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Role of Oxidized Lipids in Permeation of H2O2 Through a Lipid Membrane: Molecular Mechanism of an Inhibitor to Promoter Switch.
Ouchi, Y, Unoura, K, Nabika, H
Scientific reports. 2019;(1):12497
Abstract
H2O2 permeation through a cell membrane significantly affects living organisms, and permeation is controlled by the physico-chemical nature of lipids and other membrane components. We investigated the molecular relationship between H2O2 permeation and lipid membrane structure using three oxidized lipids. POVPC and PazePC act as intra- and inter-molecular permeation promoters, respectively; however, their underlying mechanisms were different. The former changed the partition equilibrium, while the latter changed the permeation pathway. PoxnoPC inhibited permeation under our experimental conditions via an intra-molecular configuration change. Thus, both intra- and inter-molecular processes were found to control the role of oxidized lipids as inhibitors and promoters towards H2O2 permeation with different mechanisms depending on structure and composition. Here, we identified two independent H2O2 permeation routes: (i) permeation through lipid membrane with increased partition coefficient by intra-molecular configurational change and (ii) diffusion through pores (water channels) formed by inter-molecular configurational change of oxidized lipids. We provide new insight into how biological cells control permeation of molecules through intra- and inter-molecular configurational changes in the lipid membrane. Thus, by employing a rational design for both oxidized lipids and other components, the permeation behaviour of H2O2 and other ions and molecules through a lipid membrane could be controlled.
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Genipin protects against H2O2-induced oxidative damage in retinal pigment epithelial cells by promoting Nrf2 signaling.
Zhao, H, Wang, R, Ye, M, Zhang, L
International journal of molecular medicine. 2019;(2):936-944
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Abstract
Oxidative stress serves a vital function in the pathogenesis of age‑related macular degeneration (AMD); genipin (GP) possesses antioxidative properties. The present study aimed to investigate the effects of GP on retinal pigment epithelial (RPE) cells induced by H2O2 and the underlying mechanism. ARPE‑19 cells were subjected to H2O2 treatment to induce oxidative damage. Cell viability was determined via an MTT assay. Reactive oxygen species (ROS) levels and cell apoptosis were detected by flow cytometry. Nuclear factor‑erythroid 2‑related factor‑2 (Nrf2) signaling‑associated and the expression of apoptosis‑associated factors were measured using reverse transcription‑quantitative polymerase chain reaction assay and western blotting. The results revealed that 200 µM H2O2 and 30 µM GP were determined to be the optimal concentrations for subsequent experimentation. GP reversed the inhibitory effects of H2O2 by promoting cell viability, attenuating ROS accumulation and cell apoptosis, and increased the expression of Nrf2, heme oxygenase‑1 (HO‑1) and NAD(P)H: Quinine oxidoreductase 1 (NQO1); Nrf2 silencing inhibited HO‑1 and NQO1 expression. In addition, Nrf2 silencing enhanced the effects of H2O2 by promoting ROS production and cell apoptosis. Compared with H2O2, Nrf2 silencing further decreased the expression levels of B‑cell lymphoma‑2 (Bcl‑2), but increased that of Bcl‑2‑associated X protein and cleaved‑caspase‑3. The results of the present study revealed that Nrf2 silencing attenuated the protective effects of GP on H2O2‑induced injury in ARPE‑19 cells by promoting apoptosis and oxidation. Collectively, GP attenuated oxidative damage induced by H2O2 in ARPE‑19 cells. Furthermore, the molecular mechanism may be associated with the Nrf2 signaling pathway. The findings of the present study nay provide insight into a potential therapeutic agent for the treatment of AMD.
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Hydrogen peroxide metabolism and functions in plants.
Smirnoff, N, Arnaud, D
The New phytologist. 2019;(3):1197-1214
Abstract
Contents Summary 1197 I. Introduction 1198 II. Measurement and imaging of H2 O2 1198 III. H2 O2 and O2·- toxicity 1199 IV. Production of H2 O2 : enzymes and subcellular locations 1200 V. H2 O2 transport 1205 VI. Control of H2 O2 concentration: how and where? 1205 VII. Metabolic functions of H2 O2 1207 VIII. H2 O2 signalling 1207 IX. Where next? 1209 Acknowledgements 1209 References 1209 SUMMARY Hydrogen peroxide (H2 O2 ) is produced, via superoxide and superoxide dismutase, by electron transport in chloroplasts and mitochondria, plasma membrane NADPH oxidases, peroxisomal oxidases, type III peroxidases and other apoplastic oxidases. Intracellular transport is facilitated by aquaporins and H2 O2 is removed by catalase, peroxiredoxin, glutathione peroxidase-like enzymes and ascorbate peroxidase, all of which have cell compartment-specific isoforms. Apoplastic H2 O2 influences cell expansion, development and defence by its involvement in type III peroxidase-mediated polymer cross-linking, lignification and, possibly, cell expansion via H2 O2 -derived hydroxyl radicals. Excess H2 O2 triggers chloroplast and peroxisome autophagy and programmed cell death. The role of H2 O2 in signalling, for example during acclimation to stress and pathogen defence, has received much attention, but the signal transduction mechanisms are poorly defined. H2 O2 oxidizes specific cysteine residues of target proteins to the sulfenic acid form and, similar to other organisms, this modification could initiate thiol-based redox relays and modify target enzymes, receptor kinases and transcription factors. Quantification of the sources and sinks of H2 O2 is being improved by the spatial and temporal resolution of genetically encoded H2 O2 sensors, such as HyPer and roGFP2-Orp1. These H2 O2 sensors, combined with the detection of specific proteins modified by H2 O2 , will allow a deeper understanding of its signalling roles.
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Plant peroxisomes at the crossroad of NO and H2 O2 metabolism.
Corpas, FJ, Del Río, LA, Palma, JM
Journal of integrative plant biology. 2019;(7):803-816
Abstract
Plant peroxisomes are subcellular compartments involved in many biochemical pathways during the life cycle of a plant but also in the mechanism of response against adverse environmental conditions. These organelles have an active nitro-oxidative metabolism under physiological conditions but this could be exacerbated under stress situations. Furthermore, peroxisomes have the capacity to proliferate and also undergo biochemical adaptations depending on the surrounding cellular status. An important characteristic of peroxisomes is that they have a dynamic metabolism of reactive nitrogen and oxygen species (RNS and ROS) which generates two key molecules, nitric oxide (NO) and hydrogen peroxide (H2 O2 ). These molecules can exert signaling functions by means of post-translational modifications that affect the functionality of target molecules like proteins, peptides or fatty acids. This review provides an overview of the endogenous metabolism of ROS and RNS in peroxisomes with special emphasis on polyamine and uric acid metabolism as well as the possibility that these organelles could be a source of signal molecules involved in the functional interconnection with other subcellular compartments.
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Reduction of hydrogen peroxide in gram-negative bacteria - bacterial peroxidases.
Nóbrega, CS, Pauleta, SR
Advances in microbial physiology. 2019;:415-464
Abstract
Bacteria display an array of enzymes to detoxify reactive oxygen species that cause damage to DNA and to other biomolecules leading to cell death. Hydrogen peroxide is one of these species, with endogenous and exogenous sources, such as lactic acid bacteria, oxidative burst of the immune system or chemical reactions at oxic-anoxic interfaces. The enzymes that detoxify hydrogen peroxide will be the focus of this review, with special emphasis on bacterial peroxidases that reduce hydrogen peroxide to water. Bacterial peroxidases are periplasmic cytochromes with either two or three c-type haems, which have been classified as classical and non-classical bacterial peroxidases, respectively. Most of the studies have been focus on the classical bacterial peroxidases, showing the presence of a reductive activation in the presence of calcium ions. Mutagenesis studies have clarified the catalytic mechanism of this enzyme and were used to propose an intramolecular electron transfer pathway, with far less being known about the intermolecular electron transfer that occurs between reduced electron donors and the enzyme. The physiological function of these enzymes was not very clear until it was shown, for the non-classical bacterial peroxidase, that this enzyme is required for the bacteria to use hydrogen peroxide as terminal electron acceptor under anoxic conditions. These non-classical bacterial peroxidases are quinol peroxidases that do not require reductive activation but need calcium ions to attain maximum activity and share similar catalytic intermediates with the classical bacterial peroxidases.
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The role of thiols in antioxidant systems.
Ulrich, K, Jakob, U
Free radical biology & medicine. 2019;:14-27
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Abstract
The sulfur biochemistry of the thiol group endows cysteines with a number of highly specialized and unique features that enable them to serve a variety of different functions in the cell. Typically highly conserved in proteins, cysteines are predominantly found in functionally or structurally crucial regions, where they act as stabilizing, catalytic, metal-binding and/or redox-regulatory entities. As highly abundant low molecular weight thiols, cysteine thiols and their oxidized disulfide counterparts are carefully balanced to maintain redox homeostasis in various cellular compartments, protect organisms from oxidative and xenobiotic stressors and partake actively in redox-regulatory and signaling processes. In this review, we will discuss the role of protein thiols as scavengers of hydrogen peroxide in antioxidant enzymes, use thiol peroxidases to exemplify how protein thiols contribute to redox signaling, provide an overview over the diverse set of low molecular weight thiol-based redox systems found in biology, and illustrate how thiol-based redox systems have evolved not only to protect against but to take full advantage of a world full of molecular oxygen.
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Transcriptional Regulation Contributes to Prioritized Detoxification of Hydrogen Peroxide over Nitric Oxide.
Adolfsen, KJ, Chou, WK, Brynildsen, MP
Journal of bacteriology. 2019;(14)
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Abstract
Hydrogen peroxide (H2O2) and nitric oxide (NO·) are toxic metabolites that immune cells use to attack pathogens. These antimicrobials can be present at the same time in phagosomes, and it remains unclear how bacteria deal with these insults when simultaneously present. Here, using Escherichia coli, we observed that simultaneous exposure to H2O2 and NO· leads to prioritized detoxification, where enzymatic removal of NO· is impeded until H2O2 has been eliminated. This phenomenon is reminiscent of carbon catabolite repression (CCR), where preferred carbon sources are catabolized prior to less desirable substrates; however, H2O2 and NO· are toxic, growth-inhibitory compounds rather than growth-promoting nutrients. To understand how NO· detoxification is delayed by H2O2 whereas H2O2 detoxification proceeds unimpeded, we confirmed that the effect depended on Hmp, which is the main NO· detoxification enzyme, and used an approach that integrated computational modeling and experimentation to delineate and test potential mechanisms. Plausible interactions included H2O2-dependent inhibition of hmp transcription and translation, direct inhibition of Hmp catalysis, and competition for reducing equivalents between Hmp and H2O2-degrading enzymes. Experiments illustrated that Hmp catalysis and NAD(P)H supply were not impaired by H2O2, whereas hmp transcription and translation were diminished. A dependence of this phenomenon on transcriptional regulation parallels CCR, and we found it to involve the transcriptional repressor NsrR. Collectively, these data suggest that bacterial regulation of growth inhibitor detoxification has similarities to the regulation of growth substrate consumption, which could have ramifications for infectious disease, bioremediation, and biocatalysis from inhibitor-containing feedstocks.IMPORTANCE Bacteria can be exposed to H2O2 and NO· concurrently within phagosomes. In such multistress situations, bacteria could have evolved to simultaneously degrade both toxic metabolites or preferentially detoxify one over the other. Here, we found that simultaneous exposure to H2O2 and NO· leads to prioritized detoxification, where detoxification of NO· is hampered until H2O2 has been eliminated. This phenomenon resembles CCR, where bacteria consume one substrate over others in carbon source mixtures. Further experimentation revealed a central role for transcriptional regulation in the prioritization of H2O2 over NO·, which is also important to CCR. This study suggests that regulatory scenarios observed in bacterial consumption of growth-promoting compound mixtures can be conserved in bacterial detoxification of toxic metabolite mixtures.
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Removal of Acid Orange 51 by micro zero-valent iron under different operational conditions and evaluation of toxicity.
Ghariani, B, Messaoud, M, Louati, I, Mtibaà, R, Nasri, M, Mechichi, T
Environmental science and pollution research international. 2019;(18):18392-18402
Abstract
The removal of Acid Orange 51 (AO 51) dye in aqueous solution by microscale zero-valent iron (m-ZVI) was investigated. The m-ZVI powder was characterized granulometrically by laser particle sizer and morphologically by transmission electron microscopy (TEM). The effects of pH, m-ZVI concentration, H2O2 addition, and dye concentration on the decolorization of AO 51 were experimentally investigated. Results indicate that the removal efficiency is independent from pH values, increases with increasing ZVI dosage, and decreases with dye concentration. With 1 g/L of m-ZVI, AO 51 was effectively removed without and with addition of 25 mM H2O2, yielding a decolorization efficiency of around 70% and 98%, respectively, at pH 3 within 60 min of reaction time. The involvement of ˙OH in oxidizing AO 51 was examined by measuring the removal rates based on ˙OH scavenging molecule. Finally, the disappearance of AO 51 was estimated by monitoring the UV-Vis spectral evolution after 120 min of treatment while the Fourier-Transform Infrared spectroscopy (FT-IR) was performed to verify the occurrence of organic sorption on m-ZVI surface. The scanning electron microscope (SEM) images before and after the reaction illustrated morphological changes on m-ZVI surface. The detoxification of the treated solution was demonstrated using phytotoxicity test.
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Root Adaptation to H2O2-Induced Oxidative Stress by ARF-GEF BEN1- and Cytoskeleton-Mediated PIN2 Trafficking.
Zwiewka, M, Bielach, A, Tamizhselvan, P, Madhavan, S, Ryad, EE, Tan, S, Hrtyan, MN, Dobrev, P, Vankovï, R, Friml, J, et al
Plant & cell physiology. 2019;(2):255-273
Abstract
Abiotic stress poses constant challenges for plant survival and is a serious problem for global agricultural productivity. On a molecular level, stress conditions result in elevation of reactive oxygen species (ROS) production causing oxidative stress associated with oxidation of proteins and nucleic acids as well as impairment of membrane functions. Adaptation of root growth to ROS accumulation is facilitated through modification of auxin and cytokinin hormone homeostasis. Here, we report that in Arabidopsis root meristem, ROS-induced changes of auxin levels correspond to decreased abundance of PIN auxin efflux carriers at the plasma membrane (PM). Specifically, increase in H2O2 levels affects PIN2 endocytic recycling. We show that the PIN2 intracellular trafficking during adaptation to oxidative stress requires the function of the ADP-ribosylation factor (ARF)-guanine-nucleotide exchange factor (GEF) BEN1, an actin-associated regulator of the trafficking from the PM to early endosomes and, presumably, indirectly, trafficking to the vacuoles. We propose that H2O2 levels affect the actin dynamics thus modulating ARF-GEF-dependent trafficking of PIN2. This mechanism provides a way how root growth acclimates to stress and adapts to a changing environment.
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Efficient decolourization of malachite green with biosynthesized iron oxide nanoparticles loaded carbonated hydroxyapatite as a reusable heterogeneous Fenton-like catalyst.
Ergüt, M, Uzunoğlu, D, Özer, A
Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering. 2019;(8):786-800
Abstract
In this study, iron oxide nanoparticles (IO-NPs) with a mean diameter of 102.85 nm were firstly synthesized via a facile green route using Ulva spp. aqueous extract as a bioreductant agent. Then, IO-NPs were loaded into carbonated hydroxyapatite (c-Hap) and the final product was named as the iron oxide nanoparticles loaded carbonated hydroxyapatite (IO-NPs-Lc-Hap). Subsequently, IO-NPs-Lc-Hap was characterized by FT-IR, SEM, XRD and EDX analysis methods. MG colour removal efficiencies of Ulva spp., Hap, IO-NPs and IO-NPs-Lc-Hap materials were also evaluated by adsorption and/or Fenton-like reaction methods. IO-NPs-Lc-Hap with the highest decolourization capacity was chosen as a heterogeneous Fenton-like catalyst for Malachite Green (MG). For Fenton-like decolourization of MG, the optimum H2O2 concentration, initial dye concentration and catalyst concentration were determined to be 30 mM, 100 mg/L and 1.0 g/L, respectively. At these optimum conditions, 100% decolourization efficiency and 33.3% COD removal were obtained. On the other hand, 94% decolourization efficiency and 42% COD removal were achieved for the real textile wastewater at the obtained optimum conditions. The experimental decolourization reaction rate for MG was determined as -rd = 0.0779 [(mg dye0.3) (g cat-0.3) (min-1)] × qt0.7. Also, the catalyst had high decolourization efficiencies at the end of six sequence usages.