Nidia Basso

Enalapril and losartan attenuate mitochondrial dysfunction in aged rats

Renin‐angiotensin system (RAS) inhibition can attenuate the effects of aging on renal function and structure; however, its effect on mitochondrial aging is unknown. To investigate whether an angiotensin‐converting enzyme inhibitor (enalapril) or an angiotensin II receptor blocker (losartan) could mitigate age‐associated changes in kidney mitochondria, male Wistar rats (14 mo old) received during 8 mo water containing either enalapril (10 mg/kg/day) (Enal), or losartan (30 mg/kg/day) (Los), or no additions (Old). Four‐month‐old untreated rats (Young) were also studied. In Old rats mitochondrial respiratory control, ADP/O, nitric oxide synthase activity, and uncoupling protein 2 levels were lower (46, 42, 27, and 76%, respectively), and Mn‐SOD activity was higher (70%) than in Young, Enal, and Los rats. In Old rats mitochondrial hydrogen peroxide production was higher than in both Young (197%) and Enal or Los (40%) rats. In Old rats, kidney GSH/GSSG was lower than in both Young (80%) and Enal (57%) or Los (68%) rats. In Old rats electron microscopy showed effacement of microvilli in tubular epithelial cells, ill‐defined mitochondrial cristae, lower mitochondrial numbers, and enhanced number of osmiophilic bodies relative to Young, Enal, or Los rats. In conclusion, enalapril and losartan can protect against both age‐related mitochondrial dysfunction and ultrastructural alterations, underscoring the role of RAS in the aging process. An association with oxidative stress modulation is suggested.

Protective effect of the inhibition of the renin-angiotensin system on aging.

Experimental studies indicate that chronic long-term inhibition of the renin-angiotensin system (RAS) can prevent most of the deleterious effects due to aging in the cardiovascular system and in the kidney of the normal mouse and rat. In this review, all the information available on this subject provided by several studies performed by our research group during the last years is been described. Treatment was initiated either after weaning or at 12 months of age that is about half the normal life span of the rat. A converting enzyme inhibitor: enalapril or an angiotensin II type 1 (AT1) receptor blocker: losartan were used to inhibit the RAS. Cognitive behaviour, emotionality, and locomotor activity were also determined at 10 and 18 months of age in treated since weaning and untreated control rats to elucidate the participation of angiotensin II in memory disfunction. A similar observation was obtained in animals treated from 12 to 18 months of age. Results have demonstrated a significant protective effect on the function and the structure of the cardiovascular system, the kidney and the brain in all the treated animals. Damage observed at 12 months of age was not very significant, but treatment stop further deterioration that was evident in untreated animals. The similarity of the results detected with either enalapril or losartan treatment, clearly indicates that most of the effects are exerted through AT1 receptors. Analysis of the nitric oxide and antioxidant enzymes systems suggest that the protective effect is related to an antioxidant action of the RAS inhibitors and a reduced formation of reactive oxygen species. AngII inhibition might produce changes in the mechanisms of oxidative stress specially at the mitochondrial level. Prevention of mitochondrial decrease and/or damage would be related with the delay of the normal aging process.

Advances in our understanding of aging: role of the renin-angiotensin system.

Knowledge about the pathophysiological role of the renin-angiotensin system is constantly improving and its relationship with mechanisms of oxidative stress suggests its possible involvement with the deleterious effects of aging. Recent data opens a new field of investigation in this area.

Effect of chronic angiotensin II inhibition on the nitric oxide synthase in the normal rat during aging

Objective To assess the effect on the cardiovascular system, of enalapril (E) or losartan (L) given since weaning during 6 or 18 months to normal rats. Methods Animals were divided in three groups: control (C), E-treated and L-treated; treated rats received 10 mg/kg per day of drug. Systolic blood pressure (SBP), body weight, water and food intake (WI, FI), cardiac, left ventricular and aortic weight as well as the length of the tail were recorded. NADPH-diaphorase activity was determined as a marker of nitric oxide synthase (NOS) activity in aorta, arterioles of small intestine, heart and kidney of normal rats. NOS activity was measured as optical density (OD) in the stained tissue. Nitrate + nitrite urinary excretion was measured in 24 h urine. Only significant differences (P < 0.05) are reported. Results SBP, absolute cardiac, left ventricular and aortic weight increased with age. Both treatments delayed these increments. At 6 and 18 months, NOS activity was higher in aortic endothelium (Em) of L- and E-treated animals. Losartan treatment during 6 months also increased NOS activity in aortic smooth muscle (SM). Aortic Em NOS activity fell in the 18 months-treated and untreated animals. E increased NOS activity in the SM of intestinal arterioles at 6 months but reduced it at 18 months. Conclusions The fact that both E and L delayed cardiac hypertrophy/hyperplasia and aortic growth and raised aortic endothelium NOS activity indicates a protective effect on cardiovascular damage due to aging, exerted through inhibition of angiotensin II.

Effect of chronic angiotensin II inhibition on the cardiovascular system of the normal rat

Previous studies have demonstrated in normal rats that chronic treatment, from weaning to 30 days, with either enalapril or losartan, induced significant changes in cardiovascular structure and function. The present study was performed to assess the effect of either enalapril or losartan on the structure and function of the heart and arteries given to normal rats from weaning until 6 months of age. Animals (n = 48) were divided into three groups: control, enalapril treated, and losartan treated; treated rats received 10 mg/kg/day of drug. Blood pressure, body weight, and water intake were recorded for that time period. DNA, cGMP, collagen, degree of fibrosis, and nitric oxide synthase-NADPH-diaphorase-dependent activity in the heart and arteries were determined. Only significant differences (P < .05) are reported. Blood pressure increased only in control rats (13 +/- 1 mm Hg), enalapril treatment enhanced water intake and reduced the rate of body growth (control, 672.9 +/- 15.4 g; losartan, 692.4 +/- 21.8 g; enalapril, 541.8 +/- 13.8 g). In the heart, DNA (control, 120 +/- 5; losartan, 99 +/- 4; enalapril, 93 +/- 6 microg/100 mg), collagen (control, 2.5 +/- 0.2; enalapril, 1.85 +/- 0.08 microg/100 mg), and fibrosis (control, 3.5 +/- 0.4%; losartan, 2.2 +/- 0.3%; enalapril, 2.1 +/- 0.4%) were reduced by treatment. In the aorta, cGMP (control, 0.15 +/- 0.01; losartan, 0.24 +/- 0.02 pmol/mg), and NADPH-diaphorase (control, 0.114 +/- 0.003; losartan, 0.148 +/- 0.006; enalapril, 0.169 +/- 0.003 as optical density) were enhanced. The enzyme was also higher in the aortic endothelium of treated animals (control, 0.193 +/- 0.010; losartan, 0.228 +/- 0.009; enalapril, 0.278 +/- 0.005). The lower rate of body weight increase, the enhanced water intake, and the reduced cardiac and left ventricular weight attributable to enalapril treatment do not seem to be related to inhibition of the renin-angiotensin system. On the other hand, renin-angiotensin system inhibition induces a protective effect on the heart and aorta through structural and functional changes. Most of this action seems to be exerted through angiotensin II type 1 receptors.

Rosuvastatin Given During Reperfusion Decreases Infarct Size and Inhibits Matrix Metalloproteinase-2 Activity in Normocholesterolemic and Hypercholesterolemic Rabbits

There is evidence that statin treatment before ischemia protects myocardium from ischemia/reperfusion injury. The objective is to determine whether rosuvastatin administered during reperfusion modifies infarct size and the recovery of postischemic ventricular dysfunction in normocholesterolemic and hypercholesterolemic rabbits. In addition, we also evaluated the role of matrix metalloproteinase type 2 (MMP)-2 activation. Langendorff-perfused rabbit hearts were subjected to 30 minutes of ischemia and 120 minutes of reperfusion. In group 2, we added rosuvastatin after 30 minutes of ischemia and from the beginning of reperfusion. In group 3, an MMP inhibitor (doxycycline) was administered during the first 2 minutes of reperfusion. Finally, we repeated these groups but in hypercholesterolemic rabbits (groups 4, 5, and 6). The infarct size was 16.6% ± 3.9% in group 1 and 25.6% ± 2.7% in group 4. Rosuvastatin reduced infarct size to 4.5% ± 1.1% and 6.1% ± 1.5% in groups 2 and 5, respectively (P < 0.05). Rosuvastatin significantly decreased MMP-2 activity during reperfusion, and doxycycline induced an inhibition of MMP-2 activity and a reduction of infarct size in normocholesterolemic (4.9% ± 0.9%) and hypercholesterolemic animals (8.3% ± 1.6%) (P < 0.05). Rosuvastatin reduces infarct size and attenuates MMP-2 activity. These data and the correlation between MMP-2 and infarct size suggest that MMP-2 plays an important role in the mechanisms of cardioprotection afforded by rosuvastatin.

Divergent Regulation of Circulating and Intrarenal Renin-Angiotensin Systems in Response to Long-Term Blockade

Background/Aims: Long-term treatment with angiotensin-converting enzyme (ACE) inhibitors or angiotensin (Ang) II type I (AT1) receptor blockers can improve kidney function and attenuate the progressive decline in kidney function associated with age. In this study in Wistar rats medicated for 22 months, we determined the effects of enalapril (10 mg/kg/day) and losartan (30 mg/kg/day) treatment, in comparison with vehicle (tap water), on renal AngII receptor density and circulating and urinary components of the renin-angiotensin system (RAS). Methods: Kidney sections were incubated with [125I-sarcosine1-threonine8]AngII (0.6 nM) for Ang receptor density, and Ang peptides were determined using radioimmunoassays. Results: Receptor density was ∼50% higher in vasa recta, glomeruli, and tubulointerstitium in enalapril-treated rats and lower in vasa recta and glomeruli in losartan-treated relative to vehicle-treated rats. Losartan and enalapril treatment elevated plasma levels of AngI and Ang-(1–7) while AngII increased only in losartan-treated rats. In contrast, both treatments were associated with a reduction in urinary excretion of all three Ang peptides as compared with control rats. Conclusion: The reduction in urinary Ang peptides with losartan and enalapril treatment suggests that blockade of intrarenal AngII may be an important mechanism underlying the renoprotection seen with such treatments.

The Renin-Angiotensin System in Different Stages of Spontaneous Hypertension in the Rat (S H R)

The present study analyzed the concentration of renin-like activity and angiotensinogen concentration (AoC) in different brain areas related to cardiovascular control in SHR and Wistar Kyoto (WKY) animals. Male rats of both strains were studied at 8, 16 and 30 weeks of age. The following brain areas were isolated: anterior, medial and posterior hypothalamus, septal area, periaqueductal gray (PG) and the remaining brain stem; nucleus tractus solitarius (NTS) and the remaining medulla oblongata. Plasma renin activity (PRA) and plasma and cerebrospinal fluid (CSF) AoC were determined. Renin-like concentration was higher in SHR than in WKY in the anterior hypothalamus, PG and NTS at different stages of hypertension development. AoC was also higher in some areas of the SHR brain during different periods. PRA, plasma and CSF angiotensinogen concentration showed significant differences between both strain of rats during the development of high blood pressure. Present data support the possibility that the central and peripheral renin-angiotensin system may participate in the maintenance of high blood pressure in the SHR animals.

Changes seen in the aging kidney and the effect of blocking the renin—angiotensin system

Background: The objective was to evaluate structural changes of glomeruli during aging and the role of chronic renin—angiotensin system inhibition (RASi) on these changes; starting RASi on Wistar rats at two different moments: the first group after weaning and the second at the midpoint of their lifespan (12 months). Methods: Thirty rats were divided, after weaning, into three groups of 10: group 1: control (C); group 2 : 30 mg/kg/day losartan (L); group 3 : 10 mg/kg/day enalapril (E). At 18 months, rats were placed in metabolic cages to evaluate proteinuria, then killed. Another group of 24 rats, 12 months old, were divided into three groups of eight: group 1: C; group 2: L; group 3: E. At 18 months the same procedure described above was carried out. Finally, a third group of 20 rats was studied as healthy controls and killed: 10 rats at 7 months and ten at 12 months of age. Tissue samples were collected after sacrifice. To evaluate glomerular fibrotic changes, both focal and periglomerular sclerosis, and mesangial matrix expansion, a scoring scale was established. We also evaluated anti-α-SM-actin and anti-collagen-III immunolabeling. Glomerular area was measured using an image analyzer. Results: Proteinuria and serum creatinine increased with age but were reduced in treated animals. Main glomerular changes present in 18-month-old rats were reduced by half in treated animals. Glomerular area showed significant increase with normal aging and all treatment strategies protected against it. Conclusion: RAS plays a central role in natural process of renal aging, probably by producing effects influencing the biology of aging, the effects of which can be attenuated by RASi.

The Brain Renin—Angiotensin System and the Development of Doc - Salt Hypertension

UNLABELLED The effect of captopril, given in the drinking fluid, on the development of DOC-salt hypertension was analyzed. Although captopril did not prevent an increase in blood pressure (BP) elicited by DOC-salt, captopril did diminish BP in both DOC-salt and control animals. From the first week of treatment DOC-salt rats increased their fluid intake (FI). At the end of the experiment, captopril reduced this increment (655% to 357%). At the same time plasma angiotensinogen was diminished (-35%; p less than 0.001) and cerebrospinal fluid (CSF) substrate concentration increased (+33%; p less than 0.02) in DOC-salt rats, captopril did not modify these changes. In control rats captopril did not alter FI, depleted plasma angiotensinogen, (-73%; p less than 0.001), did not change the central prohormone and increased plasma renin activity (PRA) (+260%; p less than 0.001). IN CONCLUSION CSF angiotensinogen concentration changes as previously found in CNS while a clear dissociation between plasma and CSF angiotensinogen was found in DOC-salt rats. In these animals the hypertension was not clearly affected by captopril treatment. However the effect of the converting enzyme inhibitor suggests that the central renin-angiotensin system could participate in the increase in FI.