Vascular and cardiac benefits of angiotensin receptor blockers

ACEi/ ARB and Deaths of COVID-19 Patients

The practice of angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers (ACEi/ARB) in COVID-19 hypertensive patients is still an open question for clinicians to answer. The present study was conducted to find out the association between the use of ACEI/ARB and the mortality rate of COVID-19 patients. The search was conducted from December 2019 to October 2020 in PubMed to identify relevant published studies. RevMan 5 was used for the analysis of the data. The random-effect model was used to calculate the odds ratio. In total, 07 studies were found to be appropriate, reporting a total of 1,566 subjects. The odds ratio was found to be 0.86 [0.41, 1.81], indicating no association between ACEI/ARB and the mortality rate of COVID- 19 patients. In conclusion, we may suggest continuing the use of ACEi/ARB in COVID-19 patients till further pieces of evidence are generated.

Treatment for Diabetic Peripheral Neuropathy: What have we Learned from Animal Models?

INTRODUCTION

Animal models have been widely used to investigate the etiology and potential treatments for diabetic peripheral neuropathy. What we have learned from these studies and the extent to which this information has been adapted for the human condition will be the subject of this review article.

METHODS

A comprehensive search of the PubMed database was performed, and relevant articles on the topic were included in this review.

RESULTS

Extensive study of diabetic animal models has shown that the etiology of diabetic peripheral neuropathy is complex, with multiple mechanisms affecting neurons, Schwann cells, and the microvasculature, which contribute to the phenotypic nature of this most common complication of diabetes. Moreover, animal studies have demonstrated that the mechanisms related to peripheral neuropathy occurring in type 1 and type 2 diabetes are likely different, with hyperglycemia being the primary factor for neuropathology in type 1 diabetes, which contributes to a lesser extent in type 2 diabetes, whereas insulin resistance, hyperlipidemia, and other factors may have a greater role. Two of the earliest mechanisms described from animal studies as a cause for diabetic peripheral neuropathy were the activation of the aldose reductase pathway and increased non-enzymatic glycation. However, continuing research has identified numerous other potential factors that may contribute to diabetic peripheral neuropathy, including oxidative and inflammatory stress, dysregulation of protein kinase C and hexosamine pathways, and decreased neurotrophic support. In addition, recent studies have demonstrated that peripheral neuropathy-like symptoms are present in animal models, representing pre-diabetes in the absence of hyperglycemia.

CONCLUSION

This complexity complicates the successful treatment of diabetic peripheral neuropathy, and results in the poor outcome of translating successful treatments from animal studies to human clinical trials.

Differential Effects of Angiotensin-II Compared to Phenylephrine on Arterial Stiffness and Hemodynamics: A Placebo-Controlled Study in Healthy Humans

The α₁-adrenoceptor agonist phenylephrine (PE) and Angiotensin II (Ang II) are both potent vasoconstrictors at peripheral resistance arteries. PE has pure vasoconstrictive properties. Ang II, additionally, modulates central nervous blood pressure (BP) control via sympathetic baroreflex resetting. However, it is unknown whether Ang II vs. PE mediated vasoconstriction at equipressor dose uniformly or specifically modifies arterial stiffness. We conducted a three-arm randomized placebo-controlled cross-over trial in 30 healthy volunteers (15 female) investigating the effects of Ang II compared to PE at equal systolic pressor dose on pulse wave velocity (PWV), pulse wave reflection (augmentation index normalized to heart rate 75/min, AIx) and non-invasive hemodynamics by Mobil-O-Graph™ and circulating core markers of endothelial (dys-)function. PE but not Ang II-mediated hypertension induced a strong reflex-decrease in cardiac output. Increases in PWV, AIx, total peripheral resistance and pulse pressure, in contrast, were stronger during PE compared to Ang II at equal mean aortic BP. This was accompanied by minute changes in circulating markers of endothelial function. Moreover, we observed differential hemodynamic changes after stopping either vasoactive infusion. Ang II- and PE-mediated BP increase specifically modifies arterial stiffness and hemodynamics with aftereffects lasting beyond mere vasoconstriction. This appears attributable in part to different interactions with central nervous BP control including modified baroreflex function.

Renin Cells, the Kidney, and Hypertension

Renin cells are essential for survival perfected throughout evolution to ensure normal development and defend the organism against a variety of homeostatic threats. During embryonic and early postnatal life, they are progenitors that participate in the morphogenesis of the renal arterial tree. In adult life, they are capable of regenerating injured glomeruli, control blood pressure, fluid-electrolyte balance, tissue perfusion, and in turn, the delivery of oxygen and nutrients to cells. Throughout life, renin cell descendants retain the plasticity or memory to regain the renin phenotype when homeostasis is threatened. To perform all of these functions and maintain well-being, renin cells must regulate their identity and fate. Here, we review the major mechanisms that control the differentiation and fate of renin cells, the chromatin events that control the memory of the renin phenotype, and the major pathways that determine their plasticity. We also examine how chronic stimulation of renin cells alters their fate leading to the development of a severe and concentric hypertrophy of the intrarenal arteries and arterioles. Lastly, we provide examples of additional changes in renin cell fate that contribute to equally severe kidney disorders.

Pleiotropic Properties of Valsartan: Do They Result from the Antiglycooxidant Activity? Literature Review and In Vitro Study

Valsartan belongs to angiotensin II type 1 (AT1) receptor blockers (ARB) used in cardiovascular diseases like heart failure and hypertension. Except for its AT1-antagonism, another mechanism of drug action has been suggested in recent research. One of the supposed actions refers to the positive impact on redox balance and reducing protein glycation. Our study is aimed at assessing the antiglycooxidant properties of valsartan in an in vitro model of oxidized bovine serum albumin (BSA). Glucose, fructose, ribose, glyoxal (GO), methylglyoxal (MGO), and chloramine T were used as glycation or oxidation agents. Protein oxidation products (total thiols, protein carbonyls (PC), and advanced oxidation protein products (AOPP)), glycooxidation products (tryptophan, kynurenine, N-formylkynurenine, and dityrosine), glycation products (amyloid-β structure, fructosamine, and advanced glycation end products (AGE)), and albumin antioxidant activity (total antioxidant capacity (TAC), DPPH assay, and ferric reducing antioxidant power (FRAP)) were measured in each sample. In the presence of valsartan, concentrations of protein oxidation and glycation products were significantly lower comparing to control. Moreover, albumin antioxidant activity was significantly higher in those samples. The drug's action was comparable to renowned antiglycation agents and antioxidants, e.g., aminoguanidine, metformin, Trolox, N-acetylcysteine, or alpha-lipoic acid. The conducted experiment proves that valsartan can ameliorate protein glycation and oxidation in vitro in various conditions. Available animal and clinical studies uphold this statement, but further research is needed to confirm it, as reduction of protein oxidation and glycation may prevent cardiovascular disease development.

Alternative antibiotic feed additives alleviate pneumonia with inhibiting ACE-2 expression in the respiratory system of piglets

Weaning piglets often suffer from pneumonia during growth, so in general, antibiotics are used by owners to make piglets grow smoothly. However, antibiotics may be accompanied by many side effects such as gastrointestinal discomfort and allergies. The aim of this study was to develop an alternative antibiotic herbal veterinary medicine for alleviating pneumonia in weanling piglets. As observed in the pig ranches, many weanling piglets suffer from the pneumonia and also show high expression of angiotensin-converting enzyme 2 (ACE-2) in their respiratory and intestinal tracts. ACE inhibitors have been reported that can decrease pneumonia risk through their main mechanism of action. Thus, we also try to find alternative antibiotic feed additives that can reduce expression of ACE-2 in piglets. We selected the Guizhi Li-Zhong Tang Extract Granules (GLZ) as a natural product for piglets. Then, we compared the serum immunoglobulin levels of piglets with sham, tilmicosin antibiotic (TAB), and GLZ treatments. Our results showed that piglets with GLZ treatment had significantly a higher expression of immunoglobulin A and immunoglobulin G but a lower expression of immunoglobulin E than those with sham and TAB treatments. In addition, piglets with GLZ treatment showed obviously low pneumonia incidence than those with sham and TAB treatments. Similarly, piglets with GLZ treatment showed significantly lower expressions of ACE-2 in their tracheal, bronchial, and lung tissues than those with sham and TAB treatments. GLZ seems to be an alternative ACE inhibitor that can decrease pneumonia risk through inhibiting ACE-2 expression and alleviating allergies in their respiratory systems. Thus, we suggest that GLZ can be an alternative antibiotic feed additive for weaning piglets.

Characterization of the Renin-Angiotensin System in Aged Cavernosal Tissue and its Role in Penile Fibrosis

BACKGROUND

The renin-angiotensin system (RAS) plays an important role in erectile function. The RAS contains 2 major axes: one deleterious, composed of ACE-Ang II-AT1 receptor, and another protective, composed of ACE2-Ang-(1-7)-Mas receptor. While aging is a well-known cause for development of male sexual disorders, little is known about local regulation of the RAS in age-related erectile dysfunction (ED).

AIM

The present study aimed to assess regulation of the RAS in aging-associated ED rat model and evaluate possible options for disease management through pharmacological modulation of the RAS.

METHODS

Penile tissues were harvested from 3-, 12-, and 24-month-old Wistar rats. Local expression of major RAS components and ED markers was measured by RT-PCR. Protein expression of RAS components was assessed by western blot. Collagen deposition was measured by Sirius Red and immunohistochemical staining. Evaluation of collagen content was also performed in penile sections of Mas-knockout mice by Sirius Red and Masson's trichrome stainings. Finally, the effect of Ang-(1-7) pretreatment on TGF-β-induced myofibroblast activation was studied in primary cavernosal and immortalized fibroblasts.

OUTCOMES

Experimental results highlighted the essential role of the RAS in modulation of cavernosal fibrosis.

RESULTS

The present study demonstrates local expression of angiotensinogen mRNA alongside with major RAS components, which suggests local autonomous functioning of the RAS within penile tissue. Gene expression analysis revealed strong positive correlation between ACE-Ang II-AT1 axis with markers for inflammation and fibrosis. While corpus cavernosum from 24-month-old rats was characterized by increased collagen deposition, protein expression of ACE, AT1, and Mas was shown to be upregulated in the penile tissue of this group. At the same time, penile sections from Mas-knockout mice (FVB/N background) were also shown to have increased collagen deposition. Finally, it was demonstrated that Ang-(1-7) treatment of primary cavernosal and immortalized fibroblasts was able to alleviate TGF-β-induced fibroblast-to-myofibroblast transition.

CLINICAL TRANSLATION

The present study suggests Ang-(1-7) treatment as a possible strategy for pharmacological management of fibrosis-associated ED in aging.

STRENGTHS & LIMITATIONS

The link between the RAS and penile fibrosis, indicated by a holistic screening of different ED markers, was confirmed by in vivo and in vitro data. However, results, presented in the manuscript, need to be further reinforced by human data. Important to note, the main goal of the study was to characterize RAS regulation in aging condition rather than state any causal relationships.

CONCLUSION

Present study characterizes RAS regulation in aging-associated ED and indicates its important role in cavernosal fibrosis. Bragina ME, Costa-Fraga F, Sturny M, et al. Characterization of the Renin-Angiotensin System in Aged Cavernosal Tissue and its Role in Penile Fibrosis. J Sex Med 2020;17:2129-2140.

Overexpression of ACE in Myeloid Cells Increases Immune Effectiveness and Leads to a New Way of Considering Inflammation in Acute and Chronic Diseases

PURPOSE OF REVIEW

To review recent studies exploring how myeloid cell overexpression of angiotensin-converting enzyme (ACE) affects the immune response and to formulate an approach for considering the effectiveness of inflammation in cardiovascular disease RECENT FINDINGS: While it is widely appreciated that the renin-angiotensin system affects aspects of inflammation through the action of angiotensin II, new studies reveal a previously unknown role of ACE in myeloid cell biology. This was apparent from analysis of two mouse lines genetically modified to overexpress ACE in monocytes/macrophages or neutrophils. Cells overexpressing ACE demonstrated an increased immune response. For example, mice with increased macrophage ACE expression have increased resistance to melanoma, methicillin-resistant Staphylococcus aureus, a mouse model of Alzheimer's disease, and ApoE-knockout-induced atherosclerosis. These data indicate the profound effect of increasing myeloid cell function. Further, they suggest that an appropriate way to evaluate inflammation in both acute and chronic diseases is to ask whether the inflammatory infiltrate is sufficient to eliminate the immune challenge. The expression of ACE by myeloid cells induces a heightened immune response by these cells. The overexpression of ACE is associated with immune function beyond that possible by wild type (WT) myeloid cells. A heightened immune response effectively resolves disease in a variety of acute and chronic models of disease including models of Alzheimer's disease and atherosclerosis.

Changes of Bax, Bcl-2, CCR-2, MCP-1, and TGF-β1 genes in the left ventricle of spontaneously hypertensive rat after losartan treatment

Purpose

Increased apoptosis was recently found in the hypertrophied left ventricle of spontaneously hypertensive rats (SHRs). Although the available evidence suggests that apoptosis can be induced in cardiac cells by various insults including pressure overload, cardiac apoptosis appears to result from an exaggerated local production of angiotensin in adult SHRs. Altered expressions of Bcl associated X (Bax), Bcl-2, chemokine receptor (CCR)-2, monocyte chemoattractant protein (MCP)-1, transforming growth factor (TGF)-β1, phosphorylated extracellular signal-regulated kinases (PERK), and connexin 43 proteins, and kallikrein mRNA were investigated to explore the effects of losartan on the SHR model.

Methods

Twelve-week-old male rats were grouped as follows: control (C), SHR (hypertension: H), and losartan (L; SHRs were treated with losartan [10 mg/kg/day] for 5 weeks). Western blot and reverse transcription polymerase chain reaction assays were performed.

Results

Expression of Bax, CCR-2, MCP-1, TGF-β1, PERK, and connexin 43 proteins, and kallikrein mRNA was significantly increased in the H group compared to that in the C group at weeks 3 and 5. Expression of Bax, CCR-2, MCP-1, TGF-β1, and connexin 43 proteins and kallikrein mRNA was significantly decreased after losartan treatment at week 5. PERK protein expression was significantly decreased after losartan treatment at weeks 3 and 5. Bcl-2 protein expression was significantly decreased in the H group compared to that in the C group at weeks 3 and 5.

Conclusion

Losartan treatment reduced expression of Bax, CCR-2, MCP-1, TGF-β1, PERK, and connexin 43 proteins, and kallikrein mRNA in SHRs, along with decreased inflammation and apoptosis.

PPARs: regulators of metabolism and as therapeutic targets in cardiovascular disease. Part II: PPAR-β/δ and PPAR-γ

The PPARs are a subfamily of three ligand-inducible transcription factors, which belong to the superfamily of nuclear hormone receptors. In mammals, the PPAR subfamily consists of three members: PPAR-α, PPAR-β/δ and PPAR-γ. PPARs control the expression of a large number of genes involved in metabolic homeostasis, lipid, glucose and energy metabolism, adipogenesis and inflammation. PPARs regulate a large number of metabolic pathways that are implicated in the pathogenesis of metabolic diseases such as metabolic syndrome, Type 2 diabetes mellitus, nonalcoholic fatty liver disease and cardiovascular disease. The aim of this review is to provide up-to-date information about the biochemical and metabolic actions of PPAR-β/δ and PPAR-γ, the therapeutic potential of their agonists currently under clinical development and the cardiovascular disease outcome of clinical trials of PPAR-γ agonists, pioglitazone and rosiglitazone.

Fluorescence-Based Binding Assay for Screening Ligands of Angiotensin Receptors

Binding assay is a common technique used to characterize ability of a ligand to interact with a specific biological target. A number of parameters, such as binding affinity, receptor density, and association/dissociation rate constants, can be measured by means of this technique. In most cases, implementation of the binding assay requires specific infrastructure for labeling and detecting the ligand, which impedes realization of this technique in a standard laboratory. Here we describe a simple fluorescence-based binding assay for angiotensin peptides and receptors, which does not require complex equipment and can be used for initial screening of the novel ligands or mutational studies.

The effects of alpha 1-adrenoceptor blockade and angiotensin converting enzyme inhibition on central and brachial blood pressure and vascular reactivity: the doxazosin-ramipril study

We aimed to study whether inhibition of the renin–angiotensin–aldosterone system has effects on vascular structure and function beyond the effects on blood pressure reduction alone. Patients with mild-to-moderate hypertension (n = 61, age 54 ± 12 years, 34% women) received the angiotensin converting enzyme inhibitor ramipril 10 mg or the alpha 1-adrenoceptor blocker doxazosin 8 mg double-blind for 12 weeks. Aortic blood pressure, pulse wave velocity, and augmentation index were assessed by applanation tonometry. Endothelial function was studied by forearm post-ischemic flow mediated vasodilatation and by pulse wave analysis with beta 2-adrenoceptor agonist stimulation. Skin microvascular reactivity was assessed by laser Doppler fluxmetry and iontophoresis. Treatment with doxazosin or ramipril reduced aortic and brachial blood pressures (all P < 0.001), with greater reductions in aortic than brachial systolic blood pressures (P = 0.021) and aortic/brachial pulse pressure ratio (P = 0.005). Compared to doxazosin, ramipril reduced carotid-femoral and carotid-radial pulse wave velocity (both P < 0.05). Forearm endothelial dependent and independent vasodilatation, assessed by post-ischemic flow mediated vasodilatation and glyceryl trinitrate, and by pulse wave analysis remained unchanged by both doxazosin and ramipril. In addition, skin microvascular endothelial dependent (acetylcholine) and independent vasodilatation (sodium nitroprusside) remained unchanged. In conclusion, ramipril reduced indices of aortic stiffness, suggesting that angiotensin converting enzyme inhibitor therapy may have effects beyond blood pressure reduction. However, treatment did not appear to influence endothelial function. Evidence of endothelial dysfunction and its possible improvement by antihypertensive treatment might require more advanced hypertension.

This study is registered at ClinicalTrials.gov (NCT02901977) and at EudraCT (# 2007-000631-25).

Palliation of heart failure

Heart failure is the major cause of morbidity and mortality in the United States. Stage D heart failure has a greater mortality rate than many cancers and has equivalent symptom burden and severity. There has been a paradigm shift in our understanding of the pathophysiology of heart failure. Progressive heart failure is associated with ventricular remodeling and a maladaptive neurohumoral response. Drug classes have evolved that curtail ventricular remodeling, and blunt neurohumoral responses reduce morbidity and mortality. Despite combination drug and device therapies, the management of Stage D heart failure includes palliation. Both cardiology and palliative specialists need to learn from one another in order to palliate these highly symptomatic patients. Such collaboration will enhance care and are the basis for well-conceived research trials.

Protecting the Heart with Cardiac Medication in Patients with Left Ventricular Dysfunction Undergoing Major Noncardiac Vascular Surgery

Patients with left ventricular dysfunction who are undergoing major noncardiac vascular surgery are at increased risk of adverse postoperative events. We sought to evaluate whether perioperative medication use, including angiotensin-converting enzyme (ACE) inhibitors,b-blockers, statins, and aspirin, was associated with a reduced incidence of postoperative in-hospital mortality in these high-risk patients. The study enrolled 511 patients with left ventricular dysfunction (left ventricular ejection fraction <30%) who were undergoing major noncardiac vascular surgery. Cardiac risk factors and medication use were noted before surgery. Preoperative dobutamine stress echocardiography (DSE) was performed to identify patients with stress-induced myocardial ischemia. The end point was postoperative in-hospital mortality. Univariate and multivariate logistic regression analyses were performed to evaluate the relation between perioperative medication use and mortality. The mean age of the study population was 64 ± 11 years, and 75% were men. Perioperative use of ACE inhibitors, b-blockers, statins, and aspirin was recorded in 215 (48%), 139 (27%), 107 (21%), and 125 patients (24%), respectively. Stress-induced myocardial ischemia occurred in 82 patients (16%). Sixty-four patients (13%) died. Perioperative use of ACE inhibitors (odds ratio [OR], 0.33; 95% confidence interval [CI], 0.12-0.91), b-blockers (OR, 0.03; 95% CI, 0.01-0.26), statins (OR, 0.06; 95% CI, 0.01-0.53), and aspirin (OR, 0.13; 95% CI, 0.03-0.55), was significantly associated with a reduced incidence of mortality, after adjusting for cardiac risk factors and DSE results. In conclusion, the present study showed that the perioperative use of ACE inhibitors,b-blockers, statins, and aspirin is independently associated with a reduced incidence of in-hospital mortality in patients with left ventricular dysfunction who are undergoing major noncardiac vascular surgery.

Fruitflow®: the first European Food Safety Authority-approved natural cardio-protective functional ingredient

Hyperactive platelets, in addition to their roles in thrombosis, are also important mediators of atherogenesis. Antiplatelet drugs are not suitable for use where risk of a cardiovascular event is relatively low. It is therefore important to find alternative safe antiplatelet inhibitors for the vulnerable population who has hyperactive platelets in order to reduce the risk of cardiovascular disease. Potent antiplatelet factors were identified in water-soluble tomato extract (Fruitflow^®), which significantly inhibited platelet aggregation. Human volunteer studies demonstrated the potency and bioavailability of active compounds in Fruitflow^®. Fruitflow^® became the first product in Europe to obtain an approved, proprietary health claim under Article 13(5) of the European Health Claims Regulation 1924/2006 on nutrition and health claims made on foods. Fruitflow^® is now commercially available in different countries worldwide. In addition to its reduction in platelet reactivity, Fruitflow^® contains anti-angiotensin-converting enzyme and anti-inflammatory factors, making it an effective and natural cardio-protective functional food.

Salt, Angiotensin II, Superoxide, and Endothelial Function

Proper function of the vascular endothelium is essential for cardiovascular health, in large part due to its antiproliferative, antihypertrophic, and anti-inflammatory properties. Crucial to the protective role of the endothelium is the production and liberation of nitric oxide (NO), which not only acts as a potent vasodilator, but also reduces levels of reactive oxygen species, including superoxide anion (O2•-). Superoxide anion is highly injurious to the vasculature because it not only scavenges NO molecules, but has other damaging effects, including direct oxidative disruption of normal signaling mechanisms in the endothelium and vascular smooth muscle cells. The renin-angiotensin system plays a crucial role in the maintenance of normal blood pressure. This function is mediated via the peptide hormone angiotensin II (ANG II), which maintains normal blood volume by regulating Na+ excretion. However, elevation of ANG II above normal levels increases O2•- production, promotes oxidative stress and endothelial dysfunction, and plays a major role in multiple disease conditions. Elevated dietary salt intake also leads to oxidant stress and endothelial dysfunction, but these occur in the face of salt-induced ANG II suppression and reduced levels of circulating ANG II. While the effects of abnormally high levels of ANG II have been extensively studied, far less is known regarding the mechanisms of oxidant stress and endothelial dysfunction occurring in response to chronic exposure to abnormally low levels of ANG II. The current article focuses on the mechanisms and consequences of this less well understood relationship among salt, superoxide, and endothelial function.

Vascular Impairment of Epineurial Arterioles of the Sciatic Nerve: Implications for Diabetic Peripheral Neuropathy

This article reviews the impact of diabetes and its treatment on vascular function with a focus on the reactivity of epineurial arterioles, blood vessels that provide circulation to the sciatic nerve. Another focus is the relationship between the dysregulation of neurovascular function and diabetic peripheral neuropathy. Diabetic peripheral neuropathy is a debilitating disorder that occurs in more than 50 percent of patients with diabetes. The etiology involves metabolic, vascular, and immunologic pathways besides neurohormonal growth factor deficiency and extracellular matrix remodeling. In the light of this complex etiology, an effective treatment for diabetic peripheral neuropathy has not yet been identified. Current opinion postulates that any effective treatment for diabetic peripheral neuropathy will require a combination of life style and therapeutic interventions. However, a more comprehensive understanding of the factors contributing to neurovascular and neural dysfunction in diabetes is needed before such a treatment strategy can be developed. After reading this review, the reader should have gained insight into the complex regulation of vascular function and blood flow to the sciatic nerve, and the impact of diabetes on numerous elements of vascular reactivity of epineurial arterioles of the sciatic nerve.

Effect of Angiotensin Receptor Blockers on Flow-Mediated Vasodilation: A Meta-Analysis of Randomized Controlled Trials

Background: In a meta-analysis, we investigated the effects of angiotensin receptor blockers (ARBs) in comparison to placebo or other classes of antihypertensive drugs on endothelial function, which was measured by brachial flow-mediated vasodilation (FMD). Methods: We searched for randomized controlled trials that compared ARBs with placebo or other classes of antihypertensive drugs in improving FMD. A random-effect model was used to compute pooled estimates. Results: In 13 trials (n = 529), ARBs were more efficacious in improving brachial FMD than placebo [pooled weighted mean change difference (WMD) 1.34%, 95% CI, 0.93-1.75%, p < 0.001]. In 15 trials (n = 918), treatment with ARBs had a significant effect on brachial FMD when compared with other antihypertensive drugs (pooled WMD 0.59%, 95% CI, 0.20-0.98%, p = 0.003 with significant heterogeneity). ARBs were also more efficacious in improving brachial FMD than calcium channel blockers (CCBs; pooled WMD 1.61%, 95% CI, 0.72-2.49%, p < 0.001) but not the other classes of drugs (p ≥ 0.072). Conclusions: This meta-analysis shows that ARBs improve brachial FMD, a marker of endothelial function, and that they are superior to placebo and CCBs. There was no significant difference in the effect on brachial FMD between ARBs and the other antihypertensive drugs.

Inhibition of angiotensin-converting enzyme by aqueous extract of tomato

PURPOSE

To investigate the presence of anti-angiotensin converting enzyme (ACE) factors in aqueous extract of tomato.

METHODS

The bio-guided fractionation of the aqueous extract of tomato produced a sugar-free, heat-stable fraction with molecular mass <1,000 Da from tomatoes. The sugar-free tomato extract (TE) was tested for its anti-ACE activity using human plasma and rabbit lung pure ACE. In addition, its effect on human platelet aggregation induced by ADP, collagen or arachidonic acid was determined. The mechanism of platelet inhibitory action of TE was investigated by measuring platelet factor 4 (PF4) release and cAMP synthesis by platelets.

RESULTS

Typically, 100 g tomatoes produced 72.2 ± 4.7 mg of TE. This extract inhibited both platelet aggregation and plasma ACE activity in a dose-dependent manner. It inhibited platelet aggregation in response to ADP, collagen or arachidonic acid, and inhibitory action was mediated in part by reducing platelet PF4 release and by stimulating cAMP synthesis. The IC50 value of TE for ADP-induced platelet aggregation was 0.4 ± 0.02 mg/ml, whereas the IC50 value for ACE enzyme inhibition was 1.40 ± 0.04 mg/ml. Both the TE and commercially available sugar-free TE, Fruitflow(®)-2 had similar amount of catechin, and also had equal inhibitory potencies against platelet aggregation and plasma ACE activity.

CONCLUSION

Together these data indicate that aqueous extract of tomatoes contain anti-ACE factors in addition to previously described anti-platelet factors.

Role of the renin-angiotensin system on abdominal aortic aneurysms

BACKGROUND

Abdominal aortic aneurysm (AAA) is a complex degenerative disease, which leads to morbidity and mortality in a large portion of the elderly population. Current treatment options for AAA are quite limited as there is no proven indication for pharmacological therapy and surgery is recommended for AAA larger than 5·5 cm in luminal diameter. Thus, there is a great need to elucidate the underlying pathophysiological cellular and molecular mechanisms to develop effective therapies. In this narrative review, we will discuss recent findings concerning some potential molecular and clinical aspects of the renin-angiotensin system (RAS) in AAA pathophysiology.

MATERIALS AND METHODS

This narrative review is based on the material found on MEDLINE and PubMed up to April 2013. We looked for the terms 'angiotensin, AT1 receptor, ACE inhibitors' in combination with 'abdominal aortic aneurysm, pathophysiology, pathways'.

RESULTS

Several basic research and clinical studies have recently investigated the role of the RAS in AAA. In particular, the subcutaneous infusion of Angiotensin II has been shown to induce AAA in Apo56 knockout mice. On the other hand, the pharmacological treatments targeting this system have been shown as beneficial in AAA patients.

CONCLUSIONS

Emerging evidence suggests that RAS may act as a molecular and therapeutic target for treating AAA. However, several issues on the role of RAS and the protective activities of angiotensin-converting enzyme (ACE) inhibitors and Angiotensin 1 receptors blockers against AAA require further clarifications.

Pathophysiological role of the renin-angiotensin system on erectile dysfunction

BACKGROUND

The renin-angiotensin system (RAS) has been shown to play an active role within the erectile tissues. The aim of this narrative review is to summarize the literature addressing the pathophysiological role of RAS on erectile function. Additionally, we update evidence on recent findings on the role of the Ang-(1-7) and Mas receptor on the erectile function and its therapeutic potential for treating erectile dysfunction (ED).

MATERIALS AND METHODS

This narrative review is based on the material searched and obtained via MEDLINE and PubMed up to November 2012. The search terms we used are 'angiotensin, erectile dysfunction, renin, Mas receptor' in combination with 'pathophysiology, fibrosis, pathways'.

RESULTS

The levels of angiotensin (Ang) II, the main component of this system, are increased in the corpus cavernosum as compared to those found in the systemic circulation. Moreover, emerging evidence indicates that an increased activity of Ang II via AT1 receptor might contribute to the development of ED, whereas the pharmacological blockage of Ang II/AT1 actions has beneficial effects on the erection. On the other hand, the heptapeptide Ang-(1-7), known as a major endogenous counter-regulator of Ang II actions, favours penile erection via the activation of Mas receptor.

CONCLUSIONS

Ang-(1-7) and Mas receptor pathway might be considered as a promising therapeutic target for the treatment of ED.

Opportunities for targeting the angiotensin-converting enzyme 2/angiotensin-(1-7)/mas receptor pathway in hypertension

It is well known that the renin-angiotensin system (RAS) plays a pivotal role in the pathophysiology of cardiovascular diseases. This is well illustrated by the great success of ACE inhibitors and angiotensin (Ang) II AT(1) blockers in the treatment of hypertension and its complications. In the past decade, the classical concept of RAS orchestrated by a series of enzymatic reactions culminating in the linear generation and action of Ang II has expanded and become more complex. From the discoveries of new components such as the angiotensin converting enzyme 2 and the receptor Mas emerged a novel concept of dual opposite branches of the RAS: one vasoconstrictor and pro-hypertensive composed of ACE/Ang II/AT1; and other vasodilator and anti-hypertensive composed of ACE2/Ang-(1-7)/Mas. In this review we will discuss recent findings concerning the biological role of the ACE2/Ang-(1-7)/Mas arm in the cardiovascular system and highlight the initiatives to develop potential therapeutic strategies based on this axis for treating hypertension.

Hepatic fibrosis and the renin-angiotensin system

The renin-angiotensin system (RAS) is involved in hepatic fibrosis. To date there is no known effective treatment for hepatic fibrosis. Modulation of the RAS with angiotensin converting enzyme inhibitors and angiotensin receptor blockers may be a promising therapeutic option for the treatment of hepatic fibrosis. This review provides an update about the role of RAS in hepatic fibrosis, and treatment of hepatic fibrosis in the light of different studies in animals and humans is also updated. RAS induces key steps involved in hepatic fibrosis, such as activation of hepatic stellate cells and expression of transforming growth factor β1. Treatment with angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers attenuate fibrosis progression in both animal and human studies. Further, controlled studies are required to evaluate the role of RAS inhibitors and angiotensin-converting enzyme 2 in patients with chronic liver diseases in whom the causative agent cannot be removed.

Irbesartan, an angiotensin receptor blocker, exhibits metabolic, anti-inflammatory and antioxidative effects in patients with high-risk hypertension

Irbesartan, an angiotensin II receptor blocker (ARB), acts as a selective PPAR-γ (peroxisome proliferator-activated receptor-γ) modulator, and thus may have anti-inflammatory and antioxidative effects, as well as beneficial effects on glucose and lipid metabolism. We enrolled 118 high-risk hypertensive outpatients, defined as those with the presence of at least one complication such as coronary artery disease, cerebrovascular disease or diabetes, and who were receiving any ARB except for irbesartan (67±10 years, 80% male subjects). After a 4-week control period, all ARBs were switched to an equivalent dose of irbesartan. We evaluated changes in lipid parameters, inflammatory markers and derivatives of reactive oxygen metabolites (d-ROMs) as an oxidative stress index. After 12 weeks of irbesartan, there were significant decreases in triglycerides (138±73 versus 123±65 mg dl(-1), P<0.05), high-sensitivity C-reactive protein (hs-CRP) (2.80±0.53 versus 2.66±0.50, log (ng ml(-1)), P<0.05) and d-ROMs (338±74 versus 305±62 U.CARR, P<0.001). There were significant increases in high-density lipoprotein cholesterol (50±13 versus 52±14 mg dl(-1), P<0.01) and adiponectin (9.4±6.2 versus 16.6±13.4 ng ml(-1), P<0.05). There were no significant changes in systolic and diastolic blood pressure. The change in d-ROMs from baseline to 12 weeks was positively correlated with the change in hs-CRP (R=0.34, P<0.01). Irbesartan appears to exert beneficial effects on oxidative stress, inflammation, lipid metabolism and metabolic syndrome, indicating that it may be useful in high-risk hypertensive patients.

The angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas receptor axis: a potential target for treating thrombotic diseases

Despite many therapeutic advances leading to increasingly effective drug treatments, thrombotic events (such as ischaemic stroke, pulmonary embolism, deep venous thrombosis and acute myocardial infarction) still represent a major worldwide cause of morbidity and mortality. Remarkable effort has been made to identify new drug targets. There is growing evidence indicating that the recently described counter-regulator axis of the renin-angiotensin system (RAS), composed of Angiotensin-Converting Enzyme 2 (ACE2), Angiotensin-(1-7) and the Mas receptor, has protective effects against thrombosis. In addition, it could be considered as a promising target for treating or preventing this disease. In this narrative review, we focused on the recent findings of the role of the ACE2/Angiotensin-(1-7)/Mas axis on the haemostatic process and its therapeutic potential.

Inhibition of ACE activity contributes to the intestinal structural compensation in a massive intestinal resection rat model

BACKGROUND

Intestinal adaptation in short bowel syndrome (SBS) consists of increased epithelial cells (ECs) proliferation as well as apoptosis. Angiotensin-converting enzyme (ACE) has been shown to regulate ECs apoptosis. In this study, we investigated the effect of ACE inhibition on intestinal adaptation after small bowel resection (SBR) in a rat model.

METHODS

Sprague-Dawley rats were used and were divided into four groups: (1) Sham group received an ileum transection (n = 6); (2) Sham + ACE-I group received an ileum transaction and lavage with ACE inhibitor (ACE-I, enalaprilat, 2 mg/kg/day) (n = 6); (3) SBS group received a 70 % mid-intestinal resection (n = 6); (4) SBS + ACE-I group received a 70 % mid-intestinal resection and lavage with enalaprilat (2 mg/kg/day) (n = 6). Sampling was done 10 days after surgery. ECs apoptosis was studied by TUNEL staining. ACE, angiotensin II (ANGII) receptor type 1 (AT1R) and receptor type 2 (AT2R) expressions were detected with RT-PCR and immunofluorescent confocal microscopy.

RESULTS

SBR leads to significant intestinal hypertrophy. The addition of ACE-I to SBS rat resulted in a significant decline in ECs apoptosis. ACE mRNA expression was significantly elevated after SBS creation (0.24 ± 0.07 vs. 0.42 ± 0.11), and ACE-I administration further increased mucosal ACE mRNA expression (0.54 ± 0.12). Interestingly, AT1R mRNA expression showed a significant decline in the SBS group compared to Sham levels, and ACE-I administration increased AT1R mRNA expression to Sham levels. No significant difference in AT2R mRNA expression was found between Sham and SBS group.

CONCLUSION

These results offer further insight into the role of ACE on intestinal mucosal remolding after massive bowel resection. ACE-I may be beneficial to SBS patients via a reduction of the apoptotic rate, thus facilitating the degree of adaptation.

Therapeutic targeting of the angiotensin-converting enzyme 2/Angiotensin-(1-7)/Mas cascade in the renin-angiotensin system: a patent review

INTRODUCTION

The renin-angiotensin system (RAS) is a main therapeutic target for cardiovascular diseases. Within the last two decades, novel components of the RAS have been discovered, opening new opportunities to interfere with its activity. Angiotensin(Ang)-(1-7) is synthesized by angiotensin-converting enzyme 2 (ACE2), and interacts with the G-protein-coupled receptor Mas. The axis formed by ACE2/Ang-(1-7)/Mas represents an endogenous counter regulatory pathway within the RAS.

AREAS COVERED

In this review, the authors discuss patents and recent initiatives to develop therapeutic strategies based on the ACE2/Ang-(1-7)/Mas axis.

EXPERT OPINION

Many publications and patents support a strategy to interfere with the activity of the RAS by stimulating its counter-regulatory axis mainly in two different ways: i) To increase the activity of ACE2, which will impact the system by increasing the inactivation of Ang II and the production of Ang-(1-7); ii) To stimulate Mas, taking advantage of nanostructured formulations of the natural peptide or analogues of Ang-(1-7). Although the preclinical studies are compelling, the possible impact of these novel therapeutic tools for the treatment of cardiometabolic diseases will only be known after completion of the ongoing clinical studies.

New cardiovascular and pulmonary therapeutic strategies based on the Angiotensin-converting enzyme 2/angiotensin-(1-7)/mas receptor axis

Angiotensin (Ang)-(1–7) is now recognized as a biologically active component of the renin-angiotensin system (RAS). The discovery of the angiotensin-converting enzyme homologue ACE2 revealed important metabolic pathways involved in the Ang-(1–7) synthesis. This enzyme can form Ang-(1–7) from Ang II or less efficiently through hydrolysis of Ang I to Ang-(1–9) with subsequent Ang-(1–7) formation. Additionally, it is well established that the G protein-coupled receptor Mas is a functional ligand site for Ang-(1–7). The axis formed by ACE2/Ang-(1–7)/Mas represents an endogenous counter regulatory pathway within the RAS whose actions are opposite to the vasoconstrictor/proliferative arm of the RAS constituted by ACE/Ang II/AT₁ receptor. In this review we will discuss recent findings concerning the biological role of the ACE2/Ang-(1–7)/Mas arm in the cardiovascular and pulmonary system. Also, we will highlight the initiatives to develop potential therapeutic strategies based on this axis.

Mineralocorticoid receptor blocker eplerenone improves endothelial function and inhibits Rho-associated kinase activity in patients with hypertension

Hypertension is associated with endothelial dysfunction and activated Rho-associated kinases (ROCKs). The purpose of this study was to evaluate the effects of the selective mineralocorticoid receptor blocker, eplerenone, on endothelial function and ROCK activity in patients with hypertension. The study was carried out over 48 weeks in 60 untreated patients with hypertension who were randomly assigned to eplerenone, nifedipine, and losartan groups. We evaluated the effects of each treatment on flow-mediated vasodilation (FMD) and ROCK activity in peripheral leukocytes. Eplerenone increased FMD and decreased leukocyte ROCK activity. Nifedipine decreased ROCK activity but did not alter FMD. Losartan increased FMD but did not alter ROCK activity. Hypotensive effects were similar in the three groups, as was nitroglycerin-induced vasodilation during the follow-up period. There were no significant differences between the groups with respect to other parameters. The study results show that eplerenone improves endothelial function and inhibits ROCK activity in patients with essential hypertension.

Apelin mediates the induction of profibrogenic genes in human hepatic stellate cells

Apelin is a peptide with relevant functions in angiogenesis and inflammation. Recent studies have demonstrated that apelin is overexpressed in hepatic stellate cells (HSCs) of cirrhotic rats. Moreover, patients with cirrhosis show high circulating levels of this peptide. We evaluated the role of endogenous apelin system in fibrogenesis-related gene induction in human HSCs. Messenger expression and immunolocalization of apelin were analyzed in human cirrhotic liver and in control samples. Apelin expression was analyzed in a human HSC line (LX-2) under hypoxic conditions or in the presence of proinflammatory or profibrogenic stimuli. LX-2 cells were stimulated with apelin, and a selected profile of fibrogenesis-related genes was quantified. In vivo inactivation of apelin was analyzed in the liver of fibrotic rats after administrating specific blockers of the molecules triggering apelin induction. Apelin was overexpressed in HSCs from human cirrhotic liver. Neither hypoxia nor proinflammatory substances induced the expression of apelin in LX-2. By contrast, both profibrogenic molecules angiotensin II (AII) and endothelin-1 (ET-1) enhanced apelin expression in these cells. Apelin increased the synthesis of collagen-I and platelet-derived growth factor receptor β (PDGFRβ) in LX-2. AII and ET-1 stimulated collagen-I and PDGFRβ expression, and this induction was drastically reduced when apelin receptor was blocked in these cells. In accordance, AII or ET-1 receptor antagonists reduced the hepatic synthesis of apelin, collagen-I, and PDGFRβ in fibrotic rats.

CONCLUSIONS

apelin mediates some of the fibrogenic effects triggered by AII and ET-1, thus suggesting that apelin could be an important mediator of fibrogenesis in human liver disease.

Effects of the AT1 receptor antagonist L-158,809 on microglia and neurogenesis after fractionated whole-brain irradiation

Cognitive dysfunction develops in approximately 50% of patients who receive fractionated whole-brain irradiation and survive 6 months or more. The mechanisms underlying these deficits are unknown. A recent study demonstrated that treatment with the angiotensin II type 1 receptor antagonist (AT(1)RA) L-158,809 before, during and after fractionated whole-brain irradiation prevents or ameliorates radiation-induced cognitive deficits in adult rats. Given that (1) AT(1)RAs may function as anti-inflammatory drugs, (2) inflammation is thought to contribute to radiation injury, and (3) radiation-induced inflammation alters progenitor cell populations, we tested whether the cognitive benefits of L-158,809 treatment were associated with amelioration of the sustained neuroinflammation and changes in neurogenesis that are induced by fractionated whole-brain irradiation. In rats examined 28 and 54 weeks after irradiation, L-158,809 treatment did not alter the effects of radiation on the number and activation of microglia in the perirhinal cortex and hippocampus, nor did it prevent the radiation-induced decrease in proliferating cells and immature neurons in the hippocampus. These findings suggest that L-158,809 does not prevent or ameliorate radiation-induced cognitive deficits by modulation of chronic inflammatory mechanisms, but rather may reduce radiation-induced changes that occur earlier in the postirradiation period and that lead to cognitive dysfunction.

Increased expression of vascular endothelin type B and angiotensin type 1 receptors in patients with ischemic heart disease

Background

Endothelin-1 and angiotensin II are strong vasoconstrictors. Patients with ischemic heart disease have elevated plasma levels of endothelin-1 and angiotensin II and show increased vascular tone. The aim of the present study was to examine the endothelin and angiotensin II receptor expression in subcutaneous arteries from patients with different degrees of ischemic heart disease.

Methods

Subcutaneous arteries were obtained, by biopsy from the abdomen, from patients undergoing coronary artery bypass graft (CABG) surgery because of ischemic heart disease (n = 15), patients with angina pectoris without established myocardial infarction (n = 15) and matched cardiovascular healthy controls (n = 15). Endothelin type A (ET_A) and type B (ET_B), and angiotensin type 1 (AT₁) and type 2 (AT₂) receptors expression and function were examined using immunohistochemistry, Western blot and in vitro pharmacology.

Results

ET_A and, to a lesser extent, ET_B receptor staining was observed in the healthy vascular smooth muscle cells. The level of ET_B receptor expression was higher in patients undergoing CABG surgery (250% ± 23%; P < 0.05) and in the patients with angina pectoris (199% ± 6%; P < 0.05), than in the healthy controls (100% ± 28%). The data was confirmed by Western blotting. Arteries from CABG patients showed increased vasoconstriction upon administration of the selective ET_B receptor agonist sarafotoxin S6c, compared to healthy controls (P < 0.05). No such difference was found for the ET_A receptors. AT₁ and, to a lesser extent, AT₂ receptor immunostaining was seen in the vascular smooth muscle cells. The level of AT₁ receptor expression was higher in both the angina pectoris (128% ± 25%; P < 0.05) and in the CABG patients (203% ± 41%; P < 0.05), as compared to the healthy controls (100% ± 25%). The increased AT₁ receptor expression was confirmed by Western blotting. Myograph experiment did however not show any change in vasoconstriction to angiotensin II in CABG patients compared to healthy controls (P = n.s).

Conclusion

The results demonstrate, for the first time, upregulation of ET_B and AT₁ receptors in vascular smooth muscle cells in ischemic heart disease. These receptors may play a role in the pathophysiology of ischemic heart disease and could provide important targets for pharmaceutical interventions.

Keeping pace with ACE: are ACE inhibitors and angiotensin II type 1 receptor antagonists potential doping agents?

In the decade since the angiotensin-converting enzyme (ACE) gene was first proposed to be a 'human gene for physical performance', there have been numerous studies examining the effects of ACE genotype on physical performance phenotypes such as aerobic capacity, muscle function, trainability, and athletic status. While the results are variable and sometimes inconsistent, and corroborating phenotypic data limited, carriers of the ACE 'insertion' allele (the presence of an alu repeat element in intron 16 of the gene) have been reported to have higher maximum oxygen uptake (VO2max), greater response to training, and increased muscle efficiency when compared with individuals carrying the 'deletion' allele (absence of the alu repeat). Furthermore, the insertion allele has been reported to be over-represented in elite athletes from a variety of populations representing a number of endurance sports. The mechanism by which the ACE insertion genotype could potentiate physical performance is unknown. The presence of the ACE insertion allele has been associated with lower ACE activity (ACEplasma) in number of studies, suggesting that individuals with an innate tendency to have lower ACE levels respond better to training and are at an advantage in endurance sporting events. This could be due to lower levels of angiotensin II (the vasoconstrictor converted to active form by ACE), higher levels of bradykinin (a vasodilator degraded by ACE) or some combination of the two phenotypes. Observations that individuals carrying the ACE insertion allele (and presumably lower ACEplasma) have an enhanced response to training or are over-represented amongst elite athletes raises the intriguing question: would individuals with artificially lowered ACEplasma have similar training or performance potential? As there are a number of drugs (i.e. ACE inhibitors and angiotensin II type 1 receptor antagonists [angiotensin receptor blockers--ARBs]) that have the ability to either reduce ACEplasma activity or block the action of angiotensin II, the question is relevant to the study of ergogenic agents and to the efforts to rid sports of 'doping'. This article discusses the possibility that ACE inhibitors and ARBs, by virtue of their effects on ACE or angiotensin II function, respectively, have performance-enhancing capabilities; it also reviews the data on the effects of these medications on VO2max, muscle composition and endurance capacity in patient and non-patient populations. We conclude that, while the direct evidence supporting the hypothesis that ACE-related medications are potential doping agents is not compelling, there are insufficient data on young, athletic populations to exclude the possibility, and there is ample, albeit indirect, support from genetic studies to suggest that they should be. Unfortunately, given the history of drug experimentation in athletes and the rapid appropriation of therapeutic agents into the doping arsenal, this indirect evidence, coupled with the availability of ACE-inhibiting and ACE-receptor blocking medications may be sufficiently tempting to unscrupulous competitors looking for a shortcut to the finish line.

The role of Angiotensin II type 1a receptor on intestinal epithelial cells following small bowel resection in a mouse model

AIM

We have previously shown that inhibition of angiotensin converting enzyme (ACE) significantly reduced intestinal epithelial cell (EC) apoptosis and improved morphometric intestinal adaptation in a mouse model of massive small-bowel resection (SBR). This study attempted to further examine the downstream signaling factors in this system by blocking the action of angiotensin II (ATII), hypothesizing that this would lead to similar improvement of intestinal adaptation after SBR.

METHOD

Two groups of mice (C57BL/6J) underwent either a 60% mid-intestinal resection (SBR group) or a transection/re-anastomosis (Sham group). Because real-time PCR studies showed that only ATII receptor type 1a (ATII-1a) expression was significantly increased after SBR, compared to SHAM mice, we decided to use the specific ATII-1a receptor antagonist Losartan to block this signaling pathway. An additional two groups of mice received daily i.p. injections of Losartan (SBR + Losartan and Sham + Losartan group). At 7 days, the adaptive response was assessed in the remnant gut including villus height, crypt depth, EC apoptosis (TUNEL staining) and proliferation (BrdU incorporation). The apoptotic and proliferation signaling pathways were addressed by analysis of EC mRNA expression.

RESULT

SBR (with and without Losartan) led to a significant increase in villus height and crypt depth. Losartan treatment did not significantly change EC proliferation, but did significantly reduce EC apoptosis rates as compared to the non-treated SBR group. Losartan treatment was associated with a significant reduction of the bax-to-bcl-2 ratio and TNF-alpha expression after SBR compared to non-treated groups. Interestingly, Losartan-treated groups showed a tremendous increase in proliferation of signaling factors EGFR, KGFR and IL7R, which may indicate an expanded potential for further intestinal adaptation also beyond 7 days after SBR.

CONCLUSION

This study showed that the ATII-1a receptor may be of crucial importance for the modulation of intestinal EC apoptosis, and for regulating the post-resectional EC adaptive response.

Cytokines and renin-angiotensin system signaling in hepatic fibrosis

Hepatic fibrosis is the result of a complex interplay between resident hepatic cells, infiltrating inflammatory cells, and a number of locally acting peptides called cytokines. Key mediators include transforming growth factor b1, vasoactive substances, adipokines, inflammatory cytokines and chemokines. Angiotensin II, the main effector of the renin-angiotensin system, is a true cytokine that plays a major role in liver fibrosis. Angiotensin II is locally synthesized in the injured liver and induces profibrogenic actions in hepatic stellate cells. Drugs blocking the renin-angiotensin system are promising antifibrotic agents. There are multiple signal transduction pathways involved in cytokine signaling. Drugs interfering intracellular pathways involved in increased collagen production are potential therapies for liver fibrosis.

Modulation of mouse intestinal epithelial cell turnover in the absence of angiotensin converting enzyme

Angiotensin converting enzyme (ACE) has been shown to be involved in regulation of apoptosis in nonintestinal tissues. This study examined the role of ACE in the modulation of intestinal adaptation utilizing ACE knockout mice (ACE-/-). A 60% small bowel resection (SBR) was used, since this model results in a significant increase in intestinal epithelial cell (EC) apoptosis as well as proliferation. Baseline villus height, crypt depth, and intestinal EC proliferation were higher, and EC apoptosis rates were lower in ACE-/- compared with ACE+/+ mice. After SBR, EC apoptosis rates remained significantly lower in ACE-/- compared with ACE+/+ mice. Furthermore, villus height and crypt depth after SBR continued to be higher in ACE-/- mice. The finding of a lower bax-to-bcl-2 protein ratio in ACE-/- mice may account for reduced EC apoptotic rates after SBR in ACE-/- compared with ACE+/+ mice. The baseline higher rate of EC proliferation in ACE-/- compared with ACE+/+ mice may be due to an increase in the expression of several EC growth factor receptors. In conclusion, ACE appears to have an important role in the modulation of intestinal EC apoptosis and proliferation and suggests that the presence of ACE in the intestinal epithelium has a critical role in guiding epithelial cell adaptive response.

Obesity and vascular dysfunction

One of the most profound challenges facing public health and public health policy in Western society is the increased incidence and prevalence of both overweight and obesity. While this condition can have significant consequences for patient mortality and quality of life, it can be further exacerbated as overweight/obesity can be a powerful stimulus for the development of additional risk factors for a negative cardiovascular outcome, including increased insulin resistance, dyslipidemia and hypertension. This manuscript will present the effects of systemic obesity on broad issues of vascular function in both afflicted human populations and in the most relevant animal models. Among the topics that will be covered are alterations to vascular reactivity (both dilator and constrictor responses), adaptations in microvascular network and vessel wall structure, and alterations to the patterns of tissue/organ perfusion as a result of the progression of the obese condition. Additionally, special attention will be paid to the contribution of chronic inflammation as a contributor to alterations in vascular function, as well as the role of perivascular adipose tissue in terms of impacting vessel behavior. When taken together, it is clearly apparent that the development of the obese condition can have profound, and frequently difficult to predict, impacts on integrated vascular function. Much of this complexity appears to have its basis in the extent to which other co-morbidities associated with obesity (e.g., insulin resistance) are present and exert contributing effects.

Involvement of tumor necrosis factor-alpha in angiotensin II-mediated effects on salt appetite, hypertension, and cardiac hypertrophy

Hypertension is considered a low-grade inflammatory condition induced by various proinflammatory cytokines, including tumor necrosis factor (TNF)-alpha. Recent studies have implicated an involvement of TNF-alpha in the development of salt-sensitive hypertension induced by angiotensin II (Ang II). To understand further the relationship between TNF-alpha and Ang II, we examined the responses to Ang II in TNF-alpha knockout (TNF-alpha(-/-)) mice in the present study. A continuous infusion of Ang II (1 microg/kg per minute) for 2 weeks was given to both TNF-alpha(-/-) and wild-type (WT) mice with implanted osmotic minipumps. Daily measurement of water intake, salt intake, and urine output were performed using metabolic cages. Blood pressure was monitored continuously with implanted radiotelemetry. Ang II administration for 2 weeks caused increases in salt (0.2+/-0.07 to 5.6+/-0.95 mL/d) and water (5.4+/-0.34 to 11.5+/-1.2 mL/d) intake and in mean arterial pressure (115+/-1 to 151+/-3 mm Hg) in wild-type mice, but these responses were absent in TNF-alpha(-/-) mice (0.2+/-0.04 to 0.3+/-0.09 mL/d, 5.5+/-0.2 to 6.1+/-0.07 mL/d, and 113+/-2 to 123+/-3 mm Hg, respectively). Cardiac hypertrophy induced by Ang II was significantly attenuated in TNF-alpha(-/-) mice compared with wild-type mice. In a group of TNF-alpha(-/-) mice, when replacement therapy was made with recombinant TNF-alpha, Ang II induced similar responses in salt appetite, mean arterial pressure, and cardiac hypertrophy, as observed in wild-type mice. These results suggest that TNF-alpha plays a mechanistic role in mediating chronic Ang II-induced effects on salt appetite and blood pressure, as well as on cardiac hypertrophy.

Intestinal intraepithelial lymphocyte derived angiotensin converting enzyme modulates epithelial cell apoptosis

BACKGROUND & AIMS

Intestinal adaptation in short bowel syndrome (SBS) consists of increased epithelial cell (EC) proliferation as well as apoptosis. Previous microarray analyses of intraepithelial lymphocytes (IEL) gene expression after SBS showed an increased expression of angiotensin converting enzyme (ACE). Because ACE has been shown to promote alveolar EC apoptosis, we examined if IEL-derived ACE plays a role in intestinal EC apoptosis.

METHODS

Mice underwent either a 70% mid-intestinal resection (SBS group) or a transection (Sham group) and were studied at 7 days. ACE expression was measured, and ACE inhibition (ACE-I, enalaprilat) was used to assess ACE function.

RESULTS

IEL-derived ACE was significantly elevated in SBS mice. The addition of an ACE-I to SBS mice resulted in a significant decline in EC apoptosis. To address a possible mechanism, tumor necrosis factor alpha (TNF-alpha) mRNA expression was measured. TNF-alpha was significantly increased in SBS mice, and decreased with ACE-I. Interestingly, ACE-I was not able to decrease EC apoptosis in TNF-alpha knockout mice.

CONCLUSIONS

This study shows a previously undescribed expression of ACE by IEL. SBS was associated with an increase in IEL-derived ACE. ACE appears to be associated with an up-regulation of intestinal EC apoptosis. ACE-I significantly decreased EC apoptosis.

The role of angiotensin II type 1 receptor blockers in the prevention and management of diabetes mellitus

Angiotensin II Receptor blockers (ARBs) are an important addition to the current range of medications available for treating a wide spectrum of diseases including cardiovascular diseases. Coronary heart disease (CHD) is the most common cause of death in the United Kingdom and worldwide. More importantly, the presence of the metabolic syndrome and the likelihood of diabetes mellitus taking on epidemic proportions in the years to come all threaten to maintain the mortality rate due to CHD. This review article focuses on the clinical studies that have helped define the trends in the usage of these agents in the prevention and treatment of diabetes mellitus and its complications and also explores possible mechanisms of action and future developments.

The effect of angiotensin receptor blockers for preventing atrial fibrillation

Atrial fibrillation is the most common sustained cardiac arrhythmia in clinical practice, and causes significant burden to patients and health care systems. Clinicians treat existing atrial fibrillation with anticoagulation and/or drugs that utilize either a rate or rhythm control strategy. It remains unclear how best to reduce cardiovascular morbidity and mortality in this population. Prevention of atrial fibrillation using angiotensin receptor blockers, which affect ion currents and refractoriness in atrial myocytes, regress or prevent atrial fibrosis, decrease left atrial size, regress left ventricular hypertrophy, modulate sympathetic nerve activity, reduce inflammation, and reduce blood pressure, may become an important and desirable alternative.

Immunopathogenesis of hepatitis C virus infection and hepatic fibrosis: New insights into antifibrotic therapy in chronic hepatitis C

Fibrosis and cirrhosis represent the consequences of a sustained wound-healing response to chronic liver injury of any cause. Chronic hepatitis C virus (HCV) has emerged as a leading cause of cirrhosis in the USA and throughout the world. HCV may induce fibrogenesis directly by hepatic stellate cell activation or indirectly by promoting oxidative stress and apoptosis of infected cells. The ultimate result of chronic HCV injury is the accumulation of extracellular matrix with high density type I collagen within the subendothelial space of Disse, culminating in cirrhosis with hepatocellular dysfunction. The treatment of hepatitis C with the combination of pegylated interferon and ribavirin is still both problematic and costly, has suboptimal efficacy, serious side effects and a high level of intolerance, and is contraindicated in many patients. Hence, new approaches have assumed greater importance, for which there is an urgent need. The sustained progress in understanding the pathophysiology of hepatic fibrosis in the past two decades has increased the possibility of developing drugs specifically targeting the fibrogenic process. Future efforts should identify genetic markers associated with fibrosis risk in order to tailor the treatment of HCV infection based on genetically regulated pathways of injury and/or fibrosis. Such advances will expand the arsenal to overcome liver fibrosis, particularly in patients with hepatic diseases who have limited treatment options, such as those patients with chronic hepatitis C who have a high risk of fibrosis progression and recurrent HCV disease after liver transplantation.