Are free radicals involved in thiol-based redox signaling?

The clinical potential of thiol redox proteomics

Introduction: Protein thiols are susceptible to oxidation in health and disease. Redox proteomics methods facilitate the identification, quantification, and rationalization of oxidation processes including those involving protein thiols. These residues are crucial to understanding redox homeostasis underpinning normal cell functioning and regulation as well as novel biomarkers of pathology and promising novel drug targets.Areas covered: This article reviews redox proteomic approaches to study of protein thiols in some important human pathologies and assesses the clinical potential of individual Cys residues as novel biomarkers for disease detection and as targets for novel treatments.Expert commentary: Although protein thiols are not as routinely used as redox biomarkers as some other lesions such as carbonylation, there has been growing recent interest in their potential. Driven largely by developments in high-resolution mass spectrometry it is possible now to identify proteins that are redox modified at thiol groups or that interact with regulatory oxidoreductases. Thiols that are specifically susceptible to modification by reactive oxygen species can be routinely identified now and quantitative MS can be used to quantify the proportion of a protein that is redox modified.

Manganese Porphyrin-Based SOD Mimetics Produce Polysulfides from Hydrogen Sulfide

Manganese-centered porphyrins (MnPs), MnTE-2-PyP⁵⁺ (MnTE), MnTnHex-2-PyP⁵⁺ (MnTnHex), and MnTnBuOE-2-PyP⁵⁺ (MnTnBuOE) have received considerable attention because of their ability to serve as superoxide dismutase (SOD) mimetics thereby producing hydrogen peroxide (H₂O₂), and oxidants of ascorbate and simple aminothiols or protein thiols. MnTE-2-PyP⁵⁺ and MnTnBuOE-2-PyP⁵⁺ are now in five Phase II clinical trials warranting further exploration of their rich redox-based biology. Previously, we reported that SOD is also a sulfide oxidase catalyzing the oxidation of hydrogen sulfide (H₂S) to hydrogen persulfide (H₂S₂) and longer-chain polysulfides (H₂S_n, n = 3–7). We hypothesized that MnPs may have similar actions on sulfide metabolism. H₂S and polysulfides were monitored in fluorimetric assays with 7-azido-4-methylcoumarin (AzMC) and 3′,6′-di(O-thiosalicyl)fluorescein (SSP4), respectively, and specific polysulfides were further identified by mass spectrometry. MnPs concentration-dependently consumed H₂S and produced H₂S₂ and subsequently longer-chain polysulfides. This reaction appeared to be O₂-dependent. MnP absorbance spectra exhibited wavelength shifts in the Soret and Q bands characteristic of sulfide-mediated reduction of Mn. Taken together, our results suggest that MnPs can become efficacious activators of a variety of cytoprotective processes by acting as sulfide oxidation catalysts generating per/polysulfides.

Monitoring cytosolic H2O2 fluctuations arising from altered plasma membrane gradients or from mitochondrial activity

Genetically encoded probes monitoring H₂O₂ fluctuations in living organisms are key to decipher redox signaling events. Here we use a new probe, roGFP2-Tpx1.C169S, to monitor pre-toxic fluctuations of peroxides in fission yeast, where the concentrations linked to signaling or to toxicity have been established. This probe is able to detect nanomolar fluctuations of intracellular H₂O₂ caused by extracellular peroxides; expression of human aquaporin 8 channels H₂O₂ entry into fission yeast decreasing membrane gradients. The probe also detects H₂O₂ bursts from mitochondria after addition of electron transport chain inhibitors, the extent of probe oxidation being proportional to the mitochondrial activity. The oxidation of this probe is an indicator of steady-state levels of H₂O₂ in different genetic backgrounds. Metabolic reprogramming during growth in low-glucose media causes probe reduction due to the activation of antioxidant cascades. We demonstrate how peroxiredoxin-based probes can be used to monitor physiological H₂O₂ fluctuations.

Reliable methods of measuring intracellular H₂O₂ fluctuations are necessary to advance redox biology. Here the authors design a H₂O₂ sensor based on the fission yeast peroxiredoxin Tpx1 to sense nanomolar fluctuations of intracellular H₂O₂ in response to genetic and environmental perturbations.

Endometrium and endometriosis tissue mitochondrial energy metabolism in a nonhuman primate model

BACKGROUND

Endometriosis is the growth of uterine lining (endometrium) outside of the uterus. In other chronic inflammatory diseases, mitochondrial dysfunction is suspected of playing a role in disease pathogenesis. However, little is known about endometriosis mitochondrial function or its effects on tissue metabolism. The objectives of this study were to analyze mitochondrial function in nonhuman primate (NHP) endometrium and endometriosis tissue and to identify the metabolic features of these tissues that may contribute to disease.

METHODS

Mitochondrial function in endometriosis tissue and endometrium was measured using mitochondrial respirometry analysis to determine if changes in oxidative phosphorylation exist in endometrium and endometriosis tissue compared to control endometrium from clinically healthy NHPs. Targeted metabolomics and multidimensional statistical analysis were applied to quantify key metabolites in energy and amino acid biosynthesis pathways.

RESULTS

Mitochondrial respirometry assays showed endometrium from NHPs with endometriosis had reduced complex II-mediated oxygen consumption rates (OCR) across all energy states (basal, p = 0.01; state 3, p = 0.02; state 3u, p = 0.04; state 4o, p = 0.008) and endometriosis tissue had reduced state 3, complex I-mediated OCR (p = 0.02) and respiratory control rates (p = 0.01) compared to normal endometrium. Targeted metabolomics performed on tissue revealed carnitine (p = 0.001), creatine phosphate (p = 0.01), NADH (p = 0.0001), FAD (p = 0.001), tryptophan (p = 0.0009), and malic acid (p = 0.005) were decreased in endometriosis tissue compared to normal endometrium samples. FAD (p = 0.004), tryptophan (p = 0.0004) and malic acid (p = 0.03) were significantly decreased in endometrium from NHPs with endometriosis compared to normal endometrium. Significant metabolites identified in endometriosis and endometrium samples from animals with endometriosis were part of amino acid biosynthesis or energy metabolism pathways.

CONCLUSIONS

Here, endometrial mitochondrial energy production and metabolism were decreased in endometrium and endometriosis tissue. Decreased mitochondrial energy production may be due to oxidative stress-induced damage to mitochondrial DNA or membranes, a shift in cell metabolism, or decreased energy substrate; however, the exact cause remains unknown. Additional research is needed to determine the implications of reduced mitochondrial energy production and metabolism on endometriosis and endometrium.

Hydrogen sulfide, reactive sulfur species and coping with reactive oxygen species

Life began in a ferruginous (anoxic and Fe²⁺ dominated) world around 3.8 billion years ago (bya). Hydrogen sulfide (H₂S) and other sulfur molecules from hydrothermal vents and other fissures provided many key necessities for life's origin including catalytic platforms (primordial enzymes) that also served as primitive boundaries (cell walls), substrates for organic synthesis and a continuous source of energy in the form of reducing equivalents. Anoxigenic photosynthesis oxidizing H₂S followed within a few hundred million years and laid the metabolic groundwork for oxidative photosynthesis some half-billion years later that slightly and episodically increased atmospheric oxygen around 2.3 bya. This oxidized terrestrial sulfur to sulfate which was washed to the sea where it was reduced creating vast euxinic (anoxic and sulfidic) areas. It was in this environment that eukaryotic cells appeared around 1.5 bya and where they evolved for nearly 1 billion additional years. Oxidative photosynthesis finally oxidized the oceans and around 0.6 bya oxygen levels in the atmosphere and oceans began to rise toward present day levels. This is purported to have been a life-threatening event due to the prevalence of reactive oxygen species (ROS) and thus necessitated the elaboration of chemical and enzymatic antioxidant mechanisms. However, these antioxidants initially appeared around the time of anoxigenic photosynthesis suggesting a commitment to metabolism of reactive sulfur species (RSS). This review examines these events and suggests that many of the biological attributes assigned to ROS may, in fact, be due to RSS. This is underscored by observations that ROS and RSS are chemically similar, often indistinguishable by analytical methods and the fact that the bulk of biochemical and physiological experiments are performed in unphysiologically oxic environments where ROS are artifactually favored over RSS.

Overexpression of Peroxidase Gene GsPRX9 Confers Salt Tolerance in Soybean

Peroxidases play prominent roles in antioxidant responses and stress tolerance in plants; however, their functions in soybean tolerance to salt stress remain unclear. Here, we investigated the role of a peroxidase gene from the wild soybean (Glycine soja), GsPRX9, in soybean tolerance to salt stress. GsPRX9 gene expression was induced by salt treatment in the roots of both salt-tolerant and -sensitive soybean varieties, and its relative expression level in the roots of salt-tolerant soybean varieties showed a significantly higher increase than in salt-sensitive varieties after NaCl treatment, suggesting its possible role in soybean response to salt stress. GsPRX9-overexpressing yeast (strains of INVSc1 and G19) grew better than the control under salt and H2O2 stress, and GsPRX9-overexpressing soybean composite plants showed higher shoot fresh weight and leaf relative water content than control plants after NaCl treatment. Moreover, the GsPRX9-overexpressing soybean hairy roots had higher root fresh weight, primary root length, activities of peroxidase and superoxide dismutase, and glutathione level, but lower H2O2 content than those in control roots under salt stress. These findings suggest that the overexpression of the GsPRX9 gene enhanced the salt tolerance and antioxidant response in soybean. This study would provide new insights into the role of peroxidase in plant tolerance to salt stress.

Age-related changes and effects of regular low-intensity exercise on gait, balance, and oxidative biomarkers in the spinal cord of Wistar rats

The present study aimed to analyze age-related changes to motor coordination, balance, spinal cord oxidative biomarkers in 3-, 6-, 18-, 24-, and 30-month-old rats. The effects of low-intensity exercise on these parameters were also analyzed in 6-, 18-, and 24-month-old rats. Body weight, blood glucose, total cholesterol, and high-density lipoprotein (HDL) cholesterol were assessed for all rats. The soleus muscle weight/body weight ratio was used to estimate skeletal muscle mass loss. Body weight increased until 24 months; only 30-month-old rats exhibited decreased blood glucose and increased total cholesterol and HDL cholesterol. The soleus muscle weight/body weight ratio increased until 18 months, followed by a small decrease in old rats. Exercise did not change any of these parameters. Stride length and step length increased from adult to middle age, but decreased at old age. Stride width increased while the sciatic functional index decreased in old rats. Performance in the balance beam test declined with age. While gait did not change, balance improved after exercise. Aging increased superoxide anion generation, hydrogen peroxide levels, total antioxidant capacity, and superoxide dismutase activity while total thiol decreased and lipid hydroperoxides did not change. Exercise did not significantly change this scenario. Thus, aging increased oxidative stress in the spinal cord, which may be associated with age-induced changes in gait and balance. Regular low-intensity exercise is a good alternative for improving age-induced changes in balance, while beneficial effects on gait and spinal cord oxidative biomarkers cannot be ruled out because of the small number of rats investigated (n=5 or 6/group).

A caffeine-supplemented diet modulates oxidative stress markers and prevents oxidative damage in the livers of Nile tilapia (Oreochromis niloticus) exposed to hypoxia

Recent evidence has revealed the involvement of oxidative stress and oxidative damage with health impairment and mortality in fish exposed to hypoxia. Thus, natural compounds with antioxidant and free-radical-scavenging properties, such as caffeine, might help to prevent or reduce hepatic damage elicited by hypoxia. Thus, the aim of this study was to evaluate whether dietary supplementation with caffeine could prevent or reduce oxidative damage in the livers of Nile tilapia (Oreochromis niloticus) exposed to hypoxia. Hepatic reactive oxygen species, lipid peroxidation levels, and xanthine oxidase (XO) activity were higher in fish exposed to hypoxia compared with normoxia. Hepatic catalase, glutathione peroxidase, and glutathione S-transferase activities, as well as the antioxidant capacity against peroxyl radical levels, were lower in fish exposed to hypoxia compared with normoxia. No significant difference between groups was observed regarding hepatic superoxide dismutase activity. Dietary supplementation with 8% caffeine prevented all alterations elicited by hypoxia. Based on this evidence, the use of dietary supplementation with 8% caffeine can be an interesting approach to preventing hepatic lipid damage and impairment of the antioxidant defense system elicited by hypoxia, and this effect can be mediated by protective effects on XO activity.

Effects of inhibiting antioxidant pathways on cellular hydrogen sulfide and polysulfide metabolism

Elaborate antioxidant pathways have evolved to minimize the threat of excessive reactive oxygen species (ROS) and to regulate ROS as signaling entities. ROS are chemically and functionally similar to reactive sulfur species (RSS) and both ROS and RSS have been shown to be metabolized by the antioxidant enzymes, superoxide dismutase and catalase. Here we use fluorophores to examine the effects of a variety of inhibitors of antioxidant pathways on metabolism of two important RSS, hydrogen sulfide (H₂S with AzMC) and polysulfides (H₂S_n, where n = 2-7, with SSP4) in HEK293 cells. Cells were exposed to inhibitors for up to 5 days in normoxia (21% O₂) and hypoxia (5% O₂), conditions also known to affect ROS production. Decreasing intracellular glutathione (GSH) with l-buthionine-sulfoximine (BSO) or diethyl maleate (DEM) decreased H₂S production for 5 days but did not affect H₂S_n. The glutathione reductase inhibitor, auranofin, initially decreased H₂S and H₂S_n but after two days H₂S_n increased over controls. Inhibition of peroxiredoxins with conoidin A decreased H₂S and increased H₂S_n, whereas the glutathione peroxidase inhibitor, tiopronin, increased H₂S. Aminoadipic acid, an inhibitor of cystine uptake did not affect either H₂S or H₂S_n. In buffer, the glutathione reductase and thioredoxin reductase inhibitor, 2-AAPA, the glutathione peroxidase mimetic, ebselen, and tiopronin variously reacted directly with AzMC and SSP4, reacted with H₂S and H₂S₂, or optically interfered with AzMC or SSP4 fluorescence. Collectively these results show that antioxidant inhibitors, generally known for their ability to increase cellular ROS, have various effects on cellular RSS. These findings suggest that the inhibitors may affect cellular sulfur metabolism pathways that are not related to ROS production and in some instances they may directly affect RSS or the methods used to measure them. They also illustrate the importance of carefully evaluating RSS metabolism when biologically or pharmacologically attempting to manipulate ROS.

Oxidative stress and antioxidant responses in Nile tilapia Oreochromis niloticus experimentally infected by Providencia rettgeri

Bacterial diseases are one of the major problems in freshwater fish culture and have been linked to significant losses and high mortality rate. In this study, Nile tilapia Oreochromis niloticus was infected by Providencia rettgeri to evaluate the oxidative stress and antioxidant responses in the fish tissues. Juvenile Nile tilapia was divided into two groups, as follow: control (uninfected) and experimentally infected with 100 μL of P. rettgeri suspension containing 2.4 × 10⁷ viable cells/fish, and the liver and kidney tissues were collected on days 7 and 14 post-infection (PI). Liver and kidney ROS and lipid peroxidation levels were high in infected fish on day 14 PI compared to control group, while superoxide dismutase activity was lower in liver (days 7 and 14 PI) and kidney (day 14 PI) compared to their respective control groups. Liver and kidney antioxidant capacity against peroxyl radicals, non-proteic, and proteic thiols levels was lower in infected tilapia on day 14 PI compared to control group. Based on these results, P. rettgeri infection may elicit oxidative damage via increased ROS production, decreased ROS elimination and inhibits enzymatic and non-enzymatic antioxidant defense systems; which may contribute directly to disease pathophysiology of infected animals.

The glutathione system and the related thiol network in Caenorhabditis elegans

Advances in the field of redox biology have contributed to the understanding of the complexity of the thiol-based system in mediating signal transduction. The redox environment is the overall spatiotemporal balance of oxidation-reduction systems within the integrated compartments of the cell, tissues and whole organisms. The ratio of the reduced to disulfide glutathione redox couple (GSH:GSSG) is a key indicator of the redox environment and its associated cellular health. The reaction mechanisms of glutathione-dependent and related thiol-based enzymes play a fundamental role in the function of GSH as a redox regulator. Glutathione homeostasis is maintained by the balance of GSH synthesis (de novo and salvage pathways) and its utilization through its detoxification, thiol signalling, and antioxidant defence functions via GSH-dependent enzymes and free radical scavenging. As such, GSH acts in concert with the entire redox network to maintain reducing conditions in the cell. Caenorhabditis elegans offers a simple model to facilitate further understanding at the multicellular level of the physiological functions of GSH and the GSH-dependent redox network. This review discusses the C. elegans studies that have investigated glutathione and related systems of the redox network including; orthologs to the protein-encoding genes of GSH synthesis; glutathione peroxidases; glutathione-S-transferases; and the glutaredoxin, thioredoxin and peroxiredoxin systems.

Oxidative stress linked to changes of cholinesterase and adenosine deaminase activities in experimentally infected chicken chicks with Eimeria spp

Both oxidative stress and alterations in adenosinergic and cholinergic systems participate in initiation and progression of parasitic infectious diseases. Nevertheless, the involvement of these pathways during eimeriosis remains poorly understood. Therefore, the aim of this study was to evaluate the involvement of adenosinergic and cholinergic systems in regulation of inflammatory response and oxidative stress in chicken chicks experimentally infected with Eimeria spp. Two groups were formed for comparison at 3 time points (days 5, 10 and 15) of infection (PI): uninfected (control) and infected. Erythrocyte counts, hematocrit and hemoglobin levels were lower in infected chicks on day 15 post-infection (PI). Total leukocytes, heterophil and lymphocyte counts were higher in infected chicks on days 5 and 10 PI, while eosinophil counts were higher only on day 10 PI. Serum levels of total protein and globulins were higher in infected chicks on days 10 and 15 PI, while triglycerides and cholesterol levels were lower on day 15 PI. Acetylcholinesterase activity in total blood and butyrylcholinesterase activity in serum were higher in infected chicks on day 15 PI, while adenosine deaminase activity was higher on day 10 PI and lower on day 15 PI compared with the respective control. Finally, serum levels of reactive oxygen species and catalase activity in total blood were higher in infected chicks on day 15 PI, while superoxide dismutase activity in total blood was lower at the same time of infection. These data suggest that cholinergic and adenosinergic systems display a pro-inflammatory profile that contributes to impairment of immune and inflammatory responses in a mixed Eimeria infection. Furthermore, oxidative stress may contribute to clinical signs of disease as well as to pathogenesis. In summary, the impairment of immune response and alterations in blood antioxidant/oxidant status contributes to disease pathophysiology.

Intestinal injury caused by Eimeria spp. impairs the phosphotransfer network and gain weight in experimentally infected chicken chicks

Parasitic infections caused by protozoan belonging to genus Eimeria are considered important for the poultry industry, due to their severe intestinal lesions and high mortality rates, causing significant economic losses. Although several mechanisms of coccidiosis pathogenesis are known, the effects of this infection on intestinal enzymes linked to adenosine triphosphate (ATP) metabolism, as creatine kinase (CK), adenylate kinase (AK), and pyruvate kinase (PK), remain unknown. Thus, the aim of this study was to evaluate whether coccidiosis impairs enzymes linked ATP metabolism in the intestine of chicken chicks. For this, 42 animals that were 2 days old were divided into two groups: uninfected (the negative control group) and experimentally infected on second day of life (the positive control group). On days 5, 10, and 15 post-infection (PI), fecal samples were collected for oocyst counts; intestinal tissue was collected in order to evaluate CK, AK, and PK activities, as well as parameters of the oxidative stress and histopathology. On days 10 and 15 PI, infected animals showed high counts of oocysts in fecal samples and intestinal lesions compared to the control group. Cytosolic CK activity was higher in infected animals on days 10 and 15 PI compared to the control group, while mitochondrial CK activity was lower on days 5, 10, and 15 PI. Also, AK activity was lower in infected animals on days 10 and 15 PI compared to control group, while no differences were observed between groups regarding PK activity. In relation to parameters of oxidative stress, intestinal lipid peroxidation and reactive oxygen species levels were higher in infected animals on days 10 and 15 PI compared to the control group, while non-protein thiol levels were lower on day 10 PI. On the 15th day, infected animals had lower body weight (P < 0.05). Based on this evidence, inhibition of mitochondrial CK activity causes an impairment of intestinal energetic homeostasis possibly through depletion on ATP levels, although the cytosolic CK activity acted as an attempt to restore the mitochondrial ATP levels through a feedback mechanism. Moreover, the impairment on energy metabolism appears to be mediated by excessive production of intestinal ROS, as well as oxidation of lipids and thiol groups.

Lipid peroxidation and protein oxidation in broiler breast fillets with white striping myopathy

The aim of this study was to evaluate whether broiler breast fillets with severe white striping (WS) had elevated levels of lipid peroxidation and protein oxidation, as well as antioxidant responses. A total of 45 breast muscles from broiler chickens were divided into three groups (n = 15): normal, moderate (stripes <1 mm) and severe (stripes >1 mm). Chicken breasts with severe WS showed muscular cells with small areas and diameters (p < 0.05), as well as the presence of inflammatory cells. Higher percentages of moisture content, fat, collagen, and smaller protein content than did WS breast samples compared control. Breast samples with moderate and severe degrees of WS had higher reactive oxygen species levels and advanced oxidation protein products than did the control group, and animals with severe WS had higher lipid peroxidation levels. The activities of glutathione peroxidase and glutathione S-transferase were higher (p < 0.0001) in animals with moderate WS than those in the control. PRACTICAL APPLICATIONS: White striping myopathy in broiler breast fillets is characterized by the presence of parallel white stripes in the same direction as the muscular fiber, commonly occurring in the pectoralis major muscle. The results showed that chicken breasts with WS demonstrated imbalances of antioxidant/oxidant status, characterizing increases of lipid peroxidation and protein oxidation in muscle. This situation does not prevent the consumption of the meat, but negatively affects its quality.

Hydrogen peroxide metabolism and functions in plants

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.

Detecting Intermediates and Products of Fast Heterogeneous Reactions on Liquid Surfaces via Online Mass Spectrometry

One of the research priorities in atmospheric chemistry is to advance our understanding of heterogeneous reactions and their effect on the composition of the troposphere. Chemistry on aqueous surfaces is particularly important because of their ubiquity and expanse. They range from the surfaces of oceans (360 million km2), cloud and aerosol drops (estimated at ~10 trillion km2) to the fluid lining the human lung (~150 m2). Typically, ambient air contains reactive gases that may affect human health, influence climate and participate in biogeochemical cycles. Despite their importance, atmospheric reactions between gases and solutes on aqueous surfaces are not well understood and, as a result, generally overlooked. New, surface-specific techniques are required that detect and identify the intermediates and products of such reactions as they happen on liquids. This is a tall order because genuine interfacial reactions are faster than mass diffusion into bulk liquids, and may produce novel species in low concentrations. Herein, we review evidence that validates online pneumatic ionization mass spectrometry of liquid microjets exposed to reactive gases as a technique that meets such requirements. Next, we call attention to results obtained by this approach on reactions of gas-phase ozone, nitrogen dioxide and hydroxyl radicals with various solutes on aqueous surfaces. The overarching conclusion is that the outermost layers of aqueous solutions are unique media, where most equilibria shift and reactions usually proceed along new pathways, and generally faster than in bulk water. That the rates and mechanisms of reactions at air-aqueous interfaces may be different from those in bulk water opens new conceptual frameworks and lines of research, and adds a missing dimension to atmospheric chemistry.

Isoliquiritigenin Induces Mitochondrial Dysfunction and Apoptosis by Inhibiting mitoNEET in a Reactive Oxygen Species-Dependent Manner in A375 Human Melanoma Cells

The mitochondrial protein mitoNEET is a type of iron-sulfur protein localized to the outer membrane of mitochondria and is involved in a variety of human pathologies including cystic fibrosis, diabetes, muscle atrophy, and neurodegeneration. In the current study, we found that isoliquiritigenin (ISL), one of the components of the root of Glycyrrhiza glabra L., could decrease the expression of mitoNEET in A375 melanoma cells. We also demonstrated that mitoNEET could regulate the content of reactive oxygen species (ROS), by showing that the ISL-mediated increase in the cellular ROS content could be mitigated by the mitoNEET overexpression. We also confirmed the important role of ROS in ISL-treated A375 cells. The increased apoptosis rate and the decreased mitochondrial membrane potential were mitigated by the overexpression of mitoNEET in A375 cells. These findings indicated that ISL could decrease the expression of mitoNEET, which regulated ROS content and subsequently induced mitochondrial dysfunction and apoptosis in A375 cells. Our findings also highlight mitoNEET as a promising mitochondrial target for cancer therapy.

Diagonal Electrophoresis for the Detection of Proteins Involved in Disulfide Bonds

The formation and reduction of disulfide bonds through thiol-disulfide exchange is an important cellular mechanism for the regulation of protein activity and plays a crucial role in redox signaling. Thiol-disulfide exchange on key regulatory cysteine residues offers an efficient and reversible mechanism for regulatory control in response to alterations in the intracellular redox environment. Cysteines are one of the most rarely used amino acids in proteins, but when conserved in proteins, they usually play critical roles in protein structure, function, or regulation. Diagonal electrophoresis is a relatively simple technique to analyze the formation of protein disulfides by sequential nonreducing/reducing electrophoresis. Proteins that do not form disulfides migrate identically in both dimensions and form a diagonal after the second dimension; proteins that contained intra-chain disulfides lie above the diagonal, while proteins involved in inter-disulfides fall below the diagonal. This technique allows for the detection and subsequent identification of proteins with inter-disulfides and has been applied in combination with mass spectrometry to identify proteins involved in redox signaling cascades.

Listeria monocytogenes impairs enzymes of the phosphotransfer network and alters antioxidant/oxidant status in cattle brain structures

Several evidences have suggested the involvement of enzymes belonging to the phosphotransfer network, formed by creatine kinase (CK), pyruvate kinase (PK) and adenylate kinase (AK), as well the oxidative stress on the pathogenesis of infectious diseases associated with the central nervous system (CNS). Thus, the aim of this study was to evaluate whether listeriosis alters the brain energy metabolism and/or causes oxidative stress in different brain structures of cattle experimentally infected by Listeria monocytogenes. The cytosolic CK activity was inhibited in the cerebral cortex, cerebellum, brainstem and hippocampus of infected animals compared to uninfected animals, while the mitochondrial CK activity was increased. The PK activity was inhibited in all brain structures of infected animals, while the AK activity was unchanged. Na⁺, K⁺-ATPase activity decreased in the cerebral cortex, cerebellum and hippocampus of animals infected by L. monocytogenes. Regarding the oxidative strees variables, the cerebellum and brainstem of infected animals showed increased thiobarbituric acid reactive substances, while the catalase activity was inhibited. Glutathione S-transferarase was inhibited in the cerebral cortex and brainstem of infected animals, and it was increased in the cerebellum. L. monocytogenes was quantified in the liver (n = 5/5) and cerebral cortex (n = 4/5) of the infected cattle. Based on these evidences, the nucleocytoplasmic communication between CK isoenzymes was insufficient to avoid an impairment of cerebral bioenergetics. Moreover, the inhibition on brain PK activity caused an impairment in the communication between sites of ATP generation and ATP utilization. The lipid peroxidation and alteration on antioxidant status observed in some brain structures were also involved during the disease. In summary, these alterations contribute to disease pathogenesis linked to CNS during cattle listeriosis.

How Biochemical Environments Fine-Tune a Redox Process: From Theoretical Models to Practical Applications

In this study, we give a new physical insight into how enzymatic environments influence a redox process. This is particularly important in a biochemical context, in which oxidoreductase enzymes and low-molecular-weight cofactors create a microenvironment, fine-tuning their specific redox potential. We present a new theoretical model, quantitatively backed up by quantum chemically calculated data obtained for key biological sulfur-based model reactions involved in preserving the cellular redox homeostasis during oxidative stress. We show that environmental effects can be quantitatively predicted from the thermodynamic cycle linking ΔΔ G(OX/RED)_ref-ligand values to the differential interaction energy ΔΔ G_int of the reduced and oxidized species with the environment. Our obtained data can be linked to hydrogen-bond patterns found in protein active sites. The thermodynamic model is further understood in the framework of molecular orbital theory. The key insight of this work is that the intrinsic properties of neither a redox couple nor the interacting environment (e.g., ligand) are enough by themselves to uniquely predict reduction potentials. Instead, system-environment interactions need to be considered. This study is of general interest as redox processes are pivotal to empower, protect, or damage organisms. Our presented thermodynamic model allows a pragmatically evaluation on the expected influence of a particular environment on a redox process, necessary to fully understand how redox processes take place in living organisms.

Preliminary evidence of reductive stress in human cytotoxic T cells following exercise

This study investigated immunophenotypic differences in intracellular thiol redox state of peripheral blood mononuclear cells (PBMCs) isolated from trained [ n = 9, means ± SD: age 28 ± 5 yr; (body mass index) BMI 23.2 ± 2.6 kg/m2; V̇o2max (maximal oxygen intake)56.9 ± 6.1 ml·kg−1·min−1] and recreationally active (RA, n = 11, means ± SD: age 27 ± 6 yr; BMI 24.2 ± 3.7 kg/m2; V̇o2max 45.1 ± 6.4 ml·kg−1·min−1) participants before and after a maximal aerobic exercise tolerance test. Blood samples were taken before (Pre), during (sample acquired at 70% maximum heart rate), immediately after (Post + 0), and 15 min postexercise (Post + 15). PBMCs were isolated, and reduced thiol analysis [fluorescein-5 maleimide (F5M)] by immunophenotype [cluster of differentiation (CD)3+, CD4+, and CD8+] was performed using flow cytometry. A significant increase in cellular F5M fluorescence was observed in CD3+ T cells at Post + 0, with changes driven to a greater extent by CD8+ T cells (fold change in both groups CD4: +2.3, CD8: +2.8; P < 0.05). Further analysis revealed a population of highly reduced CD8+ T cells (CD8+T-reduced+) that significantly increased from Pre to Post + 0 in RA participants only (RA: +272 cell/µl, P < 0.05). To understand these results further, CD8+T-reduced+ and CD8+T-reduced− cells were analyzed for immunophenotype in response to the same exercise protocol ( n = 6, means ± SD: age 24 ± 5 yr; BMI 25.7 ± 4.1 kg·m−2; V̇o2max 41.33 ± 7.63 ml·kg−1·min−1). CD8+T-reduced+ had significantly less lymphoid homing potential (chemokine receptor type 7) Post + 0 compared with Pre. This study is the first, to our knowledge, to demonstrate that lymphocyte populations become more reductive in response to acute exercise.

NEW & NOTEWORTHY The study presented provides the first evidence to suggest that cytotoxic T cells become transiently reductive in healthy individuals following a single bout of cycling. Detection of these cells was enabled via the use of a flow cytometric assay that incorporates the thiol reactive probe fluorescein-5 maleimide. Using this method, transient reductive stress in viable T cells is permissible and provides the basis for further research in the area of exercise immunology.

Persulfide Dioxygenase From Acidithiobacillus caldus: Variable Roles of Cysteine Residues and Hydrogen Bond Networks of the Active Site

Persulfide dioxygenases (PDOs) are abundant in Bacteria and also crucial for H2S detoxification in mitochondria. One of the two pdo-genes of the acidophilic bacterium Acidithiobacillus caldus was expressed in Escherichia coli. The protein (AcPDO) had 0.77 ± 0.1 Fe/subunit and an average specific sulfite formation activity of 111.5 U/mg protein (Vmax) at 40°C and pH 7.5 with sulfur and GSH following Michaelis-Menten kinetics. KM for GSH and Kcat were 0.5 mM and 181 s-1, respectively. Glutathione persulfide (GSSH) as substrate gave a sigmoidal curve with a Vmax of 122.3 U/mg protein, a Kcat of 198 s-1 and a Hill coefficient of 2.3 ± 0.22 suggesting positive cooperativity. Gel permeation chromatography and non-denaturing gels showed mostly tetramers. The temperature optimum was 40-45°C, the melting point 63 ± 1.3°C in thermal unfolding experiments, whereas low activity was measurable up to 95°C. Site-directed mutagenesis showed that residues located in the predicted GSH/GSSH binding site and in the central hydrogen bond networks including the iron ligands are essential for activity. Among these, the R139A, D141A, and H171A variants were inactive concomitant to a decrease of their melting points by 3-8 K. Other variants were inactivated without significant melting point change. Two out of five cysteines are likewise essential, both of which lie presumably in close proximity at the surface of the protein (C87 and C224). MalPEG labeling experiments suggests that they form a disulfide bridge. The reducing agent Tris(2-carboxyethyl)phosphine was inhibitory besides N-ethylmaleimide and iodoacetamide suggesting an involvement of cysteines and the disulfide in catalysis and/or protein stabilization. Mass spectrometry revealed modification of C87, C137, and C224 by 305 mass units equivalent to GSH after incubation with GSSH and with GSH in case of the C87A and C224A variants. The results of this study suggest that disulfide formation between the two essential surface-exposed cysteines and Cys-S-glutathionylation serve as a protective mechanism against uncontrolled thiol oxidation and the associated loss of enzyme activity.

Spectral Characterization of Three-Electron Two-Center (3e-2c) Bonds of Gaseous CH3S∴S(H)CH3 and (CH3SH)2+ and Enhancement of the 3e-2c Bond upon Protonation

The three-electron two-center (3e-2c) bond plays an important role in structures and electron communication in biological systems involving cationic sulfur compounds. Although the nature of 3e-2c bonds and their theoretical formalism have attracted great interest, direct spectral identifications of 3e-2c-bound molecules are scarce. We observed the infrared spectra of the weakly 3e-2c-bound CH₃S∴S(H)CH₃ and the strongly 3e-2c-bound (CH₃SH)₂⁺ in a supersonic jet using infrared (IR) dissociation with vacuum-ultraviolet photoionization and time-of-flight detection. Protonation of CH₃S∴S(H)CH₃ to form [CH₃(H)S∴S(H)CH₃]⁺ significantly enhances the 3e-2c bond, characterized by a large red shift of the SH-stretching band with enhanced IR intensity, shortening of the calculated S-S distance from 3.00 to 2.86 Å, and a dissociation energy increased from ∼23 to 162 kJ mol^-1.

Biological hydropersulfides and related polysulfides - a new concept and perspective in redox biology

The chemical biology of thiols (RSH, e.g., cysteine and cysteine-containing proteins/peptides) has been a topic of extreme interest for many decades due to their reported roles in protein structure/folding, redox signaling, metal ligation, cellular protection, and enzymology. While many of the studies on thiol/sulfur biochemistry have focused on thiols, relatively ignored have been hydropersulfides (RSSH) and higher order polysulfur species (RSS_n H, RSS_n R, n > 1). Recent and provocative work has alluded to the prevalence and likely physiological importance of RSSH and related RSS_n H. RSSH of cysteine (Cys-SSH) has been found to be prevalent in mammalian systems along with Cys-SSH-containing proteins. The RSSH functionality has not been examined to the extent of other biologically relevant sulfur derivatives (e.g., sulfenic acids, disulfides, etc.), whose roles in cell signaling are strongly indicated. The recent finding of Cys-SSH biosynthesis and translational incorporation into proteins is an unequivocal indication of its fundamental importance and necessitates a more profound look into the physiology of RSSH. In this Review, we discuss the currently reported chemical biology of RSSH (and related species) as a prelude to discussing their possible physiological roles.

Oxidant-specific biomarkers of oxidative stress. Association with atherosclerosis and implication for antioxidant effects

The unregulated oxidative modification of lipids, proteins, and nucleic acids induced by multiple oxidants has been implicated in the pathogenesis of many diseases. Antioxidants with diverse functions exert their roles either directly or indirectly in the physiological defense network to inhibit such deleterious oxidative modification of biological molecules and resulting damage. The efficacy of antioxidants depends on the nature of oxidants. Therefore, it is important to identify the oxidants which are responsible for modification of biological molecules. Some oxidation products produced selectively by specific oxidant enable to identify the responsible oxidants, while other products are produced by several oxidants similarly. In this review article, several oxidant-specific products produced selectively by peroxyl radicals, peroxynitrite, hypochlorous acid, lipoxygenase, and singlet oxygen were summarized and their potential role as biomarker is discussed. It is shown that the levels of specific oxidation products including hydroxylinoleate isomers, nitrated and chlorinated products, and oxysterols produced by the above-mentioned oxidants are elevated in the human atherosclerotic lesions, suggesting that all these oxidants may contribute to the development of atherosclerosis. Further, it was shown that the reactivities of physiological antioxidants toward the above-mentioned oxidants vary extensively, suggesting that multiple antioxidants effective against these different oxidants are required, since no single antioxidant alone can cope with these multiple oxidants.

Redox responses are preserved across muscle fibres with differential susceptibility to aging

Age-related loss of muscle mass and function is associated with increased frailty and loss of independence. The mechanisms underlying the susceptibility of different muscle types to age-related atrophy are not fully understood. Reactive oxygen species (ROS) are recognised as important signalling molecules in healthy muscle and redox sensitive proteins can respond to intracellular changes in ROS concentrations modifying reactive thiol groups on Cysteine (Cys) residues. Conserved Cys residues tend to occur in functionally important locations and can have a direct impact on protein function through modifications at the active site or determining protein conformation. The aim of this work was to determine age-related changes in the redox proteome of two metabolically distinct murine skeletal muscles, the quadriceps a predominantly glycolytic muscle and the soleus which contains a higher proportion of mitochondria. To examine the effects of aging on the global proteome and the oxidation state of individual redox sensitive Cys residues, we employed a label free proteomics approach including a differential labelling of reduced and reversibly oxidised Cys residues. Our results indicate the proteomic response to aging is dependent on muscle type but redox changes that occur primarily in metabolic and cytoskeletal proteins are generally preserved between metabolically distinct tissues.

BIOLOGICAL SIGNIFICANCE

Skeletal muscle containing fast twitch glycolytic fibres are more susceptible to age related atrophy compared to muscles with higher proportions of oxidative slow twitch fibres. Contracting skeletal muscle generates reactive oxygen species that are required for correct signalling and adaptation to exercise and it is also known that the intracellular redox environment changes with age. To identify potential mechanisms for the distinct response to age, this article combines a global proteomic approach and a differential labelling of reduced and reversibly oxidised Cysteine residues in two metabolically distinct skeletal muscles, quadriceps and soleus, from adult and old mice. Our results indicate that the global proteomic changes with age in skeletal muscles are dependent on fibre type. However, redox specific changes are preserved across muscle types and accompanied with a reduction in the number of redox sensitive Cysteine residues.

Comparative toxicity and bioaccumulation of two dinotefuran metabolites, UF and DN, in earthworms (Eisenia fetida)

Dinotefuran, as the latest generation of neonicotinoid insecticide, has broad application prospects around the world. However, dinotefuran is easily metabolized and the two main metabolites are 1-methyl-3-(tetrahydro-3-furylmethyl) urea (UF) and 1-methyl-3-(tetrahydro-3-furylmethyl) guanidium dihydrogen (DN). In the present study, the risks of UF and DN in soil on typical non-target species earthworm were investigated. In the same time, the degradation in soil and accumulation in earthworms of UF and DN were monitored. The present results showed that the toxicities of UF and DN were similar in their effect on earthworms and they were supertoxic pollutants to earthworms. The degradation trend in soil and accumulation trend in earthworms of UF and DN were consistent throughout the whole exposure period. At 1.0 mg/kg and 2.0 mg/kg, UF and DN could induce the excess production of ROS, resulting in oxidative stress effects in earthworm cells. The excess ROS induce changes in antioxidant enzyme activities, damage in biomacromolecules, and abnormal expression of function genes. The present results showed that UF and DN may have high risks for earthworms.

Plant bioactives and redox signaling: (-)-Epicatechin as a paradigm

Polyphenols are bioactives claimed to be responsible for some of the health benefits provided by fruit and vegetables. It is currently accepted that the bioactivities of polyphenols can be mostly ascribed to their interactions with proteins and lipids. Such interactions can affect cell oxidant production and cell signaling, and explain in part the ability of polyphenols to promote health. EC can modulate redox sensitive signaling by: i) defining the extent of oxidant levels that can modify cell signaling, function, and fate, e.g. regulating enzymes that generate superoxide, hydrogen peroxide and nitric oxide; or ii) regulating the activation of transcription factors sensible to oxidants. The latter includes the regulation of the nuclear factor E2-related factor 2 (Nfr2) pathway, which in turn can promote the synthesis of antioxidant defenses, and of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) pathway, which mediates the expression of oxidants generating enzymes, as well as proteins not involved in redox reactions. In summary, a significant amount of data vindicates the participation of EC in redox regulated signaling pathways. Progress in the understanding of the molecular mechanisms involved in EC biological actions will help to define recommendations in terms of which fruit and vegetables are healthier and the amounts necessary to provide health effects.

Redox homeostasis and age-related deficits in neuromuscular integrity and function

Skeletal muscle is a major site of metabolic activity and is the most abundant tissue in the human body. Age-related muscle atrophy (sarcopenia) and weakness, characterized by progressive loss of lean muscle mass and function, is a major contributor to morbidity and has a profound effect on the quality of life of older people. With a continuously growing older population (estimated 2 billion of people aged >60 by 2050), demand for medical and social care due to functional deficits, associated with neuromuscular ageing, will inevitably increase. Despite the importance of this 'epidemic' problem, the primary biochemical and molecular mechanisms underlying age-related deficits in neuromuscular integrity and function have not been fully determined. Skeletal muscle generates reactive oxygen and nitrogen species (RONS) from a variety of subcellular sources, and age-associated oxidative damage has been suggested to be a major factor contributing to the initiation and progression of muscle atrophy inherent with ageing. RONS can modulate a variety of intracellular signal transduction processes, and disruption of these events over time due to altered redox control has been proposed as an underlying mechanism of ageing. The role of oxidants in ageing has been extensively examined in different model organisms that have undergone genetic manipulations with inconsistent findings. Transgenic and knockout rodent studies have provided insight into the function of RONS regulatory systems in neuromuscular ageing. This review summarizes almost 30 years of research in the field of redox homeostasis and muscle ageing, providing a detailed discussion of the experimental approaches that have been undertaken in murine models to examine the role of redox regulation in age-related muscle atrophy and weakness.

Metabolism of hydrogen sulfide (H2S) and Production of Reactive Sulfur Species (RSS) by superoxide dismutase

Reactive sulfur species (RSS) such as H₂S, HS^•, H₂S_n, (n = 2–7) and HS₂^•- are chemically similar to H₂O and the reactive oxygen species (ROS) HO^•, H₂O₂, O₂^•- and act on common biological effectors. RSS were present in evolution long before ROS, and because both are metabolized by catalase it has been suggested that “antioxidant” enzymes originally evolved to regulate RSS and may continue to do so today. Here we examined RSS metabolism by Cu/Zn superoxide dismutase (SOD) using amperometric electrodes for dissolved H₂S, a polysulfide-specific fluorescent probe (SSP4), and mass spectrometry to identify specific polysulfides (H₂S₂-H₂S₅). H₂S was concentration- and oxygen-dependently oxidized by 1 μM SOD to polysulfides (mainly H₂S₂, and to a lesser extent H₂S₃ and H₂S₅) with an EC₅₀ of approximately 380 μM H₂S. H₂S concentrations > 750 μM inhibited SOD oxidation (IC₅₀ = 1.25 mM) with complete inhibition when H₂S > 1.75 mM. Polysulfides were not metabolized by SOD. SOD oxidation preferred dissolved H₂S over hydrosulfide anion (HS^-), whereas HS^- inhibited polysulfide production. In hypoxia, other possible electron donors such as nitrate, nitrite, sulfite, sulfate, thiosulfate and metabisulfite were ineffective. Manganese SOD also catalyzed H₂S oxidation to form polysulfides, but did not metabolize polysulfides indicating common attributes of these SODs. These experiments suggest that, unlike the well-known SOD-mediated dismutation of two O₂^•- to form H₂O₂ and O_2^, SOD catalyzes a reaction using H₂S and O₂ to form persulfide. These can then combine in various ways to form polysulfides and sulfur oxides. It is also possible that H₂S (or polysulfides) interact/react with SOD cysteines to affect catalytic activity or to directly contribute to sulfide metabolism. Our studies suggest that H₂S metabolism by SOD may have been an ancient mechanism to detoxify sulfide or to regulate RSS and along with catalase may continue to do so in contemporary organisms.

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Polysulfides are reactive sulfide species (RSS) and are similar to reactive oxygen species (ROS).

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RSS may be the antecedent of redox regulatory and stress-related modalities.

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RSS likely persist in modern-day organisms and are regulated by SOD.

'Molecular habituation' as a potential mechanism of gradual homeostatic loss with age

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Constitutive signals indicate homeostatic dysregulation but their effect on signal transduction remains largely unexplored.

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A theoretical approach is undertaken to examine how oxidative stress may affect redox signal transduction.

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Constitutive signals can result in a ‘molecular habituation’ effect that interferes with information transmission.

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The robustness of such a theoretical observation to the underlying methodology hints at the generality of this principle.

The ability of reactive oxygen species (ROS) to cause molecular damage has meant that chronic oxidative stress has been mostly studied from the point of view of being a source of toxicity to the cell. However, the known duality of ROS molecules as both damaging agents and cellular redox signals implies another perspective in the study of sustained oxidative stress. This is a perspective of studying oxidative stress as a constitutive signal within the cell. In this work, we adopt a theoretical perspective as an exploratory and explanatory approach to examine how chronic oxidative stress can interfere with signal processing by redox signalling pathways in the cell. We report that constitutive signals can give rise to a ‘molecular habituation’ effect that can prime for a gradual loss of biological function. This is because a constitutive signal in the environment has the potential to reduce the responsiveness of a signalling pathway through the prolonged activation of negative regulators. Additionally, we demonstrate how this phenomenon is likely to occur in different signalling pathways exposed to persistent signals and furthermore at different levels of biological organisation.

Fluoride-induced oxidative stress and apoptosis are involved in the reducing of oocytes development potential in mice

The present study was conducted to investigate the mechanisms of excessive-fluoride-induced reduction of oocyte development potential in mice. The development morphology of oocyte and the changes of pathomorphology in ovary were observed. The protein expression levels of apoptosis factors, including Bax, Bcl-2, casepase-3, casepase-9 and cytochrome c, and the mRNA expression levels of antioxidant enzymes, including SOD1, GSH-Px1, CAT and inducible nitric oxide synthase were measured by Western blot and real-time PCR, respectively. DNA damage in the ovary was analysed by single cell gel electrophoresis and TUNEL staining. Results indicated that the structure and function of ovarian cells were seriously damaged, followed, the development potential of oocyte was reduced by excessive fluoride. The expression levels of apoptosis factors were up-regulated and antioxidant enzymes were significantly down-regulated. Meanwhile, the contents of ROS, MDA, NO and iNOS were significantly increased. Whereas, the activities of SOD1, GSH-Px1 and CAT was significantly decreased compared with the control group. Simultaneously, the results of DNA analysis indicated that the tail length and tailing ratio of ovarian cells were significantly increased in the fluoride group. In summary, the results provided compelling evidence that excessive fluoride intake can reduce the development potential of oocyte by inducing oxidative stress and apoptosis in the ovary of female mice.

Redox-active nanomaterials for nanomedicine applications

Nanomedicine utilizes the remarkable properties of nanomaterials for the diagnosis, treatment, and prevention of disease. Many of these nanomaterials have been shown to have robust antioxidative properties, potentially functioning as strong scavengers of reactive oxygen species. Conversely, several nanomaterials have also been shown to promote the generation of reactive oxygen species, which may precipitate the onset of oxidative stress, a state that is thought to contribute to the development of a variety of adverse conditions. As such, the impacts of nanomaterials on biological entities are often associated with and influenced by their specific redox properties. In this review, we overview several classes of nanomaterials that have been or projected to be used across a wide range of biomedical applications, with discussion focusing on their unique redox properties. Nanomaterials examined include iron, cerium, and titanium metal oxide nanoparticles, gold, silver, and selenium nanoparticles, and various nanoscale carbon allotropes such as graphene, carbon nanotubes, fullerenes, and their derivatives/variations. Principal topics of discussion include the chemical mechanisms by which the nanomaterials directly interact with biological entities and the biological cascades that are thus indirectly impacted. Selected case studies highlighting the redox properties of nanomaterials and how they affect biological responses are used to exemplify the biologically-relevant redox mechanisms for each of the described nanomaterials.

Chemical Biology of Hydropersulfides and Related Species: Possible Roles in Cellular Protection and Redox Signaling

SIGNIFICANCE

For >20 years, physiological signaling associated with the endogenous generation of hydrogen sulfide (H₂S) has been of significant interest. Despite its presumed importance, the biochemical mechanisms associated with its actions have not been elucidated. Recent Advances: Recently it has been found that H₂S-related or derived species are highly prevalent in mammalian systems and that these species may be responsible for some, if not the majority, of the biological actions attributed to H₂S. One of the most prevalent and intriguing species are hydropersulfides (RSSH), which can be present at significant levels. Indeed, it appears that H₂S and RSSH are intimately linked in biological systems and likely to be mutually inclusive.

CRITICAL ISSUES

The fact that H₂S and polysulfides such as RSSH are present simultaneously means that the biological actions previously assigned to H₂S can be instead because of the presence of RSSH (or other polysulfides). Thus, it remains possible that hydropersulfides are the biological effectors, and H₂S serves, to a certain extent, as a marker for persulfides and polysulfides. Addressing this possibility will to a large extent be based on the chemistry of these species.

FUTURE DIRECTIONS

Currently, it is known that persulfides possess unique and novel chemical properties that may explain their biological prevalence. However, significantly more work will be required to establish the possible physiological roles of these species. Moreover, an understanding of the regulation of their biosynthesis and degradation will become important topics in piecing together their biology. Antioxid. Redox Signal. 00, 000-000.

Involvement of xanthine oxidase activity with oxidative and inflammatory renal damage in silver catfish experimentally infected with Streptococcus agalactiae: Interplay with reactive oxygen species and nitric oxide

Xanthine oxidase (XO) is a final enzyme of purine metabolism linked with initiation and progression of infectious diseases, since is considered an important source of reactive oxygen species (ROS) and nitric oxide (NO), developing a pro-oxidant and pro-inflammatory profile in some infectious diseases. Thus, the aim of this study was to evaluate the involvement of XO activity in the renal oxidative and inflammatory damage, as well as the interplay with ROS and metabolites of nitric oxide (NOx) levels in silver catfish experimentally infected with Streptococcus agalactiae. Xanthine oxidase activity, and uric acid, ROS and NOx levels increased in renal tissue of infected animals compared to uninfected animals. Moreover, the histopathological analyses revealed the presence of necrosis, generalized edema and nuclear degeneration of renal tubules. Based on these evidences, the upregulation on renal XO activity exerts a pro-oxidant and pro-inflammatory profile in kidney of fish infected with S. agalactiae. The excessive uric acid levels induced the release of oxidative and inflammatory mediators, such as ROS and NOx, that directly contribute to renal oxidative and inflammatory damage. In summary, the upregulation on XO activity may be considered a pathway involved in the renal injury during S. agalactiae infection.

Lipids on the Second Day in Ischemic and Normoxemic Term Neonates

INTRODUCTION

In hypoxic newborns requiring oxygen, lipid peroxidation affects the peripheral blood lipids.

OBJECTIVES

Determine the influence of perinatal oxygen therapy for hypoxia on serum lipid concentrations on the second day of life.

MATERIALS AND METHODS

Our study included 50 newborns with perinatal hypoxia requiring oxygen and 50 healthy newborns without oxygen therapy. Arterialized capillary blood was taken for categorization of hypoxia (pO2) after birth in both groups. Lipid concentrations: total cholesterol (TC), high density lipoproteins (HDL), low density lipoproteins (LDL), and triglycerides (TG) were measured on day 2 in both groups.

RESULTS

TC, LDL, HDL, TG, HC03 levels were statistically lower in the study group compared to the control one, while pCO2 and BE levels were statistically higher in newborns with perinatal hypoxia.

CONCLUSION

Lower lipid levels in hypoxic newborns may suggest that circulating lipids are oxidized, peroxidized, and removed from the peripheral circulation.

Exercise redox biochemistry: Conceptual, methodological and technical recommendations

Exercise redox biochemistry is of considerable interest owing to its translational value in health and disease. However, unaddressed conceptual, methodological and technical issues complicate attempts to unravel how exercise alters redox homeostasis in health and disease. Conceptual issues relate to misunderstandings that arise when the chemical heterogeneity of redox biology is disregarded: which often complicates attempts to use redox-active compounds and assess redox signalling. Further, that oxidised macromolecule adduct levels reflect formation and repair is seldom considered. Methodological and technical issues relate to the use of out-dated assays and/or inappropriate sample preparation techniques that confound biochemical redox analysis. After considering each of the aforementioned issues, we outline how each issue can be resolved and provide a unifying set of recommendations. We specifically recommend that investigators: consider chemical heterogeneity, use redox-active compounds judiciously, abandon flawed assays, carefully prepare samples and assay buffers, consider repair/metabolism, use multiple biomarkers to assess oxidative damage and redox signalling.

Real-time quantification of subcellular H2O2 and glutathione redox potential in living cardiovascular tissues

Detecting and measuring the dynamic redox events that occur in vivo is a prerequisite for understanding the impact of oxidants and redox events in normal and pathological conditions. These aspects are particularly relevant in cardiovascular tissues wherein alterations of the redox balance are associated with stroke, aging, and pharmacological intervention. An ambiguous aspect of redox biology is how redox events occur in subcellular organelles including mitochondria, and nuclei. Genetically-encoded Rogfp2 fluorescent probes have become powerful tools for real-time detection of redox events. These probes detect hydrogen peroxide (H₂O₂) levels and glutathione redox potential (E_GSH), both with high spatiotemporal resolution. By generating novel transgenic (Tg) zebrafish lines that express compartment-specific Rogfp2-Orp1 and Grx1-Rogfp2 sensors we analyzed cytosolic, mitochondrial, and the nuclear redox state of endothelial cells and cardiomyocytes of living zebrafish embryos. We provide evidence for the usefulness of these Tg lines for pharmacological compounds screening by addressing the blocking of pentose phosphate pathways (PPP) and glutathione synthesis, thus altering subcellular redox state in vivo. Rogfp2-based transgenic zebrafish lines represent valuable tools to characterize the impact of redox changes in living tissues and offer new opportunities for studying metabolic driven antioxidant response in biomedical research.

Detection of ROS Induced Proteomic Signatures by Mass Spectrometry

Reversible and irreversible post-translational modifications (PTMs) induced by endogenously generated reactive oxygen species (ROS) in regulatory enzymes and proteins plays an essential role in cellular signaling. Almost all cellular processes including metabolism, transcription, translation and degradation have been identified as containing redox regulated proteins. Specific redox modifications of key amino acids generated by ROS offers a dynamic and versatile means to rapidly alter the activity or functional structure of proteins in response to biochemical, environmental, genetic and pathological perturbations. How the proteome responds to these stimuli is of critical importance in oxidant physiology, as it can regulate the cell stress response by reversible and irreversible PTMs, affecting protein activity and protein-protein interactions. Due to the highly labile nature of many ROS species, applying redox proteomics can provide a signature footprint of the ROS species generated. Ideally redox proteomic approaches would allow; (1) the identification of the specific PTM, (2) identification of the amino acid residue that is modified and (3) the percentage of the protein containing the PTM. New developments in MS offer the opportunity of a more sensitive targeted proteomic approach and retrospective data analysis. Subsequent bioinformatics analysis can provide an insight into the biochemical and physiological pathways or cell signaling cascades that are affected by ROS generation. This mini-review will detail current redox proteomic approaches to identify and quantify ROS induced PTMs and the subsequent effects on cellular signaling.