Cardiovascular actions of the furoxan CAS 1609, a novel nitric oxide donor

Proteomics Studies Suggest That Nitric Oxide Donor Furoxans Inhibit In Vitro Vascular Smooth Muscle Cell Proliferation by Nitric Oxide-Independent Mechanisms

Physiologically, smooth muscle cells (SMC) and nitric oxide (NO) produced by endothelial cells strictly cooperate to maintain vasal homeostasis. In atherosclerosis, where this equilibrium is altered, molecules providing exogenous NO and able to inhibit SMC proliferation may represent valuable antiatherosclerotic agents. Searching for dual antiproliferative and NO-donor molecules, we found that furoxans significantly decreased SMC proliferation in vitro, albeit with different potencies. We therefore assessed whether this property is dependent on their thiol-induced ring opening. Indeed, while furazans (analogues unable to release NO) are not effective, furoxans' inhibitory potency parallels with the electron-attractor capacity of the group in 3 of the ring, making this effect tunable. To demonstrate whether their specific block on G1-S phase could be NO-dependent, we supplemented SMCs with furoxans and inhibitors of GMP- and/or of the polyamine pathway, which regulate NO-induced SMC proliferation, but they failed in preventing the antiproliferative effect. To find the real mechanism of this property, our proteomics studies revealed that eleven cellular proteins (with SUMO1 being central) and networks involved in cell homeostasis/proliferation are modulated by furoxans, probably by interaction with adducts generated after degradation. Altogether, thanks to their dual effect and pharmacological flexibility, furoxans may be evaluated in the future as antiatherosclerotic molecules.

Antiaggregant effects of (1,2,5-oxadiazolyl)azasydnone ring assemblies as novel antiplatelet agents

A series of biheterocyclic assemblies comprising of 1,2,5-oxadiazole and azasydnone scaffolds were synthesized and biologically evaluated as novel nitric oxide (NO)-donor and antiplatelet agents. Depending on functional substituents at the biheterocyclic core, all studied compounds demonstrated good NO-donor profiles releasing NO in a wide range of concentrations (19.2%-195.1%) according to a Griess assay. (1,2,5-Oxadiazolyl)azasydnones showed excellent antiplatelet activity in the case of ADP and adrenaline used as inducers completely suppressing the aggregate formation even at the lowest test concentration of 0.0375 μmol/ml, which is a rather unique feature. Moreover, studied biheterocycles possess a selective mechanism of inhibition of platelet aggregation mediated only by ADP and adrenaline, which are considered to be the main inducers causing thrombus formation. In addition, (1,2,5-oxadiazolyl)azasydnones were found to be completely non-toxic to hybrid endothelial cells EaHy 926. Studies of hydrolytic degradation of the synthesized compounds afforded benzoic acid as a sole detectable decomposition product, which is considered advantageous in drug design. Therefore, (1,2,5-oxadiazolyl)azasydnones represent a novel class of promising drug candidates with improved antiplatelet profile and reduced toxicity enabling their huge potential in medicinal chemistry and drug design.

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.

Recent Advances in the Synthesis and Biomedical Applications of Heterocyclic NO-Donors

Nitric oxide (NO) is a key signaling molecule that acts in various physiological processes such as cellular metabolism, vasodilation and transmission of nerve impulses. A wide number of vascular diseases as well as various immune and neurodegenerative disorders were found to be directly associated with a disruption of NO production in living organisms. These issues justify a constant search of novel NO-donors with improved pharmacokinetic profiles and prolonged action. In a series of known structural classes capable of NO release, heterocyclic NO-donors are of special importance due to their increased hydrolytic stability and low toxicity. It is no wonder that synthetic and biochemical investigations of heterocyclic NO-donors have emerged significantly in recent years. In this review, we summarized recent advances in the synthesis, reactivity and biomedical applications of promising heterocyclic NO-donors (furoxans, sydnone imines, pyridazine dioxides, azasydnones). The synthetic potential of each heterocyclic system along with biochemical mechanisms of action are emphasized.

Pharmacokinetics and pharmacodynamics of nitric oxide mimetic agents

Drug discovery focusing on NO mimetics has been hamstrung due to its unconventional nature. Central to these challenges is the fact that direct measurement of molecular NO in biological systems is exceedingly difficulty. Hence, drug development of NO mimetics must rely upon measurement of the NO donating specie (i.e., a prodrug) and a downstream marker of efficacy without directly measuring the molecule, NO, that is responsible for biological effect. The focus of this review is to catalog in vivo attempts to monitor the pharmacokinetics (PK) of the NO donating specie and the pharmacodynamic (PD) readout of NO bioactivity.

Controlled Delivery of Nitric Oxide for Cancer Therapy

Nitric oxide (NO) is a short-lived, endogenously produced, signaling molecule which plays multiple roles in mammalian physiology. Underproduction of NO is associated with several pathological processes; hence a broad range of NO donors have emerged as potential therapeutics for cardiovascular and respiratory disorders, wound healing, the immune response to infection, and cancer. However, short half-lives, chemical reactivity, rapid systemic clearance, and cytotoxicity have hindered the clinical development of most low molecular weight NO donors. Hence, for controlled NO delivery, there has been extensive effort to design novel NO-releasing biomaterials for tumor targeting. This review covers the effects of NO in cancer biology, NO releasing moieties which can be used for NO delivery, and current advances in the design of NO releasing biomaterials focusing on their applications for tumor therapy.

Selective Methylmagnesium Chloride Mediated Acetylations of Isosorbide: A Route to Powerful Nitric Oxide Donor Furoxans

Isosorbide was functionalized with furoxan for the first time to give adducts that release nitric oxide up to 7.5 times faster than the commercial vasodilator, isosorbide-5-mononitrate (Is5N). The synthesis was facilitated by MeMgCl-mediated selective acetylation of isosorbide or selective deacetylation of isosorbide-2,5-diacetate, which was rationalized in terms of a more stable 5-alkoxide magnesium salt using DFT. Isosorbide-furoxans are safer to handle than Is5N due to greater thermal stability.

Chalcone Derivatives: Promising Starting Points for Drug Design

Medicinal chemists continue to be fascinated by chalcone derivatives because of their simple chemistry, ease of hydrogen atom manipulation, straightforward synthesis, and a variety of promising biological activities. However, chalcones have still not garnered deserved attention, especially considering their high potential as chemical sources for designing and developing new effective drugs. In this review, we summarize current methodological developments towards the design and synthesis of new chalcone derivatives and state-of-the-art medicinal chemistry strategies (bioisosterism, molecular hybridization, and pro-drug design). We also highlight the applicability of computer-assisted drug design approaches to chalcones and address how this may contribute to optimizing research outputs and lead to more successful and cost-effective drug discovery endeavors. Lastly, we present successful examples of the use of chalcones and suggest possible solutions to existing limitations.

New furoxan derivatives for the treatment of ocular hypertension

A small series of water-soluble NO-donor furoxans bearing a basic center at the 4-position, having a wide lipophilic-hydrophilic balance range, and endowed with different NO-release capacities, were synthesized and characterized. Selected members were studied for their IOP-lowering activity in the transient ocular hypertensive rabbit model at 1% dose. The most effective IOP-lowering products were compounds 3 and 7, whose activity 60min after administration was similar to that of Timolol. Notably, 7 was characterized by a long-lasting action. The IOP-lowering activity in this series of products appeared to be modulated by the lipophilic-hydrophilic balance rather than by the NO-donor capacity.

Theoretical investigation of methoxide ion reaction on the 7-methyl-4,6-dinitrobenzofuroxan

Reaction of the methoxide ion on the 7-methyl-4,6-dinitrobenzofuroxan (DNBF) 1 has been studied theoretically by means of DFT/B3LYP technique to interpret the kinetic–thermodynamic competition between the three possible compounds that are carbanion DNBF− 4 and the two complexed forms (2, 3) of the methoxide group in positions 5 and 7, respectively. Optimized geometry, nbo atomic charge distribution, thermodynamic/kinetic parameters (ΔrH°T, ΔrS°T, ΔrG°T, ΔH*, ΔS*, and ΔG*) and IRC path have been calculated for possible products and their transitional states using water as solvent. All obtained ΔrG°T are negative, ranging from −19.16 to −42.87 kcal mol−1 (1 cal = 4.184 J), indicating the possible observation of all products, but the experimenters only detected the anionic form DNBF−. Fukui indices, which were calculated by means of NBO atomic charge distribution, confirm the electrophilicity of the sites C5 and C7. Transition states barriers, ΔG*, are 14.97, 15.16, and 21.94 kcal mol−1 for the three possible products 2, 3, and 4, respectively, in water. As expected, the most stable compound is carbanion, but it also exhibits the highest activation barrier. If this situation formally engenders a double kinetic–thermodynamic competition, the very weak activation energy of the two complexes in C5 and C7 makes improbable the simultaneous detection of the three expected compounds.

Theoretical and experimental reinvestigation of methoxide ion reaction with 7-methyl 4-nitro benzofuroxan

DFT/B3LYP theoretical study has been performed in order to interpret the kinetic-thermodynamic competition between compounds obtained by reaction of the methoxide ion on the 7-methyl 4-nitro benzofuroxan. Geometry, atomic charge distribution, transition states, IRC path, thermodynamic, and kinetic parameters ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]*, [Formula: see text]*, and [Formula: see text]*) have been calculated for all possible products. In gaseous state or in the presence of water as solvent, all [Formula: see text] values were found to be negative, ranging from [Formula: see text]12.54[Formula: see text]kcal mol[Formula: see text] to [Formula: see text]29.85[Formula: see text]kcal mol[Formula: see text] in water, indicating that all possible products should form spontaneously. Those values indicated the possible observation of all products but experimenters only detect simultaneously two [Formula: see text]-complexes in C5 and C7 among three possibilities. The Fukui indices obtained by NBO atomic charge distribution confirm the super electrophilicity of those two sites. For transition states barriers, [Formula: see text]* ranged from 18.98[Formula: see text]kcal mol[Formula: see text] to 42.12[Formula: see text]kcal mol[Formula: see text] in gaseous state and from 18.59[Formula: see text]kcal mol[Formula: see text] to 24.22[Formula: see text]kcal mol[Formula: see text] in water. The unexpected result of our calculations is that the most stable compound is the unobserved carbanion but it also exhibits the highest activation barrier. Our results indicated the existence of two consecutive kinetic/thermodynamic competitions that occur in separate periods. The simultaneous observation of the three compounds is impossible because compound 4 occurs as a trace at the time compound 2 disappears completely. Experimental reinvestigation of the studied reaction leads by a very slow process to the earlier unobserved carbanion. Reaction mechanisms were also discussed on the basis of IRC calculations.

In Vitro Metabolic Stability and in Vivo Biodistribution of 3-Methyl-4-furoxancarbaldehyde Using PET Imaging in Rats

Painful diabetic neuropathy (PDN) is a type of peripheral neuropathic pain that is currently difficult to treat using clinically available analgesics. Recent work suggests a progressive depletion of nitric oxide (NO) in nerve cells may be responsible for the pathobiology of PDN. The nitric oxide donor, 3-methyl-4-furoxancarbaldehyde (PRG150), has been shown to produce dose-dependent analgesia in a rat model of PDN. To gain insight into the mechanism of analgesia, methods to radiolabel PRG150 were developed to assess the in vivo biodistribution in rats. The furoxan ring was labeled with (13)N to follow any nitric oxide release and the 3-methyl substituent was labeled with (11)C to track the metabolite using PET imaging. The in vitro metabolic stability of PRG150 was assessed in rat liver microsomes and compared to in vivo metabolism of the synthesized radiotracers. PET images revealed a higher uptake of (13)N over (11)C radioactivity in the spinal cord. The differences in radioactive uptake could indicate that a NO release in the spinal cord and other components of the somatosensory nervous system may be responsible for the analgesic effects of PRG150 seen in the rat model of PDN.

Nitric oxide treatments as adjuncts to reperfusion in acute myocardial infarction: a systematic review of experimental and clinical studies

Unmodified reperfusion therapy for acute myocardial infarction (AMI) is associated with irreversible myocardial injury beyond that sustained during ischemia. Studies in experimental models of ischemia/reperfusion and in humans undergoing reperfusion therapy for AMI have examined potential beneficial effects of nitric oxide (NO) supplemented at the time of reperfusion. Using a rigorous systematic search approach, we have identified and critically evaluated all the relevant experimental and clinical literature to assess whether exogenous NO given at reperfusion can limit infarct size. An inclusive search strategy was undertaken to identify all in vivo experimental animal and clinical human studies published in the period 1990–2014 where NO gas, nitrite, nitrate or NO donors were given to ameliorate reperfusion injury. Articles were screened at title and subsequently at abstract level, followed by objective full text analysis using a critical appraisal tool. In twenty-one animal studies, all NO treatments except nitroglycerin afforded protection against measures of reperfusion injury, including infarct size, creatinine kinase release, neutrophil accumulation and cardiac dysfunction. In three human AMI RCT’s, there was no consistent evidence of infarct limitation associated with NO treatment as an adjunct to reperfusion. Despite experimental evidence that most NO treatments can reduce infarct size when given as adjuncts to reperfusion, the value of these interventions in clinical AMI is unproven. Our study raises issues for the design of further clinical studies and emphasises the need for improved design of animal studies to reflect more accurately the comorbidities and other confounding factors seen in clinical AMI.

NO-Donor Dihydroartemisinin Derivatives as Multitarget Agents for the Treatment of Cerebral Malaria

Hybrid products in which the dihydroartemisinin scaffold is combined with NO-donor furoxan and NONOate moieties have been synthesized and studied as potential tools for the treatment of cerebral malaria (CM). The designed products were able to dilate rat aorta strips precontracted with phenylephrine with a NO-dependent mechanism. All hybrid compounds showed preserved antiplasmodial activity in vitro and in vivo against Plasmodium berghei ANKA, comparable to artesunate and artemether. Hybrid 10, selected for additional studies, was capable of increasing survival of mice with late-stage CM from 27.5% to 51.6% compared with artemether. Artemisinin-NO-donor hybrid compounds show promise as potential new drugs for treating cerebral malaria.

Synthesis and Antimicrobial Activity of Bis-4,6-sulfonamidated 5,7-Dinitrobenzofuroxans

A new series of bis-4,6-sulfonamidated 5,7-dinitrbenzofuroxans  7–11had been synthesized and tested for antimicrobial activity. The structures of new sulfanilamide derivatives were characterized by elemental analysis, IR spectroscopy, and mass spectrometry (MALDITOF). The synthesized compounds were tested for theirin vitroantimicrobial activity using the disk diffusion method against Gram-positive bacteriaStaphylococcus aureus; the Gram-negative bacteriaEscherichia coli, Pseudomonas aeruginosa, andProteus mirabilis; the fungal strainAspergillus niger; and the yeast-like pathogenic fungusCandida albicans. Our results indicate that the compounds7–11exhibit potent antimicrobial activity. The stability of the compounds was evaluated by TG and DSC methods.

Exogenous intravascular nitric oxide enhances ventricular function after hemodilution with plasma expander

AIMS

This study evaluated the hypothesis that exogenous nitric oxide (NO) supplementation during acute hemodilution with plasma expander (PE) provides beneficial effects on cardiac function.

MAIN METHODS

Acute hemodilution in golden Syrian hamsters was induced by a 40% of blood volume exchange with dextran 70 kDa. Intravascular NO supplementation after hemodilution was accomplished with a NO donor, diethylenetriamine NONOate (DETA NONOate). The test group was treated with DETA NONOate, while the control group received only vehicle. Left ventricular cardiac function was studied using pressure-volume measurements obtained with a miniaturized conductance catheter.

KEY FINDINGS

Cardiac output increased to 122±5% and 107±1% of the baseline in the group treated with NO donor and the vehicle group, respectively. Stroke work per stroke volume (SW/SV) after hemodilution reduced to 90% of the baseline and the NO donor significantly reduced SW/SV compared to the vehicle. The minimum rate of pressure change (dP/dt(min)) was significantly lower in animals treated with the NO donor compared to vehicle treated animals. Systemic vascular resistance (SVR) decreased to 62±5% of the baseline in the NO donor group whereas the vehicle group SVR decreased to 83±5% of the baseline. Using intravital microscopy analysis of microvessel in the dorsal skinfold window chamber, we established that the NO donor group induced significant vasodilation compared to the vehicle group.

SIGNIFICANCE

NO supplementation in an acute hemodilution with PE has beneficial effects on cardiac performance. However, the NO supplementation effects with a NO donor are dose-independent and short-lasting.

Role of carbon monoxide and nitric oxide in adult rat hepatocytes proliferating in vitro: Effects of CAS 1609

During liver regeneration in vivo carbon monoxide (CO) and nitric oxide (NO) are supposed to play a significant role. We raise the question whether CO and NO are involved in the growth process of cultured hepatocytes. Rat hepatocytes were stimulated into proliferation, growth being estimated by DNA content, mRNA by quantitative RT-PCR, and inducible NO synthase (iNOS) activity by GC-MS. Dexamethasone proved obligatory for fast proliferation. It suppressed the spontaneous rise of iNOS-mRNA in cultures devoid of glucocorticoids, but did not counteract the rise in mRNA in actively dividing cultures. Expression of iNOS-mRNA and cell growth were further enhanced by LiCl (10 mM). NOS activity was completely suppressed by the iNOS-specific inhibitors N-(3-(aminomethyl)benzyl) acetamidine (1400 W,100 microM) and L-N(6)-(1-iminoethyl)lysine (L-NIL, 500 microM), however, without a decrease in hepatocyte growth. Proliferation was attenuated only by very high concentrations (>0.5 mM) of N-nitro-L-arginine methyl ester (L-NAME) and asymmetric dimethylarginine (ADMA). Various NO donors (at 100 microM) did not stimulate cell growth. The furoxan CAS 1609 stimulated growth, decreased iNOS-mRNA expression and transiently increased haem oxygenase-1 (HO-1)-mRNA without releasing considerable amounts of NO. 1H-[1,2,4]Oxadiazolo[4,3,-alpha]quinoxalin-1-one (ODQ) attenuated the action of CAS 1609. Proliferation was stimulated by Co-protoporphyrin and tricarbonyldichlororuthenium(II) dimer (CORM-2). We conclude that CAS 1609 triggers hepatocyte mitosis most likely via direct, NO-independent induction of HO-1 expression, pointing to CO as a growth-promoting signal in the proliferation cascade in cultured hepatocytes.

Multitarget drugs: Focus on the NO-donor hybrid drugs

The article addresses the design of multitarget drugs, namely, compounds capable of interacting with more than one target simultaneously. These agents could be useful tools in the therapy of complex diseases such as cardiovascular and inflammatory diseases. An interesting case of multitarget compounds are nitric oxide (NO)-donor hybrids, structures which combine the physiological properties of NO with those of a lead drug. In particular, the authors discuss the symbiotic approach used to design NO-donor nonsteroidal anti-inflammatory drugs (NO-NSAIDs) and NO-donor antioxidants. The former could be useful agents in the treatment of anti-inflammatory diseases being devoid of gastro- and cardiotoxicity, the latter could be a valid approach to the treatment of many cardiovascular diseases.

NO-donor melatonin derivatives: synthesis and in vitro pharmacological characterization

Numerous studies document that melatonin possesses a broad-spectrum antioxidant activity. It traps a number of reactive oxygen species (ROS) such as hydroxyl and peroxyl radicals, singlet oxygen and hypochlorous acid. It also inhibits peroxynitrite-induced reactions. It is known that atherosclerosis progression involves ROS-induced oxidation of low-density lipoproteins in sub-endothelial space and the depletion of nitric oxide (NO) in blood vessels, as well as a decreased sensitivity of the vessels to the actions of NO. Considering this, a series of new NO-donor antioxidants were designed and synthesized by joining melatonin with NO-donor nitrooxy and furoxan moieties as polyvalent agents potentially useful for the treatment of cardiovascular diseases involving atherosclerotic vascular changes. The in vitro antioxidant properties of the resulting products were assessed in the thiobarbituric acid reactive substances assay (TBARS), the ABTS(+.) as well as in the alkaline phosphatase (ALP) assay. The antioxidant capacities of NO-donor melatonins to inhibit lipoperoxidation (TBARS-IC(50)) was predominantly dependent on their lipophilicity, and therefore on their partitioning process into membranes. On the other hand, their comparable capacity to inhibit protein oxidation (ALP-IC(50)) was independent of their lipophilicity and was consistent with their similar ability to participate in electron transfer reactions. All the NO-donor melatonins were also evaluated for their ability to relax rat aorta strips precontracted with 1 microM phenylephrine. Finally, binding affinities and intrinsic activity studies, carried out at MT(1) and MT(2) receptor subtypes, showed a rather complex picture in need of further investigation.

Amphiphilic NO-Donor Antioxidants

Models of amphiphilic NO-donor antioxidants 24-26 were designed and synthesized. The products were obtained by linking a lipophilic tail (C(6), C(8), C(10)) with a polar head constituted by the 2,6-dimethoxyphenol antioxidant joined to the NO-donor 3-furoxancarboxamide substructure through a bridge containing a quaternary ammonium group. Compound 23, containing the shortest C(2)-alkyl chain, was also studied as a reference. The antioxidant properties (TBARS and LDL oxidation assays) and the vasodilator properties of the compounds were studied in vitro. The ability of these products to interact with phospholipid vesicles was also investigated by NMR techniques. The results indicate that both activities are modulated by the ability of the compounds to accumulate on phospholipid layers.

NO-Donor Phenols: A New Class of Products Endowed with Antioxidant and Vasodilator Properties

The synthesis and study of the antioxidant and vasodilator properties of a new class of phenols able to release nitric oxide are described. The products were designed through a symbiotic approach using selected phenols and selected nitrooxy and furoxan NO-donors as reference models. The antioxidant activities of the hybrid products were assessed by detecting the 2-thiobarbituric acid reactive substances (TBARS) produced in the ferrous salt/ascorbate-induced autoxidation of lipids present in microsomial membranes of rat hepatocytes. The vasodilator activity was assessed on rat aortic strips precontracted with phenylephrine. Some of the products (13, 35, 37, 60-62, 64) behave principally as vasodilators and others as antioxidants (24, 32, 72), and the two properties are relatively balanced in 19, 41, and 68. Further in vivo studies should clarify whether some of these products may become preclinical candidates for the treatment of cardiovascular disease underpinned by atheroma.

Aged endothelial nitric oxide synthase knockout mice exhibit higher mortality concomitant with impaired open-field habituation and alterations in forebrain neurotransmitter levels

Endothelial nitric oxide synthase (eNOS) has been implicated in various brain and peripheral pathologies such as renal failure, heart failure or stroke. Consequently, the mortality rate of aged eNOS knockout mice (eNOS-/-) was higher than that of age-matched (18-22 months old) controls. Only seven of the original 14 eNOS-/- animals that participated in the study reached the age of 18 months or older, whereas no control mice died during this life span. In order to assess the behavioral and neurochemical consequences of chronic eNOS deficiency we examined whether the surviving aged eNOS-/- mice showed changes in terms of motor, emotional, exploratory and neurochemical parameters. Aged eNOS-/- mice showed reduced exploratory activity in the open-field with no habituation observable neither within sessions nor after repeated exposures. Pole test performance of eNOS-/- mice was comparable to controls. In the elevated plus-maze eNOS-/- mice did not differ from controls in terms of time spent in and entries into arms, but showed less locomotion on the open arms. The most prominent neurochemical alterations in the forebrains of aged eNOS-/- mice were: (a) increased acetylcholine levels in the neostriatum; (b) decreased noradrenaline concentrations in the ventral striatum; and (c) lower serotonin levels in the frontal cortex and ventral striatum. The present findings suggest that mice which survived chronic eNOS-deficiency into old age, show some behavioral and neurochemical phenotypes distinct from adult eNOS-/- mice.

Platelet antiaggregatory effects and haemodynamic activity of two terfuroxan isomer pairs

A couple of terfuroxan isomer pairs 1a,b and 2a,b were studied for their in vivo vasodilating activity and in vitro antiplatelet action. The haemodynamic profiles of the products resemble that of other NO-donors. Their in vitro antiaggregating activity is influenced both by terfuroxan system and by the substituents.

Venodilator action of an organotransition-metal nitrosyl complex

Nitrovasodilators, such as nitroglycerin, cause endothelium-independent dilatation of arterial and capacitance vessels via the release of nitric oxide (NO). This study examined the venodilator effect of CpCr(NO)(2)Cl (organotransition-metal nitrosyl complex) relative to that of nitroglycerin in conscious, unrestrained rats. Organotransition-metal nitrosyl complexes have releasable NO directly attached to metal centres. The dose-response effects of CpCr(NO)(2)Cl and nitroglycerin on the mean arterial pressure and the mean circulatory filling pressure (index of the body venous tone) were obtained in rats continuously infused with either normal saline or noradrenaline. The results show that both CpCr(NO)(2)Cl and nitroglycerin reduced the mean arterial pressure in rats with normal or elevated vasomotor tone. However, maximum depressor response of CpCr(NO)(2)Cl was greater than that of nitroglycerin. In vehicle-treated rats, both compounds increased the mean circulatory filling pressure. In rats with elevated vasomotor tone through the infusion of noradrenaline, both agents reduced the mean circulatory filling pressure. These results show that CpCr(NO)(2)Cl is an efficacious depressor and venodilator agent.

A new class of ibuprofen derivatives with reduced gastrotoxicity

A new series of nonsteroidal antiinflammatory drugs (NSAIDs) obtained by linking ibuprofen to selected furoxan moieties and to related furazans were synthesized and tested for their antiinflammatory, antiaggregatory, and ulcerogenic properties. All the derivatives are endowed with antiinflammatory activity comparable to that of ibuprofen, but, unlike this drug, they display reduced acute gastrotoxicity. The masking of the ibuprofen-free carboxylic group seems to be principally at the basis of this reduced topical irritant action. The two furoxan derivatives 8 and 9 also trigger potent antiaggregatory effects, principally as a consequence of their NO-donor ability.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.