Abnormal flow-mediated epicardial vasomotion in human coronary arteries is improved by angiotensin-converting enzyme inhibition: a potential role of bradykinin

Interplay of Angiotensin Peptides, Vasopressin, and Insulin in the Heart: Experimental and Clinical Evidence of Altered Interactions in Obesity and Diabetes Mellitus

The present review draws attention to the specific role of angiotensin peptides [angiotensin II (Ang II), angiotensin-(1-7) (Ang-(1-7)], vasopressin (AVP), and insulin in the regulation of the coronary blood flow and cardiac contractions. The interactions of angiotensin peptides, AVP, and insulin in the heart and in the brain are also discussed. The intracardiac production and the supply of angiotensin peptides and AVP from the systemic circulation enable their easy access to the coronary vessels and the cardiomyocytes. Coronary vessels and cardiomyocytes are furnished with AT1 receptors, AT2 receptors, Ang (1-7) receptors, vasopressin V1 receptors, and insulin receptor substrates. The presence of some of these molecules in the same cells creates good conditions for their interaction at the signaling level. The broad spectrum of actions allows for the engagement of angiotensin peptides, AVP, and insulin in the regulation of the most vital cardiac processes, including (1) cardiac tissue oxygenation, energy production, and metabolism; (2) the generation of the other cardiovascular compounds, such as nitric oxide, bradykinin (Bk), and endothelin; and (3) the regulation of cardiac work by the autonomic nervous system and the cardiovascular neurons of the brain. Multiple experimental studies and clinical observations show that the interactions of Ang II, Ang(1-7), AVP, and insulin in the heart and in the brain are markedly altered during heart failure, hypertension, obesity, and diabetes mellitus, especially when these diseases coexist. A survey of the literature presented in the review provides evidence for the belief that very individualized treatment, including interactions of angiotensins and vasopressin with insulin, should be applied in patients suffering from both the cardiovascular and metabolic diseases.

Sustained Activation of CLR/RAMP Receptors by Gel-Forming Agonists

Background: Adrenomedullin (ADM), adrenomedullin 2 (ADM2), and CGRP family peptides are important regulators of vascular vasotone and integrity, neurotransmission, and fetoplacental development. These peptides signal through CLR/RAMP1, 2, and 3 receptors, and protect against endothelial dysfunction in disease models. As such, CLR/RAMP receptor agonists are considered important therapeutic candidates for various diseases. Methods and Results: Based on the screening of a series of palmitoylated chimeric ADM/ADM2 analogs, we demonstrated a combination of lipidation and accommodating motifs at the hinge region of select peptides is important for gaining an enhanced receptor-activation activity and improved stimulatory effects on the proliferation and survival of human lymphatic endothelial cells when compared to wild-type peptides. In addition, by serendipity, we found that select palmitoylated analogs self-assemble to form liquid gels, and subcutaneous administration of an analog gel led to the sustained presence of the peptide in the circulation for >2 days. Consistently, subcutaneous injection of the analog gel significantly reduced the blood pressure in SHR rats and increased vasodilation in the hindlimbs of adult rats for days. Conclusions: Together, these data suggest gel-forming adrenomedullin analogs may represent promising candidates for the treatment of various life-threatening endothelial dysfunction-associated diseases such as treatment-resistant hypertension and preeclampsia, which are in urgent need of an effective drug.

Impact of Antihypertensive Drug Class on Outcomes in the SPRINT

BACKGROUND

The primary objective of this analysis is to assess if greater exposure to any major antihypertensive drug class was associated with reduced primary composite outcome events in SPRINT (Systolic Blood Pressure Intervention Trial).

METHODS

This is a secondary analysis of the SPRINT trial evaluating whether longitudinal, time varying exposure to any major antihypertensive drug class had any impact on primary outcome events, after adjusting for effects of randomization arm, time varying achieved systolic blood pressure, other drug class exposure, and baseline characteristics.

RESULTS

Nine thousand two hundred fifty-two participants were included. After adjustments, exposure of one year or greater to thiazide-type diuretics or renin-angiotensin system blockers was associated with significantly fewer primary events than exposure of less than one year (hazard ratio, 0.78 [95% CI, 0.64-0.94]). There was no significant difference with longer versus shorter exposure to calcium channel blockers. Greater exposure to beta-blockers was associated with an increase in primary events compared with exposure of <1 year (hazard ratio, 1.35 [95% CI, 1.13-1.62]). Furthermore, thiazide-type diuretics were associated with a reduction in heart failure events and renin-angiotensin system blockers with reduced myocardial infarction. Both were associated with less cardiovascular deaths.

CONCLUSIONS

The SPRINT trial demonstrated a lower target blood pressure led to reductions in adverse cardiovascular events. This analysis suggests greater exposure to thiazide-type diuretics and renin-angiotensin system blockers also contributed to reduced adverse cardiovascular events. Greater exposure to beta-blockers was associated with increased cardiovascular events.

Reducing Cardiac Injury during ST-Elevation Myocardial Infarction: A Reasoned Approach to a Multitarget Therapeutic Strategy

The significant reduction in ‘ischemic time’ through capillary diffusion of primary percutaneous intervention (pPCI) has rendered myocardial-ischemia reperfusion injury (MIRI) prevention a major issue in order to improve the prognosis of ST elevation myocardial infarction (STEMI) patients. In fact, while the ischemic damage increases with the severity and the duration of blood flow reduction, reperfusion injury reaches its maximum with a moderate amount of ischemic injury. MIRI leads to the development of post-STEMI left ventricular remodeling (post-STEMI LVR), thereby increasing the risk of arrhythmias and heart failure. Single pharmacological and mechanical interventions have shown some benefits, but have not satisfactorily reduced mortality. Therefore, a multitarget therapeutic strategy is needed, but no univocal indications have come from the clinical trials performed so far. On the basis of the results of the consistent clinical studies analyzed in this review, we try to design a randomized clinical trial aimed at evaluating the effects of a reasoned multitarget therapeutic strategy on the prevention of post-STEMI LVR. In fact, we believe that the correct timing of pharmacological and mechanical intervention application, according to their specific ability to interfere with survival pathways, may significantly reduce the incidence of post-STEMI LVR and thus improve patient prognosis.

Underlying Genes Involved in Atherosclerotic Macrophages: Insights from Microarray Data Mining

Background

In an atherosclerotic artery wall, monocyte-derived macrophages are the principal mediators that respond to pathogens and inflammation. The present study aimed to investigate potential genetic changes in gene expression between normal tissue-resident macrophages and atherosclerotic macrophages in the human body.

Material/Methods

The expression profile data of GSE7074 acquired from the Gene Expression Omnibus (GEO) database, which includes the transcriptome of 4 types of macrophages, was downloaded. Differentially expressed genes (DEGs) were identified using R software, then we performed functional enrichment, protein-protein interaction (PPI) network construction, key node and module analysis, and prediction of microRNAs (miRNAs)/transcription factors (TFs) targeting genes.

Results

After data processing, 236 DEGs were identified, including 21 upregulated genes and 215 downregulated genes. The DEG set was enriched in 22 significant Gene Ontology (GO) terms and 25 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and the PPI network constructed with these DEGs comprised 6 key nodes with degrees ≥8. Key nodes in the PPI network and simultaneously involved in the prime modules, including rhodopsin (RHO), coagulation factor V (F5), and bestrophin-1 (BEST1), are promising for the prediction of atherosclerotic plaque formation. Furthermore, in the miRNA/TF-target network, hsa-miR-3177-5p might be involved in the pathogenesis of atherosclerosis via regulating BEST1, and the transcription factor early growth response-1 (EGR1) was found to be a potential promoter in atherogenesis.

Conclusions

The identified key hub genes, predicted miRNAs/TFs, and underlying molecular mechanisms may be involved in atherogenesis, thus potentially contributing to the treatment and diagnosis of patients with atherosclerotic disease.

Peripheral Microvascular Function Reflects Coronary Vascular Function

Objectives- Coronary endothelial dysfunction is a precursor of atherosclerosis and adverse outcomes. Whether endothelial dysfunction is a localized or generalized phenomenon in humans remains uncertain. We simultaneously measured femoral and coronary vascular function with the hypothesis that peripheral vascular endothelial function will be reflective of coronary endothelial function. Approach and Results- Eighty-five subjects underwent coronary angiography for evaluation of chest pain or abnormal stress tests. Endothelium-dependent and -independent vascular function were measured using intracoronary and intrafemoral infusions of acetylcholine and sodium nitroprusside, respectively. Coronary flow reserve was assessed using intracoronary adenosine infusion. Flow velocity was measured in each circulation using a Doppler wire (FloWire, EndoSonics). Coronary vascular resistance and femoral vascular resistance were calculated as mean arterial pressure (mm Hg)/coronary blood flow (mL/min) and mean arterial pressure (mm Hg)/femoral average peak velocity (cm/s), respectively. Mean age was 53±11 years, 37% were female, 44% had hypertension, 12% had diabetes mellitus, and 38% had obstructive coronary artery disease. There was a correlation between the change in femoral vascular resistance with acetylcholine and acetylcholine-mediated changes in both the coronary vascular resistance ( r=0.27; P=0.014) and in the epicardial coronary artery diameter ( r=-0.25; P=0.021), indicating that subjects with normal endothelial function in the femoral circulation had normal endothelial function in the coronary epicardial and microcirculation and vice versa. The coronary vasodilator response to adenosine also correlated with the femoral vasodilatation with acetylcholine ( r=0.4; P=0.0002). There was no correlation between the coronary and femoral responses to sodium nitroprusside. Conclusions- Endothelial functional changes in the peripheral and coronary circulations were modestly correlated. Thus, peripheral microvascular endothelial function reflects endothelium-dependent coronary epicardial and microvascular function and the coronary flow reserve. Visual Overview- An online visual overview is available for this article.

Kallikrein-kinin system as the dominant mechanism to counteract hyperactive renin-angiotensin system

The renin-angiotensin system (RAS) generates, maintains, and makes worse hypertension and cardiovascular diseases (CVDs) through its biologically active component angiotensin II (Ang II), that causes vasoconstriction, sodium retention, and structural alterations of the heart and the arteries. A few endogenous vasodilators, kinins, natriuretic peptides, and possibly angiotensin (1-7), exert opposite actions and may provide useful therapeutic agents. As endothelial autacoids, the kinins are potent vasodilators, active natriuretics, and protectors of the endothelium. Indeed, the kallikrein-kinin system (KKS) is considered the dominant mechanism for counteracting the detrimental effects of the hyperactive RAS. The 2 systems, RAS and KKS, are controlled by the angiotensin-converting enzyme (ACE) that generates Ang II and inactivates the kinins. Inhibitors of ACE can reduce the impact of Ang II and potentiate the kinins, thus contributing to restore the cardiovascular homeostasis. In the last 20 years, ACE-inhibitors (ACE-Is) have become the drugs of first choice for the treatments of the major CVDs. ACE-Is not only reduce blood pressure, as sartans also do, but by protecting and potentiating the kinins, they can reduce morbidity and mortality and improve the quality of life for patients with CVDs. This paper provides a brief review of the literature on this topic.

High Angiotensin II Responsiveness is Associated with Decreased Endothelium-Dependent Relaxation in Human Arteries

Introduction. Animal studies demonstrated an interaction between angiotensin II (Ang II) responsiveness and endothelium-dependent relaxation (EDR). However, this relation has not been well described in humans. Therefore, we investigated the relation between Ang II responsiveness and EDR in isolated human arteries.

Materials and Methods. Segments of the internal mammary artery (IMA) were harvested from 89 patients undergoing coronary bypass surgery. Rings of these segments were exposed in organ bath experiments to metacholine (ME; 10 nmol/L -0.1 mmol/L) after precontraction with phenylephrine (PE; 10 µmol/L), and secondly to increasing concentrations of Ang II (0.1 nmol/L —1 µmol/L).

Results. Patients with the highest contraction to Ang II showed the lowest ME relaxation (r=0.312; p=0.003). Angiotensin-converting enzyme (ACE)-inhibition significantly increased Ang II sensitivity (p=0.03). This increase was accompanied by a tendency toward decreased EDR (p=0.07). The inverse relation between Ang responsiveness and endotheliumdependent relaxation could not be explained by an increased tissue or serum ACE-inhibition in patients with a higher endothelium-dependent relaxation.

Conclusions. High Ang II responsiveness inversely correlates to EDR in IMA's of patients with established coronary artery disease. Short-term treatment with an ACE-inhibitor increased the response to Ang II, but had an adverse effect on EDR.

Myocardial ischemia and angiotensin-converting enzyme inhibition: comparison of ischemia during mental and physical stress

OBJECTIVE

Mental stress provokes myocardial ischemia in many patients with stable coronary artery disease (CAD). Mental stress-induced myocardial ischemia (MSIMI) portends a worse prognosis, independent of standard cardiac risk factors or outcome of traditional physical stress testing. Angiotensin II plays a significant role in the physiological response to stress, but its role in MSIMI remains unknown. Our aim was to evaluate whether the use of angiotensin-converting enzyme inhibitors (ACEIs) is associated with a differential effect on the incidence of MSIMI compared with ischemia during physical stress.

METHODS

Retrospective analysis of 218 patients with stable CAD, including 110 on ACEI, was performed. 99m-Tc-sestamibi myocardial perfusion imaging was used to define ischemia during mental stress, induced by a standardized public speaking task, and during physical stress, induced by either exercise or adenosine.

RESULTS

Overall, 40 patients (18%) developed MSIMI and 80 patients (37%) developed ischemia during physical stress. MSIMI occurred less frequently in patients receiving ACEIs (13%) compared with those not on ACEIs (24%; p = .030, adjusted odds ratio = 0.42, 95% confidence interval = 0.19-0.91). In contrast, the frequency of myocardial ischemia during physical stress testing was similar in both groups (39% versus 35% in those on and not on ACEIs, respectively); adjusted odds ratio = 0.91, 95% confidence interval = 0.48-1.73).

CONCLUSION

In this retrospective study, patients using ACEI therapy displayed less than half the risk of developing ischemia during mental stress but not physical stress. This possible beneficial effect of ACEIs on MSIMI may be contributing to their salutary effects in CAD.

Intracoronary EnalaPrilat to Reduce MICROvascular Damage During Percutaneous Coronary Intervention (ProMicro) study

OBJECTIVES

This study investigated the influence of intracoronary enalaprilat on coronary microvascular function and peri-procedural outcome measures in patients with stable angina undergoing percutaneous coronary intervention (PCI).

BACKGROUND

Intracoronary angiotensin-converting enzyme inhibitors have been shown to relieve myocardial ischemia in stable patients and to improve epicardial flow in patients with ST-segment elevation myocardial infarction. Yet, it is still unclear whether these effects are mediated by a modulation of the coronary microcirculation.

METHODS

We randomly assigned 40 patients to receive either an intracoronary bolus of enalaprilat (50 μg) or placebo before elective PCI. The index of microvascular resistance was measured at baseline, 10 minutes after study drug administration, and after PCI. High-sensitivity cardiac troponin T was measured as a marker of myocardial injury.

RESULTS

Infusion of enalaprilat resulted in a significant reduction in index of microvascular resistance (27 ± 11 at baseline vs. 19 ± 9 after drug vs. 15 ± 8 after PCI), whereas a significant post-procedural increase in index of microvascular resistance levels was observed in the placebo group (24 ± 15 at baseline vs. 24 ± 15 after drug vs. 33 ± 19 after PCI). Index of microvascular resistance levels after PCI were significantly lower in the enalaprilat group (p < 0.001). Patients pre-treated with enalaprilat also showed lower peak values (mean: 21.7 ng/ml, range: 8.2 to 34.8 ng/ml vs. mean: 32.3 ng/ml, range: 12.6 to 65.2 ng/ml, p = 0.048) and peri-procedural increases of high-sensitivity cardiac troponin T (mean: 9.9 ng/ml, range: 2.7 to 19.0 ng/ml vs. mean: 26.6 ng/ml, range: 6.3 to 60.5 ng/ml, p = 0.025).

CONCLUSIONS

Intracoronary enalaprilat improves coronary microvascular function and protects myocardium from procedure-related injury in patients with coronary artery disease undergoing PCI. Larger studies are warranted to investigate whether these effects of enalaprilat could result into a significant clinical benefit.

Vascular endothelial function and hypertension: insights and directions

Hypertension contributes significantly to worldwide cardiovascular morbidity and mortality. Hypertension appears to have a complex association with endothelial dysfunction, a phenotypical alteration of the vascular endothelium that precedes the development of adverse cardiovascular events and portends future cardiovascular risk. This review concentrates on recent findings with respect to the mechanisms of hypertension-associated endothelial dysfunction, the interrelationship between these two entities, and the relationship of the efficacy of antihypertensive therapies to improvements in vascular homeostasis beyond blood pressure reduction. Current evidence suggests that hypertension and endothelial dysfunction are integrally related with respect to pathophysiologic mechanisms. Future studies will need to identify the key connections between hypertension and endothelial dysfunction to allow novel interventions to be designed and promulgated.

Impaired relaxation of cerebral arteries in the absence of elevated salt intake in normotensive congenic rats carrying the Dahl salt-sensitive renin gene

This study evaluated endothelium-dependent vascular relaxation in response to acetylcholine (ACh) in isolated middle cerebral arteries (MCA) from Dahl salt-sensitive (Dahl SS) rats and three different congenic strains that contain a portion of Brown Norway (BN) chromosome 13 introgressed onto the Dahl SS genetic background through marker-assisted breeding. Two of the congenic strains carry a 3.5-Mbp portion and a 2.6-Mbp portion of chromosome 13 that lie on opposite sides of the renin locus, while the third contains a 2.0-Mbp overlapping region that includes the BN renin allele. While maintained on a normal salt (0.4% NaCl) diet, MCAs from Dahl SS rats and the congenic strains retaining the Dahl SS renin allele failed to dilate in response to ACh, whereas MCAs from the congenic strain carrying the BN renin allele exhibited normal vascular relaxation. In congenic rats receiving the BN renin allele, vasodilator responses to ACh were eliminated by nitric oxide synthase inhibition with N(G)-nitro-l-arginine methyl ester, angiotensin-converting enzyme inhibition with captopril, and AT(1) receptor blockade with losartan. N(G)-nitro-l-arginine methyl ester-sensitive vasodilation in response to ACh was restored in MCAs of Dahl SS rats that received either a 3-day infusion of a subpressor dose of angiotensin II (3 ng·kg(-1)·min(-1) iv), or chronic treatment with the superoxide dismutase mimetic tempol (15 mg·kg(-1)·day(-1)). These findings indicate that the presence of the Dahl SS renin allele plays a crucial role in endothelial dysfunction present in the cerebral circulation of the Dahl SS rat, even in the absence of elevated dietary salt intake, and that introgression of the BN renin allele rescues endothelium-dependent vasodilator responses by restoring normal activation of the renin-angiotensin system.

Obesity and vascular dysfunction

One of the most profound challenges facing public health and public health policy in Western society is the increased incidence and prevalence of both overweight and obesity. While this condition can have significant consequences for patient mortality and quality of life, it can be further exacerbated as overweight/obesity can be a powerful stimulus for the development of additional risk factors for a negative cardiovascular outcome, including increased insulin resistance, dyslipidemia and hypertension. This manuscript will present the effects of systemic obesity on broad issues of vascular function in both afflicted human populations and in the most relevant animal models. Among the topics that will be covered are alterations to vascular reactivity (both dilator and constrictor responses), adaptations in microvascular network and vessel wall structure, and alterations to the patterns of tissue/organ perfusion as a result of the progression of the obese condition. Additionally, special attention will be paid to the contribution of chronic inflammation as a contributor to alterations in vascular function, as well as the role of perivascular adipose tissue in terms of impacting vessel behavior. When taken together, it is clearly apparent that the development of the obese condition can have profound, and frequently difficult to predict, impacts on integrated vascular function. Much of this complexity appears to have its basis in the extent to which other co-morbidities associated with obesity (e.g., insulin resistance) are present and exert contributing effects.

Acute EGCG supplementation reverses endothelial dysfunction in patients with coronary artery disease

BACKGROUND

Epidemiological studies demonstrate an inverse relation between dietary flavonoid intake and cardiovascular risk. Recent studies with flavonoid-containing beverages suggest that the benefits of these nutrients may relate, in part, to improved endothelial function.

OBJECTIVE

We hypothesized that dietary supplementation with epigallocatechin gallate (EGCG), a major catechin in tea, would improve endothelial function in humans.

DESIGN

We examined the effects of EGCG on endothelial function in a double blind, placebo-controlled, crossover design study. We measured brachial artery flow-mediated dilation by vascular ultrasound at six time points: prior to treatment with EGCG or placebo, two hours after an initial dose of EGCG (300 mg) or placebo, and after two weeks of treatment with EGCG (150 mg twice daily) or placebo. The order of treatments (EGCG or placebo) was randomized and there was a one-week washout period between treatments.

RESULTS

A total of 42 subjects completed the study, and brachial artery flow-mediated dilation improved from 7.1 +/- 4.1 to 8.6 +/- 4.7% two hours after the first dose of 300 mg of EGCG (P = 0.01), but was similar to baseline (7.8 +/- 4.2%, P = 0.12) after two weeks of treatment with the final measurements made approximately 14 hours after the last dose. Placebo treatment had no significant effect, and there were no changes in reactive hyperemia or the response to sublingual nitroglycerin. The changes in vascular function paralleled plasma EGCG concentrations, which increased from 2.6 +/- 10.9 to 92.8 +/- 78.7 ng/ml after acute EGCG (P < 0.001), but were unchanged from baseline after two weeks of treatment (3.4 +/- 13.1 ng/ml).

CONCLUSION

EGCG acutely improves endothelial function in humans with coronary artery disease, and may account for a portion of the beneficial effects of flavonoid-rich food on endothelial function.

Adjunctive pharmacologic use in carotid endarterectomy: a review

Although carotid endarterectomy (CEA) is now widely accepted as the surgical therapy for carotid stenosis, the role of and indications and evidence for many pharmacologic agents that are used adjunctively in the perioperative setting have not been conclusively established. Aspirin (acetylsalicylic acid) is the pharmaceutical agent that has been studied most extensively in conjunction with CEA; other than aspirin and dextran, the use of many agents before, during, and after CEA has not been standardized. Prospective randomized trials are still needed to demonstrate efficacy, predict outcome, and determine the optimal use of these medications in their adjunctive use during CEA to improve patient care and obtain optimal surgical outcomes.

Optimal Vascular Protection: A Case for Combination Antihypertensive Therapy

Endothelial dysfunction is an important factor in the pathogenesis of atherosclerosis, hypertension, and heart failure. The endothelium mediates vascular tone, structure, and function by the release and regulation of multiple vasoactive substances that promote or inhibit vasodilation, vasoconstriction, cell growth, and other mechanisms. The effect of antihypertensive drugs on endothelial function may be an important indicator of their ability to reduce risks for cardiovascular morbidity and mortality. Endothelium-dependent vasodilation induced by various antihypertensive drugs is accurately measured with high-resolution ultrasound of flow-mediated dilation of the brachial artery. Calcium channel blockers and angiotensin-converting enzyme inhibitors have been shown to reverse endothelial dysfunction. The benefits of angiotensin-converting enzyme inhibitors and calcium channel blockers on the endothelium are believed to derive from their effects on nitric oxide production and antioxidant effects, possibly independent of blood pressure reduction. Due to their complementary mechanisms of action, it has been hypothesized that the combination of an angiotensin-converting enzyme inhibitor and a calcium channel blocker will provide superior cardiovascular protection, in part by producing an additive effect of increased nitric oxide availability, when compared with either agent alone.

The relationship between flow-mediated brachial artery vasodilation and coronary vasomotor responses to bradykinin: comparison with those to acetylcholine

Flow-mediated dilation (FMD) of brachial artery provides a noninvasive assessment of coronary endothelial dysfunction. Acetylcholine (ACh) has been used as an agent for estimating coronary endothelial function. In contrast to ACh, there is no evidence for a relationship between FMD and coronary vasodilation to bradykinin (BK). The aim of this study was to compare the flow-mediated vasodilation of brachial artery with coronary vasomotor responses to intracoronary ACh or BK in patients with an angiographically normal left anterior descending coronary artery. Ninety-one patients underwent the cardiac catheterization examination with coronary endothelial function testing and the brachial ultrasound study. BK (0.2, 0.6, 2.0 microg/min) and ACh (3, 10, 30 microg/min) were administered into the left coronary artery in a stepwise manner. Coronary blood flow was evaluated by the Doppler flow velocity measurement. Coronary diameters were measured by the quantitative coronary angiography. The assessment of endothelial function in the brachial artery was made in response to reactive hyperemia with high-resolution ultrasound. Bradykinin induced dose-dependent increases in epicardial coronary diameter and blood flow. There was a significant positive correlation between FMD- and BK-induced vasodilations of epicardial coronary arteries (0.2 microg/min: r = 0.30; 0.6 microg/min: r = 0.42; 2.0 microg/min: r = 0.44, P < 0.01, respectively) and resistance coronary arteries (0.2 microg/min: r = 0.40; 0.6 microg/min: r = 0.56; 2.0 microg/min: r = 0.59, P < 0.0001, respectively). FMD correlated with ACh-induced vasomotions of resistance but not epicardial coronary arteries. No correlation was seen between nitroglycerin-induced brachial artery vasodilation and BK-induced coronary vasodilation. The endothelial dysfunction of peripheral arteries correlated well with that of the coronary arteries especially vasomotor responses to BK.

Endothelin receptor blockade improves endothelial function in atherosclerotic patients on angiotensin converting enzyme inhibition

OBJECTIVES

Endothelin-1 (ET-1) and angiotensin II may contribute to endothelial dysfunction, which is associated with increased risk of events in patients with coronary artery disease. The objective was to test whether dual ETA/ETB receptor antagonism improves endothelium-dependent vasodilatation (EDV) in atherosclerotic patients, also on treatment with angiotensin converting enzyme (ACE) inhibitor.

DESIGN AND SETTING

EDV and endothelium-independent vasodilatation were determined in 37 patients with atherosclerosis during measurement of forearm blood flow (FBF) with venous occlusion plethysmography. The patients were then randomized to treatment with ramipril 10 mg o.d. (n=21) or placebo (n=16) for 3 months in a double-blind fashion.

RESULTS

Intra-arterial infusion of the ETA receptor antagonist BQ123 and the ETB receptor antagonist BQ788 (both 10 nmol min(-1)) increased basal FBF by 42 +/- 4% (P <0.001) and enhanced EDV (P <0.001). Following 3 months ramipril treatment, ET receptor blockade still enhanced EDV. Acetylcholine 10 and 30 mg min(-1) increased FBF by 68 +/- 12 and 64 +/- 12 mL min(-1)/1000 mL before vs. 101 +/- 17 and 101 +/- 16 mL min(-1)/1000 mL following ET receptor blockade in the ramipril group (P <0.001).

CONCLUSIONS

Dual ETA/ETB receptor blockade improves endothelial function and exerts direct vasodilator effects in patients with atherosclerosis, also on treatment with ramipril suggesting that ET receptor blockade may have important therapeutic effects when added to ACE inhibition in these patients.

Cathepsin G is associated with atheroma formation in human carotid artery

OBJECTIVE

To elucidate the organization of the tissue angiotensin system, we investigated the expression and cellular localization of angiotensin system components and cathepsins D and G, potentially involved in intraparietal angiotensin II formation and atheroma.

METHODS

Total RNA was extracted from atheroma plaque, fatty streaks and macroscopically intact tissue obtained during carotid endarterectomy in 21 hypertensive patients. mRNA levels were compared between these tissues using a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). In situ hybridization and immunohistochemistry were used to define the cellular localization of the transcripts and their respective proteins.

RESULTS

Apart from renin and angiotensin type 2 (AT2) receptors, which were never detected, the studied mRNAs could be measured in all patients. Angiotensin-converting enzyme (ACE) mRNA was increased five-fold in atheroma, and angiotensin type 1 receptor (AT1) mRNA decreased 2.5-fold in atheroma and 1.4-fold in fatty streaks compared to intact tissue. A two-fold increase in cathepsin G mRNA was observed in atheroma plaque. In atheroma and intact tissue, significant positive correlations were found between cathepsin G and angiotensinogen, AT1 receptor and ACE mRNAs. Angiotensinogen and cathepsin mRNAs and proteins were detected in both arterial layers. AT1 immunoreactivity was mainly associated with alpha-actin-positive cells.

CONCLUSION

All components required for angiotensin II formation are expressed locally in the arterial wall, where, in the absence of renin, cathepsin G could be a major angiotensin-generating enzyme. Overexpression of ACE and cathepsin G may lead to angiotensin II overproduction and contribute, with decreased number of differentiated smooth muscle cells, to the lower amount of AT1 receptor in atheroma.

Beneficial effects of quinaprilat on coronary vasomotor function, endothelial oxidative stress, and endothelin activation after human heart transplantation

BACKGROUND

We evaluated the potential of angiotensin-converting enzyme inhibition (ACEI) to modulate resting coronary vasomotor tone and endothelial dysfunction, and to decrease vascular oxidative stress and endothelin (ET)-1 activity in human heart transplant recipients.

METHODS

Coronary vasomotor responses and transcardiac metabolism of glutathione, oxidized glutathione, and ET-1 were determined before and after quinaprilat infusion in 32 heart transplant recipients. Furthermore, the potential effects of ACEI on endothelial oxidative stress, ET-1 activity, and nitrosoglutathione formation were investigated using endothelial cell cultures.

RESULTS

Epicardial diameter increased in response to quinaprilat by 6% +/- 1% (proximal segments; P<0.05) and 14% +/- 3% (distal segments; P<0.01). Coronary flow velocity increased by 2.2 +/- 0.2 (P<0.03). Coronary vasodilation to quinaprilat was negatively correlated with preexisting functional and structural coronary alterations. Quinaprilat selectively improved epicardial vasomotor response in segments with endothelial dysfunction, whereas microvascular endothelial dysfunction was unchanged. Transcardiac glutathione and big ET levels decreased after quinaprilat, whereas oxidized glutathione and ET-1 concentrations remained unchanged. Cell culture studies showed antioxidative effects of quinaprilat, revealed concentration-dependent down-regulation of endothelial ET-1 release, and indicated formation of nitrosoglutathione by quinaprilat. CONCLUSION.: ACE regulates resting coronary vasomotor tone. Quinaprilat reduces vascular oxidative stress and ET-1 activity and mediates formation of nitrosoglutathione, effects that might contribute to long-term vasculoprotective effects of ACEI after heart transplantation.

Chronic infusion of bradykinin delays the progression of heart failure and preserves vascular endothelium-mediated vasodilation in conscious dogs

BACKGROUND

This study examined the effects of chronic bradykinin infusion on hemodynamics and myocardial and endothelial functions during the development of heart failure.

METHODS AND RESULTS

Sixteen instrumented dogs were randomized to receive through the left atria either vehicle or bradykinin (1 microg/min) during ventricular pacing (250 bpm, 5 weeks). Hemodynamic and left ventricular (LV) parameters and the vasodilator responses to intravenous acetylcholine (0.3 to 3 microg/kg) and nitroglycerin (1 to 10 microg/kg) were examined in the control and after 3 and 5 weeks of pacing. The expression of endothelial NOS in femoral, carotid, and renal arteries was determined by Western blot analysis. After 3 weeks of pacing, changes in LV diastolic and systolic parameters were significantly lower in bradykinin-treated than vehicle-treated dogs (LV end-diastolic pressure, +10+/-3 versus +19+/-2 mm Hg; time constant of LV isovolumic relaxation, +11+/-2 versus +17+/-1 ms; LV wall thickening, -33+/-18% versus -75+/-9%; and cardiac output, -16+/-6% versus -32+/-6%; all P<0.05). Compared with vehicle-treated dogs, bradykinin-treated dogs had a reduced rightward shift of the diastolic LV pressure-diameter relation and a reduced diastolic LV wall stress. Similar trends were observed after 5 weeks. The vasodilator response to nitroglycerin was preserved in both groups. The response to acetylcholine was blunted in vehicle-treated but preserved in bradykinin-treated dogs. Vascular endothelial NOS expression decreased in vehicle-treated but was preserved in bradykinin-treated dogs.

CONCLUSIONS

In conscious dogs, chronic bradykinin infusion delays the heart failure progression by preserving LV diastolic and systolic functions and by preserving vascular endothelial function.

The clinical implications of endothelial dysfunction

Defining new approaches for the prevention and treatment of atherosclerosis is an important priority. Recently, measurement of endothelial function in patients has emerged as a useful tool for atherosclerosis research. Risk factors are associated with impaired endothelial function, and clinical syndromes relate, in part, to a loss of endothelial control of vascular homeostasis. Recent studies have shown that the severity of endothelial dysfunction relates to cardiovascular risk. A growing number of interventions known to reduce cardiovascular risk have been shown to improve endothelial function. This work suggests that studies of endothelial function could be used in the care of patients and as a surrogate marker for the evaluation of new therapeutic strategies. This article will review this growing literature in an effort to evaluate the current clinical utility of endothelial dysfunction.

ACE inhibition may decrease diabetes risk by boosting the impact of bradykinin on adipocytes

The findings of the recent HOPE trial strongly suggest that ACE inhibitor therapy may reduce risk for type 2 diabetes in patients who are non-diabetic at baseline. This finding is readily rationalized by previous evidence that bradykinin, acting via B2 receptors, can potentiate the insulin responsiveness of both adipocytes and muscle fibers; this effect may be mediated by a reduction in the activity of a tyrosine phosphatase that targets the insulin receptor. ACE inhibitors, in turn, increase the availability of bradykinin by suppressing its proteolytic degradation. In light of the fact that the development of insulin resistance in adipocytes is responsible for the excessive free fatty acid flux that gives rise to the diabetic syndrome, a favorable impact of ACE inhibition on adipocyte insulin responsiveness - complemented by a potentiation of the direct action of bradykinin on skeletal muscle - offers a satisfying explanation for the prevention of diabetes observed during ACE inhibitor therapy. Since the population at risk for diabetes is huge and increasing dramatically, the recent development of orally absorbable food-derived peptides with clinically significant ACE inhibitory activity - such as 'Katsuobushi oligopeptides' derived from bonito - may make it more logistically feasible to achieve this protection on a widescale basis, while simultaneously promoting blood pressure control and reducing risk for atherothrombotic disease.

AT1-receptor antagonism improves endothelial function in coronary artery disease by a bradykinin/B2-receptor-dependent mechanism

Impaired flow-dependent, endothelium-mediated vasodilation is an early finding in patients with coronary artery disease (CAD). Experimental and some clinical studies observed that angiotensin type-1 receptor antagonists (AT1A) enhance endothelium-dependent relaxation in CAD. The present study was designed to determine whether AT1A improves flow-dependent dilation (FDD) in patients with CAD and, if so, whether bradykinin and NO are involved. High-resolution ultrasound was used to measure radial artery diameter at rest and during reactive hyperemia, causing endothelium-mediated vasodilation. Twenty patients with CAD were randomly assigned to receive intrabrachial infusion of candesartan (800 microg/min) with and without icatibant, a bradykinin B2-receptor antagonist (90 microg/min; group A) or N-monomethyl-l-arginine (L-NMMA), an NO-synthase inhibitor (7 micromol/min; group B). The AT1A candesartan improved FDD by >40%, an effect that was inhibited by icatibant (group A: control, 7.3+/-0.9; candesartan, 10.3+/-1.1; candesartan+icatibant, 5.0+/-0.5%). Similarly, L-NMMA blunted the beneficial effect of candesartan (group B: control, 6.3+/-0.6; candesartan, 8.9+/-0.6; candesartan+L-NMMA: 4.7+/-0.5%; each P<0.01). The angiotensin type-1 receptor antagonist candesartan improves flow-dependent, endothelium-mediated vasodilation in patients with CAD. This effect is inhibited by either icatibant and or L-NMMA, suggesting that both bradykinin and NO contribute to the vascular effects of AT1-receptor antagonists in this patient population.

Risk assessment by myocardial perfusion imaging for coronary revascularization, medical therapy, and noncardiac surgery

Stress myocardial perfusion imaging (MPI) has become an important tool in risk stratification of patients with known coronary artery disease. A normal myocardial perfusion scan has a high negative predictive value and is associated with low annual mortality rate (< 1%). Patients with extensive ischemia (> 20% of the left ventricle), defects in more than 1 coronary vascular territory, transient or persistent left ventricular cavity dilation, and ejection fraction less than 45% have a high annual mortality rate (> 3%). Those patients should undergo coronary revascularization whenever feasible, as the cardiac event rate increases in proportion to the magnitude of the jeopardized myocardium. Stress MPI can be used to demonstrate ischemia in patients with symptoms early after coronary artery bypass surgery (< 5 years) or in those without symptoms late (>/= 5 years) after coronary artery bypass surgery. With respect to patients who underwent percutaneous interventions, stress MPI can help detect in-stent restenosis early after the intervention (3-6 months) or assess the progression of native coronary disease afterward. Since preliminary data suggest that a reduction in the perfusion defect size may translate to a reduction of coronary events, stress MPI can help assess the efficacy of medical management of coronary disease. Finally, stress MPI is indicated for perioperative cardiac risk stratification for noncardiac surgery in patients with intermediate risk predictors (mild angina, prior myocardial infarction or heart failure symptoms, diabetes mellitus, renal insufficiency) and poor functional capacity or in those who undergo high-risk surgery with significant implications in further preoperative management.

The L-arginine-nitric oxide pathway in hypertension

Nitric oxide is involved in the regulation of resting vascular tone, adaptation of blood flow to metabolic demand of tissue, and adaptation of vessel diameter to volume of inflow, ie, flow-mediated dilation. Arterial hypertension is associated with an increased vascular tone of resistance vessels, a reduced compliance of conduit arteries, along with a thickening of the intima-media leading to vascular remodeling. Dysfunctional endothelium triggers such maladaptive processes. A reduced bioavailability of nitric oxide has been shown in hypertensive individuals dependent on the duration and severity of arterial hypertension. Angiotensin-converting enzyme inhibitors reverse endothelial dysfunction, whereas a concomitant reduction in significant cardiac events due to improved bioavailability has yet to be established. Long-term follow-up studies in individuals with manifest endothelial dysfunction and in offspring from hypertensive patients underscore the prognostic and genetic significance of a reduced nitric oxide bioavailability for the pathophysiology of arterial hypertension.

Coronary vasodilation and improvement in endothelial dysfunction with endothelin ET(A) receptor blockade

The endothelium-derived peptide endothelin-1 (ET-1) causes vasoconstriction predominantly via smooth muscle ET(A) receptor activation. We hypothesized that ET(A) receptor inhibition would improve human coronary vascular function. We studied unobstructed coronary arteries of 44 patients with atherosclerosis or its risk factors. Epicardial diameter (D) and Doppler flow velocity were measured, and coronary vascular resistance (CVR) was calculated during intracoronary infusions of acetylcholine (ACH) and sodium nitroprusside (SNP), and during cold pressor testing, before and after a 60-minute intracoronary infusion of the ET(A) receptor antagonist BQ-123. BQ-123 dilated the coronary circulation; D increased by 5.6+/-1.0% (P<0.0001), and CVR fell by 12+/-3% (P<0.01). The D response to ACH, corrected for the SNP response, improved in segments that constricted with ACH at baseline (P=0.03), whereas segments that initially dilated with ACH did not change with BQ-123 (P=NS). Improvement in D and CVR responses to ACH with BQ-123 inversely correlated with baseline ACH responses (r=-0.44 [P=0.006] and r=-0.78 [P=0.001], respectively), indicating greater improvement in those with endothelial dysfunction. Similarly, cold pressor testing-mediated epicardial vasoconstriction (-2.0+/-1.1%) was reversed after BQ-123 (+1.0+/-0.7%), especially in dysfunctional segments (from -5.6+/-0.9% to +2.2+/-0.9%, P<0.001). There was no correlation between any risk factor and the response to BQ-123. An arteriovenous difference in ET-1 levels developed after BQ-123, which was consistent with enhanced cardiac clearance of ET-1, probably via ET(B) receptors. Thus, ET-1 acting via the ET(A) receptor contributes to basal human coronary vasoconstrictor tone and endothelial dysfunction. This suggests that ET(A) receptor antagonism may have therapeutic potential in the treatment of endothelial dysfunction and atherosclerosis.

Anti-ischemic effects of angiotensin- converting enzyme inhibition in hypertension

OBJECTIVES

We investigated whether augmentation of bradykinin (BK) bioavailability with angiotensin-converting enzyme (ACE) inhibition is associated with reduced exercise-induced myocardial ischemia in hypertension.

BACKGROUND

Bradykinin responses are depressed in hypertension, and endothelial dysfunction contributes to myocardial ischemia by promoting abnormal coronary vasomotion during stress.

METHODS

Fourteen hypertensive (HT) and 17 normotensive (NT), mildly symptomatic patients with coronary artery disease (CAD) and ST-segment depression during exercise were studied before and after seven days of oral enalapril (EN), which was titrated from 2.5 to 20 mg daily. Patients underwent two treadmill exercise tests and determination of forearm vasodilator response to BK.

RESULTS

Despite receiving a lower dose of EN (7.8 vs. 14.8 mg, p < 0.001), NT patients had a significant reduction in blood pressure compared to HT patients. Compared to pre-EN, the ischemic threshold, defined as the rate-pressure product at the onset of 1-mm ST depression (p = 0.045), the duration of exercise to 1-mm ST depression (180 +/- 54 s, p = 0.007) and the maximum exercise duration (94 +/- 18 s, p < 0.001) were greater after EN in HT patients, but not in NT subjects (all p > or = 0.3). Patients with a greater drop in blood pressure experienced no improvement in exercise-induced ischemia. Forearm blood flow responses to BK were improved with EN in all patients to a similar extent. Moreover, no correlation was observed between the basal response to BK or the magnitude of its improvement with EN and with either the dose of EN or the improvement in exercise ischemic threshold.

CONCLUSIONS

Exercise-induced myocardial ischemia is ameliorated in HT patients with CAD by ACE inhibition.

Angiotensin type 1 receptor antagonism reverses abnormal coronary vasomotion in atherosclerosis

OBJECTIVES

This study was performed to determine whether angiotensin type 1 (AT1) receptor inhibition improves abnormal coronary vasomotion and endothelial dysfunction in patients with atherosclerosis or its risk factors.

BACKGROUND

Endothelial dysfunction, an early feature of atherosclerosis, contributes to abnormal vasomotion during stress. Angiotensin II may contribute to endothelial dysfunction in atherosclerosis.

METHODS

In 25 patients, mean age 59 +/- 2 years, with atherosclerosis or its risk factors, we measured coronary vasomotion during flow-mediated dilation (FMD) in response to adenosine, cold pressor test (CPT) and exercise before and after AT1 receptor blockade with intracoronary losartan (5 mg).

RESULTS

Losartan did not alter resting coronary vascular tone, but epicardial FMD improved from 5.6 +/- 1.5% to 8.9 +/- 1.8% (p = 0.02). Abnormal epicardial vasomotion during CPT and exercise also improved with losartan from -1.7 +/- 0.8% to 1.5 +/- 0.1% (p = 0.02) and -0.6 +/- 0.9% to 3.4 +/- 1.2% (p = 0.009), respectively. Improvement in epicardial vasomotion was most prominent in segments with baseline endothelial dysfunction evidenced as constriction during stress. Microvascular dilation during adenosine, an endothelium-independent response, was unchanged with losartan.

CONCLUSIONS

Inhibition of the coronary vascular AT1 receptors in patients with atherosclerosis improves epicardial vasomotion during stress, probably by improving endothelial dysfunction. Whether AT1 receptor blockade will provide long-term therapeutic benefits in atherosclerosis needs further investigation.

Pathophysiology of vascular endothelium and circulating platelets: implications for coronary revascularisation and treatment

Constant vasodilatation, inhibition of platelet and leukocyte adhesion, and local thrombolysis are the mechanisms through which an intact endothelial layer exerts its protective action on coronary circulation. A loss in these features is not only the first step in the development of atherosclerosis, but also a potent trigger for complications after revascularisation procedures. Percutaneous coronary interventions, particularly in the course of stenting, induce endothelial injury that can last up to months after the procedure. On the other hand, the preservation of endothelial function appears the best feature of arterial versus venous grafts after coronary bypass surgery. An early diagnosis either by invasive or non-invasive techniques has important implications for prognosis, and endothelial dysfunction can be effectively counteracted by medical treatment (ACE inhibitors, statins). Activated circulating platelets are present in the course of coronary artery disease, increasing the risk of thrombotic occlusion and/or plaque regrowth, after both percutaneous and surgical revascularisation. New antiplatelet agents are under development to reduce endothelium-platelet interaction. On the basis of the latest studies, coronary revascularisation should be integrated in a more complete treatment, which would take into account the complex processes involving the underlying atherosclerotic plaque.

Endothelial function during stimulation of renin-angiotensin system by low-sodium diet in humans

We examined whether physiological stimulation of the endogenous renin-angiotensin system results in impaired endothelium-dependent vasodilatation in forearm resistance vessels of healthy subjects and whether this impairment can be prevented by angiotensin II type 1 receptor blockade. A low-sodium diet was administered to 27 volunteers who were randomized to concomitant treatment with losartan (100 mg once daily) or matched placebo in a double-blind fashion. Forearm blood flow was assessed by venous occlusion plethysmography at baseline and after 5 days. Endothelium-dependent and -independent vasodilation was assessed by intra-arterial infusion of methacholine and verapamil, respectively. The low-sodium diet resulted in significantly decreased urine sodium excretion (placebo: 146 +/- 64 vs. 10 +/- 9 meq/24 h, P < 0.001; losartan: 141 +/- 56 vs. 14 +/- 14 meq/24 h, P < 0.001) and increased plasma renin activity (placebo: 1.0 +/- 0.5 vs. 5.0 +/- 2.5 ng x ml(-1) x h(-1), P < 0.001; losartan: 3.8 +/- 7.2 vs. 19.1 +/- 11.2 ng x ml(-1) x h(-1), P = 0.006) in both the losartan and placebo groups. With the baseline study as the reference, the diet intervention was not associated with any significant change in endothelium-dependent vasodilation to methacholine in either the placebo (P = 0.74) or losartan (P = 0.40) group. We conclude that short-term physiological stimulation of the renin-angiotensin system does not cause clinically significant endothelial dysfunction. Losartan did not influence endothelium-dependent vasodilation in humans with a stimulated renin-angiotensin system.

Bradykinin stimulates the release of tissue plasminogen activator in human coronary circulation: effects of angiotensin-converting enzyme inhibitors

OBJECTIVES

The goal of this study was to determine: 1) whether bradykinin (BK) directly stimulates tissue plasminogen activator (tPA) secretion in human coronary circulation, and 2) whether angiotensin-converting enzyme (ACE) inhibition favorably alters the fibrinolytic balance regulated by BK.

BACKGROUND

Bradykinin is a potent stimulator of tPA secretion in endothelial cells; however, the effect of BK on tPA release in the human coronary circulation has not been studied.

METHODS

Fifty-six patients with atypical chest pain were randomly assigned to two groups: 25 patients were treated with the ACE inhibitor enalapril (ACE inhibitor group), and 31 were not treated with ACE inhibitors (non-ACE inhibitor group). Graded doses of BK (0.2, 0.6, 2.0 microg/min), acetylcholine (ACh) (30 microg/min) and papaverine (PA) (12 mg) were administered into the left coronary artery. Coronary blood flow (CBF) was evaluated by Doppler flow velocity measurement. Blood samples were taken from the aorta (Ao) and the coronary sinus (CS).

RESULTS

Bradykinin induced similar increases in CBF in both groups. The net tPA release induced by BK was dose-dependently increased in both groups, and the extent of that increase in the ACE inhibitor group was greater than that in the non-ACE inhibitor group. Bradykinin did not alter plasminogen activator inhibitor-1 (PAI-1) levels in the Ao or CS in either group. Neither ACh nor PA altered tPA levels or PAI-1 levels in either group.

CONCLUSIONS

Intracoronary infusion of BK stimulates tPA release without causing any change in PAI-1 levels in the human coronary circulation. In addition, this effect of BK is augmented by an ACE inhibitor.

Contribution of bradykinin receptor dysfunction to abnormal coronary vasomotion in humans

OBJECTIVES

The aim of our study was to investigate coronary vascular kinin receptor function in patients with atherosclerosis or its risk factors.

BACKGROUND

Although acetylcholine (ACH) is used as a probe for testing vascular function in vivo, endogenous bradykinin (BK) regulates resting and flow-mediated epicardial tone.

METHODS

In 53 patients with mild atherosclerosis or its risk factors and 9 control subjects, endothelium-dependent vasomotion was tested with intracoronary ACH (30 microg/min) and BK (62.5 ng/min and 4 microg/min), and endothelium-independent function with sodium nitroprusside. Metabolic vasodilation was assessed during cardiac pacing (n = 19). Correlation with serum angiotensin-converting enzyme (ACE) levels and the ACE insertion/deletion genotype was performed.

RESULTS

There was progressive impairment in ACH-mediated microvascular dilation with increasing numbers of risk factors (p = 0.025, analysis of variance). By contrast, BK- and sodium nitroprusside-mediated microvascular dilation was similar in all groups. Similarly, there was no correlation between epicardial coronary responses to ACH and BK; segments that constricted or dilated with ACH had similar dilator responses with BK. Bradykinin, but not ACH-mediated vasomotion, was depressed in epicardial segments that constricted with pacing. Finally, epicardial BK responses were depressed in patients with high ACE levels and in those with the ACE DD genotype.

CONCLUSIONS

Endothelial dysfunction in atherosclerosis appears to be receptor-specific, involving the muscarinic receptor with relative sparing of the kinin receptor pathways. Abnormal reactivity of epicardial coronary arteries during physiologic stress is better represented by BK and not by ACH responses. Bradykinin activity and, hence, physiologic coronary vasomotion appears to be influenced by serum ACE levels and the ACE insertion/deletion genotype.

Insertion-deletion polymorphism of the ACE gene modulates reversibility of endothelial dysfunction with ACE inhibition

BACKGROUND

The aim of this study was to examine whether angiotensin-converting enzyme (ACE) inhibition improves coronary endothelial dysfunction in patients with atherosclerosis and its risk factors and whether this was related to the ACE insertion-deletion (I/D) polymorphism.

METHODS AND RESULTS

In 56 patients with atherosclerosis or its risk factors, we studied endothelium-dependent responses with acetylcholine and endothelium-independent function with sodium nitroprusside, before and after ACE inhibition with enalaprilat. Enalaprilat did not alter either resting coronary tone or vasodilation with sodium nitroprusside. However, it potentiated the coronary microvascular and epicardial responses with acetylcholine; coronary blood flow increased from 82+/-7 to 90+/-8 mL/min (P=0.05) after enalaprilat. Patients with depressed endothelial function (P<0.001) and those with ACE DD or ID genotypes (P=0.002) but not those homozygous for the I allele had the greatest improvement by multivariate analysis. Similarly, acetylcholine-mediated epicardial vasomotion improved in segments that initially constricted (endothelial dysfunction): from -10.1+/-1% to -1.4+/-2% (P<0.001) after enalaprilat. No augmentation was observed in segments that dilated (normal endothelial dysfunction) with acetylcholine. Patients with the D allele, hypercholesterolemia, and smokers (all P<0.05) had greater improvement.

CONCLUSIONS

Acute ACE inhibition improves coronary epicardial and microvascular endothelium-dependent vasomotion in patients with atherosclerosis or its risk factors who have endothelial dysfunction and presence of the D allele.

Renin angiotensin system and ASCVD

The renin angiotensin system was first described over 100 years ago and is still the focus of intense clinical and basic science investigation. The renin angiotensin system was demonstrated to play a major pathogenetic role in hypertension. The development of inhibitors of angiotensin-converting enzyme and specific receptor blockers for angiotensin-II represent a major advance in the treatment of elevated blood pressure. However, the renin angiotensin system is intimately involved in a number of conditions that increase the risk for atherosclerosis. Components of the renin angiotensin system have demonstrated to play a significant role in the initial phases of atherosclerosis. Additionally, plaque vulnerability and the potential for an acute atherosclerotic event are also modulated by the renin angiotensin system. Angiotensin-II plays a significant role in the balance between intravascular clot formation and fibrinolytic potential. Therefore, blocking the generation of angiotensin-II or inhibiting its binding to specific receptors may decrease the subsequent risk for unstable angina and acute myocardial infarction. Increased renin activity has been correlated as a statistical risk factor for coronary heart disease and converting enzyme inhibition has been demonstrated to decrease the incidence of acute ischemic events. This review will center on the role of modulation of the renin angiotensin system as a means to alter the clinical course of coronary atherosclerosis.

Intracoronary enalaprilat improves metabolic coronary vasodilation in patients with idiopathic dilated cardiomyopathy

Coronary flow reserve is reduced in patients with idiopathic dilated cardiomyopathy (DCM). We examined acute effects of intracoronary enalaprilat on metabolic coronary vasodilation during pacing tachycardia in patients. Coronary blood flow (Doppler guidewire) and diameter (quantitative angiography) were measured in seven patients with DCM and seven control subjects. In the DCM group, tachypacing increased coronary blood flow by 37 +/- 22% from the baseline before enalaprilat and by 65 +/- 22% (p < 0.01 vs. before treatment) after enalaprilat (0.5 microg/kg/min for 5 min, i.c.) at comparable double product. Pacing-induced dilation of the epicardial coronary artery also was greater after enalaprilat (p < 0.05). Effects of enalaprilat on coronary blood flow and diameter during pacing tachycardia were abolished by pretreatment with intracoronary administration of the nitric oxide (NO) synthesis inhibitor, N(G)-monomethyl-L-arginine. These beneficial effects of enalaprilat on large and small coronary vasodilation were not observed in control patients. Thus, intracoronary enalaprilat acutely augmented dilator responses of the large and small coronary arteries to pacing tachycardia in patients with DCM, and NO appeared to play an important role in mediating the effects of enalaprilat. These favorable effects of enalaprilat on the coronary circulation may be of clinical significance in patients with heart failure due to nonischemic DCM. Further long-term studies of the effects of angiotensin-converting enzyme inhibition on coronary vasodilation will be needed in this population.