12/15-Lipoxygenase targets neuronal mitochondria under oxidative stress

12/15-Lipoxygenase (12/15-LOX) is an important mediator of brain injury following experimental stroke in rodents. It contributes to neuronal death, but the underlying mechanism remains unclear. We demonstrate here that in neuronal HT22 cells subjected to glutamate-induced oxidative stress, 12/15-LOX damages mitochondria, and this represents the committed step that condemns the cell to die. Importantly these events, including breakdown of the mitochondrial membrane potential, the production of reactive oxygen species, and cytochrome c release, can all be replicated by incubation of 12/15-LOX with mitochondria in vitro , without the need to add other cytosolic factors. Proteasome activity is required downstream of mitochondrial damage to complete the cell death cascade, but proteasome inhibition is only partially protective. These findings position 12/15-LOX as the central executioner in an oxidative stress-related neuronal death program.     

Mitochondrial dysfunction, oxidative stress, regulation of exocytosis and their relevance to neurodegenerative diseases

A common feature in the early stages of many neurodegenerative diseases lies in mitochondrial dysfunction, oxidative stress, and reduced levels of synaptic transmission. Many genes associated with neurodegenerative diseases are now known to regulate either mitochondrial function, redox state, or the exocytosis of neurotransmitters. Mitochondria are the primary source of reactive oxygen species and ATP and control apoptosis. Mitochondria are concentrated in synapses and significant alterations to synaptic mitochondrial localization, number, morphology, or function can be detrimental to synaptic transmission. Mitochondrial by-products are capable of regulating various steps of neurotransmission and mitochondrial dysfunction and oxidative stress occur in the early stages of many neurodegenerative diseases. This mini-review will highlight the prospect that mitochondria regulates synaptic exocytosis by controlling synaptic ATP and reactive oxygen species levels and that dysfunctional exocytosis caused by mitochondrial abnormalities may be a common underlying phenomenon in the initial stages of some human neurodegenerative diseases.     

Dietary restriction attenuates age-associated muscle atrophy by lowering oxidative stress in mice even in complete absence of CuZnSOD

Age-related loss of muscle mass and function, sarcopenia, has a major impact on the quality of life in the elderly. Among the proposed causes of sarcopenia are mitochondrial dysfunction and accumulated oxidative damage during aging. Dietary restriction (DR), a robust dietary intervention that extends lifespan and modulates age-related pathology in a variety of species, has been shown to protect from sarcopenia in rodents. Although the mechanism(s) by which DR modulates aging are still not defined, one potential mechanism is through modulation of oxidative stress and mitochondrial dysfunction. To directly test the protective effect of DR against oxidative stress-induced muscle atrophy in vivo, we subjected mice lacking a key antioxidant enzyme, CuZnSOD (Sod1) to DR (60% of ad libitum fed diet). We have previously shown that the Sod1(-/-) mice exhibit an acceleration of sarcopenia associated with high oxidative stress, mitochondrial dysfunction, and severe neuromuscular innervation defects. Despite the dramatic atrophy phenotype in the Sod1(-/-) mice, DR led to a reversal or attenuation of reduced muscle function, loss of innervation, and muscle atrophy in these mice. DR improves mitochondrial function as evidenced by enhanced Ca(2+) regulation and reduction of mitochondrial reactive oxygen species (ROS). Furthermore, we show upregulation of SIRT3 and MnSOD in DR animals, consistent with reduced mitochondrial oxidative stress and reduced oxidative damage in muscle tissue measured as F(2) -isoprostanes. Collectively, our results demonstrate that DR is a powerful mediator of mitochondrial function, mitochondrial ROS production, and oxidative damage, providing a solid protection against oxidative stress-induced neuromuscular defects and muscle atrophy in vivo even under conditions of high oxidative stress.     

The daily rhythms of mitochondrial gene expression and oxidative stress regulation are altered by aging in the mouse liver

The circadian clock regulates many cellular processes, notably including the cell cycle, metabolism and aging. Mitochondria play essential roles in metabolism and are the major sites of reactive oxygen species (ROS) production in the cell. The clock regulates mitochondrial functions by driving daily changes in NAD⁺ levels and Sirt3 activity. In addition to this central route, in the present study, we find that the expression of some mitochondrial genes is also rhythmic in the liver, and that there rhythms are disrupted by the Clock^Δ19 mutation in young mice, suggesting that they are regulated by the core circadian oscillator. Related to this observation, we also find that the regulation of oxidative stress is rhythmic in the liver. Since mitochondria and ROS play important roles in aging, and mitochondrial functions are also disturbed by aging, these related observations prompt the compelling hypothesis that circadian oscillators influence aging by regulating ROS in mitochondria. During aging, the expression rhythms of some mitochondrial genes were altered in the liver and the temporal regulation over the dynamics of mitochondrial oxidative stress was disrupted. However, the expression of clock genes was not affected. Our results suggested that mitochondrial functions are combinatorially regulated by the clock and other age-dependent mechanism(s), and that aging disrupts mitochondrial rhythms through mechanisms downstream of the clock.     

Changes in the antigenic properties of proteins of laboratory mice during oxidative stress

Changes in the level of oxidative damage to proteins in CD1 outbred mice γ irradiated with a dose of 3 Gy have been studied. The changes were estimated from the amount of carbonyl groups (CG) in the proteins. It was found that two hours after exposure to γ radiation, the amount of CG in the cytoplasmic and nuclear fractions of the liver, heart, brain, and spleen sharply increased. Two months after irradiation, the level of CG in the cytoplasmic and nuclear subcellular fractions of the liver and brain decreased to the level of CG in the control animals, which were not exposed to radiation. In the subcellular fractions of the heart and spleen, the increase in the degree of damage was more significant and a high level of damage was observed even two months after irradiation. An enhancement of the antigenic properties of proteins from the liver, heart, and spleen in the postirradiation period was found. Spleen proteins were most immunogenic. A comparison of the antigenic properties of proteins isolated from the tissues 60 days after irradiation revealed a correlation between the level of oxidative damage and the immunogenicity of the total protein fraction.     

Nitric oxide pretreatment enhances antioxidant defense and glyoxalase systems to confer PEG-induced oxidative stress in rapeseed

Nitric oxide (NO) is dynamic molecule implicated in diverse biological functions demonstrating its protective effect against damages provoked by abiotic stresses. The present study investigated that exogenous NO pretreatment (500?µM sodium nitroprusside, 24?h) prevented the adverse effect of drought stress [induced by 10% and 20% polyethylene glycol (PEG), 48?h] on rapeseed seedlings. Drought stress resulted in reduced relative water content with increased proline (Pro) level. Drought stress insisted high H₂O₂ generation and consequently increased membrane lipid peroxidation which are clear indications of oxidative damage. Drought stress disrupted the glyoxalase system too. Exogenous NO successfully alleviated oxidative damage effects on rapeseed seedlings through improving the levels of nonenzymatic antioxidant pool and upregulating antioxidant enzymes’ activities. Improvement of glyoxalase system (glyoxalase I and glyoxalase II activities) by exogenous NO was significant to improve plants’ tolerance. Nonetheless, regulation of Pro level and improvement of plant–water status were vital to confer drought stress tolerance.     

Oxidative stress and enzymic-non-enzymic antioxidant responses in children with acute pneumonia

In this article, oxidative stress and enzymic-non-enzymic antioxidants status were investigated in children with acute pneumonia. Our study included 28 children with acute pneumonia and 29 control subjects. The age ranged from 2 to 11 years (4.57+/-2.13 years) and 2 to 12 years (4.89+/-2.22 years) in the study and control groups, respectively. Whole blood malondialdehyde (MDA) and reduced glutathione (GSH), serum beta-carotene, retinol, vitamin C, vitamin E, catalase (CAT), ceruloplasmin (CLP), total bilirubin, erythrocyte superoxide dismutase (SOD) and glutathione peroxidase (GPx) levels were studied in all subjects. There was a statistically significant difference between the groups for all parameters except for serum CAT. Whole blood MDA, serum CLP and total bilirubin levels were higher in the study group than those of the control group. However, SOD, GPx, beta-carotene, retinol, vitamin C, vitamin E and GSH levels were lower in the study group compared with the control group. All antioxidant vitamin activities were decreased in children with acute pneumonia. Our study demonstrated that oxidative stress was increased whereas enzymic and non-enzymic antioxidant activities were significantly decreased in children with acute pneumonia.     

Plant sugars are crucial players in the oxidative challenge during abiotic stress: extending the traditional concept

Plants suffering from abiotic stress are commonly facing an enhanced accumulation of reactive oxygen species (ROS) with damaging as well as signalling effects at organellar and cellular levels. The outcome of an environmental challenge highly depends on the delicate balance between ROS production and scavenging by both enzymatic and metabolic antioxidants. However, this traditional classification is in need of renewal and reform, as it is becoming increasingly clear that soluble sugars such as disaccharides, raffinose family oligosaccharides and fructans – next to their associated metabolic enzymes – are strongly related to stress‐induced ROS accumulation in plants. Therefore, this review aims at extending the current concept of antioxidants functioning during abiotic stress, with special focus on the emanate role of sugars as true ROS scavengers. Examples are given based on their cellular location, as different organelles seem to exploit distinct mechanisms. Moreover, the vacuole comes into the picture as important player in the ROS signalling network of plants. Elucidating the interplay between the mechanisms controlling ROS signalling during abiotic stress will facilitate the development of strategies to enhance crop tolerance to stressful environmental conditions.     

Retinol supplementation induces oxidative stress and modulates antioxidant enzyme activities in rat Sertoli cells

Recent intervention studies revealed that supplementation with retinoids resulted in a higher incidence of lung cancer. Recently the causal mechanism has begun to be clarified. We report here that retinol caused cellular oxidative stress and modulated superoxide dismutase, catalase and glutathione peroxidase activities. Retinol (7 μM) significantly increased TBARS, conjugated dienes, and hydroperoxide-initiated chemiluminescence in cultured Sertoli cells. In response to retinol treatment superoxide dismutase, catalase and glutathione peroxidase activities increased. TBARS content and catalase activities were decreased by a free radical scavenger. These findings suggest that retinol may induce oxidative stress and modulate antioxidant enzyme activities in Sertoli cells.     

Alterations in bioenergetic function induced by Parkinson's disease mimetic compounds: lack of correlation with superoxide generation

J. Neurochem. (2012) 122, 941-951. ABSTRACT: In vitro and in vivo models of Parkinson's disease (PD) suggest that increased oxidant production leads to mitochondrial dysfunction in dopaminergic neurons and subsequent cell death. However, it remains unclear if cell death in these models is caused by inhibition of mitochondrial function or oxidant production. The objective of this study was to determine the relationship between mitochondrial dysfunction and oxidant production in response to multiple PD neurotoxicant mimetics. MPP(+) caused a dose-dependent decrease in the basal oxygen consumption rate in dopaminergic N27 cells, indicating a loss of mitochondrial function. In parallel, we found that MPP(+) only modestly increased oxidation of hydroethidine as a diagnostic marker of superoxide production in these cells. Similar results were found using rotenone as a mitochondrial inhibitor, or 6-hydroxydopamine (6-OHDA) as a mechanistically distinct PD neurotoxicant, but not with exposure to paraquat. In addition, the extracellular acidification rate, used as a marker of glycolysis, was stimulated to compensate for oxygen consumption rate inhibition after exposure to MPP(+) , rotenone, or 6-OHDA, but not paraquat. Together these data indicate that MPP(+) , rotenone, and 6-OHDA dramatically shift bioenergetic function away from the mitochondria and towards glycolysis in N27 cells.     

Copper-induced oxidative stress and antioxidant defence in Arabidopsis thaliana

Content of reactive oxygen species (ROS): O2*-, H2O2 and OH* as well as activities of antioxidant enzymes: superoxide dismutase (SOD), guaiacol peroxidase (POX) and catalase (CAT) were studied in leaves of Arabidopsis thaliana ecotype Columbia, treated with Cu excess (0, 5, 25, 30, 50, 75, 100, 150 and 300 microM). After 7 days of Cu action ROS content and the activity of SOD and POX increased, while CAT activity decreased in comparison with control. Activities of SOD, POX and CAT were correlated both with Cu concentration (0-75 microM) in the growth medium and with OH* content in leaves. Close correlation was also found between OH* content and Cu concentration. Oxidative stress in A. thaliana under Cu treatment expressed in elevated content of O2*-, H2O2 and OH* in leaves. To overcome it very active the dismutase- and peroxidase-related (and not catalase-related, as in other plants) ROS scavenging system operated in A. thaliana. Visual symptoms of phytotoxicity: chlorosis, necrosis and violet colouring of leaves as well as a reduction of shoot biomass occurred in plants.     

Mitochondrially encoded methionine is inversely related to longevity in mammals

Methionine residues in proteins react readily with reactive oxygen species making them particularly sensitive to oxidation. However, because oxidized methionine can be reduced back in a catalyzed reaction, it has been suggested that methionine residues act as oxidant scavengers, protecting not only the proteins where they are located but also the surrounding macromolecules. To investigate whether methionine residues may be selected for or against animal longevity, we carried out a meta-examination of mitochondrial genomes from mammalian species. Our analyses unveiled a hitherto unnoticed observation: mitochondrially encoded polypeptides from short-lived species are enriched in methionine when compared with their long-lived counterparts. We show evidence suggesting that methionine addition to proteins in short-lived species, rather than methionine loss from proteins in long-lived species, is behind the reported difference in methionine usage. The inverse association between longevity and methionine, which persisted after correction for body mass and phylogenetic interdependence, was paralleled by the methionine codon AUA, but not by the codon AUG. Although nuclear encoded mitochondrial polypeptides exhibited higher methionine usage than nonmitochondrial proteins, correlation with longevity was only found within the group of those polypeptides located in the inner mitochondrial membrane. Based on these results, we propose that short-lived animals subjected to higher oxidative stress selectively accumulate methionine in their mitochondrially encoded proteins, which supports the role of oxidative damage in aging.     

Metabolic defence against oxidative stress: the road less travelled so far

Bacteria have survived, and many have thrived, since antiquity in the presence of the highly‐reactive chalcogen—oxygen (O₂). They are known to evoke intricate strategies to defend themselves from the reactive by‐products of oxygen—reactive oxygen species (ROS). Many of these detoxifying mechanisms have been extensively characterized; superoxide dismutase, catalases, alkyl hydroperoxide reductase and the glutathione (GSH)‐cycling system are responsible for neutralizing specific ROS. Meanwhile, a pool of NADPH—the reductive engine of many ROS‐combating enzymes—is maintained by metabolic enzymes including, but not exclusively, glucose‐6 phosphate dehydrogenase (G6PDH) and NADP‐dependent isocitrate dehydrogenase (ICDH‐NADP). So, it is not surprising that evidence continues to emerge demonstrating the pivotal role metabolism plays in mitigating ROS toxicity. Stemming from its ability to concurrently decrease the production of the pro‐oxidative metabolite, NADH, while augmenting the antioxidative metabolite, NADPH, metabolism is the fulcrum of cellular redox potential. In this review, we will discuss the mounting evidence positioning metabolism and metabolic shifts observed during oxidative stress, as critical strategies microbes utilize to thrive in environments that are rife with ROS. The contribution of ketoacids—moieties capable of non‐enzymatic decarboxylation in the presence of oxidants—as ROS scavengers will be elaborated alongside the metabolic pathways responsible for their homeostases. Further, the signalling role of the carboxylic acids generated following the ketoacid‐mediated detoxification of the ROS will be commented on within the context of oxidative stress.     

氧化应激对肠屏障功能障碍发病的影响

机体累积过量的活性氧自由基所导致的氧化应激是多种肠道疾病发生的共同病理生理基础。肠上皮细胞间的紧密连接是维持肠屏障功能的重要结构基础之一。近年来研究表明,氧化应激能通过多种途径破坏肠上皮细胞间的紧密连接,导致肠上皮屏障功能障碍。本文对蛋白激酶C、丝裂原活化蛋白激酶、蛋白质的修饰以及缺氧诱导因子-1(HIF-1)在肠屏障功能障碍中的作用机制进行简要概述,旨在为肠屏障功能障碍的治疗和预后提供新的思路。