Biochemistry of nitric oxide and its redox-activated forms

Nitric oxide in plants: an insight on redox activity and responses toward abiotic stress signaling

Plants, as sessile organisms, are subjected to diverse abiotic stresses, including salinity, desiccation, metal toxicity, thermal fluctuations, and hypoxia at different phases of plant growth. Plants can activate messenger molecules to initiate a signaling cascade of response toward environmental stresses that results in either cell death or plant acclimation. Nitric oxide (NO) is a small gaseous redox-active molecule that exhibits a plethora of physiological functions in growth, development, flowering, senescence, stomata closure and responses to environmental stresses. It can also facilitate alteration in protein function and reprogram the gene profiling by direct or indirect interaction with different target molecules. The bioactivity of NO can be manifested through different redox-based protein modifications including S-nitrosylation, protein nitration, and metal nitrosylation in plants. Although there has been considerable progress in the role of NO in regulating stress signaling, still the physiological mechanisms regarding the abiotic stress tolerance in plants remain unclear. This review summarizes recent advances in understanding the emerging knowledge regarding NO function in plant tolerance against abiotic stresses. The manuscript also highlighted the importance of NO as an abiotic stress modulator and developed a rational design for crop cultivation under a stress environment.

The effects of nitric oxide in Alzheimer's disease

Alzheimer's disease (AD), the most prevalent cause of dementia, is a progressive neurodegenerative condition that commences subtly and inexorably worsens over time. Despite considerable research, a specific drug that can fully cure or effectively halt the progression of AD remains elusive. Nitric oxide (NO), a crucial signaling molecule in the nervous system, is intimately associated with hallmark pathological changes in AD, such as amyloid-beta deposition and tau phosphorylation. Several therapeutic strategies for AD operate through the nitric oxide synthase/NO system. However, the potential neurotoxicity of NO introduces an element of controversy regarding its therapeutic utility in AD. This review focuses on research findings concerning NO's role in experimental AD and its underlying mechanisms. Furthermore, we have proposed directions for future research based on our current comprehension of this critical area.

Interorgan, intraorgan and interplant communication mediated by nitric oxide and related species

Plant survival to a potential plethora of diverse environmental insults is underpinned by coordinated communication amongst organs to help shape effective responses to these environmental challenges at the whole plant level. This interorgan communication is supported by a complex signal network that regulates growth, development and environmental responses. Nitric oxide (NO) has emerged as a key signalling molecule in plants. However, its potential role in interorgan communication has only recently started to come into view. Direct and indirect evidence has emerged supporting that NO and related species (S-nitrosoglutathione, nitro-linolenic acid) are mobile interorgan signals transmitting responses to stresses such as hypoxia and heat. Beyond their role as mobile signals, NO and related species are involved in mediating xylem development, thus contributing to efficient root-shoot communication. Moreover, NO and related species are regulators in intraorgan systemic defence responses aiming an effective, coordinated defence against pathogens. Beyond its in planta signalling role, NO and related species may act as ex planta signals coordinating external leaf-to-leaf, root-to-leaf but also plant-to-plant communication. Here, we discuss these exciting developments and emphasise how their manipulation may provide novel strategies for crop improvement.

Nitric oxide action in the digestive fluid of Nepenthes × ventrata is linked to the modulation of ROS level

Nepenthes are carnivorous plants with photoactive leaves converted into jug-shaped containers filled with the digestive fluid. The digestion requires various enzymes and reactive oxygen species (ROS) that facilitate proteolysis. Reactive nitrogen species are present in the digestive fluid of Nepenthes × ventrata, and the increased nitric oxide (NO) formation is associated with protein degradation. The aim of the work was to verify the beneficial effect of NO application into the trap on the dynamics of protein digestion and ROS homeostasis. Measurements were done using the digestive fluid or the tissue collected from the mature pitcher plants (fed) grown in a greenhouse. Two independent methods confirmed NO formation in the digestive fluid of fed and non-fed traps. NO supplementation with food into the trap accelerated protein degradation in the digestive fluid by increasing the proteolytic activity. NO modulated free radical formation (as the result of direct impact on NADPH oxidase), stimulated ROS scavenging capacity, increased -SH groups and flavonoids content, particularly at the beginning of the digestion. In non-fed traps, the relatively high level of protein nitration in the digestive fluid may prevent self-protein proteolysis. Whereas, after initiation of the digestion decreasing level of nitrated proteins in the fluid may indicate their accelerated degradation. Therefore, it can be assumed that NO exhibits a protective effect on the fluid and the trap tissue before digestion, while during digestion, NO is an accelerator of protein decomposition and the ROS balance keeper.

Nitric Oxide Ameliorates the Effects of Hypoxia in Mice by Regulating Oxygen Transport by Hemoglobin

Xiaoying Zhou, Wenting Su, Quanwei Bao, Yu Cui, Xiaoxu Li, Yidong Yang, Chengzhong Yang, Chengyuan Wang, Li Jiao, Dewei Chen, and Jian Huang. Nitric oxide ameliorates the effects of hypoxia in mice by regulating oxygen transport by hemoglobin. High Alt Med Biol. 25:174-185, 2024.-Hypoxia is a common pathological and physiological phenomenon in ischemia, cancer, and strenuous exercise. Nitric oxide (NO) acts as an endothelium-derived relaxing factor in hypoxic vasodilation and serves as an allosteric regulator of hemoglobin (Hb). However, the ultimate effects of NO on the hematological system in vivo remain unknown, especially in extreme environmental hypoxia. Whether NO regulation of the structure of Hb improves oxygen transport remains unclear. Hence, we examined whether NO altered the oxygen affinity of Hb (Hb-O2 affinity) to protect extremely hypoxic mice. Mice were exposed to severe hypoxia with various concentrations of NO, and the survival time, exercise capacity, and other physical indexes were recorded. The survival time was prolonged in the 5 ppm NO (6.09 ± 1.29 minutes) and 10 ppm NO (6.39 ± 1.58 minutes) groups compared with the 0 ppm group (4.98 ± 1.23 minutes). Hypoxia of the brain was relieved, and the exercise exhaustion time was prolonged when mice inhaled 20 ppm NO (24.70 ± 6.87 minutes vs. 20.23 ± 6.51 minutes). In addition, the differences in arterial oxygen saturation (SO2%) (49.64 ± 7.29% vs. 42.90 ± 4.30%) and arteriovenous SO2% difference (25.14 ± 8.95% vs. 18.10 ± 6.90%) obviously increased. In ex vivo experiments, the oxygen equilibrium curve (OEC) left shifted as P50 decreased from 43.77 ± 2.49 mmHg (0 ppm NO) to 40.97 ± 1.40 mmHg (100 ppm NO) and 38.36 ± 2.78 mmHg (200 ppm NO). Furthermore, the Bohr effect of Hb was enhanced by the introduction of 200 ppm NO (-0.72 ± 0.062 vs.-0.65 ± 0.051), possibly allowing Hb to more easily offload oxygen in tissue at lower pH. The crystal structure reveals a greater distance between Asp94β-His146β in nitrosyl -Hb(NO-Hb), NO-HbβCSO93, and S-NitrosoHb(SNO-Hb) compared to tense Hb(T-Hb, 3.7 Å, 4.3 Å, and 5.8 Å respectively, versus 3.5 Å for T-Hb). Moreover, hydrogen bonds were less likely to form, representing a key limitation of relaxed Hb (R-Hb). Upon NO interaction with Hb, hydrogen bonds and salt bridges were less favored, facilitating relaxation. We speculated that NO ameliorated the effects of hypoxia in mice by promoting erythrocyte oxygen loading in the lung and offloading in tissues.

Quercetin in semen extender curtails reactive oxygen and nitrogen species and improves functional attributes of cryopreserved buck semen

Cryopreservation of goat spermatozoa is challenging due to several factors, including one of the most essential, i.e., oxidative stress. It is particularly essential in goat semen due to its scanty ejaculate volume and high sperm concentration. This leaves a narrow sperm-to-seminal plasma ratio owing to marginal antioxidant support; moreover, semen extension further dilutes the antioxidant level, leading to an imbalance of oxidant-antioxidant equilibrium. The present study aimed to evaluate the effect of quercetin on curtailing oxidative stress and its reflection on the post-thaw survivability and membrane integrity of goat spermatozoa. For this study, six bucks were selected. Six ejaculates from each buck totaling 36 ejaculates were collected, which were then split into five parts; furthermore, each part was added with a semen extender having a particular concentration of additive. Group C without quercetin and T1 containing Vitamin E at 3 mmol/mL were considered the control and positive control respectively, whereas T2, T3, and T4 contain 10, 20, and 30 μmol/mL of Quercetin respectively. The final sperm concentration of each group was kept at 200 × 106 spermatozoa/mL. All groups were subjected to equilibration at 4 °C for 4 h, then filled in French mini (0.25 mL) straws, followed by sealing and cryopreservation. Samples after 72 h of cryopreservation were subjected to evaluation of plasma membrane integrity and viability through staining, acrosomal integrity, and mitochondrial membrane activity through flow cytometry. Evaluation of sperm kinematics as well as the oxidant-antioxidant status of sperm (ROS and nitric oxide) and seminal plasma (SOD, CAT, GPx, FRAP, and lipid peroxidation through MDA estimation) were also carried out. Quercetin, when supplemented at 20 μmol/mL in buck semen extender, significantly (p < 0.01) improved cryopreserved sperm functions in terms of plasma membrane integrity, viability, acrosomal integrity, mitochondrial membrane activity, and sperm kinematics of buck semen. Similarly, Quercetin supplementation at 20 μmol/mL significantly reduced reactive oxygen and nitrogen species (RONS) in sperm and improved the antioxidant status of seminal plasma, which was indicated by reduced oxidative damage and improved the antioxidant status of buck semen. In conclusion, Quercetin at 20 μmol/mL reduced oxidative stress, improved semen antioxidant status, and improved sperm membranes integrity and kinematics.

Interplay between glypican-1, amyloid-β and tau phosphorylation in human neural stem cells

INTRODUCTION

Alzheimer's disease (AD) is characterized by accumulation of amyloid beta (Aβ) and hyperphosphorylated tau (Tau-P) in the brain. Aβ enhances the activity of kinases involved in the formation of Tau-P. Phosphorylation at Thr 181 determines the propagation of multiple tau phosphorylations. Aβ is derived from the amyloid precursor protein (APP). Cleavage of APP by β-secretase also initiates release of heparan sulfate (HS) from the proteoglycan glypican-1 (GPC1).

OBJECTIVES

In this study, we have explored possible connections between GPC1 expression, HS release, APP processing and Tau-P formation in human neural stem cells.

METHODS

GPC1 formation was suppressed by using CRISPR/Cas9 and increased by using a vector encoding GPC1. HS release from GPC1 was increased by growing cells in medium containing Arg and ascorbate. Effects were monitored by immunofluorescence microscopy and slot immunoblotting using antibodies/antisera recognizing Aβ, GPC1, HS released from GPC1, total Tau, and Tau phosphorylated at Thr-181, 217 or 231. The latter have been used as blood biomarkers for AD.

RESULTS

Suppression of GPC1 expression resulted in increased phosphorylation at Thr 181 and Thr 217. When GPC1 was overexpressed, phosphorylation at Thr 217 decreased. Stimulation of HS release from GPC1 diminished tau phosphorylation at all of the three Thr positions, while expression of GPC1 was unaffected. Simultaneous stimulation of HS release and APP processing by the cytokine TNF-α also suppressed tau phosphorylation.

CONCLUSION

The increased release of GPC1-derived HS may interfere with Aβ formation and/or Aβ interaction with tau.

Uncovering the Potential Mechanisms and Effects of Hyperuricemia and its Associated Diseases on Male Reproduction

Male fertility and metabolic disorders, including obesity and diabetes, are closely connected. Since hyperuricemia and metabolic syndrome are strongly related, male fertility and hyperuricemia may, to some degree, be associated. According to recent studies, hyperuricemia imposes various effects on sex hormones, semen quality, and male erectile dysfunction. Some researchers claim that uric acid worsens male semen and raises the risk of erectile dysfunction (ED), while others state that it safeguards both penile erection and male semen. Additionally, it has been shown that gout and metabolic syndrome also raise the risk of ED. To clarify this controversy, the influence and potential mechanisms of hyperuricemia on ED, semen quality, sex hormone levels, and the effects of hyperuricemia-related disorders on ED will be comprehensively summarized.

Nitrogen monoxide and calix[4]pyrrolato aluminate: structural constraint enabled NO dimerization

The dimerization of nitrogen monoxide (NO) is highly relevant in homo- and heterogeneous biochemical and environmental redox processes, but a broader understanding is challenged by the endergonic nature of this equilibrium. The present work describes NO-dimerization leveraged by structurally constrained aluminum and metal-ligand cooperativity at the anionic calix[4]pyrrolato aluminate(III). Quantum chemical calculations reveal the driving force for N-N bond formation, while reactivity tests shed light on subsequent redox chemistry and NO decomposition at metal surfaces. Inhibiting the dimerization pathway by saturating NO's unpaired electron with a phenyl group (nitrosobenzene) allows trapping the 1,2-adduct as a key intermediate. Elevated temperatures result in an unprecedented and high-yielding rearrangement of the calix[4]pyrrolato ligand scaffold. Kinetic and theoretical studies provide a comprehensive picture of the rearrangement mechanism and delineate systematics for ring modification of the prominent calix[4]pyrrole macrocycle.

Reactive nitrogen species act as the enhancers of glutathione pool in embryonic axes of apple seeds subjected to accelerated ageing

MAIN CONCLUSION

Reactive nitrogen species mitigate the deteriorative effect of accelerated seed ageing by affecting the glutathione concentration and activities of GR and GPX-like. The treatment of apple (Malus domestica Borkh.) embryos isolated from accelerated aged seeds with nitric oxide-derived compounds increases their vigour and is linked to the alleviation of the negative effect of excessive oxidation processes. Reduced form of glutathione (GSH) is involved in the maintenance of redox potential. Glutathione peroxidase-like (GPX-like) uses GSH and converts it to oxidised form (GSSG), while glutathione reductase (GR) reduces GSSG into GSH. The aim of this work was to investigate the impact of the short-time NOx treatment of embryos isolated from apple seeds subjected to accelerated ageing on glutathione-related parameters. Apple seeds were subjected to accelerated ageing for 7, 14 or 21 days. Isolated embryos were shortly treated with NOx and cultured for 48 h. During ageing, in the axes of apple embryos, GSH and GSSG levels as well as half-cell reduction potential remained stable, while GR and GPX-like activities decreased. However, the positive effect of NOx in the vigour preservation of embryos isolated from prolonged aged seeds is linked to the increased total glutathione pool, and above all, higher GSH content. Moreover, NOx increased the level of transcripts encoding GPX-like and stimulated enzymatic activity. The obtained results indicate that high seed vigour related to the mode of action of NO and its derivatives is closely linked to the maintenance of higher GSH levels.

Unveiling the significance of inducible nitric oxide synthase: Its impact on cancer progression and clinical implications

The intricate role of inducible nitric oxide synthase (iNOS) in cancer pathophysiology has garnered significant attention, highlighting the complex interplay between tumorigenesis, immune response, and cellular metabolism. As an enzyme responsible for producing nitric oxide (NO) in response to inflammatory stimuli. iNOS is implicated in various aspects of cancer development, including DNA damage, angiogenesis, and evasion of apoptosis. This review synthesizes the current findings from both preclinical and clinical studies on iNOS across different cancer types, reflecting the variability depending on cellular context and tumor microenvironment. We explore the molecular mechanisms by which iNOS modulates cancer cell growth, survival, and metastasis, emphasizing its impact on immune surveillance and response to treatment. Additionally, the potential of targeting iNOS as a therapeutic strategy in cancer treatment is examined. By integrating insights from recent advances, this review aims to elucidate the significant role of iNOS in cancer and pave the way for novel diagnostic and therapeutic approaches.

Nonheme binuclear transition metal complexes with hydrosulfide and polychalcogenides

The intriguing chemistry of chalcogen (S, Se)-containing ligands and their capability to bridge multiple metal centres have resulted in a plethora of reports on transition metal complexes featuring hydrosulfide (HS-) and polychalcogenides (En2-, E = S, Se). While a large number of such molecules are strictly organometallic complexes, examples of non-organometallic complexes featuring HS- and En2- with N-/O-donor ligands are relatively rare. The general synthetic procedure for the transition metal-hydrosulfido complexes involves the reaction of the corresponding metal salts with HS-/H2S and this is prone to generate sulfido bridged oligomers in the absence of sterically demanding ligands. On the other hand, the synthetic methods for the preparation of transition metal-polychalcogenido complexes include the reaction of the corresponding metal salts with En2- or the two electron oxidation of low-valent metals with elemental chalcogen, often at an elevated temperature and/or for a long time. Recently, we have developed new synthetic methods for the preparation of two new classes of binuclear transition metal complexes featuring either HS-, or Sn2- and Sen2- ligands. The new method for the synthesis of transition metal-hydrosulfido complexes involved transition metal-mediated hydrolysis of thiolates at room temperature (RT), while the method for the synthesis of transition metal-polychalcogenido complexes involved redox reaction of coordinated thiolates and exogenous elemental chalcogens at RT. An overview of the synthetic aspects, structural properties and intriguing reactivity of these two new classes of transition metal complexes is presented.

A hypothesis of teleological evolution, via endogenous acetylcholine, nitric oxide, and calmodulin pathways

The Extended Evolutionary Synthesis (EES) addresses the issues in evolutionary biology which cannot be explained by neo-Darwinian theory. The EES paradigm recognises teleology and agency in living systems, and identifies that organisms can directly affect their evolutionary trajectory in a goal-directed manner, yet the physiological pathways via which this occurs remain unidentified. Here, I propose a physiological pathway via which organisms can alter their genotype and phenotype by making behavioural decisions with respect their activity levels, partitioning of resources either toward growth, defence against disease, or their behavioural response to stressors. Specifically, I hypothesize that agential, teleological decisions mediated by acetylcholine result in induced nitric oxide (NO) activity, which regulates metabolism, blood flow, and immune response. Nitric oxide, however, is also a key epigenetic molecule, being involved in DNA acetylation, methylation, and de-methylation. Further, NO alters the histone complexes which scaffold nuclear DNA strands, and is thus a good candidate in identifying a system which allows an organisms to make teleological genetic changes. The proposed mechanisms of inheritance of these genetic changes is via the paternal line, whereby epigenetic changes in the somatic Sertoli cells in animals are transcribed by mRNA and included in the germline cells - the male gametes. The microsporangium in plants, and the sporophore cells in fungi, meanwhile, are proposed to form similar systems in response to sensory detection of stressors. Whilst the hypothesis is presented as a simplified model for future testing, it opens new avenues for study in evolutionary biology.

Redox regulation in primary nitrate response: Nitric oxide in the spotlight

Nitrogen (N) is the main macronutrient of plants that determines growth and productivity. Nitrate is the major source form of N in soils and its uptake and assimilatory pathway has been extensively studied. The early events that occur after the perception of nitrate is known as primary nitrate response (PNR). In this review, new findings on the redox signal that impacts PNR are discussed. We will focus on the novel role of Nitric Oxide (NO) as a signal molecule and the mechanisms that are involved to control NO homeostasis during PNR. Moreover, the role of Reactive Oxygen Species (ROS) and the possible interplay with NO in the PNR are discussed. The sources of NO during PNR will be analyzed as well as the regulation of its intracellular levels. Furthermore, we explored the relevance of the direct action of NO through the S-nitrosation of the transcription factor NLP7, one of the master regulators in the nitrate signaling cascade. This review gives rise to an interesting field with new actors to mark future research directions. This allows us to increase the knowledge of the physiological and molecular fine-tuned modulation during nitrate signaling processes in plants. The discussion of new experimental data will stimulate efforts to further refine our understanding of the redox regulation of nitrate signaling.

Location of S-nitrosylated cysteines in protein three-dimensional structures

Although S-nitrosylation of cysteines is a common protein posttranslational modification, little is known about its three-dimensional structural features. This paper describes a systematic survey of the data available in the Protein Data Bank. Several interesting observations could be made. (1) As a result of radiation damage, S-nitrosylated cysteines (Snc) are frequently reduced, at least partially. (2) S-nitrosylation may be a protection against irreversible thiol oxidation; because the NO group of Snc is relatively accessible to the solvent, it may act as a cork to protect the sulfur atoms of cysteines from oxidation by molecular oxygen to sulfenic, sulfinic, and sulfonic acid; moreover, Snc are frequently found at the start or end of helices and strands and this might shield secondary structural elements from unfolding.

Nanomaterials-Induced Redox Imbalance: Challenged and Opportunities for Nanomaterials in Cancer Therapy

Cancer cells typically display redox imbalance compared with normal cells due to increased metabolic rate, accumulated mitochondrial dysfunction, elevated cell signaling, and accelerated peroxisomal activities. This redox imbalance may regulate gene expression, alter protein stability, and modulate existing cellular programs, resulting in inefficient treatment modalities. Therapeutic strategies targeting intra- or extracellular redox states of cancer cells at varying state of progression may trigger programmed cell death if exceeded a certain threshold, enabling therapeutic selectivity and overcoming cancer resistance to radiotherapy and chemotherapy. Nanotechnology provides new opportunities for modulating redox state in cancer cells due to their excellent designability and high reactivity. Various nanomaterials are widely researched to enhance highly reactive substances (free radicals) production, disrupt the endogenous antioxidant defense systems, or both. Here, the physiological features of redox imbalance in cancer cells are described and the challenges in modulating redox state in cancer cells are illustrated. Then, nanomaterials that regulate redox imbalance are classified and elaborated upon based on their ability to target redox regulations. Finally, the future perspectives in this field are proposed. It is hoped this review provides guidance for the design of nanomaterials-based approaches involving modulating intra- or extracellular redox states for cancer therapy, especially for cancers resistant to radiotherapy or chemotherapy, etc.

Recent advances on the development of NO-releasing molecules (NORMs) for biomedical applications

Nitric oxide (NO) is an important biological messenger as well as a signaling molecule that participates in a broad range of physiological events and therapeutic applications in biological systems. However, due to its very short half-life in physiological conditions, its therapeutic applications are restricted. Efforts have been made to develop an enormous number of NO-releasing molecules (NORMs) and motifs for NO delivery to the target tissues. These NORMs involve organic nitrate, nitrite, nitro compounds, transition metal nitrosyls, and several nanomaterials. The controlled release of NO from these NORMs to the specific site requires several external stimuli like light, sound, pH, heat, enzyme, etc. Herein, we have provided a comprehensive review of the biochemistry of nitric oxide, recent advancements in NO-releasing materials with the appropriate stimuli of NO release, and their biomedical applications in cancer and other disease control.

Oxidative Stress and Cerebral Vascular Tone: The Role of Reactive Oxygen and Nitrogen Species

The brain's unique characteristics make it exceptionally susceptible to oxidative stress, which arises from an imbalance between reactive oxygen species (ROS) production, reactive nitrogen species (RNS) production, and antioxidant defense mechanisms. This review explores the factors contributing to the brain's vascular tone's vulnerability in the presence of oxidative damage, which can be of clinical interest in critically ill patients or those presenting acute brain injuries. The brain's high metabolic rate and inefficient electron transport chain in mitochondria lead to significant ROS generation. Moreover, non-replicating neuronal cells and low repair capacity increase susceptibility to oxidative insult. ROS can influence cerebral vascular tone and permeability, potentially impacting cerebral autoregulation. Different ROS species, including superoxide and hydrogen peroxide, exhibit vasodilatory or vasoconstrictive effects on cerebral blood vessels. RNS, particularly NO and peroxynitrite, also exert vasoactive effects. This review further investigates the neuroprotective effects of antioxidants, including superoxide dismutase (SOD), vitamin C, vitamin E, and the glutathione redox system. Various studies suggest that these antioxidants could be used as adjunct therapies to protect the cerebral vascular tone under conditions of high oxidative stress. Nevertheless, more extensive research is required to comprehensively grasp the relationship between oxidative stress and cerebrovascular tone, and explore the potential benefits of antioxidants as adjunctive therapies in critical illnesses and acute brain injuries.

Defense signaling pathways in resistance to plant viruses: Crosstalk and finger pointing

Resistance to infection by plant viruses involves proteins encoded by plant resistance (R) genes, viz., nucleotide-binding leucine-rich repeats (NLRs), immune receptors. These sensor NLRs are activated either directly or indirectly by viral protein effectors, in effector-triggered immunity, leading to induction of defense signaling pathways, resulting in the synthesis of numerous downstream plant effector molecules that inhibit different stages of the infection cycle, as well as the induction of cell death responses mediated by helper NLRs. Early events in this process involve recognition of the activation of the R gene response by various chaperones and the transport of these complexes to the sites of subsequent events. These events include activation of several kinase cascade pathways, and the syntheses of two master transcriptional regulators, EDS1 and NPR1, as well as the phytohormones salicylic acid, jasmonic acid, and ethylene. The phytohormones, which transit from a primed, resting states to active states, regulate the remainder of the defense signaling pathways, both directly and by crosstalk with each other. This regulation results in the turnover of various suppressors of downstream events and the synthesis of various transcription factors that cooperate and/or compete to induce or suppress transcription of either other regulatory proteins, or plant effector molecules. This network of interactions results in the production of defense effectors acting alone or together with cell death in the infected region, with or without the further activation of non-specific, long-distance resistance. Here, we review the current state of knowledge regarding these processes and the components of the local responses, their interactions, regulation, and crosstalk.

Regulatory effects of curcumin on nitric oxide signaling in the cardiovascular system

The continuously rising prevalence of cardiovascular disease (CVD) globally substantially impacts the economic growth of developing countries. Indeed, one of the leading causes of death worldwide is unfavorable cardiovascular events. Reduced nitric oxide (NO) generation is the pathogenic foundation of endothelial dysfunction, which is regarded as the first stage in the development of a number of CVDs. Nitric oxide exerts an array of biological effects, including vasodilation, the suppression of vascular smooth muscle cell proliferation and the functional control of cardiac cells. Numerous treatment strategies aim to increase NO synthesis or upregulate downstream NO signaling pathways. The major component of Curcuma longa, curcumin, has long been utilized in traditional medicine to treat various illnesses, especially CVDs. Curcumin improves CV function as well as having important pleiotropic effects, such as anti-inflammatory and antioxidant, through its ability to increase the bioavailability of NO and to positively impact NO-related signaling pathways. In this review, we discuss the scientific literature relating to curcumin's positive effects on NO signaling and vascular endothelial function.

Cardiac nitric oxide scavenging: role of myoglobin and mitochondria

Vascular production of nitric oxide (NO) regulates vascular tone. However, highly permeable NO entering the cardiomyocyte would profoundly impact metabolism and signalling without scavenging mechanisms. The purpose of this study was to establish mechanisms of cardiac NO scavenging. Quantitative optical studies of normoxic working hearts demonstrated that micromolar NO concentrations did not alter mitochondria redox state or respiration despite detecting NO oxidation of oxymyoglobin to metmyoglobin. These data are consistent with proposals that the myoglobin/myoglobin reductase (Mb/MbR) system is the major NO scavenging site. However, kinetic studies in intact hearts reveal a minor role (∼9%) for the Mb/MbR system in NO scavenging. In vitro, oxygenated mitochondria studies confirm that micromolar concentrations of NO bind cytochrome oxidase (COX) and inhibit respiration. Mitochondria had a very high capacity for NO scavenging, importantly, independent of NO binding to COX. NO is also known to quickly react with reactive oxygen species (ROS) in vitro. Stimulation of NO scavenging with antimycin and its inhibition by substrate depletion are consistent with NO interacting with ROS generated in Complex I or III under aerobic conditions. Extrapolating these in vitro data to the intact heart supports the hypothesis that mitochondria are a major site of cardiac NO scavenging. KEY POINTS: Cardiomyocyte scavenging of vascular nitric oxide (NO) is critical in maintaining normal cardiac function. Myoglobin redox cycling via myoglobin reductase has been proposed as a major NO scavenging site in the heart. Non-invasive optical spectroscopy was used to monitor the effect of NO on mitochondria and myoglobin redox state in intact beating heart and isolated mitochondria. These non-invasive studies reveal myoglobin/myoglobin reductase plays a minor role in cardiac NO scavenging. A high capacity for NO scavenging by heart mitochondria was demonstrated, independent of cytochrome oxidase binding but dependent on oxygen and high redox potentials consistent with generation of reactive oxygen species.

An enzyme that selectively S-nitrosylates proteins to regulate insulin signaling

Acyl-coenzyme A (acyl-CoA) species are cofactors for numerous enzymes that acylate thousands of proteins. Here, we describe an enzyme that uses S-nitroso-CoA (SNO-CoA) as its cofactor to S-nitrosylate multiple proteins (SNO-CoA-assisted nitrosylase, SCAN). Separate domains in SCAN mediate SNO-CoA and substrate binding, allowing SCAN to selectively catalyze SNO transfer from SNO-CoA to SCAN to multiple protein targets, including the insulin receptor (INSR) and insulin receptor substrate 1 (IRS1). Insulin-stimulated S-nitrosylation of INSR/IRS1 by SCAN reduces insulin signaling physiologically, whereas increased SCAN activity in obesity causes INSR/IRS1 hypernitrosylation and insulin resistance. SCAN-deficient mice are thus protected from diabetes. In human skeletal muscle and adipose tissue, SCAN expression increases with body mass index and correlates with INSR S-nitrosylation. S-nitrosylation by SCAN/SNO-CoA thus defines a new enzyme class, a unique mode of receptor tyrosine kinase regulation, and a revised paradigm for NO function in physiology and disease.

Computational Exploration of Minimum Energy Reaction Pathway of N2O Formation from Intermediate I of P450nor Using an Active Center Model

P450nor is a heme-containing enzyme that catalyzes the conversion of nitric oxide (NO) to nitrous oxide (N2O). Its catalytic mechanism has attracted attention in chemistry, biology, and environmental engineering. The catalytic cycle of P450nor is proposed to consist of three major steps. The reaction mechanism for the last step, N2O generation, remains unknown. In this study, the reaction pathway of the N2O generation from the intermediate I was explored with the B3LYP calculations using an active center model after the examination of the validity of the model. In the validation, we compared the heme distortions between P450nor and other oxidoreductases, suggesting a small effect of protein environment on the N2O generation reaction in P450nor. We then evaluated the electrostatic environment effect of P450nor on the hydride affinity to the active site with quantum mechanics/molecular mechanics (QM/MM) calculations, confirming that the affinity was unchanged with or without the protein environment. The active center model for P450nor showed that the N2O generation process in the enzymatic reaction undergoes a reasonable barrier height without protein environment. Consequently, our findings strongly suggest that the N2O generation reaction from the intermediate I depends sorely on the intrinsic reactivity of the heme cofactor bound on cysteine residue.

Acetylacetonate Ruthenium Nitrosyls: A Gateway to Nitric Oxide Release in Water under Near-Infrared Excitation by Two-Photon Absorption

A fundamental challenge for phototriggered therapies is to obtain robust molecular frameworks that can withstand biological media. Photoactivatable nitric oxide (NO) releasing molecules (photoNORMs) based on ruthenium nitrosyl (RuNO) complexes are among the most studied systems due to several appealing features that make them attractive for therapeutic applications. Nevertheless, the propensity of the NO ligand to be attacked by nucleophiles frequently manifests as significant instability in water for this class of photoNORMs. Our approach to overcome this limitation involved enhancing the Ru-NO π-backbonding to lower the electrophilicity at the NO by replacing the commonly employed 2,2'-bipyridine (bpy) ligand by an anionic, electron-rich, acetylacetonate (acac). A versatile and convenient synthetic route is developed and applied for the preparation of a large library of RuNO photoNORMs with the general formula [RuNO(tpy)(acac)]2+ (tpy = 2,2':6',2″-terpyridine). A combined theoretical and experimental analysis of the Ru-NO bonding in these complexes is presented, supported by extensive single-crystal X-ray diffraction experiments and by topological analyses of the electron charge density by DFT. The enhanced π-back-bonding, systematically evidenced by several techniques, resulted in a remarkable stability in water for these complexes, where significant NO release efficiencies were recorded. We finally demonstrate the possibility of obtaining sophisticated water-stable multipolar NO-delivery platforms that can be activated in the near-IR region by two-photon absorption (TPA), as demonstrated for an octupolar complex with a TPA cross section of 1530 GM at λ = 800 nm and for which NO photorelease was demonstrated under TPA irradiation in aqueous media.

Uncovering Nitrosyl Reactivity at N-Heterocyclic Carbene Center

N-heterocyclic carbenes (NHCs) have garnered much attention due to their unique properties, such as strong σ-donating and π-accepting abilities, as well as their transition-metal-like reactivity toward small molecules. In 2015, we discovered that NHCs can react with nitric oxide (NO) gas to form radical adducts that resemble transition metal nitrosyl complexes. To elucidate the analogy between NHC and transition metal NO adducts, here we have undertaken a systematic investigation of the electron- and proton-transfer chemistry of [NHC-NO]⋅ (N-heterocyclic carbene nitric oxide radical) compounds. We have accessed a suite of compounds, comprised of [NHC-NO]+ , [NHC-NO]- , [NHC-NOH]0 , and [NHC-NHOH]+ species. In particular, [NHC-NO]- was isolated as potassium and lithium ion adducts. Most interestingly, a monomeric potassium [NHC-NO]- compound was isolated with the assistance of 18-crown-6, which is the first instance of a monomeric alkali N-oxyl compound to the best of our knowledge. Our results demonstrate that [NHC-NO]⋅ exhibits redox behavior broadly similar to metal nitrosyl complexes, which opens up more possibilities for utilizing NHCs to build on the known reactivity of metal complexes.

Effect of alpha-lipoic acid and caffeine-loaded chitosan nanoparticles on obesity and its complications in liver and kidney in rats

The present work investigated the effect of α-lipoic acid (ALA) and caffeine-loaded chitosan nanoparticles (CAF-CS NPs) on obesity and its hepatic and renal complications in rats. Rats were divided into control, rat model of obesity induced by high fat diet (HFD), and obese rats treated with ALA and/or CAF-CS NPs. At the end of the experiment, the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) and the levels of urea, creatinine, interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) were determined in the sera of animals. In addition, malondialdehyde (MDA), nitric oxide (NO), and reduced glutathione (GSH) were measured in hepatic and renal tissues. Renal Na+, K+-ATPase was assessed. The histopathological changes were examined in the hepatic and renal tissues. Obese rats showed a significant increase in AST, ALT, ALP, urea, and creatinine. This was associated with a significant increase in IL-1β, TNF-α, MDA, and NO. A significant decrease in hepatic and renal GSH and renal Na+, K+-ATPase activity was recorded in obese rats. Obese rats also showed histopathological alterations in hepatic and renal tissues. Treatment with ALA and/or CAF-CS NPs reduced the weight of obese rats and ameliorated almost all the hepatic and renal biochemical and histopathological changes induced in obese rats. In conclusion, the present findings indicate that ALA and/or CAF-CS NPs offered an effective therapy against obesity induced by HFD and its hepatic and renal complications. The therapeutic effect of ALA and CAF-CS NPs could be mediated through their antioxidant and anti-inflammatory properties.

NO-ferroheme is a signaling entity in the vasculature

Despite wide appreciation of the biological role of nitric oxide (NO) synthase (NOS) signaling, questions remain about the chemical nature of NOS-derived bioactivity. Here we show that NO-like bioactivity can be efficiently transduced by mobile NO-ferroheme species, which can transfer between proteins, partition into a hydrophobic phase and directly activate the sGC-cGMP-PKG pathway without intermediacy of free NO. The NO-ferroheme species (with or without a protein carrier) efficiently relax isolated blood vessels and induce hypotension in rodents, which is greatly potentiated after the blockade of NOS activity. While free NO-induced relaxations are abolished by an NO scavenger and in the presence of red blood cells or blood plasma, a model compound, NO-ferroheme-myoglobin preserves its vasoactivity suggesting the physiological relevance of NO-ferroheme species. We conclude that NO-ferroheme behaves as a signaling entity in the vasculature.

Proteomics Studies Suggest That Nitric Oxide Donor Furoxans Inhibit In Vitro Vascular Smooth Muscle Cell Proliferation by Nitric Oxide-Independent Mechanisms

Physiologically, smooth muscle cells (SMC) and nitric oxide (NO) produced by endothelial cells strictly cooperate to maintain vasal homeostasis. In atherosclerosis, where this equilibrium is altered, molecules providing exogenous NO and able to inhibit SMC proliferation may represent valuable antiatherosclerotic agents. Searching for dual antiproliferative and NO-donor molecules, we found that furoxans significantly decreased SMC proliferation in vitro, albeit with different potencies. We therefore assessed whether this property is dependent on their thiol-induced ring opening. Indeed, while furazans (analogues unable to release NO) are not effective, furoxans' inhibitory potency parallels with the electron-attractor capacity of the group in 3 of the ring, making this effect tunable. To demonstrate whether their specific block on G1-S phase could be NO-dependent, we supplemented SMCs with furoxans and inhibitors of GMP- and/or of the polyamine pathway, which regulate NO-induced SMC proliferation, but they failed in preventing the antiproliferative effect. To find the real mechanism of this property, our proteomics studies revealed that eleven cellular proteins (with SUMO1 being central) and networks involved in cell homeostasis/proliferation are modulated by furoxans, probably by interaction with adducts generated after degradation. Altogether, thanks to their dual effect and pharmacological flexibility, furoxans may be evaluated in the future as antiatherosclerotic molecules.

Cathepsin B S-nitrosylation promotes ADAR1-mediated editing of its own mRNA transcript via an ADD1/MATR3 regulatory axis

Genetic information is generally transferred from RNA to protein according to the classic "Central Dogma". Here, we made a striking discovery that post-translational modification of a protein specifically regulates the editing of its own mRNA. We show that S-nitrosylation of cathepsin B (CTSB) exclusively alters the adenosine-to-inosine (A-to-I) editing of its own mRNA. Mechanistically, CTSB S-nitrosylation promotes the dephosphorylation and nuclear translocation of ADD1, leading to the recruitment of MATR3 and ADAR1 to CTSB mRNA. ADAR1-mediated A-to-I RNA editing enables the binding of HuR to CTSB mRNA, resulting in increased CTSB mRNA stability and subsequently higher steady-state levels of CTSB protein. Together, we uncovered a unique feedforward mechanism of protein expression regulation mediated by the ADD1/MATR3/ADAR1 regulatory axis. Our study demonstrates a novel reverse flow of information from the post-translational modification of a protein back to the post-transcriptional regulation of its own mRNA precursor. We coined this process as "Protein-directed EDiting of its Own mRNA by ADAR1 (PEDORA)" and suggest that this constitutes an additional layer of protein expression control. "PEDORA" could represent a currently hidden mechanism in eukaryotic gene expression regulation.

Metabolic Performance and Fate of Electrons during Nitrate-Reducing Fe(II) Oxidation by the Autotrophic Enrichment Culture KS Grown at Different Initial Fe/N Ratios

Autotrophic nitrate-reducing Fe(II)-oxidizing (NRFeOx) microorganisms fix CO2 and oxidize Fe(II) coupled to denitrification, influencing carbon, iron, and nitrogen cycles in pH-neutral, anoxic environments. However, the distribution of electrons from Fe(II) oxidation to either biomass production (CO2 fixation) or energy generation (nitrate reduction) in autotrophic NRFeOx microorganisms has not been quantified. We therefore cultivated the autotrophic NRFeOx culture KS at different initial Fe/N ratios, followed geochemical parameters, identified minerals, analyzed N isotopes, and applied numerical modeling. We found that at all initial Fe/N ratios, the ratios of Fe(II)oxidized to nitratereduced were slightly higher (5.11 to 5.94 at Fe/N ratios of 10:1 and 10:0.5) or lower (4.27 to 4.59 at Fe/N ratios of 10:4, 10:2, 5:2, and 5:1) than the theoretical ratio for 100% Fe(II) oxidation being coupled to nitrate reduction (5:1). The main N denitrification product was N2O (71.88 to 96.29% at Fe/15N ratios of 10:4 and 5:1; 43.13 to 66.26% at an Fe/15N ratio of 10:1), implying that denitrification during NRFeOx was incomplete in culture KS. Based on the reaction model, on average 12% of electrons from Fe(II) oxidation were used for CO2 fixation while 88% of electrons were used for reduction of NO3- to N2O at Fe/N ratios of 10:4, 10:2, 5:2, and 5:1. With 10 mM Fe(II) (and 4, 2, 1, or 0.5 mM nitrate), most cells were closely associated with and partially encrusted by the Fe(III) (oxyhydr)oxide minerals, whereas at 5 mM Fe(II), most cells were free of cell surface mineral precipitates. The genus Gallionella (>80%) dominated culture KS regardless of the initial Fe/N ratios. Our results showed that Fe/N ratios play a key role in regulating N2O emissions, for distributing electrons between nitrate reduction and CO2 fixation, and for the degree of cell-mineral interactions in the autotrophic NRFeOx culture KS. IMPORTANCE Autotrophic NRFeOx microorganisms that oxidize Fe(II), reduce nitrate, and produce biomass play a key role in carbon, iron, and nitrogen cycles in pH-neutral, anoxic environments. Electrons from Fe(II) oxidation are used for the reduction of both carbon dioxide and nitrate. However, the question is how many electrons go into biomass production versus energy generation during autotrophic growth. Here, we demonstrated that in the autotrophic NRFeOx culture KS cultivated at Fe/N ratios of 10:4, 10:2, 5:2, and 5:1, ca. 12% of electrons went into biomass formation, while 88% of electrons were used for reduction of NO3- to N2O. Isotope analysis also showed that denitrification during NRFeOx was incomplete in culture KS and the main N denitrification product was N2O. Therefore, most electrons stemming from Fe(II) oxidation seemed to be used for N2O formation in culture KS. This is environmentally important for the greenhouse gas budget.

Role of antioxidants in fertility preservation of sperm - A narrative review

Male fertility is affected by multiple endogenous stressors, including reactive oxygen species (ROS), which greatly deteriorate the fertility. However, physiological levels of ROS are required by sperm for the proper accomplishment of different cellular functions including proliferation, maturation, capacitation, acrosomal reaction, and fertilization. Excessive ROS production creates an imbalance between ROS production and neutralization resulting in oxidative stress (OS). OS causes male infertility by impairing sperm functions including reduced motility, deoxyribonucleic acid damage, morphological defects, and enhanced apoptosis. Several in-vivo and in-vitro studies have reported improvement in quality-related parameters of sperm following the use of different natural and synthetic antioxidants. In this review, we focus on the causes of OS, ROS production sources, mechanisms responsible for sperm damage, and the role of antioxidants in preserving sperm fertility.

3,3'-Diselenodipropionic acid immobilised gelatin gel: a biomimic catalytic nitric oxide generating material for topical wound healing application

Nitric oxide (NO) plays a pivotal role in the wound healing process and promotes the generation of healthy endothelium. In this work, a simple method has been developed for fabricating a diselenide grafted gelatin gel, which reduces NO donors such as S-nitroso-N-acetylpenicillamine (SNAP) by glutathione peroxidase-like mechanism to produce NO. Briefly, the process involved covalently conjugating 3,3'-diselenodipropionic acid (DSePA) with gelatin via carbodiimide coupling. The resulting gelatin-DSePA conjugate (G-Se-Se-G) demonstrated NO production upon incubation with SNAP and glutathione (GSH) with the flux of 4.8 ± 0.6 nmol cm^-2 min^-1 and 1.6 ± 0.1 nmol cm^-2 min^-1 at 10 min and 40 min, respectively. The G-Se-Se-G recovered even after 5 days of incubation with the reaction mixture retaining catalytic activity up to 74%. Subsequently, G-Se-Se-G was suspended (5% w/v) in water with lecithin (6% w/w of gelatin) and F127 (3% w/w of gelatin) to prepare gel through temperature dependant gelation method. The fabricated G-Se-Se-G gel exhibited desirable rheological characteristics and excellent mechanical stability under storage conditions and did not cause any significant toxicity in normal human keratinocytes (HaCaT) and fibroblast cells (WI38) up to 50 μg ml^-1 of selenium equivalent. Finally, mice studies confirmed that topically applied G-Se-Se-G gel and SNAP promoted faster epithelization and collagen deposition at the wound site. In conclusion, the development of a biomimetic NO generating gel with sustained activity and biocompatibility was achieved.

A ruthenium nitrosyl complex-based highly selective colorimetric sensor for biological H2S and H2S-NO cross-talk regulated release of NO

A ruthenium nitrosyl complex (1·NO) and 1·NO incorporated phospholipid-based liposomes (Lip-1·NO) were reported for highly selective colorimetric detection of H₂S. The probe 1·NO "cross-talks" with H₂S and releases nitric oxide (NO) in the process. The detection limit for H₂S was found to be 0.31 μM and 0.45 μM in the cases of 1·NO and Lip-1·NO, respectively. The DAF-FM DA assay has been performed to confirm the H₂S-induced NO release from 1·NO and Lip-1·NO. The sensing of H₂S was also verified by ESI-MS and FT-IR spectroscopy. It was also observed that external stimuli, H₂S and light worked in an almost similar way to release NO as observed by UV-Vis spectroscopy. A molecular logic gate operation "OR" was applied to the probe 1·NO in combination with inputs 'light' and 'H₂S' to give the output 'NO release'. Hence, the probe 1·NO performs the dual work of sensing H₂S with a colorimetric response, releasing NO upon cross-talk between NO and H₂S.

Unraveling signatures of chicken genetic diversity and divergent selection in breed-specific patterns of early myogenesis, nitric oxide metabolism and post-hatch growth

Introduction: Due to long-term domestication, breeding and divergent selection, a vast genetic diversity in poultry currently exists, with various breeds being characterized by unique phenotypic and genetic features. Assuming that differences between chicken breeds divergently selected for economically and culturally important traits manifest as early as possible in development and growth stages, we aimed to explore breed-specific patterns and interrelations of embryo myogenesis, nitric oxide (NO) metabolism and post-hatch growth rate (GR). Methods: These characteristics were explored in eight breeds of different utility types (meat-type, dual purpose, egg-type, game, and fancy) by incubating 70 fertile eggs per breed. To screen the differential expression of seven key myogenesis associated genes (MSTN, GHR, MEF2C, MYOD1, MYOG, MYH1, and MYF5), quantitative real-time PCR was used. Results: We found that myogenesis associated genes expressed in the breast and thigh muscles in a coordinated manner showing breed specificity as a genetic diversity signature among the breeds studied. Notably, coordinated ("accord") expression patterns of MSTN, GHR, and MEFC2 were observed both in the breast and thigh muscles. Also, associated expression vectors were identified for MYOG and MYOD1 in the breast muscles and for MYOG and MYF5 genes in the thigh muscles. Indices of NO oxidation and post-hatch growth were generally concordant with utility types of breeds, with meat-types breeds demonstrating higher NO oxidation levels and greater GR values as compared to egg-type, dual purpose, game and fancy breeds. Discussion: The results of this study suggest that differences in early myogenesis, NO metabolism and post-hatch growth are breed-specific; they appropriately reflect genetic diversity and accurately capture the evolutionary history of divergently selected chicken breeds.

Hydrogen sulfide and nitric oxide regulate the adaptation to iron deficiency through affecting Fe homeostasis and thiol redox modification in Glycine max seedlings

Iron (Fe) is a vital microelement required for the growth and development of plants. Hydrogen sulfide (H₂S) and nitric oxide (NO), as messenger molecules, participated in the regulation of plant physiological processes. Here, we studied the interaction effects of H₂S and NO on the adaptation to Fe deficiency in Glycine max L. Physiological, biochemical and molecular approaches were conducted to analyze the role of H₂S and NO in regulating the adaptation to Fe deficiency in soybean. We found that H₂S and NO had obvious rescuing function on the Fe deficiency-induced the plant growth inhibition, which was significantly correlated with the increase in Fe content in the leaves, stems, and roots of soybean. Meanwhile, H⁺-flux, ferric chelate reductase (FCR) activity, and root apoplast Fe content were significantly affected by H₂S and NO. Under Fe deficiency conditions NO and H₂S regulated the expression of genes related to Fe homeostasis. Moreover, photosynthesis (Pn) and photosystem II (PSII) efficiency were enhanced by H₂S and NO, and thiol redox modification was important for regulating the adaptation of Fe deficiency. The aforementioned affirmative influences caused by H₂S and NO were also totally reversed by cPTIO (a NO scavenger). Our results suggested that H₂S might act upstream of NO in response to Fe deficiency by affecting the Fe homeostasis enzyme activities and gene expression, and by promoting Fe accumulation in plant tissues as well as by enhancing thiol redox modification and photosynthesis in soybean plants.

ROS and RNS Alterations in the Digestive Fluid of Nepenthes × ventrata Trap at Different Developmental Stages

The carnivorous pitcher plant, Nepenthes × ventrata (Hort. ex Fleming = N. ventricosa Blanco × N. alata Blanco), produces passive traps containing digestive fluid. Although reactive oxygen species (ROS) in the fluid were detected in some pitcher plants, the participation of reactive nitrogen species (RNS) in the digestion process has not yet been examined. The aim of this work was to investigate the production of superoxide anion (O2•-), nitric oxide (NO) and peroxynitrite (ONOO-) levels in the digestive fluid of traps throughout organ development. We revealed the ROS and RNS occurrence in the digestive fluid, linked to the ROS-scavenging capacity and total phenolics content. In digestive fluid from the fed traps, NO emission was higher than in the fluid from the developed unfed pitcher. The concentration of nitrite (NO2-) decreased in the fluid from the fed traps in comparison to the unfed ones, pointing at NO2- as the key source of NO. The enhanced emission of NO was associated with lowered content of ONOO- in the fluid, probably due to lower production of O2•-. At the same time, despite a decline in total phenolics, the maximum ROS scavenging capacity was detected. In addition, ROS and RNS were noted even in closed traps, suggesting their involvement not only in digestion per se but also their action as signaling agents in trap ontogeny.

Synthesis, Biophysical Interaction of DNA/BSA, Equilibrium and Stopped-Flow Kinetic Studies, and Biological Evaluation of bis(2-Picolyl)amine-Based Nickel(II) Complex

Reaction of bis(2-picolyl)amine (BPA) with Ni(II) salt yielded [(BPA)NiCl2(H2O)] (NiBPA). The Ni(II) in NiBPA bound to a BPA ligand, two chloride, and one aqua ligands. Because most medications inhibit biological processes by binding to a specific protein, the stopped-flow technique was used to investigate DNA/protein binding in-vitro, and a mechanism was proposed. NiBPA binds to DNA/protein more strongly than BPA via a static quenching mechanism. Using the stopped-flow technique, a mechanism was proposed. BSA interacts with BPA via a fast reversible step followed by a slow irreversible step, whereas NiBPA interacts via two reversible steps. DNA, on the other hand, binds to BPA and NiBPA via the same mechanism through two reversible steps. Although BSA interacts with NiBPA much faster, NiBPA has a much higher affinity for DNA (2077 M) than BSA (30.3 M). Compared to NiBPA, BPA was found to form a more stable BSA complex. When BPA and NiBPA bind to DNA, the Ni(II) center was found to influence the rate but not the mechanism, whereas, for BSA, the Ni(II) center was found to change both the mechanism and the rate. Additionally, NiBPA exhibited significant cytotoxicity and antibacterial activity, which is consistent with the binding constants but not the kinetic stability. This shows that in our situation, biological activity is significantly more influenced by binding constants than by kinetic stability. Due to its selectivity and cytotoxic activity, complex NiBPA is anticipated to be used in medicine.

Selective gene expression profiling contributes to a better understanding of the molecular pathways underlying the histological changes observed after RHMVL

Background

In previous studies, five vasoactive drugs were investigated for their effect on the recovery process after extended liver resection without observing relevant improvements. We hypothesized that an analysis of gene expression could help to identify potentially druggable pathways and could support the selection of promising drug candidates.

Methods

Liver samples obtained from rats after combined 70% partial hepatectomy and right median hepatic vein ligation (n = 6/group) sacrificed at 0 h, 24 h, 48 h, and 7days were selected for this study. Liver samples were collected from differentially perfused regions of the median lobe (obstruction-zone, border-zone, normal-zone). Gene expression profiling of marker genes regulating hepatic hemodynamics, vascular remodeling, and liver regeneration was performed with microfluidic chips. We used 3 technical replicates from each sample. Raw data were normalized using LEMming and differentially expressed genes were identified using LIMMA.

Results

The strongest differences were found in obstruction-zone at 24 h and 48 h postoperatively compared to all other groups. mRNA expression of marker genes from hepatic hemodynamics pathways (iNOS,Ptgs2,Edn1) was most upregulated.

Conclusion

These upregulated genes suggest a strong vasoconstrictive effect promoting arterial hypoperfusion in the obstruction-zone. Reducing iNOS expression using selective iNOS inhibitors seems to be a promising approach to promote vasodilation and liver regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01364-z.

Stereoselective Synthesis of Benzo[a]quinolizidines via Aerobic DDQ-Catalyzed Allylation and Reductive Cyclization

Stereoselective synthesis of C₄-substituted benzo[a]quinolizidines via redox-controlled catalytic C-C-bond-forming reactions was carried out. Aerobic DDQ-catalyzed allylation of N-Cbz tetrahydroisoquinolines efficiently provided α-allylated products 5, which were transformed to enones 6 via cross-metathesis reactions using the second-generation Hoveyda-Grubbs catalyst. Palladium-catalyzed hydrogenation of 6 prompted alkene reduction, protecting group removal, and intramolecular reductive amination in one step to afford the desired benzo[a]quinolizidines 7 as single diastereomers.

Phosphatidic acid binds to and stimulates the activity of ARGAH2 from Arabidopsis

Phosphatidic acid (PA) has emerged as an important lipid signal during abiotic and biotic stress conditions such as drought, salinity, freezing, nutrient starvation, wounding and microbial elicitation. PA acts during stress responses primarily via binding and translocating target proteins or through modulating their activity. Owing to the importance of PA during stress signaling and developmental stages, it is imperative to identify PA interacting proteins and decipher their specific roles. In the present study, we have identified PA binding proteins from the leaves of Arabidopsis thaliana. Mass spectroscopy analysis led to the identification of 21 PA binding proteins with known roles in various cellular processes. One of the PA-binding proteins identified during this study, AtARGAH2, was further studied to unravel the role of PA interaction. Recombinant AtARGAH2 binding with immobilized PA on a solid support validated PA-AtARGAH2 binding invitro. PA binding to AtARGAH2 leads to the enhancement of arginase enzymatic activity in a dose dependent manner. Enzyme kinetics of recombinant AtARGAH2 demonstrated a lower K_m value in presence of PA, suggesting role of PA in efficient enzyme-substrate binding. This simple approach could systematically be applied to perform an inclusive study on lipid binding proteins to elucidate their role in physiology of plants.

Stimulation of Akt Phosphorylation and Glucose Transport by Metalloporphyrins with Peroxynitrite Decomposition Catalytic Activity

Iron porphyrin molecules such as hemin and iron(III) 4,4′,4″,4‴-(porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid) (FeTBAP) have previously been shown to influence insulin signaling and glucose metabolism. We undertook this study to determine whether a catalytic action of iron porphyrin compounds would be related to their stimulation of insulin signaling and glucose uptake in C2C12 myotubes. FeTBAP did not display nitrite reductase activity or alter protein S-nitrosylation in myotubes, eliminating this as a candidate mode by which FeTBAP could act. FeTBAP displayed peroxynitrite decomposition catalytic activity in vitro. Additionally, in myotubes FeTBAP decreased protein nitration. The peroxynitrite decomposition catalyst Fe(III)5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato chloride (FeTPPS) also decreased protein nitration in myotubes, but the iron porphyrin Fe(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachlorideporphyrin pentachloride (FeTMPyP) did not. FeTBAP and FeTPPS, but not FeTMPyP, showed in vitro peroxidase activity. Further, FeTBAP and FeTPPs, but not FeTMPyP, increased Akt phosphorylation and stimulated glucose uptake in myotubes. These findings suggest that iron porphyrin compounds with both peroxynitrite decomposition activity and peroxidase activity can stimulate insulin signaling and glucose transport in skeletal muscle cells.

Inhaled nitric oxide: role in the pathophysiology of cardio-cerebrovascular and respiratory diseases

Nitric oxide (NO) is a key molecule in the biology of human life. NO is involved in the physiology of organ viability and in the pathophysiology of organ dysfunction, respectively. In this narrative review, we aimed at elucidating the mechanisms behind the role of NO in the respiratory and cardio-cerebrovascular systems, in the presence of a healthy or dysfunctional endothelium. NO is a key player in maintaining multiorgan viability with adequate organ blood perfusion. We report on its physiological endogenous production and effects in the circulation and within the lungs, as well as the pathophysiological implication of its disturbances related to NO depletion and excess. The review covers from preclinical information about endogenous NO produced by nitric oxide synthase (NOS) to the potential therapeutic role of exogenous NO (inhaled nitric oxide, iNO). Moreover, the importance of NO in several clinical conditions in critically ill patients such as hypoxemia, pulmonary hypertension, hemolysis, cerebrovascular events and ischemia-reperfusion syndrome is evaluated in preclinical and clinical settings. Accordingly, the mechanism behind the beneficial iNO treatment in hypoxemia and pulmonary hypertension is investigated. Furthermore, investigating the pathophysiology of brain injury, cardiopulmonary bypass, and red blood cell and artificial hemoglobin transfusion provides a focus on the potential role of NO as a protective molecule in multiorgan dysfunction. Finally, the preclinical toxicology of iNO and the antimicrobial role of NO-including its recent investigation on its role against the Sars-CoV2 infection during the COVID-19 pandemic-are described.

The enzymatic function of the honorary enzyme: S-nitrosylation of hemoglobin in physiology and medicine

The allosteric transition within tetrameric hemoglobin (Hb) that allows both full binding to four oxygen molecules in the lung and full release of four oxygens in hypoxic tissues would earn Hb the moniker of 'honorary enzyme'. However, the allosteric model for oxygen binding in hemoglobin overlooked the essential role of blood flow in tissue oxygenation that is essential for life (aka autoregulation of blood flow). That is, blood flow, not oxygen content of blood, is the principal determinant of oxygen delivery under most conditions. With the discovery that hemoglobin carries a third biologic gas, nitric oxide (NO) in the form of S-nitrosothiol (SNO) at β-globin Cys93 (βCys93), and that formation and export of SNO to dilate blood vessels are linked to hemoglobin allostery through enzymatic activity, this title is honorary no more. This chapter reviews evidence that hemoglobin formation and release of SNO is a critical mediator of hypoxic autoregulation of blood flow in tissues leading to oxygen delivery, considers the physiological implications of a 3-gas respiratory cycle (O2/NO/CO2) and the pathophysiological consequences of its dysfunction. Opportunities for therapeutic intervention to optimize oxygen delivery at the level of tissue blood flow are highlighted.

Understanding the Performance of Metal-Organic Frameworks for Modulation of Nitric oxide Release from S-nitrosothiols

S-Nitrosothiols (RSNOs) which were important intermediates in circulating reservoirs of nitric oxide (NO), transport and numerous NO signaling pathway plays intricate roles in the etiology of several pathologies. However, it is still a challenge to control release of NO from nitrosylated compounds under physiological pH. In this paper, for the first time, we report the catalytic activity and kinetic study for modulation of NO release from RSNOs by an array of metal-organic frameworks (MOFs) (M-MOF (M'); M = Zr, Cu; and M' = Cu, Pd, no metal) under physiological conditions via time-dependent absorbance spectra. The result showed that metal active site and the morphology and pore size of MOFs exhibited different activities toward RSNOs. The order of catalytic activity of these MOFs toward RSNOs is ordered in the decreasing sequence: Cu-MOF(Pd) ˃ Cu-MOF(Cu) ˃ Cu-MOF(no metal) ˃ Zr-MOF(Pd) ˃ Zr-MOF(Cu) ˃ Zr-MOF(no metal). In addition, Zr-MOF(Pd) was as model for cell experiment, demonstrated Zr-MOF(Pd) could react with RSNOs to generate NO in the complex environment of cell. Collectively, these findings establish a platform for MOFs-based, highly catalyze RSNOs in biological samples, a powerful tool for expanding the knowledge of the biology and chemistry of NO-mediated phenomena.

Photolytic Measurement of Tissue S-Nitrosothiols in Rats and Humans In Vivo

S-nitrosothiols are labile thiol-NO adducts formed in vivo primarily by metalloproteins such as NO synthase, ceruloplasmin, and hemoglobin. Abnormal S-nitrosothiol synthesis and catabolism contribute to many diseases, ranging from asthma to septic shock. Current methods for quantifying S-nitrosothiols in vivo are suboptimal. Samples need to be removed from the body for analysis, and the S-nitrosothiols can be broken down during ex vivo processing. Here, we have developed a noninvasive device to measure mammalian tissue S-nitrosothiols in situ non-invasively using ultraviolet (UV) light, which causes NO release in proportion to the S-nitrosothiol concentration. We validated the assay in vitro; then, we applied it to measure S-nitrosothiols in vivo in rats and in humans. The method was sensitive to 0.5 µM, specific (did not detect other nitrogen oxides), and was reproducible in rats and in humans. This noninvasive approach to S-nitrosothiol measurements may be applicable for use in human diseases.