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Microbial Biotechnology Sep 2020Heavy metal contamination is a serious environmental problem. Understanding the toxicity mechanisms may allow to lower concentration of metals in the metal-based...
Heavy metal contamination is a serious environmental problem. Understanding the toxicity mechanisms may allow to lower concentration of metals in the metal-based antimicrobial treatments of crops, and reduce metal content in soil and groundwater. Here, we investigate the interplay between metal efflux systems and the superoxide dismutase (SOD) in the purple bacterium Rubrivivax gelatinosus and other bacteria through analysis of the impact of metal accumulation. Exposure of the Cd -efflux mutant ΔcadA to Cd caused an increase in the amount and activity of the cytosolic Fe-Sod SodB, thereby suggesting a role of SodB in the protection against Cd . In support of this conclusion, inactivation of sodB gene in the ΔcadA cells alleviated detoxification of superoxide and enhanced Cd toxicity. Similar findings were described in the Cu -efflux mutant with Cu . Induction of the Mn-Sod or Fe-Sod in response to metals in other bacteria, including Escherichia coli, Pseudomonas aeruginosa, Pseudomonas putida, Vibrio cholera and Bacillus subtilis, was also shown. Both excess Cd or Cu and superoxide can damage [4Fe-4S] clusters. The additive effect of metal and superoxide on the [4Fe-4S] could therefore explain the hypersensitive phenotype in mutants lacking SOD and the efflux ATPase. These findings underscore that ROS defence system becomes decisive for bacterial survival under metal excess.
Topics: Burkholderiales; Metals, Heavy; Superoxide Dismutase; Superoxides
PubMed: 32558268
DOI: 10.1111/1751-7915.13589 -
Journal of Inorganic Biochemistry Jan 2021Neuronal nitric oxide synthase (nNOS) generates superoxide, particularly at sub-optimal l-arginine (l-Arg) substrate concentrations. Heat shock protein 90 (Hsp90) was...
Neuronal nitric oxide synthase (nNOS) generates superoxide, particularly at sub-optimal l-arginine (l-Arg) substrate concentrations. Heat shock protein 90 (Hsp90) was reported to inhibit superoxide generation from nNOS protein. However, commercially available Hsp90 product from bovine brain tissues with unspecified Hsp90α and Hsp90β contents and an undefined Hsp90 protein oligomeric state was utilized. These two Hsp90s can have opposite effect on superoxide production by NOS. Importantly, emerging evidence indicates that nNOS splice variants are involved in different biological functions by functioning distinctly in redox signaling. In the present work, purified recombinant human Hsp90α, in its native dimeric state, was used in electron paramagnetic resonance (EPR) spin trapping experiments to study the effects of Hsp90α on superoxide generation from nNOS splice variants nNOSμ and nNOSα. Human Hsp90α was found to significantly increase superoxide generation from nNOSμ and nNOSα proteins under l-Arg-depleted conditions and Hsp90α influenced superoxide production by nNOSμ and nNOSα at varying degrees. Imidazole suppressed the spin adduct signal, indicating that superoxide was produced at the heme site of nNOS in the presence of Hsp90α, whereas l-Arg repletion diminished superoxide production by the nNOS-Hsp90α. Moreover, NADPH consumption rate values exhibited a similar trend/difference as a function of Hsp90α and l-Arg. Together, these EPR spin trapping and NADPH oxidation kinetics results demonstrated noticeable Hsp90α-induced increases in superoxide production by nNOS and a distinguishable effect of Hsp90α on nNOSμ and nNOSα proteins.
Topics: Animals; HSP90 Heat-Shock Proteins; Humans; Nitric Oxide Synthase Type I; Rats; Superoxides
PubMed: 33181440
DOI: 10.1016/j.jinorgbio.2020.111298 -
Annual Review of Microbiology 2015Bacteria live in a toxic world in which their competitors excrete hydrogen peroxide or superoxide-generating redox-cycling compounds. They protect themselves by... (Review)
Review
Bacteria live in a toxic world in which their competitors excrete hydrogen peroxide or superoxide-generating redox-cycling compounds. They protect themselves by activating regulons controlled by the OxyR, PerR, and SoxR transcription factors. OxyR and PerR sense peroxide when it oxidizes key thiolate or iron moieties, respectively; they then induce overlapping sets of proteins that defend their vulnerable metalloenzymes. An additional role for OxyR in detecting electrophilic compounds is possible. In some nonenteric bacteria, SoxR appears to control the synthesis and export of redox-cycling compounds, whereas in the enteric bacteria it defends the cell against the same agents. When these compounds oxidize its iron-sulfur cluster, SoxR induces proteins that exclude, excrete, or modify them. It also induces enzymes that defend the cell against the superoxide that such compounds make. Recent work has brought new insight into the biochemistry and physiology of these responses, and comparative studies have clarified their evolutionary histories.
Topics: Bacteria; Bacterial Proteins; Hydrogen Peroxide; Oxidation-Reduction; Reactive Oxygen Species; Superoxides; Transcription Factors
PubMed: 26070785
DOI: 10.1146/annurev-micro-091014-104322 -
Thorax Apr 2005
Topics: Gene Expression Regulation; Humans; Hypoxia; Nitric Oxide; Oxygen; Superoxides
PubMed: 15790976
DOI: 10.1136/thx.2004.038471 -
The Journal of Biological Chemistry Jul 1997
Review
Topics: Animals; Bacterial Proteins; Escherichia coli Proteins; Humans; Mutation; Regulon; Superoxide Dismutase; Superoxides; Trans-Activators; Transcription Factors
PubMed: 9228011
DOI: 10.1074/jbc.272.30.18515 -
Proceedings of the National Academy of... Mar 2021Plants must coordinate photosynthetic metabolism with the daily environment and adapt rhythmic physiology and development to match carbon availability. Circadian clocks...
Plants must coordinate photosynthetic metabolism with the daily environment and adapt rhythmic physiology and development to match carbon availability. Circadian clocks drive biological rhythms which adjust to environmental cues. Products of photosynthetic metabolism, including sugars and reactive oxygen species (ROS), are closely associated with the plant circadian clock, and sugars have been shown to provide metabolic feedback to the circadian oscillator. Here, we report a comprehensive sugar-regulated transcriptome of and identify genes associated with redox and ROS processes as a prominent feature of the transcriptional response. We show that sucrose increases levels of superoxide (O), which is required for transcriptional and growth responses to sugar. We identify circadian rhythms of O-regulated transcripts which are phased around dusk and find that O is required for sucrose to promote expression of TIMING OF CAB1 in the evening. Our data reveal a role for O as a metabolic signal affecting transcriptional control of the circadian oscillator in .
Topics: Arabidopsis; Circadian Rhythm; Gene Expression Profiling; Gene Expression Regulation, Plant; Sucrose; Superoxides
PubMed: 33674383
DOI: 10.1073/pnas.2020646118 -
Free Radical Biology & Medicine Apr 2010Hydroethidine (HE; or dihydroethidium) is the most popular fluorogenic probe used for detecting intracellular superoxide radical anion. The reaction between superoxide... (Review)
Review
Hydroethidine (HE; or dihydroethidium) is the most popular fluorogenic probe used for detecting intracellular superoxide radical anion. The reaction between superoxide and HE generates a highly specific red fluorescent product, 2-hydroxyethidium (2-OH-E(+)). In biological systems, another red fluorescent product, ethidium, is also formed, usually at a much higher concentration than 2-OH-E(+). In this article, we review the methods to selectively detect the superoxide-specific product (2-OH-E(+)) and the factors affecting its levels in cellular and biological systems. The most important conclusion of this review is that it is nearly impossible to assess the intracellular levels of the superoxide-specific product, 2-OH-E(+), using confocal microscopy or other fluorescence-based microscopic assays and that it is essential to measure by HPLC the intracellular HE and other oxidation products of HE, in addition to 2-OH-E(+), to fully understand the origin of red fluorescence. The chemical reactivity of mitochondria-targeted hydroethidine (Mito-HE, MitoSOX red) with superoxide is similar to the reactivity of HE with superoxide, and therefore, all of the limitations attributed to the HE assay are applicable to Mito-HE (or MitoSOX) as well.
Topics: Chromatography, High Pressure Liquid; Culture Media; Cytochromes c; Drug Stability; Electrophoresis; Ethidium; False Positive Reactions; Fluorescent Dyes; Hydrogen Peroxide; Metalloporphyrins; Microscopy, Confocal; Mitochondria; Phenanthridines; Reactive Oxygen Species; Superoxides; Ultrasonics
PubMed: 20116425
DOI: 10.1016/j.freeradbiomed.2010.01.028 -
Free Radical Research Mar 2018Superoxide radical represents one of the most biologically relevant reactive oxygen species involved in numerous physiological and pathophysiological processes....
Superoxide radical represents one of the most biologically relevant reactive oxygen species involved in numerous physiological and pathophysiological processes. Superoxide measurement through the decay of an electron paramagnetic resonance (EPR) signal of a triarylmethyl (TAM) radical possesses the advantage of a high selectivity and relatively high rate constant of TAM reaction with the superoxide. Hereby we report a straightforward synthesis and characterization of a TAM-TAM biradical showing a high reactivity with superoxide (second-order rate constant, (6.7 ± 0.2) × 10 M s) enabling the measurement of superoxide radical by following the increase of a sharp EPR signal associated with the formation of a TAM-quinone-methide monoradical product.
Topics: Electron Spin Resonance Spectroscopy; Superoxides; Trityl Compounds
PubMed: 28817975
DOI: 10.1080/10715762.2017.1369058 -
Free Radical Biology & Medicine Sep 2010The quinone/semiquinone/hydroquinone triad (Q/SQ(*-)/H(2)Q) represents a class of compounds that has great importance in a wide range of biological processes. The... (Review)
Review
The quinone/semiquinone/hydroquinone triad (Q/SQ(*-)/H(2)Q) represents a class of compounds that has great importance in a wide range of biological processes. The half-cell reduction potentials of these redox couples in aqueous solutions at neutral pH, E degrees ', provide a window to understanding the thermodynamic and kinetic characteristics of this triad and their associated chemistry and biochemistry in vivo. Substituents on the quinone ring can significantly influence the electron density "on the ring" and thus modify E degrees' dramatically. E degrees' of the quinone governs the reaction of semiquinone with dioxygen to form superoxide. At near-neutral pH the pK(a)'s of the hydroquinone are outstanding indicators of the electron density in the aromatic ring of the members of these triads (electrophilicity) and thus are excellent tools to predict half-cell reduction potentials for both the one-electron and two-electron couples, which in turn allow estimates of rate constants for the reactions of these triads. For example, the higher the pK(a)'s of H(2)Q, the lower the reduction potentials and the higher the rate constants for the reaction of SQ(*-) with dioxygen to form superoxide. However, hydroquinone autoxidation is controlled by the concentration of di-ionized hydroquinone; thus, the lower the pK(a)'s the less stable H(2)Q to autoxidation. Catalysts, e.g., metals and quinone, can accelerate oxidation processes; by removing superoxide and increasing the rate of formation of quinone, superoxide dismutase can accelerate oxidation of hydroquinones and thereby increase the flux of hydrogen peroxide. The principal reactions of quinones are with nucleophiles via Michael addition, for example, with thiols and amines. The rate constants for these addition reactions are also related to E degrees'. Thus, pK(a)'s of a hydroquinone and E degrees ' are central to the chemistry of these triads.
Topics: Benzoquinones; Biochemistry; Humans; Hydrogen Peroxide; Oxidation-Reduction; Superoxides; Thermodynamics
PubMed: 20493944
DOI: 10.1016/j.freeradbiomed.2010.05.009 -
Redox Biology Apr 2021In this paper, we describe an assay to analyze simultaneously the oxygen consumption rate (OCR) and superoxide production in a biological system. The analytical set-up...
In this paper, we describe an assay to analyze simultaneously the oxygen consumption rate (OCR) and superoxide production in a biological system. The analytical set-up uses electron paramagnetic resonance (EPR) spectroscopy with two different isotopically-labelled sensors: N-PDT (4-oxo-2,2,6,6-tetramethylpiperidine-d-N-1-oxyl) as oxygen-sensing probe and N-CMH (1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine, a cyclic hydroxylamine, as sensor of reactive oxygen species (ROS). The superoxide contribution to CMH oxidation is assessed using SOD or PEGSOD as controls. Because the EPR spectra are not superimposable, the variation of EPR linewidth of N-PDT (linked to OCR) and the formation of the nitroxide from N-CMH (linked to superoxide production) can be recorded simultaneously over time on a single preparation. The EPR toolbox was qualified in biological systems of increasing complexity. First, we used an enzymatic assay based on the hypoxanthine (HX)/xanthine oxidase (XO) which is a well described model of oxygen consumption and superoxide production. Second, we used a cellular model of superoxide production using macrophages exposed to phorbol 12-myristate 13-acetate (PMA) which stimulates the NADPH oxidase (NOX) to consume oxygen and produce superoxide. Finally, we exposed isolated mitochondria to established inhibitors of the electron transport chain (rotenone and metformin) in order to assess their impact on OCR and superoxide production. This EPR toolbox has the potential to screen the effect of intoxicants or drugs targeting the mitochondrial function.
Topics: Electron Spin Resonance Spectroscopy; Oxidation-Reduction; Oxygen Consumption; Reactive Oxygen Species; Superoxides
PubMed: 33418140
DOI: 10.1016/j.redox.2020.101852