Significance of nitrosative stress and glycoxidation products in the diagnosis of COVID-19.

Nitrosative stress promotes protein glycoxidation, and both processes can occur during an infection with the SARS-CoV-2 virus. Therefore, the aim of this study was to assess selected nitrosative stress parameters and protein glycoxidation products in COVID-19 patients and convalescents relative to healthy subjects, including in reference to the severity of COVID-19 symptoms. The diagnostic utility of nitrosative stress and protein glycoxidation biomarkers was also evaluated in COVID-19 patients. The study involved 218 patients with COVID-19, 69 convalescents, and 48 healthy subjects. Nitrosative stress parameters (NO, S-nitrosothiols, nitrotyrosine) and protein glycoxidation products (tryptophan, kynurenine, N-formylkynurenine, dityrosine, AGEs) were measured in the blood plasma or serum with the use of colorimetric/fluorometric methods. The levels of NO (p = 0.0480), S-nitrosothiols (p = 0.0004), nitrotyrosine (p = 0.0175), kynurenine (p < 0.0001), N-formylkynurenine (p < 0.0001), dityrosine (p < 0.0001), and AGEs (p < 0.0001) were significantly higher, whereas tryptophan fluorescence was significantly (p < 0.0001) lower in COVID-19 patients than in the control group. Significant differences in the analyzed parameters were observed in different stages of COVID-19. In turn, the concentrations of kynurenine (p < 0.0001), N-formylkynurenine (p < 0.0001), dityrosine (p < 0.0001), and AGEs (p < 0.0001) were significantly higher, whereas tryptophan levels were significantly (p < 0.0001) lower in convalescents than in healthy controls. The ROC analysis revealed that protein glycoxidation products can be useful for diagnosing infections with the SARS-CoV-2 virus because they differentiate COVID-19 patients (KN: sensitivity-91.20%, specificity-92.00%; NFK: sensitivity-92.37%, specificity-92.00%; AGEs: sensitivity-99,02%, specificity-100%) and convalescents (KN: sensitivity-82.22%, specificity-84.00%; NFK: sensitivity-82,86%, specificity-86,00%; DT: sensitivity-100%, specificity-100%; AGE: sensitivity-100%, specificity-100%) from healthy subjects with high sensitivity and specificity. Nitrosative stress and protein glycoxidation are intensified both during and after an infection with the SARS-CoV-2 virus. The levels of redox biomarkers fluctuate in different stages of the disease. Circulating biomarkers of nitrosative stress/protein glycoxidation have potential diagnostic utility in both COVID-19 patients and convalescents.

Identification of Protein Targets of S-Nitroso-Coenzyme A-Mediated S-Nitrosation Using Chemoproteomics.

S-Nitrosation is a cysteine post-translational modification fundamental to cellular signaling. This modification regulates protein function in numerous biological processes in the nervous, cardiovascular, and immune systems. Small molecule or protein nitrosothiols act as mediators of NO signaling by transferring the NO group (formally NO+) to a free thiol on a target protein through a transnitrosation reaction. The protein targets of specific transnitrosating agents and the extent and functional effects of S-nitrosation on these target proteins have been poorly characterized. S-nitroso-coenzyme A (CoA-SNO) was recently identified as a mediator of endogenous S-nitrosation. Here, we identified direct protein targets of CoA-SNO-mediated transnitrosation using a competitive chemical-proteomic approach that quantified the extent of modification on 789 cysteine residues in response to CoA-SNO. A subset of cysteines displayed high susceptibility to modification by CoA-SNO, including previously uncharacterized sites of S-nitrosation. We further validated and functionally characterized the functional effects of S-nitrosation on the protein targets phosphofructokinase (platelet type), ATP citrate synthase, and ornithine aminotransferase.

Protocol for preparing Thiopropyl Sepharose resin used for capturing S-nitrosylated proteins.

S-nitrosothiol (SNO)-Resin Assisted Capture (SNO-RAC) relies on a Thiopropyl Sepharose resin to identify S-nitrosylated proteins (SNO-proteins) and sites of S-nitrosylation. Here, we present a protocol for preparing Thiopropyl Sepharose resin with efficiency of SNO-protein capture comparable to the discontinued commercial version. We describe steps for amine coupling, disulfide reduction, and generation of thiol reactive resin. We then detail quality control procedures. This resin is also suitable for Acyl-RAC assays to capture palmitoylated proteins. For complete details on the use and execution of the SNO-RAC protocol, please refer to Forrester et al.,1 Fonseca et al.,2 and Seth et al.3.

Erythrocytic metabolism of ATLX-0199: An agent that increases minute ventilation.

Both L- and D-isomers of S-nitrosocysteine (CSNO) can bind to the intracellular domain of voltage-gated potassium channels in vitro. CSNO binding inhibits these channels in the carotid body, leading to increased minute ventilation in vivo. However, only the l-isomer is active in vivo because it requires the l-amino acid transporter (LAT) for transmembrane transport. In rodents and dogs, the esterified D-CSNO precursor-d-cystine dimethyl ester (ATLX-0199)-overcomes opioid- and benzodiazepine-induced respiratory depression while maintaining analgesia. Although ATLX-0199 can enter cells independently of LAT because it is an ester, its stability in plasma is limited by the presence of esterases. Here, we hypothesized that the drug could be sequestered in erythrocytes to avoid de-esterification in circulation. We developed a liquid chromatography-mass spectrometry method for detecting ATLX-0199 and characterized a new metabolite, S-nitroso-d-cysteine monomethyl ester (DNOCE), which is also a D-CSNO precursor. We found that both ATLX-0199 and DNOCE readily enter erythrocytes and neurons and remain stable over 20 min; thus ATLX-0199 can enter cells where the ester is stable, but the thiol is reduced. Depending on hemoglobin conformation, the reduced ester can be S-nitrosylated and enter carotid body neurons, where it then increases minute ventilation. These data may help explain the paradox that ATLX-0199, a dimethyl ester, can avoid de-esterification in plasma and exert its effects at the level of the carotid body.

Promotion of S-nitrosation of cysteine by a {Co(NO)2}10 complex.

S-Nitrosothiols (SNOs) serve as endogenous carriers and donors of NO within living cells, releasing nitrosonium ions (NO+), NO, or other nitroso derivatives. In this study, we present a bioinspired {Co(NO)2}10 complex 1 that achieved S-nitrosation towards Cys residues. The incorporation of a ferrocenyl group in 1 allowed for fine-tuning of the nitrosation reaction, taking advantage of the redox ability of Cys residues. Complex 1 was synthesized and characterized, demonstrating its NO translation reactivity. Furthermore, complex 1 successfully converted Cys into S-nitrosocysteine (Cys-SNO), as confirmed by UV-Vis, IR, and XAS spectroscopy. This study presents a promising approach for S-nitrosation of Cys residues for further exploration in the modification of Cys-containing peptides.

TRAP1 S-nitrosylation as a model of population-shift mechanism to study the effects of nitric oxide on redox-sensitive oncoproteins.

S-nitrosylation is a post-translational modification in which nitric oxide (NO) binds to the thiol group of cysteine, generating an S-nitrosothiol (SNO) adduct. S-nitrosylation has different physiological roles, and its alteration has also been linked to a growing list of pathologies, including cancer. SNO can affect the function and stability of different proteins, such as the mitochondrial chaperone TRAP1. Interestingly, the SNO site (C501) of TRAP1 is in the proximity of another cysteine (C527). This feature suggests that the S-nitrosylated C501 could engage in a disulfide bridge with C527 in TRAP1, resembling the well-known ability of S-nitrosylated cysteines to resolve in disulfide bridge with vicinal cysteines. We used enhanced sampling simulations and in-vitro biochemical assays to address the structural mechanisms induced by TRAP1 S-nitrosylation. We showed that the SNO site induces conformational changes in the proximal cysteine and favors conformations suitable for disulfide bridge formation. We explored 4172 known S-nitrosylated proteins using high-throughput structural analyses. Furthermore, we used a coarse-grained model for 44 protein targets to account for protein flexibility. This resulted in the identification of up to 1248 proximal cysteines, which could sense the redox state of the SNO site, opening new perspectives on the biological effects of redox switches. In addition, we devised two bioinformatic workflows ( https://github.com/ELELAB/SNO_investigation_pipelines ) to identify proximal or vicinal cysteines for a SNO site with accompanying structural annotations. Finally, we analyzed mutations in tumor suppressors or oncogenes in connection with the conformational switch induced by S-nitrosylation. We classified the variants as neutral, stabilizing, or destabilizing for the propensity to be S-nitrosylated and undergo the population-shift mechanism. The methods applied here provide a comprehensive toolkit for future high-throughput studies of new protein candidates, variant classification, and a rich data source for the research community in the NO field.

Expanding roles for S-nitrosylation in the regulation of plant immunity.

Following pathogen recognition, plant cells produce a nitrosative burst resulting in a striking increase in nitric oxide (NO), altering the redox state of the cell, which subsequently helps orchestrate a plethora of immune responses. NO is a potent redox cue, efficiently relayed between proteins through its co-valent attachment to highly specific, powerfully reactive protein cysteine (Cys) thiols, resulting in formation of protein S-nitrosothiols (SNOs). This process, known as S-nitrosylation, can modulate the function of target proteins, enabling responsiveness to cellular redox changes. Key targets of S-nitrosylation control the production of reactive oxygen species (ROS), the transcription of immune-response genes, the triggering of the hypersensitive response (HR) and the establishment of systemic acquired resistance (SAR). Here, we bring together recent advances in the control of plant immunity by S-nitrosylation, furthering our appreciation of how changes in cellular redox status reprogramme plant immune function.

Photoactivation of tDodSNO induces localized vasodilation in rats: Metabolically stable S-nitrosothiols can act as targeted nitric oxide donors in vivo.

Nitric oxide (NO) is a key vasodilatory signalling molecule and NO releasing molecules (NO donors) are being examined as potential treatments for many pathologies. The photoresponsive NO donor tert-dodecane S-nitrosothiol (tDodSNO) has been designed to be highly resistant to metabolism; in principle photoactivation of tDodSNO should therefore enable the controlled release of NO in situ via light modulation. To investigate the therapeutic utility of tDodSNO, we tested drug efficacy in Sprague Dawley rats to assess systemic and localised hemodynamic responses under photoactivation, and to confirm drug safety. For comparison, drug action was evaluated alongside the existing NO donors sodium nitroprusside (SNP) and S-nitrosoglutathione (GSNO). Across a dosing range (0.1-3.0 mg/kg) tDodSNO exerted markedly reduced systemic hypotensive action compared to these standard NO donors, inducing a slight decrease in mean arterial pressure (maximum 14.2 ± 3.0%) without affecting heart rate. Target limb photoactivation of tDodSNO resulted in a substantial localized vasodilatory response, with increases to mean (26.0 ± 7.3%) and maximum (53.2 ± 10.4%) blood flow and decreases to vascular resistance (27.1 ± 3.9%) that were restricted to light exposed tissue. In comparison GSNO and SNP showed variable peripheral effects and were not responsive to photoactivation. tDodSNO did not induce met-Hb formation in blood, or display any signs of toxicity, and was rapidly cleared from the systemic circulation, with no hemodynamic effects detectable 5 min post administration. These data are the first demonstration that drugs based upon a metabolically stable S-nitrosothiol group can be photoactivated in vivo to release NO, and that such agents cause less systemic side effects than existing NO donors. Our data support the use of S-nitrosothiols to enable the spatiotemporal control of NO for therapeutic applications.

Nitric oxide alleviates salt stress through protein S-nitrosylation and transcriptional regulation in tomato seedlings.

MAIN CONCLUSION: NO enhances the resistance of tomato seedlings to salt stress through protein S-nitrosylation and transcriptional regulation, which involves the regulation of MAPK signaling and carbohydrate metabolism. Nitric oxide (NO) regulates various physiological and biochemical processes and stress responses in plants. We found that S-nitrosoglutathione (GSNO) treatment significantly promoted the growth of tomato seedling under NaCl stress, indicating that NO plays a positive role in salt stress resistance. Moreover, GSNO pretreatment resulted in an increase of endogenous NO level, S-nitrosothiol (SNO) content, S-nitrosoglutathione reductase (GSNOR) activity and GSNOR expression under salt stress, implicating that S-nitrosylation might be involved in NO-alleviating salt stress. To further explore whether S-nitrosylation is a key molecular mechanism of NO-alleviating salt stress, the biotin-switch technique and liquid chromatography/mass spectrometry/mass spectrometry (LC-MS/MS) were conducted. A total of 1054 putative S-nitrosylated proteins have been identified, which were mainly enriched in chloroplast, cytoplasm and mitochondrion. Among them, 15 and 22 S-nitrosylated proteins were involved in mitogen-activated protein kinase (MAPK) signal transduction and carbohydrate metabolism, respectively. In MAPK signaling, various S-nitrosylated proteins, SAM1, SAM3, SAM, PP2C and SnRK, were down-regulated and MAPK, MAPKK and MAPKK5 were up-regulated at the transcriptional level by GSNO treatment under salt stress compared to NaCl treatment alone. The GSNO pretreatment could reduce ethylene production and ABA content under NaCl stress. In addition, the activities of enzyme identified in carbohydrate metabolism, their expression at the transcriptional level and the metabolite content were up-regulated by GSNO supplication under salt stress, resulting in the activation of glycolysis and tricarboxylic acid cycle (TCA) cycles. Thus, these results demonstrated that NO might beneficially regulate MAPK signaling at transcriptional levels and activate carbohydrate metabolism at the post-translational and transcriptional level, protecting seedlings from energy deficiency and salinity, thereby alleviating salt stress-induced damage in tomato seedlings. It provides initial insights into the regulatory mechanisms of NO in response to salt stress.

A multienzyme S-nitrosylation cascade regulates cholesterol homeostasis.

Accumulating evidence suggests that protein S-nitrosylation is enzymatically regulated and that specificity in S-nitrosylation derives from dedicated S-nitrosylases and denitrosylases that conjugate and remove S-nitrosothiols, respectively. Here, we report that mice deficient in the protein denitrosylase SCoR2 (S-nitroso-Coenzyme A Reductase 2; AKR1A1) exhibit marked reductions in serum cholesterol due to reduced secretion of the cholesterol-regulating protein PCSK9. SCoR2 associates with endoplasmic reticulum (ER) secretory machinery to control an S-nitrosylation cascade involving ER cargo-selection proteins SAR1 and SURF4, which moonlight as S-nitrosylases. SAR1 acts as a SURF4 nitrosylase and SURF4 as a PCSK9 nitrosylase to inhibit PCSK9 secretion, while SCoR2 counteracts nitrosylase activity by promoting PCSK9 denitrosylation. Inhibition of PCSK9 by an NO-based drug requires nitrosylase activity, and small-molecule inhibition of SCoR2 phenocopies the PCSK9-mediated reductions in cholesterol observed in SCoR2-deficient mice. Our results reveal enzymatic machinery controlling cholesterol levels through S-nitrosylation and suggest a distinct treatment paradigm for cardiovascular disease.

Myocardial protection of S-nitroso-L-cysteine in diabetic cardiomyopathy mice.

Diabetic cardiomyopathy (DCM) is a severe complication of diabetes mellitus that is characterized by aberrant myocardial structure and function and is the primary cause of heart failure and death in diabetic patients. Endothelial dysfunction plays an essential role in diabetes and is associated with an increased risk of cardiovascular events, but its role in DCM is unclear. Previously, we showed that S-nitroso-L-cysteine(CSNO), an endogenous S-nitrosothiol derived from eNOS, inhibited the activity of protein tyrosine phosphatase 1B (PTP1B), a critical negative modulator of insulin signaling. In this study, we reported that CSNO treatment induced cellular insulin-dependent and insulin-independent glucose uptake. In addition, CSNO activated insulin signaling pathway and promoted GLUT4 membrane translocation. CSNO protected cardiomyocytes against high glucose-induced injury by ameliorating excessive autophagy activation, mitochondrial impairment and oxidative stress. Furthermore, nebulized CSNO improved cardiac function and myocardial fibrosis in diabetic mice. These results suggested a potential site for endothelial modulation of insulin sensitivity and energy metabolism in the development of DCM. Data from these studies will not only help us understand the mechanisms of DCM, but also provide new therapeutic options for treatment.

BR-Mediated Protein S-Nitrosylation Alleviated Low-Temperature Stress in Mini Chinese Cabbage (Brassica rapa ssp. pekinensis).

Brassinosteroids (BRs), a novel plant hormone, are widely involved in plant growth and stress response processes. Nitric oxide (NO), as an important gas signaling molecule, can regulate target protein activity, subcellular localization and function in response to various stresses through post-translational S-nitrosylation modifications. However, the relationship between BR and NO in alleviating low-temperature stress of mini Chinese cabbage remains unclear. The hydroponic experiment combined with the pharmacological and molecular biological method was conducted to study the alleviating mechanism of BR at low temperature in mini Chinese cabbage. The results showed that low temperature inhibited the growth of mini Chinese cabbage seedlings, as evidenced by dwarf plants and yellow leaves. Treatment with 0.05 mg/L BR and 50 µM NO donor S-nitrosoglutathione (GSNO) significantly increased the leaf area, stem diameter, chlorophyll content, dry and fresh weight and proline content. Meanwhile, the malondialdehyde (MDA) content in 0.05 mg/L BR- and 50 µM GSNO-treated leaves were significantly lower than those in other treated leaves under low-temperature conditions. In addition, BR and GSNO applications induced an increase in NO and S-nitrosothiol (SNO) levels in vivo under low-temperature stress. Similarly, spraying BR after the elimination of NO also increased the level of S-nitrosylation in vivo, while spraying GSNO after inhibiting BR biosynthesis decreased the level of NO and SNO in vivo. In contrast, the S-nitrosoglutathione reductase (BrGSNOR) relative expression level and GSNOR enzyme activity were downregulated and inhibited by BR treatment, GSNO treatment and spraying BR after NO clearance, while the relative expression level of BrGSNOR was upregulated and GSNOR enzyme activity was also increased when spraying GSNO after inhibiting BR synthesis. Meanwhile, the biotin switch assay showed that exogenous BR increased the level of total nitrosylated protein in vivo under low-temperature stress. These results suggested that BR might act as an upstream signal of NO, induced the increase of NO content in vivo and then induced the protein S-nitrosylation modification to alleviate the damage of mini Chinese cabbage seedlings under low-temperature stress.

S-Nitroso-l-cysteine and ventilatory drive: A pediatric perspective.

Though endogenous S-nitroso-l-cysteine (l-CSNO) signaling at the level of the carotid body increases minute ventilation (v̇E ), neither the background data nor the potential clinical relevance are well-understood by pulmonologists in general, or by pediatric pulmonologists in particular. Here, we first review how regulation of the synthesis, activation, transmembrane transport, target interaction, and degradation of l-CSNO can affect the ventilatory drive. In particular, we review l-CSNO formation by hemoglobin R to T conformational change and by nitric oxide (NO) synthases (NOS), and the downstream effects on v̇E through interaction with voltage-gated K+ (Kv) channel proteins and other targets in the peripheral and central nervous systems. We will review how these effects are independent of-and, in fact may be opposite to-those of NO. Next, we will review evidence that specific elements of this pathway may underlie disorders of respiratory control in childhood. Finally, we will review the potential clinical implications of this pathway in the development of respiratory stimulants, with a particular focus on potential pediatric applications.

A new look at the role of nitric oxide in preeclampsia: Protein S-nitrosylation.

The formation of S-nitrosothiols (SNOs) occurs with the reaction of nitric oxide (NO) and free thiol groups in proteins. This process, called S-nitrosylation, allows NO to interfere with or even modulate a variety of cellular functions, culminating with the modification of protein trafficking, redox state, and cell cycle. Furthermore, NO plays a role in modulating a wide range of functions in endothelial cells specifically, including inflammation, apoptosis, permeability, migration, and cell growth. As such, NO acts as a mediator in several physiological processes. The interaction between endothelial nitric oxide synthase (eNOS) and proteins that are to be targeted for S-nitrosylation is a key determinant of the specificity of NO signaling. Deficits in the bioavailability of NO have been associated with pregnancy-related disorders, such as preeclampsia (PE). The study of S-nitrosylation in PE, as well as the identification of targeted proteins, may contribute to a better understanding of its pathophysiology and the development of drugs for the treatment of PE patients. In this review, we aimed to present the mechanism of S-nitrosylation, the regulatory pathways, and some proteins by which S-nitrosylation can modulate NO availability with a potential impact on PE.

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.

Looking at denitrosylation to understand the myogenesis gone awry theory of rhabdomyosarcoma.

S-nitrosylation of proteins is a nitric oxide (NO)-based post-translational modification of cysteine residues. By removing the NO moiety from S-nitrosothiol adducts, denitrosylases restore sulfhydryl protein pool and act as downstream tuners of S-nitrosylation signaling. Alterations in the S-nitrosylation/denitrosylation dynamics are implicated in many pathological states, including cancer ontogenesis and progression, skeletal muscle myogenesis and function. Here, we aim to provide and link different lines of evidence, and elaborate on the possible role of S-nitrosylation/denitrosylation signaling in rhabdomyosarcoma, one of the most common pediatric mesenchymal malignancy.

Mechanisms of nitric oxide generation in living systems.

In modern chemical and biochemical studies, special attention is paid to molecular systems capable of generating nitric oxide (NO), which is one of the most important signalling molecules in the body and can trigger a whole cascade of reactions. Despite the importance of this molecule, the mechanisms of its formation in living organisms remain a subject of debate. This review combines the most important methods of releasing NO from endogenous and exogenous sources. The history of endogenous NO donors dates back more than 150 years, since the synthesis of nitroglycerin, which remains the standard vasodilator today, even though it is known that it and many other similar compounds lead to the development of a nitrate tolerance. Particular awareness is devoted to the mechanisms of NO formation without the participation of enzymes, since these methods are most important for creating exogenous sources of NO as drugs. The study of NO formation methods is centred on both the creation of new NO donors and understanding the mechanisms of tolerance to them.

Analysis of glutathione mediated S-(de)nitrosylation in complex biological matrices by immuno-spin trapping and identification of two novel substrates.

The intracellular concentration of reduced glutathione (GSH) lies in the range of 1-10 mM, thereby indisputably making it the most abundant intracellular thiol. Such a copious amount of GSH makes it the most potent and robust cellular antioxidant that plays a crucial role in cellular defence against redox stress. The role of GSH as a denitrosylating agent is well established; in this study, we demonstrate GSH mediated denitrosylation of HepG2 cell-derived protein nitrosothiols (PSNOs), by a unique spin-trapping mechanism, using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as the spin trapping agent, followed by a western blot analysis. We also report our findings of two, hitherto unidentified substrates of GSH mediated S-denitrosylation, namely S-nitrosoglutaredoxin 1 (Grx1-SNO) and S-nitrosylated R1 subunit of ribonucleotide reductase (R1-SNO).

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 ß-globin Cys93 (ßCys93), 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.

S-nitrosothiols signaling in cystic fibrosis airways.

S-nitrosothiols (SNOs) are small naturally occurring thiol and nitric oxide adducts that participate in many cell signaling pathways in living organisms. SNOs receive widespread attention in cell biology, biochemistry and chemistry because they can donate nitric oxide and/or nitrosonium ions in S-nitrosylation reactions, which are comparable to phosphorylation, acetylation, glutathionylation, and palmitoylation reactions. SNOs have advantageous effects in respiratory diseases and other systems in the body. S-nitrosylation signaling is a metabolically regulated physiological process that leads to specific post-translational protein modifications. S-nitrosylation signaling is faulty in cystic fibrosis (CF) and many other lung diseases. CF is an inherited, lethal autosomal recessive multisystem disease resulting from mutations in the gene encoding the CF transmembrane conductance regulatory (CFTR) protein. F508del CFTR is the most common mutation associated with CF, which results in CFTR misfolding because a phenylalanine is deleted from the primary structure of CFTR. The majority of wild-type CFTR and almost all F508del is degraded before reaching the cell surface. Ultimately, CF researchers have been looking to correct the mutated CFTR protein in the CF patients. Remarkably, researchers have found that SNOs levels are low in the CF lower airway compared to non-CF patients. We have been interested in determining whether SNOs increase CFTR maturation through S-nitrosylation. Maturation of both wild type and mutant F508del CFTR increases SNOs, which up-regulate CFTR maturation. In this review, we summarized our current knowledge of S-nitrosothiols signaling in cystic fibrosis airways.