Activities Of Major Antioxidant Enzymes Research Articles

Glycated LDL generates reactive species that damage cell components, oxidize hemoglobin and alter surface morphology in human erythrocytes

Low-density lipoprotein (LDL) transports cholesterol to various tissues via the blood. Glycation of LDL occurs during hyperglycemic condition which is characterised by persistently high blood glucose level. Circulating erythrocytes can come in direct contact with glycated LDL (G-LDL). The objective of this study was to investigate the effect of G-LDL on human erythrocytes, specifically on hemoglobin, intracellular generation of reactive species and the antioxidant defence system. Isolated erythrocytes were incubated with G-LDL (3 and 6 mg/ml) and native LDL (6 mg/ml) at 37 °C for 24 h. Native LDL and G-LDL untreated erythrocytes were similarly incubated at 37 °C and served as control. G-LDL treatment increased hemolysis compared to control and native LDL-treated erythrocytes. Incubation of erythrocytes with G-LDL led to an increase in protein oxidation and lipid peroxidation while greatly decreasing the total sulfhydryl content. It also significantly enhanced hemoglobin oxidation, heme degradation, and the release of free iron moiety. Treatment with G-LDL led to an appreciable increase in the production of reactive oxygen and nitrogen species. The antioxidant power and activities of major antioxidant enzymes were drastically reduced, while critical membrane-bound enzymes were inhibited. The surface morphology of G-LDL-treated erythrocytes was altered leading to the formation of echinocytes. Importantly, treatment of erythrocytes with native LDL did not significantly affect the above-mentioned parameters and values were similar to the corresponding controls. Thus, G-LDL is cytotoxic to human erythrocytes and causes oxidative damage to cell components. This can reduce the oxygen-transporting ability of blood and also result in red cell senescence and anemia.

Zinc Oxide Nanoparticles Alleviate Salt Stress in Cotton (Gossypium hirsutum L.) by Adjusting Na+/K+ Ratio and Antioxidative Ability.

Soil salinization poses a threat to the sustainability of agricultural production and has become a global issue. Cotton is an important cash crop and plays an important role in economic development. Salt stress has been harming the yield and quality of many crops, including cotton, for many years. In recent years, soil salinization has been increasing. It is crucial to study the mechanism of cotton salt tolerance and explore diversified materials and methods to alleviate the salt stress of cotton for the development of the cotton industry. Nanoparticles (NPs) are an effective means to alleviate salt stress. In this study, zinc oxide NPs (ZnO NPs) were sprayed on cotton leaves with the aim of investigating the intrinsic mechanism of NPs to alleviate salt stress in cotton. The results show that the foliar spraying of ZnO NPs significantly alleviated the negative effects of salt stress on hydroponic cotton seedlings, including the improvement of above-ground and root dry and fresh weight, leaf area, seedling height, and stem diameter. In addition, ZnO NPs can significantly improve the salt-induced oxidative stress by reducing the levels of MDA, H2O2, and O2- and increasing the activities of major antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Furthermore, RNA-seq showed that the foliar spraying of ZnO NPs could induce the expressions of CNGC, NHX2, AHA3, HAK17, and other genes, and reduce the expression of SKOR, combined with the CBL-CIPK pathway, which alleviated the toxic effect of excessive Na+ and reduced the loss of excessive K+ so that the Na+/K+ ratio was stabilized. In summary, our results indicate that the foliar application of ZnO NPs can alleviate high salt stress in cotton by adjusting the Na+/K+ ratio and regulating antioxidative ability. This provides a new strategy for alleviating the salt stress of cotton and other crops, which is conducive to the development of agriculture.

Allantoin and Tissue Specific Redox Regulation in Mud Crab Scylla serrata under Varied Natural Water Physico-Chemical Parameters

Effects of varied sediment and physico-chemical properties of water on allantoin content in tissues of Scylla serrata and its role in antioxidant homeostasis were investigated. Tissues of crabs were sampled from different coastal natural habitats of S. serrata of India during summer, winter, and rainy seasons and were analyzed to detect the variation in allantoin content and lipid peroxidation (LPx) and oxidative stress (OS) neutralizing antioxidant factors. High allantoin content in hepatopancreas over muscle tissue was observed in all seasons and sampling sites. The correlation coefficient values between allantoin and environmental factors, i.e., temperature, pH, salinity, organic carbon, Mg, and Ca, strongly support the stress-induced allantoin variation level in tissues. The level of allantoin had a negative correlation with levels of ROS, which was probably due to the upregulation of the activity of major antioxidant enzymes and assisting enzymes such as glutathione peroxidase (GPx), glutathione reductase (GR), and biotransforming enzyme glutathione -s- transferases (GST). A significant seasonal variation in the level of allantoin was correlated with the activity of including superoxide dismutase, catalase, GPx, GR, and GST, which was clearly noticed as a function of abiotic factors. Additionally, the level of allantoin did not correlate with small antioxidant molecules, such as ascorbic acid and reduced glutathione. Discriminant function analysis revealed that the level of allantoin and CAT and GR activities were the major contributing factors for the clear discrimination of groups. Therefore, allantoin can be considered as a significant factor for the seasonal modulation of OS physiology in mud crab Scylla serrata.

CLERODENDRUM INFORTUNATUM ATTENUATES PANCREATIC OXIDATIVE STRESS AND DYSREGULATED CARBOHYDRATE METABOLISM IN STREPTOZOTOCIN-INDUCED EXPERIMENTAL DIABETES

The prevalence of diabetes mellitus is increasing at an alarming rate and is gravely troubling human health and quality of life. Side effects of synthetic hypoglycemic agents have led to investigations on alternative sources such as herbal drugs in treating diabetes. Anti-diabetic properties of Clerodendrum infortunatum in streptozotocin-induced experimental diabetes were evaluated and compared with the standard anti-diabetic drug glibenclamide. Aqueous extract of C. infortunatum on carbohydrate metabolism revealed its hypoglycemic effect in diabetic conditions. Furthermore, it could significantly modulate insulin secretion, glycolysis, gluconeogenesis and glycogen metabolism for effective glucose homeostasis. Notably, the drug could accelerate the activities of major antioxidant enzymes and reduce the content of lipid peroxidation products in the pancreas. The study proves the efficacy of C. infortunatum as a potent source of phytochemicals in ameliorating diabetic complications and suggests the medicinal plant as a nutraceutical agent.

7β-Hydroxycholesterol and 7-ketocholesterol: New oxidative stress biomarkers of sarcopenia inducing cytotoxic effects on myoblasts and myotubes

Aging is a complex biological process which can be associated with skeletal muscle degradation leading to sarcopenia. The aim of this study consisted i) to determine the oxidative and inflammatory status of sarcopenic patients and ii) to clarify the impact of oxidative stress on myoblasts and myotubes. To this end, various biomarkers of inflammation (C-reactive protein (CRP), TNF-α, IL-6, IL-8, leukotriene B4 (LTB4)) and oxidative stress (malondialdehyde, conjugated dienes, carbonylated proteins and antioxidant enzymes: catalase, superoxide dismutase, glutathione peroxidase) as well as oxidized derivatives of cholesterol formed by cholesterol autoxidation (7-ketocholesterol, 7β-hydroxycholesterol), were analyzed. Apelin, a myokine which contributes to muscle strength, was also quantified. To this end, a case-control study was conducted to evaluate the RedOx and inflammatory status in 45 elderly subjects (23 non-sarcopenic; 22 sarcopenic) from 65 years old and higher. SARCopenia-Formular (SARC-F) and Timed Up and Go (TUG) tests were used to distinguish between sarcopenic and non-sarcopenic subjects. By using red blood cells, plasma and/or serum, we observed in sarcopenic patients an increased activity of major antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase) associated with lipid peroxidation and protein carbonylation (increased level of malondialdehyde, conjugated dienes and carbonylated proteins). Higher levels of 7-ketocholesterol and 7β-hydroxycholesterol were also observed in the plasma of sarcopenic patients. Significant differences were only observed with 7β-hydroxycholesterol. In sarcopenic patients comparatively to non-sarcopenic subjects, significant increase of CRP, LTB4 and apelin were observed whereas similar levels of TNF-α, IL-6 and IL-8 were found. The increased plasma level of 7-ketocholesterol and 7β-hydroxycholesterol in sarcopenic patients led us to study the cytotoxic effect of these oxysterols on undifferentiated (myoblasts) and differentiated (myotubes) murine C2C12 cells. With the fluorescein diacetate and sulforhodamine 101 assays, an induction of cell death was observed both on undifferentiated and differentiated cells: the cytotoxic effects were less pronounced with 7-ketocholesterol. In addition, IL-6 secretion was never detected whatever the culture conditions, TNF-α secretion was significantly increased on undifferentiated and differentiated C2C12 cells treated with 7-ketocholesterol- and 7β-hydroxycholesterol, and IL-8 secretion was increased on differentiated cells. 7-ketocholesterol- and 7β-hydroxycholesterol-induced cell death was strongly attenuated by α-tocopherol and Pistacia lentiscus L. seed oil both on myoblasts and/or myotubes. TNF-α and/or IL-8 secretions were reduced by α-tocopherol and Pistacia lentiscus L. seed oil. Our data support the hypothesis that the enhancement of oxidative stress observed in sarcopenic patients could contribute, especially via 7β-hydroxycholesterol, to skeletal muscle atrophy and inflammation via cytotoxic effects on myoblasts and myotubes. These data bring new elements to understand the pathophysiology of sarcopenia and open new perspectives for the treatment of this frequent age-related disease.

Curcumin from Curcuma longa Linn. (Family: Zingiberaceae) attenuates hypochlorous acid-induced cytotoxicity and oxidative damage to human red blood cells

Hypochlorous acid (HOCl) is a major oxidant produced by activated neutrophils via the myeloperoxidase catalyzed reaction. The production of HOCl eliminates a wide range of pathogens. However, HOCl can also cause significant oxidative damage in cells and tissues where it is generated. The protective effect of curcumin was studied on HOCl-induced oxidative damage to human red blood cells (RBC). Isolated RBC were incubated with HOCl at 37°C in absence or presence of different concentrations of curcumin. Hemolysates were prepared and assayed for various biochemical parameters. Treatment of RBC with HOCl alone increased hemolysis, protein carbonyls, heme degradation and chloramines as compared to untreated control cells. This was accompanied by reduction in glutathione level, total sulfhydryls and free amino groups. HOCl also lowered the activities of major antioxidant enzymes and diminished the antioxidant power of RBC. Pre-treatment of RBC with different concentrations of curcumin resulted in concentration-dependent attenuation in all these parameters while curcumin alone had no significant effect. Scanning electron microscopy showed that curcumin prevented HOCl-induced morphological changes in RBC and restored their normal biconcave shape. Thus curcumin can be used as a chemoprotective agent to mitigate HOCl-induced oxidative damage to cells. These results also explain the beneficial effects of curcumin against Helicobacter pylori induced stomach ulcers, caused by excessive production of HOCl at the site of bacterial infection.

Disulfiram Enhances the Antineoplastic Activity and Sensitivity of Murine Hepatocellular Carcinoma to 5-FU via Redox Management.

The efficacy of anticancer drug 5-FU is suppressed due to various factors, including severe side effects and decreased insensitivity during prolonged chemotherapy. Elevated endogenous copper (Cu) levels are one of the prominent hallmark features of cancer cells. In the present investigation, this feature was targeted in diethyl nitrosamine-phenobarbital-induced hepatocellular carcinoma (HCC) in a rat model system by an established anticancer drug, 5-FU, co-administered with copper and its chelating agent, disulfiram. After treatment with the test chemicals in HCC-induced rats, blood and liver samples were subjected to biochemical, molecular, and histopathological analyses. The analysis revealed that reactive oxygen species-mediated oxidative stress is the crucial etiological reason for the pathogenesis of HCC in rats, as evidenced by the significantly compromised activity of major antioxidant enzymes and elevated levels of oxidative damaged products with major histological alterations compared to the control. However, the combination of 5-FU with DSF demonstrated a significant improvement in most of the parameters, followed by 5-FU-Cu in the combination-treated groups. The combination treatment improved the histological details and triggered apoptosis in the cancer cells to a remarkable extent, as the levels of cleaved PARP and caspase-3 were significantly higher than those in the HCC rats treated with the drug alone. The present study envisages that manipulating the Cu-level greatly enhances the antineoplastic activity of 5-FU and sensitizes cancer cells to the increased efficacy of the drug.

Oxidative Stress Potential, Genotoxic and Histopathological Effects of Ethanolic Extract of Alternanthera philoxeroides on Clarias gariepinus (Cat Fish)

This study used static bioassay to evaluate oxidative and genotoxic effect caused by ethanolic extract of A. philoxeroides in the liver of C. gariepinus as well as the Histopathological damages caused by the extract on the liver, gills and intestine of the fish. LC50 of the ethanolic extract of A. philoxeroides was determined by probit regression analysis. Fishes were exposed to the sublethal concentration of the extract at the rate of 1% and 10% concentration of the LC50 value in replicate for 21days. During the cause of exposure the fishes exhibited some behavioral changes such as erratic swimming pattern, restlessness and excessive mucus secretion. The oxidative stress study revealed that antioxidant enzyme activities were lower in the liver suggesting deficiency of the antioxidant system to compensate for oxidative stress. DNA damage was high in liver of the exposed fish indicating genotoxic effects. The histological structure of the liver of the fish showed the presence of traces to mild onset of nuclei degeneration. The gills of fish exposed to the extract showed severe collapse of the secondary lamella in conjunction with hyperplasia of the pillar cells within the lamella as well as severe atrophy of the cells, degeneration of the primary lamella and severe cellular and structural damages of the gills. The intestine of the fish group exposed to the extract revealed a small amount of PAS-positively stained substances in the lamina propria, mucus cells and the apical borders of the epithelial cells showing the presence of mucous substances. This study concluded that exposure of C. gariepinus to ethanolic extract of Alternanthera philoxeroides have the ability to negatively affect the behavior, suppress the activities of major antioxidant enzymes of the liver thereby causing oxidative stress, with consequent degeneration of liver and gill tissue which expresses its genotoxicity.

Photosystems and antioxidative system of rye, wheat and triticale under Pb stress

Lead (Pb2+) pollution in the soil sub-ecosystem has been a continuously growing problem due to economic development and ever-increasing anthropogenic activities across the world. In this study, the photosynthetic performance and antioxidant capacity of Triticeae cereals (rye, wheat and triticale) were compared to assess the activities of antioxidants, the degree of oxidative damage, photochemical efficiency and the levels of photosynthetic proteins under Pb stress (0.5 mM, 1 mM and 2 mM Pb (NO3)2). Compared with triticale, Pb treatments imposed severe oxidative damage in rye and wheat. In addition, the highest activity of major antioxidant enzymes (SOD, POD, CAT, and GPX) was also found to be elevated. Triticale accumulated the highest Pb contents in roots. The concentration of mineral ions (Mg, Ca, and K) was also high in its leaves, compared with rye and wheat. Consistently, triticale showed higher photosynthetic activity under Pb stress. Immunoblotting of proteins revealed that rye and wheat have significantly lower levels of D1 (photosystem II subunit A, PsbA) and D2 (photosystem II subunit D, PsbD) proteins, while no obvious decrease was noticed in triticale. The amount of light-harvesting complex II b6 (Lhcb6; CP24) and light-harvesting complex II b5 (Lhcb5; CP26) was significantly increased in rye and wheat. However, the increase in PsbS (photosystem II subunit S) protein only occurred in wheat and triticale exposed to Pb treatment. Taken together, these findings demonstrate that triticale shows higher antioxidant capacity and photosynthetic efficiency than wheat and rye under Pb stress, suggesting that triticale has high tolerance to Pb and could be used as a heavy metal-tolerant plant.

Exogenous foliar ascorbic acid applications enhance salt-stress tolerance in peanut plants through increase in the activity of major antioxidant enzymes

• The application of AsA increment physiological and biochemical defense mechanisms in plants. • The exogenous application of AsA can be strategy to withstand or avoid stress imposed by salinity. • Salt tolerance conferred by exogenous application of AsA can be associated with the modulation of ROS- scavenging enzymes. Although ascorbic acid (AsA) is an antioxidant that can protect plants from oxidative damages, little is known about physiological and biochemical responses of exogenous AsA-regulated antioxidant systems to stressful-conditions in peanut plants. This study aimed to evaluate the effects of AsA-foliar applications on antioxidant defense responses in peanut plants irrigated with saline water. The experiment was carried out in a completely randomized design with four treatments formed by combining and not AsA under salt-stressful conditions (control, 50 mM AsA, 50 mM NaCl and 50 mM NaCl + 50 mM AsA). AsA application was performed twice a week spraying plant shoot. After a period of 40 days post germination, plants were collected and evaluated for the following parameters: total chlorophyll and carotenoids contents; dry biomass; malondialdehyde (MDA) and H 2 O 2 contents, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GSH-Px) and glutathione reductase (GR). AsA increased total chlorophyll and carotenoid contents, reduced Na + concentration, and oxidative damages by modifying antioxidant defense systems. Therefore, the exogenous application of AsA is an efficient strategy to withstand or avoid stress imposed by salt, which can be attributed to increased SOD, CAT, APX, GSH-Px and GR activities in peanut plants, and enhance salt tolerance.

The inhibitory effects of simulated light sources on the activity of algae cannot be ignored in photocatalytic inhibition

Harmful algal blooms (HABs) destroy the balance of the aquatic ecosystem, causing huge economic losses and even further endangers human health. In addition to traditional methods of algae removal, photocatalytic inhibition of algae is drawing more and more interests with rich application scenarios and considerable potential. Simulated visible light sources are used to excite photocatalytic materials and optimize their performance. However, most of the light irradiation intensities used in the study exceeded 50 mW/cm2. And the effects of intense light irradiation conditions on algal growth have rarely been addressed in previous studies. So we focused on the effect of different intensity of light irradiation on the growth of algae. We explored the relationship between light irradiation intensity and algal inactivation rate, and investigated the changes in ROS levels in algal cells under different light irradiation and the resulting response of the antioxidant system. We have found that several major antioxidant enzyme activities, such as SOD and CAT, were significantly higher and lipid peroxidation products (MDA) were accumulating. Intense light irradiation had the most direct effect on the photosynthetic system of algal cells, with the photosynthetic rate and relative electron transfer rate decaying to almost 0 within 30 min, indicating that algal photosynthesis was inhibited in a fairly short period of time. We further observed the physiological and morphological changes of algal cells during this process using TEM and found that the progressive dissolution of the cell membrane system and the damage of organelles associated with photosynthesis play a major role in promoting cell death. We thus conclude that light irradiation has a significant effect on the physiological activity of algal cells and is a non-negligible factor in the study of photocatalytic removal of harmful algae. It will provide theoretical guidance for the future study of photocatalysis on algae inhibition.

Effect of a Biostimulant Based on Polyphenols and Glycine Betaine on Tomato Plants’ Responses to Salt Stress

Climate change accentuates abiotic stress conditions putting at risk several commercial cultivars particularly vulnerable to salinity in the early stages of development, which makes adopting new technologies in tune with the environment necessary to mitigate its impact. In this study, we tested the possible effects of a commercial biostimulant (BALOX®) on enhancing salt stress tolerance in salt-treated tomato plants, analysing plant growth and several stress biochemical markers: photosynthetic pigments, ion contents in roots and leaves, leaf concentrations of different osmolytes, oxidative stress markers, non-enzymatic antioxidants, and the specific activities of major antioxidant enzymes. The experimental design consisted of three soil salinity levels (non-saline, saline, and very saline), two biostimulant doses (0.4 mL and 0.8 mL of the BALOX® stock per litre of irrigation water), and the non-treated control (without biostimulant), evaluated at 30 and 60 days of treatment. The biostimulant favoured plant growth, especially at the root level and in saline soils. In addition, it helped reduce Na+ and Cl− uptake by the roots and seemed to stimulate, to some extent, K+ and Ca2+ transport to the aerial part of the plant. The BALOX® application significantly reduced the level of stress affecting the plants in saline soils, as shown by the decrease in the contents of proline and oxidative stress biomarkers and the activity of salt-induced antioxidant enzymes. Some of the biostimulant effects were also observed under low salinity conditions; therefore, in addition to enhancing salt stress responses, BALOX® appears to stimulate the growth of tomato plants through a general improvement of photosynthesis and primary metabolism.

Alleviation of Ammonium Toxicity in Salvia splendens ‘Vista Red’ with Silicon Supplementation

Ammonium (NH4+) toxicity seriously hampers the yield and quality of salvia plants because most varieties or sub-species are highly sensitive to NH4+. Silicon (Si) is an alternative that is used to minimize these disturbances and maintain better growth under NH4+ toxicity. Nevertheless, the mitigatory effects of Si on NH4+-stressed salvia are unknown. Therefore, this study was carried out to determine how Si assists to alleviate the NH4+ toxicity degree in salvia. To this end, salvia plants were cultivated in a controlled environment supplied with a constant N (nitrogen) level (13 meq·L−1) in the form of three NH4+:NO3− ratios (0:100, 50:50, 100:0), each with (1.0 meq·L−1) or without Si. Physiological disorders and typical NH4+ toxicity symptoms, as well as interrupted photosynthesis, were observed in the 100% NH4+-treated plants. Furthermore, cation uptake inhibition and oxidative damage were also imposed by the 100% NH4+ supply. In contrast, in the presence of Si, the NH4+ toxicity degree was attenuated and plant growth was ensured. Accordingly, the NH4+ toxicity appearance ratio decreased significantly. Furthermore, Si-treated plants showed an ameliorated photosynthetic ability, elevated internal K and Ca levels, and enhanced antioxidative capacity, as reflected by improved major antioxidant enzyme activities, as well as diminished accumulation of ROS (reactive oxygen species) and MDA (malondialdehyde). Our findings enlightened the agronomic importance of additional Si to nutrient solutions, especially pertaining to bedding plants at risk of NH4+ toxicity.

Effects of faba bean (Vicia faba L.) on fillet quality of Yellow River carp (Cyprinus carpio) via the oxidative stress response

In order to further explain the fillet texture improvement of Yellow River carp (Cyprinus carpio) fed with faba bean (Vicia faba L.), a three-month rearing trial was conducted to investigate fatty acid composition, antioxidant capacity, myofiber development, collagen deposition and transcriptome in white muscle of two farmed carp groups (One was fed only faba bean, the other was fed commercial diet). As a strong oxidant, faba bean changed fatty acids composition in white muscle, especially DHA and EPA, up-regulated the levels of reactive oxygen species (ROS) and down-regulated major antioxidant enzyme activities in the hepatopancreas and white muscle. Through the analysis of transcriptome and subsequent verification analysis, we speculated that the increase of ROS led to the decrease of myofiber diameter and collagen metabolism. This study provides a theoretical basis for further understanding the regulation of faba bean on fillet texture characteristic of Yellow River carp.

Hypochlorous acid decreases antioxidant power, inhibits plasma membrane redox system and pathways of glucose metabolism in human red blood cells.

Hypochlorous acid (HOCl) is generated at a high concentration by activated neutrophils at sites of inflammation in a myeloperoxidase catalyzed reaction. The increased and sustained production of HOCl at inflammatory sites may lead to tissue injury and this process is believed to play an important role in the progression of several diseases like chronic inflammation, atherosclerosis and some types of cancers. We have examined the effect of HOCl on human red blood cells (RBCs) under in vitro conditions. Treatment of RBC with different concentrations of HOCl (0.05-2.5mM) at 37°C resulted in decreased activities of major antioxidant enzymes while the antioxidant power of RBC was weakened, as shown by lowered metal-reducing and free radical quenching ability of HOCl treated cells. RBC plasma membrane redox system was also inhibited suggesting membrane damage. The enzymes of glucose metabolism were inhibited indicating deranged energy metabolism. Electron microscopic images showed gross morphological changes in HOCl treated RBC. These results show that HOCl causes major alterations in the cellular antioxidant defense system and inhibition of glycolytic pathways, which increase the susceptibility of RBC to oxidative damage.

P-Coumaric acid induces antioxidant capacity and defense responses of sweet cherry fruit to fungal pathogens

Abstract Phenolic acids are important secondary metabolites involved in multiple physiological activities in plants, such as enzymatic activities and nutrient uptake. Given their health-promoting benefits, phenolic acids have attracted considerable research interests. However, their functions in maintaining postharvest fruit quality and suppressing disease incidence are seldom documented. Here, we reported that p-coumaric acid (p-CA) dramatically reduced the natural decay rate and maintained organoleptic quality of sweet cherry fruit, which was mainly attributed to activation of phenylpropanoid metabolic pathway and cell wall remodeling, elevated contents of non-enzymatic antioxidants and improved activities of major antioxidant enzymes. Moreover, p-CA also significantly inhibited mycelial growth of Botrytis cinerea and Penicillium expansum, and it also reduced patulin production from P. expansum. Collectively, these results demonstrated that p-CA can improve antioxidant capacity and defense responses of sweet cherry fruit to fungal pathogens, which may provide references for understanding the freshness-keeping mechanisms relevant to plant-derived phenolic acids.

Exogenous silicon and salicylic acid applications improve tolerance to boron toxicity in field pea cultivars by intensifying antioxidant defence systems.

Field peas (Pisum sativum L.) are widely cultivated throughout the world as a cool season grain and forage crop. Boron (B) toxicity is caused by high B concentration in the soil or irrigation water, and is particularly problematic in medium or heavier textured soil types with moderate alkalinity and low annual rainfall. Previous studies have indicated that B-toxicity increases oxidative stress in plants, and B-tolerance has been considered an important target in field pea plant breeding programmes. Inducers of tolerance may be a promising alternative for plant breeding. Little research has been conducted on the combined use of silicon (Si) and salicylic acid (SA) to remediate B-toxicity in field peas. The present study revealed the physiological and biochemical plant responses of applying Si+SA under B-toxicity (15mgB L-1) on two Brazilian field pea cultivars (Iapar 83 and BRS Forrageira). A semi-hydroponic experiment was conducted using a completely randomized factorial design (2×5): with two field pea cultivars and five treatments which were formed by individual and combined applications of Si and SA under B-toxicity plus a control (control, B, B+Si, B+SA, and B+Si+SA). Si (2mmolL-1) was applied to plants in two forms (root and leaf), while for SA (36 μmol L-1) only foliar applications were applied. Our results demonstrated that the combined use of exogenous Si+SA in field peas increased tolerance to B-toxicity through an intensified antioxidant plant defence system, resulting in a better regulation of reactive oxygen species (ROS) production and degradation. It significantly increased total chlorophyll and carotenoids contents, the activities of major antioxidant enzymes, and reduced MDA and H2O2 contents, resulting in increased fresh shoot and total plant dry biomass. The application of Si+SA alleviated the inhibitory effects of boron toxicity in field peas, resulting in greater plant growth by preventing oxidative membrane damage through an increased tolerance to B-excess within the plant tissue. Therefore, the use of Si+SA is an important and sustainable strategy to alleviate B-toxicity in field pea cultivation.

Salicylic acid-induced nitric oxide enhances arsenic toxicity tolerance in maize plants by upregulating the ascorbate-glutathione cycle and glyoxalase system

The role of nitric oxide (NO) in salicylic acid (SA)-induced tolerance to arsenic (As) stress in maize plants is not reported in the literature. Before starting As stress (AsS) treatments, SA (0.5 mM) was sprayed to the foliage of maize plants. Thereafter, AsV (0.1 mM as sodium hydrogen arsenate heptahydrate) stress (AsS) was initiated and during the stress period, sodium nitroprusside (SNP 0.1 mM), a NO donor, was sprayed individually or in combination with SA. Furthermore, cPTIO (0.1 mM) was also applied as a NO scavenger during the stress period. Arsenic stress led to significant reductions in plant growth, photosynthesis, water relation parameters and endogenous NO content, but it increased hydrogen peroxide, malondialdehyde, electrolyte leakage, methylglyoxal, proline, the activities of major antioxidant enzymes, and leaf and root As content. The combined treatment of SA+SNP was more effective to reverse oxidative stress related parameters and reduce the As content in both leaves and roots, with a concomitant increase in antioxidant defense system, the ascorbate-glutathione (AsA-GSH) cycle-related enzymes, glyoxalase system enzymes, plant growth, and photosynthetic traits. The beneficial effects of SA were completely abolished with cPTIO supply by blocking the NO synthesis in AsS-maize plants, indicating that NO effectively participated in SA-improved tolerance to AsS in maize plants.

Glutamate alleviates cadmium toxicity in rice via suppressing cadmium uptake and translocation

Cadmium (Cd), a naturally occurring heavy metal, is toxic to animals and plants. Minimization of Cd in rice grain is important to human health since rice is the main source of Cd intake for human populations feeding on it as staple food. Glutamate (Glu) is reportedly involved in plant abiotic stress responses, whereas the underlying molecular mechanism remains poorly understood. In this study, we showed that supplement of Glu, but not glutamine, significantly alleviated Cd toxicity in hydroponically grown rice plants. Cd accumulation was reduced by 44.1% and 65.6% in root and shoot of rice plants respectively, after Glu supplementation (3 mM). Glu supplement restored chlorophyll biosynthesis and significantly ameliorated Cd-induced oxidative stress with reduced levels of H2O2, 1O2, MDA, and increased activities of major anti-oxidant enzymes, catalase, peroxidase and glutathione S-transferase. Levels of stress-associated free amino acids proline, arginine and γ-aminobutyric acid were also reduced after Glu supplement. We further demonstrated that Glu supplement suppressed the Cd-induced expression of metal transporter genes OsNramp1, OsNramp5, OsIRT1, OsIRT2, OsHMA2 and OsHMA3 in roots of Cd-treated plants. Taken together, our results suggest that Glu supplement could alleviate Cd toxicity in rice by suppressing Cd uptake and translocation.

Copper(II) generates ROS and RNS, impairs antioxidant system and damages membrane and DNA in human blood cells.

Copper (Cu) is widely used in various industries, and human exposure to this metal results in severe multi-organ toxicity, which is thought to be due to the generation of free radicals by Fenton-like reaction. The generation of reactive oxygen as well as nitrogen species and free radicals results in induction of oxidative stress in the cell. We have studied the effect of different concentrations of Cu(II) on human erythrocytes and lymphocytes. Incubation of erythrocytes with copper chloride, a Cu(II) compound, enhanced the production of reactive oxygen and nitrogen species, decreased glutathione and total sulphydryl content and increased protein oxidation and lipid peroxidation. All changes were in a Cu(II) concentration-dependent manner. This strongly suggests that Cu(II) causes oxidative damage in erythrocytes. The activities of major antioxidant enzymes were altered, and antioxidant power was lowered. Cu(II) treatment also resulted in membrane damage in erythrocytes as seen by electron microscopy and lowered activities of plasma membrane-bound enzymes. Incubation of human lymphocytes with Cu(II) resulted in DNA damage when studied by the sensitive comet assay. These results show that Cu(II) exerts cytotoxic and genotoxic effects on human blood cells probably by enhancing the generation of reactive oxygen and nitrogen species.