Non-enzymatic Reactive Oxygen Species Research Articles

Control of postharvest soft rot of green peppers by Bacillus subtilis through regulating ROS metabolism

Soft rot caused by Pectobacterium carotovorum is one of the most serious postharvest bacterial diseases of green peppers. The present research aimed to determine the biocontrol effect of Bacillus subtilis on postharvest soft rot of green peppers and to further delve into biocontrol mechanisms by analyzing the metabolism of reactive oxygen species (ROS) in green peppers. As key results, soft rot occurrence of green peppers was alleviated with the increase of the concentration of B. subtilis, and the disease incidence and index of the fruits treated with 1 × 109 CFU/mL of B. subtilis for 4 d were 28.3% and 12.7%, respectively, which were significantly decreased compared with that of the control. B. subtilis could significantly increase NADPH oxidase (NOX) activity in green peppers to trigger ROS outbreaks, which induced defense response of the fruits. Furthermore, it promoted the enzymatic activities of the ROS scavenging system, including antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), ascorbic acid-glutathione (AsA-GSH) cycle-related enzymes (ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR)), glutathione peroxidase (GPX) cycle-related enzymes (GPX, GR and glutathione-s-transferase (GST)). Besides, B. subtilis increased the non-enzymatic ROS scavenging system contents, including ascorbate (AsA) and glutathione (GSH) in green peppers. Importantly, the levels of O2−·, H2O2 and malondialdehyde (MDA) in green peppers were reduced, thereby enhancing green pepper disease resistance. This study offers novel insights to advanced strategies in preventing and controlling postharvest soft rot in green peppers.

Monascus pigment prevent the oxidative cytotoxicity in myotube derived hydrogen peroxide.

The amounts of Reactive oxygen species (ROS) become higher by strenuous exercises which consume larger amounts of oxygen in active muscles. Since these ROS directly injured muscles, the high ROS concentration involves muscle fatigue. Thus, an immediate ROS scavenging system in the muscle is desired. Since Monascus pigment (MP) involves physiologically active substances which scavenge ROS, it may be a clue to save the muscle injury. However, there are no reports examining MP effects on oxidative stress in skeletal muscle. In this study, we investigated the effect and mechanism of MP on skeletal muscle cells damaged by oxidative stress. The ability to directly eliminate ROS was evaluated by mixing MP solutions with •OH and O2 •-, a type of ROS. The effect of peroxidation in C2C12 cells was evaluated by cell viability assay and Western blotting. MP scavenges •OH and O2 •-. MP treatment increases the survival rate under oxidative stress. At that time, the expression of catalase was increased: the enzyme change H2O2 into H2O to rescue the cells under oxidative stress. We conclude that monascus pigment suppressed myotube damage under oxidative stress by both non-enzymatic ROS scavenging and up-regulation of catalase expression.

ROS Stress and Cell Membrane Disruption are the Main Antifungal Mechanisms of 2-Phenylethanol against Botrytis cinerea.

2-Phenylethanol (2-PE), a common compound found in plants and microorganisms, exhibits broad-spectrum antifungal activity. Using Botrytis cinerea, we demonstrated that 2-PE suppressed mycelium growth in vitro and in strawberry fruit and reduced natural disease without adverse effects to fruit quality. 2-PE caused structural damage to mycelia, as shown by scanning and transmission electron microscopy. From RNA sequencing analysis we found significantly upregulated genes for enzymatic and nonenzymatic reactive oxygen species (ROS) scavenging systems including sulfur metabolism and glutathione metabolism, indicating that ROS stress was induced by 2-PE. This was consistent with results from assays demonstrating an increase ROS and hydrogen peroxide levels, antioxidant enzyme activities, and malondialdehyde content in treated cells. The upregulation of ATP-binding cassette transporter genes, the downregulation of major facilitator superfamily transporters genes, and the downregulation of ergosterol biosynthesis genes indicated a severe disruption of cell membrane structure and function. This was consistent with results from assays demonstrating compromised membrane integrity and lipid peroxidation. To summarize, 2-PE exposure suppressed B. cinerea growth through ROS stress and cell membrane disruption.

The Sweetpotato Voltage-Gated K+ Channel β Subunit, KIbB1, Positively Regulates Low-K+ and High-Salinity Tolerance by Maintaining Ion Homeostasis.

Voltage-gated K+ channel β subunits act as a structural component of Kin channels in different species. The β subunits are not essential to the channel activity but confer different properties through binding the T1 domain or the C-terminal of α subunits. Here, we studied the physiological function of a novel gene, KIbB1, encoding a voltage-gated K+ channel β subunit in sweetpotato. The transcriptional level of this gene was significantly higher in the low-K+-tolerant line than that in the low-K+-sensitive line under K+ deficiency conditions. In Arabidopsis, KIbB1 positively regulated low-K+ tolerance through regulating K+ uptake and translocation. Under high-salinity stress, the growth conditions of transgenic lines were obviously better than wild typr (WT). Enzymatic and non-enzymatic reactive oxygen species (ROS) scavenging were activated in transgenic plants. Accordingly, the malondialdehyde (MDA) content and the accumulation of ROS such as H2O2 and O2− were lower in transgenic lines under salt stress. It was also found that the overexpression of KIbB1 enhanced K+ uptake, but the translocation from root to shoot was not affected under salt stress. This demonstrates that KIbB1 acted as a positive regulator in high-salinity stress resistance through regulating Na+ and K+ uptake to maintain K+/Na+ homeostasis. These results collectively suggest that the mechanisms of KIbB1 in regulating K+ were somewhat different between low-K+ and high-salinity conditions.

Linking Reactive Oxygen Species (ROS) to Abiotic and Biotic Feedbacks in Plant Microbiomes: The Dose Makes the Poison.

In nature, plants develop in complex, adaptive environments. Plants must therefore respond efficiently to environmental stressors to maintain homeostasis and enhance their fitness. Although many coordinated processes remain integral for achieving homeostasis and driving plant development, reactive oxygen species (ROS) function as critical, fast-acting orchestrators that link abiotic and biotic responses to plant homeostasis and development. In addition to the suite of enzymatic and non-enzymatic ROS processing pathways that plants possess, they also rely on their microbiota to buffer and maintain the oxidative window needed to balance anabolic and catabolic processes. Strong evidence has been communicated recently that links ROS regulation to the aggregated function(s) of commensal microbiota and plant-growth-promoting microbes. To date, many reports have put forth insightful syntheses that either detail ROS regulation across plant development (independent of plant microbiota) or examine abiotic–biotic feedbacks in plant microbiomes (independent of clear emphases on ROS regulation). Here we provide a novel synthesis that incorporates recent findings regarding ROS and plant development in the context of both microbiota regulation and plant-associated microbes. Specifically, we discuss various roles of ROS across plant development to strengthen the links between plant microbiome functioning and ROS regulation for both basic and applied research aims.

Oxidative Stress Under Macronutrient Deficiency in Plants

Mineral nutrients play crucial functions in the growth and development of plants as they are intimately involved in the plant cell organization and metabolic functions. The mineral nutrients are either structural/functional constituents of enzymes or act as activators or regulators of various enzyme activities. The macronutrients like N (nitrogen) and P (phosphorus) form structural constituents of building block materials, and some of them [K (potassium), Ca (calcium), and Mg (magnesium)] are regulator or activator of enzymes. Deficiencies of macronutrient affect various physiological or metabolic activities including increased production of reactive oxygen species (ROS) in the organisms. Excess production of ROS causes oxidative stress in the plants. To counter with the oxidative stress, plants have evolved both enzymatic and non-enzymatic ROS scavenging system for protection of cellular components against deleterious ROS. Antioxidant machinery is comprised of various antioxidant enzymes such as peroxidases (POD), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S-transferase (GST), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR), and non-enzyme molecules such as ascorbate (AA), glutathione (GSH), carotenoids and α-tocopherols. Reactive oxygen species can attack cellular structures such as cell membranes and various biomolecules including proteins and nucleic acids and causes lipid peroxidation and protein damage. In this review, we summarize recent developments on oxidative stress and antioxidant responses of plants induced by macronutrient deficiency. Further, we discuss possible ROS signaling events involved in oxidative stress and antioxidant responses induced due to different macronutrient deficiency.

Proline is a quencher of singlet oxygen and superoxide both in in vitro systems and isolated thylakoids.

Proline is a versatile plant metabolite, which is produced in large amounts in plants exposed to osmotic and oxidative stress. Proline has been shown to provide protection against various reactive oxygen species (ROS), such as hydrogen peroxide and hydroxyl radicals. On the other hand, its protective effect against singlet oxygen has been debated, and it is considered ineffective against superoxide. Here we used various methods for the detection of singlet oxygen (electron paramagnetic resonance, EPR, spin trapping by 2,2,6,6-tetramethyl-4-piperidone, fluorescence probing by singlet oxygen sensor green, SOSG, and oxygen uptake due to chemical trapping) and superoxide (oxygen uptake due to oxygen reduction) in vitro and in isolated thylakoids. We demonstrated that proline does quench both singlet oxygen and superoxide in vitro. By comparing the effects of chemical scavengers and physical quenchers, we concluded that proline eliminates singlet oxygen via a physical mechanism, with a bimolecular quenching rate of ca. 1.5-4 106 M-1 s-1 . Our data also show that proline can eliminate superoxide in vitro in a process that is likely to proceed via an electron transfer reaction. We could also show that proline does quench both singlet oxygen and superoxide produced in isolated thylakoids. The scavenging efficiency of proline is relatively small on a molar basis, but considering its presence in high amounts in plant cells under stress conditions it may provide a physiologically relevant contribution to ROS scavenging, supplementing other nonenzymatic ROS scavengers of plant cells.

Synergisms of Microbial Consortia, N Forms, and Micronutrients Alleviate Oxidative Damage and Stimulate Hormonal Cold Stress Adaptations in Maize.

AimsLow soil temperature in spring is a major constraint for the cultivation of tropical crops in temperate climates. This study aims at the exploitation of synergistic interactions of micronutrients, consortia of plant growth-promoting microorganisms and N forms as cold-stress protectants.MethodsMaize seedlings were exposed for two weeks to low root zone temperatures at 8–14°C under controlled conditions on a silty clay-loam soil (pH 6.9) collected from a maize field cultivation site. A pre-selection trial with fungal and bacterial PGPM strains revealed superior cold-protective performance for a microbial consortium of Trichoderma harzianum OMG16 and Bacillus spp. with Zn/Mn supplementation (CombiA+), particularly in combination with N-ammonium as a starting point for the characterization of the underlying physiological and molecular mechanisms.ResultsIn nitrate-treated plants, the cold stress treatment increased oxidative leaf damage by 133% and reduced the shoot biomass by 25%, related with reduced acquisition of phosphate (P), zinc (Zn) and manganese (Mn). The supplying of N as ammonium improved the Zn and Mn nutritional status and increased the ABA shoot concentration by 33%, as well as moderately increased detoxification of reactive oxygen species (ROS). Moreover, use of N as ammonium also increased the root auxin (IAA) concentration (+76%), with increased expression of auxin-responsive genes, involved in IAA synthesis (ZmTSA), transport (ZmPIN1a), and perception (ZmARF12). Additional inoculation with the microbial consortium promoted root colonization with the inoculant strain T. harzianum OMG16 in combination with ammonium fertilization (+140%). An increased ABA/cytokinin ratio and increased concentrations of jasmonic (JA) and salicylic acids (SA) were related to a further increase in enzymatic and non-enzymatic ROS detoxification. Additional supplementation with Zn and Mn further increased shoot IAA, root length and total antioxidants, resulting in the highest shoot biomass production and the lowest leaf damage by oxidative chemical species.ConclusionOur results suggest the mitigation of cold stress and reduction of stress priming effects on maize plants due to improved ROS detoxification and induction of hormonal stress adaptations relying on the strategic combination of stress-protective nutrients with selected microbial inoculants.

Improvement of ionizing gamma irradiation tolerance of Chlorella vulgaris by pretreatment with polyethylene glycol

Purpose: To evaluate the effects of polyethylene glycol (PEG) 6000 pretreatment on growth and physiological responses of eukaryotic microalga Chlorella vulgaris exposed to ionizing irradiation.Materials and methods: The microalgal cells pretreated with different PEG concentrations (0, 5, 10 and 20%) and then exposed to 300 Gray gamma irradiation at a dose rate of 0.5 Gy s−1. The various growth and physiological parameters including algal growth, cell size, the degree of electrolyte leakage (EL) and lipid peroxidation, the content of pigments and proline and the activity of antioxidant enzymes under gamma-free or 300 Gray gamma irradiation conditions were examined.Results: The results showed that PEG stimulated a higher growth and cell size under both stress-free and gamma-stress conditions. The maximum growth and cell size was reported when the algae was pretreated with 10% PEG. A relative increase of catalase activity was observed in all samples after exposing to gamma irradiation. However, the highest value was recorded for the gamma-radiated algae pretreated with 10% PEG. In the absence of PEG, gamma irradiation induced a significant reduction in ascorbate peroxidase activity, but with PEG pretreatment, the enzyme activity remained constant or even increased after gamma irradiation. On the other hand, although gamma irradiation stress generally suppressed the activity of superoxide dismutase in all cells, pretreating the algae with PEG could diminish this suppressing effect at all applied concentrations. Compared to the PEG-free controls, a lower rate of chlorophylls and membrane integrity loss was shown in the PEG-treated algae when exposed to gamma stress. Total carotenoid content in PEG-treated algae was also similar under both gamma-free and gamma-radiated conditions. A PEG-independent increase in proline accumulation was reported under gamma-irradiation treatment.Conclusions: Overall, the results suggested that PEG pretreatment could improve gamma-irradiation tolerance in C. vulgaris probably by stimulating a range of enzymatic and non-enzymatic reactive oxygen species scavenging systems. The microalgae may also consume PEG to break down and use it as an alternative source of carbon during stress which should be further studied in detail.

Metabolomics Studies on Cytoplasmic Male Sterility during Flower Bud Development in Soybean.

Abnormal reactive oxygen species (ROS) may mediate cytoplasmic male sterility (CMS). To observe the effect of ROS on soybean CMS, metabolite content and antioxidant enzyme activity in the flower buds between soybean N8855-derived CMS line and its maintainer were compared. Of the 612 metabolites identified, a total of 74 metabolites were significantly differentiated in flower buds between CMS line and its maintainer. The differential metabolites involved 32 differential flavonoids, 13 differential phenolamides, and 1 differential oxidized glutathione (GSSG) belonging to a non-enzymatic ROS scavenging system. We observed lower levels of flavonoids and antioxidant enzyme activities in flower buds of the CMS line than in its maintainer. Our results suggest that deficiencies of enzymatic and non-enzymatic ROS scavenging systems in soybean CMS line cannot eliminate ROS in anthers effectively, excessive accumulation of ROS triggered programmed cell death and ultimately resulted in pollen abortion of soybean CMS line.

Response of Ornamental Pepper to High-Temperature Stress and Role of Exogenous Salicylic Acid in Mitigating High Temperature

Ornamental pepper (Capsicum annuum L.) is an important economic decorative plant well known for its abundant genetic diversity. However, high-temperature (HT) stress seriously affects its aesthetic and commercial value. In this work, we analyzed the effects of exogenous salicylic acid (SA) on seed germination and seedling growth of ornamental pepper under HT stress. The inherent physiological and biochemical basis of the alleviating effect of salicylic acid was further analyzed. The findings revealed SA with 0.01 mM and 0.1 mM was most effective in enhancing thermotolerance in seeds and seedlings, respectively. SA treatment increased the germination rate and germination potential, and reduced the oxidative damage of seeds under HT stress. For seedlings, spraying SA with 0.1 mM significantly alleviated yellow leaves and dwarfing under HT stress. SA could maintain high root vigor, inhibit water loss, and maintain the integrity of cell structure by regulating osmotic substance content under HT. SA-induced thermotolerance development involved in the activation of antioxidant defense system. SA decreased the production of reactive oxygen species (ROS), increased the activity of protective enzymes, and the content of non-enzymatic ROS scavengers in plants under HT. The changes of chlorophyll fluorescence parameters showed that SA was beneficial to maintain a high level of photosynthetic capacity of ornamental pepper seedlings under HT stress. Moreover, recovery also showed a mitigatory effect on injuries induced by HT stress. Taken together, this study provided evidence for the ability of exogenous SA application to moderate the detrimental effects by HT stress.

Genotypic and environmental effects on the level of ascorbic acid, phenolic compounds and related gene expression during pineapple fruit development and ripening

Pineapple (Ananas comosus (L.) Merr.) is a non-climacteric tropical fruit whose ripening could be accompanied by oxidative processes and the concurrent activation of enzymatic and non-enzymatic reactive oxygen species (ROS) scavenging systems. To better understand the variability of these processes among climatic environments or genotypes in pineapple, the temporal expression dynamics for genes encoding oxidative and antioxidative stress enzymes were analyzed by real-time RT-PCR during fruit development and ripening, among three cultivars: Queen Victoria, Flhoran 41 and MD-2 hybrid, and in two climatic areas. Pineapple development and ripening involved changes in the levels of transcripts encoding for polyphenol oxidase and transcripts involved in the first steps of the phenylpropanoid pathway and in the balance of ROS, especially those encoding for ascorbate peroxydase and metallothioneins, regardless of the cultivar. Our results confirm the same dynamic in gene expression from the two environmental crop areas, however climatic conditions influenced the level of the expression of the major transcripts studied that were linked to these oxidative and antioxidant metabolisms. MT3a and MT3b transcripts were not influenced by genetic factor. The genetic effect was not significant on the various transcripts linked to the first steps of the phenylpropanoid pathway and to phenol oxidation, except 4CL ones. In ripe pineapple, highly significant relationships were found between the contents in antioxidant metabolites, i.e., ascorbic acid and total phenolic compounds, and the transcript levels of genes involved in the enzymatic ROS-scavenging system and in the biosynthesis or regeneration of ROS-scavenging compounds, like phenylpropanoids, ascorbic acid, metallothioneins.

A novel synthesis of non-aggregated spinel nickel ferrite nanosheets for developing non-enzymatic reactive oxygen species sensor in biological samples

Herein, the synthesis of novel non-aggregated spinel nickel ferrite, NiFe2O4 nanosheets (NiFe2O4 NSs) and its application towards the selective electrocatalytic reduction of hydrogen peroxide are described. Initially, NiFe2O4 NSs is synthesized by one-step hydrothermal approach, and numerous characterizations deliberately explain the compound's composition and structure. Finally, the NiFe2O4 NSs underwent direct non-enzymatic electrochemistry and succeeded, it as mimicking Horseradish Peroxidase properties. The significance of non-aggregated NiFe2O4 NSs together with good electrocatalytic properties leads the material to the platform for electrochemical sensors. Moreover, NiFe2O4 NSs is fabricated and validated as an enzyme-free biosensor for the sensitive detection of H2O2. The demonstrated sensor revealed excellent detection of H2O2 with the pico-molar detection limit (12.4 pM), and also it offered good analytical parameters with more extensive linear range and higher sensitivity. Likewise, the non-enzymatic biosensor annexes good durability, reproducibility, and selectivity towards the determination of H2O2. Due to the nourishing capacity of the prepared NiFe2O4 NSs, it is employed for the enzyme-free detection of H2O2 in human blood and rat brain serum samples.

Enhanced oxidative stress in the jasmonic acid-deficient tomato mutant def-1 exposed to NaCl stress

Jasmonic acid (JA) has been mostly studied in responses to biotic stresses, such as herbivore attack and pathogenic infection. More recently, the involvement of JA in abiotic stresses including salinity was highlighted; yet, its role in salt stress remained unclear. In the current study, we compared the physiological and biochemical responses of wild-type (WT) tomato (Solanum lycopersicum) cv Castlemart and its JA-deficient mutant defenseless-1 (def-1) under salt stress to investigate the role of JA. Plant growth, photosynthetic pigment content, ion accumulation, oxidative stress-related parameters, proline accumulation and total phenolic compounds, in addition to both enzymatic and non-enzymatic antioxidant activities, were measured in both genotypes after 14 days of 100 mM NaCl treatment. Although we observed in both genotypes similar growth pattern and sodium, calcium and potassium levels in leaves under salt stress, def-1 plants exhibited a more pronounced decrease of nitrogen content in both leaves and roots and a slightly higher level of sodium in roots compared to WT plants. In addition, def-1 plants exposed to salt stress showed reactive oxygen species (ROS)-associated injury phenotypes. These oxidative stress symptoms in def-1 were associated with lower activity of both enzymatic antioxidants and non-enzymatic antioxidants. Furthermore, the levels of the non-enzymatic ROS scavengers proline and total phenolic compounds increased in both genotypes exposed to salt stress, with a higher amount of proline in the WT plants. Overall the results of this study suggest that endogenous JA mainly enhanced tomato salt tolerance by maintaining ROS homeostasis.

Extra-Cellular But Extra-Ordinarily Important for Cells: Apoplastic Reactive Oxygen Species Metabolism.

Reactive oxygen species (ROS), by their very nature, are highly reactive, and it is no surprise that they can cause damage to organic molecules. In cells, ROS are produced as byproducts of many metabolic reactions, but plants are prepared for this ROS output. Even though extracellular ROS generation constitutes only a minor part of a cell’s total ROS level, this fraction is of extraordinary importance. In an active apoplastic ROS burst, it is mainly the respiratory burst oxidases and peroxidases that are engaged, and defects of these enzymes can affect plant development and stress responses. It must be highlighted that there are also other less well-known enzymatic or non-enzymatic ROS sources. There is a need for ROS detoxification in the apoplast, and almost all cellular antioxidants are present in this space, but the activity of antioxidant enzymes and the concentration of low-mass antioxidants is very low. The low antioxidant efficiency in the apoplast allows ROS to accumulate easily, which is a condition for ROS signaling. Therefore, the apoplastic ROS/antioxidant homeostasis is actively engaged in the reception and reaction to many biotic and abiotic stresses.

Response of ROS-Scavenging Systems to Salinity Stress in Two Different Wheat (Triticum aestivum L.) Cultivars

Salinity leads to oxidative stress in plant cells due to increased production of reactive oxygen species. The response of two wheat (Triticum aestivum L.) cultivars, salt sensitive (‘Darab2’) and salt-tolerant (‘Arta’) were studied to salinity-induced oxidative stress (0, 75 and 150 mM NaCl). Increasing of lipid peroxidation caused oxidative stress in both sensitive and tolerant cultivars. The result showed that reactive oxygen species (ROS) viz., superoxide and hydrogen peroxide increased in leaves of ‘Darab2’ under salinity stress. Under salinity stress, the salt-tolerant cv. ‘Arta’ showed higher activity of the ROS scavenging enzymes like ascorbate peroxidase and peroxidases than ‘Darab2’. Furthermore, in sensitive cv. ‘Darab2’ the activities of these enzymes in leaves were unable to prevent the scavenging of H2O2. Unlike ‘Arta’, there were no significant differences in superoxide dismutases and glutathione reductase activities in sensitive cv. ‘Darab2’ under salinity stress. The amount of reduced glutathione, reduced/oxidized glutathione ratio in leaves of ‘Darab2’ was lower than ‘Arta’ under saline conditions. It seems that in salt tolerant cultivars like ‘Arta’, both enzymatic and non-enzymatic ROS scavenging machineries is critical point to overcome salinity-induced oxidative stress.

Physiological Responses of Two Rubber Tree Clones with Differential Cold-Tolerant Potential to Cold Stress

Improvement of cold tolerance in rubber tree is essential for sustainable increase of natural rubber production when the planting region has been extending outside of the traditional areas. In the present study, physiological responses to cold stress were determined in two rubber tree clones with differential cold tolerance. Upon cold stress, the level of endogenous hydrogen peroxide was significantly higher in the cold-tolerant rubber tree clone 93–114 than that in the cold-sensitive rubber tree clone Reken501 at the time intervals of 2 h, 4 h and 48 hours. The level of vitamin C (Vc) and proline within 48 h and glutathione (GSH) within 8 h in the cold-tolerant clone was significantly (P<0.05) higher than that in the cold-sensitive clone. The activity of superoxide dismutase (SOD) and peroxidase (POD) within 48 h and catalase (CAT) within 12 h was significantly (P<0.05) higher in the cold-tolerant clone than that in the cold-sensitive clone. By contrast, the content of malondialdehyde (MDA) within 48 h in the cold-tolerant clone was significantly (P<0.05) lower than that in the cold-sensitive clone. The content (μmol/ mg·FW) of chlorophyll a and b changed between 2.12±0.1 and 2.52±0.09 and between 0.41±0.03 and 0.53±0.01 at most time intervals in the cold-tolerant clone, which was approximately as the control value (2.25±0.04 for chlorophyll a and 0.49±0.03 for chlorophyll b). The content of chlorophyll a and b significantly (P <0.05) decreased from the control value 2.24±0.11 and 0.5±0.03 to 1.65±0.15 and 0.30±0.04 within 4 h under cold stress in the cold-sensitive clone. The cold tolerance of rubber tree clone 93–114 may be associated with the pulsed production of endogenous hydrogen peroxide and the enhanced activation of the enzymatic and non-enzymatic reactive oxygen species (ROS) scavengers in response to cold stress.

Pre-storage cold acclimation maintained quality of cold-stored cucumber through differentially and orderly activating ROS scavengers

Cucumber fruit are susceptible to chilling injury (CI) during storage and shipping at temperatures below 7–10°C. Pre-storage cold acclimation (PsCA) is a promising postharvest method for reducing CI and maintaining quality, but the reported duration of PsCA varies greatly, partly because no method so far has been developed for evaluating the chilling tolerance induced by PsCA at an early time. Following PsCA at 10°C for 6h, 12h, 24h, 48h and 72h, CI, secondary diseases and relative electrolyte leakage of cucumbers stored at 5°C decreased with PsCA duration, indicating PsCA-induced chilling tolerance in cucumber was positively correlated with the length of exposure to PsCA. Meanwhile, PsCA increased soluble solids and ascorbic acid, and reduced malondialdehyde, O2− and H2O2, suggesting that PsCA improved quality by inhibiting reactive oxygen species (ROS) and maintaining cell membrane integrity. In addition, PsCA enhanced gene expression and activities of four enzymatic ROS scavengers, superoxide dismutase, peroxidase, ascorbate peroxidase, catalase and two non-enzymatic ROS scavengers, AsA and glutathione. However, different ROS scavengers had variable transition points before they were consistently activated, suggesting that ROS scavengers were differentially activated in an orderly way and that the chilling tolerance is positively correlated with the number of activated ROS scavengers, but require enough number of ROS scavengers to be effective. This study provides possibility for early evaluation of PsCA-induced chilling tolerance and for timely arrangement of marketing and processing to reduce losses.

Melatonin protects female rats against steatosis and liver oxidative stress induced by oestrogen deficiency

AimsMelatonin has been shown to protect cells against oxidative and inflammatory damage via endocrine, paracrine and autocrine actions. Postmenopausal condition is associated with a high incidence of many features of metabolic syndrome including obesity, steatosis and liver oxidative injuries. The aim of this work was to investigate whether treatment with melatonin improves metabolic disturbances associated with oestrogen deficiency in ovariectomised (OVX) rats. Main methodsOVX and control (CON) female rats were treated with melatonin (10mg/kg×day for 3weeks, p.o.). Body weight gain, adiposity index, plasma biochemical parameters, liver lipid content, hepatic mitochondrial respiration, fatty acid oxidation and mitochondrial H2O2 generation and the activity of the most important enzymatic and non-enzymatic reactive oxygen species (ROS) scavenger systems were measured. Key findingsIn OVX rats, melatonin suppressed lipid accumulation and cellular oxidative stress in the liver. There was a reduction in the levels of carbonylated proteins in the mitochondria and cytosol, reduction in the malondialdehyde contents in the liver homogenates, stimulation of cytosolic glutathione peroxidase and glutathione reductase activities and restoration of reduced glutathione contents to normal levels. SignificanceExogenous melatonin protects the liver of OVX rats against steatosis and cellular oxidative stress, possibly via activation of antioxidant enzymes related to glutathione metabolism and by a direct radical scavenging activity.

Determination of F2-isoprostanes in cultured human lung epithelial cells after exposure to metal oxide and silica nanoparticles by high-performance liquid chromatography/tandem mass spectrometry

The environmental impact of nanotechnology has caused a great concern. Many in vitro studies showed that many types of nanoparticles were cytotoxic. However, whether these nanoparticles caused cell membrane damage was not well studied. F2-isoprostanes are specific products of arachidonic acid peroxidation by nonenzymatic reactive oxygen species and are considered as reliable biomarkers of oxidative stress and lipid peroxidation. In this article, we investigated the cytotoxicity of different nanoparticles and the degree of cellular membrane damage by using F2-isoprostanes as biomarkers after exposure to nanoparticles. The human lung epithelial cell line A549 was exposed to four silica and metal oxide nanoparticles: SiO2 (15 nm), CeO2 (20 nm), Fe2O3 (30 nm), and ZnO (70 nm). The levels of F2-isoprostanes were determined by using high-performance liquid chromatography/mass spectrometry. The F2-isoprostanes’ peak was identified by retention time and molecular ion m/z at 353. Oasis HLB cartridge was used to extract F2-isoprostanes from cell medium. The results showed that SiO2, CeO2, and ZnO nanoparticles increased F2-isoprostanes levels significantly in A549 cells. Fe2O3 nanoparticle also increased F2-isoprostanes level, but was not significant. This implied that SiO2, CeO2, ZnO, and Fe2O3 nanoparticles can cause cell membrane damage due to the lipid peroxidation. To the best of our knowledge, this is the first report on the investigation of effects of cellular exposure to metal oxide and silica nanoparticles on the cellular F2-isoprostanes levels.