Endogenous Nitric Oxide Levels Research Articles

Antiaging in a Bottle: Bioactive Competency of Plasma-Generated Nitric Oxide Water for Modulation of Aging-Related Signature in Human Dermal Cells.

Nitric oxide (NO), a potential therapeutic antiaging molecule, modulates various physiological and cellular processes. However, alterations in endogenous NO levels brought on by aging impact multiple organ systems and heighten susceptibility to age-related skin diseases. This correlation underscores the importance of investigating NO-based antiaging interventions. Nonthermal plasma-generated NO is a promising avenue for cosmetic and regenerative medicine due to its capacity to stimulate cellular growth. Herein, we examine the potential of plasma-generated nitric oxide water (NOW) as a bioactive agent in human dermal fibroblasts, emphasizing gene expression patterns linked to extracellular matrix (ECM) breakdown and cellular senescence. The findings of our study indicate that administering NOW at lower dosages enhances cell migration and proliferation. Moreover, the genetic signatures associated with ECM synthesis, antioxidant defense, and antisenescence pathways have been analyzed in NOW-exposed cells. Notably, the downregulation of ECM-degrading enzyme transcripts─collagenase, elastase, and hyaluronidase─suggests NOW's potential in mitigating the intrinsic skin aging phenomena, emphasizing the promise of NO-based interventions in advancing antiaging strategies within regenerative medicine.

Engineered microparticles modulate arginine metabolism to repolarize tumor-associated macrophages for refractory colorectal cancer treatment

BackgroundArginase is abundantly expressed in colorectal cancer and disrupts arginine metabolism, promoting the formation of an immunosuppressive tumor microenvironment. This significant factor contributes to the insensitivity of colorectal cancer to immunotherapy. Tumor-associated macrophages (TAMs) are major immune cells in this environment, and aberrant arginine metabolism in tumor tissues induces TAM polarization toward M2-like macrophages. The natural compound piceatannol 3ʹ-O-glucoside inhibits arginase activity and activates nitric oxide synthase, thereby reducing M2-like macrophages while promoting M1-like macrophage polarization.MethodsThe natural compounds piceatannol 3ʹ-O-glucoside and indocyanine green were encapsulated within microparticles derived from tumor cells, termed PG/ICG@MPs. The enhanced cancer therapeutic effect of PG/ICG@MP was assessed both in vitro and in vivo.ResultsPG/ICG@MP precisely targets the tumor site, with piceatannol 3ʹ-O-glucoside concurrently inhibiting arginase activity and activating nitric oxide synthase. This process promotes increased endogenous nitric oxide production through arginine metabolism. The combined actions of nitric oxide and piceatannol 3ʹ-O-glucoside facilitate the repolarization of tumor-associated macrophages toward the M1 phenotype. Furthermore, the increase in endogenous nitric oxide levels, in conjunction with the photodynamic effect induced by indocyanine green, increases the quantity of reactive oxygen species. This dual effect not only enhances tumor immunity but also exerts remarkable inhibitory effects on tumors.ConclusionOur research results demonstrate the excellent tumor-targeting effect of PG/ICG@MPs. By modulating arginine metabolism to improve the tumor immune microenvironment, we provide an effective approach with clinical translational significance for combined cancer therapy.

The role of microenvironmental factors in the pre-ovulatory oocyte in the pathogenesis of “poor” ovarian response to in vitro fertilization (IVF) programs

Background. The “poor” response to ovarian stimulation during IVF (in vitro fertilization) cycles depends on various factors, including the biochemical composition of the follicle microenvironment. Recent studies have focused on the relationship between vascular tone regulators, angiogenic factors, oxidative stress, and the quality of oocytes. Despite this, there is still no consensus on the exact effect of these factors on folliculogenesis or their role in “poor” responses.Objective. To evaluate the content of biochemical factors and regulators of vascular tone and angiogenesis in follicular fluid in patients with a “poor” ovarian response to stimulation in IVF programs, compared to similar indicators in women with a normal ovarian response.Materials and methods. An open prospective cohort study was conducted, including 56 patients who were part of the IVF program. The criterion for separating the cohort of women was their response to controlled ovarian stimulation during the IVF cycle. Women with a “poor” response (n=32) were placed in the main group, while those with a normal response (n=24) were in the comparison group. Follicular fluid samples from women with a “poor” response were divided into two subgroups based on the presence or absence of an oocyte-cumulus complex in the follicle. The biochemical and soluble regulatory factors in follicular fluid were analyzed in both groups after controlled ovarian stimulation was completed. Statistical analysis of the data was done using methods from variation statistics. A critical level of significance for the differences was set at p ≤0.05.Result. The levels of urea, glucose, high-density lipoprotein, and total antioxidant status (TAOS) in follicular fluid (FF) from patients with a “poor” ovarian response were statistically significantly higher compared to those in the control group. The levels of bilirubin, low-density lipoprotein, and uric acid were also significantly lower in VF from patients in the main group compared to the control group, p<0.05. The indices of vascular endothelial growth factor (VEGF-A) and vascular endothelial growth receptor-2 (VEGFR-2) in FF from women with a “poor” response were significantly lower than those from patients with a normal response, while the levels of endogenous nitric oxide were significantly higher in the former group compared to the latter, p<0.05.Conclusion. The absence of an oocyte-cumulus complex in the pre-ovulatory follicle, which is associated with a “poor” response of the ovary to stimulation, is likely due to a disruption in vascularization processes. This is supported by a decrease in the levels of pro- and anti-angiogenic factors, such as VEGF-A and VEGFR-2.

Nitric oxide shifts the impact of ionic liquid on microbial community structure in rhizosphere of Arabidopsis

ABSTRACT Ionic liquids (ILs) are widely used in various fields due to their excellent properties. Despite their utility, there is limited knowledge regarding the phytotoxic properties of ILs and the mechanisms by which plants develop resistance to them. This is particularly true when considering the role of nitric oxide (NO) in response to ILs stress. Herein, we investigated the mechanism by which endogenous NO reduces the ILs’ phytotoxicity in Arabidopsis from the perspective of rhizosphere microorganisms. We investigated the impact of 1,3-dibutyl imidazole bromide (DIB) on microbial diversity and community in the rhizosphere of Arabidopsis lines with varying endogenous NO levels, using a high throughput sequencing method. DIB did not affect microbial taxon numbers, richness, or evenness; however, it did alter microbial beta diversity and community structure in the rhizosphere of Arabidopsis. Elevated endogenous NO increased fungal richness and evenness, shifted DIB’s impact on microbial community structure, and enriched more resistant species and toxin-decomposing species. These findings suggest a potential mechanism for plants to resist IL stress. Our study not only elucidates the toxicological mechanisms of ILs but also reveals the involvement of NO in plant responses to IL stress, providing valuable insights for future environmental risk assessments and mitigation strategies.

Deciphering the alleviation potential of nitric oxide, for low temperature and chromium stress via maintaining photosynthetic capacity, antioxidant defence, and redox homeostasis in rice (Oryza sativa)

Sodium nitroprusside (SNP) is a potent nitric oxide (NO) donor that enhances plant tolerance to various abiotic stresses. This research aims to assess the effect of SNP application on rice seedlings subjected to individual and combined exposure to two abiotic stresses viz., low-temperature (LT) and chromium (Cr). Exposure to LT, Cr, and LT+Cr caused severe oxidative damage by stimulating greater production and accumulation of reactive oxygen species (ROS) leading to lipid peroxidation and cell membrane instability. The combined LT+CR stress more intensly increased the cellular oxidative stress and excessive Cr uptake that in turn deteriorated the chlorophyll pigments and photosynthesis, as well as effected the level of tetrapyrrole biosynthesis in rice plants. The reduction in rice seedling growth was more obvious under LT+Cr treatment than their individual effects. The exogenous application of SNP diminished the toxic impact of LT and Cr stress. This was attributed to the positive role of SNP in regulating the endogenous NO levels, free amino acids (FAAs) contents, tetrapyrrole biosynthesis and antioxidants. Consequently, SNP-induced NO decreased photorespiration, ROS generation, lipid peroxidation, and electrolyte leakage. Moreover, exogenous SNP diminished the Cr uptake and accumulation by modulating the ionic homeostasis and strengthening the heavy metals detoxification mechanism, thus improving plant height, biomass and photosynthetic indexes. Essentially, SNP boosts plant tolerance to LT and Cr stress by regulating antioxidants, detoxification mechanism, and the plant's physio-biochemical. Hence, applying SNP is an effective method for boosting rice plant resilience and productivity in the face of escalating environmental stresses and pollutants.

Nitric oxide signal is required for glutathione-induced enhancement of photosynthesis in salt-stressed Solanum lycopersicum L.

Reduced glutathione (γ-glutamyl-cysteinyl-glycine, GSH), the primary non-protein sulfhydryl group in organisms, plays a pivotal role in the plant salt stress response. This study aimed to explore the impact of GSH on the photosynthetic apparatus, and carbon assimilation in tomato plants under salt stress, and then investigate the role of nitric oxide (NO) in this process. The investigation involved foliar application of 5 mM GSH, 0.1% (w/v) hemoglobin (Hb, a nitric oxide scavenger), and GSH+Hb on the endogenous NO levels, rapid chlorophyll fluorescence, enzyme activities, and gene expression related to the Calvin cycle in tomato seedlings (Solanum lycopersicum L. cv. 'Zhongshu No. 4') subjected short-term salt stress (100 mM NaCl) for 24, 48 and 72 hours. GSH treatment notably boosted nitrate reductase (NR) and NO synthase (NOS) activities, elevating endogenous NO signaling in salt-stressed tomato seedling leaves. It also mitigated chlorophyll fluorescence (OJIP) curve distortion and damage to the oxygen-evolving complex (OEC) induced by salt stress. Furthermore, GSH improved photosystem II (PSII) electron transfer efficiency, reduced QA - accumulation, and countered salt stress effects on photosystem I (PSI) redox properties, enhancing the light energy absorption index (PIabs). Additionally, GSH enhanced key enzyme activities in the Calvin cycle and upregulated their genes. Exogenous GSH optimized PSII energy utilization via endogenous NO, safeguarded the photosynthetic reaction center, improved photochemical and energy efficiency, and boosted carbon assimilation, ultimately enhancing net photosynthetic efficiency (Pn) in salt-stressed tomato seedling leaves. Conversely, Hb hindered Pn reduction and NO signaling under salt stress and weakened the positive effects of GSH on NO levels, photosynthetic apparatus, and carbon assimilation in tomato plants. Thus, the positive regulation of photosynthesis in tomato seedlings under salt stress by GSH requires the involvement of NO.

Interplay between Energy Supply and Glutamate Toxicity in the Primary Cortical Culture.

Limited substrate availability because of the blood-brain barrier (BBB) has made the brain develop specific molecular mechanisms to survive, using lactate synthesized by astrocytes as a source of energy in neurons. To understand if lactate improves cellular viability and susceptibility to glutamate toxicity, primary cortical cells were incubated in glucose- or lactate-containing media and toxic concentrations of glutamate for 24 h. Cell death was determined by immunostaining and lactate dehydrogenase (LDH) release. Mitochondrial membrane potential and nitric oxide (NO) levels were measured using Tetramethylrhodamine, methyl ester (TMRM) and 4-Amino-5-Methylamino-2',7'-Difluorofluorescein Diacetate (DAF-FM) live staining, respectively. LDH activity was quantified in single cells in the presence of lactate (LDH substrate) and oxamate (LDH inhibitor). Nuclei of cells were stained with DAPI and neurons with MAP2. Based on the distance between neurons and glial cells, they were classified as linked (<10 µm) and non-linked (>10 µm) neurons. Lactate increased cell death rate and the mean value of endogenous NO levels compared to glucose incubations. Mitochondrial membrane potential was lower in the cells cultured with lactate, but this effect was reversed when glutamate was added to the lactate medium. LDH activity was higher in linked neurons compared to non-linked neurons, supporting the hypothesis of the existence of the lactate shuttle between astrocytes and at least a portion of neurons. In conclusion, glucose or lactate can equally preserve primary cortical neurons, but those neurons having a low level of LDH activity and incubated with lactate cannot cover high energetic demand solely with lactate and become more susceptible to glutamate toxicity.

The Crucial Role of SlGSNOR in Regulating Postharvest Tomato Fruit Ripening.

S-nitrosoglutathione reductase (GSNOR) is a well-known regulator in controlling protein S-nitrosylation modification and nitric oxide (NO) homeostasis. Here, a GSNOR inhibitor N6022 and SlGSNOR silencing were applied to investigate the roles of SlGSNOR in tomato fruit postharvest ripening. We found that the application of N6022 and S-nitrosoglutathione (GSNO, a NO donor), and SlGSNOR silencing delayed the transition of fruit skin color by improving total chlorophyll level by 88.57%, 44.78%, and 91.03%, respectively. Meanwhile, total carotenoid and lycopene contents were reduced by these treatments. Concurrently, the activity of chlorophyll biosynthesis enzymes and the expression of related genes were upregulated, and the transcript abundances of total carotenoid bioproduction genes were downregulated, by N6022 and GSNO treatments and SlGSNOR silencing. In addition, fruit softening was postponed by N6022, GSNO, and SlGSNOR silencing, through delaying the decrease of firmness and declining cell wall composition; structure-related enzyme activity; and gene expression levels. Furthermore, N6022, GSNO, and SlGSNOR silencing enhanced the accumulation of titratable acid; ascorbic acid; total phenol; and total flavonoid, but repressed the content of soluble sugar and soluble protein accompanied with the expression pattern changes of nutrition-related genes. In addition, the endogenous NO contents were elevated by 197.55%; 404.59%; and 713.46%, and the endogenous SNOs contents were enhanced by 74.65%; 93.49%; and 94.85%; by N6022 and GSNO treatments and SlGSNOR silencing, respectively. Altogether, these results indicate that SlGSNOR positively promotes tomato postharvest fruit ripening, which may be largely on account of its negative roles in the endogenous NO level.

β-Aminobutyric Acid Effectively Postpones Senescence of Strawberry Fruit by Regulating Metabolism of NO, H2S, Ascorbic Acid, and ABA

Current researchis focused on the influence of β-aminobutyric acid (BABA) on the metabolism of nitric oxide (NO), hydrogen sulfide (H2S), ascorbic acid, and abscisic acid (ABA) in strawberry fruit. The increases in ion leakage and malondialdehyde (MDA) concentration in strawberry fruit and the degradation of chlorophyll in the sepals of the fruit were markedly inhibited by BABA at 20 mM. BABA-immersed fruit exhibited lower activities and expressions of polygalacturonase (PG), pectinmethylesterase (PME), and ethylene biosynthetic enzymes compared to the control. Furthermore, BABA immersion evidently upgraded the metabolic levels of NO and H2S, including the enzymatic activities and intermediary contents of metabolites, which collectively enhanced the levels of endogenous NO and H2S contents in strawberry fruit. The high enzymatic activities and gene expressions of the AsA biosynthesis pathway jointly maintained AsA accumulation in the BABA-treated sample. The application of BABA led to a decrease in ABA concentration, which was associated with reduced activities and gene expression levels of key enzymes participating in ABA metabolism. Our experimental observations showed that immersion with BABA may be a highly promising means to delay senescence and reduce natural decay in strawberry fruit, and the alleviation in senescence using BABA may be attributed to the modulation of NO, H2S, AsA, and ABA metabolism.

The Cardioprotective Role of Nitrate-Rich Vegetables.

Nitric oxide (NO) is an inorganic radical produced by both the non-enzymatic nitrate (NO3-)-nitrite (NO2-)-NO pathway and enzymatic reactions catalyzed by nitric oxide synthase (NOS). Also, as nitrate and nitrite from dietary and other endogenous sources can be reduced back to nitric oxide in vivo, the endogenous NO level can be increased through the consumption of nitrate-rich vegetables. Ingestion of dietary NO3- has beneficial effects which have been attributed to a subsequent increase in NO: a signaling molecule that may regulate various systems, including the cardiovascular system. A diet rich in NO3- from green leafy and root vegetables has cardioprotective effects, with beetroot products being particularly good sources of NO3-. For example, various studies have demonstrated a significant increase in nitrite levels (regarded as markers of NO) in plasma after the intake of beetroot juice. The present review describes the current literature concerning the role of nitrate-rich vegetables (especially beetroot products) in the prophylaxis and treatment of cardiovascular diseases (CVDs). This review is based on studies identified in electronic databases, including PubMed, ScienceDirect, Web of Knowledge, Sci Finder, Web of Science, and SCOPUS.

Auxin acts upstream of nitric oxide to regulate cell wall xyloglucan and its aluminium-binding capacity in Arabidopsis thaliana.

Auxin acts upstream of NO through NOA and XXT5 pathways to regulate the binding capacity of the root cell wall to Al. In our previous study, we identified an unknown mechanism by which 1-naphthaleneacetic acid (NAA) decreased the fixation of aluminum (Al) in the cell wall. Here, we observed that external application of the nitric oxide (NO) donor S-nitrosoglutathion (GSNO) increased the inhibition of Al on root elongation. Further analysis indicated that GSNO could induce Al accumulation in the roots and root cell walls, which is consistent with lower xyloglucan content. In comparison to the Columbia-0 (Col-0) wild type (WT), endogenous NO-reduced mutants noa1 (NOA pathway) and nia1nia2 (NR pathway) were more resistant to Al, with lower root Al content, higher xyloglucan content, and more Al accumulation in the root cell walls. By contrast, the xxt5 mutant with reduced xyloglucan content exhibited an Al-sensitive phenotype. Interestingly, Al treatment increased the endogenous auxin and NO levels, and the auxin levels induced under Al stress further stimulated NO production. Auxin application reduced Al retention in hemicellulose and decreased the xyloglucan content, similar to the effects observed with GSNO. In yucca and aux1-7 mutants, exogenous application of NO resulted in responses similar to those of the WT, whereas exogenous auxin had little effect on the noa1 mutant under Al stress. In addition, as auxin had similar effects on the nia1nia2 mutant and the WT, exogenous auxin and NO had little effect on the xxt5 mutant under Al stress, further confirming that auxin acts upstream of NO through NOA and XXT5 pathways to regulate the binding capacity of the root cell wall to Al.

Nitric oxide sensor NsrR is the key direct regulator of magnetosome formation and nitrogen metabolism in Magnetospirillum.

Nitric oxide (NO) plays an essential role as signaling molecule in regulation of eukaryotic biomineralization, but its role in prokaryotic biomineralization is unknown. Magnetospirillum gryphiswaldense MSR-1, a model strain for studies of prokaryotic biomineralization, has the unique ability to form magnetosomes (magnetic organelles). We demonstrate here that magnetosome biomineralization in MSR-1 requires the presence of NsrRMg (anNO sensor) and a certain level of NO. MSR-1 synthesizes endogenous NO via nitrification-denitrification pathway to activate magnetosome formation. NsrRMg was identified as a global transcriptional regulator that acts as a direct activator of magnetosome gene cluster (MGC) and nitrification genes but as a repressor of denitrification genes. Specific levels of NO modulate DNA-binding ability of NsrRMg to various target promoters, leading to enhancing expression of MGC genes, derepressing denitrification genes, and repressing nitrification genes. These regulatory functions help maintain appropriate endogenous NO level. This study identifies for the first time the key transcriptional regulator of major MGC genes, clarifies the molecular mechanisms underlying NsrR-mediated NO signal transduction in magnetosome formation, and provides a basis for a proposed model of the role of NO in the evolutionary origin of prokaryotic biomineralization processes.

Development of a urea-bond cleavage reaction induced by nitric oxide for fluorescence imaging.

Nitric oxide (NO) is a multifunctional signalling molecule with indispensable roles in physiological processes, but its abnormal production is implicated in various disease conditions. Detecting NO is crucial for interrogating its biological roles. Although many o-phenylenediamine-based fluorescent probes have been developed, only a small fraction has been employed in vivo. Moreover, these probes largely require direct modifications of the fluorophore backbones to render NO responsiveness, which restricts the general applicability of o-phenylenediamine-based probe designs to other types of fluorophores. Here, we report the rational development, optimization, and application of a NO-induced urea-bond cleavage reaction for selective fluorescence detection and imaging of NO in living systems. Through rational design and extensive screening, we identified a 2-aminophenylurea-derived functionality that can react with NO through N-nitrosation, acyltriazole formation, and hydrolysis to induce the cleavage of the urea bond and release of the amino-containing coumarin fluorophore. By caging different amino-containing fluorophore scaffolds with the 2-aminophenylurea-derived functionality, we modularly developed a series of NO fluorescent probes with different excitation and emission profiles for the detection of NO in aqueous solutions and live cells. Among these probes, the near-infrared probe has been demonstrated to enable in vivo fluorescence visualization of elevated endogenous levels of NO in a murine inflammation model. Overall, this study provides a NO-induced urea-bond cleavage reaction and establishes the utility of this reaction for the general and modular development of NO fluorescent probes, thus opening new opportunities for studying and manipulating NO in biological systems.

Exhaled Nitric Oxide and Pulmonary Oxygen Toxicity Susceptibility.

Individual susceptibility to pulmonary oxygen toxicity (PO2tox) is highly variable and currently lacks a reliable biomarker for predicting pulmonary hyperoxic stress. As nitric oxide (NO) is involved in many respiratory system processes and functions, we aimed to determine if expired nitric oxide (FENO) levels can provide an indication of PO2tox susceptibility in humans. Eight U.S. Navy-trained divers volunteered as subjects. The hyperoxic exposures consisted of six- and eight-hour hyperbaric chamber dives conducted on consecutive days in which subjects breathed 100% oxygen at 202.65 kPa. Subjects' individual variability in pulmonary function and FENO was measured twice daily over five days and compared with their post-dive values to assess susceptibility to PO2tox. Only subjects who showed no decrements in pulmonary function following the six-hour exposure conducted the eight-hour dive. FENO decreased by 55% immediately following the six-hour oxygen exposure (n = 8, p < 0.0001) and by 63% following the eight-hour exposure (n = 4, p < 0.0001). Four subjects showed significant decreases in pulmonary function immediately following the six-hour exposure. These subjects had the lowest baseline FENO, had the lowest post-dive FENO, and had clinical symptoms of PO2tox. Individuals with low FENO were the first to develop PO2tox symptoms and deficits in pulmonary function from the hyperoxic exposures. These data suggest that endogenous levels of NO in the lungs may protect against the development of PO2tox.

Improving Endogenous Nitric Oxide Enhances Cadmium Tolerance in Rice through Modulation of Cadmium Accumulation and Antioxidant Capacity

Nitric oxide (NO) plays an important role in plant stress responses. However, the mechanisms underlying NO-induced stress resistance to cadmium (Cd) stress in rice remain elusive. In this study, rat neuron NO synthase (nNOS)-overexpressing rice plants with higher endogenous NO level showed higher cadmium stress tolerance than the wild-type plants. The results showed that nNOS-overexpressing rice plants accumulated less cadmium in the roots and shoots by downregulating the expression of Cd uptake and transport related genes including OsCAL1, OsIRT2, OsNramp5, and OsCd1. Moreover, nNOS-overexpressing rice plants accumulated less hydrogen peroxide (H2O2), accompanying with higher expression of antioxidant enzyme genes (OsCATA, OsCATB, and OsPOX1) and corresponding higher enzyme activities under cadmium stress. Furthermore, the transcription of melatonin biosynthetic genes, including OsASMT1, OsTDC1, OsTDC3, and OsSNAT2, was also upregulated in nNOS-overexpressing plants, resulting in increased content of melatonin under cadmium treatment compared with the wild-type controls. Taken together, this study indicates that nNOS overexpression improves Cd tolerance of rice seedlings through decreasing cadmium accumulation and enhancing the antioxidant capacity and melatonin biosynthesis of the plants.

Seed Treatment with Sodium Nitroprusside Ensures a Long-Term Physiological and Protective Effect on Wheat under Salinity.

Although salinity inhibits plant growth, the use of a nitric oxide (NO) gasotransmitter can reduce its negative effects. In this study, the influence of 200 μM sodium nitroprusside (SNP) (donor of NO) on wheat plants (Triticum aestivum L., cv. Salavat Yulaev) in conditions of salinization (100 mM NaCl) was analyzed in pot experiments. Seed priming regulated the level of endogenous NO in normal and salinity conditions throughout the entire experiment (30 and 60 days). Salinity led to the strong accumulation of NO and H2O2, which is negative for plants, and significantly reduced leaf area and photosynthetic pigments (chlorophyll a and b and carotenoids). In addition, stress caused a drop in the content of reduced glutathione (GSH) and ascorbic acid (ASA), an accumulation of oxidized glutathione (GSSG), and significantly activated glutathione reductase (GR), ascorbate peroxidase (APX), and lipid peroxidation (LPO) in wheat leaves. SNP treatment significantly attenuated the negative effects of salinity on leaf area and photosynthetic pigments. An important indicator of reducing the damaging effect of salinity on treated plants is the stabilization of the content of GSH and ASA throughout the experiment (60 days). This condition has been associated with long-term modulation of GR and APX activity. Such an effect of 200 μM SNP may be related to its ability to reduce stress-induced accumulation of NO. Additional accumulation of proline also mitigated the negative effect of salinity on plants, and this also evidenced decreased LPO and H2O2 in them. For the first time, in natural growing conditions (small-scale field experiments), it was found that pre-sowing seed treatment with 200 μM SNP led to an improvement in the main yield indicators and an increase in the content of essential amino acids in wheat grains. Thus, SNP treatment can be used as an effective approach for prolonged protection of wheat plants under salinity and to improve grain yield and its quality.

Melatonin-mediated endogenous nitric oxide coordinately boosts stability through proline and nitrogen metabolism, antioxidant capacity, and Na+/K+ transporters in tomato under NaCl stress.

The interactions between nitric oxide (NO) and melatonin in alleviating sodium chloride (NaCl) toxicity in plants are poorly comprehended. Here, the associations between the exogenous application of melatonin and endogenous NO levels in inducing tomato seedlings' defense response during NaCl toxicity were investigated. The results indicated that the application of melatonin (150 μM) increased height (23.7%) and biomass (32.2%), improved chlorophyll (a (137%) and b (92.8%)), and proline metabolisms, and reduced the contents of superoxide anion radicals (49.6%), hydrogen peroxide (31.4%), malondialdehyde (38%), and electrolyte leakage (32.6%) in 40-day-old tomato seedlings grown under NaCl (150 mM) treatment. Melatonin increased the antioxidant defense system in NaCl-stressed seedlings by increasing the activity of the antioxidant enzymes. Melatonin also improved N metabolism and endogenous NO content in NaCl-stressed seedlings by upregulating the activity of enzymes implicated in N assimilation. Furthermore, melatonin improved ionic balance and reduced Na content in NaCl-exposed seedlings by upregulating the expression of genes involved in K/Na ratio homeostasis (NHX1-4) and increasing the accumulation of mineral nutrients (P, N, Ca, and Mg). However, the addition of cPTIO (100 μM; an NO scavenger) reversed the beneficial impacts of melatonin, indicating the effective function of NO in melatonin-induced defense mechanisms in NaCl-stressed tomato seedlings. Therefore, our results revealed that melatonin improves the tolerance of tomato plants during NaCl toxicity by mediating internal NO.

Nitric oxide promotes adventitious root formation in cucumber under cadmium stress through improving antioxidant system, regulating glycolysis pathway and polyamine homeostasis.

Cadmium (Cd) as a potentially toxic heavy metal that not only pollutes the environment but also interferes with plant growth. Nitric oxide (NO) regulates plant growth and development as well as abiotic stress response. However, the mechanism underpinning NO-induced adventitious root development under Cd stress remains unclear. In this study, cucumber (Cucumis sativus 'Xinchun No. 4') was used as the experimental material to investigate the effect of NO on the development of adventitious roots in cucumber under Cd stress. Our results revealed that, as compared to Cd stress, 10 μM SNP (a NO donor) could considerably increase the number and length of adventitious roots by 127.9% and 289.3%, respectively. Simultaneously, exogenous SNP significantly increased the level of endogenous NO in cucumber explants under Cd stress. Our results revealed that supplementation of Cd with SNP significantly increased endogenous NO content by 65.6% compared with Cd treatment at 48 h. Furthermore, our study indicated that SNP treatment could improve the antioxidant capacity of cucumber explants under Cd stress by up-regulating the gene expression level of antioxidant enzymes, as well as reducing the levels of malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide anion ( ) to alleviate oxidative damage and membrane lipid peroxidation. Application of NO resulted in a decrease of the , MDA, and H2O2 level by 39.6%, 31.4% and 60.8% as compared to Cd-alone treatment, respectively. Besides that, SNP treatment significantly increased the expression level of related genes involved in glycolysis processes and polyamine homeostasis. However, application of NO scavenger 2-(4-carboxy -2-phenyl)-4, 4, 5, 5-tetramethy limidazoline -1-oxyl -3-oxide (cPTIO) and the inhibitor tungstate significantly reversed the positive role of NO in promoting the adventitious root formation under Cd stress. These results suggest that exogenous NO can increase the level of endogenous NO, improve antioxidation ability, promote glycolysis pathway and polyamine homeostasis to enhance the occurrence of adventitious roots in cucumber under Cd stress. In summary, NO can effectively alleviate the damage of Cd stress and significantly promote the development of adventitious root of cucumber under Cd stress.

Trehalose and NO work together to alleviate Cd toxicity in pepper (Capsicum annuum L.) plants by regulating cadmium sequestration and distribution within cells and the antioxidant defense system

The response of plants to trehalose (TR) and nitric oxide (NO) has been tested in different stressful conditions, but the contribution of endogenous TR to plant tolerance to cadmium stress (Cd-S) induced by NO is still unclear. Ten days after germination, among the pepper seedlings, half were immersed for 12 h in a solution containing 15.0 mM TR or 0.6 mM sodium citrate (SC), an inhibitor of trehalose-6-phosphate phosphatase (TPP). Then, the plants were exposed to control (no addition of Cd) or Cd-S (0.1 mM CdCl2) up to two additional weeks. Throughout the stress period, both treatments were combined with sodium nitroprusside (SNP; 0.1 mM), a NO donor, supplied through the nutrient solution. Plants exposed to Cd-S experienced a substantial reduction in plant growth, photosynthesis, and leaf water relation parameters, but an increase in oxidative stress parameters, free proline, phytochelatins (PCs), and the activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), glutathione reductase (GR), and ascorbate peroxidase (APX). The detrimental effects of Cd-S on the afore-mentioned traits were reversed by the supplementation of SNP, which in turn significantly increased the endogenous NO and TR levels, and leaf calcium (Ca2+) and potassium (K+), and reduced the leaf H2O2, MDA, and Cd contents as well as membrane leakage. SNP raised the amounts of GSH and PCs in Cd-S- plants, thereby modulating Cd sequestration to render it nontoxic. The treatment of SNP encouraged Cd build-up in the cell walls of root and leaf in order to prevent Cd from being transported to other vital cell organelles to safeguard them from metal toxicity. The supplementation of SC, a scavenger of TPP, eliminated TR content, thereby reversing the positive effect of SNP on Cd-S plants. Exogenous application of TR together with SNP+SC reversed the negative effect of SC. This suggests that TR is necessary for NO to be effective in improving the pepper plant Cd-S tolerance.

PS-B03-2: SGC STIMULATOR, BAY41 8543, FOR THE TREATMENT OF HEART FAILURE WITH REDUCED EJECTION FRACTION AND CARDIORENAL SYNDROME

Objective: Heart failure with reduced ejection fraction (HFrEF) imposes a significant health and socioeconomic burden. The life expectancy and prognosis are particularly dreadful for patients that develop simultaneous renal dysfunction, so called cardiorenal syndrome, hence new treatment strategies are still in a great demand. Recent therapies for HFrEF include targeting the nitric oxide (NO)/ soluble guanylyl cyclase (sGC)/ cyclic guanosine monophosphate (cGMP) pathway by sGC stimulators. These compounds bind to the heme moiety of the sGC and stimulate the sGC in the absence of NO (NO independent action), but also they sensitize sGC to low levels of endogenous NO by stabilizing NO/sGC binding. Design and method: We explored the efficiency of sGC stimulator (BAY41 8543, an analogue of vericiguat) in the animal model of HFrEF with kidney dysfunction. We used ren2 transgenic hypertensive rats (TGR) with aortocaval fistula (ACF), in which HFrEF is due to volume overload. Firstly, we investigated the long term activity of BAY41 given alone (3 mg/kg/day in the food) or combined with an ACE inhibitor (ACEi, Trandolapril, 0.25 mg/kg/day in drinking water) on the survival rate of ACF induced HFrEF in TGR (30 weeks). In separate series of experiments the impact of BAY41 on blood pressure was measured by telemetry. Blood, urine and in the end tissue samples were collected to evaluate the levels of cGMP, albuminuria and the production of nitric oxide during the two week treatment. Results: sGC stimulator significantly improved the survival rate of ACF TGR in comparison to untreated animals with ACF. However, BAY41 administered together with ACEi decreased its beneficial activity. The overall survival in BAY41+ACEi treated group was 50%, while in the group which received only ACEi it was still 90% in the end of the observation. Noteworthy, a temporary blood pressure decrease (10 mmHg) was recorded during first few days after sGC stimulator administration, but early on SBP started to rise and by the end it was on the same level as in untreated ACF TGR (127 ± 3 vs 131 ± 6 mmHg, respectively; NS). Conclusions: It seems that the NO independent stimulation of sGC is a promising strategy to treat HFrEF with cardiorenal syndrome, however, more caution and additional studies are necessary to enlighten the puzzling decrease in survival rate in the group that received combined treatment with sGC stimulator and ACEi. Perhaps selected dose regimen was not optimal for the combined treatment (e.g. due to hypotension).