Nancy J. Brown

Angiotensin-Converting Enzyme Inhibitors

ACE inhibitors have achieved widespread usage in the treatment of cardiovascular and renal disease. ACE inhibitors alter the balance between the vasoconstrictive, salt-retentive, and hypertrophic properties of angiotensin II (Ang II) and the vasodilatory and natriuretic properties of bradykinin and alter the metabolism of a number of other vasoactive substances. ACE inhibitors differ in the chemical structure of their active moieties, in potency, in bioavailability, in plasma half-life, in route of elimination, in their distribution and affinity for tissue-bound ACE, and in whether they are administered as prodrugs. Thus, the side effects of ACE inhibitors can be divided into those that are class specific and those that relate to specific agents. ACE inhibitors decrease systemic vascular resistance without increasing heart rate and promote natriuresis. They have proved effective in the treatment of hypertension, they decrease mortality in congestive heart failure and left ventricular dysfunction after myocardial infarction, and they delay the progression of diabetic nephropathy. Ongoing studies will elucidate the effect of ACE inhibitors on cardiovascular mortality in essential hypertension, the role of ACE inhibitors in patients without ventricular dysfunction after myocardial infarction, and the role of ACE inhibitors compared with newly available angiotensin AT1 receptor antagonists.

2011 ACCF/AHA Guideline for Coronary Artery Bypass Graft Surgery

Alice K. Jacobs, MD, FACC, FAHA, Chair Jeffrey L. Anderson, MD, FACC, FAHA, Chair-Elect Nancy Albert, PhD, CCNS, CCRN, FAHA Mark A. Creager, MD, FACC, FAHA Steven M. Ettinger, MD, FACC Robert A. Guyton, MD, FACC Jonathan L. Halperin, MD, FACC, FAHA Judith S. Hochman, MD, FACC, FAHA

Effect of Bradykinin-Receptor Blockade on the Response to Angiotensin-Converting–Enzyme Inhibitor in Normotensive and Hypertensive Subjects

BACKGROUND Angiotensin-converting-enzyme (ACE) inhibitors not only decrease the production of angiotensin II but also decrease the degradation of bradykinin. In this study, a specific bradykinin-receptor antagonist, icatibant acetate (HOE 140), was used to determine the contribution of bradykinin to the short-term effects of ACE inhibition on blood pressure and plasma renin activity in both normotensive and hypertensive subjects. METHODS We compared the hemodynamic, renal, and endocrine effects of captopril alone (25 mg), captopril plus icatibant (100 microg per kilogram of body weight), the angiotensin II subtype 1-receptor antagonist losartan (75 mg), and placebo in 20 subjects with normal blood pressure and 7 subjects with hypertension. The subjects were studied while they were salt depleted (i.e., in balance on a diet in which they were allowed 10 mmol of sodium per day). The drugs were administered on four separate study days in a single-blind, randomized fashion. RESULTS The coadministration of icatibant significantly attenuated the hypotensive effect of captopril (maximal decrease in mean arterial pressure for all subjects combined, 10.5+/-1.0 mm Hg, as compared with 14.0+/-1.0 mm Hg for captopril alone; P=0.001), in such a way that the decrease in blood pressure after the administration of captopril plus icatibant was similar to that after the administration of losartan (maximal decrease in mean arterial pressure, 11.0+/-1.7 mm Hg). Icatibant did not alter the renal hemodynamic response to captopril, but it significantly altered the change in plasma renin activity in response to ACE inhibition (-0.4+/-0.4 ng of angiotensin I per milliliter per hour, as compared with 2.0+/-0.7 ng per milliliter per hour for captopril alone; P=0.007). The magnitude of these effects was similar in both the normotensive and the hypertensive subjects, as well as in both the black subjects and the white subjects. CONCLUSIONS These data confirm that bradykinin contributes to the short-term effects of ACE inhibition on blood pressure in normotensive and hypertensive persons and suggest that bradykinin also contributes to the short-term effects of ACE inhibition on the renin-angiotensin system.

Established and Emerging Plasma Biomarkers in the Prediction of First Atherothrombotic Events

In the current Adult Treatment Panel guidelines for cardiovascular risk detection,1 the plasma-based markers recommended for use in global risk assessment or in the definition of the metabolic syndrome are low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, and triglycerides. It is widely recognized, however, that more than half of all future vascular events occur in individuals without overt hyperlipidemia. For example, in a recent large-scale analysis of >27 000 healthy American women, 77% of all future events occurred in those with LDL-C levels <4.14 mmol/L (<160 mg/dL) and 45% of all events occurred in those with LDL-C values <3.36 mmol/L (<130 mg/dL).2 Although risk-scoring systems that additionally evaluate traditional risk factors such as smoking, hypertension, and diabetes greatly improve risk prediction, multiple studies demonstrate that 20% to 25% of all future events occur in individuals with only 1 of these factors.3 Moreover, the prevalence of traditional risk factors is almost as high in those without disease as in affected individuals.4 As our understanding of the pathobiology of atherothrombosis has improved, researchers have attempted to evaluate the activities of these biological processes by measuring markers in plasma or urine (ie, biomarkers). Indeed, a series of candidate biomarkers reflecting inflammation, hemostasis, thrombosis, and oxidative stress have been evaluated as potential clinical tools in an effort to improve risk prediction. To be useful in a clinical setting, the biomarker of interest must be shown in multiple prospective studies to predict future cardiovascular events. Retrospective studies are of limited value because they are prone to bias and cannot exclude the possibility that the particular biomarker is elevated as a result of, rather than a cause of, disease. To be used widely, the proposed biomarker should provide independent information on risk or prognosis beyond that available from global assessment algorithms such …

Clinical Experience Over 48 Years With Pheochromocytoma

OBJECTIVE To analyze the presentation, localization, surgical management, pathology, and long-term outcome of a large series of patients with pheochromocytomas. SUMMARY BACKGROUND DATA There are several areas of controversy pertaining to pheochromocytomas. Although many studies report a higher rate of malignancy for extraadrenal pheochromocytomas than for adrenal pheochromocytomas, the number of patients with the former tumor are small and statistical analysis is lacking. There has also been recent debate as to whether microscopic features of the tumor may be predictive of future behavior. METHODS From 1950 to 1998, the authors observed 108 pheochromocytomas in 104 patients. The outcome of these patients has been followed prospectively. The medical records of these patients were reviewed for data on the presentation, localization, surgical management, pathology, and outcome. Patient survival was analyzed using Kaplan-Meier survival distributions. RESULTS This study included 66 female patients and 38 male patients. The average age at surgery was 42.3 years. Sporadic cases accounted for 84% of the patients; the other 16% had multiple endocrine neoplasia type 2, von Recklinghausens disease, von Hippel-Lindau disease, or Carneys syndrome. Of 64 adrenal tumors, 55 were initially considered benign, 6 had microscopic malignant features, and 3 had malignant disease. Mean patient follow-up was 12.6 years. To date, in five additional patients (none with microscopic disease) malignant disease developed (13% overall rate of malignancy). Recurrence occurred as late as 15 years after resection. Of 26 extraadrenal pheochromocytomas, 14 were initially considered benign, 8 had microscopic malignant features, and 4 had malignant disease. Thus, 46% of patients had either malignant disease or tumors with malignant features. Mean patient follow-up was 11.5 years. In one patient with benign disease and in one patient with malignant features, malignant disease developed (23% overall rate of malignancy). The difference in the rate of malignancy was not statistically significant between adrenal and extraadrenal pheochromocytomas. Patients with adrenal and extraadrenal pheochromocytomas also had similar rates of survival (p = NS). CONCLUSIONS The data suggest that patients with extraadrenal pheochromocytomas have the same risk of malignancy and the same overall survival as patients with adrenal pheochromocytomas. Lifelong follow-up of these patients is mandatory.

Effect of Activation and Inhibition of the Renin-Angiotensin System on Plasma PAI-1

Increased plasma renin activity (PRA) has been associated with an increased risk of myocardial infarction (MI), whereas angiotensin-converting enzyme (ACE) inhibition appears to reduce the risk of recurrent MI in patients with left ventricular dysfunction. These observations may be partially explained by an interaction between the renin-angiotensin system (RAS) and fibrinolytic system. To test this hypothesis, we examined the effect of salt depletion on tissue-type plasminogen activator (tPA) antigen and plasminogen activator inhibitor-1 (PAI-1) activity and antigen in normotensive subjects in the presence and absence of quinapril (40 mg BID). Under low (10 mmol/d) and high (200 mmol/d) salt conditions there was significant diurnal variation in PAI-1 antigen and activity and tPA antigen. Morning (8 AM through 2 PM) PAI-1 antigen levels were significantly higher during low salt intake compared with high salt intake conditions (ANOVA, F=5.8, P=0.048). PAI-1 antigen correlated with aldosterone (r=0.56, P<10(-7)) during low salt intake. ACE inhibition significantly decreased 24-hour (ANOVA for 24 hours, F=6. 7, P=0.04) and morning (F=24, P=0.002) PAI-1 antigen and PAI-1 activity (F=6.48, P=0.038) but did not alter tPA antigen. Thus, the mean morning PAI-1 antigen concentration was significantly higher during low salt intake than during either high salt intake or low salt intake and concomitant ACE inhibition (22.7+/-4.6 versus 16. 1+/-3.3 and 16.3+/-3.7 ng/mL, respectively; P<0.05). This study provides evidence of a direct functional link between the RAS and fibrinolytic system in humans. The data suggest that ACE inhibition has the potential to reduce the incidence of thrombotic cardiovascular events by blunting the morning peak in PAI-1.

Black Americans have an increased rate of angiotensin converting enzyme inhibitor‐associated angioedema

To study the association of race and other patient characteristics associated with angiotensin converting enzyme (ACE) inhibitor‐associated angioedema.

G protein-coupled receptor kinase 4 gene variants in human essential hypertension

Essential hypertension has a heritability as high as 30–50%, but its genetic cause(s) has not been determined despite intensive investigation. The renal dopaminergic system exerts a pivotal role in maintaining fluid and electrolyte balance and participates in the pathogenesis of genetic hypertension. In genetic hypertension, the ability of dopamine and D1-like agonists to increase urinary sodium excretion is impaired. A defective coupling between the D1 dopamine receptor and the G protein/effector enzyme complex in the proximal tubule of the kidney is the cause of the impaired renal dopaminergic action in genetic rodent and human essential hypertension. We now report that, in human essential hypertension, single nucleotide polymorphisms of a G protein-coupled receptor kinase, GRK4γ, increase G protein-coupled receptor kinase (GRK) activity and cause the serine phosphorylation and uncoupling of the D1 receptor from its G protein/effector enzyme complex in the renal proximal tubule and in transfected Chinese hamster ovary cells. Moreover, expressing GRK4γA142V but not the wild-type gene in transgenic mice produces hypertension and impairs the diuretic and natriuretic but not the hypotensive effects of D1-like agonist stimulation. These findings provide a mechanism for the D1 receptor coupling defect in the kidney and may explain the inability of the kidney to properly excrete sodium in genetic hypertension.

Functional Variant of CYP4A11 20-Hydroxyeicosatetraenoic Acid Synthase Is Associated With Essential Hypertension

Background—The CYP4A11 arachidonic acid monooxygenase oxidizes endogenous arachidonic acid (AA) to 20-hydroxyeicosatetraenoic acid (20-HETE), a metabolite with renovascular and tubular functions. Mice with targeted disruption of Cyp4a14, a murine homologue of CYP4A11, have severe hypertension. We combined molecular and biochemical approaches to identify a functional variant of the CYP4A11 20-HETE synthase and determine its association with hypertensive status in 2 independent human populations. Methods and Results—A thymidine-to-cytosine polymorphism at nucleotide 8590 resulted in a phenylalanine-to-serine substitution at amino acid 434. Expression of cDNA with serine 434 resulted in a protein with a significantly reduced AA and lauric acid metabolizing activity. In a population of 512 whites from Tennessee, the age, body mass index, and gender-adjusted OR of having hypertension attributable to the 8590C variant was 2.31 (95% CI 1.41 to 3.78) compared with the reference 8590TT genotype. In subjects from the Framingham Heart Study, the adjusted ORs of hypertension associated with the 8590C variant were 1.23 (CI 0.94 to 1.59; n=1538) in all subjects and 1.33 (CI 1.01 to 1.77; n=1331) when subjects with diabetes were excluded. No association of the variant with hypertension was detected in a population of 120 blacks. Conclusions—We identified a variant of the human CYP4A11 (T8590C) that encodes for a monooxygenase with reduced 20-HETE synthase activity. The association of the T8590C variant with hypertension supports its role as a polygenic determinant of blood pressure control in humans, and results obtained from the large population database suggest that the relevance of the variant may vary according to hypertension comorbidity.

Bradykinin Stimulates Tissue Plasminogen Activator Release From Human Forearm Vasculature Through B2 Receptor–Dependent, NO Synthase–Independent, and Cyclooxygenase-Independent Pathway

BackgroundBradykinin stimulates dose-dependent tissue plasminogen activator (tPA) release from human endothelium. Although bradykinin is known to cause vasodilation through B2 receptor–dependent effects on NO, prostacyclin, and endothelium-derived hyperpolarizing factor production, the mechanism(s) underlying tPA release is unknown. Methods and ResultsWe measured the effects of intra-arterial bradykinin (100, 200, and 400 ng/min), acetylcholine (15, 30, and 60 &mgr;g/min), and nitroprusside (0.8, 1.6, and 3.2 &mgr;g/min) on forearm vasodilation and tPA release in healthy volunteers in the presence and absence of (1) the B2 receptor antagonist HOE 140 (100 &mgr;g/kg IV), (2) the NO synthase inhibitor l-NG-monomethyl-l-arginine (L-NMMA, 4 &mgr;mol/min intra-arterially), and (3) the cyclooxygenase inhibitor indomethacin (50 mg PO TID). B2 receptor antagonism attenuated vasodilator (P =0.004) and tPA (P =0.043) responses to bradykinin, without attenuating the vasodilator response to nitroprusside (P =0.36). L-NMMA decreased basal forearm blood flow (from 2.35±0.31 to 1.73±0.22 mL/min per 100 mL, P =0.01) and blunted the vasodilator response to acetylcholine (P =0.013) and bradykinin (P =0.07, P =0.038 for forearm vascular resistance) but not that to nitroprusside (P =0.47). However, there was no effect of L-NMMA on basal (P =0.7) or bradykinin-stimulated tPA release (P =0.45). Indomethacin decreased urinary excretion of the prostacyclin metabolite 2,3-dinor-6-keto-prostaglandin F1&agr; (P =0.04). The vasodilator response to endothelium-dependent (P =0.019 for bradykinin) and endothelium-independent (P =0.019) vasodilators was enhanced during indomethacin administration. In contrast, there was no effect of indomethacin alone (P =0.99) or indomethacin plus L-NMMA (P =0.36) on bradykinin-stimulated tPA release. ConclusionsThese data indicate that bradykinin stimulates tPA release from human endothelium through a B2 receptor–dependent, NO synthase–independent, and cyclooxygenase-independent pathway. Bradykinin-stimulated tPA release may represent a marker for the endothelial effects of endothelium-derived hyperpolarizing factor.