Tetrahydrobiopterin inhibitor-based antioxidant metabolic strategy for enhanced cancer ferroptosis-immunotherapy

The induction of immunogenic ferroptosis in cancer cell is limited by the complex and delicate antioxidant system in the organism. Synergistic induction of oxidative damage and inhibition of the defensive redox system in tumor cells is critical to promote lethal accumulation of lipid peroxides and activate immunogenic death (ICD). To address this challenge, we present a multifunctional and dual-responsive layered double hydroxide (LDH) nanosheet to enhance immunogenic ferroptosis. The MTX-LDH@MnO2 nanoplatform is constructed by intercalating methotrexate (MTX) into LDH interlayers and electrostatically absorbing biomineralized ovalbumin (OVA)-MnO2 onto the LDH surface. Specifically, the released Mn2+ from the incorporated MnO2 triggers a Fenton-like reaction, leading to reactive oxygen species (ROS) accumulation, while the depletion of reduced glutathione (GSH) further intensifies oxidative stress, resulting in the induction of ferroptosis. MTX is released in response to the acidic environment of tumor cells and inhibits the regeneration of tetrahydrobiopterin (BH4), modulating the GTP cyclic hydrolase 1 (GCH1)/BH4 axis. MTX disrupts the antioxidant metabolic activity regulated by GCH1/BH4 axis and inhibits ROS consumption, further boosting the ferroptosis effect, which promoted the release of damage-associated molecular patterns (DAMPs) and triggered ICD in the tumor. This activation subsequently leads to significant antitumor immune reactions, including DCs maturation, infiltration of CD4+/CD8+ T cells and cytokines release. The redox-controllable nanoplatform demonstrates promising anticancer efficacy in a mouse breast model providing a novel strategy for cancer immunotherapy.

Effect of halophyte-based management in physiological and biochemical responses of tomato plants under moderately saline greenhouse conditions

Salinity, both in irrigation water and in soils, is one of the major abiotic constraints for agriculture activity worldwide. Phytodesalinization is a low-cost plant-based bioremediation strategy that can effectively amend salt-affected soils by cultivating salt tolerant plants. However, very few studies have evaluated the use of halophyte plants in crop management systems. In this work, we apply two different tomato crop management strategies involving the halophyte Arthrocaulon macrostachyum L. in a moderately saline soil: intercropping (mixed cultivation) and sequential cropping (cultivation of tomato where halophytes were previously grown). We investigated the effect of the different crop managements in some physiological and biochemical variables in tomato plants, including mineral nutrients content, photosynthesis, chlorophyll and flavonol contents, antioxidant metabolism and fruit production and quality. At soil level, both intercropping and sequential cropping decreased chloride content, sodium adsorption ratio and electrical conductivity, leading to reduced soil salinity. In tomato plants, halophyte-dependent management improved nutrient homeostasis and triggered a mild oxidative stress, whereas photosynthesis performance was enhanced by intercropping. In tomato fruits, the sequential cropping led to a 27% production increase and a slight decrease in the soluble sugar contents. We suggest the use of A. macrostachyum, and hence of halophyte plants, as an environmentally friendly phytoremediation strategy to improve plant performance while improving crop production, leading to a more sustainable agriculture and enhancing biodiversity.

Glycine betaine inhibits postharvest softening and quality decline of winter jujube fruit by regulating energy and antioxidant metabolism

Winter jujube fruit easily softens after harvest. To investigate the effects of glycine betaine (N,N,N-trimethylglycine; GB) treatment on the quality of postharvest jujubes, fresh winter jujubes (Zizyphus jujuba Mill. cv. Dongzao) were immersed in 20 mmol·L^-1 GB for 20 min. The results showed that GB application can effectively maintain cell wall component content by restraining gene expression and enzyme activities, including PG, CX, PME and β-Glu. Meanwhile, the activities of antioxidant enzymes (APX, CAT, SOD, POD) and the contents of nonenzymatic antioxidants (MDA, H₂O₂, ASA, GSH) were enhanced in treated jujubes, thereby reducing the content of ROS. In addition, energy metabolism enzyme activities (H⁺-ATPase, Ca²⁺-ATPase, SDH and CCO) and gene expression were also significantly increased, thus maintaining higher energy levels (ATP, ADP, AMP and EC). In summary, GB enhances ATP biosynthesis by increasing energy metabolism. It offers essential energy for the antioxidant metabolism, thus retarding the softening of postharvest jujubes.

Molecular, biochemical and micromorphological responses of cacao seedlings of the Parinari series, carrying the lethal gene Luteus-Pa, in the presence and absence of cotyledons

Investigations of the compatibility between cacao genotypes of the population of the Parinari series (Pa), resulting from the reciprocal crossing of Pa 30 × Pa 169 and Pa 121 × Pa 169, allowed the verification of the occurrence of the recessive lethal single character called Luteus-Pa. These genotypes have this gene in heterozygosity, which when intercross or self-fertilize, segregate in a 3:1 ratio. Normal (NS) and mutant (MS) seedlings grow normally and, after a period of approximately 30 days of age, MS leaves begin to show a metallic yellow color, followed by necrotic spots, and death of the entire seedling, approximately 40 days after the emergency. The work evaluate the molecular, biochemical and micromorphological responses in NS and MS, with and without cotyledons, resulting from the crossing of the Pa 30 × Pa 169 cacao genotypes, aiming to elucidate the possible lethal mechanisms of the homozygous recessive Luteus-Pa. The presence of the lethal gene Luteus-Pa in the seedlings of the cacao genotypes of the population of the Parinari (Pa), with and without cotyledons, resulting from the crossing of Pa 30 × Pa 169, in addition to regulating the synthesis of proteins related to the photosynthetic and stress defense processes, promoted an increase in the synthesis of proteins involved in the glycolic pathway, induced oxidative stress, altered the mobilization of cotyledonary reserves, the integrity of cell membranes, leaf micromorphology and induced the death of seedlings, soon after depletion of protein and carbohydrate reserves, especially in the absence of cotyledons.

Selenium increases photosynthetic capacity, daidzein biosynthesis, nodulation and yield of peanuts plants (Arachis hypogaea L.)

This study aimed to investigate the roles of selenium (Se) application on the profile of photosynthetic pigments, oxidant metabolism, flavonoids biosynthesis, nodulation, and its relation to agronomic traits of peanut plants. Two independent experiments were carried out: one conducted in soil and the other in a nutrient solution. When the plants reached the V2 growth stage, five Se doses (0, 7.5, 15, 30, and 45 μg kg^-1) and four Se concentrations (0, 5, 10, and 15 μmol L^-1) were supplied as sodium selenate. The concentration of photosynthetic pigments, activity of antioxidant enzymes and the concentration of total sugars in peanut leaves increased in response to Se fertilization. In addition, Se improves nitrogen assimilation efficiency by increasing nitrate reductase activity which results in a higher concentration of ureides, amino acids and proteins. Se increases the synthesis of daidzein and genistein in the root, resulting in a greater number of nodules and concentration and transport of ureides to the leaves. Se-treated plants showed greater growth, biomass accumulation in shoots and roots, yield and Se concentration in leaves and grains. Our results contribute to food security and also to increase knowledge about the effects of Se on physiology, biochemistry and biological nitrogen fixation in legume plants.

Hydrogen sulfide alleviates chilling injury in peach fruit by maintaining cell structure integrity via regulating endogenous H2S, antioxidant and cell wall metabolisms

Effects of hydrogen sulfide (H₂S) on chilling injury (CI), H₂S, antioxidant and cell-wall metabolisms of refrigerated peaches treated with H₂S and hypotaurine (HT, H₂S scavenger) were investigated in present study. Results revealed that H₂S treatment enhanced endogenous H₂S content, which was associated with increased related H₂S synthase enzymes activities, while HT showed the opposite results. Moreover, H₂S treatment induced the accumulation of ascorbic acid, glutathione and the enhancement of antioxidant enzymes activities compared to control and HT, contributing to lower hydrogen peroxide content and superoxide radical production. Furthermore, H₂S suppressed the increase of cell-wall degradation enzymes accompanied by higher levels of water-insoluble pectin, 24% KOH-soluble hemicellulose and cellulose, while HT accelerated these components degradation. Therefore, results indicated that H₂S mitigated CI of refrigerated peaches by regulating H₂S, antioxidant and cell-wall metabolisms, maintaining higher H₂S and antioxidants contents, suppressing cell-wall degradation, thereby contributing to redox homeostasis maintenance and cell structure integrity.

Cumulus cell antioxidant system is modulated by patients' clinical characteristics and correlates with embryo development

PURPOSE

To study whether the cumulus cell antioxidant system varies accordingly to patients clinical characteristics' as age, infertility diagnosis, BMI, and stimulation protocol applied and if the antioxidant profile of cumulus cells could be used as a predictor of embryo development.

METHODS

A prospective study including 383 human cumulus samples provided by 191 female patients undergoing intracytoplasmic sperm injection during in vitro fertilization treatments from a local in vitro fertilization center and processed in university laboratories. Catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione S-transferase (GST) enzyme activity levels and reduced glutathione (GSH) levels were measured in cumulus oophorus cells individually collected from each aspirated cumulus-oocyte complex, and the results of each sample were compared considering the oocytes outcome after ICSI and patients clinical characteristics. A total of 223 other human cumulus samples from previous studies were submitted to a gene expression meta-analysis.

RESULTS

The antioxidant system changes dramatically depending on patients' age, infertility diagnosis, stimulation protocol applied, and oocyte quality. SOD activity in cumulus cells revealed to be predictive of top-quality blastocysts for young patients with male factor infertility (P < 0.05), while GST levels were shown to be extremely influenced by infertility cause (P < 0.0001) and stimulation protocol applied (P < 0.05), but nonetheless, it can be used as a complementary tool for top-quality blastocyst prediction in patients submitted to intracytoplasmic sperm injection technique (ICSI) by male factor infertility (P < 0.05).

CONCLUSION

Through a simple and non-invasive analysis, the evaluation of redox enzymes in cumulus cells could be used to predict embryo development, in a personalized matter in specific patient groups, indicating top-quality oocytes and improving success rates in in vitro fertilization treatments.

TRIAL REGISTRATION

The trial was registered at UFRGS Research Ethics Committee and Plataforma Brasil under approval number 68081017.2.0000.5347 in June 6, 2019.

Physiological mechanism of strigolactone enhancing tolerance to low light stress in cucumber seedlings

Strigolactone is a newly discovered type of plant hormone that has multiple roles in modulating plant responses to abiotic stress. Herein, we aimed to investigate the effects of exogenous GR24 (a synthetic analogue of strigolactone) on plant growth, photosynthetic characteristics, carbohydrate levels, endogenous strigolactone content and antioxidant metabolism in cucumber seedlings under low light stress. The results showed that the application of 10 μM GR24 can increase the photosynthetic efficiency and plant biomass of low light-stressed cucumber seedlings. GR24 increased the accumulation of carbohydrates and the synthesis of sucrose-related enzyme activities, enhanced antioxidant enzyme activities and antioxidant substance contents, and reduced the levels of H₂O₂ and MDA in cucumber seedlings under low light stress. These results indicate that exogenous GR24 might alleviate low light stress-induced growth inhibition by regulating the assimilation of carbon and antioxidants and endogenous strigolactone contents, thereby enhancing the tolerance of cucumber seedlings to low light stress.

Seed soaking with melatonin promotes seed germination under chromium stress via enhancing reserve mobilization and antioxidant metabolism in wheat

Chromium (Cr) pollution has serious harm to crop growth, while little is known on the role of melatonin (MT) on seed germination and physiology in Cr-stressed wheat. The effects of seed soaking with MT on growth, reserve mobilization, osmotic regulation and antioxidant capacity of wheat seeds during germination under hexavalent chromium (100 μM) stress were investigated. The results indicated that Cr toxicity decreased the seed germination rate by 16% and suppressed the growth of germinated seeds compared to unstressed seeds. MT in the concentration-dependent manner increased germination rate and promoted subsequent growth when seeds were exposed to Cr stress, but the effect could be counteracted at high concentration. Seed soaking with MT (100 μM) markedly decreased Cr accumulation in seeds, radicals and coleoptiles by 15%, 6% and 15%, respectively, and enhanced α-amylase activity and soluble sugar and free amino acids content in seeds to improve reserve mobilization under Cr stress, compared with Cr treatment. Furthermore, decreasing the level of osmotic regulators (soluble sugar and soluble protein) in radicles under MT combined with Cr treatment confirmed the reduction of osmotic stress caused by Cr stress. Importantly, MT pretreatment reduced H₂O₂ content by 19% and O₂·^- release rate by 45% in radicles under Cr toxicity compared with Cr-stressed wheat, in terms of promoting scavenging ability and decreasing production ability, which was to upregulate the activities and encoding genes expression levels of superoxide dismutase (SOD), catalase (CAT), ascorbic acid peroxidase (APX) and peroxidase (POD) and to downregulate plasma membrane-bound NADPH oxidase (NOX) encoding genes (TaRbohD, TaRbohF) expression, respectively. In all, these results provided evidence that seed soaking with MT could be a potentially method to protect wheat seeds from Cr toxicity, which effectively ameliorated germination under Cr stress by enhancing reserve mobilization and antioxidant metabolism in wheat.

Roles of selenium in mineral plant nutrition: ROS scavenging responses against abiotic stresses

Agronomic biofortification of crops with selenium (Se) is an important strategy to minimize hidden hunger and increase nutrient intake in poor populations. Selenium is an element that has several physiological and biochemical characteristics, such as the mitigation of different types of abiotic stress. Selenoproteins act as powerful antioxidants in plant metabolism through the glutathione peroxidase (GSH) pathway, and provide an increased activity for enzymatic (SOD, CAT, and APX) and non-enzymatic (ascorbic acid, flavonoids, and tocopherols) compounds that act in reactive oxygen species (ROS) scavenging system and cell detoxification. Selenium helps to inhibit the damage caused by climate changes such as drought, salinity, heavy metals, and extreme temperature. Also, Se regulates antenna complex of photosynthesis, protecting chlorophylls by raising photosynthetic pigments. However, Se concentrations in soils vary widely in the earth's crust. Soil Se availability regulates the uptake, transport, accumulation, and speciation in plants. Foliar Se application at the concentration 50 g ha^-1 applied as sodium selenate increases the antioxidant, photosynthetic metabolism, and yield of several crops. Foliar Se application is a strategy to minimize soil adsorption and root accumulation. However, the limit between the beneficial and toxic effects of Se requires research to establish an optimal dose for each plant species under different edaphoclimatic conditions. In this review, we present the compilation of several studies on agronomic biofortification of plants with Se to ensure food production and food security to mitigate hidden hunger and improve the health of the population.

Selenium biofortification enhances ROS scavenge system increasing yield of coffee plants

There are conclusive evidences of selenium (Se) deficiency in Brazilian soils and foods. Brazil is the largest producer and consumer of coffee worldwide, which favors agronomic biofortification of its coffee. This study aimed to evaluate effects of foliar application of three formulations and six rates of Se on antioxidant metabolism, agronomic biofortification and yield of coffee beans. Seven Se concentrations (0, 10, 20, 40, 80, 100 and 160 mg L^-1) were applied from three formulations of Se (sodium selenate, nano-Se 1500, and nano-Se 5000). Selenium application up to 40 mg L^-1 increased the concentration of photosynthetic pigments such as chlorophylls, pheophytins and carotenoids in coffee leaves. Foliar application of Se ranging from 20 to 80 mg L^-1 decreased lipid peroxidation and concentration of hydrogen peroxide, but increased superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase activities in coffee leaves. These results indicated that foliar Se application stimulates antioxidative metabolism to mitigate reactive oxygen species. Foliar application of 20 mg Se L^-1 of sodium selenate increased coffee yield by 38%, and 160 mg Se L^-1 of nano-Se 5000 increased dramatically coffee yield by 42%. Selenium concentration in grains ranged from 0.116 to 4.47 mg kg^-1 (sodium selenate), 4.84 mg kg^-1 (nano-Se 1500) and 5.82 mg kg^-1 (nano-Se 5000). The results suggest the beneficial effect of Se on the increment of photosynthetic pigments, antioxidative metabolism, increased coffee yield and nutritional quality of grains. The recommended foliar Se application in this study can mitigate abiotic stressors such as high temperatures resulting in higher yield of coffee plants.

Hormesis in plants: Physiological and biochemical responses

Hormesis is a favorable response to low level exposures to substance or to adverse conditions. This phenomenon has become a target to achieve greater crop productivity. This review aimed to address the physiological mechanisms for the induction of hormesis in plants. Some herbicides present a hormetic dose response. Among them, those with active ingredients glyphosate, 2,4-D and paraquat. The application of glyphosate as a hormesis promoter is therefore showing promess . Glyphosate has prominent role in shikimic acid pathway, decreasing lignin synthesis resulting in improved growth and productivity of several crops. Further studies are still needed to estimate optimal doses for other herbicides of crops or agricultural interest. Biostimulants are also important, since they promote effects on secondary metabolic pathways and production of reactive oxygen species (ROS). When ROS are produced, hydrogen peroxide act as a signaling molecule that promote cell walls malleability allowing inward water transport causing cell expansion. . Plants'ability to overcome several abiotic stress conditions is desirable to avoid losses in crop productivity and economic losses. This review compiles information on how hormesis in plants can be used to achieve new production levels.

Photoprotection and antioxidative metabolism in Ulva lactuca exposed to coastal oceanic acidification scenarios in the presence of Irgarol

Anthropogenic changes such as ocean acidification, eutrophication, and the release of hazardous chemicals affect coastal environments and aquatic organisms. We investigated the effects of seawater pH (7.4 and 8.2) isolated and in combination with Irgarol on Ulva lactuca. Stress indicators such as membrane damage, lipid peroxidation, and hydrogen peroxide content were assessed. In addition, chlorophyll fluorescence and antioxidant enzyme activities were measured. The photosynthetic yield was affected by low pH in assays with and without Irgarol. However, the combination of low pH and Irgarol promoted photoinhibition, besides the induction of non-photochemical quenching (NPQ) and changes in photosynthetic pigment contents. The induction of NPQ was directly influenced by low pH. The membrane damage was increased in low pH with and without Irgarol exposure. Total soluble protein and carbohydrate contents decreased in low pH, and in presence of Irgarol. The H₂O₂ content and lipid peroxidation were not affected by low pH. In contrast, Irgarol exposure strongly increased lipid peroxidation in both pHs, suggesting a possible synergistic effect. To avoid the harmful effects of high H₂O₂, U. lactuca increased antioxidant enzyme activities in treatments under low pH and in presence of Irgarol. Our results indicate that U. lactuca is tolerant to low pH by inducing NPQ, changing pigment contents, and increasing antioxidant defenses. In contrast, these protective mechanisms could not avoid the harmful effects of the combination with Irgarol.

Assessment of selenium spatial distribution using μ-XFR in cowpea (Vigna unguiculata (L.) Walp.) plants: Integration of physiological and biochemical responses

Low concentrations of selenium (Se) are beneficial for plant growth. Foliar Se application at high concentrations is toxic to plants due to the formation of reactive oxygen species (ROS). This study characterized Se toxicity symptoms using X-ray fluorescence (XRF) technique in response to foliar Se application in cowpea plants. Five Se concentrations (0, 10, 25, 50, 100 e 150 g ha^-1) were sprayed on leaves as sodium selenate. The visual symptoms of Se toxicity in cowpea leaves were separated into two stages: I) necrotic points with an irregular distribution and internerval chlorosis at the leaf limb border (50-100 g ha^-1); II) total chlorosis with the formation of dark brown necrotic lesions (150 g ha^-1). Foliar Se application at 50 g ha^-1 increased photosynthetic pigments and yield. Ultrastructural analyses showed that Se foliar application above 50 g ha^-1 disarranged the upper epidermis of cowpea leaves. Furthermore, Se application above 100 g ha^-1 significantly increased the hydrogen peroxide concentration and lipid peroxidation inducing necrotic leaf lesions. Mapping of the elements in leaves using the XRF revealed high Se intensity, specifically in leaf necrotic lesions accompanied by calcium (Ca) as a possible attenuating mechanism of plant stress. The distribution of Se intensities in the seeds was homogeneous, without specific accumulation sites. Phosphorus (P) and sulfur (S) were found primarily located in the embryonic region. Understanding the factors involved in Se accumulation and its interaction with Ca support new preventive measurement technologies to prevent Se toxicity in plants.

Enhancing Salix viminalis L.-mediated phytoremediation of polycyclic aromatic hydrocarbon-contaminated soil by inoculation with Crucibulum laeve (white-rot fungus)

Although plant-white-rot fungi (WRF) remediation is considered efficient in improving polycyclic aromatic hydrocarbon (PAH)-contaminated soil, the prospects for using it remain poorly known. Therefore, we evaluated whether the WRF Crucibulum laeve could improve the phytoremediation of PAH-contaminated soil by Salix viminalis L. A 60-day pot experiment was conducted to investigate the effects of C. laeve inoculation (using two inoculation treatments and a non-inoculated control) on the phytoremediation potential, growth, and antioxidant metabolism of S. viminalis cultivated in PAH-contaminated soil. The S. viminalis-C. laeve association synergistically caused the highest PAH removal rate. Under the S. viminalis-C. laeve treatment, 80% of the biological concentration and translocation factors for all tissues of S. viminalis were > 1, whereas only 20% of these factors were > 1 when S. viminalis was used alone. C. laeve inoculation remarkably enhanced phytoremediation by promoting S. viminalis-based phytoextraction of PAHs from soils. Furthermore, although C. laeve inoculation altered the antioxidant metabolism of S. viminalis by inducing oxidative stress, thereby inhibiting plant growth, the plant's hardiness enabled it to survive and grow normally for 60 days after treatment. Therefore, phytoremediation using S. viminalis inoculated with C. laeve can be considered a feasible approach for the phytoremediation of PAH-contaminated soil.

Selenate and selenite affect photosynthetic pigments and ROS scavenging through distinct mechanisms in cowpea (Vigna unguiculata (L.) walp) plants

Selenium (Se) is a beneficial element to higher plants. Application of Se at low concentrations enhances the antioxidant metabolism reducing the reactive oxygen species (ROS) generated by plant membrane cells. This study aimed to evaluate how the application of Se in the forms sodium selenate and sodium selenite regulates ROS scavenging in field-grown cowpea plants. Seven Se application rates (0; 2.5; 5; 10; 20; 40 and 60 g ha^-1) of each of the two Se forms were applied to plants via the soil. Photosynthetic pigments concentration, gas exchange parameters, lipid peroxidation by malondialdehyde (MDA) concentration, hydrogen peroxide concentration, activity of catalase (CAT, EC:1.11.1.6), glutathione reductase (GR, EC:1.6.4.2), ascorbate peroxidase (APX, EC:1.11.1.11) and Se concentration in leaves and grains were evaluated. In general, Se application led to a decrease in chlorophyll a concentration whilst leading to an increase in chlorophyll b, indicating conservation of total chlorophyll concentration. Application of 2.5 g ha^-1 of Se as selenate provided a notable increase in total chlorophyll and total carotenoids compared to the other application rates. Selenate and selenite application decreased lipid peroxidation. However, each Se source acted in a different pathway to combat ROS. While selenate showed more potential to increase activity of APX and GR, selenite showed a higher potential to increase CAT activity. The negative correlation between CAT and GR is indicative that both pathways might be activated under distinct circumstances. The more prominent activity of CAT under high rates of selenite resulted in a negative correlation of this enzyme with chlorophyll a and carotenoids. Both selenate and selenite application increased sucrose and total sugars concentration in leaves of cowpea plants. Overall, these results indicate that application of Se in cowpea under field conditions stimulates distinct pathways to scavenge ROS. This could prove beneficial to mitigate oxidative stress during plant development.

Mechanisms of cadmium-stress avoidance by selenium in tomato plants

Cadmium (Cd) is probably the most damaging metal to plant species; with a long biological half-life, it can be taken up by plants, disrupting the cell homeostasis and triggering several metabolic pathways. Selenium (Se) improves plant defence systems against stressful conditions, but the biochemical antioxidant responses to Cd stress in tomato plants is poorly understood. To further address the relationship of Cd-stress responses with Se mineral uptake, Cd and Se concentration, proline content, MDA and H₂O₂ production, and the activity of SOD, APX, CAT and GR enzymes were analyzed in Micro-Tom (MT) plants submitted to 0.5 mM Cd. The results revealed different responses according to Se combination and Cd application. For instance, roots and leaves of MT plants treated with Se exhibited an increase in dry mass and nutritional status, exhibited lower proline content and higher APX and GR activities when compared with plants with no Se application. Plants submitted to 0.5 mM Cd, irrespective of Se exposure, exhibited lower proline, MDA and H₂O₂ content and higher SOD, CAT and GR activities. Selenium may improve tolerance against Cd, which allowed MT plants exhibited less oxidative damage to the cell, even under elevated Cd accumulation in their tissues. The results suggest that Se application is an efficient management technique to alleviate the deleterious effects of Cd-stress, enhancing the nutritional value and activity of ROS-scavenging enzymes in tomato plants.

Generating stem-like memory T cells with antioxidants for adoptive cell transfer immunotherapy of cancer

Among the multiple factors that are responsible for the success of adoptive cell transfer (ACT) immunotherapy for cancer, the differentiation status of the in vitro expanded T cell product at the time of transfer seems to play a major role. In particular, less differentiated memory CD8⁺ T cells endowed with self-renewing capacity and multipotency exert the most potent antitumor activity. To this aim, expansion protocols that generate sufficient numbers of tumor-specific CD8⁺ T cells with superior capacity to persist in vivo following ACT are needed. We describe a procedure for the differentiation of TCF-1⁺ stem-like CD8⁺ memory T cells from peripheral blood naïve precursors that takes advantage of the use of antioxidants, in particular N-acetylcysteine (NAC), in combination with T cell receptor stimulation and proinflammatory cytokines. We additionally describe how to conduct in vitro assays to test the stem-like features of the generated cells at the phenotypic, functional and metabolic level. Balancing the oxidative metabolism by the addition of antioxidants during in vitro manipulation of CD8⁺ T cells results in the generation of cell products with potent antitumor characteristics following ACT.

The cryoprotectant PVS2 plays a crucial role in germinating Passiflora ligularis embryos after cryopreservation by influencing the mobilization of lipids and the antioxidant metabolism

Cryopreservation is a process whereby biological structures are preserved in liquid nitrogen (-196 °C) without losing their viability. Many cryopreservation techniques use the Plant Vitrification Solution 2 (PVS2) for cryoprotection. This study will therefore evaluate the influence of different exposure times to the cryoprotectant PVS2 and discuss the importance of the mobilization of reserves and the antioxidant metabolism during the germination of cryopreserved Passiflora ligularis embryos. The composition of P. ligularis seeds was analytically determined. We tested the germination capacity and the Germination Speed Index (GSI) of embryos (that is, seeds without external tegument) which were exposed to different PVS2 exposure times (0, 30, 60 and 120 min) at 30 days after thawing. Proline content, hydrogen peroxide, activity of isocitrate lyase (ICL), malate synthase (MSy), lipid peroxidation and antioxidant enzyme activities (SOD, CAT, APX) were measured at 7, 14 and 21 days after cryopreservation. The germination from cryopreserved embryos was maximal (85%) after 60 min PVS2 exposure with a GSI of 0.6. At 60 min, the highest activity of the enzymes involved in the glyoxylate cycle, ICL and MSy were recorded. We hypothesize that a 60 min exposure to PVS2 accelerates the reserve mobilization which correlates positively with germination. Until 60 min, there was a positive correlation between the PVS2 exposure time and the proline content, as well as the activity of antioxidant enzymes (SOD, CAT, APX), and a negative correlation with the lipid peroxidation. This study enables us to optimize the long-term conservation of this species. In conclusion, fundamental research is necessary to optimize the cryopreservation procedure, and this study offers an effective and efficient workflow which can be extrapolated to other (oil-rich) species.

Identification of the antioxidant defense genes which may provide enhanced salt tolerance in Oryza sativa L

Antioxidative mechanisms are important to protect cells from the hazardous effects of reactive oxygen species (ROS). Salt stress is one of the environmental stress factors that leads to accumulation of ROS at toxic levels. In this study, we analyzed the responses of two rice (Oryza sativa L.) cultivars against NaCl stress at enzymatic and transcriptional levels. In 14 day-old-seedlings, different antioxidant enzyme activities were observed. These findings were also supported by transcriptional analyses of the responsible genes. According to the results, Cyt-APX, CAT A, Cyt-GR1 and proline metabolism-related genes were differentially expressed between two rice varieties under different salt concentrations. Their regulational differences cause different salt sensitivities of the varieties. By this study, we provided an insight into understanding of the correlation between antioxidant defence genes and ROS enzymes under salt stress.

Effect of cerium on growth and antioxidant metabolism of Lemna minor L

An increasing input rate of rare earth elements in the environment is expected because of the intense extraction of such elements form their ores to face human technological needs. In this study Lemna minor L. plants were grown under laboratory conditions and treated with increasing concentrations of cerium (Ce) ions to investigate the effects on plant growth and antioxidant systems. The growth increased in plants treated with lower Ce concentrations and reduced in plants treated with higher concentrations, compared to control plants. In plants treated with higher Ce concentrations lower levels of chlorophyll and carotenoid and the appearance of chlorotic symptoms were also detected. Increased levels of hydrogen peroxide, antioxidant metabolites and antioxidant activity confirmed that higher Ce concentrations are toxic to L. minor. Ce concentration in plant tissues was also determined and detectable levels were found only in plants grown on Ce-supplemented media. The use of duckweed plants as a tool for biomonitoring of Ce in freshwater is discussed.

Genotypic variation in growth and metabolic responses of perennial ryegrass exposed to short-term waterlogging and submergence stress

Physiological mechanisms of waterlogging (WL) and submergence (SM) tolerance are not well understood in perennial grasses used for turf and forage. The objective of this study was to characterize growth, antioxidant activity and lipid peroxidation of perennial ryegrass (Lolium perenne) exposed to short-term WL and SM. 'Silver Dollar' (turf-type cultivar), 'PI418714' (wild accession), 'Kangaroo Valley' (forage-type cultivar) and 'PI231569' (unknown status) varying in growth habits and leaf texture were subjected to 7 d of WL and SM in a growth chamber. Plant height was unaffected by WL but was significantly reduced by SM for all grasses except PI418714. The SM treatment caused greater reductions in leaf chlorophyll and total carotenoid concentrations. Substantial declines in water-soluble carbohydrate concentrations were found in the shoots and roots under SM, particularly in Kangaroo Valley and PI231569, two relatively fast-growing genotypes. Significant increases in malondialdehyde concentrations were noted in the shoots and roots of all genotypes exposed to WL and SM, but to a greater extent in Kangaroo Valley and PI231569 under SM. Shoot activities of catalase (CAT) and peroxidase (POD) increased under SM, more pronounced in Silver Dollar and PI418714, two relatively slow-growing genotypes. Waterlogging or SM stresses decreased root activities of superoxide dismutase, CAT, POD and ascorbate peroxidase, especially for Kangaroo Valley and PI231569. The results indicated that maintenance of antioxidant activity and carbohydrate and minimization of lipid peroxidation could contribute to better waterlogging or submergence tolerance of perennial ryegrasses.

Short-term physiological changes in roots and leaves of sugarcane varieties exposed to H2O2 in root medium

The aim of this study was to evaluate the differential sensitivity of sugarcane genotypes to H2O2 in root medium. As a hypothesis, the drought tolerant genotype would be able to minimize the oxidative damage and maintain the water transport from roots to shoots, reducing the negative effects on photosynthesis. The sugarcane genotypes IACSP94-2094 (drought tolerant) and IACSP94-2101 (drought sensitive) were grown in a growth chamber and exposed to three levels of H2O2 in nutrient solution: control; 3 mmol L(-1) and 80 mmol L(-1). Leaf gas exchange, photochemical activity, root hydraulic conductance (Lr) and antioxidant metabolism in both roots and leaves were evaluated after 15 min of treatment with H2O2. Although, root hydraulic conductance, stomatal aperture, apparent electron transport rate and instantaneous carboxylation efficiency have been reduced by H2O2 in both genotypes, IACSP94-2094 presented higher values of those variables as compared to IACSP94-2101. There was a significant genotypic variation in relation to the physiological responses of sugarcane to increasing H2O2 in root tissues, being root changes associated with modifications in plant shoots. IACSP94-2094 presented a root antioxidant system more effective against H2O2 in root medium, regardless H2O2 concentration. Under low H2O2 concentration, water transport and leaf gas exchange of IACSP94-2094 were less affected as compared to IACSP94-2101. Under high H2O2 concentration, the lower sensitivity of IACSP94-2094 was associated with increases in superoxide dismutase activity in roots and leaves and increases in catalase activity in roots. In conclusion, we propose a general model of sugarcane reaction to H2O2, linking root and shoot physiological responses.

A novel field transplantation technique reveals intra-specific metal-induced oxidative responses in strains of Ectocarpus siliculosus with different pollution histories

A novel field transplantation technique, in which seaweed material is incorporated into dialysis tubing, was used to investigate intra-specific responses to metals in the model brown alga Ectocarpus siliculosus. Metal accumulation in the two strains was similar, with higher concentrations in material deployed to the metal-contaminated site (Ventanas, Chile) than the pristine site (Quintay, Chile). However, the oxidative responses differed. At Ventanas, strain Es147 (from low-polluted site) underwent oxidative damage whereas Es524 (from highly polluted site) was not affected. Concentrations of reduced ascorbate (ASC) and reduced glutathione (GSH) were significantly higher in Es524. Activities of the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and glutathione reductase (GR) all increased in Es524, whereas only SOD increased in Es147. For the first time, employing a field transplantation technique, we provide unambiguous evidence of inter-population variation of metal-tolerance in brown algae and establish that antioxidant defences are, in part, responsible.