Effects of a dual inhibitor of angiotensin converting enzyme and neutral endopeptidase, MDL 100,240, on endocrine and renal functions in healthy volunteers

OBJECTIVE: To investigate the endocrine and renal effects of the dual inhibitor of angiotensin converting enzyme and neutral endopeptidase, MDL 100,240. DESIGN: A randomized, placebo-controlled, crossover study was performed in 12 healthy volunteers. METHODS: MDL 100,240 was administered intravenously over 20 min at single doses of 6.25 and 25 mg in subjects with a sodium intake of 280 (n = 6) or 80 (n = 6) mmol/day. Measurements were taken of supine and standing blood pressure, plasma angiotensin converting enzyme activity, angiotensin II, atrial natriuretic peptide, urinary atrial natriuretic peptide and cyclic GMP excretion, effective renal plasma flow and the glomerular filtration rate as p-aminohippurate and inulin clearances, electrolytes and segmental tubular function by endogenous lithium clearance. RESULTS: Supine systolic blood pressure was consistently decreased by MDL 100,240, particularly after the high dose and during the low-salt intake. Diastolic blood pressure and heart rate did not change. Plasma angiotensin converting enzyme activity decreased rapidly and dose-dependently. In both the high- and the low-salt treatment groups, plasma angiotensin II levels fell and renin activity rose accordingly, while plasma atrial natriuretic peptide levels remained unchanged. In contrast, urinary atrial natriuretic peptide excretion increased dose-dependently under both diets, as did urinary cyclic GMP excretion. Effective renal plasma flow and the glomerular filtration rate did not change. The urinary flow rate increased markedly during the first 2 h following administration of either dose of MDL 100,240 (P < 0.001) and, similarly, sodium excretion tended to increase from 0 to 4 h after the dose (P = 0.07). Potassium excretion remained stable. Proximal and distal fractional sodium reabsorption were not significantly altered by the treatment. Uric acid excretion was increased. The safety and clinical tolerance of MDL 100,240 were good. CONCLUSIONS: The increased fall in blood pressure in normal volunteers together with the preservation of renal hemodynamics and the increased urinary volume, atrial natriuretic peptide and cyclic GMP excretion distinguish MDL 100,240 as a double-enzyme inhibitor from inhibitors of the angiotensin converting enzyme alone. The differences appear to be due, at least in part, to increased renal exposure to atrial natriuretic peptide following neutral endopeptidase blockade.     

Combined inhibition of neutral endopeptidase with angiotensin converting enzyme or endothelin converting enzyme in experimental diabetes

OBJECTIVE: The effects of combined inhibition of neutral endopeptidase (NEP) with either angiotensin-converting enzyme (ACE), or endothelin-converting enzyme (ECE) on blood pressure, urinary albumin excretion and heart weight were explored in experimental diabetes. DESIGN : Streptozotocin-induced diabetic Sprague-Dawley rats were treated with vehicle, the NEP/ACE inhibitor S 21402, the NEP/ECE inhibitor CGS 26303, the NEP inhibitor SCH 42495, the ACE inhibitor captopril or the endothelin receptor antagonist bosentan for 4 weeks. METHODS: Blood pressure was measured by tail-cuff method and radiotelemetry. Albuminuria, plasma renin activity and plasma atrial natriuretic peptide (ANP) were determined by radioimmunoassay. NEP binding was assessed by in vitro quantitative autoradiography. Metabolic and biochemistry parameters including food intake, 24-h urine volume, plasma glucose, glycated hemoglobin, glomerular filtration rate (GFR) and urinary sodium excretion were also determined. RESULTS: Mean blood pressure over the 4-week study period after commencement of treatment was reduced to a similar extent by a range of treatments including the ACE inhibitor, NEP/ACE inhibitor, endothelin receptor antagonist, NEP/ECE inhibitor, but not the NEP inhibitor, compared with vehicle-treated diabetic rats. Heart to body weight ratio in diabetic rats was only reduced by the NEP/ACE and the NEP/ECE inhibitor. Increased albuminuria in diabetic rats (1.1 times/divided by 1.2 mg/day) was reduced by the NEP/ACE (0.6 times/divided by 1.2 mg/day) and the NEP/ECE inhibitors (0.4 times/divided by 1.2 mg/day). Renal NEP was reduced by the NEP/ACE inhibitor (35 +/- 4%) or NEP/ECE inhibitor (38 +/- 4%) as well as by the pure NEP inhibitor (27 +/- 4%) compared with the untreated diabetic group. Other abnormal metabolic and biochemical parameters in diabetic rats were not influenced by any drug treatment. CONCLUSIONS: Combined inhibition of NEP/ACE or NEP/ECE confers beneficial effects on blood pressure, albuminuria and heart to body weight ratio in experimental diabetes.     

In-vitro and in-vivo inhibition of rat neutral endopeptidase and angiotensin converting enzyme with the vasopeptidase inhibitor gemopatrilat

OBJECTIVES: Vasopeptidase inhibitors are single molecules that simultaneously inhibit neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE). The aim of this study was to characterize in-vitro and in-vivo inhibition of NEP and ACE in the rat with the vasopeptidase inhibitor gemopatrilat. DESIGN AND METHODS: In-vitro NEP and ACE inhibition was studied by radioinhibitory binding assay using rat renal membranes and the specific NEP inhibitor radioligand 125I-RB104 and the specific ACE inhibitor radioligand 125I-MK351A, respectively (n = 3 per curve). In-vivo NEP and ACE inhibition was studied using in-vitro autoradiography in rats that received oral gemopatrilat (1, 3, 10 mg/kg; n = 4 per dose) and were killed 1 h later, or received oral gemopatrilat (3, 10 mg/kg) and were killed at time points 1, 2, 4, 8, 18, 24 and 48 h (n = 4 per time point). RESULTS: Gemopatrilat caused a concentration-dependent displacement of specific radioligands from renal membrane NEP (IC50 305 +/- 5.4 nmol/I) and ACE (IC50 3.6 +/- 0.02 nmol/). In the dose-response study gemopatrilat (1, 3 and 10 mg/kg) caused significant inhibition of plasma ACE (P< 0.01), and renal ACE and NEP (3, 10 mg/kg, P < 0.01). In the time course experiment, gemopatrilat (10 mg/kg) increased plasma renin activity for 8 h (P< 0.01) and inhibited plasma ACE (P< 0.05), renal NEP (P< 0.01) and renal ACE (P< 0.05) for 48 h. CONCLUSIONS: Gemopatrilat is a potent in-vitro vasopeptidase inhibitor that also causes prolonged inhibition of circulating and renal ACE and renal NEP after a single oral dose. The data suggest that gemopatrilat may be a useful addition to existing vasopeptidase inhibitors in the treatment of cardiovascular disease.     

Neutral endopeptidase inhibitor versus angiotensin converting enzyme inhibitor in a rat model of the metabolic syndrome

The antihypertensive treatment in patients with metabolic syndrome is unclear. We therefore used a rat model of the metabolic syndrome and compared the effects of enalapril, an angiotensin-converting-enzyme inhibitor, with candoxatril, a neutral endopeptidase inhibitor that inhibits degradation of atrial natriuretic peptide and, in addition to lowering blood pressure, exerts metabolically beneficial activity. Ten male Sprague Dawley rats were fed regular rat chow for 5 weeks. Fifty male Sprague Dawley rats were fed a high-fructose diet for 3 weeks, followed by addition of enalapril, 10 mg/Kg/d, or candoxatril, 25, 50, or 100 mg/Kg/d, for 2 weeks. Systolic blood pressure, plasma triglyceride level, and insulin level were measured at baseline and after 3 weeks and 5 weeks. Three weeks of a high-fructose diet led to a significant increase in all metabolic parameters. Candoxatril and enalapril lowered systolic blood pressure significantly (candoxatril −10 ± 1 to −22 ± 1 mm Hg and enalapril −27 ± 2 mm Hg). High-dose candoxatril and enalapril significantly decreased plasma triglyceride levels (by 17.8% and 32.8%, respectively), but only high-dose candoxatril decreased plasma insulin levels significantly (by 25.3%). High-dose candoxatril is a metabolically favorable option for lowering blood pressure in a rat model of metabolic syndrome.     

Protective effects of a dual endothelin converting enzyme/neutral endopeptidase inhibitor on the development of pulmonary hypertension secondary to cardiac dysfunction in the rat

Endothelium‐derived nitric oxide (NO) and endothelin (ET)‐1 interact to regulate the vascular tone in pulmonary hypertension (PH). We investigated the protective effects of an orally active, dual endothelin converting enzyme (ECE)/neutral endopeptidase (NEP) inhibitor/CGS 26393 on pulmonary vascular remodeling and pulmonary expressions of ET‐1 and endothelial nitric oxide synthase (eNOS) during the development of PH secondary to cardiac dysfunction. Significant increases in the mean pulmonary arterial pressure, pulmonary arteriolar medial thickness, and pulmonary expression of ET‐1 were seen in rats subjected to aortic banding for 4 weeks, compared with sham‐operated rats. Treatment with CGS 26393 (30 mg/kg, twice daily, p.o.) began on 1 day after aortic banding. CGS 26393 treated rats had lower mean pulmonary arterial pressure (15 ± 1 mmHg, mean ± SEM, P < 0.05) compared to vehicle‐treated rats (37 ± 1 mmHg). It also normalized pulmonary arteriolar medial thickness and reduced the levels of pulmonary ET‐1 and big ET‐1 by 55% (P < 0.05) and 28% (P < 0.01), respectively, when compared with vehicle‐treated animals. Meanwhile, the expressions of eNOS mRNA and eNOS protein and cGMP levels in the lung of CGS 26393‐treated rats were increased by 62% (P < 0.05), 100% (P < 0.05), and 32% (P < 0.01), respectively, compared to the vehicle‐treated rats. These results suggest that CGS 26393 could offer preventive effects on the development of PH by ameliorating pulmonary remodeling, decreasing ET‐1 production, and up‐regulating eNOS and cGMP in aorta‐banded rats. However, the molecular mechanisms by which treatment with CGS 26393 results in altered expressions of eNOS and cGMP awaits further investigation. Pediatr Pulmonol. 2010;45:1076–1085. © 2010 Wiley‐Liss, Inc.     

Vasopeptidase inhibitors, neutral endopeptidase inhibitors, and dual inhibitors of angiotensin-converting enzyme and neutral endopeptidase

Vasopeptidase inhibitors represent a new class of cardiovascular drugs. They function as a combined angiotensin-converting enzyme (ACE) inhibitor and neutral endopeptidase (NEP) inhibitor, the latter of which potentiates the actions of atrial natriuretic peptide (ANP) by minimizing its degradation in the circulation. The consequence of such dual inhibition is a synergistic reduction of vasoconstriction and enhancement of vasodilation, thereby serving to more effectively reduce blood pressure. Furthermore, inhibition of the renin-angiotensin-aldosterone system (RAAS) prevents physiologic compensatory responses in vivo seen with NEP inhibition alone. Vasopeptidase inhibitors have also shown to potentiate bradykinin and adrenomedullin, which additionally contribute to cardiovascular regulation. The most extensively researched and promising agents within the class of VP inhibitors is omapatrilat, a mercaptoacyl derivative of a bicyclic thiazepinone dipeptide. It is a single molecule with equal potency and affinity for ACE and NEP inhibition. Although ACE inhibition tends to more selectively benefit high-renin models of hypertension, vasopeptidase inhibition has been shown to be equally efficacious in low-, normal-, and high-renin models. Contrary to NEP inhibition alone, omapatrilat has also demonstrated the ability to significantly reduce blood pressure in spontaneously hypertensive rats, the equivalent of essential hypertension in humans. Studies also suggest that omapatrilat has cardioprotective properties, especially in the setting of congestive heart failure. More specifically, animal models have demonstrated omapatrilat to be more effective than ACE inhibition alone in remodeling the heart and improving its contractile function. Human studies have documented the efficacy of omapatrilat in the treatment of both hypertension and, to a lesser extent, heart failure. Safety concerns (specifically angioedema) are currently being addressed before the widespread utilization of this promising new agent.     

Carotid thickening,cardiac hypertrophy,and angiotensin converting enzyme gene polymorphism in patients with hypertension

An insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE) gene has been associated with increased risk for myocardial infarction, cardiomyopathy, carotid thickening, and cardiac hypertrophy. However, a conclusive agreement about the role of ACE genotype in the genetics of cardiovascular disease has not yet been reached. This study was undertaken to investigate the relationship of the I/D polymorphism of the ACE gene with carotid intima-media thickness (IMT) and left ventricular mass (LVM) in 175 Chinese patients with mild-to-moderate hypertension. The I/D genotypes were detected by the polymerase chain reaction using primers flanking the polymorphic region in intron 16 of the ACE gene. The IMT was measured in the common carotid and carotid bifurcation by B-mode ultrasound. The LVM was calculated with M-mode echocardiographic measures of the left ventricle. Patients with the DD genotype (n = 41) showed significant greater carotid IMT (1.593 ± 0.879 v1.309 ± 0.703 and 1.171 ± 0.583 mm, P = .01) but insignificant higher LVM index (123.8 ± 36.6 v 123.7 ± 37.4 and 118.2 ± 33.0 g/m², P = .61) than did those with the DI (n = 69) and II (n = 65) genotypes. The deletion polymorphism of the ACE gene (P = .04) was a significant predictor for carotid IMT on multiple regression analysis, controlling all the potential confounding factors including age (P = .001), systolic blood pressure (P = .09), smoking (P = .08), and plasma tissue plasminogen activator antigen (P = .03), but the LVM correlated only with age (P = .02), sex (P < .001), and body mass index (P < .001). These results indicated that the DD genotype of the ACE gene could be considered a risk factor for the development of early atherosclerosis in carotid arteries but not for left ventricular hypertrophy in the hypertensive population.     

Omapatrilat, a dual angiotensin-converting enzyme and neutral endopeptidase inhibitor, prevents fatty streak deposit in apolipoprotein E-deficient mice

Angiotensin-converting enzyme (ACE) is mainly responsible for converting angiotensin I (AI) to angiotensin II (AII), and ACE inhibitors prevent atherosclerosis in animal models. Neutral endopeptidase 24.11 (NEP) degrades substance P, kinins and atrial natriuretic peptide (ANP), and aortic wall NEP activity was found to be increased in atherosclerosis. In the present study, we have evaluated the effect of candoxatril, a NEP inhibitor, and of omapatrilat, a dual ACE and NEP inhibitor, on the development of fatty streak in apolipoprotein E (apoE)-deficient mice. Groups of ten male apoE-deficient mice were given either placebo, candoxatril 50 mg/kg per day, or omapatrilat 10, or 100 mg/kg per day for 4 months. None of the treatments influenced body weight, serum total or HDL-cholesterol. Compared with the placebo, candoxatril did not protect the mice from fatty streak deposit. In contrast, omapatrilat dose dependently inhibited the constitution of fatty streak in apoE-deficient mice. The precise advantages of the dual ACE and NEP inhibition versus the inhibition of only ACE should now be considered in the prevention of atherosclerosis as well as in the occurrence of its complications.     

Sustained antihypertensive actions of a dual angiotensin-converting enzyme neutral endopeptidase inhibitor, sampatrilat, in black hypertensive subjects.

Our objective was to evaluate the safety and antihypertensive efficacy of sampatrilat, a novel dual inhibitor of both angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP), in subjects poorly responsive to ACE inhibitor monotherapy. The ability of sampatrilat (50 to 100 mg daily) (n = 28) to lower blood pressure was compared with that of the ACE inhibitor lisinopril (10 to 20 mg daily) (n = 30) using a double-blind, randomized, parallel group study design over a 56-day treatment period in black hypertensives. Changes in systolic (SBP) and diastolic (DBP) blood pressure were determined using repeated ambulatory blood pressure (ABP) monitoring. Both sampatrilat and lisinopril decreased plasma ACE concentrations after 28 and 56 days. The decrease in plasma ACE concentrations (U/L) was greater after lisinopril (-9.33 +/- 0.52) as compared with sampatrilat (-6.31 +/- 0.70) (P = .0001) therapy. Lisinopril, but not sampatrilat, increased plasma renin activity. Lisinopril produced a transient decrease in mean 24-h ABP (mm Hg) at 28 days (SBP = -9.0 +/- 2.3, DBP = -5.7 +/- 1.3; P < .01), which returned to pretreatment values by 56 days of therapy. Alternatively, sampatrilat produced a sustained decrease in mean ABP over the 56-day treatment period (day 28: SBP = -7.3 +/- 1.8, DBP = -5.2 +/- 1.2; P < .01: day 56: SBP = -7.8 +/- 1.5; DBP = -5.2 +/- 0.95; P < 0.01) with a greater treatment effect on DBP than that of lisinopril at day 56 (P = .05). Treatment-emergent adverse events were noted to be similar between both treatment groups. We conclude that the antihypertensive actions of ACE/NEP inhibitor monotherapy in black subjects offers a novel therapeutic approach to patients otherwise resistant to the sustained antihypertensive actions of ACE inhibitor monotherapy.     

Protective action of angiotensin converting enzyme inhibitors on cardiac hypertrophy in the aortic-banded rat

Imidapril, enalapril and quinapril were subcutaneously administered to aortic-banded rats by osmotic minipumps to compare the suppressive actions of these angiotensin converting enzyme (ACE) inhibitors on pressure-induced cardiac hypertrophy. Among the three drugs tested, imidapril was most potent for the prevention of cardiac hypertrophy, although equipotent hypotensive doses were used. Imidapril reduced both serum and cardiac ACE activities, while enalapril reduced only the former. Quinapril also reduced both, however, it was less potent at reducing the former compared to imidapril. Moreover, only imidapril significantly decreased left ventricular end diastolic pressure, which tended to be increased by aortic-banding. The lipophilicity of ACE inhibitors could not explain the more potent suppressive action of imidapril on cardiac hypertrophy because the lipophilicity of imidaprilat, an active metabolite of imidapril, was as low as an active metabolite of enalapril; i.e., much lower than an active metabolite of quinapril. The efficacy of ACE inhibitors on pressure-induced cardiac hypertrophy depends not only on an inhibitory effect on cardiac ACE activity, but also on other actions such as their effect on left ventricular end diastolic pressure.     

Aspirin, angiotensin converting enzyme inhibitors and cardiac insufficiency

The possible negative therapeutic interaction between aspirin and angiotensin converting enzyme inhibitors arose from the conclusions of several experimental studies and retrospective analysis of large scale mortality trials with converting enzyme inhibitors. Some experimental results show inhibition of the vasodilatation of converting enzyme inhibitors, increase in pulmonary pressures, vascular resistances and blood pressure, and degradation of renal function and exercise capacity. However, other studies did not confirm these results. In large scale therapeutic trials, some retrospective analyses, but not all of them, have shown less benefit on morbi-mortality of converting enzyme inhibitors in patients on aspirin. The differences between the doses of aspirin, the type and dosage of the converting enzyme inhibitors and neuro-hormonal activation of the patients could explain the discordant results. The results of randomised trials are awaited but, in the meantime, it is logical to propose small doses of aspirin (< or = 100 mg/day) for patients with cardiac failure and atherosclerosis and to avoid the association in all the other patients.     

Hypoglycemic syncope induced by a combination of cibenzoline and angiotensin converting enzyme inhibitor

A 65-year-old Japanese woman with dilated cardiomyopathy, hypothyroidism and refractory sustained ventricular tachycardia experienced a near-death hypoglycemic syncope. The attack seemed to be induced by a high level of serum insulin, probably due to cibenzoline and by concomitant use of an angiotensin converting enzyme inhibitor (ACEI). Additionally, decreased food intake because of a severe toothache may have contributed to the deterioration of her condition. This case warns cardiologists that a combined cibenzoline and ACEI therapy can provoke serious adverse effects such as hypoglycemic syncope in the elderly. Therefore, the possibility of a hypoglycemic attack associated with these drugs should be explained to patients who are in poor condition.     

Clinical pharmacology of the angiotensin converting enzyme inhibitor, enalapril

Enalapril is a new angiotensin converting enzyme inhibitor which, when absorbed by the digestive tract, is converted to enalaprilat. This metabolite is, in fact, the active form of enalapril. Its duration of action is sufficiently long so that enalapril can be administered in a single daily dose. Enalapril has been proved to be a highly effective therapeutic agent which is well tolerated by patients with arterial hypertension or severe congestive heart failure.     

Endothelin-converting enzyme/neutral endopeptidase inhibitor SLV338 prevents hypertensive cardiac remodeling in a blood pressure-independent manner

Hypertensive heart disease is a major contributor to cardiovascular mortality. Endothelin is a potent vasoconstrictive and profibrotic mediator produced by the endothelin-converting enzyme (ECE), whereas natriuretic peptides, degraded by the neutral endopeptidase (NEP), have diuretic, vasodilatory, and antifibrotic properties. Thus, combined ECE/NEP inhibition may halt hypertensive cardiac remodeling. This study examined effects of SLV338, a novel ECE/NEP inhibitor, on cardiac protection in experimental renovascular hypertension (2-kidney, 1-clip [2K1C]). Male rats were allocated to 5 groups: sham-operated rats, untreated animals with 2K1C, 2K1C animals treated with oral SLV338 (30 and 100 mg/kg per day), and 2K1C animals treated with oral losartan (20 mg/kg per day). Treatment duration was 12 weeks. Blood pressure was assessed every 4 weeks. At study end, hearts were taken for histology/computer-aided histomorphometry/immunohistochemistry. Pharmacological properties of SLV338 are described. SLV338 is a dual ECE/NEP inhibitor, as demonstrated both in vitro and in vivo. In the 2K1C study, losartan lowered blood pressure by ≤46 mm Hg, whereas both dosages of SLV338 had no effect. However, SLV338 (both dosages) completely normalized cardiac interstitial fibrosis, perivascular fibrosis, myocyte diameter, and media:lumen ratio of cardiac arteries, as did losartan. Cardiac transforming growth factor-β1 expression was significantly enhanced in untreated 2K1C rats versus controls, whereas treatment with SLV338 and losartan prevented this effect. Taken together, dual ECE/NEP inhibitor SLV338 prevents cardiac remodeling to the same extent as losartan, but in a blood pressure-independent manner, in a rat model of renovascular hypertension. This effect is at least partially mediated via suppression of cardiac transforming growth factor-β1 expression.     

Dual angiotensin-converting enzyme/neutral endopeptidase inhibition on cardiac and renal fibrosis and inflammation in DOCA-salt hypertensive rats

OBJECTIVES: The relative roles of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) inhibition on cardiac and renal fibrosis in deoxycorticosterone acetate (DOCA)-salt hypertensive rats were studied. METHODS: The ACE/NEP inhibitor omapatrilat (40 mg/kg per day), the ACE inhibitor enalapril (10 mg/kg per day) and the NEP inhibitor CGS 25462(100 mg/kg per day) were administrated for 3 weeks to DOCA rats. Collagen was stained with Sirius red, and mediators of inflammation were identified by immunolabeling (vascular cell adhesion molecule, nuclear factor-kappaB, infiltrating ED-1-positive macrophages and monocyte chemotactic protein-1) or by western blot (platelet-endothelial cell adhesion molecule-1). RESULTS: Elevated systolic blood pressure of DOCA rats was significantly reduced (P < 0.05) by omapatrilat and CGS 25462. Omapatrilat and CGS 25462 significantly (P < 0.05) decreased interstitial collagen density in the left ventricle of DOCA rats compared with untreated DOCA rats. Enalapril only decreased the subepicardial collagen of DOCA rats. Omapatrilat significantly (P < 0.05) decreased renal mesangial collagen deposition in DOCA rats. Cardiac and renal expression of surface adhesion molecules, nuclear factor-kappaB, monocyte chemotactic protein and ED-1-positive cells were decreased in omapatrilat-treated DOCA rats compared with untreated DOCA rats. Enalapril and CGS 25462 did not alter mesangial collagen of DOCA rats. CONCLUSIONS: Dual ACE/NEP inhibition was more effective than ACE or NEP inhibition in decreasing inflammatory mediators, and improving cardiac and renal fibrosis. This suggests a role for NEP inhibition added to blockade of the renin-angiotensin system that may explain the greater efficacy of omapatrilat.     

Neutral endopeptidase and angiotensin I converting enzyme insertion/deletion gene polymorphism in humans

Neutral endopeptidase (NEP) hydrolyses angiotensins (Ang) I and II and generates angiotensin-(1-7) [Ang-(1-7)]. In humans, the insertion/deletion (I/D) angiotensin-I converting enzyme (ACE) gene polymorphism determined plasma ACE levels by 40%. In rats, a similar polymorphism determines ACE levels which are inversely associated to NEP activity. The objective of this study is to evaluate the relationship between ACE expression and plasma NEP activity in normotensive subjects and in hypertensive patients. In total, 58 consecutive patients with hypertension, evaluated in our Hypertension Clinic, were compared according to their ACE I/D genotypes with 54 control subjects in terms of both plasma ACE activity and NEP activities. Plasma ACE activity was elevated 51 and 70% in both DD ACE groups (normotensives and hypertensives) compared with their respective ID and II ACE groups (P<0.001). A significant effect of the ACE polymorphism and of the hypertensive status on ACE activity was observed (P<0.001). In normotensive DD ACE subjects, NEP activity was 0.30+/-0.02 U/ml, whereas in the normotensive II ACE and in the normotensive ID ACE subjects NEP activity was increased 65 and 48%, respectively (P<0.001). In the hypertensive DD ACE patients, NEP activity was 0.47+/-0.03 U/mg. An effect of the I/D ACE genotypes on NEP activity (P<0.04) and an interaction effect between the I/D ACE genotype and the hypertensive status were also observed (P<0.001). These results are consistent with a normal and inverse relationship between the ACE polymorphism and NEP activity in normotensive humans (as is also observed in rats). This normal relationship is not observed in hypertensive patients.     

Role of osteopontin in cardiac fibrosis and remodeling in angiotensin II-induced cardiac hypertrophy

Osteopontin (OPN) is upregulated in several experimental models of cardiac fibrosis and remodeling. However, its direct effects remain unclear. We examined the hypothesis that OPN is important for the development of cardiac fibrosis and remodeling. Moreover, we examined whether the inhibitory effect of eplerenone (Ep), a novel aldosterone receptor antagonist, was mediated through the inhibition of OPN expression against cardiac fibrosis and remodeling. Wild-type (WT) and OPN-deficient mice were treated with angiotensin II (Ang II) for 4 weeks. WT mice receiving Ang II were divided into 2 groups: a control group and an Ep treatment group. Ang II treatment significantly elevated blood pressure and caused cardiac hypertrophy and fibrosis in WT mice. Ep treatment and OPN deficiency could reduce the Ang II-induced elevation of blood pressure and ameliorate the development of cardiac fibrosis, whereas Ep-only treatment abolished the development of cardiac hypertrophy. Most compelling, the reduction of cardiac fibrosis led to an impairment of cardiac systolic function and subsequent left ventricular dilatation in Ang II-treated OPN-deficient mice. These results suggest that OPN has a pivotal role in the development of Ang II-induced cardiac fibrosis and remodeling. Moreover, the effect of Ep on the prevention of cardiac fibrosis, but not cardiac hypertrophy, might be partially mediated through the inhibition of OPN expression.     

心房颤动患者心房组织的血管紧张素转换酶2表达及血管紧张素转换酶抑制剂干预的影响

目的 探讨心房颤动（房颤）患者心房肌组织中血管紧张素转换酶2（ACE2）的表达和血管紧张素转换酶抑制剂（ACEI）干预的影响及可能的信号传导途径。方法 选取接受开胸手术的风湿性心脏病患者47例,手术中取右心耳处心房肌标本。采用RT-PCR法检测心房肌ACE2和ACEmRNA水平,采用Western blot法检测ACE、ACE2、细胞外信号调节激酶1／2（ERK1／2）和磷酸化的细胞外信号调节激酶1／2（pERK1／2）蛋白表达水平,应用放射免疫法检测心房肌组织血管紧张素Ⅱ（AngⅡ）水平。结果 与窦性心律组相比,持续性房颤组心房肌组织中ACE2表达显著减少（P〈0．05）,而ACE的表达和AngⅡ含量显著增加（P〈0．05）。ERK1／2的活化水平在持续性房颤组较窦性心律组明显增加（P〈0．05）。与持续性房颤组相比,ACEⅠ干预组ACE2表达水平显著增加（P〈0．01）,ERK1／2的活化水平显著降低（P〈0．05）,而ACE表达和AngⅡ含量差异无统计学意义。结论 房颤患者心房肌组织中ACE2表达下调,ACE／ACE2平衡失调;ACEⅠ对房颤的长期临床效应可能与其上调ACE2、抑制有丝分裂素激活蛋白激酶信号途径有关。