Catalase catalyzes nitrotyrosine formation from sodium azide and hydrogen peroxide

Sirtuins and redox signaling interplay in neurogenesis, neurodegenerative diseases, and neural cell reprogramming

Since the discovery of Neural Stem Cells (NSCs) there are still mechanism to be clarified, such as the role of mitochondrial metabolism in the regulation of endogenous adult neurogenesis and its implication in neurodegeneration. Although stem cells require glycolysis to maintain their stemness, they can perform oxidative phosphorylation and it is becoming more and more evident that mitochondria are central players, not only for ATP production but also for neuronal differentiation's steps regulation, through their ability to handle cellular redox state, intracellular signaling, epigenetic state of the cell, as well as the gut microbiota-brain axis, upon dietary influences. In this scenario, the 8-oxoguanine DNA glycosylase (OGG1) repair system would link mitochondrial DNA integrity to the modulation of neural differentiation. On the other side, there is an increasing interest in NSCs generation, from induced pluripotent stem cells, as a clinical model for neurodegenerative diseases (NDs), although this methodology still presents several drawbacks, mainly related to the reprogramming process. Indeed, high levels of reactive oxygen species (ROS), associated with telomere shortening, genomic instability, and defective mitochondrial dynamics, lead to pluripotency limitation and reprogramming efficiency's reduction. Moreover, while a physiological or moderate ROS increase serves as a signaling mechanism, to activate differentiation and suppress self-renewal, excessive oxidative stress is a common feature of NDs and aging. This ROS-dependent regulatory effect might be modulated by newly identified ROS suppressors, including the NAD⁺-dependent deacetylase enzymes family called Sirtuins (SIRTs). Recently, the importance of subcellular localization of NAD synthesis has been coupled to different roles for NAD in chromatin stability, DNA repair, circadian rhythms, and longevity. SIRTs have been described as involved in the control of both telomere's chromatin state and expression of nuclear gene involved in the regulation of mitochondrial gene expression, as well as in several NDs and aging. SIRTs are ubiquitously expressed in the mammalian brain, where they play important roles. In this review we summarize the current knowledge on how SIRTs-dependent modulation of mitochondrial metabolism could impact on neurogenesis and neurodegeneration, focusing mainly on ROS function and their role in SIRTs-mediated cell reprogramming and telomere protection.

The Reactive Species Interactome in the Brain

Significance: Redox pioneer Helmut Sies attempted to explain reactive species' challenges faced by organelles, cells, tissues, and organs via three complementary definitions: (i) oxidative stress, that is, the disturbance in the prooxidant-antioxidant defense balance in favor of the prooxidants; (ii) oxidative eustress, the low physiological exposure to prooxidants; and (iii) oxidative distress, the supraphysiological exposure to prooxidants. Recent Advances: Identification, concentration, and interactions are the most important elements to improve our understanding of reactive species in physiology and pathology. In this context, the reactive species interactome (RSI) is a new multilevel redox regulatory system that identifies reactive species families, reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species, and it integrates their interactions with their downstream biological targets. Critical Issues: We propose a united view to fully combine reactive species identification, oxidative eustress and distress, and the RSI system. In this view, we also propose including the forgotten reactive carbonyl species, an increasingly rediscovered reactive species family related to the other reactive families, and key enzymes within the RSI. We focus on brain physiology and pathology to demonstrate why this united view should be considered. Future Directions: More studies are needed for an improved understanding of the contributions of reactive species through their identification, concentration, and interactions, including in the brain. Appreciating the RSI in its entirety should unveil new molecular players and mechanisms in physiology and pathology in the brain and elsewhere.

The duet of surface and radical-based carbocatalysis for oxidative destructions of aqueous contaminants over built-in nanotubes of graphite

Metal-free mesoporous graphitic frameworks with built-in nanotubes (CPGs) were synthesized via facile co-pyrolysis of cyclodextrin and a cobalt salt with subsequent acid pickling to remove the embedded metal species. Due to the high graphitic degree and built-in few-layer nanotubes, the as-synthesized carbonaceous materials possess a higher catalytic ozonation activity than that of the state-of-the-art carbon nanotubes (CNTs) and LaMnO₃ perovskite catalysts for the destruction of different aqueous contaminants. For recalcitrant oxalic acid removal, 50 mg L^-1 oxalic acid was completely degraded in 20 min. Compared with other nanocarbons, the as-synthesized materials also demonstrated robust structural stability and reusability. The electron paramagnetic resonance (EPR) and selective radical quenching tests revealed that the destruction of the aqueous organics predominantly relied on surface-adsorbed complexes (O*_ad and O₂*) from activated ozone molecules. Owing to the occurrence of this surface oxidation pathway, the compatibility of the CPGs/O₃ system was significantly enhanced for treatment of real wastewater, where the inorganic anions and organic natural organic matter would inhibit radical oxidation as radical scavengers. Furthermore, by employing organics with different ionization potentials (IPs) as the target pollutants, the CPGs/O₃ system was discovered to obtain a high oxidation potential.

Hypertonic HBOC-201 decreases neutrophil activation after hemorrhagic shock

OBJECTIVE

To evaluate neutrophil activation after exposure to standard HBC-201 (suspended in lactate Ringer's solution) versus HBOC-201 suspended in hypertonic 7.5% saline solution.

METHODS

We use plasma and tissue obtained from pigs subjected to controlled hemorrhagic shock and an ex vivo model of stimulated human whole blood. The pigs were resuscitated with the following (n = 8 per group) standard HBOC-201, or hypertonic HBOC-201. We used HTS 7.5%, Ringer's lactate as control resuscitation. Human blood was stimulated with same fluids. We measured the following neutrophil markers; IL-8, H2O2 in pig plasma, MPO in pig tissue, and H2O2, IL-8, and CD11b/CD18 in human whole blood.

RESULTS

H2O2 and IL-8 as well as tissue MPO were significantly decreased in pigs resuscitated with HT-HBOC-201 and HT 7.5%. Ex vivo experiments blood diluted with HTS and HT-HBOC-201 revealed lower expression of CD11b/CD18, H2O2, and IL-8. Blood diluted with HBOC-201 had a higher CD11b/CD18 expression than blood diluted with LR solution.

CONCLUSION

Our in vivo and ex vivo experiments indicate that HBOC-201 suspended in hypertonic 7.5% saline solution is associated with significantly less neutrophil activation when compared to standard HBOC-201 suspended in lactate Ringer's solution.

Controlled free radical attack in the apoplast: a hypothesis for roles of O, N and S species in regulatory and polysaccharide cleavage events during rapid abscission by Azolla

Shedding of organs by abscission is a key terminal step in plant development and stress responses. Cell wall (CW) loosening at the abscission zone can occur through a combination chain breakage of apoplastic polysaccharides and tension release of cellulose microfibrils. Two distinctly regulated abscission cleavage events are amenable to study in small water ferns of the genus Azolla; one is a rapid abscission induced by environmental stimuli such as heat or chemicals, and the other is an ethylene-induced process occurring more slowly through the action of hydrolytic enzymes. Although free radicals are suggested to be involved in the induction of rapid root abscission, its mechanism is not fully understood. The apoplast contains peroxidases, metal-binding proteins and phenolic compounds that potentially generate free radicals from H2O2 to cleave polysaccharides in the CW and middle lamella. Effects of various thiol-reactive agents implicate the action of apoplastic peroxidases having accessible cysteine thiols in rapid abscission. The Ca(2+) dependency of rapid abscission may reflect the stabilization Ca(2+) confers to peroxidase structure and binding to pectin. To spur further investigation, we present a hypothetical model for small signaling molecules H2O2 and NO and their derivatives in regulating, via modification of putative protein thiols, free radical attack of apoplastic polysaccharides.

Resveratrol sensitizes acute myelogenous leukemia cells to histone deacetylase inhibitors through reactive oxygen species-mediated activation of the extrinsic apoptotic pathway

Histone deacetylase inhibitors (HDACIs) activate the prosurvival nuclear factor-κB (NF-κB) pathway by hyperacetylating RelA/p65, whereas the chemopreventive agent resveratrol inhibits NF-κB by activating the class III histone deacetylase Sirt1. Interactions between resveratrol and pan-HDACIs (vorinostat and panobinostat) were examined in human acute myelogenous leukemia (AML) cells. Pharmacologically achievable resveratrol concentrations (25-50 μM) synergistically potentiated HDACI lethality in AML cell lines and primary AML blasts. Resveratrol antagonized RelA acetylation and NF-κB activation in HDACI-treated cells. However, short hairpin RNA Sirt1 knockdown failed to modify HDACI sensitivity, which suggests that factors other than or in addition to Sirt1 activation contribute to resveratrol/HDACI interactions. These interactions were associated with death receptor 5 (DR5) up-regulation and caspase-8 activation, whereas cells expressing dominant-negative caspase-8 were substantially protected from resveratrol/HDACI treatment, which suggests a significant functional role for the extrinsic apoptotic pathway in lethality. Exposure to resveratrol with HDACI induced sustained reactive oxygen species (ROS) generation, which was accompanied by increased levels of DNA double-strand breaks, as reflected in γH2A.X and comet assays. The free radical scavenger Mn(III)tetrakis(4-benzoic acid)porphyrin chloride blocked ROS generation, DR5 up-regulation, caspase-8 activation, DNA damage, and apoptosis, which indicates a primary role for oxidative injury in lethality. Analyses of cell-cycle progression and 5-ethynyl-2'-deoxyuridine incorporation through flow cytometry revealed that resveratrol induced S-phase accumulation; this effect was abrogated by HDACI coadministration, which suggests that cells undergoing DNA synthesis may be particularly vulnerable to HDACI lethality. Collectively, these findings indicate that resveratrol interacts synergistically with HDACIs in AML cells through multiple ROS-dependent actions, including death receptor up-regulation, extrinsic apoptotic pathway activation, and DNA damage induction. They also raise the possibility that S-phase cells may be particularly susceptible to these actions.

Mitochondrial protein tyrosine nitration

Mitochondria are primary loci for the intracellular formation and reactions of reactive oxygen and nitrogen species including superoxide (O₂•⁻), hydrogen peroxide (H₂O₂) and peroxynitrite (ONOO⁻). Depending on formation rates and steady-state levels, the mitochondrial-derived short-lived reactive species contribute to signalling events and/or mitochondrial dysfunction through oxidation reactions. Among relevant oxidative modifications in mitochondria, the nitration of the amino acid tyrosine to 3-nitrotyrosine has been recognized in vitro and in vivo. This post-translational modification in mitochondria is promoted by peroxynitrite and other nitrating species and can disturb organelle homeostasis. This study assesses the biochemical mechanisms of protein tyrosine nitration within mitochondria, the main nitration protein targets and the impact of 3-nitrotyrosine formation in the structure, function and fate of modified mitochondrial proteins. Finally, the inhibition of mitochondrial protein tyrosine nitration by endogenous and mitochondrial-targeted antioxidants and their physiological or pharmacological relevance to preserve mitochondrial functions is analysed.

Blue-light irradiation regulates proliferation and differentiation in human skin cells

Sunlight influences the physiology of the human skin in beneficial as well as harmful ways, as has been shown for UV light. However, little is known about the effects of other wavelengths of solar irradiation. In this study we irradiated human keratinocytes and skin-derived endothelial cells with light-emitting-diode devices of distinct wavelengths to study the effects on cell physiology. We found that light at wavelengths of 632-940 nm has no effect, but irradiation with blue light at 412-426 nm exerts toxic effects at high fluences. Light at 453 nm is nontoxic up to a fluence of 500 J/cm(2). At nontoxic fluences, blue light reduces proliferation dose dependently by up to 50%, which is attributable to differentiation induction as shown by an increase of differentiation markers. Experiments with BSA demonstrate that blue-light irradiation up to 453 nm photolytically generates nitric oxide (NO) from nitrosated proteins, which is known to initiate differentiation in skin cells. Our data provide evidence for a molecular mechanism by which blue light may be effective in treating hyperproliferative skin conditions by reducing proliferation due to the induction of differentiation. We observed a photolytic release of NO from nitrosated proteins, indicating that they are light acceptors and signal transducers up to a wavelength of 453 nm.

Chemical target and pathway toxicity mechanisms defined in primary human cell systems

INTRODUCTION

The ability to predict the health effects resulting from drug or chemical exposure has been challenging due to the complexity of human biology. Approaches that detect and discriminate a broad range of mechanisms in testing formats that are predictive and yet cost-effective are needed.

METHODS

Here, we evaluated the performance of BioMAP systems, primary human cell-based disease models, as a platform for characterization of chemical toxicity mechanisms. For this we tested a set of compounds with known or well-studied mechanisms in a panel of 8 BioMAP assays relevant to human respiratory, skin, immune and vascular exposure sites.

RESULTS

We evaluated the ability to detect and distinguish compounds based on mechanisms of action, comparing the BioMAP activity profiles generated in a reduced sample number format to reference database profiles derived from multiple experiments. We also studied the role of BioMAP assay panel size and concentration effects, both of which were found to contribute to the ability to discriminate chemicals and mechanisms.

DISCUSSION

Compounds with diverse mechanisms, including modulators of the NFkappaB pathway, microtubule function and mitochondrial activity, could be discriminated and classified into target and pathway mechanisms in both assay formats. Certain inhibitors of mitochondrial function, such as rotenone and sodium azide, but not others, were classified with inducers of endoplasmic reticulum stress, providing insight into the toxicity mechanisms of these agents. This method may have utility in classifying novel agents with unknown modes of action according to their effects on toxicity pathways.

Reactive nitrogen species formation in eosinophils and imbalance in nitric oxide metabolism are involved in atopic dermatitis-like skin lesions in NC/Nga mice

Nitric oxide (NO) and reactive nitrogen species (RNS) have been implicated in the pathogenesis of inflammatory diseases. However, the involvement of NO and RNS in atopic dermatitis (AD), a pruritic inflammatory skin diseases, is not fully understood. In this study, we investigated the contribution of NO and RNS to the development of AD-like skin lesions in NC/Nga mice, an animal model for human AD. AD-like skin lesions were observed in NC/Nga mice kept under conventional conditions but not in specific pathogen-free conditions. The expression of inducible NO synthase (iNOS) and endothelial NOS (eNOS) proteins was upregulated in the dermal lesions, and that of neuronal NOS (nNOS) was downregulated in the epidermal lesions of the skin. Although the concentrations of NO2(-) and NO3(-) were lower, protein-bound nitrotyrosine content was significantly increased in the skin lesions. Immunohistochemical localization of nitrotyrosine was observed in almost all eosinophils. These results suggest that RNS formation in eosinophils and imbalance of NO metabolism are involved in the pathogenesis of AD-like skin lesions in NC/Nga mice.

Analysis of urinary 8-nitroguanine, a marker of nitrative nucleic acid damage, by high-performance liquid chromatography-electrochemical detection coupled with immunoaffinity purification: association with cigarette smoking

We have developed an analytical method to quantitate urinary 8-nitroguanine, a product of nitrative nucleic acid damage caused by reactive nitrogen species such as peroxynitrite and nitrogen dioxide. 8-Nitroguanine was purified from human urine using immunoaffinity columns with an anti-8-nitroguanine antibody, followed by quantitation by high-performance liquid chromatography-electrochemical detection. Four sequential electrodes were used to (a) oxidize interfering compounds (+250 mV), (b) reduce nitrated bases (two online electrodes at -1000 mV), and (c) quantitate reduced derivatives (+150 mV). Using this system 8-nitroxanthine can also be detected, with the detection limits being 25 and 50 fmol/injection for 8-nitroguanine and 8-nitroxanthine, respectively. The method was used to analyze both adducts in the urine of smokers (n=12) and nonsmokers (n=17). We found that smokers excrete more 8-nitroguanine [median, 6.1 fmol/mg creatinine; interquartile range (IQR), 23.8] than nonsmokers (0; IQR, 0.90) (p=0.018), and although 8-nitroxanthine was detected in human urine, its level was not related to smoking status. This is the first report to show that 8-nitroguanine is present in human urine and the methodology developed can be used to study the pathogenic roles of this adduct in the etiology of cancers associated with cigarette smoking and inflammation.

Mapping Sites of Tyrosine Nitration by Matrix‐Assisted Laser Desorption/Ionization Mass Spectrometry

Protein tyrosine nitration is an important part of nitric oxide biology. This posttranslational modification occurs under normal physiological conditions and is substantially enhanced under various pathological conditions. Studies reveal that protein tyrosine nitration is a dynamic and selective process that influences protein function and turnover and can be considered a diagnostic biomarker of pathology. The identification of nitrated tyrosine residues directly within any given nitrated protein is important for studies on in vivo mechanisms of nitration and for the explanation of functional consequences of nitration. Specific nitrated tyrosines in given proteins may be also more informative as oxidative biomarkers than overall nitrotyrosine levels. However, localization of the sites of nitration remains a methodological challenge. Mass spectrometry (MS) is an ideal method for identifying nitrated tyrosines in proteins because of its sensitivity and specificity. This chapter is not intended to thoroughly discuss the various MS-based approaches for nitrotyrosine identification and merely focuses on the analysis of peptides containing nitrotyrosine by matrix-assisted laser desorption ionization MS (MALDI-MS). The data summarized show that the MALDI-MS pattern of a tyrosine-nitrated peptide includes the unique combination of ions that provides unequivocal evidence for the presence of nitrotyrosine in a given peptide and could be used for mapping sites of tyrosine nitration in proteins.

Extracellular catalase induces cyclooxygenase 2, interleukin 8, and stromelysin genes in primary human chondrocytes

We investigated the expression of genes in response to exposure of primary human chondrocytes to extracellular catalase. The addition of catalase to culture medium caused a significant up-regulation of cyclooxygenase 2, interleukin 8, and stromelysin mRNA levels. Similar pattern of gene activation occurred in chondrocytes incubated with horseradish peroxidase. On the contrary, ebselen, a glutathione peroxidase mimetic agent, did not affect expression of catalase-inducible genes. Taken together, these observations imply that catalase action is mediated by its side peroxidase-like activity, rather than elimination of H2O2. Genistein suppressed catalase-mediated effects on gene expression. This finding implies that tyrosine kinases are implicated in underlying signaling pathway.

Effects of albumin and Ringer's lactate on production of lung cytokines and hydrogen peroxide after resuscitated hemorrhage and endotoxemia in rats

RATIONALE AND HYPOTHESIS

Acute lung injury is a frequent complication of severe sepsis or blood loss and is often associated with an excessive inflammatory response requiring mechanical ventilation. We tested the hypothesis that the types of fluids used during early resuscitation have an important effect on the evolution of lung injury.

METHODS

Rats were subjected to either hemorrhage or endotoxemia for 1 hr, followed by resuscitation to a controlled mean blood pressure with Ringer's lactate, 5% albumin, or 25% albumin for 1 hr. After resuscitation, blood cytokine levels were measured. The lung was then excised and ventilated with a tidal volume of 30 mL/kg for 2 hrs.

RESULTS

The volume of fluids required was significantly smaller in the albumin-treated groups than in the Ringer's lactate groups. In the hemorrhagic shock model, plasma concentrations of tumor necrosis factor-alpha, interleukin-6, and macrophage inflammatory protein-2 were significantly lower and interleukin-10 was significantly higher in the albumin-treated groups compared with the Ringer's lactate-treated group. The levels of tumor necrosis factor-alpha and macrophage inflammatory protein-2 in bronchoalveolar lavage fluid were lower and interleukin-10 was higher in the albumin-treated groups than in the Ringer's lactate group. The decreased cytokine production was associated with a reduction of hydrogen peroxide formation with albumin resuscitation. The lung wet/dry ratio was lower in the 5% albumin (0.54 +/- 0.01) and 25% albumin (0.55 +/- 0.02) groups than in the Ringer's lactate group (0.62 +/- 0.02; both p <.05). These effects of albumin seen in the hemorrhagic shock model were not observed in the endotoxic shock model.

CONCLUSIONS

We conclude that resuscitation with albumin may have utility in reducing ventilator-induced lung injury after hemorrhagic shock, but not after endotoxic shock. These findings suggest that the mechanisms leading to ventilator-induced lung injury after hemorrhage differ from those after endotoxemia.

Methylene blue photosensitized oxidation of hypotaurine in the presence of azide generates reactive nitrogen species: formation of nitrotyrosine

In our previous study on the hypotaurine (HTAU) oxidation by methylene blue (MB) photochemically generated singlet oxygen (1O2) we found that azide, usually used as 1O2 quencher, produced, instead, an evident enhancing effect on the oxidation rate [L. Pecci, M. Costa, G. Montefoschi, A. Antonucci, D. Cavallini, Biochem. Biophys. Res. Commun. 254 (1999) 661-665]. We show here that this effect is strongly dependent on pH, with a maximum at approximately pH 5.7. When the MB photochemical system containing HTAU and azide was performed in the presence of tyrosine, 3-nitrotyrosine was produced with maximum yield at pH 5.7, suggesting that azide, by the combined action of HTAU and singlet oxygen, generates nitrogen species which contribute to tyrosine nitration. In addition to HTAU, cysteine sulfinic acid, and sulfite were found to induce the formation of 3-nitrotyrosine. No detectable tyrosine nitration was observed using taurine, the oxidation product of HTAU, or thiol compounds such as cysteine and glutathione. It is shown that during the MB photooxidation of HTAU in the presence of azide, nitrite, and nitrate are produced. Evidences are presented, indicating that nitrite represents the nitrogen species involved in the production of 3-nitrotyrosine. A possible mechanism accounting for the enhancing effect of azide on the photochemical oxidation of HTAU and the production of nitrogen species is proposed.