Katrina M Miranda
Work Summary
We seek to produce new drugs that harness molecules produced during the natural immune response in order to treat cancer and pain. Such compounds may also provide new treatments for heart failure and alcoholism.
We seek to produce new drugs that harness molecules produced during the natural immune response in order to treat cancer and pain. Such compounds may also provide new treatments for heart failure and alcoholism.
PMID: 12538052;Abstract:
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.
PMID: 12855429;Abstract:
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.
PMID: 12704230;PMCID: PMC154380;Abstract:
Nitroxyl anion (HNO/NO-), 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 β-adrenergic stimulation and is accompanied by increased plasma calcitonin gene-related peptide (CGRP). HNO/NO- generated by Angelis' salt (AS) was infused (10 μg/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 β-adrenergic and calcium signaling in the former. Inotropic effects of AS were additive to dobutamine, whereas DEA/NO blunted β-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 β-adrenergic stimulation and stimulates CGRP release. This suggests potential of HNO/NO- donors for the treatment of heart failure.
PMID: 16529464;PMCID: PMC3164114;Abstract:
Isopropylamine diazeniumdiolate, IPA/NO, the product of the reaction of isopropylamine and nitric oxide, NO, decomposes in a pH-dependent manner to afford nitroxyl, HNO, in the pH range of 13 to above 5, and NO below pH 7. Theoretical studies using B3LYP/6-311+G(d) density functional theory, the polarizable continuum and conductor-like polarizable continuum solvation models, and the high-accuracy CBS-QB3 method on the simplified model compound methylamine diazeniumdiolate predict a mechanism involving HNO production via decomposition of the unstable tautomer MeNN+(O-)NHO -. The production of NO at lower pH is predicted to result from fragmentation of the amide/NO adduct upon protonation of the amine nitrogen. © 2006 American Chemical Society.
PMID: 16101426;Abstract:
Recent comparisons of the pharmacological effects of nitric oxide (NO) and nitroxyl (HNO) donors have demonstrated that the responses to these redox-related nitrogen oxides are nearly universally dissimilar. These analyses have suggested the existence of mutually exclusive signaling pathways as a result of discrete chemical interactions of HNO and NO with a variety of critical biomolecules. Although the mechanisms of action are currently unresolved, the pharmacological responses to HNO are promising for clinical treatment of cardiovascular diseases such as heart failure, myocardial infarction and stroke. This review provides a detailed discussion of the most commonly utilized donors of HNO as well as a guideline for the characterization of novel donors. © 2005 Bentham Science Publishers Ltd.