The oxidant/antioxidant network: role of melatonin

Melatonin is now known to be a multifaceted free radical scavenger and antioxidant. It detoxifies a variety of free radicals and reactive oxygen intermediates including the hydroxyl radical, peroxynitrite anion, singlet oxygen and nitric oxide. Additionally, it reportedly stimulates several antioxidative enzymes including glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and superoxide dismutase; conversely, it inhibits a prooxidative enzyme, nitric oxide synthase. Melatonin also crosses all morphophysiological barriers, e.g., the blood-brain barrier, placenta, and distributes throughout the cell; these features increase the efficacy of melatonin as an antioxidant. Melatonin has been shown to markedly protect both membrane lipids and nuclear DNA from oxidative damage. In every experimental model in which melatonin has been tested, it has been found to resist macromolecular damage and the associated dysfunction associated with free radicals.     

冬小麦旗叶旱促衰老过程中氧化伤害与抗氧化系统的尖

研究了土壤缓慢干旱胁迫下抗旱性不同的２个冬小麦品种旗叶老过程中氧化丰以及酶促与硕果发现,在抗旱性强的品种中,冬泪科叶片旱个衰老与膜脂过氧化程度之间并无直接的联系。超氧化物歧化酶（ＳＯＤ）活性在不同抗旱性品种中均呈现持志下降的趋势,但在生强的品种中下降幅度较小,过氧化氢酶（ＣＡＴ）活性在胁迫初期基本不变,至中后期明显下降,且在抗旱性弱的品种中下降幅度较大,抗坏血酸过氧化物酶（ＡＰ）和谷胱甘肽还原酶（     

Cardiac mitochondrial damage and loss of ROS defense after burn injury: the beneficial effects of antioxidant therapy.

Mechanisms of burn-related cardiac dysfunction may involve defects in mitochondria. This study determined 1) whether burn injury alters myocardial mitochondrial integrity and function; and 2) whether an antioxidant vitamin therapy prevented changes in cardiac mitochondrial function after burn. Sprague-Dawley rats were given a 3 degrees burn over 40% total body surface area and fluid resuscitated. Antioxidant vitamins or vehicle were given to sham and burn rats. Mitochondrial and cytosolic fractions were prepared from heart tissues at several times postburn. In mitochondria, lipid peroxidation was measured to assess oxidative stress, mitochondrial outer membrane damage and cytochrome-c translocation were determined to estimate mitochondrial integrity, and activities of SOD and glutathione peroxidase were examined to evaluate mitochondrial antioxidant defense. Cardiac function was measured by Langendorff model in sham and burn rats given either vitamins or vehicle. Twenty-four hours postburn, mitochondrial outer membrane damage was progressively increased to approximately 50%, and cytosolic cytochrome-c gradually accumulated to approximately three times more than that measured in shams, indicating impaired mitochondrial integrity. Maximal decrease of mitochondrial SOD activity occurred 8 h postburn ( approximately 63.5% of shams), whereas maximal decrease in glutathione peroxidase activity persisted 2-24 h postburn ( approximately 60% of shams). In burn animals, lipid peroxidation in cardiac mitochondria increased 30-50%, suggesting burn-induced oxidative stress. Antioxidant vitamin therapy prevented burn-related loss of membrane integrity and antioxidant defense in myocardial mitochondria and prevented cardiac dysfunction. These data suggest that burn-mediated mitochondrial dysfunction and loss of reactive oxygen species defense may play a role in postburn cardiac dysfunction.     

Oxidative damage and antioxidant defense system in leaves of Vicia faba major L. cv. Bartom during soil flooding and subsequent drainage

The adaptive reactions of Vicia faba major L. cv. Bartom to 13-27 days soil flooding and to 14 days of drainage following 13-days of soil flooding were studied. Under flooding, oxygen diffusion rate (ODR) in the root zone decreased from 2.28–3.44 to 0.09–0.28?µmol O₂ m^?2 s^?1; the soil redox potential (Eh) decreased from 543 to 70 mV. Upon drainage of flooded soil the ODR and Eh values returned to the control levels. Oxidative damage and defense systems in leaves were assessed by the concentration of thiobarbituric acid reactive substances (TBARs) and by the activities of superoxide dismutase (SOD) and glutathione reductase (GR). Two stages of stress development are described. During the first stage (1–13 days) shoot dry mass did not decrease, the TBARs concentration and SOD activity increased, the GR activity decreased. The second stage (13–27 days) was characterized by a decrease in the TBARs concentration, SOD and GR activities, pigment concentrations and shoot dry mass. Drainage of flooded soil resulted in elevated concentrations of TBARs and also increased the activities of SOD and GR. Increased SOD activity in the first stage of hypoxic stress development and activations of SOD and GR at oxygen re-entry to soil are responsible for tolerance of Vicia faba to hypoxic and post hypoxic stress associated with soil flooding and subsequent drainage.     

Mechanism underlying the antioxidant activity of taurine: prevention of mitochondrial oxidant production

An important function of the β-amino acid, taurine, is the regulation of oxidative stress. However, taurine is neither a classical scavenger nor a regulator of the antioxidative defenses, leaving uncertain the mechanism underlying the antioxidant activity of taurine. In the present study, the taurine antagonist and taurine transport inhibitor, β-alanine, was used to examine the mechanism underlying the antioxidant activity of taurine. Exposure of isolated cardiomyocytes to medium containing β-alanine for a period of 48?h led to a 45% decrease in taurine content and an increase in mitochondrial oxidative stress, as evidenced by enhanced superoxide generation, the inactivation of the oxidant sensitive enzyme, aconitase, and the oxidation of glutathione. Associated with the increase in oxidative stress was a decline in electron transport activity, with the activities of respiratory chain complexes I and III declining 50–65% and oxygen consumption falling 30%. A reduction in respiratory chain activity coupled with an increase in oxidative stress is commonly caused by the development of a bottleneck in electron transport that leads to the diversion of electrons from the respiratory chain to the acceptor oxygen forming in the process superoxide. Because β-alanine exposure significantly reduces the levels of respiratory chain complex subunits, ND5 and ND6, the bottleneck in electron transport appears to be caused by impaired synthesis of key subunits of the electron transport chain complexes. Co-administration of taurine with β-alanine largely prevents the mitochondrial effects of β-alanine, but treatment of the cells with 5?mM taurine in the absence of β-alanine has no effect on the mitochondria, likely because taurine treatment has little effect on cellular taurine levels. Thus, taurine serves as a regulator of mitochondrial protein synthesis, thereby enhancing electron transport chain activity and protecting the mitochondria against excessive superoxide generation.     

Iron release and oxidant damage in human myoblasts by divicine

Divicine is an aglycone derived from vicine, a glucosidic compound contained in fava beans (Vicia faba major or broad beans). In this study, we investigated the effect of divicine on cultured human myoblasts from normal subjects, in order to see if the drug may induce signs of oxidant stress in these cells. Myoblasts incubated 24 hours in the presence of 1 mM divicine, showed an increase of carbonyl groups and 4-hydroxynonenal (4-HNE) bound to cell proteins, as well as a significant release of iron and lactate dehydrogenase in the culture medium. Desferrioxamine (DFO), an iron chelator, significantly prevented protein oxidation and formation 4-HNE adducts. Our results can be interpreted as indicating that divicine autooxidizes both at extracellular level and into myoblasts thus inducing the release of free iron, which initiates oxidation of cellular proteins and lipids. DFO protects the cells by subtracting the free iron both at intracellular and extracellular level.     

Oxidative damage and antioxidant enzyme activities in experimental hypothyroidism

Free radicals are now well known to damage cellular components. To investigate whether age and thyroid level affect peroxidation speed, we examined the levels of malondialdehyde and antioxidant enzyme activities in different age groups of hypothyroid rats. Hypothyroidism was induced in 30- and 60-day-old Wistar Albino rats by the i.p. administration of propylthiouracil (10 mg kg(-1) body weight) for 15 days. While malondialdehyde levels of 30- or 60-day-old hypothyroid rats were increased in liver, they were decreased in the tissues of the heart and thyroid. While glucose-6-phosphate dehydrogenase activity levels did not change in heart, brain and liver tissues of 30-day-old rats, they increased in brain and heart tissues of 60-day-old experimental groups, but decreased in the liver. Catalase activities decreased in the liver and heart of rats with hypothyroidism, but increased in erythrocytes. In control groups while malondialdehyde levels increased in brain, heart and thymus with regard to age, they decreased in plasma. Glucose-6-phosphate dehydrogenase and catalase activities were not affected by age in tissues of the thymus, thyroid and brain, but they were decreased in the heart tissue. The changes in the levels of lipid peroxidation and antioxidant enzyme activities which were determined in different tissues of hypothyroid rats indicate a cause for functional disorder of these tissues. Moreover, there may be changes depending on age at lipid peroxidation and antioxidant enzyme activity levels.     

Oxidative DNA damage processing in nuclear and mitochondrial DNA

Living organisms are constantly exposed to oxidative stress from environmental agents and from endogenous metabolic processes. The resulting oxidative modifications occur in proteins, lipids and DNA. Since proteins and lipids are readily degraded and resynthesized, the most significant consequence of the oxidative stress is thought to be the DNA modifications, which can become permanent via the formation of mutations and other types of genomic instability. Many different DNA base changes have been seen following some form of oxidative stress, and these lesions are widely considered as instigators for the development of cancer and are also implicated in the process of aging. Several studies have documented that oxidative DNA lesions accumulate with aging, and it appears that the major site of this accumulation is mitochondrial DNA rather than nuclear DNA. The DNA repair mechanisms involved in the removal of oxidative DNA lesions are much more complex than previously considered. They involve base excision repair (BER) pathways and nucleotide excision repair (NER) pathways, and there is currently a great deal of interest in clarification of the pathways and their interactions. We have used a number of different approaches to explore the mechanism of the repair processes, to examine the repair of different types of oxidative lesions and to measure different steps of the repair processes. Furthermore, we can measure the DNA damage processing in the nuclear DNA and separately, in the mitochondrial DNA. Contrary to widely held notions, mitochondria have efficient DNA repair of oxidative DNA damage.     

Oxidative stress during exercise: Implication of antioxidant nutrients

Research evidence has accumulated in the past decade that strenuous aerobic exercise is associated with oxidative stress and tissue damage in the body. There is indication that generation of oxygen free radicals and other reactive oxygen species may be the underlying mechanism for exercise-induced oxidative damage, but a causal relationship remains to be established. Enzymatic and nonenzymatic antioxidants play a vital role in protecting tissues from excessive oxidative damage during exercise. Depletion of each of the antioxidant systems increases the vulnerability of various tissues and cellular components to reactive oxygen species. Because acute strenuous exercise and chronic exercise training increase the consumption of various antioxidants, it is conceivable that dietary supplementation of specific antioxidants would be beneficial.     

Complementary antioxidant defense by cytoplasmic and mitochondrial peroxiredoxins in Leishmania infantum

In Kinetoplastida 2-Cys peroxiredoxins are the ultimate members of unique enzymatic cascades for detoxification of peroxides, which are dependent on trypanothione, a small thiol specific to these organisms. Here we report on two distinct Leishmania infantum peroxiredoxins, LicTXNPx and LimTXNPx, that may be involved in such a pathway. LicTXNPx, found in the cytoplasm, is a typical 2-Cys peroxiredoxin encoded by LicTXNPx, a member of a multicopy gene family. LimTXNPx, encoded by a single copy gene, LimTXNPx, is confined to the mitochondrion and is unusual in possessing an Ile-Pro-Cys motif in the distal redox center, replacing the common peroxiredoxin Val-Cys-Pro sequence, apart from an N-terminal mitochondrial leader sequence. Based on sequence and subcellular localization, the peroxiredoxins of Kinetoplastida can be separated in two distinct subfamilies. As an approach to investigate the function of both peroxiredoxins in the cell, L. infantum promastigotes overexpressing LicTXNPx and LimTXNPx were assayed for their resistance to H(2)O(2) and tert-butyl hydroperoxide. The results show evidence that both enzymes are active as peroxidases in vivo and that they have complementary roles in parasite protection against oxidative stress.     

Potential role of oxidized lipids and lipoproteins in antioxidant defense

The atherogenic oxidative modification of low-density lipoprotein is suggested to occur in the aortic intima. There is reasonable evidence to suggest that antioxidants might be beneficial in preventing or retarding the progression of atherosclerosis. Exercise, estrogens, and substitution of polyunsaturated fat for saturated fat are beneficial in the prevention of atherosclerosis. Yet, paradoxically, they are capable of inducing an oxidative stress. To reconcile with this paradox, we postulate that under certain conditions an oxidative stress might be beneficial by inducing antioxidant enzymes in arterial cells. However, those with genetic deficiency in antioxidant enzymes or those who poorly respond to oxidative stress or those with overwhelming plasma oxidative stress might need additional antioxidant protection.     

Oxidative stress and antioxidant defense responses of Etroplus suratensis to acute temperature fluctuations

Fishes are always exposed to various environmental stresses and the chances of succumbing to such stresses are of great physiological concern. Any change in temperature from the ambient condition can induce various metabolic and physiological changes in the body. The present study evaluates the effects of temperature induced stress on the antioxidant profile of Etroplus suratensis such as superoxide dismutase, catalase, glutathione peroxidase and lipid peroxidation. Fishes of same size were kept in a thermostatized bath at three different temperature regimes viz 16 °C, 27 °C (ambient temperature) and 38 °C for 72 h. These temperatures were selected based on the CT Max (Critical Thermal Maximum) and CT Min (Critical Thermal Minimum) exhibited by E. suratensis. Superoxide dismutase and catalase activity was found maximum in brain and muscle respectively during the 48th hour of exposure in fishes kept at 38 °C. At 16 °C the antioxidant response of glutathione peroxidase was maximum in muscles, whereas the lipid peroxidation rate was found to be high in gills compared to other tissues. The profound increase in the levels of oxidative stress related biomarkers indicate that the thermal stressors severely affected oxidative state of E. suratensis by the second day of experiment. Such down-regulation of redox state accompanied with the induction of oxidative stress cascade may lead to physiological damage in various tissues in fishes, in vivo. However current data indicate that a transition to low and high temperature environment from ambient condition severely affected the levels and profile of the antioxidant markers overtime in E. suratensis.     

Oxidative burden and antioxidant defense system in polymorphonuclear leukocytes of human lung diseases

Superoxide anion (O2.-) and hydrogen peroxide (H2O2) production was significantly higher in blood neutrophils (PMNs) of patients with lung cancer and non-malignant lung diseases when compared to the controls (p<0.001). Superoxide dismutase (SOD) activity was significantly decreased in PMNs of patients with lung cancer (p<0.001). Similarly, catalase and glutathione peroxidase (GPx) activities were lower in PMNs of lung cancer patients as compared to non-malignant lung diseases and controls. There was an increase in HMP shunt activity as measured by rate of formation of 14CO2 from [1-14C]-glucose in PMNs of lung cancer patients. Modifications in the antioxidant defense system in PMNs of malignant and nonmalignant lung diseases, the changes being more in the malignancy are indicated.     

Potential role of oxidized lipids and lipoproteins in antioxidant defense

The atherogenic oxidative modification of low-density lipoprotein is suggested to occur in the aortic intima. There is reasonable evidence to suggest that antioxidants might be beneficial in preventing or retarding the progression of atherosclerosis. Exercise, estrogens, and substitution of polyunsaturated fat for saturated fat are beneficial in the prevention of atherosclerosis. Yet, paradoxically, they are capable of inducing an oxidative stress. To reconcile with this paradox, we postulate that under certain conditions an oxidative stress might be beneficial by inducing antioxidant enzymes in arterial cells. However, those with genetic deficiency in antioxidant enzymes or those who poorly respond to oxidative stress or those with overwhelming plasma oxidative stress might need additional antioxidant protection.     

Lysosomal enzymes promote mitochondrial oxidant production, cytochrome c release and apoptosis.

Exposure of mammalian cells to oxidant stress causes early (iron catalysed) lysosomal rupture followed by apoptosis or necrosis. Enhanced intracellular production of reactive oxygen species (ROS), presumably of mitochondrial origin, is also observed when cells are exposed to nonoxidant pro-apoptotic agonists of cell death. We hypothesized that ROS generation in this latter case might promote the apoptotic cascade and could arise from effects of released lysosomal materials on mitochondria. Indeed, in intact cells (J774 macrophages, HeLa cells and AG1518 fibroblasts) the lysosomotropic detergent O-methyl-serine dodecylamide hydrochloride (MSDH) causes lysosomal rupture, enhanced intracellular ROS production, and apoptosis. Furthermore, in mixtures of rat liver lysosomes and mitochondria, selective rupture of lysosomes by MSDH promotes mitochondrial ROS production and cytochrome c release, whereas MSDH has no direct effect on ROS generation by purifed mitochondria. Intracellular lysosomal rupture is associated with the release of (among other constituents) cathepsins and activation of phospholipase A2 (PLA2). We find that addition of purified cathepsins B or D, or of PLA2, causes substantial increases in ROS generation by purified mitochondria. Furthermore, PLA2 - but not cathepsins B or D - causes rupture of semipurified lysosomes, suggesting an amplification mechanism. Thus, initiation of the apoptotic cascade by nonoxidant agonists may involve early release of lysosomal constituents (such as cathepsins B and D) and activation of PLA2, leading to enhanced mitochondrial oxidant production, further lysosomal rupture and, finally, mitochondrial cytochrome c release. Nonoxidant agonists of apoptosis may, thus, act through oxidant mechanisms.     

Influence of lung oxidant and antioxidant status on alveolarization: role of light-exposed total parenteral nutrition

Parenteral multivitamins (MVP) are linked to the generation of peroxides, which cause oxidant injury in lungs associated with alveolar remodelling linked to lung disease of prematurity. This study was to investigate the relationship between alveolar development and lung oxidant-antioxidant status as modulated by the mode of administration of multivitamins with total parenteral nutrition (TPN). Four groups of guinea pig pups received parenteral nutrition differing by 1) mode of MVP admixture: with amino acid solution (AA-MVP) or lipid emulsion (LIP-MVP); 2) light exposure: TPN exposed (LE) or shielded from light (LP). After 2 or 4 days of TPN, vitamins C and E, 8-isoprostaneF(2alpha) and alveolarization index were determined in lungs and GSSG/GSH in lungs and blood. Exposure to light and the mode of MVP admixture did not influence vitamin E and isoprostane levels. Blood glutathione redox potential was more oxidized in LE and LIP-MVP groups after 4-day infusions, whereas lung redox potential was more reduced in LE groups. LP and LIP-MVP had a beneficial effect, with higher number of alveoli. Globally, results indicate that in this model, alveolarization and modifications in lung redox potential are two independent events induced by light exposed TPN.     

Upregulation of mitochondrial function and antioxidant defense in the differentiation of stem cells

Stem cell research has received increasing attention due to their invaluable potentials in the clinical applications to cure degenerative diseases, genetic disorders and even cancers. A great number of studies have been conducted with an aim to elucidate the molecular mechanisms involved in the regulation of self-renewal of stem cells and the mysterious circuits guiding them to differentiate into all kinds of progenies that can replenish the cell pools. However, little effort has been made in studying the metabolic aspects of stem cells. Mitochondria play essential roles in mammalian cells in the generation of ATP, Ca²⁺ homeostasis, compartmentalization of biosynthetic pathways and execution of apoptosis. Considering the metabolic roles of mitochondria, they must be also critical in stem cells. This review is primarily focused on the biogenesis and bioenergetic function of mitochondria in the differentiation process and metabolic features of stem cells. In addition, the involvement of reactive oxygen species and hypoxic signals in the regulation of stem cell pluripotency and differentiation is also discussed.     

Effect of TiO2 nanoparticles on oxidative damage and antioxidant defense systems in chickpea seedlings during cold stress

The effects of TiO₂ nanoparticles (NPs) on physiologo-biochemical responses were studied in two chickpea (Cicer arietimun L.) genotypes differing in cold sensitivity (tolerant Sel11439 and sensitive ILC533) during cold stress (CS). The results showed that hydrogen peroxide and MDA contents and electrolyte leakage index (ELI) increased under CS conditions in both genotypes and that these damage indices were higher in ILC533 than in Sel11439 plants. In plants treated with TiO₂ NPs, a decreased H₂O₂ level was accompanied by a decrease in the MDA content and ELI compared to control plants, and these changes occurred more effectively in Sel11439 than in ILC533 plants. The antioxidant enzymes were more effective in cell protection against CS in Sel11439 plants compared to ILC533 plants, as well as in plants treated with TiO₂ NPs compared to control plants. The lipoxygenase activity was induced efficiently only in Sel11439 plants treated with TiO₂ NPs during CS, probably indicating its role in stress response (which was confirmed by measuring allen oxide synthase activity). TiO₂ NPs caused stability of chlorophyll and carotenoid contents during CS. Results suggest that TiO₂ NPs confer an increased tolerance of chickpea plants to CS, decreasing the level of injuries and increasing the capacity of defense systems.