Combination therapy with angiotensin converting enzyme inhibition and AT1 receptor inhibitor on ventricular remodeling after myocardial infarction in rats

The role of oxidative stress and lipid peroxidation in ventricular remodeling induced by tobacco smoke exposure after myocardial infarction

OBJECTIVE

To evaluate the roles of oxidative stress and lipid peroxidation in the ventricular remodeling that is induced by tobacco smoke exposure after myocardial infarction.

METHODS

After induced myocardial infarction, rats were allocated into two groups: C (control, n=25) and ETS (exposed to tobacco smoke, n=24). After 6 months, survivors were submitted to echocardiogram and biochemical analyses.

RESULTS

Rats in the ETS group showed higher diastolic (C = 1.52 +/- 0.4 mm(2), ETS = 1.95 +/- 0.4 mm(2); p=0.032) and systolic (C = 1.03 +/- 0.3, ETS = 1.36 +/- 0.4 mm(2)/g; p=0.049) ventricular areas, adjusted for body weight. The fractional area change was smaller in the ETS group (C = 30.3 +/- 10.1 %, ETS = 19.2 +/- 11.1 %; p=0.024) and E/A ratios were higher in ETS animals (C = 2.3 +/- 2.2, ETS = 5.1 +/- 2.5; p=0.037). ETS was also associated with a higher water percentage in the lung (C = 4.8 (4.3-4.8), ETS = 5.5 (5.3-5.6); p=0.013) as well as higher cardiac levels of reduced glutathione (C = 20.7 +/- 7.6 nmol/mg of protein, ETS = 40.7 +/- 12.7 nmol/mg of protein; p=0.037) and oxidized glutathione (C = 0.3 +/- 0.1 nmol/g of protein, ETS = 0.9 +/- 0.3 nmol/g of protein; p=0.008). No differences were observed in lipid hydroperoxide levels (C = 0.4 +/- 0.2 nmol/mg of tissue, ETS = 0.1 +/- 0.1 nmol/mg of tissue; p=0.08).

CONCLUSION

In animals exposed to tobacco smoke, oxidative stress is associated with the intensification of ventricular remodeling after myocardial infarction.

Retinoic acid supplementation attenuates ventricular remodeling after myocardial infarction in rats

The objective of this study was to evaluate the role of retinoic acid in experimental postinfarction myocardial remodeling. Wistar rats were subjected to myocardial infarction (MI) and treated with retinoic acid (RA), 0.3 mg/(kg x d) (MI-RA, n = 29), or fed a control diet (MI, n = 34). After 6 mo, the surviving rats (MI-RA = 18 and MI = 22) underwent echocardiograms, and isolated hearts were tested for function in vitro. The cross-sectional area of the myocyte (CSA) and interstitial collagen fraction (IC) were measured in a cross section of the heart stained by hematoxylin-eosin and picrosirius red, respectively. The CSA was smaller in the MI-RA group [229 (220,234) microm2] [medians (lower quartile, upper quartile)] than in the MI group [238 (232,241) microm2] (P = 0.01) and IC was smaller in the MI-RA group [2.4 (1.7, 3.1)%] than in the MI group [3.5 (2.6, 3.9)%] (P = 0.05). The infarct size did not differ between the groups [MI = 44.6 (40.8, 48.4)%, MI-RA = 45 (38.6, 47.2)%]. Maximum rate of rise of left ventricular pressure (+dp/dt) was greater in the MI-RA group (2645 +/- 886 mm Hg/s) than in the MI group (2081 +/- 617 mm Hg/s) (P = 0.05). The other variables tested did not differ between groups. Retinoic acid supplementation of rats for 6 mo attenuates the ventricular remodeling process after MI.

Beta-carotene supplementation results in adverse ventricular remodeling after acute myocardial infarction

OBJECTIVE

We studied the effects of beta-carotene (BC) on ventricular remodeling after myocardial infarction.

METHODS

Myocardial infarction was induced in Wistar rats that were then treated with a BC diet (500 mg/kg of diet per day; MI-BC; n = 27) or a regular diet (MI; n = 27). Hearts were analyzed in vivo and in vitro after 6 mo.

RESULTS

BC caused decreased left ventricular wall thickness (MI = 1.49 +/- 0.3 mm, MI-BC = 1.23 +/- 0.2 mm, P = 0.027) and increased diastolic (MI = 0.83 +/- 0.15 cm2, MI-BC = 0.98 +/- 0.14 cm2, P = 0.020) and systolic (MI = 0.56 +/- 0.12 cm2, MI-BC = 0.75 +/- 0.13 cm2, P = 0.002) left ventricular chamber areas. With respect to systolic function, the BC group presented less change in fractional area than did controls (MI = 32.35 +/- 6.67, MI-BC = 23.77 +/- 6.06, P = 0.004). There was no difference in transmitral diastolic flow velocities between groups. In vitro results showed decreased maximal isovolumetric systolic pressure (MI = 125.5 +/- 24.1 mmHg, MI-BC = 95.2 +/- 28.4 mmHg, P = 0.019) and increased interstitial myocardial collagen concentration (MI = 3.3 +/- 1.2%, MI-BC = 5.8 +/- 1.7%, P = 0.004) in BC-treated animals. Infarct sizes were similar between groups (MI = 45.0 +/- 6.6%, MI-BC = 48.0 +/- 5.8%, P = 0.246).

CONCLUSION

Taken together, these data suggest that BC has adverse effects on ventricular remodeling after myocardial infarction.

beta-carotene attenuates the paradoxical effect of tobacco smoke on the mortality of rats after experimental myocardial infarction

The objective of this study was to investigate the effects of exposure to tobacco smoke (ETS) in rats that were or were not supplemented with dietary beta-carotene (BC), on ventricular remodeling and survival after myocardial infarction (MI). Rats (n = 189) were allocated to 4 groups: the control group, n = 45; group BC administered 500 mg/kg diet, n = 49, BC supplemented rats; group ETS, n = 55, rats exposed to tobacco smoke; and group BC+ETS, n = 40. Wistar rats weighing 100 g were administered one of the treatments until they weighed 200 to 250 g (approximately 5 wk). The ETS rats were exposed to cigarette smoke for 30 min 4 times/d, in a chamber connected to a smoking device. After reaching a weight of 200-250 g, rats were subjected to experimental MI (coronary artery occlusion) and mortality rates were determined over the next 105 d. In addition, echocardiographic, isolated heart, morphometrical, and biochemical studies were performed. Mortality data were tested using Kaplan-Meyer curves and other data by 2-way ANOVA. Survival rates were greater in the ETS group (58.2%) than in the control (33.3%) (P = 0.001) and BC+ETS rats (30.0%) (P = 0.007). The groups did not differ in the other comparisons. Left ventricular end-diastolic diameter normalized to body weight was greater and maximal systolic pressures were lower in the ETS groups than in non-ETS groups. Previous exposure to tobacco smoke induced a process of cardiac remodeling after MI. There is a paradoxical protector effect with tobacco smoke exposure, characterized by lower mortality, which is offset by BC supplementation.

Changes in Ventricular Size and Function in Patients Treated With Valsartan, Captopril, or Both After Myocardial Infarction

Background— Angiotensin-converting enzyme (ACE) inhibitors have been shown to attenuate left ventricular (LV) enlargement in association with reducing mortality after myocardial infarction (MI). Preclinical data suggest that angiotensin receptor blockers (ARBs) may have similar structural and functional effects after MI. The Valsartan in Acute Myocardial Infarction (VALIANT) Echo study was designed to test the hypothesis that the ARB valsartan, either alone or in combination with captopril, could attenuate progressive LV enlargement or improve LV ejection fraction to a greater extent than captopril alone.

Methods and Results— Six hundred ten patients enrolled in the main VALIANT study who experienced MI and evidence of LV dysfunction, heart failure, or both were enrolled in the VALIANT Echo study. Patients were randomized to receive valsartan 160 mg PO BID, captopril 50 mg PO TID, or valsartan 80 mg PO BID plus captopril 50 mg PO TID between 1 and 10 days after MI. Six hundred three patients had echocardiograms of sufficient quality for quantitative analysis. Echocardiograms were digitized, and endocardial borders were traced manually from 2 short-axis and 2 apical views. Ventricular volumes, ejection fractions, combined areas, and infarct segment length were measured, and changes in echocardiographic measures from baseline to 20 months were compared between treatment groups. Baseline clinical and echocardiographic characteristics were similar in the 3 treatment arms. The changes from baseline to 20 months in all echocardiographic parameters were similar in all 3 treatment arms. Baseline echocardiographic measures of ejection fraction, end-diastolic volume, and infarct segment length were highly predictive of outcomes including total mortality, death or hospitalization for heart failure, or death or any cardiovascular event (heart failure, MI, stroke, resuscitated sudden death), even after adjustment for known covariates.

Conclusions— Treatment with the ACE inhibitor captopril, valsartan, or the combination of captopril plus valsartan resulted in similar changes in cardiac volume, ejection fraction, and infarct segment length between baseline and 20 months after MI. Baseline echocardiographic measures were powerfully and independently predictive of all major outcomes.

Valsartan for the treatment of heart failure

Heart failure (HF) still has a discouraging prognosis. Therapeutic strategies aim to reduce mortality as well as slow the progression of the disease, improve symptoms and reduce the frequency of hospital admission. Activation of the renin-angiotensin-aldosterone system (RAAS) is a hallmark of several cardiocirculatory diseases, including HF. Drugs for evidence-based therapy of HF are angiotensin-converting enzyme inhibitors (ACEIs), beta-blockers and aldosterone antagonists. A promising alternative is a more complete action on the RAAS through selective blockade of the angiotensin type 1 (AT(1)) receptors, taking into account not only physiopathological issues but also pharmacological, experimental and clinical data. The effect of valsartan, an orally-active, selective antagonist of AT(1) receptors, on the outcome in patients with chronic and symptomatic HF was evaluated in a large-scale, international, placebo-controlled clinical study, the Valsartan in Heart Failure Trial (Val-HeFT). In this study, overall mortality was similar in the valsartan and placebo groups (19.7 and 19.4%, respectively). However, valsartan, in addition to recommended therapy of HF including an ACEI, significantly reduced the combined end point of mortality and morbidity, with a significant reduction in the risk of hospitalisation, paralleled by improvements in New York Heart Association (NYHA) functional class, signs and symptoms and quality of life. Valsartan also improved left ventricular anatomy and function and significantly reduced neurohormonal activation. These results were confirmed and extended by the CHARM trial, where the benefits of candesartan were proved not only in all 7599 patients with HF, but also in the 2548 given an ACEI, the 2028 not given an ACEI and in the 3023 patients with an ejection fraction of > 40%. In conclusion, the first choice for HF remains an ACEI with a beta-blocker, but two new options are emerging. In patients intolerant to ACEI, the combination of valsartan or candesartan with a beta-blocker is proposed, whereas an ACEI with either valsartan or candesartan can be considered in patients intolerant to or with contraindications to beta-blockers.

An AT1-receptor antagonist and an angiotensin-converting enzyme inhibitor protect against hypoxia-induced apoptosis in human aortic endothelial cells through upregulation of endothelial cell nitric oxide synthase activity

The protective effects and roles of AT1-receptor antagonists (AT1-RA) or angiotensin-converting enzyme inhibitors (ACEI) on vascular endothelial cell (EC) injury during hypoxia are not entirely known. Therefore, we investigated these effects and mechanisms in human aortic (HA) EC. DNA fragmentation, Lactate dehydrogenase (LDH) release, and caspase-3 activity were measured in cultured HAEC after exposure to hypoxia in the presence or absence of an AT1-RA (candesartan, CS) and/or an ACEI (temocaprilat, TC). Next, we investigated endothelial cell nitric oxide synthase (ecNOS) and inducible (i) NOS to determine the role of the bradykinin(BK)-NO pathway in the protective effect on ACEI and AT1-RA in the setting of hypoxia-induced apoptosis. Exposure to hypoxia increased DNA fragmentation in HAEC associated with the activation of caspase-3, but did not affect LDH release. In addition, hypoxia induced ecNOS mRNA but not mRNA iNOS. CS and/or TC reduced apoptosis induced by hypoxia in a dose-dependent manner, and significantly increased BK and ecNOS expression. This effect was attenuated by the kinin B2 receptor antagonist, HOE 140, and the NOS inhibitor, N-nitro-L-arginine methylester (L-NMMA). Hypoxia activates the pathway leading to apoptosis by enhancing caspase-3 activity. Both CS and TC can ameliorate hypoxia-induced apoptosis in HAEC through inhibiting caspase-3 activation by enhancing ecNOS activity, via the accumulation of BK.

The renin-angiotensin-aldosterone system and vascular remodeling

Cardiac fibrosis can be accompanied initially by diastolic and ultimately by systolic ventricular dysfunction. Clinical and experimental evidence suggests a clear association between such adverse structural remodeling and activation of the circulating renin-angiotensin-aldosterone system (RAAS). Infusion of either of two RAAS effector hormones, angiotensin II and aldosterone, in rats evokes perivascular fibrosis of arteries and arterioles of the heart and kidneys. Additionally, increasing evidence indicates locally produced angiotensin II and aldosterone have important paracrine and autocrine actions that play a role in vascular remodeling. Both angiotensin II and aldosterone receptor antagonists have been shown to attenuate the appearance of cardiac and renal fibrosis.