Electron Paramagnetic Resonance (EPR) Spectroscopy in Studies of the Protective Effects of 24-Epibrasinoide and Selenium against Zearalenone-Stimulation of the Oxidative Stress in Germinating Grains of Wheat

Tracking Long-Lived Free Radicals in Dandelion Caused by Air Pollution Using Electron Paramagnetic Resonance Spectroscopy

Studies on particulate air pollution indicate that a new type of pollutant should be considered from mainly fossil fuel combustion and automobile exhaust emissions, i.e., environmentally persistent free radicals. These radicals, ubiquitous in the environment, have a long life span and are capable of producing harmful reactive oxygen species. Samples of dandelion were collected in 2020 and 2021 in spring and late summer. Roots, leaves, flower stalks, and inflorescences of Taraxacum sp. were collected from six sites with three plants each, along with monitoring of particulate matter air pollution. Four sites were located at streets with heavy traffic and two were control sites in the rural part of the city. The free radical content in each part of the plant was measured by electron paramagnetic resonance. The leaf was selected as the most appropriate part of the plant for the measurement of carbon-derived free radicals. The geff value and the total number of spins were calculated. Relationships were found between location, season, and measurements. The electron paramagnetic resonance spectrum consists of at least two components, which can be attributed to C-type radicals and mixed C + O radicals. Their increase in numbers in the fall seasons, compared to the spring seasons, is also noticeable. It has also been observed that leaves collected in autumn have a higher geff value, which is probably related to the higher amount of oxygen- and carbon-derived free radicals.

Preclinical Assessment of Enhanced Chemodynamic Therapy by an FeMnOx-Based Nanocarrier: Tumor-Microenvironment-Mediated Fenton Reaction and ROS-Induced Chemotherapeutic for Boosted Antitumor Activity

In recent studies, iron-containing Fenton nanocatalysts have demonstrated significant promise for clinical use due to their effective antitumor activity and low cytotoxicity. A new approach was reported in this work utilizing cation exchange synthesis to fabricate FeMnOx nanoparticles (NPs) that boost Fenton reactions and responses to the tumor microenvironment (TME) for chemodynamic therapy (CDT) and chemotherapy (CT). Within the TME, the redox metal pair of Fe2+/Mn2+ helps break down endogenous hydrogen peroxide (H2O2) into very harmful hydroxyl radicals (•OH) while simultaneously deactivating glutathione (GSH) to boost CDT performance. To further enhance the therapeutic potential, FeMnOx NPs were encapsulated with thioketal-linked camptothecin (CPT-TK-COOH), a reactive oxygen species (ROS)-responsive prodrug, achieving a high CPT-loading capacity of up to 51.1%. Upon ROS generation through the Fenton reaction, the prodrug TK linkage was disrupted, releasing 80% of the CPT payload within 48 h. Notably, FeMnOx@CPT exhibited excellent dual-modal imaging capabilities, enabling magnetic resonance and fluorescence imaging for image-guided therapy. In vitro studies showed the cytocompatibility of FeMnOx NPs using MDA-Mb-231 and 4T1 cells, but in the presence of H2O2, they induced significant cytotoxicity, resulting in 80% cell death through CDT and CT effects. Upon intravenous administration, FeMnOx@CPT displayed remarkable tumor accumulation, which enhanced tumor suppression in xenografts through improved CDT and CT effects. Moreover, no significant adverse effects were observed in the FeMnOx NP-treated animals. In the current study, the FeMnOx@CPT anticancer platform, with its boosted •OH-producing capability and ROS-cleavable drug release, has been validated utilizing in vitro and animal studies, suggesting its capacity as a viable strategy for clinical trials.

Boron clusters (ferrabisdicarbollides) shaping the future as radiosensitizers for multimodal (chemo/radio/PBFR) therapy of glioblastoma

Glioblastoma multiforme (GBM) is the most common and fatal primary brain tumor, and is highly resistant to conventional radiotherapy and chemotherapy. Therefore, the development of multidrug resistance and tumor recurrence are frequent. Given the poor survival with the current treatments, new therapeutic strategies are urgently needed. Radiotherapy (RT) is a common cancer treatment modality for GBM. However, there is still a need to improve RT efficiency, while reducing the severe side effects. Radiosensitizers can enhance the killing effect on tumor cells with less side effects on healthy tissues. Herein, we present our pioneering study on the highly stable and amphiphilic metallacarboranes, ferrabis(dicarbollides) ([o-FESAN]^- and [8,8'-I2-o-FESAN]^-), as potential radiosensitizers for GBM radiotherapy. We propose radiation methodologies that utilize secondary radiation emissions from iodine and iron, using ferrabis(dicarbollides) as iodine/iron donors, aiming to achieve a greater therapeutic effect than that of a conventional radiotherapy. As a proof-of-concept, we show that using 2D and 3D models of U87 cells, the cellular viability and survival were reduced using this treatment approach. We also tested for the first time the proton boron fusion reaction (PBFR) with ferrabis(dicarbollides), taking advantage of their high boron (¹¹B) content. The results from the cellular damage response obtained suggest that proton boron fusion radiation therapy, when combined with boron-rich compounds, is a promising modality to fight against resistant tumors. Although these results are encouraging, more developments are needed to further explore ferrabis(dicarbollides) as radiosensitizers towards a positive impact on the therapeutic strategies for GBM.

Protective responses of tolerant and sensitive wheat seedlings to systemic and local zearalenone application - Electron paramagnetic resonance studies

BACKGROUND

Mycotoxins are among the environmental stressors whose oxidative action is currently widely studied. The aim of this paper was to investigate the response of seedling leaves to zearalenone (ZEA) applied to the leaves (directly) and to the grains (indirectly) in tolerant and sensitive wheat cultivars.

RESULTS

Biochemical analyses of antioxidant activity were performed for chloroplasts and showed a similar decrease in this activity irrespective of plant sensitivity and the way of ZEA application. On the other hand, higher amounts of superoxide radical (microscopic observations) were generated in the leaves of plants grown from the grains incubated in ZEA solution and in the sensitive cultivar. Electron paramagnetic resonance (EPR) studies showed that upon ZEA treatment greater numbers of Mn - aqua complexes were formed in the leaves of the tolerant wheat cultivar than in those of the sensitive one, whereas the degradation of Fe-protein complexes occurred independently of the cultivar sensitivity.

CONCLUSION

The changes in the quantity of stable, organic radicals formed by stabilizing reactive oxygen species on biochemical macromolecules, indicated greater potential for their generation in leaf tissues subjected to foliar ZEA treatment. This suggested an important role of these radical species in protective mechanisms mainly against direct toxin action. The way the defense mechanisms were activated depended on the method of the toxin application.

In Vitro Evaluation of the Inhibitory Activity of Different Selenium Chemical Forms on the Growth of a Fusarium proliferatum Strain Isolated from Rice Seedlings

In this study, the in vitro effects of different Se concentrations (5, 10, 15, 20, and 100 mg kg−1) from different Se forms (sodium selenite, sodium selenate, selenomethionine, and selenocystine) on the development of a Fusarium proliferatum strain isolated from rice were investigated. A concentration-dependent effect was detected. Se reduced fungal growth starting from 10 mg kg−1 and increasing the concentration (15, 20, and 100 mg kg−1) enhanced the inhibitory effect. Se bioactivity was also chemical form dependent. Selenocystine was found to be the most effective at the lowest concentration (5 mg kg−1). Complete growth inhibition was observed at 20 mg kg−1 of Se from selenite, selenomethionine, and selenocystine. Se speciation analysis revealed that fungus was able to change the Se speciation when the lowest Se concentration was applied. Scanning Electron Microscopy showed an alteration of the fungal morphology induced by Se. Considering that the inorganic forms have a higher solubility in water and are cheaper than organic forms, 20 mg kg−1 of Se from selenite can be suggested as the best combination suitable to inhibit F. proliferatum strain. The addition of low concentrations of Se from selenite to conventional fungicides may be a promising alternative approach for the control of Fusarium species.

Plant biochemistry influences tropospheric ozone formation, destruction, deposition, and response

Tropospheric ozone (O₃) is among the most damaging air pollutant to plants. Plants alter the atmospheric O₃ concentration in two distinct ways: (i) by the emission of volatile organic compounds (VOCs) that are precursors of O_3; and (ii) by dry deposition, which includes diffusion of O₃ into vegetation through stomata and destruction by nonstomatal pathways. Isoprene, monoterpenes, and higher terpenoids are emitted by plants in quantities that alter tropospheric O₃. Deposition of O₃ into vegetation is related to stomatal conductance, leaf structural traits, and the detoxification capacity of the apoplast. The biochemical fate of O₃ once it enters leaves and reacts with aqueous surfaces is largely unknown, but new techniques for the tracking and identification of initial products have the potential to open the black box.

Hydroxyapatite nanophases augmented with selenium and manganese ions for bone regeneration: Physiochemical, microstructural and biological characterization

Hydroxyapatite (HAP) nanopowders with different manganese (Mn) and selenium (Se) contents with Mn/Ca and Se/P molar ratio of 1 mol%, 2.5 mol% and 5 mol% were synthesized by wet-co-chemical precipitation method. The results revealed that with either Mn or Se doping, ion-substituted apatite phase was achieved with good crystallographic features. The combined evidence obtained from spectrometric techniques revealed that nanocrystalline HAP was effectively doped with Mn and Se ions, where Se in form of SeO₃^2- replaced PO₄^3- and Mn²⁺ replaced Ca²⁺. Mn and Se doped HAP samples exhibited rod-like and needle-like morphology with strong tendency to form agglomerates. HAP enriched with Mn and Se represented a strong antibacterial effect and also showed prominent blood compatibility. From the biocompatibility testing, it was evident that Mn and Se doped HAP augmented the osteoblasts adhesion, migration and proliferation in a dose-dependent manner. To conclude from this study, it is clearly evident that the doping amount of both Mn and Se ions can determine the size and morphology of the final HAP product. Therefore, Mn and Se HAP nanopowders with molar ratio less than 5 mol% without any heat treatment can provide good crystallographic features to HAP with satisfying micro-structural, thermal and biological properties.

Impact of seed color and storage time on the radish seed germination and sprout growth in plasma agriculture

The use of low-temperature plasma for the pre-sowing seed treatment is still in the early stage of research; thus, numerous factors affecting germination percentage, seedling growth, and yield remains unknown. This study aimed to estimate how two critical factors, such as harvest year and seed coat color, affect the percentage of germination and seedling growth after plasma treatment. Radish seeds stored for 2 and 1 year after harvesting (harvested in 2017 and 2018) were sorted into two colors (brown and grey) to investigate the plasma effect on harvest year and seed coat color. We analyzed the amounts of seed phytohormones and antioxidant (γ-tocopherol) were analyzed using mass spectrometry, and physical changes were studied using SEM, EDX, and EPR to understand the mechanism of plasma-induced changes in radish seeds. The obtained results revealed that plasma treatment on seeds affects the germination kinetics, and the maximal germination percentage depends on seed color and the time of seed storage after harvest. Through this study, for the first time, we demonstrated that physical and chemical changes in radish seeds after plasma treatment depends upon the seed color and harvest year. Positive effects of plasma treatment on growth are stronger for sprouts from seeds harvested in 2017 than in 2018. The plasma treatment effect on the sprouts germinated from grey seeds effect was stronger than sprouts from brown radish seeds. The amounts of gibberellin A3 and abscisic acid in control seeds strongly depended on the seed color, and plasma induced changes were better in grey seeds harvested in 2017. Therefore, this study reveals that Air scalar-DBD plasma's reactive oxygen and nitrogen species (RONS) can efficiently accelerate germination and growth in older seeds.

Translocation of elements and sugars in wheat genotypes at vegetative and generative stages under continuous selenium exposure

BACKGROUND

Biofortification with selenium (Se) elevates its concentration in feed and fodder plants and helps to prevent health problems in animals and humans. The aim of this study was to describe Se-induced modifications in the accumulation of elements important for the proper functioning of wheat, one of the most popular cereals. The presence of Se correlated with carbohydrate synthesis and electron paramagnetic resonance (EPR). This explained the mechanisms of Se's antioxidant activity.

RESULTS

Selenium accumulation in vegetative and generative leaves, and in the grains of three wheat genotypes (cv. Parabola, cv. Raweta and cv. Manu), differing in their stress tolerance and grown hydroponically in the presence of 10 or 20 μM Na₂ SeO_4, , was proportional to its content in the medium. Stronger Se accumulation was typical of a stress-sensitive genotype. Selenium generally promoted the uptake of macronutrients and micronutrients but their distribution depended on tissue and genotype. Changes in the Se-induced EPR signals of paramagnetic metals and organic radicals corresponded with stress tolerance of the tested genotypes.

CONCLUSIONS

Se application increased the accumulation of nutrients and carbohydrates that are vital for proper plant growth and development. Accelerated uptake of molybdenum (Mo), an element improving dietary properties of grains, may be an additional advantage of Se fertilization. The mechanisms of Se-induced changes in removing Mn and iron (Fe) ions from macromolecules may be one of the factors that differentiate plant tolerance to oxidative stress. © 2019 Society of Chemical Industry.

Manganese protects wheat from the mycotoxin zearalenone and its derivatives

Searching for factors that reduce zearalenone (ZEN) toxicity is an important challenge in wheat production, considering that this crop is a basic dietary ingredient. ZEN, absorbed by cells, is metabolized into α-zearalenol and α-zearalanol, and this study focused on the function of manganese ions as potential protectants against the mycotoxins. Stress effects were invoked by an application of 30 µM ZEN and its derivatives. Manganese ions were applied at 100 µM, not stress-inducing concentration. Importance of the biomembrane structures in the absorption of the mycotoxins was demonstrated in in vitro wheat calli and on model membranes. ZEN showed the greatest and α-zearalanol the smallest stressogenic effect manifested as a decrease in the calli growth. This was confirmed by variable increase in antioxidant enzyme activity. Mn ions added to the toxin mixture diminished stressogenic properties of the toxins. Variable decrease in total lipid content and the percentage of phospholipid fraction detected in calli cells exposed to ZEN and its metabolites indicated significance of the membrane structure. An analysis of physicochemical parameters of model membranes build from phosphatidylcholine, a basic lipid in native membranes, and its mixture with the tested toxins made by Langmuir technique and verified by Brewster angle microscopy, confirmed variable contribution of ZEN and its derivatives to the modification of membrane properties. The order of toxicity was as follows: ZEN ≥ α-zearalenol > α-zearalanol. Manganese ions present in the hydrophilic phase interacted with polar lipid groups and reduced the extent of membrane modification caused by the mycotoxins.

The role of chloroplasts in the oxidative stress that is induced by zearalenone in wheat plants - The functions of 24-epibrassinolide and selenium in the protective mechanisms

This study focused on the idea that the toxic effect of zearalenone (ZEA) and the protective actions of the brassinosteroid - 24-epibrassinolide (EBR) as well as selenium are dependent on its accumulation in chloroplasts to a high degree. These organelles were isolated from the leaves of oxidative stress-sensitive and stress-tolerant wheat cultivars that had been grown from grains that had been incubated in a solution of ZEA (30 μM), Na₂SeO₄ (Se, 10 μM), EBR (0.1 μM) or in a mixture of ZEA with Se or EBR. Ultra-high performance liquid chromatography techniques indicated that ZEA was adsorbed in higher amounts in the chloroplasts in the sensitive rather than tolerant cultivar. Although the brassinosteroids and Se were also accumulated in the chloroplasts, higher levels were only found in the tolerant cultivar. The application of EBR increased the homocastasterone content, especially in the chloroplasts of the tolerant plant and after the addition of ZEA. The presence of both protectants caused a decrease in the ZEA content in studied organelles and resulted in diminishing of the oxidative stress (i.e. changes in the activity of the antioxidative enzymes). Moreover, a recovery of photosystem II and decrease in the negative impact of ZEN on Hsp90 transcript accumulation was observed in plants.

Exposure of human lymphoma cells (U-937) to the action of a single mycotoxin as well as in mixtures with the potential protectors 24-epibrassinolide and selenium ions

The progressive contamination of food products by mycotoxins such as zearalenone (ZEN) has prompted the search for specific substances that can act as protectors against an accumulation of these toxins. This paper discusses the effect of selenium ions and 24-epibrassinolide (EBR) as non-organic and organic compounds that preserve human lymphoblastic cells U-937 under ZEN stressogenic conditions. Based on measurements of cell viability and a DAPI test, concentrations of ZEN at 30 μmol/l, Se at 2.5 μmol/l and EBR at 0.005 μmol/l were selected. The addition of both protectors resulted in an increase in the viability of ZEN-treated cells by about 16%. This effect was connected with a decrease in lipid peroxidation (a decrease in the malonyldialdehyde content) and the generation of reactive oxygen species, which were determined by a cellular ROS/superoxide detection assay and the SOD activity. The Se protection was observed as the blocking of the all excess ROS, while the EBR action was mainly concentrated on something other than the superoxide radical itself. The experiments on the model lipid membranes that mimic the environment of U-937 cells confirmed the affect of ZEN on the structure and physicochemical properties of human membranes. Although the presence of both Se and EBR reduced the effect of ZEN by blocking its interaction with a membrane, the action of Se was more evident.

Foliar application of selenium for protection against the first stages of mycotoxin infection of crop plant leaves

BACKGROUND

The aim of this study was to investigate whether the application of selenium (Se) ions directly to the leaf surface can protect plants against infection by the fungal toxin zearalenone (ZEA). The experiments were performed for the most common and agronomically important crops such as wheat, oat, and barley (both tolerant and sensitive varieties) because mycotoxin accumulation in plants is the cause of many diseases in animals and people.

RESULTS

ZEA at a concentration of 10 µmol L^-1 either alone or in combination with Se (5 µmol L^-1 Na₂ SeO₄ ) was applied to the second leaf of seedlings. Visualization of leaf temperature profiles by infrared thermography demonstrated a decrease in temperature at the location of ZEA infection that was more noticeable in sensitive genotypes. The presence of Se significantly suppressed changes at the site of ZEA application in all tested plants, especially the tolerant genotypes. Microscopic observations confirmed that foliar administration of ZEA resulted in its penetration to deeper localized cells and that damage induced by ZEA (mainly to chloroplasts) decreased after Se application. Analyses of antioxidant enzymes demonstrated the involvement of Se in antioxidation mechanisms, in particular by activating SOD and CAT under ZEA-induced stress conditions.

CONCLUSION

The foliar application of Se to seedling leaves may be a non-invasive method of protecting crops against the first steps of ZEA infection. © 2018 Society of Chemical Industry.