Tissue Angiotensin-converting Enzyme Research Articles

Tissue ACE Inhibitors for Secondary Prevention of Cardiovascular Disease in Patients With Preserved Left Ventricular Function: A Pooled Meta-analysis of Randomized Placebo-controlled Trials

A pooled meta-analysis of published, randomized placebo-controlled clinical trials to evaluate the role of tissue angiotensin-converting enzyme (ACE) inhibitors in secondary prevention of cardiovascular disease in patients with preserved left ventricular function. Peer-reviewed journals listed in Index Medicus/MEDLINE, the Cochrane Central Register of Controlled Clinical Trials, and the Cochrane Database of Systematic Reviews. Randomized placebo-controlled clinical trials of at least 12 months' duration, in patients with a prior cardiovascular event or at high risk for cardiovascular events, were analyzed. DATA SYNTHESIS AND ANALYSIS: A total of 31,555 patients (136,882 patient-years) from 4 trials were selected for the meta-analysis. Relative risk estimations were made using data pooled from these trials, and statistical significance was determined using the chi2 test. The number of patients needed to treat was also calculated for each outcome. Tissue ACE inhibitors significantly reduced the risk of all-cause mortality, cardiovascular mortality, acute myocardial infarction, and stroke (P < .001 for each). The need for invasive coronary revascularization was reduced (P = .03), as was the risk of hospitalization for congestive heart failure (P = .001). The occurrence of new-onset diabetes was also significantly reduced (P < .001), but the risk of hospitalization for angina was not significantly affected (P = .677). Treating about 100 patients for about 4.5 years would prevent 1 death, 1 non-fatal myocardial infarction, 1 cardiovascular death, or 1 invasive coronary revascularization. Tissue ACE inhibitors have demonstrated benefit when used for secondary prevention of cardiovascular disease in patients with preserved left ventricular function in randomized placebo-controlled clinical trials.

Contribution of perindopril to cardiology: 20 years of success

Cardiovascular risk factors such as hypertension and diabetes are known to initiate a chain of events that include oxidative stress, endothelial dysfunction, and vascular remodelling, and that if left to progress unchecked, will eventually culminate in end-stage cardiovascular disease. Perindopril is a long-acting lipophilic inhibitor of tissue angiotensin-converting enzyme (ACE) that has been studied in a variety of patient populations, ranging from those with hypertension to more advanced-stage cardiovascular disease. Although the role of ACE inhibitors is well established for patients with hypertension or heart failure, large morbidity–mortality trials have proved the efficacy of perindopril in a comparatively wide range of patients at risk of cardiovascular events, including patients with a history of stroke or transient ischaemic attack, irrespective of whether hypertension was present, and patients with stable coronary artery disease without heart failure or substantial hypertension. In addition, relative to a standard antihypertensive regimen based on a b-blocker/ diuretic, a calcium antagonist/perindopril-based regimen has been shown to provide more effective broad-spectrum prevention of cardiovascular events in hypertensive patients. Early studies revealed that, in addition to sustained 24 h antihypertensive activity with once-daily dosing, perindopril is able to reverse arterial remodelling in hypertensive patients. Furthermore, subanalyses of data from morbidity–mortality trials have shown that reversal of abnormal endothelial function and reductions in central aortic pressure may help to account for benefits observed with perindopril that extend beyond those expected from reductions in brachial blood pressure alone. In summary, although it is already a well-established antihypertensive drug, pivotal clinical trials are still helping to unravel the true potential of perindopril across the cardiovascular continuum.

Angiotensin-converting enzyme gene polymorphism (ACEGP) and cancer cachexia (CC): Is there a link?

9011 Background: ACEGP greatly influences functional status and is currently the gene most involved in human fitness. The insertion allele (II) (a 287 bp fragment) rather than the deletion allele (DD) for the angiotensin-converting enzyme (ACE) gene is associated with low ACE levels in tissues and enhanced metabolic efficiency, as demonstrated by an improved response to vigorous training in healthy individuals. In addition, lower tissue ACE activity in mice was associated with decreased insulin resistance, greater glucose uptake in the skeletal muscle, and higher glycogen and fat stores. The aim of the study was to gather preliminary data on the potential association between muscle mass and ACEGP in advanced cancer patients (ACP). Methods: Buffy coat serum and plasma was obtained from 55 patients 18 years or older, newly diagnosed with Stage III (inoperable)-IV non-small cell lung cancer and unresectable/ metastatic gastrointestinal cancers seen within the McGill University Health Center. Muscle surface area (MSA-cm2) was calculated from computerized tomography slices at the L3 vertebrae using TOMOVISION SliceOmatic software version 4.3. Muscularity (M-cm2/m2) and lean body mass (LBM-kg) were calculated by extrapolation of image analysis used to quantify lean tissue. Results: ANOVA confirmed significant difference (p&lt;0.001) among MSA (II: 134.04±35.23; ID: 122.37±29.74; DD: 115.22±27.55), M (47.72±8.67; 41.65±9.26; 41.80±9.26), and LBM (43.00±11.21; 39.29±9.46; 37.01±8.77). In a multiple linear regression model, the II allele was associated with higher M (p=0.042) and a trend for higher MSA and LBM (p=0.059) independent of age, gender, diagnosis, and treatment received. Conclusions: Our data suggest ACEGP influences muscle mass in ACP. Further investigations in a larger sample of ACP are underway to determine whether ACEGP is an important predisposing factor to CC-associated muscle wasting. No significant financial relationships to disclose.

CHRONIC SALT LOADING AND CARDIOVASCULAR‐ASSOCIATED CHANGES IN EXPERIMENTAL DIABETES IN RATS

1. High-sodium intake may increase blood pressure and diabetes is a salt-sensitive condition. In the present study, we evaluated cardiovascular changes and their neurohumoral mechanisms in streptozotocin (STZ)-diabetic rats that underwent chronic salt loading. 2. We studied male Wistar rats (150-280 g) 14 days after the injection of either STZ (50 mg/kg, i.v.; D; n = 18) or citrate buffer (C; n = 16). After the induction of diabetes, animals were maintained for 14 days with free access to standard rat chow and tap water (C and D groups) or 1% NaCl solution (C-S and D-S groups). We conducted two experiments. Experiment 1 consisted of basal arterial pressure (AP) measurement (30 min) followed by the evaluation of AP responsiveness to phenylephrine and sodium nitroprusside. One day later, with the rats anaesthetized, a blood sample was collected to test for glycaemia, plasma angiotensin-converting enzyme (ACE) activity and renin. Kidneys were removed for the determination of tissue ACE activity. Experiment 2 comprised 24 h urine collection followed by 3 days of cardiovascular records, which consisted of a 30 min basal AP measurement, followed by injection of blockers of the vasopressin system, the renin-angiotensin system (RAS) and the sympathetic system. Basal haemodynamic data, baroreflex evaluation and AP responses to blockade of the vasopressin system with vasopressin V(1) receptor antagonist (aAVP; 10 mg/kg, i.v.), the RAS by losartan (10 mg/kg, i.v.) and the sympathetic system by hexamethonium (20 mg/kg, i.v.) were determined. 3. Glycaemia was similar between C and C-S (P = 0.612) and between D and D-S (P = 0.552), but higher in diabetic compared with non-diabetic rats (P < 0.0001). The D-S rats had an increment of 24% in mean AP compared with D (120 +/- 4 vs 97 +/- 2 mmHg, respectively; P = 0.0001), which was not seen in C-S compared with C rats. A positive association was noted between urinary sodium and mean AP (r = 0.37; P = 0.04). Plasma renin was undetectable in D-S rats. The response to acute drug blockade of vasopressin and the RAS was similar among groups, but hexamethonium elicited a more pronounced decrease in AP in D-S compared with D rats (P = 0.001). 4. The main neurohumoral mechanisms of salt-induced cardiovascular changes in STZ-diabetes are increased sodium and vascular sensitivity to adrenergic stimuli, which act in combination to produce a final result of higher AP levels, a finding not observed in control rats. Baroreflex derangements induced by diabetes were not affected by salt overload.

Angiotensin‐converting enzyme activity in plasma and tissues of spontaneously hypertensive rats after the short‐ and long‐term intake of hydrolysed egg white

This paper evaluates the effects of the short- (1 g/kg) and long-term (0.5 and 1 g/kg/day) oral intake of egg white hydrolysed with pepsin (hEW) and the long-term oral intake (1 g/kg/day) of egg white (EW) on local angiotensin-converting enzyme (ACE) activities in plasma and other tissues of spontaneously hypertensive rats (SHR), as compared to the effect of the ACE inhibitor prototype captopril. The rats treated with hEW were classed in a different group than the control rats and the rats treated with EW by cluster analysis, taking into account their tissue ACE activities and their systolic blood pressure (SBP). Principal component analysis (PCA) showed that SBP in SHR was negatively related with ACE activity in plasma and positively related with ACE activity in aorta and kidney. ACE activity in plasma significantly increased after the long-term treatment with hEW (0.5 g/kg/day). ACE activity in aorta and kidney was significantly inhibited 4 h after the short-term administration of hEW. The long-term treatment with hEW caused local effects on ACE activity in aorta, kidney and lungs that followed a pattern similar, but less pronounced, than that caused by captopril.

Increased chymase-like activity in a dog with congenital pulmonic stenosis

Objectives This study was intended to compare the tissue chymase-like activity and angiotensin converting enzyme (ACE) activity in the right and left ventricles of a dog with congenital pulmonic stenosis (PS), with normal dogs, and to discuss the potential clinical implications of these findings. Animals, materials and methods Study subjects included a one-year-old Beagle dog with spontaneous PS and six clinically normal Beagles. Chymase-like and ACE activities were determined in all hearts by high pressure liquid chromatography. Results In the PS dog right ventricular (RV) chymase-like activity (49.79 nmol/min/g tissue) and left ventricular (LV) chymase-like activity (36.85 nmol/min/g tissue) were elevated vs normal Beagle dogs (mean ± standard deviation, RV: 20.17 ± 5.24 nmol/min/g, LV: 19.03 ± 3.27 nmol/min/g). Conclusions Activation of the tissue RAA system was detected in a dog with congenital PS. This interesting finding should be pursued with further studies to validate this result, and to explore whether pharmacological blockade of chymase, or the angiotensin II receptor, represents a useful strategy to prevent myocardial remodeling in this condition.

Anti-inflammatory Actions of Quinapril

The role of angiotensin II (Ang-II) in inflammation and the mechanisms through which it exerts this role are explored. Signaling through angiotensin stimulation of inflammatory cells often amplifies inflammation. Formation of Ang-II from tissue angiotensin-converting enzyme (ACE) has been shown to be of greater importance in the development and progression of inflammatory diseases than plasma ACE. Quinapril, which is a potent and selective inhibitor of both plasma and tissue ACE, has demonstrated anti-inflammatory properties in many disease states such as atherosclerosis, nephritis, scleroderma, diabetes and arthritis, and, thus, offers new therapeutic possibilities for disease treatment.

The role and regulation of cardiac angiotensin-converting enzyme for noninvasive molecular imaging in heart failure

Congestive heart failure is a pathologic condition characterized by progressive decrease in left ventricular contractility and consequent decline of cardiac output. There is convincing clinical and experimental evidence that the renin-angiotensin system (RAS) and its primary effector peptide, angiotensin II, are linked to the pathophysiology of interstitial fibrosis, cardiac remodeling, and heart failure. In addition to the traditional endocrine or circulating RAS, an active tissue RAS has been characterized. Tissue angiotensin-converting enzyme and locally synthesized angiotensin II, for example, by chymase, exert local trophic effects that modulate gene expression, which regulates growth and proliferation in both myocytes and nonmyocytes. The existence of the tissue RAS offers an opportunity for targeted imaging, which may be of considerable value for guiding medical therapy.

Angiotensin Converting Enzyme Activity in Compensatory Renal Hypertrophy

Serum and tissue (kidney's) angiotensin-converting enzyme (ACE) activity has been examined in Wistar rats (10 males and 10 females), seven days after unilateral nephrectomy. Renal hypertrophy was determined by measurement of kidney absolute mass. Serum and tissue ACE activity was determined by spectrophotometric method using hippuryl-l-histidyl-l-leucine (Hip-His-Leu) as a substrate. The ACE serum activity was expressed in units that correspond to 1 nmol of hippuric acid released by enzymatic hydrolysis of Hip-His-Leu substrate per minute/ml serum. The ACE tissue activity was expressed in units that correspond to 1 nmol of hippuric acid released by enzymatic hydrolysis of Hip-His-Leu substrate per minute/mg protein or mg kidney's tissue. The ACE serum activity significantly increased (p<0,05) seven days after unilateral nephrectomy. The ACE tissue activity, expressed in units that corresponds to 1 nmol of hippuric acid released by hydrolysis of Hip-His-Leu substrate per minute/mg protein, was higher seven days after unilateral nephrectomy then in kidney control, but the difference was not significant compared to the values determined in kidney control. The ACE tissue activity, expressed in units that correspond to 1 nmol of hippuric acid released by hydrolysis of Hip-His-Leu substrate per minute/mg tissue, was increased seven days after unilateral nephrectomy, which is statistically significant compared to the activity of the same enzyme in kidney control (p<0,01). The results indicate that ACE, probably has an important role in development of adaptive compensatory mechanisms after unilateral nephrectomy.

Tissue angiotensin‐converting enzyme inhibitors for the prevention of cardiovascular disease in patients with diabetes mellitus without left ventricular systolic dysfunction or clinical evidence of heart failure: a pooled meta‐analysis of randomized placebo‐controlled clinical trials

The aim of this study was to determine the role of tissue angiotensin-converting enzyme (ACE) inhibitors in the prevention of cardiovascular disease in patients with diabetes mellitus without left ventricular systolic dysfunction or clinical evidence of heart failure in randomized placebo-controlled clinical trials using pooled meta-analysis techniques. Randomized placebo-controlled clinical trials of at least 12 months duration in patients with diabetes mellitus without left ventricular systolic dysfunction or heart failure who had experienced a prior cardiovascular event or were at high cardiovascular risk were selected. A total of 10 328 patients (43 517 patient-years) from four selected trials were used for meta-analysis. Relative risk estimations were made using data pooled from the selected trials and statistical significance was determined using the Chi-squared test (two-sided alpha error <0.05). The number of patients needed to treat was also calculated. Tissue ACE inhibitors significantly reduced the risk of cardiovascular mortality by 14.9% (p = 0.022), myocardial infarction by 20.8% (p = 0.002) and the need for invasive coronary revascularization by 14% (p = 0.015) when compared to placebo. The risk of all-cause mortality also tended to be lower among patients randomized to tissue ACE inhibitors, whereas the risks of stroke and hospitalization for heart failure were not significantly affected. Treating about 65 patients with tissue ACE inhibitors for about 4.2 years would prevent one myocardial infarction, whereas treating about 85 patients would prevent one cardiovascular death. Pooled meta-analysis of randomized placebo-controlled trials suggests that tissue ACE inhibitors modestly reduce the risk of myocardial infarction and cardiovascular death and tend to reduce overall mortality in diabetic patients without left ventricular systolic dysfunction or heart failure.

The Usefulness of Angiotensin Converting Enzyme in the Differential Diagnosis of Crohn's Disease and Intestinal Tuberculosis

BackgroundSince the pathologic findings of Crohn's disease (CD) and intestinal tuberculosis (IT) overlap to a large degree, the development of other biomarkers will be of great help for making the differential diagnosis of these 2 diseases. The aim of the present study is to examine the clinical efficacy of using the tissue angiotensin converting enzyme (ACE) assay in making the differential diagnosis between CD and IT.MethodsTissue specimens were obtained from 36 patients who were diagnosed with CD or IT by the colonoscopic biopsy, as well as by the clinical findings. The expression of tissue ACE was detected by immunohistochemical staining. The optimal cut-off value of the immunoreactive scoring (IRS) system we used to differentiate CD from IT was determined by analysis of the ROC curve and AUROC.ResultsGranuloma was present in 15 of 19 patients with CD (78.9%) and in 15 of 17 patients with IT (88.2%). ACE was present in the cytoplasm of the epithelioid cells in the granulomas from 13 of 15 patients with CD and in 14 of 15 patients with IT. The IRS scores of ACE were greater in the patients with CD than that of the patients with IT (8.07±4.38 vs. 4.13±2.47, respectively, p=0.006). In differentiating CD from IT, the AUROC curve for the IRS of ACE was 0.767 with a sensitivity of 66.7%, a specificity of 93.3% and the cut-off point was 7.5.ConclusionsThe results of our study suggest that the assessment of the tissue ACE expression can be helpful for making the differential diagnosis between CD and IT.

Role of Perindopril in the Prevention of Stroke

Stroke is one of the leading causes of disability and death worldwide and is a more common cause of cardiovascular morbidity and mortality than myocardial infarction among patients with hypertension. Identifying and modifying key risk factors is crucial to reduce morbidity and mortality from stroke. Hypertension is the most important modifiable risk factor for ischemic stroke, and antihypertensive treatment is of paramount importance to reduce the incidence of stroke mortality and morbidity. Perindopril is a third-generation long acting, once-daily lipophilic angiotensin-converting enzyme inhibitor with high tissue angiotensin-converting enzyme affinity, lowering angiotensin II and potentiating bradykinin. Its efficacy, safety and tolerability are well established in the treatment of hypertension and heart failure. The purpose of this article is to review the evidence from clinical trials as well as from recent patents that has been gathered in regard to perindopril, demonstrating not only its efficacy in reducing blood pressure, but also to other cardiovascular protective properties that act in addition to the obvious blood-pressure-lowering effect in the prevention of stroke in patients with essential hypertension, with particular attention paid to the results from the Perindopril Protection Against Recurrent Stroke Study (PROGRESS).

Abstract 4192: Tissue ACE Inhibitors for Secondary Prevention of Adverse Cardiovascular Events in Patients with Preserved Left Ventricular Function: A Pooled Meta-Analysis

Introduction: Although the role of angiotensin converting enzyme (ACE) inhibitors in patients with depressed left ventricular function is well established, their role in patients with preserved ventricular function is uncertain. We conducted a meta-analysis of recent clinical trials to evaluate the role of tissue ACE inhibitors in secondary prevention of cardiovascular disease in patients with preserved left ventricular function. Study Selection: Randomized placebo-controlled clinical trials of at least 12 months duration, conducted in patients who had experienced an acute cardiovascular event or were at high risk for cardiovascular events. Data Synthesis and Analysis: A total of 31,555 patients from 4 selected trials were analyzed. Relative risk estimations were made using pooled data from the 4 trials. Statistical significance was determined using the Chi-square test (two-sided alpha error &lt;0.05). Results: When compared to placebo, the use of tissue ACE inhibitors was associated with significant relative risk reductions in all-cause mortality (p&lt;0.001), cardiovascular mortality (p&lt;0.001), fatal &amp; non-fatal myocardial infarction (p&lt;0.001) and stroke (p&lt;0.001), as well as hospitalization for congestive heart failure (p=0.001) &amp; occurrence of new-onset diabetes mellitus (p&lt;0.001). The need for invasive coronary revascularization was also reduced (p&lt;0.03), but the risk of hospitalization for angina was not significantly affected. Conclusion: Tissue ACE inhibitors decrease mortality and cardiovascular morbidity in high risk patients with cardiovascular disease and preserved left ventricular function in randomized placebo-controlled clinical trials.

Tissue ACE Inhibitors Decrease the Risk of Hospitalization for Heart Failure and Cardiovascular Morbidity and Mortality in Patients with Cardiovascular Disease and Preserved Ventricular Function – A Pooled Meta-Analysis

Introduction: Although the role of angiotensin converting enzyme (ACE) inhibitors in patients with depressed left ventricular function is well established, their role in patients with preserved ventricular function is uncertain. We conducted a meta-analysis of recent clinical trials to evaluate the role of tissue-specific ACE inhibitors in secondary prevention of cardiovascular disease in patients with normal left ventricular function. Study Selection: Randomized placebo-controlled clinical trials of at least 12 months duration, which included patients who had experienced an acute cardiovascular event or were at high risk for cardiovascular events.

Intracrine renin and angiotensin II: a novel role in cardiovascular and renal cellular regulation

Since renin was discovered by Robert Tigerstedt more than a century ago, interest in the renin–angiotensin system (RAS) remains stronger than ever [1]. Tigerstedt injected saline extracts prepared from a rabbit kidney into other rabbits and observed marked increases in arterial blood pressure, which led to the hypothesis that the kidney might release an endocrine substance to control systemic blood pressure [1]. This pressor substance was named renin by Tigerstedt. It was Harry Goldblatt who confirmed and extended Tigerstedt’s discovery of the RAS in his legendary studies on two-kidney, one-clip renal hypertension in 1934 [2]. For several decades, angiotensin II was known as an endocrine peptide that is formed by the actions of kidney-derived renin and lung-derived angiotensin-converting enzyme (ACE) and causes systemic hypertension. The RAS is now well recognized as a dual vasoactive system, acting as both a circulating endocrine system and a local tissue paracrine/autocrine system [3,4]. Re further defined intracrine angiotensin II as the effector peptide that is either synthesized within a cell via interactions of renin, angiotensinogen and ACE or internalized from extracellular angiotensin II [5]. Most or all major components of the RAS cascade, including angiotensinogen, renin, ACE and angiotensin II receptors (AT1 or AT2), have been demonstrated in the heart, adrenal glands, brain and blood vessels [6,7]. Renin, the rate-limiting enzyme in the cascade, acts on the hepatocyte-synthesized substrate angiotensinogen to form angiotensin I, which is converted to angiotensin II by ACE. Angiotensin II is further metabolized by aminopeptidases into the active fragments angiotensin III and/or angiotensin IV. The principal effector molecule of the RAS cascade is angiotensin II, although other angiotensin fragments such as angiotensin III, angiotensin 1–7 and angiotensin IV have been shown to be biologically active [6]. The presence of renin, angiotensinogen and ACE in many tissues makes local formation of angiotensin II possible, whereas expression of angiotensin II receptors is essential for angiotensin II to induce biological effects at target sites. Two major classes of angiotensin II receptors are expressed in the heart, kidney, brain, adrenals and blood vessels, AT1 and AT2 [6,7]. AT1 is a G protein-coupled receptor belonging to the superfamily of seven transmembrane-spanning proteins. Two subtypes of AT1, designated AT1A and AT1B, have been identified in rodents, but the former is the predominant isoform in the kidney, blood vessels, and heart [6]. Although the pressor effect of angiotensin II is historically considered its primary action, it also stimulates aldosterone synthesis, promotes body salt and fluid retention, and induces cellular growth and proliferation in cardiovascular and renal tissues [4,6]. Most of the known actions of angiotensin II are mediated by the AT1 receptor, which is coupled to multiple signaling pathways, including phospholipase C, D, and A2 signaling, mitogen-activated protein kinase, and tyrosine kinase. Activation of AT1 leads to phosphoinositide hydrolysis, mobilization of intracellular calcium, and inhibition of adenylate cyclase [6–8].

Effects of genistein on angiotensin-converting enzyme in rats

Genistein (4,5,7-trihydroxyisoflavone), a phytoestrogen with selective estrogen receptor modulator properties, has received a great deal of attention over the last few years because of its potentially preventive roles against cardiovascular diseases. However, the precise molecular mechanisms for this modulation are not fully elucidated. In this study, we investigated (both in vivo and in vitro) the relationship between genistein and the changes of angiotensin-converting enzyme (ACE) in rat aortic endothelial cells (RAECs), serum and tissue (aorta). ACE expression was assessed by the immunofluorescence and the reverse transcriptase-polymerase chain reaction (RT-PCR) assay. Serum and tissue ACE activity was detected with a commercial kit. Genistein exhibited a concentration-dependent inhibitory effect on the expression of ACE, particularly at higher concentrations (24.70 ± 1.20 at 100 μM, P < 0.01, and 18.22 ± 0.92 at 200 μM, P < 0.01 compared with the control group 50.49 ± 5.19). The estrogen receptor blocker tamoxifen at 100 μM attenuated this effect of genistein. The extracellular signal-regulated kinase 1/2 (ERK1/2) blocker PD98059 also markedly inhibited this effect. The observations in vivo were highly consistent with the data in RAECs. These results indicate that genistein inhibits the expression of ACE via estrogen receptor and subsequently ERK1/2 signaling pathway in RAECs. Our results suggest that the down-regulation of ACE with a consequent change in the circulating levels of angiotensin II (Ang II), vasorelaxant angiotensin-(1–7) [Ang-(1–7)] and bradykinin plays an important role in cardiovascular effects of genistein through the ERK1/2 pathway.

Increase in ACE2 and Neprilysin Activity in the Hypothalamus of (mRen2)27 Transgenic Rats

Angiotensin converting enzyme (ACE), ACE2 and neprilysin, key enzymes in the renin-angiotensin system (RAS), are involved in the formation of angiotensin (Ang ) II and Ang-(1–7). Both peptides plays are major players in the modulation of fluid balance and cardiovascular function. The regulation of the enzymes responsible for their formation and metabolism in the hypothalamus over the long term is not known. We measured ACE, ACE2 and neprilysin mRNA in hypothalamic tissue of Sprague-Dawley (SD) and (mRen2)27 transgenic rats with over-expression of brain renin using using real time PCR. ACE mRNA was not different between the two strains (1.036 ± 0.07 vs 1.132 ± 0.14 relative gene expression). ACE2 and neprilysin mRNAs were ~30% and 60% higher, respectively, in tissue obtained from (mRen2)27 rats compared with SD rats. The lack of downregulation of ACE may account for the 10-fold elevation of Ang II in the hypothalamus of (mRen2)rats. We speculate that the increases in neprilysin and ACE2 would account for greater metabolism of Ang II and the increase in formation of Ang-(1–7) in the (mRen2)rats as a compensatory mechanism. (Support: HL-51952)

The expression of angiotensin and endothelin family members in mature ovarian follicles during periovulatory period after GnRH in the cow

There is the strong evidence that follicle maturation and ovulation are closely related with hemodynamics and hence vascular activity. The aim of this study was to investigate the mRNA expression for the members of angiotensin and endothelin systems in bovine mature follicles before and after GnRH application and shortly after ovulation. The ovaries were collected by transvaginal ovariectomy (n=5 cows/group) and the follicles were classified into 5 groups: before LH surge; 3–5h after GnRH application (during LH surge); 10h after GnRH; 20h after GnRH; 25h after GnRH (peri-ovulation) and early corpus luteum (CL, d 1–3). For better characterization of follicle classes, prostaglandin (PG)F2alpha and PGE2 were determined by EIA in follicular fluid (FF). The concentration of PGF2alpha and PGE2 in FF increased at 20h after GnRH and showed the maximal level in the follicles just before ovulation. For the angiotensin system, the mRNA expression of angiotensin converting enzyme (ACE) and angiotensin type1 receptor (AT1R) in follicle tissue (theca plus granulosa layers) significantly decreased in follicles after GnRH application, but AT2R mRNA expression remained unchanged. Contrary to ACE mRNA expression, Ang II peptide concentrations in FF increased continuously after GnRH application to the maximum level in follicles just before ovulation. For the endothelin system, the mRNA expression of endothelin converting enzyme-1 (ECE-1), and ET receptors (ETR-A and ETR-B) in follicle tissue decreased after GnRH with further decrease before ovulation (25h after GnRH), while the endothelin-1 (ET-1) mRNA expression remained unchanged. The data strongly support the idea that Ang II is induced by LH surge and this vasoactive peptide is a potential stimulator of PG synthesis in the bovine preovulatory follicle.

Cellular Immunostaining of Angiotensin-Converting Enzyme in Human Coronary Atherosclerotic Plaques

The aim of this study was to determine the cellular localization of angiotensin I-converting enzyme (ACE) in the atherosclerotic plaque and its correlation with inflammation and cellular proliferation. Angiotensin I-converting enzyme inhibitors reduce the incidence of vascular events; therefore, tissue ACE may play a determinant role in the pathophysiology of the atherosclerotic plaque. Histology and immunocytochemistry of de novo coronary plaques retrieved with directional coronary atherectomy from 141 patients were analyzed: 87 with stable angina, 39 with subacute unstable angina, and 15 with acute unstable angina. Compared with stable patients, unstable patients showed more thrombotic lesions (72% vs. 27%, p < 0.0001), smaller areas of fibrous plaque (2.3 +/- 1.2 mm2 vs. 2.8 +/- 1.1 mm2, p = 0.02), higher cellular proliferative score (0.78 +/- 0.9 vs. 0.27 +/- 0.6, p = 0.003), larger content of ACE-stained cells (26.3 +/- 23% vs. 12.6 +/- 15%, p = 0.005) and larger areas of inflammation as identified by CD68 immunostaining (29.5 +/- 22% vs. 20.2 +/- 19%, p = 0.02). A significant linear correlation was found between CD68- and ACE-stained areas (mm2) among unstable patients (r = 0.6, p = 0.0001), but it was absent among stable patients (r = 0.006, p = 0.9). Co-localization of ACE, CD68, and alpha-actin was confirmed by double immunostaining. Patients with Ki-67-positive staining as an index of cell proliferation showed also significantly larger areas of ACE immunoactivity (p = 0.004). Our data demonstrate ACE immunoactivity in inflammatory and proliferative cells of coronary atherosclerotic plaques. In particular, patients with unstable angina showed larger areas of ACE immunoactive tissue and proliferating cells compared with stable patients. These observations support a role of the enzyme in the pathophysiology of coronary unstable plaques and suggest potentially different effects of ACE inhibitors according to clinical presentation.

Cardioprotective Strategies to Improve Long-Term Outcomes Following Coronary Artery Bypass Surgery

Cardioprotective strategies implemented to prevent ischemic events in patients at risk for cardiovascular disease have decreased morbidity and prolonged survival. In this review, we have used evidence-based medicine and number-needed-to-treat (NNT) analyses to determine which interventions are most beneficial in minimizing ischemic events and prolonging survival following coronary artery bypass graft (CABG) surgery. Therapeutic interventions available to minimize ischemic events in the post-CABG patient were analyzed using ACC/AHA Classifications and Level of Evidence Criteria. Based on these recommendations, NNT analyses were performed to determine the effectiveness of each intervention compared to the number of patients needed to be treated before a benefit was apparent. The most beneficial intervention to improve mortality following CABG was the use of high tissue angiotensin-converting enzyme inhibitors, followed by statins and smoking cessation. NNT analyses and evidence-based medicine recommendations provide surgeons with cardioprotective strategies to improve long-term outcomes following CABG surgery.