Glutathione Regeneration Research Articles

Changes in redox network expression during Caco-2 cell differentiation into enterocytes

Graphical abstract Abstract Objective This work characterized fluctuations in cell components involved in the regulation of cell redox homeostasis during Caco-2 cell differentiation into enterocytes. Methods Caco-2 cells were differentiated for 10 days. Gene expression of NADPH oxidases; enzymes that metabolize superoxide anion and hydrogen peroxide, proteins involved in the production and/or regeneration of glutathione, thioredoxin, and in NADPH production, and NRF2-dependent genes were measured by qPCR at 0, 1, 4, 7, and 10 days post-confluence. Results NADPH oxidase 1 mRNA levels decreased with Caco-2 cell differentiation, in agreement with its role in regulating cell proliferation. NADPH oxidase 4, DUOX2, superoxide dismutase 1, and catalase mRNA levels increased with differentiation. NRF2 mRNA levels increased with differentiation up to day 4 post-confluence, reaching a plateau until day 10. A similar pattern was observed for the NRF2-regulated genes: NAD(P)H quinone dehydrogenase 1, glutathione reductase 1, and thioredoxin reductase 1. On the contrary, glutamate-cysteine ligase catalytic subunit mRNA levels decreased after reaching a maximum 4 days post-confluence. This and the finding of a correlation between glutathione reductase 1 and thioredoxin reductase 1 mRNA levels suggest that recycling of glutathione and thioredoxin is more relevant than their synthesis during Caco-2 cell differentiation. Conclusion Results support the relevance of redox homeostasis for cell fate decisions and in preparing enterocytes to interact with their environment. Significance statement Current findings resemble changes in redox components previously characterized in vivo. This stresses the concept that Caco-2 cells are an appropriate model to be used to evaluate redox-regulated mechanisms in human enterocytes.

Response of photosynthetic characteristics and antioxidant system in the leaves of safflower to NaCl and NaHCO3.

Compared with NaCl, NaHCO3 caused more serious oxidative damage and photosynthesis inhibition in safflower by down-regulating the expression of related genes. Salt-alkali stress is one of the important factors that limit plant growth. NaCl and sodium bicarbonate (NaHCO3) are neutral and alkaline salts, respectively. This study investigated the physiological characteristics and molecular responses of safflower (Carthamus tinctorius L.) leaves treated with 200mmolL-1 of NaCl or NaHCO3. The plants treated with NaCl treatment were less effective at inhibiting the growth of safflower, but increased the content of malondialdehyde (MDA) in leaves. Meanwhile, safflower alleviated stress damage by increasing proline (Pro), soluble protein (SP), and soluble sugar (SS). Both fresh weight and dry weight of safflower was severely decreased when it was subjected to NaHCO3 stress, and there was a significant increase in the permeability of cell membranes and the contents of osmotic regulatory substances. An enrichment analysis of the differentially expressed genes (DEGs) using Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes identified significant enrichment of photosynthesis and pathways related to oxidative stress. Furthermore, a weighted gene co-expression network analysis (WGCNA) showed that the darkgreen module had the highest correlation with photosynthesis and oxidative stress traits. Large numbers of transcription factors, primarily from the MYB, GRAS, WRKY, and C2H2 families, were predicted from the genes within the darkgreen module. An analysis of physiological indicators and DEGs, it was found that under saline-alkali stress, genes related to chlorophyll synthesis enzymes were downregulated, while those related to degradation were upregulated, resulting in inhibited chlorophyll biosynthesis and decreased chlorophyll content. Additionally, NaCl and NaHCO3 stress downregulated the expression of genes related to the Calvin cycle, photosynthetic antenna proteins, and the activity of photosynthetic reaction centers to varying degrees, hindering the photosynthetic electron transfer process, suppressing photosynthesis, with NaHCO3 stress causing more pronounced adverse effects. In terms of oxidative stress, the level of reactive oxygen species (ROS) did not change significantly under the NaCl treatment, but the contents of hydrogen peroxide and the rate of production of superoxide anions increased significantly under NaHCO3 stress. In addition, treatment with NaCl upregulated the levels of expression of the key genes for superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), the ascorbate-glutathione cycle, and the thioredoxin-peroxiredoxin pathway, and increased the activity of these enzymes, thus, reducing oxidative damage. Similarly, NaHCO3 stress increased the activities of SOD, CAT, and POD and the content of ascorbic acid and initiated the glutathione-S-transferase pathway to remove excess ROS but suppressed the regeneration of glutathione and the activity of peroxiredoxin. Overall, both neutral and alkaline salts inhibited the photosynthetic process of safflower, although alkaline salt caused a higher level of stress than neutral salt. Safflower alleviated the oxidative damage induced by stress by regulating its antioxidant system.

NADPH Oxidase-Like Nanozyme for High-Efficiency Tumor Therapy Through Increasing Glutathione Consumption and Blocking Glutathione Regeneration.

To counteract the high level of reactive oxygen species (ROS) caused by rapid growth, tumor cells resist oxidative stress by accelerating the production and regeneration of intracellular glutathione (GSH). Numerous studies focus on the consumption of GSH, but the regeneration of GSH will enhance the reduction level of tumor cells to resist oxidative stress. Therefore, inhibiting the regeneration of GSH; while, consuming GSH is of great significance for breaking the redox balance of tumor cells. Herein, a simple termed MnOx-coated Au (AMO) nanoflower, as a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) nanoenzyme, is reported for efficient tumor therapy. Au nanoparticles exhibit the capability to catalyze the oxidation of NADPH, hindering GSH regeneration; while, concurrently functioning as a photothermal agent. During the process of eliminating intracellular GSH, MnOx releases Mn2+ that subsequently engages in Fenton-like reactions, ultimately facilitating the implementation of chemodynamic therapy (CDT). Overall, this NOX enzyme-based nanoplatform enhances ROS generation and disrupts the state of reduction equilibrium, inducing apoptosis and ferroptosis by blocking GSH regeneration and increasing GSH consumption, thereby achieving collaborative treatments involving photothermal therapy (PTT), CDT, and catalytic therapy. This research contributes to NADPH and GSH targeted tumor therapy and showcases the potential of nanozymes.

Modification in the ascorbate-glutathione cycle leads to a better acclimation to high light in the rose Bengal resistant mutant of Nannochloropsis oceanica

Understanding how to adapt outdoor cultures of Nannochloropsis oceanica to high light (HL) is vital for boosting productivity. The N. oceanica RB2 mutant, obtained via ethyl methanesulfonate mutagenesis, was chosen for its tolerance to Rose Bengal (RB), a singlet oxygen (1O2) generator. Compared to the wild type (WT), the RB2 mutant showed higher resilience to excess light conditions. Analyzing the ascorbate-glutathione cycle (AGC), involving ascorbate peroxidases (APX, EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and glutathione reductase (GR, EC 1.8.1.7), in the RB2 mutant under HL stress provided valuable insights. At 250 μmol photon m−2 s−1 (HL), the WT strain displayed superoxide anion radicals (O2▪-) and hydrogen peroxide (H2O2) accumulation, increased lipid peroxidation, and cell death compared to normal light (NL) conditions (50 μmol photon m−2 s−1). The RB2 mutant didn't accumulate O2▪- and H2O2 after HL exposure, and exhibited increased APX, DHAR, and GR activities and transcript levels compared to WT and remained consistent after HL treatment. Although the RB2 mutant had a smaller ascorbate (AsA) pool than the WT, its ability to regenerate dehydroascorbate (DHA) increased post HL exposure, indicated by a higher AsA/DHA ratio. Additionally, under HL conditions, the RB2 mutant displayed an improved glutathione (GSH) regeneration rate (GSH/GSSG ratio) without changing the GSH pool size. Remarkably, H2O2 or menadione (a O2▪- donor) treatment induced cell death in the WT strain but not in the RB2 mutant. These findings emphasize the essential role of AGC in the RB2 mutant of Nannochloropsis in handling photo-oxidative stress.

Functional-metabolic coupling in distinct renal cell types coordinates organ-wide physiology and delays premature ageing

Precise coupling between cellular physiology and metabolism is emerging as a vital relationship underpinning tissue health and longevity. Nevertheless, functional-metabolic coupling within heterogenous microenvironments in vivo remains poorly understood due to tissue complexity and metabolic plasticity. Here, we establish the Drosophila renal system as a paradigm for linking mechanistic analysis of metabolism, at single-cell resolution, to organ-wide physiology. Kidneys are amongst the most energetically-demanding organs, yet exactly how individual cell types fine-tune metabolism to meet their diverse, unique physiologies over the life-course remains unclear. Integrating live-imaging of metabolite and organelle dynamics with spatio-temporal genetic perturbation within intact functional tissue, we uncover distinct cellular metabolic signatures essential to support renal physiology and healthy ageing. Cell type-specific programming of glucose handling, PPP-mediated glutathione regeneration and FA β-oxidation via dynamic lipid-peroxisomal networks, downstream of differential ERR receptor activity, precisely match cellular energetic demands whilst limiting damage and premature senescence; however, their dramatic dysregulation may underlie age-related renal dysfunction.

α-LA attenuates microcystin-LR-induced hepatocellular oxidative stress in mice through Nrf2-mediated antioxidant and detoxifying enzymes

Microcystins constitute a class of toxins synthesized by cyanobacteria and are known to inflict significant damage on the antioxidant defense system of living organisms, primarily targeting the liver. α-Lipoic acid (α-LA) is universally recognized as a potent antioxidant in biological systems. It exerts its beneficial effects through multiple mechanisms—directly neutralizing reactive oxygen species (ROS) and free radicals, and indirectly enhancing antioxidant defenses by facilitating the regeneration of glutathione (GSH). However, the precise modus operandi of α-LA's protective effect against Microcystin-LR-induced hepatotoxicity remains incompletely elucidated. The present study, therefore, employed α-LA to explore its protective role against Microcystin-LR exposure in mice. A model of Microcystin-LR-induced hepatic injury was established by administering Microcystin-LR into the peritoneal cavity of BALB/c mice daily over a two-week period. Thereafter, BALB/c mice were pre-treated with varying concentrations of α-LA via oral gavage for a duration of 7 days, followed by a 7-day exposure to Microcystin-LR. Our findings reveal that α-LA pre-treatment significantly mitigated hepatic pathologies in Microcystin-LR-exposed mice. Furthermore, α-LA administration led to a notable elevation in the activities and expression levels of nuclear factor erythroid 2-related factor 2, superoxide dismutase, glutathione peroxidase, glutathione S-transferase, and glutathione—indicative of its antioxidative capacity. Concurrently, a significant decrease was observed in the activities and expression levels of malondialdehyde and cytochrome P450 2E1. Consequently, α-LA emerges as a promising therapeutic candidate for the amelioration of liver oxidative damage subsequent to Microcystin-LR exposure.

Measuring Glutathione Regeneration Capacity in Stem Cells.

Glutathione (GSH) is a chief cellular antioxidant, affecting stem cell functions. The cellular GSH level is dynamically altered by the redox buffering system and transcription factors, including NRF2. Additionally, GSH is differentially regulated in each organelle. We previously reported a protocol for monitoring the real-time GSH levels in live stem cells using the reversible GSH sensor FreSHtracer. However, GSH-based stem cell analysis needs be comprehensive and organelle-specific. Hence, in this study, we demonstrate a detailed protocol to measure the GSH regeneration capacity (GRC) in living stem cells by measuring the intensities of the FreSHtracer and the mitochondrial GSH sensor MitoFreSHtracer using a high-content screening confocal microscope. This protocol typically analyses the GRC in approximately 4 h following the seeding of the cells onto plates. This protocol is simple and quantitative. With some minor modifications, it can be employed flexibly to measure the GRC for the whole-cell area or just the mitochondria in all adherent mammalian stem cells.

Investigating the Effect of Curcumin and Betanin Nanoparticles on Antioxidant and Inflammatory Response in Rats Suffering from Brain Ischemia/Reperfusion

Introduction: Natural products can help in the treatment of many diseases due to their low side effects. In the present study the effect of pretreatment of nanobetanin and nanocurcumin in cerebral ischemia rats was investigated.
 Methods: The present study was experimental. 40 male Wistar rats were divided into eight groups of healthy control, healthy animals receiving nanobetanin, healthy animals receiving nanocurcumin, healthy animals receiving nanobetanin+nanocurcumin, cerebral I/R, cerebral I/R receiving nanobetanin, cerebral I/R receiving nanocurcumin and cerebral I/R receiving nanobetanin + nanocurcumin. Oral administration of nanobetanin and nanocurcumin started five days before Bilateral Common Carotid Artery Occlusion induction in rats and continued three days later. Neurological disorders scores were assessed. After preparing the brain homogenate, the intensity of oxidative stress, the activity of antioxidant enzymes and the expressions of interleukin-1β (IL-1β), interleukin 6 (IL-6) and alpha tumor necrosis factor (TNF-α) cytokines were measured by relevant kits. Data analysis was done in GraphPad prism V.8 software.
 Results: Nanobetanin and nanocurcumin showed strong anti-inflammatory and antioxidant effects in cerebral ischemia/reperfusion (I/R) rats. The content of reactive oxygen species (ROS) in the brain of I/R rats receiving nanobetanin and nanocurcumin decreased (P=0.00001) and the activity of antioxidant enzyme such as superoxide dismutase improved (P=0.00002), and the content of glutathione regeneration showed an increasing trend (P=0.0004). A decrease in neurological disorders scores (P=0.009) was observed in cerebral I/R rats receiving nanobetanin and nanocurcumin. Furthermore, nanobetanin and nanocurcumin administration reduced the expression levels of inflammatory cytokines IL-1β (P=0.00003), IL-6 (P=0.00006), TNF-α (P=0.008) in the rats with cerebral I/R injury.
 Conclusion: Nanobetanin and nanocurcumin has neuroprotective effects in cerebral I/R condition due to its antioxidant and anti-inflammation properties, which can be considered as a suitable treatment option in stroke conditions.

Safe and Effective Antioxidant: The Biological Mechanism and Potential Pathways of Ergothioneine in the Skin

Ergothioneine, a sulfur-containing micromolecular histidine derivative, has attracted increasing attention from scholars since it was confirmed in the human body. In the human body, ergothioneine is transported and accumulated specifically through OCTN-1, especially in the mitochondria and nucleus, suggesting that it can target damaged cells and tissues as an antioxidant. It shows excellent antioxidant, anti-inflammatory effects, and anti-aging properties, and inhibits melanin production. It is a mega antioxidant that may participate in the antioxidant network system and promote the reducing glutathione regeneration cycle. This review summarizes studies on the antioxidant effects of ergothioneine on various free radicals in vitro to date and systematically introduces its biological activities and potential mechanisms, mostly in dermatology. Additionally, the application of ergothioneine in cosmetics is briefly summarized. Lastly, we propose some problems that require solutions to understand the mechanism of action of ergothioneine. We believe that ergothioneine has good prospects in the food and cosmetics industries, and can thus meet some needs of the health and beauty industry.

Ferroptosis-modulating small molecules for targeting drug-resistant cancer: Challenges and opportunities in manipulating redox signaling.

Ferroptosis is an iron-dependent cell death program that is characterized by excessive lipid peroxidation. Triggering ferroptosis has been proposed as a promising strategy to fight cancer and overcome drug resistance in antitumor therapy. Understanding the molecular interactions and structural features of ferroptosis-inducing compounds might therefore open the door to efficient pharmacological strategies against aggressive, metastatic, and therapy-resistant cancer. We here summarize the molecular mechanisms and structural requirements of ferroptosis-inducing small molecules that target central players in ferroptosis. Focus is placed on (i) glutathione peroxidase (GPX) 4, the only GPX isoenzyme that detoxifies complex membrane-bound lipid hydroperoxides, (ii) the cystine/glutamate antiporter system Xc - that is central for glutathione regeneration, (iii) the redox-protective transcription factor nuclear factor erythroid 2-related factor (NRF2), and (iv) GPX4 repression in combination with induced heme degradation via heme oxygenase-1. We deduce common features for efficient ferroptotic activity and highlight challenges in drug development. Moreover, we critically discuss the potential of natural products as ferroptosis-inducing lead structures and provide a comprehensive overview of structurally diverse biogenic and bioinspired small molecules that trigger ferroptosis via iron oxidation, inhibition of the thioredoxin/thioredoxin reductase system or less defined modes of action.

Exogenous Application of Melatonin to Green Horn Pepper Fruit Reduces Chilling Injury during Postharvest Cold Storage by Regulating Enzymatic Activities in the Antioxidant System.

Chilling injury (CI) caused by exposure to low temperatures is a serious problem in the postharvest cold storage of pepper fruit. Melatonin (MT) has been reported to minimize CI in several plants. To evaluate the effectiveness of MT to minimize CI in green horn pepper and the possible mechanism involved, freshly picked green horn peppers were treated with MT solution at 100 μmol L−1 or water and then stored at 4 °C for 25 d. Results showed that MT treatment reduced CI in green horn pepper fruit, as evidenced by lower CI rate and CI index. MT treatment maintained lower postharvest metabolism rate and higher fruit quality of green horn peppers, as shown by reduced weight loss and respiratory rate, maintened fruit firmness and higher contents of chlorophyll, total phenols, flavonoids, total soluble solids and ATP. Additionally, the contents of hydrogen peroxide, superoxide radical, and malondialdehyde were kept low in the MT-treated fruit, and the activities of the enzymes peroxidase, superoxide dismutase, and catalase were significantly elevated. Similarly, the ascorbate–glutathione cycle was enhanced by elevating the activities of ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase, to increase the regeneration of ascorbic acid and glutathione. Our results show that MT treatment protected green horn pepper fruit from CI and maintained high fruit quality during cold storage by triggering the antioxidant system

Fe2O3-modified graphene oxide mitigates nanoplastic toxicity via regulating gas exchange, photosynthesis, and antioxidant system in Triticum aestivum

The ever-increasing plastic pollution in soil and water resources raises concerns about its effects on terrestrial plants and agroecosystems. Although there are many reports about the contamination with nanoplastics on plants, the presence of magneto-assisted nanomaterials enabling the removal of their adverse impacts still remains unclear. Therefore, the purpose of the current study is to evaluate the potential of nanomaterial Fe2O3-modified graphene oxide (FGO, 50–250 mg L−1) to eliminate the adverse effects of nanoplastics in plants. Wheat plants exposed to polystyrene nanoplastics concentrations (PS, 10, 50 and 100 mg L−1) showed decreased growth, water content and loss of photosynthetic efficiency. PS toxicity negatively altered gas exchange, antenna structure and electron transport in photosystems. Although the antioxidant system was partially activated (only superoxide dismutase (SOD), NADPH oxidase (NOX) and glutathione reductase (GR)) in plants treated with PS, it failed to prevent PS-triggered oxidative damage, as showing lipid peroxidation and hydrogen peroxide (H2O2) levels. FGOs eliminated the adverse impacts of PS pollution on growth, water status, gas exchange and oxidative stress markers. In addition, FGOs preserve the biochemical reactions of photosynthesis by actively increasing chlorophyll fluorescence parameters in the stressed-wheat leaves. The activities of all enzymatic antioxidants increased, and the H2O2 and TBARS contents decreased. GSH-mediated detoxifying antioxidants such as glutathione S-transferase (GST) and glutathione peroxidase (GPX) were stimulated by FGOs against PS pollution. FGOs also triggered the enzymes and non-enzymes related to the Asada-Halliwell cycle and protected the regeneration of ascorbate (AsA) and glutathione (GSH). Our findings indicated that FGO had the potential to mitigate nanoplastic-induced damage in wheat by regulating water relations, protecting photosynthesis reactions and providing efficient ROS scavenging with high antioxidant capacity. This is the first report on removing PS-induced damage by FGO applications in wheat leaves.

Polystyrene nanoplastic contamination mixed with polycyclic aromatic hydrocarbons: Alleviation on gas exchange, water management, chlorophyll fluorescence and antioxidant capacity in wheat

Polycyclic aromatic hydrocarbons (PAHs) constitute a significant environmental pollution group that reaches toxic levels with anthropogenic activities. The adverse effects of nanoplastics accumulating in ecosystems with the degradation of plastic wastes are also a growing concern. Previous studies have generally focused on the impact of single PAH or plastic fragments exposure on plants. However, it is well recognized that these contaminants co-exist at varying rates in agricultural soil and water resources. Therefore, it is critical to elucidate the phytotoxicity and interaction mechanisms of mixed pollutants. The current study was designed to comparatively investigate the single and combined effects of anthracene (ANT, 100 mg L-1), fluorene (FLU, 100 mg L-1) and polystyrene nanoplastics (PS, 100 mg L-1) contaminations in wheat. Plants exposed to single ANT, FLU and PS treatments demonstrated decline in growth, water content, high stomatal limitations and oxidative damage. The effect of ANT + FLU on these parameters was more detrimental. In addition, ANT and/or FLU treatments significantly suppressed photosynthetic capacity as determined by carbon assimilation rate (A) and chlorophyll a fluorescence transient. The antioxidant system was not fully activated (decreased superoxide dismutase, peroxidase and glutathione reductase) under ANT + FLU, then hydrogen peroxide (H2O2) content (by 2.7-fold) and thiobarbituric acid reactive substances (TBARS) (by 2.8-fold) increased. Interestingly, ANT + PS and FLU + PS improved the growth, water relations and gas exchange parameters. The presence of nanoplastics recovered the adverse effects of ANT and FLU on growth by protecting the photosynthetic photochemistry and reducing oxidative stress. PAH plus PS reduced the ANT and FLU accumulation in wheat leaves. In parallel, the increased antioxidant system, regeneration of ascorbate, glutathione and glutathione redox status observed under ANT + PS and FLU + PS. These findings will provide an information about the phytotoxicity mechanisms of mixed pollutants in the environment.

Blocking glutathione regeneration: Inorganic NADPH oxidase nanozyme catalyst potentiates tumoral ferroptosis

Emerging cancer cell ferroptosis features the direct depletion of glutathione (GSH) and resultant chemical inhibition on glutathione peroxidase 4 (GPX4) bioactivity, which, unfortunately, is counteracted considerably by nicotinamide adenine dinucleotide phosphate (NADPH)-enabled regeneration of antioxidant GSH. Herein, a Pt-MIL-101 (Fe)-based nanocatalytic medicine (NCM) is proposed to catalyze NADPH oxidation and the following nanozyme catalytic cascade reactions to produce hydroxyl radicals and prevent GSH regeneration, thus promoting the ferroptotic death of cancer cells. Briefly, the Pt-MIL-101 nanomedicine possessing NADPH oxidase (NOX)-like activity catalyzes the superoxide anions (O2•−) generation by promoting the electron transfer from NADPH to O2, followed by Pt-MIL-101-catalyzed O2•− disproportionation producing H2O2 using its superoxide dismutase (SOD) nanozyme catalytic activity. The generated H2O2 further serves as substrate for toxic ∙OH production via Fenton reaction with Fe3+/Fe2+ at the structure center of the MIL-101. Moreover, the NOX nanozyme-catalyzed NADPH depletion by the nanomedicine largely prevents the GSH regeneration and de-activates GPX4, promoting lipid peroxidation for ferroptotic cell death. This work highlights an effective NADPH-initiated nanozyme cascade nanocatalytic strategy for ferroptosis-based tumor therapy.

Targeting AKT-Dependent Regulation of Antioxidant Defense Sensitizes AKT-E17K Expressing Cancer Cells to Ionizing Radiation.

Aberrant activation of the phosphatidyl-inositol-3-kinase/protein kinase B (AKT) pathway has clinical relevance to radiation resistance, but the underlying mechanisms are incompletely understood. Protection against reactive oxygen species (ROS) plays an emerging role in the regulation of cell survival upon irradiation. AKT-dependent signaling participates in the regulation of cellular antioxidant defense. Here, we were interested to explore a yet unknown role of aberrant activation of AKT in regulating antioxidant defense in response to IR and associated radiation resistance.We combined genetic and pharmacologic approaches to study how aberrant activation of AKT impacts cell metabolism, antioxidant defense, and radiosensitivity. Therefore, we used TRAMPC1 (TrC1) prostate cancer cells overexpressing the clinically relevant AKT-variant AKT-E17K with increased AKT activity or wildtype AKT (AKT-WT) and analyzed the consequences of direct AKT inhibition (MK2206) and inhibition of AKT-dependent metabolic enzymes on the levels of cellular ROS, antioxidant capacity, metabolic state, short-term and long-term survival without and with irradiation.TrC1 cells expressing the clinically relevant AKT1-E17K variant were characterized by improved antioxidant defense compared to TrC1 AKT-WT cells and this was associated with increased radiation resistance. The underlying mechanisms involved AKT-dependent direct and indirect regulation of cellular levels of reduced glutathione (GSH). Pharmacologic inhibition of specific AKT-dependent metabolic enzymes supporting defense against oxidative stress, e.g., inhibition of glutathione synthase and glutathione reductase, improved eradication of clonogenic tumor cells, particularly of TrC1 cells overexpressing AKT-E17K.We conclude that improved capacity of TrC1 AKT-E17K cells to balance antioxidant defense with provision of energy and other metabolites upon irradiation compared to TrC1 AKT-WT cells contributes to their increased radiation resistance. Our findings on the importance of glutathione de novo synthesis and glutathione regeneration for radiation resistance of TrC1 AKT-E17K cells offer novel perspectives for improving radiosensitivity in cancer cells with aberrant AKT activity by combining IR with inhibitors targeting AKT-dependent regulation of GSH provision.

Ex-foliar applied extremolyte ectoine improves water management, photosystem, antioxidant system and redox homeostasis in Zea mays under cadmium toxicity

Stress-protective osmolytes stabilize biomolecules and mediate plant defense responses, which help to remove the negative effects of stress in plants. However, the responses of ectoine (ECT, 1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid), as an osmolyte, need to be investigated for a better understanding of the defense pathways on water status, antioxidant system, and photosynthetic machinery against heavy metal stress. The different ECT concentrations (0.25–0.5 mM) were applied to Zea mays L. cv Karadeniz Yildizi with/without cadmium stress (100–200 μM Cd). Stress caused an inhibition in growth (RGR), water content (RWC), and osmotic potential (ΨΠ). After stress exposure, ECTs provided effective water management by elevating RGR, RWC and ΨΠ. The maize exposed to stress exhibited notable repression in the photosynthetic system depending on decreasing Fv/Fm, qP and, ΦPSII and increasing NPQ. The consumption of excess energy on photosynthetic machinery was controlled by ECTs via reversing these parameters. Cd toxicity resulted in downregulated-transcript levels of psbA, psbD, and psaB, which impaired the stability of PSI and PSII. After both Cd treatments, ECTs markedly induced the expression levels of psaA and psaB, which showed effective protection of photochemical activity. Cd-applied plants exhibited a decrease in superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione peroxidase (GPX), and glutathione reductase (GR), causing the accumulation of TBARS in lipid peroxidation. Under Cd+ECTs, SOD, glutathione S-transferase (GST) and POX had effective radical scavenging, thereby maintaining low contents of H2O2 and TBARS. ECTs alleviated the low Cd treatment-impaired redox state and participated in the ascorbate (AsA) and glutathione (GSH) regeneration. Consequently, ECT-mediated tolerance of maize was proved by increased growth, water potential, antioxidant capacity (especially SOD, POX), up-regulation of genes encoding proteins related to PSI, and PSII and AsA-GSH redox systems under Cd toxicity.

The Benevolent Bile: Bile Acids as Stimulants of Liver Regeneration

The Benevolent Bile: Bile Acids as Stimulants of Liver Regeneration

Praseodymium enhanced the tolerance of maize seedlings subjected to cadmium stress by up-regulating the enzymes in the regeneration and biosynthetic pathways of ascorbate and glutathione

To test whether praseodymium (Pr) regulates cadmium (Cd) tolerance, we explored the effects of Pr on enzymatic activities in the regeneration and biosynthetic pathways of ascorbate and glutathione in maize seedlings under Cd stress. The findings demonstrated that Cd stress increased enzymatic activities in the regeneration pathway (ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR)) and in the biosynthetic pathway of ascorbate and glutathione (γ-ECS and GalLDH), as well as ascorbate (AsA) and glutathione (GSH) contents. However, Cd stress significantly decreased AsA/dehydroascorbic acid (DHA) ratio and GSH/oxidised glutathione (GSSG) ratio, net photosynthetic rate (P<sub>n</sub>), chlorophylls (Chl) and carotenoids (Car) contents, maximum photochemical efficiency of PSII (F<sub>v</sub>/F<sub>m</sub>), photochemical quenching (qP) and quantum efficiency of PSII photochemistry (Φ<sub>PSII</sub>), as well as plant height and biomass. Application of Pr to Cd-stressed seedlings enhanced above enzymatic activities, AsA and GSH contents, AsA/DHA and GSH/GSSG ratios, P<sub>n</sub>, Chl and Car contents, F<sub>v</sub>/F<sub>m</sub>, qP and Φ<sub>PSII</sub>, as well as plant height and biomass. Meanwhile, the application of Pr to Cd-stressed seedlings reduced malondialdehyde (MDA) content and electrolyte leakage. The above results indicated that Pr enhanced Cd tolerance of maize by up-regulating enzymatic activities in regeneration and biosynthetic pathways of ascorbate and glutathione.

Salicylic acid mitigates cadmium toxicity in bean (Phaseolus vulgaris L.) seedlings by modulating cellular redox status

The effects of salicylic acid treatments on the antioxidant status were investigated on cadmium (Cd)-exposed bean (Phaseolus vulgaris L.) seedlings. Seeds were germinated in presence of different Cd concentrations (0, 50, 500, 1000 μM, CdCl2) combined or not with SA (1000 μM) for 6 days. Cadmium alone induced a slight decrease in the rate of germination. Besides, Cd accumulated in a dose- and tissue-dependent manner, leading to a significant reduction in biomass growth and the inhibition of mineral transport from cotyledons to embryonic axes, as compared to the control. All these negative effects were reversed by salicylic acid application. Cadmium stress generated an oxidative stress as reflected by the increasing levels of lipid peroxidation and loss of membrane integrity. This was associated with a stimulation of antioxidant enzyme (superoxide dismutase, catalase, ascorbate peroxidase, and gaiacol peroxidase) activities and increasing levels of polyphenolic compounds, tannins and flavonoids in both embryonic axes and cotyledons. Salicylic acid application had a protective effect on membrane integrity and concomitantly decreased antioxidant enzyme activities and levels of polyphenols, tannins and flavonoids in embryonic axes as compared with Cd treatment only. Furthermore, the ameliorative effects of salicylic acid lead to increase of endogenous NO and H2S accumulations which boost glutathione regeneration pathways including glutathione reductase, glutathione S-transferase, and S-nitrosoglutathione reductase activities as well as glyoxalase system. Hence, it can be concluded that salicylic acid improves seedlings tolerance to Cd stress by (i) maintaining the freeing of mineral nutrients from cotyledons to embryonic tissues and (ii) mitigating oxidative stress impact on membrane integrity associated to losses in polyphenols, tannins and flavonoids and enhancement of glutathione regeneration system.

Nicotinamide adenine dinucleotides are associated with distinct redox control of germination in Acer seeds with contrasting physiology.

Seed germination is a complex process enabling plant reproduction. Germination was found to be regulated at the proteome, metabolome and hormonal levels as well as via discrete post-translational modification of proteins including phosphorylation and carbonylation. Redox balance is also involved but less studied. Acer seeds displaying orthodox and recalcitrant characteristics were investigated to determine the levels of redox couples of nicotinamide adenine dinucleotide (NAD) phosphate (NADP) and integrated with the levels of ascorbate and glutathione. NAD and NADP concentrations were higher in Norway maple seeds and exceptionally high at the germinated stage, being the most contrasting parameter between germinating Acer seeds. In contrast, NAD(P)H/NAD(P)+ ratios were higher in sycamore seeds, thus exhibiting higher reducing power. Despite distinct concentrations of ascorbate and glutathione, both seed types attained in embryonic axes and cotyledons had similar ratios of reduced/oxidized forms of ascorbate and half-cell reduction potential of glutathione at the germinated stage. Both species accomplished germination displaying different strategies to modulate redox status. Sycamore produced higher amounts of ascorbate and maintained pyridine nucleotides in reduced forms. Interestingly, lower NAD(P) concentrations limited the regeneration of ascorbate and glutathione but dynamically drove metabolic reactions, particularly in this species, and contributed to faster germination. We suggest that NAD(P) is an important player in regulating redox status during germination in a distinct manner in Norway maple and sycamore seeds.