Nitrate tolerance

P300/CBP associated factor regulates nitroglycerin-dependent arterial relaxation by N(ε)-lysine acetylation of contractile proteins

OBJECTIVE

To address the role of epigenetic enzymes in the process of arterial vasorelaxation and nitrate tolerance, in vitro and in vivo experiments were performed in the presence or absence of glyceryl trinitrate (GTN) or histone deacetylases/histone acetylases modulators.

METHODS AND RESULTS

In vitro single GTN administration rapidly increased cGMP synthesis and protein N(ε)-lysine acetylation in rat smooth muscle cells, including myosin light chain and smooth muscle actin. This phenomenon determined a decrease in myosin light chain phosphorylation and actomyosin formation. These effects were abolished by prolonged exposure to GTN and rescued by treatment with trichostatin A. In vivo, adult male rats were treated for 72 hours with subcutaneous injections of GTN alone or in combination with the histone deacetylases inhibitors trichostatin A, suberoylanilide hydroxamic acid, MS-27-275, or valproic acid. Ex vivo experiments performed on aortic rings showed that the effect of tolerance was reversed by all proacetylation drugs, including the p300/CREB binding protein-associated factor activator pentadecylidenemalonate 1b (SPV106). Any response to GTN was abolished by anacardic acid, a potent histone acetylases inhibitor.

CONCLUSIONS

This study establishes the following points: (1) GTN treatment increases histone acetylases activity; (2) GTN-activated p300/CREB binding protein-associated factor increases protein N(ε)-lysine acetylation; (3) N(ε)-lysine acetylation of contractile proteins influences GTN-dependent vascular response. Hence, combination of epigenetic drugs and nitroglycerin may be envisaged as a novel treatment strategy for coronary artery disease symptoms and other cardiovascular accidents of ischemic origin.

Effects and development of tolerance using transdermal nitrates in the treatment of congestive heart failure

Vasodilator therapy is an accepted mode of treating patients with severe congestive heart failure (CHF). Nitrates have a predominantly beneficial effect on preload, but also afterload may be beneficially modulated with higher doses. There is some evidence that long-term treatment with isosorbide dinitrate is beneficial in patients with CHF. By contrast, recent reports of 24 hour hemodynamics following transdermal delivery seem disappointing and rapid development of tolerance has been observed.

Effect of intermittent administration of sustained release isosorbide dinitrate (sr-ISDN) in rats with pressure-overload heart

Recent studies have demonstrated the benefits of nitric oxide (NO) on myocardial hypertrophy and myocardial fibrosis. It was suggested that NO has a protective effect on myocardial cell through the neurohormonal system. This effect serves to highlight the important role of NO in maintaining the function and form of heart with chronic heart failure. However, there are no known reports about on the effect of prolonged administration of nitrate on pressure over-load heart. This study was conducted to examine the long-term effect of oral nitrate therapy in rats with pressure-overloaded heart. An abdominal aorta constricted (AC) model of pressure-overloaded heart was created in male Wistar rats. Sustained release isosorbide dinitrate (sr-ISDN) (5 mg/kg once a daily) was administered to the rats once a daily for 12 weeks. The animals were euthanized during the study period, and the heart was collected and weighed. Histopathological examination was performed to evaluate the effect of sr-ISDN on myocardial hypertrophy and fibrosis. The ratio of heart to body weight increased significantly in AC rat and this increase was significantly prevented by sr-ISDN treatment. Histopathological examination showed significant increase in fibrotic area of AC rat compared to sham rat, this increase was inhibited by sr-ISDN treatment. Cardiomyocyte transverse diameter was significantly increased in AC rat compared with sham rat, but this increase tended to decrease by sr-ISDN treatment. In conclusion, intermittent administration with sr-ISDN has mild effect in inhibiting cardiac hypertrophy and marked effect in inhibiting fibrosis due to pressure-overload.

The effect of intermittent administration of sustained release isosorbide dinitrate (sr-ISDN) in rats with volume overload heart

Recently, it has been reported that intermittent administration of nitrate, with a nitrate-free interval of 10 to 12 hr eliminated expression of tolerance, and maintained its hypotensive effect. In the present study, we evaluated whether nitrate tolerance developed or not with an intermittent administration of sr-ISDN (5 mg/kg/ once a day) in Wistar rats. The effect of this administration protocol for sr-ISDN on the volume overload heart model, aortovenous fistula, was also examined. Furthermore, blood pressure was monitored by radio telemetry during sr-ISDN (5 mg/kg/once a day) administration. Nitrate tolerance did not develop, and eccentric hypertrophy due to volume overload was moderated by sr-ISDN administration. Sr-ISDN administration maintained blood pressure lower level than the placebo group. In conclusion, prolonged intermittent administration of sr-ISDN maintained its hypotensive effect during the entire experiment period, without developing tolerance, and moderated efferent hypertrophy with attenuated volume overload.

The control of adrenergic function in heart failure: therapeutic intervention

Chronic heart failure is characterised by excess adrenergic activity that augurs a poor prognosis. The reasons for increased adrenergic activity are complex and incompletely understood. The circumstantial evidence relating increased activity to adverse outcome is powerful, but not yet conclusive. In normal subjects, autonomic control of the circulation is predominantly under the control of sympatho-inhibitory inputs from the arterial and cardiopulmonary baroreceptors, with a small input from the excitatory ergo- and chemo-receptors. In heart failure, the situation is reversed, with loss of the restraining input from the baroreceptors and an increase in the excitatory inputs, resulting in excessive adrenergic activity. The circumstantial evidence linking neuroendocrine activation with poor outcome coupled with the clinical success of inhibition of the renin-angiotensin-aldosterone system has long suggested that inhibition of adrenergic activity might be beneficial in heart failure. There is a number of potential ways of achieving this. Improved treatment of heart failure itself may reduce sympathetic drive. There is an interplay between angiotensin II, aldosterone and the sympathetic nervous system, and thus RAAS antagonists, such as angiotensin converting enzyme inhibitors and spironolactone could directly reduce sympathetic activation. Exercise rehabilitation may similarly reduce sympathetic activity.Recently, beta-adrenergic receptor antagonists have been conclusively shown to improve symptoms, reduce hospitalisations and increase survival. However, the demonstration that central reduction of sympathetic activity with agents such as moxonidine increases morbidity and mortality suggests that we do not properly understand the role of sympathetic activation in the pathophysiology of heart failure.

Effects of a novel, selective and potent phosphodiesterase type V inhibitor, E4021, on myocardial ischemia in guinea pigs

The anti-ischemic effects of a new, selective and potent cyclic 3',5'-guanosine monophosphate-specific phosphodiesterase (phosphodiesterase type V) inhibitor, sodium 1-[6-chloro-4-(3,4-methylenedioxybenzyl)aminoquinazolin-2-yl ]piperidine-4- carboxylate (E4021), in a vasopressin-induced guinea pig anginal model were examined and compared with those of coronary vasodilators with a guanylate cyclase-activating action. An intravenous injection of vasopressin (0.2 IU/kg) into anesthetized guinea pigs produced ST segment elevation on the electrocardiogram (an index of myocardial ischemia) of 0.28 +/- 0.02 mV (n = 10) from the baseline within 30 s. E4021 administered intravenously at doses of 0.03 and 0.1 mg/kg, 5 min before the injection of vasopressin, significantly inhibited the ST segment elevation to 0.15 +/- 0.03 mV (n = 6, P < 0.01) and 0.17 +/- 0.02 mV (n = 6, P < 0.01), respectively. Three guanylate cyclase activators, isosorbide dinitrate (0.1 mg/kg), nicorandil (0.1 mg/kg), and FK409 (0.3 mg/kg), also significantly reduced the ST segment elevation to 0.18 +/- 0.03, 0.11 +/- 0.02 and 0.17 +/- 0.02 mV, respectively. In a second experiment, E4021 was administered intraduodenally 30 min before the injection of vasopressin to examine its oral effectiveness. Intraduodenal E4021, at doses of 1.0 and 3.0 mg/kg, also significantly inhibited the ST segment elevation to 0.16 +/- 0.02 mV (n = 6, P < 0.01) and 0.13 +/- 0.02 mV (n = 6, P < 0.01), respectively. It is concluded that the potent phosphodiesterase type V inhibitor, E4021, administered intravenously or intraduodenally, ameliorated myocardial ischemia similarly to guanylate cyclase activators. Thus, E4021 may be an orally effective drug in the treatment of angina pectoris.

Comparative evaluation of three dosages of slow-release isosorbide dinitrate (60, 80, 100 mg) in chronic angina of the aged

In a single-blind, placebo-controlled study the acute and chronic antianginal effects of three slow-release (SR) new formulations of isosorbide dinitrate (ISDN 60, 80, 100 mg) have been comparatively evaluated in a group of aged affected by chronic stable effort-induced angina. Compared to placebo, overall the active dose paritetically improved the effort tolerance up to 24 h after the first assumption. In the time course of the trial (2 and 4 weeks) the resting hemodynamic changes induced by the first dose were partially blunted without affecting the exercise related-parameters. Also if plasma levels of ISDN and of its metabolites did not correlate to the degree of physical improvement, the peak increase in effort tolerance was observed under 100 mg treatment. Mild to moderate transient headache was experienced by 50% of actively treated and by 20% of placebo treated patients and no other serious adverse effects have been noted. One may conclude that ISDN in slow-release formulations of 60-100 mg isan effective, safe and well tolerated medication in the management of angina in the aged.

Nitrates: why and how should they be used today? Current status of the clinical usefulness of nitroglycerin, isosorbide dinitrate and isosorbide-5-mononitrate

Nitrates are highly effective both in terminating acute attacks of angina pectoris and in the prophylaxis of symptomatic and asymptomatic myocardial ischemia. Preload reduction by venodilatation is the prevailing mechanism of nitrates in patients with chronic stable angina and is the unique feature distinguishing them from beta and calcium-channel blockers. Nitrates dilate coronary arteries not only in pre- and poststenotic vessels, but also in eccentric lesions. In patients with endothelial dysfunction, nitrates seem to be the physiological substitute for endothelium-derived relaxing factor. During the past decade, however, there has been substantial evidence of a clinically relevant loss of the anti-ischemic effects ("nitrate tolerance"). Many studies with oral dosing of isosorbide dinitrate or isosorbide-5-mononitrate at least three times daily have proven nitrate tolerance in patients with coronary artery disease and/or congestive heart failure. Complete loss of anti-ischemic effects after repetitive, continuous patch attachments has also been found. As we first showed in 1983, intermittent therapy with once-daily ingestion of high-dose sustained-release isosorbide dinitrate was successful in preventing the development of tolerance. Similarly, tolerance to isosorbide-5-mononitrate also does not develop when it is ingested once daily. It is now generally accepted that a daily low-nitrate interval is required to prevent tolerance development. Although the minimal patch-free interval required to prevent tolerance needs further investigation, a 12-h patch-free interval should prevent tolerance in most patients. The prolonged duration of action of once-daily high-dosage administration of sustained-release formulations, the improved patient compliance with a single daily administration, and the increased likelihood of maximal anti-ischemic effects are important reasons for recommending high single daily doses of isosorbide dinitrate or isosorbide-5-mononitrate.

Lack of tolerance after chronic administration of controlled-release isosorbide-5-mononitrate. Interaction of nitrate and gallopamil

The effect of a controlled-release formulation of isosorbide-5-mononitrate (IS-5-MN) was studied in patients with coronary heart disease (CHD), with the aim of comparing the acute effect with that after chronic administration on parameters of ischemia. To determine whether any tolerance developed, several aspects of ischemia were observed: ECG signs, clinical parameters, and left ventricular function. Fifteen patients with angiographically proven CHD were examined with 12-lead exercise ECG before, 2 h and 4 h after the first dose and after 10 days of therapy with 60 mg IS-5-MN (Coleb-Duriles) once daily. After 7 days, three radionuclide ventriculographies were performed: control, 2 h after nitrate and 2 h after 75 mg gallopamil. Plasma concentrations of IS-5-MN were measured before every exercise test. The results showed a reduction of total ST-segment depression from 0.59 mV to 0.29 mV after 2 h (NS) and 4 h (P less than 0.05) on the 1st day and from 0.48 mV to 0.32 mV (P less than 0.05) and 0.31 mV (NS) after 10 days. The severity of angina pectoris was diminished by about 50%. The effect on exercise duration and time to ST-segment depression by more than 0.1 mV remained unchanged after 10 days, whereas the effect on blood pressure, heart rate and time to onset of angina was attenuated. The mean decrease in ejection fraction (EF) from rest to exercise was reduced from--5.9% to -1.9% (P less than 0.05) after nitrate, while an increase of +1.4% was seen after gallopamil (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Vasodilator therapy without converting-enzyme inhibition in congestive heart failure--usefulness and limitations

Despite a well-established rationale for pharmacologically induced arterial and venous vasodilatation in congestive heart failure, the clinical usefulness of long-term vasodilator therapy without concomitant converting-enzyme inhibition generally has been disappointing. With the exception of nitrates and, possibly, the combination of nitrates and hydralazine, the use of converting-enzyme inhibitors in many aspects appears preferable in the majority of patients. This article reviews the pathophysiology of inappropriate vasoconstriction in heart failure, the cellular mode of action of the various vasodilators, hemodynamic effects with respect to the peripheral site of action, clinical usefulness and limitations of different vasodilators, and the various determinants of clinical efficacy. Finally, an attempt is made to assess when and how to introduce vasodilator treatment with and without concomitant ACE inhibition.

Effect of intravenous isosorbide dinitrate versus nitroglycerin on elevated pulmonary arterial wedge pressure during acute myocardial infarction

To compare the acute and sustained effect of intravenous isosorbide dinitrate to intravenous nitroglycerin in patients with acute myocardial infarction and elevated pulmonary artery wedge pressure, 111 patients were randomized and studied within 96 hours of admission to the coronary care unit. All patients had a pulmonary artery wedge pressure greater than or equal to 10 mm Hg and received either isosorbide dinitrate (74 patients) or nitroglycerin (37 patients) for 24 to 48 hours. Blood pressure, heart rate, pulmonary artery wedge pressure, cardiac output, medication dose in micrograms per minute and retitration episodes were compared at baseline and at 6, 12, 18 and 24 hours. Both drugs significantly (p less than 0.05) lowered pulmonary artery wedge pressure and blood pressure and increased cardiac output. Isosorbide dinitrate required fewer retitration episodes and less increases in dosage than nitroglycerin at 24 hours. In the patient with acute myocardial infarction complicated by high pulmonary artery wedge pressure who requires intravenous nitrates for 24 hours, isosorbide dinitrate may offer the benefit of a more stable hemodynamic effect.

Apparent tolerance to the acute effect of nicotine results in part from distribution kinetics

Persons exposed to nicotine develop tolerance to many of its effects. When heart rate and forearm venous blood concentration are plotted against time after intravenous administration of nicotine, a greater increase in heart rate is seen for a given nicotine concentration during the rising phase of nicotine concentrations than during the decreasing phase. This could be due to acute tolerance or to more rapid distribution of drug to effect site (brain) than to venous blood. To distinguish between these possibilities, six rabbits were given nicotine intravenously. Blood samples were taken from the internal jugular vein (reflecting brain concentration), and the femoral vein and artery. Brain concentrations peaked before femoral venous concentrations. Seven men received intravenous infusions of nicotine. Peripheral venous blood concentrations and cardiovascular responses were measured. Heart rate peaked before venous concentrations. A physiological kinetic model, fit to the rabbit data, was scaled to humans and used to predict "brain" concentrations in them. Heart rate and predicted brain concentrations peaked simultaneously. We conclude that the rapid development of tolerance to the cardioaccelerating effect of nicotine can be attributed, at least in part, to its distribution kinetics.

Induction and circumvention of nitrate tolerance applying different dosage intervals

There is increasing evidence that constant nitrate plasma levels, as induced by at least three-times-daily ingestions of isosorbide dinitrate in sustained-release form, lead to an attenuation or even complete loss of the anti-ischemic effects (nitrate tolerance). Therefore, the dependence of tolerance development on dosage intervals according to once-daily and twice-daily ingestions was assessed. Tablets of isosorbide dinitrate (80 mg) in sustained-release form were administered once-daily at 8 A.M. (dosage interval 24 hours) or twice-daily at 8 A.M. and 8 P.M. (dosage interval 12 hours), as well as at 8 A.M. and 2 P.M., respectively (maximal dosage interval 18 hours). A total of 34 patients with angiographically proven coronary artery disease, a history of stable, exercise-dependent angina pectoris, and a reproducible, exercise-induced ST-segment depression of at least 0.15 mV (1.5 mm), who initially showed a response to 80 mg of isosorbide dinitrate, were enrolled. The anti-ischemic effects of isosorbide dinitrate on exercise-induced ischemia were objectively determined by the measurement of exercise-induced ST-segment depression before as well as two, six, and 12 hours after the ingestion at the first and the 15th day of the studies. Since the dosage interval of 12 hours resulted in constant plasma levels, the initially beneficial anti-ischemic effects of isosorbide dinitrate were considerably attenuated after two weeks of treatment. In contrast, the once-daily regimen with its intermittent peaks and valleys of nitrate plasma levels showed identical anti-ischemic effects at the 15th day as compared with the first day. Ingestions at 8 A.M. and 2 P.M. also circumvented the development of nitrate tolerance, however, combined with an even more pronounced anti-ischemic effect after 12 hours as compared with the once-daily regimen. Thus, the circumvention of nitrate tolerance requires a daily "nitrate-poor" interval. The best compromise between a maximal possible anti-ischemic effect and the circumvention of tolerance development was found for the "eccentric" dosage regimen in which the tablets were ingested in the morning and early afternoon.

Comparison of nifedipine and isosorbide dinitrate when added to maximal propranolol therapy in stable angina pectoris

A study was performed to compare isosorbide dinitrate and nifedipine as adjunctive therapy in 14 patients with coronary artery disease and stable angina pectoris taking maximal beta-blocking drugs. Drug titration phases ensured maximal therapy of propranolol, isosorbide or nifedipine. The combination of nifedipine and propranolol was more effective than the combination of isosorbide and propranolol in reducing angina and increasing exercise capacity (323 vs 416 seconds, p less than 0.005) during exercise treadmill testing. Nifedipine produced a greater reduction in systolic blood pressure at submaximal exercise than isosorbide. Global and regional ejection fraction at rest and exercise was assessed with radionuclide ventriculography. The substitution of nifedipine for isosorbide depressed the global ejection fraction at rest (0.61 to 0.56 p less than 0.05) and produced a slight improvement in exercise ejection fraction (0.47 to 0.51, difference not significant). The decrease in ejection fraction from rest to exercise was 0.14 to 0.04 with nifedipine (p less than 0.005). The benefit of nifedipine compared with isosorbide occurred in regions with marked exercise-induced ischemia. In patients treated with maximal beta-blocking therapy, nifedipine is an effective alternative to isosorbide as a combination agent with propranolol. The salutary effects of nifedipine included afterload reduction with exercise and possible improvements in coronary blood supply.

Clinical experience with a transdermal nitroglycerin system

Forty-seven patients with chronic stable angina pectoris entered a thirteen-week open-label study with a transdermal therapeutic system of nitroglycerin in order to evaluate its clinical efficacy, safety, and patient acceptance. In 19 patients, a beta-blocker and in 17 patients a calcium-channel blocker were continued throughout the study period without alteration of their doses. The study consisted of a two-week run-in period and an eleven-week active drug period. Acute titration was done with nitroglycerin patches on the basis of weekly patient diaries on frequency of angina and sublingual nitroglycerin consumption. Overall, reductions in frequency of angina and in nitroglycerin consumption were statistically significant (p less than 0.05). Adverse reactions were common but tolerable. The reported side effects were headache in 32, skin rash in 18, dizziness in 10, palpitation and itching in 9 each, nausea in 7, flushing in 3, and vomiting in 1 patient. In conclusion, the present study demonstrates that individual dose titration with nitroglycerin patches for obtaining significant antianginal effect is essential. The present therapeutic system is convenient to use and well tolerated and had acceptable side effects in our study population.

The haemodynamic and anti-ischaemic effects of a single tablet of 80 mg isosorbide dinitrate in slow-release formulation and a review of nitrate tolerance

There is increasing evidence that relatively constant plasma nitrate concentrations induced by 3-times-daily administration of isosorbide dinitrate can lead to an attenuation or even complete loss of the drug's anti-ischaemic effects (nitrate tolerance). We therefore assessed the dependence of nitrate tolerance development from the haemodynamic and anti-ischaemic effects of a slow-release tablet formulation of isosorbide dinitrate 80 mg, administered according to different daily dosage regimens in patients with angina. It was found that a once-daily regimen, with its consequent peak and trough plasma nitrate concentrations, is capable of protecting against exercise-induced myocardial ischaemia for about 12 hours with the circumvention of nitrate tolerance.

Nitrate tolerance

Nitrates are widely used in anginal prophylaxis. In spite of the fact that the concept of nitrate tolerance was first put forward many years ago, the question of tolerance has remained controversial. There is widespread agreement that tolerance does occur to the effects of nitrates on arterial pressure. In contrast, tolerance to the venous and pulmonary effects is disputed. Similarly, the possibility of tolerance to the antianginal effects remains at issue. In this review, I discuss the factors which may have contributed to conflicting results in different studies, in particular recent findings on the rapidity of onset and reversal of tolerance. Tolerance develops rapidly on initiation of treatment and disappears equally rapidly on its discontinuation. In addition, tolerance appears to be a function of plasma nitrate profile. It is most likely to occur when plasma nitrate levels are constant and least likely when nitrate levels fluctuate. Furthermore, the provision of a daily nitrate free interval may protect against the development of tolerance. I then discuss the implications of these findings for patient management. They suggest that nitrate prophylaxis should not be used continuously, if this can be avoided. Rather, prophylaxis should be tailored to the individual to provide protection at times of maximum susceptibility, while allowing nitrate levels to fall at other times. The adequacy of antianginal protection with drug regimens incorporating a nitrate free interval requires further assessment. Similarly, the possibility that a nitrate free interval might lead to withdrawal effects and exacerbation of angina needs to be excluded.