NCX4016 (NO-aspirin) reduces infarct size and suppresses arrhythmias following myocardial ischaemia/reperfusion in pigs

cGMP and mitochondrial K+ channels-Compartmentalized but closely connected in cardioprotection

The 3',5'-cGMP pathway triggers cytoprotective responses and improves cardiomyocyte survival during myocardial ischaemia and reperfusion (I/R) injury. These beneficial effects were attributed to NO-sensitive GC induced cGMP production leading to activation of cGMP-dependent protein kinase I (cGKI). cGKI in turn phosphorylates many substrates, which eventually facilitate opening of mitochondrial ATP-sensitive potassium channels (mitoK_ATP ) and Ca²⁺ -activated potassium channels of the BK type (mitoBK). Accordingly, agents activating mitoK_ATP or mitoBK provide protection against I/R-induced damages. Here, we provide an up-to-date summary of the infarct-limiting actions exhibited by the GC/cGMP axis and discuss how mitoK_ATP and mitoBK, which are present at the inner mitochondrial membrane, confer mito- and cytoprotective effects on cardiomyocytes exposed to I/R injury. In view of this, we believe that the functional connection between the cGMP cascade and mitoK⁺ channels should be exploited further as adjunct to reperfusion therapy in myocardial infarction.

Cardio-renal safety of non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used therapeutic class in clinical medicine. These are sub-divided based on their selectivity for inhibition of cyclooxygenase (COX) isoforms (COX-1 and COX-2) into: (1) non-selective (ns-NSAIDs), and (2) selective NSAIDs (s-NSAIDs) with preferential inhibition of COX-2 isozyme. The safety and pathophysiology of NSAIDs on the renal and cardiovascular systems have continued to evolve over the years following short- and long-term treatment in both preclinical models and humans. This review summarizes major learnings on cardiac and renal complications associated with pharmaceutical inhibition of COX-1 and COX-2 with focus on preclinical to clinical translatability of cardio-renal data.

cGMP at the centre of attention: emerging strategies for activating the cardioprotective PKG pathway

The nitric oxide (NO)-protein kinase G (PKG) pathway has been known for some time to be an important target for cardioprotection against ischaemia/reperfusion injury and heart failure. While many approaches for reducing infarct size in patients have failed in the past, the advent of novel drugs that modulate cGMP and its downstream targets shows very promising results in recent preclinical and clinical studies. Here, we review main aspects of the NO-PKG pathway in light of recent drug development and summarise potential cardioprotective strategies in which cGMP is the main player.

A review of strategies for infarct size reduction during acute myocardial infarction

Advances in medical and interventional therapy over the last few decades have revolutionized the treatment of acute myocardial infarction. Despite the ability to restore epicardial coronary artery patency promptly through percutaneous coronary intervention, tissue level damage may continue. The reported 30-day mortality after all acute coronary syndromes is 2 to 3%, and around 5% following myocardial infarction. Post-infarct complications such as heart failure continue to be a major contributor to cardiovascular morbidity and mortality. Inadequate microvascular reperfusion leads to worse clinical outcomes and potentially strategies to reduce infarct size during periods of ischemia-reperfusion can improve outcomes. Many strategies have been tested, but no single strategy alone has shown a consistent result or benefit in large scale randomised clinical trials. Herein, we review the historical efforts, current strategies, and potential novel concepts that may improve myocardial protection and reduce infarct size.

Nonsteroidal Anti-Inflammatory Therapy: A Journey Toward Safety

The efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) against inflammation, pain, and fever has been supporting their worldwide use in the treatment of painful conditions and chronic inflammatory diseases until today. However, the long-term therapy with NSAIDs was soon associated with high incidences of adverse events in the gastrointestinal tract. Therefore, the search for novel drugs with improved safety has begun with COX-2 selective inhibitors (coxibs) being straightaway developed and commercialized. Nevertheless, the excitement has fast turned to disappointment when diverse coxibs were withdrawn from the market due to cardiovascular toxicity. Such events have once again triggered the emergence of different strategies to overcome NSAIDs toxicity. Here, an integrative review is provided to address the breakthroughs of two main approaches: (i) the association of NSAIDs with protective mediators and (ii) the design of novel compounds to target downstream and/or multiple enzymes of the arachidonic acid cascade. To date, just one phosphatidylcholine-associated NSAID has already been approved for commercialization. Nevertheless, the preclinical and clinical data obtained so far indicate that both strategies may improve the safety of nonsteroidal anti-inflammatory therapy.

Contractile function assessment by intraventricular balloon alters the ability of regional ischaemia to evoke ventricular fibrillation

BACKGROUND AND PURPOSE

In drug research using the rat Langendorff heart preparation, it is possible to study left ventricular (LV) contractility using an intraventricular balloon (IVB), and arrhythmogenesis during coronary ligation-induced regional ischaemia. Assessing both concurrently would halve animal requirements. We aimed to test the validity of this approach.

EXPERIMENTAL APPROACH

The electrocardiogram (ECG) and LV function (IVB) were recorded during regional ischaemia of different extents in a randomized and blinded study.

KEY RESULTS

IVB-induced proarrhythmia was anticipated, but in hearts with an ischaemic zone (IZ) made deliberately small, an inflated IVB reduced ischaemia-induced ventricular fibrillation (VF) incidence as a trend. Repeating studies in hearts with large IZs revealed the effect to be significant. There were no changes in QT interval or other variables that might explain the effect. Insertion of an IVB that was minimally inflated had no effect on any variable compared with 'no IVB' controls. The antiarrhythmic effect of verapamil (a positive control drug) was unaffected by IVB inflation. Removal of an inflated (but not a non-inflated) IVB caused a release of lactate commensurate with reperfusion of an endocardial/subendocardial layer of IVB-induced ischaemia. This was confirmed by intracellular (31) phosphorus ((31) P) nuclear magnetic resonance (NMR) spectroscopy.

CONCLUSIONS AND IMPLICATIONS

IVB inflation does not inhibit VF suppression by a standard drug, but it has profound antiarrhythmic effects of its own, likely to be due to inflation-induced localized ischaemia. This means rhythm and contractility cannot be assessed concurrently by this approach, with implications for drug discovery and safety assessment.

Pathophysiology of cyclooxygenases in cardiovascular homeostasis

Cyclooxygenase (COX) catalyzes the conversion of arachidonic acid into prostaglandin H(2) (PGH(2)), which is subsequently converted to the prostanoids PGE(2), PGI(2), PGF(2alpha), and thromboxane A(2). COX has 2 distinct membrane-anchored isoenzymes: COX-1 and COX-2. COX-1 is constitutively expressed in most normal tissues; COX-2 is highly induced by proinflammatory mediators in the setting of inflammation, injury, and pain. Inhibitors of COX activity include conventional nonselective nonsteroidal anti-inflammatory drugs and selective nonsteroidal anti-inflammatory drugs, such as COX-2 inhibitors. The adverse effects of COX inhibitors on the cardiovascular system have been addressed in the last few years. In general, COX inhibitors have many effects, but those most important to the cardiovascular system can be direct (through the effects of prostanoids) and indirect (through alterations in fluid dynamics). Despite reports of detrimental human cardiovascular events associated with COX inhibitors, short, long, and lifetime preclinical toxicology studies in rodents and nonrodents have failed to identify these risks. This article focuses on the expression and function of COX enzymes in normal and pathologic conditions of the cardiovascular system and discusses the cardiovascular pathophysiologic complications associated with COX inhibition.

Modulation of gap junctions by nitric oxide contributes to the anti-arrhythmic effect of sodium nitroprusside?

BACKGROUND AND PURPOSE

Nitric oxide (NO) donors provide a preconditioning-like anti-arrhythmic protection in the anaesthetized dog. As NO may modulate gap junction (GJ) function, the present study investigated whether this anti-arrhythmic effect is due to a modification of GJs by NO, derived from the NO donor sodium nitroprusside (SNP).

EXPERIMENTAL APPROACH

In chloralose-urethane-anaesthetized, open-chest dogs, either saline (controls; n= 11) or SNP (0.2 microg x kg(-1) x min(-1); n= 10) was infused at a rate of 0.5 mL x min(-1) by the intracoronary route. The infusions were started 20 min prior to and maintained throughout the entire 60 min occlusion period of the left anterior descending coronary artery. The severity of ischaemia and of arrhythmias, tissue electrical impedance and permeability, as well as the phosphorylation of connexin43, were assessed.

KEY RESULTS

Compared with the controls, SNP infusion markedly suppressed the total number of ventricular premature beats (666 +/- 202 vs. 49 +/- 18; P < 0.05), and the number of ventricular tachycardiac episodes (8.1 +/- 2.3 vs. 0.2 +/- 0.1; P < 0.05) without significantly modifying the incidence of ventricular tachycardia or ventricular fibrillation. The severity of ischaemia (epicardial ST-segment changes, inhomogeneity of electrical activation) and tissue electrical impedance changes were significantly less in the SNP-treated dogs. SNP improved GJ permeability and preserved the phosphorylated form of connexin43.

CONCLUSION AND IMPLICATIONS

The anti-arrhythmic protection resulting from SNP infusion in the anaesthethized dog may, in part, be associated with the modulation of gap junctional function by NO.

Mitochondria as a target for the cardioprotective effects of nitric oxide in ischemia-reperfusion injury

During cardiac ischemia-reperfusion (IR) injury, excessive generation of reactive oxygen species (ROS) and overload of Ca(2+) at the mitochondrial level both lead to opening of the mitochondrial permeability transition (PT) pore on reperfusion. This can result in the depletion of ATP, irreversible oxidation of proteins, lipids, and DNA within the cardiomyocyte, and can trigger cell-death pathways. In contrast, mitochondria are also implicated in the cardioprotective signaling processes of ischemic preconditioning (IPC), to prevent IR-related pathology. Nitric oxide (NO*) has emerged as a potent effector molecule for a variety of cardioprotective strategies, including IPC. Whereas NO* is most noted for its activation of the "classic" soluble guanylate cyclase (sGC) signaling pathway, emerging evidence indicates that NO can directly act on mitochondria, independent of the sGC pathway, affording acute cardioprotection against IR injury. These direct effects of NO* on mitochondria are the focus of this review.

Cardioprotective effects of nitric oxide-aspirin in myocardial ischemia-reperfused rats

In this study, the cardioprotective effects of nitric oxide (NO)-aspirin, the nitroderivative of aspirin, were compared with those of aspirin in an anesthetized rat model of myocardial ischemia-reperfusion. Rats were given aspirin or NO-aspirin orally for 7 consecutive days preceding 25 min of myocardial ischemia followed by 48 h of reperfusion (MI/R). Treatment groups included vehicle (Tween 80), aspirin (30 mg·kg−1·day−1), and NO-aspirin (56 mg·kg−1·day−1). NO-aspirin, compared with aspirin, displayed remarkable cardioprotection in rats subjected to MI/R as determined by the mortality rate and infarct size. Mortality rates for vehicle ( n = 23), aspirin ( n = 22), and NO-aspirin groups ( n = 22) were 34.8, 27.3, and 18.2%, respectively. Infarct size of the vehicle group was 44.5 ± 2.7% of the left ventricle (LV). In contrast, infarct size of the LV decreased in the aspirin- and NO-aspirin-pretreated groups, 36.7 ± 1.8 and 22.9 ± 4.3%, respectively (both P < 0.05 compared with vehicle group; P < 0.05, NO-aspirin vs. aspirin ). Moreover, NO-aspirin also improved ischemiareperfusion-induced myocardial contractile dysfunction on postischemic LV developed pressure. In addition, NO-aspirin downregulated inducible NO synthase (iNOS; 0.37-fold, P < 0.01) and cyclooxygenase-2 (COX-2; 0.61-fold, P < 0.05) gene expression compared with the vehicle group after 48 h of reperfusion. Treatment with NG-nitro-l-arginine methyl ester (l-NAME; 20 mg/kg), a nonselective NOS inhibitor, aggravated myocardial damage in terms of mortality and infarct size but attenuated effects when coadministered with NO-aspirin. l-NAME administration did not alter the increase in iNOS and COX-2 expression but did reverse the NO-aspirin-induced inhibition of expression of the two genes. The beneficial effects of NO-aspirin appeared to be derived largely from the NO moiety, which attenuated myocardial injury to limit infarct size and better recovery of LV function following ischemia and reperfusion.

Role of oxygen in postischemic myocardial injury

Myocardial function is dependent on a constant supply of oxygen from the coronary circulation. A reduction of oxygen supply due to coronary obstruction results in myocardial ischemia, which leads to cardiac dysfunction. Reperfusion of the ischemic myocardium is required for tissue survival. Thrombolytic therapy, coronary artery bypass surgery and coronary angioplasty are some of the treatments available for the restoration of blood flow to the ischemic myocardium. However, the restoration of blood flow may also lead to reperfusion injury, resulting in myocyte death. Thus, any imbalance between oxygen supply and metabolic demand leads to functional, metabolic, morphologic, and electrophysiologic alterations, causing cell death. Myocardial ischemia reperfusion (IR) injury is a multifactorial process that is mediated by oxygen free radicals, neutrophil activation and infiltration, calcium overload, and apoptosis. Controlled reperfusion of the ischemic myocardium has been advocated to prevent the IR injury. Studies have shown that reperfusion injury and postischemic cardiac function are related to the quantity and delivery of oxygen during reperfusion. Substantial evidence suggests that controlled reoxygenation may ameliorate postischemic organ dysfunction. In this review, we discuss the role of oxygenation during reperfusion and subsequent biochemical and pathologic alterations in reperfused myocardium and recovery of heart function.

Recent developments in nitric oxide donor drugs

During the 1980s, the free radical, nitric oxide (NO), was discovered to be a crucial signalling molecule, with wide-ranging functions in the cardiovascular, nervous and immune systems. Aside from providing a credible explanation for the actions of organic nitrates and sodium nitroprusside that have long been used in the treatment of angina and hypertensive crises respectively, the discovery generated great hopes for new NO-based treatments for a wide variety of ailments. Decades later, however, we are still awaiting novel licensed agents in this arena, despite an enormous research effort to this end. 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.

Therapeutic effects of nitric oxide-aspirin hybrid drugs

This review examines the therapeutic potential and mechanisms of action of drugs known as nitric oxide (NO)-aspirins. Drugs of this class have an NO-releasing moiety joined by ester linkage to the aspirin molecule. NO-aspirins have the capability to release NO in addition to retaining the cyclooxygenase-inhibitory action of aspirin. The protective nature of NO led to the development of NO-aspirins in the hope that they might avoid the gastric side effects associated with aspirin. However, it has become apparent that the drug-derived NO instills potential for a wide range of added beneficial effects over the parent compound. In this review, the authors focus on the analgesic, anti-inflammatory, cardiovascular and chemopreventative actions of compounds of this emerging drug class.

Prevention of Postischemic Myocardial Reperfusion Injury by the Combined Treatment of NCX-4016 and Tempol

Nitric oxide (NO) plays a protective role in myocardial ischemia-reperfusion (I/R) injury. However, the concomitant production of superoxide and other reactive oxygen species (ROS) during I/R may diminish the bioavailability of NO and hence compromise the beneficial effects. The objective of this study was to investigate the protective effect of the coadministration of NCX-4016 [2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester] (an NO donor) with antioxidants Tempol, superoxide dismutase (SOD), or urate on I/R injury. Isolated rat hearts, perfused with Krebs-Henseleit buffer, were subjected to 30 minutes of global ischemia, followed by 45 minutes of reperfusion. Before the induction of ischemia, the hearts were infused for 1 minute with NCX-4016 (100 microM) either alone or in combination with Tempol (100 microM), SOD (200 U/mL), or urate (100 microM). Hearts pretreated with NCX-4016 showed a significantly enhanced recovery of function and decreased infarct size and LDH/CK release compared with the controls. However, treatment of hearts with NCX-4016 + Tempol, SOD, or urate showed a significantly enhanced recovery of heart function compared with NCX-4016 alone. The treatment of hearts with NCX-4016 + Tempol showed significantly enhanced NO generation and decreased ROS and dityrosine (a marker of peroxynitrite) formation. In conclusion, NCX-4016 in combination with Tempol demonstrated significant cardioprotection and, thus, may offer a novel therapeutic strategy to prevent I/R-mediated myocardial injury.

Influence of nitric oxide-donating nonsteroidal anti-inflammatory drugs on the evolution of acute pancreatitis

Microcirculatory disturbances and leukocyte activation are main events in the pathogenesis of acute pancreatitis (AP) that is characterized by inflammatory up-regulation. Nitric oxide-donating nonsteroidal anti-inflammatory drugs (NO-NSAIDs) regulate vascular function and mitigate inflammation. To investigate the influence of NO-NSAIDs on AP. AP was induced by the biliopancreatic duct outlet exclusion-closed duodenal loops model. Treatment with NO-flurbiprofen, NO-ibuprofen, NO-aspirin, or their parental drugs was done (i) 1 h before, (ii) 1 h after, (iii) 1 h before and 4 h after, or (iv) 4 h after surgery. The degree of severity was evaluated using biochemical and histopathological analyses. NO-NSAIDs given before and during the first hour of the noxia decreased blood levels of amylase, lipase, C-reactive protein, IL-6, IL-10, heat shock protein 72, prostaglandin E2 inactive metabolite, and 8-isoprostane, as well as pancreatic and lung myeloperoxidase and cyclooxygenase. Acinar and fat necrosis, hemorrhage, and leukocyte infiltrate were also reduced. The best protection was achieved when treatment was performed 1 h before and 4 h after triggering AP. NO-flurbiprofen was the most effective drug. AP severity was significantly ameliorated by NO-NSAIDs being the administration time essential to achieve optimal pancreatic protection that may result to be useful in the prevention of postendoscopic severe AP.

Pharmacologic Profile and Therapeutic Potential of NCX 4016, a Nitric Oxide-releasing Aspirin, for Cardiovascular Disorders

NCX 4016, 2-(acetyloxy)benzoic acid 3-[(nitrooxy)methyl]phenyl ester, is a new molecule in which a nitric oxide (NO)-releasing moiety is covalently linked to aspirin. After enzymatic metabolism, NCX 4016 releases both components. In vitro and in some animal models, these components exert their pharmacologic effects simultaneously. Nitric oxide (NO) is a small gaseous molecule that exerts several activities which may prevent atherothrombotic disorders. Moreover, it displays a protective activity on the gastric mucosa. NCX 4016 has been shown to inhibit platelet activation in vitro more effectively than aspirin, to inhibit smooth muscle cell proliferation, to exert an endothelial cell protective activity and to suppress the function of several inflammatory cells potentially involved in atherothrombosis. In animal models, NCX 4016 protected from platelet thromboembolism, prevented restenosis in atherosclerosis-prone animals, protected the heart from ischemia/reperfusion injury, and induced neoangiogenesis in critically ischemic limbs. Moreover, it displayed little or no gastric toxicity and appeared to protect stomach from noxious stimuli, including aspirin. NCX 4016 has been evaluated in healthy volunteers and found to inhibit platelet cyclo-oxygenase-1 (COX-1) similarly to or slightly less than aspirin, to raise the circulating levels of NO-degradation products, and to have little or no gastric toxicity in short term studies. In particular, in phase II studies, NCX 4016 had favorable effects on effort-induced endothelial dysfunction in intermittent claudication and on platelet-activation parameters elicited by short-term hyperglycemia in type II diabetics. In patients with type II diabetes the effects of NCX 4016 on microalbuminuria and on some hemodynamic parameters were promising. The pharmacokinetics of in vivo aspirin- and NO- released by NCX 4016, as well as the bioavailability of the two molecules, were not yet adequately studied. Also, the long-term tolerability of NCX 4016, as well as its possible effectiveness in preventing ischemic cardiovascular events and progression of atherosclerosis, should be explored.

Mechanism of action of novel NO-releasing furoxan derivatives of aspirin in human platelets

Incorporation of a nitric oxide (NO)-releasing moiety in aspirin can overcome its gastric side effects. We investigated the NO-release patterns and antiplatelet effects of novel furoxan derivatives of aspirin (B8 and B7) in comparison to existing antiplatelet agents. Cyclooxygenase (COX) activity was investigated in purified enzyme using an electron paramagnetic resonance-based technique. Concentration-response curves for antiplatelet agents +/- the soluble guanylate cyclase inhibitor, ODQ (50 microM) were generated in platelet-rich plasma (PRP) and washed platelets (WP) activated with collagen using turbidometric aggregometry. NO was detected using an isolated NO electrode. The furoxan derivatives of aspirin (B8, B7) and their NO-free furazan equivalents (B16, B15; all 100 microM) significantly inhibited COX activity (P < 0.01; n = 6) in vitro and caused aspirin-independent, cGMP-dependent inhibition of collagen-induced platelet aggregation in WP. B8 was more potent than B7 (PRP IC(50) = 0.62 +/- 0.1 microM for B8; 400 +/- 89 microM for B7; P < 0.0001. WP IC(50)s = 0.6 +/- 0.1 and 62 +/- 10 microM, respectively). The NO-free furazan counterparts were less potent antiplatelet agents (WP IC(50)s = 54 +/- 3 microM and 62 +/- 10 microM, respectively; P < 0.0001, B8 vs B16). Of the hybrids investigated, only B8 retained antiplatelet activity in PRP.NO release from furoxan-aspirin hybrids was undetectable in buffer alone, but was accelerated in the presence of either plasma or plasma components, albumin (4%), glutathione (GSH; 3 microM) and ascorbate (50 microM), the effects of which were additive for B7 but not B8. NO generation from furoxans was greatly enhanced by platelet extract, an effect that could largely be explained by the synergistic effect of intracellular concentrations of GSH (3 mM) and ascorbate (1 mM). We conclude that the decomposition of furoxan-aspirin hybrids to generate biologically active NO is catalysed by endogenous agents which may instil a potential for primarily intracellular delivery of NO. The blunting of the aspirin effects of furoxan hybrids is likely to be due to loss of the acetyl moiety in plasma; the observed antiplatelet effects are thereby primarily mediated via NO release. Compounds of this class might represent a novel means of inhibiting platelet aggregation by a combination of NO generation and COX inhibition.

Influence of hydrocortisone, prednisolone, and NO association on the evolution of acute pancreatitis

Leukocyte activation, inflammatory up-regulation, and microcirculatory disruption associated with ischemia-reperfusion injury are hallmarks in the pathogenesis of acute pancreatitis (AP). NO donors ensure microvascular integrity, while glucocorticoids act as anti-inflammatory and immune modulator drugs. AP was induced by the biliopancreatic duct outlet exclusion-closed duodenal loops (BPDOE-CDLs) model. Treatment with hydrocortisone (6 mg/kg) or prednisolone (0.5 mg/kg) alone or together with DETA-NO (0.5 mg/kg) was done (a)1 hr pre or (b)1 hr post, or (c) 1 hr pre and 4 hr post ,or (d) 4 hr post triggering AP. NOS inhibition by L-NAME (15 mg/kg) and glucocorticoid receptor blockage by mifepristone (3 mg/kg) was considered. AP severity was assessed by biochemical and histopathological analyses. Treatment with glucocorticoids together with DETA-NO 1 hr pre and 4 hr post BPDOE-CDLs reduced serum amylase, lipase, C-reactive protein, IL-6, IL-10, hsp72, and 8-isoprostane as well as pancreatic and lung myeloperoxidase. Acinar and fat necrosis, hemorrhage, and neutrophil infiltrate were also decreased. Hydrocortisone together with DETA-NO rendered the best results. We conclude that AP severity was significantly diminished by glucocorticoids associated with DETA-NO, with the optimal dose and time point of administration being crucial to provide adequate protection against AP.

Histidine button engineered into cardiac troponin I protects the ischemic and failing heart

The myofilament protein troponin I (TnI) has a key isoform-dependent role in the development of contractile failure during acidosis and ischemia. Here we show that cardiac performance in vitro and in vivo is enhanced when a single histidine residue present in the fetal cardiac TnI isoform is substituted into the adult cardiac TnI isoform at codon 164. The most marked effects are observed under the acute challenges of acidosis, hypoxia, ischemia and ischemia-reperfusion, in chronic heart failure in transgenic mice and in myocytes from failing human hearts. In the isolated heart, histidine-modified TnI improves systolic and diastolic function and mitigates reperfusion-associated ventricular arrhythmias. Cardiac performance is markedly enhanced in transgenic hearts during reperfusion despite a high-energy phosphate content similar to that in nontransgenic hearts, providing evidence for greater energetic economy. This pH-sensitive 'histidine button' engineered in TnI produces a titratable molecular switch that 'senses' changes in the intracellular milieu of the cardiac myocyte and responds by preferentially augmenting acute and long-term function under pathophysiological conditions. Myofilament-based inotropy may represent a therapeutic avenue to improve myocardial performance in the ischemic and failing heart.

The effect of NCX4016 [2-acetoxy-benzoate 2-(2-nitroxymethyl)-phenyl ester] on the consequences of ischemia and reperfusion in the streptozotocin diabetic rat

The aim of this study was to assess the effect of chronic administration of NCX4016 [2 acetoxy-benzoate 2-(2-nitroxymethyl)-phenyl ester], a nitric oxide-releasing aspirin derivative on the consequences of coronary artery occlusion in streptozotocin-diabetic rats. Rats were made diabetic by injection of streptozotocin (60 mg kg(-1)) and received insulin (2.5 U kg(-1) s.c.) daily for 4 weeks. Animals received vehicle (1 ml kg(-1) polyethylene glycol), aspirin (65.2 mg kg(-1)), NCX4016 (60 mg kg(-1)), or (iv) NCX4016 (120 mg kg(-1)) orally, once daily for the last 5 days before coronary artery occlusion (CAO). One hour after the last dose, pentobarbital-anesthetized rats were subjected to CAO for 30 min followed by 120-min reperfusion. Neither drug significantly modified initial hemodynamics or plasma glucose levels compared with vehicle treatment in either nondiabetic or diabetic rats. Neither drug modified the total ventricular premature beat (VPB) count in normal animals, although NCX4016, but not aspirin, reduced the total VPB count and the incidence of ventricular tachycardia in diabetic rats. In nondiabetic animals, both aspirin and NCX4016 reduced infarct size. However, in diabetic rats, infarct size was reduced only by the larger dose of NCX4016 (120 mg kg(-1)) but not by aspirin or the lower dose of NCX4016. These results demonstrate that the cardioprotective effects of NCX4016 are reduced in the presence of diabetes compared with the effects seen in nondiabetic animals. In summary, the present study confirms the protective effect of NCX4016 against ischemia-reperfusion injury in the normal rat heart and demonstrates for the first time its protective effect in the heart of streptozotocin-diabetic rats.

Direct and irreversible inhibition of cyclooxygenase-1 by nitroaspirin (NCX 4016)

Benzoic acid, 2-(acetyl-oxy)-3-[(nitrooxy)methyl]phenyl ester (NCX 4016), a new drug made by an aspirin molecule linked, through a spacer, to a nitric oxide (NO)-donating moiety, is now under clinical testing for the treatment of atherothrombotic conditions. Aspirin exerts its antithrombotic activity by irreversibly inactivating platelet cyclooxygenase (COX)-1. NCX 4016 in vivo undergoes metabolism into deacetylated and/or denitrated metabolites, and it is not known whether NCX 4016 needs to liberate aspirin to inhibit COX-1, or whether it can block it as a whole molecule. The aim of our study was to evaluate the effects of NCX 4016 and its analog or metabolites on platelet COX-1 and whole blood COX-2 and on purified ovine COX (oCOX)-1 and oCOX-2. In particular, we have compared the mechanism by which NCX 4016 inhibits purified oCOX enzymes with that of aspirin using a spectrophotometric assay. All the NCX 4016 derivatives containing acetylsalicylic acid inhibited the activity of oCOX-1 and oCOX-2, whereas the deacetylated metabolites and the nitric oxide-donating moiety were inactive. Dialysis experiments showed that oCOX-1 inhibition by NCX 4016, similar to aspirin, is irreversible. Reversible COX inhibitors (indomethacin) or salicylic acid incubated with the enzyme before NCX 4016 prevent the irreversible inhibition of oCOX-1 by NCX 4016 as well as by aspirin. In conclusion, our data show that NCX 4016 acts as a direct and irreversible inhibitor of COX-1 and that the presence of a spacer and NO-donating moiety in the molecule slows the kinetics of COX-1 inhibition by NCX 4016, compared with aspirin.

The vascular and cardioprotective effects of liriodenine in ischemia-reperfusion injury via NO-dependent pathway

Liriodenine is an aporphine derivative isolated from the plant Fissistigma glaucescens. Electrophysiological action, particularly the blockage of Na+ and K+ channels, contributes to the drug's well-known anti-arrhythmic action. However, liriodenine's cardioprotective efficacy and the relation of the channel blockages to the efficacy are poorly known, as is the drug's effect on coronary flow and endothelial function. The present study evaluated the protection conveyed by liriodenine to myocardium and coronary endothelial cells under conditions of ischemia-reperfusion and to assess the involvement of a nitric oxide (NO)-dependent mechanism. In the Langendorff model utilizing Sprague-Dawley rat hearts, the left main coronary artery was occluded for 30 min and reperfusion for 120 min. Liriodenine (1 microM) significantly promoted the recovery of coronary flow and decreased myocardial infarction compared with vehicle-treated hearts. The drug attenuated the reduction of endothelial reactivity and NO release. To simulate the condition that occurs in the ischemic stage, human umbilical vein endothelial cells (HUVEC) were cultured in serum free conditions. Liriodenine showed concentration-dependent effects on cell viability associated with anti-apoptosis under serum-deprivation. Liriodenine prevented eNOS reduction in serum-deprived HUVEC and ischemia-reperfusion hearts. The vascular and cardioprotective effects were reversed by N(G)-nitro-L-arginine methyl ester. Another Na+ and K+ channel blocker with similar activities as liriodenine (quinidine) failed to protect endothelial cells and myocytes. These results demonstrate that liriodenine reduces the extent of cardiovascular injuries under ischemia-reperfusion conditions mainly by preserving the eNOS and the NO production.

Advances in antiplatelet therapy

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality in the western world. These disorders share a common pathophysiology -- atherosclerosis, which affects various arterial beds, leading to protean manifestations (coronary artery disease [CAD], stroke, peripheral arterial disease [PAD]). The platelet plays a pivotal role in the perpetuation and clinical expression of these disorders. The platelet, once believed to have a role confined to modulation of thrombosis and haemostasis, also plays an active role in vascular inflammation. Antiplatelet agents have become first-line therapy for CVD, and their unequivocal benefits are demonstrated in various basic and experimental models and supported by overwhelming evidence from clinical trials. Search is underway for more effective and safer antiplatelet therapy. Novel therapies are emerging to target the redundant pathways of platelet adhesion, activation and aggregation. Efforts are also ongoing to enhance implementation of existent therapy, target therapy selectively to high-risk patients and to those likely to respond (pharmacogenomics), and study the incremental benefits and safety of various antiplatelet combinations and their interaction with other medications in patients with CVD treated with polypharmacy.

Nitric oxide-releasing aspirin inhibits vasoconstriction in perfused tail artery of normotensive and spontaneously hypertensive rats

The aim of this study was to investigate the capacity of the 2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester (NCX 4016), a nitric oxide (NO)-releaser derivative of aspirin, to decrease blood pressure in spontaneously hypertensive rats (SHR) and to counteract the adrenergic vasoconstriction in perfused tail artery of these animals. Oral treatment for 10 consecutive days with NCX 4016 (100 micromol/kg) in SHR and their genetic controls Wistar Kyoto (WKY) rats resulted in a reduction of blood pressure in SHR but not in WKY rats. In SHR, the NCX 4016 treatment increased the serum nitrite/nitrate and diminished the serum thromboxane B2, whereas aspirin did not change blood pressure but abolished the serum thromboxane B2. Perfused tail arteries excised from vehicle-treated SHR exhibited a significant impairment of endothelium-dependent vasorelaxant function. These vessels, prepared from SHR or WKY rats treated orally with NCX 4016 (10, 30 and 100 micromol/kg for 7 consecutive days), revealed a dose-dependent decrease in vasoconstriction in response to transmural nerve stimulation and norepinephrine, whereas aspirin was ineffective. Furthermore, in tail arteries of both SHR and WKY rats treated orally with NCX 4016 (100 micromol/kg for 7 consecutive days), the cGMP increased significantly. In conclusion, NCX 4016, by releasing NO and increasing cGMP in vascular tissue, reduces sympathetic-mediated vasoconstriction in resistance vessels and lowers blood pressure in SHR.

The Nitric Oxide-Releasing Naproxen Derivative Displays Cardioprotection in Perfused Rabbit Heart Submitted to Ischemia-Reperfusion

In this study, the pharmacological activity of HCT-3012 [(S)-6-methoxy-alpha-methyl-2-naphtaleneacetic acid 4-(nitrooxy)butyl ester], a nitric oxide (NO)-releasing derivative of naproxen, was compared with that of naproxen in a model of acute ischemia (40 min) and reperfusion (20 min) of the rabbit heart. HTC-3012 (3-100 microM), in spite of inhibition of 6-keto-prostaglandin F(1alpha) generation by the cardiac tissues, brought about a dose-dependent normalization of coronary perfusion pressure, associated with a reduction of ventricular contracture during ischemia with remarkable improvement of left ventricular developed pressure at reperfusion. These beneficial effects were accompanied by a substantial release of nitrite/nitrate in the heart perfusates, indicating that NO has been released by HCT-3012 and donated to the cardiac tissue. These events were paralleled by a significant reduction of creatine kinase activity in heart perfusates during reperfusion. Naproxen (10-100 microM) aggravated the myocardial damage in ischemic reperfused hearts, severely depressing the postischemic ventricular dysfunction. Perfusion of the heart with N(G)-monomethyl-l-arginine (10 microM) caused a marked aggravation of myocardial damage of the reperfused hearts, and this effect was dose dependently prevented by HCT-3012 but not by naproxen. The results of the present experiments clearly indicate that HCT-3012, by donating NO, displays a noticeable anti-ischemic effect in reperfused ischemic rabbit hearts. The safer gastrointestinal profile of HCT-3012 and its ability to control experimental hypertension, suggest that this compound may have therapeutical potential in cardiovascular disease, namely in the prevention of myocardial ischemic events, and may represent a better alternative to conventional nonsteroidal anti-inflammatory drugs.

Antioxidant activity of nitro derivative of aspirin against ischemia-reperfusion in hamster cheek pouch microcirculation

Aspirin that has been chemically combined with a nitric oxide (NO) donor (NCX-4016) has been shown to inhibit cyclooxygenase and prostaglandin generation while maintaining the inhibitory effects of aspirin. The possible role of reactive oxygen species (ROS) in the action of NCX-4016 in ischemia-reperfusion (I/R) has not been studied. Furthermore, we were interested in comparing the effects of a conventional NO donor [2,2'-hydroxynitrosohydrazino-bis-etanamine (DETA/NO)] and NCX-4016 at the microvascular level in the hamster cheek pouch visualized by using an intravital fluorescent microscopy technique. Microvascular injury was assessed by measuring diameter change, the perfused capillary length (PCL), and leukocyte adhesion. Animals were treated with NCX-4016 (100 mg/kg or 30 mg.kg(-1).day(-1) for 5 days po) or DETA-NO (0.5 mg/kg). Mean arterial blood pressure increased slightly but significantly after NCX-4016 treatment. During 5- and 15-min reperfusion, lipid peroxides in the systemic blood increased by 72 and 89% vs. baseline, respectively, and were still higher than in basal conditions after 30-min reperfusion in the I/R group. Pretreatment with NCX-4016 maintained ROS at normal levels; increased arteriolar diameter, blood flow, and PCL; and decreased leukocyte adhesion (P < 0.05). DETA-NO decreased ROS during 30-min reperfusion; however, later there was a significant increase during reperfusion. DETA-NO decreased leukocyte adhesion (P < 0.05) but microvascular permeability increased after 30 min of reperfusion. In conclusion, NCX-4016 attenuates oxidative stress and prevents arteriolar constriction during I/R, whereas DETA-NO increases lipid peroxides in the systemic blood and permeability after reperfusion.

Effects of NCX 4050, a new NO donor, in rabbit and human corpus cavernosum

The effects of NCX 4050, a drug belonging to a new class of NO donors, was investigated in isolated preparations of human and rabbit corpus cavernosum (CC) and in human foetal corpora cavernosa (hfCC) smooth muscle cells. In strips of rabbit CC, NCX 4050 (0.001-100 microM) induced a concentration-dependent relaxation which was influenced neither by Nw-nitro-l-arginine-methyl-ester (l-NAME; 100 microm) nor by endothelium deprivation. The NCX 4050-induced relaxation was significantly reduced by the guanylate cyclase inhibitor 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 1 microm) and enhanced by a specific phosphodiesterase 5 inhibitor, sildenafil (300 nm). Moreover, NCX 4050 (0.01-1 microm), induced a concentration-dependent potentiation of the relaxant response induced by electrical field stimulation (EFS) in rabbit preparations pre-treated with guanethidine and indomethacin. The relaxant effect of NCX 4050 was similar to that obtained by increasing concentrations (0.001-100 microm) of sodium nitroprusside (SNP) in either rabbit or human preparations. To further investigate the activity of NCX 4050 on human corpora cavernosa, we exposed cultured hfCC smooth muscle cells to increasing concentrations of NCX 4050 and SNP. We found that both compounds dose-dependently reduced cell proliferation. The antiproliferative effect of all the concentration tested of NCX 4050 was completely blocked by ODQ (1 microm). These results suggest that in rabbit and human corpora cavernosa NCX 4050 acts by activating guanylate cyclase activity, induces smooth muscle relaxation and quiescence. Our results provide a rationale for a possible future use of NCX 4050 in the pharmacotherapy of erectile dysfunction linked to an impaired release of NO from the endothelium.

Pharmacology and potential therapeutic applications of nitric oxide-releasing non-steroidal anti-inflammatory and related nitric oxide-donating drugs

This review examines the biological significance, therapeutic potential and mechanism(s) of action of a range of nitric oxide-releasing non-steroidal anti-inflammatory drugs (NO-NSAID) and related nitric oxide-releasing donating drugs (NODD). The slow release of nitric oxide (NO) from these compounds leads to subtle changes in the profile of pharmacological activity of the parent, non-steroidal anti-inflammatory drugs (NSAID). For example, compared with NSAID, NO-NSAID cause markedly diminished gastrointestinal toxicity and improved anti-inflammatory and anti-nociceptive efficacy. In addition, nitroparacetamol exhibits hepatoprotection as opposed to the hepatotoxic activity of paracetamol. The possibility that NO-NSAID or NODD may be of therapeutic benefit in a wide variety of disease states including pain and inflammation, thrombosis and restenosis, neurodegenerative diseases of the central nervous system, colitis, cancer, urinary incontinence, liver disease, impotence, bronchial asthma and osteoporosis is discussed.

NCX 4016, a nitric oxide-releasing aspirin, modulates adrenergic vasoconstriction in the perfused rat tail artery

1. The ability of the nitric oxide (NO)-releasing aspirin, NCX 4016, to control vasoconstrictor responses induced by electrical field stimulation (TNS) or by exogenous norepinephrine (NE) was investigated in perfused rat tail artery with intact endothelium. 2. NCX 4016 (25, 50 and 100 microM) dose-dependently antagonized the vasoconstriction caused by TNS (from 0.5 to 64 Hz) and by NE (from 0.01 to 10 microM). The vasorelaxant activity of NCX 4016 (100 microM) in NE-precontracted arteries was concomitant with a marked increase of tissue cyclic GMP (4.9 fold, P<0.001) and was significantly antagonized by the inhibitors of soluble guanylate cyclase, methylene blue and 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one. 3. The effect of NCX 4016 was endothelium NO-independent since, in preparations perfused with N(G)-monomethyl-L-arginine (10 microM), this compound prevented the rise in basal perfusion pressure and reversed the accentuation of vasoconstrictor responses caused by NO synthase inhibition. 4. Aspirin-moiety released by NCX 4016 inhibited the 6-keto-PGF(1alpha) formation without interfering with the vasorelaxant activity of NCX 4016, while aspirin (100 microM) was devoid of any activity against vasoconstriction induced by both TNS and NE in perfused rat tail artery. 5. NCX 4016 moderated adrenergic vasoconstriction in perfused rat tail arteries by a direct donation of NO without involving the relaxant factors such as PGI(2) and NO from endothelial cells. 6. The results obtained with NCX 4016 in perfused rat tail artery bears some therapeutical potential in conditions associated with vascular smooth muscle hyperreactivity to adrenergic stimulation.

Nitric oxide donor drugs: current status and future trends

Nitric oxide synthesised in endothelial cells that line blood vessels has a wide range of functions that are vital for maintaining a healthy cardiovascular system. Reduced nitric oxide availability is implicated in the initiation and progression of many cardiovascular diseases and delivery of supplementary nitric oxide to help prevent disease progression is an attractive therapeutic option. Nitric oxide donor drugs represent a useful means of systemic nitric oxide delivery and organic nitrates have been used for many years as effective therapies for symptomatic relief from angina. However, nitrates have limitations and a number of alternative nitric oxide donor classes have emerged since the discovery that nitric oxide is a crucial biological mediator. This review focuses on novel advances and possible future directions in nitric oxide donor drug development.