Kinetics and mechanisms of catalase in peroxisomes of the mitochondrial fraction

Residual effects of 12 weeks of power-oriented resistance training plus high-intensity interval training on muscle dysfunction, systemic oxidative damage, and antioxidant capacity after 10 months of training cessation in older people with COPD

OBJECTIVE

This study aimed to assess the residual effects of a 12-week concurrent training program (power training + high-intensity interval training) in older adults with chronic obstructive pulmonary disease (COPD).

METHODS

A total of 21 older adults with COPD [intervention (INT), n = 8; control (CON), n = 13; 76.9 ± 6.8 years] were assessed at baseline and 10 months after the completion of the intervention by the short physical performance battery (SPPB), health-related quality of life (EQ-5D-5L), vastus lateralis muscle thickness (MT), peak pulmonary oxygen uptake (peak VO2 ) and peak work rate (Wpeak ), early and late isometric rate of force development (RFD), leg and chest press maximum muscle power (LPmax and CPmax ), and systemic oxidative damage and antioxidant capacity.

RESULTS

Compared to baseline, after 10 months of detraining, the INT group presented increased SPPB (∆ = 1.0 point), health-related quality of life (∆ = 0.07 points), early RFD (∆ = 834 N∙s-1 ), LPmax (∆ = 62.2 W), and CPmax (∆ = 16.0 W) (all p < 0.05). In addition, a positive effect was noted in INT compared to CON regarding MT and Wpeak (both p < 0.05). No between-group differences were reported in peak VO2 , late RFD, systemic oxidative damage, and antioxidant capacity from baseline to 10 months after the completion of the intervention (all p > 0.05).

CONCLUSIONS

Twelve weeks of concurrent training were enough to ensure improved physical function, health-related quality of life, early RFD and maximum muscle power and to preserve MT and Wpeak but not peak VO2 , late RFD, systemic oxidative damage and antioxidant capacity in the subsequent 10 months of detraining in older adults with COPD.

Redox balance and autophagy regulation in cancer progression and their therapeutic perspective

Cellular ROS production participates in various cellular functions but its accumulation decides the cell fate. Malignant cells have higher levels of ROS and active antioxidant machinery, a characteristic hallmark of cancer with an outcome of activation of stress-induced pathways like autophagy. Autophagy is an intracellular catabolic process that produces alternative raw materials to meet the energy demand of cells and is influenced by the cellular redox state thus playing a definite role in cancer cell fate. Since damaged mitochondria are the main source of ROS in the cell, however, cancer cells remove them by upregulating the process of mitophagy which is known to play a decisive role in tumorigenesis and tumor progression. Chemotherapy exploits cell machinery which results in the accumulation of toxic levels of ROS in cells resulting in cell death by activating either of the pathways like apoptosis, necrosis, ferroptosis or autophagy in them. So understanding these redox and autophagy regulations offers a promising method to design and develop new cancer therapies that can be very effective and durable for years. This review will give a summary of the current therapeutic molecules targeting redox regulation and autophagy for the treatment of cancer. Further, it will highlight various challenges in developing anticancer agents due to autophagy and ROS regulation in the cell and insights into the development of future therapies.

Coherently synchronized reaction of methane oxidation by green oxidizer–hydrogen peroxide – over the biomimetic catalyst iron pentafluorotetraphenylporphyrin deposited on alumina

The activity of penta- FTPhPFe(III)/Al2O3 biomimetic catalyst in the reaction of methane direct conversion into methanol by green oxidant hydrogen peroxide was studied at T = 150–350 °C and atmospheric pressure, where methanol yield was 19.2% with methane conversion of 28%. Based on the results of the structural analysis of the Al2O3 support and the biomimetic catalyst sample the mesoporosity of support with pore size in the range of dp = 2.4–22.2 nm in the cylindric shape with an open end and the synthesized biomimetic nanostructure were determined. The data on the definition of the nature and quantitative assessment of Al2O3 support acid–base centers are given that made possible to describe probable mechanism of methane coherent-synchronized oxidation into methanol on the biomimetic.

Implication of Dietary Iron-Chelating Bioactive Compounds in Molecular Mechanisms of Oxidative Stress-Induced Cell Ageing

One of the prevailing perceptions regarding the ageing of cells and organisms is the intracellular gradual accumulation of oxidatively damaged macromolecules, leading to the decline of cell and organ function (free radical theory of ageing). This chemically undefined material known as "lipofuscin," "ceroid," or "age pigment" is mainly formed through unregulated and nonspecific oxidative modifications of cellular macromolecules that are induced by highly reactive free radicals. A necessary precondition for reactive free radical generation and lipofuscin formation is the intracellular availability of ferrous iron (Fe²⁺) ("labile iron"), catalyzing the conversion of weak oxidants such as peroxides, to extremely reactive ones like hydroxyl (HO^•) or alcoxyl (RO^•) radicals. If the oxidized materials remain unrepaired for extended periods of time, they can be further oxidized to generate ultimate over-oxidized products that are unable to be repaired, degraded, or exocytosed by the relevant cellular systems. Additionally, over-oxidized materials might inactivate cellular protection and repair mechanisms, thus allowing for futile cycles of increasingly rapid lipofuscin accumulation. In this review paper, we present evidence that the modulation of the labile iron pool distribution by nutritional or pharmacological means represents a hitherto unappreciated target for hampering lipofuscin accumulation and cellular ageing.

Are mitochondria the main contributor of reactive oxygen species in cells?

Physiologists often assume that mitochondria are the main producers of reactive oxygen species (ROS) in cells. Consequently, in biomedicine, mitochondria are considered as important targets for therapeutic treatments, and in evolutionary biology, they are considered as mediators of life-history tradeoffs. Surprisingly, data supporting such an assumption are lacking, at least partially due to the technical difficulties in accurately measuring the level of ROS produced by different subcellular compartments in intact cells. In this Commentary, we first review three potential reasons underlying the misassumption of mitochondrial dominance in the production of cellular ROS. We then introduce some other major sites/enzymes responsible for cellular ROS production. With the use of a recently developed cell-based assay, we further discuss the contribution of mitochondria to the total rate of ROS release in cell lines and primary cells of different species. In these cells, the contribution of mitochondria varies between cell types but mitochondria are never the main source of cellular ROS. This indicates that although mitochondria are one of the significant sources of cellular ROS, they are not necessarily the main contributor under normal conditions. Intriguingly, similar findings were also observed in cells under a variety of stressors, life-history strategies and pathological stages, in which the rates of cellular ROS production were significantly enhanced. Finally, we make recommendations for designing future studies. We hope this paper will encourage investigators to carefully consider non-mitochondrial sources of cellular ROS in their study systems or models.

Diabetic cardiomyopathy attenuated the protective effect of ischaemic post-conditioning against ischaemia-reperfusion injury in the isolated rat heart model

The present study was designed to investigate the efficacy of post-conditioning (POC) in the diabetic heart with myopathy (DCM) against ischaemia-reperfusion (I/R) injury in an isolated rat heart model. Present work includes three groups of male Wistar rat viz., (i) normal, (ii) diabetes mellitus (DM) and (iii) DCM and each group was subdivided into normal perfusion, I/R, and POC. Isolated heart from the rats was analysed for tissue injury, contractile function, mitochondrial function, and oxidative stress. Results demonstrated that unlike in DM heart and normal heart, POC procedure failed to recover the DCM heart from I/R induced cardiac dysfunction (measured via cardiac hemodynamics and infarct size. POC was unsuccessful in preserving mitochondrial subsarcolemmal fraction during I/R when compared with DM and normal heart. To conclude, the development of myopathy in diabetic heart abolished the cardioprotective efficacy of POC and the underlying pathology was linked with the mitochondrial dysfunction.KEY MESSAGESEarly studies reported contradicting response of diabetic heart towards post-conditioning mediated cardioprotection.Deteriorated mitochondrial function underlines the failure of post-conditioning in DCM.Efficacy of cardioprotection depends on the varying pathology of different diabetes stages.

High-fat diet effect on periapical lesions and hepatic enzymatic antioxidant in rats

AIMS

To evaluate the effects of a high-fat diet (HFD) on the progression of apical periodontitis (AP), local inflammation, systemic antioxidant status, and blood lipid profile in rats.

MAIN METHODS

Sixteen male Wistar rats were fed a standard diet (SD) or a HFD. At the sixth experimental week, the pulp chambers of the mandibular first molars were exposed to develop AP. A glucose tolerance test was performed the week before euthanasia. At the tenth experimental week, the animals were euthanized and the livers were collected to estimate catalase (CAT) and reduced glutathione (GSH) levels. Blood was acquired for biochemical analysis. The size of AP was estimated from radiographs and described as AP size-to-body weight ratio; inflammatory grade of AP was determined by histological analysis.

KEY FINDINGS

At the end of the experimental period, the rats fed the HFD had 30% less weight (P < 0.0001) and higher blood glucose levels after 30 min of sucrose intake (P < 0.05) than those fed the SD. Animals from the HFD group had lower levels of CAT (P < 0.01), but the same was not observed in the GSH levels. Plasma insulin and total cholesterol were not affected by the diet. The rats fed the HFD presented greater AP than those fed the SD (P < 0.05). However, the local inflammatory infiltrate was similar in both groups.

SIGNIFICANCE

The alterations promoted by the consumption of a HFD were not only observed systemically, but also locally, producing greater AP in rats than a SD.

Findings in redox biology: From H2O2 to oxidative stress

My interest in biological chemistry proceeded from enzymology in vitro to the study of physiological chemistry in vivo Investigating biological redox reactions, I identified hydrogen peroxide (H2O2) as a normal constituent of aerobic life in eukaryotic cells. This finding led to developments that recognized the essential role of H2O2 in metabolic redox control. Further research included studies on GSH, toxicological aspects (the concept of "redox cycling"), biochemical pharmacology (ebselen), nutritional biochemistry and micronutrients (selenium, carotenoids, flavonoids), and the concept of "oxidative stress." Today, we recognize that oxidative stress is two-sided. It has its positive side in physiology and health in redox signaling, "oxidative eustress," whereas at higher intensity, there is damage to biomolecules with potentially deleterious outcome in pathophysiology and disease, "oxidative distress." Reflecting on these developments, it is gratifying to witness the enormous progress in redox biology brought about by the science community in recent years.

Subcellular compartmentalization of the plant antioxidant system: an integrated overview

The antioxidant system (AOS) maintains the optimal concentration of reactive oxygen species (ROS) in a cell and protects it against oxidative stress. In plants, the AOS consists of seven main classes of antioxidant enzymes, low-molecular antioxidants (e.g., ascorbate, glutathione, and their oxidized forms) and thioredoxin/glutaredoxin systems which can serve as reducing agents for antioxidant enzymes. The number of genes encoding AOS enzymes varies between classes, and same class enzymes encoded by different gene copies may have different subcellular localizations, functional loads and modes of evolution. These facts hereafter reinforce the complex nature of AOS regulation and functioning. Further studies can describe new trends in the behavior and functioning of systems components, and provide new fundamental knowledge about systems regulation. The system is revealed to have a lot of interactions and interplay pathways between its components at the subcellular level (antioxidants, enzymes, ROS level, and hormonal and transcriptional regulation). These facts should be taken into account in further studies during the AOS modeling by describing the main pathways of generating and utilizing ROS, as well as the associated signaling processes and regulation of the system on cellular and organelle levels, which is a complicated and ambitious task. Another objective for studying the phenomenon of the AOS is related to the influence of cell dynamics and circadian rhythms on it. Therefore, the AOS requires an integrated and multi-level approach to study. We focused this review on the existing scientific background and experimental data used for the systems biology research of the plant AOS.

Diabetic animal fed with high-fat diet prevents the protective effect of myocardial ischemic preconditioning effect in isolated rat heart perfusion model

Diabetic heart (diabetes mellitus [DM]) has been shown to attenuate the beneficial effect of ischemic preconditioning (IPC) in rat heart. But the effect of IPC on diabetic rat heart that develops myopathy remains unclear. This study was designed to test the impact of IPC on diabetic cardiomyopathy (DCM) rat heart. Male Wistar rats were grouped as (a) normal, (b) DM (streptozotocin: 65 mg/kg; fed with normal diet), and (c) DCM (streptozotocin: 65 mg/kg; fed with high-fat diet). Isolated rat hearts from each group were randomly subjected to (a) normal perfusion, (b) ischemia-reperfusion (I/R), and (c) IPC procedure. At the end of the perfusion experiments, hearts were analyzed for injury, contractile function, mitochondrial activity, and oxidative stress. The results obtained from hemodynamics, cardiac injury markers, and caspase-3 activity showed that DCM rat displayed prominent I/R-associated cardiac abnormalities than DM rat heart. But the deteriorated physiological performance and cardiac injury were not recovered in both DM and DCM heart by IPC procedure. Unlike normal rat heart, IPC did not reverse mitochondrial dysfunction (determined by electron transport chain enzymes activity, ATP level, and membrane integrity, expression levels of genes like PGC-1ɑ, GSK3β, complex I, II, and V) in DCM and DM rat heart. The present study demonstrated that IPC failed to protect I/R-challenged DCM rat heart, and the underlying pathology was associated with deteriorated mitochondrial function.

H2O2 Metabolism in Normal Thyroid Cells and in Thyroid Tumorigenesis: Focus on NADPH Oxidases

Thyroid hormone synthesis requires adequate hydrogen peroxide (H₂O₂) production that is utilized as an oxidative agent during the synthesis of thyroxin (T4) and triiodothyronine (T3). Thyroid H₂O₂ is generated by a member of the family of NADPH oxidase enzymes (NOX-es), termed dual oxidase 2 (DUOX2). NOX/DUOX enzymes produce reactive oxygen species (ROS) as their unique enzymatic activity in a timely and spatially regulated manner and therefore, are important regulators of diverse physiological processes. By contrast, dysfunctional NOX/DUOX-derived ROS production is associated with pathological conditions. Inappropriate DUOX2-generated H₂O₂ production results in thyroid hypofunction in rodent models. Recent studies also indicate that ROS improperly released by NOX4, another member of the NOX family, are involved in thyroid carcinogenesis. This review focuses on the current knowledge concerning the redox regulation of thyroid hormonogenesis and cancer development with a specific emphasis on the NOX and DUOX enzymes in these processes.

Evaluating the impact of diabetes and diabetic cardiomyopathy rat heart on the outcome of ischemia-reperfusion associated oxidative stress

Earlier literature underlines that oxidative stress plays a major role in the pathology of myocardial ischemia-reperfusion (I/R) injury, diabetic cardiomyopathy (DCM), diabetes mellitus (DM), fibrosis and hypertrophy which could adversely affect the normal cardiac function. However, the contributory role of oxidative stress in I/R pathology of heart with pre-existing abnormalities or diseases like DM and DCM remains to be explored. I/R injury was induced in normal (normal diet), DM (normal diet + streptozotocin: multiple low dose of 30 mg/kg) and DCM (high fat diet (40% fat) + streptozotocin: multiple low dose of 30 mg/kg) rat hearts using Langendorff isolated heart perfusion apparatus. Cardiac physiological recovery after I/R was assessed by hemodynamic parameters like LVDP, and LVSP, whereas cardiac injury was measured by tissue infarct size, and apoptosis, LDH, and CK release in coronary effluent. The oxidative stress was evaluated in myocardial homogenate, mitochondrial subpopulation, and microsomes. Reperfusing the ischemic DCM heart significantly deteriorated cardiac physiological recovery and elevated the cardiac injury (infarct size: 60%), compared to the control. But in DM heart, physiological recovery was prominent in the initial phase of reperfusion but deteriorated towards the end of reperfusion, supported by less infarct size. In addition, elevated lipid peroxidation (70% in DCM-I/R vs Sham) and impaired antioxidant enzymes (% decline vs Sham: GSH - 56% (DM), 63% (DCM); Catalase - 58% (DM), 35% (DCM); GPx - 19% (DM), 27% (DCM) and GR - 28% (DCM)) was observed in myocardial tissue from both DM and DCM. Interestingly, upon reperfusion, only normal heart showed significant deterioration in the antioxidant defense system. Collectively these results demonstrated that I/R induced oxidative stress is minimal in DM and DCM rat heart, despite high infarct size and low cardiac performance. This may be due to the prior adaptive modification in the antioxidant system associated with disease pathology.

Physiological role of reactive oxygen species as promoters of natural defenses

It has been 60 yr since the discovery of reactive oxygen species (ROS) in biology and the beginning of the scientific community's attempt to understand the impact of the unpaired electron of ROS molecules in biological pathways, which was eventually noted to be toxic. Several studies have shown that the presence of ROS is essential in triggering or acting as a secondary factor for numerous pathologies, including metabolic and genetic diseases; however, it was demonstrated that chronic treatment with antioxidants failed to show efficacy and positive effects in the prevention of diseases or health complications that result from oxidative stress. On the contrary, such treatment has been shown to sometimes even worsen the disease. Because of the permanent presence of ROS in organisms, elaborate mechanisms to adapt with these reactive molecules and to use them without necessarily blocking or preventing their actions have been studied. There is now a large body of evidence that shows that living organisms have conformed to the presence of ROS and, in retrospect, have adapted to the bioactive molecules that are generated by ROS on proteins, lipids, and DNA. In addition, ROS have undergone a shift from being molecules that invoked oxidative damage in regulating signaling pathways that impinged on normal physiological and redox responses. Working in this direction, this review unlocks a new conception about the involvement of cellular oxidants in the maintenance of redox homeostasis in redox regulation of normal physiological functions, and an explanation for its essential role in numerous pathophysiological states is noted.-Roy, J., Galano, J.-M., Durand, T., Le Guennec, J.-Y., Lee, J. C.-Y. Physiological role of reactive oxygen species as promoters of natural defenses.

Toxicity evaluation of silver nanoparticles synthesized by chemical and green route in different experimental models

With the increased exposure of silver nanoparticles (AgNPs) to human beings, the risk and safety should be considered. In this study, nephro-toxicity of AgNPs prepared by chemical and green route (aqueous extract of Desmodium gangeticum root) in rat, proximal epithelial cell lines and renal mitochondria was evaluated. AgNPs (100 mg/kg) were administered orally to the wistar rats. After 15 d, we observed significant changes in the renal architecture of both AgNPs, supported by the urine and blood chemistry data. Further, exposure towards renal epithelial cells and renal mitochondria also confirm the toxic similarities between the AgNPs synthesized from two routes.

Chemical approaches to discovery and study of sources and targets of hydrogen peroxide redox signaling through NADPH oxidase proteins

Hydrogen peroxide (H2O2) is a prime member of the reactive oxygen species (ROS) family of molecules produced during normal cell function and in response to various stimuli, but if left unchecked, it can inflict oxidative damage on all types of biological macromolecules and lead to cell death. In this context, a major source of H2O2 for redox signaling purposes is the NADPH oxidase (Nox) family of enzymes, which were classically studied for their roles in phagocytic immune response but have now been found to exist in virtually all mammalian cell types in various isoforms with distinct tissue and subcellular localizations. Downstream of this tightly regulated ROS generation, site-specific, reversible covalent modification of proteins, particularly oxidation of cysteine thiols to sulfenic acids, represents a prominent posttranslational modification akin to phosphorylation as an emerging molecular mechanism for transforming an oxidant signal into a dynamic biological response. We review two complementary types of chemical tools that enable (a) specific detection of H2O2 generated at its sources and (b) mapping of sulfenic acid posttranslational modification targets that mediate its signaling functions, which can be used to study this important chemical signal in biological systems.

Catalytic antioxidant therapy by metallodrugs: lessons from metallocorroles

This article provides a perspective on the utility of metal-based catalytic antioxidants for disease prevention or treatment, with focus on their mode of action and its dependence (DCA) or independence (ICA) on the involvement of cofactors.

High cell density culture with S. cerevisiae CEN.PK113-5D for IL-1β production: optimization, modeling, and physiological aspects

Saccharomyces cerevisiae CEN.PK113-5D, a strain auxotrophic for uracil belonging to the CEN.PK family of the yeast S. cerevisiae, was cultured in aerated fed-batch reactor as such and once transformed to express human interleukin-1β (IL-1β), aiming at obtaining high cell densities and optimizing IL-1β production. Three different exponentially increasing glucose feeding profiles were tested, all of them "in theory" promoting respiratory metabolism to obtain high biomass/product yield. A non-structured non-segregated model was developed to describe the performance of S. cerevisiae CEN.PK113-5D during the fed-batch process and, in particular, its capability to metabolize simultaneously glucose and ethanol which derived from the precedent batch growth. Our study showed that the proliferative capacity of the yeast population declined along the fed-batch run, as shown by the exponentially decreasing specific growth rates on glucose. Further, a shift towards fermentative metabolism occurred. This shift took place earlier the higher was the feed rate and was more pronounced in the case of the recombinant strain. Determination of some physiological markers (acetate production, intracellular ROS accumulation, catalase activity and cell viability) showed that neither poor oxygenation nor oxidative stress was responsible for the decreased specific growth rate, nor for the shift to fermentative metabolism.

Soluble, prefibrillar α-synuclein oligomers promote complex I-dependent, Ca2+-induced mitochondrial dysfunction

α-Synuclein (αSyn) aggregation and mitochondrial dysfunction both contribute to the pathogenesis of Parkinson disease (PD). Although recent studies have suggested that mitochondrial association of αSyn may disrupt mitochondrial function, it is unclear what aggregation state of αSyn is most damaging to mitochondria and what conditions promote or inhibit the effect of toxic αSyn species. Because the neuronal populations most vulnerable in PD are characterized by large cytosolic Ca(2+) oscillations that burden mitochondria, we examined mitochondrial Ca(2+) stress in an in vitro system comprising isolated mitochondria and purified recombinant human αSyn in various aggregation states. Using fluorimetry to simultaneously measure four mitochondrial parameters, we observed that soluble, prefibrillar αSyn oligomers, but not monomeric or fibrillar αSyn, decreased the retention time of exogenously added Ca(2+), promoted Ca(2+)-induced mitochondrial swelling and depolarization, and accelerated cytochrome c release. Inhibition of the permeability transition pore rescued these αSyn-induced changes in mitochondrial parameters. Interestingly, the mitotoxic effects of αSyn were specifically dependent upon both electron flow through complex I and mitochondrial uptake of exogenous Ca(2+). Our results suggest that soluble prefibrillar αSyn oligomers recapitulate several mitochondrial phenotypes previously observed in animal and cell models of PD: complex I dysfunction, altered membrane potential, disrupted Ca(2+) homeostasis, and enhanced cytochrome c release. These data reveal how the association of oligomeric αSyn with mitochondria can be detrimental to the function of cells with high Ca(2+)-handling requirements.

Thioredoxins, glutaredoxins, and peroxiredoxins--molecular mechanisms and health significance: from cofactors to antioxidants to redox signaling

Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and "antioxidants". Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions.

Electrochemical study of hydrogen peroxide formation in isolated mitochondria

Mitochondrial respiration generates reactive oxygen species that are involved in physiological and pathological processes. The majority of methods, with exception of electron paramagnetic resonance, used to evaluate the identity, the rate and the conditions of the reactive oxygen species produced by mitochondria, are mainly based on oxidation sensitive markers. Following latest electrochemical methodology, we implemented a novel electrochemical assay for the investigation of aerobic metabolism in preparations of isolated mitochondria through simultaneous measurement of O₂ consumption and reactive species production. This electrochemical assay reveals active H₂O₂ production by respiring mouse liver mitochondria, and shows that ATP synthase activation and moderate depolarization increase the rate of H₂O₂ formation, suggesting that ATP synthesizing (state 3) mitochondria might contribute to oxidative stress or signaling.

Signaling functions of reactive oxygen species

We review signaling by reactive oxygen species, which is emerging as a major physiological process. However, among the reactive oxygen species, H(2)O(2) best fulfills the requirements of being a second messenger. Its enzymatic production and degradation, along with the requirements for the oxidation of thiols by H(2)O(2), provide the specificity for time and place that are required in signaling. Both thermodynamic and kinetic considerations suggest that among possible oxidation states of cysteine, formation of sulfenic acid derivatives or disulfides can be relevant as thiol redox switches in signaling. In this work, the general constraints that are required for protein thiol oxidation by H(2)O(2) to be fast enough to be relevant for signaling are discussed in light of the mechanism of oxidation of the catalytic cysteine or selenocysteine in thiol peroxidases. While the nonenzymatic reaction between thiol and H(2)O(2) is, in most cases, too slow to be relevant in signaling, the enzymatic catalysis of thiol oxidation by these peroxidases provides a potential mechanism for redox signaling.

Signaling functions of reactive oxygen species

We review signaling by reactive oxygen species, which is emerging as a major physiological process. However, among the reactive oxygen species, H(2)O(2) best fulfills the requirements of being a second messenger. Its enzymatic production and degradation, along with the requirements for the oxidation of thiols by H(2)O(2), provide the specificity for time and place that are required in signaling. Both thermodynamic and kinetic considerations suggest that among possible oxidation states of cysteine, formation of sulfenic acid derivatives or disulfides can be relevant as thiol redox switches in signaling. In this work, the general constraints that are required for protein thiol oxidation by H(2)O(2) to be fast enough to be relevant for signaling are discussed in light of the mechanism of oxidation of the catalytic cysteine or selenocysteine in thiol peroxidases. While the nonenzymatic reaction between thiol and H(2)O(2) is, in most cases, too slow to be relevant in signaling, the enzymatic catalysis of thiol oxidation by these peroxidases provides a potential mechanism for redox signaling.

Changing paradigms in thiology from antioxidant defense toward redox regulation

The history of free radical biochemistry is briefly reviewed in respect to major trend shifts from the focus on radiation damage toward enzymology of radical production and removal and ultimately the role of radicals, hydroperoxides, and related fast reacting compounds in metabolic regulation. Selected aspects of the chemistry of radicals and hydroperoxides, the enzymology of peroxidases, and the biochemistry of adaptive responses and regulatory phenomena are compiled and discussed under the perspective of how the fragments of knowledge can be merged to biologically meaningful concepts of regulation. It is concluded that (i) not radicals but H(2)O(2), hydroperoxides, and peroxynitrite are the best candidates for oxidant signals, (ii) peroxidases of the GPx and Prx family or functionally equivalent proteins have the chance to specifically sense hydroperoxides and to transduce the oxidant signal, (iii) redox signaling proceeds via reactions known from thiol peroxidase and redoxin chemistry, (iv) proximal targets are proteins that are modified at SH groups, and (v) redoxins are documented signal transducers but also used as terminators. The importance of kinetics for forward signaling and for sensitivity modulation by competition is emphasized and ways to restore resting conditions are discussed. Research needs to validate emerging concepts are outlined.

Mitochondrial targeting of electron scavenging antioxidants: Regulation of selective oxidation vs random chain reactions

Effective regulation of highly compartmentalized production of reactive oxygen species and peroxidation reactions in mitochondria requires targeting of small molecule antioxidants and antioxidant enzymes into the organelles. This review describes recently developed approaches to mitochondrial targeting of small biologically active molecules based on: (i) preferential accumulation in mitochondria because of their hydrophobicity and positive charge (hydrophobic cations), (ii) binding with high affinity to an intra-mitochondrial constituent, and (iii) metabolic conversions by specific mitochondrial enzymes to reveal an active entity. In addition, targeted delivery of antioxidant enzymes via expression of leader sequences directing the proteins into mitochondria is considered. Examples of successful antioxidant and anti-apoptotic protection based on the ability of targeted cargoes to inhibit cytochrome c-catalyzed peroxidation of a mitochondria-specific phospholipid cardiolipin, in vitro and in vivo are presented. Particular emphasis is placed on the employment of triphenylphosphonium- and hemi-gramicidin S-moieties as two effective vehicles for mitochondrial delivery of antioxidants.

Fatty acids decrease mitochondrial generation of reactive oxygen species at the reverse electron transport but increase it at the forward transport

Long-chain nonesterified ("free") fatty acids (FFA) can affect the mitochondrial generation of reactive oxygen species (ROS) in two ways: (i) by depolarisation of the inner membrane due to the uncoupling effect and (ii) by partly blocking the respiratory chain. In the present work this dual effect was investigated in rat heart and liver mitochondria under conditions of forward and reverse electron transport. Under conditions of the forward electron transport, i.e. with pyruvate plus malate and with succinate (plus rotenone) as respiratory substrates, polyunsaturated fatty acid, arachidonic, and branched-chain saturated fatty acid, phytanic, increased ROS production in parallel with a partial inhibition of the electron transport in the respiratory chain, most likely at the level of complexes I and III. A linear correlation between stimulation of ROS production and inhibition of complex III was found for rat heart mitochondria. This effect on ROS production was further increased in glutathione-depleted mitochondria. Under conditions of the reverse electron transport, i.e. with succinate (without rotenone), unsaturated fatty acids, arachidonic and oleic, straight-chain saturated palmitic acid and branched-chain saturated phytanic acid strongly inhibited ROS production. This inhibition was partly abolished by the blocker of ATP/ADP transfer, carboxyatractyloside, thus indicating that this effect was related to uncoupling (protonophoric) action of fatty acids. It is concluded that in isolated rat heart and liver mitochondria functioning in the forward electron transport mode, unsaturated fatty acids and phytanic acid increase ROS generation by partly inhibiting the electron transport and, most likely, by changing membrane fluidity. Only under conditions of reverse electron transport, fatty acids decrease ROS generation due to their uncoupling action.

Enhanced ROS production and antioxidant defenses in cybrids harbouring mutations in mtDNA

It has been suggested that mutations in mitochondrial DNA (mtDNA) can produce an increase in reactive oxygen species (ROS) and that this can play a major role in the pathogenic mechanisms of mitochondrial encephalomyopathies. Many studies exist using electron transport chain (ETC) inhibitors, however there are only a few studies that examine ROS production associated with mutations in the mtDNA. To investigate this issue, we have studied ROS production, antioxidant defences and oxidative damage to lipids and proteins in transmitochondrial cybrids carrying different mtDNA mutations. Here, we report that two different mutant cell lines carrying mutations in their mitochondrial tRNA genes (A3243G in tRNA LeuUUR and A8344G in tRNA Lys) showed an increased ROS production with a parallel increase in the antioxidant enzyme activities, which may protect cells from oxidative damage in our experimental conditions (no overt oxidative damage to lipids and proteins has been observed). In contrast, cytochrome c oxidase (COX) mutant cybrids (carrying the stop-codon mutation G6930A in the COXI gene) showed neither an increase in ROS production nor elevation of antioxidant enzyme activities or oxidative damage. These results suggest that the specific location of mutations in mtDNA has a strong influence on the phenotype of the antioxidant response. Therefore, this issue should be carefully considered when antioxidant therapies are investigated in patients with mitochondrial disorders.

Catalase-dependent measurement of H2O2 in intact mitochondria

Mitochondria generate potentially damaging amounts of superoxide and H2O2 during oxidative metabolism. Although many assays are available to measure mitochondrial H2O2 generation, most detect H2O2 that has escaped the organelle. To measure H2O2 within mitochondria that contain catalase, we have developed an assay based on the ability of H2O2 to inhibit catalase in the presence of 3-amino-1,2,4-triazole. The assay is simple to perform, does not require expensive instrumentation, and is specific for H2O2. Results from this assay show that H2O2 generation in rat heart mitochondria reflects the activity of the electron transport chain. Further, liver mitochondria prepared from selenium-deficient rats have increased succinate-stimulated rates of H2O2 generation. This indicates that mitochondrial selenoenzymes are important for H2O2 removal. It also demonstrates the utility of this assay in measuring H2O2 release from mitochondria that do not contain catalase. The assay should be useful for study of both superoxide-dependent H2O2 generation in situ, and the role of endogenous mitochondrial catalase in H2O2 removal.

Characterization of the Oxidase Activity in Mammalian Catalase

Catalase is a highly conserved heme-containing antioxidant enzyme known for its ability to degrade hydrogen peroxide into water and oxygen. In low concentrations of hydrogen peroxide, the enzyme also exhibits peroxidase activity. We report that mammalian catalase also possesses oxidase activity. This activity, which is detected in purified catalases, cell lysates, and intact cells, requires oxygen and utilizes electron donor substrates in the absence of hydrogen peroxide or any added cofactors. Using purified bovine catalase and 10-acetyl-3,7-dihydroxyphenoxazine as the substrate, the oxidase activity was found to be temperature-dependent and displays a pH optimum of 7-9. The Km for the substrate is 2.4 x 10(-4) m, and Vmax is 4.7 x 10(-5) m/s. Endogenous substrates, including the tryptophan precursor indole, the neurotransmitter precursor beta-phenylethylamine, and a variety of peroxidase and laccase substrates, as well as carcinogenic benzidines, were found to be oxidized by catalase or to inhibit this activity. Several dietary plant micronutrients that inhibit carcinogenesis, including indole-3-carbinol, indole-3-carboxaldehyde, ferulic acid, vanillic acid, and epigallocatechin-3-gallate, were effective inhibitors of the activity of catalase oxidase. Difference spectroscopy revealed that catalase oxidase/substrate interactions involve the heme-iron; the resulting spectra show time-dependent decreases in the ferric heme of the enzyme with corresponding increases in the formation of an oxyferryl intermediate, potentially reflecting a compound II-like intermediate. These data suggest a mechanism of oxidase activity involving the formation of an oxygen-bound, substrate-facilitated reductive intermediate. Our results describe a novel function for catalase potentially important in metabolism of endogenous substrates and in the action of carcinogens and chemopreventative agents.

Effects of scavengers for active oxygen species on cell death by cryptogein

The hypersensitive reaction is a type of programmed cell death in plants. Cryptogein is a proteinaceous elicitor secreted from Phythophthora cryptogea. In one current model, active oxygen species (AOS) trigger programmed cell death in plants. In this study, we examined a variety of AOS scavengers to elucidate the function of AOS in the death program. Most of these AOS scavengers, including tiron, a scavenger for superoxide radical, catalase for hydrogen peroxide, and hydroquinone, sodium ascorbate and propyl gallate for free radicals, almost completely removed extracellular AOS. However, none of the reagents completely blocked the cell death process. Other reagents, such as histidine and dimethylfuran, scavengers for singlet oxygen, and diphenyleneiodonium chloride, an inhibitor of NADPH oxidase, showed significant toxicity in BY-2 cells. These results indicate that AOS produced in the extracellular space do not play a role in hypersensitive cell death.

UVB light stimulates production of reactive oxygen species: unexpected role for catalase

In keratinocytes, UVB light stimulates the production of reactive oxygen species (ROS). Lysates of these cells were found to possess a non-dialyzable, trypsin- and heat-sensitive material capable of generating ROS in response to UVB light. Using ion exchange, metal affinity, and size exclusion chromatography, a 240-kDa protein was isolated with ROS generating activity. The protein exhibited strong absorption in the 320-360 nm range with additional soret peaks around 400-410 nm, suggesting the presence of heme. Sequencing using liquid chromatography-ion trap mass spectrometry identified the protein as catalase. Using purified catalases from a variety of species, the ROS generating activity was found to be temperature- and O2-dependent, stimulated by inhibitors of the catalatic activity of catalase, including 3-aminotriazole and azide, and inhibited by cyanide. A marked increase in the production of ROS was observed in UVB-treated cells overexpressing catalase and decreased generation of oxidants was found in UVB-treated keratinocytes with reduced levels of catalase. Our data indicate that catalase plays a direct role in generating oxidants in response to UVB light. The finding that catalase mediates the production of ROS following UVB treatment is both novel and highly divergent from the well known antioxidant functions of the enzyme. We hypothesize that, through the actions of catalase, high energy DNA damaging UVB light is absorbed by the enzyme and converted to reactive chemical intermediates that can be detoxified by cellular antioxidant enzymes. Accumulation of excessive ROS, generated through the action of catalase, may lead to oxidative stress, DNA damage, and the development of skin cancer.

Identification of a functional peroxisome proliferator-activated receptor response element in the rat catalase promoter

Peroxisomal proliferator-activated receptor (PPAR)gamma has been shown to decrease the inflammatory response via transrepression of proinflammatory transcription factors. However, the identity of PPARgamma responsive genes that decrease the inflammatory response has remained elusive. Because generation of the reactive oxygen species hydrogen peroxide (H(2)O(2)) plays a role in the inflammatory process and activation of proinflammatory transcription factors, we wanted to determine whether the antioxidant enzyme catalase might be a PPARgamma target gene. We identified a putative PPAR response element (PPRE) containing the canonical direct repeat 1 motif, AGGTGA-A-AGTTGA, in the rat catalase promoter. In vitro translated PPARgamma and retinoic X receptor-alpha proteins were able to bind to the catalase PPRE. Promoter deletion analysis revealed that the PPRE was functional, and a heterologous promoter construct containing a multimerized catalase PPRE demonstrated that the PPRE was necessary and sufficient for PPARgamma-mediated activation. Treatment of microvascular endothelial cells with PPARgamma ligands led to increases in catalase mRNA and activity. These results demonstrate that PPARgamma can alter catalase expression; this occurs via a PPRE in the rat catalase promoter. Thus, in addition to transrepression of proinflammatory transcription factors, PPARgamma may also be modulating catalase expression, and hence down-regulating the inflammatory response via scavenging of reactive oxygen species.

Substrate flow in catalases deduced from the crystal structures of active site variants of HPII from Escherichia coli

The active site of heme catalases is buried deep inside a structurally highly conserved homotetramer. Channels leading to the active site have been identified as potential routes for substrate flow and product release, although evidence in support of this model is limited. To investigate further the role of protein structure and molecular channels in catalysis, the crystal structures of four active site variants of catalase HPII from Escherichia coli (His128Ala, His128Asn, Asn201Ala, and Asn201His) have been determined at approximately 2.0-A resolution. The solvent organization shows major rearrangements with respect to native HPII, not only in the vicinity of the replaced residues but also in the main molecular channel leading to the heme distal pocket. In the two inactive His128 variants, continuous chains of hydrogen bonded water molecules extend from the molecular surface to the heme distal pocket filling the main channel. The differences in continuity of solvent molecules between the native and variant structures illustrate how sensitive the solvent matrix is to subtle changes in structure. It is hypothesized that the slightly larger H(2)O(2) passing through the channel of the native enzyme will promote the formation of a continuous chain of solvent and peroxide. The structure of the His128Asn variant complexed with hydrogen peroxide has also been determined at 2.3-A resolution, revealing the existence of hydrogen peroxide binding sites both in the heme distal pocket and in the main channel. Unexpectedly, the largest changes in protein structure resulting from peroxide binding are clustered on the heme proximal side and mainly involve residues in only two subunits, leading to a departure from the 222-point group symmetry of the native enzyme. An active role for channels in the selective flow of substrates through the catalase molecule is proposed as an integral feature of the catalytic mechanism. The Asn201His variant of HPII was found to contain unoxidized heme b in combination with the proximal side His-Tyr bond suggesting that the mechanistic pathways of the two reactions can be uncoupled.

Copper-adenine catalyst for O(2) production from H(2)O(2)

In solutions of CuCl2 and adenine copper can be bound to adenine. Two Cu(adenine)(2) complexes [Cu(C(5)H(5)N(5))(2)]2+/Cu(C(5)H(4)N(5))(2)] are in equilibrium with free adenine. Copper-adenine complexes present a catalytic activity (e.g., H(2)O(2) disproportionation into O(2) and water) but depending on complex concentration H(2)O(2) also strongly oxidizes the adenine within the complexes. Raman spectroscopy quantifies copper-adenine complex formation and H(2)O(2) consumption; polarography quantifies O(2) production. As for C(40) catalase, optimal catalytic capacities depend on physiological conditions, such as pH and temperature. The comparative analysis of kinetic parameters shows that the affinity for H(2)O(2) of Cu(adenine)(2) is 37-fold lower than that of C(40) catalase and that the molar activity for O(2) production is 200-fold weaker for Cu(adenine)(2) than for the enzyme. In the 10(-6)-10(-3) M range, the strong decrease of activity with raising complex concentration is explained by aggregation or stacking, which protects Cu(adenine)(2) entities from H(2)O(2) oxidation, but also decreases O(2) production.

Plasma pharmacokinetics, nervous system biodistribution and biostability, and spinal cord permeability at the blood-brain barrier of putrescine-modified catalase in the adult rat

Free radical-mediated oxidative damage has been proposed to be an underlying mechanism in several neurodegenerative disorders. Previous investigations in our laboratory have shown that putrescine-modified catalase (PUT-CAT) has increased permeability at the blood-brain (BBB) and blood-nerve barriers with retained enzymatic activity after parenteral administration when compared to native catalase (CAT). The goals of the present study were to examine the plasma stability, spinal cord BBB permeability, nervous system biodistribution, and spinal cord enzyme activity of CAT and PUT-CAT after parenteral administration in the adult rat. TCA precipitation and chromatographic analyses revealed that CAT and PUT-CAT were found intact in the plasma and in the central nervous system (CNS) after iv, ip, or sc bolus injections. The highest percentages of intact CAT or PUT-CAT proteins were found in the plasma after iv administration, and similar percentages of intact CAT or PUT-CAT were found in the CNS following all three types of administration. Increases of 2.4- to 4.7-fold in permeability at the BBB and similar increases in the levels of intact PUT-CAT were found in different brain regions compared to the levels of CAT. A 2.4-fold higher level of intact PUT-CAT compared to that of CAT (P < 0.05) was found in the spinal cord 60 min after a sc bolus injection. CAT enzyme activity in the spinal cord was 50% higher (P < 0.05) in rats treated with PUT-CAT continuously for 1 week by subcutaneously implanted, osmotic pumps than the activity found in rats treated with PBS. These results provide evidence that intact, enzymatically active PUT-CAT is efficiently delivered to the nervous system following iv, ip, and sc administration and suggest that sc administration of PUT-CAT may be effective in treating neurodegenerative disorders in which the underlying mechanisms involve the action of free radicals and oxidative damage.

Dynamics of Acetaldehyde Production during Anoxia and Post-Anoxia in Red Bell Pepper Studied by Photoacoustic Techniques

Acetaldehyde (AA), ethanol, and CO2 production in red bell pepper (Capsicum annum L.) fruit has been measured in a continuous flow system as the fruit was switched between 20% O2 and anaerobic conditions. Minimum gas phase concentrations of 0.5 nL L-1, 10 nL L-1, and 1 mL L-1, respectively, can be detected employing a laser-based photoacoustic technique. This technique allows monitoring of low production rates and transient features in real time. At the start of anaerobic treatment respiration decreases by 60% within 0.5 h, whereas AA and ethanol production is delayed by 1 to 3 h. This suggests a direct slow-down of the tricarboxylic acid cycle and a delayed onset of alcoholic fermentation. Reexposure of the fruit to oxygen results in a 2- to 10-fold upsurge in AA production. A short anoxic period leads to a sharp transient peak lasting about 40 min, whereas after numerous and longer anoxic periods, post-anoxic AA production stays high for several hours. High sensitivity of the fruit tissue to oxygen is further evidenced by a sharp decrease in post-anoxic AA production upon an early return to anaerobic conditions. Ethanol oxidation by the "peroxidatic" action of catalase is proposed to account for the immediate post-anoxic AA upsurge.

Alcohol:NAD+ oxidoreductase is present in rat liver peroxisomes

Alcohol:NAD+ oxidoreductase was found in the peroxisomes of animal liver for the first time as follows. The distribution of alcohol:NAD+ oxidoreductase activity with nonanol as substrate in the light mitochondrial fraction (peroxisome-enriched fraction) of rat liver was examined by centrifugation in a sucrose density gradient. Most of the enzyme activity was localized in the mitochondria, with some activity in the peroxisomes. The administration of clofibrate, a peroxisome proliferator, to rats resulted in a marked increase of the enzyme activity in the peroxisomes, but not in the mitochondria. The enzyme was found to be located in the matrix of the peroxisomes. The evidence was obtained that the enzyme differed from alcohol dehydrogenases and alcohol oxidizing systems found previously. The enzyme activity was not affected by pyrazole, an inhibitor of alcohol dehydrogenase and sodium azide, an inhibitor of catalase. The enzyme was NAD(+)-dependent and oxidized straight chain aliphatic alcohols with a variety of carbon chains (C2-C18), showing the maximum on nonanol. Km values toward these aliphatic alcohols decreased with increasing chain length. The major reaction product was identified as the carboxylic acid by using high performance liquid chromatography.

Acatalasemia

The abnormalities in acatalasemia at the gene level as well as properties of the residual catalase in Japanese acatalasemia are historically reviewed. The replacement of the fifth nucleic acid, guanine, in the fourth intron by adenine in the acatalasemic gene causes a splicing mutation and hence a deficiency of mRNA. The guanine-to-adenine substitution was detected in two Japanese acatalasemic cases from different families. The properties of the residual catalase are similar to those of normal catalase; the exons are identical. The properties of the residual catalase and the molecular defect in the catalase gene are compared among Japanese, Swiss, and mouse acatalasemias. The physiological role of catalase, as judged from human acatalasemic blood and acatalasemic mice, is also described.