Inhibition of angiotensin converting enzyme cannot prevent increases in angiotensin II production in coronary circulation

Effects of angiotensin II and angiotensin II type 1 receptor blockade on neointimal formation after stent implantation

BACKGROUND

To evaluate the effect of supraphysiological levels of angiotensin II and selective angiotensin II type 1 receptor (AT1-receptor) blockade on neointimal formation and systemic endothelial function after stent implantation in the rat abdominal aorta.

METHODS

Male Wistar rats were randomized to one of three groups; control (n=8), angiotensin II infusion (n=9, 200 ng/kg/min), or candesartan cilexetil (n=8,AT1-receptor blocker; rats received 14.4 mg kg(-1) day(-1)). Stents were implanted in the abdominal aorta. Histological analyses were performed at 4 weeks. Endothelial function was determined in isolated thoracic aortic rings.

RESULTS

Neointimal area was increased in the angiotensin II treated group versus the control group, 0.88 mm(2)+/-0.21 versus 0.66 mm(2)+/-0.16 (P<0.05). Neointimal thickness was 171 microm+/-44 in angiotensin II treated animals and 120 microm+/-25 in the control group (P<0.05). In addition, endothelial function was attenuated in angiotensin II treated animals (P=0.01). Candesartan cilexetil treatment did not result in reduction of neointimal area and did not reduce neointimal thickness compared to the control group. Candesartan had no effect on endothelial function.

CONCLUSIONS

Supraphysiological levels of angiotensin II aggravates neointimal formation in the stented rat abdominal aorta, and in parallel decreases endothelial function. AT1-receptor blockade does not reduce neointimal formation in rats without supraphysiological angiotensin II levels.

D2 dopamine receptor blockade prevents cognitive effects of Ang IV and des-Phe6 Ang IV

Angiotensins, especially angiotensin IV (Ang IV), have recently been found to be potent cognitive enhancers in rodents. However, the precise mechanisms of their memory improving effects remain unknown. In this study we tested the hypothesis that D2 dopamine receptors at least partially mediate cognitive effects of Ang IV and its derivative des-Phe6 Ang IV. Namely, the well known cognitive effects of both peptides [facilitation of a conditioned avoidance responses (CARs) acquisition, increase of a passive avoidance behavior (PAB) retrieval, and improvement of object recognition] were evaluated in rats either pretreated or not with a selective D2 dopamine receptor antagonist remoxipride {(S)-(-)-3-Bromo-N-[(1-ethyl-2-pyrrolidinylOmethyl]2,6-dimethoxybenzamide hydrochloride}. To control for the unspecific motor and emotional effects of our treatments that could confound results of the memory tests we used respectively, 'open' field and elevated 'plus' maze tests. Ang IV as well as des-Phe6 Ang IV remarkably improved learning of CARs, recall of PAB and recognition of the previously seen objects. D2 receptors blockade by remoxipride abolished all these effects of both peptides. In the elevated 'plus' maze remoxipride abolished anxiogenic effects of both Ang IV and des-Phe6 Ang IV. Also, the drug followed by Ang IV decreased number of crossings and by des-Phe6 Ang IV number of crossings and rearings. The results point to importance of the functional D2 dopamine receptors in cognitive effects of Ang IV and its naturally occurring product devoid of C-terminal Phe6.

Pre-procedural ACE-activity does not predict symptomatic in-stent restenosis

BACKGROUND

Several studies indicate that ACE-activity is related to atherosclerosis. We investigated the correlation between ACE-activity, in plasma as well as in the atherosclerotic plaque, and in-stent restenosis.

METHODS AND RESULTS

ACE-activity was measured in blood samples from 178 patients who underwent a percutaneous coronary intervention with stent placement. During 8 months follow-up, 51 of these patients had an adverse clinical event. ACE-activity did not differ between patients with or without adverse events (21.5 vs. 23.1 nM/ml/min; P=0.36). Tissue samples were obtained with an atherectomy catheter before elective stent placement in another group of 13 patients with de novo stenosis. In this tissue, we determined the ACE-content immunohistologically. These patients were scheduled for follow-up quantitative coronary angiography after 12 months. In this group, the quantity of ACE was not correlated to the late luminal loss (0.31 vs. 0.38 mm; P=0.76).

CONCLUSION

In this study, pre-procedural ACE-activity, in plasma as well as in the atherosclerotic plaque, does not predict the occurrence of in-stent restenosis.

Renin-Angiotensin System Intervention to Prevent In-Stent Restenosis

The occurrence of in-stent restenosis is a major drawback of percutaneous transluminal coronary angioplasty with stent placement. Target vessel revascularization is necessary in 15% of patients who receive a stent. Recent advances in the development of drug-eluting stents have reduced these numbers tremendously. However refinement of antirestenotic therapies remains obligatory. The emerging interest in more physiological antirestenotic therapies might unchain an interest in the well-known inhibitors of the rennin-angiotensin system (RAS), the angiotensin-converting enzyme inhibitors, and the angiotensin II type I receptor blockers. Contradictory results overshadow the discussion of whether intervention in the RAS could prevent in-stent restenosis. This review discusses the pathophysiology of in-stent restenosis, the role of the RAS in in-stent restenosis, and the possible role of RAS intervention in the prevention of in-stent restenosis.

Involvement of D1 dopamine receptors in the cognitive effects of angiotensin IV and des-Phe6 angiotensin IV

An important role for angiotensin IV (Ang IV) in the processes of learning and memory has now been well established. We have previously found that intracerebroventricular (ICV) administration of Ang IV as well as des-Phe6-Ang IV enhances learning of conditioned avoidance responses (CARs), facilitates recall of a passive avoidance (PA) task, and improves object recognition (OR) in rats. Since the dopaminergic system is crucial for the cognitive processes, in this study our aim was to determine the dopaminergic D1 mediation of these effects using SCH 23390 as a selective D1 receptor antagonist. Male Wistar rats (180-200 g), pretreated with SCH 23390 (R-[+]-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine) 0.05 mg/kg intraperitoneally (IP), were given Ang IV or des-Phe6-Ang IV (1 nmol ICV) 1 h later and then tested in the above cognitive paradigms, as well as in the open field and an elevated 'plus' maze to control for the unspecific, respectively, motor and emotional, effects of our treatments. Both, Ang IV and des-Phe6-Ang IV effectively enhanced learning of CARs (P < 0.05), recall of PA (P < 0.001), and improved OR (P < 0.001). Pretreatment with SCH 23390 abolished the cognitive effects of both peptides. SCH 23390, Ang IV, and des-Phe6-Ang IV, given at the same doses and routes as in the cognitive tests, did not significantly influence crossings, rearings and bar approaches in the open field, nor the parameters measured in the elevated 'plus' maze, thus making a major contribution of the unspecific effects of our treatments to the results of the memory tests improbable. In conclusion, these results indicate that the functional dopaminergic D1 receptors are necessary for the Ang IV and des-Phe6-Ang IV cognitive effects to occur.

Role of a selective aldosterone blocker in mice with chronic heart failure

BACKGROUND

Spironolactone, a nonselective aldosterone blocker, has a cardioprotective effect; however, significant endocrine side effects limit its use. Eplerenone is a new selective aldosterone blocker. We investigated whether eplerenone attenuates cardiac remodeling and improves function in a mouse model of heart failure and whether coadministration of eplerenone and an angiotensin-converting enzyme inhibitor (ACEi) provides better cardioprotection than either agent alone.

METHODS AND RESULTS

C57BL/6J mice were subjected to myocardial infarction (MI) by ligating the left anterior descending coronary artery. Two weeks later, the mice were either left untreated or treated with (1) eplerenone, (2) ACEi, or (3) eplerenone plus ACEi for 12 weeks. Systolic blood pressure (SBP) was measured and echocardiography performed before MI and weekly thereafter. At the end of the study, interstitial collagen fraction (ICF) and myocyte cross-sectional area (MCSA) were examined histologically. We found that (1) eplerenone significantly improved ejection fraction and cardiac output and decreased left ventricular (LV) systolic area, LV weight, ICF, and MCSA independently of changes in SBP compared with untreated animals; (2) ACEi had similar beneficial effects, accompanied by a significant reduction in SBP; and (3) combined treatment offered limited additional benefit beyond monotherapy.

CONCLUSIONS

In mice with MI, eplerenone attenuates progression of heart failure comparably to ACEi, and its effect is independent of BP lowering.

Effects of intracoronary low-dose enalaprilat as an adjunct to primary percutaneous transluminal coronary angiography in acute myocardial infarction

Bradykinin accumulation is a potent cardioprotective mechanism underlying angiotensin-converting enzyme (ACE) inhibition in ischemia and/or reperfusion injury. There is, however, concern about treatment with ACE inhibitors in the very early phase of acute myocardial infarction (AMI) due to adverse systemic hemodynamic effects. We tested the hypothesis that cardiac bradykinin metabolism can be influenced by very low doses of intracoronary ACE inhibitors without harmful systemic effects in patients with AMI. Twenty-two patients with AMI in Killip classes II to III who underwent primary percutaneous transluminal coronary angiography (PTCA) were randomized to intracoronary enalaprilat (50 microg) or saline, given immediately after reopening of the infarct-related artery. Hemodynamics and electrocardiograms were monitored continuously and samples for determination of ACE activity, angiotensin II, bradykinin, kininogen, and cardiac marker proteins were collected from pulmonary arterial and central venous blood. Enalaprilat had no adverse effects on systemic hemodynamics, but rather stabilized arterial pressure and cardiac rhythm during reperfusion. Enalaprilat induced a 70% reduction of ACE activity and a significant increase of bradykinin in pulmonary arterial blood. Angiotensin II was not significantly affected by enalaprilat either in pulmonary arterial or in central venous blood. Myoglobin release was lower and the duration of reperfusion arrhythmias was significantly reduced in the enalaprilat group (p <0.05). Thus, in this pilot study, intracoronary enalaprilat infusion in the infarct-related artery is feasible in the setting of primary angioplasty and is safe and well tolerated. Effective cardiac ACE inhibition can be achieved by low-dose intracoronary enalaprilat, which primarily causes a potentiation of bradykinin.

No effects on myocardial ischaemia in patients with stable ischaemic heart disease after treatment with ramipril for 6 months

OBJECTIVE: To assess the effects of a 6-month angiotensin-converting enzyme (ACE) inhibitor intervention on myocardial ischaemia. METHOD: We randomized 389 patients with stable coronary artery disease to double-blind treatment with ramipril 5 mg/day (n = 133), ramipril 1.25 mg/day (n = 133), or placebo (n = 123). Forty-eight-hour ambulatory electrocardiography was performed at baseline, and after 1 and 6 months. RESULTS: Relevant baseline variables were similar in all groups. Changes over 6 months in duration of >/= 1 mm ST-segment depression (STD), total ischaemic burden and maximum STD did not differ significantly between the treatment groups. There was no difference in the frequency of adverse events between the groups. CONCLUSION: ACE inhibitor treatment has little impact on incidence and severity of myocardial ischaemia in patients with stable ischaemic heart disease.