Angiotensin converting enzyme inhibitors, left ventricular hypertrophy and fibrosis

Edema formation in congestive heart failure and the underlying mechanisms

Congestive heart failure (HF) is a complex disease state characterized by impaired ventricular function and insufficient peripheral blood supply. The resultant reduced blood flow characterizing HF promotes activation of neurohormonal systems which leads to fluid retention, often exhibited as pulmonary congestion, peripheral edema, dyspnea, and fatigue. Despite intensive research, the exact mechanisms underlying edema formation in HF are poorly characterized. However, the unique relationship between the heart and the kidneys plays a central role in this phenomenon. Specifically, the interplay between the heart and the kidneys in HF involves multiple interdependent mechanisms, including hemodynamic alterations resulting in insufficient peripheral and renal perfusion which can lead to renal tubule hypoxia. Furthermore, HF is characterized by activation of neurohormonal factors including renin-angiotensin-aldosterone system (RAAS), sympathetic nervous system (SNS), endothelin-1 (ET-1), and anti-diuretic hormone (ADH) due to reduced cardiac output (CO) and renal perfusion. Persistent activation of these systems results in deleterious effects on both the kidneys and the heart, including sodium and water retention, vasoconstriction, increased central venous pressure (CVP), which is associated with renal venous hypertension/congestion along with increased intra-abdominal pressure (IAP). The latter was shown to reduce renal blood flow (RBF), leading to a decline in the glomerular filtration rate (GFR). Besides the activation of the above-mentioned vasoconstrictor/anti-natriuretic neurohormonal systems, HF is associated with exceptionally elevated levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). However, the supremacy of the deleterious neurohormonal systems over the beneficial natriuretic peptides (NP) in HF is evident by persistent sodium and water retention and cardiac remodeling. Many mechanisms have been suggested to explain this phenomenon which seems to be multifactorial and play a major role in the development of renal hyporesponsiveness to NPs and cardiac remodeling. This review focuses on the mechanisms underlying the development of edema in HF with reduced ejection fraction and refers to the therapeutic maneuvers applied today to overcome abnormal salt/water balance characterizing HF.

Diabetic Heart Failure with Preserved Left Ventricular Ejection Fraction: Review of Current Pharmacotherapy

Diabetes is associated with several diabetic-related abnormalities which increase the risk of onset or worsening of heart failure. Recent studies showed that the majority of diabetic patients present with heart failure with preserved ejection fraction (HFpEF), and the prevalence of HFpEF in diabetics is alarming. Moreover, outcomes in HFpEF are poor and could be compared to those of heart failure with reduced ejection fraction (HFrEF), with 1-year mortality ranging between 10 and 30%. In contrast to HFrEF, there is very limited evidence for pharmacologic therapy in symptomatic patients with preserved ejection fraction, and therefore, the optimal selection of treatment for diabetic HFpEF remains challenging. This narrative review article summarizes the currently available data on the pharmacological treatment of HFpEF in patients with diabetes.

Angiotensin-(1-7)-A Potential Remedy for AKI: Insights Derived from the COVID-19 Pandemic

Membrane-bound angiotensin converting enzyme (ACE) 2 serves as a receptor for the Sars-CoV-2 spike protein, permitting viral attachment to target host cells. The COVID-19 pandemic brought into light ACE2, its principal product angiotensin (Ang) 1-7, and the G protein-coupled receptor for the heptapeptide (MasR), which together form a still under-recognized arm of the renin–angiotensin system (RAS). This axis counteracts vasoconstriction, inflammation and fibrosis, generated by the more familiar deleterious arm of RAS, including ACE, Ang II and the ang II type 1 receptor (AT1R). The COVID-19 disease is characterized by the depletion of ACE2 and Ang-(1-7), conceivably playing a central role in the devastating cytokine storm that characterizes this disorder. ACE2 repletion and the administration of Ang-(1-7) constitute the therapeutic options currently tested in the management of severe COVID-19 disease cases. Based on their beneficial effects, both ACE2 and Ang-(1-7) have also been suggested to slow the progression of experimental diabetic and hypertensive chronic kidney disease (CKD). Herein, we report a further step undertaken recently, utilizing this type of intervention in the management of evolving acute kidney injury (AKI), with the expectation of renal vasodilation and the attenuation of oxidative stress, inflammation, renal parenchymal damage and subsequent fibrosis. Most outcomes indicate that triggering the ACE2/Ang-(1-7)/MasR axis may be renoprotective in the setup of AKI. Yet, there is contradicting evidence that under certain conditions it may accelerate renal damage in CKD and AKI. The nature of these conflicting outcomes requires further elucidation.

Studies to Elucidate the Mechanism of Cardio Protective and Hypotensive Activities of Anogeissus acuminata (Roxb. ex DC.) in Rodents

Anogeissus acuminata (Roxb. ex DC.) is a folkloric medicinal plant in Asia; including Pakistan; used as a traditional remedy for cardiovascular disorders. This study was planned to establish a pharmacological basis for the trivial uses of Anogeissus acuminata in certain medical conditions related to cardiovascular systems and to explore the underlying mechanisms. Mechanistic studies suggested that crude extract of Anogeissus acuminata (Aa.Cr) produced in vitro cardio-relaxant and vasorelaxant effects in isolated paired atria and aorta coupled with in vivo decrease in blood pressure by invasive method; using pressure and force transducers connected to Power Lab Data Acquisition System. Moreover; Aa.Cr showed positive effects in left ventricular hypertrophy in Sprague Dawley rats observed hemodynamically by a decrease in cardiac cell size and fibrosis; along with absence of inflammatory cells; coupled with reduced levels of angiotensin converting enzyme (ACE) and renin concentration along with increased concentrations of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP). In Acute Myocardial Infarction (AMI) model; creatine kinase (CK), creatine kinase-MB (CK-MB) and lactic acid dehydrogenase (LDH levels) were found to be decreased; along with decreased necrosis; edema and recruitment of inflammatory cells histologically. In vivo and ex vivo studies of Anogeissus acuminata provided evidence of vasorelaxant; hypotensive and cardioprotective properties facilitated through blockage of voltage-gated Ca⁺⁺ ion channel; validating its use in cardiovascular diseases.

Peristrophe roxburghiana leaf extracts exhibited anti-hypertensive and anti-lipidemic properties in L-NAME hypertensive rats

AIMS

Hypertension is a global disease that has been combating the world health for ages. Peristrophe roxburghiana (PR) is used in traditional medicine to treat hypertension and other ailments. The present study examined phytochemical constituents, antioxidant activities and GC-MS analysis of extracts of PR leaf and also evaluated their anti-hypertensive and anti-lipidemic effects in NG-nitro-L-arginine methyl ester (L-NAME) hypertensive rats.

METHODS

Wistar rats were grouped into two groups: control and hypertensive. Hypertension was induced in the hypertensive group by oral gavage of 60 mg/kg b.w of L-NAME for 3 weeks. After induction, the hypertensive group was randomly sub-grouped into hypertensive, hypertensive treated and hypertensive untreated groups. These were orally gavaged respectively with 60 mg/kg b.w of L-NAME, 60 mg/kg b.w/day of L-NAME +200 mg/kg b.w of different extracts of PR (aqueous, ethanolic and methanolic extracts) and 60 mg/kg b.w of L-NAME +20 mg/kg b.w ramipril for 3 weeks. The blood pressure was measured by tail-cuff method at the third and sixth weeks.

KEY FINDINGS

The results showed that the extracts of PR significantly decrease blood pressure, pro-atherogenic lipids and atherogenic ratios in L-NAME hypertensive rats. White blood cells count, neutrophil count and creatinine level were also effectively decreased by the extracts. Furthermore, the extracts increase serum nitric oxide (NO) level, anti-atherogenic lipid, glutathione level, lymphocyte and platelet count in the rats.

SIGNIFICANCE

Extracts of PR leaf decrease blood pressure and increase NO level in L-NAME hypertensive rats and also corrected the hyperlipidemia and inflammatory response arising from the reduction in NO bioavailability.

Pathological cardiac remodeling occurs early in CKD mice from unilateral urinary obstruction, and is attenuated by Enalapril

Cardiovascular disease constitutes the leading cause of mortality in patients with chronic kidney disease (CKD) and end-stage renal disease. Despite increasing recognition of a close interplay between kidney dysfunction and cardiovascular disease, termed cardiorenal syndrome (CRS), the underlying mechanisms of CRS remain poorly understood. Here we report the development of pathological cardiac hypertrophy and fibrosis in early stage non-uremic CKD. Moderate kidney failure was induced three weeks after unilateral urinary obstruction (UUO) in mice. We observed pathological cardiac hypertrophy and increased fibrosis in UUO-induced CKD (UUO/CKD) animals. Further analysis indicated that this cardiac fibrosis was associated with increased expression of transforming growth factor β (TGF-β) along with significant upregulation of Smad 2/3 signaling in the heart. Moreover early treatment of UUO/CKD animals with an angiotensin-converting-enzyme inhibitor (ACE I), Enalapril, significantly attenuated cardiac fibrosis. Enalapril antagonized activation of the TGF-β signaling pathway in the UUO/CKD heart. In summary our study demonstrates the presence of pathological cardiac hypertrophy and fibrosis in mice early in UUO-induced CKD, in association with early activation of the TGF-β/Smad signaling pathway. We also demonstrate the beneficial effect of ACE I in alleviating this early fibrogenic process in the heart in UUO/CKD animals.

Reduction in nitric oxide bioavailability shifts serum lipid content towards atherogenic lipoprotein in rats

Nitric oxide (NO) is major endothelial relaxing factor and reduction in its bioavailabilty has been linked to hypertension. Furthermore, high lipid content is a strong risk factor predisposing to cardiovascular diseases. The principal focus of this study was to investigate the effect of blockade of nitric oxide synthase (NOS) on serum lipid content in rats. Male Wistar rats (150-170 g, n = 15) were randomly divided into two groups designated control (n = 5), and L-Name group (n = 10) and were gavage with distilled water and 60 mg/kg of L-NAME respectively daily for three weeks. After 3 weeks, the L-NAME group was sub-divided into two sub-groups (n = 5 each): L-NAME (60 mg/kg of L-NAME), and L-NAME plus ramipril (LR) (60 mg/kg of L-NAME plus 20 mg/kg of ramipril) and were treated daily for another three weeks. The blood pressure (BP) of the conscious rats was measured by tail-cuff method at the onset, at the third and at the sixth weeks of the experiment; while serum lipid contents and NO were measured at the third and sixth weeks. At the end of the experiment blood sample was drawn by ocular puncture for evaluation of lipid profile and NO, and the animals were later euthanized by overdose of anaesthesia. Data were analyzed using ANOVA at p < 0.05. There was a significant increase in BP, triglyceride, total cholesterol, low density lipoprotein-cholesterol, and atherogenic indices in L-NAME group compared to the control and LR group (p < 0.05); NO and high density lipoprotein-cholesterol was significant lower in the L-NAME group compared to control and LR (p < 0.05). In conclusion, reduction in NO bioavailability alters lipid metabolism, which was rectified by ramipril.

Local angiotensin II promotes adipogenic differentiation of human adipose tissue mesenchymal stem cells through type 2 angiotensin receptor

Obesity is often associated with high systemic and local activity of renin-angiotensin system (RAS). Mesenchymal stem cells of adipose tissue are the main source of adipocytes. The aim of this study was to clarify how local RAS could control adipose differentiation of human adipose tissue derived mesenchymal stem cells (ADSCs). We examined the distribution of angiotensin receptor expressing cells in human adipose tissue and found that type 1 and type 2 receptors are co-expressed in its stromal compartment, which is known to contain mesenchymal stem cells. To study the expression of receptors specifically in ADSCs we have isolated them from adipose tissue. Up to 99% of cultured ADSCs expressed angiotensin II (AngII) receptor type 1 (AT1). Using the analysis of Ca²⁺ mobilization in single cells we found that only 5.2±2.7% of ADSCs specifically respond to serial Ang II applications via AT1 receptor and expressed this receptor constantly. This AT1^const ADSCs subpopulation exhibited increased adipose competency, which was triggered by endogenous AngII. Inhibitory and expression analyses showed that AT1^const ADSCs highly co-express AngII type 2 receptor (AT2), which was responsible for increased adipose competency of this ADSC subpopulation.

Imaging of Myocardial Fibrosis in Patients with End-Stage Renal Disease: Current Limitations and Future Possibilities

Cardiovascular disease in patients with end-stage renal disease (ESRD) is driven by a different set of processes than in the general population. These processes lead to pathological changes in cardiac structure and function that include the development of left ventricular hypertrophy and left ventricular dilatation and the development of myocardial fibrosis. Reduction in left ventricular hypertrophy has been the established goal of many interventional trials in patients with chronic kidney disease, but a recent systematic review has questioned whether reduction of left ventricular hypertrophy improves cardiovascular mortality as previously thought. The development of novel imaging biomarkers that link to cardiovascular outcomes and that are specific to the disease processes in ESRD is therefore required. Postmortem studies of patients with ESRD on hemodialysis have shown that the extent of myocardial fibrosis is strongly linked to cardiovascular death and accurate imaging of myocardial fibrosis would be an attractive target as an imaging biomarker. In this article we will discuss the current imaging methods available to measure myocardial fibrosis in patients with ESRD, the reliability of the techniques, specific challenges and important limitations in patients with ESRD, and how to further develop the techniques we have so they are sufficiently robust for use in future clinical trials.

Native T1 mapping: inter-study, inter-observer and inter-center reproducibility in hemodialysis patients

BACKGROUND

Native T1 mapping is a cardiovascular magnetic resonance (CMR) technique that associates with markers of fibrosis and strain in hemodialysis patients. The reproducibility of T1 mapping in hemodialysis patients, prone to changes in fluid status, is unknown. Accurate quantification of myocardial fibrosis in this population has prognostic potential.

METHODS

Using 3 Tesla CMR, we report the results of 1) the inter-study, inter-observer and intra-observer reproducibility of native T1 mapping in 10 hemodialysis patients; 2) inter-study reproducibility of left ventricular (LV) structure and function in 10 hemodialysis patients; 3) the agreement of native T1 map and native T1 phantom analyses between two centres in 20 hemodialysis patients; 4) the effect of changes in markers of fluid status on native T1 values in 10 hemodialysis patients.

RESULTS

Inter-study, inter-observer and intra-observer variability of native T1 mapping were excellent with co-efficients of variation (CoV) of 0.7, 0.3 and 0.4% respectively. Inter-study CoV for LV structure and function were: LV mass = 1%; ejection fraction = 1.1%; LV end-diastolic volume = 5.2%; LV end-systolic volume = 5.6%. Inter-centre variability of analysis techniques were excellent with CoV for basal and mid-native T1 slices between 0.8-1.2%. Phantom analyses showed comparable native T1 times between centres, despite different scanners and acquisition sequences (centre 1: 1192.7 ± 7.5 ms, centre 2: 1205.5 ± 5 ms). For the 10 patients who underwent inter-study testing, change in body weight (Δweight) between scans correlated with change in LV end-diastolic volume (ΔLVEDV) (r = 0.682;P = 0.03) representing altered fluid status between scans. There were no correlations between change in native T1 between scans (ΔT1) and ΔLVEDV or Δweight (P > 0.6). Linear regression confirmed ΔT1 was unaffected by ΔLVEDV or Δweight (P > 0.59).

CONCLUSIONS

Myocardial native T1 is reproducible in HD patients and unaffected by changes in fluid status at the levels we observed. Native T1 mapping is a potential imaging biomarker for myocardial fibrosis in patients with end-stage renal disease.

Effects of a novel ACE inhibitor, 3-(3-thienyl)-l-alanyl-ornithyl-proline, on endothelial vasodilation and hepatotoxicity in l-NAME-induced hypertensive rats

Nitric oxide (NO) is a widespread biological mediator involved in many physiological and pathological processes, eg, in the regulation of vascular tone and hypertension. Chronic inhibition of NO synthase by N^G-nitro-l-arginine methyl ester (l-NAME) hydrochloride results in the development of hypertension accompanied by an increase in vascular responsiveness to adrenergic stimuli. Recently, we developed a novel sulfur-containing angiotensin-converting enzyme inhibitor: 3-(3-thienyl)-l-alanyl-ornithyl-proline (TOP). Our previous studies indicated a superior nature of the molecule as an antihypertensive agent in spontaneously hypertensive rats (showing the involvement of renin–angiotensin–aldosterone system) in comparison to captopril. The aim of the present study was to investigate the effect of TOP on NO pathway in l-NAME-induced hypertensive rats, and captopril was included as the standard treatment group. Treatment with both TOP (20 mg/kg) and captopril (40 mg/kg) prevented the development of hypertension in l-NAME model, but TOP showed better restoration of NO and normal levels of angiotensin-converting enzyme. In addition, in vitro vasorelaxation assay showed an improvement in endothelium-dependent vasodilation in both the cases. Further, the biochemical (malondialdehyde, alanine aminotransferase, and aspartate aminotransferase) and the histopathological effects of TOP on rat liver tissues revealed a protective nature of TOP in comparison to captopril in the l-NAME model. In conclusion, TOP at 50% lesser dose than captopril was found to be better in the l-NAME model.

Dynamic role of extracellular matrix metalloproteinases in heart failure

In chronic congestive heart failure, an illness affecting more than 4 million Americans, there is extensive myocardial extracellular matrix (ECM) remodeling. Failing human ventricular myocardium contains activated matrix metalloproteinases (MMPs) which are involved in adverse ECM remodeling. Our studies support the concept that impaired ECM remodeling and MMP activation are, in part, responsible for the cardiac structural deformation during heart failure. There is no known program which has declared its aim the investigation of regulation of fibrosis in hypertrophy and disruption of ECM in cardiac dilatation and failure. The development of transgenic technology, and emerging techniques for in vivo gene transfer, suggest a strategy for improving cardiac function by overexpressing or down regulation of the ECM components such as MMPs, tissue inhibitor of metalloproteinases (TIMPs), transforming growth factor β1 (TGFβ), decorin, collagen, and integrins in heart failure.

Early co-expression of cyclooxygenase-2 and renin in the rat kidney cortex contributes to the development of N(G)-nitro-L-arginine methyl ester induced hypertension

We investigated the involvement of cyclooxygenase-2 (COX-2) and the renin-angiotensin system in N(G)-nitro-L-arginine methyl ester (L-NAME)-induced hypertension. Male Wistar rats were treated with L-NAME (75.0 mg·(kg body mass)(-1)·day(-1), in their drinking water) for different durations (1-33 days). COX-2 and renin mRNA were measured using real-time PCR in the renal cortex, and prostanoids were assessed in the renal perfusate, whereas angiotensin II (Ang II) and Ang (1-7) were quantified in plasma. In some rats, nitric oxide synthase inhibition was carried out in conjunction with oral administration of captopril (30.0 mg·kg(-1)·day(-1)) or celecoxib (1.0 mg·kg(-1)·day(-1)) for 2 or 19 days. We found a parallel increase in renocortical COX-2 and renin mRNA starting at day 2 of treatment with L-NAME, and both peaked at 19-25 days. In addition, L-NAME increased renal 6-Keto-PGF(1α) (prostacyclin (PGI2) metabolite) and plasma Ang II from day 2, but reduced plasma Ang (1-7) at day 19. Captopril prevented the increase in blood pressure, which was associated with lower plasma Ang II and increased COX-2-derived 6-Keto-PGF(1α) at day 2 and plasma Ang (1-7) at day 19. Celecoxib partially prevented the increase in blood pressure; this effect was associated with a reduction in plasma Ang II. These findings indicate that renal COX-2 expression increased in parallel with renin expression, renal PGI2 synthesis, and plasma Ang II in L-NAME-induced hypertension.

Cardiovascular changes in spontaneously hypertensive rats are improved by chronic treatment with zofenopril

BACKGROUND AND PURPOSE

The aim of this study was to investigate the effect of chronic treatment with antihypertensive and non-antihypertensive doses of zofenopril on cardiovascular changes in spontaneously hypertensive rats (SHR).

EXPERIMENTAL APPROACH

Male SHR were treated with 0.5 or 10 mg kg(-1) per day of zofenopril (Z(0.5) and Z(10)) for 3 months. SHR and Wistar-Kyoto rats (WKY) receiving vehicle were used as controls. Systolic blood pressure was measured using the tail cuff method. Left ventricular weight/body weight ratio was calculated as cardiac hypertrophy index. Angiotensin converting enzyme (ACE) activity was determined in plasma and tissues by a fluorimetric method. Vascular reactivity was evaluated on aortic rings by acetylcholine and sodium nitroprusside relaxations. Effects on vascular structure were assessed by lumen diameter, wall thickness and medial cross-sectional area determination. Superoxide anion generation was quantified using lucigenin-amplified chemiluminescence in aorta.

RESULTS

Long-term daily administration of zofenopril (10 mg kg(-1)) to SHR reduced blood pressure to WKY values, decreased cardiac hypertrophy, improved the acetylcholine-induced relaxant response and reversed the vascular remodelling. ACE inhibition and antioxidant activity were involved in these effects. 0.5 mg kg(-1) per day of zofenopril slightly modified blood pressure and the other effects were weaker.

CONCLUSIONS AND IMPLICATIONS

Antihypertensive effects of chronic treatment with zofenopril were accompanied by recovery of endothelial function and improvement of cardiovascular structure. Low-dose zofenopril had little effect on blood pressure, with some benefits on cardiovascular structure and function. Inhibition of ACE and antioxidant activity were involved in these effects.

A Novel Category of Anti-Hypertensive Drugs for Treating Salt-Sensitive Hypertension on the Basis of a New Development Concept

Terrestrial animals must conserve water and NaCl to survive dry environments. The kidney reabsorbs 95% of the sodium filtered from the glomeruli before sodium reaches the distal connecting tubules. Excess sodium intake requires the renal kallikrein-kinin system for additional excretion. Renal kallikrein is secreted from the distal connecting tubule cells of the kidney, and its substrates, low molecular kininogen, from the principal cells of the cortical collecting ducts (CD). Formed kinins inhibit reabsorption of NaCl through bradykinin (BK)-B₂ receptors, localized along the CD. Degradation pathway of BK by kinin-destroying enzymes in urine differs completely from that in plasma, so that ACE inhibitors are ineffective. Urinary BK is destroyed mainly by a carboxypeptidase-Y-like exopeptidase (CPY) and partly by a neutral endopeptidase (NEP). Inhibitors of CPY and NEP, ebelactone B and poststatin, respectively, were found. Renal kallikrein secretion is accelerated by potassium and ATP-sensitive potassium (KATP) channel blockers, such as PNU-37883A. Ebelactone B prevents DOCA-salt hypertension in rats. Only high salt intake causes hypertension in animals deficient in BK-B2 receptors, tissue kallikrein, or kininogen. Hypertensive patients, and spontaneously hypertensive rats, excrete less kallikrein than normal subjects, irrespective of races, and become salt-sensitive. Ebelactone B, poststatin, and KATP channel blockers could become novel antihypertensive drugs by increase in urinary kinin levels. Roles of kinin in cardiovascular diseases were discussed.

Are there effects of renin-angiotensin system antagonists beyond blood pressure control?

Angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) are recognized to reduce cardiovascular and renal morbidity and mortality, which is primarily attributed to their antihypertensive effects. Activation of the renin-angiotensin system (RAS) may also play an important role in the pathogenesis of cardiovascular and renal disease through blood pressure-independent mechanisms mediated by angiotensin II. Thus, inhibiting the RAS with either an ARB or an ACE inhibitor may confer additional benefit in people with advanced nephropathy that cannot be explained totally by reductions in blood pressure. Preclinical evidence suggests that blood pressure lowering is not solely responsible for the organ and tissue protective effects of ACE inhibitors or ARBs. Furthermore, clinical studies evaluating effects on end organs and surrogate markers have shown that these agents have blood pressure-independent effects. There is also intriguing evidence that agents in the same class may differ in their effects on renal function despite similar blood pressure control. Support for blood pressure-independent effects comes from outcome studies. Agents evaluated in such studies and that appear to have effects independent of blood pressure lowering include irbesartan, losartan, ramipril, and telmisartan. Taken together, this body of evidence indicates that the clinical benefits of ARBs and ACE inhibitors in patients with advanced nephropathy extend beyond blood pressure reduction. Therefore, although antihypertensive efficacy is of primary importance in choosing a treatment to provide cardiovascular and renal protection, consideration should be given to the effects of an agent that extend beyond blood pressure.

Effect of melatonin, captopril, spironolactone and simvastatin on blood pressure and left ventricular remodelling in spontaneously hypertensive rats

OBJECTIVE

Melatonin was shown to reduce blood pressure, oxidative load and to increase nitric oxide bioavailability predisposing melatonin to have antiremodelling potential.

DESIGN

The aim of this study was to show whether melatonin can reverse left ventricular remodelling in spontaneously hypertensive rats (SHR) and to compare this potential protective effect with captopril, spironolactone, or simvastatin.

METHODS

Six groups of 3-month old rats (eight per group) were treated for 5 weeks: control untreated Wistar rats, control SHR, SHR plus melatonin (10 mg/kg per 24 h), SHR plus captopril (100 mg/kg per 24 h), SHR plus spironolactone (200 mg/kg per 24 h) and SHR plus simvastatin (10 mg/kg per 24 h). Their systolic blood pressure (SBP) was measured by the tail-cuff method. The relative weights of the left ventricle, nitric oxide synthase (NOS) activity, endothelial NOS and nuclear factor kappa B (NF-kappaB) protein expression, conjugated dienes concentration, level of collagenous proteins and hydroxyproline were measured.

RESULTS

SBP was reduced by all drugs investigated but most prominently by captopril in SHR. The activity of NOS and endothelial NOS expression increased in the left ventricles of SHR compared with controls. Melatonin and spironolactone further increased NOS expression. Left ventricular oxidative load, estimated by NF-kappaB expression and conjugated dienes concentration, increased in SHR. Only melatonin reduced NF-kappaB expression and decreased conjugated diens concentration. Only captopril reduced left ventricular hypertrophy in SHR, whereas melatonin reduced collagenous protein concentration and hydroxyproline content in the left ventricle.

CONCLUSION

It is concluded that although melatonin, in comparison with captopril, did not reverse left ventricle hypertrophy, it reversed left ventricular fibrosis. This protection by melatonin may be caused by its prominent antioxidative effect.

Hypertrophy and fibrosis in the cardiomyopathy of uremia--beyond coronary heart disease

Cardiac disease is the leading cause of death in uremic patients. In contrast to previous opinion, coronary events account for a relatively small proportion of cardiac deaths, the most common causes being sudden death and heart failure. Against this background the current text will discuss noncoronary cardiac pathology, specifically the pathogenesis and the morphological findings caused by (pathological) cardiac hypertrophy, cardiac interstitial fibrosis and microvascular disease.

Anti-hypertensive effects of the methanol/methylene chloride stem bark extract of Mammea africana in l-NAME-induced hypertensive rats

AIM OF THE STUDY

The methanol/methylene chloride (CH(3)OH/CH(2)Cl(2)) extract from the stem bark of Mammea africana was showed to possess vasodilating effect in the presence and the absence of N(omega)-nitro-l-arginine methyl ester (l-NAME). The present study was designed to evaluate the effects of the methanol/methylene chloride from the stem bark of Mammea africana.

MATERIALS AND METHODS

The extract (200 mg/(kg day)) was administered orally in rats treated concurrently with l-NAME (40 mg/(kg day)). l-Arginine (100 mg/(kg day)) and captopril (20 mg/(kg day))were used as positive controls. Bodyweight, systolic arterial blood pressure and heart rate were measured weekly throughout the experiment period (28 days). At the end of treatment, animals were killed and the cardiac mass index evaluated. The aorta was used to evaluate the endothelium-dependant relaxation to carbachol. The aorta contraction induced by noradrenalin was also examined and expressed as a percentage of that induced by KCl.

RESULTS

The extract neither affected the body weight nor the heart rate. The extract as captopril completely prevented the development of arterial hypertension. Both the substances failed to restore the endothelium-dependent vascular relaxation and increased the vascular contraction to norepinephrine in relation to KCl contraction. They also significantly reduced the left ventricular hypertrophy induced by l-NAME.

CONCLUSION

These findings are in agreement with the traditional use of Mammea africana in the treatment of arterial hypertension and indicate that it may have a beneficial effect in patients with NO deficiency but will be unable to improve their endothelium-dependent vasorelaxation.

Effects of purified herbal extract of Salvia miltiorrhiza on ischemic rat myocardium after acute myocardial infarction

In the current study, we compared purified Salvia miltiorrhiza extract (PSME) with Angiotensin-converting enzyme inhibitor, Ramipril, in in vitro experiments and also in vivo using animal model of myocardial infarction. PSME was found to have a significantly higher trolox equivalent antioxidant capacity which indicated a great capacity for scavenging free radicals. PSME could also prevent pyrogallo red bleaching and DNA damage. After 2 weeks treatment with PSME or Ramipril, survival rates of rats with experimental myocardial infarction were marginally increased (68.2% and 71.4%) compared with saline (61.5%). The ratios of infarct size to left ventricular size in both PSME-and Ramipril-treated rats were significantly less than that in the saline-treated group. Activity of cardiac antioxidant enzyme superoxide dismutase (SOD) was significant higher while level of Thiobarbituric acid-reactive substances (TBARs) was lower in the PSME treated group. Purified and standardized Chinese herb could provide an alternative regimen for the prevention of ischemic heart disease.

[Anastomotic leakage in the gastrointestinal tract-repair and prognosis]

Anastomotic leakage is still a serious complication in surgery, resulting in increased morbidity and mortality. The reasons for its onset are various and due to two main reasons: general risk factors of the individual patient and technical surgical factors influencing the outcome after gastrointestinal anastomoses. Changes in the extracellular matrices, particularly due to collagen metabolism, and related disturbances are assumed to be important factors influencing wound healing processes. The technique chosen and the surgical skill are important with regard to inflammation and tissue necroses at the anastomotic line. Analysis of data obtained by clinical studies that concern clinical risk factors for anastomotic leakage reveal an inhomogeneous picture. Attempts to develop risk profiles or scores based on these results have failed until now. Problems encompass the complexity of wound healing processes, and it is questionable whether our current knowledge about them is complete. Therefore, profound understanding of anastomotic leakage requires in-depth analysis of the interaction of extracellular matrix components. Preliminary results indicate the presence of a risk population with collagen metabolism disturbances that have a major effect on wound healing after gastrointestinal anastomosis.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure; production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells; as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

Angiotensin converting enzyme inhibition for cardiac hypertrophy in patients with end-stage renal disease: what is the evidence?

Dialysis patients show a high prevalence of cardiovascular complications among which left ventricular hypertrophy is one of the most frequent and is independently predictive of mortality. A recent study indicates that partial regression of left ventricular hypertrophy improves mortality and reduces cardiovascular events in end-stage renal disease (ESRD) patients, suggesting the importance of targeting therapeutic strategies to reduce cardiac hypertrophy and improve the outcome in these patients. The pathogenesis of left ventricular hypertrophy in ESRD patients is multifactorial and includes hypertension, activation of the renin-angiotensin system, increased sympathetic activity, chronic volume overload, chronic anaemia and hyperparathyroidism. In this paper, we review the available experimental and clinical evidence showing the important contribution of the renin-angiotensin system as well as its interaction with the sympathetic nervous system in the pathogenesis of left ventricular hypertrophy in ESRD patients. Furthermore, we summarize the results of currently available clinical studies that examined the effects of angiotensin-converting enzyme inhibition or angiotensin receptor antagonism on left ventricular hypertrophy in ESRD patients, and review evidences that support the use of angiotensin-converting enzyme inhibitors or angiotensin receptor antagonists in the ESRD population.

Diverse effects of Ace inhibitors and angiotensin II receptor antagonists on prevention of cardiac hypertrophy and collagen distribution in spontaneously hypertensive rats

This study has compared the effects of two structurally different angiotensin converting enzyme inhibitors (ACEis) such as zofenopril (Zof, with sulfhydrylic group) and lisinopril (Lis, with carboxylic group) and an angiotensin II AT(1) receptor antagonist (losartan, Los) on the prevention of cardiac hypertrophy and collagen distribution in spontaneously hypertensive rats (SHRs). The SHRs were untreated or received: Zof (10 mg/kg/day), Lis (10 mg/kg/day) or Los (20 mg/kg/day) in drinking water starting at 4 weeks of age. At 8, 16 and 24 weeks of age, 8 rats/group were sacrificed for determination of blood pressure, cardiac hypertrophy and collagen distribution. All treatments significantly decreased blood pressure and cardiac indices, expressed as the ventricles to body weight ratio, both variables being significantly correlated. Total ventricular collagen content was similarly decreased in all treated groups. Zof significantly increased the expression of collagen type III and normalized the collagen type I/III ratio. These results suggest that the effects of these drugs on different types of collagen are independent from angiotensin II formation. Similar findings obtained with captopril seem to indicate that the antioxidant sulfhydrylic group of these ACEis can play a role in the distribution of collagen during cardiac hypertrophy.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure;production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells;as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

Direct inhibition of neutral endopeptidase in vasopeptidase inhibitor-mediated amelioration of cardiac remodeling in rats with chronic heart failure

Vasopeptidase inhibitors possess dual inhibitory actions on neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE) and have beneficial effects on cardiac remodeling. However, the contribution of NEP inhibition to their effects is not yet fully understood. To address the role of cardiac NEP inhibition in the anti-remodeling effects of a vasopeptidase inhibitor, we examined the effects of omapatrilat on the development of cardiac remodeling in rats with left coronary artery ligation (CAL) and those on collagen synthesis in cultured fibroblast cells. In vivo treatment with omapatrilat (30 mg/kg/day for 5 weeks) inhibited cardiac NEP activity in rats with CAL, which was associated with a suppression of both cardiac hypertrophy and collagen deposition. In cultured cardiac fibroblasts, omapatrilat (10(-7) to approximately 10(-5) M) inhibited NEP activity and augmented the ANP-induced decrease in [3H]-proline incorporation. ONO-BB, an active metabolite of the NEP selective inhibitor ONO-9902, also augmented the ANP-induced response, whereas captopril, an ACE inhibitor, did not. The angiotensin I-induced increase in [3H]-proline incorporation was prevented by omapatrilat and captopril, but not by ONO-BB. The results suggest that vasopeptidase inhibitor suppressed cardiac remodeling in the setting of chronic heart failure, possibly acting through the direct inhibition of cardiac NEP. Vasopeptidase inhibitors may have therapeutic advantages over the classical ACE and NEP inhibitors alone with respect to the regression of cardiac fibrosis.

Chronic inhibition of nitric oxide synthase induces hypertension and cardiomyocyte mitochondrial and myocardial collagen remodelling in the absence of hypertrophy

OBJECTIVES

To evaluate the morphometric and ultrastructural alterations of the heart produced by long-term inhibition of nitric oxide (NO) synthase with N(omega)-nitro-l-arginine methyl ester (l-NAME) and to examine whether the changes are caused by l-NAME-induced hypertension or a lack of NO.

METHODS

Male Wistar rats were divided randomly into three sets: control group, standard diet/l-NAME-treated group, and standard diet/l-NAME + captopril-treated group.

RESULTS

Chronic inhibition of NO synthesis with l-NAME given for 4 weeks promoted a time-dependent hypertensive response which was not accompanied by an increase in cardiac mass, myocellular hypertrophy or other evidence of myocyte damage. However, this response was associated with left ventricular cardiomyocyte mitochondrial remodelling and discrete interstitial fibrosis in both the left and right ventricles. The remodelling was characterized by an increase in the number and size of mitochondria. Importantly, systolic pressure overload did not result in left ventricle decompensation. The concomitant treatment with l-NAME and captopril abolished the development of hypertension and left ventricular cardiomyocyte subcellular remodelling, but not the discrete interstitial fibrosis in the left and right ventricle.

CONCLUSIONS

The present study suggests that, in the l-NAME model of hypertension, decreased NO production could be an important means of controlling cardiovascular hypertensive stress by regulating mitochondrial biogenesis and function in the tissue. On the other hand, discrete interstitial ventricular myocardial fibrosis observed in l-NAME-treated rats, either hypertensive or rendered normotensive with captopril, clearly indicates that this response depends on a process associated with NO insufficiency.

A story of two ACEs

According to the World Health Organization predictions cardiovascular diseases will be the leading cause of death by the year 2020. High blood pressure is a major risk factor for myocardial infarction, cerebrovascular disease, and stroke. Modulation of the renin-angiotensin system, particularly inhibition of the angiotensin-converting enzyme (ACE), has become a prime strategy in the treatment of hypertension and heart failure. Recently the gene of a new ACE, termed ACE2, has been characterized. The ACE2 gene maps to defined quantitative trait loci on the X chromosome in three different rat models of hypertension, suggesting ACE2 as a candidate gene for hypertension. In mice the targeted disruption of ACE2 resulted in increased systemic angiotensin II levels, impaired cardiac contractility, and upregulation of hypoxia-induced genes in the heart. Since mice deficient in both ACE2 and ACE show completely normal heart function, it appears that ACE and ACE2 negatively regulate each other. The mechanisms and physiological significance of the interplay between ACE and ACE2 are not yet elucidated, but it may involve several new peptides and peptide systems. In view of drug development the increasing complexity of the renin-angiotensin system offers both challenge and opportunity to develop new and refined treatment strategies against cardiovascular diseases.

Beneficial effects of sampatrilat, a novel vasopeptidase inhibitor, on cardiac remodeling and function of rats with chronic heart failure following left coronary artery ligation

Sampatrilat is a novel vasopeptidase inhibitor that may offer a greater benefit than traditional angiotensin-converting enzyme (ACE) inhibitors in the treatment of chronic heart failure (CHF). The present study was undertaken to determine whether sampatrilat improves hemodynamic function and cardiac remodeling through a direct action on the failing heart in rats with CHF following left coronary artery ligation (CAL). Sampatrilat (30 mg/kg a day) was administered orally to the animals from the 1st to 6th week after the operation. Sampatrilat reduced the mortality of the rats with CAL (20 versus 57% for untreated rats). Treatment with sampatrilat for 5 weeks suppressed tissue ACE and neutral endopeptidase (NEP) activities. Sampatrilat did not affect the arterial blood pressure, whereas it attenuated the CAL-induced increases in the left ventricular end-diastolic pressure, heart weight, and collagen content of the viable left ventricle. To assess the direct effects of sampatrilat on collagen synthesis, we measured the incorporation of [(3)H]proline into cultured cardiac fibroblasts. Sampatrilat at concentrations that inhibited NEP activity in vitro augmented the atrial natriuretic peptide-induced decrease in [(3)H]proline incorporation by the cells. In addition, sampatrilat prevented the angiotensin I-induced increase in [(3)H]proline incorporation, whereas captopril did not. The results suggest that long-term treatment with sampatrilat regresses cardiac remodeling in rats with CAL, which is associated with improvement of hemodynamic function. The mechanism by which sampatrilat improved cardiac remodeling may be attributable to the direct inhibition of cardiac fibrosis, possibly acting through the cardiac natriuretic peptide system.

Norepinephrine induces alveolar epithelial apoptosis mediated by alpha-, beta-, and angiotensin receptor activation

Norepinephrine (NE) induces apoptosis in cardiac myocytes, and autocrine production of angiotensin (ANG) II is required for apoptosis of alveolar epithelial cells (AECs) (Wang R, Zagariya A, Ang E, Ibarra-Sunga O, and Uhal BD. Am J Physiol Lung Cell Mol Physiol 277: L1245--L1250, 1999; Wang R, Alam G, Zagariya A, Gidea C, Pinillos H, Lalude O, Choudhary G, and Uhal BD. J Cell Physiol 185: 253--259, 2000). On this basis, we hypothesized that NE might induce apoptosis of AECs in a manner inhibitable by ANG system antagonists. Purified NE induced apoptosis in the human A549 AEC-derived cell line or in primary cultures of rat AECs, with EC(50) values of 200 and 20 nM, respectively. Neither the alpha-agonist phenylephrine nor the beta-agonist isoproterenol could mimic NE when tested alone but when applied together could induce apoptosis with potency equal to NE. Apoptosis and net cell loss (47--59% in 40 h) in response to NE was completely abrogated by the ANG-converting enzyme inhibitor lisinopril or the ANG II receptor antagonist saralasin, each at concentrations capable of blocking Fas- or tumor necrosis factor-alpha-induced apoptosis. These data suggest that NE induces apoptosis of human and rat AECs through a mechanism involving the combination of alpha- and beta-adrenoceptor activation followed by autocrine generation of ANG II.

Chronic inhibition of NO synthesis per se promotes structural intimal remodeling of the rat aorta

OBJECTIVE

We characterized, using histomorphometry and transmission and scanning electron microscopy, the intimal remodeling of the thoracic aorta of normocholesterolemic young rats chronically-treated with N(omega)-nitro-L-arginine methylester (L-NAME) and examined the question whether these changes were caused by the lack of NO per se or by the hypertension which L-NAME administration induces.

METHODS

Male Wistar rats were divided randomly into three sets: control group, standard diet/L-NAME-treated group, and standard diet/L-NAME + captopril-treated group.

RESULTS

The treatment of rats with L-NAME for 4 weeks resulted in increased blood pressure (by 32% at the end of the treatment) as compared with the control value and intimal remodeling comprising a continuous layer of enlarged endothelial cells with irregular nuclear and cytoplasmic contours, lying over a thickened layer of fibrocollagenous support tissue focally expanded with lymphomononuclear cells and mainly diffuse foci of smooth muscle cells. In addition, the NO synthase inhibition caused a marked thickened tunica intima (150% thicker than the control value) and a significantly augmented intima : media ratio (126% higher than the control value). On the other hand, captopril prevented hypertension in rats simultaneously treated with L-NAME as compared with controls, and induced intimal remodeling comprising the same qualitative changes as those observed in L-NAME-treated rats. The tunica intima of l-NAME + captopril-treated rats was moderately thickened (60% increase in comparison with that of controls and 65% thinner as compared with L-NAME-treated rats). In the same way, the mean intima : media ratio of rats concomitantly treated with L-NAME and captopril was moderately increased (45% more) as compared with controls and significantly lower in comparison with rats administered L-NAME alone (36% less).

CONCLUSIONS

Chronic inhibition of NO synthesis per se promotes structural intimal remodeling of the rat aorta, which is potentiated by L-NAME-induced hypertension. Most important, the present findings favor the idea that blockade of NO synthesis by causing intimal remodeling might be a primary cause, as individual biologic phenomenon, in the development of an atherosclerotic plaque.

Fluvastatin inhibits O2- and ICAM-1 levels in a rat model with aortic remodeling induced by pressure overload

Upregulation of intercellular adhesion molecule-1 (ICAM-1) expression is suggested to play an important role in the pathogenesis of vascular remodeling. The aim of the present study was to investigate the effects of the 3-hydroxy-3-methylglutaryl (HMG) CoA reductase inhibitor fluvastatin on superoxide anion (O2-) production and ICAM-1 expression in a rat model with vascular remodeling induced by pressure overload. Two weeks after aortic banding, marked increases in O2- production and ICAM-1 protein levels were observed in the aorta. O2- formation and ICAM-1 immunoreactivity were mainly increased in the endothelium and adventitia of the aorta in banded rats. Oral administration of fluvastatin prevented both these changes and the development of perivascular fibrosis and increased the expression of endothelial nitric oxide synthase. Cholesterol and lipid peroxide levels in serum did not change in the banded rats. Thus the beneficial effects of fluvastatin seen in this study as well as its cholesterol-lowering effect may contribute to attenuate the atherosclerotic process.

The effects of ACE inhibitor therapy on left ventricular myocardial mass and diastolic filling in previously untreated hypertensive patients: a cine MRI study

Cardiac remodeling in case of hypertension induces hypertrophy of myocytes and elevated collagen content and, subsequently, impaired diastolic filling of the left ventricle. The purpose of this prospective study was to evaluate changes of left ventricular (LV) myocardial mass, as well as diastolic filling properties, in hypertensive patients treated with the ACE inhibitor fosinopril. Sixteen hypertensive patients with echocardiographically documented LV hypertrophy and diastolic dysfunction received fosinopril (10-20 mg daily). Measurements of LV myocardial mass and properties of diastolic filling (peak filling fraction (PFF); peak filling rate (PFR)) were performed prior to medication, as well as after 3 and 6 months of therapy using cine magnetic resonance imaging (MRI). Ten healthy subjects served as a control group. LV myocardial mass (g/m2) decreased continuously within 3-6 months of follow-up by 32% (148 +/- 40 vs. 120 +/- 26 vs. 101 +/- 22 g/m2; P < 0.0001/0.005). The extent of regression correlated to the severity of LV hypertrophy at baseline (r = 0.77; P < 0.004). Early diastolic filling increased significantly within 6 months of therapy (PFF (%): 36 +/- 6 vs. 61 +/- 7, P < 0.0001; PFR (mL/second): 211 +/- 48 vs. 282 +/- 48, P < 0.001). Cine MRI can be used to assess the time course of pharmacological effects on cardiac remodeling in the course of hypertension. ACE inhibitor therapy results in a significant reduction of LV mass within 3 months and is accompanied by a normalization of diastolic filling that is completed after 6 months.

Long-term effect of N-acetyl-seryl-aspartyl-lysyl-proline on left ventricular collagen deposition in rats with 2-kidney, 1-clip hypertension

BACKGROUND

N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural inhibitor of pluripotent hematopoietic stem cell proliferation. Ac-SDKP plasma concentration is increased 5-fold after angiotensin-converting enzyme inhibition. Here we studied the effect of Ac-SDKP on monocyte/macrophage infiltration, fibroblast proliferation, and collagen deposition in the rat heart in renovascular hypertension.

METHODS AND RESULTS

We investigated whether long-term Ac-SDKP administration would prevent left ventricular (LV) hypertrophy and interstitial collagen deposition in rats with 2-kidney, 1-clip (2K-1C) hypertension. Ac-SDKP (400 microgram. kg(-1). d(-1)) did not affect development of hypertension. Mean blood pressure was similar in rats with 2K-1C hypertension whether they were given vehicle or Ac-SDKP and was higher than in controls. Both LV weight and cardiomyocyte size were significantly increased in rats with 2K-1C hypertension compared with controls and were unaffected by Ac-SDKP. Proliferating cell nuclear antigen- and monocyte/macrophage-positive cells were increased in the LV of 2K-1C hypertensive rats; this increase was significantly blunted by Ac-SDKP (P<0.001). LV interstitial collagen fraction was also increased in 2K-1C hypertensive rats given vehicle (10.1+/-0.8%) compared with sham (5.3+/-0.1%, P<0.0001), and this increase was prevented by Ac-SDKP (5.4+/-0.4%, P<0.001).

CONCLUSIONS

Ac-SDKP inhibited monocyte/macrophage infiltration, cell proliferation, and collagen deposition in the LV of hypertensive rats without affecting blood pressure or cardiac hypertrophy, suggesting that it may be partly responsible for the cardioprotective effect of angiotensin-converting enzyme inhibitors.

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.

Effects of ACE inhibition and bradykinin antagonism on cardiovascular changes in uremic rats

BACKGROUND

Cardiovascular death continues to be a major problem in renal failure. Structural abnormalities of the heart and the vasculature contribute to the increased cardiovascular risk. They are ameliorated by angiotensin-converting enzyme (ACE) inhibitors, but because of the nonspecifity of ACE inhibition, it is uncertain whether the beneficial effect is mediated by interfering with angiotensin II (Ang II) or by modulating other effector systems, for example, bradykinin.

METHODS

To assess a potential role of bradykinin, subtotally nephrectomized Sprague-Dawley rats (SNX) received either the ACE inhibitor Ramipril (Rami, 0.2 mg/kg body weight p.o.), the specific B2 bradykinin receptor antagonist Hoe140 (0.2 mg/kg body weight, s.c.), or a combination of both, and were compared to sham-operated controls. To separately assess the effect of Ramipril on development and reversal of structural abnormalities, animals were either treated from the third day after SNX or from the fourth week after SNX onward (0.01 mg/kg body weight, p.o.).

RESULTS

Heart and aorta were evaluated by morphometric and stereologic techniques. The weight of the perfused left ventricle, as an index of cardiac hypertrophy, was significantly higher in untreated SNX. While it was significantly lower in animals with early and late Ramipril treatment, the beneficial effect was completely antagonized by Hoe140. The wall-to-lumen ratio of intramyocardial arterioles was significantly higher in untreated SNX compared with controls, but failed to be modified by administration of either Ramipril or Hoe140. In the heart, the intercapillary distance was significantly higher in SNX, but it was not lowered by either early or late Ramipril or Hoe140 treatment. Treatment of SNX with Hoe140 alone, however, resulted in a marked further increase in intercapillary distance. The wall thickness of the aorta was significantly higher in SNX than in controls; early and late Ramipril treatment prevented such increase, and this effect was antagonized by Hoe140.

CONCLUSION

These findings illustrate that bradykinin plays an important role for the beneficial effect of Ramipril in preventing (and potentially reversing) abnormal cardiovascular structure in uremic hypertensive rats.

The possible role of myocardial biopsy in systemic sclerosis

The histopathological features of heart involvement in systemic sclerosis (SSc) are not widely known. In internal and transplantation medicine, myocardial biopsies are increasingly used to diagnose cardiomyopathies including myocarditis. In two SSc patients presenting with dyspnoea with no evidence of pulmonary involvement, the cause of the compromised heart function was sought by myocardial biopsy. Immunohistological analysis revealed an increased number of CD3+ + T cells indicating myocarditis in one, and increased amounts of fibroblasts in both SSc patients. The authors think that myocardial involvement in SSc should be differentially evaluated and they propose the use of myocardial biopsies as a tool to distinguish between inflammatory and fibrotic forms of heart involvement in SSc patients.

Regression of chronic L -NAME-treatment-induced left ventricular hypertrophy: effect of captopril

Long-term administration of N(G)-nitro- L -arginine methyl ester (L -NAME) induces development of NO-deficient hypertension and left ventricular (LV) hypertrophy. In this work, we examined the effect of spontaneous and captopril-induced recovery on LV hypertrophy and protein composition in rats with developed L -NAME-induced hypertension. Four groups of rats were investigated: control L -NAME 40 mg/kg/day for 4 weeks (L -NAME) L -NAME 40 mg/kg/day for 4 weeks followed by 3-week spontaneous recovery (L -NAME+R) L -NAME 40 mg/kg/day for 4 weeks followed by 3 weeks of captopril treatment at a dose of 100 mg/kg/day (L -NAME+C). LV hypertrophy in the L -NAME group was associated with an increase in content and concentration of left ventricular DNA and RNA, concentration of metabolic proteins (MP) and soluble collagenous proteins (SCP). Spontaneous recovery period reduced the hypertension, without regression of LV hypertrophy. Left ventricular DNA and RNA content were increased in the L -NAME+R group. In this group, concentrations of MP, contractile proteins (CP), and collagenous proteins did not differ from those in the L -NAME group. Captopril treatment caused total regression of hypertension and LV hypertrophy and decreased both content and concentration of DNA and RNA, as well as the contents of MP, CP and SCP v the L -NAME group. However, after captopril treatment, concentration of collagenous and non-collagenous protein fractions remained increased v control. We conclude that spontaneous regression of L -NAME-induced hypertension is not associated with regression of LV hypertrophy. LV hypertrophy was regressed only in captopril-treated animals.

Bradykinin-induced reductions in collagen gene expression involve prostacyclin

Cardiac fibrosis after myocardial infarction and in chronic hypertension involves an increase in the synthesis and deposition of collagen within the myocardium. Angiotensin-converting enzyme (ACE) inhibitors limit hypertrophy and fibrosis; their mechanism of action remains controversial, although kinins have been implicated to play a role. Because both bradykinin and prostaglandins (PG) have been shown to reduce collagen gene expression in cardiac fibroblasts, the goal of this study was to determine whether the bradykinin effect was mediated through enhanced prostaglandin formation by cardiac fibroblasts. Bradykinin increased [3H]arachidonic acid metabolite release 2.3-fold over control and stimulated a dose-dependent increase in 6-keto PGF1alpha (the stable metabolite of PGI2) release from these cells, in which 1 nmol/L bradykinin produced a 4-fold increase in 6-keto PGF1alpha release. Beraprost (a PGI2 analogue) reduced steady-state proalpha1(I) and proalpha1(III) collagen mRNA levels by 35.6+/-6.6% and 34.2+/-10.0%, respectively. Bradykinin-induced reductions in collagen type I and III gene expression were reversed by pretreatment with indomethacin. Our results indicate that one mechanism by which bradykinin modulates collagen biosynthesis via the rabbit cardiac fibroblast involves formation of arachidonic acid metabolites, particularly PGI2. The results of the present study argue that stabilization of endogenous kinins (as by ACE inhibitors) would enhance prostacyclin production and result in the attenuation of collagen gene expression, with potential implications for collagen synthesis and deposition within the myocardium.

Endothelial dysfunction coincides with an enhanced nitric oxide synthase expression and superoxide anion production

We investigated the effects of aortic banding-induced hypertension on the endothelium-dependent vasodilator responses in the aorta and coronary circulation of Sprague-Dawley rats. We studied the influence of hypertension on the endothelial nitric oxide synthase (NOS III) expression, assessed by Western blot and reverse transcription-polymerase chain reactions experiments, and on the superoxide anion (O2-) production. Two weeks after aortic banding, the endothelium-dependent relaxations were not altered. At this time, the expression of NOS III in the aorta and in confluent coronary microvascular endothelial cells (RCMECs) exhibited no marked changes, whereas O2- production was enhanced 1.9-fold in aortas from aortic-banded rats. Six weeks after aortic banding, the endothelium-dependent dilations were markedly impaired in the heart (50% decrease) and aorta (35% decrease). Analysis of NOS III protein and mRNA levels revealed marked increases in both aortas and confluent RCMECs (2.6- to 4-fold) from aortic-banded compared with sham-operated rats. There was no further increase in O2production in both the aorta and confluent RCMECs from aortic-banded rats. An enhanced nitrotyrosine protein level was also detected in the aorta from 6-week aortic-banded rats. These findings indicate that in hypertension induced by aortic banding, an enhanced O2- production alone is not sufficient to produce endothelial dysfunction. Endothelial vasodilator hyporesponsiveness was observed only when NOS III expression and O2- production were increased and was associated with the appearance of enhanced nitrotyrosine residues. This would suggest that the development of endothelial dysfunction is linked to an overproduction of not one, but two, endothelium-derived radicals that might lead to the formation of peroxynitrite.

Circulating angiotensin converting enzyme levels are increased in concentric, but not eccentric, left ventricular hypertrophy in elderly men

OBJECTIVE

To study the cross-sectional relationship between circulating angiotensin converting enzyme (ACE) activity and echocardiographically determined left ventricular geometry in a study of 380 70-year-old men participating in a health-survey reexamination and 50 patients with hypertension.

METHODS

Two-dimensional guided M-mode and Doppler echocardiography. Fluorometric assay of serum ACE activity.

RESULTS

The serum ACE activity was higher in the elderly men with left ventricular concentric hypertrophy than it was in men with normal geometry and left ventricular eccentric hypertrophy (32, 27, and 26 U/l, respectively, P < 0.01 for both comparisons before and after adjustment for the 24 h mean arterial pressure, body mass index, and use of antihypertensive medication). The serum ACE activity correlated with the thickness of the left ventricular interventricular septum (r = 0.12, P = 0.0095), the left ventricular relative wall thickness (r = 0.13, P = 0.0053 ), and the total peripheral resistance (r = 0.16, P = 0.0034), but not with the left ventricular mass (r = -0.039, P = 0.45) of these elderly men. The serum ACE activity in the hypertensive patients also correlated with the left ventricular interventricular septum thickness (r = 0.34, P = 0.020) independently of the 24 h mean arterial blood pressure, age, sex, body mass index, and insulin sensitivity.

CONCLUSION

Levels of serum ACE activity are associated with left ventricular geometry.