NADPH Oxidase-dependent Reactive Oxygen Species Production Research Articles

Awakening adult neural stem cells: NOX signalling as a positive regulator of the quiescence-to-proliferation transition in the Xenopus retina.

A growing wealth of data suggest that reactive oxygen species (ROS) signalling might be crucial in conferring embryonic or adult stem cells their specific properties. However, how stem cells control ROS production and scavenging, and how ROS in turn contribute to stemness, remain poorly understood. Using the Xenopus retina as a model system, we first investigated the redox status of retinal stem cells (RSCs). We discovered that they exhibit higher ROS levels compared with progenitors and retinal neurons, and express a set of specific redox genes. We next addressed the question of ROS functional involvement in these cells. Using pharmacological or genetic tools, we demonstrate that inhibition of NADPH oxidase-dependent ROS production increases the proportion of quiescent RSCs. Surprisingly, this is accompanied by an apparent acceleration of the mean division speed within the remaining proliferating pool. Our data further unveil that such impact on RSC cell cycling is achieved by modulation of the Wnt/Hedgehog signalling balance. Altogether, we highlight that RSCs exhibit distinctive redox characteristics and exploit NADPH oxidase signalling to limit quiescence and fine-tune their proliferation rate.

Glucose-6-phosphate dehydrogenase and abscisic acid mediate programmed cell death induced by aluminum toxicity in soybean root tips

Programmed cell death (PCD) induced by aluminum (Al) is considered an important reason of Al phytotoxicity. However, the underlying mechanism of how Al induces PCD remains largely unknown in plants. The roles of glucose-6-phosphate dehydrogenase (G6PDH) and abscisic acid (ABA) in regulating Al-induced PCD were investigated in soybean roots. Al treatment increased G6PDH activity, while inhibition of G6PDH activity alleviated PCD occurrence and reactive oxygen species (ROS) accumulation under Al stress. Overexpression of cytosolic G6PDH1 enhanced G6PDH activity, thus promoting ROS production and cell death under Al exposure. Inhibition of NADPH oxidase activity mitigated ROS generation and cell death under Al stress. Further investigation demonstrated that G6PDH positively regulated the activity of NADPH oxidase under Al treatment using pharmacological and transgenic approach. Furthermore, Al stress increased ABA production, while inhibition of ABA biosynthesis alleviated PCD occurrence and ROS accumulation under Al stress. Interestingly, ABA upregulated G6PDH1 expression and G6PDH activity under Al stress. These results suggest that G6PDH mediates Al-induced PCD occurrence through the activation of NADPH oxidase-dependent ROS production, and ABA acts upstream of G6PDH in this process. This study will provide novel clues for the improvement of Al phytotoxicity in acidic soils.

Oxidative stress in the skin: Impact and related protection.

Skin, our first interface to the external environment, is subjected to oxidative stress caused by a variety of factors such as solar ultraviolet, infrared and visible light, environmental pollution, including ozone and particulate matters, and psychological stress. Excessive reactive species, including reactive oxygen species and reactive nitrogen species, exacerbate skin pigmentation and aging, which further lead to skin tone unevenness, pigmentary disorder, skin roughness and wrinkles. Besides these, skin microbiota are also a very important factor ensuring the proper functions of skin. While environmental factors such as UV and pollutants impact skin microbiota compositions, skin dysbiosis results in various skin conditions. In this review, we summarize the generation of oxidative stress from exogenous and endogenous sources. We further introduce current knowledge on the possible roles of oxidative stress in skin pigmentation and aging, specifically with emphasis on oxidative stress and skin pigmentation. Meanwhile, we summarize the science and rationale of using three well-known antioxidants, namely vitamin C, resveratrol and ferulic acid, in the treatment of hyperpigmentation. Finally, we discuss the strategy for preventing oxidative stress-induced skin pigmentation and aging.

Sulfur dioxide promotes seed germination by modulating reactive oxygen species production in maize

Sulfur dioxide (SO2) is generally considered to be toxic to cells, but recent studies have shown that SO2 has positive roles in stress defense responses in plants. However, whether SO2 functions as a signaling molecule in the developmental process, especially in seed germination, is yet to be studied. Here, we present data supporting the role of SO2 in seed germination and possible molecular mechanisms. SO2 treatment significantly promoted the seed germination and seed vigor in maize. The germinating seeds treated with SO2 treatment exhibited higher reactive oxygen species (ROS) levels and NADPH oxidase activities. Furthermore, the specific NADPH oxidase inhibitor diphenyleneiodinium (DPI) strongly inhibited ROS accumulations, and SO2-promoted seed germination and vigor. Meanwhile, α-Amylase activity and transcripts in germinating seeds treated with SO2 were significantly elevated. These data have demonstrated that NADPH oxidase-dependent ROS production contributes to the induction of α-Amylase activity, thereby promoting seed germination upon SO2 exposure. SO2 might function as a signaling molecule in plant growth and development, especially in seed germination. This study might provide a theoretical foundation for the potential exploitation of hydrated SO2 in seed germination control in crop management.

Higher Circulating Trimethylamine N-oxide Sensitizes Sevoflurane-Induced Cognitive Dysfunction in Aged Rats Probably by Downregulating Hippocampal Methionine Sulfoxide Reductase A.

Gut microbiota-derived metabolite trimethylamine N-oxide (TMAO) has recently been shown to promote oxidative stress and inflammation in the peripheral tissues, contributing to the pathogenesis of many diseases. Here we examined whether pre-existing higher circulating TMAO would influence cognitive function in aged rats after anesthetic sevoflurane exposure. Aged rats received vehicle or TMAO treatment for 3weeks. After 2weeks of treatment, these animals were exposed to either control or 2.6% sevoflurane for 4h. Oneweek after exposure, freezing as measured by fear conditioning test, microglia activity, proinflammatory cytokine expression and NADPH oxidase-dependent reactive oxygen species (ROS) production in the hippocampus (a key brain structure involved in learning and memory) were comparable between vehicle-treated rats exposed to control and vehicle-treated rats exposed to sevoflurane. TMAO treatment, which increased plasma TMAO before and 1week after control or sevoflurane exposure, significantly reduced freezing to contextual fear conditioning, which was associated with increases in microglia activity, proinflammatory cytokine expression and NADPH oxidase-dependent ROS production in the hippocampus in rats exposed to sevoflurane but not in rats exposed to control. Moreover, hippocampal expression of antioxidant enzyme methionine sulfoxide reductase A (MsrA) was reduced by TMAO treatment in both groups, and TMAO-induced reduction in MsrA expression was negatively correlated with increased proinflammatory cytokine expression in rats exposed to SEV. These findings suggest that pre-existing higher circulating TMAO downregulates antioxidant enzyme MsrA in the hippocampus, which may sensitize the hippocampus to oxidative stress, resulting in microglia-mediated neuroinflammation and cognitive impairment in aged rats after sevoflurane exposure.

The Effects of Mg Deficiency on Activities and Isoenzyme Patterns of Antioxidant Enzymes in Cotton Roots

Magnesium (Mg) is an essential nutrient that takes vital roles in biochemical processes related to energy metabolism, regulation of enzyme activity, nucleic acid biosynthesis and carbohydrate metabolism. Mg deficiency in arable lands is an emerging problem. Loss of balance in different metabolic pathways due to Mg deficiency causes increased production of reactive oxygen species (ROS) such as O2.-, H2O2 and HO. in the roots. The aim of this work was to elucidate the antioxidant response of roots of cotton (Gossypium hirsutum) to Mg deficiency. For this aim, antioxidant enzyme activities were measured and changes in their isoenzymes were determined. In addition, NADPH oxidase (NOX) activity was investigated to determine the changes in ROS signaling. Moreover, H2O2 and lipid peroxidation levels were also measured as an indicator of oxidative damage. Findings of this work indicate that Mg deficiency does not cause oxidative load in roots of Gossypium hirsutum plants that overwhelms cellular antioxidant defence system, as evident by H2O2 and TBARS levels. However, to adjust to the new redox status, root cells drastically downregulate NOX dependent ROS production and induced total superoxide dismutase activity. These findings indicate that site of O2.- production is mitochondria in roots. Although, catalase and ascorbate peroxidase activities were decreased with Mg deficiency induced peroxidase activity seems to limit H2O2 accumulation. These adaptive responses and changes in antioxidant defence were sufficient to prevent excess ROS accumulation and occurrence of oxidative damage in roots of Gossypium hirsutum plants under Mg deficiency

Tumour-elicited neutrophils engage mitochondrial metabolism to circumvent nutrient limitations and maintain immune suppression

Neutrophils are a vital component of immune protection, yet in cancer they may promote tumour progression, partly by generating reactive oxygen species (ROS) that disrupts lymphocyte functions. Metabolically, neutrophils are often discounted as purely glycolytic. Here we show that immature, c-Kit+ neutrophils subsets can engage in oxidative mitochondrial metabolism. With limited glucose supply, oxidative neutrophils use mitochondrial fatty acid oxidation to support NADPH oxidase-dependent ROS production. In 4T1 tumour-bearing mice, mitochondrial fitness is enhanced in splenic neutrophils and is driven by c-Kit signalling. Concordantly, tumour-elicited oxidative neutrophils are able to maintain ROS production and T cell suppression when glucose utilisation is restricted. Consistent with these findings, peripheral blood neutrophils from patients with cancer also display increased immaturity, mitochondrial content and oxidative phosphorylation. Together, our data suggest that the glucose-restricted tumour microenvironment induces metabolically adapted, oxidative neutrophils to maintain local immune suppression.

Targeting reactive oxygen species for respiratory infection: Fact or fancy?

Targeting reactive oxygen species for respiratory infection: Fact or fancy?

FERONIA Receptor Kinase at the Crossroads of Hormone Signaling and Stress Responses.

Plant receptor-like kinases (RLKs) are involved in nearly all aspects of plant life including growth, development and stress response. Recent studies show that FERONIA (FER), a CrRLK1L subfamily member, is a versatile regulator of cell expansion and serves as a signaling node mediating cross-talk among multiple phytohormones. As a receptor for the RALF (Rapid Alkalinization Factor) peptide ligand, FER triggers a downstream signaling cascade that leads to a rapid cytoplasmic calcium increase and inhibition of cell elongation in plants. Moreover, FER recruits and activates small G proteins through the guanine nucleotide exchange factor-Rho-like GTPase (GEF-ROP) network to regulate both auxin and ABA responses that cross-talk with the RALF signaling pathway. One of the downstream processes is NADPH oxidase-dependent ROS (reactive oxygen species) production that modulates cell expansion and responses to both abiotic and biotic stress responses. Intriguingly, some pathogenic fungi produce RALF-like peptides to activate the host FER-mediated pathway and thus increase their virulence and cause plant disease. Studies so far indicate that FER may serve as a central node of the cell signaling network that integrates a number of regulatory pathways targeting cell expansion, energy metabolism and stress responses. This review focuses on recent findings and their implications in the context of FER action as a modulator that is crucial for hormone signaling and stress responses.

Reactive Oxygen Species-Producing Myeloid Cells Act as a Bone Marrow Niche for Sterile Inflammation-Induced Reactive Granulopoiesis.

Both microbial infection and sterile inflammation augment bone marrow (BM) neutrophil production, but whether the induced accelerated granulopoiesis is mediated by a common pathway and the nature of such a pathway are poorly defined. We recently established that BM myeloid cell-derived reactive oxygen species (ROS) externally regulate myeloid progenitor proliferation and differentiation in bacteria-elicited emergency granulopoiesis. In this article, we show that BM ROS levels are also elevated during sterile inflammation. Similar to in microbial infection, ROS were mainly generated by the phagocytic NADPH oxidase in Gr1+ myeloid cells. The myeloid cells and their ROS were uniformly distributed in the BM when visualized by multiphoton intravital microscopy, and ROS production was both required and sufficient for sterile inflammation-elicited reactive granulopoiesis. Elevated granulopoiesis was mediated by ROS-induced phosphatase and tensin homolog oxidation and deactivation, leading to upregulated PtdIns(3,4,5)P3 signaling and increased progenitor cell proliferation. Collectively, these results demonstrate that, although infection-induced emergency granulopoiesis and sterile inflammation-elicited reactive granulopoiesis are triggered by different stimuli and are mediated by distinct upstream signals, the pathways converge to NADPH oxidase-dependent ROS production by BM myeloid cells. Thus, BM Gr1+ myeloid cells represent a key hematopoietic niche that supports accelerated granulopoiesis in infective and sterile inflammation. This niche may be an excellent target in various immune-mediated pathologies or immune reconstitution after BM transplantation.

Coronatine Inhibits Stomatal Closure through Guard Cell-Specific Inhibition of NADPH Oxidase-Dependent ROS Production.

Microbes trigger stomatal closure through microbe-associated molecular patterns (MAMPs). The bacterial pathogen Pseudomonas syringae pv. tomato (Pst) synthesizes the polyketide toxin coronatine, which inhibits stomatal closure by MAMPs and by the hormone abscisic acid (ABA). The mechanism by which coronatine, a jasmonic acid-isoleucine analog, achieves this effect is not completely clear. Reactive oxygen species (ROS) are essential second messengers in stomatal immunity, therefore we investigated the possible effect of coronatine on their production. We found that coronatine inhibits NADPH oxidase-dependent ROS production induced by ABA, and by the flagellin-derived peptide flg22. This toxin also inhibited NADPH oxidase-dependent stomatal closure induced by darkness, however, it failed to prevent stomatal closure by exogenously applied H2O2 or by salicylic acid, which induces ROS production through peroxidases. Contrary to what was observed on stomata, coronatine did not affect the oxidative burst induced by flg22 in leaf disks. Additionally, we observed that in NADPH oxidase mutants atrbohd and atrbohd/f, as well as in guard cell ABA responsive but flg22 insensitive mutants mpk3, mpk6, npr1-3, and lecrk-VI.2-1, the inhibition of ABA stomatal responses by both coronatine and the NADPH oxidase inhibitor diphenylene iodonium was markedly reduced. Interestingly, coronatine still impaired ABA-induced ROS synthesis in mpk3, mpk6, npr1-3, and lecrk-VI.2-1, suggesting a possible feedback regulation of ROS on other guard cell ABA signaling elements in these mutants. Altogether our results show that inhibition of NADPH oxidase-dependent ROS synthesis in guard cells plays an important role during endophytic colonization by Pst through stomata.

TRPM2 regulates TXNIP-mediated NLRP3 inflammasome activation via interaction with p47 phox under high glucose in human monocytic cells.

Excessive production of reactive oxygen species (ROS) induced by hyperglycemia increased the secretion of interleukin-1β (IL-1β), which contributes to the pathogenesis of diabetes and its complications. Although high glucose (HG)-induced oxidative stress and aberrant Ca2+ channels activity causes an increase in transmembrane Ca2+ influx, however the relative contribution of Transient receptor potential (TRP) channels is not well studied. Here, we identified that HG (30 mM glucose for 48 h) induced the activation of the NLRP3-ASC inflammasome, leading to caspase-1 activation, and IL-1β and IL-18 secretion in human monocytic cell lines. Moreover, we used a hyperglycemia model in U937 monocytes, showing that the activation of TRPM2 was augmented, and TRPM2-mediated Ca2+ influx was critical for NLRP3 inflammasome activation. This pathway involved NADPH oxidase-dependent ROS production and TXNIP-NLRP3 inflammasome pathway. Furthermore, the inhibition of TRPM2 reduced ROS production and lowered NADPH oxidase activity via cooperatively interaction with p47 phox in response to HG. These results provided a mechanistic linking between TRPM2-mediated Ca2+ influx and p47 phox signaling to induce excess ROS production and TXNIP-mediated NLRP3 inflammasome activation under HG, and suggested that TRPM2 represented a potential target for alleviating NLRP3 inflammasome activation related to hyperglycemia-induced oxidative stress in Type 2 diabetes Mellitus (T2DM).

Cluster Differentiating 36 (CD36) Deficiency Attenuates Obesity-Associated Oxidative Stress in the Heart.

RationaleObesity is often associated with a state of oxidative stress and increased lipid deposition in the heart. More importantly, obesity increases lipid influx into the heart and induces excessive production of reactive oxygen species (ROS) leading to cell toxicity and metabolic dysfunction. Cluster differentiating 36 (CD36) protein is highly expressed in the heart and regulates lipid utilization but its role in obesity-associated oxidative stress is still not clear.ObjectiveThe aim of this study was to determine the impact of CD36 deficiency on cardiac steatosis, oxidative stress and lipotoxicity associated with obesity.Methods and ResultsStudies were conducted in control (Lean), obese leptin-deficient (Lepob/ob) and leptin-CD36 double null (Lepob/obCD36-/-) mice. Compared to lean mice, cardiac steatosis, and fatty acid (FA) uptake and oxidation were increased in Lepob/ob mice, while glucose uptake and oxidation was reduced. Moreover, insulin resistance, oxidative stress markers and NADPH oxidase-dependent ROS production were markedly enhanced. This was associated with the induction of NADPH oxidase expression, and increased membrane-associated p47phox, p67phox and protein kinase C. Silencing CD36 in Lepob/ob mice prevented cardiac steatosis, increased insulin sensitivity and glucose utilization, but reduced FA uptake and oxidation. Moreover, CD36 deficiency reduced NADPH oxidase activity and decreased NADPH oxidase-dependent ROS production. In isolated cardiomyocytes, CD36 deficiency reduced palmitate-induced ROS production and normalized NADPH oxidase activity.ConclusionsCD36 deficiency prevented obesity-associated cardiac steatosis and insulin resistance, and reduced NADPH oxidase-dependent ROS production. The study demonstrates that CD36 regulates NADPH oxidase activity and mediates FA-induced oxidative stress.

Tyrosine kinases as key modulators of smooth muscle function in health and disease

This issue contains two review articles based on talks given as part of a symposium entitled ‘Tyrosine kinases and smooth muscle function’ that took place in London, July 2014, hosted by the Physiological Society and supported by The Journal of Physiology. The symposium examined evidence for the involvement of non-receptor tyrosine kinases in multiple aspects of smooth muscle function, including their role in normal contractile responses to various stimuli and potentially important contributions to hyper-contractile states and vascular remodelling in hypertension. Senior speakers at the symposium were Professor Gervaise Loirand (University of Nantes, France), Professor Ralph Schermuly (Max-Plank Institute for Heart and Lung Research, Germany), and Dr Jacqueline Ohanian (Institute of Cardiovascular Sciences, University of Manchester, UK).

Park7 interacts with p47(phox) to direct NADPH oxidase-dependent ROS production and protect against sepsis.

Inappropriate inflammation responses contribute to mortality during sepsis. Through Toll-like receptors (TLRs), reactive oxygen species (ROS) produced by NADPH oxidase could modulate the inflammation responses. Parkinson disease (autosomal recessive, early onset) 7 (Park7) has a cytoprotective role by eliminating ROS. However, whether Park7 could modulate inflammation responses and mortality in sepsis is unclear. Here, we show that, compared with wild-type mice, Park7(-/-) mice had significantly increased mortality and bacterial burdens in sepsis model along with markedly decreased systemic and local inflammation, and drastically impaired macrophage phagocytosis and bacterial killing abilities. Surprisingly, LPS and phorbol-12-myristate-13-acetate stimulation failed to induce ROS and proinflammatory cytokine production in Park7(-/-) macrophages and Park7-deficient RAW264.7 cells. Through its C-terminus, Park7 binds to p47(phox), a subunit of the NADPH oxidase, to promote NADPH oxidase-dependent production of ROS. Restoration of Park7 expression rescues ROS production and improves survival in LPS-induced sepsis. Together, our study shows that Park7 has a protective role against sepsis by controlling macrophage activation, NADPH oxidase activation and inflammation responses.

Control of vascular smooth muscle function by Src-family kinases and reactive oxygen species in health and disease.

Reactive oxygen species (ROS) are now recognised as second messenger molecules that regulate cellular function by reversibly oxidising specific amino acid residues of key target proteins. Amongst these are the Src-family kinases (SrcFKs), a multi-functional group of non-receptor tyrosine kinases highly expressed in vascular smooth muscle (VSM). In this review we examine the evidence supporting a role for ROS-induced SrcFK activity in normal VSM contractile function and in vascular remodelling in cardiovascular disease. VSM contractile responses to G-protein-coupled receptor stimulation, as well as hypoxia in pulmonary artery, are shown to be dependent on both ROS and SrcFK activity. Specific phosphorylation targets are identified amongst those that alter intracellular Ca(2+) concentration, including transient receptor potential channels, voltage-gated Ca(2+) channels and various types of K(+) channels, as well as amongst those that regulate actin cytoskeleton dynamics and myosin phosphatase activity, including focal adhesion kinase, protein tyrosine kinase-2, Janus kinase, other focal adhesion-associated proteins, and Rho guanine nucleotide exchange factors. We also examine a growing weight of evidence in favour of a key role for SrcFKs in multiple pro-proliferative and anti-apoptotic signalling pathways relating to oxidative stress and vascular remodelling, with a particular focus on pulmonary hypertension, including growth-factor receptor transactivation and downstream signalling, hypoxia-inducible factors, positive feedback between SrcFK and STAT3 signalling and positive feedback between SrcFK and NADPH oxidase dependent ROS production. We also discuss evidence for and against the potential therapeutic targeting of SrcFKs in the treatment of pulmonary hypertension.

Chlorella induces stomatal closure via NADPH oxidase-dependent ROS production and its effects on instantaneous water use efficiency in Vicia faba.

Reactive oxygen species (ROS) have been established to participate in stomatal closure induced by live microbes and microbe-associated molecular patterns (MAMPs). Chlorella as a beneficial microorganism can be expected to trigger stomatal closure via ROS production. Here, we reported that Chlorella induced stomatal closure in a dose-and time-dependent manner in epidermal peels of Vicia faba. Using pharmacological methods in this work, we found that the Chlorella-induced stomatal closure was almost completely abolished by a hydrogen peroxide (H2O2) scavenger, catalase (CAT), significantly suppressed by an NADPH oxidase inhibitor, diphenylene iodonium chloride (DPI), and slightly affected by a peroxidase inhibitor, salicylhydroxamic acid (SHAM), suggesting that ROS production involved in Chlorella-induced stomatal closure is mainly mediated by DPI-sensitive NADPH oxidase. Additionally, Exogenous application of optimal concentrations of Chlorella suspension improved instantaneous water use efficiency (WUEi) in Vicia faba via a reduction in leaf transpiration rate (E) without a parallel reduction in net photosynthetic rate (Pn) assessed by gas-exchange measurements. The chlorophyll fluorescence and content analysis further demonstrated that short-term use of Chlorella did not influence plant photosynthetic reactions center. These results preliminarily reveal that Chlorella can trigger stomatal closure via NADPH oxidase-dependent ROS production in epidermal strips and improve WUEi in leave levels.

Oxidative Stress and Atrial Fibrillation

Atrial fibrillation (AF), one of the most prevalent cardiac arrhythmias, afflicts >3 million people in the United States.1 Because the risk of developing AF increases with age, the prevalence of AF is projected to be 7.6 million in 2050,1 when 1 in 5 Americans will be over the age of 65.2 AF not only causes debilitating symptoms and functional impairments owing to worsened hemodynamics and embolic stroke, it also increases the risk of mortality up to 1.5- to 1.9-fold.3 Despite the significant morbidity and mortality burden incurred with AF, there are limited therapeutic options that may improve the outcomes of AF patients, and these options are associated with significant AF recurrence rates.4 Article see p 1748 One possible explanation for the limitations of current therapies is that they do not address effectively or completely the underlying causes of AF. Evidence has been mounting that AF is associated with systemic and cardiac oxidation.4,5 Risk factors for AF are similar to those of atherosclerosis, a disease known to be perpetuated by oxidative stress. These risk factors, such as hypertension, aging, diabetes mellitus, and coronary artery bypass surgery, have each been associated with increases in the systemic markers of oxidation.4 In addition, there is also evidence of increased cardiac oxidation of myofibrillar protein5 and membrane lipids6 with AF or with risk factors linked to AF. Although it is not clear whether cardiac oxidation leads to systemic markers of oxidation or whether systemic oxidation leads to cardiac oxidation, the association of oxidative stress and AF is robust and suggests that AF is possibly a manifestation of a systemic disease. Despite the link between oxidative stress and AF, systemic antioxidant therapy for arrhythmias has not met with much success in clinical trials.7, …

188: Dengue infection generates an early NADPH-oxidase dependent ROS production required for antiviral and inflammatory responses

The rapid host response to virus infection is crucial for establishment of the antiviral state and for the release of pro-inflammatory mediators that coordinate the adaptive immune response. Induction of antiviral and inflammatory genes is achieved largely through recognition of viral nucleic acid motifs by pattern recognition receptors. Dengue virus (DENV) is a significant human pathogen that causes a wide spectrum of clinical symptoms, ranging from mild dengue fever to severe hemorrhagic fever and shock syndrome. The cytosolic receptors RIG-I/MDA5 as well as the membrane-bound TLR3/TLR7 localized in the endosomes are important sensors of DENV infection. The role of reactive oxygen species (ROS) in the activation of biological processes such as autophagy, necrosis, and inflammasome activation adds another layer of complexity to the regulation of immune sensing. Transcriptome analysis of DENV-infected human monocyte-derived dendritic cells (Mo-DC) revealed the activation of distinct patterns of gene transcription, with involvement of pathways including the antiviral response, the TNF superfamily and late activation of death receptor signaling. Interestingly, a dominant early gene network associated with the Nrf2-dependent antioxidant response was also identified; DENV infection induced an early production of ROS that was dependent on NADPH-oxidase, and was essential for the activation of inflammatory and antiviral programs, through NF-κB and IRF-3 transcription factors, respectively. Using a high throughput qPCR assay, we demonstrated that interfering with NADPH-oxidase inhibited DENV-induced antiviral and inflammatory responses. We also demonstrated that the antioxidant pathway controlled by the transcription factor Nrf2 is a pivotal upstream link to the regulation of DENV-induced antiviral and inflammatory responses under oxidative conditions. In conclusion, these findings demonstrate that ROS production is crucial for effective activation of pathways leading to innate immune responses against DENV infection in human Mo-DC.

Melamine activates NFκB/COX-2/PGE2 pathway and increases NADPH oxidase–dependent ROS production in macrophages and human embryonic kidney cells

Melamine is a wildly used compound in manufactures of plastics and resins. A variety of toxic effects from melamine, including nephrolithiasis, chronic kidney inflammation, and bladder carcinoma, have been mentioned. Oxidative stress is considered to be an important pathogenic mechanism of kidney disease which may develop from an increasing free radical production through inflammation. The aim of this study is to investigate melamine-induced oxidative stress and inflammation in macrophage-like cell line RAW 264.7 and human embryonic kidney cell line HEK293. Results indicated melamine activated nuclear factor (NF)-κB through increasing IκB-α degradation and NF-κB p65/p50 DNA-binding activity. In addition, melamine significantly increased COX-2 expression and prostaglandin E2 (PGE2) production. Moreover, melamine activated NADPH oxidase (NOX), including NOX1, NOX2 and NOX4, accompanied with an increase in reactive oxygen species (ROS) production. Furthermore, melamine-induced ROS production could be attenuated by apocynin, a NOX inhibitor. In conclusion, our findings suggest melamine increased inflammation and oxidative stress via activation of NF-κB/COX-2 and NOX/ROS pathway, and first revealed the critical role of NOX in melamine-induced ROS production, suggesting the potential of NOX inhibitor against melamine toxicity.