Response Of Antioxidant System Research Articles

Red tide dinoflagellate Cochlodinium polykrikoides induces significant oxidative stress and DNA damage in the gill tissue of the red seabream Pagrus major

The ichthyotoxic Cochlodinium polykrikoides is one of the most harmful bloom-forming dinoflagellates. In the present study, the economically important red seabream Pagrus major was exposed to sublethal concentrations of C. polykrikoides (i.e., 1,000 and 3,000 cells mL−1) for 24 h, and the antioxidant defense system and DNA damage dose-specific responses were analyzed during the exposure and additional depuration period (2 h) in the gill tissue. No significant ichthyotoxicity was observed under different light and dark conditions, while significantly lower levels of opercular respiratory rate were measured in the C. polykrikoides-exposed red seabream. Intracellular malondialdehyde (MDA) content increased significantly in the 3,000 cells-exposed gill tissues at 24 h and the increased level was maintained during depuration. Intracellular glutathione (GSH) levels were significantly depleted following exposure to 3,000 cells mL-1 of C. polykrikoides, but the levels increased significantly in the depuration phase. Overall, significantly higher activity of antioxidant defense system enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx) were observed in the 3,000 cells mL−1-exposed gill tissues at 24 h and during depuration. Analysis of the two reliable DNA damage parameters, Olive tail moment and percent tail DNA, showed significantly elevated levels of DNA damage in the 1,000 and 3,000 cells mL−1-exposed gill tissue. Increases in the activity of the antioxidant defense system and DNA damage may be one of the major mechanisms mediating C. polykrikoides-induced devastation in aquaculture and fisheries.

Putrescine affects tomato growth and response of antioxidant defense system due to exposure to cinnamic acid

ABSTRACTThe present study deals with the mitigating effects of putrescine (Put) against cinnamic acid (CA). Cinnamic acid in root and shoot exudates of tomato (Solanum lycopersicum L.) acts as an autotoxin, inhibiting growth and metabolic activities. Put has significant role in plant growth and development, as well as in defense against abiotic and biotic challenges. There are no reports on mitigation of allelopathic effects due to CA by Put. Tomato seedlings exposed to CA decreased root and shoot length, fresh and dry weights, photosynthetic pigments, protein and sugar contents, and nitrate reductase activity. These parameters increased when Put were applied in combination with CA and alone. Lipid peroxidation enhanced in seedlings treated with CA, but decreased in combined CA-Put treatment. Histochemical staining indicated that CA-induced oxidative damage which is evident from the presence of reactive oxygen species (ROS) such as O2– and H2O2 in tomato leaves. Put decreased ROS activity and plays promising role in regulation of antioxidant enzyme activities against production of free radicals and improved seedling growth exposed to CA. Put induced tolerance of tomato seedlings to CA autotoxicity was reflected through enhanced growth of the seedlings. Our findings reveal that Put is efficient to mitigate the allelopathic and adverse effects of CA and buttressed the defense system of tomato and eliminated the autotoxic effects of endogenous CA in tomato.

Changes in the Selected Antioxidant Defense Parameters in the Blood of Patients after High Resolution Computed Tomography.

Ionizing radiation generated during high resolution computed tomography (HRCT) scanning may have an indirect effect on the mechanisms regulating the oxidative-antioxidant balance in the human body, which is one of the necessary factors ensuring the maintenance of its homeostasis. The aim of the study was to analyze the response of antioxidant systems through the determination of the antioxidant markers in the blood of patients exposed to oxidative stress resulting from the routine HRCT examination of the chest. Blood of 35 people aged 60.77 ± 10.81 taken before and at four time points after the examination constituted the test material. The determination of the total antioxidant capacity expressed as ferric reducing ability of plasma (FRAP) and ferric reducing antioxidant activity and ascorbic acid concentration (FRASC) were performed together with an examination of catalase activity and the concentration of the reduced glutathione. The organism’s response to ionizing radiation was associated with a significant decrease in the antioxidant markers’ levels at all time-points and showed a significant negative correlation depending on the radiation dose. Visible down-regulation of these markers is a response to increased oxidative stress. In light of the obtained results, the measurement of the selected markers of antioxidant defense may be a useful parameter of oxidative stress caused by ionizing radiation.

Ethylene signaling involves in seeds germination upon submergence and antioxidant response elicited confers submergence tolerance to rice seedlings

BackgroundFlooding has negative impact on agriculture. The plant hormone ethylene is involved in plant growth and stress responses, which are important role in tolerance and adaptation regulatory mechanisms during submergence stress. Ethylene signaling crosstalk with gibberellin signaling enhances tolerance in lowland rice (Flood Resistant 13A) through a quiescence strategy or in deepwater rice through an escape strategy when rice is submerged. Information regarding ethylene-mediated priming in submergence stress tolerance in rice is scant. Here, we used 1-aminocyclopropane-1-carboxylic acid, an ethylene precursor, to evaluate the response in submerged rice seedlings.ResultsThe germination rate and mean germination times of rice seeds was higher in seedlings under submergence only when ethylene signaling was inhibited by supplemented with silver nitrate (AgNO3). Reduced leaf chlorophyll contents and induced senescence-associated genes in rice seedlings under submergence were relieved by pretreatment with an ethylene precursor. The ethylene-mediated priming by pretreatment with an ethylene precursor enhanced the survival rate and hydrogen peroxide (H2O2) and superoxide (O2−) anion accumulation and affected antioxidant response in rice seedlings.ConclusionsPretreatment with an ethylene precursor leads to reactive oxygen species generation, which in turn triggered the antioxidant response system, thus improving the tolerance of rice seedlings to complete submergence stress. Thus, H2O2 signaling may contribute to ethylene-mediated priming to submergence stress tolerance in rice seedlings.

Growth and antioxidant system responses of maize (Zea mays L.) seedling to different concentration of pyrene in a controlled environment

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic pollutants effecting different aspects of plants physiology. To assess the physiological responses of plants to PAHs, maize (Zea mays) was treated with 25, 50, 75, and 100 ppm of pyrene and after 21 days, the activity of some antioxidant enzymes, malondialdehyde (MDA), total flavonoid, total anthocyanin, and soluble sugar contents were measured in shoots and roots of plants. Pyrene led to increase MDA content as well as CAT, POD, and SOD activities. Increase in pyrene concentration reduced all studied growth variables and significantly increased photosynthetic pigments contents of plants. Soluble sugar content was significantly higher in the shoot, while that was reduced in the roots through increasing of pyrene concentration (p < 0.05). Also, the increase of pyrene concentration decreased total flavonoid content compared to anthocyanin content. In conclusion, these findings supported the hypothesis that pyrene toxicity induces oxidative stress in the maize plant and it also increases the antioxidant systems in order to moderating stress condition. However, the antioxidant system of maize was not strong enough to eliminate all produced ROS at high concentrations, thus this caused oxidative damage to the plant and decreased its growth variables.

Effect of Different Concentrations of Ozone on in Vitro Plant Pathogens Development, Tomato Yield and Quality, Photosynthetic Activity and Enzymatic Activities

ABSTRACTAs an effective alternative to traditional pesticides, ozonated water has been used for direct immersion and spraying applications, respectively, against the pathogenic bacterium Ralstonia solanacearum (R. solanacearum) and fungus Alternaria solani (A. solani) that are pathogens of tomato. Immersing R. solanacearum in 0.8 mg/L ozonated water resulted in complete inactivation, while the growth-inhibition rates of the A. solani radial mycelia gradually increased with a 67.0% decrease compared to those of the control at an ozonated water concentration of 7.5 mg/L. This indicated that ozonated water was effective at restraining pathogens in the tomato plant. In addition, spraying wild tomato species (Solanum lycopersicum) plants with ozonated water at concentrations below 10 mg/L for 25 d had no negative effects after treatment compared to those of the control. Photosynthetic activities and the antioxidant system response in the untreated and ozonated water-treated plant leaves had no observable changes. To determine the optimal ozonated water concentration for the pathogen and its host plant, we examined a variety of modes of action, and then, below 10 mg/L of ozonated water. Thus, ozonated water not only inhibits the proliferation of plant pathogens, but is an effective alternative to the pesticides traditionally used to prevent disease in agricultural production.

Acute toxicity and responses of antioxidant systems to dibutyl phthalate in neonate and adult Daphnia magna.

Dibutyl phthalate (DBP) poses a severe threat to aquatic ecosystems, introducing hazards to both aquatic species and human health. The ecotoxic effects of DBP on aquatic organisms have not been fully investigated. This study investigates acute toxicity, oxidative damage, and antioxidant enzyme parameters in neonate and adult Daphnia magna exposed to DBP. The obtained results show comparable DBP toxic responses in neonates and adults. The median lethal concentrations (LC50) of DBP in neonates exposed for 24 and 48 h were 3.48 and 2.83 mg/L, respectively. The LC50 of adults for the same DBP exposure durations were 4.92 and 4.31 mg/L, respectively. Increased hydrogen peroxide and malondialdehyde were found in neonates and adults at both 24 and 48 h, while the total antioxidant capacity decreased. Superoxide dismutase activity increased significantly in neonates and adults exposed to 0.5 mg/L DBP, and subsequently diminished at higher DBP concentrations and prolonged exposure. Catalase and glutathione S-transferases activities both decreased markedly in neonates and adults. The changes observed were found to be time and concentration dependent. Overall, these data indicated that the acute toxic effects of DBP exposure on neonates were more pronounced than in adults, and oxidative injury may be the main mechanism of DBP toxicity. These results provide a functional link for lipid peroxidation, antioxidant capacity, and antioxidant enzyme levels in the Daphnia magna response to DBP exposure.

Growth, physiological function, and antioxidant defense system responses of Lemna minor L. to decabromodiphenyl ether (BDE-209) induced phytotoxicity

Polybrominated diphenyl ethers (PBDEs), represent one of the new types of persistent organic pollutants (POPs) that are currently found in ambient aquatic ecosystems. Lemna minor L. is a floating freshwater plant, which is widely employed for phytotoxicity studies of xenobiotic substances. For this study, we investigated the growth, physiological functions, and antioxidant capacities of L. minor, which were exposed to 0–20 mg L−1 decabromodiphenyl ether (BDE-209) for 14 days. A logistic model was suitable for describing the growth of L. minor when the BDE-209 concentration was in the range of from 0 to 15 mg L−1. When exposed to 5 and 10 mg L−1 BDE-209, the growth of L. minor was significantly increased, where the intrinsic rate (r) and the maximum capacity of the environment (K) of L. minor were significantly higher than those of the control. In this case, the chlorophyll content and soluble proteins were also markedly increased. Moreover, the photosynthetic function (Fv/Fm, PI) was enhanced. However, for 15 mg L−1 BDE-29 treated group, the growth of L. minor was significantly inhibited, with decreases in chlorophyll and the soluble protein content, until the L. minor yellowed and expired under a concentration of 20 mg L−1. Photosynthetic functions were also negatively correlated with increasing increments of BDE-209 (15 and 20 mg L−1). The malondialdehyde (MDA), superoxide anion radical (O2̄·) content, and permeability of the plasma membranes increased with higher BDE-209 concentrations (0–20 mg L−1). The superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities of L. minor increased when the BDE-209 concentration ranged from 0 to 10 mg L−1; however, the activities of SOD and POD were decreased. Only the CAT activity remained higher in contrast to the control group under 15–20 mg L−1 BDE-209. These results demonstrated that 15 mg L−1 BDE-209 imparted high toxicity to L. minor, which was a consequence of the overproduction of reactive oxygen species (ROS), which conveyed oxidative damage to plant cells. This study provided a theoretical understanding of BDE-209 induced toxicity as relates to the physiology and biochemistry of higher hydrophytes.

Influences of Biochar Application on Root Aerenchyma and Radial Oxygen Loss of Acorus calamus in Relation to Subsurface Flow in a Constructed Wetland

In the subsurface flow of a constructed wetland (CW) used for treating wastewater, low oxygen diffusion results in long-term anoxic or anaerobic surroundings, which cannot meet the needs of plant respiration and poses a threat to the survival of macrophytes. Although sweet sedge (Acorus calamus L.) has a significant ability to resist hypoxia, membrane lipid oxidation would still occur in the plant due to the long-term hypoxia in the CW. According to reports in the existing literature, activation of the antioxidative response system could be promoted by adding biochar, thereby significantly decreasing the malonic dialdehyde in the plants. However, the specific reasons why biochar alleviates the stress from anoxia are still not clear. Thus, the responses of macrophyte roots to biochar application were studied in five different CWs built in a greenhouse, using plant ecology analyses combined with root aerenchyma, root porosity, and radial oxygen loss (ROL). The results showed that adding biochar to CW was beneficial for sweet sedge to form root aerenchyma and to increase root porosity. Moreover, there was a significant positive correlation between root porosity and the amount of biochar applied. Photosynthetic metabolism could be indirectly promoted by biochar application by increasing oxygen partial pressure in the blades, helping to transport O2 to underground parts through aerenchyma, and spreading O2 to the rhizosphere in the form of ROL. The reduction environment could be improved by applying biochar in CWs, which was also beneficial for ROL. Compared with other light conditions, 3000 μmol·(m2·s)-1 was more suitable for the growth of A. calamus in CWs with biochar, where the ability of the plants to secrete oxygen would be stimulated and enhanced. However, the effect of the biochar application ratio on ROL was not significant.

Coordinated responses of mitochondrial antioxidative enzymes, respiratory pathways and metabolism in Arabidopsis thaliana thioredoxin trxo1 mutants under salinity

Plant cells suffer alterations of their redox state and increase mitochondrial ROS generation during salinity. To avoid this, they activate several mitochondrial antioxidant and redox systems including the alternative oxidase (AOX), superoxide dismutase (SOD) and the ascorbate-glutathione (ASC-GSH) cycle components in a coordinated manner. The redox-sensitive mitochondrial thioredoxin (Trx) system may be responsible for this coordination through the redox regulation of target proteins. On top of this, metabolic perturbations induced by salinity may lead to alterations of the redox state of the Trx system. In order to explore the association between redox and metabolic changes occurring in mitochondria under saline conditions, we analyzed the salt-stress responses of mitochondrial antioxidant systems and metabolism in wild type (WT) and two knock-out (KO) AtTrxo1 lines. The activities of Mn-SOD and components of the ASC-GSH cycle were determined in isolated mitochondria, together with an evaluation of the AOX redox state, the oxidative stress, and catalase activity. Moreover, the in vivo activities of cytochrome (COX) and alternative mitochondrial respiratory pathways and primary metabolites profile were determined. Our results show that the lack of Trxo1 neither resulted in oxidative stress at the mitochondrial level nor in an upregulation of the antioxidant enzymes under salinity, although glutathione reductase (GR) maintained its high constitutive level as observed in control conditions. Moreover, the AOX was found invariably in its reduced monomeric state and displayed a reduction of its in vivo activity in all genotypes after the salt treatment, probably due to the mild severity of the treatment. Interestingly, trxo1 mutants displayed altered patterns in AOX isoforms and in the activities of the ASC-GSH cycle components and the electron partitioning to the AOX pathway indicating a reorganization of the different antioxidant systems. Furthermore, decreases on glucose and fructose levels in both trxo1 mutants coincided with an increased respiration through the COX pathway under control conditions. All these changes collaborate to maintain a low oxidative stress and the energy demand in both, control and salinity conditions and reflect the acclimation of all the genotypes to the applied stress.

The effect of recycling culture medium after harvesting of Chlorella vulgaris biomass by flocculating bacteria on microalgal growth and the functionary mechanism

Microalgal cultivation and harvesting are two main factors that restrict the development of microalgae. To help solve these two questions, flocculating bacteria and recycling culture medium were investigated in this study. Proteins in bacterial cells of Bacillus sp. y3 and y6 exhibited direct flocculation activities on Chlorella vulgaris cells. The recycling culture media after harvest of microalgal biomass by strain y3 and y6 could promote C. vulgaris growth. The determination of bacterial community confirmed that strain Bw in C. vulgaris phycosphere was the bacterial species that played the major promotion effect on microalgal growth. The functionary mechanism of strain y3 and y6 on microalgal growth was determined that they can influence C. vulgaris growth by changing the concentration of strain Bw to regulate algal ROS and antioxidant system response. The present study can provide effective research ideas and the application potential for the cultivation and harvesting of microalgae.

Enzyme and osmotic adjustment compounds of key species can help explain shrub encroachment in a semiarid sandy grassland

RationaleIn arid and semiarid grasslands where shrub encroachment usually occurs, water plays an important role and might control the process of shrub encroachment. Understanding how species adapt to different sandy environments can help explain the shrub encroachment process. Central methodsFour different grades of shrub encroached grasslands were selected as follows: the Agriophyllum squarrosum community in shifting sandy land (SA), the Artemisia ordosica community in semifixed sandy land (SFA), the A. ordosica community in fixed sandy land (FA) and the Stipa bungeana community in fixed sandy land (FS), which are located on the Ordos Plateau (China) and were selected to analyze the dynamics of enzyme and osmotic adjustment compounds of species in different stages of shrub encroachment. Key resultsThe results showed that from the community in shifting sandy land to the community in fixed sandy land, the average enzyme activities of species decreased and then increased; the malondialdehyde content increased, and the osmotic adjustment compounds increased (or increased and then decreased). The enzyme activities of grasses were significantly higher than those of shrubs. However, there were no significant differences in the malondialdehyde contents of grasses and shrubs. The proline and soluble protein contents of shrubs were significantly higher than those of grasses. The soluble sugar content of grasses was significantly higher than those of shrubs. The D values indicated that the drought resistance of the five species decreased as follows: S. bungeana in FS > S. bungeana in FA > Caragana korshinskii in FA > C. korshinskii in FS > A. ordosica in FS > A. squarrosum in SA > Artemisia sphaerocephala in SFA > A. sphaerocephala in SA > A. ordosica in FA > A. ordosica in SFA. Main conclusionsThe results suggest that the five dominant species in different shrub encroachment stages could enhance their drought resistance by upregulating the antioxidant system and osmotic adjustment in response to drought stress. S. bungeana had a higher drought resistance. For different plant functions, grass had a higher drought resistance than shrubs. It is concluded that S. bungeana can adapt to a drier environment; when the surface soil layer becomes dry, S. bungeana communities developed well due to its high drought ability. Compared to A. ordosica, the S. bungeana community can be a dominant community when human disturbance decreased in the Ordos Plateau.

Effects of water depth gradient on physiological characteristics of Vallisneria natans

For the purpose of studying the response of the Vallisneria natans antioxidant enzyme defense system to different water depths, we selected seedlings with well-preserved rhizomes, consistent germination and positive growth as experimental plants and put them into 10 plexiglass barrels at depth gradients. After 60 days of simulation experiments, we tested the malondialdehyde (MDA), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), chlorophyll and soluble protein contents and root activity. The results showed that (1) the contents of Chla, Chlb, Chl (a + b) and Car first increased with water depth and then decreased, reaching maximum values of 0.99, 0.38, 1.37 and 0.20 mg/g, at 110 cm respectively; (2) SOD and POD decreased with increased water depth, with a significant decreasing trend particularly between 30 and 60 days, and MDA showed the same trend as POD. CAT decreased with increased water depth but then showed a two-fold increase trend, probably due to the gradual effects of long-term water stress the antioxidant enzyme system in V. natans leaves. (3) Soluble protein had the same trend as MDA. Root activity implied that the more active the root system is, the more ramets and biomass are produced. In this experiment, the plant grew well at depths of less than 120 cm and showed clear signs of aging or death beyond this depth; the results showed that the antioxidant enzyme defense system engaged a series of antioxidant protection mechanisms to increase plant stress resistance ability and reduce or eliminate the damage of plants, but when the stress increased beyond the tolerance of the plant, the antioxidant defense system was destroyed, which eventually led to the death of the plant.

Evaluation of oxidant/antioxidant status in serum of sheep experimentally envenomated with Hemiscorpius lepturus scorpion venom.

Scorpion envenomation is a main general health problem in developing countries, especially in tropical and subtropical regions. Hemiscorpius lepturus as a member of the Hemiscorpiidae family is cause of the most scorpion sting lethality in Iran. In the present study, the oxidative stress and antioxidant defense in serum of envenomated sheep with the venom of Hemiscorpius lepturus were investigated. Nine sheep were randomly divided into three groups (three in each). Groups A, B and C received 0.10, 0.05 and 0.01 mg kg-1 of H. lepturus venom subcutaneously, respectively. Blood sampling were performed 30 min before envenomation (control) and 30 min, 1, 2, 3 and 6 hr after envenomation and serum levels of total antioxidant capacity (TAC), malonedialdehyde (MDA) and protein carbonyl (PCO) were determined. The TAC was significantly increased at the doses of 0.10 mg kg-1 (at 3 hr) and 0.05 mg kg-1 (at 6 hr) compared to pre-injection time. However, no significant differences were observed in serum levels of MDA and PCO in different groups. It can be concluded that the dose of 0.01 mg kg-1 of venom had no effect on stress factors of serum, but according to increased level of TAC at the doses of 0.05 and 0.10 and no significant changes in serum levels of MDA and PCO, the oxidative damage has been prevented by the antioxidant defense system response.

The responses of enzymatic and non-enzymatic antioxidant systems of scion on different rootstocks under water stress deficit

Selecting of the specific type of rootstock is an appropriate and short-tSelecting of the specific type of rootstock is an appropriate and short-term method for increasing drought tolerance by improving the antioxidant systems in plants. In this research, the responses of the antioxidant systems of fig scion ‘Sabz’ were investigated on various rootstocks at different irrigation levels. Graft combinations were ‘Sabz’ on ‘Sabz’ (Sa/Sa), ‘Siah’ (Sa/Si) and ‘Torch’ (Sa/T) rootstocks, plus ‘Sabz’, ‘Siah’ and ‘Torch’ cultivars with no grafting, for a total of six groups. The plants were irrigated with 4 levels of 25, 50, 75 and 100% of water requirement (WR) for a duration of 12 weeks. The experiment was performed in a randomized complete design with 5 replications per treatment. The results showed that the ‘Torch’ rootstock induced the greatest amount of anthocyanin, glutathione and ascorbic acid in ‘Sabz’ (Sa/T) at 25% WR. Superoxide dismutase and catalase activities of ‘Sabz’ grafted on ‘Siah’ were more evidence compared to ‘Sabz’ grafted on ‘Torch’ rootstock at 25% of WR. The cv. Sabz grafted on both ‘Siah’ and ‘Torch’ rootstocks indicated higher chlorophyll content, chlorophyll stability index and shoot growth than cv. Sabz with no grafting. As a result, both rootstocks (T and Si) with the activation of enzymatic and non-enzymatic antioxidant systems caused the scion protects its integrity and be able to tolerate more water stress.

Physiological and immunological responses to mass mortality in noble scallop Chlamys nobilis cultured in Nan'ao waters of Shantou, China

The noble scallop Chlamys nobilis has been a commercially important marine cultured bivalve in the Southern Sea of China for decades. Mass mortality events, however, often occur during scallops' cultivation. Mortality of up to 67%–90% was recorded at the beginning of March in 2017 in some culture areas of Nan'ao (Shantou, China), spreading to all scallops within a week. In the present study, in order to investigate the response of the noble scallop at the physiological and molecular level during mass mortality, scallops with different mortalities of 90%, 67%, and 6% were sampled from three sites at Hunter bay, Baisha bay, and Longhai, respectively. Total carotenoids content (TCC), total antioxidant capacity (TAC), malondialdehyde (MDA) content and the expression levels of three immune-related genes (toll-like receptor, C-type lectin receptor and big defensing) in different scallop tissues were determined. The scallops were divided into three groups of sub-health, lesion, and health. TAC, TCC, as well as transcript levels of CnTLR-1, Cnlec-1 and CnBD in sub-health and lesion scallops were all significantly lower (P < 0.05) than those in health scallops, while MDA in sub-health and lesion scallops were significantly higher than those in health scallops (P < 0.05). Similarly, TCC and TAC in lesion scallops were both higher than sub-health scallops. Moreover, significantly positive correlations were found between TCC and TAC (P < 0.05) and between CnTLR-1 and Cnlec-1 (P < 0.05), while significantly negative correlations were found between TCC and CnTLR-1 (P < 0.05), TCC and Cnlec-1 (P < 0.05), TAC and CnBD (P < 0.05), as well as between MDA and Cnlec-1 (P < 0.001). All the results indicate that noble scallops significantly change their physiological and molecular levels when suffering from stress, and that their antioxidant and immune response systems play important defense functions.

Carbon dioxide induces minor antioxidant responses in Eucalyptus urophylla chloroplasts

Minor effect on the chloroplast antioxidant proteins was detected in Eucalyptus urophylla cultivated in high-CO2 atmosphere. Global climate change can significantly alter plant cell metabolism. A higher atmospheric CO2 scenario may be beneficial for C3 plants through the stimulation of photosynthesis. This predicted increase in the rate of carbon assimilation may also increase the expression of enzymes involved in the antioxidant cellular defense. Here, we studied the responses of the chloroplastic antioxidant system of Eucalyptus urophylla plants cultivated in a high-CO2 condition. Plants exposed to a high concentration (980 ppm) of CO2 showed an increase in the H2O2 concentration and MDA content in relation to those cultivated at 410 and 680 ppm. With the discovery proteomics approach used herein, we identified 19 chloroplastic antioxidant proteoforms and pinpointed differentially regulated isoforms of an ascorbate peroxidase and a superoxidase dismutase upon cultivation in a high-CO2 atmosphere. Our data indicate that the CO2 stimulus induces only minor changes in the antioxidant metabolism of E. urophylla chloroplasts.

Oxidative Stress in Methylmercury-Induced Cell Toxicity

Methylmercury (MeHg) is a hazardous environmental pollutant, which elicits significant toxicity in humans. The accumulation of MeHg through the daily consumption of large predatory fish poses potential health risks, and the central nervous system (CNS) is the primary target of toxicity. Despite well-described neurobehavioral effects (i.e., motor impairment), the mechanisms of MeHg-induced toxicity are not completely understood. However, several lines of evidence point out the oxidative stress as an important molecular mechanism in MeHg-induced intoxication. Indeed, MeHg is a soft electrophile that preferentially interacts with nucleophilic groups (mainly thiols and selenols) from proteins and low-molecular-weight molecules. Such interaction contributes to the occurrence of oxidative stress, which can produce damage by several interacting mechanisms, impairing the function of various molecules (i.e., proteins, lipids, and nucleic acids), potentially resulting in modulation of different cellular signal transduction pathways. This review summarizes the general aspects regarding the interaction between MeHg with regulators of the antioxidant response system that are rich in thiol and selenol groups such as glutathione (GSH), and the selenoenzymes thioredoxin reductase (TrxR) and glutathione peroxidase (Gpx). A particular attention is directed towards the role of the PI3K/Akt signaling pathway and the nuclear transcription factor NF-E2-related factor 2 (Nrf2) in MeHg-induced redox imbalance.

Depletion of Sirt3 leads to the impairment of adipogenic differentiation and insulin resistance via interfering mitochondrial function of adipose-derived human mesenchymal stem cells

Upregulation of mitochondrial function and oxidative metabolism is a hallmark in the differentiation of stem cells. However, the mechanism underlying the metabolic reprogramming and upregulation of mitochondrial function during the differentiation of human mesenchymal stem cells (hMSCs) is largely unclear. Sirt3 has emerged as a sensor in regulating mitochondrial function and antioxidant defence system in cellular response to energy demand or environmental stimuli, but its roles in stem cell differentiation have not been fully understood. In this study, we used adipose-derived hMSCs (ad-hMSCs) to investigate the role of Sirt3 in adipogenic differentiation and in the function of mature adipocytes. We showed that at the early stage of adipogenic differentiation, Sirt3 upregulation is essential for the activation of biogenesis and bioenergetic function of mitochondria. In addition, we found that induction of Forkhead Box O 3a (FoxO3a), an upstream factor that regulates MnSOD gene transcription, is involved in the upregulation of antioxidant enzymes at the early stage of adipogenic differentiation. Silencing of Sirt3 by shRNA decreased the protein level of FoxO3a and subsequently downregulated a number of FoxO3a-mediated antioxidant enzymes and increased oxidative stress in ad-hMSCs after adipogenic induction. Importantly, depletion of Sirt3 compromised the ability of ad-hMSCs to undergo adipogenic differentiation and led to adipocyte dysfunction and insulin resistance. These findings suggest that Sirt3-mediated protein deacetylation plays an important role in regulating oxidative metabolism and antioxidant defence in stem cell differentiation, and that Sirt3 deficiency may be related to insulin resistance.

Differential responses of antioxidative defense system to NaCl in grain and forage sorghum during germination and seedling establishment

Differential responses of antioxidative defense system to NaCl in grain and forage sorghum during germination and seedling establishment