Removal Of Reactive Oxygen Species Research Articles

Mitochondrial TXN2 attenuates amyloidogenesis via selective inhibition of BACE1 expression.

Thioredoxin-2 (TXN2) is a mitochondrial protein and represents one of the intrinsic antioxidant enzymes. It has long been recognized that mitochondrial dysfunction and oxidative stress contribute to the pathogenesis of Alzheimer's disease (AD). We hypothesized that mitochondrial TXN2 might play a role in AD-like pathology. In this study, we found that in SH-SY5Y and HEK cells stably express full-length human amyloid-β precursor protein (HEK-APP), TXN2 silencing or over-expression selectively increased or decreased the transcription of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), respectively, without altering the protein levels of others enzymes involved in the catalytic processing of APP. As a result, β-amyloid protein (Aβ) levels were significantly decreased by TXN2. In addition, in cells treated with 3-nitropropionic acid (3-NP) that is known to increase reactive oxygen species (ROS) and promote mitochondrial dysfunction, TXN2 silencing resulted in further enhancement of BACE1 protein levels, suggesting a role of TXN2 in ROS removal. The downstream signaling might involve NFκB, as TXN2 reduced the phosphorylation of p65 and IκBα; and p65 knockdown significantly attenuated TXN2-mediated regulation of BACE1. Concomitantly, the levels of cellular ROS, apoptosis-related proteins and cell viability were altered by TXN2 silencing or over-expression. In APPswe/PS1E9 mice, an animal model of AD, the cortical and hippocampal TXN2 protein levels were decreased at 12months but not at 6months, suggesting an age-dependent decline. Collectively, TXN2 regulated BACE1 expression and amyloidogenesis via cellular ROS and NFκB signaling. TXN2 might serve as a potential target especially for early intervention of AD.

Comprehensive analysis of the Ppatg3 mutant reveals that autophagy plays important roles in gametophore senescence in Physcomitrella patens

BackgroundAutophagy is an evolutionarily conserved system for the degradation of intracellular components in eukaryotic organisms. Autophagy plays essential roles in preventing premature senescence and extending the longevity of vascular plants. However, the mechanisms and physiological roles of autophagy in preventing senescence in basal land plants are still obscure.ResultsHere, we investigated the functional roles of the autophagy-related gene PpATG3 from Physcomitrella patens and demonstrated that its deletion prevents autophagy. In addition, Ppatg3 mutant showed premature gametophore senescence and reduced protonema formation compared to wild-type (WT) plants under normal growth conditions. The abundance of nitrogen (N) but not carbon (C) differed significantly between Ppatg3 mutant and WT plants, as did relative fatty acid levels. In vivo protein localization indicated that PpATG3 localizes to the cytoplasm, and in vitro Y2H assays confirmed that PpATG3 interacts with PpATG7 and PpATG12. Plastoglobuli (PGs) accumulated in Ppatg3, indicating that the process that degrades damaged chloroplasts in senescent gametophore cells was impaired in this mutant. RNA-Seq uncovered a detailed, comprehensive set of regulatory pathways that were affected by the autophagy mutation.ConclusionsThe autophagy-related gene PpATG3 is essential for autophagosome formation in P. patens. Our findings provide evidence that autophagy functions in N utilization, fatty acid metabolism and damaged chloroplast degradation under non-stress conditions. We identified differentially expressed genes in Ppatg3 involved in numerous biosynthetic and metabolic pathways, such as chlorophyll biosynthesis, lipid metabolism, reactive oxygen species removal and the recycling of unnecessary proteins that might have led to the premature senescence of this mutant due to defective autophagy. Our study provides new insights into the role of autophagy in preventing senescence to increase longevity in basal land plants.

Antioxidant Enhancing Effect of Azadirachta indica A. Juss. Leaf Fractionated Extracts on Naja nigricollis Reinhardt Venom in Albino Rats

The lethality of snake venom is mainly attributed to its phospholipase A2 component that hydrolyzes cellular phospholipids, leading to the release of arachidonic acid that generates potentially toxic reactive oxygen species (ROS). Imbalance between excessive generation and poor removal of ROS causes lipid peroxidation leading to cellular damage. Hence, this research was aimed at evaluating the antioxidant-enhancing effect of Azadirachta indica leaf fractionated extracts on Naja nigricollis venom in albino rats. A. indica leaf was collected, authenticated and extracted using 95% methanol followed by fractionation using hexane and ethyl acetate. Ferric reducing antioxidant power assay was used for the in vitro test, while, in vivo experiments were conducted using Albino rats. The in vitro antioxidant effect of the hexane and ethyl acetate fractions presented ferric reducing power of 68.80 ± 1.40% and 71.54 ± 2.12% respectively. This are closely related to those of ascorbic acid (78.50 ± 2.80%) and α-tocopherol (75.00 ± 1.85%). The results of the in vivo tests indicated that a single injection (0.195 mg/kg b. wt.) of N. nigricollis venom caused significant (P<0.05) elevation of hepatic and renal ROS levels (7 and 8 folds respectively) with a concomitant increase in lipid peroxidation (LPO) compared to the control group. The ROS levels were decreased significantly leading to the decrease in the level of LPO in the envenomed rats treated with the hexane and ethyl acetate fractions compared to the venom control. The treatments significantly (P<0.05) increased the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) in both the hepatic and renal homogenates compared to the venom control. The degree of protection against LPO by reducing the levels of ROS as well as increasing the activities of the antioxidant enzymes has significantly (P<0.05) increased when combine treatment of standard antivenin and any of the hexane or ethyl acetate fractions was considered compared to when each of them was used alone. Based on these findings, it has been established that, the tested extracts have antioxidant as well as antioxidant-enhancing effects against the oxidative toxicity of N. nigricollis venom.

Strategy for Highly Efficient Radioprotection by a Selenium-Containing Polymeric Drug with Low Toxicity and Long Circulation.

Because of the rapid development and extensive use of nuclear technology, ionizing radiation has become a large threat to human health. Until now, there has been no practicable radioprotector for routine clinical application because of severe side effects, high toxicity, and short elimination half-life. Herein, we develop a highly efficient radioprotection strategy using a selenium-containing polymeric drug with low toxicity and long circulation by removing reactive oxygen species (ROSs). The selenium-containing polymeric drug is prepared by copolymerization of vinyl phenylselenides (VSe) and N-(2-hydroxyethyl) acrylamide (HEA). The in vitro radioprotective efficacy of the polymeric drug is increased by 40% with lower cytotoxicity compared with the small-molecular VSe monomer. Importantly, the radioprotection activity of the polymeric drug shows more remarkable effects both in cell culture and mice model compared to the commercially available drug ebselen and also exhibits a much longer retention time in blood (half-life ∼ 10 h). This work may unfold a new area for highly efficient radioprotection by polymeric drugs instead of small-molecular agents.

Hydrogenases and the Role of Molecular Hydrogen in Plants.

Molecular hydrogen (H2) has been suggested to be a beneficial treatment for a range of species, from humans to plants. Hydrogenases catalyze the reversible oxidation of H2, and are found in many organisms, including plants. One of the cellular effects of H2 is the selective removal of reactive oxygen species (ROS) and reactive nitrogen species (RNS), specifically hydroxyl radicals and peroxynitrite. Therefore, the function of hydrogenases and the action of H2 needs to be reviewed in the context of the signalling roles of a range of redox active compounds. Enzymes can be controlled by the covalent modification of thiol groups, and although motifs targeted by nitric oxide (NO) can be predicted in hydrogenases sequences it is likely that the metal prosthetic groups are the target of inhibition. Here, a selection of hydrogenases, and the possibility of their control by molecules involved in redox signalling are investigated using a bioinformatics approach. Methods of treating plants with H2 along with the role of H2 in plants is also briefly reviewed. It is clear that studies report significant effects of H2 on plants, improving growth and stress responses, and therefore future work needs to focus on the molecular mechanisms involved.

Reactive Oxygen Species: Participation in Cellular Processes and Progression of Pathology

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are not only side products of chemical reactions, but participants in various cellular processes as well. ROS and RNS are involved in the defense against pathogenic microorganisms (H2O2, HOCl, ONOO–, $${\text{O}}_{2}^{{\centerdot - }},$$ and OH•), fertilization (H2O2), cell division $$\left( {{\text{O}}_{2}^{{\centerdot - }}} \right),$$ apoptosis (H2O2), regeneration (H2O2), coordination of a direction of the cellular movement, regulation of the vascular tone (NO•), etc. A balance between the production and the removal of ROS and RNS results in an intracellular homeostasis, whereas their overproduction causes cell damage and most probably leads to changes in the cellular metabolism. ROS and RNS can act as intracellular messengers, i.e., change the intracellular oxidative–reductive state and/or structure and function of a protein by means of a modification of amino acid residues (mainly cysteines), and the red-ox state of a number of proteins can affect the cellular metabolism. Hydrogen peroxide is the main form of ROS which participates in oxidative–reductive transduction of signals in eukaryotes. Alterations in antioxidant systems contribute to aging and a development of the age-related diseases. Primarily, aging is associated with an increased level of oxidative stress, various types of macromolecular changes, and an accumulation of DNA damage. Ageing can, to some extent, be a consequence of disorders in the proteostasis regulation and changes in the proteome functioning, because proteins are responsible for most of the cellular functions. Moreover, not all the cellular proteins can be resynthesized due to the age-related DNA damage. Thus, reactive oxygen and nitrogen species that are permanently generated in an organism are important participants in regulatory mechanisms in a cell, but also a reason for several pathological states, including cancers. ROSs are known to regulate the metabolism of signal molecules which are necessary for the cell cycle. Moreover, ROSs are able to change the activity of the iron-containing proteins. The aging that is associated with an ineffective functioning of the antioxidant defense is connected with the oxidative stress, various changes in cellular structures and macromolecules, an accumulation of metabolic products which can have a negative effect, the DNA damage (for example, owing to mistakes during a replication by DNA polymerases), and disorders in functioning of reparation systems.

A 2-Cys peroxiredoxin gene from Tamarix hispida improved salt stress tolerance in plants

BackgroundPeroxiredoxins (Prxs) are a large family of antioxidant enzymes that respond to biotic and abiotic stress by decomposing reactive oxygen species (ROS). In this study, the stress tolerance function of the Th2CysPrx gene was further analysed. It lays a foundation for further studies on the salt tolerance molecular mechanism of T. hispida and improved salt tolerance via transgenic plants.ResultsIn this study, the stress tolerance function of the Th2CysPrx gene was further analysed. The results of transgenic tobacco showed higher seed germination rates, root lengths, and fresh weight under salt stress than wild-type tobacco. Simultaneously, physiological indicators of transgenic tobacco and T. hispida showed that Th2CysPrx improved the activities of antioxidant enzymes and enhanced ROS removal ability to decrease cellular damage under salt stress. Moreover, Th2CysPrx improved the expression levels of four antioxidant genes (ThGSTZ1, ThGPX, ThSOD and ThPOD).ConclusionsOverall, these results suggested that Th2CysPrx enhanced the salt tolerance of the transgenic plants. These findings lay a foundation for further studies on the salt tolerance molecular mechanism of T. hispida and improved salt tolerance via transgenic plants.

Effects of Sudden Drop in Salinity on Osmotic Pressure Regulation and Antioxidant Defense Mechanism of Scapharca subcrenata.

Salinity is an important ecological factor that impacts the growth and survival of aquatic organisms. The salinity of seawater in coastal and estuarine areas is often subject to dynamic changes because of seasonal rainfall and continental runoff. Thus, the current study investigated the effects of sudden changes in salinity on the survival rate and osmotic pressure regulation mechanisms of bottom-sowing seedlings of the economically important ark shell, Scapharca subcrenata. By simulating the sudden changes that occur in seawater salinity after rainstorms, the results showed that the osmotic pressure of the hemolymph and Na+, K+, Ca2+, and Cl– concentrations first decreased and then increased. When the salinity decreased from 30 to 14‰, hemoglobin, soluble total protein, taurine, and total free amino acid gradually increased; maximum levels of hemoglobin, soluble total protein, and taurine occurred once the salinity increased to 22‰ at 96 h. After 96 h, the total free amino acid content increased until 144 h. The reactive oxygen species (ROS) content and total antioxidant capacity (T-AOC) peaked at 96 h, whereas the expression levels of Mn-superoxide dismutase (MnSOD) and catalase (CAT) increased earlier, indicating that, with continuous ROS generation, antioxidant defense mechanisms were activated to avoid oxidative damage. Expression levels of cathepsin C (CTSC), cathepsin D (CTSD), heat shock protein 20 (HSP20), and heat shock protein 70 (HSP70) were significantly higher than in the control group at 48 h (salinity level 14‰); the expression levels of HSP20, heat shock protein 90 (HSP90), MnSOD, and glutathione peroxidase (GPx) remained high, indicating that they were still required for osmotic pressure regulation to maintain the dynamic balance between the generation and removal of ROS as the salinity level increased. These results not only add to our basic understanding of the aquatic ecology of S. subcrenata, but also provide a theoretical ground for improving the survival rate of bottom-sowing, propagation, and release of S. subcrenata seedlings.

Clinical effect and mechanism of alkaline reduced water

Recently, alkaline ionized water (AIW) generated by water electrolysis has received increasing attention because of its shown benefits in treatment and prevention of diseases. The Korean and the Japanese governments officially acknowledged the efficacy of AIW as a novel material for the improvement of abnormal intestinal fermentation, chronic diarrhea, gastric hyperacidity and dyspepsia. It was reported that intake of AIW has various beneficial effects such as removal of reactive oxygen species, improving constipation, suppressed accumulation of body fats, early expulsion of melamine, reduction of ultraviolet radiation-induced skin damage, modulation of immune response and ameliorating diabetes. The effect of AIW is thought to be accounted to its negative oxidation reduction potential, and abundant dissolved hydrogen. The major role of AIW as an antioxidant due to its high content of hydrogen had long been established. Furthermore, drinking hydrogen water and inhaling hydrogen gas demonstrated protection against oxidative diseases. However, our recent study on alkaline reduced water (ARW) from spring water which exhibits different properties from AIW showed a salutary effect through oral administration and bathing. This finding led us to explore further the potential benefits of alkaline reduced water on health and its accompanying mechanism.

Lactic acid accumulation under heat stress related to accelerated glycolysis and mitochondrial dysfunction inhibits the mycelial growth of Pleurotus ostreatus.

High temperature is a major threat to Pleurotus ostreatus cultivation. In this study, a potential mechanism by which P. ostreatus mycelia growth is inhibited under heat stress was explored. Lactate, as a microbial fermentation product, was found unexpectedly in the mycelia of P. ostreatus under heat stress, and the time-dependent accumulation and corresponding inhibitory effect of lactate on mycelial growth was further confirmed. The addition of a glycolysis inhibitor, 2-deoxy-D-glucose (2DG), reduced the lactate content in mycelia and slightly restored mycelial growth under high-temperature conditions, which indicated the accumulation of lactate can be inhibited by glycolysis inhibition. Further data revealed mitochondrial dysfunction under high-temperature conditions, with evidence of decreased oxygen consumption and adenosine triphosphate (ATP) synthesis and increased reactive oxygen species (ROS). The removal of ROS with ascorbic acid decreased the lactate content, and mycelial growth recovered to a certain extent, indicating lactate accumulation could be affected by the mitochondrial ROS. Moreover, metabolic data showed that glycolysis and the tricarboxylic acid cycle were enhanced. This study reported the accumulation of lactate in P. ostreatus mycelia under heat stress and the inhibitory effect of lactate on the growth of mycelia, which might provide further insights into the stress response mechanism of edible fungi. Key Points • Lactate can accumulate in Pleurotus ostreatus mycelia under heat stress and inhibit its growth. • The accumulation of lactate may be due to the acceleration of glycolysis and the dysfunction of mitochondria of P. ostreatus mycelia under high-temperature stress. • The glycolysis and tricarboxylic acid cycle of P. ostreatus mycelia were accelerated under high-temperature stress.

Physiological and biochemical insights into the basal level of resistance of two maize hybrids in response to Fusarium verticillioides infection

Fusarium stalk rot (FSR), caused by Fusarium verticillioides, is one of the most destructive diseases impacting maize yield worldwide. In this study, net carbon assimilation rate (A), stomatal conductance to water vapor (gs), transpiration rate (E), and internal CO2 concentration (Ci) were evaluated on leaves and the activities of enzymes (chitinase (CHI), β-1-3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), polyphenoloxidase (PPO), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POX)) as well the concentrations of total soluble phenolics (TSP), lignin-thioglycolic acid (LTGA) derivatives, and malondialdehyde (MDA) were evaluated in the internodes and nodes of plants from maize hybrids moderately resistant (BRS 1035) and susceptible (30F35Y) to FSR. The upward relative lesion length (URLL) and radial fungal colonization (RFC) were 46 and 29% lower for the BRS 1035 hybrid in comparison to 30F35Y hybrid, respectively, at 30 after inoculation (dai). For both hybrids, A, gs, and E values significantly decreased while the Ci values increased on infected leaves compared to noninoculated plants. Inoculated plants from BRS 1035 hybrid showed an increase in A compared to inoculated plants from 30F35Y hybrid, and the increase in Ci values was greater for plants from 30F35Y hybrid at 30 dai compared to plants from BRS 1035 hybrid. The CHI, GLU, PPO, CAT, APX, and POX activities increased for inoculated plants from both hybrids compared to the noninoculated plants. In the internodes region, the increase in the activities of CHI (during the infection process of F. verticillioides) and GLU (at earlier stages of F. verticillioides infection) was more pronounced for plants from BRS 1035 hybrid than for plants from 30F35Y hybrid. In the region of the nodes, activities of CHI (during the infection process of F. verticillioides), PAL (at 20 dai), PPO (at 30 dai), and CAT and POX (both at three dai) were more pronounced for plants from BRS 1035 hybrid than for plants from 30F35Y hybrid. In the internodes region, the lower TSP concentration at 30 dai was linked to a high concentration of LTGA derivatives for inoculated plants from BRS 1035 hybrid compared to inoculated plants from 30F35Y hybrid. Taking together, the results of the present study allowed to conclude that the infection by F. verticillioides triggered physiological and biochemical changes on the stalk of maize plants influencing photosynthesis on leaves. A more robust antioxidative metabolism for reactive oxygen species removal in association with an efficient and strong activity of defense enzymes helped to minimize the cellular damage caused by F. verticillioides infection resulting, therefore, in an increase in maize resistance to FSR.

Genome-wide analysis of the superoxide dismutase (SOD) gene family in Zostera marina and expression profile analysis under temperature stress.

Superoxide dismutases (SODs) serve as the first line of defense in the plant antioxidant enzyme system, and play a primary role in the removal of reactive oxygen species (ROS). However, our understanding of the functions of the SOD family in Zostera marina is limited. In this study, a systematic analysis was conducted on the characteristics of the SOD genes in Z. marina at the whole-genome level. Five SOD genes were identified, consisting of two Cu/ZnSODs, two FeSODs, and one MnSOD. Phylogenetic analysis showed that ZmSOD proteins could be divided into two major categories (Cu/ZnSODs and Fe-MnSODs). Sequence motifs, gene structure, and the 3D-modeled protein structures further supported the phylogenetic analysis, with each subgroup having similar motifs, exon-intron structures, and protein structures. Additionally, several cis-elements were identified that may respond to biotic and abiotic stresses. Transcriptome analysis revealed expression diversity of ZmSODs in various tissues. Moreover, qRT-PCR analysis showed that the expression level of most ZmSOD genes trended to decreased expression with the increase of temperature, indicating that heat stress inhibits expression of ZmSODs and may result in reduced ability of ZmSODs to scavenge ROS. Our results provide a basis for further functional research on the SOD gene family in Z. marina, which will help to determine the molecular mechanism of ZmSOD genes in response to environmental stress.

Magnesium-organic framework-based stimuli-responsive systems that optimize the bone microenvironment for enhanced bone regeneration

Biomaterials that could synchronize with complex tissue physiological healing processes would have significant potential in bioengineering applications. Inspired by the “scatter shot” pattern in the embryonal intramembranous ossification process, a multifunctionalized scaffold is proposed to provide multiple osteogenic nucleation sites for bone regeneration multicellular unit (BRMU). First, an inherently therapeutic nanoplatform was fabricated that is composed of a gallic-acid-magnesium-based metal-organic frameworks (Mg-MOF) core and a biodegradable calcium phosphate (CaP) shell. The obtained MOF@CaP can be used for efficient bioactive factor protection and can mimic the physiological inflammation resolution response through the release of the inflammatory microenvironment (low pH) stimuli-responsive IL4. In addition, the MOF@CaP nanoplatform can provide a preferable repair microenvironment, such as by supplying magnesium for angiogenesis, gallic acid for reactive oxygen species removal, and calcium and phosphate to ensure that the extracellular bone matrix is calcified. Subsequently, IL4-MOF@CaP served as the discrete core of the bone islands by BRMU, was incorporated into collagen (Col) scaffolds to fabricate a multifunctional biodegradable scaffold. Remarkable in vivo functional bone regeneration was achieved with an in situ bone island pattern formed internally. Thus, the biomaterials replicating the developmental process can be an attractive strategy for enhancing tissue regeneration.

Metabolic Rate and Oxygen Radical Levels Increase But Radical Generation Rate Decreases with Male Age in Drosophila melanogaster Sperm.

Oxidative damage increases with age in a variety of cell types, including sperm, which are particularly susceptible to attack by reactive oxygen species (ROS). While mitochondrial respiration is the main source of cellular ROS, the relationship between the rates of aerobic metabolism and ROS production, and how this relationship may be affected by age, both in sperm and in other cell types, is unclear. Here, we investigate in Drosophila melanogaster sperm, the effects of male age on (i) the level of hydrogen peroxide in the mitochondria, using a transgenic H2O2 reporter line; (ii) the in situ rate of non-H2O2 ROS production, using a novel biophysical method; and (iii) metabolic rate, using fluorescent lifetime imaging microscopy. Sperm from older males had higher mitochondrial ROS levels and a higher metabolic rate but produced ROS at a lower rate. In comparison, a somatic tissue, the gut epithelium, also showed an age-related increase in mitochondrial ROS levels but a decrease in metabolic rate. These results support the idea of a tissue-specific optimal rate of aerobic respiration balancing the production and removal of ROS, with aging causing a shift away from this optimum and leading to increased ROS accumulation. Our findings also support the view that pathways of germline and somatic aging can be uncoupled, which may have implications for male infertility treatments.

Unlocking the mystery of plants’ survival capability under waterlogging stress

Waterlogging is a major abiotic stress affecting crop plants throughout the world, which hampers crop growth and causes yield loss. There are various types of responses in plants under this stress through the combined operation of different signaling and physiological pathways. However, the correlation between these pathways is extremely limited and not well described in the published papers. Therefore, the complex waterlogging stress-tolerance mechanisms need to be presented most coherently for a comprehensive understanding of this stress. Here, we present sequential responses in plants under oxygen-deprivation stress. The regulation of the N-end rule pathway may be treated as the initial signaling in plants after facing waterlogging stress, but still, it remains a controversial topic. All the pathways under waterlogging stress are directly or indirectly related to glycolysis, tricarboxylic acid (TCA) cycle, programmed cell death (PCD) and removal of reactive oxygen species (ROS). Scientists may consider alanine aminotransferase as the main controlling switch for surviving of plants under waterlogging stress. Triggering the genes responsible for alanine aminotransferase may act as a crucial one to develop a waterlogging tolerant plant due to its ability to control anaerobic fermentation, TCA cycle and efficient utilization of carbons.

The pivotal function of dehydroascorbate reductase in glutathione homeostasis in plants.

Under natural conditions, plants are exposed to various abiotic and biotic stresses that trigger rapid changes in the production and removal of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2). The ascorbate-glutathione pathway has been recognized to be a key player in H2O2 metabolism, in which reduced glutathione (GSH) regenerates ascorbate by reducing dehydroascorbate (DHA), either chemically or via DHA reductase (DHAR), an enzyme belonging to the glutathione S-transferase (GST) superfamily. Thus, DHAR has been considered to be important in maintaining the ascorbate pool and its redox state. Although some GSTs and peroxiredoxins may contribute to GSH oxidation, analysis of Arabidopsis dhar mutants has identified the key role of DHAR in coupling H2O2 to GSH oxidation. The reaction of DHAR has been proposed to proceed by a ping-pong mechanism, in which binding of DHA to the free reduced form of the enzyme is followed by binding of GSH. Information from crystal structures has shed light on the formation of sulfenic acid at the catalytic cysteine of DHAR that occurs with the reduction of DHA. In this review, we discuss the molecular properties of DHAR and its importance in coupling the ascorbate and glutathione pools with H2O2 metabolism, together with its functions in plant defense, growth, and development.

Neuroprotection by Walnut-Derived Peptides through Autophagy Promotion via Akt/mTOR Signaling Pathway against Oxidative Stress in PC12 Cells.

Natural-derived peptides are effective substances in attenuating oxidative stress. However, their specific mechanisms have not been fully elucidated, especially in peptide-mediated autophagy. In the present study, TWLPLPR, YVLLPSPK, and KVPPLLY, novel peptides from Juglans mandshurica Maxim, prevented reactive oxygen species (ROS) production, elevated glutathione peroxidase (GSH-Px) activity and adenosine 5'-triphosphate (ATP) levels, and ameliorated apoptosis in Aβ25-35 (at a concentration of 50 μM for 24 h)-induced PC12 cells (P < 0.01). Both western blot and immunofluorescence analysis illustrated that the peptides regulated Akt/mTOR signaling through p-Akt (Ser473) and p-mTOR (S2481) and promoted autophagy by increasing the levels of LC3-II/LC3-I and Beclin-1 while lowering p62 expression (P < 0.01). The autophagy inhibitor (3-methyladenine, 3-MA) and inducer (rapamycin, RAPA) were combined used to confirm the contribution of peptide-regulated autophagy in antioxidative effects. Moreover, the peptides increased the levels of LAMP1, LAMP2, and Cathepsin D (P < 0.05) and promoted the fusion with lysosomes to form autolysosomes, accelerating ROS removal. These data suggested that walnut-derived peptides regulated oxidative stress by promoting autophagy in the Aβ25-35-induced PC12 cells.

The Radical Scavenger NZ-419 Suppresses Intestinal Polyp Development in Apc-Mutant Mice.

Colorectal cancer is the fourth leading cause of cancer death worldwide, and it is important to establish effective methods for preventing colorectal cancer. One effective prevention strategy could be the use of antioxidants. However, the role of the direct antioxidative function of antioxidants against carcinogenesis has not been clarified. Thus, we aimed to determine whether the direct removal of reactive oxygen species by a hydroxyl radical scavenger, NZ-419, could inhibit colorectal carcinogenesis. NZ-419 is a creatinine metabolite that has been shown to be safe and to inhibit the progression of chronic kidney disease in rats, and it is now under clinical development. In the present study, we demonstrated that NZ-419 eliminated reactive oxygen species production in HCT116 cells after H2O2 stimulation and suppressed H2O2-induced Nrf2 promoter transcriptional activity. The administration of 500 ppm NZ-419 to Apc-mutant Min mice for 8 weeks resulted in a decrease in the number of polyps in the middle segment of the small intestine to 62.4% of the value in the untreated control (p < 0.05 vs. control group). As expected, NZ-419 treatment affected the levels of reactive carbonyl species, which are oxidative stress markers in the serum of Min mice. Suppression of the mRNA levels of the proliferation-associated factor c-Myc was observed in intestinal polyps of Min mice after NZ-419 treatment, with a weak suppression of epithelial cell proliferation assessed by proliferation cell nuclear antigen (PCNA) staining in the intestinal polyps. This study demonstrated that NZ-419 suppress the development of intestinal polyps in Min mice, suggesting the utility of radical scavenger/antioxidants as a cancer chemopreventive agent.

An Extract of Young Olive Fruit Residues Attenuates Oxidative Stress in HaCaT Keratinocytes through the Ativation of Nrf2 Signaling.

Residues of olive fruit (ROF) after the extraction of oils are an increasing source of industrial waste, because olive oil is becoming more popular as a healthy food. It has been reported that olives have some polyphenols that have an antioxidation capability. On the other hand, excess oxidative stress disrupts epidermal barrier function. This study was conducted to determine whether ROF could be utilized as an antioxidant source to reduce industrial wastes and to identify possible active materials to maintain healthy skin. Olive fruits are categorized into two groups depending on the time of harvest, young fruit (YF) and mature fruit (MF). Thus, we examined the antioxidant potentials of extracts from YF and from MF to remove reactive oxygen species (ROS) from biological and chemical aspects. HaCaT keratinocytes cultured with extracts of YF or MF had reduced levels of intracellular ROS in spite of the relatively low chemical capability against ROS scavenging. The biological effects of the YF extract were superior to those of the MF extract. The YF extract showed effective reductions of intracellular ROS and carbonylated proteins that were elevated by the stress-related hormone cortisol. In addition, the YF extract reinforced the intracellular antioxidation capability through the activation of Nrf2 signaling. Taken together, the YF extract was an effective source to reinforce the intracellular antioxidation capability. We conclude from these results that utilizing ROF would lead to the reduction of industrial wastes and would supply active materials to maintain healthy skin.

Cardiovascular Therapeutic Potential of the Redox Siblings, Nitric Oxide (NO•) and Nitroxyl (HNO), in the Setting of Reactive Oxygen Species Dysregulation.

Reactive oxygen species (ROS) dysregulation is a hallmark of cardiovascular disease, characterised by an imbalance in the synthesis and removal of ROS. ROS such as superoxide (•O2-), hydrogen peroxide (H2O2), hydroxyl (OH•) and peroxynitrite (ONOO-) have a marked impact on cardiovascular function, contributing to the vascular impairment and cardiac dysfunction associated with diseases such as angina, hypertension, diabetes and heart failure. Central to the vascular dysfunction is a reduction in bioavailability and/or physiological effects of vasoprotective nitric oxide (NO•), leading to vasoconstriction, inflammation and vascular remodelling. In a cardiac context, increased ROS generation can also lead to modification of key proteins involved in cardiac contractility. Whilst playing a key role in the pathogenesis of cardiovascular disease, ROS dysregulation also limits the clinical efficacy of current therapies, such as nitrosovasodilators. As such, alternate therapies are sought. This review will discuss the impact of ROS dysregulation on the therapeutic utility of NO• and its redox sibling, nitroxyl (HNO). Both nitric oxide (NO) and nitroxyl (HNO) donors signal through soluble guanylyl cyclase (sGC). NO binds to the Fe(II) form of sGC and nitroxyl possibly to both sGC heme and thiol groups. In the vasculature, nitroxyl can also signal through voltage-dependent (Kv) and ATP-sensitive (KATP) K+ channels as well as calcitonin gene-related peptide (CGRP). In the heart, HNO directly targets critical thiols to increase myocardial contractility, an effect not seen with NO. The qualitative effects via elevation of cGMP are similar, i.e. lusitropic in the heart and inhibitory on vasoconstriction, inflammation, aggregation and vascular remodelling. Of pathophysiological significance is the fact the efficacy of NO donors is impaired by ROS, e.g. through chemical scavenging of NO, to generate reactive nitrogen oxide species (RNOS), whilst nitroxyl is apparently not.