Nitric oxide enhances desiccation tolerance of recalcitrant Antiaris toxicaria seeds via protein S-nitrosylation and carbonylation

The viability of recalcitrant seeds is lost following stress from either drying or freezing. Reactive oxygen species (ROS) resulting from uncontrolled metabolic activity are likely responsible for seed sensitivity to drying. Nitric oxide (NO) and the ascorbate-glutathione cycle can be used for the detoxification of ROS, but their roles in the seed response to desiccation remain poorly understood. Here, we report that desiccation induces rapid accumulation of H(2)O(2), which blocks recalcitrant Antiaris toxicaria seed germination; however, pretreatment with NO increases the activity of antioxidant ascorbate-glutathione pathway enzymes and metabolites, diminishes H(2)O(2) production and assuages the inhibitory effects of desiccation on seed germination. Desiccation increases the protein carbonylation levels and reduces protein S-nitrosylation of these antioxidant enzymes; these effects can be reversed with NO treatment. Antioxidant protein S-nitrosylation levels can be further increased by the application of S-nitrosoglutathione reductase inhibitors, which further enhances NO-induced seed germination rates after desiccation and reduces desiccation-induced H(2)O(2) accumulation. These findings suggest that NO reinforces recalcitrant seed desiccation tolerance by regulating antioxidant enzyme activities to stabilize H(2)O(2) accumulation at an appropriate concentration. During this process, protein carbonylation and S-nitrosylation patterns are used as a specific molecular switch to control antioxidant enzyme activities.     

Proline and glycinebetaine enhance antioxidant defense and methylglyoxal detoxification systems and reduce NaCl-induced damage in cultured tobacco cells

Salt stress impairs reactive oxygen species (ROS) and methylglyoxal (MG) detoxification systems, and causes oxidative damage to plants. Up-regulation of the antioxidant and glyoxalase systems provides protection against NaCl-induced oxidative damage in plants. Thiol–disulfide contents, glutathione content and its associated enzyme activities involved in the antioxidant defense and glyoxalase systems, and protein carbonylation in tobacco Bright Yellow-2 cells grown in suspension culture were investigated to assess the protection offered by proline and glycinebetaine against salt stress. Salt stress increased protein carbonylation, contents of thiol, disulfide, reduced (GSH) and oxidized (GSSG) forms of glutathione, and the activity of glutathione-S-transferase and glyoxalase II enzymes, but decreased redox state of both thiol–disulfide and glutathione, and the activity of glutathione peroxidase and glyoxalase I enzymes involved in the ROS and MG detoxification systems. Exogenous application of proline or glycinebetaine resulted in a reduction of protein carbonylation, and in an increase in glutathione redox state and activity of glutathione peroxidase, glutathione-S-transferase and glyoxalase I under salt stress. Neither proline nor glycinebetaine, however, had any direct protective effect on NaCl-induced GSH-associated enzyme activities. The present study, therefore, suggests that both proline and glycinebetaine provide a protective action against NaCl-induced oxidative damage by reducing protein carbonylation, and enhancing antioxidant defense and MG detoxification systems.     

The MnSOD Ala16Val SNP: Relevance to human diseases and interaction with environmental factors

Abstract

The relevance of reactive oxygen species (ROS) production relies on the dual role shown by these molecules in aerobes. ROS are known to modulate several physiological phenomena, such as immune response and cell growth and differentiation; on the other hand, uncontrolled ROS production may cause important tissue and cell damage, such as deoxyribonucleic acid oxidation, lipid peroxidation, and protein carbonylation. The manganese superoxide dismutase (MnSOD) antioxidant enzyme affords the major defense against ROS within the mitochondria, which is considered the main ROS production locus in aerobes. Structural and/or functional single nucleotide polymorphisms (SNP) within the MnSOD encoding gene may be relevant for ROS detoxification. Specifically, the MnSOD Ala16Val SNP has been shown to alter the enzyme localization and mitochondrial transportation, affecting the redox status balance. Oxidative stress may contribute to the development of type 2 diabetes, cardiovascular diseases, various inflammatory conditions, or cancer. The Ala16Val MnSOD SNP has been associated with these and other chronic diseases; however, inconsistent findings between studies have made difficult drawing definitive conclusions. Environmental factors, such as dietary antioxidant intake and exercise have been shown to affect ROS metabolism through antioxidant enzyme regulation and may contribute to explain inconsistencies in the literature. Nevertheless, whether environmental factors may be associated to the Ala16Val genotypes in human diseases still needs to be clarified.     

Deterioration of Antioxidant Competence in Barley Lesion Mimic Mutant 194

A barley mutant, 194, was observed to exhibit a leaf spot phenotype over the whole course of its growing period. In this study, the phenotype and antioxidant competence were studied in the lesion mimic mutant 194. Plant height was slightly higher in mutant 194 than in the wild type (WT). In addition, leaf spot per plant in mutant 194 was significantly higher than in WT. Antioxidant competence, as indicated by reactive oxygen species (ROS) accumulation, antioxidant enzyme activity, and the expression of antioxidant enzyme-encoding genes was also assessed in mutant 194. Compared to the WT, mutant 194 displayed a relatively higher accumulation of ROS, accompanied by lower activities of some antioxidant enzymes and downregulation of antioxidant enzyme-encoding genes. This demonstrated reduced antioxidant competence in mutant 194. The results suggested that this lower antioxidant competence of mutant 194 could lead to the accumulation of excessive ROS. This excess of ROS could induce programmed cell death and has the potential to promote disease resistance in mutant 194.     

Antioxidant activity of flavonoids evaluated with myoglobin method

Antioxidant activities of four flavonoids (rutin, quercetin, luteolin, and kaempferol) and two non-flavonoids (chlorogenic acid and pyrocatechol) against four reactive oxygen species (ROS) have been measured with a myoglobin method developed by our group. The myoglobin method uses the absorbance changes of myoglobin (a probe molecule) due to the reaction with the ROS as an indicator for the antioxidant activity measurement. Myoglobin protective ratio (MPR) was defined to express the antioxidant activities of the specimens. Antioxidant activities against hypochlorite ion, hydroxyl radical, peroxyl radical, and peroxynitrite were measured with the myoglobin method. The antioxidant activities were comprehensively evaluated by plotting MPR against four ROS and vitamin C equivalent concentration evaluated by DPPH quenching method in 5-axe cobweb charts. The four flavonoids show a very similar pattern in the 5-axe cobweb charts, while the patterns of two non-flavonoids are quite different from that of the flavonoids. This procedure combining the myoglobin method with the cobweb charts is useful in the evaluation of antioxidant activities of plant-derived food, and also can be extended to monitor antioxidant condition of media for plant cell cultures.     

Bat fly species richness in Neotropical bats: correlations with host ecology and host brain

Patterns of ectoparasite species richness in mammals have been investigated in various terrestrial mammalian taxa such as primates, ungulates and carnivores. Several ecological or life traits of hosts are expected to explain much of the variability in species richness of parasites. In the present comparative analysis we investigate some determinants of parasite richness in bats, a large and understudied group of flying mammals, and their obligate blood-sucking ectoparasite, streblid bat flies (Diptera). We investigate the effects of host body size, geographical range, group size and roosting ecology on the species richness of bat flies in tropical areas of Venezuela and Peru, where both host and parasite diversities are high. We use the data from a major sampling effort on 138 bat species from nine families. We also investigate potential correlation between bat fly species richness and brain size (corrected for body size) in these tropical bats. We expect a relationship if there is a potential energetic trade-off between costly large brains and parasite-mediated impacts. We show that body size and roosting in cavities are positively correlated with bat fly species richness. No effects of bat range size and group size were observed. Our results also suggest an association between body mass-independent brain size and bat fly species richness. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Antimicrobial peptides increase tolerance to oxidant stress in Drosophila melanogaster

It is well appreciated that reactive oxygen species (ROS) are deleterious to mammals, including humans, especially when generated in abnormally large quantities from cellular metabolism. Whereas the mechanisms leading to the production of ROS are rather well delineated, the mechanisms underlying tissue susceptibility or tolerance to oxidant stress remain elusive. Through an experimental selection over many generations, we have previously generated Drosophila melanogaster flies that tolerate tremendous oxidant stress and have shown that the family of antimicrobial peptides (AMPs) is over-represented in these tolerant flies. Furthermore, we have also demonstrated that overexpression of even one AMP at a time (e.g. Diptericin) allows wild-type flies to survive much better in hyperoxia. In this study, we used a number of experimental approaches to investigate the potential mechanisms underlying hyperoxia tolerance in flies with AMP overexpression. We demonstrate that flies with Diptericin overexpression resist oxidative stress by increasing antioxidant enzyme activities and preventing an increase in ROS levels after hyperoxia. Depleting the GSH pool using buthionine sulfoximine limits fly survival, thus confirming that enhanced survival observed in these flies is related to improved redox homeostasis. We conclude that 1) AMPs play an important role in tolerance to oxidant stress, 2) overexpression of Diptericin changes the cellular redox balance between oxidant and antioxidant, and 3) this change in redox balance plays an important role in survival in hyperoxia.     

Ectoparasites of the particolored bat (Vespertilio murinus Linnaeus, 1758, Chiroptera,Mammalia) in the Urals and adjacent regions

The ectoparasite fauna on the most widespread synanthropic chiropteran species, the particolored bat (Vespertilio murinus L., 1758), is described from localities in the Urals and West Siberia. 86 individual bats have been examined, off which 463 ectoparasite specimens from 8 species have been collected. The species composition and ecology of these arthropods are analyzed. The core of the ectoparasite fauna on the particolored bat in the Urals has been found to consist of gamasine mites of the genus Steatonyssus.     

Effects of thermal stress on lipid peroxidation and antioxidant enzyme activities of the predatory mite,Neoseiulus cucumeris (Acari: Phytoseiidae)

Changes in temperature are known to cause a variety of physiological stress responses in insects and mites. Thermal stress responses are usually associated with the increased generation of reactive oxygen species (ROS), resulting in oxidative damage. In this study, we examined the time-related effect (durations for 1, 2, 3, and 5 h) of thermal stress conditions—i.e., relatively low (0, 5, 10, and 15 °C) or high (35, 38, 41, and 44 °C) temperatures—on the activities of antioxidant enzymes including catalase (CAT), superoxide dismutase (SOD), peroxidase (POX), glutathione S-transferases (GSTs), and total antioxidant capacity (T-AOC) of the predatory mite Neoseiulus cucumeris. Also the lipid peroxidation (LPO) levels of the predatory mite were measured under thermal stress conditions. The results confirmed that thermal stress results in a condition of so-called oxidative stress and the four antioxidant enzymes play an important role in combating the accumulation of ROS in N. cucumeris. CAT and POX activity changed significantly when the mites were exposed to cold and heat shock, respectively. The elevated levels of SOD and GSTs activity, expressed in a time-dependent manner, may have an important role in the process of antioxidant response to thermal stress. However, the levels of LPO in N. cucumeris were high, serving as an important signal that these antioxidant enzyme-based defense mechanisms were not always adequate to counteract the surplus ROS. Thus, we hypothesize that thermal stress, especially extreme temperatures, may contribute much to the generation of ROS in N. cucumeris, and eventually to its death.     

Differential Indicators of Diabetes-Induced Oxidative Stress in New Zealand White Rabbits: Role of Dietary Vitamin E Supplementation

Determination of reliable bioindicators of diabetes-induced oxidative stress and the role of dietary vitamin E supplementation were investigated. Blood (plasma) chemistries, lipid peroxidation (LPO), and antioxidant enzyme activities were measured over 12 weeks in New Zealand White rabbits (control, diabetic, and diabetic + vitamin E). Cholesterol and triglyceride levels did not correlate with diabetic state. PlasmaLPOwas influenced by diabetes and positively correlated with glucose concentration only, not cholesterol or triglycerides. Liver glutathione peroxidase (GPX) activity negatively correlated with glucose and triglyceride levels. Plasma and erythrocyte GPX activities positively correlated with glucose, cholesterol, and triglyceride concentrations. Liver superoxide dismutase activity positively correlated with glucose and cholesterol concentration. Vitamin E reduced plasma LPO, but did not affect the diabetic state. Thus, plasmaLPOwas the most reliable indicator of diabetes-induced oxidative stress. Antioxidant enzyme activities and types of reactive oxygen species generated were tissue dependent. Diabetes-induced oxidative stress is diminished by vitamin E supplementation.     

Extracellular superoxide dismutase in biology and medicine

Accumulated evidence has shown that reactive oxygen species (ROS) are important mediators of cell signaling events such as inflammatory reactions (superoxide) and the maintenance of vascular tone (nitric oxide). However, overproduction of ROS such as superoxide has been associated with the pathogenesis of a variety of diseases including cardiovascular diseases, neurological disorders, and pulmonary diseases. Antioxidant enzymes are, in part, responsible for maintaining low levels of these oxygen metabolites in tissues and may play key roles in controlling or preventing these conditions. One key antioxidant enzyme implicated in the regulation of ROS-mediated tissue damage is extracellular superoxide dismutase (EC-SOD). EC-SOD is found in the extracellular matrix of tissues and is ideally situated to prevent cell and tissue damage initiated by extracellularly produced ROS. In addition, EC-SOD is likely to play an important role in mediating nitric oxide-induced signaling events, since the reaction of superoxide and nitric oxide can interfere with nitric oxide signaling. This review will discuss the regulation of EC-SOD and its role in a variety of oxidant-mediated diseases.     

Hydrogen-rich water mediates redox regulation of the antioxidant system,mycelial regeneration and fruiting body development in Hypsizygus marmoreus

Hypsizygus marmoreus is an important industrialized mushroom, yet the lack of basic research on this fungus has hindered further development of its economic value. In this study, mycelia injured by scratching were treated with hydrogen-rich water (HRW) to investigate the involvement of the redox system in fruiting body development. Compared to the control group, damaged mycelia treated with HRW regenerated earlier and showed significantly enhanced fruiting body production. Antioxidant capacity increased significantly in damaged mycelia after HRW treatment, as indicated by higher antioxidant enzyme activities and antioxidant contents; the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) were also reduced at the mycelial regeneration stage after treatment with HRW. Furthermore, genes involved in ROS, Ca²⁺, MAPK and oxylipin signaling pathways were up-regulated by HRW treatment. In addition, laccase and manganese peroxidase activities and mycelial biomass were higher after HRW treatment, suggesting that HRW might enhance the substrate-degradation rate to provide more carbon sources for fruiting body production.     

Protein synthesis and antioxidant capacity in aging mice: effects of long-term voluntary exercise

Exercise increases metabolic rate and the production of reactive oxygen species (ROS) but also elevates protein turnover. ROS cause damage to macromolecules (e.g., proteins) and thereby contribute to aging. Protein turnover removes and replaces damaged proteins. The balance between these two responses may underlie beneficial effects of physical activity on aging. Effects of lifelong exercise on antioxidant enzyme activities and fractional synthesis rate of protein (FSRP) were examined at various ages (2-26 mo) in heart, liver, and muscle of mice that had been selectively bred for high wheel-running activity, housed with (S+) or without (S-) a running wheel, and their random-bred controls (C+) housed with running wheels. FSRP decreased with age and increased in muscle of young, but not old, activity-selected mice. Enzyme activity of superoxide dismutase and glutathione peroxidase decreased with age and showed a peak at 10 mo of age in liver. Selection for wheel-running activity did not affect antioxidant enzyme activity. Daily energy expenditure correlated positively with antioxidant levels in liver. This might indicate that oxidative stress (ROS production) increases with metabolic rate, driving upregulation of antioxidant enzymes. Alternatively, the elevated energy expenditure may reflect the energetic cost of elevated protection, consistent with the disposable-soma hypothesis and with other studies showing positive links between energy expenditure and life span. Long-term elevations in voluntary exercise did not result in elevations in antioxidant enzyme activities or protein synthesis rates.     

Intense physical activity enhances neutrophil antioxidant enzyme gene expression. Immunocytochemistry evidence for catalase secretion

We studied the effects of intense exercise on the neutrophil antioxidant enzyme activities and gene expression. Blood samples were taken from seven cyclists in basal conditions and 3 h after two competition stages of 165 km. Serum creatine kinase (CK) activity, plasma carbonyl derivatives and uric acid levels increased after exercise. The cycling stage induced neutrophilia and increased myeloperoxidase (MPO) activity and reactive oxygen species (ROS) production. Antioxidant enzyme activities (catalase, glutathione peroxidase and superoxide dismutase) decreased after exercise, although gene expression increased. Immunocytochemistry showed catalase (CAT) enzyme equally distributed between the cytoplasm and organelles before exercise, and after exercise the cytoplasmic CAT levels were reduced and were absent in the compartments. After in vitro stimulation with opsonized zymosan (OZ) the extracellular CAT levels increased. This suggests a CAT secretion in order to avoid neutrophil-induced oxidative damage at a local level or to regulate the function of ROS as extracellular signalling molecules.     

Intense physical activity enhances neutrophil antioxidant enzyme gene expression. Immunocytochemistry evidence for catalase secretion

We studied the effects of intense exercise on the neutrophil antioxidant enzyme activities and gene expression. Blood samples were taken from seven cyclists in basal conditions and 3 h after two competition stages of 165 km. Serum creatine kinase (CK) activity, plasma carbonyl derivatives and uric acid levels increased after exercise. The cycling stage induced neutrophilia and increased myeloperoxidase (MPO) activity and reactive oxygen species (ROS) production. Antioxidant enzyme activities (catalase, glutathione peroxidase and superoxide dismutase) decreased after exercise, although gene expression increased. Immunocytochemistry showed catalase (CAT) enzyme equally distributed between the cytoplasm and organelles before exercise, and after exercise the cytoplasmic CAT levels were reduced and were absent in the compartments. After in vitro stimulation with opsonized zymosan (OZ) the extracellular CAT levels increased. This suggests a CAT secretion in order to avoid neutrophil-induced oxidative damage at a local level or to regulate the function of ROS as extracellular signalling molecules.     

Antioxidant enzyme activities and lipid peroxidation in the freshwater cladoceran Daphnia magna exposed to redox cycling compounds

Contaminant-related changes in antioxidative processes in the freshwater crustacea Daphnia magna exposed to model redox cycling contaminant were assessed. Activities of key antioxidant enzymes including catalase, superoxide dismutase, glutathione peroxidase and glutathione S-transferases and levels of lipid peroxidation measured as thiobarbituric acid-reactive substances (TBARS) and lipofucsin pigment content were determined in D. magna juveniles after being exposed to sublethal levels of menadione, paraquat, endosulfan, cadmium and copper for 48 h. Results denoted different patterns of antioxidant enzyme responses, suggesting that different toxicants may induce different antioxidant/prooxidant responses depending on their ability to produce reactive oxygen species and antioxidant enzymes to detoxify them. Low responses of antioxidant enzyme activities for menadione and endosulfan, associated with increasing levels of lipid peroxidation and enhanced levels of antioxidant enzyme activities for paraquat, seemed to prevent lipid peroxidation, whereas high levels of both antioxidant enzyme activities and lipid peroxidation were found for copper. For cadmium, low antioxidant enzyme responses coupled with negligible increases in lipid peroxidation indicated low potential for cadmium to alter the antioxidant/prooxidant status in Daphnia. Among the studied enzymes, total glutathione peroxidase, catalase and glutathione S-transferase appeared to be the most responsive biomarkers of oxidative stress.     

Effect of Terminalia arjuna on antioxidant defense system in cancer

Constant production of reactive oxygen species (ROS) during aerobic metabolism is balanced by antioxidant defense system of an organism. Although low level of ROS is important for various physiological functions, its accumulation has been implicated in the pathogenesis of age-related diseases such as cancer and coronary heart disease and neurodegenerative disorders such as Alzheimer’s disease. It is generally assumed that frequent consumption of phytochemicals derived from vegetables, fruits, tea and herbs may contribute to shift the balance towards an adequate antioxidant status. The present study is aimed to investigate the effect of aqueous extract of medicinal plant Terminalia arjuna on antioxidant defense system in lymphoma bearing AKR mice. Antioxidant action of T. arjuna is monitored by the activities of catalase, superoxide dismutase and glutathione S transferase which constitute major antioxidant defense system by scavenging ROS. These enzyme activities are low in lymphoma bearing mice indicating impaired antioxidant defense system. Oral administration of different doses of aqueous extract of T. arjuna causes significant elevation in the activities of catalase, superoxide dismutase and glutathione S transferase. T. arjuna is found to down regulate anaerobic metabolism by inhibiting the activity of lactate dehydrogenase in lymphoma bearing mice, which was elevated in untreated cancerous mice. The results indicate the antioxidant action of aqueous extract of T. arjuna, which may play a role in the anti carcinogenic activity by reducing the oxidative stress along with inhibition of anaerobic metabolism.     

Vitamin E-enriched diet reduces adaptive responses to training determining respiratory capacity and redox homeostasis in rat heart

We investigated whether reactive oxygen species (ROS) are involved in heart adaptive responses administering a vitamin E-enriched diet to trained rats. Using the homogenates and/or mitochondria from rat hearts we determined the aerobic capacity, tissue level of mitochondrial proteins, and expression of cytochrome c and factors (PGC-1, NRF-1, and NRF-2) involved in mitochondrial biogenesis. We also determined the oxidative damage, glutathione peroxidase (GPX) and reductase activities, glutathione content, mitochondrial ROS release rate, and susceptibility to in vitro oxidative challenge. Glutathione (GSH) content was not affected by both training and antioxidant supplementation. Conversely, antioxidant supplementation prevented metabolic adaptations to training, such as the increases in oxidative capacity, tissue content of mitochondrial proteins, and cytochrome c expression, attenuated some protective adaptations, such as the increase in antioxidant enzyme activities, and did not modify the decrease in ROS release by succinate supplemented mitochondria. Moreover, vitamin E prevented the training-linked increase in tissue capacity to oppose an oxidative attach. The antioxidant effects were associated with decreased levels of PGC-1, NRF-1, and NRF-2 expression. Our results support the idea that some heart adaptive responses to training depend on ROS produced during the exercise sessions and are mediated by the increase in PGC-1 expression which is involved in both the regulation of respiratory capacity and antioxidant protection. However, vitamin inability to prevent some adaptations suggests that other signaling pathways impinging on PGC-1 can modify the response to the antioxidant integration.