Evidence for direct local effect of angiotensin in vascular hypertrophy. In vivo gene transfer of angiotensin converting enzyme

Current understanding of the link between angiotensin-converting enzyme and pain perception

The renin-angiotensin system (RAS) is known to affect diverse physiological processes that affect the functioning of many key organs. Angiotensin-converting enzyme (ACE) modulates a variety of bioactive peptides associated with pain. ACE inhibitors (ACEis) have found applications in the treatment of cardiovascular, kidney, neurological and metabolic disorders. However, ACEis also tend to display undesirable effects, resulting in increased pain sensitization and mechanical allodynia. In this review, we provide comprehensive discussion of preclinical and clinical studies involving the evaluation of various clinically approved ACEis. With the emerging knowledge of additional factors involved in RAS signaling and the indistinct pharmacological role of ACE substrates in pain, extensive studies are still required to elucidate the mechanistic role of ACE in pain perception.

Rodent models of hypertension

Elevated blood pressure (BP), or hypertension, is the main risk factor for cardiovascular disease. As a multifactorial and systemic disease that involves multiple organs and systems, hypertension remains a challenging disease to study. Models of hypertension are invaluable to support the discovery of the specific genetic, cellular and molecular mechanisms underlying essential hypertension, as well as to test new possible treatments to lower BP. Rodent models have proven to be an invaluable tool for advancing the field. In this review, we discuss the strengths and weaknesses of rodent models of hypertension through a systems approach. We highlight the ways how target organs and systems including the kidneys, vasculature, the sympathetic nervous system (SNS), immune system and the gut microbiota influence BP in each rodent model. We also discuss often overlooked hypertensive conditions such as pulmonary hypertension and hypertensive-pregnancy disorders, providing an important resource for researchers.

Vasculopathy and Coagulopathy Associated with SARS-CoV-2 Infection

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has resulted in > 500,000 deaths worldwide, including > 125,000 deaths in the U.S. since its emergence in late December 2019 and June 2020. Neither curative anti-viral drugs nor a protective vaccine is currently available for the treatment and prevention of COVID-19. Recently, new clinical syndromes associated with coagulopathy and vasculopathy have emerged as a cause of sudden death and other serious clinical manifestations in younger patients infected with SARS-CoV-2 infection. Angiotensin converting enzyme 2 (ACE2), the receptor for SARS-CoV-2 and other coronaviruses, is a transmembrane protein expressed by lung alveolar epithelial cells, enterocytes, and vascular endothelial cells, whose physiologic role is to induce the maturation of angiotensin I to generate angiotensin 1-7, a peptide hormone that controls vasoconstriction and blood pressure. In this review, we provide the general context of the molecular and cellular mechanisms of SARS-CoV-2 infection with a focus on endothelial cells, describe the vasculopathy and coagulopathy syndromes in patients with SARS-CoV-2, and outline current understanding of the underlying mechanistic aspects.

Bioenergetic shift and actin cytoskeleton remodelling as acute vascular adaptive mechanisms to angiotensin II in murine retina and ophthalmic artery

Ocular vascular dysfunction is a major contributing factor to the pathogenesis of glaucoma. In recent years, there has been a renewed interest in the role of angiotensin II (Ang II) in mediating the disease progression. Despite its (patho)physiological importance, the molecular mechanisms underlying Ang II-mediated oxidative stress remain largely unexplored in the ocular vasculature. Here, we provide the first direct evidence of the alterations of proteome and signalling pathways underlying Ang II-elicited oxidative insult independent of arterial pressure changes in the ophthalmic artery (OA) and retina (R) employing an in vitro experimental model. Both R and OA were isolated from male C57Bl/6J mice (n = 15/group; n = 5/biological replicate) and incubated overnight in medium containing either vehicle or Ang II (0.1 μM) at physiological conditions. Label-free quantitative mass spectrometry (MS)-based proteomics analysis identified a differential expression of 107 and 34 proteins in the R and OA, respectively. Statistical and bioinformatics analyses revealed that protein clusters involved in actin cytoskeleton and integrin-linked kinase signalling were significantly activated in the OA. Conversely, a large majority of differentially expressed retinal proteins were involved in dysregulation of numerous energy-producing and metabolic signalling pathways, hinting to a possible shift in retinal cell bioenergetics. Particularly, Ang II-mediated downregulation of septin-7 (Sept7; p < 0.01) and superoxide dismutase [Cu-Zn] (Sod1; p < 0.05), and upregulation of troponin T, fast skeletal muscle (Tnnt3; p < 0.05) and tropomyosin alpha-3 chain (Tpm3; p < 0.01) in the OA, and significant decreased expressions of two crystallin proteins (Cryab; p < 0.05 and Crybb2; p < 0.0001) in the R were verified at the mRNA level, corroborating our proteomics findings. In summary, these results demonstrated that exogenous application of Ang II over an acute time period caused impairment of retinal bioenergetics and cellular demise, and actin cytoskeleton-mediated vascular remodelling in the OA.

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Acute Ang II stimulation elicits oxidative stress in ocular vasculature without pressor effect. .

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Dysregulation of energy-producing and metabolic pathways are implicated in the retina. .

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Actin cytoskeleton remodelling are vascular adaptation processes in the ophthalmic artery. .

Relationship of the rs1799752 polymorphism of the angiotensin-converting enzyme gene and the rs699 polymorphism of the angiotensinogen gene to the process of in-stent restenosis in a population of Polish patients with stable coronary artery disease

PURPOSE

The renin-angiotensin-aldosterone system may influence in-stent restenosis (ISR) via angiotensin II, which stimulates the production of growth factors for smooth muscle cells. The aim of this work is to assess the influence of the rs1799752 polymorphism of the angiotensin-converting enzyme (ACE) gene and the rs699 polymorphism of the angiotensinogen (AGT) gene on the ISR in Polish patients with stable coronary artery disease (SCAD) who underwent stent implantation.

MATERIAL/METHODS

Two hundred and sixty-five patients with SCAD were included in the study. All patients underwent stent implantation upon admission to the hospital and had subsequent coronary angiography performed. The patients were divided into two groups - those with significant ISR (n=53) and those without ISR (n=212). The ACE polymorphism was assessed using the classical PCR method and the AGT polymorphism was determined using the TaqMan method for SNP genotyping.

RESULTS

No difference in the frequency of angiographically significant ISR occurrence associated with the different ACE and AGT gene polymorphisms was observed. In a multivariable analysis, after correction for clinical variables, the relationship between the ACE and AGT genotypes within the scope of the analyzed polymorphisms and the process of restenosis was not found using a dominant, recessive and log-additive model. Late lumen loss was also independent of the genotypes of the polymorphisms before and after correction with angiographic variables.

CONCLUSIONS

The rs1799752 polymorphism and the rs699 polymorphism had no relationship with the occurrence of angiographically significant ISR and late lumen loss in a group of Polish patients who underwent metal stent implantation.

Post-translational modifications regulate class IIa histone deacetylase (HDAC) function in health and disease

Class IIa histone deacetylases (HDACs4, -5, -7, and -9) modulate the physiology of the human cardiovascular, musculoskeletal, nervous, and immune systems. The regulatory capacity of this family of enzymes stems from their ability to shuttle between nuclear and cytoplasmic compartments in response to signal-driven post-translational modification. Here, we review the current knowledge of modifications that control spatial and temporal histone deacetylase functions by regulating subcellular localization, transcriptional functions, and cell cycle-dependent activity, ultimately impacting on human disease. We discuss the contribution of these modifications to cardiac and vascular hypertrophy, myoblast differentiation, neuronal cell survival, and neurodegenerative disorders.

Angiotensin-converting enzyme gene polymorphism and middle cerebral artery stenosis in a Chinese Han population

The angiotensin-converting enzyme gene is a candidate gene of stroke. The present study involved 62 healthy volunteers and 148 patients with middle cerebral artery stenosis as confirmed by brain color ultrasound from a Han population in North China, and determined the peripheral blood angiotensin-converting enzyme genotype using PCR-restriction fragment length polymorphism analysis. The results showed that the frequencies of the DD genotype and D allele were increased in patients with middle cerebral artery stenosis, but the difference was not statistically significant compared with healthy controls. The findings of this study on the relationship between stroke genes and middle cerebral artery stenosis indicate no significant correlation between the frequencies of the DD genotype and D allele of angiotensin-converting enzyme and middle cerebral artery stenosis in this Han population from North China. In the future, studies will be carried out to investigate correlations between multiple stroke candidate gene synergy and middle cerebral artery stenosis to provide a foundation for the development of gene therapy.

The contribution of vascular smooth muscle to aortic stiffness across length scales

The operation of the cardiovascular system in health and disease is inherently mechanical. Clinically, aortic stiffness has proven to be of critical importance as an early biomarker for subsequent cardiovascular disease; however, the mechanisms involved in aortic stiffening are still unclear. The etiology of aortic stiffening with age has been thought to primarily involve changes in extracellular matrix protein composition and quantity, but recent studies suggest a significant involvement of the differentiated contractile vascular smooth muscle cells in the vessel wall. Here, we provide an overview of vascular physiology and biomechanics at different spatial scales. The processes involved in aortic stiffening are examined with particular attention given to recent discoveries regarding the role of vascular smooth muscle.

Association between angiotensin converting enzyme gene insertion/deletion polymorphism and ischemic stroke in north Indian population: a case-control study and meta-analysis

OBJECTIVE

The purpose of this case-control study was to determine the relationship between angiotensin converting enzyme (ACE) insertion/deletion polymorphism and serum ACE level in north Indian patients with ischemic stroke.

METHODS

In the present study, 224 ischemic stroke patients and 224 age- and sex-matched control participants were recruited. Genotyping was performed using polymerase chain reaction (PCR) method. Serum ACE levels were measured by colorimetric method. Our results were integrated with other reported studies from India for a meta-analysis.

RESULTS

We observed that DD genotypes were more frequently distributed in cases (32·6%) compared with controls (26·8%). Borderline significance was observed between DD genotype and risk of small vessel disease (SVD) stroke as compared to controls (OR, 1·9; 95% CI, 0·88-4·4; P value 0·09) assuming dominant model of inheritance. The mean ACE serum level in IU/l for II, ID, and DD genotypes were 17·1 ± 7·7, 26 ± 12·4, and 51·3 ± 21 (P value < 0·001) in cases and 16·5 ± 9·4, 26·8 ± 13, and 45·19 ± 18·3 (P value < 0·001) in controls, respectively.

DISCUSSION

The results of the study show lack of significant association between ACE insertion/deletion polymorphism and ischemic stroke, however, higher risk was observed with DD genotype in small vessel disease stroke, but with borderline significance. Meta-analysis of studies from India showed that DD genotype is associated with risk of ischemic stroke.

Angiotensin-converting enzyme-induced activation of local angiotensin signaling is required for ascending aortic aneurysms in fibulin-4-deficient mice

Aortic aneurysms are life-threatening and often associated with defects in connective tissues and mutations in smooth muscle cell (SMC) contractile proteins. Despite recent advances in understanding altered signaling in aneurysms of Marfan syndrome, the underlying mechanisms and options for pharmacological treatment for other forms of aneurysms are still under investigation. We previously showed in mice that deficiency in the fibulin-4 gene in vascular SMCs (Fbln4(SMKO)) leads to loss of the SMC contractile phenotype, hyperproliferation, and ascending aortic aneurysms. We report that abnormal up-regulation of angiotensin-converting enzyme (ACE) in SMCs and subsequent activation of angiotensin II (AngII) signaling are involved in the onset of aortic aneurysms in Fbln4(SMKO) mice. In this model, aneurysm formation was completely prevented by inhibition of the AngII pathway with losartan or captopril within a narrow therapeutic window during the first month of life, even though the altered mechanical properties of blood vessel walls were not reversed by the pharmacological treatment. The therapeutic effects of losartan in Fbln4(SMKO) mice do not require the AngII receptor type 2 (Agtr2) but likely require both type 1a (Agtr1a) and 1b (Agtr1b) receptors. The results indicate that fibulin-4 is a vascular matrix component required for regulation of local angiotensin signaling and development and maintenance of the SMC phenotype.

Nanoparticle drug- and gene-eluting stents for the prevention and treatment of coronary restenosis

Percutaneous coronary intervention (PCI) has become the most common revascularization procedure for coronary artery disease. The use of stents has reduced the rate of restenosis by preventing elastic recoil and negative remodeling. However, in-stent restenosis remains one of the major drawbacks of this procedure. Drug-eluting stents (DESs) have proven to be effective in reducing the risk of late restenosis, but the use of currently marketed DESs presents safety concerns, including the non-specificity of therapeutics, incomplete endothelialization leading to late thrombosis, the need for long-term anti-platelet agents, and local hypersensitivity to polymer delivery matrices. In addition, the current DESs lack the capacity for adjustment of the drug dose and release kinetics appropriate to the disease status of the treated vessel. The development of efficacious therapeutic strategies to prevent and inhibit restenosis after PCI is critical for the treatment of coronary artery disease. The administration of drugs using biodegradable polymer nanoparticles as carriers has generated immense interest due to their excellent biocompatibility and ability to facilitate prolonged drug release. Despite the potential benefits of nanoparticles as smart drug delivery and diagnostic systems, much research is still required to evaluate potential toxicity issues related to the chemical properties of nanoparticle materials, as well as to their size and shape. This review describes the molecular mechanism of coronary restenosis, the use of DESs, and progress in nanoparticle drug- or gene-eluting stents for the prevention and treatment of coronary restenosis.

Influence of the angiotensin converting enzyme insertion or deletion genetic variant and coronary restenosis risk: evidence based on 11,193 subjects

The insertion/deletion (I/D) polymorphism of the gene encoding angiotensin converting enzyme is a controversial risk factor for restenosis after percutaneous transluminal coronary angioplasties (PTCA) in patients. Genetic association studies can be problematic to reproduce due to insufficient power, phenotypic heterogeneity, population stratification, small effect of the variant and even publication biases. To derive a more precise estimation of the relationship as well as to quantify the between-study heterogeneity and potential bias, a meta-analysis including 11,193 patients from 33 published cohort studies was performed. In a combined analysis, the summary per-allele odds ratio for restenosis was 1.31 (95% CI: 1.08-1.58, P = 0.006), and 1.22 (95% CI: 0.95-1.56, P = 0.12), for PTCA-stent and PTCA-balloon, respectively. In the subgroup analysis by ethnicity, significantly increased restenosis risks after PTCA-stent were found in Asians for the polymorphism; whereas no significant associations were found among Caucasians. As for restenosis risks after PTCA-balloon, no evidence of any gene-disease association was obtained in the stratified analyses according to ethnicity and study size. In conclusion, this meta-analysis demonstrated that the DD homozygous of ACE I/D polymorphism was significantly associated with elevated restenosis susceptibility after PTCA-stent among Asian populations.

Angiotensin-converting enzyme insertion/deletion polymorphism contributes to ischemic stroke risk: a meta-analysis of 50 case-control studies

Background

Many studies have investigated the association between the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and risk of ischemic stroke. However, the evidence is inadequate to draw robust conclusions because most studies were generally small and conducted in heterogeneous populations. To shed light on these inconclusive findings, we conducted a large meta-analysis of studies relating the ACE I/D polymorphism to the risk of ischemic stroke.

Methods

Relevant studies were identified by searching PubMed and Embase through February 2012 and by reviewing the references of retrieved articles. We included studies that reported odds ratio (OR) with 95% confidence interval (CI) for the association between this polymorphism and ischemic stroke risk.

Results

Fifty independent publications, with 10 070 stroke cases and 22 103 controls, were included. The results indicated that the DD homozygote carriers had a 37% higher risk of ischemic stroke when compared with the homozygotes II and heterozygote ID [odds ratio (OR) = 1.37, 95% confidence interval (CI): 1.22–1.53]. Subgroup analyses indicated that this higher risk was more pronounced among Asians, hospital-based studies, and small vessel disease (SVD). Potential publication bias may exist, but correction for this bias using a formal statistical method did not materially alter the combined risk estimate.

Conclusion

The results of our meta-analysis indicate that the D allele of ACE I/D polymorphism is a low-penetrance susceptibility marker of ischemic stroke.

Early Changes in Vascular Dynamics in Relation to Twin-Twin Transfusion Syndrome

Aclearer understanding of the early determinants of normal and abnormal vascular development is pivotal in order to identify those at increased risk of later vascular disease, and perhaps to prevent it by early intervention. Measurement of pulse wave velocity(PWV) has been used in the postnatal evaluation of the monochorionic(MC) twins. They are genetically identical and those with twin-twin transfusion syndrome(TTTS) provide an ideal natural model in whom to study the influence of differing haemodynamic stresses on the developing vascular tree. We investigated firstly whether surviving twin pairs with TTTS have altered arterial distensibility in childhood by comparing PWV in the radial arteries of surviving MC twin pairs with TTTS and in two control groups, one cohort of MC twins without TTTS and another dichorionic group (DC) Secondly, we tested a cohort of TTTS twin pair survivors treated with laser photocoagulation. The co-twin pairs in the group managed palliatively with amnioreduction showed increased PWV in the donor and reduced PWV in the recipient twins. This was neither seen in the laser-treated, nor in the control groups. Our studies suggest that a period of haemodynamic imbalance gives rise to changes in a muscular conduit artery that persist at least into infancy and it seems that by correcting the abnormal haemodynamics relatively soon after the disease process had begun, the alterations in elasticity are prevented. These studies are the first to demonstrate fetal programming of the vascular bed in humans, and prevention or reversal of this programming by an intervention in mid-gestation.

Do all antihypertensive drugs improve carotid intima-media thickness? A network meta-analysis of randomized controlled trials

The many clinical trials investigating the effect of various antihypertensive drugs on carotid intima-media thickness (CIMT) produced conflicting results. We used meta-analysis to evaluate CIMT changes and network meta-analysis to rank drugs according to the magnitude of these changes. We identified 31 randomized controlled trials listed in three databases as of January 2008. Using a random-effects model, we found a significant CIMT decrease with antihypertensive drugs compared to placebo (-0.10 [-0.16; -0.04]). Overall effect sizes vs. placebo were significant for angiotensin-converting enzyme (ACE) inhibitors (-0.08 [-0.14; -0.02]), and a trend was found for beta-blockers (-0.09 [-0.19; 0.01]). The data did not allow other direct comparisons vs. placebo. Significant benefits were found for calcium-channel blockers (CCBs) compared to both ACE inhibitors (0.37 [0.20; 0.54]), as well as for angiotensin II receptor blockers (ARBs) compared to beta-blockers (0.42 [0.29; 0.55]). Diuretics were less efficient than CCBs (-0.09 [-0.16; -0.02]). Indirect comparisons with network meta-analysis showed significant effects of CCBs and ARBs vs. placebo (both P < 0.05) and vs. diuretics (both P < 0.001). The CIMT decrease with ACE inhibitors and beta-blockers was greater than with diuretics (both P < 0.05) but was not different from the placebo effect. In subgroup analyses, significant benefits occurred with lower baseline CIMT values and shorter treatment durations but were unrelated to the size of the blood pressure decrease. In conclusion, among antihypertensive drugs, CCBs and ARBs have the greatest effect on CIMT.

Gender association of the angiotensin-converting enzyme gene with ischaemic stroke

We examined the association of the NG011648 polymorphism (insertion/deletion) of the angiotensin-converting enzyme (ACE) gene with ischaemic stroke occurrence, subtype of ischaemic stroke and ischaemic stroke patients’ gender. Patients with first ever ischaemic stroke were recruited prospectively in a period of 18 months. Controls were matched with the patients for age, gender, and known risk factors for stroke. Demographic data, medical history, and vascular risk factors were collected. Genotypes were determined by polymerase chain reaction (PCR) and restriction enzyme analysis. Stroke and control groups were compared in regard to the prevalence of the NG011648 polymorphism. One hundred and seventy-six patients with ischaemic stroke and 178 controls were recruited and genotyped for NG011648 polymorphism (I/D) of the ACE gene. No significant difference in allele and genotype distributions emerged between control and patient groups, nor in the two subtype groups of lacunars and large artery atherosclerosis. After the data were stratified by gender, a low incidence of II homozygosity in female patients versus female controls ( p = 0.05) and male patients ( p = 0.013, Z score: -2.49) was found. Our results indicate that I/D polymorphisms may have a role in stroke onset, in respect to gender, with a possible favourable effect of II genotype in females.

Review: Stem cells and gene therapy

Both stem cell and gene therapy research are currently the focus of intense research in institutions and companies around the world. Both approaches hold great promise by offering radical new and successful ways of treating debilitating and incurable diseases effectively. Gene therapy is an approach to treat, cure, or ultimately prevent disease by changing the pattern of gene expression. It is mostly experimental, but a number of clinical human trials have already been conducted. Gene therapy can be targeted to somatic or germ cells; the most common vectors are viruses. Scientists manipulate the viral genome and thus introduce therapeutic genes to the target organ. Viruses, in this context, can cause adverse events such as toxicity, immune and inflammatory responses, as well as gene control and targeting issues. Alternative modalities being considered are complexes of DNA with lipids and proteins. Stem cells are primitive cells that have the capacity to self renew as well as to differentiate into 1 or more mature cell types. Pluripotent embryonic stem cells derived from the inner cell mass can develop into more than 200 different cells and differentiate into cells of the 3 germ cell layers. Because of their capacity of unlimited expansion and pluripotency, they are useful in regenerative medicine. Tissue or adult stem cells produce cells specific to the tissue in which they are found. They are relatively unspecialized and predetermined to give rise to specific cell types when they differentiate. The current review provides a summary of our current knowledge of stem cells and gene therapy as well as their clinical implications and related therapeutic options.

AT1 receptor induced alterations in histone H2A reveal novel insights into GPCR control of chromatin remodeling

Chronic activation of angiotensin II (AngII) type 1 receptor (AT(1)R), a prototypical G protein-coupled receptor (GPCR) induces gene regulatory stress which is responsible for phenotypic modulation of target cells. The AT(1)R-selective drugs reverse the gene regulatory stress in various cardiovascular diseases. However, the molecular mechanisms are not clear. We speculate that activation states of AT(1)R modify the composition of histone isoforms and post-translational modifications (PTM), thereby alter the structure-function dynamics of chromatin. We combined total histone isolation, FPLC separation, and mass spectrometry techniques to analyze histone H2A in HEK293 cells with and without AT(1)R activation. We have identified eight isoforms: H2AA, H2AG, H2AM, H2AO, H2AQ, Q96QV6, H2AC and H2AL. The isoforms, H2AA, H2AC and H2AQ were methylated and H2AC was phosphorylated. The relative abundance of specific H2A isoforms and PTMs were further analyzed in relationship to the activation states of AT(1)R by immunochemical studies. Within 2 hr, the isoforms, H2AA/O exchanged with H2AM. The monomethylated H2AC increased rapidly and the phosphorylated H2AC decreased, thus suggesting that enhanced H2AC methylation is coupled to Ser1p dephosphorylation. We show that H2A125Kme1 promotes interaction with the heterochromatin associated protein, HP1α. These specific changes in H2A are reversed by treatment with the AT(1)R specific inhibitor losartan. Our analysis provides a first step towards an awareness of histone code regulation by GPCRs.

Genetic variation in the renin-angiotensin system and arterial stiffness. The Rotterdam Study

We studied the associations of three renin-angiotensin system polymorphisms, angiotensin-converting enzyme (ACE) I/D, angiotensinogen 235 M/T, and angiotensin II receptor type I 573 C/T, with arterial stiffness. The study was embedded in the Rotterdam Study, a population-based study older adults. The association of the polymorphisms with pulse wave velocity, the carotid distensibility, and pulse pressure was investigated in 3706 subjects. We found no association of the ACE I/D polymorphism with pulse wave velocity, but the D-allele was associated with a lower distensibility coefficient (p = 0.05) and higher pulse pressure (p = 0.01). For the angiotensinogen 235 M/T polymorphism, no significant associations with either pulse wave velocity (p = 0.71), the distensibility coefficient (p = 0.16) or pulse pressure (p = 0.34) were found. Also, we found no significant associations of pulse wave velocity (PWV) (p = 0.32), the distensibility coefficient (p = 0.08), and pulse pressure (p = 0.09) with the angiotensin II receptor type 1 573 C/T polymorphism. No epistatic effects were observed between the three renin-angiotensin system (RAS) genes with arterial stiffness. Our findings suggest that genetic variation in the renin-angiotensin system may play a role in determining carotid distensibility and pulse pressure.

Cell signaling, internalization, and nuclear localization of the angiotensin converting enzyme in smooth muscle and endothelial cells

The angiotensin converting enzyme (ACE) catalyzes the extracellular formation of angiotensin II, and degradation of bradykinin, thus regulating blood pressure and renal handling of electrolytes. We have previously shown that exogenously added ACE elicited transcriptional regulation independent of its enzymatic activity. Because transcriptional regulation generates from protein-DNA interactions within the cell nucleus we have investigated the initial cellular response to exogenous ACE and the putative internalization of the enzyme in smooth muscle cells (SMC) and endothelial cells (EC). The following phenomena were observed when ACE was added to cells in culture: 1) it bound to SMC and EC with high affinity (K(d) = 361.5 +/- 60.5 pM) and with a low binding occupancy (B(max) = 335.0 +/- 14.0 molecules/cell); 2) it triggered cellular signaling resulting in late activation of focal adhesion kinase and SHP2; 3) it modulated platelet-derived growth factor receptor-beta signaling; 4) it was endocytosed by SMC and EC; and 5) it transited through the early endosome, partially occupied the late endosome and the lysosome, and was localized to the nuclei. The incorporation of ACE or a fragment of it into the nuclei reached saturation at 120 min, and was preceded by a lag time of 40 min. Internalized ACE was partially cleaved into small fragments. These results revealed that extracellular ACE modulated cell signaling properties, and that SMC and EC have a pathway for delivery of extracellular ACE to the nucleus, most likely involving cell surface receptor(s) and requiring transit through late endosome/lysosome compartments.

Angiotensin II, mechanotransduction, and pulsatile arterial hemodynamics in hypertension

The aortic blood pressure curve involves two components: a steady component, the mean arterial pressure (MAP), which is dependent on cardiac output and vascular resistance, and a pulsatile component pulse pressure (PP), which is dependent on arterial stiffness and pulse wave reflections. The transduction mechanisms of MAP and PP differ markedly, involving focal adhesion kinase for MAP and oxygen free radicals for PP. Angiotensin II (ANG II) and its blockade are associated with changed vascular resistance and MAP; however, their effects on PP (peripheral and mostly central PP) have been inadequately investigated. In hypertensive rats, when compared with their normotensive controls, ANG II blockade normalizes central PP (<50 mmHg) but not MAP when the same drug dosage is used for each. In hypertensive patients, ANG II blockade reduces arterial stiffness and pulse wave reflections, but with the same reduction in MAP, there is a greater reduction in central than peripheral PP, thereby increasing carotid-brachial PP amplification. With long-term ANG II blockade, the hypertensive arteriolar hypertrophy observed at baseline is corrected in association with reduced arteriolar reflection coefficients, reduced carotid arterial attachments linking alpha(5)-integrin to its ligand fibronectin, and decreased circulating C-reactive protein. When given a normal salt diet, each of these factors contributes separately in reducing arterial stiffness and wave reflections. These responses disappear with a high-salt diet, a condition that usually involves the activation of the local vascular renin-angiotensin-aldosterone system and can be prevented by its selective blockade. Thus ANG II inhibition seems to contribute independently in reducing central PP and aortic stiffness.

Clinical achievements of impedance analysis

Various models and derived measures of arterial function have been proposed to describe and quantify pulsatile hemodynamics in humans. A major distinction can be drawn between lumped models based on circuit theory that assume infinite pulse wave velocity versus distributed, propagative models based on transmission line theory that acknowledge finite wave velocity and account for delays, wave reflection, and spatial and temporal pressure gradients within the arterial system. Although both approaches have produced useful insights into human arterial pathophysiology, there are important limitations of the lumped approach. The arterial system is heterogeneous and various segments respond differently to cardiovascular disease risk factors including advancing age. Lumping divergent change into aggregate summary variables can obscure abnormalities in regional arterial function. Analysis of a limited number of summary variables obtained by measuring aortic input impedance may provide novel insights and inform development of new treatments aimed at preventing or reversing abnormal pulsatile hemodynamics.

Angiotensin-converting enzyme and vascular remodeling

Vascular remodeling is the result of a close interplay of changes in vascular tone and structure. In this review, the role of angiotension-converting enzyme (ACE) and the impact of ACE inhibition on vascular remodeling processes during vascular injury and restenosis, hypertension, atherosclerosis, and aneurysm formation are discussed. The role of ACE and angiotensin II (Ang II) in neointimal thickening has been firmly established by animal studies and is mediated by Ang II type 1 (AT(1)) receptor signaling events via monocyte chemoattractant protein-1 and NAD(P)H oxidase. ACE and Ang II are involved in the remodeling of large and resistance arteries during hypertension; here, cell proliferation and matrix remodeling are also regulated by signaling events downstream of the AT(1) receptor. In atherosclerosis, Ang II is involved in the inflammatory and tissue response, mediated by various signaling pathways downstream of the AT(1) receptor. Although ACE inhibition has been shown to inhibit atherosclerotic processes in experimental animal models, results of large clinical trials with ACE inhibitors were not conclusive. Remodeling of vessel dimensions and structure during aneurysm formation is counteracted by ACE inhibition. Here, a direct effect of ACE inhibitors on matrix metalloproteinase activity has to be considered as part of the working mechanism. The role of ACE2 in vascular remodeling has yet to be established; however, ACE2 has been shown to be associated with vascular changes in hypertension and atherosclerosis.

Role of the T cell in the genesis of angiotensin II induced hypertension and vascular dysfunction

Hypertension promotes atherosclerosis and is a major source of morbidity and mortality. We show that mice lacking T and B cells (RAG-1^−/− mice) have blunted hypertension and do not develop abnormalities of vascular function during angiotensin II infusion or desoxycorticosterone acetate (DOCA)–salt. Adoptive transfer of T, but not B, cells restored these abnormalities. Angiotensin II is known to stimulate reactive oxygen species production via the nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase in several cells, including some immune cells. Accordingly, adoptive transfer of T cells lacking the angiotensin type I receptor or a functional NADPH oxidase resulted in blunted angiotensin II–dependent hypertension and decreased aortic superoxide production. Angiotensin II increased T cell markers of activation and tissue homing in wild-type, but not NADPH oxidase–deficient, mice. Angiotensin II markedly increased T cells in the perivascular adipose tissue (periadventitial fat) and, to a lesser extent the adventitia. These cells expressed high levels of CC chemokine receptor 5 and were commonly double negative (CD3⁺CD4⁻CD8⁻). This infiltration was associated with an increase in intercellular adhesion molecule-1 and RANTES in the aorta. Hypertension also increased T lymphocyte production of tumor necrosis factor (TNF) α, and treatment with the TNFα antagonist etanercept prevented the hypertension and increase in vascular superoxide caused by angiotensin II. These studies identify a previously undefined role for T cells in the genesis of hypertension and support a role of inflammation in the basis of this prevalent disease. T cells might represent a novel therapeutic target for the treatment of high blood pressure.

Angiotensin II stimulates protein kinase D-dependent histone deacetylase 5 phosphorylation and nuclear export leading to vascular smooth muscle cell hypertrophy

BACKGROUND

Angiotensin II (Ang II) induces the phenotypic modulation and hypertrophy of vascular smooth muscle cells (VSMCs), which is implicated in the pathogenesis of hypertension, atherosclerosis, and diabetes. In this study, we tested the hypothesis that histone deacetylases 5 (HDAC5) and its signal pathway play a role in Ang II-induced VSMC hypertrophy.

METHODS AND RESULTS

VSMCs were isolated from the thoracic aortas of male Sprague-Dawley rats and treated with Ang II. We found that Ang II rapidly stimulated phosphorylation of HDAC5 at Serine259/498 residues in a time- and dose- dependent manner. Ang II receptor-1, protein kinase C, and protein kinase D1 (PKD1) mediated HDAC5 phosphorylation. Furthermore, we observed that Ang II stimulated HDAC5 nuclear export, which was dependent on its PKD1-dependent phosphorylation. Consequently, both inhibiting PKD1 and HDAC5 Serine259/498 to Alanine mutant significantly attenuated Ang II-induced myocyte enhancer factor-2 (MEF2) transcriptional activity and protein synthesis in VSMCs.

CONCLUSION

These findings demonstrate for the first time that PKD1-dependent HDAC5 phosphorylation and nuclear export mediates Ang II-induced MEF2 activation and VSMC hypertrophy, and suggest that PKD1 and HDAC5 may emerge as potential targets for the treatment of pathological vascular hypertrophy.

Angiotensin-Converting Enzyme Genotype Interacts With Systolic Blood Pressure to Determine Coronary Heart Disease Risk in Healthy Middle-Aged Men

The impact of the ACE I/D polymorphism on coronary heart disease (CHD) risk is modest at most, however it may act as a modifier gene. ACE genotype was determined in 2711 healthy middle-aged men (mean age 56 years) followed for 15 years. No genotype-CHD risk association was found, but when analyzed by quartiles of systolic blood pressure (SBP), compared with II homozygotes, carriage of each additional D allele was protective at lower SBP, but in the highest quartile (SBP >150 mm Hg) conferred almost 1.5 times the risk for CHD (genotype interaction P=0.003). When SBP was analyzed as a continuous variable, again a highly significant association was seen, with the hazard ratio ([95% CI]) for a 1 SD increase in SBP being 0.90 [0.70 to 1.15] for IIs and 1.40 [1.21 to 1.61] for ID/DD (genotype SBP interaction P=0.002). The D allele was protective against CHD at lower SBP but would overtake the II risk at higher SBP. In hypertension, the proinflammatory or prohypertrophic properties of angiotensin II may explain this association. The LPL S447X polymorphism also impacts on CHD risk through interaction with hypertension, and there was an additive action of these 2 polymorphisms and SBP on CHD risk (hazard ratio for 1 SD increase in SBP for combined genotypes 1.78 [1.30 to 2.45]). Thus in the presence of hypertension, common variation in "modifier" genes confers significant CHD risk.

Nanoparticulate carriers for the treatment of coronary restenosis

The current treatment for coronary restenosis following balloon angioplasty involves the use of a mechanical or a drug-eluting stent. Despite the high usage of commercially-available drug-eluting stents in the cardiac field, there are a number of limitations. This review will present the background ofrestenosis, go briefly into the molecular and cellular mechanisms of restenosis, the use of mechanical stents in coronary restenosis, and will provide an overview of the drugs and genes tested to treat restenosis. The primary focus of this article is to present a comprehensive overview on the use of nanoparticulate delivery systems in the treatment of restenosis both in-vitro and in-vivo. Nanocarriers have been tested in a variety of animal models and in human clinical trials with favorable results. Polymer-based nanoparticles, liposomes, and micelles will be discussed, in addition to the findings presented in the field of cardiovascular drug targeting. Nanocarrier-based delivery presents a viable alternative to the current stent based therapies.

Long-term trandolapril treatment is associated with reduced aortic stiffness: the prevention of events with angiotensin-converting enzyme inhibition hemodynamic substudy

The Prevention of Events with Angiotensin Converting Enzyme inhibition (PEACE) trial evaluated angiotensin-converting enzyme inhibition with trandolapril versus placebo added to conventional therapy in patients with stable coronary disease and preserved left ventricular function. The PEACE hemodynamic substudy evaluated effects of trandolapril on pulsatile hemodynamics. Hemodynamic studies were performed in 300 participants from 5 PEACE centers a median of 52 months (range, 25 to 80 months) after random assignment to trandolapril at a target dose of 4 mg per day or placebo. Central pulsatile hemodynamics and carotid-femoral pulse wave velocity were assessed by using echocardiography, tonometry of the carotid and femoral arteries, and body surface transit distances. Patients randomly assigned to trandolapril tended to be older (mean+/-SD: 64.2+/-7.9 versus 62.9+/-7.7 years; P=0.14), with a higher body mass index (28.5+/-4.0 versus 27.8+/-3.9 kg/m(2); P=0.09) and lower ejection fraction (57.1+/-8.1% versus 58.7+/-8.4%; P<0.01). At the time of the hemodynamic substudy, the trandolapril group had lower mean arterial pressure (93.1+/-10.2 versus 96.3+/-11.3 mm Hg; P<0.01) and lower carotid-femoral pulse wave velocity (geometric mean [95% CI]: 10.4 m/s [10.0 to 10.9 m/s] versus 11.2 m/s [10.7 to 11.8 m/s]; P=0.02). The difference in carotid-femoral pulse wave velocity persisted (P<0.01) in an analysis that adjusted for baseline characteristics and follow-up mean pressure. In contrast, there was no difference in aortic compliance, characteristic impedance, augmentation index, or total arterial compliance. Angiotensin-converting enzyme inhibition with trandolapril produced a modest reduction in carotid-femoral pulse wave velocity, a measure of aortic wall stiffness, beyond what would be expected from blood pressure lowering or differences in baseline characteristics alone.

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.

Signaling by the angiotensin-converting enzyme

Inhibition of the angiotensin-converting enzyme (ACE) protects against the progression of several cardiovascular diseases. Because of its dual role in regulating angiotensin II and bradykinin levels, the positive clinical effects of ACE inhibitors were thought to be the consequence of concomitant reductions in the production of angiotensin II and the degradation of bradykinin. Recent evidence suggests that some of the beneficial effects of ACE inhibitors on cardiovascular function and homeostasis can be attributed to novel mechanisms. These include the accumulation of the ACE substrate N-acetyl-seryl-aspartyl-lysyl-proline, which blocks collagen deposition in the injured heart, as well as the activation of an ACE signaling cascade that involves the activation of the kinase CK2 and the c-Jun N-terminal kinase in endothelial cells and leads to changes in gene expression. Moreover, at least one other ACE homologue (ACE2) is proposed to counteract the detrimental effects associated with the activation of the classical renin-angiotensin system. These data reveal hitherto unexpected levels of internal regulation of the renin-angiotensin system.

The tissue renin-angiotensin system and intracellular signalling

PURPOSE OF REVIEW

The renin-angiotensin system is not what it was, or for that matter not necessarily where we thought it should be. For example, there is a novel angiotensin I-metabolizing enzyme that generates angiotensin 1-7 rather than angiotensin II. Moreover, we are slowly realizing the importance of local rather than circulating angiotensin II.

RECENT FINDINGS

Rather than concentrating on the systemic renin-angiotensin system, recent work has concentrated on elucidating the consequences of increasing angiotensin II production within specific organs, such as the heart and vasculature, as well as in the pancreas and in adipose tissue. Inhibition of angiotensin II production either using angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers not only reverses remodelling but also increases tissue insulin sensitivity. Targeting the renin-angiotensin system clinically delays the onset of type 2 diabetes, but the mechanisms involved are not clearly understood. Moreover, at least one other angiotensin-converting enzyme homologue (ACE2) plays a significant role in the regulation of heart and kidney function, and as it generates angiotensin 1-7 from angiotensin I, it is proposed to counteract the detrimental effects associated with the activation of the classic renin-angiotensin system.

SUMMARY

There is a need to re-evaluate the role(s) played by the molecular components of the "extended" local renin-angiotensin system and their role in vascular disease and type 2 diabetes.

Pathophysiologie der chronischen Herzinsuffizienz

Heart failure is a progressive and often fatal disease process. In general, the pathophysiologic mechanisms responsible for progressive myocyte dysfunction and cell loss, cardiac remodeling and arrhythmias involve signaling mechanisms that alter myocardial gene expression. These changes in gene expression are complex and involve contractile proteins, ion channels, Ca(++) handling, apoptosis, cell metabolism, the extracellular matrix, signal transduction pathways and growth factors. In the failing heart, several changes occur in cardiac adrenergic receptor-signal transduction pathways. The most striking of these changes occur in beta-adrenergic receptors, and of the changes in beta-adrenergic receptors beta1-receptor down-regulation is the most prominent. Other changes include uncoupling of beta2-adrenergic receptors and increased activity of the inhibitory G-protein. Most of these changes appear to be related to increased activity of the adrenergic nervous system, i.e. increased exposure to norepinephrine. Antagonists of the adrenergic nervous system may improve left ventricular function and outcome in patients with heart failure. This fact supports the notion that activation of these neurohormonal systems exerts a net long-term detrimental effect on the natural history of chronic heart failure and that myocardial adrenergic desensitization phenomena are at least partially maladaptive in the setting of left ventricular dysfunction. In addition to functional alterations structural remodeling plays a major role in the progression of various heart diseases to congestive heart failure. Major contributors to this remodeling process in the heart include alterations in myocyte shape, myocyte number and extracellular matrix. However, it is unclear as to which of these changes is most critical in the development of congestive heart failure, and this may vary by etiology.

Angiotensin-converting enzyme (ACE) dimerization is the initial step in the ACE inhibitor-induced ACE signaling cascade in endothelial cells

The binding of angiotensin-converting enzyme (ACE) inhibitors to ACE initiates a signaling cascade that involves the phosphorylation of the enzyme on Ser1270 as well as activation of the c-Jun NH2-terminal kinase (JNK) and leads to alterations in gene expression. To clarify how ACE inhibitors activate this pathway, we determined their effect on the ability of the enzyme to dimerize and the role of ACE dimerization in the initiation of the ACE signaling cascade. In endothelial cells, ACE was detected as a monomer as well as a dimer in native gel electrophoresis and dimerization/oligomerization was confirmed using the split-ubiquitin assay in yeast. ACE inhibitors elicited a rapid, concentration-dependent increase in the dimer/monomer ratio that correlated with that of the ACE inhibitorinduced phosphorylation of ACE. Cell treatment with galactose and glucose to prevent the putative lectin-mediated self-association of ACE or with specific antibodies shielding the N terminus of ACE failed to affect either the basal or the ACE inhibitor-induced dimerization of the enzyme. In ACE-expressing Chinese hamster ovary cells, ACE inhibitors elicited ACE dimerization and phosphorylation as well as the activation of JNK with similar kinetics to those observed in endothelial cells. However, these effects were prevented by the mutation of the essential Zn2+-complexing histidines in the C-terminal active site of the enzyme. Mutation of the N-terminal active site of ACE was without effect. Together, our data suggest that ACE inhibitors can initiate the ACE signaling pathway by inducing ACE dimerization, most probably via the C-terminal active site of the enzyme.

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.

Pulsatile hemodynamic effects of candesartan in patients with chronic heart failure: the CHARM Program

BACKGROUND

Abnormal large artery function and increased pulsatile load are exacerbated by excess angiotensin-II acting through the AT1 receptor and contribute to the pathogenesis and progression of chronic heart failure (CHF).

AIMS

To evaluate effects of the AT1 receptor blocker candesartan (N = 30) or placebo (N = 34) on pulsatile hemodynamics in participants with CHF in the CHARM program.

METHODS AND RESULTS

Noninvasive hemodynamics were assessed following 6 and 14 months of treatment and averaged. Using calibrated tonometry and aortic outflow Doppler, characteristic impedance was calculated as the ratio of the change in carotid pressure and aortic flow in early systole. Total arterial compliance was calculated by the diastolic area method. Brachial blood pressure, cardiac output and peripheral resistance did not differ between groups. Lower central pulse pressure in the candesartan group (57+/-20 vs. 67+/-17 mmHg, P = 0.043) was accompanied by lower characteristic impedance (200+/-78 vs. 240+/-74 dyne s/cm5, P = 0.039) and higher total arterial compliance (1.87+/-0.70 vs. 1.47+/-0.48 ml/mmHg, P = 0.008). Similar favorable differences were seen when analyses were stratified for ejection fraction (< or = 0.40 vs. >0.40) and baseline angiotensin converting enzyme inhibitor use.

CONCLUSIONS

Candesartan has a favorable effect on large artery function in patients with chronic heart failure.

The lord of the ring: mandatory role of the kidney in drug therapy of hypertension

Strong evidence supports the idea that total peripheral resistance (TPR) is increased in all forms of human and experimental hypertension. Although the etiological participation of TPR in the origin and long-term maintenance of hypertension has been extensively debated, it now seems clear that the renal, nonadaptive, infinite gain-working, pressure-sensitive natriuresis and diuresis is the main mechanism of blood pressure control in the long term. The tissue, cellular, biochemical, and genetic sensors and executors of this process have not been fully identified yet, but the role of the renal medulla has gained growing attention as the physiopathological scenario in which the key regulatory elements reside. Specifically, the functionality of the renomedullary vasculature seems to be highly responsible for blood pressure control. The vasculature of the renal medulla becomes a new and more specific target for the therapeutic intervention of hypertension. Recent data on the effect of baroreceptor-controlled renal sympathetic activity on the long-term regulation of blood pressure are integrated. The renomedullary effects of the main antihypertensive drugs are discussed, and new perspectives for the therapeutic intervention of hypertension are outlined. Comparison of the genetic program of the renal medulla before and after the development of hypertension in spontaneously hypertensive and experimentally induced animal models might provide a mechanism for identifying the key genes that become activated or suppressed in the development of high blood pressure. These genes, their encoded proteins, or other elements related to their signalling and genetic pathways might serve as new and more specific targets for the pharmacological treatment of abnormally elevated blood pressure. Besides, proteins specifically located to the luminal side of the renomedullary vascular endothelium may serve as potential targets for site-directed drug and gene therapy.

Effects of angiotensin-converting enzyme polymorphism on aortic elastic parameters in athletes

BACKGROUND

Physiologic adaptations in an athlete's heart include increased left and right ventricular chamber size, left ventricular wall thickness and mass. Angiotensin-converting enzyme (ACE) is a key enzyme in angiotensin II production causing cardiac hypertrophy. The cloning of the ACE gene has made it possible to identify a deletion (D)-insertion (I) polymorphism that appears to affect the level of serum ACE activity. Therefore, the ACE genes, which have been shown to be polymorphic, could be candidate genes for large-artery stiffness.

METHODS

56 endurance athletes and 46 sedentary subjects were included in this study, and they underwent both complete echocardiographic examination, and analysis of ACE insertion (I) and deletion (D) allele frequencies in peripheral blood. The aortic diameter was recorded by M-mode echocardiography at a level 3 cm above the aortic valve. Aortic systolic diameter was measured at the time of full opening of the aortic valve, and diastolic diameter was measured at the peak of QRS. Aortic strain, stiffness index and distensibility were calculated.

RESULTS

Left ventricular mass index and left ventricular ejection fraction were significantly higher in athletes than controls (p < 0.001). The aortic distensibility index and strain were significantly greater in athletes compared with controls (respectively: 5.8 +/- 2.7 vs. 4.7 +/- 1.8 cm(-2) dyn(-1) 10(-6), p = 0.017; 12.3 +/- 2.4 vs. 9.3 +/- 3.1, p < 0.001). The aortic stiffness index was significantly lower in athletes than in controls (4.8 +/- 1.9 vs. 6.1 +/- 2.1, p < 0.001). The aortic distensibility index and strain were statistically different in ACE DD vs. DI groups and DD vs. II groups of athletes. The aortic stiffness index was statistically different in ACE DD vs. II groups of athletes. Aortic parameters were similar according to ACE genotypes in controls.

CONCLUSION

The results of this study indicate that aortic distensibility was increased by prolonged training in endurance athletes, particularly in those with the ACE II genotype. This effect represents an extracardiac adaptation to chronic prolonged training in athletes.

New fACEs to the Renin-Angiotensin System

Inhibition of the angiotensin-converting enzyme (ACE) protects against the progression of several cardiovascular diseases. Recent evidence suggests that some of the beneficial effects of ACE inhibitors can be attributed to the activation of a distinct ACE signaling cascade rather than to the changes in angiotensin II and bradykinin levels. Moreover, at least one other ACE homolog (ACE2) plays a significant role in the regulation of heart and kidney function.

Angiotensin-converting enzyme gene polymorphism and common carotid stiffness. The Rotterdam study

The insertion/deletion (I/D) polymorphism of the ACE gene may be involved in structural arterial changes. Aim of the present study was to assess the relationship between the ACE I/D gene and vessel wall stiffness among older adults. The study was conducted within the Rotterdam study, a population-based cohort study including subjects aged 55 years and older. The II, ID and DD genotypes of the ACE gene were determined in all subjects. The distensibility coefficient (10(-3)/kPa) of the carotid artery and the carotid-femoral pulse wave velocity were measured during the third phase of the Rotterdam study (1997-1999) and were used as measure of arterial stiffness. Data on both carotid stiffness and the ACE genotype were available for 3001 participants. After adjustment for age and gender, subjects with the ID and DD genotype had higher carotid stiffness compared to subjects with II genotype (distensibility coefficient (10(-3)/kPa) 10.24 (95% CI, 10.06-10.43), 10.27 (95% CI, 10.02-10.52), 10.65 (95% CI, 10.37-10.93), respectively (ID versus II genotype, P = 0.017), (DD versus II genotype, P = 0.037)). In stratified analyses, the association was strongest in subjects younger than 70 years. No difference was seen for pulse wave velocity among genotypes. In conclusion, the results of this population-based study show that the ACE ID/DD genotypes are associated with higher common carotid stiffness.

Tissue renin angiotensin systems

The RAAS is a powerful regulator of vascular tone and intravascular volume and of tissue architecture and a variety of other functions. The recent appreciation of the immunoregulatory role of angiotensin II and its possible involvement in the genesis of atherosclerosis and in plaque rupture all speak to the wide-ranging physiologic and pathophysiologic activities of the peptide. So do its actions in fat cell differentiation and in neuromodulation. The system exists in the circulation, and RAASs, whole or partial, exist in many tissues. These systems are regulated at many levels ranging from the synthesis of renin to the dimerization of angiotensin receptors. Regulation occurs in multiple tissues and, as a result, tissue concentrations of angiotensin II and the concentration of other RAS components and their active metabolites can vary independently of the circulating system in these tissues. An RAS seems also to function within certain cells. Therapeutic interventions involving ACEIs and ARBs seem likely to provide benefit at least in part through the interruption of local systems. It is to be expected that with enhanced understanding of the biology of the multiple RASs, new suggestions for therapeutic interventions will be forthcoming.

Oxidants in receptor tyrosine kinase signal transduction pathways

The accumulation of oxygen in the atmosphere created an evolutionary stress for organisms to survive because oxygen, while the by-product of photosynthesis and an important substrate in oxidative metabolism, can also be partially reduced to form toxic products. These forms of oxygen, reduced by one electron or two electrons, yield superoxide anion (O(2).-) and hydrogen peroxide (H(2)O(2)), respectively. Recent studies suggest that reactive oxygen species (ROS) such as O(2).- and H(2)O(2) function as mitogenic mediators of activated growth-factor receptor signaling. Reported data imply that growth factor-stimulated ROS generation can mediate intracellular signaling pathways by activating protein tyrosine kinases, inhibiting protein tyrosine phosphatase, and regulating redox-sensitive gene expression. This review examines the mechanisms of growth factor-induced generation of ROS and their roles in specific receptor tyrosine kinase signaling pathways.

Involvement of renal ACE activity in proteinuria-associated renal damage in untreated and treated adriamycin nephrotic rats

Proteinuria is assumed to play a pathogenetic role in progressive renal damage. Angiotensin-converting enzyme (ACE) inhibition reduces proteinuria and provides renoprotection. This suggests that ACE activity might play a pathogenetic role in the development of proteinuria-induced renal structural damage. We investigated this hypothesis in untreated and treated established adriamycin nephrosis, a model of proteinuria-induced renal damage. In a time-course experiment, the development of renal structural damage in untreated adriamycin nephrotic rats was paralleled by a significant rise in renal ACE activity. Moreover, on cross-sectional analysis, a consistent positive correlation between renal, but not plasma, ACE activity and proteinuria, focal glomerulosclerosis and interstitial injury was present. Notably, these associations were present, not only in the untreated condition, but also during intervention with either ACE inhibition or AT(1)-receptor antagonism. Interestingly, we found that higher renal ACE activity is associated with more severe renal damage for a given amount of proteinuria, suggesting that renal ACE activity may be either a permissive or a promoting factor in the processes by which proteinuria eventually leads to renal structural damage. This relationship was abolished by renin-angiotensin system (RAS)-blockade, suggesting that RAS-mediated effects are involved in the relationship between renal ACE activity and proteinuria-induced renal damage. In conclusion, in untreated as well as treated adriamycin nephrotic rats, renal ACE activity is closely associated with renal outcome. This association appears to be independent of the specific mode of blockade of the RAS. Renal ACE activity is a consistent marker of individual differences in proteinuria-associated renal damage: further studies are needed to investigate a possible pathogenetic role in renal damage.

DNA microarray profiling to identify angiotensin-responsive genes in vascular smooth muscle cells: potential mediators of vascular disease

Angiotensin II (Ang II) induces changes in vessel structure by its capacity to activate genes that are coupled to signaling pathways such as extracellular signal-regulated kinase (ERK), p38, and phosphatidylinositol 3-kinase (PI3K). Using a DNA microarray containing 5088 genes and expressed sequence tags, we initially established a database of replicated experiments (n=4) to define the variances in mRNA expression in response to Ang II versus vehicle treatment. We observed a wide range of values for the coefficients of variation in a gene-specific manner. Guided by power calculations, we used statistical inference on a sufficient number of experimental replicates to minimize the number of false-negatives and define a subset of Ang II-responsive genes (P<0.05). To further characterize the molecular circuitry that couples Ang II stimulation with mRNA expression, we assessed expression profiles in the presence and absence of inhibitors of ERK, p38, and PI3K. Using two different methods of computational cluster analysis, we identified a subset of six matricellular proteins (eg, osteopontin and plasminogen activator inhibitor-1) that are coordinately upregulated by Ang II via an ERK/p38-dependent pathway. In addition, these cluster analyses identified calpactins I and II as novel Ang II-responsive genes. Given that Ang II promotes vascular lesion formation, we examined whether this matricellular gene cluster was also coordinately regulated in vivo. Indeed, we demonstrate that both calpactin I and osteopontin are upregulated in response to vascular injury. Taken together, the combined use of DNA microarrays, statistical inference, and cluster analysis identified novel, coordinately regulated Ang II-responsive genes that may mediate vascular lesion formation.

Transcription factor decoys for the prevention of vein bypass graft failure

Failure of vein bypass grafts, performed for either coronary or lower extremity arterial occlusions, is a common clinical problem that incurs significant morbidity and mortality. Vein grafts provide a unique opportunity for genetic interventions, since the target tissue is available for manipulation ex vivo prior to implantation, and prior to the onset of the pathophysiologic events that lead to graft disease. Smooth muscle cell proliferation is a hallmark of neointimal hyperplasia in vein grafts and arteries, and is an attractive target for molecular therapy. Gene blockade strategies can be accomplished by delivery of small oligodeoxynucleotides (ODN) that target specific mRNAs ('antisense') or that competitively inhibit transcription factors ('decoys'). Transcription factors are attractive targets for molecular therapy since they influence the expression of a large number of genes involved in a coordinated cellular program. An ODN decoy approach has been developed targeting the transcription factor E2F, which is critically involved in cell cycle progression. Brief (10 minute) incubation of the ODN in solution, using non-distending pressure, results in efficient delivery of the ODN to >80% of cells in the vein wall. Preclinical studies in a rabbit model of vein grafting and hypercholesterolemia demonstrated a marked reduction in neointima formation, as well as prolonged resistance to graft atherosclerosis. Phase I/II studies conducted in lower extremity and coronary bypass patients have demonstrated safety and feasibility, and have also suggested possible efficacy. Large, randomized multicenter, phase III trials are currently under way to evaluate the efficacy of E2F decoy treatment on preventing vein bypass failure in both peripheral and coronary grafting procedures. These studies herald the arrival of a new class of molecular agents into the armamentarium of cardiovascular therapies.

An interaction between systolic blood pressure and angiotensin-converting enzyme gene polymorphism on carotid atherosclerosis

The insertion/deletion (I/D) polymorphism of the human angiotensin-converting enzyme (ACE) gene is a major determinant of circulating ACE activity, with the D allele being associated with higher ACE levels than the I allele. Thus, chronic exposure to high levels of circulating and tissue ACE may well predispose to vascular wall thickening and atherosclerosis. However, the effect of the ACE gene on carotid atherosclerosis remains controversial. We investigated the association between ACE gene I/D polymorphism and risk factor-dependent augmentation of carotid arterial remodeling in subjects with several risk factors for atherosclerosis. We evaluated sclerotic lesions of the common carotid artery with intima-media thickness (IMT) by ultrasonography in 184 patients (mean age +/- SD, 67 +/- 14 years old) and studied whether any risk factor-gene interactions were associated with carotid atherosclerosis. Out of the 184 subjects, 71 had the ACE II genotype, 87 the ID genotype and 26 the DD genotype. There was no significant difference in IMT among the three ACE genotypes. In total subjects, multiple regression analysis showed that age, total-cholesterol (T-C), and HDL-cholesterol (HDL-C) were significantly associated with IMT. However, the association between risk factors and IMT was genotype-specific. Systolic blood pressure (SBP) and HDL-C were significantly associated with IMT in ACE D carriers (DD+ID), but not in subjects with the ACE II genotype. Similarly, T-C was significantly associated with IMT only in subjects with the ACE II genotype. A general linear model of the interaction between the ACE genotype and the conventional risk factors showed that the SBP-ACE genotype interaction were significantly associated with IMT (F = 7.915; p = 0.005). This finding further supports the idea that analysis of risk factor-gene interaction could be a useful tool for deriving specific predictive information about the development of atherosclerosis.