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Nazareno Paolocci

Publications and source records attributed to Nazareno Paolocci.

At least 19 recordsLinked to original sources
PubMed2006

Nitroxyl improves cellular heart function by directly enhancing cardiac sarcoplasmic reticulum Ca2+ cycling.

Heart failure remains a leading cause of morbidity and mortality worldwide. Although depressed pump function is common, development of effective therapies to stimulate contraction has proven difficult. This is thought to be attributable to their frequent reliance on cAMP stimulation to increase activator Ca(2+). A potential alternative is nitroxyl (HNO), the 1-electron reduction product of nitric oxide (NO) that improves contraction and relaxation in normal and failing hearts in vivo. The mechanism for myocyte effects remains unknown. Here, we show that this activity results from a direct interaction of HNO with the sarcoplasmic reticulum Ca(2+) pump and the ryanodine receptor 2, leading to increased Ca(2+) uptake and release from the sarcoplasmic reticulum. HNO increases the open probability of isolated ryanodine-sensitive Ca(2+)-release channels and accelerates Ca(2+) reuptake into isolated sarcoplasmic reticulum by stimulating ATP-dependent Ca(2+) transport. Contraction improves with no net rise in diastolic calcium. These changes are not induced by NO, are fully reversible by addition of reducing agents (redox sensitive), and independent of both cAMP/protein kinase A and cGMP/protein kinase G signaling. Rather, the data support HNO/thiolate interactions that enhance the activity of intracellular Ca(2+) cycling proteins. These findings suggest HNO donors are attractive candidates for the pharmacological treatment of heart failure.

Adenosine Triphosphate↗
PubMed2006

The pharmacology of nitroxyl (HNO) and its therapeutic potential: not just the Janus face of NO.

Nitroxyl (HNO), the 1-electron reduced and protonated congener of nitric oxide (NO), has received recent attention as a potential pharmacological agent for the treatment of heart failure and as a preconditioning agent for the mitigation of ischemia-reperfusion injury. Interest in the pharmacology and biology of HNO has prompted examination, or in some instances reexamination, of many of its chemical properties. Such studies have provided insight into the chemical basis for the biological effects of HNO, although the biochemical mechanisms for many of these effects remain to be established. In this review, a brief description of the biologically relevant chemistry of HNO is given, followed by a more detailed discussion of the pharmacology and potential toxicology of HNO.

Alcoholism↗
PubMed2006

Peroxynitrite and myocardial contractility: in vivo versus in vitro effects.

Generation of peroxynitrite (ONOO-) as a result of altered redox balance has been shown to affect cardiac function; however, inconsistencies in the data exist, particularly for myocardial contractility. The hypothesis that the cardiac impact of ONOO- formation depends on its site of generation, intravascular or intramyocardial, was examined. Cardiac contractility was assessed by pressure-volume analysis to delineate vascular versus cardiac changes on direct infusion of ONOO- into the right atria of conscious dogs both with normal cardiac function and in heart failure. Additionally, ONOO- was administered to isolated murine cardiomyocytes to mimic in situ cardiac generation. When infused in vivo, ONOO- had little impact on inotropy but led to systemic arterial dilation, likely as a result of rapid decomposition to NO2- and NO3-. In contrast, infused ONOO- was long lived enough to abolish beta-adrenergic (dobutamine)-stimulated contractility/relaxation, most likely through catecholamine oxidation to aminochrome. When administered to isolated murine cardiomyocytes, ONOO- induced a rapid reduction in sarcomere shortening and whole cell calcium transients, although neither decomposed ONOO- or NaNO2 had any effect. Thus, systemic generation of ONOO- is unlikely to have primary cardiac effects, but may modulate cardiac contractile reserve, via blunted beta-adrenergic stimulation, and vascular tone, as a result of generation of NO2- and NO3-. However, myocyte generation of ONOO- may impair contractile function by directly altering Ca2+ handling. These data demonstrate that the site of generation within the cardiovascular system largely dictates the ability of ONOO- to directly or indirectly modulate cardiac pump function.

Adrenergic beta-Agonists↗
PubMed2006

Metalloproteinase inhibitor counters high-energy phosphate depletion and AMP deaminase activity enhancing ventricular diastolic compliance in subacute heart failure.

Cardiac matrix metalloproteinases (MMPs) stimulated by the sympathomimetic action of angiotensin II (AII) exacerbate chamber diastolic stiffening in models of subacute heart failure. Here we tested the hypothesis that MMP inhibition prevents such stiffening by favorably modulating high-energy phosphate (HEP) stores more than by effects on matrix remodeling. Dogs were administered AII i.v. for 1 week with tachypacing superimposed in the last two days (AII+P; n = 8). A second group (n = 9) underwent the same AII+P protocol but was preceded by oral treatment with an MMP inhibitor PD166793 [(S)-2-(4-bromo-biphenyl-4-sulfonylamino-3-methyl butyric acid] 1 week before and during the AII+P period. Pressure-volume analysis was performed in conscious animals, and myocardial tissue was subjected to in vitro and in situ zymography, collagen content, and HEP analysis (high-performance liquid chromatography). As reported previously, AII+P activated MMP9 and MMP2 and specifically exacerbated diastolic stiffening (+130% in chamber stiffness). PD166793 cotreatment prevented these changes, although myocardial collagen content, subtype, and cross-linking were unaltered. AII+P also reduced ATP, free energy of ATP hydrolysis (DeltaG(ATP)), and phosphocreatine while increasing free [ADP], AMP catabolites (nucleoside-total purines), and lactate. PD166793 reversed most of these changes, in part due to its inhibition of AMP deaminase. MMP activation may influence cardiac diastolic function by mechanisms beyond modulation of extracellular matrix. Interaction between MMP activation and HEP metabolism may play an important role in mediating diastolic dysfunction. Furthermore, these data highlight a potential major role for increased AMP deaminase activity in diastolic dysfunction.

AMP Deaminase↗
PubMed2005

Comparison of the NO and HNO donating properties of diazeniumdiolates: primary amine adducts release HNO in Vivo.

Diazeniumdiolates, more commonly referred to as NONOates, have been extremely useful in the investigation of the biological effects of nitric oxide (NO) and related nitrogen oxides. The NONOate Angeli's salt (Na(2)N(2)O(3)) releases nitroxyl (HNO) under physiological conditions and exhibits unique cardiovascular features (i.e., positive inotropy/lusitropy) that may have relevance for pharmacological treatment of heart failure. In the search for new, organic-based compounds that release HNO, we examined isopropylamine NONOate (IPA/NO; Na[(CH(3))(2)CHNH(N(O)NO]), which is an adduct of NO and a primary amine. The chemical and pharmacological properties of IPA/NO were compared to those of Angeli's salt and a NO-producing NONOate, DEA/NO (Na[Et(2)NN(O)NO]), which is a secondary amine adduct. Under physiological conditions IPA/NO exhibited all the markers of HNO production (e.g., reductive nitrosylation, thiol reactivity, positive inotropy). These data suggest that primary amine NONOates may be useful as HNO donors in complement to the existing series of secondary amine NONOates, which are well-characterized NO donors.

Animals↗
PubMed2005

Compartmentalized phosphodiesterase-2 activity blunts beta-adrenergic cardiac inotropy via an NO/cGMP-dependent pathway.

beta-Adrenergic signaling via cAMP generation and PKA activation mediates the positive inotropic effect of catecholamines on heart cells. Given the large diversity of protein kinase A targets within cardiac cells, a precisely regulated and confined activity of such signaling pathway is essential for specificity of response. Phosphodiesterases (PDEs) are the only route for degrading cAMP and are thus poised to regulate intracellular cAMP gradients. Their spatial confinement to discrete compartments and functional coupling to individual receptors provides an efficient way to control local [cAMP]i in a stimulus-specific manner. By performing real-time imaging of cyclic nucleotides in living ventriculocytes we identify a prominent role of PDE2 in selectively shaping the cAMP response to catecholamines via a pathway involving beta3-adrenergic receptors, NO generation and cGMP production. In cardiac myocytes, PDE2, being tightly coupled to the pool of adenylyl cyclases activated by beta-adrenergic receptor stimulation, coordinates cGMP and cAMP signaling in a novel feedback control loop of the beta-adrenergic pathway. In this, activation of beta3-adrenergic receptors counteracts cAMP generation obtained via stimulation of beta1/beta2-adrenoceptors. Our study illustrates the key role of compartmentalized PDE2 in the control of catecholamine-generated cAMP and furthers our understanding of localized cAMP signaling.

Adenine↗
PubMed2005

Discriminating formation of HNO from other reactive nitrogen oxide species.

Nitroxyl (HNO) exhibits unique pharmacological properties that often oppose those of nitric oxide (NO), in part due to differences in reactivity toward thiols. Prior investigations suggested that the end products arising from the association of HNO with thiols were condition-dependent, but were inconclusive as to product identity. We therefore used HPLC techniques to examine the chemistry of HNO with glutathione (GSH) in detail. Under biological conditions, exposure to HNO donors converted GSH to both the sulfinamide [GSONH2] and the oxidized thiol (GSSG). Higher thiol concentrations generally favored a higher GSSG ratio, suggesting that the products resulted from competitive consumption of a single intermediate (GSNHOH). Formation of GSONH2 was not observed with other nitrogen oxides (NO, N2O3, NO2, or ONOO(-)),indicating that it is a unique product of the reaction of HNO with thiols. The HPLC assay was able to detect submicromolar concentrations of GSONH2. Detection of GSONH2 was then used as a marker for HNO production from several proposed biological pathways, including thiol-mediated decomposition of S-nitrosothiols and peroxidase-driven oxidation of hydroxylamine (an end product of the reaction between GSH and HNO) and NG-hydroxy-l-arginine (an NO synthase intermediate). These data indicate that free HNO can be biosynthesized and thus may function as an endogenous signaling agent that is regulated by GSH content.

Arginine↗
PubMed2005

Oxidant stress from nitric oxide synthase-3 uncoupling stimulates cardiac pathologic remodeling from chronic pressure load.

Cardiac pressure load stimulates hypertrophy, often leading to chamber dilation and dysfunction. ROS contribute to this process. Here we show that uncoupling of nitric oxide synthase-3 (NOS3) plays a major role in pressure load-induced myocardial ROS and consequent chamber remodeling/hypertrophy. Chronic transverse aortic constriction (TAC; for 3 and 9 weeks) in control mice induced marked cardiac hypertrophy, dilation, and dysfunction. Mice lacking NOS3 displayed modest and concentric hypertrophy to TAC with preserved function. NOS3(-/-) TAC hearts developed less fibrosis, myocyte hypertrophy, and fetal gene re-expression (B-natriuretic peptide and alpha-skeletal actin). ROS, nitrotyrosine, and gelatinase (MMP-2 and MMP-9) zymogen activity markedly increased in control TAC, but not in NOS3(-/-) TAC, hearts. TAC induced NOS3 uncoupling in the heart, reflected by reduced NOS3 dimer and tetrahydrobiopterin (BH4), increased NOS3-dependent generation of ROS, and lowered Ca(2+)-dependent NOS activity. Cotreatment with BH4 prevented NOS3 uncoupling and inhibited ROS, resulting in concentric nondilated hypertrophy. Mice given the antioxidant tetrahydroneopterin as a control did not display changes in TAC response. Thus, pressure overload triggers NOS3 uncoupling as a prominent source of myocardial ROS that contribute to dilatory remodeling and cardiac dysfunction. Reversal of this process by BH4 suggests a potential treatment to ameliorate the pathophysiology of chronic pressure-induced hypertrophy.

Animals↗
PubMed2005

Mechanism of aerobic decomposition of Angeli's salt (sodium trioxodinitrate) at physiological pH.

The recent determination that Angeli's salt may have clinical application as a nitrogen oxide donor for treatment of cardiovascular diseases such as heart failure has led to renewed interest in the mechanism and products of thermal decomposition of Angeli's salt under physiological conditions. In this report, several mechanisms are evaluated experimentally and by quantum mechanical calculations to determine whether HNO is in fact released from Angeli's salt in neutral, aerobic solution. The mechanism of product autoxidation is also considered.

Hydrogen-Ion Concentration↗
PubMed2004

Calcitonin gene-related peptide in vivo positive inotropy is attributable to regional sympatho-stimulation and is blunted in congestive heart failure.

Calcitonin gene-related peptide (CGRP) is a nonadrenergic/noncholinergic (NANC) peptide with vasodilatative/inotropic action that may benefit the failing heart. However, precise mechanisms for its in vivo inotropic action remain unclear. To assess this, dogs with normal or failing (sustained tachypacing) hearts were instrumented for pressure-dimension analysis. In control hearts, CGRP (20 pmol/kg per minute) enhanced cardiac contractility (eg, +33+/-4.2% in end-systolic elastance) and lowered afterload (-14.2+/-2% in systemic resistance, both P<0.001). The inotropic response was markedly blunted by heart failure (+6.5+/-2%; P<0.001 versus control), whereas arterial dilation remained unaltered (-19.3+/-5%). CGRP-positive inotropy was not attributable to reflex activation because similar changes were observed in the presence of a ganglionic blocker. However, it was fully prevented by the beta-receptor antagonist (timolol), identifying a dominant role of sympatho-stimulatory signaling. In control hearts, myocardial interstitial norepinephrine assessed by microdialysis almost doubled in response to CGRP infusion, whereas systemic plasma levels were unchanged. In addition, CGRP receptors were not observed in ventricular myocardium but were prominent in coronary arteries and the stellate ganglia. Ventricular myocytes isolated from normal and failing hearts displayed no inotropic response to CGRP, further supporting indirect sympatho-stimulation as the primary in vivo mechanism. In contrast, the peripheral vasodilatative capacity of CGRP was similar in femoral vascular rings from normal and failing hearts in dogs. Thus, CGRP-mediated positive inotropy is load-independent but indirect and attributable to myocardial sympathetic activation rather than receptor-coupled stimulation in canine hearts. This mechanism is suppressed in heart failure, so that afterload reduction accounts for CGRP-enhanced function in this setting.

Adrenergic beta-Agonists↗
PubMed2004

The chemistry of nitrosative stress induced by nitric oxide and reactive nitrogen oxide species. Putting perspective on stressful biological situations.

This review addresses many of the chemical aspects of nitrosative stress mediated by N2O3. From a cellular perspective, N2O3 and the resulting reactive nitrogen oxide species target specific motifs such as thiols, lysine active sites, and zinc fingers and is dependant upon both the rates of production as well as consumption of NO and must be taken into account in order to access the nitrosative environment. Since production and consumption are integral parts of N2O3 generation, we predict that nitrosative stress occurs under specific conditions, such as chronic inflammation. In contrast to conditions of stress, nitrosative chemistry may also provide cellular protection through the regulation of critical signaling pathways. Therefore, a careful evaluation of the chemistry of nitrosation based upon specific experimental conditions may provide a better understanding of how the subtle balance between oxidative and nitrosative stress may be involved in the etiology and control of various disease processes.

Amines↗
PubMed2004

The chemical dynamics of NO and reactive nitrogen oxides: a practical guide.

Nitric oxide has emerged as one of the most important and diverse players in physiology. This small diatomic radical stunned researchers because of its existence and unique biological properties in human physiology. Over the last two decades it was found that NO often has fickle behavior in pathophysiological mechanisms. Where benefiting the host in one case yet inducing and augmenting injury in another. This has lead to confusion in is NO good or bad? Much of the answers to this dichotomy lies in the chemistry of NO and its related nitrogen oxide species. To help understand the complex chemistry with perspective to biology, a discussion on the chemical biology of NO is useful. The chemical biology defines the relevant chemical reaction of NO and nitrogen monoxide in the context of the biological conditions. We discuss in this article the chemistry of nitrogen oxide with different types of biological motifs. Reaction of NO with metal complexes and radicals require low concentration, where formation of reactive nitrogen oxide species require considerably higher amounts and generally are isolated to specific microenvironments in vivo. Though many reactive nitrogen oxide species are formed from chemical reactions with NO, there are several which appear to not require NO to be present, HNO and NO(2). These two species have unique physiological effects and represent additional complexity to this biological picture. From this discussion, a picture can be formed concerning the possible chemical dynamics, which can be plausible in different biological mechanisms.

Guanylate Cyclase↗
PubMed2003

A biochemical rationale for the discrete behavior of nitroxyl and nitric oxide in the cardiovascular system.

The redox siblings nitroxyl (HNO) and nitric oxide (NO) have often been assumed to undergo casual redox reactions in biological systems. However, several recent studies have demonstrated distinct pharmacological effects for donors of these two species. Here, infusion of the HNO donor Angeli's salt into normal dogs resulted in elevated plasma levels of calcitonin gene-related peptide, whereas neither the NO donor diethylamine/NONOate nor the nitrovasodilator nitroglycerin had an appreciable effect on basal levels. Conversely, plasma cGMP was increased by infusion of diethylamine/NONOate or nitroglycerin but was unaffected by Angeli's salt. These results suggest the existence of two mutually exclusive response pathways that involve stimulated release of discrete signaling agents from HNO and NO. In light of both the observed dichotomy of HNO and NO and the recent determination that, in contrast to the O2/O2- couple, HNO is a weak reductant, the relative reactivity of HNO with common biomolecules was determined. This analysis suggests that under biological conditions, the lifetime of HNO with respect to oxidation to NO, dimerization, or reaction with O2 is much longer than previously assumed. Rather, HNO is predicted to principally undergo addition reactions with thiols and ferric proteins. Calcitonin gene-related peptide release is suggested to occur via altered calcium channel function through binding of HNO to a ferric or thiol site. The orthogonality of HNO and NO may be due to differential reactivity toward metals and thiols and in the cardiovascular system, may ultimately be driven by respective alteration of cAMP and cGMP levels.

Animals↗
PubMed2003

Orthogonal properties of the redox siblings nitroxyl and nitric oxide in the cardiovascular system: a novel redox paradigm.

Endogenous formation of nitric oxide (NO) and related nitrogen oxides in the vascular system is critical to regulation of multiple physiological functions. An imbalance in the production or availability of these species can result in progression of disease. Nitrogen oxide research in the cardiovascular system has primarily focused on the effects of NO and higher oxidation products. However, nitroxyl (HNO), the one-electron-reduction product of NO, has recently been shown to have unique and potentially beneficial pharmacological properties. HNO and NO often induce discrete biological responses, providing an interesting redox system. This article discusses the emerging aspects of HNO chemistry and attempts to provide a framework for the distinct effects of NO and HNO in vivo.

Animals↗
PubMed2003

Positive inotropic and lusitropic effects of HNO/NO- in failing hearts: independence from beta-adrenergic signaling.

Nitroxyl anion (HNONO(-)), the one-electron reduced form of nitric oxide (NO), induces positive cardiac inotropy and selective venodilation in the normal in vivo circulation. Here we tested whether HNO/NO(-) augments systolic and diastolic function of failing hearts, and whether contrary to NO/nitrates such modulation enhances rather than blunts beta-adrenergic stimulation and is accompanied by increased plasma calcitonin gene-related peptide (CGRP). HNO/NO(-) generated by Angelis' salt (AS) was infused (10 microg/kg per min, i.v.) to conscious dogs with cardiac failure induced by chronic tachycardia pacing. AS nearly doubled contractility, enhanced relaxation, and lowered cardiac preload and afterload (all P < 0.001) without altering plasma cGMP. This contrasted to modest systolic depression induced by an NO donor diethylamine(DEA)NO or nitroglycerin (NTG). Cardiotropic changes from AS were similar in failing hearts as in controls despite depressed beta-adrenergic and calcium signaling in the former. Inotropic effects of AS were additive to dobutamine, whereas DEA/NO blunted beta-stimulation and NTG was neutral. Administration of propranolol to nonfailing hearts fully blocked isoproterenol stimulation but had minimal effect on AS inotropy and enhanced lusitropy. Arterial plasma CGRP rose 3-fold with AS but was unaltered by DEA/NO or NTG, supporting a proposed role of this peptide to HNO/NO(-) cardiotropic action. Thus, HNO/NO(-) has positive inotropic and lusitropic action, which unlike NO/nitrates is independent and additive to beta-adrenergic stimulation and stimulates CGRP release. This suggests potential of HNO/NO(-) donors for the treatment of heart failure.

Animals↗
PubMed2003

Comparison of the reactivity of nitric oxide and nitroxyl with heme proteins. A chemical discussion of the differential biological effects of these redox related products of NOS.

Investigations on the biological effects of nitric oxide (NO) derived from nitric oxide synthase (NOS) have led to an explosion in biomedical research over the last decade. The chemistry of this diatomic radical is key to its biological effects. Recently, nitroxyl (HNO/NO(-)) has been proposed to be another important constituent of NO biology. However, these redox siblings often exhibit orthogonal behavior in physiological and cellular responses. We therefore explored the chemistry of NO and HNO with heme proteins in different redox states and observed that HNO favors reaction with ferric heme while NO favors ferrous, consistent with previous reports. Further results show that HNO and NO were equally effective in inhibiting cytochrome P450 activity, which involves ferric and ferrous complexes. The differential chemical behavior of NO and HNO toward heme proteins provides insight into mechanisms of activity that not only helps explain some of the opposing effects observed in NOS-mediated events, but offers a unique control mechanism for the biological action of NO.

Animals↗