Activity Of Ascorbate Research Articles

Nanomaterial sulfonated graphene oxide advances the tolerance against nitrate and ammonium toxicity by regulating chloroplastic redox balance, photochemistry of photosystems and antioxidant capacity in Triticum aestivum

The current study was designed to assess nanomaterial sulfonated graphene oxide (SGO) potential in improving tolerance of wheat chloroplasts against nitrate (NS) and ammonium (AS) toxicity. Triticum aestivum cv. Ekiz was grown under SGOs (50–250–500 mg L−1) with/without 140 mM NS and 5 mM AS stress. SGOs were eliminated the adverse effects produced by stress on chlorophyll fluorescence, potential photochemical efficiency and physiological state of the photosynthetic apparatus. SGO reversed the negative effects on these parameters. Upon SGOs exposure, the induced expression levels of photosystems-related reaction center proteins were observed. SGOs reverted radical accumulation triggered by NS by enabling the increased superoxide dismutase (SOD) activity and ascorbate (AsA) regeneration. Under AS, the turnover of both AsA and glutathione (GSH) was maintained by 50–250 mg L−1 SGO by increasing the enzymes and non-enzymes related to AsA-GSH cycle. 500 mg L−1 SGO prevented the radical over-accumulation produced by AS via the regeneration of AsA and peroxidase (POX) activity rather than GSH regeneration. 50–250 mg L−1 SGO protected from the NS+AS-induced disruptions through the defense pathways connected with AsA-GSH cycle represented the high rates of AsA/DHA and, GSH/GSSG and GSH redox state. Our findings specified that SGO to NS and AS-stressed wheat provides a new potential tool to advance the tolerance mechanism.

CHITOSAN AGAINST TO BORON TOXICITY IN MAIZE

In this study; growth, chlorophyll, carotenoid, proline and MDA contents, the amounts of reactive oxygen species (ROS) (superoxide (O2.-) and hydrogen peroxide (H2O2)), and antioxidants (superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR) activities and its isoenzyme profiles, (ascorbate (AsA), dehydro ascorbate (DHA) and glutathione (GSH)) quantities in maize plants ((Zea mays L. cv. Hido) exposed to boron toxicity (B) (8 mM B(OH)3) and B+chitosan (0.01%, foliar (A) and seed soaking (B) applications) conditions in hydroponic culture have been studied comparatively. Boron toxicity significantly reduced growth parameters, chlorophyll, carotenoid, AsA, DHA and CAT activity while increased proline, MDA, oxidants (O2.- and H2O2), SOD, POD, APX and GR activities and GSH levels. B+Chitosan A and B applications significantly reversed the B toxicity-based inhibition in these parameters. It has been suggested that chitosan can be used as a reliable chemical for boron toxicity in maize, since chitosan applications (A and B) cause improvements in terms of all the parameters in the damage caused by B toxicty.

High doses of sodium ascorbate interfere with the expansion of glioblastoma multiforme cells in vitro and in vivo

AimsConstant development of chemotherapeutic strategies has considerably improved the efficiency of tumor treatment. However, adverse effects of chemotherapeutics enforce premature treatment cessation, which leads to the tumor recurrence and accelerated death of oncologic patients. Recently, sodium ascorbate (ASC) has been suggested as a promising drug for the adjunctive chemotherapy of glioblastoma multiforme (GBM) and prostate cancer (PC). To estimate whether ASC can interfere with tumor recurrence between the first and second-line chemotherapy, we analyzed the effect of high ASC doses on the expansion of cells in vitro and in vivo. Main methodsBrightfield microscopy-assisted approaches were used to estimate the effect of ASC (1–14 mM) on the morphology and invasiveness of human GBM, rat PC and normal mouse 3T3 cells, whereas cytostatic/pro-apoptotic activity of ASC was estimated with flow cytometry. These assays were complemented by the in vitro CellROX-assisted analyses of intracellular oxidative stress and in vivo estimation of GBM tumor invasion. Key findingsASC considerably decreased the proliferation and motility of GBM and PC cells. This effect was accompanied by intracellular ROS over-production and necrotic death of tumor cells, apparently resulting from their “autoschizis”. In vivo studies demonstrated the retardation of GBM tumor growth and invasion in the rats undergone intravenous ASC administration, in the absence of detectable systemic adverse effects of ASC. SignificanceOur data support previous notions on anti-tumor activity of high ASC doses. However, autoschizis-related cell responses to ASC indicate that its application in human adjunctive tumor therapy should be considered with caution.

Accumulation of rosmarinic acid and behaviour of ROS processing systems in Melissa officinalis L. under heat stress

Heat stress (HS) due to increased air temperature is a major agricultural problem. On the other hand, short-term HS can represent a natural easy-to-use elicitor of bioactive compounds in plants. Similar elicitations can be induced by biotechnological approaches such as hydroponic cultures. The present study pioneering investigated the capability of using a short-term HS (38 °C, 5 h) as a tool to rapidly elicit rosmarinic acid (RA) content in leaves of Melissa officinalis L. (a species for which RA is the dominant active phenolic compound) hydroponic cultures, highlighting the cross-talk among antioxidant and signalling molecules involved in the heat acclimation. During HS treatment, we found an elicitation of RA biosynthesis associated with (i) an imbalance in reactive oxygen species (ROS) production and scavenging, (ii) an involvement of reduced ascorbate (AsA) in maintaining a high normal reduced state of cells, (iii) an induction of heat shock proteins (i.e. HSP101-like), and (iv) a stimulation of phytohormones. The RA biosynthesis lasted also during the recovery, although plants activated cellular processes to partially control ROS production, as confirmed by the increased activity of AsA regenerating enzymes, the accumulation of total carotenoids and the stimulation of total antioxidant capacity. The unchanged values of abscisic acid, ethylene and salicylic and jasmonic acids during the recovery phase also documented a reduced demand for protection. The present study represents a wide-ranging investigation of the potential use of HS (without drought interaction) as a technological application for improving bioactive compound production.

Exogenous Silicon Attenuates Cadmium-Induced Oxidative Stress in Brassica napus L. by Modulating AsA-GSH Pathway and Glyoxalase System.

Cadmium (Cd) brings a devastating health hazard to human being as a serious consequence of agricultural and environmental contamination. We demonstrated the protective effect of silicon (Si) on cadmium (Cd)-stressed rapeseed (Brassica napus L. cv. BINA Sharisha 3) plants through regulation of antioxidant defense and glyoxalase systems. Twelve-day-old seedlings were exposed to Cd stress (0.5 and 1.0 mM CdCl2) separately and in combination with Si (SiO2, 1.0 mM) for 2 days. Cadmium toxicity was evident by an obvious oxidative stress through sharp increases in H2O2 content and lipid peroxidation (malondialdehyde, MDA content), and visible sign of superoxide and H2O2. Cadmium stress also decreased the content of ascorbate (AsA) and glutathione (GSH) as well as their redox pool. The activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and catalase (CAT) were decreased by Cd while ascorbate peroxidase (APX) and glutathione S-transferase (GST) activities were increased. The enzymes of glyoxalase system (glyoxalase I, Gly I and glyoxalase II, Gly II) were also inefficient under Cd stress. However, exogenous application of Si in Cd treated seedlings reduced H2O2 and MDA contents and improved antioxidant defense mechanism through increasing the AsA and GSH pools and activities of AsA-GSH cycle (APX, MDHAR, DHAR and GR) and glyoxalase system (Gly I and Gly II) enzymes and CAT. Thus Si reduced oxidative damage in plants to make more tolerant under Cd stress through augmentation of different antioxidant components and methylglyoxal detoxification system.

Jasmonic acid-induced hydrogen peroxide activates MEK1/2 in upregulating the redox states of ascorbate and glutathione in wheat leaves

We studied the relationship between hydrogen peroxide (H2O2) and MEK1/2 in jasmonic acid (JA) signaling in regulating the redox states of ascorbate (AsA) and glutathione (GSH). JA increased H2O2 production, MEK1/2 phosphorylation, the transcription levels and activities of AsA and GSH metabolic enzymes (APX, GR, DHAR, MDHAR, GalLDH and γ-ECS), AsA and GSH contents, and the redox states of AsA and GSH (ratios of AsA/DHA and GSH/GSSG). Above increases were inhibited by applications of H2O2 synthesis inhibitor DPI and scavenger DMTU. However, applications of MEK1/2 inhibitors PD98059 and U0126 had no significant effect on JA-induced H2O2 production. Treatments with exogenous H2O2 also increased MEK1/2 phosphorylation, the transcription levels and activities of AsA and GSH metabolic enzymes, AsA and GSH contents, and the redox states of AsA and GSH. Above increases except the transcription level and activity of γ-ECS were all suppressed by pretreatments with PD98059 and U0126. Our results suggested that JA-induced H2O2 could trigger MEK1/2 phosphorylation and activation leading to the upregulation of AsA and GSH metabolic enzymes.

Transferrin iron uptake is stimulated by ascorbate via an intracellular reductive mechanism

Although ascorbate has long been known to stimulate dietary iron (Fe) absorption and non-transferrin Fe uptake, the role of ascorbate in transferrin Fe uptake is unknown. Transferrin is a serum Fe transport protein supplying almost all cellular Fe under physiological conditions. We sought to examine ascorbate's role in this process, particularly as cultured cells are typically ascorbate-deficient. At typical plasma concentrations, ascorbate significantly increased 59Fe uptake from transferrin by 1.5–2-fold in a range of cells. Moreover, ascorbate enhanced ferritin expression and increased 59Fe accumulation in ferritin. The lack of effect of cycloheximide or the cytosolic aconitase inhibitor, oxalomalate, on ascorbate-mediated 59Fe uptake from transferrin indicate increased ferritin synthesis or cytosolic aconitase activity was not responsible for ascorbate's activity. Experiments with membrane-permeant and -impermeant ascorbate-oxidizing reagents indicate that while extracellular ascorbate is required for stimulation of 59Fe uptake from 59Fe-citrate, only intracellular ascorbate is needed for transferrin 59Fe uptake. Additionally, experiments with l-ascorbate analogs indicate ascorbate's reducing ene-diol moiety is necessary for its stimulatory activity. Importantly, neither N-acetylcysteine nor buthionine sulfoximine, which increase or decrease intracellular glutathione, respectively, affected transferrin-dependent 59Fe uptake. Thus, ascorbate's stimulatory effect is not due to a general increase in cellular reducing capacity. Ascorbate also did not affect expression of transferrin receptor 1 or 125I-transferrin cellular flux. However, transferrin receptors, endocytosis, vacuolar-type ATPase activity and endosomal acidification were required for ascorbate's stimulatory activity. Therefore, ascorbate is a novel modulator of the classical transferrin Fe uptake pathway, acting via an intracellular reductive mechanism.

Cinnamic acid pretreatment mitigates chilling stress of cucumber leaves through altering antioxidant enzyme activity

To elucidate the physiological mechanism of chilling stress mitigated by cinnamic acid (CA) pretreatment, a cucumber variety ( Cucumis sativus cv. Jinchun no. 4) was pretreated with 50 μM CA for 2 d and was then cultivated at two temperatures (15/8 and 25/18 °C) for 1 d. We investigated whether exogenous CA could protect cucumber plantlets from chilling stress (15/8 °C) and examined whether the protective effect was associated with the regulation of antioxidant enzymes and lipid peroxidation. At 2 d, exogenous CA did not influence plant growth, but induced the activities of some antioxidant enzymes, including superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), guaiacol peroxidase (GPX, EC 1.11.1.7), glutathione peroxidase (GSH-Px, EC 1.6.4.2) and ascorbate peroxidase (APX, EC 1.11.1.11) in cucumber leaves, and it also elevated the contents of reduced glutathione (GSH) and ascorbate (AsA). When CA was rinsed and the CA-pretreated seedlings were exposed to different temperatures, the antioxidant activities in leaves at 3 d had undergone additional change. Chilling increased the activities of CAT, GSH-PX, APX, GSH and AsA in leaves, but the combination of CA pretreatment and chilling enhanced the antioxidant activities even more. Moreover, chilling inhibited plant growth and increased the contents of malonaldehyde (MDA), superoxide radical (O 2 −) and hydrogen peroxide (H 2O 2) in cucumber leaves, and the stress resulted in 87.5% of the second leaves being withered. When CA pretreatment was combined with the chilling stress, we observed alleviated growth inhibition and decreased contents of MDA, H 2O 2 and O 2 − in comparison to non-pretreated stressed plants, and found that the withered leaves occurred at a rate of 25.0%. We propose that CA pretreatment increases antioxidant enzyme activities in chilling-stressed leaves and decreases lipid peroxidation to some extent, enhancing the tolerance of cucumber leaves to chilling stress.

Antioxidant defense mechanisms of cereal aphids based on ascorbate and ascorbate peroxidase

AbstractEffects of plant o-dihydroxyphenols on ascorbate (ASA) content and ascorbate peroxidase (APOX) activity in the tissues of the grain aphid Sitobion avenae and the bird cherry-oat aphid Rhopalosiphum padi were studied. Among the aphid morphs, the highest ASA content and APOX activity were noted for larvae and the lowest for wingless apterae. When exposed to o-dihydroxyphenols, aphids of both species contained significantly lower concentrations of ASA and higher APOX activity than the controls. Among the studied compounds, caffeic acid had the strongest effect on ASA-based antioxidant responses in that caffeic acid caused a 5-fold decrease of ASA in aphid tissues. The influences of the plant o-dihydroxyphenols on antioxidant defense mechanisms within the cereal aphid species are discussed.

Salinity up-regulates the antioxidative system in root mitochondria and peroxisomes of the wild salt-tolerant tomato species Lycopersicon pennellii.

The effect of salinity on the antioxidative system of root mitochondria and peroxisomes of a cultivated tomato Lycopersicon esculentum (Lem) and its wild salt-tolerant related species L. pennellii (Lpa) was studied. Salt stress induced oxidative stress in Lem mitochondria, as indicated by the increased levels of lipid peroxidation and H(2)O(2). These changes were associated with decreased activities of superoxide dismutase (SOD) and guaiacol peroxidases (POD) and contents of ascorbate (ASC) and glutathione (GSH). By contrast, in mitochondria of salt-treated Lpa plants both H(2)O(2) and lipid peroxidation levels decreased while the levels of ASC and GSH and activities of SOD, several isoforms of ascorbate peroxidase (APX), and POD increased. Similarly to mitochondria, peroxisomes isolated from roots of salt-treated Lpa plants exhibited also decreased levels of lipid peroxidation and H(2)O(2) and increased SOD, ascorbate peroxidase (APX), and catalase (CAT) activities. In spite of the fact that salt stress decreased activities of antioxidant enzymes in Lem peroxisome, oxidative stress was not evident in these organelles.

Inactivation of phosphorylated rat tyrosine hydroxylase by ascorbate in vitro.

Tyrosine hydroxylase activity is reversibly controlled by the actions of several protein kinases. Previous studies showed that, following phosphorylation by protein kinase A, physiological concentrations of ascorbate irreversibly inactivate tyrosine hydroxylase. Several studies were performed to establish the mechanism of inactivation. We found that inactivation occurred under oxygen-free conditions. The results of this and other experiments suggest that oxygenated species such as superoxide or hydrogen peroxide were not required for inactivation by ascorbate. Inhibition of tyrosine hydroxylase by low concentrations of ascorbate raised the question concerning the mechanism for maintaining enzyme activity under physiological conditions. We report that tyrosine, N alpha-methyl tyrosine, 3-iodotyrosine, and phenylalanine protected the phosphorylated enzyme against ascorbate inactivation. Catecholamines (dopamine, norepinephrine, and some of their analogues) also protected the enzyme against ascorbate inactivation. We performed studies to assess conformational changes of tyrosine hydroxylase by measuring the extrinsic fluorescence using 8-anilino-1-naphthalenesulfonic acid as a reporter group. Phosphorylation of tyrosine hydroxylase by protein kinase A decreased the extrinsic fluorescence. Treatment of tyrosine hydroxylase with ascorbate produced a further decrease in fluorescence. These results provide evidence for conformational changes following these treatments. In contrast to extrinsic fluorescence, the circular dichroic spectrum of tyrosine hydroxylase failed to change following phosphorylation by protein kinase A or inhibition by ascorbate. The spectrum was consistent with a secondary structure of tyrosine hydroxylase with 55% alpha helix, 20% beta sheet, 2% beta turn, and 23% random coil.