPK/JNK, mitigated apoptosis and alleviated liver injury. These data suggest that NOX-derived ROS might be a crucial late stage detrimental factor in LPS/D-Gal-induced acute liver injury via promoting the activation of the pro-apoptotic AMPK/JNK pathway, and the NOX inhibitor might have important value in the pharmacological intervention of inflammation-base liver damage.

Impact of Prebiotics on Enteric Diseases and Oxidative Stress

In animals, the gastrointestinal microbiota are reported to play a major role in digestion, nutrient absorption and the release of energy through metabolism of food. Therefore, microbiota may be a factor for association between diet and enteric diseases and oxidative stress. The gut microbial composition and concentration are affected by diet throughout the life of an animal, and respond rapidly and efficiently to dietary alterations, in particular to the use of prebiotics. Prebiotics, which play an important role in mammalian nutrition, are defined as dietary ingredients that lead to specific changes in both the composition and activity of the gastrointestinal microbiota through suppressing the proliferation of pathogens and by modifying the growth of beneficial microorganisms in the host intestine. A review of the evidence suggests possible beneficial effects of prebiotics on host intestinal health, including immune stimulation, gut barrier enhancement and the alteration of the gastrointestinal microbiota, and these effects appear to be dependent on alteration of the bacterial composition and short-chain fatty acid (SCFA) production. The production of SCFAs depends on the microbes available in the gut and the type of prebiotics available. The SCFAs most abundantly generated by gastrointestinal microbiota are acetate, butyrate and propionate, which are reported to have physiological effects on the health of the host. Nowadays, prebiotics are widely used in a range of food products to improve the intestinal microbiome and stimulate significant changes to the immune system. Thus, a diet with prebiotic supplements may help prevent enteric disease and oxidative stress by promoting a microbiome associated with better growth performance. This paper provides an overview of the hypothesis that a combination of ingestible prebiotics, chitosan, fructooligosaccharides and inulin will help relieve the dysbiosis of the gut and the oxidative stress of the host.

Preconditioning of Human Decidua Basalis Mesenchymal Stem/Stromal Cells with Glucose Increased Their Engraftment and Anti-diabetic Properties

Background:

Mesenchymal stem/stromal cells (MSCs) from the decidua basalis (DBMSCs) of the human placenta have important functions that make them potential candidates for cellular therapy. Previously, we showed that DBMSC functions do not change significantly in a high oxidative stress environment, which was induced by hydrogen peroxide (H₂O₂) and immune cells. Here, we studied the consequences of glucose, another oxidative stress inducer, on the phenotypic and functional changes in DBMSCs.

Methods:

DBMSCs were exposed to a high level of glucose, and its effect on DBMSC phenotypic and functional properties was determined. DBMSC expression of oxidative stress and immune molecules after exposure to glucose were also identified.

Results:

Conditioning of DBMSCs with glucose improved their adhesion and invasion. Glucose also increased DBMSC expression of genes with survival, proliferation, migration, invasion, anti-inflammatory, anti-chemoattractant and antimicrobial properties. In addition, DBMSC expression of B7H4, an inhibitor of T cell proliferation was also enhanced by glucose. Interestingly, glucose modulated DBMSC expression of genes involved in insulin secretion and prevention of diabetes.

Conclusion:

These data show the potentially beneficial effects of glucose on DBMSC functions. Preconditioning of DBMSCs with glucose may therefore be a rational strategy for increasing their therapeutic potential by enhancing their engraftment efficiency. In addition, glucose may program DBMSCs into insulin producing cells with ability to counteract inflammation and infection associated with diabetes. However, future in vitro and in vivo studies are essential to investigate the findings of this study further.

Electronic supplementary material

The online version of this article (10.1007/s13770-020-00239-7) contains supplementary material, which is available to authorized users.

A closer look into NADPH oxidase inhibitors: Validation and insight into their mechanism of action

NADPH-oxidases (NOXs) purposefully produce reactive-oxygen-species (ROS) and are found in most kingdoms of life. The seven human NOXs are each characterized by a specific expression profile and a fine regulation to spatio-temporally tune ROS concentration in cells and tissues. One of the best known roles for NOXs is in host protection against pathogens but ROS themselves are important second messengers involved in tissue regeneration and the modulation of pathways that induce and sustain cell proliferation. As such, NOXs are attractive pharmacological targets in immunomodulation, fibrosis and cancer. We have studied an extensive number of available NOX inhibitors, with the specific aim to identify bona fide ligands versus ROS-scavenging molecules. Accordingly, we have established a comprehensive platform of biochemical and biophysical assays. Most of the investigated small molecules revealed ROS-scavenging and/or assay-interfering properties to various degrees. A few compounds, however, were also demonstrated to directly engage one or more NOX enzymes. Diphenylene iodonium was found to react with the NOXs' flavin and heme prosthetic groups to form stable adducts. We also discovered that two compounds, VAS2870 and VAS3947, inhibit NOXs through the covalent alkylation of a cysteine residue. Importantly, the amino acid involved in covalent binding was found to reside in the dehydrogenase domain, where the nicotinamide ring of NADPH is bound. This work can serve as a springboard to guide further development of bona fide ligands with either agonistic or antagonistic properties toward NOXs.

NOX4 is the main NADPH oxidase involved in the early stages of hematopoietic differentiation from human induced pluripotent stem cells

Reactive oxygen species (ROS) produced in hematopoietic stem cells (HSCs) are involved in the balance between quiescence, self-renewal, proliferation and differentiation processes. However the role of NOX enzymes on the early stages of hematopoietic differentiation is poorly investigated. For that, we used induced pluripotent stem cells (iPSCs) derived from X-linked Chronic Granulomatous Disease (X⁰CGD) patients with deficiency in NOX2, and AR22⁰CGD patients with deficiency in p22^phox subunit which decreases NOX1, NOX2, NOX3 and NOX4 activities. CD34⁺ hematopoietic progenitors were obtained after 7, 10 and 13 days of iPS/OP9 co-culture differentiation system. Neither NOX expression nor activity was found in Wild-type (WT), X⁰CGD and AR22⁰CGD iPSCs. Although NOX2 and NOX4 mRNA were found in WT, X⁰CGD and AR22⁰CGD iPSC-derived CD34⁺ cells at day 10 and 13 of differentiation, NOX4 protein was the only NOX enzyme expressed in these cells. A NADPH oxidase activity was measured in WT and X⁰CGD iPSC-derived CD34⁺ cells but not in AR22⁰CGD iPSC-derived CD34⁺ cells because of the absence of p22^phox, which is essential for the NOX4 activity. The absence of NOX4 activity and the poor NOX-independent ROS production in AR22⁰CGD iPSC-derived CD34⁺ cells favored the CD34⁺ cells production but lowered their hematopoietic potential compared to WT and X⁰CGD iPSC-derived CD34⁺ cells. In addition we found a large production of primitive AR22⁰CGD iPSC-derived progenitors at day 7 compared to the WT and X⁰CGD cell types. In conclusion NOX4 is the major NOX enzyme involved in the early stages of hematopoietic differentiation from iPSCs and its activity can modulate the production, the hematopoietic potential and the phenotype of iPSC-derived CD34⁺.

An overview of how on-call consultant paediatricians can recognise and manage severe primary immunodeficiencies

Severe primary paediatric immunodeficiency syndromes are rare and potentially fatal unless suspected, diagnosed and treated early. We provide clinical guidance and support for on-call consultant paediatricians working in secondary level hospitals on how to recognise and manage children with these conditions. Our paper addresses four conditions that risk the most severe outcomes if they are not adequately cared for during on-call periods, such as weekends: severe combined immunodeficiency, haemophagocytic lymphohistiocytosis, severe congenital neutropaenia and chronic granulomatous disease. CONCLUSION: On-call paediatricians are provided with advice on handling the most severe primary immunodeficiencies.

Equine bone marrow-derived mesenchymal stromal cells inhibit reactive oxygen species production by neutrophils

BACKGROUND

Polymorphonuclear neutrophils (PMN) are the largest leukocyte population in the blood of most mammals including horses, and play an important defensive role in many infectious diseases. However, the mechanisms that increase PMN as one of the main cellular subsets in the defense against pathogens could also be involved in the pathophysiology of dysregulated inflammatory conditions. Mesenchymal stem/stromal cells (MSCs) are a heterogeneous population with a modulatory potential on the inflammatory response and are known to interact with nearly all cells of the immune system, including PMN. In this study, the in vitro modulation of equine bone marrow-derived MSCs on equine PMN phagocytosis, ROS production, and NETs generation was assessed.

RESULTS

In co-culture with MSCs, unstimulated PMN produce less ROS (2.88 % ± 1.43) than PMN in single culture (5.89 % ± 2.63) (p = 0.016). Moreover, PMN co-cultured with MSCs remain conditioned to produce fewer ROS after PMA stimulation in comparison to PMN in single culture (p < 0.05). Additionally, it was found that incubation with MSC supernatant strongly inhibited ROS production (83 % ± 6.35 less than control) without affecting phagocytosis or capacity for NETosis (p < 0.01).

CONCLUSIONS

These results suggest a modulatory effect of equine BM-derived MSCs on PMN respiratory burst, without impairing other important microbicidal functions. This supports the potential use of equine MSCs in excessive or persistent inflammatory conditions in which neutrophils are the main effector cells.

A Manganese-Superoxide Dismutase From Thermus thermophilus HB27 Suppresses Inflammatory Responses and Alleviates Experimentally Induced Colitis

BACKGROUND

Superoxide dismutase (SOD) is an attractive therapeutic agent to ameliorate oxidative stress that is critical for the initiation and progression of inflammatory bowel disease (IBD). However, the short life of SOD limits its clinical application. In this study, we aim to examine the therapeutic effects of a hyperthermostable SOD from the Thermus thermophilus HB27 (TtSOD) for treatment of experimentally induced IBD.

METHODS

A recombinant TtSOD was expressed and purified from Escherichia coli, and its therapeutic effects were examined in 2 experimental IBD animal models.

RESULTS

In IBD induced by 2,4,6-trinitrobenzenesulfonic acid in zebrafish, TtSOD treatment decreased intestinal enlargement and attenuated neutrophil infiltration, resulting in alleviation of enterocolitis. In mice, SOD activity was substantially increased in the intestine after oral gavage of TtSOD, which ameliorated gut inflammation, preserved gut barrier function, and attenuated the severity of dextran sulfate sodium-induced colitis. Furthermore, TtSOD inhibited lipopolysaccharide-induced production of reactive oxygen species and inflammatory responses in mouse bone marrow-derived macrophages.

CONCLUSIONS

Our results demonstrate that TtSOD possesses therapeutic activities toward experimentally induced IBD, offering new clinical treatment options for patients with IBD.

A novel NOX2 inhibitor attenuates human neutrophil oxidative stress and ameliorates inflammatory arthritis in mice

Neutrophil infiltration plays a significant pathological role in inflammatory diseases. NADPH oxidase type 2 (NOX2) is a respiratory burst oxidase that generates large amounts of superoxide anion (O₂^•−) and subsequent other reactive oxygen species (ROS). NOX2 is an emerging therapeutic target for treating neutrophilic inflammatory diseases. Herein, we show that 4-[(4-(dimethylamino)butoxy)imino]-1-methyl-1H-benzo[f]indol-9(4H)-one (CYR5099) acts as a NOX2 inhibitor and exerts a protective effect against complete Freund's adjuvant (CFA)-induced inflammatory arthritis in mice. CYR5099 restricted the production of O₂^•− and ROS, but not the elastase release, in human neutrophils activated with various stimulators. The upstream signaling pathways of NOX2 were not inhibited by CYR5099. Significantly, CYR5099 inhibited NOX2 activity in activated human neutrophils and in reconstituted subcellular assays. In addition, CYR5099 reduced ROS production, neutrophil infiltration, and edema in CFA-induced arthritis in mice. Our findings suggest that CYR5099 is a NOX2 inhibitor and has therapeutic potential for treating neutrophil-dominant oxidative inflammatory disorders.

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CYR5099 is a NOX2 inhibitor.

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CYR5099 inhibits human neutrophil respiratory burst and adhesion.

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CYR5099 reduces ROS production, neutrophil infiltration, and edema on mouse arthritis.

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CYR5099 has potential to treat neutrophil-mediated inflammatory diseases.

Kinetic Analysis of Phagosomal ROS Generation

Phagosomal ROS generation is critical for our immune defense against microbial infections. Quantitative assessment of phagosomal ROS production is required to understand the complex relationship between the phagocyte and the microbe, in particular for pathogens that resist phagosomal destruction. ROS detection is difficult due to the transient nature of the reactive species and their multiple interactions with the environment. Direct labeling of phagocytic prey with a ROS-sensitive dye allows to target the dye into the phagosome and to follow the kinetics of phagosomal ROS production on a single phagosome base. Here we describe the basic labeling procedure, the quality assessment, and the imaging technique to achieve this kinetic analysis.

Structure and mechanisms of ROS generation by NADPH oxidases

NADPH oxidases (NOXs) are integral membrane enzymes that produce reactive oxygen species. Humans have seven NOX enzymes that feature a very similar catalytic core but distinct regulatory mechanisms. The recent structural elucidation of the NOX catalytic domains has been a step forward in the field. NADPH, FAD, and two hemes form a linear array of redox cofactors that transfer electrons across to the two sides of the membrane. Oxygen is reduced through an unusual outer sphere mechanism that does not involve any covalent intermediate with the heme iron. Several recent studies have expanded the roles of NOXs in cell signaling, innate immune response, and cell proliferation including oncogenic transformation. This work reinforces NOX-generated ROS as powerful signaling molecules. A challenging question is to understand the specific mechanisms of enzyme regulation and to harness the growing insight on NOXs' structure and biochemistry to generate more powerful small-molecule modulators of NOX activities.

Reactive species and pathogen antioxidant networks during phagocytosis

This review discusses the generation of phagosomal cytotoxic reactive species by activated macrophages and neutrophils for the control of intracellular pathogens, and the mechanisms by which microbes combat host-derived oxidants via antioxidant networks that mitigate the redox-dependent control of infection.

The generation of phagosomal cytotoxic reactive species (i.e., free radicals and oxidants) by activated macrophages and neutrophils is a crucial process for the control of intracellular pathogens. The chemical nature of these species, the reactions they are involved in, and the subsequent effects are multifaceted and depend on several host- and pathogen-derived factors that influence their production rates and catabolism inside the phagosome. Pathogens rely on an intricate and synergistic antioxidant armamentarium that ensures their own survival by detoxifying reactive species. In this review, we discuss the generation, kinetics, and toxicity of reactive species generated in phagocytes, with a focus on the response of macrophages to internalized pathogens and concentrating on Mycobacterium tuberculosis and Trypanosoma cruzi as examples of bacterial and parasitic infection, respectively. The ability of pathogens to deal with host-derived reactive species largely depends on the competence of their antioxidant networks at the onset of invasion, which in turn can tilt the balance toward pathogen survival, proliferation, and virulence over redox-dependent control of infection.

Missense variants in NOX1 and p22phox in a case of very-early-onset inflammatory bowel disease are functionally linked to NOD2

Whole-genome and whole-exome sequencing of individual patients allow the study of rare and potentially causative genetic variation. In this study, we sequenced DNA of a trio comprising a boy with very-early-onset inflammatory bowel disease (veoIBD) and his unaffected parents. We identified a rare, X-linked missense variant in the NAPDH oxidase NOX1 gene (c.C721T, p.R241C) in heterozygous state in the mother and in hemizygous state in the patient. We discovered that, in addition, the patient was homozygous for a common missense variant in the CYBA gene (c.T214C, p.Y72H). CYBA encodes the p22phox protein, a cofactor for NOX1. Functional assays revealed reduced cellular ROS generation and antibacterial capacity of NOX1 and p22phox variants in intestinal epithelial cells. Moreover, the identified NADPH oxidase complex variants affected NOD2-mediated immune responses, and p22phox was identified as a novel NOD2 interactor. In conclusion, we detected missense variants in a veoIBD patient that disrupt the host response to bacterial challenges and reduce protective innate immune signaling via NOD2. We assume that the patient's individual genetic makeup favored disturbed intestinal mucosal barrier function.

Engineering stability in NADPH oxidases: A common strategy for enzyme production

NADPH oxidases (NOXs) are membrane enzymes whose sole function is the generation of reactive oxygen species. Humans have seven NOX isoenzymes that feature distinct functions in immune response and cell signaling but share the same catalytic core comprising a FAD-binding dehydrogenase domain and a heme-binding transmembrane domain. We previously described a mutation that stabilizes the dehydrogenase domain of a prokaryotic homolog of human NOX5. The thermostable mutant exhibited a large 19 °C increase in the apparent melting temperature (app T_m) and a much tighter binding of the FAD cofactor, which allowed the crystallization and structure determination of the domain holo-form. Here, we analyze the transferability of this mutation onto prokaryotic and eukaryotic full-length NOX enzymes. We found that the mutation exerts a significative stabilizing effect on the full-length NOX5 from both Cylindrospermum stagnale (app T_m increase of 8 °C) and Homo sapiens (app ΔT_m of 2 °C). Enhanced thermal stability resulted in more homogeneous preparations of the bacterial NOX5 with less aggregation problems. Moreover, we also found that the mutation increases the overall expression of recombinant human NOX4 and NOX5 in mammalian cells. Such a 2-5-fold increase is mainly due to the lowered cell toxicity, which leads to higher biomasses. Because of the high sequence identity of the catalytic core within this family of enzymes, this strategy can be a general tool to boost the production of all NOXs.

Identification of Two Missense Mutations in DUOX1 (p.R1307Q) and DUOXA1 (p.R56W) That Can Cause Congenital Hypothyroidism Through Impairing H2O2 Generation

Context: The DUOX/DUOXA systems play a key role in H₂O₂ generation in thyroid cells, which is required for iodine organification and thyroid hormone synthesis. DUOX2/DUOXA2 defects can cause congenital hypothyroidism (CH), but it is unknown whether DUOX1/DUOXA1 mutations can also cause CH. Objective: We aimed to identify DUOX1/DUOXA1 mutations and explore their role in the development of CH by investigating their functional impacts on H₂O₂ generation. Patients and Methods: Forty-three children with CH with goiter were enrolled, in whom all exons and flanking intronic regions of DUOX1/DUOXA1 were directly sequenced. We characterized the functional effects of identified mutations on the expression of DUOX1 and DUOXA1 and H₂O₂ generation. Results: We identified a heterozygous DUOX1 missense mutation (G > A base substitution at nucleotide 3920 in exon 31) that changed a highly conserved arginine to glutamine at residual 1307 (p.R1307Q) in patient 1. A heterozygous-missense mutation (c.166 C>T; p.R56W) was identified in DUOXA1 in patient 2. Functional studies demonstrated that both p.R1307Q mutant or p.R56W mutant decreased the DUOX1 expression at mRNA and protein levels, with a corresponding impairment in H₂O₂ generation (P < 0.01). The results also showed that intact DUOXA1 was required for full activity of DUOX1 and H₂O₂ generation. Conclusions: We have identified two heterozygous missense mutations in DUOX1 and DUOXA1 in two patients that can cause CH through disrupting the coordination of DUOX1 and DUOXA1 in the generation of H₂O₂. This study for the first time demonstrates that the DUOX1/DUOXA1 system, if genetically defective, can cause CH.

Imaging Intestinal ROS in Homeostatic Conditions Using L-012

Reactive oxygen species (ROS) are critical redox regulators of cellular dynamics controlling homeostasis. Although numerous fluorescent probes are currently available to measure ROS in cell-based assays, the short-lived nature of these molecules renders their detection challenging in more complex biological systems, such as the gastrointestinal tract in vivo. However, in the past decade, significant progress has been made in the development of novel imaging technologies and probes, facilitating ROS quantification with high sensitivity, selectivity, and temporal resolution. The IVIS Spectrum (PerkinElmer) is an optical imaging system for small animal imaging allowing precise and noninvasive visualization of fluorescent or bioluminescent signals. Here, we describe a reproducible and comprehensive method for the measurement of physiological intestinal NADPH oxidase-derived ROS by using the chemiluminescent probe L-012. Using transgenic mice deficient in Nox isoforms expressed in the intestinal mucosa, we delineate the contribution of gut epithelial versus immune cell NADPH oxidase activity in homeostatic conditions. We also discuss L-012 probe specificity and potential alternatives for in vivo studies.

NAPDH Oxidases in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD), categorized as ulcerative colitis (UC), Crohn's disease (CD), or IBD-undetermined (IBDU), are increasing in incidence. IBD is understood to result from environmental factors interacting with a pre-existing genetic susceptibility. Approximately 1% of all patients with inflammatory bowel disease (IBD) are diagnosed before the age of 6 years, designated as very-early-onset IBD (VEOIBD). This cohort of patients is distinguished from other age groups by differences in disease phenotype and by a higher burden of genetic mutations. Recent studies have linked mutations in NADPH oxidase function to VEOIBD and even pediatric IBD. Loss-of-function NOX2 variants expressed in phagocytes and NOX1/DUOX2 variants expressed in intestinal epithelial cells have been associated with VEOIBD and pediatric and adult IBD in patients. Cell and animal studies suggest a protective role for these reactive oxygen species (ROS)-producing enzymes in intestinal homeostasis-a paradigm that challenges the conventional concept that only increased ROS result in cell and tissue damage. Examining the role of NADPH oxidases in VEOIBD may improve our understanding of the pathophysiology of this disease and will uncover new therapeutic possibilities.

The Plasma Membrane: A Platform for Intra- and Intercellular Redox Signaling

Membranes are of outmost importance to allow for specific signal transduction due to their ability to localize, amplify, and direct signals. However, due to the double-edged nature of reactive oxygen species (ROS)—toxic at high concentrations but essential signal molecules—subcellular localization of ROS-producing systems to the plasma membrane has been traditionally regarded as a protective strategy to defend cells from unwanted side-effects. Nevertheless, specialized regions, such as lipid rafts and caveolae, house and regulate the activated/inhibited states of important ROS-producing systems and concentrate redox targets, demonstrating that plasma membrane functions may go beyond acting as a securing lipid barrier. This is nicely evinced by nicotinamide adenine dinucleotide phosphate (NADPH)-oxidases (NOX), enzymes whose primary function is to generate ROS and which have been shown to reside in specific lipid compartments. In addition, membrane-inserted bidirectional H₂O₂-transporters modulate their conductance precisely during the passage of the molecules through the lipid bilayer, ensuring time-scaled delivery of the signal. This review aims to summarize current evidence supporting the role of the plasma membrane as an organizing center that serves as a platform for redox signal transmission, particularly NOX-driven, providing specificity at the same time that limits undesirable oxidative damage in case of malfunction. As an example of malfunction, we explore several pathological situations in which an inflammatory component is present, such as inflammatory bowel disease and neurodegenerative disorders, to illustrate how dysregulation of plasma-membrane-localized redox signaling impacts normal cell physiology.

Newborn Screening and Molecular Profile of Congenital Hypothyroidism in a Chinese Population

is the most gene mutation in Chinese CH patients.

Targeted next-generation sequencing of thirteen causative genes in Chinese patients with congenital hypothyroidism

To identify the spectrum and prevalence of thirteen causative genes mutations in congenital hypothyroidism (CH) patients, we collected blood samples and extracted genomic DNA of 106 CH patients, and designed a customized targeted next-generation sequencing panel containing 13 CH-causing genes to detect mutations. A total of 132 mutations were identified in 65.09% of patients (69/106) on the following nine genes: DUOX2, TG, TPO, TSHR, TTF1, TTF2, NKX2-5, PAX8 and GNAS. 69.70% (92/132) mutations related to thyroid dyshormonogenesis genes, including DUOX2 (n = 49), TG (n = 35), and TPO (n = 8). 21.21% (28/132) mutations related to thyroid dysgenesis genes, including TSHR (n = 19), TTF1 (n = 5), TTF2 (n = 1), PAX8 (n = 2), and NKX2-5 (n = 1). 9.09% (12/132) mutations related to GNAS, which was associated with thyrotropin resistance. No mutation of THRA, TSHB, IYD or SLC5A5 was detected. Among 69 mutations detected patients, 41 (59.42%) patients were two or more mutations detected, and mutations of 30 (43.48%) patients related to two or three genes. According to the pathomechanism of the mutant genes, 57.97% CH patients were classified as thyroid dyshormonogenesis. Overall, DUOX2, TG and TSHR mutations were the most common genetic defects in Chinese CH patients, and thyroid dyshormonogenesis could be the first genetic etiology of CH in Chinese. Besides, multiple mutations accounts for a part of genetic pathogenesis.

Redox Signaling of NADPH Oxidases Regulates Oxidative Stress Responses, Immunity and Aging

An accumulating body of evidence suggests that transient or physiological reactive oxygen species (ROS) generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidases act as a redox signal to re-establish homeostasis. The capacity to re-establish homeostasis progressively declines during aging but is maintained in long-lived animals to promote healthy aging. In the model organism Caenorhabditis elegans, ROS generated by dual oxidases (Duox) are important for extracellular matrix integrity, pathogen defense, oxidative stress resistance, and longevity. The Duox enzymatic activity is tightly regulated and under cellular control. Developmental molting cycles, pathogen infections, toxins, mitochondrial-derived ROS, drugs, and small GTPases (e.g., RHO-1) can activate Duox (BLI-3) to generate ROS, whereas NADPH oxidase inhibitors and negative regulators, such as MEMO-1, can inhibit Duox from generating ROS. Three mechanisms-of-action have been discovered for the Duox/BLI-3-generated ROS: (1) enzymatic activity to catalyze crosslinking of free tyrosine ethyl ester in collagen bundles to stabilize extracellular matrices, (2) high ROS bursts/levels to kill pathogens, and (3) redox signaling activating downstream kinase cascades to transcription factors orchestrating oxidative stress and immunity responses to re-establish homeostasis. Although Duox function at the cell surface is well established, recent genetic and biochemical data also suggests a novel role for Duoxs at the endoplasmic reticulum membrane to control redox signaling. Evidence underlying these mechanisms initiated by ROS from NADPH oxidases, and their relevance for human aging, are discussed in this review. Appropriately controlling NADPH oxidase activity for local and physiological redox signaling to maintain cellular homeostasis might be a therapeutic strategy to promote healthy aging.

Pulmonary metastatic colonisation and granulomas in NOX2-deficient mice

Metastasis is the leading cause of death in cancer patients, and successful colonisation of a secondary organ by circulating tumour cells (CTCs) is the rate‐limiting step of this process. We used tail‐vein injection of B16‐F10 melanoma cells into mice to mimic the presence of CTCs and to allow for the assessment of host (microenvironmental) factors that regulate pulmonary metastatic colonisation. We found that mice deficient for the individual subunits of the NADPH oxidase of myeloid cells, NOX2 (encoded by Cyba, Cybb, Ncf1, Ncf2, and Ncf4), all showed decreased pulmonary metastatic colonisation. To understand the role of NOX2 in controlling tumour cell survival in the pulmonary microenvironment, we focused on Cyba‐deficient (Cyba^tm1a) mice, which showed the most significant decrease in metastatic colonisation. Interestingly, histological assessment of pulmonary metastatic colonisation was not possible in Cyba^tm1a mice, owing to the presence of large granulomas composed of galectin‐3 (Mac‐2)‐positive macrophages and eosinophilic deposits; granulomas of variable penetrance and severity were also found in Cyba^tm1a mice that were not injected with melanoma cells, and these contributed to their decreased survival. The decreased pulmonary metastatic colonisation of Cyba^tm1a mice was not due to any overt defects in vascular permeability, and bone marrow chimaeras confirmed a role for the haematological system in the reduced metastatic colonisation phenotype. Examination of the lymphocyte populations, which are known key regulators of metastatic colonisation, revealed an enhanced proportion of activated T and natural killer cells in the lungs of Cyba^tm1a mice, relative to controls. The reduced metastatic colonisation, presence of granulomas and altered immune cell populations observed in Cyba^tm1a lungs were mirrored in Ncf2‐deficient (Ncf2^tm1a) mice. Thus, we show that NOX2 deficiency results in both granulomas and the accumulation of antitumoural immune cells in the lungs that probably mediate the decreased pulmonary metastatic colonisation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

NADPH Oxidase and Guanylate Binding Protein 5 Restrict Survival of Avirulent Type III Strains of Toxoplasma gondii in Naive Macrophages

Toxoplasma infections in humans and other mammals are largely controlled by IFN-γ produced by the activated adaptive immune system. However, we still do not completely understand the role of cell-intrinsic functions in controlling Toxoplasma or other apicomplexan infections. The present work identifies intrinsic activities in naive macrophages in counteracting T. gondii infection. Using an avirulent strain of T. gondii, we highlight the importance of Nox complexes in conferring protection against parasite infection both in vitro and in vivo. We also identify Gbp5 as a novel macrophage factor involved in limiting intracellular infection by avirulent strains of T. gondii. The rarity of human infections caused by type III strains suggests that these mechanisms may also be important in controlling human toxoplasmosis. These findings further extend our understanding of host responses and defense mechanisms that act to control parasitic infections at the cellular level.

Phagocytic cells are the first line of innate defense against intracellular pathogens, and yet Toxoplasma gondii is renowned for its ability to survive in macrophages, although this paradigm is based on virulent type I parasites. Surprisingly, we find that avirulent type III parasites are preferentially cleared in naive macrophages, independent of gamma interferon (IFN-γ) activation. The ability of naive macrophages to clear type III parasites was dependent on enhanced activity of NADPH oxidase (Nox)-generated reactive oxygen species (ROS) and induction of guanylate binding protein 5 (Gbp5). Macrophages infected with type III parasites (CTG strain) showed a time-dependent increase in intracellular ROS generation that was higher than that induced by type I parasites (GT1 strain). The absence of Nox1 or Nox2, gp91 subunit isoforms of the Nox complex, reversed ROS-mediated clearance of CTG parasites. Consistent with this finding, both Nox1^−/− and Nox2^−/− mice showed higher susceptibility to CTG infection than wild-type mice. Additionally, Gbp5 expression was induced upon infection and the enhanced clearance of CTG strain parasites was reversed in Gbp5^−/− macrophages. Expression of a type I ROP18 allele in CTG prevented clearance in naive macrophages, suggesting that it plays a role counteracting Gbp5. Although ROS and Gbp5 have been linked to activation of the NLRP3 inflammasome, clearance of CTG parasites did not rely on induction of pyroptosis. Collectively, these findings reveal that not all strains of T. gondii are adept at avoiding clearance in macrophages and define new roles for ROS and Gbps in controlling this important intracellular pathogen.

Astaxanthin, a xanthophyll carotenoid, prevents development of dextran sulphate sodium-induced murine colitis

Astaxanthin is a xanthophyll carotenoid, which possesses strong scavenging effect on reactive oxygen species. In this study, we examined the effect of astaxanthin on dextran sulfate sodium (DSS)-induced colitis in mice. Experimental colitis was induced by the oral administration of 4% w/v DSS in tap water in C57BL/6J mice. Astaxanthin was mixed with a normal rodent diet (0.02 or 0.04%). Astaxanthin significantly ameliorated DSS-induced body weight loss and reduced the disease activity index. The ameliorating effects was observed in a dose-dependent manner. Immunochemical analyses showed that astaxanthin markedly suppressed DSS-induced histological inflammatory changes (inflammatory cell infiltration, edematous changes and goblet cell depletion). Plasma levels of malondialdehyde and 8-hydroxy-2-deoxyguanosine were significantly reduced by the administration of 0.04% astaxanthin. Astaxanthin significantly suppressed the mucosal mRNA expression of IL-1β, IL-6, TNF-α, IL-36α and IL-36γ. Astaxanthin blocked the DSS-induced translocation of NF-κB p65 and AP-1 (c-Jun) into the nucleus of mucosal epithelial cells, and also suppressed DSS-induced mucosal activation of MAPKs (ERK1/2, p38 and JNK). In conclusion, astaxanthin prevented the development of DSS-induced colitis via the direct suppression of NF-κB, AP-1 and MAPK activation. These findings suggest that astaxanthin is a novel candidate as a therapeutic option for the treatment of inflammatory bowel disease.

Conformation of the N-Terminal Ectodomain Elicits Different Effects on DUOX Function: A Potential Impact on Congenital Hypothyroidism Caused by a H2O2 Production Defect

BACKGROUND

Dual oxidases (DUOX1 and DUOX2) were initially identified as H₂O₂ sources involved in thyroid hormone synthesis. Congenital hypothyroidism (CH) resulting from inactivating mutations in the DUOX2 gene highlighted that DUOX2 is the major H₂O₂ provider to thyroperoxidase. The role of DUOX1 in the thyroid remains unknown. A recent study suggests that it could compensate for DUOX2 deficiency in CH. Both DUOX enzymes and their respective maturation factors DUOXA1 and DUOXA2 form a stable complex at the cell surface, which is fundamental for their enzymatic activity. Recently, intra- and intermolecular disulfide bridges were identified that are essential for the structure and the function of the DUOX2-DUOXA2 complex. This study investigated the involvement of cysteine residues conserved in DUOX1 toward the formation of disulfide bridges, which could be important for the function of the DUOX1DUOXA1 complex.

METHODS

To analyze the role of these cysteine residues in both the targeting and function of dual oxidase, different human DUOX1 mutants were constructed, where the cysteine residues were replaced with glycine. The effect of these mutations on cell surface expression and H₂O₂-generating activity of the DUOX1-DUOXA1 complex was analyzed.

RESULTS

Mutations of two cysteine residues (C118 and C1165), involved in the formation of the intramolecular disulfide bridge between the N-terminal ectodomain and one of the extracellular loops, mildly altered the function and the targeting of DUOX1, while this bridge is crucial for DUOX2 function. Unlike DUOXA2, with respect to DUOX2, the stability of the maturation factor DUOXA1 is not dependent on the oxidative folding of DUOX1. Only mutation of C579 induced a strong alteration of both targeting and function of the oxidase by preventing the covalent interaction between DUOX1 and DUOXA1.

CONCLUSION

An intermolecular disulfide bridge rather than an intramolecular disulfide bridge is important for both the trafficking and H₂O₂-generating activity of the DUOX1-DUOXA1 complex.

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.

Hydrogen peroxide production by lactobacilli promotes epithelial restitution during colitis

Inflammatory bowel disease (IBD) is a multifactorial chronic inflammatory disease of the gastrointestinal tract, characterized by cycles of acute flares, recovery and remission phases. Treatments for accelerating tissue restitution and prolonging remission are scarce, but altering the microbiota composition to promote intestinal homeostasis is considered a safe, economic and promising approach. Although probiotic bacteria have not yet fulfilled fully their promise in clinical trials, understanding the mechanism of how they exert beneficial effects will permit devising improved therapeutic strategies. Here we probe if one of the defining features of lactobacilli, the ability to generate nanomolar H2O2, contributes to their beneficial role in colitis. H2O2 generation by wild type L. johnsonii was modified by either deleting or overexpressing the enzymatic H2O2 source(s) followed by orally administering the bacteria before and during DSS colitis. Boosting luminal H2O2 concentrations within a physiological range accelerated recovery from colitis, while significantly exceeding this H2O2 level triggered bacteraemia. This study supports a role for increasing H2O2 within the physiological range at the epithelial barrier, independently of the enzymatic source and/or delivery mechanism, for inducing recovery and remission in IBD.

Clinical and Genomic Correlates of Neutrophil Reactive Oxygen Species Production in Pediatric Patients With Crohn's Disease

BACKGROUND & AIMS

Individuals with monogenic disorders of phagocyte function develop chronic colitis that resembles Crohn's disease (CD). We tested for associations between mutations in genes encoding reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, neutrophil function, and phenotypes of CD in pediatric patients.

METHODS

We performed whole-exome sequence analysis to identify mutations in genes encoding NADPH oxidases (such as CYBA, CYBB, NCF1, NCF2, NCF4, RAC1, and RAC2) using DNA from 543 pediatric patients with inflammatory bowel diseases. Blood samples were collected from an additional 129 pediatric patients with CD and 26 children without IBD (controls); we performed assays for neutrophil activation, reactive oxygen species (ROS) production, and bacteria uptake and killing. Whole-exome sequence analysis was performed using DNA from 46 of the children with CD to examine associations with NADPH gene mutations; RNA sequence analyses were performed using blood cells from 46 children with CD to test for variations in neutrophil gene expression associated with ROS production.

RESULTS

We identified 26 missense mutations in CYBA, CYBB, NCF1, NCF2, and NCF4. Patients with CD who carried mutations in these genes were 3-fold more likely to have perianal disease (P = .0008) and stricturing complications (P = .002) than children with CD without these mutations. Among patients with CD with none of these mutations, 9% had undergone abdominal surgery; among patients with mutations in these NADPH oxidase genes, 31% had undergone abdominal surgery (P = .0004). A higher proportion of neutrophils from children with CD had low ROS production (47%) than from controls (15%) among the 129 patients tested for ROS (P = .002). Minor alleles of the NADPH genes were detected in 7% of children with CD whose neutrophils produced normal levels of ROS vs 38% of children whose neutrophils produced low levels of ROS (P = .009). Neutrophils that produced low levels of ROS had specific alterations in genes that regulate glucose metabolism and antimicrobial responses.

CONCLUSIONS

We identified missense mutations in genes that encode NADPH oxidases in children with CD; these were associated with a more aggressive disease course and reduced ROS production by neutrophils from the patients.

Differential cell surface recruitment of the superoxide-producing NADPH oxidases Nox1, Nox2 and Nox5: The role of the small GTPase Sar1

Transmembrane glycoproteins, synthesized at the endoplasmic reticulum (ER), generally reach the Golgi apparatus in COPII-coated vesicles en route to the cell surface. Here, we show that the bona fide nonglycoprotein Nox5, a transmembrane superoxide-producing NADPH oxidase, is transported to the cell surface in a manner resistant to co-expression of Sar1 (H79G), a GTP-fixed mutant of the small GTPase Sar1, which blocks COPII vesicle fission from the ER. In contrast, Sar1 (H79G) effectively inhibits ER-to-Golgi transport of glycoproteins including the Nox5-related oxidase Nox2. The trafficking of Nox2, but not that of Nox5, is highly sensitive to over-expression of syntaxin 5 (Stx5), a t-SNARE required for COPII ER-to-Golgi transport. Thus, Nox2 and Nox5 mainly traffic via the Sar1/Stx5-dependent and -independent pathways, respectively. Both participate in Nox1 trafficking, as Nox1 advances to the cell surface in two differentially N-glycosylated forms, one complex and one high mannose, in a Sar1/Stx5-dependent and -independent manner, respectively. Nox2 and Nox5 also can use both pathways: a glycosylation-defective mutant Nox2 is weakly recruited to the plasma membrane in a less Sar1-dependent manner; N-glycosylated Nox5 mutants reach the cell surface in part as the complex form Sar1-dependently, albeit mainly as the high-mannose form in a Sar1-independent manner.

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.

Biosensors for spatiotemporal detection of reactive oxygen species in cells and tissues

Redox biology has become a major issue in numerous areas of physiology. Reactive oxygen species (ROS) have a broad range of roles from signal transduction to growth control and cell death. To understand the nature of these roles, accurate measurement of the reactive compounds is required. An increasing number of tools for ROS detection is available; however, the specificity and sensitivity of these tools are often insufficient. Furthermore, their specificity has been rarely evaluated in complex physiological conditions. Many ROS probes are sensitive to environmental conditions in particular pH, which may interfere with ROS detection and cause misleading results. Accurate detection of ROS in physiology and pathophysiology faces additional challenges concerning the precise localization of the ROS and the timing of their production and disappearance. Certain ROS are membrane permeable, and certain ROS probes move across cells and organelles. Targetable ROS probes such as fluorescent protein-based biosensors are required for accurate localization. Here we analyze these challenges in more detail, provide indications on the strength and weakness of current tools for ROS detection, and point out developments that will provide improved ROS detection methods in the future. There is no universal method that fits all situations in physiology and cell biology. A detailed knowledge of the ROS probes is required to choose the appropriate method for a given biological problem. The knowledge of the shortcomings of these probes should also guide the development of new sensors.

A Case-Control Study of the Genetic Variability in Reactive Oxygen Species-Metabolizing Enzymes in Melanoma Risk

Recent studies have shown that ultraviolet (UV)-induced chemiexcitation of melanin fragments leads to DNA damage; and chemiexcitation of melanin fragments requires reactive oxygen species (ROS), as ROS excite an electron in the melanin fragments. In addition, ROS also cause DNA damages on their own. We hypothesized that ROS producing and metabolizing enzymes were major contributors in UV-driven melanomas. In this case-control study of 349 participants, we genotyped 23 prioritized single nucleotide polymorphisms (SNPs) in nicotinamide adenine dinucleotide phosphate (NADPH) oxidases 1 and 4 (NOX1 and NOX4, respectively), CYBA, RAC1, superoxide dismutases (SOD1, SOD2, and SOD3) and catalase (CAT), and analyzed their associated melanoma risk. Five SNPs, namely rs1049255 (CYBA), rs4673 (CYBA), rs10951982 (RAC1), rs8031 (SOD2), and rs2536512 (SOD3), exhibited significant genotypic frequency differences between melanoma cases and healthy controls. In simple logistic regression, RAC1 rs10951982 (odds ratio (OR) 8.98, 95% confidence interval (CI): 5.08 to 16.44; p < 0.001) reached universal significance (p = 0.002) and the minor alleles were associated with increased risk of melanoma. In contrast, minor alleles in SOD2 rs8031 (OR 0.16, 95% CI: 0.06 to 0.39; p < 0.001) and SOD3 rs2536512 (OR 0.08, 95% CI: 0.01 to 0.31; p = 0.001) were associated with reduced risk of melanoma. In multivariate logistic regression, RAC1 rs10951982 (OR 6.15, 95% CI: 2.98 to 13.41; p < 0.001) remained significantly associated with increased risk of melanoma. Our results highlighted the importance of RAC1, SOD2, and SOD3 variants in the risk of melanoma.

NADPH Oxidase Deficiency: A Multisystem Approach

The immune system is a complex system able to recognize a wide variety of host agents, through different biological processes. For example, controlled changes in the redox state are able to start different pathways in immune cells and are involved in the killing of microbes. The generation and release of ROS in the form of an “oxidative burst” represent the pivotal mechanism by which phagocytic cells are able to destroy pathogens. On the other hand, impaired oxidative balance is also implicated in the pathogenesis of inflammatory complications, which may affect the function of many body systems. NADPH oxidase (NOX) plays a pivotal role in the production of ROS, and the defect of its different subunits leads to the development of chronic granulomatous disease (CGD). The defect of the different NOX subunits in CGD affects different organs. In this context, this review will be focused on the description of the effect of NOX2 deficiency in different body systems. Moreover, we will also focus our attention on the novel insight in the pathogenesis of immunodeficiency and inflammation-related manifestations and on the protective role of NOX2 deficiency against the development of atherosclerosis.

Ischemic Retinopathies: Oxidative Stress and Inflammation

Ischemic retinopathies (IRs), such as retinopathy of prematurity (ROP), diabetic retinopathy (DR), and (in many cases) age-related macular degeneration (AMD), are ocular disorders characterized by an initial phase of microvascular changes that results in ischemia, followed by a second phase of abnormal neovascularization that may culminate into retinal detachment and blindness. IRs are complex retinal conditions in which several factors play a key role during the development of the different pathological stages of the disease. Increasing evidence reveals that oxidative stress and inflammatory processes are important contributors to the pathogenesis of IRs. Despite the beneficial effects of the photocoagulation and anti-VEGF therapy during neovascularization phase, the need to identify novel targets to prevent initial phases of these ocular pathologies is still needed. In this review, we provide an update on the involvement of oxidative stress and inflammation in the progression of IRs and address some therapeutic interventions by using antioxidants and anti-inflammatory agents.

Thermodynamic Aspects and Reprogramming Cellular Energy Metabolism during the Fibrosis Process

Fibrosis is characterized by fibroblast proliferation and fibroblast differentiation into myofibroblasts, which generate a relaxation-free contraction mechanism associated with excessive collagen synthesis in the extracellular matrix, which promotes irreversible tissue retraction evolving towards fibrosis. From a thermodynamic point of view, the mechanisms leading to fibrosis are irreversible processes that can occur through changing the entropy production rate. The thermodynamic behaviors of metabolic enzymes involved in fibrosis are modified by the dysregulation of both transforming growth factor β (TGF-β) signaling and the canonical WNT/β-catenin pathway, leading to aerobic glycolysis, called the Warburg effect. Molecular signaling pathways leading to fibrosis are considered dissipative structures that exchange energy or matter with their environment far from the thermodynamic equilibrium. The myofibroblastic cells arise from exergonic processes by switching the core metabolism from oxidative phosphorylation to glycolysis, which generates energy and reprograms cellular energy metabolism to induce the process of myofibroblast differentiation. Circadian rhythms are far-from-equilibrium thermodynamic processes. They directly participate in regulating the TGF-β and WNT/β-catenin pathways involved in energetic dysregulation and enabling fibrosis. The present review focusses on the thermodynamic implications of the reprogramming of cellular energy metabolism, leading to fibroblast differentiation into myofibroblasts through the positive interplay between TGF-β and WNT/β-catenin pathways underlying in fibrosis.

The NOX Family of Proteins Is Also Present in Bacteria

Transmembrane NADPH oxidase (NOX) enzymes have been so far only characterized in eukaryotes. In most of these organisms, they reduce molecular oxygen to superoxide and, depending on the presence of additional domains, are called NOX or dual oxidases (DUOX). Reactive oxygen species (ROS), including superoxide, have been traditionally considered accidental toxic by-products of aerobic metabolism. However, during the last decade it has become evident that both O₂^•− and H₂O₂ are key players in complex signaling networks and defense. A well-studied example is the production of O₂^•− during the bactericidal respiratory burst of phagocytes; this production is catalyzed by NOX2. Here, we devised and applied a novel algorithm to search for additional NOX genes in genomic databases. This procedure allowed us to discover approximately 23% new sequences from bacteria (in relation to the number of NOX-related sequences identified by the authors) that we have added to the existing eukaryotic NOX family and have used to build an expanded phylogenetic tree. We cloned and overexpressed the identified nox gene from Streptococcus pneumoniae and confirmed that it codes for an NADPH oxidase. The membrane of the S. pneumoniae NOX protein (SpNOX) shares many properties with its eukaryotic counterparts, such as affinity for NADPH and flavin adenine dinucleotide, superoxide dismutase and diphenylene iodonium inhibition, cyanide resistance, oxygen consumption, and superoxide production. Traditionally, NOX enzymes in eukaryotes are related to functions linked to multicellularity. Thus, the discovery of a large family of NOX-related enzymes in the bacterial world brings up fascinating questions regarding their role in this new biological context.

NADPH oxidase (NOX) enzymes have not yet been reported in bacteria. Here, we carried out computational and experimental studies to provide the first characterization of a prokaryotic NOX. Out of 996 prokaryotic proteins showing NOX signatures, we initially selected, cloned, and overexpressed four of them. Subsequently, and based on preliminary testing, we concentrated our efforts on Streptococcus SpNOX, which shares many biochemical characteristics with NOX2, the referent model of NOX enzymes. Our work makes possible, for the first time, the study of pure forms of this important family of enzymes, allowing for biophysical and molecular characterization in an unprecedented way. Similar advances regarding other membrane protein families have led to new structures, further mechanistic studies, and the improvement of inhibitors. In addition, biological functions of these newly described bacterial enzymes will be certainly discovered in the near future.

NADPH oxidases as drug targets and biomarkers in neurodegenerative diseases: What is the evidence?

Neurodegenerative disease are frequently characterized by microglia activation and/or leukocyte infiltration in the parenchyma of the central nervous system and at the molecular level by increased oxidative modifications of proteins, lipids and nucleic acids. NADPH oxidases (NOX) emerged as a novel promising class of pharmacological targets for the treatment of neurodegeneration due to their role in oxidant generation and presumably in regulating microglia activation. The unique function of NOX is the generation of superoxide anion (O₂^•-) and hydrogen peroxide (H₂O₂). However in the context of neuroinflammation, they present paradoxical features since O₂^•-/H₂O₂ generated by NOX and/or secondary reactive oxygen species (ROS) derived from O₂^•-/H₂O₂ can either lead to neuronal oxidative damage or resolution of inflammation. The role of NOX enzymes has been investigated in many models of neurodegenerative diseases by using either genetic or pharmacological approaches. In the present review we provide a critical assessment of recent findings related to the role of NOX in the CNS as well as how the field has advanced over the last 5 years. In particular, we focus on the data derived from the work of a consortium (Neurinox) funded by the European Commission's Programme 7 (FP7). We discuss the evidence gathered from animal models and human samples linking NOX expression/activity with neuroinflammation in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Creutzfeldt-Jakob disease as well as autoimmune demyelinating diseases like multiple sclerosis (MS) and chronic inflammatory demyelinating polyneuropathy (CIDP). We address the possibility to use measurement of the activity of the NOX2 isoform in blood samples as biomarker of disease severity and treatment efficacy in neurodegenerative disease. Finally we clarify key controversial aspects in the field of NOX, such as NOX cellular expression in the brain, measurement of NOX activity, impact of genetic deletion of NOX in animal models of neurodegeneration and specificity of NOX inhibitors.

DUOX2 Mutations Are Associated With Congenital Hypothyroidism With Ectopic Thyroid Gland

CONTEXT

Thyroid dysgenesis (TD) is the leading cause of congenital hypothyroidism (CH). The etiology of TD remains unknown in ∼90% of cases, the most common form being thyroid ectopia (TE) (48% to 61%).

OBJECTIVE

To search for candidate genes in hypothyroid children with TE.

DESIGN, SETTING, AND PARTICIPANTS

We followed a cohort of 268 children with TD and performed whole-exome sequencing (WES) in three children with CH with TE (CHTE) and compared them with 18 thyroid-healthy controls. We then screened an additional 41 children with CHTE by Sanger sequencing and correlated the WES and Sanger molecular findings with in vitro functional analysis.

MAIN OUTCOME MEASURES

Genotyping, mutation prediction analysis, and in vitro functional analysis.

RESULTS

We identified seven variants in the DUOX2 gene, namely G201E, L264CfsX57, P609S, M650T, E810X, M822V, and E1017G, and eight known variations. All children carrying DUOX2 variations had high thyroid-stimulating hormone levels at neonatal diagnosis. All mutations were localized in the N-terminal segment, and three of them led to effects on cell surface targeting and reactive oxygen species generation. The DUOX2 mutants also altered the interaction with the maturation factor DUOXA2 and the formation of a stable DUOX2/DUOXA2 complex at the cell surface, thereby impairing functional enzymatic activity. We observed no mutations in the classic genes related to TD or in the DUOX1 gene.

CONCLUSION

Our findings suggest that, in addition to thyroid hormonogenesis, the DUOX2 N-terminal domain may play a role in thyroid development.

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.

Defensive Mutualism Rescues NADPH Oxidase Inactivation in Gut Infection

NOX/DUOX family of NADPH oxidases are expressed in diverse tissues and are the primary enzymes for the generation of reactive oxygen species (ROS). The intestinal epithelium expresses NOX1, NOX4, and DUOX2, whose functions are not well understood. To address this, we generated mice with complete or epithelium-restricted deficiency in the obligatory NOX dimerization partner Cyba (p22(phox)). We discovered that NOX1 regulates DUOX2 expression in the intestinal epithelium, which magnified the epithelial ROS-deficiency. Unexpectedly, epithelial deficiency of Cyba resulted in protection from C. rodentium and L. monocytogenes infection. Microbiota analysis linked epithelial Cyba deficiency to an enrichment of H2O2-producing bacterial strains in the gut. In particular, elevated levels of lactobacilli physically displaced and attenuated C. rodentium virulence by H2O2-mediated suppression of the virulence-associated LEE pathogenicity island. This transmissible compensatory adaptation relied on environmental factors, an important consideration for prevention and therapy of enteric disease.

Digenic DUOX1 and DUOX2 Mutations in Cases With Congenital Hypothyroidism

CONTEXT

The DUOX2 enzyme generates hydrogen peroxide (H2O2), a crucial electron acceptor for the thyroid peroxidase-catalyzed iodination and coupling reactions mediating thyroid hormone biosynthesis. DUOX2 mutations result in dyshormonogenetic congenital hypothyroidism (CH) that may be phenotypically heterogeneous, leading to the hypothesis that CH severity may be influenced by environmental factors (e.g., dietary iodine) and oligogenic modifiers (e.g., variants in the homologous reduced form of NAD phosphate-oxidase DUOX1). However, loss-of-function mutations in DUOX1 have not hitherto been described, and its role in thyroid biology remains undefined.

CASE DESCRIPTION

We previously described a Proband and her brother (P1, P2) with unusually severe CH associated with a DUOX2 homozygous nonsense mutation (p.R434*); P1, P2: thyrotropin >100 µU/mL [reference range (RR) 0.5 to 6.3]; and P1: free T4 (FT4) <0.09 ng/dL (RR 0.9 to 2.3). Subsequent studies have revealed a homozygous DUOX1 mutation (c.1823-1G>C) resulting in aberrant splicing and a protein truncation (p.Val607Aspfs*43), which segregates with CH in this kindred.

CONCLUSION

This is a report of digenic mutations in DUOX1 and DUOX2 in association with CH, and we hypothesize that the inability of DUOX1 to compensate for DUOX2 deficiency in this kindred may underlie the severe CH phenotype. Our studies provide evidence for a digenic basis for CH and support the notion that oligogenicity as well as environmental modulators may underlie phenotypic variability in genetically ascertained CH.

Neutrophils to the ROScue: Mechanisms of NADPH Oxidase Activation and Bacterial Resistance

Reactive oxygen species (ROS) generated by NADPH oxidase play an important role in antimicrobial host defense and inflammation. Their deficiency in humans results in recurrent and severe bacterial infections, while their unregulated release leads to pathology from excessive inflammation. The release of high concentrations of ROS aids in clearance of invading bacteria. Localization of ROS release to phagosomes containing pathogens limits tissue damage. Host immune cells, like neutrophils, also known as PMNs, will release large amounts of ROS at the site of infection following the activation of surface receptors. The binding of ligands to G-protein-coupled receptors (GPCRs), toll-like receptors, and cytokine receptors can prime PMNs for a more robust response if additional signals are encountered. Meanwhile, activation of Fc and integrin directly induces high levels of ROS production. Additionally, GPCRs that bind to the bacterial-peptide analog fMLP, a neutrophil chemoattractant, can both prime cells and trigger low levels of ROS production. Engagement of these receptors initiates intracellular signaling pathways, resulting in activation of downstream effector proteins, assembly of the NADPH oxidase complex, and ultimately, the production of ROS by this complex. Within PMNs, ROS released by the NADPH oxidase complex can activate granular proteases and induce the formation of neutrophil extracellular traps (NETs). Additionally, ROS can cross the membranes of bacterial pathogens and damage their nucleic acids, proteins, and cell membranes. Consequently, in order to establish infections, bacterial pathogens employ various strategies to prevent restriction by PMN-derived ROS or downstream consequences of ROS production. Some pathogens are able to directly prevent the oxidative burst of phagocytes using secreted effector proteins or toxins that interfere with translocation of the NADPH oxidase complex or signaling pathways needed for its activation. Nonetheless, these pathogens often rely on repair and detoxifying proteins in addition to these secreted effectors and toxins in order to resist mammalian sources of ROS. This suggests that pathogens have both intrinsic and extrinsic mechanisms to avoid restriction by PMN-derived ROS. Here, we review mechanisms of oxidative burst in PMNs in response to bacterial infections, as well as the mechanisms by which bacterial pathogens thwart restriction by ROS to survive under conditions of oxidative stress.