In vitro nonenzymatic glycation enhances the role of myoglobin as a source of oxidative stress

Metmyoglobin (Mb) was glycated by glucose in a nonenzymatic in vitro reaction. Amount of iron release from the heme pocket of myoglobin was found to be directly related with the extent of glycation. After in vitro glycation, the unchanged Mb and glycated myoglobin (GMb) were separated by ion exchange (BioRex 70) chromatography, which eliminated free iron from the protein fractions. Separated fractions of Mb and GMb were converted to their oxy forms -MbO₂ and GMbO₂, respectively. H₂O₂-induced iron release was significantly higher from GMbO₂ than that from MbO₂. This free iron, acting as a Fenton reagent, might produce free radicals and degrade different cell constituents. To verify this possibility, degradation of different cell constituents catalyzed by these fractions in the presence of H₂O₂ was studied. GMbO₂ degraded arachidonic acid, deoxyribose and plasmid DNA more efficiently than MbO₂. Arachidonic acid peroxidation and deoxyribose degradation were significantly inhibited by desferrioxamine (DFO), mannitol and catalase. However, besides free iron-mediated free radical reactions, role of iron of higher oxidation states, formed during interaction of H₂O₂ with myoglobin might also be involved in oxidative degradation processes. Formation of carbonyl content, an index of oxidative stress, was higher by GMbO₂. Compared to MbO₂, GMbO₂ was rapidly auto-oxidized and co-oxidized with nitroblue tetrazolium, indicating increased rate of Mb and superoxide radical formation in GMbO₂. GMb exhibited more peroxidase activity than Mb, which was positively correlated with ferrylmyoglobin formation in the presence of H₂O₂. These findings correlate glycation-induced modification of myoglobin and a mechanism of increased formation of free radicals. Although myoglobin glycation is not significant within muscle cells, free myoglobin in circulation, if becomes glycated, may pose a serious threat by eliciting oxidative stress, particularly in diabetic patients.     

Calcium microdomains and oxidative stress

The phenomenon of calcium microdomains is firmly established in the field of subcellular physiology. These regions of localized, transient calcium increase are exemplified by the spontaneous 'sparks' released through the ryanodine receptor in myocytes, but include subplasmalemmal microdomains, focal calcium oscillations and microdomains enclosed within organelles, such as the endoplasmic reticulum, golgi and mitochondria. Increasing evidence suggests that oxidative stress regulates both the formation and disappearance of microdomains. Calcium release channels and transporters are all modulated by redox state, while several mechanisms that generate oxidative or nitrosative stress are regulated by calcium. Here, we discuss the evidence for the regulation of calcium microdomains by redox state, and, by way of example, demonstrate that the frequency of calcium sparks in cardiomyocytes is increased in response to oxidative stress. We consider the evidence for the existence of analogous microdomains of reactive oxygen and nitrogen species and suggest that the refinement of imaging techniques for these species might lead to similar concepts. The interaction between Ca(2+) microdomains and proteins that modulate their formation results in a complex and dynamic, spatial signaling mechanism, which is likely to be broadly applicable to different cell types, adding new dimensions to the calcium signaling 'toolkit'.     

Phorate triggers oxidative stress and mitochondrial dysfunction to enhance micronuclei generation and DNA damage in human lymphocytes

Herein, we studied phorate for its toxicological effects in human lymphocytes. Phorate treatment for 3 h has induced significant increase in the lymphocytic DNA damage. Compared to control, comet data from highest concentration of phorate (1000 µM) showed 8.03-fold increase in the Olive tail moment (OTM). Cytokinesis blocked micronucleus (CBMN) assay revealed 6.4-fold increase in binucleated micronucleated (BNMN) cells following the exposure with phorate (200 µM) for 24 h. The nuclear division index (NDI) in phorate (200 µM) treated cells reduced to 1.8 vis-à-vis control cells showed NDI of 1.94. Comparative to untreated control, 60.43% greater DCF fluorescence was quantitated in lymphocytes treated with phorate (500 µM), affirming reactive oxygen species (ROS) generation and oxidative stress. Flow cytometric data of phorate (200 µM) treated lymphocytes showed 81.77% decline in the fluorescence of rhodamine 123 (Rh123) dye, confirming the perturbation of mitochondrial membrane potential (ΔΨm). Calf thymus DNA (ct-DNA) treated with phorate (1000 µM) exhibited 2.3-fold higher 8-Hydroxy-2′-deoxyguanosine (8-oxodG) DNA adduct formation, signified the oxidative DNA damage. The alkaline unwinding assay revealed 4.0 and 6.5 ct-DNA strand breaks when treated to phorate and phorate-Cu (II) complex. Overall, the data unequivocally suggests the cyto- and genotoxic potential of phorate in human lymphocytes, which may induce comparable toxicological consequences in persons occupationally or non-occupationally exposed to insecticide phorate.     

Enhanced Nox1 expression and oxidative stress resistance in c-kit-positive hematopoietic stem/progenitor cells

Although stem cells are generally thought to be resistant to oxidative stress, the fact and in detail molecular mechanism are still to be clearly identified. We herein tried to understand the overall characterization of redox regulatory signaling in hematopoietic stem cells. We purified c-kit-positive hematopoietic stem/progenitor cells from the bone marrow of healthy mice, and then evaluated their redox regulatory property. Compared to the c-kit-negative matured mononuclear cells, c-kit-positive stem/progenitor cells showed lower basic levels of intracellular reactive oxygen species, faster clearance of the accumulated intracellular reactive oxygen species, and higher resistant to oxidative stress. An overall view on the gene expression profile associated with redox regulation showed to be widely differed between cell types. We confirmed that the c-kit-positive stem/progenitor cells expressed significantly higher of Nox1 and catalase, but less of lactoperoxidase than these matured mononuclear cells. Our data suggests that stem cells keep specific redox regulatory property for defensing against oxidative stress.     

大肠埃希菌中DPS对氧应激的抵抗

DPS是一种广泛存在于原核生物中的DNA结合蛋白,它能够在细菌乏营养等多种应激状态下为细菌提供保护。大肠埃希菌DPS已经被深入研究。本文从蛋白结构和铁隔离、DNA结合,铁氧化酶活性,调节基因表达四个方面介绍大肠埃希菌DPS的基本特性和作用机制。     

Peroxisomes, oxidative stress, and inflammation

Peroxisomes are intracellular organelles mediating a wide variety of biosynthetic and biodegradative reactions.Included among these are the metabolism of hydrogen peroxide and other reactive species,molecules whose levels help define the oxidative state of cells.Loss of oxidative equilibrium in cells of tissues and organs potentiates inflammatory responses which can ultimately trigger human disease.The goal of this article is to review evidence for connections between peroxisome function,oxidative stress,and inflammation in the context of human health and degenerative disease.Dysregulated points in this nexus are identified and potential remedial approaches are presented.     

Hyperglycemia-induced oxidative stress in diabetic complications

Reactive oxygen species are increased by hyperglycemia. Hyperglycemia, which occurs during diabetes (both type 1 and type 2) and, to a lesser extent, during insulin resistance, causes oxidative stress. Free fatty acids, which may be elevated during inadequate glycemic control, may also be contributory. In this review, we will discuss the role of oxidative stress in diabetic complications. Oxidative stress may be important in diabetes, not just because of its role in the development of complications, but because persistent hyperglycemia, secondary to insulin resistance, may induce oxidative stress and contribute to beta cell destruction in type 2 diabetes. The focus of this review will be on the role of oxidative stress in the etiology of diabetic complications.     

Pharmacological consequences of oxidative stress in ocular tissues

The eye is a unique organ because of its constant exposure to radiation, atmospheric oxygen, environmental chemicals and physical abrasion. That oxidative stress mechanisms in ocular tissues have been hypothesized to play a role in diseases such as glaucoma, cataract, uveitis, retrolental fibroplasias, age-related macular degeneration and various forms of retinopathy provides an opportunity for new approaches to their prevention and treatment, In the anterior uvea, both H₂O₂ and synthetic peroxides exert pharmacological/toxicological actions tissues of the anterior uvea especially on the sympathetic nerves and smooth muscles of the iris–ciliary bodies of several mammalian species. Effects produced by peroxides require the presence of trace amounts of extracellular calcium and the functional integrity of mitochondrial calcium stores. Arachidonic acid metabolites appear to be involved in both the excitatory action of peroxides on sympathetic neurotransmission and their inhibitory effect on contractility of the iris smooth muscle to muscarinic receptor activation. In addition to the peroxides, isoprostanes (products of free radical catalyzed peroxidation of arachidonic acid independent of the cyclo-oxygenase enzyme) can also alter sympathetic neurotransmission in anterior uveal tissues. In the retina, both H₂O₂ and synthetic peroxides produced an inhibitory action on potassium depolarization induced release of [³H] d-aspartate, in vitro and on the endogenous glutamate and glycine concentrations in vivo. Effects caused by peroxides in the retina are mediated, at least in part, by second messengers such as nitric oxide, prostaglandins and isoprostanes. The ability of H₂O₂ to alter the integrity of neurotransmitter pools from sympathetic nerves in the anterior uvea and glutaminergic nerves in the retina could underlie its role in the etiology of glaucoma.     

Nicotine-induced memory impairment by increasing brain oxidative stress

Male Wistar rats were subjected to chronic nicotine treatment (0.3 mg/kg; 7 continuous days) and their memory performance was studied by means of Y-maze and multi-trial passive avoidance tasks. Nicotine significantly decreased spontaneous alternation in Y-maze task and step-through-latency in the multi-trial passive avoidance task, suggesting effects on both short-term memory and long-term memory, respectively. In addition, nicotine induced neuronal apoptosis, DNA fragmentation, reduced antioxidant enzymes activity, and increased production of lipid peroxidation and reactive oxygen species, suggesting pro-oxidant activity. Our results provide further support that nicotine-induced memory impairment is due to an increase in brain oxidative stress in rats.     

Commentary: oxidative stress reconsidered

All definitions of the terms ‘oxidative stress’ and ‘antioxidants’ implicate that oxidants are just damaging. However, there is increasing evidence that reactive oxygen species (ROS) are not only toxic but that we need them for healthy life. This change in paradigm has been discussed at the third international symposium on ‘Nutrition, oxygen biology and medicine—micronutrients, exercise, energy and aging disorders’, of the Society for Free Radical Research France and the Oxygen Club of California on April 8–10, 2009 in Paris. The beneficial effect of a low to moderate concentration of oxidants produced during exercise was taken as most discussed example. In this case, ROS are required for normal force production in skeletal muscle, for the development of training-induced adaptation in endurance performance, as well as for the induction of endogenous defense systems. Taking antioxidants during training prevents adaptation. Although substantial progress on the understanding of the physiological functions of ROS was communicated at the meeting, it remained obvious that a lot of work is needed to fully understand the conditions and individual situations under which ROS are beneficial or detrimental.     

The oxidative stress response in Bacillus subtilis

Abstract Bacillus subtilis undergoes a typical bacterial stress response when exposed to low concentrations (0.1 mM) of hydrogen peroxide. Protection is thereby induced against otherwise lethal, challenge concentrations (10 mM) of this oxidant and a number of proteins are induced including the scavenging enzymes, catalase and alkyl hydroperoxide reductase, and a putative DNA binding and protecting protein. Induced protection against higher concentrations (10–30 mM) of hydrogen peroxide is eliminated in a catalase-deficient mutant. Both RecA and Spo0A influence the basal but not the induced resistance to hydrogen peroxide. A regulatory mutation has been characterized that affects the inducible phenotype and is constitutively resistant to high concentrations of hydrogen peroxide. This mutant constitutively overexpresses the proteins induced by hydrogen peroxide in the wild-type. The resistance of spores to hydrogen peroxide is partly attributable to binding of small acid soluble proteins by the spore DNA and partly to a second step which coincides with the depletion of the NADH pool, which may inhibit the generation of hydroxyl radicals from hydrogen peroxide.     

Down regulation of DJ-1 enhances cell death by oxidative stress, ER stress, and proteasome inhibition

Mutations in DJ-1 gene have been linked to autosomal recessive early onset parkinsonism (AR-EOP). Although the mechanism of neuronal cell death due to DJ-1 mutation has not been fully elucidated, loss of DJ-1 function was considered to cause the phenotype. Here, we demonstrated that the down regulation of endogenous DJ-1 of the neuronal cell line by siRNA enhanced the cell death which was induced by oxidative stress, ER stress, and proteasome inhibition, but not by pro-apoptotic stimulus. The cell death with hydrogen peroxide was dramatically rescued by over-expression of wild-type DJ-1, but not by that of L166P mutant DJ-1. Furthermore, DJ-1 rescued the cell death caused by over-expression of Pael receptor, which was a substrate of Parkin, another gene product for autosomal recessive juvenile parkinsonism. These results suggest that loss of protective activity of DJ-1 from neuro-toxicity induced by these stresses contributes to neuronal cell death in AR-EOP with mutant DJ-1.     

Piceatannol markedly upregulates heme oxygenase-1 expression and alleviates oxidative stress in skeletal muscle cells

Piceatannol (PIC), a phytochemical, is abundant in passion fruit (Passiflora edulis) seeds. In this study, we investigated the effects of PIC on the expression levels of antioxidant enzymes in C2C12 skeletal muscle cells and compared its effects with those of PIC analogues and polyphenols. We also evaluated its effects on hydrogen peroxide–induced accumulation of reactive oxygen species in C2C12 myotubes. Treatment with PIC led to dose-dependent upregulation of heme oxygenase-1 (Ho-1) and superoxide dismutase 1 (Sod1) mRNA expression in C2C12 myotubes. PIC was the most potent inducer of Ho-1 among the PIC analogues and major polyphenols tested. In addition, treatment with PIC suppressed the hydrogen peroxide–induced increase in intracellular reactive oxygen species levels. Our results suggest that PIC protects skeletal muscles from oxidative stress by activating antioxidant enzymes such as HO-1 and SOD1 and can therefore help prevent oxidative stress–induced muscle dysfunction such as muscle fatigue and sarcopenia.     

Mitochondria,oxidative stress and cell death

In addition to the well-established role of the mitochondria in energy metabolism, regulation of cell death has recently emerged as a second major function of these organelles. This, in turn, seems to be intimately linked to their role as the major intracellular source of reactive oxygen species (ROS), which are mainly generated at Complex I and III of the respiratory chain. Excessive ROS production can lead to oxidation of macromolecules and has been implicated in mtDNA mutations, ageing, and cell death. Mitochondria-generated ROS play an important role in the release of cytochrome c and other pro-apoptotic proteins, which can trigger caspase activation and apoptosis. Cytochrome c release occurs by a two-step process that is initiated by the dissociation of the hemoprotein from its binding to cardiolipin, which anchors it to the inner mitochondrial membrane. Oxidation of cardiolipin reduces cytochrome c binding and results in an increased level of “free” cytochrome c in the intermembrane space. Conversely, mitochondrial antioxidant enzymes protect from apoptosis. Hence, there is accumulating evidence supporting a direct link between mitochondria, oxidative stress and cell death.     

Environmental stress increases skeletal fluctuating asymmetry in the moor frog Rana arvalis

Whether fluctuating asymmetry (FA) provides a useful metric indicator of the degree of environmental stress experienced by populations is still a contentious issue. We investigated whether the degree of FA in skeletal elements is useful in elucidating the degree of environmental stress experienced by frog populations, and further, tested the proposition that a trait’s sensitivity to stress—as reflected in the degree of FA—is related to the degree of directional selection experienced by the given trait. We compared the degree of FA in four bilateral skeletal elements of male and female moor frogs (Rana arvalis) originating from low (acidified) and neutral pH populations. While the degree of uncorrected FA was unrelated to the degree of acidity, the growth rate and age of the individuals, the size-corrected FA was significantly higher in low than in neutral pH populations and decreased with individual ages and growth rates. In addition, both measures of FA were significantly higher in males and in particular in traits presumably under high sexual selection as indicated by the degree of sexual size dimorphism. All in all, the results indicate that individuals from acidified localities are smaller, younger and exhibit a significantly higher degree of FA than individuals from neutral pH populations. These results constitute the first assessment of FA in amphibians and suggest that the degree of FA in skeletal traits can be a useful indicator of the degree of environmental stress experienced by amphibian populations.     

Role of oxidative stress in epileptic seizures

Oxidative stress resulting from excessive free-radical release is likely implicated in the initiation and progression of epilepsy. Therefore, antioxidant therapies aimed at reducing oxidative stress have received considerable attention in epilepsy treatment. However, much evidence suggests that oxidative stress does not always have the same pattern in all seizures models. Thus, this review provides an overview aimed at achieving a better understanding of this issue. We summarize work regarding seizure models (i.e., genetic rat models, kainic acid, pilocarpine, pentylenetetrazol, and trimethyltin), oxidative stress as an etiologic factor in epileptic seizures (i.e., impairment of antioxidant systems, mitochondrial dysfunction, involvement of redox-active metals, arachidonic acid pathway activation, and aging), and antioxidant strategies for seizure treatment. Combined, this review highlights pharmacological mechanisms associated with oxidative stress in epileptic seizures and the potential for neuroprotection in epilepsy that targets oxidative stress and is supported by effective antioxidant treatment.     

Both oxidative and nitrosative stress are associated with muscle wasting in tumour-bearing rats

Reactive oxygen and nitrogen species (ROS and RNS) have been proposed as mechanisms of cancer-induced cachexia. In this study, we assessed using Western blot analysis the levels of total protein carbonylation (2,4-dinitrophenylhydrazine assay), both malondialdehyde- (MDA-) and 2-hydroxy-4-nonenal- (HNE-) protein adducts, Mn-superoxide dismutase (Mn-SOD), catalase, heme oxygenase-1 (HO-1) and 3-nitrotyrosine formation in gastrocnemius muscles of rats bearing the Yoshida AH-130 hepatoma. In the muscles of the tumour-bearing animals, protein carbonylation as measured by total levels of carbonyl group formation and both HNE and MDA-protein adducts, and protein tyrosine nitration were significantly greater than in control muscles. Protein levels of the antioxidant enzymes Mn-SOD, catalase, and HO-1 were not significantly modified in the rat cachectic muscles compared to controls. The inefficiency of the antioxidant enzymes in neutralizing excessive ROS production may account for elevated markers of protein oxidation and be responsible for the development of both oxidative and nitrosative stress in cancer-induced cachexia.     

Role of oxidative stress in experimental sepsis and multisystem organ dysfunction

Massive increase in radical species can lead to oxidative stress, promoting cell injury and death. This review focuses on experimental evidence of oxidative stress in critical illnesses, sepsis and multisystem organ dysfunction. Oxidative stress could negatively affect organ injury and thus overall survival of experimental models. Based on this experimental evidence, we could improve the rationale of supplementation of antioxidants alone or in combination with standard therapies aimed to reduce oxidative stress as novel adjunct treatment in critical care.