Nitric Oxide Signaling Pathway Research Articles

L-Arginine enhanced perylenequinone production in the endophytic fungus Shiraia sp. Slf14(w) via NO signaling pathway.

Perylenequinones (PQ) are natural polyketides used as anti-microbial, -cancers, and -viral photodynamic therapy agents. Herein, the effects of L-arginine (Arg) on PQ biosynthesis of Shiraia sp. Slf14(w) and the underlying molecular mechanism were investigated. The total content of PQ reached 817.64 ± 72.53mg/L under optimal conditions of Arg addition, indicating a 30.52-fold improvement over controls. Comparative transcriptome analysis demonstrated that Arg supplement promoted PQ precursors biosynthesis of Slf14(w) by upregulating the expression of critical genes associated with the glycolysis pathway, and acetyl-CoA and malonyl-CoA synthesis. By downregulating the expression of genes related to the glyoxylate cycle pathway and succinate dehydrogenase, more acetyl-CoA flow into the formation of PQ. Arg supplement upregulated the putative biosynthetic gene clusters for PQ and activated the transporter proteins (MFS and ABC) for exudation of PQ. Further studies showed that Arg increased the gene transcription levels of nitric oxide synthase (NOS) and nitrate reductase (NR), and activated NOS and NR, thus promoting the formation of nitric oxide (NO). A supplement of NO donor sodium nitroprusside (SNP) also confirmed that NO triggered promoted biosynthesis and efflux of PQ. PQ production stimulated by Arg or/and SNP can be significantly inhibited upon the addition of NO scavenger carboxy-PTIO, NOS inhibitor Nω-nitro-L-arginine, or soluble guanylate cyclase inhibitor NS-2028. These results showed that Arg-derived NO, as a signaling molecule, is involved in the biosynthesis and regulation of PQ in Slf14(W) through the NO-cGMP-PKG signaling pathway. Our results provide a valuable strategy for large-scale PQ production and contribute to further understanding of NO signaling in the fungal metabolite biosynthesis. KEY POINTS: • PQ production of Shiraia sp. Slf14(w) was significantly improved by L-arginine addition. • Arginine-derived NO was firstly reported to be involved in the biosynthesis and regulation of PQ. • The NO-cGMP-PKG signaling pathway was proposed for the first time to participate in PQ biosynthesis.

Structure-activity relationships of oomycete elicitins uncover the role of reactive oxygen and nitrogen species in triggering plant defense responses

Elicitins are proteinaceous elicitors that induce the hypersensitive response and plant resistance against diverse phytopathogens. Elicitin recognition by membrane receptors or high-affinity sites activates a variety of fast responses including the production of reactive oxygen species (ROS) and nitric oxide (NO), leading to induction of plant defense genes. Beta-cryptogein (CRY) is a basic β-elicitin secreted by the oomycete Phytophthora cryptogea that shows high necrotic activity in some plant species, whereas infestin 1 (INF1) secreted by the oomycete P. infestans belongs to acidic α-elicitins with a significantly weaker capacity to induce necrosis. We compared several mutated forms of β-CRY and INF1 with a modulated capacity to trigger ROS and NO production, bind plant sterols and induce cell death responses in cell cultures of Nicotiana tabacum L. cv. Xanthi. We evidenced a key role of the lysine residue in position 13 in basic elicitins for their biological activity and enhancement of necrotic effects of acidic INF1 by the replacement of the valine residue in position 84 by larger phenylalanine. Studied elicitins activated in differing intensity signaling pathways of ROS, NO and phytohormones jasmonic acid, ethylene and salicylic acid, known to be involved in triggering of hypersensitive response and establishment of systemic resistance.

Understanding the Performance of Metal-Organic Frameworks for Modulation of Nitric Oxide Release from S-Nitrosothiols.

S-Nitrosothiols (RSNOs) which are important intermediates in circulating reservoirs of nitric oxide (NO), transport and numerous NO signaling pathways play intricate roles in the etiology of several pathologies. However, it is still a challenge to control the 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 the 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 sites as well as 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.

Nitric oxide signaling pathway in medicinal plants

Nitrogen monoxide or nitric oxide is a biological active growth regulator that a wide range of studies have recently shown that it acts as a growth regulator (signaling molecule) in plants. As soon as Nitric Oxide (NO) known as a new biological agent in plants and animals, biological branches of sciences like medicine, biochemistry, physiology and genetics have paid special attention to it. NO is a very reactive gas shape free radical which has attracted much attention during recent years. This compound is produced by the plant and it has increased the shelf life of some fruits, vegetables and cut flowers in low concentrations. NO is mostly synthesized from enzymatic and non-enzymatic pathways whose enzymatic biosynthesis pathway is done by reductase nitrate biosynthesis pathway through the cytosol, also it is known as an important and very reactive signaling molecule with short life which is produced by a group of enzymes known as synthesize NO which transforms L-arginine to L-citrulline and NO. It has been revealed that plants use NO as a growth regulator which regulates and modifies antimicrobial defensive responses. Recently, it has been approved that this material plays a vital role in regulating the normal physiological activities of plants such as pores closing, aging, increasing the vase life of cut flowers after harvesting, respiration and photosynthesis, antioxidant enzymes activities and growth.

SMA-BmobaSNO: an intelligent photoresponsive nitric oxide releasing polymer for drug nanoencapsulation and targeted delivery

Nitric oxide (NO) is an important biological signalling molecule that acts to vasodilate blood vessels and change the permeability of the blood vessel wall. Due to these cardiovascular actions, co-administering NO with a therapeutic could enhance drug uptake. However current NO donors are not suitable for targeted drug delivery as they systemically release NO. To overcome this limitation we report the development of a smart polymer, SMA-BmobaSNO, designed to release NO in response to a photostimulus. The polymer’s NO releasing functionality is an S-nitrosothiol group that, at 10 mg ml−1, is highly resistant to both thermal (t 1/2 16 d) and metabolic (t 1/2 32 h) decomposition, but rapidly brakes down under photoactivation (2700 W m−2, halogen source) to release NO (t 1/2 25 min). Photoresponsive NO release from SMA-BmobaSNO was confirmed in a cardiovascular preparation, where irradiation resulted in a 12-fold decrease in vasorelaxation EC50 (from 5.2 μM to 420 nM). To demonstrate the polymer’s utility for drug delivery we then used SMA-BmobaSNO to fabricate a nanoparticle containing the probe Nile Red (NR). The resulting SMA-BmobaSNO-NR nanoparticle exhibited spherical morphology (180 nm diameter) and sustained NR release (≈20% over 5 d). Targeted delivery was characterised in an abdominal preparation, where photoactivation (450 W m−2) caused localized increases in vasodilation and blood vessel permeability, resulting in a 3-fold increase in NR uptake into photoactivated tissue. Nanoparticles fabricated from SMA-BmobaSNO therefore display highly photoresponsive NO release and can apply the Trojan Horse paradigm by using endogenous NO signalling pathways to smuggle a therapeutic cargo into target tissue.

Resveratrol Relaxes Human Gastric Smooth Muscles Through High Conductance Calcium-Activated Potassium Channel in a Nitric Oxide-independent Manner.

Resveratrol, as a polyphenolic compound that can be isolated from plants, and also a component of red wine has broad beneficial pharmacological properties. The aim was to investigate the role of nitric oxide and potassium channels in resveratrol-induced relaxation of human gastric smooth muscle. Gastric tissues were obtained from patients who underwent sleeve gastrectomy for severe obesity (n = 10 aged 21–48; BMI 48.21 ± 1.14). The mechanical activity from the muscle strips was detected under isometric conditions as the response to increasing concentrations of resveratrol before and after different pharmacological treatments. Resveratrol caused an observable, dose-dependent gastric muscle relaxation. The maximal response caused by the highest concentration of resveratrol was 83.49 ± 2.85% (p < 0.0001) of the control. Preincubation with L-NNA, L-NAME, or ODQ did not prevent the resveratrol-induced relaxation. Apamin, glibenclamide, 4AP or tamoxifen, did not inhibit the relaxing effect of resveratrol, as well. In turn, blocking BKCa by TEA, iberiotoxin, or charybdotoxin resulted in inhibition of resveratrol-induced relaxation (91.08 ± 2.07, p < 0.05; 95.60 ± 1.52, p < 0.01 and 89.58 ± 1.98, p < 0.05, respectively). This study provides the first observation that the relaxant effects of resveratrol in human gastric muscle strips occur directly through BKCa channels and independently of nitric oxide signaling pathways. Furthermore, there is considerable potential for further extensive clinical studies with resveratrol as an effective new drug or health supplement to treat gastrointestinal dyspepsia and other gastric hypermotility disorders.

Acutely applied melatonin prevents CCl4-induced testicular lesions in rats: the involvement of the oxidative capacity and arginine metabolism

Carbon tetrachloride (CCl4) represents an organic chemical that causes reactive oxygen species derived organ disturbances including male infertility. Melatonin (MLT) is a neurohormone with strong antioxidant capacity, involved in numerous physiological processes. In this study we evaluated the capability of MLT, administered in a single dose of 50 mg/kg, to preserve the testicular tissue function after an acute administration of CCl4 to rats. The disturbance in testicular tissue and the effects of MLT after CCl4 exposure were estimated using biochemical parameters that enabled us to determine the tissue (anti)oxidant status and the intensity of arginine/nitric oxide metabolism. Also, the serum levels of testosterone and the histopathological analysis of tissue gave us a better insight into the occurring changes. A significant diminution in tissue antioxidant defences, arginase activity and serum testosterone levels, followed by the increased production of nitric oxide and extensive lipid and protein oxidative damage, was observed in the CCl4-treated group. The application of MLT after the CCl4 caused changes, clearly visible at both biochemical and histological level, which could be interpreted mainly as a consequence of general antioxidant system stimulation and a radical scavenger. On the other hand, the application of MLT exerted a limited action on the nitric oxide signalling pathway.

Expression GWAS of PGIP1 Identifies STOP1-Dependent and STOP1-Independent Regulation of PGIP1 in Aluminum Stress Signaling in Arabidopsis.

To elucidate the unknown regulatory mechanisms involved in aluminum (Al)-induced expression of POLYGALACTURONASE-INHIBITING PROTEIN 1 (PGIP1), which is one of the downstream genes of SENSITIVE TO PROTON RHIZOTOXICITY 1 (STOP1) regulating Al-tolerance genes, we conducted a genome-wide association analysis of gene expression levels (eGWAS) of PGIP1 in the shoots under Al stress using 83 Arabidopsis thaliana accessions. The eGWAS, conducted through a mixed linear model, revealed 17 suggestive SNPs across the genome having the association with the expression level variation in PGIP1. The GWAS-detected SNPs were directly located inside transcription factors and other genes involved in stress signaling, which were expressed in response to Al. These candidate genes carried different expression level and amino acid polymorphisms. Among them, three genes encoding NAC domain-containing protein 27 (NAC027), TRX superfamily protein, and R-R-type MYB protein were associated with the suppression of PGIP1 expression in their mutants, and accordingly, the system affected Al tolerance. We also found the involvement of Al-induced endogenous nitric oxide (NO) signaling, which induces NAC027 and R-R-type MYB genes to regulate PGIP1 expression. In this study, we provide genetic evidence that STOP1-independent NO signaling pathway and STOP1-dependent regulation in phosphoinositide (PI) signaling pathway are involved in the regulation of PGIP1 expression under Al stress.

Mathematical Modeling of Severe Acute Respiratory Syndrome Coronavirus 2 Infection Network with Cytokine Storm, Oxidative Stress, Thrombosis, Insulin Resistance, and Nitric Oxide Pathways.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is a systemic disease affecting not only the lungs but also multiple organ systems. Clinical studies implicate that SARS-CoV-2 infection causes imbalance of cellular homeostasis and immune response that trigger cytokine storm, oxidative stress, thrombosis, and insulin resistance. Mathematical modeling can offer in-depth understanding of the SARS-CoV-2 infection and illuminate how subcellular mechanisms and feedback loops underpin disease progression and multiorgan failure. We report here a mathematical model of SARS-CoV-2 infection pathway network with cytokine storm, oxidative stress, thrombosis, insulin resistance, and nitric oxide (NO) pathways. The biochemical systems theory model shows autocrine loops with positive feedback enabling excessive immune response, cytokines, transcription factors, and interferons, which can imbalance homeostasis of the system. The simulations suggest that changes in immune response led to uncontrolled release of cytokines and chemokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor α (TNFα), and affect insulin, coagulation, and NO signaling pathways. Increased production of NETs (neutrophil extracellular traps), thrombin, PAI-1 (plasminogen activator inhibitor-1), and other procoagulant factors led to thrombosis. By analyzing complex biochemical reactions, this model forecasts the key intermediates, potential biomarkers, and risk factors at different stages of COVID-19. These insights can be useful for drug discovery and development, as well as precision treatment of multiorgan implications of COVID-19 as seen in systems medicine.

Vascular Dysfunction in Malaria: Understanding the Role of the Endothelial Glycocalyx.

Malaria caused by Plasmodium falciparum results in over 400,000 deaths annually, predominantly affecting African children. In addition, non-falciparum species including vivax and knowlesi cause significant morbidity and mortality. Vascular dysfunction is a key feature in malaria pathogenesis leading to impaired blood perfusion, vascular obstruction, and tissue hypoxia. Contributing factors include adhesion of infected RBC to endothelium, endothelial activation, and reduced nitric oxide formation. Endothelial glycocalyx (eGC) protects the vasculature by maintaining vessel integrity and regulating cellular adhesion and nitric oxide signaling pathways. Breakdown of eGC is known to occur in infectious diseases such as bacterial sepsis and dengue and is associated with adverse outcomes. Emerging studies using biochemical markers and in vivo imaging suggest that eGC breakdown occurs during Plasmodium infection and is associated with markers of malaria disease severity, endothelial activation, and vascular function. In this review, we describe characteristics of eGC breakdown in malaria and discuss how these relate to vascular dysfunction and adverse outcomes. Further understanding of this process may lead to adjunctive therapy to preserve or restore damaged eGC and reduce microvascular dysfunction and the morbidity/mortality of malaria.

Antioxidant Properties of Hydrogen Gas Attenuates Oxidative Stress in Airway Epithelial Cells.

Oxidative stress plays a crucial role in the development of airway diseases. Recently, hydrogen (H2) gas has been explored for its antioxidant properties. This study investigated the role of H2 gas in oxidative stress-induced alveolar and bronchial airway injury, where A549 and NCI-H292 cells were stimulated with hydrogen peroxide (H2O2) and lipopolysaccharide (LPS) in vitro. Results show that time-dependent administration of 2% H2 gas recovered the cells from oxidative stress. Various indicators including reactive oxygen species (ROS), nitric oxide (NO), antioxidant enzymes (catalase, glutathione peroxidase), intracellular calcium, and mitogen-activated protein kinase (MAPK) signaling pathway were examined to analyze the redox profile. The viability of A549 and NCI-H292 cells and the activity of antioxidant enzymes were reduced following induction by H2O2 and LPS but were later recovered using H2 gas. Additionally, the levels of oxidative stress markers, including ROS and NO, were elevated upon induction but were attenuated after treatment with H2 gas. Furthermore, H2 gas suppressed oxidative stress-induced MAPK activation and maintained calcium homeostasis. This study suggests that H2 gas can rescue airway epithelial cells from H2O2 and LPS-induced oxidative stress and may be a potential intervention for airway diseases.

Cholecystokinin acts in the dorsomedial hypothalamus of young male rats to suppress appetite in a nitric oxide-dependent manner

Cholecystokinin (CCK) is an appetite-suppressing hormone that acts in the dorsomedial hypothalamus (DMH) in adult rats to suppress food intake. It remains unknown, however, whether CCK has the same affect in young animals, despite the rising prevalence of childhood obesity and drastic need for research in this area. At the synaptic level, CCK has been shown to inhibit putative orexigenic DMH neurons in young male rats by increasing GABA release onto these neurons via a CCK2 receptor and nitric oxide-dependent pathway. Whether this pathway leads to appetite suppression in young rats is not known. We therefore investigated whether intra-DMH administration of CCK, with or without inhibitors of the CCK2 receptor and nitric oxide signaling pathways, affects food intake in young, male, fasted Sprague-Dawley rats. We implanted bilateral guide cannulas into the DMH and allowed animals to recover from the surgery. Animals were then fasted for 24 h, following which they received intra-DMH microinjections of vehicle, CCK-8S, or CCK-8S combined with either LY-225910 (CCK2 receptor antagonist), L-NAME (a nitric oxide synthase inhibitor), or ODQ (a soluble guanylate cyclase inhibitor) and were given access to regular chow. Following a two hour refeeding period during which food intake, latency to feed, and body weight were measured, brains were subsequently removed to confirm cannula placement in the DMH. The effect of CCK on these parameters in rats given a high fat diet were also measured. Here we show that intra-DMH administration of CCK suppresses food intake and body weight in young rats. This effect requires activation of CCK2 receptors and nitric oxide signaling. Finally, CCK has no effect on consumption of a high fat diet when administered into the DMH. Overall, these findings demonstrate a potential pathway through which CCK might suppress appetite in young rats.

Comparison of P25 and nanobelts on Kruppel-like factor-mediated nitric oxide pathways in human umbilical vein endothelial cells.

Recently, we reported that titanium dioxide (TiO2 ) materials activated endothelial cells via Kruppel-like factor (KLF)-mediated nitric oxide (NO) dysfunction, but the roles of physical properties of materials are not clear. In this study, we prepared nanobelts from P25 particles and compared their adverse effects to human umbilical vein endothelial cells (HUVECs). TiO2 nanobelts had belt-like morphology but comparable surface areas as P25 particles. When applied to HUVECs, P25 particles or nanobelts did not induce cytotoxicity, although nanobelts were much more effective to increase intracellular Ti element concentrations compared the same amounts of P25 particles. Only nanobelts significantly induced THP-1 adhesion onto HUVECs. Consistently, nanobelts were more significant to induce the expression of intracellular adhesion molecule-1 (ICAM1) and the release of soluble ICAM-1 (sICAM-1), indicating that nanobelts were more potent to induce endothelial activation in vitro. As the mechanisms for endothelial activation, both P25 and nanobelts reduced the generation of intracellular NO as well as the expression of NO regulators KLF2 and KLF4. Combined, the results from this study indicated that the different morphologies of P25 particles and nanobelts only changed their internalization into HUVECs but showed minimal impact on KLF-mediated NO signaling pathways.

Nitric Oxide Signaling Pathway in Ventral Tegmental Area is Involved in Regulation of 7,8-Dihydroxyflavone on Alcohol Consumption in Rats.

We recently reported that intraperitoneal injection of 7,8-dihydroxyflavone (7,8-DHF), a brain-derived neurotrophic factor-mimicking small compound, could attenuate alcohol-related behaviors in a two-bottle choice ethanol consumption procedure (IA2BC) in rats via tropomyosin receptor kinase B in the ventral tegmental area (VTA), which is closely related to alcohol use disorder. However, the detailed mechanisms underlying the regulation of 7,8-DHF on alcohol drinking behavior remain elusive. In this study, we determined the role of nitric oxide (NO), a pleiotropic signaling molecule, in the VTA in the action of 7,8-DHF upon alcohol drinking behavior. Intermittent alcohol exposure led to the overexpression of NO in the VTA, especially 72h after withdrawal from four weeks of ethanol exposure in IA2BC rats. A higher amount of alcohol intake was also found at the same time point, consistent with the overexpression of NO in the VTA. Microinjection of NG-Nitro-l-Arginine Methyl Ester, (NO synthase inhibitor) or 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NO scavenger) into the VTA inhibited alcohol intake, whereas application of S-Nitroso-N-acetyl-DL-penicillamine (SNAP, the NO donor) in the VTA further enhanced alcohol consumption in IA2BC rats. Interestingly, either 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (a sGC inhibitor) or KT5823 [a selective protein kinase G (PKG) inhibitor] blocked NO's enhancing effect on ethanol intake. Intraperitoneal injection of 7,8-DHF reduced the overexpression of NO; SNAP microinjected into the VTA reversed the inhibitory effects of 7,8-DHF on alcohol consumption. Our findings suggest that NO-cGMP-PKG might be involved in regulation of 7,8-DHF on alcohol consumption in IA2BC rats.

Exogenous ferulic acid treatment increases resistance against Botrytis cinerea in tomato fruit by regulating nitric oxide signaling pathway

This study was to explore the effect of ferulic acid (FA) treatment in response to Botrytis cinerea (B. cinerea) infection of tomato fruit and potential mechanisms of action. The results showed that fruit treated with 100 μM FA increased resistance against B. cinerea as revealed by decreased disease incidence and lesion area. In addition, the activities of phenylalanine ammonialyase (PAL), polyphenol oxidase (PPO), chitinase (CHI) and β-1,3-glucanase (GLU) were significantly higher in tomato fruit treated with 100 μM FA. The increase of disease resistance was accompanied by a higher expression of genes (PR1, NPR1, MYC2, LoxD) related to salicylicacid (SA) and jasmonic acid (JA) signaling pathway. Furthermore, the activity of nitric oxide synthase (NOS) also enhanced by FA treatment and consequently increased the content of nitric oxide (NO). However, the simultaneous addition of 0.2 mM Nω-nitro-l-arginine (l-NNA), a specific inhibitor of NOS, abolished such effects of 100 μM FA produced as well as decreased the expression of genes (C3H, C4H, COMT, PAL) related to FA biosynthesis. Additionally, FA treatment improved the correlations of NOS with MYC2 (r = 0.85*), GLU (r = 0.93**) and CHI (r = 0.94**). These findings indicated that FA treatment could be a promising approach to improve resistance against B. cinerea in tomato fruit, which was related to NO signaling pathway.

Identification of Adrenomedullin-Induced S-Nitrosylated Proteins in JEG-3 Placental Cells

Extravillous cytotrophoblast (EVCT) is responsible for trophoblast invasion, which is important during placentation. Dysregulation of the process leads to pregnancy complications. S-nitrosylation of proteins is associated with cell invasion in many cell types. Adrenomedullin (ADM), a polypeptide expressed abundantly in the first-trimester placentas, induces EVCT invasion by upregulation of protein S-nitrosylation. This study aimed to identify the S-nitrosylated proteins induced by ADM in the JEG-3 placental cells. By using affinity chromatography followed by mass spectrometric analysis, tubulin, enolase, eukaryotic translation initiation factor 4A1, actin, annexin II (ANX II), and glyceraldehyde 3-phosphate dehydrogenaseprotein-1 were found to be S-nitrosylated by ADM. In vitro treatment with ADM or S-Nitrosoglutathione (GSNO) significantly increased the ANX II surface expression, but not its total expression in the JEG-3 cells. Translocation of ANX II to cell surface has been reported to act as a cell surface receptor to plasmin, plasminogen, and tissue plasminogen activator (tPA), thereby stimulating cell invasion and migration. However, in this study, ADM-induced surface expression of ANX II in the JEG-3 cells was not associated with changes in the secretory and membrane-bound tPA activities. Future studies are required to understand the roles of surface expression of S-nitrosylated ANX II on trophoblast functions. To conclude, this study provided evidences that ADM regulated the nitric oxide signaling pathway and modulated trophoblast invasion.

Neonatal Extracellular Superoxide Dismutase Knockout Mice Increase Total Superoxide Dismutase Activity and VEGF Expression after Chronic Hyperoxia.

Bronchopulmonary dysplasia (BPD) is a common lung disease affecting premature infants that develops after exposure to supplemental oxygen and reactive oxygen intermediates. Extracellular superoxide dismutase (SOD3) is an enzyme that processes superoxide radicals and has been shown to facilitate vascular endothelial growth factor (VEGF) and nitric oxide (NO) signaling in vascular endothelium. We utilized a mouse model of neonatal hyperoxic lung injury and SOD3 knockout (KO) mice to evaluate its function during chronic hyperoxia exposure. Wild-type age-matched neonatal C57Bl/6 (WT) and SOD3−/− (KO) mice were placed in normoxia (21% FiO2, RA) or chronic hyperoxia (75% FiO2, O2) within 24 h of birth for 14 days continuously and then euthanized. Lungs were harvested for histologic evaluation, as well as comparison of antioxidant enzyme expression, SOD activity, VEGF expression, and portions of the NO signaling pathway. Surprisingly, KO-O2 mice survived without additional alveolar simplification, microvascular remodeling, or nuclear oxidation when compared to WT-O2 mice. KO-O2 mice had increased total SOD activity and increased VEGF expression when compared to WT-O2 mice. No genotype differences were noted in intracellular antioxidant enzyme expression or the NO signaling pathway. These results demonstrate that SOD3 KO mice can survive prolonged hyperoxia without exacerbation of alveolar or vascular phenotype.

An Overview of NO Signaling Pathways in Aging.

Nitric Oxide (NO) is a potent signaling molecule involved in the regulation of various cellular mechanisms and pathways under normal and pathological conditions. NO production, its effects, and its efficacy, are extremely sensitive to aging-related changes in the cells. Herein, we review the mechanisms of NO signaling in the cardiovascular system, central nervous system (CNS), reproduction system, as well as its effects on skin, kidneys, thyroid, muscles, and on the immune system during aging. The aging-related decline in NO levels and bioavailability is also discussed in this review. The decreased NO production by endothelial nitric oxide synthase (eNOS) was revealed in the aged cardiovascular system. In the CNS, the decline of the neuronal (n)NOS production of NO was related to the impairment of memory, sleep, and cognition. NO played an important role in the aging of oocytes and aged-induced erectile dysfunction. Aging downregulated NO signaling pathways in endothelial cells resulting in skin, kidney, thyroid, and muscle disorders. Putative therapeutic agents (natural/synthetic) affecting NO signaling mechanisms in the aging process are discussed in the present study. In summary, all of the studies reviewed demonstrate that NO plays a crucial role in the cellular aging processes.

Endogenous Hemoprotein-Dependent Signaling Pathways of Nitric Oxide and Nitrite.

Interdisciplinary research at the interface of chemistry, physiology, and biomedicine have uncovered pivotal roles of nitric oxide (NO) as a signaling molecule that regulates vascular tone, platelet aggregation, and other pathways relevant to human health and disease. Heme is central to physiological NO signaling, serving as the active site for canonical NO biosynthesis in nitric oxide synthase (NOS) enzymes and as the highly selective NO binding site in the soluble guanylyl cyclase receptor. Outside of the primary NOS-dependent biosynthetic pathway, other hemoproteins, including hemoglobin and myoglobin, generate NO via the reduction of nitrite. This auxiliary hemoprotein reaction unlocks a "second axis" of NO signaling in which nitrite serves as a stable NO reservoir. In this Forum Article, we highlight these NO-dependent physiological pathways and examine complex chemical and biochemical reactions that govern NO and nitrite signaling in vivo. We focus on hemoprotein-dependent reaction pathways that generate and consume NO in the presence of nitrite and consider intermediate nitrogen oxides, including NO2, N2O3, and S-nitrosothiols, that may facilitate nitrite-based signaling in blood vessels and tissues. We also discuss emergent therapeutic strategies that leverage our understanding of these key reaction pathways to target NO signaling and treat a wide range of diseases.

Protein Phosphorylation in Cancer: Role of Nitric Oxide Signaling Pathway.

Nitric oxide (NO), a free radical, plays a critical role in a wide range of physiological and pathological processes. Due to its pleiotropic function, it has been widely investigated in various types of cancers and is strongly associated with cancer development. Mounting pieces of evidence show that NO regulates various cancer-related events, which mainly depends on phosphorylating the key proteins in several signaling pathways. However, phosphorylation of proteins modulated by NO signaling pathway may lead to different effects in different types of cancer, which is complex and remains unclear. Therefore, in this review, we focus on the effect of protein phosphorylation modulated by NO signaling pathway in different types of cancers including breast cancer, lung cancer, prostate cancer, colon cancer, gastric cancer, pancreatic cancer, ovarian cancer, and neuroblastoma. Phosphorylation of key proteins, including p38 MAPK, ERK, PI3K, STAT3, and p53, modified by NO in various signaling pathways affects different cancer-related processes including cell apoptosis, proliferation, angiogenesis, metastasis, and several cancer therapies. Our review links the NO signaling pathway to protein phosphorylation in cancer development and provides new insight into potential targets and cancer therapy.