Expression of angiotensin-converting enzyme in remaining viable myocytes of human ventricles after myocardial infarction

[Loss of Myeloid-Derived Growth Factor Leads to Increased Fibrosis in Mice After Myocardial Infarction]

Objective

To investigate the effect of the loss of myeloid-derived growth factor (Mydgf) on the transformation of cardiac fibroblasts into myofibroblasts after myocardial infarction (MI).

Methods

Two adult mouse groups, including a wild-type (WT) group and another group with Mydgf knockout (Mydgf-KO), were examined in the study. The mice in these two groups were tested for their cardiac function by measuring left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) (n=10). Quantitative real-time PCR (qRT-PCR) (n=3) was performed to determine the mRNA expression levels of myofibroblast markers, including α-smooth muscle actin (α-SMA), periostin (postn), type Ⅷ collagen (col8al), and connective tissue growth factor (ctgf). Western blot (n=3) was performed to verify the protein expression levels of α-SMA. MI modeling was performed on the WT and the Mydgf-KO mice. Postoperative LVEF and LVFS (n=10) were then measured. The hearts were harvested and Masson staining was performed to determine the infarcted area (n=10). The heart samples of Mydgf-KO and WT mice were collected at d 7 and d 14 after MI, respectively, to verify the expression of myofibroblast markers (n=3).

Results

Compared with WT mice, LVEF and LVFS in adult Mydgf-KO mice showed no significant changes (all P>0.05). However, the mRNA levels of α-SMA and postn were upregulated, and α-SMA protein expression was also increased (all P<0.05). After MI, compared with WT mice, LVEF and LVFS in Mydgf-KO mice decreased, and the infarcted area increased significantly (all P<0.05). Furthermore, mRNA levels of α-SMA, col8al, postn, and ctgf were increased in Mydgf-KO mice. In addition, the α-SMA protein expression level was upregulated and α-SMA-positive fibroblasts were increased (P<0.05).

Conclusion

Mydgf deletion promotes the transformation of cardiac fibroblasts into myofibroblasts and aggravates myocardial fibrosis after MI.

Cardiac Fibroblastic Niches in Homeostasis and Inflammation

Fibroblasts are essential for building and maintaining the structural integrity of all organs. Moreover, fibroblasts can acquire an inflammatory phenotype to accommodate immune cells in specific niches and to provide migration, differentiation, and growth factors. In the heart, balancing of fibroblast activity is critical for cardiac homeostasis and optimal organ function during inflammation. Fibroblasts sustain cardiac homeostasis by generating local niche environments that support housekeeping functions and by actively engaging in intercellular cross talk. During inflammatory perturbations, cardiac fibroblasts rapidly switch to an inflammatory state and actively communicate with infiltrating immune cells to orchestrate immune cell migration and activity. Here, we summarize the current knowledge on the molecular landscape of cardiac fibroblasts, focusing on their dual role in promoting tissue homeostasis and modulating immune cell-cardiomyocyte interaction. In addition, we discuss potential future avenues for manipulating cardiac fibroblast activity during myocardial inflammation.

Unravelling the Interplay between Cardiac Metabolism and Heart Regeneration

Ischemic heart disease (IHD) is the leading cause of heart failure (HF) and is a significant cause of morbidity and mortality globally. An ischemic event induces cardiomyocyte death, and the ability for the adult heart to repair itself is challenged by the limited proliferative capacity of resident cardiomyocytes. Intriguingly, changes in metabolic substrate utilisation at birth coincide with the terminal differentiation and reduced proliferation of cardiomyocytes, which argues for a role of cardiac metabolism in heart regeneration. As such, strategies aimed at modulating this metabolism-proliferation axis could, in theory, promote heart regeneration in the setting of IHD. However, the lack of mechanistic understanding of these cellular processes has made it challenging to develop therapeutic modalities that can effectively promote regeneration. Here, we review the role of metabolic substrates and mitochondria in heart regeneration, and discuss potential targets aimed at promoting cardiomyocyte cell cycle re-entry. While advances in cardiovascular therapies have reduced IHD-related deaths, this has resulted in a substantial increase in HF cases. A comprehensive understanding of the interplay between cardiac metabolism and heart regeneration could facilitate the discovery of novel therapeutic targets to repair the damaged heart and reduce risk of HF in patients with IHD.

Current Trends and Applications of Food-derived Antihypertensive Peptides for the Management of Cardiovascular Disease

Abstract:

Food derived Antihypertensive peptides is considered as a natural supplement for controlling the hypertension. Food protein not only serve as a macronutrient but also act as raw material for biosynthesis of physiologically active peptides. Food sources like milk and milk products, animal protein such as meat, chicken, fish, eggs and plant derived proteins from soy, rice, wheat, mushroom, pumpkins contain high amount of antihypertensive peptides. The food derived antihypertensive peptides has ability to supress the action of rennin and Angiotesin converting enzyme (ACE) which is mainly involved in regulation of blood pressure by RAS. The biosynthesis of endothelial nitric oxide synthase is also improved by ACE inhibitory peptides which increase the production of nitric oxide in vascular walls and encourage vasodilation. Interaction between the angiotensin II and its receptor is also inhibited by the peptides which help to reduce hypertension. This review will explore the novel sources and applications of food derived peptides for the management of hypertension.

Retinoic acid signaling is directly activated in cardiomyocytes and protects mouse hearts from apoptosis after myocardial infarction

Retinoic acid (RA) is an essential signaling molecule for cardiac development and plays a protective role in the heart after myocardial infarction (MI). In both cases, the effect of RA signaling on cardiomyocytes, the principle cell type of the heart, has been reported to be indirect. Here we have developed an inducible murine transgenic RA-reporter line using CreER^T2 technology that permits lineage tracing of RA-responsive cells and faithfully recapitulates endogenous RA activity in multiple organs during embryonic development. Strikingly, we have observed a direct RA response in cardiomyocytes during mid-late gestation and after MI. Ablation of RA signaling through deletion of the Aldh1a1/a2/a3 genes encoding RA-synthesizing enzymes leads to increased cardiomyocyte apoptosis in adults subjected to MI. RNA sequencing analysis reveals Tgm2 and Ace1, two genes with well-established links to cardiac repair, as potential targets of RA signaling in primary cardiomyocytes, thereby providing novel links between the RA pathway and heart disease.

Cardiac Fibrosis: Cellular Effectors, Molecular Pathways, and Exosomal Roles

Cardiac fibrosis, a common pathophysiologic process in most heart diseases, refers to an excess of extracellular matrix (ECM) deposition by cardiac fibroblasts (CFs), which can lead to cardiac dysfunction and heart failure subsequently. Not only CFs but also several other cell types including macrophages and endothelial cells participate in the process of cardiac fibrosis via different molecular pathways. Exosomes, ranging in 30-150 nm of size, have been confirmed to play an essential role in cellular communications by their bioactive contents, which are currently a hot area to explore pathobiology and therapeutic strategy in multiple pathophysiologic processes including cardiac fibrosis. Cardioprotective factors such as RNAs and proteins packaged in exosomes make them an excellent cell-free system to improve cardiac function without significant immune response. Emerging evidence indicates that targeting selective molecules in cell-derived exosomes could be appealing therapeutic treatments in cardiac fibrosis. In this review, we summarize the current understandings of cellular effectors, molecular pathways, and exosomal roles in cardiac fibrosis.

Outbreak of SARS-CoV2: Pathogenesis of infection and cardiovascular involvement

Since the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) has emerged from China, the infection (novel corona virus disease-2019, COVID-19) has affected many countries and led to many deaths worldwide. Like SARS-CoV, angiotencin converting enzyme (ACE)2 as a functional receptor for SARS-CoV2 is essential for the virus to make an entry into the cell. ACE2 is a part of Renin-Angiotensin-Aldosterone System, which is expressed in several organs that opposes the angiotensin (Ang) II functions by converting Ang II to Ang (1-7), the one with vasodilation effects. The death rate of COVID-19 is estimated to be approximately 3.4%; however, some comorbid conditions like underlying cardiovascular disease, hypertension, and diabetes increase the risk of mortality. In addition, cardiovascular involvement as a complication of SARS-CoV2 could be direct through either ACE2 receptors that are expressed tremendously in the heart, or by the surge of different cytokines or by acute respiratory distress syndrome-induced hypoxia. Traditional risk factors could aggravate the process of COVID-19 infection that urges the triage of these high-risk patients for SARS-CoV2. Currently, there is no effective, proven treatment or vaccination for COVID-19, but many investigators are struggling to find a treatment strategy as soon as possible. Some potential medications like chloroquine by itself or in combination with azithromycin and some protease inhibitors used for the treatment of COVID-19 have cardiovascular adverse effects, which should be kept in mind while the patients taking these medications are being closely monitored.

Cardiac fibrosis

Myocardial fibrosis, the expansion of the cardiac interstitium through deposition of extracellular matrix proteins, is a common pathophysiologic companion of many different myocardial conditions. Fibrosis may reflect activation of reparative or maladaptive processes. Activated fibroblasts and myofibroblasts are the central cellular effectors in cardiac fibrosis, serving as the main source of matrix proteins. Immune cells, vascular cells and cardiomyocytes may also acquire a fibrogenic phenotype under conditions of stress, activating fibroblast populations. Fibrogenic growth factors (such as transforming growth factor-β and platelet-derived growth factors), cytokines [including tumour necrosis factor-α, interleukin (IL)-1, IL-6, IL-10, and IL-4], and neurohumoral pathways trigger fibrogenic signalling cascades through binding to surface receptors, and activation of downstream signalling cascades. In addition, matricellular macromolecules are deposited in the remodelling myocardium and regulate matrix assembly, while modulating signal transduction cascades and protease or growth factor activity. Cardiac fibroblasts can also sense mechanical stress through mechanosensitive receptors, ion channels and integrins, activating intracellular fibrogenic cascades that contribute to fibrosis in response to pressure overload. Although subpopulations of fibroblast-like cells may exert important protective actions in both reparative and interstitial/perivascular fibrosis, ultimately fibrotic changes perturb systolic and diastolic function, and may play an important role in the pathogenesis of arrhythmias. This review article discusses the molecular mechanisms involved in the pathogenesis of cardiac fibrosis in various myocardial diseases, including myocardial infarction, heart failure with reduced or preserved ejection fraction, genetic cardiomyopathies, and diabetic heart disease. Development of fibrosis-targeting therapies for patients with myocardial diseases will require not only understanding of the functional pluralism of cardiac fibroblasts and dissection of the molecular basis for fibrotic remodelling, but also appreciation of the pathophysiologic heterogeneity of fibrosis-associated myocardial disease.

Effects of sacubitril/valsartan on ventricular remodeling in patents with left ventricular systolic dysfunction following acute anterior wall myocardial infarction

OBJECTIVE

The aim of this study was to investigate the effect of sacubitril/valsartan (Sal/Val) on left ventricular (LV) remodeling in patients with LV systolic dysfunction following acute anterior wall myocardial infarction (AAMI).

METHODS

AAMI patients with LV systolic dysfunction were enrolled in this study. All patients underwent percutaneous coronary intervention. After hemodynamic stabilization, patients were randomly assigned either to group T (Sal/Val treatment) or group C (enalapril treatment). Changes in echocardiographic parameters and plasma biochemical markers were used to evaluate the effects of Sal/Val on LV remodeling and cardiac function. The incidence of major cardiac adverse events (MACEs) and adverse reactions during follow-ups was also recorded.

RESULTS

In total, 137 eligible patients were prospectively included. Compared to group C, LV ejection fraction significantly improved (P < 0.05), while the LV end-systolic volume index and wall motion score index showed a tendency to decrease in group T. There was no difference in the LV end-diastolic volume index between groups. During follow-ups, the plasma N-terminal pro-B-type natriuretic peptide and soluble suppression of tumorigenesis-2 levels in both groups decreased (all P < 0.05), and the change was more prominent in group T. Additionally, drug-related adverse effects were similar between the two groups (P > 0.05); however, the incidence of MACEs was lower in group T than in group C (39.71% vs. 53.62%, P = 0.103), although the difference was insignificant.

CONCLUSION

Sac/Val attenuated LV remodeling and dysfunction and was safe and effective in LV systolic dysfunction patients post AAMI.

Cardiac fibrosis: Cell biological mechanisms, molecular pathways and therapeutic opportunities

Cardiac fibrosis is a common pathophysiologic companion of most myocardial diseases, and is associated with systolic and diastolic dysfunction, arrhythmogenesis, and adverse outcome. Because the adult mammalian heart has negligible regenerative capacity, death of a large number of cardiomyocytes results in reparative fibrosis, a process that is critical for preservation of the structural integrity of the infarcted ventricle. On the other hand, pathophysiologic stimuli, such as pressure overload, volume overload, metabolic dysfunction, and aging may cause interstitial and perivascular fibrosis in the absence of infarction. Activated myofibroblasts are the main effector cells in cardiac fibrosis; their expansion following myocardial injury is primarily driven through activation of resident interstitial cell populations. Several other cell types, including cardiomyocytes, endothelial cells, pericytes, macrophages, lymphocytes and mast cells may contribute to the fibrotic process, by producing proteases that participate in matrix metabolism, by secreting fibrogenic mediators and matricellular proteins, or by exerting contact-dependent actions on fibroblast phenotype. The mechanisms of induction of fibrogenic signals are dependent on the type of primary myocardial injury. Activation of neurohumoral pathways stimulates fibroblasts both directly, and through effects on immune cell populations. Cytokines and growth factors, such as Tumor Necrosis Factor-α, Interleukin (IL)-1, IL-10, chemokines, members of the Transforming Growth Factor-β family, IL-11, and Platelet-Derived Growth Factors are secreted in the cardiac interstitium and play distinct roles in activating specific aspects of the fibrotic response. Secreted fibrogenic mediators and matricellular proteins bind to cell surface receptors in fibroblasts, such as cytokine receptors, integrins, syndecans and CD44, and transduce intracellular signaling cascades that regulate genes involved in synthesis, processing and metabolism of the extracellular matrix. Endogenous pathways involved in negative regulation of fibrosis are critical for cardiac repair and may protect the myocardium from excessive fibrogenic responses. Due to the reparative nature of many forms of cardiac fibrosis, targeting fibrotic remodeling following myocardial injury poses major challenges. Development of effective therapies will require careful dissection of the cell biological mechanisms, study of the functional consequences of fibrotic changes on the myocardium, and identification of heart failure patient subsets with overactive fibrotic responses.

Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers Are Associated With Improved Outcome but Do Not Prevent New-Onset Atrial Fibrillation After Acute Myocardial Infarction

BACKGROUND

Treatment with renin-angiotensin system (RAS) inhibitors might restrain the structural/electrical remodeling associated with atrial fibrillation (AF). Limited evidence exists regarding the potential benefits of RAS inhibition post-acute myocardial infarction (AMI) in patients with AF. This study sought to assess the association between RAS inhibition and all-cause mortality and new-onset AF in patients with/without congestive heart failure (CHF) post-AMI.

METHODS AND RESULTS

Patients hospitalized for AMI between 2006 and 2012 were identified in Swedish registries. Patients were stratified in 4 subgroups; patients with CHF and AF (n=11 489); patients with CHF without AF (n=31 676); patients with AF without CHF (n=10 066); and patients without both CHF and AF (n=59 417). Patients exposed to RAS inhibition were compared to nontreated. Three-year risk of all-cause mortality and new-onset AF was assessed using adjusted Cox regression analyses. At discharge, 83 291 (73.9%) patients received RAS inhibition. RAS inhibition was associated with lower 3-year risk of all-cause mortality in CHF patients with AF, adjusted hazard ratio (HR) with 95% CI 0.75 (0.70-0.81), CHF patients without AF, HR 0.65 (0.60-0.69), AF patients without CHF, HR 0.82 (0.75-0.90), and in patients without CHF and AF, HR 0.76 (0.72-0.81), respectively. RAS inhibition was not associated with lower 3-year risk of new-onset AF in patients without AF but with/without CHF; HR 0.96 (0.84-1.10) and 1.12 (1.02-1.22), respectively.

CONCLUSIONS

RAS inhibition post-AMI was associated with lower risk of all-cause mortality. In patients with/without CHF, RAS inhibition was not associated with lower incidence of new-onset AF.

Tissue ACE Inhibitors for Secondary Prevention of Cardiovascular Disease in Patients With Preserved Left Ventricular Function: A Pooled Meta-analysis of Randomized Placebo-controlled Trials

Objective. A pooled meta-analysis of published, randomized placebo-controlled clinical trials to evaluate the role of tissue angiotensin-converting enzyme (ACE) inhibitors in secondary prevention of cardiovascular disease in patients with preserved left ventricular function. Sources. Peer-reviewed journals listed in Index Medicus/MEDLINE, the Cochrane Central Register of Controlled Clinical Trials, and the Cochrane Database of Systematic Reviews. Study selection . Randomized placebo-controlled clinical trials of at least 12 months' duration, in patients with a prior cardiovascular event or at high risk for cardiovascular events, were analyzed. Data synthesis and analysis. A total of 31 555 patients (136 882 patient-years) from 4 trials were selected for the meta-analysis. Relative risk estimations were made using data pooled from these trials, and statistical significance was determined using the χ2 test. The number of patients needed to treat was also calculated for each outcome. Results. Tissue ACE inhibitors significantly reduced the risk of all-cause mortality, cardiovascular mortality, acute myocardial infarction, and stroke ( P < .001 for each). The need for invasive coronary revascularization was reduced ( P = .03), as was the risk of hospitalization for congestive heart failure ( P = .001). The occurrence of new-onset diabetes was also significantly reduced ( P < .001), but the risk of hospitalization for angina was not significantly affected ( P = .677). Treating about 100 patients for about 4.5 years would prevent 1 death, 1 non-fatal myocardial infarction, 1 cardiovascular death, or 1 invasive coronary revascularization. Conclusions. Tissue ACE inhibitors have demonstrated benefit when used for secondary prevention of cardiovascular disease in patients with preserved left ventricular function in randomized placebo-controlled clinical trials.

Update on RAAS Modulation for the Treatment of Diabetic Cardiovascular Disease

Since the advent of insulin, the improvements in diabetes detection and the therapies to treat hyperglycemia have reduced the mortality of acute metabolic emergencies, such that today chronic complications are the major cause of morbidity and mortality among diabetic patients. More than half of the mortality that is seen in the diabetic population can be ascribed to cardiovascular disease (CVD), which includes not only myocardial infarction due to premature atherosclerosis but also diabetic cardiomyopathy. The importance of renin-angiotensin-aldosterone system (RAAS) antagonism in the prevention of diabetic CVD has demonstrated the key role that the RAAS plays in diabetic CVD onset and development. Today, ACE inhibitors and angiotensin II receptor blockers represent the first line therapy for primary and secondary CVD prevention in patients with diabetes. Recent research has uncovered new dimensions of the RAAS and, therefore, new potential therapeutic targets against diabetic CVD. Here we describe the timeline of paradigm shifts in RAAS understanding, how diabetes modifies the RAAS, and what new parts of the RAAS pathway could be targeted in order to achieve RAAS modulation against diabetic CVD.

Association of common variations on chromosome 4q25 and left atrial volume in patients with atrial fibrillation

AIMS

Recent studies have shown that several genetic variants near the PITX2 locus on chromosome 4q25 are associated with atrial fibrillation (AF). However, the mechanism that mediates this association remains unclear. Basic murine studies suggest that reduced PITX2 expression is associated with left atrial dilatation. We sought to examine the association between single nucleotide polymorphisms (SNPs) near PITX2 and left atrial size in patients with AF.

METHODS

We prospectively enrolled 96 consecutive patients (mean age 60 ± 10 years, 72% male) with drug-resistant AF (57% paroxysmal, 38% persistent, and 5% long-standing persistent) who underwent catheter ablation. Following DNA extraction from blood obtained pre-operatively, SNPs rs10033464 and rs2200733 were genotyped using the Sequenom MassARRAY. Left atrial volume (LAV) was determined using three-dimensional imaging (CT or MRI prior to first ablation) and by investigators blinded to genotype results.

RESULTS

The minor allele frequencies at SNPs rs10033464 and rs2200733 were 0.14 and 0.25, respectively. Using multivariable linear regression, homozygosity for the minor allele at rs10033464 (recessive model) was independently associated with larger LAV (P = 0.002) after adjustment for age, gender, BMI, height, type, and duration of AF, left ventricular ejection fraction, history of hypertension, valve disease, and antiarrhythmic drug use. The strength of the association was reconfirmed in a bootstrap study with 1000 resamplings. In contrast, no association was found between rs2200733 variant alleles and LAV.

CONCLUSION

SNP rs10033464 near the PITX2 locus on 4q25 is associated with LAV. Left atrial dilatation may mediate the association of common variants at 4q25 with AF.

Not all angiotensin-converting enzyme inhibitors are equal: focus on ramipril and perindopril

Angiotensin-converting enzyme (ACE) inhibitors are a heterogeneous class, varying in pharmacologic properties, which have different therapeutic impacts on patient profiles, including lipophilicity, tissue-ACE binding, duration of action, half-life, and increased bradykinin availability. Among the ACE inhibitor class, the agent perindopril, in particular, has pleiotropic effects that are not equally shared by other ACE inhibitors, including bradykinin site selectivity and subsequent enhancement of nitric oxide and inhibition of endothelial cell apoptosis. Moreover, there is a large amount of evidence to suggest that perindopril therapy may reduce cardiovascular event rates in patients, yet perindopril is rarely prescribed in the United States. Ramipril is another ACE inhibitor with both a favorable clinical profile and impressive outcomes data. Our review compares the pharmacologic and trial data among perindopril, ramipril, and other ACE inhibitors. In patients with or at high risk for coronary heart disease who do not have heart failure, or in patients with heart failure with preserved ejection fraction, perindopril should be among the preferred treatment agents in the ACE inhibitor class. Ramipril has an impressive track record of improving cardiovascular outcomes, too, and should be considered a preferred agent among the ACE inhibitor class.

Role of circulating angiotensin converting enzyme 2 in left ventricular remodeling following myocardial infarction: a prospective controlled study

Angiotensin-converting enzyme 2 (ACE2) cleaves Angiotensin-II to Angiotensin-(1-7), a cardioprotective peptide. Serum soluble ACE2 (sACE2) activity is raised in chronic heart failure, suggesting a compensatory role in left ventricular dysfunction. Our aim was to study the relationship between sACE2 activity, infarct size, left ventricular systolic function and remodeling following ST-elevation myocardial infarction (STEMI). A contrast-enhanced cardiac magnetic resonance study was performed acutely in 95 patients with first STEMI and repeated at 6 months to measure LV end-diastolic volume index, ejection fraction and infarct size. Baseline sACE2 activities, measured by fluorescent enzymatic assay 24 to 48 hours and at 7 days from admission, were compared to that obtained in 22 matched controls. Patients showed higher sACE2 at baseline than controls (104.4 [87.4-134.8] vs 74.9 [62.8-87.5] RFU/µl/hr, p<0.001). At seven days, sACE2 activity significantly increased from baseline (115.5 [92.9-168.6] RFU/µl/hr, p<0.01). An inverse correlation between sACE2 activity with acute and follow-up ejection fraction was observed (r = -0.519, p<0.001; r = -0.453, p = 0.001, respectively). Additionally, sACE2 directly correlated with infarct size (r = 0.373, p<0.001). Both, infarct size (β = -0.470 [95%CI:-0.691:-0.248], p<0.001) and sACE2 at 7 days (β = -0.025 [95%CI:-0.048:-0.002], p = 0.030) were independent predictors of follow-up ejection fraction. Patients with sACE2 in the upper tertile had a 4.4 fold increase in the incidence of adverse left ventricular remodeling (95% confidence interval: 1.3 to 15.2, p = 0.027). In conclusion, serum sACE2 activity rises in relation to infarct size, left ventricular systolic dysfunction and is associated with the occurrence of left ventricular remodeling.

Angiotensin-Converting Enzyme 2 (ACE2) Is a Key Modulator of the Renin Angiotensin System in Health and Disease

Angiotensin-converting enzyme 2 (ACE2) shares some homology with angiotensin-converting enzyme (ACE) but is not inhibited by ACE inhibitors. The main role of ACE2 is the degradation of Ang II resulting in the formation of angiotensin 1–7 (Ang 1–7) which opposes the actions of Ang II. Increased Ang II levels are thought to upregulate ACE2 activity, and in ACE2 deficient mice Ang II levels are approximately double that of wild-type mice, whilst Ang 1–7 levels are almost undetectable. Thus, ACE2 plays a crucial role in the RAS because it opposes the actions of Ang II. Consequently, it has a beneficial role in many diseases such as hypertension, diabetes, and cardiovascular disease where its expression is decreased. Not surprisingly, current therapeutic strategies for ACE2 involve augmenting its expression using ACE2 adenoviruses, recombinant ACE2 or compounds in these diseases thereby affording some organ protection.

Angiotensin-(1-7)-mediated signaling in cardiomyocytes

The Renin-Angiotensin System (RAS) acts at multiple targets and has its synthesis machinery present in different tissues, including the heart. Actually, it is well known that besides Ang II, the RAS has other active peptides. Of particular interest is the heptapeptide Ang-(1-7) that has been shown to exert cardioprotective effects. In this way, great compilations about Ang-(1-7) actions in the heart have been presented in the literature. However, much less information is available concerning the Ang-(1-7) actions directly in cardiomyocytes. In this paper, we show the actual knowledge about Ang-(1-7)-mediated signaling in cardiac cells more specifically we provide a brief overview of ACE2/Ang-(1-7)/Mas axis; and highlight the discoveries made in cardiomyocyte physiology through the use of genetic approaches. Finally, we discuss the protective signaling induced by Ang-(1-7) in cardiomyocytes and point molecular determinants of these effects.

The role of renin angiotensin system intervention in stage B heart failure

This article outlines the link between the renin angiotensin aldosterone system (RAAS) and various forms of cardiomyopathy, and also reviews the understanding of the effectiveness of RAAS intervention in this phase of ventricular dysfunction. The authors focus their discussion predominantly on patients who have had previous myocardial infarction or those who have left ventricular hypertrophy and also briefly discuss the role of RAAS activation and intervention in patients with alcoholic cardiomyopathy.

Angiotensin-converting enzyme 2 is a key modulator of the renin-angiotensin system in cardiovascular and renal disease

PURPOSE OF REVIEW

Angiotensin-converting enzyme 2 (ACE2) has recently emerged as a key regulator of the renin-angiotensin system in both health and disease.

RECENT FINDINGS

ACE2 deficiency is associated with elevated tissue and circulating levels of angiotensin II and reduced levels of angiotensin 1-7. Phenotypically, this results in a modest elevation in systolic blood pressure and left ventricular hypertrophy. In atherosclerosis-prone apolipoprotein E knockout mice, ACE2 deficiency results in augmented vascular inflammation and an inflammatory response that contributes to increased atherosclerotic plaque formation. In the kidney, ACE2 deficiency is associated with progressive glomerulosclerosis. Interventions such as ACE2 replenishment or augmentation of its actions have proven successful in reducing hypertension, plaque accumulation, and renal and cardiac damage in a range of different models. Although promising, the balance of the renin-angiotensin system remains complicated, with some evidence that overexpression of ACE2 may have adverse cardiac effects, and ACE2 and its metabolic products may promote epithelial-to-mesenchymal transition.

SUMMARY

Repletion of ACE2's activities offers a new strategy to complement current clinical interventions in treating hypertension, renal and cardiovascular disease. In particular conditions where ACE inhibition and angiotensin receptor blockade are partially effective, the adjunctive actions of ACE2 may not only reduce clinical escape but also augment the efficacy of interventions.

Effects of telmisartan on markers of ventricular remodeling in patients with acute myocardial infarction: comparison with enalapril

Enalapril is effective in the suppression of left ventricular remodeling after acute myocardial infarction (AMI), but the effect of telmisartan is unclear. The consecutive 163 AMI patients underwent primary percutaneous coronary intervention and were randomized to telmisartan (n = 82) or enalapril (n = 81). Left ventriculography was performed in the acute and chronic (6 months) phases. Matrix metalloproteinase (MMP)-2 and MMP-9 activities were measured by zymography in the acute (days 1, 7, and 14) and chronic (6 months) phases. Plasma pentraxin3 (PTX3), a marker of vascular inflammation, was also measured. There were no adverse effects in the telmisartan group. The analysis of the left ventriculograms in the acute and chronic phases revealed no difference between the two groups. MMP-9 activities at days 7 and 14 and in the chronic phase were decreased compared to that at day 1 in both groups. MMP-2 activity was also decreased in the acute phase, but increased in the chronic phase in both groups. There was no difference in the plasma PTX3 level in the acute phase, but in the chronic phase, PTX3 was significantly lower in telmisartan than in enalapril group (2.6 ± 1.4 vs. 3.2 ± 1.6 ng/ml, p = 0.04). Telmisartan is well tolerated, shows similar effects on the markers of left ventricular remodeling to those of enalapril, and suppresses vascular inflammation more effectively than enalapril in AMI patients. Telmisartan can be an alternative to angiotensin converting enzyme inhibitor in patients with AMI.

Angiotensin-converting enzymes and drug discovery in cardiovascular diseases

Angiotensin-converting enzyme (ACE) is a major target in the treatment of cardiovascular diseases (CVDs). In addition to ACE, ACE2 - which is a homolog of ACE and promotes the degradation of angiotensin II (Ang II) to Ang (1-7) - has been recognized recently as a potential therapeutic target in the management of CVDs. This article reviews different metabolic pathways of ACE and ACE2 (Ang I-Ang II-AT1 receptors and Ang I-Ang (1-7)-Mas receptors) in the regulation of cardiovascular function and their potential in new drug development in the therapy of CVDs. In addition, recent progress in the study of angiotensin and ACE in fetal origins of CVD, which might present an interesting field in perinatal medicine and preventive medicine, is briefly summarized.

Synergistic inhibitory effect of angiotensin II receptor blocker and thiazide diuretic on the tissue renin-angiotensin-aldosterone system

ARBs are conceptually more potent in a high renin state than in a low renin state at blood pressure reduction and cardiovascular protection, whereas the potency of thiazide diuretics in the contrary. However, the additive effect of the agents when used in combination remains unclear. Thus, the goal of the present review was to analyse available data to explain the mechanistic actions of the ARB-thiazide diuretic combination. Although the circulating renin-angiotensin-aldosterone system (RAAS) has been well characterised in the context of cardiovascular disease, recent attention has also focused on the role of the tissue RAAS. For example, both angiotensin II and aldosterone are produced in small amounts within cardiac tissue, and the angiotensin II type 1 receptor is widely distributed and activated within cardiovascular tissues. Recent reports also suggest that the mineralocorticoid receptor is activated through Rac1 GTP-ase in high salt-intake rats. Thus, many components of the RAAS are activated in cardiovascular tissues under high salt-intake conditions, and a low salt diet or use of diuretics likely suppresses the tissue RAAS. Since ARBs can block the effect of both tissue angiotensin II and circulating angiotensin II, it follows that the combination of an ARB and a thiazide diuretic results in synergistic inhibition of the tissue RAAS.

Brain natriuretic peptide (BNP) level is closely related to the extent of left ventricular sympathetic overactivity in chronic ischemic heart failure

OBJECTIVE

Both brain natriuretic peptide (BNP) and cardiac sympathetic activity are useful surrogate markers of congestive heart failure. BNP is known to be secreted in response to sympathetic tone. This study examined the relationship between the cardiac sympathetic system and BNP.

PATIENTS AND METHODS

Sixty patients with chronic ischemic heart failure (mean age,72 years-old; 46 males and 14 females) who had undergone cardiac catheterization and were classified as NYHA II underwent resting (99m)Tc-sestamibi quantitative gated imaging (MIBI) and (123)I-metaiodobenzylguanidine imaging (MIBG). MIBI was used to obtain left ventricular (LV) dimension. MIBG was used to obtain the washout rate and the H/M ratios as well as the extent of LV washout rate abnormality (RSNA), which was defined as the number of regions with a regional washout rate of more than mean+2SD of 15 normal subjects on a two-dimensional polar map divided into 20 regions. Blood samples were obtained to measure neurohormones such as BNP, renin activity, noradrenaline, and angiotensin II.

RESULTS

Simple linear regression analysis showed that BNP had significant correlations to age, LVEF, LV end diastolic volume, LV end systolic volume, RSNA, global washout rate, myocardial ischemia, and LV end diastolic pressure. Among them, multiple linear regression analysis showed that only RSNA (partial regression coefficient =0.618, p<0.002) had a significant positive correlation with BNP.

CONCLUSION

This study suggested that the extent of cardiac sympathetic overactivity in the LV could enhance BNP release.

Genetic models provide unique insight into angiotensin and bradykinin peptides in the extravascular compartment of the heart in vivo

1. There is continuing uncertainty about the tissue compartments where angiotensin and bradykinin peptide formation occurs. Mice with angiotensin-converting enzyme (ACE) expression targeted to the cardiomyocyte membrane provide a unique experimental model to detect ACE substrates in the extravascular compartment of the heart in vivo. 2. Angiotensin (Ang) I and II, bradykinin-(1-7) and bradykinin-(1-9) were measured in blood and cardiac ventricles of wild-type (WT) mice, mice with a non-functional somatic ACE gene promoter (KO), mice homozygous (8/8) and heterozygous (1/8) for cardiomyocyte-targeted ACE expression and a non-functional somatic ACE gene promoter, and mice heterozygous for cardiomyocyte-targeted ACE expression and heterozygous for the WT ACE allele (WT/8). 3. Cardiac AngII levels of 8/8, 1/8, WT/8 and WT mice were higher than KO levels. Cardiac AngII levels in 8/8 and 1/8 mice were also higher than WT levels, but the levels in WT/8 mice were similar to WT levels. Cardiac bradykinin-(1-9) levels of WT, but not 8/8 mice, were lower than in KO mice, whereas bradykinin-(1-7) levels in 8/8 mice were lower than in KO mice. 4. We conclude that AngI and bradykinin-(1-7) are present in the cardiac extravascular compartment of mice lacking vascular ACE and that extravascular ACE produces AngII and metabolises bradykinin-(1-7) in this compartment. The data suggest that the vascular compartment is the main site of AngI and bradykinin-(1-9) formation and metabolism and that vascular ACE may limit AngI entry to the extravascular compartment of WT mice.

ACE phenotyping as a first step toward personalized medicine for ACE inhibitors. Why does ACE genotyping not predict the therapeutic efficacy of ACE inhibition?

Angiotensin (Ang)-converting enzyme (ACE) inhibitors are widely used for the treatment of cardiovascular diseases. Not all patients respond to ACE inhibitors, and it has been suggested that genetic variation might be a useful marker to predict the therapeutic efficacy of these drugs. In particular, the ACE insertion (I)/deletion (D) polymorphism has been investigated in this regard. Despite a decade of intensive research involving the genotyping of thousands of patients, we still do not know whether ACE genotyping helps in predicting the success of ACE inhibition. This review critically addresses the concept that predictive information on therapeutic efficacy of ACE inhibitors might be obtained based on ACE genotyping. It answers the following questions: Do higher ACE levels really result in higher Ang II levels? Is ACE the only converting enzyme in humans? Does ACE inhibition affect ACE expression? Why does ACE have 2 catalytically active domains? What is the relevance of ACE inhibitor-induced signaling through membrane-bound ACE? The review ends with the proposal that ACE phenotyping may prove to be a better first step toward personalized medicine for ACE inhibitors than ACE genotyping.

Physiology of Local Renin-Angiotensin Systems

Since the first identification of renin by Tigerstedt and Bergmann in 1898, the renin-angiotensin system (RAS) has been extensively studied. The current view of the system is characterized by an increased complexity, as evidenced by the discovery of new functional components and pathways of the RAS. In recent years, the pathophysiological implications of the system have been the main focus of attention, and inhibitors of the RAS such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin (ANG) II receptor blockers have become important clinical tools in the treatment of cardiovascular and renal diseases such as hypertension, heart failure, and diabetic nephropathy. Nevertheless, the tissue RAS also plays an important role in mediating diverse physiological functions. These focus not only on the classical actions of ANG on the cardiovascular system, namely, the maintenance of cardiovascular homeostasis, but also on other functions. Recently, the research efforts studying these noncardiovascular effects of the RAS have intensified, and a large body of data are now available to support the existence of numerous organ-based RAS exerting diverse physiological effects. ANG II has direct effects at the cellular level and can influence, for example, cell growth and differentiation, but also may play a role as a mediator of apoptosis. These universal paracrine and autocrine actions may be important in many organ systems and can mediate important physiological stimuli. Transgenic overexpression and knock-out strategies of RAS genes in animals have also shown a central functional role of the RAS in prenatal development. Taken together, these findings may become increasingly important in the study of organ physiology but also for a fresh look at the implications of these findings for organ pathophysiology.

The relationship between ACE insertion/deletion polymorphism and coronary artery disease with or without myocardial infarction

OBJECTIVES

Presence of the D allele or homozygosity for the deletion (D) allele of the angiotensicen-converting enzyme (ACE) insertion/deletion (I/D) polymorphism has been discussed as potent risk factor for coronary artery disease (CAD) and myocardial infarction (MI). The D allele is associated with higher levels of circulating ACE and therefore may predispose one to cardiovascular damage.

DESIGN AND METHODS

The study presented here was performed to investigate the association between the ACE genotype and ACE levels. The study group was comprised of 118 angiographically verified CAD patients. 65 patients were MI (+) and 53 patients were MI (-) in this group. A total of 70 healthy individuals were taken as controls. Genomic DNA of 188 subjects was extracted from whole blood. The polymerase chain reaction was used for ACE genotyping, and ACE levels were measured by ELISA.

RESULTS

The D allele was found to be significantly more frequent in patients with MI (+) compared with controls (P = 0.024). ACE levels were significantly higher in both MI (-) and MI (+) groups with CAD patients than in controls (P < 0.005). Plasma ACE level was higher in all three groups in the DD genotype compared to II genotype. In groups I and III, this was statistically significant (P < 0.0001, P < 0.01).

CONCLUSIONS

It was shown that the I/D polymorphism in the gene for ACE is a genetic risk factor for CAD patients who have a history of MI. ACE insertion/deletion gene polymorphism is also associated with plasma ACE levels in CAD patients with a history of MI.

Enalapril suppresses ventricular remodeling more effectively than losartan in patients with acute myocardial infarction

BACKGROUND

Ventricular remodeling after acute myocardial infarction (AMI) is associated with increased morbidity and mortality. ELITE II study showed that losartan, an angiotensin receptor blocker, shows a survival benefit to the same degree as captopril, an angiotensin-converting enzyme inhibitor, does in patients with heart failure. However, recent OPTIMAAL study showed that clinical outcomes after losartan are not superior to those after captopril in patients with AMI. We examined the effect of losartan on ventricular remodeling after AMI comparatively with that of enalapril.

METHODS

We enrolled 203 consecutive patients with AMI (mean age 62 +/- 11 years). All patients underwent primary percutaneous coronary intervention and were randomly assigned to losartan (25-50 mg, n = 101) or enalapril (2.5-10 mg, n = 102) treatment. Biplane left ventriculography was performed just after primary percutaneous transluminal coronary angioplasty (acute phase) and 6 months after the onset of AMI.

RESULTS

Any of the maximal creatine kinase level, left ventricular end-diastolic volume index, end-systolic volume index, and ejection fraction measured at acute phase was not different between losartan and enalapril groups. However, changes in left ventricular end-diastolic index (18 +/- 25 vs 8 +/- 24 mL/m2) and left ventricular end-systolic volume index (10 +/- 20 vs 2 +/- 18 mL/m2) from acute phase to 6 months were significantly greater in losartan than in enalapril group. Change in left ventricular ejection fraction (0.2% +/- 10.3% vs 3.4% +/- 11.6%) from acute phase to 6 months was significantly smaller in losartan than in enalapril group. The plasma level of brain natriuretic peptide at 6 months was significantly higher in losartan than in enalapril group (all P < .05).

CONCLUSION

These indicate that enalapril suppresses ventricular remodeling after AMI more effectively than losartan.

Rethinking the renin-angiotensin system and its role in cardiovascular regulation

Angiotensin-converting enzyme (ACE) plays a pivotal role in the renin-angiotensin system (RAS) and ACE-inhibitors are widely used in several clinical conditions, including hypertension and heart failure. Recently, a homologue of ACE, ACE(2) has been discovered. Both ACE and ACE(2) are emerging as key enzymes of the RAS, where ACE(2) may play a role as negative regulator of ACE. Moreover, ACE(2) appears to be an important enzyme outside the classical RAS, as it hydrolyzes apelins, dynorphin A 1-13, des-Arg-bradykinin and other peptide substrates. The precise interplay between tissue ACE, ACE(2), and their substrates and by-products are presently still unclear.ACE-inhibitors reduce angiotensin II formation and bradykinin degradation, but do not inhibit ACE(2) activity. Moreover, ACE-inhibitors differ in their affinity for tissue ACE, and it has been suggested that tissue ACE affinity might be responsible for some of the beneficial properties of these drugs. ACE-inhibitors also increase nitric oxide availability, and activate several kinases that may regulate protein synthesis by interacting with the nucleus of the cells (outside-in signaling). The outside-in signaling may also be activated by bradykinin itself. Although, the precise significance of the outside-in signaling is still unclear, this new role of ACE-inhibitors may represent a discriminant factor versus angiotensin II receptors antagonists. This mini review will summarize some new aspects concerning the recently discovered biological functions of RAS and in particular of ACE, ACE(2) and ACE-inhibitors in cardiovascular system.

ACE2: A novel therapeutic target for cardiovascular diseases

Hypertension afflicts over 65 million Americans and poses an increased risk for cardiovascular morbidity such as stroke, myocardial infarction and end-stage renal disease resulting in significant mortality. Overactivity of the renin-angiotensin system (RAS) has been identified as an important determinant that is implicated in the etiology of these diseases and therefore represents a major target for therapy. In spite of the successes of drugs inhibiting various elements of the RAS, the incidence of hypertension and cardiovascular diseases remain steadily on the rise. This has lead many investigators to seek novel and innovative approaches, taking advantage of new pathways and technologies, for the control and possibly the cure of hypertension and related pathologies. The main objective of this review is to forward the concept that gene therapy and the genetic targeting of the RAS is the future avenue for the successful control and treatment of hypertension and cardiovascular diseases. We will present argument that genetic targeting of angiotensin-converting enzyme 2 (ACE2), a newly discovered member of the RAS, is ideally poised for this purpose. This will be accomplished by discussion of the following: (i) summary of our current understanding of the RAS with a focus on the systemic versus tissue counterparts as they relate to hypertension and other cardiovascular pathologies; (ii) the newly discovered ACE2 enzyme with its physiological and pathophysiological implications; (iii) summary of the current antihypertensive pharmacotherapy and its limitations; (iv) the discovery and design of ACE inhibitors; (v) the emerging concepts for ACE2 drug design; (vi) the current status of genetic targeting of the RAS; (vii) the potential of ACE2 as a therapeutic target for hypertension and cardiovascular disease treatment; and (viii) future perspectives for the treatment of cardiovascular diseases.

Effects of perindopril on cardiac sympathetic nerve activity in patients with congestive heart failure: comparison with enalapril

PURPOSE

The production of aldosterone in the heart is suppressed by the angiotensin-converting enzyme (ACE) inhibitor perindopril in patients with congestive heart failure (CHF). Moreover, perindopril has been reported to have more cardioprotective effects than enalapril.

MATERIALS AND METHODS

Forty patients with CHF [left ventricular ejection fraction (LVEF) <45%; mean 33+/-7%] were randomly assigned to perindopril (2 mg/day; n = 20) or enalapril (5 mg/day; n = 20). All patients were also treated with diuretics. The delayed heart/mediastinum count (H/M) ratio, delayed total defect score (TDS) and washout rate (WR) were determined from 123I-meta-iodobenzylguanidine (MIBG) images, and plasma brain natriuretic peptide (BNP) concentrations were measured before and 6 months after treatment. The left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV) and LVEF were also determined by echocardiography.

RESULTS

After treatment, in patients receiving perindopril, TDS decreased from 39+/-10 to 34+/-9 (P < 0.01), H/M ratios increased from 1.62+/-0.27 to 1.76+/-0.29 (P < 0.01), WR decreased from 50+/-14% to 42+/-14% (P < 0.05) and plasma BNP concentrations decreased from 226+/-155 to 141+/-90 pg/ml (P < 0.0005). In addition, the LVEDV decreased from 180+/-30 to 161+/-30 ml (P < 0.05) and the LVESV decreased from 122+/-35 to 105+/-36 ml (P < 0.05). Although the LVEF tended to increase, the change was not statistically significant (from 33+/-8% to 36+/-12%; P = NS). On the other hand, there were no significant changes in these parameters in patients receiving enalapril.

CONCLUSION

Plasma BNP concentrations, 123I-MIBG scintigraphic and echocardiographic parameters improved after 6 months of perindopril treatment. These findings indicate that perindopril treatment can ameliorate the cardiac sympathetic nerve activity and the left ventricular performance in patients with CHF.

Left atrial diameter is a simple indicator of a deficiency in atrial natriuretic peptide secretion in patients with mitral stenosis: efficacy of postoperative supplementation with synthetic human alpha-atrial natriuretic peptide

OBJECTIVE

With regard to a deficiency in atrial natriuretic peptide (ANP) secretion, the relationship between plasma ANP and left atrial diameter measured by echocardiography was examined and the efficacy of postoperative supplementation was evaluated.

METHODS

(1) Ninety-six patients with mitral valve disease from 1997 to 2002 (M:F = 65:31, mean-age 65.3 +/- 8.9 years) were studied for relationship analyses. (2) Twenty-six patients with mitral stenosis and left atrial diameter > or = 60 mm undergoing mitral valve replacement (M:F = 17:9, mean-age 67.4 +/- 7.5 years) were randomly allocated to one of two groups; ANP-treated group (n = 13, 0.05 microg/kg/min of synthetic human alpha-ANP was postoperatively administered) and Control group (n = 13).

RESULTS

(1) There were significant positive correlations between left atrial diameter and plasma renin-activity (r = 0.690, P < 0.01) and between left atrial diameter and plasma aldosterone (r = 0.757, P < 0.01). The maximum value of plasma ANP was 249.5 pg/mL accompanied with 56.2 mm of left atrial diameter in 29 patients suffering from mitral stenosis. There was a significant negative correlation between left atrial diameter and ANP in patients with left atrial diameter > 56.2 mm (r = - 0.725, P < 0.0001), whereas there was a significant positive correlation in patients with left atrial diameter < or = 56.2 mm (r = 0.529, P = 0.0066). (2) At 24 hours after operation, the ANP-treated group showed significantly lower plasma renin-activity (9.2 +/- 3.3 versus 36.2 +/- 7.4 ng/mL/h) and aldosterone (113.6 +/- 36.9 versus 473.8 +/- 95.8 pg/mL) than the Control group.

CONCLUSIONS

Left atrial diameter can be a simple and useful indicator of a deficiency in endogenous ANP secretion in patients with mitral stenosis, and postoperative ANP supplementation contributes to suppressing further activation of renin-angiotensin system during the immediate postoperative period.

Myocardial infarction increases ACE2 expression in rat and humans

AIMS

Angiotensin converting enzyme (ACE) 2 catalyses the cleavage of angiotensin (Ang) I to Ang 1-9 and of Ang II to Ang 1-7. ACE2 deficiency impairs cardiac contractility and upregulates hypoxia-induced genes, suggesting a link with myocardial ischaemia. We studied the expression of ACE2 after myocardial infarction (MI) in the rat as well as in human failing hearts.

METHODS AND RESULTS

Rats were killed at days 1, 3, and 28 after MI, or treated for 4 weeks with the ACE inhibitor ramipril (1 mg/kg). Cardiac gene and protein expression of ACE and ACE2 were assessed by quantitative real-time reverse transcriptase-polymerase chain reaction and immunohistochemistry/activity assays/in vitro autoradiography, respectively. Both ACE (P = 0.022) and ACE2 (P = 0.015) mRNA increased in the border/infarct area compared with the viable area at day 3 after MI. By day 28, increases in ACE (P = 0.005) and ACE2 (P = 0.006) mRNA were also seen in the viable myocardium of MI rats compared with myocardium of control rats. ACE2 protein localized to macrophages, vascular endothelium, smooth muscle, and myocytes. Ramipril attenuated cardiac hypertrophy and inhibited cardiac ACE. In contrast, ramipril had no effect on cardiac ACE2 mRNA, which remained elevated in all areas of the MI rat heart. Immunoreactivity of both ACE and ACE2 increased in failing human hearts.

CONCLUSION

The increase in ACE2 after MI suggests that it plays an important role in the negative modulation of the renin angiotensin system in the generation and degradation of angiotensin peptides after cardiac injury.

Local cardiac renin-angiotensin system: hypertension and cardiac failure

In addition to the effect on arterial pressure, angiotensin II, the effector peptide of the renin-angiotensin system (RAS), exerts mitogenic and growth promoting effects on cardiac myocytes and non-myocytic elements; and both of these effects significantly contribute to the development and progression of hypertensive heart disease (HHD). The traditional concept of the RAS as a systemic, endocrine system has been expanded and the identification of its components in many organs and tissue has been amassed. This paper reviews evidence that supports the concept that the cardiac RAS participate importantly in the development and risk of HHD.

Trandolapril reduces infarction area after middle cerebral artery occlusion in rats

In this study, we investigated whether angiotensin-converting enzyme (ACE) is involved in the progression of cerebral infarct lesions after middle cerebral artery (MCA) occlusion in rats. After placebo or trandolapril was administered orally for 7 days, we infarcted in the territory of the right MCA by extracranial vascular occlusion and studied the effect of trandolapril on brain ACE activity and infarct size 7 days after MCA occlusion. In placebo-treated rats, brain ACE activity in the infarct side was increased by a significant 1.34-fold compared with that in the non-infarct side 7 days after MCA occlusion. Brain ACE activities in the infarct sides were suppressed to 39.8% by trandolapril treatment. The ratios of unilateral infarcts to the total coronal sectional areas in placebo- and trandolapril-treated rats were 48.1 +/- 3.3% and 37.4 +/- 2.3%, respectively, and the difference between these values was significant. These results demonstrate that inhibition of the increased brain ACE activity in infarct lesions can reduce the infarction area after MCA occlusion.

Effects of perindopril on aldosterone production in the failing human heart

The present study was designed to examine whether the production of aldosterone from the heart is suppressed by angiotensin-converting enzyme (ACE) inhibition in patients with heart failure. Forty-one patients with left ventricular systolic dysfunction were randomly divided into either the perindopril group (n = 21, perindopril 4 mg/day) or the placebo group (n = 20). Plasma levels of aldosterone and ACE activity were measured in the anterior interventricular vein, coronary sinus, and aortic root during cardiac catheterization. The levels of aldosterone as well as ACE activity were significantly higher at the anterior interventricular vein and the coronary sinus than at the aortic root in the placebo group (aldosterone: 92.1 +/- 9.0 vs 70.6 +/- 8.3 pg/ml [p <0.001]; 90.3 +/- 9.2 vs 70.6 +/- 8.3 pg/ml [p <0.001], respectively; ACE activity: 13.6 +/- 0.8 vs 12.2 +/- 0.7 IU/L [p <0.001], 13.4 +/- 0.8 vs 12.2 +/- 0.7 IU/L [p <0.001], respectively). On the other hand, there were no differences in the levels of aldosterone or ACE activity between the anterior interventricular vein and aortic root or between the coronary sinus and aortic root (aldosterone: 68.1 +/- 8.4 vs 69.9 +/- 9.4 pg/ml [p = NS]; 67.3 +/- 8.9 vs 69.9 +/- 9.4 pg/ml [p = NS], respectively; ACE activity: 9.7 +/- 0.8 vs 9.9 +/- 0.8 IU/L [p = NS]; 9.8 +/- 0.8 vs 9.9 +/- 0.8 IU/L, respectively) in the perindopril group. The levels of aldosterone as well as ACE activity were significantly lower at the anterior interventricular vein and coronary sinus in the perindopril group than in the placebo group. The difference in the level of aldosterone between the anterior interventricular vein and aortic root (Delta aldosterone [anterior interventricular vein - aortic root]) had a significant positive correlation with that of ACE activity (Delta ACE [anterior interventricular vein - aortic root]) (r = 0.536, p <0.001), whereas ACE activity in the aortic root had no significant correlation with either the aldosterone levels in the aortic root or Delta aldosterone (anterior interventricular vein - aortic root). Perindopril suppressed cardiac aldosterone production by mainly suppressing cardiac ACE activity in patients with heart failure. Thus, aldosterone production is activated in the failing ventricle and is suppressed by perindopril mainly via the suppression of cardiac ACE activity in patients with heart failure.

Cyclooxygenase-2 in myocardium stimulation by angiotensin-II in cultured cardiac fibroblasts and role at acute myocardial infarction

Myocardial infarction is followed by a complex repair process that includes a significant role for inflammatory cells. Cyclooxygenase-2 (COX-2) plays a key role in mediating inflammation. Contribution of COX-2 to inflammatory response following myocardial infarction is less certain. In an effort to evaluate the function of COX-2 and prostaglandin E(2)(PGE(2)) in myocardial infarction, we examined the role of COX-2 after angiotensin II (Ang II) stimulation in cardiac fibroblasts and in rats with experimental myocardial infarction (MI). We combined Western blot analysis and enzyme immunoassay to demonstrate COX-2 expression and PGE(2)release in cardiac fibroblasts. Isolated cardiac fibroblasts were stimulated with Ang II. Unstimulated fibroblasts showed no COX-2 protein expression. Fibroblasts stimulated with Ang II showed a strong time-dependent expression of COX-2 protein. The p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 but not the p42/44 MAPK-inhibitor PD98059 suppressed Ang II-induced COX-2 protein expression. COX-2 expression correlated with a significantly increased PGE(2)release from cardiac fibroblasts. The COX-2 specific inhibitor NS-398 suppressed the Ang II-stimulated PGE(2)production. We then investigated COX-2 expression and inflammatory cell infiltration in our rat model of myocardial infarction. MI was produced by coronary artery ligation in adult female Wistar rats. The period of coronary artery occlusion was 96 h. The selective COX-2 inhibitor rofecoxib (3 mg/kg/d), administered orally, was given one day before MI and continued for four days. Western blotting showed expression of COX-2 protein in the area of necrosis and the infarct border zone. Immunofluorescence analysis showed macrophage infiltration as well as fibroblast proliferation in the infarct border zone of 4-d infarcted tissue and a significantly reduced cell invasion and fibroblast proliferation in infarcted tissue of rats treated with rofecoxib. MI size at day 4 was comparable in untreated and treated rats. In conclusion, we demonstrate that pharmacological interference with prostaglandin synthesis in myocardial infarction is associated with reduced myocardial invasion of inflammatory cells.

The relevance of tissue angiotensin-converting enzyme: manifestations in mechanistic and endpoint data

Angiotensin-converting enzyme (ACE) is primarily localized (>90%) in various tissues and organs, most notably on the endothelium but also within parenchyma and inflammatory cells. Tissue ACE is now recognized as a key factor in cardiovascular and renal diseases. Endothelial dysfunction, in response to a number of risk factors or injury such as hypertension, diabetes mellitus, hypercholesteremia, and cigarette smoking, disrupts the balance of vasodilation and vasoconstriction, vascular smooth muscle cell growth, the inflammatory and oxidative state of the vessel wall, and is associated with activation of tissue ACE. Pathologic activation of local ACE can have deleterious effects on the heart, vasculature, and the kidneys. The imbalance resulting from increased local formation of angiotensin II and increased bradykinin degradation favors cardiovascular disease. Indeed, ACE inhibitors effectively reduce high blood pressure and exert cardio- and renoprotective actions. Recent evidence suggests that a principal target of ACE inhibitor action is at the tissue sites. Pharmacokinetic properties of various ACE inhibitors indicate that there are differences in their binding characteristics for tissue ACE. Clinical studies comparing the effects of antihypertensives (especially ACE inhibitors) on endothelial function suggest differences. More comparative experimental and clinical studies should address the significance of these drug differences and their impact on clinical events.

ACE inhibition in aortic stenosis: dangerous medicine or golden opportunity?

Conventionally angiotensin-converting enzyme (ACE) inhibitors are contraindicated in patients with aortic stenosis. Abundant evidence is now available showing that angiotensin II has a central role in the development of left ventricular hypertrophy (LVH), myocardial contractile failure and diastolic dysfunction in response to pressure overload. In animal models, ACE inhibitors have been shown to attenuate these pathological responses. In humans there is no such evidence available, however uncontrolled studies have shown that these agents are not only tolerated but are associated with acute improvements in haemodynamics and diastolic function. Further studies are merited to assess the possible role of ACE inhibitors in aortic stenosis both before and after valve replacement. Potential benefits may include prevention of LVH, improved diastolic function, reduction of arrhythmias and preservation of left ventricular function.

Pathophysiological significance and clinical application of ANP and BNP in patients with heart failure

Plasma levels of ANP and BNP increase in accordance with the severity of the heart failure. In severe cases, the amount of BNP secreted surpasses that of ANP. The main secretion site of BNP is the ventricles, and that of ANP is the atria. However, ANP is also secreted from the ventricles as heart failure advances, and thus the ventricles are important sites for both BNP and ANP. It is well known that myocardial stretch is a key factor in the stimulation of the secretion of ANP and BNP, although neurohumoral factors also play a role in the secretion mechanism. The major physiological effects of ANP and BNP are vasodilation, natriuresis, and inhibition of the renin-angiotensin-aldosterone (RAA) and the sympathetic nervous systems; all of which are supposed to suppress the progression of heart failure. The inhibitory action of ANP and BNP on the RAA system has been considered to be an extra-cardiac effect. We recently reported the activation of an angiotensin-converting enzyme and aldosterone production in failing human hearts. ANP and BNP, however, would inhibit aldosterone production, not only in the adrenal cortex but also in cardiac tissue. ANP, and especially BNP, are useful markers of the heart's status during treatment for heart failure. The infusion of synthetic ANP (hANP) or BNP (Nesiritide®) is effective in the treatment of acute heart failure. In Japan, BNP occupies an important position in the diagnosis of chronic heart failure, as ANP does in the treatment of acute heart failure.Key words: natriuretic peptide, heart failure, myocardial infarction, cardiomyopathy, aldosterone.

Activation of the cardiac renin-angiotensin system and increased myocardial collagen expression in human aortic valve disease

OBJECTIVES

We sought to determine whether the cardiac renin-angiotensin system (RAS) is activated in human aortic valve disease depending on left ventricular function, and we analyzed the concomitant regulation of the extracellular matrix components.

BACKGROUND

In animal models with pressure or volume load, activation of the cardiac RAS increases fibrosis. In human aortic valve disease, the ventricular collagen protein content is increased, but only scarce data on the activation state of the cardiac RAS and its effects on collagen and fibronectin messenger ribonucleic acid (mRNA) are available.

METHODS

In left ventricular biopsies from patients with aortic valve stenosis (AS) and aortic valve regurgitation and from control subjects, we quantitated mRNAs for angiotensin-converting enzyme (ACE), chymase, transforming growth factor-beta1 (TGF-beta1), collagen I, collagen III and fibronectin by reverse-transcription polymerase chain reaction. Proteins were localized by immunohistochemistry; ACE activity was determined by high performance liquid chromatography; and TGF-beta protein by quantitative enzyme immunoassay.

RESULTS

Protein, ACE and TGF-beta1 mRNA were significantly increased in patients with AS and AR (1.5- to 2.1-fold) and correlated with each other. The increase occurred also in patients with normal systolic function. Collagen I and III and fibronectin mRNAs were both upregulated about twofold in patients with AS and AR. In AS, collagen and fibronectin mRNA expression levels were positively correlated with left ventricular end-diastolic pressure and inversely with left ventricular ejection fraction (LVEF).

CONCLUSIONS

In human hearts, pressure and volume overload increases cardiac ACE and TGF-beta1 in the early stages. This activation of the cardiac RAS may contribute to the observed increase in collagen I and III and fibronectin mRNA expression. The increase in extracellular matrix already exists in patients with a normal LVEF, and it increases with functional impairment.

How long should angiotensin-converting enzyme inhibitors be given to patients following myocardial infarction: implications of the HOPE trial

Long-term treatment with angiotensin-converting enzyme inhibitors reduces post-infarction morbidity and mortality in patients with left ventricular (LV) systolic dysfunction or symptomatic heart failure. Until recently, the effect of such treatment in patients with preserved LV function has not been known. The results from the Heart Outcome Prevention Evaluation trial have indicated that long-term treatment with ramipril leads to a significant reduction in cardiovascular events in patients with atherosclerotic disease, including those with prior myocardial infarction and preserved LV function. These results suggest that long-term angiotensin-converting enzyme inhibition should also be considered in post-infarction patients with normal cardiac function.

The plasma levels of dehydroepiandrosterone sulfate are decreased in patients with chronic heart failure in proportion to the severity

Dehydroepiandrosterone sulfate (DHEAS) is the major secretory steroid of the human adrenal glands. The secretion of DHEAS decreases with aging. The incidence of heart failure also rises in the elderly population. We measured the plasma levels of DHEAS and cortisol in 49 patients with chronic heart failure (CHF) and 32 age-matched controls and assessed its relation to plasma levels of A-type natriuretic peptide and B-type natriuretic peptide, biochemical markers of heart failure. Plasma levels of DHEAS were significantly lower in patients with CHF than in controls, whereas there was no significant difference in plasma levels of cortisol between the two groups. In stepwise regression analysis, the plasma level of DHEAS was significantly and independently correlated with age (beta = -0.451; P < 0.0001) and the plasma level of B-type natriuretic peptide (beta = -0.338; P < 0.001), and the plasma cortisol/DHEAS ratio was significantly and independently correlated with the plasma levels of A-type natriuretic peptide (beta = 0.598; P < 0.0001) and thiobarbituric acid-reactive substances (a marker of oxidative stress; beta = 0.252; P < 0.01) and age (beta = 0.171; P < 0.05). These results indicate that the plasma levels of DHEAS are decreased in patients with CHF in proportion to its severity and that oxidative stress is associated with decreased levels of DHEAS in patients with CHF.

Inhibition of arterial thrombogenesis by quinapril but not losartan

The cardioprotective effect of angiotensin converting enzyme (ACE) inhibitors and angiotensin type I (AT1) receptor blockers may relate to their antithrombotic effect. We determined the differential effects of the ACE inhibitor quinapril and the AT1 receptor blocker losartan on arterial thrombus formation in the rat. Sprague-Dawley rats were fed regular chow or chow mixed with low-dose quinapril (0. 6 mg/kg/day), high-dose quinapril (1.2 mg/kg/day), or losartan (10 mg/kg/day) for 15 days. Abdominal aorta was exposed and wrapped with Whatman paper impregnated with 29% FeCl(3) (ferric chloride). Time to occlusive thrombus formation and weight of the thrombus were recorded. Aortic superoxide anion generation, platelet aggregation, plasma angiotensin II levels, and morphology of the thrombus were also examined. Both losartan and quinapril caused similar reductions in arterial pressure. Losartan did not affect the time to thrombus formation, whereas quinapril (both low and high doses) delayed the time to thrombus formation (P<.01 vs control). Weight of the thrombus was similar in all groups of rats. Platelet aggregation was inhibited by approximately 50 in both quinapril- and losartan-treated rats. The high-dose quinapril-treated rats showed markedly reduced vascular superoxide anion generation compared with the control rats (P<.05). Plasma angiotensin II levels were unaffected by quinapril treatment but were elevated 7-fold in losartan-treated rats (P <.001 vs. control rats). The thrombi in the control rats consisted of platelet aggregates, fibrin, and red blood cells. The intravascular platelet aggregates were much smaller in the quinapril-treated rats (P<.05 vs. control), but were similar in control and losartan-treated rats. In conclusion, quinapril but not losartan prolongs time to arterial thrombus formation and results in smaller platelet aggregates in the thrombus. Both quinapril and losartan decrease platelet aggregation, but only quinapril decreases superoxide anion generation. This effect on superoxide anion generation as well as mechanisms other than AT1 receptor blockade may underlie the salutary effect of quinapril on arterial thrombogenesis.

Cardiac angiotensin-converting enzyme activity in myocardial infarction

The cardiac renin-angiotensin system is regarded as an important modulator in the infarct heart. Little is known about their presence and regulation in human hearts. We measured angiotensin-converting enzyme (ACE) and renin activities at the aortic root and anterior interventricular vein (AIV) in 51 patients with previous myocardial infarction (MI): anterior wall MI in 31 and inferior wall MI in 20 and 33 control subjects. In the anterior wall MI group, the serum ACE activity was increased significantly in the AIV than in the aortic root (16.2 +/- 5.3 vs 15.3 +/- 5.0 nmol/min/ml, p <0.001), whereas the activity was not different between the aortic root and AIV in the control (14.4 +/- 3.7 vs 14.4 +/- 3.7 nmol/min/ ml) and in the inferior wall MI (16.5 +/- 4.8 vs. 17.0 +/-5.2 nmol/min/ml) groups. On the other hand, there was no significant difference in plasma renin activity between the AIV and aortic root in the 3 groups (control group, 1.0 +/- 0.5 vs 1.0 +/- 0.5 pg/ml/hour; anterior wall MI group, 1.3 +/- 0.8 vs 1.3 +/- 0.8 pg/ml/hour; inferior wall MI group, 1.2 +/- 0.7 vs 1.3 +/- 0.8 pg/ml/ hour). The difference in serum ACE activity between the AIV and aortic root had a significant positive linear correlation with pulmonary capillary wedge pressure (r = 0.606, p <0.001), and had a significant negative linear correlation with left ventricular ejection fraction (r = -0.620, p <0.001) in the anterior wall MI group. Serum ACE activity from the infarct region of the left ventricle was augmented in patients with MI, and the activity was increased in proportion to the severity of left ventricular dysfunction.