Chronic Angiotensin-converting Enzyme Inhibition Research Articles

Chronic angiotensin-converting enzyme inhibition attenuates frailty and protects against atrial fibrillation in aging mice

BackgroundAging is a major risk factor for atrial fibrillation (AF); however, not all individuals age at the same rate. Frailty, which is a measure of susceptibility to adverse health outcomes, can be quantified with a frailty index (FI). ObjectiveThis study aimed to determine the effects of angiotensin-converting enzyme (ACE) inhibition on AF and atrial remodeling in aging and frail mice. MethodsAging mice were treated with the ACE inhibitor enalapril for 6 months beginning at 16.5 months of age and frailty was quantified. AF susceptibility and atrial structure and function were assessed by intracardiac electrophysiology in anesthetized mice, high-resolution optical mapping in intact atrial preparations, patch clamping in isolated atrial myocytes, and histology and molecular biology in atrial tissues. ResultsEnalapril attenuated frailty in aging mice with larger effects in females. AF susceptibility was increased in aging mice but attenuated by enalapril. AF susceptibility and duration also increased as a function of FI score. P-wave duration was increased and atrial conduction velocity was reduced in aging mice and improved after enalapril treatment. Furthermore, P-wave duration and atrial conduction velocity were strongly correlated with FI score. Atrial action potential upstroke velocity (Vmax) and Na+ current (INa) were reduced whereas atrial fibrosis was increased in aging mice. Action potential Vmax, INa, and fibrosis were improved by enalapril and also correlated with FI scores. ConclusionACE inhibition with enalapril attenuates frailty and reduces AF susceptibility in aging mice by preventing atrial electrical and structural remodeling.

Chronic inhibition of angiotensin converting enzyme lowers blood pressure in spontaneously hypertensive rats by attenuation of sympathetic tone: The role of enhanced baroreflex sensitivity

Spontaneously hypertensive rats (SHR) are characterized by sympathetic hyperactivity and insufficient parasympathetic activity, and their high blood pressure (BP) can be lowered by long-term inhibition of the renin-angiotensin system. The aim of our study was to determine the influence of chronic inhibition of angiotensin converting enzyme (ACE) by captopril on cardiovascular regulation by the sympathetic and parasympathetic nervous system. Implanted radiotelemetric probes or arterial cannulas were used to measure mean arterial pressure (MAP), heart rate (HR), and arterial baroreflex in adult SHR and Wistar-Kyoto (WKY) rats under basal or stress conditions. MAP and the low-frequency component of systolic blood pressure variability (LF-SBPV, marker of sympathetic activity) were greater in SHR than in WKY rats. Under basal conditions chronic captopril treatment reduced both parameters more effectively in SHR, and the same was true during acute restraint stress. HR was similar in control rats of both strains, but WKY rats showed greater heart rate variability (HRV), indicating higher parasympathetic activity. Captopril administration increased HR in both strains, whereas HRV was decreased only in WKY. Chronic captopril treatment improved the impaired baroreflex-HR control in SHR by increasing the sensitivity but not the capacity of vagal arm of arterial baroreflex. Captopril treatment attenuated BP changes elicited by dimethylphenylpiperazinium (DMPP, agonist of nicotinic acetylcholine receptors), especially in SHR, indicating that sympathetic nerve transmission is facilitated by angiotensin II more in hypertensive than in normotensive animals. Thus, chronic ACE inhibition improves baroreflex sensitivity and lowers BP through both central and peripheral attenuation of sympathetic tone.

ACE inhibitors and angiotensin receptor blockers differentially alter the response to angiotensin II treatment in vasodilatory shock

BackgroundAngiotensin-converting enzyme inhibitor (ACEi) and angiotensin receptor blockers (ARB) medications are widely prescribed. We sought to assess how pre-admission use of these medications might impact the response to angiotensin-II treatment during vasodilatory shock.MethodsIn a post-hoc subgroup analysis of the randomized, placebo-controlled, Angiotensin Therapy for High Output Shock (ATHOS-3) trial, we compared patients with chronic angiotensin-converting enzyme inhibitor (ACEi) use, and patients with angiotensin receptor blocker (ARB) use, to patients without exposure to either ACEi or ARB. The primary outcome was mean arterial pressure after 1-h of treatment. Additional clinical outcomes included mean arterial pressure and norepinephrine equivalent dose requirements over time, and study-drug dose over time. Biological outcomes included baseline RAS biomarkers (renin, angiotensin-I, angiotensin-II, and angiotensin-I/angiotensin-II ratio), and the change in renin from 0 to 3 h.ResultsWe included n = 321 patients, of whom, 270 were ACEi and ARB-unexposed, 29 were ACEi-exposed and 22 ARB-exposed. In ACEi/ARB-unexposed patients, angiotensin-treated patients, compared to placebo, had higher hour-1 mean arterial pressure (9.1 mmHg [95% CI 7.6–10.1], p < 0.0001), lower norepinephrine equivalent dose over 48-h (p = 0.0037), and lower study-drug dose over 48-h (p < 0.0001). ACEi-exposed patients treated with angiotensin-II showed similarly higher hour-1 mean arterial pressure compared to ACEi/ARB-unexposed (difference in treatment-effect: − 2.2 mmHg [95% CI − 7.0–2.6], pinteraction = 0.38), but a greater reduction in norepinephrine equivalent dose (pinteraction = 0.0031) and study-drug dose (pinteraction < 0.0001) over 48-h. In contrast, ARB-exposed patients showed an attenuated effect of angiotensin-II on hour-1 mean arterial pressure versus ACEi/ARB-unexposed (difference in treatment-effect: − 6.0 mmHg [95% CI − 11.5 to − 0.6], pinteraction = 0.0299), norepinephrine equivalent dose (pinteraction < 0.0001), and study-drug dose (pinteraction = 0.0008). Baseline renin levels and angiotensin-I/angiotensin-II ratios were highest in ACEi-exposed patients. Finally, angiotensin-II treatment reduced hour-3 renin in ACEi/ARB-unexposed and ACEi-exposed patients but not in ARB-exposed patients.ConclusionsIn vasodilatory shock patients, the cardiovascular and biological RAS response to angiotensin-II differed based upon prior exposure to ACEi and ARB medications. ACEi-exposure was associated with increased angiotensin II responsiveness, whereas ARB-exposure was associated with decreased responsiveness. These findings have clinical implications for patient selection and dosage of angiotensin II in vasodilatory shock.Trial Registration ClinicalTrials.Gov Identifier: NCT 02338843 (Registered January 14th 2015).

BS-452682-4 EFFECTS OF CHRONIC ANGIOTENSIN CONVERTING ENZYME INHIBITION ON ATRIAL FUNCTION AND ARRHYTHMOGENESIS IN AGED AND FRAIL MICE

Aging is associated atrial remodeling and increased susceptibility to atrial fibrillation (AF); however, aging-dependent changes can be variable. Frailty measures health status independent of chronological age, can be quantified using a frailty index (FI) and can account for heterogeneity in aging individuals. Angiotensin converting enzyme inhibition (ACEi) can impact frailty however its effects on AF and atrial remodeling are unknown. To determine the effects of chronic ACEi on atrial structure, function, and arrhythmogenesis in aged and frail mice. Wildtype mice were treated with the ACEi enalapril (20 mg/kg/day) or placebo for 6 months starting at 75 weeks of age. Mice aged 10-15 weeks were used as young controls. Mice were used in intracardiac electrophysiology, high resolution optical mapping, patch-clamping, and histology. ACEi reduced FI in aged mice (0.24 vs 0.36; n=27-31; P<0.05) without altering blood pressure. AF susceptibility was increased in aged vs young mice (100 vs 17%; n=6; P<0.05) and reduced in ACEi vs aged mice (43 vs 100%; n=6-7; P<0.05). P wave duration was reduced in ACEi vs aged mice (27.4 vs 32.5 ms; n=7; P<0.05), showed variability within age/treatment groups, and was correlated and graded by FI (R=0.91; n=20; P<0.05). Optical mapping revealed an age dependent reduction in atrial conduction velocity (CV; 35.3 vs 40.2 cm/s; n=6-9; P<0.05) while ACEi improved CV in aged mice (37.7 vs 35.3 cm/s; n=6-9; P=0.05). CV was also correlated with FI score (R=0.72; n=24; P<0.05). Patch-clamp studies in isolated left atrial (LA) myocytes identified a reduction in action potential upstroke velocity (Vmax; 150.8 vs 165.4 V/s; n=18-32; P<0.05) that was associated with a reduction in peak sodium current (INa; -38.3 vs -52.1 pA/pF; n=7-19; P<0.05) in aged vs young mice. INa was increased in ACEi vs aged (-47.2 vs -38.3 pA/pF; n=14–19; P=0.09) and not different (P=0.62) vs young mice. Importantly, Vmax (R=0.32; n=73; P<0.05) and INa (R=0.5; n=36; P < 0.05) were graded by FI. LA fibrosis was increased in aged mice vs young (10.8 vs 3.9%; n=5-8; P<0.05), reduced in ACEi vs aged mice (8.9 vs 10.8%; n=5-8; P<0.05), and strongly correlated with FI (R=0.89; n=19; P<0.05). ACEi reduced frailty in aging mice and attenuated age-related AF and atrial remodeling. Aging was associated with substantial variability within groups. Frailty was a strong predictor of changes atrial function in aging mice including after ACEi treatment, independent of chronological age.

Ventricular arrhythmia susceptibility in a new porcine model of heart failure (HF) with reduced ejection fraction

Abstract Introduction Sudden death secondary to ventricular arrhythmias is common in HF patients, with no effective treatment available outside of implantable cardiac defibrillators. While animal models are essential for the discovery of anti-arrhythmic drugs, no reliable large animal HF models with associated ventricular arrhythmias have been described so far. Objectives We aimed at evaluating ventricular remodeling and arrhythmia susceptibility in an HF pig model with reduced ejection fraction (EF) following myocardial infarction (MI). Methods MI was induced in 53 male Göttingen minipigs (12–15 months, 20–25 kg) by coronary embolization in mid-left anterior descending and mid-left circumflex coronary arteries using endovascular coils. Seven other pigs underwent sham operation and were used as control. Two weeks after surgery, cardiac function was assessed by echocardiography, and animals were included based on EF&amp;lt;50% (n=15/53), assigned either to 12 weeks of vehicle (n=9) or perindopril (n=6, 1 mg/kg/d, per os) group. At the end of the study, their left ventricular (LV) electrical remodeling was studied by echocardiography/electrocardiography and a programmed-electrical stimulation protocol was performed to evaluate the susceptibility to develop ventricular arrhythmias. Results At the end of the study, animals in the vehicle group had a significant LV remodeling associated with a reduced EF (p&amp;lt;0.05 vs. sham, see table). This remodeling was associated with cardio-pulmonary congestion, significant increases in LV end-diastolic pressure, left atrial volume, and lung mass (all p&amp;lt;0.05 vs. sham, see table), fully prevented by perindopril treatment. They had also an electrical remodeling as evidenced by an increase in PR, QRS, and QTc intervals, as well as LV effective refractory period (+18%, 14%, 33%, and 13%, respectively, p&amp;lt;0.05, compared to sham animals). Electrical changes were mitigated by perindopril treatment (p=NS vs. sham). LV mechanical dispersion measured with speckle-tracking echocardiography was significantly increased in vehicle group (58±5 vs. 22±1 ms in sham group, respectively) as well as in perindopril group. Programmed-electrical stimulations induced in 6/8 vehicle animals either non-sustained (n=3) or sustained (n=2) ventricular tachycardia, or ventricular fibrillation (n=1). In sham group only 1/7 animal had a ventricular fibrillation. No inducible ventricular arrhythmia was observed in animals treated with Perindopril. Conclusion In this new pig model of congestive HF with reduced EF, LV remodeling was associated with electrical remodeling and susceptibility to develop arrhythmias. Chronic angiotensin-converting enzyme inhibitor treatment prevented congestion, mitigated electrical remodeling, and suppressed arrhythmia susceptibility. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): Servier Research Institute - CardioVascular &amp; Metabolic Diseases Center for Therapeutic Innovation Table 1

Effects of Trandolapril on Structural, Contractile and Electrophysiological Remodeling in Experimental Volume Overload Heart Failure.

Chronic volume overload induces multiple cardiac remodeling processes that finally result in eccentric cardiac hypertrophy and heart failure. We have hypothesized that chronic angiotensin-converting enzyme (ACE) inhibition by trandolapril might affect various remodeling processes differentially, thus allowing their dissociation. Cardiac remodeling due to chronic volume overload and the effects of trandolapril were investigated in rats with an aortocaval fistula (ACF rats). The aortocaval shunt was created using a needle technique and progression of cardiac remodeling to heart failure was followed for 24 weeks. In ACF rats, pronounced eccentric cardiac hypertrophy and contractile and proarrhythmic electrical remodeling were associated with increased mortality. Trandolapril substantially reduced the electrical proarrhythmic remodeling and mortality, whereas the effect on cardiac hypertrophy was less pronounced and significant eccentric hypertrophy was preserved. Effective suppression of electrical proarrhythmic remodeling and mortality but not hypertrophy indicates that the beneficial therapeutic effects of ACE inhibitor trandolapril in volume overload heart failure might be dissociated from pure antihypertrophic effects.

Treatment Effectiveness in Heart Failure with Comorbidity: Lung Disease and Kidney Disease.

To assess the clinical effectiveness of beta-blocker therapy in individuals with heart failure (HF) and chronic lung disease and of angiotensin-converting enzyme inhibitors (ACE-Is) and angiotensin II receptor blockers (ARBs) in individuals with HF and chronic kidney disease. Retrospective cohort study. Community. Individuals with HF with reduced ejection fraction (HFrEF) or HF with preserved ejection fraction (HFpEF). We undertook separate new-user cohort studies to assess the effectiveness of beta-blocker therapy in treating HF and chronic lung disease and ACE-Is and ARBs in treating HF and chronic kidney disease (CKD). Individuals with a chronic lung disease diagnosis were included in the group with HF and chronic lung disease (International Classification of Diseases, Ninth Revision, codes 490-496, 518). Individuals with an estimated glomerular filtration rate less than 60 mL/min per 1.73 m2 were included in the group with HF and CKD. The clinical outcomes of interest were death from any cause, hospitalization for HF, and hospitalization for any reason. We fitted pooled logistic marginal structural models using inverse probability weighting, stratified according to HF type. For individuals with HFrEF with chronic lung disease, beta-blocker therapy was protective against death (relative risk (RR) = 0.58, 95% confidence interval (CI) = 0.44-0.77) and hospitalization for HF (RR = 0.78, 95% CI = 0.60-1.00). For those with HFpEF, no statistically significant associations between beta-blocker therapy use and any of the outcomes were observed. We found ACE-I and ARB use to be protective against all three outcomes of interest in individuals with HFrEF (death from any cause: RR = 0.60, 95% 0.40-0.91; hospitalization for HF: RR = 0.43, 95% CI = 0.28-0.67; hospitalization for any reason: RR = 0.63, 95% CI = 0.45-0.89, respectively) and those with HFpEF (death from any cause: RR = 0.52, 95% CI = 0.33-0.81; hospitalization for HF: RR = 0.35, 95% CI = 0.18-0.68; hospitalization for any reason: RR = 0.67, 95% CI = 0.47-0.95). Large observational studies may allow for identification of important subgroups of individuals with HF that might benefit from existing treatment approaches. Our findings may also better inform the design of more-definitive future observational studies and randomized trials.

Inhibition of soluble epoxide hydrolase does not improve the course of congestive heart failure and the development of renal dysfunction in rats with volume overload induced by aorto-caval fistula.

The detailed mechanisms determining the course of congestive heart failure (CHF) and associated renal dysfunction remain unclear. In a volume overload model of CHF induced by creation of aorto-caval fistula (ACF) in Hannover Sprague-Dawley (HanSD) rats we explored the putative pathogenetic contribution of epoxyeicosatrienoic acids (EETs), active products of CYP-450 dependent epoxygenase pathway of arachidonic acid metabolism, and compared it with the role of the renin-angiotensin system (RAS). Chronic treatment with cis-4-[4-(3-adamantan-1-yl-ureido) cyclohexyloxy]benzoic acid (c-AUCB, 3 mg/l in drinking water), an inhibitor of soluble epoxide hydrolase (sEH) which normally degrades EETs, increased intrarenal and myocardial EETs to levels observed in sham-operated HanSD rats, but did not improve the survival or renal function impairment. In contrast, chronic angiotensin-converting enzyme inhibition (ACEi, trandolapril, 6 mg/l in drinking water) increased renal blood flow, fractional sodium excretion and markedly improved survival, without affecting left ventricular structure and performance. Hence, renal dysfunction rather than cardiac remodeling determines long-term mortality in advanced stage of CHF due to volume overload. Strong protective actions of ACEi were associated with suppression of the vasoconstrictor/sodium retaining axis and activation of vasodilatory/natriuretic axis of the renin-angiotensin system in the circulating blood and kidney tissue.

Impact of Angiotensin Converting Enzyme Inhibitor versus Angiotensin Receptor Blocker on Incidence of New-Onset Diabetes Mellitus in Asians.

PurposeAngiotensin converting enzyme inhibitor (ACEI) and angiotensin receptor blocker (ARB) are associated with a decreased incidence of new-onset diabetes mellitus (NODM). The aim of this study was to compare the protective effect of ACEI versus ARBs on NODM in an Asian population.Materials and MethodsWe investigated a total of 2817 patients who did not have diabetes mellitus from January 2004 to September 2009. To adjust for potential confounders, a propensity score matched (PSM) analysis was performed using a logistic regression model. The primary end-point was the cumulative incidence of NODM, which was defined as having a fasting blood glucose ≥126 mg/dL or HbA1c ≥6.5%. Multivariable cox-regression analysis was performed to determine the impact of ACEI versus ARB on the incidence of NODM.ResultsMean follow-up duration was 1839±1019 days in all groups before baseline adjustment and 1864±1034 days in the PSM group. After PSM (C-statistics=0.731), a total 1024 patients (ACEI group, n=512 and ARB group, n=512) were enrolled for analysis and baseline characteristics were well balanced. After PSM, the cumulative incidence of NODM at 3 years was lower in the ACEI group than the ARB group (2.1% vs. 5.0%, p=0.012). In multivariate analysis, ACEI vs. ARB was an independent predictor of the lower incidence for NODM (odd ratio 0.37, confidence interval 0.17-0.79, p=0.010).ConclusionIn the present study, compared with ARB, chronic ACEI administration appeared to be associated with a lower incidence of NODM in a series of Asian cardiovascular patients.

Inhibition of soluble epoxide hydrolase counteracts the development of renal dysfunction and progression of congestive heart failure in Ren-2 transgenic hypertensive rats with aorto-caval fistula.

The detailed mechanisms determining the course of congestive heart failure (CHF) in hypertensive subjects with associated renal dysfunction remain unclear. In Ren-2 transgenic rats (TGR), a model of angiotensin II (ANG II)-dependent hypertension, CHF was induced by volume overload achieved by creation of the aorto-caval fistula (ACF). In these rats we investigated the putative pathophysiological contribution of epoxyeicosatrienoic acids (EETs) and compared it with the role of the renin-angiotensin system (RAS). We found that untreated ACF TGR exhibited marked intrarenal and myocardial deficiency of EETs and impairment of renal function. Chronic treatment of these rats with cis-4-[4-(3-adamantan-1-yl-ureido)cyclohexyloxy]benzoic acid (c-AUCB, 3 mg/L in drinking water), an inhibitor of soluble epoxide hydrolase (sEH) which normally degrades EETs, increased intrarenal and myocardial EETs, markedly improved survival rate, and increased renal blood flow, glomerular filtration rate and fractional sodium excretion, without altering RAS activity. Chronic angiotensin-converting enzyme inhibition (ACEi) with trandolapril, (6 mg/L in drinking water) improved survival rate even more, and also inhibited the development of renal dysfunction; these beneficial actions were associated with significant suppression of the vasoconstrictor/sodium retaining axis and further activation of the vasodilatory/natriuretic axis of the systemic and intrarenal RAS, without modifying tissue availability of biologically active fatty acid epoxides. In conclusion, these findings strongly suggest that chronic sEH inhibition and chronic treatment with ACEi, each of them altering a different vasoactive system, delay or even prevent the onset of decompensation of CHF in ACF TGR, probably by preventing the development of renal dysfunction.

Effect of angiotensin converting enzyme inhibitors on periprocedural myocardial infarction in patients with metabolic syndrome.

Metabolic syndrome (MetS) has been reported as a risk factor for cardiovascular events. The aim of the present study is to investigate the association between chronic angiotensin-converting enzyme inhibitors (ACE-I) therapy and the rate of periprocedural myocardial infarction (PMI) after elective coronary stenting among patients with MetS. The inclusion criteria were MetS and plan for elective percutaneous coronary intervention. To assess the effect of ACE-I treatment on the incidence of PMI, measurements of cardiac biomarkers (CK-MB mass and troponin I) were performed at baseline and 24 h after the procedure. A total of 459 patients fulfilling the inclusion criteria were recruited to chronic ACE-I treatment and ACE-I naive groups in a 2/1 ratio. Baseline troponin I and CK-MB levels were similar in both treatment groups, whereas they were significantly lower in ACE-I group 24 h after the procedure. Univariate analysis identified body mass index (BMI), LDL cholesterol, nitrate and ACE-I use as significant factors for the development of PMI. Multivariate regression model revealed that body mass index increased and use of nitrate and ACE-I decreased the probability of PMI independent from confounding factors (OR 1.14, 95% CI 1.05-1.23, p = 0.002 for BMI; OR 0.26, 95% CI 0.14-0.48, p = 0.01 for nitrate use, OR 0.51, 95% CI 0.27-0.93, p = 0.03 for ACE-I use). This prospective observational cohort trial demonstrated that chronic ACE-I therapy was an independent predictor for reduced PMI among patients with MetS who underwent elective coronary intervention.

An Observation of the Correlation Between ACEI and ARB Medications and Chronic Pain Medication Utilization in a Community Pharmacy.

Background. Bradykinin has shown to affect pain hypersensitivity via reducing the pain threshold when it binds to bradykinin B1 receptors. Bradykinin B1 receptors are upregulated following tissue injury. Thus, any mechanism causing an increase in bradykinin could escalate pain perception. Angiotensin-converting enzyme inhibitors (ACEIs) increase bradykinin by blocking the ACE enzyme from inactivating bradykinin. Angiotensin receptor blockers (ARBs) do not increase bradykinin as much and may not make patients as susceptible to chronic pain by the described expected mechanism. Objective. This analysis observed retrospective data from a single community pharmacy to determine if there was a difference between patient groups who chronically used ACEIs and ARBs regarding their use of chronic pain medications. Methods. Reports were generated containing all prescription fills of ACEIs and ARBs during the 18-month period and length of therapy was determined from that report per patient. The patients meeting the length of therapy requirements were assessed for pain medication usage to determine presence and length of pain medication therapy. Results. The percentage of patients filling chronic pain medications among chronic ACEI patients was 3.99% higher than chronic ARB patients. This was not statistically different. Other evaluated group differences were not statistically significant.

Upregulation of SERCA2a following short-term ACE inhibition (by enalaprilat) alters contractile performance and arrhythmogenicity of healthy myocardium in rat.

Chronic angiotensin-converting enzyme inhibitor (ACEIs) treatment can suppress arrhythmogenesis. To examine whether the effect is more immediate and independent of suppression of pathological remodelling, we tested the antiarrhythmic effect of short-term ACE inhibition in healthy normotensive rats. Wistar rats were administered with enalaprilat (ENA, i.p., 5 mg/kg every 12 h) or vehicle (CON) for 2 weeks. Intraarterial blood pressure in situ was measured in A. carotis. Cellular shortening was measured in isolated, electrically paced cardiomyocytes. Standard 12-lead electrocardiography was performed, and hearts of anaesthetized open-chest rats were subjected to 6-min ischemia followed by 10-min reperfusion to examine susceptibility to ventricular arrhythmias. Expressions of calcium-regulating proteins (SERCA2a, cardiac sarco/endoplasmic reticulum Ca(2+)-ATPase; CSQ, calsequestrin; TRD, triadin; PLB, phospholamban; Thr(17)-PLB-phosphorylated PLB at threonine-17, FKBP12.6, FK506-binding protein, Cav1.2-voltage-dependent L-type calcium channel alpha 1C subunit) were measured by Western blot; mRNA levels of L-type calcium channel (Cacna1c), ryanodine receptor (Ryr2) and potassium channels Kcnh2 and Kcnq1 were measured by qRT-PCR. ENA decreased intraarterial systolic as well as diastolic blood pressure (by 20%, and by 31%, respectively, for both P < 0.05) but enhanced shortening of cardiomyocytes at basal conditions (by 34%, P < 0.05) and under beta-adrenergic stimulation (by 73%, P < 0.05). Enalaprilat shortened QTc interval duration (CON 78 ± 1 ms vs. ENA 72 ± 2 ms; P < 0.05) and significantly decreased the total duration of ventricular fibrillations (VF) and the number of VF episodes (P < 0.05). Reduction in arrhythmogenesis was associated with a pronounced upregulation of SERCA2a (CON 100 ± 20 vs. ENA 304 ± 13; P < 0.05) and complete absence of basal Ca(2+)/calmodulin-dependent phosphorylation of PLB at Thr(17). Short-term ACEI treatment can provide protection against I/R injury-induced ventricular arrhythmias in healthy myocardium, and this effect is associated with increased SERCA2a expression.

Abstract 420: Knockout Mice for Elastase-2, a Novel Angiotensin II Generating Enzyme, Displayed Reduced Sympathetic Modulation of Arterial Pressure and Heart Rate

A functional alternative pathway for angiotensin converting enzyme (ACE) in the generation of angiotensin II was described involving the tissue enzyme elastase-2 (ELA2). This notion was provided by studies from arteries (mesenteric and carotid) and heart of normotensive Wistar rats. The increased mRNA expression of ELA2 associated with chronic ACE inhibition in the carotid artery and heart from spontaneously hypertensive rats (SHR) is remarkable. Quite recently, our group developed the ELA2 knockout (KO) mice. Therefore, the objective of the current study was to examine the cardiovascular profile of ELA2 KO mice. Male ELA2 KO and C57BL/6j wild-type (WT) mice (10-14 weeks; n=6-10) were investigated. Five days after the cannulation of the femoral artery under isoflurane anesthesia, the arterial pressure (AP) and heart rate (HR) were recorded in conscious state. The variability of AP and pulse interval (PI) was examined in the frequency domain using Fast Fourier Transform (FFT) algorithm. AP and PI spectra were integrated in low (LF: 0.25 to 1.0 Hz) and high frequency (HF: 1.0 to 5.0 Hz) bands. The mean AP of WT and KO mice was similar (110 ± 3 vs. 117 ± 5 mmHg in KO). However, decreased HR (512 ± 13 vs. 425 ± 17 bpm) and increased PI (117 ± 5 vs. 142 ± 5 ms) were observed in KO mice. KO mice showed lower LF power (7.2 ± 1.6 vs. 1.3 ± 0.47 mmHg2) in the systolic AP spectrum indicating an attenuation of sympathetic modulation in the AP control. The LF power in the PI spectrum was lower (39 ± 4 vs. 25 ± 3.8 nu) in KO mice. The LF/HF ratio was also reduced in KO mice (0.88 ± 0.16 vs. 0.39 ± 0.07) indicating a shift towards parasympathetic modulation of the HR. In conclusion, KO mice for ELA2 displayed a reduced sympathetic modulation of AP and HR indicating that this enzyme plays a role in the cardiocirculatory control in mice.

Angiotensin-converting enzyme and the tumor microenvironment: mechanisms beyond angiogenesis

The renin angiotensin system (RAS) is a network of enzymes and peptides that coalesce primarily on the angiotensin II type 1 receptor (AT1R) to induce cell proliferation, angiogenesis, fibrosis, and blood pressure control. Angiotensin-converting enzyme (ACE), the key peptidase of the RAS, is promiscuous in that it cleaves other substrates such as substance P and bradykinin. Accumulating evidence implicates ACE in the pathophysiology of carcinogenesis. While the role of ACE and its peptide network in modulating angiogenesis via the AT1R is well documented, its involvement in shaping other aspects of the tumor microenvironment remains largely unknown. Here, we review the role of ACE in modulating the immune compartment of the tumor microenvironment, which encompasses the immunosuppressive, cancer-promoting myeloid-derived suppressor cells, alternatively activated tumor-associated macrophages, and T regulatory cells. We also discuss the potential roles of peptides that accumulate in the setting of chronic ACE inhibitor use, such as bradykinin, substance P, and N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), and how they may undercut the gains of anti-angiogenesis from ACE inhibition. These emerging mechanisms may harmonize the often-conflicting results on the role of ACE inhibitors and ACE polymorphisms in various cancers and call for further investigations into the potential benefit of ACE inhibitors in some neoplasms.

Management of Hypotension Associated With Angiotensin-Axis Blockade and General Anesthesia Administration

YPOTENSION, SOMETIMES REFRACTORY, is a well-recognized phenomenon associated with the administration of general anesthesia in patients who have angiotensin-axis blockade (AAB) because of the administration of either angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin-receptor blockers (ARBs). 1 Hypotension in such patients usually occurs within 30 minutes of the induction of anesthesia2,3 and is more frequent in patients also receiving diuretics. 4 There is an ongoing debate as to whether ACEIs and ARBs should be discontinued before surgery. 2,3,5-9 Although omitting these agents before general anesthesia may avoid hypotension,3,8,10 some argue that their discontinuation is not required because the associated hypotension is easily treatable 6,11 and subsequent hypertension may occur perioperatively requiring antihypertensive therapy. 9 Furthermore, the discontinuation of ACEIs and ARBs might remove the potential beneficial effect of AAB on myocardial protection 9,12-14 Adding to this debate, preoperative therapy with ACEIs in cardiac surgery 5 and ACEIs and ARBs in vascular surgery 15 have been found to be associated with an increased risk of mortality. In contrast, in cardiac surgery, ACEIs may confer renal protection16 ; and in

Effect of Chronic Inhibition of Converting Enzyme on Renal Handling of Salt and Water: A Study on a Pediatric Population

Background/Aims: The effect of angiotensin-converting enzyme inhibition (ACEi) is amply documented in several pathological conditions. However, there are few reports about the effect of chronic ACEi on salt and water balance. The present work evaluates the effect of chronic ACEi on salt and water balance in a population of children receiving enalapril chronically in order to reduce albuminuria elicited by a uremic hemolytic syndrome. Methods: Nine children aged from 9 to 19 years with normal glomerular filtration rate, normotension and with urinary concentration capacity preserved were treated with enalapril with doses ranging between 0.1 and 0.30 mg/kg/day. Diuresis, urinary absolute and fractional excretion of Na⁺, K⁺ and urea, creatinine clearance, osmolal clearance and tubular water reabsorption were measured under three experimental procedures: (1) with free access to water; (2) with a water load and (3) with water restriction. In the last group urinary antidiuretic hormone (ADH) was measured. These tests were performed in a paired way, just before starting ACEi treatment and after 6 months of enalapril treatment. Results: Enalapril treatment diminished the urinary concentration capacity without affecting Na⁺ and K⁺ urinary excretion. Creatinine clearance was not modified except in the condition of water load where a fall in it was found after ACEi. ADH increased after enalapril treatment in children under water restriction. Conclusion: In these children chronic ACEi decreases urinary concentration capacity.

Pressure–natriuretic and hemodynamic adjustments to chronic ACE inhibition in inbred F344 and Lewis rat strains

Genetic background has a major influence on the severity of renovascular disease. Previously we showed that Lewis rats with inducible hypertension caused by transgenic renin expression have lower blood pressure, higher renal plasma flow (RPF) and glomerular filtration rate (GFR) and are relatively protected from hypertensive renal microvascular injury compared to Fisher (F344) rats. Using a congenic/consomic approach we determined that a polymorphism of the angiotensin converting enzyme (ACE) gene is a major contributory factor in explaining these strain differences.In the current study we have compared renal function in anaesthetised, non transgenic F344 and Lewis rats. Pressure‐natriuresis (PN) and pressure‐renal blood flow (PRBF) relationships were measured in groups of rats pre‐treated with and without Captopril (80mg/L drinking water 1–2wks) to inhibit ACE activity. Control F344 rats had higher baseline blood pressure and poorer PN compared with Lewis (ie shallower slope of PN curve). Captopril treatment significantly improved RBF without affecting PN in F344 rats. Conversely, Captopril reduced the slope of the PN curve in Lewis rats without affecting RBF responses to pressure. Taken together these results indicate a dominant vascular response to ACE inhibition in F344 compared with a dominant tubular response in Lewis rats.

ACE inhibitor or angiotensin II receptor blocker use is a risk factor for contrast-induced nephropathy

The aim of the present study was to assess the influence of angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blocker (ARB) use on the incidence of contrast-induced nephropathy (CIN) in patients undergoing coronary angiography. A retrospective case control study was conducted on a total of 201 patients divided into 2 groups (CIN group and control group). CIN was defined as an increase in serum creatinine by more than 25% from baseline within 48 hours of radiocontrast exposure. The CIN group had 96 patients, and the control group had 105 patients. The 2 groups were matched for variables such as age, sex, weight, baseline serum creatinine, diabetes, dye load, use of diuretics, statins and preprocedure prophylactic measures for CIN. The incidence of CIN was found to be 4.55%. The CIN group had 96 patients out of which 56 patients (58.3%) were on chronic ACEI or ARB, while the control group had 105 patients, but only 36 of patients (34.3%) were on ACEI or ARB (p<0.001).The odds ratio for development of CIN with respect to ACEI or ARB use was 2.68 (95% confidence interval, 1.51-4.76). Use of ACEI or ARB is an independent risk factor for developing CIN. It is reasonable to discontinue their use 48 hours prior to exposure to radiocontrast agents, especially in patients with multiple risk factors.

Chronic Inhibition of Central Angiotensin-Converting Enzyme Ameliorates Colchicine Induced Memory Impairment in Mice

Preclinical and clinical studies indicated involvement of the central renin-angiotensin system (RAS) in memory functions. However, the role of central angiotensin-converting enzyme (ACE) in memory function is still unclear. The present study investigated the involvement of central ACE in colchicine-induced memory impairment in the context of cholinergic function and oxidative stress. Memory impairment was induced by intracerebral colchicine administration in mice. The ACE inhibitor, perindopril (0.05 and 0.1 mg/kg/day), was administered orally for 14 days. Memory function was evaluated by the Morris water maze (MWM) test from the 14th day on after colchicine injection. Donepezil was used as a standard. Parameters of oxidative stress and cholinergic function, ACE activity in serum and the brain were estimated after the completion of behavioral studies. Colchicine caused memory impairment as revealed by no significant change in latency to reach a hidden platform in the MWM test. Furthermore, there was a significant increase in MDA, ROS, and nitrite levels with a reduction in GSH level and acetylcholinesterase (AChE) activity in the brain of colchicine-treated mice. Colchicine significantly increased brain ACE activity without affecting serum ACE. Donepezil prevented colchicine-induced memory impairment in mice. The antidementic effect of perindopril may be attributed to reduced oxidative stress and improvement in cholinergic function. Moreover, the elevated brain ACE activity was also inhibited by perindopril. The study showed that central ACE plays an important role in colchicine-induced memory deficit, corroborating a number of studies that show that treatment with ACE inhibitors could be neuroprotective.