Isoforms of cytochrome P450 on organic nitrate-derived nitric oxide release in human heart vessels

Metabolomic Signatures of Exposure to Nitrate and Trihalomethanes in Drinking Water and Colorectal Cancer Risk in a Spanish Multicentric Study (MCC-Spain)

We investigated the metabolomic profile associated with exposure to trihalomethanes (THMs) and nitrate in drinking water and with colorectal cancer risk in 296 cases and 295 controls from the Multi Case-Control Spain project. Untargeted metabolomic analysis was conducted in blood samples using ultrahigh-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. A variety of univariate and multivariate association analyses were conducted after data quality control, normalization, and imputation. Linear regression and partial least-squares analyses were conducted for chloroform, brominated THMs, total THMs, and nitrate among controls and for case-control status, together with a N-integration model discriminating colorectal cancer cases from controls through interrogation of correlations between the exposure variables and the metabolomic features. Results revealed a total of 568 metabolomic features associated with at least one water contaminant or colorectal cancer. Annotated metabolites and pathway analysis suggest a number of pathways as potentially involved in the link between exposure to these water contaminants and colorectal cancer, including nicotinamide, cytochrome P-450, and tyrosine metabolism. These findings provide insights into the underlying biological mechanisms and potential biomarkers associated with water contaminant exposure and colorectal cancer risk. Further research in this area is needed to better understand the causal relationship and the public health implications.

The antidepressant drugs vortioxetine and duloxetine differentially and sex-dependently affect animal well-being, cognitive performance, cardiac redox status and histology in a model of osteoarthritis

Osteoarthritis represents a leading cause of disability with limited treatment options. Furthermore, it is frequently accompanied by cardiovascular and cognitive disorders, which can be exacerbated by osteoarthritis or drugs used for its treatment. Here, we examined the behavioral and cardiac effects of the novel antidepressant vortioxetine in an osteoarthritis model, and compared them to duloxetine (an established osteoarthritis treatment). Osteoarthritis was induced in male and female rats with an intraarticular sodium-monoiodoacetate injection. Antidepressants were orally administered for 28 days following induction. During this period the acetone, burrowing and novel-object-recognition tests (NORT) were used to assess the effects of antidepressants on pain hypersensitivity (cold allodynia), animal well-being and cognitive performance, respectively. Following behavioral experiments, heart muscles were collected for assessment of redox status/histology. Antidepressant treatment dose-dependently reduced cold allodynia in rats with osteoarthritis. Duloxetine (but not vortioxetine) depressed burrowing behavior in osteoarthritic rats in a dose-related manner. Osteoarthritis induction reduced cognitive performance in NORT, which was dose-dependently alleviated by vortioxetine (duloxetine improved performance only in female rats). Furthermore, duloxetine (but not vortioxetine) increased oxidative stress parameters in the heart muscles of female (but not male) rats and induced histological changes in cardiomyocytes indicative of oxidative damage. Vortioxetine displayed comparable efficacy to duloxetine in reducing pain hypersensitivity. Furthermore, vortioxetine (unlike duloxetine) dose-dependently improved cognitive performance and had no adverse effect on burrowing behavior (animal surrogate of well-being) and cardiac redox status/histology. Our results indicate that vortioxetine could be a potential osteoarthritis treatment (with better characteristics compared to duloxetine).

Effect of inflammation on cytochrome P450-mediated arachidonic acid metabolism and the consequences on cardiac hypertrophy

The incidence of heart failure (HF) is generally preceded by cardiac hypertrophy (CH), which is the enlargement of cardiac myocytes in response to stress. During CH, the metabolism of arachidonic acid (AA), which is present in the cell membrane phospholipids, is modulated. Metabolism of AA gives rise to hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs) via cytochrome P450 (CYP) ω-hydroxylases and CYP epoxygenases, respectively. A plethora of studies demonstrated the involvement of CYP-mediated AA metabolites in the pathogenesis of CH. Also, inflammation is known to be a characteristic hallmark of CH. In this review, our aim is to highlight the impact of inflammation on CYP-derived AA metabolites and CH. Inflammation is shown to modulate the expression of various CYP ω-hydroxylases and CYP epoxygenases and their respective metabolites in the heart. In general, HETEs such as 20-HETE and mid-chain HETEs are pro-inflammatory, while EETs are characterized by their anti-inflammatory and cardioprotective properties. Several mechanisms are implicated in inflammation-induced CH, including the modulation of NF-κB and MAPK. This review demonstrated the inflammatory modulation of cardiac CYPs and their metabolites in the context of CH and the anti-inflammatory strategies that can be employed in the treatment of CH and HF.

Cardiovascular Drug Interactions With Nirmatrelvir/Ritonavir in Patients With COVID-19: JACC Review Topic of the Week

Nirmatrelvir-ritonavir (NMVr) is used to treat symptomatic, nonhospitalized patients with coronavirus disease-2019 (COVID-19) who are at high risk of progression to severe disease. Patients with cardiovascular risk factors and cardiovascular disease are at a high risk of developing adverse events from COVID-19 and as a result have a higher likelihood of receiving NMVr. Ritonavir, the pharmaceutical enhancer used in NMVr, is an inhibitor of the enzymes of CYP450 pathway, particularly CYP3A4 and to a lesser degree CYP2D6, and affects the P-glycoprotein pump. Co-administration of NMVr with medications commonly used to manage cardiovascular conditions can potentially cause significant drug-drug interactions and may lead to severe adverse effects. It is crucial to be aware of such interactions and take appropriate measures to avoid them. In this review, we discuss potential drug-drug interactions between NMVr and commonly used cardiovascular medications based on their pharmacokinetics and pharmacodynamic properties.

Lopinavir-Ritonavir in SARS-CoV-2 Infection and Drug-Drug Interactions with Cardioactive Medications

Lopinavir-ritonavir combination is being used for the treatment of SARS-CoV-2 infection. A low dose of ritonavir is added to other protease inhibitors to take advantage of potent inhibition of cytochrome (CYP) P450 3A4, thereby significantly increasing the plasma concentration of coadministered lopinavir. Ritonavir also inhibits CYP2D6 and induces CYP2B6, CYP2C19, CYP2C9, and CYP1A2. This potent, time-dependent interference of major hepatic drug-metabolizing enzymes by ritonavir leads to several clinically important drug-drug interactions. A number of patients presenting with acute coronary syndrome and acute heart failure may have SARS-CoV-2 infection simultaneously. Lopinavir-ritonavir is added to their prescription of multiple cardiac medications leading to potential drug-drug interactions. Many cardiology, pulmonology, and intensivist physicians have never been exposed to clinical scenarios requiring co-prescription of cardiac and antiviral therapies. Therefore, it is essential to enumerate these drug-drug interactions, to avoid any serious drug toxicity, to consider alternate and safer drugs, and to ensure better patient care.

Circulating Extracellular Vesicles Containing Xenobiotic Metabolizing CYP Enzymes and Their Potential Roles in Extrahepatic Cells Via Cell-Cell Interactions

The cytochrome P450 (CYP) family of enzymes is known to metabolize the majority of xenobiotics. Hepatocytes, powerhouses of CYP enzymes, are where most drugs are metabolized into non-toxic metabolites. Additional tissues/cells such as gut, kidneys, lungs, blood, and brain cells express selective CYP enzymes. Extrahepatic CYP enzymes, especially in kidneys, also metabolize drugs into excretable forms. However, extrahepatic cells express a much lower level of CYPs than hepatocytes. It is possible that the liver secretes CYP enzymes, which circulate via plasma and are eventually delivered to extrahepatic cells (e.g., brain cells). CYP circulation likely occurs via extracellular vesicles (EVs), which carry important biomolecules for delivery to distant cells. Recent studies have revealed an abundance of several CYPs in plasma EVs and other cell-derived EVs, and have demonstrated the role of CYP-containing EVs in xenobiotic-induced toxicity via cell–cell interactions. Thus, it is important to study the mechanism for packaging CYP into EVs, their circulation via plasma, and their role in extrahepatic cells. Future studies could help to find novel EV biomarkers and help to utilize EVs in novel interventions via CYP-containing EV drug delivery. This review mainly covers the abundance of CYPs in plasma EVs and EVs derived from CYP-expressing cells, as well as the potential role of EV CYPs in cell–cell communication and their application with respect to novel biomarkers and therapeutic interventions.

The Endothelin Receptor Antagonist Macitentan Improves Isosorbide-5-Mononitrate (ISMN) and Isosorbide Dinitrate (ISDN) Induced Endothelial Dysfunction, Oxidative Stress, and Vascular Inflammation

Objective

Organic nitrates such as isosorbide-5-mononitrate (ISMN) and isosorbide dinitrate (ISDN) are used for the treatment of patients with chronic symptomatic stable coronary artery disease and chronic congestive heart failure. Limiting side effects of these nitrovasodilators include nitrate tolerance and/or endothelial dysfunction mediated by oxidative stress. Here, we tested the therapeutic effects of the dual endothelin (ET) receptor antagonist macitentan in ISMN- and ISDN-treated animals.

Methods and Results

Organic nitrates (ISMN, ISDN, and nitroglycerin (GTN)) augmented the oxidative burst and interleukin-6 release in cultured macrophages, whereas macitentan decreased the oxidative burst in isolated human leukocytes. Male C57BL/6j mice were treated with ISMN (75 mg/kg/d) or ISDN (25 mg/kg/d) via s.c. infusion for 7 days and some mice in addition with 30 mg/kg/d of macitentan (gavage, once daily). ISMN and ISDN in vivo therapy caused endothelial dysfunction but no nitrate (or cross-)tolerance to the organic nitrates, respectively. ISMN/ISDN increased blood nitrosative stress, vascular/cardiac oxidative stress via NOX-2 (fluorescence and chemiluminescence methods), ET1 expression, ET receptor signaling, and markers of inflammation (protein and mRNA level). ET receptor signaling blockade by macitentan normalized endothelial function, vascular/cardiac oxidative stress, and inflammatory phenotype in both nitrate therapy groups.

Conclusion

ISMN/ISDN treatment caused activation of the NOX-2/ET receptor signaling axis leading to increased vascular oxidative stress and inflammation as well as endothelial dysfunction. Our study demonstrates for the first time that blockade of ET receptor signaling by the dual endothelin receptor blocker macitentan improves adverse side effects of the organic nitrates ISMN and ISDN.

Aspalathus linearis (Rooibos) - a functional food targeting cardiovascular disease

Increasing consumer bias toward natural products and the considerable wealth of indigenous knowledge has precipitated an upturn in market-driven research into potentially beneficial medicinal plants. In this context, Aspalathus linearis (Rooibos) has been identified to be a promising candidate which may impact cardiovascular disease (CVD), which is one of the most widely studied chronic diseases of modern times. Despite these efforts, ischemic heart disease remains the number one cause of mortality globally. Apart from genetic predisposition and other aetiological mechanisms specific to particular types of CVD, co-factors from interlinked systems contribute significantly to disease development and the severity of its clinical manifestation. The bioactivity of Rooibos is directed towards multiple therapeutic targets. Experimental data to date include antioxidant, anti-inflammatory and anti-diabetic effects, as well as modulatory effects in terms of the immune system, adrenal steroidogenesis and lipid metabolism. This review integrates relevant literature on the therapeutic potential of Rooibos in the context of CVD, which is currently the most common of non-communicable diseases. The therapeutic value of whole plant extracts versus isolated active ingredients are addressed, together with the potential for overdose or herb-drug interaction. The body of research undertaken to date clearly underlines the benefits of Rooibos as both preventative and complementary therapeutic functional food in the context of CVD.

Getting to the Heart of the Matter: A Review of Drug Interactions Between HIV Antiretrovirals and Cardiology Medications

The past 20 years have seen remarkable advances in the treatment of HIV such that most people diagnosed with HIV today can live long, healthy lives by taking antiretrovirals which are usually life-long. Advancements in antiretroviral therapy include the availability of well tolerated, single tablet regimens that are associated with a lower risk of drug-drug interactions. Despite this, many people living with HIV infection might be taking antiretroviral agents that are associated with significant drug-drug interactions. Because HIV infection itself is associated with cardiovascular complications and this population is living longer, concomitant use of antiretrovirals and medications to treat cardiovascular-related diseases is often required. For this reason, it is imperative that clinicians are aware of the potential for clinically significant drug-drug interactions between antiretroviral agents and cardiac medications as well as the useful HIV drug interaction resources that might provide guidance. Available data on significant interactions are summarized and suggested guidance regarding management is discussed.

Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress

Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3',-5'-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed.

Cytochrome P450 and ischemic heart disease: current concepts and future directions

INTRODUCTION

The P450 enzymes (P450s) mediate the biotransformation of several drugs, steroid hormones, eicosanoids, cholesterol, vitamins, fatty acids and bile acids, many of which affect cardiovascular homeostasis. Experimental studies have demonstrated that several P450s modulate important steps in the pathogenesis of ischemic heart disease (IHD).

AREAS COVERED

This article discusses the current knowledge on i) the expression of P450s in cardiovascular and renal tissues; ii) the role of P450s in the pathophysiology of IHD, in particular the modulation of blood pressure and cardiac hypertrophy, coronary arterial tone, ischemia-reperfusion injury and the metabolism of cardiovascular drugs; iii) the available evidence from observational studies on the association between P450 gene polymorphisms and risk of myocardial infarction (MI); and iv) suggestions for further research in this area.

EXPERT OPINION

P450s exert important modulatory effects in experimental models of IHD and MI. However, observational studies have provided conflicting results on the association between P450 genetic polymorphisms and MI. Further, adequately powered studies are required to ascertain the biological and clinical impact of P450s on clinical IHD end-points, that is, fatal and nonfatal MI, revascularization and long-term outcomes post MI. Pharmacogenetic substudies of recently completed cardiovascular clinical trials might represent an alternative strategy in this context.

Role of cytochrome P450-mediated arachidonic acid metabolites in the pathogenesis of cardiac hypertrophy

A plethora of studies have demonstrated the expression of cytochrome P450 (CYP) and soluble epoxide hydrolase (sEH) enzymes in the heart and other cardiovascular tissues. In addition, the expression of these enzymes is altered during several cardiovascular diseases (CVDs), including cardiac hypertrophy (CH). The alteration in CYP and sEH expression results in derailed CYP-mediated arachidonic acid (AA) metabolism. In animal models of CH, it has been reported that there is an increase in 20-hydroxyeicosatetraenoic acid (20-HETE) and a decrease in epoxyeicosatrienoic acids (EETs). Further, inhibiting 20-HETE production by CYP ω-hydroxylase inhibitors and increasing EET stability by sEH inhibitors have been proven to protect against CH as well as other CVDs. Therefore, CYP-mediated AA metabolites 20-HETE and EETs are potential key players in the pathogenesis of CH. Some studies have investigated the molecular mechanisms by which these metabolites mediate their effects on cardiomyocytes and vasculature leading to pathological CH. Activation of several intracellular signaling cascades, such as nuclear factor of activated T cells, nuclear factor kappa B, mitogen-activated protein kinases, Rho-kinases, Gp130/signal transducer and activator of transcription, extracellular matrix degradation, apoptotic cascades, inflammatory cytokines, and oxidative stress, has been linked to the pathogenesis of CH. In this review, we discuss how 20-HETE and EETs can affect these signaling pathways to result in, or protect from, CH, respectively. However, further understanding of these metabolites and their effects on intracellular cascades will be required to assess their potential translation to therapeutic approaches for the prevention and/or treatment of CH and heart failure.

Organic nitrate metabolism and action: toward a unifying hypothesis and the future-a dedication to Professor Leslie Z. Benet

This review summarizes the major advances that had been reported since the outstanding contributions that Professor Benet and his group had made in the 1980s and 1990s concerning the metabolism and pharmacologic action of organic nitrates (ORNs). Several pivotal studies have now enhanced our understanding of the metabolism and the bioactivation of ORNs, resulting in the identification of a host of cysteine-containing enzymes that can carry out this function. Three isoforms of aldehyde dehydrogenase, all of which with active catalytic cysteine sites, are now known to metabolize, somewhat selectively, various members of the ORN family. The existence of a long-proposed but unstable thionitrate intermediate from ORN metabolism has now been experimentally observed. ORN-induced thiol oxidation in multiple proteins, called the "thionitrate oxidation hypothesis," can be used not only to explain the phenomenon of nitrate tolerance, but also the various consequences of chronic nitrate therapy, namely, rebound vasoconstriction, and increased morbidity and mortality. Thus, a unifying biochemical hypothesis can account for the myriad of pharmacological events resulting from nitrate therapy. Optimization of the future uses of ORN in cardiology and other diseases could benefit from further elaboration of this unifying hypothesis.

[Which future in cardiovascular therapy for nitric oxide and its derivatives?]

Nitric oxide (NO) is involved in the regulation of several physiological processes such as vascular homeostasis. Exogenous NO supply offers major therapeutic interest, especially in the treatment of coronary artery disease, ischemic syndromes and other cardiovascular pathologies. Nevertheless, the administration of NO itself is limited by its short half-life. NO prodrugs have been marketed for decades, e.g. organic nitrates for angina pectoris. These prodrugs display undeniable advantages such as angina crisis relief and preconditioning effect. Nevertheless, they suffer from several drawbacks: toxicity, tolerance, endothelial dysfunction exacerbation. These negative effects are related to massive production of reactive species derived from oxygen or nitrogen, which trigger oxidative and nitrosative stress. New NO donors are under development to overcome those disadvantages, among which the S-nitrosothiols family seems especially promising.

Prodrugs of nonsteroidal anti-inflammatory drugs (NSAIDs), more than meets the eye: a critical review

The design and the synthesis of prodrugs for nonsteroidal anti-inflammatory drugs (NSAIDs) have been given much attention by medicinal chemists, especially in the last decade. As a therapeutic group, NSAIDs are among the most widely used prescribed and over the counter (OTC) medications. The rich literature about potential NSAID prodrugs clearly shows a shift from alkyl, aryalkyl or aryl esters with the sole role of masking the carboxylic acid group, to more elaborate conjugates that contain carefully chosen groups to serve specific purposes, such as enhancement of water solubility and dissolution, nitric oxide release, hydrogen sulfide release, antioxidant activity, anticholinergic and acetylcholinesterase inhibitory (AChEI) activity and site-specific targeting and delivery. This review will focus on NSAID prodrugs that have been designed or were, later, found to possess intrinsic pharmacological activity as an intact chemical entity. Such intrinsic activity might augment the anti-inflammatory activity of the NSAID, reduce its side effects or transform the potential therapeutic use from classical anti-inflammatory action to something else. Reports discussed in this review will be those of NO-NSAIDs, anticholinergic and AChEI-NSAIDs, Phospho-NSAIDs and some miscellaneous agents. In most cases, this review will cover literature dealing with these NSAID prodrugs from the year 2006 and later. Older literature will be used when necessary, e.g., to explain the chemical and biological mechanisms of action.

Determination of the dominant arachidonic acid cytochrome p450 monooxygenases in rat heart, lung, kidney, and liver: protein expression and metabolite kinetics

Cytochrome P450 (P450)-derived arachidonic acid (AA) metabolites serve pivotal physiological roles. Therefore, it is important to determine the dominant P450 AA monooxygenases in different organs. We investigated the P450 AA monooxygenases protein expression as well as regioselectivity, immunoinhibition, and kinetic profile of AA epoxygenation and hydroxylation in rat heart, lung, kidney, and liver. Thereafter, the predominant P450 epoxygenases and P450 hydroxylases in these organs were characterized. Microsomes from heart, lung, kidney, and liver were incubated with AA. The protein expression of CYP2B1/2, CYP2C11, CYP2C23, CYP2J3, CYP4A1/2/3, and CYP4Fs in the heart, lung, kidney, and liver were determined by Western blot analysis. The levels of AA metabolites were determined by liquid chromatography-electrospray ionization mass spectroscopy. This was followed by determination of regioselectivity, immunoinhibition effect, and the kinetic profile of AA metabolism. AA was metabolized to epoxyeicosatrienoic acids and 19- and 20-hydroxyeicosatetraenoic acid in the heart, lung, kidney, and liver but with varying metabolic activities and regioselectivity. Anti-P450 antibodies were found to differentially inhibit AA epoxygenation and hydroxylation in these organs. Our data suggest that the predominant epoxygenases are CYP2C11, CYP2B1, CYP2C23, and CYP2C11/CYP2C23 for the heart, lung, kidney, and liver, respectively. On the other hand, CYP4A1 is the major ω-hydroxylase in the heart and kidney; whereas CYP4A2 and/or CYP4F1/4 are probably the major hydroxlases in the lung and liver. These results provide important insights into the activities of P450 epoxygenases and P450 hydroxylases-mediated AA metabolism in different organs and their associated P450 protein levels.

Expression and inducibility of CYP1A1, 1A2, 1B1 by β-naphthoflavone and CYP2B22, CYP3As by rifampicin in heart regions and coronary arteries of pig

In this study, the constitutive and inducible expression of the CYP genes (1A1, 1A2, 1B1, 2B22, 3A22, 3A29 and 3A46), related transcriptional factors (AhR, CAR, PXR, and Nrf2) and the antioxidant enzymes SOD, catalase, GSSH-reductase and GSH-peroxidase were investigated in the liver, heart regions and coronary arteries of control pigs and pigs treated with β-naphthoflavone (βNF) or with rifampicin (RIF). Real-time PCR experiments and enzymatic or immunoblot assays showed that CYP1A1 was predominantly enhanced by βNF in a similar manner in all the heart regions, whereas antioxidant enzyme activity was not affected. The rifampicin treatment resulted in an induction of CYP2B22 and CYP3As, at the transcriptional, activity and protein level in liver but not in heart nor in the coronary arteries, despite the expression of CAR and PXR in the cardiac tissues. These results obtained in vivo suggest that pig cardiac tissues may represent a useful model for humans.

Differential effects of organic nitrates on arterial diameter among healthy Japanese participants with different mitochondrial aldehyde dehydrogenase 2 genotypes: randomised crossover trial

OBJECTIVES

To determine whether polymorphisms at codon 487 (*1, GAA=Glu; *2, AAA=Lys) of mitochondrial aldehyde dehydrogenase 2 (ALDH2) influence nitroglycerine (glyceryl trinitrate (GTN))-induced vasodilation, and whether GTN or isosorbide dinitrate (ISDN) is a more effective antianginal agent in each ALDH2 genotype.

DESIGN

A randomised, open-label, crossover trial with 117 healthy Japanese (20-39 years) whose genotypes were determined (*1/*1, n=47; *1/*2, n=48; *2/*2, n=22) was performed at Kyushu University Hospital, Fukuoka, Japan. Participants were randomly assigned to treatment: sublingual spray of GTN (0.3 mg) or ISDN (1.25 mg). After ≥ 1 week, measurements were repeated using the other drug. The main outcome measures were the maximal rate of increase in the brachial artery diameter determined by ultrasonography, the time required to attain maximal dilation (T(max)) and the time required to attain 90% maximal dilation (T(0.9)).

RESULTS

The maximal artery diameter increase in response to GTN or ISDN did not differ among genotypes. However, GTN T(max) was significantly longer for *2/*2 (299.7 s, 269.0-330.4) than *1/*1 (254.7 s, 238.6-273.4; p=0.0190). GTN T(0.9) was significantly longer in the *1/*2 (206.1 s, 191.7-219.3) and *2/*2 (231.4 s, 211.8-251.0) genotypes than *1/*1 (174.9 s, 161.5-188.3; p=0.0068, p<0.0001, respectively). In contrast, the time-course of ISDN-induced vasodilation did not differ among genotypes. GTN T(max) and T(0.9) among *1 allele carriers (*1/*1 and *1/*2) were significantly shorter than those of ISDN, whereas the time course of GTN and ISDN vasodilation did not differ among participants carrying *2/*2.

CONCLUSIONS

The amplitude of GTN-induced vasodilation was not influenced by the ALDH2 genotype, but the response was significantly delayed in *2 allele carriers, especially *2/*2. GTN dilated the artery more quickly than ISDN in *1/*1 and *1/*2, but not in *2/*2. Trial registration number UMIN000001492 (UMIN-CTR database).

Coadministration of carvedilol attenuates nitrate tolerance by preventing cytochrome p450 depletion

BACKGROUND

Long-term administration of nitroglycerin (NTG) causes tolerance secondary to increased vascular formation of reactive oxygen species. Carvedilol, which has potent antioxidant activity in addition to functioning as an adrenergic blocker, prevents nitrate tolerance by a still to be elucidated mechanism. The present study investigated how carvedilol attenuates nitrate tolerance, particularly with reference to cytochrome P450 (CYP), an enzyme involved in the development of tolerance.

METHODS AND RESULTS

Male Wistar rats were subjected to 48-h continuous infusion of NTG alone (0.5 mg/h) or NTG with concomitant carvedilol (20 or 100 microg/h), and then compared with vehicle-treated rats (4 groups; n=6 in each group). Following the continuous administration, nitrate tolerance, assessed by bolus NTG injections, was hemodynamically prevented by coadministration of carvedilol. Levels of CYP1A1/1A2, superoxide production, and phosphorylated vasodilator-stimulated phosphoprotein at serine 239 (P-VASP) were examined in the aortic wall and heart tissue. When NTG alone was continuously administered, vascular superoxide was produced, there was a decrease in the cardiac CYP1A1/1A2 level, and depletion of P-VASP. However, each of these changes induced by continuous NTG administration was significantly attenuated by coadministration of carvedilol and the extent of attenuation was more pronounced at the higher dose (100 microg/h).

CONCLUSIONS

Coadministration of carvedilol attenuates nitrate tolerance through maintenance of NO/cGMP pathway activity by preventing free radical generation and CYP depletion.

Effect of cytochrome P450 polymorphism on arachidonic acid metabolism and their impact on cardiovascular diseases

Cardiovascular diseases (CVDs) remain the leading cause of death in the developed countries. Taking into account the mounting evidence about the role of cytochrome P450 (CYP) enzymes in cardiovascular physiology, CYP polymorphisms can be considered one of the major determinants of individual susceptibility to CVDs. One of the important physiological roles of CYP enzymes is the metabolism of arachidonic acid. CYP epoxygenases such as CYP1A2, CYP2C, and CYP2J2 metabolize arachidonic acid to epoxyeicosatrienoic acids (EETs) which generally possess vasodilating, anti-inflammatory, anti-apoptotic, anti-thrombotic, natriuretic, and cardioprotective effects. Therefore, genetic polymorphisms causing lower activity of these enzymes are generally associated with an increased risk of several CVDs such as hypertension and coronary artery disease. EETs are further metabolized by soluble epoxide hydrolase (sEH) to the less biologically active dihydroxyeicosatrienoic acids (DHETs). Therefore, sEH polymorphism has also been shown to affect arachidonic acid metabolism and to be associated with CVDs. On the other hand, CYP omega-hydroxylases such as CYP4A11 and CYP4F2 metabolize arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE) which has both vasoconstricting and natriuretic effects. Genetic polymorphisms causing lower activity of these enzymes are generally associated with higher risk of hypertension. Nevertheless, some studies have denied the association between polymorphisms in the arachidonic acid pathway and CVDs. Therefore, more research is needed to confirm this association and to better understand the pathophysiologic mechanisms behind it.

Organic nitrates and nitrate tolerance--state of the art and future developments

The hemodynamic and antiischemic effects of nitroglycerin (GTN) are lost upon chronic administration due to the rapid development of nitrate tolerance. The mechanism of this phenomenon has puzzled several generations of scientists, but recent findings have led to novel hypotheses. The formation of reactive oxygen and nitrogen species in the mitochondria and the subsequent inhibition of the nitrate-bioactivating enzyme mitochondrial aldehyde dehydrogenase (ALDH-2) appear to play a central role, at least for GTN, that is, bioactivated by ALDH-2. Importantly, these findings provide the opportunity to reconcile the two "traditional" hypotheses of nitrate tolerance, that is, the one postulating a decreased bioactivation and the concurrent one suggesting a role of oxidative stress. Furthermore, recent animal and human experimental studies suggest that the organic nitrates are not a homogeneous group but demonstrate a broad diversity with regard to induction of vascular dysfunction, oxidative stress, and other side effects. In the past, attempts to avoid nitrate-induced side effects have focused on administration schedules that would allow a "nitrate-free interval"; in the future, the role of co-therapies with antioxidant compounds and of activation of endogeneous protective pathways such as the heme oxygenase 1 (HO-1) will need to be explored. However, the development of new nitrates, for example, tolerance-free aminoalkyl nitrates or combination of nitrate groups with established cardiovascular drugs like ACE inhibitors or AT(1)-receptor blockers (hybrid molecules) may be of great clinical interest.

Cytochrome P450 enzymes and the heart

The cytochrome P450 monooxygenase system (CYP) is a multigene superfamily of heme-thiolate enzymes, which are important in the metabolism of foreign and endogenous compounds. Genetic variations, drug interactions, or pathophysiological factors can lead to reduced, absent, or increased enzymatic activity. This altered CYP activity greatly influences an individual's response to therapeutic treatment. What is not known is the impact of these changes on the many functional roles of CYP in physiological and pathophysiological processes of the heart. Many extrahepatic tissues, like heart, contain active P450 enzymes but lack information regarding their role in cellular injury or homeostasis. Much of our current knowledge about cardiac CYP has been limited to studies investigating the role of fatty acid metabolites in heart. Traditional risk factors including diabetes, smoking, and hypertension have well established links to cardiovascular disease. And new evidence strongly suggests exposure to chemicals and other environmental agents has a profound impact on the cardiovascular system. These risk factors can independently affect the expression and activity of CYP enzymes. Therefore, altered CYP activity is important from a detoxification as well as a bioactivation perspective. Considering CYP, interactions are greatly dependent on inherited differences or acquired changes in enzyme activity further research into their potential impact on pathogenesis, risk assessment, and therapy of heart disease is warranted. This review explores the expression of CYP isoforms, their functional roles, and the effects of genetic variation in the heart.

Pharmacological induction of vascular extracellular superoxide dismutase expression in vivo

Pentaerythritol tetranitrate (PETN) treatment reduces progression of atherosclerosis and endothelial dysfunction and decreases oxidation of low-density lipoprotein (LDL) in rabbits. These effects are associated with decreased vascular superoxide production, but the underlying molecular mechanisms remain unknown. Previous studies demonstrated that endogenous nitric oxide could regulate the expression of extracellular superoxide dismutase (ecSOD) in conductance vessels in vivo. We investigated the effect of PETN and overexpression of endothelial nitric oxide synthase (eNOS⁺⁺) on the expression and activity of ecSOD. C57BL/6 mice were randomized to receive placebo or increasing doses of PETN for 4 weeks and eNOS⁺⁺ mice with a several fold higher endothelial-specific eNOS expression were generated. The expression of ecSOD was determined in the lung and aortic tissue by real-time PCR and Western blot. The ecSOD activity was measured using inhibition of cytochrome C reduction. There was no effect of PETN treatment or eNOS overexpression on ecSOD mRNA in the lung tissue, whereas ecSOD protein expression increased from 2.5-fold to 3.6-fold (P < 0.05) by 6 mg PETN/kg body weight (BW)/day and 60 mg PETN/kg BW/day, respectively. A similar increase was found in aortic homogenates. eNOS⁺⁺ lung cytosols showed an increase of ecSOD protein level of 142 ± 10.5% as compared with transgene-negative littermates (P < 0.05), which was abolished by N^ω-nitro-L-arginine treatment. In each animal group, the increase of ecSOD expression was paralleled by an increase of ecSOD activity. Increased expression and activity of microvascular ecSOD are likely induced by increased bioavailability of vascular nitric oxide. Up-regulation of vascular ecSOD may contribute to the reported antioxidative and anti-atherosclerotic effects of PETN.

Effect of oral organic nitrates on expression and activity of vascular soluble guanylyl cyclase

BACKGROUND AND PURPOSE

The regulation of vascular soluble guanylyl cyclase (sGC) expression by nitric oxide (NO) is still under discussion. In vitro, NO has been shown to downregulate the expression of sGC but it is unclear if this mechanism is operative in vivo and occurs during nitrate treatment.

EXPERIMENTAL APPROACH

We investigated whether high dose isosorbide mononitrate (ISMN) or pentaerythrityl tetranitrate (PETN) treatment changes vascular sGC expression and activity in vivo. New Zealand White rabbits received a standard diet, 2 or 200 mg ISMN kg(-1) d(-1) for 16 weeks, and C57BL/6 mice received a standard diet, 6, 60 or 300 mg PETN kg(-1) d(-1) for four weeks. Absorption was checked by measuring the plasma levels of the drug/metabolite.

KEY RESULTS

Western blots of rabbit aortic rings showed similar protein levels of sGC alpha1- (P=0.2790) and beta1-subunits (P=0.6900) in all groups. Likewise, ANOVA showed that there was no difference in the expression of sGC in lungs of PETN-treated mice (P=0.0961 for alpha1 and P=0.3709 for beta1). The activities of isolated sGC in response to SNAP (1 microM-1 mM) were identical in aortae of ISMN-treated rabbits (P=0.0775) and lungs of PETN-treated mice (P=0.6348). The aortic relaxation response to SNAP slightly decreased at high ISMN but not at high PETN.

CONCLUSIONS AND IMPLICATIONS

These data refute the hypothesis that therapeutic treatment with long acting NO donors has a significant impact on the regulation of vascular sGC expression and activity in vivo.

Nitrite anion: the key intermediate in alkyl nitrates degradative mechanism

Alkyl nitrates are metabolized in vitro to yield nitric oxide, and thiol groups have long been considered necessary cofactors. Here, we report evidence that no reaction between thiols and alkyl nitrates takes place in vitro, but stronger reducing agents, such as iron(II) derivatives, are necessary; alkoxy radicals and nitrite anions are the reaction intermediates. The latter, in slightly acidic conditions, can nitrosate thiols to the corresponding S-nitrosothiols, the real NO releasers.

Improving the drug selection and development process for combination devices

Combination devices are at the interface of both pharmaceutical and medical device research. While there have been several notable successes in bringing combination devices to market there are drug selection criteria that both the pharmaceutical and medical device companies need to consider. A successful combination device creates a product that has efficacy greater than the sum of the parts. However, failure to address some aspects of the drug or biologic properties in enough detail could result in a suboptimal product, creating a challenging legacy for future iterations. This review addresses the many dimensions including opportunities and challenges of combination device development from both the device and pharmaceutical perspectives.

Number of nitrate groups determines reactivity and potency of organic nitrates: a proof of concept study in ALDH-2-/- mice

BACKGROUND AND PURPOSE

Mitochondrial aldehyde dehydrogenase (ALDH-2) has been shown to provide a pathway for bioactivation of organic nitrates and to be prone to desensitization in response to highly potent, but not to less potent, nitrates. We therefore sought to support the hypothesis that bioactivation by ALDH-2 critically depends on the number of nitrate groups within the nitrovasodilator.

EXPERIMENTAL APPROACH

Nitrates with one (PEMN), two (PEDN; GDN), three (PETriN; glyceryl trinitrate, GTN) and four (pentaerithrityl tetranitrate, PETN) nitrate groups were investigated. Vasodilatory potency was measured in isometric tension studies using isolated aortic segments of wild type (WT) and ALDH-2-/- mice. Activity of the cGMP-dependent kinase-I (reflected by levels of phosphorylated VAsodilator Stimulated Phosphoprotein, P-VASP) was quantified by Western blot analysis, mitochondrial dehydrogenase activity by HPLC. Following incubation of isolated mitochondria with PETN, PETriN-chromophore and PEDN, metabolites were quantified using chemiluminescence nitrogen detection and mass spectrometry.

KEY RESULTS

Compared to WT, vasorelaxation in response to PETN, PETriN and GTN was attenuated about 10fold in ALDH-2-/- mice, identical to WT vessels preincubated with inhibitors of ALDH-2. Reduced vasodilator potency correlated with reduced P-VASP formation and diminished biotransformation of the tetranitrate- and trinitrate-compounds. None of these findings were observed for PEDN, GDN and PEMN.

CONCLUSIONS AND IMPLICATIONS

Our results support the crucial role of ALDH-2 in bioactivating highly reactive nitrates like GTN, PETN and PETriN. ALDH-2-mediated relaxation by organic nitrates therefore depends mainly on the number of nitrate groups. Less potent nitrates like PEDN, GDN and PEMN are apparently biotransformed by other pathways.

Cytochrome P450 is Responsible for Nitric Oxide Generation from NO-Aspirin and Other Organic Nitrates

Nitric oxide (NO) biotransformation from NO-aspirin (NCX-4016) is not clearly understood. We have previously reported that cytochrome P450 (P450) plays important role in NO generation from other organic nitrates such as nitroglycerin (NTG) and isosorbide dinitrate (ISDN). The present study was designed to elucidate the role of human cytochrome P450 isoforms in NO formation from NCX-4016, using lymphoblast microsomes transfected with cDNA of human P450 or yeast-expressed, purified P450 isoforms. CYP1A2 and CYP2J2, among other isoforms, were strongly related to NO production from NCX-4016. In fact, these isoforms were detected in human coronary endothelial cells. These results suggest that NADPH-cytochrome P450 reductase and the P450 system participate in NO formation from NCX-4016, as well as other organic nitrates.

Nicorandil elevates tissue cGMP levels in a nitric-oxide-independent manner

The K(+) channel opener nicorandil is a hybrid compound that contains nitrate in its structure. It has been reported that nicorandil can relax vascular tissue in vitro via a mechanism that involves activation of K(ATP) channels and stimulation of soluble guanylyl cyclase. However, it is not known whether the increase of cGMP levels occurs through an elevation of nitric oxide (NO). The aim of the present study was to determine whether NO release was a direct effect of nicorandil. We reported here that nicorandil did not generate NO using ozone chemiluminescence detection methods in human or rat liver microsomes (P450-rich fractions) with addition of NADPH. However, nicorandil elevated cGMP levels in rat liver, aorta, and human coronary smooth muscle cells in vitro. The elevation was not inhibited by the NO trapping agent carboxy-2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (carboxy-PTIO). These results suggest that nicorandil elevates cGMP without NO generation.

Cytochrome P450 enzymes: Central players in cardiovascular health and disease

Cardiovascular disease (CVD) is a human health crisis that remains the leading cause of death worldwide. The cytochrome P450 (CYP) class of enzymes are key metabolizers of both xenobiotics and endobiotics. Many CYP enzyme families have been identified in the heart, endothelium and smooth muscle of blood vessels. Furthermore, mounting evidence points to the role of endogenous CYP metabolites, such as epoxyeicosatrienoic acids (EETs), hydroxyeicosatetraenoic acids (HETEs), prostacyclin (PGI(2)), aldosterone, and sex hormones, in the maintenance of cardiovascular health. Emerging science and the development of genetic screening have provided us with information on the differences in CYP expression among populations and groups of individuals. With this information, a link between CYP expression and activity and CVD, such as hypertension, coronary artery disease (CAD), myocardial infarction, heart failure, stroke, and cardiomyopathy and arrhythmias, has been established. In fact many currently used therapeutic modalities in CVD owe their therapeutic efficacy to their effect on CYP metabolites. Thus, the evidence for the involvement of CYP in CVD is numerous. Concentrating on treatment modalities that target the CYP pathway makes ethical sense for the affected individuals and decreases the socioeconomic burden of this disease. However, more research is needed to allow the integration of this information into a clinical setting.

Vitamin E deficiency accelerates nitrate tolerance via a decrease in cardiac P450 expression and increased oxidative stress

Organic nitrates, such as nitroglycerin (NTG), have been used to relieve the symptoms of angina pectoris. However, their biochemical mechanisms of action, particularly in relation to the development of tolerance, are incompletely defined. It has been reported that supplemental antioxidants such as vitamin E attenuate the development of nitrate tolerance. Therefore, we examined the role of vitamin E in the regulation of nitrate tolerance. Continuous NTG infusion induced nitrate tolerance in rats after 48 h, and vitamin E concentrations decreased in a time-dependent manner in tissues and plasma. Vitamin E supplementation (0.5 g/kg diet) maintained higher concentrations of vitamin E during NTG infusion. The onset and extent of the tolerance, estimated by the decrease in blood pressure following NTG bolus injection during the infusion of NTG, were accentuated in the vitamin E-deficient group. Vitamin E supplementation inhibited nitrate tolerance 48 h after NTG infusion. Cardiac P450 expression (CYP1A2) assessed by immunoblotting, markedly decreased 48 h after NTG administration in control rats. The supplementation of vitamin E significantly attenuated the decrease in P450. Treatment of NTG enhanced vascular superoxide production (L-012 chemiluminescence, DHE fluorescence). The peak of lipid peroxidation and free radical generation in the heart was reached before tolerance developed. In contrast, vitamin E-deficient hearts had lower P450 expression and higher free radical generation than control hearts. To evaluate other vitamin E-inhibitable mechanisms of nitrate tolerance, we studied the NO-cGMP pathway. NTG markedly reduced the vasodilator-stimulated phosphoprotein (VASP) serine 239 phosphorylation (specific substrate of cGMP-activated protein kinase I; cGK-I) in tolerant hearts. Vitamin E inhibited the depletion of pVASP. In conclusion, because continuous NTG infusion causes vitamin E depletion as well as nitrate tolerance, vitamin E deficiency may further accelerate nitrate tolerance via an increase in oxidative stress, the reduced bioconversion because of decreased P450 expression, and impairment of the NO/cGMP pathway in tolerant heart tissues.

ESR techniques for the detection of nitric oxide in vivo and in tissues

Plasma levels of nitrite/nitrate may not accurately reflect endothelial nitric oxide synthase (eNOS) function because of interference by dietary nitrates. Nitrosyl hemoglobin (HbNO), a metabolic product of nitric oxide (NO*), may better correlate with bioavailable NO*, but it may depend on the activity of different NOS isoforms and may be affected by dietary nitrite/nitrate. This work examined the correlation between vascular endothelial NO* release and blood levels of HbNO. We measured HbNO in mouse blood using electron spin resonance (ESR) spectrometry, and we quantified vascular production of NO* using colloid Fe(DETC)2 and ESR. C57Blk/6 mice who were fed a high-nitrate diet had levels of plasma HbNO increased 10-fold, whereas those fed a low-nitrate diet had decreased HbNO levels from 0.58 +/- 0.02 to 0.48 +/- 0.01 microM. Therefore, a low-nitrate diet is essential when using HbNO as a marker of eNOS activity. Treatment with L-NAME and the eNOS-specific inhibitor L-NIO halved HbNO formation, which reflects the complete inhibition of NO* release by aorta endothelium. Treatment of mice with the selective inducible NOS (iNOS) inhibitor, 1400W, or the selective neuronal NOS (nNOS) inhibitor N-AANG did not alter either blood HbNO levels or vascular NO*. The relationship between HbNO and NO* production by the endothelium (0.23 microM HbNO to 5.27 microM/h of NO*/mg of dry weight aorta) was found to be identical for both C57Blk/6 mice and mice with vascular smooth muscle-targeted expression of p22phox associated with strong increase in eNOS activity. These results support the important role of eNOS in the formation of circulating HbNO, whereas iNOS and nNOS do not contribute to HbNO formation under normal conditions. These data suggest that HbNO can be used as a noninvasive marker of endothelial NO* production in vivo.

Explaining the phenomenon of nitrate tolerance

During the last century, nitroglycerin has been the most commonly used antiischemic and antianginal agent. Unfortunately, after continuous application, its therapeutic efficacy rapidly vanishes. Neurohormonal activation of vasoconstrictor signals and intravascular volume expansion constitute early counter-regulatory responses (pseudotolerance), whereas long-term treatment induces intrinsic vascular changes, eg, a loss of nitrovasodilator-responsiveness (vascular tolerance). This is caused by increased vascular superoxide production and a supersensitivity to vasoconstrictors secondary to a tonic activation of protein kinase C. NADPH oxidase(s) and uncoupled endothelial nitric oxide synthase have been proposed as superoxide sources. Superoxide and vascular NO rapidly form peroxynitrite, which aggravates tolerance by promoting NO synthase uncoupling and inhibition of soluble guanylyl cyclase and prostacyclin synthase. This oxidative stress concept may explain why radical scavengers and substances, which reduce oxidative stress indirectly, are able to relieve tolerance and endothelial dysfunction. Recent work has defined a new tolerance mechanism, ie, an inhibition of mitochondrial aldehyde dehydrogenase, the enzyme that accomplishes bioactivation of nitroglycerin, and has identified mitochondria as an additional source of reactive oxygen species. Nitroglycerin-induced reactive oxygen species inhibit the bioactivation of nitroglycerin by thiol oxidation of aldehyde dehydrogenase. Both mechanisms, increased oxidative stress and impaired bioactivation of nitroglycerin, can be joined to provide a new concept for nitroglycerin tolerance and cross-tolerance. The consequences of these processes for the nitroglycerin downstream targets soluble guanylyl cyclase, cGMP-dependent protein kinase, cGMP-degrading phosphodiesterases, and toxic side effects contributing to endothelial dysfunction, such as inhibition of prostacyclin synthase, are discussed in this review.

Direct gas measurements indicate that the novel cyclooxygenase inhibitor AZD3582 is an effective nitric oxide donor in vivo

1. AZD3582 [4-(nitrooxy)butyl-(2S)-2-(6-methoxy-2-naphthyl)propanoate] is a COX-inhibiting nitric oxide donor that inhibits COX-1 and COX-2. It is as effective as naproxen in models of pain and inflammation, but causes less gastroduodenal damage. Nitric oxide (NO) is generated from AZD3582 in vitro, and this study sought to show that the drug donates NO in vivo. 2. In anaesthetised male New Zealand white rabbits, the endogenous NO concentration in exhaled air was reduced by N(G)-nitro-L-arginine methyl ester (L-NAME) (30 mg kg(- 1) i.v.) from 33.5+/-1.0 ppb (mean+/-s.e.m.; n=6 per group) to 3.0+/-1.0 ppb, while increasing blood pressure and reducing heart rate. AZD3582 (0.2, 0.6, 2.0 or 6.0 micromol kg(- 1) min(- 1)) given 30 min after L-NAME increased the concentration of NO in exhaled air (P<0.05), decreased blood pressure and increased heart rate in a dose-dependent manner versus L-NAME control values. The peak mean NO concentration obtained was 44+/-8.0 ppb. 3. In in situ-perfused rabbit lungs, L-NAME (185 micromol l(- 1)) reduced the NO concentration in exhaled air from 106+/-13 to 4.0+/-0.4 ppb (n=5). Addition of AZD3582 (6 micromol min(- 1)) to the perfusate produced an initial rapid increase in the NO concentration in exhaled air, followed by a sustained, but lower plateau. Infusion of L-NAME increased, and AZD3582 decreased, pulmonary arterial pressure. 4. In both anaesthetised rabbits and in the perfused lungs, brief periods of hypoxia increased NO concentrations generated by AZD3582. 5. We conclude that, in rabbits, AZD3582 donates NO in vivo with characteristics similar to those reported for nitroglycerin and isosorbide nitrates

The antinociceptive effect of local or systemic parecoxib combined with lidocaine/clonidine intravenous regional analgesia for complex regional pain syndrome type I in the arm

We evaluated the efficacy of local or systemic parecoxib combined with lidocaine/clonidine IV regional analgesia in complex regional pain syndrome (CRPS) type 1 in a dominant upper limb. Thirty patients with CRPS type 1 were divided into three groups. The control group (CG) received both IV saline in the healthy limb and IV loco-regional 1 mg/kg of lidocaine + 30 mug of clonidine, diluted to a 10-mL volume with saline. The systemic parecoxib group (SPG) received a regional block similar to that administered to the CG but with systemic 20 mg of parecoxib, whereas the IV regional anesthesia with parecoxib group (IVRAPG) received an extra IV 5 mg of loco-regional parecoxib compared with the CG. The block was performed once a week for 3 consecutive weeks. Analgesia was evaluated by the 10-cm visual analog scale (VAS) and rescue analgesic consumption. The IVRAPG showed less daily ketoprofen (milligrams) consumption in the second and third weeks compared with the other groups (P < 0.05). The IVRAPG also showed less ketoprofen consumption when comparing the first and second week with the third week (P < 0.05). The VAS score comparison among groups revealed that groups were similar during the first and second week observation, although the IVRAPG showed smaller VAS scores in the third week compared with both CG and SPG (P < 0.05). We conclude the IV 5 mg of parecoxib was an effective antiinflammatory drug combined with clonidine/lidocaine loco-regional block in CRPS type 1.

Continuous treatment with organic nitrate affects hepatic cytochrome P450

We previously reported that cytochrome P450 (P450) is a key enzyme of organic nitrate biotransformation and that P450 levels of the heart and its vessels markedly decreased at the development of nitrate tolerance. Escape from tolerance of organic nitrate by induction of cytochrome P450. Most organic nitrates, including nitroglycerin (NTG), are metabolized in the liver, where nitric oxide (NO) is concomitantly produced from the organic nitrates. Therefore, organic nitrate administration may also affect hepatic P450 levels, since the liver is the major organ of P450-related metabolism. Male Wistar rats were intravenously administrated NTG or isosorbide dinitrate (ISDN) for 24-96 h. Hepatic P450 was drastically decreased after 48 h or 72 h of continuous NTG or ISDN infusion, when nitrate tolerance was observed, but it recovered 48 h after cessation of the drug administration. hemeoxygenase-1 (HO-1) was induced within 24 h of continuous NTG infusion, but it returned to normal levels 48 h after cessation of the NTG. The administration of sodium nitroprusside, an agent to which the animals showed no tolerance, did not induce HO-1 or P450 depletion as judged by SDS-PAGE in combination with Western-blotting. These results suggest that P450-dependent drug metabolism may be drastically affected after continuous organic nitrate administration.

A common pathway of nitric oxide release from AZD3582 and glyceryl trinitrate

4-(Nitrooxy)-butyl-(S)-2-(6-methoxy-2-naphthyl)-propanoate (AZD3582) is a cyclooxygenase (COX)-inhibiting nitric oxide donator (CINOD). It donates nitric oxide (NO) in biological systems through as yet unidentified mechanisms. cGMP, a marker of intracellularly generated NO, was increased up to 27-fold over basal levels by AZD3582 (1-30microM) in LLC-PK1 kidney epithelial cells. A 5h pretreatment with glyceryl tinitrate (GTN, 0.1-1microM) attenuated the cGMP response to a subsequent challenge with AZD3582 or GTN. Similarly, AZD3582 (10-30microM) pretreatment reduced the increase in cGMP on subsequent incubation with AZD3582 or GTN. In contrast, cGMP stimulation by SIN-1, which releases NO independently of enzymatic catalysis, remained unimpaired in cells pretreated with GTN or AZD3582. Our results demonstrate that AZD3582 decreases the sensitivity of the guanylyl cyclase/cGMP system to GTN and vice versa. This suggests that bioactivation pathways for organic nitrates, which involve enzymatic catalysis, may be responsible for NO donation from AZD3582.

N-nitrosylation potential of mono-N-desethylamiodarone at physiological pH

Amiodarone (AMI) is frequently used for the treatment of supraventricular arrhythmias. The parent drug is rapidly dealkylated to mono-N-desethylamiodarone (MDEA) and the plasma concentrations of AMI and MDEA are comparable. MDEA is a secondary amine and may thus undergo formation to the corresponding N-nitrosamine in combination with coadministered nitrovasodilators. Previous studies have shown that nitrovasodilators release the vasoactive NO? which may nitrosylate thiol or secondary amine groups in aqueous solutions. Therefore, the nitrosylation potential of MDEA at physiological pH was investigated. N-Nitroso-monodesethylamiodarone (NO-MDEA) was synthesized, characterized and used as a reference product for the detection of the corresponding N-nitrosamine. HPLC and NMR results have shown that the NO-MDEA product is an equilibrium of two configurational isomers (syn and anti). NO-release was generated by sodium nitroprusside (SNP) which was exposed to light. The formation to NO-MDEA was assayed by HPLC-UV. It has been found that MDEA is nitrosylated in the higher nanomolar range and that varying oxygenation of the reaction mixture did not significantly affect the reaction yields. The addition of thiols such as serum albumin (0.6mM), l-cysteine (2.5mM) or N-acetylcysteine (2.5mM) inhibited the NO-MDEA formation indicating that they may prevent N-nitrosamine formation in vivo. However, as S-nitrosothiols may also release NO?, in long term exposure to elevated levels of nitric oxide the nitrosylation of secondary amines may be taken into account.

Vasodilating beta-adrenoceptor blockers as cardiovascular therapeutics

beta-Adrenoceptor blocking agents (beta-blockers) have been established as therapeutics for treatment of patients with hypertension, ischemic heart diseases, chronic heart failure, arrhythmias, and glaucoma. However, their clinical use is limited because some patients are adversely affected by their side effects. The discovery of cardioselective (beta(1)-selective) blockers has overcome some of the problems. Current retrospective studies have revealed that vasodilating beta-blockers (so-called beta-blockers of the third generation) have advantages over the conventional type of beta-blockers in terms of minimizing the adverse effects and improving the disease-derived dysfunction, thus enhancing the quality of life variables. Some of the possible advantages include improvement of insulin resistance, decrease in low-density lipoprotein cholesterol in association with increase in high-density lipoprotein cholesterol, attenuation of bronchial asthma attack and respiratory dysfunction, alleviation of coronary vasospasm provocation, peripheral circulatory disturbances, and erectile dysfunction, and better patient compliance. Release of nitric oxide, antioxidant action, beta(2)-adrenoceptor activation, Ca(2+) entry blockade, and other mechanisms underlying the vasodilating action may be responsible for the beneficial therapeutic effects of these agents.

Relaxant effect of oxime derivatives in isolated rat aorta: role of nitric oxide (NO) formation in smooth muscle

Various oxime derivatives were evaluated as nitric oxide (NO) donors in arteries. Relaxation of rat aortic rings was used for bioassay of NO production, and electron paramagnetic resonance spectroscopy for demonstration of NO elevation. In rings with or without endothelium or adventitia, hydroxyguanidine and hydroxyurea were almost inactive, whereas formamidoxime, acetaldoxime, acetone oxime, acetohydroxamic acid and formaldoxime elicited relaxation. Active compounds increased NO levels in endothelium-denuded rings. Formaldoxime was the most potent agent for both relaxation and NO elevation in aortic rings, and it also increased NO in human aortic smooth muscle cells. In endothelium-denuded rings, relaxation was inhibited by a NO scavenger (2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide) and by inhibitors of soluble guanylyl-cyclase (1H[1,2,4,]oxadiazolo[4,3-a]quinoxalin-1-one) or cyclic GMP-dependent protein kinases (Rp-8-bromo cyclic GMP monophosphorothioate). Neither N(omega)-nitro-l-arginine methylester (a NO synthases inhibitor) nor proadifen (a cytochrome P450 inhibitor) decreased the effect of oxime derivatives. However, 7-ethoxyresorufin (7-ER, an inhibitor of P4501A(1) which can also inhibit various NADPH-dependent reductases) abolished the relaxant effect of these compounds, without affecting the one of glyceryl trinitrate (GTN) or 2-(N,N-diethylamino)-diazenolate-2-oxide. 7-ER also abolished formaldoxime-induced NO increase in aortic rings. In rings tolerant to GTN, formaldoxime-induced relaxation and NO elevation were not different from those obtained in control rings. In conclusion, some oxime derivatives release NO by 7-ER-sensitive pathways in aortic smooth muscle, thus eliciting vasorelaxation. Pathways of NO formation are likely distinct from NO synthases and from those responsible for GTN biotransformation. Oxime derivatives could be useful for NO delivery in arteries in which endothelial NO synthase activity is impaired.

Continuous administration of organic nitrate decreases hepatic cytochrome P450

We previously reported that cytochrome P450 (P450) is a key enzyme of organic nitrate biotransformation and that P450 levels of the heart and its vessels markedly decreased at the development of nitrate tolerance. Although our attention was mainly focused on the circulatory organs, most organic nitrates, including nitroglycerin (NTG), are metabolized in the liver, where nitric oxide (NO) is concomitantly produced from the organic nitrates. NO reacts with various molecules such as superoxide, heme, thiols, and oxygen. This paper examined whether hepatic P450 levels are also affected after organic nitrate administration, since the liver is the major organ of P450 related metabolism. Male Wistar rats were intravenously administrated NTG or isosorbide dinitrate (ISDN) for 24-96 h. We observed the level of hemeoxygenase-1 (HO-1) as the functional marker of hepatic P450, since one of the acute phase target proteins of NO induction is an inducible type of HO-1. Hepatic P450 was drastically decreased after 48 or 72 h of continuous NTG or ISDN infusion, when nitrate tolerance was observed, but it recovered 48 h after cessation of the NTG administration. HO-1 was induced within 24 h of continuous NTG infusion, but it returned to normal levels 48 h after cessation of NTG. The administration of sodium nitroprusside, an agent to which the animals showed no tolerance, did not induce HO-1 or P450 depletion. Chronic administration of organic nitrates significantly decreased hepatic P450. These results suggest that P450-dependent drug metabolism may be drastically affected after continuous organic nitrate administration.

Organic nitrate tolerance is induced by degradation of some cytochrome P450 isoforms

The mechanism of nitrate tolerance is poorly defined. We studied the rat P450 (CYP)-catalyzed conversion of organic nitrate to nitric oxide (NO) by purified CYP isoforms and the relationship between P450 expression and nitrate tolerance following continuous infusion of organic nitrates in rats. CYP1A2 effectively formed NO from isosorbide dinitrate and nitroglycerine (NTG). The hypotensive effect of an NTG bolus injection was abolished in rats which had been previously given a continuous 48 h infusion of NTG. Nitrate tolerance was reversible to control levels 2 days after cessation of the continuous infusion. At 48 h after infusion, NTG-induced NO generation of the vessels increased in acetone (a P450 inducer)-pretreated rats, and nitrite and nitrate levels were markedly greater than in normal rats. The appearance and disappearance of P450 isoforms paralleled the conversion of organic nitrates to NO as assessed by immunohistochemistry and Western blotting. Our observations indicate that nitrate tolerance is in large part the result of decreased P450 expression and activity. Interventions that maintain or increase P450 activity may be a useful strategy to provide sustained relief from ischemic conditions in humans.

Various intracellular compartments cooperate in the release of nitric oxide from glycerol trinitrate in liver

1. Glycerol trinitrate (GTN) has been used in therapy for more than 100 years. Biological effects of GTN are due to the release of the biomediator nitric oxide (NO). However, the mechanism by which GTN provides NO, in particular in liver, is still unknown. In this study, we provide experimental evidence showing that cytoplasm, endoplasmic reticulum, and mitochondria are required for the release of NO from GTN in the liver. 2. NO and nitrite (NO(2)(-)) were determined using low-temperature electron paramagnetic resonance and the Griess reaction, respectively. 3. The first step of GTN biotransformation is the release of NO(2)(-). This step is performed in cytoplasm and catalyzed by glutathione-S-transferase. The second step is the rate-limiting step where NO(2)(-) is slowly reduced to NO. This is mainly catalyzed by cytochrome P-450. The second phase can be significantly enhanced by decreasing the pH value, a situation which occurs during ischemia. At high NADPH concentrations exceeding physiological values, cytochrome P-450 catalyzes GTN biotransformation without the involvement of cytoplasmic glutathione-S-transferase. 4. In conclusion, our data show that NO(2)(-) derived from the first step of biotransformation of GTN in the liver is the precursor of NO but not a product of NO degradation; consequently, NO(2)(-) levels are not likely to be a marker of NO release from GTN as earlier suggested.

Mediation of arachidonic acid metabolite(s) produced by endothelial cytochrome P-450 3A4 in monkey arterial relaxation

We investigated mechanisms of endothelium-dependent relaxation by acetylcholine resistant to indomethacin and N(G)-nitro-L-arginine and sensitive to cytochrome P-450 (CYP) inhibitors or charybdotoxin + apamin in the monkey lingual artery. Treatment with quinacrine, an inhibitor of phospholipase A2, abolished the relaxation by acetylcholine. However, treatment with alpha-glycyrrhetinic acid, an inhibitor of gap junctions, or catalase, an enzyme which dismutates hydrogen peroxide to form water and oxygen, did not affect the relaxation by acetylcholine. Immunohistochemistry demonstrated the presence of CYP3A4 in endothelial cells of the artery. Anti-CYP3A4 antibody inhibited relaxations by products of arachidonic acid incubated with human liver microsomes rich in CYPs in the endothelium-denuded artery. Purified CYP3A4 produced epoxyeicosatrienoic acids (EETs) from arachidonic acid, and the production was abolished by a selective CYP3A inhibitor, ketoconazole. It may be concluded that endothelium-derived relaxing substance(s) other than nitric oxide and prostanoids in the monkey lingual artery opens charybdotoxin + apamin-sensitive K+ channels in smooth muscle cells, and arachidonic acid metabolite(s) produced by endothelial CYP3A4 is likely to be the major substance.