Second generation ß-elemene nitric oxide derivatives with reasonable linkers: potential hybrids against malignant brain glioma.

Elemene is a second-line broad-spectrum anti-tumour drug that has been used in China for more than two decades. However, its main anti-tumour ingredient, ß-elemene, has disadvantages, including excessive lipophilicity and relatively weak anti-tumour efficacy. To improve the anti-tumour activity of ß-elemene, based on its minor molecular weight character, we introduced furoxan nitric oxide (NO) donors into the ß-elemene structure and designed six series of new generation ß-elemene NO donor hybrids. The synthesised compounds could effectively release NO in vitro, displayed significant anti-proliferative effects on U87MG, NCI-H520, and SW620 cell lines. In the orthotopic glioma model, compound Id significantly and continuously suppressed the growth of gliomas in nude mice, and the brain glioma of the treatment group was markedly inhibited (>90%). In short, the structural fusion design of NO donor and ß-elemene is a feasible strategy to improve the in vivo anti-tumour activity of ß-elemene.

Reaction mechanisms relevant to the formation and utilization of [Ru(edta)(NO)] complexes in aqueous media.

The advancement of Ru(edta) complexes (edta4- = ethylenediamineteraacetate) mediated reactions, including NO generation and its utilization, has not been systematically reviewed to date. This review aims to report the research progress that has been made in exploring the application of Ru(edta) complexes in trapping and generation of NO. Furthermore, utilization of the potential of Ru(edta) complexes to mimic NO synthase and nitrite reductase activity, including thermodynamics and kinetics of NO binding to Ru(edta) complexes, their NO scavenging (in vitro), and antitumor activity will be discussed. Also, the role of [Ru(edta)(NO)] in mediating electrochemical reduction of nitrite, S-nitrosylation of biological thiols, and cross-talk between NO and H2S, will be covered. Reports on the NO-related chemistry of Fe(edta) complexes showing similar behavior are contextualized in this review for comparison purposes. The research contributions compiled herein will provide in-depth mechanistic knowledge for understanding the diverse routes pertaining to the formation of the [Ru(edta)(NO)] species, and its role in effecting the aforementioned reactions of biochemical significance.

Thionitrite and Perthionitrite in NO Signaling at Zinc.

NO and H2 S serve as signaling molecules in biology with intertwined reactivity. HSNO and HSSNO with their conjugate bases - SNO and - SSNO form in the reaction of H2 S with NO as well as S-nitrosothiols (RSNO) and nitrite (NO2- ) that serve as NO reservoirs. While HSNO and HSSNO are elusive, their conjugate bases form isolable zinc complexes Ph,Me TpZn(SNO) and Ph,Me TpZn(SSNO) supported by tris(pyrazolyl)borate ligands. Reaction of Na(15-C-5)SSNO with Ph,Me TpZn(ClO4 ) provides Ph,Me TpZn(SSNO) that undergoes S-atom removal by PEt3 to give Ph,Me TpZn(SNO) and S=PEt3 . Unexpectedly stable at room temperature, these Zn-SNO and Zn-SSNO complexes release NO upon heating. Ph,Me TpZn(SNO) and Ph,Me TpZn(SSNO) quickly react with acidic thiols such as C6 F5 SH to form N2 O and NO, respectively. Increasing the thiol basicity in p-substituted aromatic thiols 4-X ArSH in the reaction with Ph,Me TpZn(SNO) turns on competing S-nitrosation to form Ph,Me TpZn-SH and RSNO, the latter a known precursor for NO.

Diatom-inspired 2D nitric oxide releasing anti-infective porous nanofrustules.

Two-dimensional (2D) nanomaterials (NM) have emerged as promising platforms for antibacterial applications. However, the inherent "flatness" of 2D NM often limits the loading of antimicrobial components needed for synergistic bactericidal actions. Here, inspired by the highly ornamented siliceous frustules of diatoms, we prepared 2D ultrathin (<20 nm) and rigid "nanofrustule" plates via the out-of-plane growth of cetyltrimethylammonium bromide (CTAB) directed silica mesostructures on the surfaces of 2D graphene oxide nanosheets. The nanofrustules were characterized by the presence of mesoporous channels with a pore size of 3 nm and a high specific surface area of 674 m2 g-1. S-nitrosothiol-modification on the silica surfaces enables the development of a novel anti-infective nitric oxide (NO) releasing NO-nanofrustule system. The cage-like mesoporous silica architecture enabled a controlled and sustainable release of NO from the NO-nanofrustules under physiological conditions. The NO-nanofrustules displayed broad antibacterial effects against Staphylococcus aureus and Escherichia coli with a minimum inhibitory concentration of 250 µg ml-1. Mechanistic studies revealed that the antibacterial property of NO-nanofrustules was attained via a unique "capture-and-release" mode-of-action. The first step entailed the capture of the bacteria by the NO-nanofrustules to form micro-aggregates. This was followed by the release of high levels of NO to the captured bacteria to elicit a potent anti-infective effect. In combination with the lack of cytotoxicity in human dermal cells, the 2D hybrid NO-nanofrustules may be utilized to combat wound infections in clinical settings.

The analytical method to identify the nitrogen source for nitric oxide synthesis.

Nitric oxide (NO) is a ubiquitous signaling molecule synthesized from various nitrogen sources. An analytical method to identify a nitrogen source for NO generation was developed using liquid chromatography with tandem mass spectrometry in combination with stable isotope labeling. Our method successfully detected the 15N-labeled NO-containing compound generated from 15N-labeled substrate nitrite in vitro and in vivo.

Copper-doped metal-organic frameworks for the controlled generation of nitric oxide from endogenous S-nitrosothiols.

Nitric oxide (NO) is an essential signaling molecule with a number of biological functions and holds great promise in biomedical applications. However, NO delivery technologies have been complicated due to the inherent properties of NO which include short half-life and limited transport distance in human tissues. In addition, the biofunctionality of NO is strongly dependent on its concentrations and locations where it is delivered. To achieve controlled NO delivery, many studies have focused on encapsulating NO donors into macromolecular scaffolds or using catalysts to realize in situ NO generation from NO prodrugs. Successful applications have been shown, however NO donor-loaded platforms experience the limitation of finite NO storage capacity. The present study reports the synthesis of a catalyst, copper-doped zeolitic imidazolate framework ZIF-8 (Cu2+/ZIF-8), that is designed to generate NO from naturally occurring endogenous NO donors. By tuning the copper doping percentages, we achieved controlled NO generation from S-nitrosoglutathione (GSNO) and S-nitrosocysteine (CysNO). Cu2+/ZIF-8 particles retained their catalytic potency after 5 NO generation cycles and we showed that our copper-doped ZIF-8 catalyst produced a 10-fold increased amount of NO compared with previous reports. As a proof-of-concept study, we demonstrated the ability of copper-doped ZIF-8 to disperse bacterial biofilms in the presence of GSNO.

Nitric Oxide-Releasing Insert for Disinfecting the Hub Region of Tunnel Dialysis Catheters.

The use of tunneled dialysis catheters (TDCs) for patients in need of hemodialysis treatments (HDs) causes a significant number of bloodstream infections (BSIs), with very few viable preventative/treatment methods. Use of antibiotics is relatively ineffective due to the development of multidrug-resistant bacterial strains and the inability to penetrate bacterial biofilms. Nitric oxide (NO) is an endogenous gas molecule that has broad-spectrum antimicrobial/antibiofilm activity. In this study, the potential of creating a NO-releasing insert device that is attached onto the hub region cap of TDCs and locally releases NO within the TDC hub is evaluated for its antimicrobial/antibiofilm effectiveness. The NO-releasing insert contains the natural NO donor S-nitrosoglutathione (GSNO), along with zinc oxide (ZnO) nanoparticles to accelerate NO release from the GSNO, within a short silicone tube that is sealed at both ends and attached to the catheter cap. An in vitro 3-d-long antimicrobial study using catheter hubs yielded >6.6 log reductions of both Pseudomonas aeruginosa and Staphylococcus aureus for the NO-releasing insert device compared to controls. Two 14-d-long sheep studies demonstrated that the NO-releasing insert devices are exceptionally potent at preventing bacteria/biofilm growth on the inner lumen walls of TDCs compared to controls that have no preventative treatment devices as well as implanted TDCs that have commercially available chlorhexidine-treated insert devices placed within the hub regions.

Nanosized copper(ii) oxide/silica for catalytic generation of nitric oxide from S-nitrosothiols.

Nitric oxide NO, mediates inflammatory and thrombotic processes and designing biomaterials capable of releasing NO in contact with biological tissues is considered to be a major factor aimed at improving their bio- and haemocompatibility and antibacterial properties. Their NO-releasing capacity however is limited by the amount of the NO-containing substance incorporated in the bulk or immobilised on the surface of a biomaterial. An alternative approach is based on the design of a material generating nitric oxide from endogenous NO bearing metabolites by their catalytic decomposition. It offers, at least in theory, an unlimited source of NO for as long as the material remains in contact with blood and the catalyst maintains its activity. In this paper we studied the catalytic properties of novel nanostructured CuO/SiO2 catalysts in generating NO by decomposition of S-nitrosoglutathione (GSNO) in vitro. CuO/SiO2 catalysts with different CuO loadings were synthesized by chemisorption of copper(ii) acetylacetonate on fumed nanosilica followed by calcination. CuO content was controlled by a number of chemisorption-calcination cycles. Fourier-transform infrared spectroscopy and thermogravimetric analysis confirmed the formation of CuO/SiO2 nanoparticles (NPs) with particle size of CuO phase in the range from 71 to 88 nm. Scanning electron microscopy images revealed a uniform distribution of NPs without their sintering or agglomeration. All the materials of the CuO/SiO2 NP series exhibited NO-generating activity from GSNO confirmed by the Griess assay and by measuring the concentration of nitrite and nitrate anions in model solutions such as phosphate buffered saline and bovine serum. This activity is dependent on the material specific surface area and CuO exposure on the surface rather than CuO bulk content. The rate of NO production increased at higher initial concentration of the NO-bearing substrate studied in the range between 0.01 mM and 1.0 mM RSNO, which covers its physiological level. CuO/SiO2 NPs can be used to design polymers with NO generating properties at blood-biomaterial interface which are expected to have improved biocompatibility thus enhancing their potential for medical applications such as surgical tubing, peripheral venous catheters, auxiliary blood circulation devices and drug-eluting balloons.

Zinc Oxide Particles Catalytically Generate Nitric Oxide from Endogenous and Exogenous Prodrugs.

Nitric oxide (NO) is a potent biological molecule that contributes to a wide spectrum of physiological processes. However, the full potential of NO as a therapeutic agent is significantly complicated by its short half-life and limited diffusion distance in human tissues. Current strategies for NO delivery focus on encapsulation of NO donors into prefabricated scaffolds or an enzyme-prodrug therapy approach. The former is limited by the finite pool of NO donors available, while the latter is challenged by the inherent low stability of natural enzymes. Zinc oxide (ZnO) particles with innate glutathione peroxidase and glycosidase activities, a combination that allows to catalytically decompose both endogenous (S-nitrosoglutathione) and exogenous (ß-gal-NONOate) donors to generate NO at physiological conditions are reported. By tuning the concentration of ZnO particles and NO prodrugs, physiologically relevant NO levels are achieved. ZnO preserves its catalytic property for at least 6 months and the activity of ZnO in generating NO from prodrugs in human serum is demonstrated. The ZnO catalytic activity will be beneficial toward generating stable NO release for long-term biomedical applications.

Synthesis of novel nitroreductase enzyme-activated nitric oxide prodrugs to site-specifically kill bacteria.

The developing antibiotic resistance crisis creates a serious need for new antimicrobial agents. In this work, novel nitroaromatic-protected piperazine diazeniumdiolate (nitric oxide donor) prodrugs are synthesized to release nitric oxide upon enzyme activation to kill bacteria. Antibacterial prodrugs could help reduce side effects due to antibiotics, only releasing the therapeutic where infections are concentrated. The nitroreductase enzyme, which is found almost exclusively in bacteria, reduces the nitroaromatic-protecting group of the synthesized compounds and catalyzes the release of nitric oxide. This paper shows that nitric oxide release from the synthesized compounds only occurs in the presence of a bacteria-derived nitroreductase enzyme, demonstrating the possibility of site-specific delivery of an antibacterial therapeutic. The amount of nitric oxide release is measured at concentrations of 0.01, 0.1, and 1 mM, and is well within antibacterial levels at concentrations of 0.1 and 1 mM. The antibacterial activity of the compounds is demonstrated after exposure of the compounds to Escherichia coli, a nitroreductase-producing bacterial species, leading to up to a 94% reduction in the number of viable bacteria after 24 h at 1 mM concentrations of the prodrug. This study is the first example of an antibacterial diazeniumdiolate prodrug activated by a nitroreductase enzyme, and further demonstrates the possibilities of antibacterial prodrugs.

Nitric oxide generation from S-nitrosoglutathione: New activity of indium and a survey of metal ion effects.

S-Nitrosothiols (RSNOs) such as S-nitrosoglutathione (GSNO) are known to produce nitric oxide (NO) through thermal, photolytic, and metal ion-promoted pathways, which has led to their increasing use as exogenous sources of therapeutic NO. Despite the burgeoning NO release applications for RSNOs, their susceptibility to metal-promoted decomposition has rarely been examined in a uniform manner through the specific measurement of NO release. In this study, the ability of various transition and post-transition metal ions to promote NO release from GSNO was surveyed by chemiluminescence-based NO detection. Substantial NO formation (>10-fold increase relative to GSNO baseline) was detected after the addition of Cu2+, Au3+, Pd2+, Pt2+, and V3+. Modest increases were observed in the cases of Co2+, Hf4+, Fe2+, Fe3+, Mn2+, Hg2+, Ni2+, Ag+, Sn2+, and Zr4+, while no effect was evident for Al3+, Cr3+, Pb2+, Sc3+, and Zn2+. It was further observed that In+ compounds initiate the apparent NO-forming decomposition of GSNO, while In0 and In3+ are inactive, indicating that In+ exerts a previously unknown effect on GSNO.

Hemilabile Proton Relays and Redox Activity Lead to {FeNO} x and Significant Rate Enhancements in NO2- Reduction.

Incorporation of the triad of redox activity, hemilability, and proton responsivity into a single ligand scaffold is reported. Due to this triad, the complexes Fe(PyrrPDI)(CO)2 (3) and Fe(MorPDI)(CO)2 (4) display 40-fold enhancements in the initial rate of NO2- reduction, with respect to Fe(MeOPDI)(CO)2 (7). Utilizing the proper sterics and p Ka of the pendant base(s) to introduce hemilability into our ligand scaffolds, we report unusual {FeNO} x mononitrosyl iron complexes (MNICs) as intermediates in the NO2- reduction reaction. The {FeNO} x species behave spectroscopically and computationally similar to {FeNO}7, an unusual intermediate-spin Fe(III) coupled to triplet NO- and a singly reduced PDI ligand. These {FeNO} x MNICs facilitate enhancements in the initial rate.

Enzyme-immobilized metal-organic framework nanosheets as tandem catalysts for the generation of nitric oxide.

An enzyme-immobilized metal-organic framework (MOF) nanosheet system was developed as a tandem catalyst, which converted glucose into gluconic acid and H2O2, and sequentially the latter could be used to catalyze the oxidation of l-arginine to generate nitric oxide in the presence of porphyrinic MOFs as artificial enzymes under physiological pH, showing great potential in cancer depleting glucose for starving-like/gas therapy.

Recent Developments in Drug Design of NO-donor Hybrid Compounds.

The free radical nitric oxide (NO) is considered one of the most versatile endogenous molecules and is a crucial signalling molecule in numerous biochemistry pathways of the human body. NO is directly related to pathological processes and plays an important role in many different and interrelated physiological processes. In some cases, a depletion of NO or an attenuation of its effector system could exist as in hypertension, angina and impotence; in others, an overproduction of NO may be a major cause of damage, as in circulatory shock, sepsis, neurodegenerative disorders and inflammatory responses. By using certain functional groups present in molecules that already have potential therapeutic value, hybrid compounds, by means of inclusion of NO-donors (e.g., ester nitrates and nitrites, S-nitrosothiols, metal complexes, furoxans, oxadiazoles, diazeniumdiolates and NO nanoparticles), can be developed that have a NO release benefit along with maintaining the activity of the native drug. The objective of the design of NO-donor hybrid compounds is to achieve a balance between the release of therapeutic amounts of NO, especially in the site of action, and maintaining the native drug activity. This review explores some of the most promising recent advances in NO-donor drug development and addresses the challenges associated with NO as a therapeutic agent.

Novel H2S-NO hybrid molecule (ZYZ-803) promoted synergistic effects against heart failure.

Therapeutic strategies that increase hydrogen sulfide (H2S) or nitric oxide (NO) are cytoprotective in various models of cardiovascular injury. However, the nature of interaction between H2S and NO in heart failure and the underlying mechanisms for the protective effects remain undefined. The present study tested the cardioprotective effect of ZYZ-803, a novel synthetic H2S-NO hybrid molecule that decomposed to release H2S and NO. ZYZ-803 dose dependently improved left ventricular remodeling and preserved left ventricular function in the setting of isoprenaline-induced heart failure. The cardioprotective effect of ZYZ-803 is significantly more potent than that of H2S and/or NO donor alone. ZYZ-803 stimulated the expression of cystathionine γ-lyase (CSE) for H2S generation and the activity of endothelial NO synthase (eNOS) for NO production. Blocking CSE and/or eNOS suppressed ZYZ-803-induced H2S and NO production and cardioprotection. ZYZ-803 increased vascular endothelial growth factor (VEGF) concentration and cyclic guanosine 5'-monophosphate (cGMP) level. Moreover, ZYZ-803 upregulated the endogenous antioxidants, glutathione peroxidase (GPx) and heme oxygenase 1 (HO-1). These findings indicate that H2S and NO cooperatively attenuates left ventricular remodeling and dysfunction during the development of heart failure through VEGF/cGMP pathway and ZYZ-803 provide expanding insight into strategies for treatment of heart failure.

Expression of a Nitric Oxide Synthesizing Protein in Arterial Endothelial Cells in Response to Different Anti-Anginal Agents Used in Acute Coronary Syndromes.

BACKGROUND: Organic "nitro" compounds such as nitroglycerine, isosorbide dinitrate are useful in the control of chest pain in acute coronary syndrome. But the mechanism of it in pain regulation remains speculative. Here, increase of NO production was investigated by the possible regulation of constitutive nitric oxide synthase (cNOS) function from goat arterial endothelial cells. This protein was purified and sequence wise characterized as protein disulfide isomerase (PDI) in response to different nitro compounds. METHOD: The NO generating protein was isolated from arterial endothelial cells and prepared to homogeneity. NO was determined by methemoglobin method. Protein sequence was analyzed by (µLC/MS/MS). RESULTS: A protein of Mr. ~57 kDa was isolated and found to be activated by not only "nitro" compounds but also by acetyl salicylic acid, insulin and glucose. The global BLAST of the protein sequence showed a significant alignment of the protein sequence with PDI. This protein trivially called pluri activator stimulated endothelial NOS (PLASENOS). The enzyme was stimulated by the above-mentioned activators in the presence of Ca2+. Lineweaver-Burk plot of this NOS like activities were demonstrated with its specific substrate l-arginine as Vmax = 5(nmol NO/mg of protein/hr) and Km≈ 0.5µM by the above activators. The enzyme activity was inhibited by the l-NAME, the specific inhibitor of NOS. CONCLUSION: The organic nitro compounds, acetyl salicylic acid, insulin and glucose were found to activate PLASENOS in the arterial endothelial cells for a continuous supply of NO to control the chest pain in acute coronary syndrome.

Synthesis and biological evaluations of new nitric oxide-anti-inflammatory drug hybrids.

Three novel series of nitroso derivatives (11-15), isoxazolopyrazoles (17a-c) and isoxazolo[3,4-d]pyridazines (18a-c) were prepared from the hydroxyimoyl chloride 10. In vitro COX1⧹2 inhibition activities were evaluated, both of 17b and 18a proved a promising inhibitory activity with IC50=1.12, 0.78µM in sequent. Carrageenan induced Paw edema, ulcer liability, nitric oxide (NO) release and histopathological study were determined. Most of the prepared compounds showed excellent activities. Reactions of 2-aminopyridine and enaminone with hydroxyimoyl chloride 10 were investigated and proved by 2D NMR. Molecular docking for most active compounds was operated giving a hint for compound-receptor interactions.

Sustained Nitric Oxide-Releasing Nanoparticles Interfere with Methicillin-Resistant Staphylococcus aureus Adhesion and Biofilm Formation in a Rat Central Venous Catheter Model.

Staphylococcus aureus is frequently isolated in the setting of infections of indwelling medical devices, which are mediated by the microbe's ability to form biofilms on a variety of surfaces. Biofilm-embedded bacteria are more resistant to antimicrobial agents than their planktonic counterparts and often cause chronic infections and sepsis, particularly in patients with prolonged hospitalizations. In this study, we demonstrate that sustained nitric oxide-releasing nanoparticles (NO-np) interfere with S. aureus adhesion and prevent biofilm formation on a rat central venous catheter (CVC) model of infection. Confocal and scanning electron microscopy showed that NO-np-treated staphylococcal biofilms displayed considerably reduced thicknesses and bacterial numbers compared to those of control biofilms in vitro and in vivo, respectively. Although both phenotypes, planktonic and biofilm-associated staphylococci, of multiple clinical strains were susceptible to NO-np, bacteria within biofilms were more resistant to killing than their planktonic counterparts. Furthermore, chitosan, a biopolymer found in the exoskeleton of crustaceans and structurally integrated into the nanoparticles, seems to add considerable antimicrobial activity to the technology. Our findings suggest promising development and translational potential of NO-np for use as a prophylactic or therapeutic against bacterial biofilms on CVCs and other medical devices.

Transition-Metal-Mediated Release of Nitric Oxide (NO) from S-Nitroso-N-acetyl-d-penicillamine (SNAP): Potential Applications for Endogenous Release of NO at the Surface of Stents Via Corrosion Products.

Nitric oxide (NO), identified over the last several decades in many physiological processes and pathways as both a beneficial and detrimental signaling molecule, has been the subject of extensive research. Physiologically, NO is transported by a class of donors known as S-nitrosothiols. Both endogenous and synthetic S-nitrosothiols have been reported to release NO during interactions with certain transition metals, primarily Cu(2+) and Fe(2+). Ag(+) and Hg(2+) have also been identified, although these metals are not abundantly present in physiological systems. Here, we evaluate Pt(2+), Fe(2+), Fe(3+), Mg(2+), Zn(2+), Mn(2+), Co(2+), Ni(2+), and Cu(2+) for their ability to generate NO from S-nitroso-N-acetyl-d-penicillamine (SNAP) under physiological pH conditions. Specifically, we report NO generation from RSNOs initiated by three transition metal ions; Co(2+), Ni(2+), and Zn(2+), which have not been previously reported to generate NO. Additionally, preliminary in vivo evidence of zinc wires implanted in the rat arterial wall and circulating blood is presented which demonstrated inhibited thrombus formation after 6 months. One potentially useful application of these metal ions capable of generating NO from RSNOs is their use in the fabrication of biodegradable metallic stents capable of generating NO at the stent-blood interface, thereby reducing stent-related thrombosis and restenosis.

Sustained Nitric Oxide-Releasing Nanoparticles Induce Cell Death in Candida albicans Yeast and Hyphal Cells, Preventing Biofilm Formation In Vitro and in a Rodent Central Venous Catheter Model.

Candida albicansis a leading nosocomial pathogen. Today, candidal biofilms are a significant cause of catheter infections, and such infections are becoming increasingly responsible for the failure of medical-implanted devices.C. albicansforms biofilms in which fungal cells are encased in an autoproduced extracellular polysaccharide matrix. Consequently, the enclosed fungi are protected from antimicrobial agents and host cells, providing a unique niche conducive to robust microbial growth and a harbor for recurring infections. Here we demonstrate that a recently developed platform comprised of nanoparticles that release therapeutic levels of nitric oxide (NO-np) inhibits candidal biofilm formation, destroys the extracellular polysaccharide matrices of mature fungal biofilms, and hinders biofilm development on surface biomaterials such as the lumen of catheters. We found NO-np to decrease both the metabolic activity of biofilms and the cell viability ofC. albicansin vitroandin vivo Furthermore, flow cytometric analysis found NO-np to induce apoptosis in biofilm yeast cellsin vitro Moreover, NO-np behave synergistically when used in combination with established antifungal drug therapies. Here we propose NO-np as a novel treatment modality, especially in combination with standard antifungals, for the prevention and/or remediation of fungal biofilms on central venous catheters and other medical devices.