NO-donor Properties Research Articles

Preparation, Antioxidant Properties and Ability to Increase Intracellular NO of a New Pyridoxine Derivative B6NO.

In the case of various pathologies, an imbalance between ROS generation and the endogenous AOS can be observed, which leads to excessive ROS accumulation, intensification of LPO processes, and oxidative stress. For the prevention of diseases associated with oxidative stress, drugs with antioxidant activity can be used. The cytotoxic, antioxidant, and NO-donor properties of the new hybrid compound B6NO (di(3-hydroxy-4,5-bis(hydroxymethyl)-2-methylpyridinium) salt of 2-(nitrooxy)butanedioic acid) were studied. It was determined that B6NO chelates iron ions by 94%, which indicates B6NO’s ability to block the Fenton reaction. The hybrid compound B6NO inhibits the process of initiated lipid peroxidation more effectively than pyridoxine. It was shown that B6NO exhibits antioxidant properties by decreasing ROS concentration in normal cells during the oxidative stress induction by tert-Butyl peroxide. At the same time, the B6NO antioxidant activity on tumor cells was significantly lower. B6NO significantly increases the intracellular nitrogen monoxide accumulation and showed low cytotoxicity for normal cells (IC50 > 4 mM). Thus, the results indicate a high potential of the B6NO as an antioxidant compound.

Novel Arylazo‐1,2,5‐oxadiazole Photoswitches: Synthesis, Photoisomerization and Nitric Oxide Releasing Properties

AbstractA series of novel molecular photoswitches incorporating an aryldiazenyl moiety linked to a 1,2,5‐oxadiazole (furazan) or 1,2,5‐oxadiazole 2‐oxide (furoxan) subunit was synthesized by a simple and step‐economic chemical route. Upon visible light irradiation, (E)‐arylazo‐1,2,5‐oxadiazoles underwent photoisomerization to the corresponding (Z)‐isomers which are stable under ambient conditions. Structural factors affecting the photoswitching ability were also revealed. Synthesized photoswitches exhibited good performance due to the absence of fatigue or decomposition over at least ten cycles under air in a temperature range of 20–60 °C. NO donor properties of the synthesized arylazofuroxans were also evaluated in vitro and it was found that (Z)‐arylazofuroxans released significantly larger amounts of NO than the corresponding (E)‐isomers, which suggests strong potential of these molecular photoswitches in photopharmacology and other biomedical applications.

NO-Donor Iron Nitrosyl Complex with N-Ethylthiourea Ligand Exhibits Selective Toxicity to Glioma A172 Cells.

We studied effects of NO-donor iron nitrosyl complex with N-ethylthiourea ligand (ETM) on normal or tumor-derived cell lines. ETM was mildly toxic to most cell lines studied except the human glioma cell line A172 that proved to be highly sensitive to the complex and underwent cell death after ETM exposure. The high susceptibility of A172 cells to ETM was attributed to its NO-donor properties since no toxicity was detected for the N-ethylthiourea ligand.

Nitric oxide donor augments antineoplastic effects of arginine deprivation in human melanoma cells

Anticancer therapy based on recombinant arginine-degrading enzymes has been proposed for the treatment of several types of malignant cells deficient in arginine biosynthesis. One of the predicted side effects of such therapy is restricted bioavailability of nitric oxide as arginine catabolic product. Prolonged NO limitation may lead to unwanted disturbances in NO-dependent vasodilation, cardiovascular and immune systems. This problem can be overcome by co-supplementation with exogenous NO donor. However, NO may potentially counteract anticancer effects of therapy based on arginine deprivation. In this study, we evaluate for the first time the effects of an exogenous NO donor, sodium nitroprusside, on viability and metastatic properties of two human melanoma cell lines SK-MEL-28 and WM793 under arginine-deprived conditions. It was revealed that NO did not rescue melanoma cells from specific effects evoked by arginine deprivation, namely decreased viability and induction of apoptosis, dramatically reduced motility, invasiveness and clonogenic potential. Moreover, sodium nitroprusside co-treatment augmented several of these antineoplastic effects. We report that a combination of NO-donor and arginine deprivation strongly and specifically impaired metastatic behavior of melanoma cells. Thus, sodium nitroprusside can be considered as an adjuvant for the more efficient treatment of malignant melanoma and possibly other tumors with arginine-degrading enzymes.

Synthesis, antiplatelet and antithrombotic activities of resveratrol derivatives with NO-donor properties

Resveratrol (RVT) is a stilbene with a protective effect on the cardiovascular system; however, drawbacks including low bioavailability and fast metabolism limit its efficacy. In this work we described new resveratrol derivatives with nitric oxide (NO) release properties, ability to inhibit platelet aggregation and in vivo antithrombotic effect. Compounds (4a–f) were able to release NO in vitro, at levels ranging from 24.1% to 27.4%. All compounds (2a–f and 4a–f) have exhibited platelet aggregation inhibition using as agonists ADP, collagen and arachidonic acid. The most active compound (4f) showed reduced bleeding time compared to acetylsalicylic acid (ASA) and protected up to 80% against in vivo thromboembolic events. These findings suggest that hybrid resveratrol-furoxan (4f) is a novel lead compound able to prevent platelet aggregation and thromboembolic events.

0494 : Vascular protective effects of an amphiphilic nitrone against hyperglycemia-induced oxidative damages

Overconsumption of sugary drinks and food has recently been implicated in the pathogenesis of cardiovascular disease. Indeed, during acute hyperglycemia, increased oxidative stress has been proposed as a key trigger of vascular dysfunction. Nitrones are well known spin traps of noxious free radicals, and therefore can act as antioxidants but exhibit NO-donor properties as well. Several series of amphiphilic nitrones, i.e. water-soluble and lipophilic at the same time, were developed with the expectation that amphiphilicity may favor intracellular localization. Consequently, our objective was to investigate the protective effect of an amphiphilic nitrone (LPBNAH) on oxidative stress impairments of vascular function following an acute hyperglycemia. In order to evaluate this hypothesis, we removed aortas from Wistar rats (n=20). Aortic rings (2-3mm) were mounted in an organ chamber between two wire hooks which were connected to a force transducer (EMKA, France) to record changes in isometric force. Endothelial vasodilatory function in response to acetylcholine (ACh, 10 -10 to 10 -4 M) was evaluated in normoglycemic (11mM) and hyperglycemic (100mM) conditions in presence or not of LPBNAH (100μM) as well as other antioxidants such as N-acetylcysteine (NAC, 10μM) or Apocynin (10μM). We observed in our study an impairment of endothelial function associated with an increased reactive oxygen species production (evaluated by EPR) in hyperglycemic conditions. Interestingly, these damages were completely reversed by both NAC and apocynin, thus confirming the well-known pro-oxidant effect of hyperglycemia. Regarding the effect of our amphiphilic nitrone, we observed a major protective effect on endothelial hyperglycemic impairments. Indeed, in presence of LPBNAH, maximal vasodilatation and ACh sensitivity were preserved from hyperglycemic impairments. Our results points out the biological protective effect of such molecule in a pro-oxidant condition such as hyperglycemia. The author hereby declares no conflict of interest

New praziquantel derivatives containing NO-donor furoxans and related furazans as active agents against Schistosoma mansoni

A series of NO-donor praziquantel hybrid compounds was obtained by combining praziquantel (PZQ) and furoxan moieties in a single entity. NO-donor properties of the furoxan derivatives were evaluated by detecting nitrite after incubation of the products in 7.4 pH buffered solution in the presence of l-cysteine. Structurally-related furazans, devoid of NO release capacity, were also synthesized for control purposes. All products were studied for their ability to inhibit recombinant Schistosoma mansoni thioredoxin glutathione reductase (TGR). Mobility and death of adult Schistosoma mansoni worms cultured in the presence of the products were evaluated versus PZQ. Analysis of the results showed that some products were endowed with both PZQ and NO-dependent antiparasitic properties. Compounds 6, 7, 18, and 24 emerged as the most interesting balanced hybrids, worthy of additional study on PZQ-resistant parasites.

The effect of NO-donors on chloride efflux, intracellular Ca2 + concentration and mRNA expression of CFTR and ENaC in cystic fibrosis airway epithelial cells

Since previous studies showed that the endogenous bronchodilator, S-nitrosglutathione (GSNO), caused a marked increase in CFTR-mediated chloride (Cl−) efflux and improved the trafficking of CFTR to the plasma membrane, and that also the nitric oxide (NO)-donor GEA3162 had a similar, but smaller, effect on Cl− efflux, it was investigated whether the NO-donor properties of GSNO were relevant for its effect on Cl− efflux from airway epithelial cells. Hence, the effect of a number of other NO-donors, sodium nitroprusside (SNP), S-nitroso-N-acetyl-dl-penicillamine (SNAP), diethylenetriamine/nitric oxide adduct (DETA-NO), and diethylenetriamine/nitric oxide adduct (DEA-NONOate) on Cl− efflux from CFBE (∆F508/∆F508-CFTR) airway epithelial cells was tested. Cl− efflux was determined using the fluorescent N-(ethoxycarbonylmethyl)-6-methoxyquinoliniu bromide (MQAE)-technique. Possible changes in the intracellular Ca2+ concentration were tested by the fluorescent fluo-4 method in a confocal microscope system. Like previously with GSNO, after 4h incubation with the NO-donor, an increased Cl− efflux was found (in the order SNAP>DETA-NO>SNP). The effect of DEA-NONOate on Cl− efflux was not significant, and the compound may have (unspecific) deleterious effects on the cells. Again, as with GSNO, after a short (5min) incubation, SNP had no significant effect on Cl− efflux. None of the NO-donors that had a significant effect on Cl− efflux caused significant changes in the intracellular Ca2+ concentration. After 4h preincubation, SNP caused a significant increase in the mRNA expression of CFTR. SNAP and DEA-NONOate decreased the mRNA expression of all ENaC subunits significantly. DETA-NO caused a significant decrease only in α-ENaC expression. After a short preincubation, none of the NO-donors had a significant effect, neither on the expression of CFTR, nor on that of the ENaC subunits in the presence and absence of l-cysteine. It can be concluded that the effect of GSNO on Cl− efflux is, at least in part, due to its properties as an NO-donor, and the effect is likely to be mediated by CFTR, not by Ca2+-activated Cl− channels.

Benzofuroxane Derivatives as Multi-Effective Agents for the Treatment of Cardiovascular Diabetic Complications. Synthesis, Functional Evaluation, and Molecular Modeling Studies

Diabetes mellitus is the major risk factor for cardiovascular disorders. Aldose reductase, the rate-limiting enzyme of the polyol pathway, plays a key role in the pathogenesis of diabetic complications. Accordingly, inhibition of this enzyme is emerging as a major therapeutic strategy for the treatment of hyperglycemia-induced cardiovascular pathologies. In this study, we describe a series of 5(6)-substituted benzofuroxane derivatives, 5a-k,m, synthesized as aldose reductase inhibitors. Besides inhibiting efficiently the target enzyme, 5a-k,m showed additional NO donor and antioxidant properties, thus emerging as novel multi-effective compounds. The benzyloxy derivative 5a, the most promising of the whole series, showed a well-balanced, multifunctional profile consisting of submicromolar ALR2 inhibitory efficacy (IC50=0.99±0.02 μM), significant and spontaneous NO generation properties, and excellent hydroxyl radical scavenging activity. Computational studies of the novel compounds clarified the aldose reductase inhibitory profile observed, thus rationalizing structure-activity relationships of the whole series.

Design, Synthesis, and Pharmacological Evaluation of Novel Hybrid Compounds to Treat Sickle Cell Disease Symptoms. Part II: Furoxan Derivatives

Phthalimide derivatives containing furoxanyl subunits as nitric oxide (NO)-donors (3a-g) were designed, synthesized, and evaluated in vitro and in vivo for their potential uses in the oral treatment of sickle cell disease symptoms. All compounds (3a-g) demonstrated NO-donor properties at different levels. Moreover, compounds 3b and 3c demonstrated analgesic activity. Compound 3b was determined to be a promising drug candidate for the aforementioned uses, and it was further evaluated in K562 culture cells to determine its ability to increase levels of γ-globin expression. After 96 h at 5 μM, compound 3b was able to induce γ-globin expression by nearly three times. Mutagenic studies using micronucleus tests in peripheral blood cells of mice demonstrated that compound 3b reduces the mutagenic profile as compared with hydroxyurea. Compound 3b has emerged as a new leading drug candidate with multiple beneficial effects for the treatment of sickle cell disease symptoms and provides an alternative to hydroxyurea treatment.

Aspirin Hybrid Molecules with Improved Antiplatelet Properties Designed As New Drug Candidates to Prevent Atherothrombosis,

Abstract 3364 Introduction.Platelets are involved in atherothrombosis as a consequence of their inappropriate and sustained activation, being thus considered an important target for pharmacological interventions. Aspirin (ASA) is the current drug standard of care of most patients; however the therapy is limited and presents several inconveniences such as lack of effectiveness and bleeding. The use of hybridization strategy allows obtaining compounds with pharmacokinetic and pharmacodynamic properties improved. In this work, we describe new compounds with significant antiplatelet activity induced by ADP. These compounds 2-(2-((4-methyl-1,2,5-oxadiazole-2-oxide)methylene)hydrazinecarbonyl) phenyl acetate (Lapdesf 1) and 2-(2-((4-phenyl-1,2,5-oxadiazole-2-oxide)methylene)hydrazinecarbonyl) phenyl acetate (Lapdesf 2) were structurally planned by modification of acetyl salicylic acid (ASA) based on the use of acylhydrazone subunit, previously reported to contribute to inhibit platelet aggregation. Furthermore, 1,2,5-oxadiazole N-oxide subunit known by its NO-donor properties were included in the hybrid structure in order to contribute for the antiplatelet activity. Methods. 1. Detection of nitrite. A solution of the appropriate compound (20 μL) in DMSO was added to 2 mL of a mixture of 50 mM phosphate buffer (pH 7.4) and methanol (1:1, v:v), containing 5 mM of L-cysteine. The final concentration of the compound was 10–4M. After 1 h at 37 °C, 1 mL of the reaction mixture was treated with 250 μL of Griess reagent. After 10 min at room temperature, the absorbance was measured at 540 nm using a spectrophotometer. Standard sodium nitrite solutions (10–80 nmol/mL) were used to construct the calibration curve. The yields of nitrite are expressed as % NO2– (mol/mol). 2. Antiplatelet activity. Blood was withdrawn from mice central artery and mixed with 3.8% trisodium citrate (9:1 v/v). Platelet-rich plasma (PRP) was prepared by centrifugation at 375 × g for 10 min at room temperature. The platelet-poor plasma (PPP) was prepared by centrifugation of the pellet at 1800 × g for 10 min at room temperature. Platelet aggregation was monitored by the turbidimetric method of Born and Cross using aggregometer. PRP (300 μL) was incubated at 37 °C for 1 min with compounds before addition of the aggregating agent. Platelet aggregation was induced by ADP (10 μM). Compounds and ASA used as control were evaluated at 150 μM. 3. Tail vein bleeding time model. Mice were anesthetized (ketamine 75mg/kg; medetomidine 1 mg/kg IP). A transverse incision is made with a scalpel over a lateral tail vein at a position where the diameter of the tail is 2.25–2.5 mm. The tail was immersed in normal saline (37°C) in a hand-held test tube. This last one is rotated to prevent the shed blood from obscuring the incision site. The time from the incision to the cessation of bleeding is recorded. The results are expressed as mean time + SEM of 6 animals per group. The data were analyzed statistically with Student’s t test at a significance level of P < 0.05. Results. 1. Detection of nitrite: Isosorbide dinitrate used as the control, induced 10.9 + 0.5 % of nitrite (mol/mol) formation while compound Lapdesf 1 and Lapdesf 2 induced 1.3 + 0.1 and 4.7 + 0.2, respectively. 2.Antiplatelet activity. The compounds inhibited platelet aggregation induced by ADP. The aggregation percentage in presence of Lapdesf 1 and Lapdesf 2 were 3.1 + 0,2 and 32 + 0,4 respectively. The aggregation percentage of control (ADP) and ASA were 40.3 + 0,3 and 57.5 + 0,4 respectively. 3. Tail vein bleeding time model. The control used showed an average of 52 + 15 seconds to stop bleeding while ASA demonstrated an average of 73 + 20 seconds. Lapdesf 1 and Lapdesf 2 showed an average of 113 + 25 seconds and 192 + 31 seconds. Conclusions. Results demonstrate that molecular hybridization approach used allows us to obtain new ASA derivatives with property of inhibited platelet aggregation induced by ADP. Lapdesf 1 and 2 demonstrated different NO-donor properties related to methyl and phenyl substitutions. Furthermore, both compounds prolonged tail vein bleeding time using mice model. These compounds could be new drug candidates, alternative to ASA, useful to prevent atherothrombosis events. Disclosures:No relevant conflicts of interest to declare.

Design, Synthesis, and Pharmacological Evaluation of Novel Hybrid Compounds To Treat Sickle Cell Disease Symptoms

A novel series of thalidomide derivatives (4a-f) designed by molecular hybridization were synthesized and evaluated in vitro and in vivo for their potential use in the oral treatment of sickle cell disease symptoms. Compounds 4a-f demonstrated analgesic, anti-inflammatory, and NO-donor properties. Compounds 4c and 4d were considered promising candidate drugs and were further evaluated in transgenic sickle cell mice to determine their capacity to reduce the levels of the proinflammatory cytokine tumor necrosis factor α (TNFα). Unlike hydroxyurea, the compounds reduced the concentrations of TNFα to levels similar to those induced with the control dexamethasone (300 μmol/kg). These compounds are novel lead drug candidates with multiple beneficial actions in the treatment of sickle cell disease symptoms and offer an alternative to hydroxyurea treatment.

Pharmacodynamic Hybrids Coupling Established Cardiovascular Mechanisms of Action with Additional Nitric Oxide Releasing Properties

The pharmacotherapy of complex pathological states at the cardiovascular level often requires different and complementary pharmacodynamic properties. This is frequently achieved through the administration of "cocktails", composed by several drugs possessing different mechanisms of action. In the last years, a revision of the "one-compound-one-target" paradigm led to a wide development of new classes of molecules, possessing more pharmacological targets. Among them, this innovative strategy produced interesting hybrid drugs, with a dual mechanism of action: a) a fundamental and well-established pharmacodynamic profile and b) the release of nitric oxide (NO), playing a pivotal role in the modulation of the function of cardiovascular system, where it induces vasorelaxing and antiplatelet responses. These new pharmacodynamic hybrids present the advantage of adding to a main mechanism of action (for example, cyclooxygenase inhibition, beta-antagonism or ACE-inhibition) also a slow release of NO, useful either to reduce the adverse side effects and/or to improve the effectiveness of the drug. This review presents the chemical features of many examples of NO-releasing hybrids of cardiovascular drugs and explains the pharmacological improvements conferred by the addition of such NO-donor properties.

Synthesis and anti‐Helicobacter pylori properties of NO‐donor/metronidazole hybrids and related compounds

AbstractTwo series (A, B) of 2‐(2‐methyl‐5‐nitro‐1H‐imidazolyl)ethyl derivatives (6–9, 18–23) conjugated through an oxygen or an aminomethyl bridge with either a furoxan NO‐donor moiety or a furazan substructure, devoid of NO‐donor properties, were synthesised. A third group (C) of 2‐(2‐methyl‐5‐nitro‐1H‐imidazolyl)ethyl derivatives conjugated with nitrooxy and dinitrooxy NO‐donor functions (35, 38) as well as the corresponding analogue without these functions (40) were prepared. All the compounds were evaluated in vitro for their activity against a number of Helicobacter pylori strains. Metronidazole (1) and its amino analogue (11) were taken as reference compounds. All the synthesised hybrids and their analogues exhibited good anti‐H. pylori activity with MIC50 in the range less than 0.0039–1, resulting in compounds more active than metronidazole. Derivatives 6–9 displayed good potency also against metronidazole‐resistant strains. Compounds lacking the 5‐nitroimidazole moiety (24–29, 30–33) proved to be inactive against H. pylori with the exception of 33. The lack of significant differences in the antibacterial potency between furoxan and furazan hybrids in both series (A, B) suggest that the role of the N‐oxide moiety of the furoxan system either as an inductor of oxidative stress or as a promoter of NO‐donor properties is marginal. The substitution of the furoxan substructures with nitrooxy moieties (35, 38) afforded active compounds. In view of their NO‐donor properties, NO‐metronidazole hybrids could represent potential therapeutic tools both in the treatment of gastric ulcer and in a number of extragastrointestinal disorders such as ischaemic heart diseases and atherosclerosis‐related to some H. pylori strains. Drug Dev. Res. 60:225–239, 2003. © 2003 Wiley‐Liss, Inc.

New potential uroselective NO-donor alpha1-antagonists.

A recent uroselective alpha(1)-adrenoceptor antagonist, REC15/2739, has been joined with nitrooxy and furoxan NO-donor moieties to give new NO-donor alpha(1)-antagonists. All the compounds studied proved to be potent and selective ligands of human cloned alpha(1a)-receptor subtype. Derivatives 6 and 7 were able to relax the prostatic portion of rat vas deferens contracted by (-)-noradrenaline because of both their alpha(1A)-antagonist and their NO-donor properties.

3-(1H-Imidazol-4-yl)propyl]guanidines containing furoxan moieties: a New Class of H3-Antagonists endowed with NO-Donor properties

Synthesis and pharmacological characterisation of a series of products obtained by coupling the H3-antagonist SKF 91486 through appropriate spacers with the NO-donor 3-phenylfuroxan-4-yloxy and 3-benzenesulfonylfuroxan-4-yloxy moieties, as well as with the corresponding furazan substructures, devoid of NO-donating properties, are reported. All the products were tested for their H3-antagonistic and H2-agonistic properties on electrically-stimulated guinea-pig ileum segments and guinea-pig papillary muscle, respectively. The whole series of compounds displayed good H3-antagonist behaviour and feeble partial H2-agonist activity. Among furoxan derivatives, the benzenesulfonyl hybrid 28, a good NO-donor, triggered a dual NO-dependent muscle relaxation and H3-antagonistic effect on guinea-pig intestine.

H 3 receptor ligands: new imidazole H 3-antagonists endowed with NO-donor properties

Synthesis and pharmacological properties of a group of compounds obtained by coupling the H 3-antagonist SKF 91486 with the NO-donor 3-phenylfuroxan-4-yloxy and 3-benzenesulfonylfuroxan-4-yloxy moieties, as well as with the corresponding furazan analogues, devoid of NO-donating properties, are reported. All the products were tested for their H 3-antagonistic and H 2-agonistic properties on electrically-simulated guinea-pig ileum segments and guinea-pig papillary muscle, respectively. All the synthesised compounds displayed good H 3-antagonistic properties (pA 2 range 7.02–8.49) while behaving only as weak partial H 2-agonists. Derivative 28, the best NO-donor of the series, was able to trigger a dual NO-dependent muscle relaxation and H 3-antagonistic effect on guinea-pig illeum.

Hydroxyurea induces fetal hemoglobin by the nitric oxide–dependent activation of soluble guanylyl cyclase

Hydroxyurea treatment of patients with sickle-cell disease increases fetal hemoglobin (HbF), which reduces hemoglobin S polymerization and clinical complications. Despite its use in the treatment of myeloproliferative diseases for over 30 years, its mechanism of action remains uncertain. Recent studies have demonstrated that hydroxyurea generates the nitric oxide (NO) radical in vivo, and we therefore hypothesized that NO-donor properties might determine the hemoglobin phenotype. We treated both K562 erythroleukemic cells and human erythroid progenitor cells with S-nitrosocysteine (CysNO), an NO donor, and found similar dose- and time-dependent induction of γ-globin mRNA and HbF protein as we observed with hydroxyurea. Both hydroxyurea and CysNO increased cGMP levels, and the guanylyl cyclase inhibitors ODQ, NS 2028, and LY 83,538 abolished both the hydroxyurea- and CysNO-induced γ-globin expression. These data provide strong evidence for an NO-derived mechanism for HbF induction by hydroxyurea and suggest possibilities for therapies based on NO-releasing or -potentiating agents.

Low molecular mass dinitrosyl nonheme-iron complexes up-regulate noradrenaline release in the rat tail artery

BackgroundDinitrosyl nonheme-iron complexes can appear in cells and tissues overproducing nitric oxide. It is believed that due to their chemical nature these species may be implicated in certain pathophysiological events. We studied the possible role of low molecular mass dinitrosyl iron complexes in the control of noradrenaline release in electrically stimulated rat tail artery.ResultsA model complex, dinitrosyl-iron-thiosulfate (at 1–10 μM) produced a concentration-dependent enhancement of electrical field stimulated [3H]noradrenaline release (up to 2 fold). At the same time, dinitrosyl-iron-thiosulfate inhibited neurogenic vasoconstriction, consistent with its nitric oxide donor properties. A specific inhibitor of cyclic GMP dependent protein kinase, Rp-8pCPT-cGMPS, partially inhibited the effect of dinitrosyl-iron-thiosulfate on neurogenic vasoconstriction, but not on [3H]noradrenaline release. Another model complex, dinitrosyl-iron-cysteine (at 3 μM) elicited similar responses as dinitrosyl-iron-thiosulfate. Conventional NO and NO+ donors such as sodium nitroprusside, S-nitroso-L-cysteine or S-nitroso-glutathione (at 10 μM) had no effect on [3H]noradrenaline release, though they potently decreased electrically-induced vasoconstriction. The "false complex", iron(II)-thiosulfate showed no activity.ConclusionsLow molecular mass iron dinitrosyl complexes can up-regulate the stimulation-evoked release of vascular [3H]noradrenaline, apparently independently of their NO donor properties. This finding may have important implications in inflammatory tissues.

Studies on agents with mixed NO-dependent and calcium channel antagonistic vasodilating activities.

To obtain new cardiovascular agents with mixed Ca2+-channel antagonistic and NO-donor properties, a series of "hybrid" 1,4-dihydropyridines (1,4-DHPs), bearing NO-donating furoxan moieties on the 3-positioned lateral ester chain were synthesized and pharmacologically characterized. Furazan analogues were also prepared and investigated for control purposes, because they are unable to release NO. Synthesis of the models was achieved by a modified Hantzsch approach. All of the final furoxan 1,4-DHPs were assessed for their ability to produce nitrite in the presence of a large excess of cysteine by the Griess reaction. Vasodilating activity was evaluated on rat aorta and expressed as EC50 and EC50MB values, obtained in the absence and in the presence of methylene blue (MB) respectively, a well-known guanylate cyclase inhibitor. Affinities to 1,4-DHP receptor on Ca2+-channels, expressed as IC50 values, were determined through displacement experiments of [3H]-nitrendipine on rat cortex homogenates. Some hybrid compounds (derivatives 15a, 15b, 16a, and 16b) displayed vasodilating activity depending predominantly on their Ca2+-channel blocker properties. By contrast, some others (derivatives 17a, 17b, and 21) behaved as well-balanced hybrids with mixed Ca2+-channel blocking and NO-dependent vasodilating activities. This work demonstrates the possibility of obtaining well-balanced hybrids endowed with mixed NO-donor and Ca2+-channel blocker properties using appropriate 1,4-DHP and furoxan moieties. A procedure for the individual evaluation of the NO-dependent vasodilator component and that due to Ca2+-channel blocking is proposed.