Beneficial actions of nitrates in cardiovascular disease

Vasodilators for Acute Heart Failure - A Systematic Review with Meta-Analysis

BACKGROUND

Acute heart failure is a public health concern. This study systematically reviewed randomized clinical trials (RCTs) to evaluate vasodilators in acute heart failure.

METHODS

The search was conducted across the databases of Medline, Embase, Latin American and the Caribbean Literature on Health Sciences, Web of Science, and the Cochrane Central Register of Controlled Trials. Inclusion criteria consisted of RCTs that compared vasodilators versus standard care, placebo, or cointerventions. The primary outcome was all-cause mortality; secondary outcomes were serious adverse events (SAEs), tracheal intubation, and length of hospital stay. Risk of bias was assessed in all trials.

RESULTS

The study included 46 RCTs that enrolled 28,374 patients with acute heart failure. Vasodilators did not reduce the risk of all-cause mortality (risk ratio, 0.95; 95% confidence interval [CI], 0.87 to 1.04; I2=9.51%; P=0.26). No evidence of a difference was seen in the risk of SAEs (risk ratio, 1.01; 95% CI, 0.97 to 1.05; I2=0.94%) or length of hospital stay (mean difference, -0.10; 95% CI, -0.28 to 0.08; I2=69.84%). Vasodilator use was associated with a lower risk of tracheal intubation (risk ratio, 0.54; 95% CI, 0.30 to 0.99; I2=51.96%) compared with no receipt of vasodilators.

CONCLUSIONS

In this systematic review with meta-analysis of patients with acute heart failure, vasodilators did not reduce all-cause mortality.

Efficacy of Glyceryl trinitrate (GTN) to facilitate the rewarming process during cardiopulmonary bypass

Background

Does Glyceryl trinitrate (GTN) administered during rewarming on cardiopulmonary bypass (CPB) impact: time to completion of rewarming prior to separation from CPB circuit, early post-op patient peripheral – core temperature gradient, time to maintenance of normothermia (core temperature > 36.5 °C) for minimum of 2 h in the initial post-op period, and plasma lactate concentrations initially post-CPB.

Methods

Single centre prospective randomized trial conducted in the Mater Misericordiae University teaching hospital in Dublin Ireland. Trial registration: ISRCTN registry, ISRCTN10480871, registered 16th of August 2017. 82 patients enrolled. Patients randomised to low dose GTN infusion (0.01 mcg/kg/min) or higher dose GTN infusion (0.5 mcg/kg/min) during rewarming on CPB.

Measurements and Main results

There was no significant difference between the treatment arms for the total time to being rewarmed, U = 759.0, p = 0.84. There were also no differences between the treatment arms for the time to achieve core temperature greater than 36.5 after two hours, U = 714.0, p = 0.52, the time to achieve plateau core skin temperature, U = 688.0, p = 0.37, and the post-intervention protamine lactate, U = 721.0, p = 0.56.

Conclusions

Higher dose GTN infusion during rewarming on CPB does not improve peripheral-core temperature gradient post operatively and has no effect on post-operative lactate concentrations.

The Effects of a Vasodilator on Transluminal Attenuation Gradient at Coronary Computed Tomography Angiography

Objective

To evaluate the effects of vasodilators on contrast enhancement and transluminal attenuation gradient (TAG) of coronary arteries at coronary computed tomography angiography (CCTA).

Materials and Methods

We retrospectively reviewed CCTA scans of patients who underwent double-acquisition CCTA; CCTA without a vasodilator, and CCTA during a intravenous (IV) infusion of nitrate. Among them, we enrolled 19 patients who had no significant atherosclerotic lesions or coronary spasms. In the control group, 28 patients were enrolled who showed normal coronary arteries on CCTA, which was acquired by a conventional method (sublingual vasodilator). We measured the TAG and Hounsfield units for each of the three major epicardial coronary arteries (reported as ‘ProxHU’) and then compared the results between the nitrate administration methods (CT without vasodilator [CT_pre], CT with IV vasodilator [CT_iv], and CT with sublingual vasodilator [CT_sub]).

Results

The mean TAG showed a significant difference between the coronary arteries (right coronary artery [RCA] > left anterior descending artery [LAD] > left circumflex artery [LCX], p < 0.05), while there was no difference in ProxHU of each coronary artery in all three types of nitrate administration methods (p > 0.05). The TAG of CT_pre group showed steeper slope than those of vasodilator groups (CT_iv and CT_sub) on LAD and LCX ([LAD: CT_pre = −22.1 ± 6.66, CT_iv = −16.76 ± 5.78, and CT_sub = −16.47 ± 5.78, p = 0.005], [LCX: CT_pre = −31.26 ± 17.43, CT_iv = −23.74 ± 14.06, and CT_sub = −20.94 ± 12.15, p = 0.051]), while that of RCA showed no significant differences (p = 0.600). When comparing proxHU, CT_iv showed higher proxHU than that of CT_pre or CT_sub, especially on LCX (CT_pre = 426.7 ± 68.3, CT_iv = 467.9 ± 84.9, and CT_sub = 404.9 ± 63.3, p = 0.013). ProxHU showed a negative correlation with TAG on all three of methods (r = −0.280, p < 0.001).

Conclusion

TAG in CCTA was significantly affected by vasodilator administration. Both TAG and ProxHU of coronary arteries tend to increase with vasodilator administration on CCTA.

The NO-donor MPC-1011 stimulates angiogenesis and arteriogenesis and improves hindlimb ischemia via a cGMP-dependent pathway involving VEGF and SDF-1α

BACKGROUND AND AIMS

Peripheral arterial disease (PAD) is an important cause of morbidity and mortality with little effective medical treatment currently available. Nitric oxide (NO) is crucially involved in organ perfusion, tissue protection and angiogenesis.

METHODS

We hypothesized that a novel NO-donor, MPC-1011, might elicit vasodilation, angiogenesis and arteriogenesis and in turn improve limb perfusion, in a hindlimb ischemia model. Hindlimb ischemia was induced by femoral artery ligation in Sprague-Dawley rats, which were randomized to receive either placebo, MPC-1011, cilostazol or both, up to 28 days. Limb blood flow was assessed by laser Doppler imaging.

RESULTS

After femoral artery occlusion, limb perfusion in rats receiving MPC-1011 alone or in combination with cilostazol was increased throughout the treatment regimen. Capillary density and the number of arterioles was increased only with MPC-1011. MPC-1011 improved vascular remodeling by increasing luminal diameter in the ischemic limb. Moreover, MPC-1011 stimulated the release of proangiogenic cytokines, including VEGF, SDF1α and increased tissue cGMP levels, reduced platelet activation and aggregation, potentiated proliferation and migration of endothelial cells which was blunted in the presence of soluble guanylyl cyclase inhibitor LY83583. In MPC-1011-treated rats, Lin^-/CD31⁺/CXCR4⁺ cells were increased by 92.0% and Lin^-/VEGFR2⁺/CXCR4⁺ cells by 76.8% as compared to placebo.

CONCLUSIONS

Here we show that the NO donor, MPC-1011, is a specific promoter of angiogenesis and arteriogenesis in a hindlimb ischemia model in an NO-cGMP-VEGF- dependent manner. This sets the basis to evaluate and confirm the efficacy of such therapy in a clinical setting in patients with PAD and impaired limb perfusion.

Photodissociation dynamics of nitric oxide from roussin’s red ester probed by time-resolved infrared spectroscopy

To explore nitric oxide (NO)-donating capability of Roussin’s red ester [Fe2(μ-RS)2(NO)4] (RRE), photodissociation of NO from RRE and its subsequent reaction dynamics were probed by monitoring the N–O stretching mode after excitation with a 400-nm photon. As a result of the experiment, the NO generation quantum yield was obtained.

Vasodilators in acute heart failure - evidence based on new studies

Acute heart failure (AHF) contributes largely to the worldwide burden of heart failure (HF) and is associated with high mortality, poor prognosis and high rehospitalization rate. The pharmacologic therapy of AHF includes diuretics and vasodilators, which are a keystone when fluid overload and congestion are present. However, vasodilators are mainly focused on controlling symptoms, and drugs that also improve long-term mortality and morbidity seem to be in high demand. In this review, we summarize the existing evidence on mortality benefits of IV vasodilators in AHF. There is lack of evidence on the mortality benefits of IV vasodilators in AHF, as well as well-designed and large-scale trials for some of them. The existing trials on nitrates have conflicting results and are insufficient to establish definitive conclusions. Other vasodilators, such as enalaprilat, clevidipine, carperitide, and ularitide, have been evaluated only in a few trials assessing mortality. Levosimendan, nesititide and carperitide are approved by some regulatory agencies; however, data regarding mortality are also conflicting and large-scale post-marketing studies would be important. Serelaxin is a recent therapy with a novel mechanism of action and seemed to be promising; although serelaxin was safe and well tolerated in earlier trials, the results of a larger phase III trial failed to meet the primary endpoints of reduction in cardiovascular death at day 180 and reduction of worsening heart failure at day 5. The absence of definitive mortality benefits and high-quality and large-scale data not allow firm conclusions to be drawn about the role of IV vasodilators in AHF. Well-designed studies are needed to clarify the role of these drugs in the long-term outcome of AHF, as well as new therapies entering the clinical investigation.

The effect of intravenous isosorbide dinitrate in acute decompensated heart failure in hospital

Background According to new recommendations for the management of acute decompensated heart failure (ADHF) in 2015, intravenous vasodilator therapy might be given as an early therapy when systolic blood pressure is normal to high (≥110 mmHg). Only 29% of patients with ADHF are treated with vasodilators without medical contraindication. Objective To evaluate the effect of the systematic use of ISDN on ADHF without contraindication especially on rehospitalization rate. Settings The 600-bed hospital (Centre Hospitalier de l'Ouest Vosgien, Neufchâteau, France). Methods This is a retrospective study with data analysed from medical records. Patients with ADHF episodes and hospitalization in the cardiology department or intensive care unit (ICU) between November 2013 and December 2015 were included resulting in 199 hospitalizations in the analysis (37 were treated by ISDN, and 162 were not). Main outcome measure Effects of ISDN on 180-day hospital readmission for ADHF or acute myocardial infarction (AMI), in-hospital mortality, length of stay, number of ICU admissions, and ICU length of stay. Results Patients who received ISDN required more ICU admissions than the other patients (54.1 vs 33.3%, p = 0.02). Nevertheless 180-day hospital readmission was lower for patients who were receiving ISDN (8.1 vs 22.8%, p = 0.04). ISDN did not influence other clinical outcomes tested. Conclusion ISDN may minimize or prevent the consequences of altered haemodynamics. Lower rehospitalization rate with ISDN was seen in this study.

Antianginal Therapy for Stable Ischemic Heart Disease

Chronic angina pectoris is associated with considerable morbidity and mortality, especially if treated suboptimally. For many patients, aggressive pharmacologic intervention is necessary in order to alleviate anginal symptoms. The optimal treatment of stable ischemic heart disease (SIHD) should be the prevention of angina and ischemia, with the goal of maximizing both quality and quantity of life. In addition to effective risk factor modification with lifestyle changes, intensive pharmacologic secondary prevention is the therapeutic cornerstone in managing patients with SIHD. Current guidelines recommend a multifaceted therapeutic approach with β-blockers as first-line treatment. Another important pharmacologic intervention for managing SIHD is nitrates. Nitrates can provide both relief of acute angina and can be used prophylactically before exposure to known triggers of myocardial ischemia to prevent angina. Additional therapeutic options include calcium channel blockers and ranolazine, an inhibitor of the late inward sodium current, that can be used alone or in addition to nitrates or β-blockers when these agents fail to alleviate symptoms. Ranolazine appears to be particularly effective for patients with microvascular angina and endothelial dysfunction. In addition, certain antianginal therapies are approved in Europe and have been shown to improve symptoms, including ivabradine, nicorandil, and trimetazidine; however, these have yet to be approved in the United States. Ultimately, there are several different medications available to the physician for managing the patient with SIHD having chronic angina, when either used alone or in combination. The purpose of this review is to highlight the most important therapeutic approaches to optimizing contemporary treatment in response to individual patient needs.

Effectiveness of isosorbide dinitrate in cyanide poisoning as a function of the administration timing

BACKGROUND

Better and safer antidotes against cyanide poisoning are needed. Prior study has shown a favorable effect of isosorbide dinitrate (ISDN) on the survival of cyanide-poisoned rabbits when administered as early as 1 min after poisoning. The aim of the current study was to further evaluate the efficacy of intravenous ISDN administered in clinically relevant timing for first responders.

METHODS

A comparative animal study using 24 rabbits in 4 randomized study groups was performed. Animals were poisoned with intravenous potassium cyanide (1 mg/kg). Animals in Group 1 served as controls and received no treatment. Groups 2-4 animals were treated intravenously with ISDN (50 μg/kg) after poisoning; one group after 3 min, another group after 5 min and the last after 7 min. Animals were observed for 30 min after poisoning. The study endpoints included survival rate, clinical status, blood pressure, pulse per minute, blood lactate and pH.

RESULTS

Five of 6 animals (83.3%) from every treatment group survived the whole observation period while all control untreated animals died. All the rabbits collapsed immediately after exposure, showing rapidly deteriorated vital signs with lactic metabolic acidosis (peak blood lactate levels of 18.1 to 19.0 mmol/L on average at 10 min post exposure). Vital signs, clinical scores, and blood gases of treated rabbits gradually improved.

CONCLUSION

Poisoned rabbits showed improved short-term survival following the administration of ISDN up to 7 min after lethal cyanide poisoning of. We see a potential for ISDN as an antidote against cyanide poisoning.

Comparison of the Effects of Nitroglycerin and Nitroprusside on Transmitral Doppler Flow Parameters in Patients with Hypertensive Urgency

BACKGROUND:

Sodium nitroprusside (NIP) and nitroglycerin (NIT) are frequently selected agents for acutely reducing blood pressure. However, it is not clear which agent is more efficacious in improving left ventricular filling pressure in hypertensive crises.

OBJECTIVE:

To compare the acute effects of nitroglycerin (NIT) and nitroprusside (NIP) on transmitral Doppler filling parameters in patients with hypertensive urgency.

METHODS:

We identified 37 patients from our emergency department with hypertensive urgency and left ventricular filling abnormalities. Hypertensive urgency was defined as a severe blood pressure elevation without evidence of progressive end-organ injury. Patients were randomized to receive an infusion of NIT or NIP. NIT was infused at a starting dose of 10 μg/min; NIP was infused at a starting dose of 0.25 μg/kg/min. The infusion rates were adjusted to decrease mean arterial pressure by 25%, and this reduction was obtained within 2 hours in all patients. Diastolic filling parameters were measured by using echocardiography before and after treatment. Pulsed-wave Doppler transmitral flow velocities were used. Early diastolic flow, atrial contraction signal, early diastolic flow/atrial contraction signal, deceleration time, and isovolumetric relaxation time (IVRT) were measured.

RESULTS:

There were no differences between groups in baseline demographic and echocardiographic parameters. Blood pressure decreased significantly in both treatment groups. In posttreatment echocardiographic examinations, atrial contraction signal, deceleration time, and IVRT were significantly decreased in both treatment groups. Early diastolic flow was significantly decreased in the NIT group. There were no significant differences between the groups in terms of posttreatment early diastolic flow, atrial contraction signal, deceleration time, and IVRT values.

CONCLUSIONS:

In hypertensive urgency with left ventricular filling abnormalities, reduction of blood pressure associated with NIT or NIP treatment may improve transmitral Doppler filling parameters. There were no differences demonstrated between the 2 agents.

Pharmacological Profile of GPD-1116, an Inhibitor of Phosphodiesterase 4

We have previously reported that GPD-1116, an inhibitor of phosphodiesterase (PDE) 4, exhibits anti-inflammatory effects in a model of cigarette smoke-induced emphysema in senescence-accelerated P1 mice. In the present study, we further characterized the pharmacological profile of GPD-1116 in several experiments in vitro and in vivo. GPD-1116 and its metabolite GPD-1133 predominantly inhibited not only human PDE4, but also human PDE1 in vitro. Moreover, GPD-1116 was effective in several disease models in animals, including acute lung injury, chronic obstructive pulmonary disease (COPD), asthma and pulmonary hypertension; the effective doses of GPD-1116 were estimated to be 0.3-2 mg/kg in these models. With regard to undesirable effects known as class effects of PDE4 inhibitors, GPD-1116 showed suppression of gastric emptying in rats and induction of emesis in dogs, but showed no such suppression of rectal temperature in rats, and these side effects of GPD-1116 seemed to be less potent than those of roflumilast. These results suggested that GPD-1116 could be a promising therapeutic agent for the treatment of inflammatory pulmonary diseases. Furthermore, the inhibitory effects of GPD-1116 for PDE1 might be associated with its excellent pharmacological profile. However, the mechanisms through which PDE1 inhibition contributes to these effects should be determined in future studies.

The Nitrate-Nitrite-NO Pathway and Its Implications for Heart Failure and Preserved Ejection Fraction

The pathogenesis of exercise intolerance in patients with heart failure and preserved ejection fraction (HFpEF) is likely multifactorial. In addition to cardiac abnormalities (diastolic dysfunction, abnormal contractile reserve, chronotropic incompetence), several peripheral abnormalities are likely to be involved. These include abnormal pulsatile hemodynamics, abnormal arterial vasodilatory responses to exercise, and abnormal peripheral O2 delivery, extraction, and utilization. The nitrate-nitrite-NO pathway is emerging as a potential target to modify key physiologic abnormalities, including late systolic left ventricular (LV) load from arterial wave reflections (which has deleterious short- and long-term consequences for the LV), arterial vasodilatory reserve, muscle O2 delivery, and skeletal muscle mitochondrial function. In a recently completed randomized trial, the administration of a single dose of exogenous inorganic nitrate has been shown to exert various salutary arterial hemodynamic effects, ultimately leading to enhanced aerobic capacity in patients with HFpEF. These effects have the potential for both immediate improvements in exercise tolerance and for long-term "disease-modifying" effects. In this review, we provide an overview of key mechanistic contributors to exercise intolerance in HFpEF, and of the potential therapeutic role of drugs that target the nitrate-nitrite-NO pathway.

Vasodilator Therapy: Nitrates and Nicorandil

Nitrates have been used to treat symptoms of chronic stable angina for over 135 years. These drugs are known to activate nitric oxide (NO)-cyclic guanosine-3',-5'-monophasphate (cGMP) signaling pathways underlying vascular smooth muscle cell relaxation, albeit many questions relating to how nitrates work at the cellular level remain unanswered. Physiologically, the anti-angina effects of nitrates are mostly due to peripheral venous dilatation leading to reduction in preload and therefore left ventricular wall stress, and, to a lesser extent, epicardial coronary artery dilatation and lowering of systemic blood pressure. By counteracting ischemic mechanisms, short-acting nitrates offer rapid relief following an angina attack. Long-acting nitrates, used commonly for angina prophylaxis are recommended second-line, after beta-blockers and calcium channel antagonists. Nicorandil is a balanced vasodilator that acts as both NO donor and arterial K(+) ATP channel opener. Nicorandil might also exhibit cardioprotective properties via mitochondrial ischemic preconditioning. While nitrates and nicorandil are effective pharmacological agents for prevention of angina symptoms, when prescribing these drugs it is important to consider that unwanted and poorly tolerated hemodynamic side-effects such as headache and orthostatic hypotension can often occur owing to systemic vasodilatation. It is also necessary to ensure that a dosing regime is followed that avoids nitrate tolerance, which not only results in loss of drug efficacy, but might also cause endothelial dysfunction and increase long-term cardiovascular risk. Here we provide an update on the pharmacological management of chronic stable angina using nitrates and nicorandil.

Early administration of isosorbide dinitrate improves survival of cyanide-poisoned rabbits

CONTEXT

More effective, rapidly delivered, safer antidotes are needed for cyanide poisoning. Previous study has demonstrated a beneficial effect of isosorbide dinitrate on the survival of cyanide-poisoned mice.

OBJECTIVE

To evaluate the effectiveness of isosorbide dinitrate compared with that of sodium nitrite in cyanide poisoning.

MATERIALS AND METHODS

A comparative animal study was performed using 18 rabbits, randomized into 3 study groups. Animals were poisoned intravenously with potassium cyanide (1 mg/kg). The first group was not given any further treatment. The second and third groups were treated intravenously 1 min after poisoning with sodium nitrite (6 mg/kg) and isosorbide dinitrate (50 μg/kg), respectively. The primary outcome was short-term survival of up to 30 min. Secondary outcomes included time to death, a clinical score, mean blood pressure, pulse, blood pH, and lactate and methemoglobin levels.

RESULTS

Rabbits treated with isosorbide dinitrate or sodium nitrite survived while only one untreated rabbit survived. Median time to death of the 5 poisoned and untreated animals was 10 min. All the animals collapsed soon after poisoning, exhibiting rapidly disturbed vital signs and developed lactic metabolic acidosis; average peak blood lactate levels were 15.5-19.1 mmol/L at 10 min after poisoning. The treated animals improved gradually with practically full recovery of the clinical scores, vital signs, and blood gas levels. Sodium nitrite administration raised methemoglobin to an average peak of 7.9%, while isosorbide dinitrate did not change methemoglobin levels.

CONCLUSION

Early administration of isosorbide dinitrate improved the short-term survival of cyanide-poisoned rabbits. Isosorbide dinitrate shows potential as an antidote for cyanide poisoning and may exert its effect using a nitric-oxide-dependent mechanism.

Changes in pulmonary hemodynamics induced by experimental myocardial ischemia in nitroglycerin- or acetylcholine-treated rabbits

The responses of cardiovascular parameters to left-ventricular myocardial ischemia induced under control conditions and after administration of nitroglycerin or acetylcholine were examined in rabbits. In nitroglycerine-treated rabbits, experimental myocardial ischemia produced less pronounced depressor BP shifts in the pulmonary artery than those produced by ischemia in controls (prior to pharmacological treatment) or by experimental ischemia provoked after acetylcholine infusion. Control and experimental ischemia (provoked after nitroglycerin or acetylcholine administration) induced the same drop in pulmonary blood fl ow accompanied with insignificant changes in vascular pulmonary resistance. Experimental ischemia produced smaller pressure increase in left atrium of nitroglycerine-treated rabbits (evidencing a smaller drop in left ventricular contractility) than the control ischemia performed prior to pharmacological treatment, or the experimental ischemia in acetylcholine-treated rabbits, which attested to protective effect of nitroglycerin against ischemia.

The effects of nitroglycerin during cardiopulmonary resuscitation

The outcome for both in-hospital and out-of hospital cardiac arrest remains dismal. Vasopressors are used to increase coronary perfusion pressure and thus facilitate return of spontaneous circulation during cardiopulmonary resuscitation. However, they are associated with a number of potential adverse effects and may decrease endocardial and cerebral organ blood flow. Nitroglycerin has a favourable haemodynamic profile which promotes forward blood flow. Several studies suggest that combined use of nitroglycerin with vasopressors during resuscitation, is associated with increased rates of resuscitation and improved post-resuscitation outcome. This article reviews the effects of nitroglycerin during cardiopulmonary resuscitation and postresuscitation period, as well as the beneficial outcomes of a combination regimen consisting of a vasopressor and a vasodilator, such as nitroglycerin.

Cardiorespiratory function associated with dietary nitrate supplementation

The advent of medical nutrition therapy and nutritional physiology affords the opportunity to link diet to specific cardiovascular mechanisms, suggesting novel treatments for cardiovascular disease. This study tests the hypothesis that beetroot juice increases the plasma nitric oxide (NO) concentration, which is associated with improvements in cardiorespiratory function at rest and during submaximal aerobic exercise. The subjects were 12 healthy, young adult, normotensive African-American females, with a body mass of 61 ± 2 kg, body fat of 28% ± 4%, and peak oxygen consumption of 26 ± 3 mL·kg(-1)·min(-1). The subjects were studied at rest and during cycle ergometer exercise at 40%, 60%, and 80% of peak oxygen consumption. Plasma NO concentration, respiratory quotient (RQ), minute ventilation, systolic and diastolic blood pressure (SBP and DBP), heart rate, and oxygen consumption were compared between isocaloric, isovolumetric placebo control orange juice and experimental beetroot juice treatments on separate days. The beetroot juice treatment increased plasma NO concentration and decreased oxygen consumption, SBP, and the heart rate-SBP product at rest and at 40%, 60%, and 80% of peak oxygen consumption in the absence of significant effects on RQ, minute ventilation, heart rate, and DBP. These findings suggest that, in healthy subjects, beetroot juice treatments increase plasma NO concentration and decrease cardiac afterload and myocardial oxygen demand at rest and during 3 submaximal levels of aerobic exercise. Future studies should determine the cellular and molecular mechanisms responsible for the improvement in cardiorespiratory function associated with dietary nitrate supplementation and whether they translate into better cardiovascular function and exercise tolerance in individuals with a compromised cardiovascular system.

Novel vasodilators in heart failure

Heart failure is an important public health problem that is increasing in prevalence throughout the world. Not only is this condition common, but it is associated with significant morbidity and mortality as well as high costs to medical care systems. Vasodilator drugs help unload the heart and may have other effects that could benefit heart failure patients. Consequently, they have emerged as an important therapeutic approach for patients with this condition. Novel vasodilator therapies that are currently in development target new pathways, potentially giving clinicians alternate options for improving outcomes in this vulnerable population. This review focuses on investigational drugs that have the ability to dilate blood vessels amongst their therapeutic properties. These drugs include the natriuretic peptides that activate particulate guanylate cyclase, the novel agent cinaciguat that activates the soluble guanylate cyclase system, and finally a recombinant form of the naturally occurring vasodilating agent relaxin, a hormone that mediates many of the changes that allows the cardiovascular system to successfully adapt to pregnancy.

Anti-inflammatory effects of saponins derived from the roots of Platycodon grandiflorus in lipopolysaccharide‑stimulated BV2 microglial cells

Radix platycodi is the root of Platycodon grandiflorus A. DC, which has been widely used as a food material and for the treatment of a number of chronic inflammatory diseases in traditional oriental medicine. In this study, the anti‑inflammatory effects of the saponins isolated from radix platycodi (PGS) on the production of inflammatory mediators and cytokines in lipopolysaccharide (LPS)-stimulated BV2 murine microglial cells were examined. We also investigated the effects of PGS on LPS‑induced nuclear factor‑κB (NF-κB) activation and phosphoinositide 3-kinase (PI3K)/AKT and mitogen-activated protein kinase (MAPK) signaling pathways. Following stimulation with LPS, elevated nitric oxide (NO), prostaglandin E2 (PGE2) and pro-inflammatory cytokine production was detected in the BV2 microglial cells. However, PGS significantly inhibited the excessive production of NO, PGE2 and pro‑inflammatory cytokines, including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in a concentration-dependent manner without causing any cytotoxic effects. In addition, PGS suppressed NF-κB translocation and inhibited the LPS-induced phosphorylation of AKT and MAPKs. Our results indicate that the inhibitory effect of PGS on LPS-stimulated inflammatory response in BV2 microglial cells is associated with the suppression of NF-κB activation and the PI3K/AKT and MAPK signaling pathways. Therefore, these findings suggest that PGS may be useful in the treatment of neurodegenerative diseases by inhibiting inflammatory responses in activated microglial cells.

Vitamin B₁₂ derivatives as activators of soluble guanylyl cyclase

Various newly prepared and previously known vitamin B₁₂ derivatives have been studied as potential soluble guanylyl cyclase (sGC) activators. All compounds tested were found to activate the sGC enzyme, although to differing extents. The best results were obtained with the derivatives synthesized from c-lactone and possessing aliphatic amides in the c- and d-positions.

Effect of L-arginine supplementation on blood pressure in pregnant women: a meta-analysis of placebo-controlled trials

OBJECTIVE

A meta-analysis of placebo-controlled trials was conducted to evaluate the effect of L-arginine supplementation on blood pressure (BP) in pregnancy.

METHODS

Trials were searched in PubMed, Embase, and Cochrane Library. A total of five trials were included in the meta-analysis.

RESULTS

L-arginine supplementation exhibited a mean decrease of 3.07 mmHg (p = 0.004) for diastolic blood pressure and a mean increase of 1.23 weeks (p = 0.002) for gestation age at delivery in pregnancy, but did not reduce systolic BP (p = 0.19) as compared to placebo.

CONCLUSION

L-arginine supplementation had a significant effect of lowering diastolic blood pressure and prolonging gestation age in pregnancy.

WISE 2005: responses of women to sublingual nitroglycerin before and after 56 days of 6° head-down bed rest

This study tested the hypothesis that cardiovascular effects of sublingual nitroglycerin (NG) would be exaggerated after 56 days of 6° head-down bed rest (HDBR) in women, and that an aerobic and resistive exercise countermeasure (EX, n = 8) would reduce the effect compared with HDBR without exercise (CON, n = 7). Middle cerebral artery maximal blood flow velocity (CBFV), cardiac stroke volume (SV), and superficial femoral artery blood flow (Doppler ultrasound) were recorded at baseline rest and for 5 min following 0.3 mg sublingual NG. Post-HDBR, NG caused greater increases in heart rate (HR) in CON compared with EX (+24.9 ± 7.7 and +18.8 ± 6.6 beats/min, respectively, P < 0.0001). The increase in HR combined with reductions in SV to maintain cardiac output. Systolic, mean, and pulse pressures were reduced 5-10 mmHg by NG, but total peripheral resistance was only slightly reduced at 3 min after NG. Reductions in CBFV of -12.5 ± 3.8 cm/s were seen after NG, but a reduction in the Doppler resistance index suggested dilation of the middle cerebral artery with no differences after HDBR. The femoral artery dilated with NG and blood flow was reduced ∼50% with the appearance of large negative waves suggesting a marked increase in downstream resistance, but there were no effects of HDBR. In general, responses of women to NG were not altered by HDBR; the greater increase in HR in CON but not EX was probably a consequence of cardiovascular deconditioning. These results contrast with the hypothesis and a previous investigation of men after HDBR by revealing no change in cardiovascular responses to exogenous nitric oxide.

Alterations in P wave duration and dispersion in depressive patients following electroconvulsive therapy

OBJECTIVE

Electroconvulsive therapy (ECT) consists of controlled convulsive seizure by electric stimulation of the brain. Although various electrocardiographic (ECG) changes have been reported during ECT, atrial conduction has not been studied extensively. The aim of the present study was to assess the effects of ECT on systemic arterial blood pressure and ECG parameters (P wave duration, P wave dispersion and heart rate).

METHODS

Thirty depressive patients undergoing ECT were included. Echocardiographic examination was performed on all patients before ECT sessions to exclude systolic heart failure and diastolic dysfunction which may affect P wave duration and dispersion. Twelve-lead ECG records were obtained before the first ECT and after the third session of ECT. Blood pressure was measured before and after convulsive therapy session.

RESULTS

Compared to baseline values, maximum P wave duration (99.3 ± 14.6 to 111.3 ± 8.2 ms, P=.001), P wave dispersion (50 ± 14.8 to 63.3 ± 10.3 ms, P=.001), and systolic (110.7 ± 12 to 116 ± 12.2 mmHg, P=.043) and diastolic blood pressures (70.7 ± 9.4 to 75.3 ± 8.2 mmHg, P=.028) were significantly increased after convulsive therapy session.

CONCLUSIONS

We proposed that ECT alone or in combination with atypical antipsychotics or antidepressants may influence atrial conduction as evidenced by the significantly prolonged maximum P wave duration and P wave dispersion. Longer-term follow-up of patients undergoing ECT may be appropriate to evaluate the possible long-term outcomes of our short-term results.

Meta-Analysis of Randomized Controlled Trials on the Efficacy of Di'ao Xinxuekang Capsule and Isosorbide Dinitrate in Treating Angina Pectoris

Objective. Randomized controlled trials (RCTs) on di'ao xinxuekang capsule (XXK) in treating angina pectoris were published only in Chinese and have not been systematically reviewed particularly for comparing XXK with isosorbide dinitrate (ISDN). This study aims to provide a comprehensive PRISMA compliant and internationally accessible systematic review and meta-analysis to evaluate the efficacies of XXK and ISDN in treating angina pectoris. Methods. The RCTs published between 1989 and 2011 on XXK and ISDN in treating angina pectoris were selected according to specific criteria. Meta-analysis was performed to evaluate the symptomatic (SYMPTOMS) and electrocardiographic (ECG) improvements after treatment. Odds ratios (OR) were used to measure effect sizes. Subgroup analysis, sensitivity analysis, and metaregression were conducted to evaluate the robustness of the results. Results. Seven RCTs with 550 participants were eligible. Overall ORs for comparing XXK with ISDN were 4.11 (95% CI :  2.57, 6.55) in SYMPTOMS and 2.37 (95% CI : 1.46, 3.84) in ECG. Subgroup analysis, sensitivity analysis, and metaregression found no significant dependence of overall ORs upon specific study characteristics. Conclusion. The meta-analysis of eligible but limited RCTs demonstrates that XXK seems to be more effective than ISDN in treating angina pectoris. Further RCTs of high quality are warranted to be conducted for update of the results of this meta-analysis.

Nitroglycerin use in myocardial infarction patients

Acute myocardial infarction (MI) and its sequelae are leading causes of morbidity and mortality worldwide. Nitroglycerin (glyceryl trinitrate [GTN]) remains a first-line treatment for angina pectoris and acute MI. Nitroglycerin achieves its benefit by giving rise to nitric oxide (NO), which causes vasodilation and increases blood flow to the myocardium. However, continuous delivery of GTN results in tolerance, limiting the use of this drug. Nitroglycerin tolerance is caused, at least in part, by inactivation of aldehyde dehydrogenase 2 (ALDH2), an enzyme that converts GTN to the vasodilator, NO. We recently found that in a MI model in animals, in addition to GTN's effect on the vasculature, sustained treatment negatively affected cardiomyocyte viability following ischemia, thus resulting in increased infarct size. Coadministration of Alda-1, an activator of ALDH2, with GTN improves metabolism of reactive aldehyde adducts and prevents the GTN-induced increase in cardiac dysfunction following MI. In this review, we describe the molecular mechanisms associated with the benefits and risks of GTN administration in MI.

A pharmacological primer of biased agonism

Biased agonism is one of the fastest growing topics in G protein-coupled receptor pharmacology; moreover, biased agonists are used in the clinic today: carvedilol (Coreg^®) is a biased agonist of beta-adrenergic receptors. However, there is a general lack of understanding of biased agonism when compared to traditional pharmacological terminology. Therefore, this review is designed to provide a basic introduction to classical pharmacology as well as G protein-coupled receptor signal transduction in order to clearly explain biased agonism for the non-scientist clinician and pharmacist. Special emphasis is placed on biased agonists of the beta-adrenergic receptors, as these drugs are highly prescribed, and a hypothetical scenario based on current clinical practices and proposed mechanisms for treating disease is discussed in order to demonstrate the need for a more thorough understanding of biased agonism in clinical settings. Since biased agonism provides a novel mechanism for treating disease, greater emphasis is being placed to develop biased agonists; therefore, it is important for biased agonism to be understood in equal measure of traditional pharmacological concepts. This review, along with many others, can be used to teach the basic concepts of biased agonism, and this review also serves to introduce the subsequent reviews that examine, in more depth, the relevance of biased agonism towards the angiotensin type 1 receptor, parathyroid hormone receptor, and natural biased ligands towards chemokine receptors.

Application of nitric oxide in drug discovery and development

INTRODUCTION

It is becoming increasingly clear that many diseases are characterized or associated with perturbations in nitric oxide (NO) production/signaling. Therapeutics or strategies designed to restore normal NO homeostasis will likely have broad application and utility in human health. This highly complex and multi-step pathway for NO production and subsequent target activation provides many steps in the endogenous pathway that may be useful targets for drug development. Important therapeutic areas for NO-based therapies are inflammatory disorders, cardiovascular diseases, erectile dysfunction and metabolic disorders.

AREAS COVERED

The following review will discuss the endogenous NO pathway, highlight the current market and indications for NO-based therapeutics, as well as identify pathway targets currently under drug development. Each step along the NO pathway will be discussed including exogenous sources of NO, use of precursors to promote NO production and downstream pathways affected by NO production with advantages and disadvantages highlighted for each.

EXPERT OPINION

Development of NO-based therapeutics is and will continue to be a major focus of biotech and pharmaceutical companies. Understanding and utilizing dietary and nutritional strategies to restore NO homeostasis could allow for safer, quicker marketing of products that may be just as efficacious as drugs designed against specific targets.

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).

C/EBPα and C/EBPβ binding proteins modulate hepatocyte apoptosis through iNOS signaling pathway

Inducible nitric oxide synthase (iNOS) and nitric oxide (NO) involve many pathophysiologic conditions. The expression of iNOS is regulated at multiple stages. Presently, the regulatory details of iNOS signaling are still unclear. This study aimed to investigate the regulatory role of C/EBPα and C/EBPβ in iNOS signaling pathway. By employing the techniques such as EMSA, ChIP assay, site-directed mutagenesis, and siRNA silencing, the relationship between iNOS and C/EBPα/C/EBPβ in rat hepatocytes was clarified. iNOS promoter was the direct transcriptional targets of the C/EBPα, C/EBPβ, and NF-κB binding proteins. There was the interactive influence between NF-κB and C/EBPα/C/EBPβ. The expression of iNOS was modulated by C/EBPα/C/EBPβ transcription factors. Moreover, the iNOS expression mediated glycochenodeoxycholate (GCDC)-induced apoptosis in hepatocytes. C/EBPα/C/EBPβ binding proteins could affect the GCDC-induced apoptosis through iNOS cascade. These findings indicate that C/EBPα and C/EBPβ regulate the iNOS expression, which may further modify cell responses such as apoptosis and cell survival.

Effect of phlorotannins isolated from Ecklonia cava on angiotensin I-converting enzyme (ACE) inhibitory activity

Inhibition of angiotensin I-converting enzyme (ACE) activity is the most common mechanism underlying the lowering of blood pressure. In the present study, five organic extracts of a marine brown seaweed Ecklonia cava were prepared by using ethanol, ethyl acetate, chloroform, hexane, and diethyl ether as solvents, which were then tested for their potential ACE inhibitory activities. Ethanol extract showed the strongest ACE inhibitory activity with an IC(50) value of 0.96 mg/ml. Five kinds of phlorotannins, phloroglucinol, triphlorethol-A, eckol, dieckol, and eckstolonol, were isolated from ethanol extract of E. cava, which exhibited potential ACE inhibition. Dieckol was the most potent ACE inhibitor and was found to be a non-competitive inhibitor against ACE according to Lineweaver-Burk plots. Dieckol had an inducible effect on the production of NO in EAhy926 cells without having cytotoxic effect. The results of this study indicate that E. cava could be a potential source of phlorotannins with ACE inhibitory activity for utilization in production of functional foods.

Organic nitrates and nitrate resistance in diabetes: the role of vascular dysfunction and oxidative stress with emphasis on antioxidant properties of pentaerithrityl tetranitrate

Organic nitrates represent a class of drugs which are clinically used for treatment of ischemic symptoms of angina as well as for congestive heart failure based on the idea to overcome the impaired NO bioavailability by “NO” replacement therapy. The present paper is focused on parallels between diabetes mellitus and nitrate tolerance, and aims to discuss the mechanisms underlying nitrate resistance in the setting of diabetes. Since oxidative stress was identified as an important factor in the development of tolerance to organic nitrates, but also represents a hallmark of diabetic complications, this may represent a common principle for both disorders where therapeutic intervention should start. This paper examines the evidence supporting the hypothesis that pentaerithrityl tetranitrate may represent a nitrate for treatment of ischemia in diabetic patients. This evidence is based on the considerations of parallels between diabetes mellitus and nitrate tolerance as well as on preliminary data from experimental diabetes studies.

Coronary MR imaging: effect of timing and dose of isosorbide dinitrate administration

PURPOSE

To quantify the effect of sublingual isosorbide dinitrate (ISDN) administration on coronary magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Written informed consent was obtained from all participants, and the HIPAA-compliant protocol was approved by the Institutional Review Board. Coronary MR imaging was performed at 1.5 T before and after administration of ISDN (2.5 or 5 mg) in 25 healthy adult volunteers (mean age, 23 years +/- 4; nine men, 16 women) with three-dimensional targeted (n = 20, randomized into four groups) or whole-heart (n = 5) acquisitions with gradient-recalled echo (GRE) or balanced steady-state free precession (SSFP) sequences. Image quality was assessed by two cardiologists on a four-point scale. Signal-to-noise ratio (SNR), vessel diameter, and vessel sharpness were characterized. A linear mixed-effects model was used for data analysis. A P value of less than .05 was considered to indicate a significant difference.

RESULTS

The maximum SNR enhancement with 5 mg of ISDN (GRE: 22.0% +/- 10.7%; SSFP: 20.1% +/- 6.0%) was similar (P > .05) to that with 2.5 mg (GRE: 21.9% +/- 5.4%; SSFP: 19.1% +/- 3.0%). However, the time to maximum SNR enhancement for the 5-mg dose (15.5 minutes +/- 6.0) was earlier (P < .01) than that for 2.5 mg (23.5 minutes +/- 6.7). The increase in vessel diameter with 5 mg of ISDN was greater than that with 2.5 mg (P < .05 for both GRE and SSFP sequences). The coronary images were sharper after ISDN administration (P < .03). Subjective image quality score significantly improved after ISDN administration for GRE images (P < .05 for both doses) but was similar for SSFP images (P = .24 for 2.5 mg; P = .27 for 5 mg). Whole-heart coronary SNR was improved about 10% after ISDN administration (P < .05).

CONCLUSION

Sublingual ISDN improves coronary MR imaging SNR. Practitioners need to consider the dose and temporal effects of ISDN when performing coronary MR imaging.

A new class of organic nitrates: investigations on bioactivation, tolerance and cross-tolerance phenomena

BACKGROUND AND PURPOSE

The chronic use of organic nitrates is limited by serious side effects including oxidative stress, nitrate tolerance and/or endothelial dysfunction. The side effects and potency of nitroglycerine depend on mitochondrial aldehyde dehydrogenase (ALDH-2). We sought to determine whether this concept can be extended to a new class of organic nitrates with amino moieties (aminoalkyl nitrates).

EXPERIMENTAL APPROACH

Vasodilator potency of the organic nitrates, in vitro tolerance and in vivo tolerance (after continuous infusion for 3 days) were assessed in wild-type and ALDH-2 knockout mice by isometric tension studies. Mitochondrial oxidative stress was analysed by L-012-dependent chemiluminescence and protein tyrosine nitration.

KEY RESULTS

Aminoethyl nitrate (AEN) showed an almost similar potency to glyceryl trinitrate (GTN), even though it is only a mononitrate. AEN-dependent vasodilatation was mediated by cGMP and nitric oxide. In contrast to triethanolamine trinitrate (TEAN) and GTN, AEN bioactivation did not depend on ALDH-2 and caused no in vitro tolerance. In vivo treatment with TEAN and GTN, but not with AEN, induced cross-tolerance to acetylcholine (ACh)-dependent and GTN-dependent relaxation. Although all nitrates tested induced tolerance to themselves, only TEAN and GTN significantly increased mitochondrial oxidative stress in vitro and in vivo.

CONCLUSIONS AND IMPLICATIONS

The present results demonstrate that not all high potency nitrates are bioactivated by ALDH-2 and that high potency of a given nitrate is not necessarily associated with induction of oxidative stress or nitrate tolerance. Obviously, there are distinct pathways for bioactivation of organic nitrates, which for AEN may involve xanthine oxidoreductase rather than P450 enzymes.

The prince and the pauper. A tale of anticancer targeted agents

Cancer rates are set to increase at an alarming rate, from 10 million new cases globally in 2000 to 15 million in 2020. Regarding the pharmacological treatment of cancer, we currently are in the interphase of two treatment eras. The so-called pregenomic therapy which names the traditional cancer drugs, mainly cytotoxic drug types, and post-genomic era-type drugs referring to rationally-based designed. Although there are successful examples of this newer drug discovery approach, most target-specific agents only provide small gains in symptom control and/or survival, whereas others have consistently failed in the clinical testing. There is however, a characteristic shared by these agents: -their high cost-. This is expected as drug discovery and development is generally carried out within the commercial rather than the academic realm. Given the extraordinarily high therapeutic drug discovery-associated costs and risks, it is highly unlikely that any single public-sector research group will see a novel chemical "probe" become a "drug". An alternative drug development strategy is the exploitation of established drugs that have already been approved for treatment of non-cancerous diseases and whose cancer target has already been discovered. This strategy is also denominated drug repositioning, drug repurposing, or indication switch. Although traditionally development of these drugs was unlikely to be pursued by Big Pharma due to their limited commercial value, biopharmaceutical companies attempting to increase productivity at present are pursuing drug repositioning. More and more companies are scanning the existing pharmacopoeia for repositioning candidates, and the number of repositioning success stories is increasing. Here we provide noteworthy examples of known drugs whose potential anticancer activities have been highlighted, to encourage further research on these known drugs as a means to foster their translation into clinical trials utilizing the more limited public-sector resources. If these drug types eventually result in being effective, it follows that they could be much more affordable for patients with cancer; therefore, their contribution in terms of reducing cancer mortality at the global level would be greater.

Limb venous tone and responsiveness in hypertensive humans

Hypertensive (HTN) animal models demonstrate lower venous compliance as well as increased venous tone and responsiveness compared with normotensive (NTN) controls. However, the extent to which findings in experimental animals can be extended to humans is unknown. Forearm and calf venous compliance were quantified in 9 NTN (23 +/- 1 yr) and 9 HTN (24 +/- 1 yr) men at baseline, after administration of nitroglycerin (NTG), during a cold pressor test (CP), and post-handgrip exercise ischemia (PEI). Individual pressure-volume relationships from a cuff deflation protocol (1 mmHg/s) were modeled with a quadratic regression. Regression parameters beta(1) and beta(2) were used to calculate compliance. A one-way ANOVA was used to compare the beta parameters and a repeated-measures ANOVA was used to compare volumes across all pressures (between groups at baseline and within groups during perturbations). Limb venous compliance was similar between groups (forearm: NTN beta(1) = 0.11 +/- 0.01 and beta(2) = -0.00097 +/- 0.0001, HTN beta(1) = 0.10 +/- 0.01 and beta(2) = -0.00088 +/- 0.0001; calf: NTN beta(1) = 0.12 +/- 0.01 and beta(2) = -0.00102 +/- 0.0001, HTN beta(1) = 0.11 +/- 0.01 and beta(2) = -0.00090 +/- 0.0001). However, at baseline, volume across all pressures (i.e., capacitance) was lower in the forearm (P < or = 0.01) and tended to be lower in the calf (P = 0.08) in HTN subjects. Venous compliance was not altered by any perturbation in either group. Forearm volume was increased during NTG in HTN subjects only. While venous compliance was similar between NTN and HTN adults, HTN adults have lower forearm venous capacitance (volume) which is increased with NTG. These data suggest that young HTN adults may have augmented venous smooth muscle tone compared with NTN controls.

Cyclic GMP and protein kinase-G in myocardial ischaemia-reperfusion: opportunities and obstacles for survival signaling

It is clear that multiple signalling pathways regulate the critical balance between cell death and survival in myocardial ischaemia-reperfusion. Recent attention has focused on the activation of survival or salvage kinases, particularly during reperfusion, as a common mechanism of many cardioprotective interventions. The phosphatidyl inositol 3'-hydroxy kinase/Akt complex (PI3K/Akt) and p42/p44 mitogen-activated protein kinase cascades have been widely promoted in this respect but the cyclic guanosine 3',5'-monophosphate/cGMP-dependent protein kinase (cGMP/PKG) signal transduction cassette has been less systematically investigated as a survival cascade. We propose that activation of the cGMP/PKG signalling pathway, following activation of soluble or particulate guanylate cyclases, may play a pivotal role in survival signalling in ischaemia-reperfusion, especially in the classical preconditioning, delayed preconditioning and postconditioning paradigms. The resurgence of interest in reperfusion injury, largely as a result of postconditioning-related research, has confirmed that the cGMP/PKG pathway is a pivotal salvage mechanism in reperfusion. Numerous studies suggest that the infarct-limiting effects of preconditioning and postconditioning, exogenously donated nitric oxide (NO), natriuretic peptides, phosphodiesterase inhibitors, and other diverse drugs and mediators such as HMG co-A reductase inhibitors (statins), Rho-kinase inhibitors and adrenomedullin, whether given before and during ischaemia, or specifically at the onset of reperfusion, may be mediated by activation or enhancement of the cGMP pathway, either directly or indirectly via endogenous NO generation downstream of PI3K/Akt. Putative mechanisms of protection include PKG regulation of Ca(2+) homeostasis through the modification of sarcoplasmic reticulum Ca(2+) uptake mechanisms, and PKG-induced opening of ATP-sensitive K(+) channels during ischaemia and/or reperfusion. At present, significant technical obstacles in defining the precise roles played by cGMP/PKG signalling include the heavy reliance on pharmacological PKG inhibitors of uncertain selectivity, difficulties in determining PKG activity in intact tissue, and the growing recognition that intracellular compartmentalisation of the cGMP pool may contribute markedly to the nucleotide's biological actions and biochemical determination. Overall, the body of experimental evidence suggests that cGMP/PKG survival signalling ameliorates irreversible injury associated with ischaemia-reperfusion and may be a tractable therapeutic target.

Effects of distension of urinary bladder on coronary conduit and resistance vessels in hyperlipidemic patients

BACKGROUND

Distension of the urinary bladder reflexly causes a change of coronary vasomotor response. The effect of such distension on the coronary circulation in hyperlipidemic patients, a condition with impaired endothelial function, remains unknown.

HYPOTHESIS

We tested the hypothesis whether urinary bladder distension caused an exaggerated vasomotor response of epicardial and resistance vasoconstriction in hyperlipidemic patients.

METHODS

Thirty patients with early atherosclerosis (< 50% diameter stenosis) were divided into three groups: Group 1 (n = 10): hyperlipidemia without doxazosin administration; Group 2 (n = 10): hyperlipidemia with pretreatment of alpha1-adrenergic receptor blocker (oral doxazosin 2 mg); and Group 3 (n = 10): normolipidemia. A prospective analysis of the results of quantitative angiograms, intracoronary Doppler flow, and lactate concentrations from aortic root and coronary sinus was performed during distension of urinary bladder.

RESULTS

Bladder distension significantly decreased coronary diameter at the stenotic segments (p = 0.004), coronary blood flow (p = 0.05), and increased coronary resistance (p = 0.006) compared with baseline values, in Group 1 patients. In Group 2 patients during bladder distension, coronary diameter, coronary blood flow, and coronary resistance showed no significant changes compared with baseline values. There were significant differences of stenotic coronary diameter (p = 0.01) between Groups 1 and 3 during bladder distension despite similar changes in rate-pressure product. No significant differences were noted among the groups in the responses of coronary diameter, coronary blood flow, and coronary resistance after nitroglycerin administration.

CONCLUSIONS

The present study showed that urinary bladder distension caused an abnormal vasomotor response of epicardial vasoconstriction and that a concomitant increased coronary resistance involved mechanisms related to alpha1-adrenoceptors. Hyperlipidemia may further impair the response. Pretreated administration of doxazosin had reversed the changes toward baseline. Vasoconstriction during bladder distension can be relieved after nitroglycerin administration, suggesting an unchanged responsiveness of vascular smooth muscle cells to such distension.

Preservation of platelet responsiveness to nitroglycerine despite development of vascular nitrate tolerance

AIMS

Organic nitrates, via nitric oxide (NO) release, induce vasodilatation and inhibit platelet aggregation. Development of nitrate tolerance in some vascular preparations may be associated with diminished responsiveness to NO. To date it is not known to what extent vascular tolerance to organic nitrates is associated with acquired platelet hypo-responsiveness to NO. In the current study we compared the acute and chronic effects of sustained release (SR) isosorbide 5' mono-nitrate (ISMN) and transdermal nitroglycerine (TD-NTG) on blood vessels (effects on apparent arterial stiffness) and platelets (effects on responsiveness to NO donors) in patients with stable angina pectoris (SAP).

METHODS

Patients (n = 34) with SAP entered a blinded randomized crossover study of ISMN (120 mg) vs. intermittent TD-NTG (15 mg 24 h(-1)). Effects of each nitrate on pulse wave reflection (augmentation index (AIx)), platelet response to adenosine di-phosphate (ADP 1 micromol l(-1)), nitroglycerine (NTG 100 micromol l(-1)) and the non-nitrate NO donor sodium nitroprusside (SNP 10 micromol l(-1)), were measured pre-dose, 4 and 8 h post dose, on three occasions: 1) at the end of a pre-nitrate phase, 2) after dosing for 7 days and 3) following 14 days of full dose therapy with either nitrate.

RESULTS

Acutely, both ISMN and TD-NTG markedly reduced AIx. After 14 days, these effects were significantly attenuated (ANOVA, P = 0.018) but not abolished, indicating development of nitrate tolerance. Neither nitrate preparation affected ADP (1 micromol l(-1))-induced platelet aggregation. Platelet responsiveness to NTG (100 micromol l(-1)) and SNP (10 micromol l(-1)) was not diminished during chronic nitrate therapy, and there was no evidence of 'rebound' hyper-aggregability during 'nitrate-free' periods.

CONCLUSIONS

Chronic therapy with either ISMN or TD-NTG is associated with development of vascular tolerance. Despite the induction of vascular tolerance, platelet responsiveness to NTG and SNP remains unaffected. Therefore, development of vascular tolerance is unlikely to compromise the anti-aggregatory effects of organic nitrates, or those of endogenous NO.

Nitroglycerin reduces myocardial oxygen consumption during exercise despite vascular tolerance

The long-term benefits of nitroglycerin (NTG) therapy are limited by the development of vascular tolerance and endothelial dysfunction in conductance coronary arteries. We have determined whether nitrate tolerance extends to NTG effects on myocardial O2 consumption (MV̇o2) and the ability of endogenous nitric oxide (NO) to modulate MV̇o2 during exercise. In chronically instrumented dogs ( n = 8), hemodynamic and MV̇o2 responses to treadmill exercise were measured before, during tolerance (3 and 7 days of NTG delivery), and 7 days after NTG withdrawal. Acute NTG delivery caused a parallel downward shift of the MV̇o2-triple product (TP) relations and reversed the disproportionate increases in MV̇o2 caused by the blockade of NO formation. After 7 days of continuous transdermal NTG delivery, vascular tolerance was displayed as a >75% reduction of coronary blood flow (CBF) responses to NTG boluses. Despite vascular nitrate tolerance, MV̇o2-TP relations were shifted downward compared with pre-NTG exercise. Seven days after NTG withdrawal, vascular responses to boluses of NTG had recovered from tolerance, and MV̇o2-TP relations during exercise were back to pre-NTG level. At that time, blockade of NO formation failed to alter MV̇o2-TP relations. Thus NTG caused a sustained reduction of cardiac MV̇o2, independent of metabolic demand during exercise, despite tolerance of the coronary microcirculation. NTG-induced vascular tolerance and MV̇o2 reductions were reversible by NTG withdrawal, but endogenous NO-dependent modulation of O2 consumption was severely impaired.

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.

Acute Congestive Heart Failure in the Emergency Department

Acute heart failure and cardiogenic pulmonary edema is a common cause of respiratory distress among patients presenting to the emergency department. The emergency department is frequently the primary entry point into the health care system for these patients and is the site of initial stabilization, evaluation, and management of the patient.Emergency physicians, alongside cardiologists, play a critical role as these patients are treated in the emergency department and transferred to the cardiac ICU. The approach to the critically ill patient who has heart failure should be multidisciplinary and involve the emergency physician and the cardiologist who will care for the patient.