Response Of Antioxidant Defense System Research Articles

Association of Stress Defense System With Fine Particulate Matter Exposure: Mechanism Analysis and Application Prospects.

The association between the stress defense system and exposure to fine particulate matter (PM2.5) is a hot topic in the field of environmental health. PM2.5 pollution is an increasingly serious issue, and its impact on health cannot be ignored. The stress defense system is an important biological mechanism for maintaining cell and internal environment homeostasis, playing a crucial role in PM2.5-induced damage and diseases. The association between PM2.5 exposure and activation of the stress defense system has been reported. Moderate PM2.5 exposure rapidly mobilizes the stress defense system, while excessive PM2.5 exposure may exceed its compensatory and coping abilities, resulting in system imbalance and dysfunction that triggers pathological changes in cells and tissues, thereby increasing the risk of chronic diseases, such as respiratory diseases, cardiovascular diseases, and cancer. This detailed review focuses on the composition, function, and regulatory mechanisms of the antioxidant defense system, autophagy system, ubiquitin-proteasome system, and inflammatory response system, which are all components of the stress defiance system. In particular, the influence of PM2.5 exposure on each of these defense systems and their roles in responding to PM2.5-induced damage was investigated to provide an in-depth understanding of the pathogenesis of PM2.5 exposure, accurately assess potential hazards, and formulate prevention and intervention strategies for health damage caused by PM2.5 exposure.

Functional characterization of peroxiredoxin 5 from yellowtail clownfish (Amphiprion clarkii): Immunological expression assessment, antioxidant activities, heavy metal detoxification, and nitrosative stress mitigation

Peroxiredoxin 5 (Prdx5) is the last recognized member of Prdx family. It is a unique, atypical, 2-Cys antioxidant enzyme, protecting cells from death caused by reactive oxygen species (ROS). In this study, the Prdx5 ortholog of Amphiprion clarkii (AcPrdx5) was identified and characterized to explore its specific structural features and functional properties. The open reading frame of AcPrdx5 is 573 bp long and encodes 190 amino acids containing a mitochondrial targeting sequence, thioredoxin domain, and two conserved cysteine residues responsible for antioxidant function. The predicted molecular weight and theoretical isoelectric point of AcPrdx5 are 20.3 kDa and 9.01, respectively. AcPrdx5 sequences were found to be highly conserved across the other orthologs from various organisms and it distinctively clustered within the fish Prdx5 subclade of the phylogenetic tree. The expression of AcPrdx5 was ubiquitously detected among twelve tested tissues, with the highest level in the brain. Furthermore, the mRNA levels of AcPrdx5 in the blood and head-kidney tissues were significantly (p < 0.05) upregulated following polyinosinic-polycytidylic acid (Poly I:C), lipopolysaccharide (LPS), and Vibrio harveyi immune challenge. A concentration-dependent antioxidant potential of recombinant AcPrdx5 was observed in insulin disulfide bond reduction, heavy metal detoxification, free radical and hydrogen peroxide (H2O2) scavenging assays. Additionally, AcPrdx5 overexpression in fathead minnow (FHM) cells upregulated the antioxidant-associated gene (Rrm1, MAPK, SOD2, and PRDX1) expression after H2O2 treatment, and promoted cell viability upon arsenic (As) exposure. In macrophages, AcPrdx5 overexpression effectively suppressed substantial nitric oxide production under lipopolysaccharide treatment. Collectively, our results suggest that AcPrdx5 may play roles in both antioxidant defense system and innate immune response against pathogenic invasions in A. clarkii.

Response of the Endogenous Antioxidant Defense System Induced in RAW 264.7 Macrophages upon Exposure to Dextran-Coated Iron Oxide Nanoparticles.

Presently, iron oxide nanoparticles are the only ones approved for clinical use as contrast agents in magnetic resonance imaging (MRI). Even though there is a high demand for these types of nanoparticles both for clinical use as well as for research, there are difficulties in obtaining stable nanoparticles with reproducible properties. In this context, in this study, we report the obtaining by an adapted coprecipitation method of dextran-coated maghemite nanoparticles (ɤ-Fe2O3 NPs). The morphology and structure of the dextran-coated maghemite nanoparticles (ɤ-Fe2O3 NPs) were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The TEM and SEM micrographs highlighted the obtaining of particles of nanometric size and spherical shape morphology. Furthermore, the high-resolution transmission electron microscopy (HRTEM), as well as selected area diffraction (SAED), revealed that the obtained samples presented the structure of cubic maghemite. In this study, we also explored the effects of the co-precipitation synthesized dextran-coated maghemite nanoparticles (ɤ-Fe2O3 NPs) on the redox status of macrophages. For cytotoxicity evaluation of these NPs, murine macrophages (RAW 264.7 cell line) were exposed to different concentrations of dextran-coated maghemite nanoparticles (ɤ-Fe2O3 NPs) corresponding to 0-500 μg Fe3+/mL and incubated for 24, 48, and 72 h. Intracellular iron uptake, changes in the oxidative stress parameters (reactive oxygen species production and malondialdehyde level), and the activity of antioxidant enzymes, as well as GSH concentration in cells, were evaluated after incubation with a lower (50 μg Fe3+/mL) and higher (500 μg Fe3+/mL) dose of NPs. The results indicated a significant decrease in RAW 264.7 cell viability after 72 h in the presence of NPs at concentrations above 25 μg Fe3+/mL. An important accumulation of NPs, dependent on dose and exposure time, was detected in macrophages, but it induced only a limited raise in the oxidative status. We showed here that the antioxidant capacity of RAW 264.7 macrophages was efficient in counteracting dextran-coated maghemite nanoparticles (ɤ-Fe2O3 NPs) toxicity even at higher doses.

Arsenic-Induced Oxidative Stress and Antioxidant Defense in Plants

The non-essential metalloid arsenic (As) is widely distributed in soil and underground water of many countries. Arsenic contamination is a concern because it creates threat to food security in terms of crop productivity and food safety. Plants exposed to As show morpho-physiological, growth and developmental disorder which altogether result in loss of productivity. At physiological level, As-induced altered biochemistry in chloroplast, mitochondria, peroxisome, endoplasmic reticulum, cell wall, plasma membrane causes reactive oxygen species (ROS) overgeneration which damage cell through disintegrating the structure of lipids, proteins, and DNA. Therefore, plants tolerance to ROS-induced oxidative stress is a vital strategy for enhancing As tolerance in plants. Plants having enhanced antioxidant defense system show greater tolerance to As toxicity. Depending upon plant diversity (As hyperaccumulator/non-hyperaccumulator or As tolerant/susceptible) the mechanisms of As accumulation, absorption or toxicity response may differ. There can be various crop management practices such as exogenous application of nutrients, hormones, antioxidants, osmolytes, signaling molecules, different chelating agents, microbial inoculants, organic amendments etc. can be effective against As toxicity in plants. There is information gap in understanding the mechanism of As-induced response (damage or tolerance response) in plants. This review presents the mechanism of As uptake and accumulation in plants, physiological responses under As stress, As-induced ROS generation and antioxidant defense system response, various approaches for enhancing As tolerance in plants from the available literatures which will make understanding the to date knowledge, knowledge gap and future guideline to be worked out for the development of As tolerant plant cultivars.

Arbuscular Mycorrhizal Fungi and Endophytic Fungi Activate Leaf Antioxidant Defense System of Lane Late Navel Orange.

Arbuscular mycorrhizal (AM) fungi and endophytic fungi collectively symbiose well with plants and, thus, stimulate plant growth; however, it is not clear whether field inoculation of the fungi enhances the resistance potential of plants, particularly in citrus. In the present study, we inoculated AM fungi (Acaulospora scrobiculata, Diversispora spurca, and D. versiformis) and endophytic fungi (Piriformospora indica) on an eight-year-old lane late navel orange (Citrus sinensis (L.) Osb) trees grafted on Poncirus trifoliata in a field, and we analyzed the response of the leaf antioxidant defense system. Approximately 2 years after inoculation, the root fungal colonization rate and soil hyphal length significantly increased. Fungal inoculation significantly increased the activity of leaf antioxidant enzymes, such as superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase, and the content of non-enzymatic antioxidants, such as reduced ascorbic acid and reduced glutathione. As a result, fungi-inoculated plants maintained lower concentrations of hydrogen peroxide and superoxide anion radicals and lower levels of membrane lipid peroxidation (according to malondialdehyde level) in leaves than uninoculated plants. Among them, inoculation of D. spurca and A. scrobiculata showed relatively higher effects in enhancing the antioxidant defense system than the other fungi. Furthermore, inoculation of D. spurca induced expressions of CsFe-SOD, CsMn-SOD, CsPOD, CsCAT1, and CsPRR7; inoculation of A. scrobiculata and D. versiformis induced expressions of CsCAT1; CsCAT1 and CsPOD were also induced by inoculation of P. indica. All four inoculations almost upregulated expressions of CsFAD6. AM fungi had superior effects than endophytic fungi (e.g., P. indica). According to our findings, inoculation with beneficial fungi, specifically mycorrhizal fungus D. spurca, activated the antioxidant defense system of field citrus trees, thus, having potentially superior resistance in inoculated plants.

Potential effects of dietary chitosan against lead-induced innate immunotoxicity and oxidative stress in Nile tilapia (Oreochromis niloticus)

Urbanization and industrialization have led to heavy metals in aquatic environments. These metals are toxic, nondegradable, and persistent. Lead (Pb) is an immunotoxicant that can adversely affect animal health, even at low levels. Chitosan (CHI) is an eco-friendly compound with exceptional antibacterial and immunostimulant characteristics. This study investigated the effect of dietary CHI on the antioxidant defense system and innate immune responses of tilapia (Oreochromis niloticus) against the cytotoxic effect of prolonged Pb exposure. The results indicated dietary CHI could nullify the toxicity of prolonged Pb exposure in fish by substantially activating the antioxidant defense system capacity and fish innate immune responses. In addition, CHI minimized the alterations in the histology of fish organs. The findings suggest that chitosan can be a commercial, eco-friendly immunostimulant and bioactive compound for mitigating the effects of heavy metal toxicity in aquaculture.

Diverse defense responses to ammonia stress in three freshwater turtles

Ammonia is a common stressor in freshwater ecosystems and usually causes oxidative damage to aquatic animals at high levels. The antioxidant defense system plays an important role in protecting animals from oxidative damage. This study compared the antioxidant defense responses of three commonly cultured freshwater turtle species, namely, the three-keeled pond turtle Chinemys reevesii, the snapping turtle Chelydra serpentina and the soft-shelled turtle Pelodiscus sinensis, under harsh ammonia stress (189.52 mg/L total ammonia nitrogen (8.2 mg/L unionized ammonia nitrogen), pH 7.8) for 96 h and subsequently recovered in the control water for 96 h, to reveal the stress response divergence of freshwater turtles that differed in morphological structure, origin and behavior, which may provide some reference for the aquaculture of freshwater turtles. We examined hematological parameters, reactive oxygen species (ROS), malondialdehyde (MDA), and antioxidant defense responses in different tissues of the three turtle species. Blood ammonia increased significantly during ammonia exposure and then recovered to the control level in all three turtles. Hemoglobin (Hb) and methemoglobin (MetHb) increased distinctly during ammonia exposure in C. reevesii and P. sinensis, while hematocrit (Hct) did not change much. In contrast, the Hct of C. serpentina decreased significantly, while Hb and MetHb levels remained constant. ROS and total antioxidant capacity (TAOC) levels in C. reevesii remained constant, but in C. serpentina, hepatic and renal ROS levels increased significantly during exposure and remained high after recovery, with hepatic TAOC declining simultaneously. In P. sinensis, both hepatic ROS and TAOC increased during exposure and then recovered. The MDA concentrations did not change much in all three species, suggesting an effective protection of the antioxidant defense system. This study found that in the process of aquaculture, a high concentration of ammonia stress will have adverse impact on freshwater turtles. When faced with the ammonia stress, the biochemistry parameter alternations and the antioxidant defense system response patterns of the three turtles were highly diverse which perhaps were in relation to their behavioral strategy and original local environment.

Antioxidant defense system responses, lysosomal membrane stability and DNA damage in earthworms (Eisenia fetida) exposed to perfluorooctanoic acid: an integrated biomarker approach to evaluating toxicity

Perfluorooctanoic acid (PFOA) is one of the most representative perfluoroalkyl substances and has garnered intense human and ecological health concerns due to its ubiquity in the environment, bio-accumulative nature and potential toxicological effects. In this study, an artificial soil containing PFOA was used to evaluate the biological toxicity of PFOA to earthworms Eisenia fetida. Six kinds of oxidative stress biomarkers, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO), as well as lysosomal membrane stability (LMS) and DNA damage in earthworms were detected after exposure to 0, 10, 20, 40, 80 and 120 mg kg−1 PFOA in the soil for 3, 7, 14, 28, and 42 days. The results of multi-biomarker responses indicated that PFOA can induce various adverse effects on earthworms, including growth inhibition, oxidative stress and genotoxicity, resulting in lipid membrane peroxidation, decreased lysosomal membrane stability and DNA damage. LPO, LMS and DNA damage all presented dose- and time-dependent relationships. An integrated biomarker response (IBR) index was applied to summarize the multi-biomarker responses to star plots, and the IBR value was calculated as the area of the plots to indicate the integrated stress of PFOA on earthworms. The IBR index showed that the integrated stress induced by PFOA increased markedly throughout the exposure period, exhibiting a concentration-related and exposure time-related effect. The graphical changing trend of the IBR star plots, along with the multi-biomarker responses, suggested that the biomarkers of the antioxidant defense system in earthworms are sufficiently sensitive for short-term PFOA biomonitoring programs, while the bioindicators that indicate actual damage in organisms are more suitable to be employed in long-term monitoring programs for the risk assessment of PFOA. This is the first study evaluating the biological toxicity of PFOA by using an integrated biomarker approach. Our results showed that PFOA can potentially damage soil ecosystems, which provides valuable information for chemical risk assessment of PFOA in the soil environment and early warning bioindicators of soils contaminated by PFOA.

Gender differences in the antioxidant response of oral administration of hydroxytyrosol and oleuropein against N-ethyl-N-nitrosourea (ENU)-induced glioma

Brain tumorigenesis has been associated not only with oxidative stress, but also with a reduced response of non-enzyme and enzyme antioxidant defense systems. In fact, the imbalance between free-radical production and the efficiency of the antioxidant defense systems triggers the process because the central nervous system (CNS) is very sensitive to free-radical damage. Phenolic compounds, mainly oleuropein and its major metabolite hydroxytyrosol, derived from olives and virgin olive oil, have been shown to exert important anticancer activities both in vitro and in vivo due to their antioxidant properties. The present study analyzes the effects of the oral administration of oleuropein, hydroxytyrosol and the mixture of both phenolic compounds in rats with transplacental N-ethyl-N-nitrosourea (ENU)-induced brain tumors to analyze their potential effect against brain tumorigenesis through the modification of redox system components. Oxidative stress parameters, non-enzyme and enzyme antioxidant defense systems and blood chemistry were assayed in the different experimental groups. The treatment with oleuropein, hydroxytyrosol and/or the mixture of both phenolic compounds promotes a limited beneficial effect as anticancer compounds in our ENU-induced animal model of brain tumor. These effects occur via redox control mechanisms involving endogenous enzymatic and non-enzymatic antioxidant defense systems, and are highly dependent on the gender of the animals.

Hepatoprotective ability of tetramethylpyrazine produced by Bacillus amyloliquefaciens

Tetramethylpyrazine (TTMP), an important aroma compound, was produced by Bacillus amyloliquefaciens XJB-104 with distillers’ grains as raw material. The yield of TTMP under optimized fermentation procedure was 3176.52 mg/L. TTMP in the fermentation broth was purified and the purity (> 99%) was measured by gas chromatography–mass spectrometry. Furthermore, the hepatoprotective activity of TTMP in ethanol–water system was evaluated by biochemical indicators of liver injury, parameters of antioxidant defense system and inflammatory response, and liver histopathological assessment in mice. Ethanol treatment increased serum levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase, suggesting liver damage. Both high and low dose of TTMP significantly decreased levels of these indicators. Furthermore, the reduction in the activities or concentrations of superoxide dismutase, catalase, reduced glutathione and malondialdehyde in liver tissue caused by ethanol was significantly alleviated by TTMP. Increased inflammatory cytokines including transcription factor, tumor necrosis factor, interleukin-1beta, interleukin, macrophage chemoattractant protein, inducible nitric oxide synthase and cyclooxygenase were also suppressed by TTMP treatment. It is concluded that TTMP in ethanol–water system has potential liver-protective activity, especially when ethanol is consumed at low doses for short periods of time.

Dietary trans-cinnamaldehyde improves oxidative stress response of channel catfish (Ictalurus punctatus) following Edwardsiella ictaluri infection

Commercial channel catfish (Ictalurus punctatus) is an economically valuable agricultural commodity in the United States, which suffers heavily from bacterial pathogens including Edwardsiella ictaluri. Our previous study revealed that dietary trans-cinnamaldehyde (TC) reduces catfish mortality after E. ictaluri infection, but there is limited knowledge of the effect of TC on the antioxidant defense system in catfish. In this study, we aimed to investigate the response of the catfish antioxidant defense system following TC feeding as well as E. ictaluri infection. In the first experiment, catfish fingerlings were fed with a basal diet or a basal diet supplemented with TC (20 mg/kg diet) for 10 days, and the level of five oxidative stress biomarkers were measured in the hepatic tissue. Compared with the control group, superoxide dismutase (SOD) activity was increased significantly and the malondialdehyde (MDA) concentration decreased significantly (P < 0.001) in hepatic tissue of catfish that were fed a TC-supplemented diet. Whereas activities of catalase (CAT) and reduced glutathione (GSH) as well as nitric oxide (NO) concentration did not show significant differences between TC and control groups. In the second experiment, catfish fingerlings were fed a TC-supplemented or normal diet followed by infection with E. ictaluri, and the activities of oxidative biomarkers were measured on 1, 6, and 14-days post-infection (dpi). Significant (P < 0.001) increases in CAT, SOD, and GSH activities were observed in catfish fed TC when compared with those fish fed a normal diet on 1, 6, and 14 dpi. A significant (P < 0.001) decrease in NO and MDA concentrations were found in catfish that received a TC diet compared to the control group at 1, 6, and 14 dpi. In conclusion, dietary TC improved the oxidative stress response in catfish following E. ictaluri challenge. These results provide information regarding the mechanisms by which TC provides protection against E. ictaluri infection.

Physiological and antioxidant responses of cultivated and wild barley under salt stress

Saline soil is a critical environmental problem affecting crop yield worldwide. Tibetan wild barley is distinguished for its vast genetic diversity and high degree of tolerance to abiotic stress, including salinity. The present study compared the response of antioxidant defense system in the XZ16 wild and CM72 cultivated barleys to salt stress. Wild barley was relatively more tolerant than cultivated CM72, salt-tolerant cultivar, with less Na&lt;sup&gt;+&lt;/sup&gt; uptake and more K&lt;sup&gt;+&lt;/sup&gt;, Ca&lt;sup&gt;2+&lt;/sup&gt;, and Mg&lt;sup&gt;2+&lt;/sup&gt; retention in plant tissues. The results of diaminobenzidine (DAB) and nitroblue tetrazolium (NBT) staining showed that XZ16 had significantly lower H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; and O&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt; concentrations than a salt-sensitive cultivar Gairdner, suggesting that the salt-tolerant genotype suffer from less oxidative damage. Moreover, XZ16 and Gairdner had the highest and lowest anti-oxidative enzyme activities and proline content in plant tissues. In addition, the microscopic examination revealed that DNA damage in cv. Gairdner was closely correlated to oxidative stress, representing that more reactive oxygen species accumulation in plants tissues leads to subsequent DNA damage. The present results show that higher salt tolerance of wild barley XZ16 is attributed to less Na&lt;sup&gt;+&lt;/sup&gt; accumulation and stronger anti-oxidative capacity.

Antioxidant Potential of Ulexite in Zebrafish Brain: Assessment of Oxidative DNA Damage, Apoptosis, and Response of Antioxidant Defense System.

In recent years, because of its significant biological roles, the usage of boron has been started in animal feeding. In this research, it was aimed to investigate the ulexite's action mechanism on the zebrafish brain with an evaluation of the oxidative parameters. The adult zebrafish were exposed to four ulexite doses (5, 10, 20, and 40 mg/l) in a static test apparatus for 96 h. For assessing the oxidative responses, multiple biochemical analyses were performed in brain tissues. The results indicated the supporting potential of low ulexite doses on the antioxidant system (< 40 mg/l) and that low-dose ulexite does not lead to oxidative stress in the zebrafish brain. Again, our results showed that low ulexite concentrations did not cause DNA damage or apoptosis. As a final result, in aquatic environments, ulexite (a boron compound) can be used in a safe manner, but it would be useful at higher concentrations to consider the damages of the cells that are probable to develop because of the oxidative stress.

Benzotriazole alleviates copper mediated lysosomal membrane damage and antioxidant defense system responses in earthworms (Eisenia fetida).

Benzotriazole (BTR) is a common corrosion inhibitor used to protect copper (Cu) and Cu alloys. To reveal the combined subacute toxicity of BTR and Cu at environmental levels on terrestrial animals, the activity of antioxidative enzymes and the glutathione levels in earthworms (Eisenia fetida) of the single or co-exposure treatments were determined. The activity of both antioxidant enzymes and non-enzymatic antioxidants was affected by BTR in earthworms. Moreover, the analyses of lysosomal neutral red retention time and total antioxidant capacity indicated a detoxification effect of BTR on Cu-induced impairments of the antioxidant defense capacity in earthworms. The apoptotic rate of coelomocytes in earthworms of the co-exposure treatment was lower than that in earthworms treated with Cu only, indicating that BTR alleviates Cu mediated lysosomal membrane damage and antioxidant defense system responses in earthworms.

Biotransformations, Antioxidant System Responses, and Histopathological Indexes in the Liver of Fish Exposed to Cyanobacterial Extract.

Radiocystis fernandoi, a microcystin (MC) producer, has been common in cyanobacterial blooms in tropical regions. Microcystin is a hepatotoxin that causes tissue damage and even death in animals, including humans; its detoxification process may involve biotransformation and activation of the antioxidant defense system. We evaluated the detoxification pathway, examined the antioxidant defense system responses, and determined the alterations and the organ histopathological indexes in the liver of the tropical fish Hoplias malabaricus after acute and subchronic intraperitoneal exposure to microcystin. The crude microcystin extract of R. fernandoi had predominantly MC-RR and MC-YR. The detoxification process was activated by increasing ethoxyresorufin-O-deethylase activity, whereas glutathione S-transferase was inhibited. The activity of the antioxidant defense enzymes superoxide dismutase (SOD) and glutathione peroxidase decreased after acute exposure; the SOD-catalase system and the glutathione level increased after subchronic exposure. The carbonyl protein level, lipid peroxidation (LPO), and DNA damage were unchanged after acute exposure, whereas protein carbonyl was unchanged, LPO decreased, and DNA damage increased after subchronic exposure. Histopathological alteration indexes differed between acute and subchronic exposure, but the histopathological organ indexes indicate liver dysfunction in both exposure periods. We conclude that MC-RR and MC-YR induce different liver responses depending on the time of exposure, and the antioxidant defense responses after subchronic exposure may help to partially restore the liver function. Environ Toxicol Chem 2020;39:1041-1051. © 2020 SETAC.

Different responses of photosystem and antioxidant defense system to three environmental stresses in wheat seedlings

To investigate the adaptive mechanism of wheat under high light, osmotic stress, and salt stress, redox regulation, and photosynthesis were compared. Under high light, the activities of antioxidant enzymes, except for catalase, significantly increased and then decreased after 1 and 3 h, respectively. Under osmotic stress, antioxidant enzyme activities significantly increased and subsequently declined. Except for superoxide dismutase, salt stress induced a significant increase in all the antioxidant enzyme activities. A significant decrease of D1 protein by high light and osmotic stress, strong photophosphorylation of D1 and D2 under high light and salt stress were observed, while all the stresses induced upregulation of PsbS protein. Eight stress-associated genes (TaMYB73, TaABC1, TaOPR1, TaASR1, TaWRKY44, TaWRKY2, TaWRKY19, and TaCIPK29) showed different expression levels under all the stresses. We conclude that the wheat plant adopted various strategies by regulating the antioxidant system, expression of stress-responsive genes, and photosystems under different abiotic stresses.

Effects of trichlorfon on oxidative stress, neurotoxicity, and cortisol levels in common carp, Cyprinus carpio L., at different temperatures

Trichlorfon (TCF) is an organophosphate compound used extensively as an anti-parasitic in aquaculture. In this study, we investigated the effects of TCF on the antioxidant defense system, acetylcholinesterase (AChE) activity, and stress responses in various tissues of common carp (Cyprinus carpio L.). C.carpio L. were exposed to different concentrations of TCF (0, 0.5, 1.0, 2.0, and 4 mg L−1) at 25 and 15 °C for two weeks (measurements were taken after week 1 and 2). TCF exposure induced significant alterations in antioxidant responses in the gills and the liver. The activities of superoxide dismutase (SOD) and glutathione S-transferase (GST) increased considerably after TCF exposure, depending on water temperature, whereas catalase (CAT) and glutathione (GSH) levels decreased notably after one and two weeks. Remarkable antioxidant responses were observed in the gills, suggesting the gills were more sensitive to oxidative stress than the liver based on CAT, GST, and GSH levels. Notable increases in MDA levels were observed in the gills and the liver. AChE activity was significantly inhibited in the brain and muscles even at the lowest TCF concentration of 0.5 mg L−1, indicating neurotoxicity following TCF exposure. As a stress indicator, plasma cortisol was significantly elevated following exposure to TCF depending on water temperature, thereby enhancing stress. These results suggest that TCF exposure can induce considerable alterations in antioxidant responses, neurotoxicity, and stress reaction depending on water temperature. The assayed enzymes are potential biomarkers of organophosphate contamination.

Physiological and biochemical impacts of silicon against water deficit in sugarcane

Silicon (Si) has been reported to minimize the impacts of water deficit, even though it is not considered an essential plant element. Sugarcane is highly impacted by water deficit and has a particular and complex mechanism to address this stressful condition. Although sugarcane is an Si-accumulating plant, there are few results on the association between Si and water deficit, and physiological and biochemical responses are unclear for this crop. This study investigated the physiological and antioxidant defense system responses in drought-tolerant (RB86-7515) and drought-sensitive (RB85-5536) sugarcane cultivars grown in soil with and without silicon fertilization and subjected to water deficit for 30 and 60 days during the tillering (first experiment) or grand growth (second experiment) phases. Four replications were evaluated in both experiments. Silicon was used at a rate equivalent to 600 kg ha−1 Si as calcium magnesium silicate (108.4 g kg−1 Si; 274 g kg−1 Ca; 481 g kg−1 Mg), which was applied in soil 11 weeks before sugarcane was transplanted. Silicon fertilization improved physiological responses by increasing the water potential and relative water content in the leaves during the tillering and grand growth phases. Additionally, Si increased proline concentrations and/or superoxide dismutase (SOD) and/or ascorbate peroxidase (APX) levels in drought-tolerant and drought-sensitive cultivars under water deficit. These results suggested that Si could play a role in the detoxification of excessive ROS production by increasing proline levels or APX activities in sugarcane grown under water deficit.

Effects of diet α-ketoglutarate (AKG) supplementation on the growth performance, antioxidant defense system, intestinal digestive enzymes, and immune response of grass carp (Ctenopharyngodon idellus)

This study was conducted to investigate the effects of diet 7.5 g/kg α-ketoglutarate (AKG) on the growth performance, antioxidant defense system, digestive enzymes, and immune response of grass carp (Ctenopharyngodon idellus). A total of 400 grass carp with an average body weight 10.81 ± 0.68 g was randomly allocated into 2 groups with 4 replicates of 50 fish respectively. The experiment was conducted in net cages (1.5 m × 1.5 m × 1.5 m) suspended in an indoor cement pool. Fish were fed a basic diet containing either 0 (control) or 7.5 g/kg AKG (supplemented diet). The experiment lasted for 8 weeks (56 days). Results indicated that compared with the control group, the final weight (FW), weight gain rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) in the AKG group were increased significantly (P < 0.05). However, the feed conversion ratio (FCR) was decreased significantly (P < 0.05). The 7.5 g/kg AKG supplementation significantly increased the activities of glutamine synthetase (GS), glutathione peroxidase (GSH-Px), catalase (CAT), total superoxide dismutase (T-SOD), and hexokinase (HK), as well as the concentrations of glutathione (GSH), total antioxidant capacity (T-AOC), and complement 3 (C3) in blood (P < 0.05), while significantly decreased the concentrations of malondialdehyde (MDA) and hemoglobin (Hb) (P < 0.05). The GS activity and GSH concentration in hepatopancreas were increased significantly (P < 0.05), whereas the glycogen concentration in hepatopancreas, and the glycogen concentration and GS activity in the muscle were significantly decreased (P < 0.05). In addition, 7.5 g/kg AKG supplementation significantly increased the concentration of GSH and the activities of amylase, protease, and lipase in fore-gut, alkaline phosphates (ALP) in the mid-gut, and Na-ATP and Ca-ATP in the gill (P < 0.05), as well as γ-glutamyl transpeptidase (γ-GT) both in fore-gut and mid-gut (P < 0.05), whereas the activity of acid phosphatase (ACP) in the mid-gut was decreased significantly (P < 0.05). In conclusion, diet 7.5 g/kg AKG supplementation in grass carp may improve the growth performance and immune response and play crucial roles in regulating the activities of GS, antioxidant defense system, and digestive enzymes.

Pre-treatment of two contrasting water-stressed genotypes of cassava (Manihot esculenta Crantz) with ascorbic acid. I. Growth, physiological and antioxidant responses.

Water deficit-stress at early growth stage is a major constraint of cassava production. Ascorbic acid is a non-enzymatic antioxidant that mitigates oxidative damage caused by water stress in plants. Growth, physiological and antioxidant defense system responses of two contrasting water-stressed cassava genotypes to pre-treatment with foliar application of ascorbic acid (AA) were investigated. The objectives of this study were to assess the growth, proline, photosynthesis pigments and antioxidant activities of young water-stressed cassava plants pre-treated with ascorbic acid. The study consisted of IITA-TMS-IBA980581 (drought tolerant) and IITA-TMS-IBA010040 (drought sensitive) cassava genotypes treated with six doses (0.00, 0.25, 0.50, 0.75 and 1.00mM) of AA before beingsubjected to water deficit (45.0% field capacity) and a water sufficient AA-untreated control. In both genotypes, water stress reduced shoot height (40.3%), leaf area (42.5%), and number of root (54.5%), biomass (28.6%), relative water content (RWC, 3.2%) and photosynthetic pigments (300.0%). However, water stress increased proline (91.3%), endogenous AA (112.0%), catalase (CAT, 300.0%) and superoxide dismutase (SOD, 15.3%) in both genotypes. Compared with IITA-TMS-IBA010040, leaf area, biomass, number of root and shoot height of IITA-TMS-IBA980581 were higher by 7.3, 24.6, 25.9 and 13.1%, respectively. By less than a quarter, chlorophylls a and b, activity of superoxide dismutase and relative water content of IITA-TMS-IBA980581 were higher compared with IITA-TMS-IBA010040. However, proline content of IITA-TMS-IBA010040 was higher than IITA-TMS-IBA980581 by 14.3%. Pre-treatment with AA improved growth parameters, photosynthetic pigments, RWC, endogenous AA, activity of CAT and SOD, but decreased proline in both genotypes with an optimum concentration at 0.5mM. Pre-treatment with 0.5mM AA increased shoot height, area of leaves, leaf number, number of root and dry weight by 46.3, 44.7, 14.4, 88.2 and 37.5%, respectively. Pre-treatment with 0.5mM AA doubled chlorophylls, tripled carotenoids content, doubled endogenous AA and slightly enhanced RWC (2.1%) and SOD (2.0%) when compared with AA-untreated water stressed plants. But pre-stress application of AA reduced proline content by one-fold, increased CAT activity by one-fold in IITA-TMS-IBA980581 and by one-third in IITA-TMS-IBA010040. The study concluded that pre-treatment of cassava young plants with AA before water deficit could alleviate oxidative stress.