Efficacy and age-related effects of nitric oxide-releasing aspirin on experimental restenosis

The Role of Platelets in Atherosclerosis: A Historical Review

Atherosclerosis is a chronic, multifactorial inflammatory disorder of large and medium-size arteries, which is the leading cause of cardiovascular mortality and morbidity worldwide. Although platelets in cardiovascular disease have mainly been studied for their crucial role in the thrombotic event triggered by atherosclerotic plaque rupture, over the last two decades it has become clear that platelets participate also in the development of atherosclerosis, owing to their ability to interact with the damaged arterial wall and with leukocytes. Platelets participate in all phases of atherogenesis, from the initial functional damage to endothelial cells to plaque unstabilization. Platelets deposit at atherosclerosis predilection sites before the appearance of manifest lesions to the endothelium and contribute to induce endothelial dysfunction, thus supporting leukocyte adhesion to the vessel wall. In particular, platelets release matrix metalloproteinases, which interact with protease-activated receptor 1 on endothelial cells triggering adhesion molecule expression. Moreover, P-selectin and glycoprotein Ibα expressed on the surface of vessel wall-adhering platelets bind PSGL-1 and β2 integrins on leukocytes, favoring their arrest and transendothelial migration. Platelet-leukocyte interactions promote the formation of radical oxygen species which are strongly involved in the lipid peroxidation associated with atherosclerosis. Platelets themselves actively migrate through the endothelium toward the plaque core where they release chemokines that modify the microenvironment by modulating the function of other inflammatory cells, such as macrophages. While current antiplatelet agents seem unable to prevent the contribution of platelets to atherogenesis, the inhibition of platelet secretion, of the release of MMPs, and of some specific pathways of platelet adhesion to the vessel wall may represent promising future strategies for the prevention of atheroprogression.

Jujuboside B Inhibits Neointimal Hyperplasia and Prevents Vascular Smooth Muscle Cell Dedifferentiation, Proliferation, and Migration via Activation of AMPK/PPAR-γ Signaling

The uncontrolled proliferation and migration of vascular smooth muscle cells is a critical step in the pathological process of restenosis caused by vascular intimal hyperplasia. Jujuboside B (JB) is one of the main biologically active ingredients extracted from the seeds of Zizyphus jujuba (SZJ), which has the properties of anti-platelet aggregation and reducing vascular tension. However, its effects on restenosis after vascular intervention caused by VSMCs proliferation and migration remain still unknown. Herein, we present novel data showing that JB treatment could significantly reduce the neointimal hyperplasia of balloon-damaged blood vessels in Sprague-Dawley (SD) rats. In cultured VSMCs, JB pretreatment significantly reduced cell dedifferentiation, proliferation, and migration induced by platelet-derived growth factor-BB (PDGF-BB). JB attenuated autophagy and reactive oxygen species (ROS) production stimulated by PDGF-BB. Besides, JB promoted the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and the expression of peroxisome proliferator-activated receptor-γ (PPAR-γ). Notably, inhibition of AMPK and PPAR-γ partially reversed the ability of JB to resist the proliferation and migration of VSMCs. Taken as a whole, our findings reveal for the first time the anti-restenosis properties of JB in vivo and in vitro after the endovascular intervention. JB antagonizes PDGF-BB-induced phenotypic switch, proliferation, and migration of vascular smooth muscle cells partly through AMPK/PPAR-γ pathway. These results indicate that JB might be a promising clinical candidate drug against in-stent restenosis, which provides a reference for further research on the prevention and treatment of vascular-related diseases.

Microvascular endothelial dysfunction in rheumatoid arthritis

The systemic autoimmune disease rheumatoid arthritis (RA) is characterized by increased cardiovascular mortality and morbidity and is an independent cardiovascular risk factor. Cardiovascular diseases (CVDs) result from accelerated atherogenesis, which is a consequence of endothelial dysfunction in the early stages of the disease. Endothelial dysfunction is a functional and reversible alteration of endothelial cells and leads to a shift in the properties of the endothelium towards reduced vasodilation, a pro-inflammatory state, and proliferative and prothrombotic properties. In RA, endothelial dysfunction can occur in the large vessels (such as the conduit arteries) and in the small vessels of the microvasculature, which supply oxygen and nutrients to the tissue and control inflammation, repair and fluid exchange with the surrounding tissues. Growing evidence suggests that microvascular endothelial dysfunction contributes to CVD development, as it precedes and predicts the development of conduit artery atherosclerosis and associated risk factors. As such, numerous studies have investigated microvascular endothelial dysfunction in RA, including its link with disease activity, disease duration and inflammation, the effect of treatments on endothelial function, and possible circulating biomarkers of microvascular endothelial dysfunction. Such findings could have important implications in the cardiovascular risk management of patients with RA.

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.

Antioxidative effect of aspirin on vascular function of aged ovariectomized rats

This study investigated the vascular effects of nonsteroidal anti-inflammatory drugs (NSAIDs) in the very late stage of postmenopausal vascular aging and looked for a better choice of anti-inflammatory drug for women in reducing the cardiovascular risk by decreasing the oxidant status in this term. The rat aorta isolated from young and old rats that were treated with either aspirin (10 mg/kg/day) or indomethacin (INDO, 1 mg/kg/day) within last 10 weeks after 16-month overiectomy (OVX) follow-up. Endothelium-dependant acetylcholine (Ach, 0.001-30 μM) and independent sodium nitroprusside (SNP, 0.0001-3 μM) relaxant; α-receptor phenylephrine (PE, 0.001-30 μM) and voltage-dependant high potassium (KCl; 40 mM) contractile responses were assessed. Total oxidant and antioxidant status were measured from the serum samples. Aged OVX rat's both aortic endothelium and smooth muscle relaxation were significantly less than of younger ones, whereas their contractile functions tended to decrease. INDO did not treat the Ach, SNP responses, whereas it increased the PE and KCl contractility. Aspirin improved the relaxation function and antioxidant capacity and decreased the oxidant status. These data demonstrate that even if they are in the very late stage of life and menopause, the analgesic choices could restore the well established endothelial dysfunction, vascular stiffness, and oxidant status.

An imbalance between VEGF and endostatin underlies impaired angiogenesis in gastric mucosa of aging rats

Gastric mucosa of aging individuals exhibits increased susceptibility to injury and delayed healing. Our previous studies in young rats showed that healing of mucosal injury depends on and is critically dependent on VEGF and angiogenesis. Since angiogenesis in aging gastric mucosa has not been examined before, in this study we examined the extent to which angiogenesis is impaired in gastric mucosa of aging vs. young rats and determined the underlying mechanisms with a focus on mucosal expression of VEGF (proangiogenic factor) and endostatin (antiangiogenic factor). Aging rats had significantly impaired gastric angiogenesis by ~12-fold, 5-fold, 4-fold, and 3-fold, respectively (vs. young rats; all P < 0.001) at 24, 48, 72, and 120 h following ethanol-induced gastric injury and reduced and delayed healing of mucosal erosions. In gastric mucosa of aging (vs. young) rats at baseline, VEGF expression was significantly reduced, whereas endostatin levels were significantly increased (P < 0.05 and P < 0.01, respectively). In contrast to young rats, gastric mucosal VEGF levels did not increase following ethanol-induced injury in aging rats. MMP-9 enzyme activity was significantly higher in gastric mucosa of aging vs. young rats both at baseline (2.7-fold) and 24 h (3.8-fold) after ethanol injury (both P < 0.001). Since endostatin is generated from collagen XVIII by MMP-9, this finding can explain the mechanism of increased endostatin expression in aging gastric mucosa. The above findings demonstrate that reduced VEGF and increased endostatin result in the impaired angiogenesis and delayed injury healing in gastric mucosa of aging rats.

Differential modulation of nitric oxide synthases in aging: therapeutic opportunities

Vascular aging is the term that describes the structural and functional disturbances of the vasculature with advancing aging. The molecular mechanisms of aging-associated endothelial dysfunction are complex, but reduced nitric oxide (NO) bioavailability and altered vascular expression and activity of NO synthase (NOS) enzymes have been implicated as major players. Impaired vascular relaxation in aging has been attributed to reduced endothelial NOS (eNOS)-derived NO, while increased inducible NOS (iNOS) expression seems to account for nitrosative stress and disrupted vascular homeostasis. Although eNOS is considered the main source of NO in the vascular endothelium, neuronal NOS (nNOS) also contributes to endothelial cells-derived NO, a mechanism that is reduced in aging. Pharmacological modulation of NO generation and expression/activity of NOS isoforms may represent a therapeutic alternative to prevent the progression of cardiovascular diseases. Accordingly, this review will focus on drugs that modulate NO bioavailability, such as nitrite anions and NO-releasing non-steroidal anti-inflammatory drugs, hormones (dehydroepiandrosterone and estrogen), statins, resveratrol, and folic acid, since they may be useful to treat/to prevent aging-associated vascular dysfunction. The impact of these therapies on life quality in elderly and longevity will be discussed.

Nitric oxide and nitrite-based therapeutic opportunities in intimal hyperplasia

Vascular intimal hyperplasia (IH) limits the long term efficacy of current surgical and percutaneous therapies for atherosclerotic disease. There are extensive changes in gene expression and cell signaling in response to vascular therapies, including changes in nitric oxide (NO) signaling. NO is well recognized for its vasoregulatory properties and has been investigated as a therapeutic treatment for its vasoprotective abilities. The circulating molecules nitrite (NO(2)(-)) and nitrate (NO(3)(-)), once thought to be stable products of NO metabolism, are now recognized as important circulating reservoirs of NO and represent a complementary source of NO in contrast to the classic L-arginine-NO-synthase pathway. Here we review the background of IH, its relationship with the NO and nitrite/nitrate pathways, and current and future therapeutic opportunities for these molecules.

Flow injection measurements of S-nitrosothiols species in biological samples using amperometric nitric oxide sensor and soluble organoselenium catalyst reagent

A novel flow injection analysis (FIA) system suitable for measurement of S-nitrosothiols (RSNOs) in blood plasma is described. In the proposed (FIA) system, samples and standards containing RSNO species are injected into a buffer carrier stream that is mixed with the reagent stream containing 3,3'-dipropionicdiselenide (SeDPA) and glutathione (GSH). SeDPA has been shown previously to catalytically decompose RSNOs in the presence of a reducing agent, such as GSH, to produce nitric oxide (NO). The liberated NO is then detected downstream by an amperometric NO sensor. This sensor is prepared using an electropolymerized m-phenylenediamine (m-PD)/resorcinol and Nafion composite films at the surface of a platinum electrode. Using optimized flow rates and reagent concentrations, detection of various RSNOs at levels in the range of 0.25-20 μM is possible. For plasma samples, detection of background sensor interference levels within the samples must first be carried out using an identical FIA arrangement, but without the added SeDPA and GSH reagents. Subtraction of this background sensor current response allows good analytical recovery of RSNOs spiked into animal plasma samples, with recoveries in the range of 90.4-101.0%.

Review: Antiplatelet Drugs: What Comes Next?

Antiplatelet drugs are important components in the management of atherothrombotic vascular disease. However, several limitations restrict the safety and efficacy of current antiplatelet therapy in clinical practice. Interpatient variability and resistance to aspirin and/or clopidogrel has spurred efforts for the development of novel agents. Indeed, several antiplatelet drugs are at various stages of evaluation; those at advanced stage of development are the focus of this review.

Age-related changes in redox signaling and VSMC function

Epidemiological studies have shown that advancing age is associated with an increased prevalence of cardiovascular disease (CVD). Vascular smooth muscle cells (VSMC) comprise the major arterial cell population, and changes in VSMC behavior, function, and redox status with age contribute to alterations in vascular remodeling and cell signaling. Over two decades of work on aged animal models provide support for age-related changes in VSMC and/or arterial tissues. Enhanced production of reactive oxygen species (ROS) and insufficient removal by scavenging systems are hallmarks of vascular aging. VSMC proliferation and migration are core processes in vascular remodeling and influenced by growth factors and signaling networks. The intrinsic link between gene regulation and aging often relates directly to transcription factors and their regulatory actions. Modulation of growth factor signaling leads to up- or downregulation of transcription factors that control expression of genes associated with VSMC proliferation, inflammation, and ROS production. Four major signaling pathways related to the transcription factors, AP-1, NF-kappaB, FoxO, and Nrf2, will be reviewed. Knowledge of age-related changes in signaling pathways in VSMC that lead to alterations in cell behavior and function consistent with disease progression may help in efforts to attenuate age-related CVD, such as atherosclerosis.

New antiplatelet drugs: beyond aspirin and clopidogrel

Antiplatelet therapy remains a cornerstone of modern management of atherothrombotic vascular disease. For many years, aspirin has been the mainstay of initial antiplatelet drug management in coronary heart disease, while the need for inhibition of other platelet activation pathways has led to the development of various other antiplatelet drugs, such as clopidogrel. An improved understanding of the underlying mechanisms involved in thrombogenesis has paved the way for further development of newer antiplatelet drug therapies. Various clinical studies have probed the effectiveness and risk profile of the newer antiplatelet drugs, such as prasugrel, in comparison with currently available drugs. Some newer agents such as prasugrel are close to being approved for clinical use, whereas other agents such as cangrelor and AZD6140 are in phase 3 clinical trials. New drug classes, such as the thromboxane receptor antagonists (such as NCX-4016 and S18886), as well as platelet adhesion antagonists and thrombin receptor antagonists are similarly being evaluated for their efficacy and risk profile in phase I and II trials.

Nitric oxide: what a vascular surgeon needs to know

Atherosclerosis in the form of peripheral arterial disease results in significant morbidity and mortality. Surgical treatment options for peripheral arterial disease include angioplasty with and without stenting, endarterectomy, and bypass grafting. Unfortunately, all of these procedures injure the vascular endothelium, which impairs its ability to produce nitric oxide (NO) and ultimately leads to neointimal hyperplasia and restenosis. To improve on current patency rates after vascular procedures, investigators are engaged in research to improve the bioavailability of NO at the site of vascular injury in an attempt to reduce the risk of thrombosis and restenosis after successful revascularization. This article reviews some of the previous research that has aimed to improve NO bioavailability after vascular procedures whether through systemic or local delivery, as well as to describe some of the NO-releasing products that are currently undergoing study for use in clinical practice.

Nitroaspirin (NCX-4016), an NO donor, is antiangiogenic through induction of loss of redox-dependent viability and cytoskeletal reorganization in endothelial cells

We recently reported that NCX-4016, a derivative of aspirin containing a nitro moiety that releases nitric oxide (NO) in a sustained fashion in biologic systems, is a potent cytotoxic agent inhibiting the proliferation of cisplatin-resistant human ovarian cancer cells. Therefore, we hypothesize that NCX-4016 possesses antiangiogenic properties. Our study with the bovine lung microvascular endothelial cells (BLMVECs) revealed that NCX-4016 significantly induced the loss of redox-dependent cell viability in a dose- and time-dependent manner, as assayed by the redox-sensitive Alamar blue cell viability assay. Fluorescence microscopy of cells labeled with NO-specific fluorophore (DAF-FM) confirmed that NCX-4016 generated significant levels of intracellular NO. NO donors, including S-nitroso-N-acetylpenicillamine, spermine NONOate, and isosorbide dinitrite, were less effective in causing loss of cell viability. Thiol-protectant, N-acetylcysteine, significantly attenuated the NCX-4016-induced loss of cell viability, suggesting the role of alteration of thiol-redox status therein. NCX-4016 also suppressed oxygen consumption, decreased transendothelial electrical resistance (EC barrier dysfunction), and induced actin cytoskeletal reorganization in BLMVECs. The in vitro assay with human umbilical vein ECs and BLMVECs revealed that NCX-4016, in a dose-dependent manner, significantly inhibited angiogenesis with almost complete inhibition at a 100-microM concentration, suggesting that NCX-4016 can act as an antiangiogenic drug.

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.

Nitric oxide-releasing aspirin: will it say NO to atherothrombosis?

Aspirin is a powerful anti-platelet drug widely used in patients with coronary atherosclerosis, but its side effects and especially its toxicity for gastrointestinal tract limit its usefulness in specific groups of patients. A new category of agents, nitric oxide-releasing aspirins (such as NCX-4016), seems to provide an alternative solution. Although this drug is still at phase II clinical trials, it has provided promising results until now. When administered in vivo, it is separated into an aspirin moiety and an NO-donating complex, providing both the antithrombotic effect of aspirin and the gastroprotective effect of NO. Additionally, it increases NO bioavailability as a vascular level, and it may have the antiatherogenic properties of endogenously produced NO. Finally, recent evidence suggests that it may also improve functional aspects of vein grafts used in CABG, with possible benefit on graft patency. However, the outcome of the large ongoing trials is needed before any conclusion is made about the role of NO-releasing aspirins in cardiovascular disease.

Clinical aspects of platelet inhibitors and thrombus formation

The platelet, once thought to be solely involved in clot formation, is now known to be a key mediator in various others processes such as inflammation, thrombosis, and atherosclerosis. Supported by the wealth of evidence from clinical trials demonstrating their benefits in patient outcomes, antiplatelet agents have become paramount in the prevention and management of various diseases involving the cardiovascular, cerebrovascular, and peripheral arterial systems. Despite being among the most widely used and studied classes of medical therapies, new discoveries regarding important clinical aspects and properties of these agents continue to be made. As our understanding of platelet biology expands, more effective and safer novel therapies continue to be developed. The use of more refined agents in conjunction with a better understanding of their effects will further the ability to provide more optimized care on an individual basis.

Functional effects of nitric oxide-releasing aspirin on vein conduits of diabetic patients undergoing CABG

BACKGROUND

Type 2 diabetes mellitus (DM) is known to negatively affect biological properties of venous vasculature, and, particularly, to reduce endothelium-derived nitric oxide release. This condition might influence venous graft function following coronary artery bypass surgery (CABG). The aim of this study was to evaluate the functional effects of a NO-releasing aspirin (NORA) on vein grafts (VG) of diabetics and control patients undergoing elective CABG.

METHODS

In 40 consecutive ischemic heart disease patients, the effects of NORA were tested on segments of saphenous vein conduits harvested during elective CABG. Twenty patients had type-2 DM (mean age 69+/-2), whereas 20 patients had no DM (NDM) and represented the control group (mean age 67+/-4). Functional responses were tested by exposing VGs to NORA and to standard vasoactive agents in an organ-bath preparation. Histological features of VGs were also assessed by light and electronic microscopy.

RESULTS

Significant impairment of endothelial-dependent vasodilation (acetylcholine induced) was documented in VGs of DM subjects. NORA induced a significant and comparable vascular relaxation in all venous segments of NDM and DM patients (56+/-12% of maximal relaxation vs 61+/-11% in the control group, respectively). Histology showed variable extent of vascular layer and cellular abnormalities in VGs of diabetics (intimal hyperplasia, calcific deposition, endothelial cell degeneration) likely responsible of the endothelial functional impairment, whereas control group VG showed preserved structures.

CONCLUSIONS

This preliminary study confirms the impairment of endothelium-dependent vasodilative property of VGs in DM patients. It also indicates that NORA effectively induces vasodilation of VGs which was effective also in DM patients thereby representing a promising therapy for diabetics undergoing CABG with the use of VGs, although further studies are mandatory to conclusively assess the safety and benefits of this pharmacological 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.

Novel therapies targeting vascular endothelium

Endothelial dysfunction has been identified as a major mechanism involved in all the stages of atherogenesis. Evaluation of endothelial function seems to have a predictive role in humans, and therapeutic interventions improving nitric oxide bioavailability in the vasculature may improve the long-term outcome in healthy individuals, high-risk subjects, or patients with advanced atherosclerosis. Several therapeutic strategies are now available, targeting both the synthesis and oxidative inactivation of nitric oxide (NO) in human vasculature. Statins seem to be currently the most powerful category of these agents, improving endothelial function and decreasing cardiovascular risk after long-term administration. Other cardiovascular agents improving endothelial function in humans are angiotensin-converting enzyme inhibitors/angiotensin receptors blockers, which increase NO bioavailability by modifying the rennin-angiotensin-aldosterone system. Newer therapeutic approaches targeting endothelial dysfunction in specific disease states include insulin sensitizers, L-arginine (the substrate for endothelial NO synthase [eNOS]) as well as substances that target eNOS "coupling," such as folates or tetrahydrobiopterin. Although there are a variety of strategies to improve NO bioavailability in human endothelium, it is still unclear whether they have any direct benefit at a clinical level.

Detection of S-nitrosothiols in biological fluids: a comparison among the most widely applied methodologies

Many different methodologies have been applied for the detection of S-nitrosothiols (RSNOs) in human biological fluids. One unsatisfactory outcome of the last 14 years of research focused on this issue is that a general consensus on reference values for physiological RSNO concentration in human blood is still missing. Consequently, both RSNO physiological function and their role in disease have not yet been clarified. Here, a summary of the values measured for RSNOs in erythrocytes, plasma, and other biological fluids is provided, together with a critical review of the most widely used analytical methods. Furthermore, some possible methodological drawbacks, responsible for the highlighted discrepancies, are evidenced.

Increased Balloon-Induced Inflammation, Proliferation, and Neointima Formation in Apolipoprotein E (ApoE) Knockout Mice

BACKGROUND AND PURPOSE

The pathophysiology of vascular lesions after balloon angioplasty remains poorly understood. A major limitation of most experimental studies in this regard is that injury was assessed in healthy arteries. Our aim was to study the effects of hypercholesterolemia in a mouse vascular injury model that mimics human balloon angioplasty.

METHODS

Carotid balloon distension was performed in wild-type (WT) mice on a normal diet (ND), in apolipoprotein E-deficient (ApoE-/-) mice on ND and in ApoE-/- mice fed a high cholesterol diet (CD).

RESULTS

Medial cell death (TUNEL) was elevated in all mice at 1 hour and 1 day after angioplasty without differences between the groups. We found enhanced intimal inflammation (%CD45-positive cells) and vascular cell adhesion molecule-1 expression at 7 days (P < 0.05; n > or = 4) as well as increased proliferation rates (BrdU-index) in ApoE-/- CD at 7 and 28 days postinjury (P < 0.05; n > or = 5). Four weeks after injury, these events led to enhanced neointima in ApoE-/- CD compared with WT ND mice (intima/media, P < 0.001; n > or = 8). The amount of lesion formation paralleled the incremental increase in total plasma cholesterol in WT ND, ApoE-/- ND and ApoE-/- CD (P < 0.01).

CONCLUSIONS

Carotid balloon distension injury in ApoE-/- mice on CD induced enhanced inflammation and proliferation leading to increased neointima. Further applications of this microballoon catheter in genetically modified mice will provide opportunities to elucidate molecular mechanisms of vascular lesion formation in a model that reflects clinical balloon angioplasty. This know-how may pave the way to catheter-based interventions of human microvessels in the peripheral or cerebral circulation.

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.

Pharmacological characterization of 2NTX-99 [4-methoxy-N1-(4-trans-nitrooxycyclohexyl)-N3-(3-pyridinylmethyl)-1,3-benzenedicarboxamide], a potential antiatherothrombotic agent with antithromboxane and nitric oxide donor activity in platelet and vascular preparations

Thromboxane (TX) A(2), prostacyclin (PGI(2)), and nitric oxide (NO) regulate platelet function and interaction with the vessel wall. Inhibition of TXA(2), implemented synthesis of PGI(2), and supply of exogenous NO may afford therapeutic benefit. 2NTX-99 [4-methoxy-N(1)-(4-trans-nitrooxycyclohexyl)-N(3)-(3-pyridinylmethyl)-1,3-benzenedicarboxamide], a new chemical entity related to picotamide, showed antithromboxane activity and NO donor properties. 2NTX-99 relaxed rabbit aortic rings precontracted with norepinephrine or U46619 (9,11-dideoxy-9alpha,11alpha-methanoepoxy-prosta-5Z,13E-dien-1-oic acid; EC(50), 7.9 and 17.1 microM, respectively), an effect abolished by 10 microM 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ). 2NTX-99 inhibited arachidonic acid (AA)-induced washed platelet aggregation (EC(50), 9.8 microM) and TXB(2) formation (-71% at 10 microM), and its potency increased in the presence of aortic rings (EC(50), 1.4 microM). In whole rabbit aorta incubated with homologous platelets, AA caused contraction and TXA(2) formation, reduced by 2NTX-99 (10-40 microM): contraction, -28 and -47%, TXA(2) formation, -37 and -75.4%, respectively, with concomitant increase in PGI(2). 2NTX-99 (20-40 microM) inhibited U46619-induced aggregation in rabbit platelet-rich plasma (PRP) (-74 +/- 6.7 and -96 +/- 2.4%, respectively) and inhibited collagen-induced aggregation in human PRP (-48.2 +/- 10 and -79.2 +/- 6%), whereas ozagrel was ineffective. In human embryonic kidney 293 cells transfected with the TXA(2) receptor isophorm alpha receptor, 2NTX-99 did not compete with the ligand, [(3)H]SQ29,548 ([(3)H][1S-[1alpha,2beta(5Z),3beta,4alpha]]-7-[3-[[2-(phenylamino)-carbonyl]hydrazino]methyl]-7-oxabicyclo[2,2,1]-hept-2-yl]-5-heptanoic acid), or prevent inositol phosphate accumulation. After oral administration (50-250 mg/kg), 2NTX-99 inhibited TXA(2) production in rat clotting blood (-71 and -91%); at 250 mg/kg, an area under the curve, 0 to 16 h, of 149.5 h/microg/ml and a t(1/2) of 6 h were calculated, with a C(max) value of 31.8 +/- 8.2 microg/ml. An excellent correlation between plasma concentrations and TXA(2) inhibition occurs. 2NTX-99 controls platelet function and vessel wall interaction by multifactorial mechanisms and possesses therapeutic potential.

Nitric oxide donor drugs: an update on pathophysiology and therapeutic potential

The discovery of the multiple physiological and pathophysiological processes in which nitric oxide (NO) is involved has promoted a great number of pharmacological researches to develop new drugs that are capable of influencing NO production directly and/or indirectly for therapeutic purposes (i.e, NO-releasing drugs, NO-inhibiting drugs, and phosphodiesterase V inhibitors). In particular, the so-called NO donor drugs could actually have an important therapeutic effect in the treatment of many diseases such as arteriopathies (atherosclerosis and its sequelae, arterial hypertension and some forms of male sexual impotence), various acute and chronic inflammatory conditions (colitis, rheumatoid arthritis and tissue remodelling), and several degenerative diseases (Alzheimer's disease and cancer). The old organic nitrates show some well-known pitfalls including the induction of tolerance and acute side effects related to abrupt vasodilation such as cephalea and hypotension, which limit their therapeutic indications. A low therapeutic index (i.e., peroxynitrite toxicity) has always characterised the sydnonimines class. A series of interesting new classes of NO donors are under intense pharmacological investigation and scrutiny (S-nitrosothiols, diazeniumdiolates and NO hybrid drugs), each characterised by a particular pharmacokinetic and pharmacodynamic profile. The most important obstacle in the field of NO donor drugs is represented by the difficulty in targeting NO release, and thereby its effects, to a particular tissue.

Reversal to cisplatin sensitivity in recurrent human ovarian cancer cells by NCX-4016, a nitro derivative of aspirin

Ovarian cancer is a gynecological malignancy that is commonly treated by cytoreductive surgery followed by cisplatin treatment. However, the cisplatin treatment, although successful initially, is not effective in the treatment of the recurrent disease that invariably surfaces within a few months of the initial treatment. The refractory behavior is attributed to the increased levels of cellular thiols apparently caused by the cisplatin treatment. This observation prompted us to choose a cytotoxic drug whose activity is potentiated by cellular thiols with enhanced specificity toward the thiol-rich cisplatin-resistant cells. We used NCX-4016 [2-(acetyloxy)benzoic acid 3-(nitrooxymethyl)phenyl ester], a derivative of aspirin containing a nitro group that releases nitric oxide in a sustained fashion for several hours in cells and in vivo, and we studied its cytotoxic efficacy against human ovarian cancer cells (HOCCs). Cisplatin-sensitive and cisplatin-resistant (CR) HOCCs were treated with 100 microM NCX-4016 for 6 h, and/or 0.5 microg/ml cisplatin for 1 h and assayed for clonogenecity. NCX-4016 significantly reduced the surviving fractions of cisplatin-sensitive (63 +/- 6%) and CR (70 +/- 10%) HOCCs. NCX-4016 also caused a 50% reduction in the levels of cellular glutathione in CR HOCCs. Treatment of cells with NCX-4016 followed by cisplatin showed a significantly greater extent of toxicity when compared with treatment of cells with NCX-4016 or cisplatin alone. In conclusion, this study showed that NCX-4016 is a potential inhibitor of the proliferation of CR HOCCs and thus might specifically kill cisplatin-refractory cancer cells in patients with recurrent ovarian cancer.

Recent advances in the understanding of the role of nitric oxide in cardiovascular homeostasis

Nitric oxide synthases (NOS) are the enzymes responsible for nitric oxide (NO) generation. To date, 3 distinct NOS isoforms have been identified: neuronal NOS (NOS1), inducible NOS (NOS2), and endothelial NOS (NOS3). Biochemically, NOS consists of a flavin-containing reductase domain, a heme-containing oxygenase domain, and regulatory sites. NOS catalyse an overall 5-electron oxidation of one Nomega-atom of the guanidino group of L-arginine to form NO and L-citrulline. NO exerts a plethora of biological effects in the cardiovascular system. The basal formation of NO in mitochondria by a mitochondrial NOS seems to be one of the main regulators of cellular respiration, mitochondrial transmembrane potential, and transmembrane proton gradient. This review focuses on recent advances in the understanding of the role of enzyme and enzyme-independent NO formation, regulation of NO bioactivity, new aspects of NO on cardiac function and morphology, and the clinical impact and perspectives of these recent advances in our knowledge on NO-related pathways.

Rationale and study design of the CardioGene Study: genomics of in-stent restenosis

BACKGROUND AND AIMS

in-stent restenosis is a major limitation of stent therapy for atherosclerosis coronary artery disease. The CardioGene Study is an ongoing study of restenosis in bare mental stents (BMS) for the treatment of coronary artery disease. The overall goal is to understand the genetic determinants of the responses to vascular injury that result in the development of restenosis in some patients but not in others. Gene expression profiling at transcriptional and translational levels provides global assessment of gene activity after vascular injury and mechanistic insight. Furthermore, the delineation of genetic biomarkers would be of value in the clinical setting of risk-stratify patients prior to stent therapy. Prospective risk stratification would allow for the rational selection of specialized treatments against the development of in-stent restenosis (ISR), such as drug-eluting stents.

SETTING

Patients are enrolled at two sites in the US with high-volume cardiac catheterization facilities: the William Beaumont Hospital in Royal Oak, MI, USA, and the Mayo Clinic in Rochester, MN, USA.

STUDY DESIGN

Two complementary study designs are used to understand the molecular mechanisms of restenosis and the genetic biomarkers predictive of restenosis. First, 350 patients are enrolled prospectively at the time of stent implantation. Blood is sampled prior to stent placement and afterwards at 2 weeks and 6 months. The clinical outcome of restenosis is determined 6 and 12 months after stent placement. The primary outcome is clinical restenosis at 6 months. The major secondary outcome is clinical restenosis at 12 months. Second, a corollary case-control analysis will be carried out with the enrollment of an additional 250 cases with a history of recurrent restenosis after treatment with BMS. Controls for this analysis are derived from the prospective cohort.

PATIENTS AND METHODS

Consecutive patients presenting to the cardiac catheterization laboratory are screened, informed about the study and enrolled after signing the consent form. Enrollment has been completed for the prospective cohort, and enrollment of the additional group is ongoing. A standardized questionnaire is used to collect clinical data primarily through direct patient interview to assess medical history, medication use, functional status, family history, environmental factors, and social history. Further data are abstracted from the medical charts and catheterization reports. A total of 276 clinical variables are collected per individual at baseline, and 49 variables are collected at each of the 6- and 12-month follow-up visits. A Clinical Events Committee adjudicates clinical outcomes. Blood samples are processed at each clinical enrollment site using standardized operating procedures. From each blood sample, several aliquots are prepared and stored of peripheral blood mononuclear cells, granulocytes, platelets, serum, and plasma. Additionally, a portion of each patient's leukocytes is cryopreserved for future cell-line creation. Samples are frozen and shipped to the National Heart, Lung and Blood Institute (NHLBI). Additional materials generated in the analysis of the samples at the NHLBI are frozen and stored, including isolated genomic DNA, total RNA, reverse transcribed cDNA libraries and labeled RNA hybridization mixtures used in microarray analysis. Per individual in the prospective cohort, high-quality transcript profiles of peripheral blood mononuclear cells at each time of blood sampling are obtained using Affymetrix U133A microarrays (Affymetrix, Santa Clara, CA, USA). Per chip, this yields 495,930 features per individual per time of sampling. This represents expression levels for 22,283 genes per patients oer time of blood sampling, including 14,500 well-characterized human genes. Proteomics of plasma is performed with multidimensional liquid chromatography and tandem mass spectrometry. Protein expression is examined similarly to mRNA expression as a measure of gene expression. Genotyping is performed in two manners. First, those genes showing differential expression at the levels of mRNA and protein are investigated using a candidate gene approach. Specific variants in known gene regulatory regions, such as promoters, are sought initially, as those variants may explain differences in expression level. Second, a genome-wide scan is used to identify genetic loci that are associated with ISR. Those regions identified are further examined for genes that show differential expression in the mRNA microarray profiling or proteomics investigations. These genes are finely investigated for candidate SNPs and other gene variants. Complementary genomic and proteomic approaches are expected to be robust. Integration of data sets is accomplished using a variety of informatics tools, organization of gene expression into functional pathways, and investigation of physical maps of up- and downregulated sets of genes.

CONCLUSIONS

The CardioGene Study is designed to understand ISR. Global gene and protein expression profiling define molecular phenotypes of patients. Well-defined clinical phenotypes will be paired with genomic data to define analyses aimed to achieve several goals. These include determining blood gene and protein expression in patients with ISR, investigating the genetic basis of ISR, developing predictive gene and protein biomarkers, and the identification of new targets for treatment.

S-nitrosoalbumin-mediated relaxation is enhanced by ascorbate and copper: effects in pregnancy and preeclampsia plasma

S-nitrosoalbumin (SNO-Alb) is a major reservoir of releasable nitric oxide (NO) in plasma. In preeclampsia, a pregnancy-specific disorder associated with endothelial dysfunction, we previously found significant elevations in plasma SNO-Alb concentrations and decreased plasma ascorbate (Asc) levels. This increased SNO-Alb may result from low-plasma Asc if Asc, along with transition metals (eg, copper [Cu]) are necessary for release of NO from S-nitrosothiols. We propose that vasodilator effects of SNO-Alb, mediated by release of NO, are fully realized only when Asc/Cu availability is sufficient. Relaxation responses to SNO-Alb or the control reduced human serum albumin (SH-Alb), and responses to pooled plasma from normal or preeclamptic pregnancies were examined in isolated mouse arteries. Arteries preconstricted with phenylephrine were exposed to SNO-Alb or SH-Alb at physiologically relevant concentrations. When free Cu was added in excess (10 mumol/L), NO release was not dependent on Asc. However, when Cu was added at lower (physiological) levels, NO release was dependent on Asc. The addition of Asc and Cu to SNO-Alb stimulated vasodilatory responses in isolated arteries >90%, whereas no change in the SH-Alb (5%) response was observed. Preeclampsia plasma with higher levels of SNO-Alb caused arteries to relax 44.1+/-4.7%, whereas normal pregnancy plasma caused 11.9+/-4.2% relaxation (P=0.007). These data indicate that SNO-Alb alone or in plasma can act as a potent vasodilator, and that sufficient Asc/Cu promotes this action. We suggest that the higher circulating levels of SNO-Alb, in women with preeclampsia, reflect a deficiency in Asc/Cu-mediated release of NO from SNO-Alb.

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.

Nitrosylhemoglobin formation after infusion of NO solutions: ESR studies in pigs

A saturated nitric oxide (NO) solution (1.88 mM) infused i.v. in the anesthetized pig at a dose of 68 nmol/kg/min for 24 min resulted in a time-dependent increase of nitrosylhemoglobin [HbFe(II)NO] as determined by electron spin resonance (ESR), reaching a C(max) of 7.99 +/- 0.42 microM at the end of the infusion, compared to 1.13 +/- 0.42 microM before (p < 0.01). This indicates that NO i.v. is efficiently bioconserved as HbFe(II)NO (approximately 34% of the NO dose) and to a greater extent than by the oxidative pathway (approximately 24% of the NO dose), as determined by measuring plasma nitrites/nitrates (chemiluminescence) and Met-Hb (ESR analysis). When the NO infusion was stopped, HbFe(II)NO declined with a t(1/2) of 15 min, indicating that it is a stable storage form of NO, able to deliver NO distally to the site of administration. No significant differences were observed in systemic and pulmonary vascular resistances during and after NO infusion, but PO(2) showed a significant decrease 15 and 30 min after the infusion. Thus, in normoxic/physiological conditions, HbFe(II)NO does not induce significant NO-dependent vasorelaxation.

Nitric oxide release and distribution following oral and intraperitoneal administration of nitroaspirin (NCX 4016) in the rat

The metabolic fate of nitric oxide (NO) released from nitroaspirin, benzoic acid, 2-(acetyloxy)-3-[(nitrooxy)methyl]phenyl ester (NCX 4016), the lead compound of a new class of NO-releasing non steroidal anti-inflammatory drugs (NO-NSAIDs), has been studied in the rat following p.o. and i.p. administration of 100 mg/kg, by monitoring in plasma the bioactive storage forms of NO (S-nitrosothiols, RS-NO) and its oxidation products (nitrites/nitrates, NOx) by a chemiluminescent assay. In parallel, plasma was analyzed for unchanged drug and metabolites by reverse-phase HPLC. In orally treated rats, no unchanged drug is observed in the 0-24 h interval post-dosing, but only salicylic acid (SA), NOx and RS-NO. The time-course of SA formation parallels that of plasma NOx (plateau after 6 h). Nitrosothiols in plasma are detectable at 1 h, peak at 4 h post-administration, and decline thereafter. The results relative to i.p. administration show a more pronounced and rapid NO delivery (peak of both NOx and RS-NO at 1 h and plateau between 1 and 2 h), still coincident with the peak of SA, and the presence in plasma of NCX 4015 (a metabolite of NCX 4016 which still bears the nitrate function). In myocardial tissue from p.o. treated rats, no drug or metabolites were ever detected, and the NOx levels were always in the range of the controls. Conversely, following i.p. treatment, we observed a rapid compartmentalization within the heart of the unchanged drug, which rapidly disappears in favour of its breakdown products NCX 4015 and SA, with a concomitant rise in myocardial NOx levels up to 2 h. To check the stability of NCX 4016 in the acidic gastric milieu and to explain the different distribution of the drug following p.o. or i.p. administration, the gastric content of the orally-treated animals at different post-dosing times was analysed by HPLC. The unchanged drug was detected up to 8 h post-dosing (levels slowly decreased with time), and the only metabolite to be detected was the O-deacetylated derivative (NCX 4023), which was present in low concentrations up to 4 h post-dosing. This indicates that NCX 4016 does not undergo biotransformation in the upper part of gastrointestinal tract (no direct release of NO in this district) and that the stomach acts as a reservoir for the drug.

Attenuation of chronic neuroinflammation by a nitric oxide-releasing derivative of the antioxidant ferulic acid

Chronic neuroinflammation and oxidative stress contribute to the neurodegeneration associated with Alzheimer's disease and represent targets for therapy. Ferulic acid is a natural compound that expresses antioxidant and anti-inflammatory activities. Nitric oxide is also a key modulator of inflammatory responses. Grafting a nitric oxide-releasing moiety onto anti-inflammatory drugs results in enhanced anti-inflammatory activity. We compared the effectiveness of ferulic acid with a novel nitric oxide-releasing derivative of ferulic acid in an animal model of chronic neuroinflammation that reproduces many interesting features of Alzheimer's disease. Lipopolysaccharide was infused into the 4th ventricle of young rats for 14 days. Various doses of ferulic acid or its nitric oxide-releasing derivative were administered daily. Both drugs produced a dose-dependent reduction in microglia activation within the temporal lobe. However, the nitric oxide-releasing ferulic acid derivative was significantly more potent. If we delayed the initiation of therapy for 14 days, we found no reduction in microglial activation. In addition, both drugs demonstrated antioxidant and hydroxyl radical scavenging abilities in in vitro studies. Overall, our results predict that a treatment using nitric oxide-releasing ferulic acid may attenuate the processes that drive the pathology associated with Alzheimer's disease if the treatment is initiated before the neuroinflammatory processes can develop.

Chemiluminescence and LC–MS/MS analyses for the study of nitric oxide release and distribution following oral administration of nitroaspirin (NCX 4016) in healthy volunteers

The metabolic fate of nitric oxide (NO) released from nitroaspirin, benzoic acid, 2-(acetyloxy)-3-[(nitrooxy)methyl]phenyl ester (NCX 4016), the lead compound of a new class of NO-releasing non-steroidal anti-inflammatory drugs (NO-NSAIDs) has been studied in eight healthy male Caucasian subjects following p.o. administration of 1600 mg (single dose), by monitoring at different times in plasma the bioactive storage forms of NO, S-nitrosothiols (RSNO) and its oxidation products (NOx). Plasma levels of NOx and RSNO and urinary levels of NOx were determined by an ozone-based chemiluminescent assay using a sensitive Nitric Oxide Analyzer (LOQ: 10 pmol NO injected). In parallel plasma samples were analyzed by a newly developed LC-MS/MS method for analysis of NCX 4015, the metabolite bearing the nitrate ester function. Using MS/MS with multiple reaction monitoring (MRM) in negative ion mode for NCX 4015 and the internal standard (NCX 4015- 13C-D2) it was possible to detect with sufficient accuracy and precision the metabolite in plasma with a quantification limit of 78.1 ng ml(-1). Concentration versus time profile of plasma NCX 4015 gave a Cmax value of 161.94 +/- 47.4 ng ml(-1) and a tmax 4.5 +/- 1 h. The results indicate that both NOx and RSNO (these last for the first time determined in vivo in man following oral administration of a NO-donor drug) are effective plasma markers of NO release in vivo, the latter being an earlier indicator of NO distribution (tmax 2.0 +/- 0.6 h versus 5.4 +/- 1.2 h).

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.

Nitric oxide-releasing drugs

Pharmacological compounds that release nitric oxide (NO) have been useful tools for evaluating the broad role of NO in physiology and therapeutics. NO deficiency has been implicated in the genesis and evolution of several disease states. Both medical needs and commercial opportunities have fostered attempts to modulate NO in the human body for therapeutic gain. Strategies for NO modulation encompass antiinflammatory, sexual dysfunction, and cardiovascular indications. Apart from newly developed drugs, several commonly used cardiovascular drugs exert their beneficial action, at least in part, by modulating the NO pathway. This review discusses the fundamental pharmacological properties and mechanisms of action of NO-releasing drugs. Some of these compounds may enter in the clinical arena providing important therapeutic benefits in human diseases.

NO-aspirin: mechanism of action and gastrointestinal safety

Nitric oxide-releasing aspirins are new chemical entities obtained by adding a nitric oxide-releasing moiety to aspirin. NCX-4016 is the prototype of this family of molecules. NCX-4016 consists of the parent molecule (aspirin) linked to a 'spacer' via an ester linkage, which is in turn connected to a nitric oxide-releasing moiety. Both aspirin and nitric oxide moieties of NCX-4016 contribute to its effectiveness, the latter occurring via both cyclic guanosyl monophosphate-dependent and -independent mechanisms. In vitro studies have shown that NCX-4016 inhibits platelet aggregation induced by aspirin-sensitive (arachidonic acid) and aspirin-insensitive (thrombin) agonist. In contrast to aspirin, NCX-4016 exerts a multilevel regulation of inflammatory target, including caspase-1 and NF-kappaB. This broad spectrum of activities translates to an increased potency of this drug in modulating cardiovascular inflammation. Human studies have shown, that while nitric oxide-aspirin maintains its anti-thrombotic activity, it spares the gastrointestinal tract. Indeed, a 7-day course of NCX-4016 results in 90% reduction of gastric damage caused by equimolar doses of aspirin. Further studies are ongoing to define whether this superior anti-inflammatory and anti-thrombotic profile translates in clinical benefits in patients with cardiovascular diseases.