Sunscreens, oxidative stress and antioxidant functions in marine organisms of the Great Barrier Reef

An overview of the biochemical photophysiology of tropical, reef-building corals is presented with a discussion on the biosynthetic relationship between natural UV-absorbing sunscreens and certain antioxidant functions in marine organisms. Our studies reveal that marine organisms, including 'UV-extremophilic' bacteria, are a rich source of novel antioxidants having potential for the development of commercial and biomedical applications. Novel sunscreening agents derived from tropical marine organisms of the Great Barrier Reef are in development. New marine-derived antioxidants are being isolated for testing as chemopreventatives in a variety of oxidatively degenerative diseases.     

Sunscreens,oxidative stress and antioxidant functions in marine organisms of the Great Barrier Reef

Abstract

An overview of the biochemical photophysiology of tropical, reef-building corals is presented with a discussion on the biosynthetic relationship between natural UV-absorbing sunscreens and certain antioxidant functions in marine organisms. Our studies reveal that marine organisms, including ‘UV-extremophilic’ bacteria, are a rich source of novel antioxidants having potential for the development of commercial and biomedical applications. Novel sunscreening agents derived from tropical marine organisms of the Great Barrier Reef are in development. New marine-derived antioxidants are being isolated for testing as chemopreventatives in a variety of oxidatively degenerative diseases.     

Light-induced oxidative stress, N-formylkynurenine, and oxygenic photosynthesis

Light stress in plants results in damage to the water oxidizing reaction center, photosystem II (PSII). Redox signaling, through oxidative modification of amino acid side chains, has been proposed to participate in this process, but the oxidative signals have not yet been identified. Previously, we described an oxidative modification, N-formylkynurenine (NFK), of W365 in the CP43 subunit. The yield of this modification increases under light stress conditions, in parallel with the decrease in oxygen evolving activity. In this work, we show that this modification, NFK365-CP43, is present in thylakoid membranes and may be formed by reactive oxygen species produced at the Mn(4)CaO(5) cluster in the oxygen-evolving complex. NFK accumulation correlates with the extent of photoinhibition in PSII and thylakoid membranes. A modest increase in ionic strength inhibits NFK365-CP43 formation, and leads to accumulation of a new, light-induced NFK modification (NFK317) in the D1 polypeptide. Western analysis shows that D1 degradation and oligomerization occur under both sets of conditions. The NFK modifications in CP43 and D1 are found 17 and 14 Angstrom from the Mn(4)CaO(5) cluster, respectively. Based on these results, we propose that NFK is an oxidative modification that signals for damage and repair in PSII. The data suggest a two pathway model for light stress responses. These pathways involve differential, specific, oxidative modification of the CP43 or D1 polypeptides.     

The mitochondrial antioxidant defence system and its response to oxidative stress

The antioxidant systems of mitochondria are not well known. Using a proteomics-based approach, we defined these mitochondrial antioxidant systems and analyzed their response to oxidative stress. It appears that the major mitochondrial antioxidant system is made of manganese superoxide dismutase on the one hand, and of peroxiredoxin III, mitochondrial thioredoxin and mitochondrial thioredoxin reductase on the other hand. With the exception of thioredoxin reductase, all these proteins are induced by oxidative stress. In addition, a change in the peroxiredoxin III pattern can also be observed.     

Alleviation of cadmium toxicity by cerium in rice seedlings is related to improved photosynthesis,elevated antioxidant enzymes and decreased oxidative stress

Cadmium contamination is a critical constraint to plant production in agricultural soils in some regions. Cerium is one of the rare earth elements, it plays a positive role in plant growth with a appropriate content. The present study was conducted to examine the role of cerium nutrition in the amelioration of effects on cadmium toxicity in rice (Oryza sativa L.) seedlings by a hydroponic experiment. Measurements included growth condition, photosynthesis related parameters, chloroplast ultra-structure and antioxidant enzymes content. Our results showed that the growth of rice seedlings was markedly inhibited by cadmium (100 μM), and the inhibition was significantly alleviated by cerium (10 μM). Fresh weight, single seedling height and chlorophyll content of rice plants in cerium treated groups were increased by 24.4, 18.2 and 32.05 % compared to those of plants cultivated in only cadmium-present condition. Additionally, in cadmium treated plants, the addition of cerium significantly increased the value of the maximum quantum yield of primary photochemistry (F _v /F _m ), indicator of PSII ‘structure and functioning’ (SFI _ABS ) and the performance index on absorption basis (PI _ABS ), elevated the activity of whole chain electron transport activity, enhanced photophosphorylation and its coupling factor Ca²⁺-ATPase activities. The result showed that the chloroplasts and thylakoid membrane of the rice seedlings leaves grown in cerium treatment developed better than that in cerium-absent group under cadmium toxicity. Moreover, addition with 10 μM cerium mitigated cadmium stress by inducing leaf enzyme activities for antioxidation like superoxide dismutase, peroxidase and catalase, dramatically depressed superoxide (O ₂ ^·? ), hydrogen peroxide and malondialdehyde accumulation. Results indicated that alleviation of cadmium toxicity by cerium application is partly related to improved light-use-efficiency, increased antioxidant enzymes, decreased oxidative stress in rice seedlings.     

Flavonoids and urate antioxidant interplay in plasma oxidative stress

Flavonoids are naturally occurring plant compounds with antioxidant properties. Their consumption has been associated with the protective effects of certain diets against some of the complications of atherosclerosis. Lowdensity lipoprotein (LDL) oxidative modification is currently thought to be a significant event in the atherogenic process. Most of the experiments concerning the inhibition of LDL oxidation used isolated LDL. We used diluted human whole plasma to study the influence of flavonoids on lipid peroxidation (LPO) promoted by copper, and their interaction with uric acid, one of the most important plasma antioxidants. Lipid peroxidation was evaluated by the formation of thiobarbituric acid reactive substances (TBARS) and of free malondialdehyde (MDA). The comparative capability of the assayed flavonoids on copper (II) reduction was tested using the neocuproine colorimetric test. In our assay system, urate disappears and free MDA and TBARS formation increase during the incubation of plasma with copper. Most of the tested flavonoids inhibited copperinduced LPO. The inhibition of LPO by flavonoids correlated positively with their capability to reduce copper (II). The urate consumption during the incubation of plasma with copper was inhibited by myricetin, quercetin and kaempferol. The inhibition of urate degradation by flavonoids correlated positively with the inhibition of LPO. Urate inhibited the copperinduced LPO in a concentrationdependent mode. Luteolin, rutin, catechin, quercetin had an antioxidant synergy with urate. Our results show that some flavonoids could protect endogenous urate from oxidative degradation, and demonstrate an antioxidant synergy between urate and some of the flavonoids.     

An antioxidant probiotic reduces postprandial lipemia and oxidative stress

Reducing postprandial oxidative stress (OxS), decreasing postprandial blood triglyceride level (TG) and improving lipoprotein status is likely to have a preventive impact on the development of cardiovascular disease (CVD). Previously we have shown that the antioxidant probiotic Lactobacillus fermentum ME-3 (DSM14241) is characterized by antiatherogenic effects. This randomized double-blind placebo-controlled study evaluated the influence of kefir enriched with an antioxidative probiotic L. fermentum ME-3 (LfKef) on postprandial OxS, blood TG response and lipoprotein status. 100 clinically healthy subjects were recruited into the study. Blood parameters of postprandial OxS, TG and lipoprotein status were determined by oxidized LDL, baseline diene conjugation in LDL (BDC-LDL), oxidized LDL complex with beta-2 glycoprotein (Beta2-GPI-oxLDL), paraoxonase (PON) activity, LDL-Chol, HDL-Chol and TG. To evaluate general body postprandial OxS-load we measured 8-isoprostanes (8-EPI) in the urine. Consumption of LfKef significantly reduced the postprandial level of oxidized LDL, BDC-LDL, Beta2-GPI-oxLDL, urinary 8-isoprostanes and postprandial TG and caused a significant increase in HDL-Chol and PON activity. This is the first evidence that kefir enriched with an antioxidant probiotic may have a positive effect on both postprandial OxS and TG response as well as on lipoprotein status.     

Lymphocyte enzymatic antioxidant responses to oxidative stress following high-intensity interval exercise

The purposes of this study were to 1) examine the immune and oxidative stress responses following high-intensity interval training (HIIT); 2) determine changes in antioxidant enzyme gene expression and enzyme activity in lymphocytes following HIIT; and 3) assess pre-HIIT, 3-h post-HIIT, and 24-h post-HIIT lymphocyte cell viability following hydrogen peroxide exposure in vitro. Eight recreationally active males completed three identical HIIT protocols. Blood samples were obtained at preexercise, immediately postexercise, 3 h postexercise, and 24 h postexercise. Total number of circulating leukocytes, lymphocytes, and neutrophils, as well as lymphocyte antioxidant enzyme activities, gene expression, cell viability (CV), and plasma thiobarbituric acid-reactive substance (TBARS) levels, were measured. Analytes were compared using a three (day) × four (time) ANOVA with repeated measures on both day and time. The a priori significance level for all analyses was P < 0.05. Significant increases in superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities were observed in lymphocytes following HIIT. No significant increases in lymphocyte SOD, CAT, or GPX gene expression were found. A significant increase in TBARS was found immediately post-HIIT on days 1 and 2. Lymphocyte CV in vitro significantly increased on days 2 and 3 compared with day 1. Additionally, there was a significant decrease in CV at 3 h compared with pre- and 24 h postexercise. These findings indicate lymphocytes respond to oxidative stress by increasing antioxidant enzyme activity. Additionally, HIIT causes oxidative stress but did not induce a significant postexercise lymphocytopenia. Analyses in vitro suggest that lymphocytes may become more resistant to subsequent episodes of oxidative stress. Furthermore, the analysis in vitro confirms that lymphocytes are more vulnerable to cytotoxic molecules during recovery from exercise.     

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.     

Spermine and putrescine enhance oxidative stress tolerance in maize leaves

The protective effects of spermine (SPM) and putrescine (PUT) against paraquat (PQ), a herbicide in agriculture and oxidative stress inducer, were investigated in the leaves of maize. Maize leaves were pretreated to SPM and PUT at concentrations of 0.2 and 1 mM and treated with PQ afterwards. Pretreatment with 1 mM of SPM and PUT significantly prevented the losses in chlorophyll and carotenoid levels induced by PQ. Ascorbic acid content in the leaves pretreated with both polyamines was found to be higher than those of the leaves pretreated with water. Also, pretreatment with SPM and PUT was determined to have some effects on the activities of superoxide dismutase (SOD) and peroxidase (POD). 1 mM of SPM increased SOD activity, but PUT has no significant effect on SOD activity. On the other hand, POD activity was recorded to increase slightly in response to both concentrations of SPM and 1 mM of PUT. The results showed that such polyamine pretreated plants may become more tolerant to oxidative stress due to increases in the antioxidative enzymes and antioxidants.     

Pro-oxidant and antioxidant potential of catecholestrogens against ferrylmyoglobin-induced oxidative stress

Ferryl heme proteins may play a major role in vivo under certain pathological conditions. Catecholestrogens, the estradiol-derived metabolites, can act either as antioxidants or pro-oxidants in iron-dependent systems. The aim of the present work was (1) to determine the effects of ferrylmyoglobin on hepatocyte cytotoxicity, and (2) to assess the pro/antioxidant potential of a series of estrogens (phenolic, catecholic and stilbene-derived) against ferrylmyoglobin induced lipid peroxidation in rat hepatocytes. Cells were exposed to metmyoglobin plus hydrogen peroxide to form ferrylmyoglobin in the presence of the transition metal chelator diethylentriaminepentaacetic acid. Results showed that ferrylmyoglobin induced an initial oxidative stress, mainly reflected in an early lipid peroxidation and further decrease in GSH and ATP. However, cells gradually adapted to this situation, by recovering the endogenous ATP and GSH levels at longer incubation times. Phenolic and stilbene-derived estrogens inhibited ferrylmyoglobin-induced lipid peroxidation to different degrees: diethylstilbestrol>estradiol>resveratrol. Catecholestrogens at concentrations higher than 1 microM also inhibited lipid peroxidation with similar efficacy. The ability of estrogens to reduce ferrylmyoglobin to metmyoglobin may account for their antioxidant activity. In contrast, physiological concentrations (100 pM-100 nM) of the catecholestrogens exerted pro-oxidant activities, 4-hydroxyestradiol being more potent than 2-hydroxyestradiol. The implications of these interactions should be considered in situations where local myoglobin or hemoglobin microbleeding takes place.     

Molecular and structural antioxidant defenses against oxidative stress in animals

In this review, it is our aim 1) to describe the high diversity in molecular and structural antioxidant defenses against oxidative stress in animals, 2) to extend the traditional concept of antioxidant to other structural and functional factors affecting the "whole" organism, 3) to incorporate, when supportable by evidence, mechanisms into models of life-history trade-offs and maternal/epigenetic inheritance, 4) to highlight the importance of studying the biochemical integration of redox systems, and 5) to discuss the link between maximum life span and antioxidant defenses. The traditional concept of antioxidant defenses emphasizes the importance of the chemical nature of molecules with antioxidant properties. Research in the past 20 years shows that animals have also evolved a high diversity in structural defenses that should be incorporated in research on antioxidant responses to reactive species. Although there is a high diversity in antioxidant defenses, many of them are evolutionary conserved across animal taxa. In particular, enzymatic defenses and heat shock response mediated by proteins show a low degree of variation. Importantly, activation of an antioxidant response may be also energetically and nutrient demanding. So knowledge of antioxidant mechanisms could allow us to identify and to quantify any underlying costs, which can help explain life-history trade-offs. Moreover, the study of inheritance mechanisms of antioxidant mechanisms has clear potential to evaluate the contribution of epigenetic mechanisms to stress response phenotype variation.     

Role of oxidative stress and antioxidant enzymes in Crohn's disease

There is increasing interest in oxidative stress being a potential aetiological factor and/or a triggering factor in Crohn's disease, rather than a concomitant occurrence during the pathogenesis of the disease. Recent research has shown that the immune mononuclear cells of Crohn's disease patients are induced to produce hydrogen peroxide (H2O2). Similarly, the regulation of antioxidant enzymes during disease in these cells has been unravelled, showing that SOD (superoxide dismutase) activity and GPx (glutathione peroxidase) activity is increased during active disease and returns to normal in remission phases. However, catalase remains constantly inhibited which supports the idea that catalase is not a redox-sensitive enzyme, but a regulator of cellular processes. ROS (reactive oxygen species) can be produced under the stimulus of different cytokines such as TNFα (tumour necrosis factor α). It has been shown in different experimental models that they are also able to regulate apoptosis and other cellular processes. The status of oxidative stress elements in Crohn's disease and their possible implications in regulating cellular processes are reviewed in the present paper.     

Insights into fluoride-induced oxidative stress and antioxidant defences in plants

Fluoride is a common pollutant which occurs in various environmental matrices considered as one of the most phytotoxic pollutants. It is essential to the living organisms in trace quantities but at its higher concentration it becomes poisonous. Excess amount of fluoride in environment not only exerts its toxic effects on human beings and animals but also on plants. Toxicological impacts of fluoride on plants have been largely debated due to reduction of growth parameters, inhibition of metabolic activities and decreased photosynthetic activity. The signs of fluoride impacts on plants may be severe, acute or chronic and toxicity of fluoride depends on dose, frequency of exposure, duration and genotype of plant. This article overviews understanding of transport, uptake and fluoride accumulation in plants and provide insights into the fluoride-induced oxidative stress and regulatory mechanisms to cope up with it. The main objective of this article is to prospect new research avenues to unravel the mechanisms explaining fluoride toxicity in various plant species.     

Chilling,oxidative stress and antioxidant responses inArabidopsis thaliana callus

Chilling ofArabidopsis thaliana (L.) Heynh. callus tissue to 4 °C led to conditions of oxidative stress, as indicated by increased levels of the products of peroxidative damage to cell membranes. Cellular H₂O₂ was also observed to increase initially upon chilling but by day 8 cellular levels had declined to below control levels. Although levels of catalase activity remained similar to those in unchilled tissue, activity of ascorbate peroxidase increased between days 4 and 8 of chilling to 4 °C. In callus held at 23 °C, levels of reduced glutathione remained static whereas they rose in callus held at 4 °C. Levels of oxidised glutathione were initially low but increased significantly by day 4 in the chilled callus. At 23 °C, however, levels of oxidised glutathione remained low. Between days 1 and 3 at 4 °C, levels of glutathione reductase activity increased but by day 8 glutathione reductase activity was similar to that in cells held at 23 °C. Exposure of callus to abscisic acid at 23 °C also led to increased activities of ascorbate peroxidase and glutathione reductase.Abbreviations ABA abscisic acid - GSH reduced glutathione - GSSG oxidised glutathione - TTC 2,35-triphenyltetrazolium chloride This work is supported by a grant from the Biotechnology and Biological Sciences Research Council.     

Waterlogging induced oxidative stress and antioxidant activity in pigeonpea genotypes

The objective of this study was to examine the role of antioxidant enzymes in waterlogging tolerance of pigeonpea (Cajanus cajan L. Halls) genotypes ICP 301 (tolerant) and Pusa 207 (susceptible). Waterlogging resulted in visible yellowing and senescence of leaves, decrease in leaf area, dry matter, relative water content and chlorophyll content in leaves, and membrane stability index in roots and leaves. The decline in all parameters was greater in Pusa 207 than ICP 301. Oxidative stress in the form of superoxide radical, hydrogen peroxide and thiobarbituric acid reactive substances (TBARS) contents initially decreased, however at 4 and 6 d of waterlogging it increased over control plants, probably due to activation of DPI-sensitive NADPH-oxidase. Antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, glutathione reductase and catalase also increased under waterlogging. The comparatively greater antioxidant enzyme activities resulting in less oxidative stress in ICP 301 could be one of the factor determining its higher tolerance to flooding as compared to Pusa 207. This study is the first to conclusively prove that waterlogging induced increase in ROS is via NADPH oxidase.     

Polyphenolics enhance red blood cell resistance to oxidative stress: in vitro and in vivo

In this study we investigated the potential antioxidant properties of blueberry polyphenolics in vitro and vivo, using red blood cell (RBC) resistance to reactive oxygen species (ROS) as the model. In vitro incubation with anthocyanins or hydroxycinnamic acids (HCA) (0.5 and 0.05 mg/ml) was found to enhance significantly RBC resistance to H2O2 (100 microM) induced ROS production. This protection was also observed in vivo following oral supplementation to rats at 100 mg/ml. However, only anthocyanins were found to afford protection at a significant level, this at 6 and 24 h post supplementation. This protection was not consistent with the measured plasma levels of anthocyanins. Indeed, plasma polyphenolic concentrations were highest after 1 h, declining considerably after 6 h and not detected after 24 h. The difference in absorption between anthocyanins and HCA is likely to have contributed to the observed difference in their abilities to afford protection to RBC. This protection represents a positive role following dietary consumption of polyphenolics from blueberries, against ROS formation within RBC in vivo.     

Tetrahydropteridines possess antioxidant roles to guard against glucose-induced oxidative stress in Dictyostelium discoideum

Glucose effects on the vegetative growth of Dictyostelium discoideum Ax2 were studied by examining oxidative stress and tetrahydropteridine synthesis in cells cultured with different concentrations (0.5X, 7.7 g L^-1; 1X, 15.4 g L^-1; 2X, 30.8 g L^-1) of glucose. The growth rate was optimal in 1X cells (cells grown in 1X glucose) but was impaired drastically in 2X cells, below the level of 0.5X cells. There were glucose-dependent increases in reactive oxygen species (ROS) levels and mitochondrial dysfunction in parallel with the mRNA copy numbers of the enzymes catalyzing tetrahydropteridine synthesis and regeneration. On the other hand, both the specific activities of the enzymes and tetrahydropteridine levels in 2X cells were lower than those in 1X cells, but were higher than those in 0.5X cells. Given the antioxidant function of tetrahydropteridines and both the beneficial and harmful effects of ROS, the results suggest glucose-induced oxidative stress in Dictyostelium, a process that might originate from aerobic glycolysis, as well as a protective role of tetrahydropteridines against this stress. [BMB Reports 2013; 46(2): 86-91]     

Evidence for an age-related attenuation of cerebral microvascular antioxidant response to oxidative stress

Effects of aging and oxidative stress were studied in cerebral microvessels and microvessel-depleted brain from 6-, 18-, and 24-month-old C57Bl/6J mice exposed to normoxia, 24 or 48 h hyperoxia, or 24 h hyperoxia followed by 24 h normoxia. Microvessels lacked smooth muscle and consisted predominantly of endothelium. Following exposure and isolation of microvessel and parenchymal proteins, Western blot analysis was performed for detection of cytosolic thioredoxin 1 (TRx 1) and mitochondrial thioredoxin 2 (TRx 2), protein carbonyl, and mitochondrial superoxide dismutase (MnSOD). Both microvessel and parenchymal TRx 1 levels were increased by hyperoxia; however, the microvascular response was limited and delayed in comparison to that of the parenchymal fraction. Whereas TRx 2 levels in microvessels were increased in older mice, irrespective of exposure condition, hyperoxia per se had little or no apparent effect. Parenchymal cells showed no age-related increase in TRx 2 level under normoxic conditions, but showed increased levels following hyperoxia. Microvessel MnSOD was lower than that in parenchymal cells, but increased with age under normoxia, and also was correlated with the duration of hyperoxia. Although hyperoxia augmented MnSOD levels in young (6 months) and middle-aged (18 months) animals, the response was less pronounced in microvessels from senescent, 24-month-old mice. Unlike microvessels, which showed a sustained age-related increase in MnSOD level under each exposure condition, parenchymal cells from normoxic mice showed no increase, and hyperoxia-induced elevations declined with prolonged 48 h exposure. These results indicate that the microvessel endothelium is (1) subjected to a more intense oxidative environment than neurons and glia and (2) is limited by aging in its ability to respond to oxidative insult.