Novel Nitric Oxide Research Articles

Abstract 2912: Nitric oxide mediates metabolic coupling of omentum-derived adipose to ovarian and endometrial cancer cells

Abstract Omental adipose stromal cells (O-ASCs) are multipotent population of mesenchymal stem cells contained in the omentum tissue which promote endometrial and ovarian tumor proliferation, migration and drug resistance. The mechanistic underpinnings of O-ASCs role in tumor progression and growth are unclear. Here, we report a novel nitric oxide (NO) mediated metabolic coupling between O-ASCs and gynecological cancer cells in which O-ASCs support NO homeostasis in malignant cells. NO is synthesized endogenously by the conversion of L-arginine into citrulline through nitric oxide synthase (NOS). Ovarian cancers have high affinity for NO which has solubility in lipids. This explains the proximity of many carcinomas to fatty tissue, and thus the high positive correlation between obesity and cancer. Through arginine depletion in the media using L-arginase and NOS inhibition in cancer cells using L-NAME, we demonstrate that patient derived O-ASCs increase NO levels in ovarian and endometrial cancer cells and promote proliferation in these cells. O-ASCs and cancer cell cocultures revealed that cancer cells utilize O-ASCs-secreted arginine and in turn secrete citrulline in the microenvironment. Interestingly, citrulline increased adipogenesis potential of the O-ASCs. Furthermore, we found that O-ASCs increased NO synthesis in cancer cells which led to decrease in mitochondrial respiration in these cells. Our findings suggest that O-ASCs upregulate glycolysis and reduce oxidative stress in cancer cells by increasing NO levels through paracrine metabolite secretion. Significantly, we found that O-ASC mediated chemoresistance in cancer cells can be deregulated by altering NO homeostasis. A combined approach of targeting secreted arginine through L-arginase, along with targeting microenvironment secreted factors induced increased NO synthesis in cancer cells using L-NAME, may be a viable therapeutic approach for targeting ovarian and endometrial cancers. Interestingly, we found that NO modulates s-nitrosation of cellular proteins mediating energy metabolism and cellular differentiation. O-ASCs were found to synthesize higher levels of NO during their differentiation to fat cells which leads to higher protein s-nitrosation. Inhibition of s-nitrosation of cellular proteins showed that NO-mediated protein modifications are strongly associated with O-ASCs adipogenesis. In summary, our data indicate that modulation of intrinsic NO substantially affects tumor growth and drug toxicity in ovarian and endometrial cancer cells. Our study will lead to significant advances in the understanding of the omentum in altering cancer metabolism and lead to novel therapeutics. Citation Format: Bahar Salimian Rizi, Kevin Chen, Inka Cajo Didelija, Juan Marini, Ann H. Klopp, Deepak Nagrath. Nitric oxide mediates metabolic coupling of omentum-derived adipose to ovarian and endometrial cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2912. doi:10.1158/1538-7445.AM2015-2912

Nitric oxide mediates metabolic coupling of omentum-derived adipose stroma to ovarian and endometrial cancer cells.

Omental adipose stromal cells (O-ASC) are a multipotent population of mesenchymal stem cells contained in the omentum tissue that promote endometrial and ovarian tumor proliferation, migration, and drug resistance. The mechanistic underpinnings of O-ASCs' role in tumor progression and growth are unclear. Here, we propose a novel nitric oxide (NO)-mediated metabolic coupling between O-ASCs and gynecologic cancer cells in which O-ASCs support NO homeostasis in malignant cells. NO is synthesized endogenously by the conversion of l-arginine into citrulline through nitric oxide synthase (NOS). Through arginine depletion in the media using l-arginase and NOS inhibition in cancer cells using N(G)-nitro-l-arginine methyl ester (l-NAME), we demonstrate that patient-derived O-ASCs increase NO levels in ovarian and endometrial cancer cells and promote proliferation in these cells. O-ASCs and cancer cell cocultures revealed that cancer cells use O-ASC-secreted arginine and in turn secrete citrulline in the microenvironment. Interestingly, citrulline increased adipogenesis potential of the O-ASCs. Furthermore, we found that O-ASCs increased NO synthesis in cancer cells, leading to decrease in mitochondrial respiration in these cells. Our findings suggest that O-ASCs upregulate glycolysis and reduce oxidative stress in cancer cells by increasing NO levels through paracrine metabolite secretion. Significantly, we found that O-ASC-mediated chemoresistance in cancer cells can be deregulated by altering NO homeostasis. A combined approach of targeting secreted arginine through l-arginase, along with targeting microenvironment-secreted factors using l-NAME, may be a viable therapeutic approach for targeting ovarian and endometrial cancers.

Synthesis and Biological Evaluation of Novel Furozan-Based Nitric Oxide-Releasing Derivatives of 23-Hydroxy Betulinic Acid and 3-oxo-23- hydroxybetulinic acid as Potential Anti-Tumor Agents

To search for novel nitric oxide (NO)-releasing anti-tumor agents, two series of furoxan-based NO-releasing derivatives of 23-Hydroxybetulinic acid and 3-oxo-23-hydroxybetulinic acid were designed and synthesized. The nitrate/nitrite levels in the cell lysates were assayed and the results showed that these derivatives could produce high levels of NO in vitro. Then the antiproliferative activity of these hybrids against four human cancer cell lines was further determined, among which, compound 20a was the most promising derivative with an IC50 under 10 μM on all tested cell lines. The preliminary structure-activity relationships were concluded based on present experimental data.

Biomimetic polymers responsive to a biological signaling molecule: nitric oxide triggered reversible self-assembly of single macromolecular chains into nanoparticles.

Novel nitric oxide (NO) responsive monomers (NAPMA and APUEMA) containing o-phenylenediamine functional groups have been polymerized to form NO-responsive macromolecular chains as truly biomimetic polymers. Upon exposure to NO--a ubiquitous cellular signaling molecule--the NAPMA- and APUEMA-labeled thermoresponsive copolymers exhibited substantial changes in solubility, clearly characterized by tuneable LCST behavior, thereby inducing self-assembly into nanoparticulate structures. Moreover, the NO-triggered self-assembly process in combination with environmentally sensitive fluorescence dyes could be employed to detect and image endogenous NO.

(S)-ZJM-289 Preconditioning Induces a Late Phase Protection Against Nervous Injury Induced by Transient Cerebral Ischemia and Oxygen-Glucose Deprivation

(S)-ZJM-289, a novel nitric oxide (NO)-releasing derivative of 3-n-butylphthalide, induces the neuroprotection in a rat model of focal cerebral ischemia/reperfusion (I/R). However, much is unknown about the late phase effect in the neuroprotection of (S)-ZJM-289 preconditioning. The purpose of this study is to explore the late phase neuroprotection of (S)-ZJM-289 preconditioning, as well as underlying mechanisms involved. Preconditioning with 40-160 mg/kg, (S)-ZJM-289 significantly reduces brain damage after I/R. (S)-ZJM-289 preconditioning is effective when applied 1-3 days before I/R. Moreover, the degrees of neuroprotection offered by (S)-ZJM-289 preconditioning and ischemic preconditioning are virtually identical. (S)-ZJM-289 preconditioning also protects primary cultured cortical neurons against oxygen-glucose deprivation and recovery-induced cytotoxicity in vitro. (S)-ZJM-289 preconditioning significantly increases the generation of NO, but has no effect on the nitric oxide synthase activities. Additionally, (S)-ZJM-289 preconditioning promotes the dissociation between nuclear-factor-E2-related factor (Nrf2) and kelch-like ECH-associated protein 1, and induces Nrf2 nuclear localization. The neuroprotection of (S)-ZJM-289 preconditioning is blocked by Nrf2-siRNA in vitro. (S)-ZJM-289 preconditioning up-regulates antioxidant enzymes against nervous injury. (S)-ZJM-289 preconditioning significantly activates extracellular regulated protein kinases (ERK) and inhibits c-Jun N-terminal kinases signaling cascade. The neuroprotection is abolished by the ERK inhibitor PD98059 in vitro. Subsequently, (S)-ZJM-289 preconditioning increases the levels of anti-apoptotic protein B cell lymphoma 2 (Bcl-2) and inhibited the translocation of Bcl-2 associated X to the mitochondria, thus attenuating the release of cytochrome c from the mitochondria and the activation of downstream caspase. These results suggest that (S)-ZJM-289 preconditioning exerts the late phase protection against nervous injury induced by transient cerebral ischemia and oxygen-glucose deprivation.

1,2,4-Triazole/oxime hybrids as new strategy for nitric oxide donors: Synthesis, anti-inflammatory, ulceroginicity and antiproliferative activities

A series of novel nitric oxide (NO) donating triazole/oxime hybrids was prepared and evaluated for their anti-inflammatory activity and antiproliferative activity. Most of the tested compounds showed significant anti-inflammatory activity using carrageenan-induced rat paw edema method compared to indomethacin. Calculation of the ulcer indices and histopathological investigation indicated that the prepared NO-donating oximes exhibited less ulcerogenicity compared to their ketone intermediates and indomethacin. The NO-donating oximes 7i and 7k achieved remarkable cell growth inhibition activity against most of the tested cell lines. Compound 7k was found to be with high selectivity against CNS subpanel with selectivity ratio of 11.99 at GI50 level.

Synthesis and characterization of a novel nitric oxide fluorescent probe CdS-PMMA nanocomposite via in-situ bulk polymerization

A novel nitric oxide (NO) fluorescent probe CdS-poly(methyl methacrylate) (PMMA) nanocomposites with different molar ratios of CdS quantum dots (QDs) to PMMA are developed successfully via in-situ bulk polymerization method. The optical properties of CdS/PMMA nanocomposites are studied by UV–Vis absorption spectra and fluorescence (FL) spectra in detail. It is demonstrated that the optical properties from such nanocomposite solution are tuned and stabilized by simply varying the concentration of CdS in the final product. X-ray diffraction (XRD) patterns of CdS-PMMA nanocomposite with higher loading of CdS show broad pattern for cubic CdS, which has narrow particle size distribution with less than 5nm in PMMA observed by transmission electron microscopy (TEM). The surface morphological characterization of the CdS-PMMA nanocomposite has been done through atomic force microscopy (AFM). The thermo-gravimetric analyses (TGA) and differential scanning calorimetry (DSC) confirm the enhanced thermal stability of CdS-PMMA nanocomposites than PMMA. NO can coordinate with Cd2+ as a ligand for transition metal complexes, which will cause a quenching effect on the fluorescence of CdS QDs. Therefore, a significant quenching effect on the fluorescence of the CdS-PMMA nanocomposite is observed in the presence of NO. The fluorescence responses are concentration-dependent and can be well described by the typical Stern–Volmer equation, and a linear calibration I0/I=1.0021+0.1944[NO] (R2=0.96052) is obtained in the range from 1.4×10−5 to 9.3×10−3mol/L NO with a detection limit of 1.0×10−6mol/L (S/N=3).

Hybrid Molecule from O2-(2,4-Dinitrophenyl)diazeniumdiolate and Oleanolic Acid: A Glutathione S-Transferase π-Activated Nitric Oxide Prodrug with Selective Anti-Human Hepatocellular Carcinoma Activity and Improved Stability

A series of hybrids from O(2)-(2,4-dinitrophenyl)diazeniumdiolate and oleanolic acid (OA) were designed, synthesized, and biologically evaluated as novel nitric oxide (NO)-releasing prodrugs that could be activated by glutathione S-transferase π (GSTπ) overexpressed in a number of cancer cells. It was discovered that the most active compound, 21, released high levels of NO selectively in HCC cells but not in the normal cells and exhibited potent antiproliferative activity in vitro as well as remarkable tumor-retarding effects in vivo. Compared with the reported GSTπ-activated prodrugs JS-K and PABA/NO, 21 exhibited remarkably improved stability in the absence of GSTπ. Importantly, the decomposition of 21 occurred in the presence of GSTπ and was much more effective than in glutathione S-transferase α. Additionally, 21 induced apoptosis in HepG2 cells by arresting the cell cycle at the G2/M phase, activating both the mitochondrion-mediated pathway and the MAPK pathway and enhancing the intracellular production of ROS.

INDQ/NO, a Bioreductively Activated Nitric Oxide Prodrug

The design, synthesis, and development of INDQ/NO, a novel nitric oxide (NO) prodrug targeted by a bioreductive trigger, are described. INDQ/NO, an indolequinone-diazeniumdiolate is found to be metabolized to produce NO by DT-diaphorase, a bioreductive enzyme that is overexpressed in certain cancers and hypoxic tumors. Cell-based assays revealed that INDQ/NO induces DNA damage and is a potent inhibitor of cancer cell proliferation.

New nitric oxide donating 1,2,4-triazole/oxime hybrids: Synthesis, investigation of anti-inflammatory, ulceroginic liability and antiproliferative activities

A series of novel nitric oxide (NO) donating triazole/oxime hybrids was prepared and evaluated for their anti-inflammatory activity. Most of the tested compounds showed significant anti-inflammatory activity using carrageenan-induced rat paw edema method compared to indomethacin. Calculation of the ulcer indices and histopathological investigation indicated that the prepared NO-donating oximes exhibited less ulcerogenicity compared to their intermediate ketones and indomethacin. The NO-donating oxime 6i revealed significant activity against renal cancer A498 cell lines with 50.52 cell growth inhibition.

Synthesis of novel furozan-based nitric oxide-releasing derivatives of 1-oxo-oridonin with anti-proliferative activity

AimTo search for novel nitric oxide (NO) releasing anti-tumor agents, a series of furoxan-based nitric oxide-releasing derivatives of 1-oxo-oridonin were designed and synthesized. MethodDifferent furozan-based NO donors (9a-i) were synthesized and conjugated with the 14-hydroxyl of 1-oxo-oridonin (2). The level of nitrate/nitrite in the cell lysates was tested by Griess assay and the anti-proliferative activity of these derivatives against four human cancer cell lines was also determined. ResultsThese furoxan-based NO-releasing derivatives could produce more than 19 μmol·L−1 of NO in vitro at the time point of 60 min. The most promising compound 10 h exhibited stronger activity than the positive control Taxol against the Bel-7402 cell line with an IC50 value 0.74 μmol·L−1. The structure-activity relationships were concluded based on the derived experimental data. ConclusionThese results suggested that NO-donor/natural product hybrids may provide a promising approach for the discovery of novel anti-tumor agents.

Abstract 94: Nitric Oxide--Regulated RGS4 Loss of Function Coordinates Vascular Growth with Cardiomyocyte Growth in the Absence of External Hypertrophic Stimuli

The mechanisms that coordinate an increase in vasculature with cardiomyocyte growth in adult heart are not known. We report that induction of angiogenesis is sufficient to promote cardiomyocyte growth and myocardial hypertrophy through a novel nitric oxide (NO)-dependent mechanism. Our hypothesis is that an increase in endothelial-derived NO release promotes the proteosomal degradation of negative regulator of G protein signaling RGS4 in cardiomyocytes (CM) thus relieving repression of hypertrophic stimulation through G proteins. Methods include cell culture systems and transgenic mouse models. We generated three conditional cardiac inducible mouse models: (1) to stimulate angiogenesis by transgenic expression of placental growth factor (PlGF); (2) to stimulate angiogenesis by PlGF and compensate for RGS4 degradation by transgenic expression of RGS4 in CM; and (3) to stimulate angiogenesis by PlGF in eNOS -/- mice. Results. In cultured rat neonatal CM, the treatment with a slow release NO donor resulted in increased degradation of RGS4 through the N-end rule pathway of protein degradation. RGS4 loss of function led to increase in cell size through Gbetagamma/PI3Kgamma-dependent Akt/mTORc1 activation. In mice, PlGF expression induced an increase in capillary/myocyte ratio and arteriolar branches (determined by microCT angiograms). Myocardial hypertrophy was induced subsequent to angiogenic stimulation and concurrent with increased in NO production. Consistent with in vitro data hypertrophic stimulation was associated with reduced RGS4 protein levels and robust activation of Akt/mTORc1 signaling. This hypertrophy was prevented by concomitant transgenic expression of RGS4 in CM, despite the persistence of angiogenesis, arteriogenesis, and increased NO release. Furthermore, the NOS inhibitor L-NAME or mTORc1 inhibitor rapamycin significantly attenuated RGS4 degradation, Akt/mTORc1 signaling, and heart size in PlGF-induced mice. A similar effect was observed upon conditional heart-specific PlGF expression in eNOS -/- mice. In conclusion, these findings support a novel NO/RGS4/G protein/Akt mechanism that couples vessel growth with myocyte growth and heart size in the absence of traditional hypertrophic stimuli.

Synthesis and Biological Evaluation of Novel Furozan-Based Nitric Oxide-Releasing Derivatives of Oridonin as Potential Anti-Tumor Agents

To search for novel nitric oxide (NO) releasing anti-tumor agents, a series of novel furoxan/oridonin hybrids were designed and synthesized. Firstly, the nitrate/nitrite levels in the cell lysates were tested by a Griess assay and the results showed that these furoxan-based NO-releasing derivatives could produce high levels of NO in vitro. Then the anti-proliferative activity of these hybrids against four human cancer cell lines was also determined, among which, 9h exhibited the most potential anti-tumor activity with IC50 values of 1.82 µM against K562, 1.81 µM against MGC-803 and 0.86 µM against Bel-7402, respectively. Preliminary structure-activity relationship was concluded based on the experimental data obtained. These results suggested that NO-donor/natural product hybrids may provide a promising approach for the discovery of novel anti-tumor agents.

Cinaciguat, a novel activator of soluble guanylate cyclase, protects against ischemia/reperfusion injury: role of hydrogen sulfide

Cinaciguat (BAY 58-2667) is a novel nitric oxide (NO)-independent activator of soluble guanylate cyclase (sGC), which induces cGMP-generation and vasodilation in diseased vessels. We tested the hypothesis that cinaciguat might trigger protection against ischemia/reperfusion (I/R) in the heart and adult cardiomyocytes through cGMP/protein kinase G (PKG)-dependent generation of hydrogen sulfide (H(2)S). Adult New Zealand White rabbits were pretreated with 1 or 10 μg/kg cinaciguat (iv) or 10% DMSO (vehicle) 15 min before I/R or with 10 μg/kg cinaciguat (iv) at reperfusion. Additionally, adult male ICR mice were treated with either cinaciguat (10 μg/kg ip) or vehicle 30 min before I/R or at the onset of reperfusion (10 μg/kg iv). The PKG inhibitor KT5283 (KT; 1 mg/kg ip) or dl-propargylglycine (PAG; 50 mg/kg ip) the inhibitor of the H(2)S-producing enzyme cystathionine-γ-lyase (CSE) were given 10 and 30 min before cinaciguat. Cardiac function and infarct size were assessed by echocardiography and tetrazolium staining, respectively. Primary adult mouse cardiomyocytes were isolated and treated with cinaciguat before simulated ischemia/reoxygenation. Cinaciguat caused 63 and 41% reduction of infarct size when given before I/R and at reperfusion in rabbits, respectively. In mice, cinaciguat pretreatment caused a more robust 80% reduction in infarct size vs. 63% reduction when given at reperfusion and preserved cardiac function following I/R, which were blocked by KT and PAG. Cinaciguat also caused an increase in myocardial PKG activity and CSE expression. In cardiomyocytes, cinaciguat (50 nM) reduced necrosis and apoptosis and increased H(2)S levels, which was abrogated by KT. Cinaciguat is a novel molecule to induce H(2)S generation and a powerful protection against I/R injury in heart.

Synthesis, anti-inflammatory activity and ulcerogenic liability of novel nitric oxide donating/chalcone hybrids

A group of novel nitric oxide (NO) donating chalcone derivatives was prepared by binding various amino chalcones with different NO donating moieties including; nitrate ester, oximes and furoxans. Most of the prepared compounds showed significant anti-inflammatory activity using carrageenan-induced rat paw edema method compared with indomethacin. The prepared compounds exhibited more protection than indomethacin in regard to gastric toxicity. Histopathological investigation confirmed the beneficial effects of the NO releasing compounds in reducing ulcer formation. The incorporation of the NO-donating group into the parent chalcone derivatives caused a moderate increase in the anti-inflammatory activity with a marked decrease in gastric ulcerations compared to their parent chalcone derivatives.

Synthesis and evaluation of nitric oxide-releasing derivatives of 3-n-butylphthalide as anti-platelet agents

Most ischemic stroke results from brain blood vessel blockage by platelet-mediated thrombus, and anti-platelet therapy has been demonstrated clinical benefits in the treatment of this disease. In the present work, novel nitric oxide (NO)-releasing derivatives of an anti-ischemic stroke drug 3-n-butylphthalide (NBP) were synthesized. Compounds 7a and 7c exhibited more potent anti-platelet activity than NBP and aspirin, and released a moderate amount of NO, which is beneficial in improving cardiovascular and cerebral circulation. These findings provide an alternative approach to the development of drugs more potent than NBP for the intervention of ischemic stroke.

Intravascular glucose/lactate sensors prepared with nitric oxide releasing poly(lactide- co-glycolide)-based coatings for enhanced biocompatibility

Intravenous amperometric needle-type enzymatic glucose/lactate sensors intended for continuous monitoring are prepared with a novel nitric oxide (NO) releasing layer to improve device hemocompatibility. To create an underlying NO release coating, the sensors with immobilized enzymes (either glucose oxidase or lactate oxidase) are prepared with a thin layer of poly(lactide- co-glycolide) (PLGA) loaded with lipophilic diazeniumdiolate species that slowly release NO via a proton driven reaction. An outer thin layer (ca. 30 μm) of PurSil (polyurethane/dimethylsiloxane copolymer) limits the flux of glucose and lactate to the inner layer of enzyme, to provide the desired linear amperometric response. A 30 μm coating of PLGA containing 33 wt% of the appropriate NO donor ( N-diazeniumdiolated dibutylhexanediamine, DBHD/N 2O 2) can release NO at a physiologically relevant rate >1 × 10 −10 mol min −1 cm −2 for at least 7 days without influencing the analytical performance of the glucose/lactate sensors. In vitro, the sensors exhibit relatively stable amperometric response over a one-week period with high selectivity over interferences (e.g., ascorbic acid) required for blood monitoring applications. Glucose sensors implanted in the veins of rabbits for 8 h exhibit significantly enhanced hemocompatibility for the NO release sensors vs. corresponding controls (without NO release in same animals), with greatly reduced thrombus formation on their surfaces. Further, the analytical performance of the NO release glucose sensors are superior to controls placed in the veins of the same animals, with a greater accuracy in measuring blood glucose levels as evaluated using a Clarke error grid type analysis.

GT-094, a NO-NSAID, Inhibits Colon Cancer Cell Growth by Activation of a Reactive Oxygen Species-MicroRNA-27a: ZBTB10-Specificity Protein Pathway

Ethyl 2-((2,3-bis(nitrooxy)propyl)disulfanyl)benzoate (GT-094) is a novel nitric oxide (NO) chimera containing an nonsteroidal anti-inflammatory drug (NSAID) and NO moieties and also a disulfide pharmacophore that in itself exhibits cancer chemopreventive activity. In this study, the effects and mechanism of action of GT-094 were investigated in RKO and SW480 colon cancer cells. GT-094 inhibited cell proliferation and induced apoptosis in both cell lines and this was accompanied by decreased mitochondrial membrane potential (MMP) and induction of reactive oxygen species (ROS), and these responses were reversed after cotreatment with the antioxidant glutathione. GT-094 also downregulated genes associated with cell growth [cyclin D1, hepatocyte growth factor receptor (c-Met), epidermal growth factor receptor (EGFR)], survival (bcl-2, survivin), and angiogenesis [VEGF and its receptors (VEGFR1 and VEGFR2)]. Results of previous RNA interference studies in this laboratory has shown that these genes are regulated, in part, by specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4 that are overexpressed in colon and other cancer cell lines and not surprisingly, GT-094 also decreased Sp1, Sp3, and Sp4 in colon cancer cells. GT-094-mediated repression of Sp and Sp-regulated gene products was due to downregulation of microRNA-27a (miR-27a) and induction of ZBTB10, an Sp repressor that is regulated by miR-27a in colon cancer cells. Moreover, the effects of GT-094 on Sp1, Sp3, Sp4, miR-27a, and ZBTB10 were also inhibited by glutathione suggesting that the anticancer activity of GT-094 in colon cancer cells is due, in part, to activation of an ROS-miR-27a:ZBTB10-Sp transcription factor pathway.

Design, synthesis and evaluation of nitric oxide releasing derivatives of 3-n-butylphthalide as antiplatelet and antithrombotic agents

Novel nitric oxide (NO) releasing derivatives (7a-7l) of 3-n-butylphthalide (NBP) were designed and synthesized. Compound 7e inhibited the adenosine diphosphate (ADP), thrombin (TH) and arachidonic acid (AA)-induced in vitro platelet aggregation, superior to NBP and aspirin, released moderate levels of NO, and improved aqueous solubility relative to NBP. Furthermore, 7e exhibited greater antithrombotic activity than NBP and aspirin in rats, and protected against collagen and adrenaline-induced thrombosis in mice. Therefore, NO-releasing NBP derivatives possessed potent antiplatelet aggregation and antithrombotic activity. Our findings may aid in the design of new therapeutic agents for the treatment of thrombosis-related ischemic stroke.

Synthesis and characterization of a novel ruthenium nitrosyl complex and studies on photolability of coordinated NO

Abstract In the present communication, we have reported the synthesis and characterization of a novel nitric oxide (NO) donating complex [Ru(L1)(PPh3)2(NO)](ClO4) ( 2 ) derived from [Ru(L1)(PPh3)2(Cl)] ( 1 ) (L1H2 is pyridine 2,6-dicarboxylic acid and H stands for dissociable proton). Characterization of 2 by UV–Vis, IR and NMR spectral studies revealed the presence of {RuNO}6 species with S = 0 ground state. ESI-MS data also supported the formation of 2 . Electrochemical studies on complex 2 were investigated. The coordinated NO was found to be photolabile under visible as well as in UV light and photocleaved NO was transferred to reduced myoglobin.