Showing papers on "Angiotensin II published in 2001"

Renoprotective Effect of the Angiotensin-Receptor Antagonist Irbesartan in Patients with Nephropathy Due to Type 2 Diabetes

Abstract: Background It is unknown whether either the angiotensin-II–receptor blocker irbesartan or the calcium-channel blocker amlodipine slows the progression of nephropathy in patients with type 2 diabetes independently of its capacity to lower the systemic blood pressure. Methods We randomly assigned 1715 hypertensive patients with nephropathy due to type 2 diabetes to treatment with irbesartan (300 mg daily), amlodipine (10 mg daily), or placebo. The target blood pressure was 135/85 mm Hg or less in all groups. We compared the groups with regard to the time to the primary composite end point of a doubling of the base-line serum creatinine concentration, the development of end-stage renal disease, or death from any cause. We also compared them with regard to the time to a secondary, cardiovascular composite end point. Results The mean duration of follow-up was 2.6 years. Treatment with irbesartan was associated with a risk of the primary composite end point that was 20 percent lower than that in the placebo gro...

A randomized trial of the angiotensin-receptor blocker valsartan in chronic heart failure.

Abstract: Background Actions of angiotensin II may contribute to the progression of heart failure despite treatment with currently recommended drugs. We therefore evaluated the long-term effects of the addition of the angiotensin-receptor blocker valsartan to standard therapy for heart failure. Methods A total of 5010 patients with heart failure of New York Heart Association (NYHA) class II, III, or IV were randomly assigned to receive 160 mg of valsartan or placebo twice daily. The primary outcomes were mortality and the combined end point of mortality and morbidity, defined as the incidence of cardiac arrest with resuscitation, hospitalization for heart failure, or receipt of intravenous inotropic or vasodilator therapy for at least four hours. Results Overall mortality was similar in the two groups. The incidence of the combined end point, however, was 13.2 percent lower with valsartan than with placebo (relative risk, 0.87; 97.5 percent confidence interval, 0.77 to 0.97; P=0.009), predominantly because of a low...

Gender Differences in the Regulation of Blood Pressure

Abstract: Men are at greater risk for cardiovascular and renal disease than are age-matched, premenopausal women. Recent studies using the technique of 24-hour ambulatory blood pressure monitoring have shown that blood pressure is higher in men than in women at similar ages. After menopause, however, blood pressure increases in women to levels even higher than in men. Hormone replacement therapy in most cases does not significantly reduce blood pressure in postmenopausal women, suggesting that the loss of estrogens may not be the only component involved in the higher blood pressure in women after menopause. In contrast, androgens may decrease only slightly, if at all, in postmenopausal women. In this review the possible mechanisms by which androgens may increase blood pressure are discussed. Findings in animal studies show that there is a blunting of the pressure-natriuresis relationship in male spontaneously hypertensive rats and in ovariectomized female spontaneously hypertensive rats treated chronically with testosterone. The key factor in controlling the pressure-natriuresis relationship is the renin-angiotensin system (RAS). The possibility that androgens increase blood pressure via the RAS is explored, and the possibility that the RAS also promotes oxidative stress leading to production of vasoconstrictor substances and reduction in nitric oxide availability is proposed.

Novel gp91 phox Homologues in Vascular Smooth Muscle Cells : nox1 Mediates Angiotensin II–Induced Superoxide Formation and Redox-Sensitive Signaling Pathways

Abstract: Emerging evidence indicates that reactive oxygen species are important regulators of vascular function. Although NAD(P)H oxidases have been implicated as major sources of superoxide in the vessel wall, the molecular identity of these proteins remains unclear. We recently cloned nox1 (formerly mox-1), a member of a new family of gp91(phox) homologues, and showed that it is expressed in proliferating vascular smooth muscle cells (VSMCs). In this study, we examined the expression of three nox family members, nox1, nox4, and gp91(phox), in VSMCs, their regulation by angiotensin II (Ang II), and their role in redox-sensitive signaling. We found that both nox1 and nox4 are expressed to a much higher degree than gp91(phox) in VSMCS: Although serum, platelet-derived growth factor (PDGF), and Ang II downregulated nox4, they markedly upregulated nox1, suggesting that this enzyme may account for the delayed phase of superoxide production in these cells. Furthermore, an adenovirus expressing antisense nox1 mRNA completely inhibited the early phase of superoxide production induced by Ang II or PDGF and significantly decreased activation of the redox-sensitive signaling molecules p38 mitogen-activated protein kinase and Akt by Ang II. In contrast, redox-independent pathways induced by PDGF or Ang II were unaffected. These data support a role for nox1 in redox signaling in VSMCs and provide insight into the molecular identity of the VSMC NAD(P)H oxidase and its potentially critical role in vascular disease.

Activation and targeting of extracellular signal-regulated kinases by beta-arrestin scaffolds.

Abstract: Using both confocal immunofluorescence microscopy and biochemical approaches, we have examined the role of β-arrestins in the activation and targeting of extracellular signal-regulated kinase 2 (ERK2) following stimulation of angiotensin II type 1a receptors (AT1aR). In HEK-293 cells expressing hemagglutinin-tagged AT1aR, angiotensin stimulation triggered β-arrestin-2 binding to the receptor and internalization of AT1aR-β-arrestin complexes. Using red fluorescent protein-tagged ERK2 to track the subcellular distribution of ERK2, we found that angiotensin treatment caused the redistribution of activated ERK2 into endosomal vesicles that also contained AT1aR-β-arrestin complexes. This targeting of ERK2 reflects the formation of multiprotein complexes containing AT1aR, β-arrestin-2, and the component kinases of the ERK cascade, cRaf-1, MEK1, and ERK2. Myc-tagged cRaf-1, MEK1, and green fluorescent protein-tagged ERK2 coprecipitated with Flag-tagged β-arrestin-2 from transfected COS-7 cells. Coprecipitation of cRaf-1 with β-arrestin-2 was independent of MEK1 and ERK2, whereas the coprecipitation of MEK1 and ERK2 with β-arrestin-2 was significantly enhanced in the presence of overexpressed cRaf-1, suggesting that binding of cRaf-1 to β-arrestin facilitates the assembly of a cRaf-1, MEK1, ERK2 complex. The phosphorylation of ERK2 in β-arrestin complexes was markedly enhanced by coexpression of cRaf-1, and this effect is blocked by expression of a catalytically inactive dominant inhibitory mutant of MEK1. Stimulation with angiotensin increased the binding of both cRaf-1 and ERK2 to β-arrestin-2, and the association of β-arrestin-2, cRaf-1, and ERK2 with AT1aR. These data suggest that β-arrestins function both as scaffolds to enhance cRaf-1 and MEK-dependent activation of ERK2, and as targeting proteins that direct activated ERK to specific subcellular locations.

Tissue Angiotensin and Pathobiology of Vascular Disease A Unifying Hypothesis

Abstract: —There is increasing evidence that direct pathobiological events in the vessel wall play an important role in vascular disease. An important mechanism involves the perturbation of the homeostatic balance between NO and reactive oxygen species. Increased reactive oxygen species can inactivate NO and produce peroxynitrite. Angiotensin II is a potent mediator of oxidative stress and stimulates the release of cytokines and the expression of leukocyte adhesion molecules that mediate vessel wall inflammation. Inflammatory cells release enzymes (including ACE) that generate angiotensin II. Thus, a local positive-feedback mechanism could be established in the vessel wall for oxidative stress, inflammation, and endothelial dysfunction. Angiotensin II also acts as a direct growth factor for vascular smooth muscle cells and can stimulate the local production of metalloproteinases and plasminogen activator inhibitor. Taken together, angiotensin II can promote vasoconstriction, inflammation, thrombosis, and vascular remodeling. In this article, we propose a model that unifies the interrelationship among cardiovascular risk factors, angiotensin II, and the pathobiological mechanisms contributing to cardiovascular disease. This model may also explain the beneficial effects of ACE inhibitors on cardiovascular events beyond blood pressure reduction.

NF-κB: pivotal mediator or innocent bystander in atherogenesis?

Abstract: Atherosclerosis and its clinical manifestations of heart attack, stroke, and peripheral vascular insufficiency are a major cause of morbidity and mortality among both men and women Multiple risk factors including hypertension, diabetes mellitus, smoking, and lipoprotein disorders are involved in the pathogenesis of this chronic inflammatory disease of arteries The development of early atherosclerotic lesions can be subdivided into initiation (formation of small fatty streaks), expansion (vertical and lateral growth and coalescence of fatty streaks), and progression to plaques (intimal smooth muscle cell recruitment, collagen deposition, and formation of a fibrous cap) (reviewed in ref1) During the initiation and expansion of fatty streaks, circulating monocytes are recruited to the arterial intima where they are transformed into lipid-engorged macrophage foam cells The arterial endothelium in these regions is activated and expresses inducible leukocyte adhesion molecules and chemokines Production of cytokines and growth factors within lesions may amplify monocyte recruitment, stimulate macrophage proliferation, and induce migration of smooth muscle cells from the media to the intima of the vessel Intimal smooth muscle cells deposit collagen and other ECM proteins, leading to the formation of a fibrous cap Although clinically significant complications of atherosclerosis, such as plaque ulceration, rupture, and thrombosis, occur in established or advanced atherosclerotic plaques, understanding the mechanisms of early lesion formation offers the hope of intervening to delay or prevent lesion progression and complications A select set of transcription factors may be critical in both the initiation and expansion of lesions, as well as in protecting the vessel wall from the formation of atherosclerotic lesions In this overview, we will focus on one transcription factor, NF-κB, whose activation has been linked to the onset of atherosclerosis NF-κB is composed of members of the Rel family that share a 300 amino acid region, known as the Rel homology domain, which mediates dimerization, nuclear translocation, DNA binding, and interaction with NF-κB inhibitors (reviewed in ref2) Activation of NF-κB is controlled by a family of inhibitors, or IκBs, that bind to NF-κB dimers and mask the nuclear localization sequence of NF-κB, thus retaining the entire complex in the cytoplasm Diverse stimuli activate NF-κB, through the phosphorylation and activation of the IκB kinase (IKK) complex This complex consists of IKK-α and IKK-β heterodimers, a number of IKK-γ subunits, and possibly other components that have less certain significance The activated IKK complex specifically phosphorylates the IκBs, which are then rapidly polyubiquitinated, targeting them for degradation by the proteosome Following release from the inhibitor, NF-κB dimers translocate from the cytoplasm to the nucleus, where they bind target genes and stimulate transcription (Figure ​(Figure1)1) NF-κB activates a variety of target genes relevant to the pathophysiology of the vessel wall, including cytokines, chemokines, and leukocyte adhesion molecules, as well as genes that regulate cell proliferation and mediate cell survival NF-κB also activates the IκBα gene, thus replenishing the cytoplasmic pool of its own inhibitor Restored expression of IκB-α decreases NF-κB activation and diminishes expression of NF-κB–dependent genes The NF-κB/IκB-α autoregulatory system ensures that the induction of NF-κB is transient and that the activated cell returns to a quiescent state Physiological modulation and pathological activation of the NF-κB system may contribute to the changes in gene expression that occur during atherogenesis Figure 1 Schematic representation of NF-κB as an integrator in atherogenesis Many of the diverse agents associated with the onset of lesion formation interact with specific receptors Angiotensin II (Ang II), cytokines, advanced glycosylation end products

The biology of white adipocyte proliferation.

Abstract: Expanded adipose tissue mass increases the risk for many clinical conditions including diabetes, hypertension, coronary atherosclerotic heart disease, and some forms of cancer. Therefore, it is imperative that we understand the mechanisms by which fat pads expand. The enlargement of fat cells during the development of obesity has been previously hypothesized to be a triggering factor for the proliferation of new fat cells. There is now a preponderance of evidence that adipose tissue is a source of growth factors such as IGF-I, IGF binding proteins, TNF alpha, angiotensin II, and MCSF that are capable of stimulating proliferation. The relative importance of these autocrine/paracrine factors in the normal control of preadipocyte proliferation is unknown. In addition, the proliferative response of preadipocytes to the paracrine milieu is undoubtedly modulated by neural inputs to fat tissue and/or serum factors. Together, these multiple regulatory controls orchestrate overall and region-specific adipose tissue cellularity responses associated with the development of hyperplastic obesity. Both in vivo and in vitro studies are needed to understand the complex, interacting physiological mechanisms by which growth of this important organ is regulated.

Effects of Angiotensin-Converting Enzyme Inhibition on the Development of the Atrial Fibrillation Substrate in Dogs With Ventricular Tachypacing–Induced Congestive Heart Failure

Abstract: Background Atrial structural remodeling creates a substrate for atrial fibrillation (AF), but the underlying signal transduction mechanisms are unknown. This study assessed the effects of ACE inhibition on arrhythmogenic atrial remodeling and associated mitogen-activated protein kinase (MAPK) changes in a dog model of congestive heart failure (CHF). Methods and Results Dogs were subjected to various durations of ventricular tachypacing (VTP, 220 to 240 bpm) in the presence or absence of oral enalapril 2 mg · kg−1 · d−1. VTP for 5 weeks induced CHF, local atrial conduction slowing, and interstitial fibrosis and prolonged atrial burst pacing–induced AF. Atrial angiotensin II concentrations and MAPK expression were increased by tachypacing, with substantial changes in phosphorylated forms of c-Jun N-terminal kinase (JNK), extracellular signal–regulated kinase (ERK), and p38-kinase. Enalapril significantly reduced tachypacing-induced changes in atrial angiotensin II concentrations and ERK expression. Enalapri...

Characterization of Apelin, the Ligand for the APJ Receptor

Abstract: The apelin peptide was recently discovered and demonstrated to be the endogenous ligand for the G protein-coupled receptor, APJ. A search of the GenBank databases retrieved a rat expressed sequence tag partially encoding the preproapelin sequence. The GenBank search also revealed a human sequence on chromosome Xq25-26.1, containing the gene encoding preproapelin. We have used the rat sequence to screen a rat brain cDNA library to obtain a cDNA encoding the full-length open reading frame of rat preproapelin. This cDNA encoded a protein of 77 amino acids, sharing an identity of 82% with human preproapelin. Northern and in situ hybridization analyses revealed both human and rat apelin and APJ to be expressed in the brain and periphery. Both sequence and mRNA expression distribution analyses revealed similarities between apelin and angiotensin II, suggesting they that share related physiological roles. A synthetic apelin peptide was injected intravenously into male Wistar rats, resulting in immediate lowering of both systolic and diastolic blood pressure, which persisted for several minutes. Intraperitoneal apelin injections induced an increase in drinking behavior within the first 30 min after injection, with a return to baseline within 1 h.

Novel Competitive Inhibitor of NAD(P)H Oxidase Assembly Attenuates Vascular O2− and Systolic Blood Pressure in Mice

Abstract: We previously reported enhanced expression of the p67 phox and gp91 phox components of NAD(P)H oxidase in angiotensin (Ang) II–induced hypertension, suggesting de novo assembly in response to Ang II. To examine the direct involvement of NAD(P)H oxidases in Ang II–induced O 2 − production, we designed a chimeric peptide that inhibits p47 phox association with gp91 phox in NAD(P)H oxidase (gp91ds- tat ). This was achieved by linking a 9-amino acid peptide (aa) derived from HIV-coat protein ( tat ) to a 9-aa sequence of gp91 phox (known to interact with p47 phox ). As a control, we constructed a chimera containing tat and a scrambled gp91 sequence (scramb- tat ). We found that gp91ds- tat decreased O 2 − levels in aortic rings treated with Ang II (10 pmol/L) but had no effect on either the O 2 − -generating enzyme xanthine oxidase or potassium superoxide–generated O 2 − . We infused vehicle, Ang II (0.75 mg · kg −1 · d −1 ), Ang II+gp91ds- tat (10 mg · kg −1 · d −1 ), or Ang II+scramb- tat intraperitoneally in C57Bl/6 mice and measured systolic blood pressure (SBP) on days 0, 3, 5, and 7 of infusion. SBP increased by day 3 in mice given Ang II and Ang II+scramb- tat but was significantly lower with Ang II+gp91- tat . On day 7, SBP was still significantly inhibited in mice given Ang II+gp91ds- tat , whereas Ang II–induced O 2 − production was inhibited throughout the aorta as detected by dihydroethidium staining, consistent with the ability of this inhibitor to block the various vascular NAD(P)H oxidase isoforms. These data support the hypothesis that inhibition of the interaction of p47 phox and gp91 phox (or its homologues) can block O 2 − production and attenuate blood pressure elevation in mice.

Pathophysiology of hypertension during preeclampsia linking placental ischemia with endothelial dysfunction.

Abstract: Studies over the past decade have provided a better understanding of the potential mechanisms responsible for the pathogenesis of preeclampsia. The initiating event in preeclampsia has been postulated to be reduced uteroplacental perfusion as a result of abnormal cytotrophoblast invasion of spiral arterioles. Placental ischemia is thought to lead to widespread activation/dysfunction of the maternal vascular endothelium that results in enhanced formation of endothelin and thromboxane, increased vascular sensitivity to angiotensin II, and decreased formation of vasodilators such as NO and prostacyclin. These endothelial abnormalities, in turn, cause hypertension by impairing renal-pressure natriuresis and increasing total peripheral resistance. The quantitative importance of the various endothelial and humoral factors in mediating the reduction in renal hemodynamic and excretory function and elevation in arterial pressure during preeclampsia are still unclear. Results from ongoing basic and clinical studies, however, should provide new and important information regarding the physiological mechanisms responsible for the elevation in arterial pressure in women with preeclampsia.

Statins as antioxidant therapy for preventing cardiac myocyte hypertrophy

Abstract: Cardiac hypertrophy is a major cause of morbidity and mortality worldwide. The hypertrophic process is mediated, in part, by small G proteins of the Rho family. We hypothesized that statins, inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase, inhibit cardiac hypertrophy by blocking Rho isoprenylation. We treated neonatal rat cardiac myocytes with angiotensin II (AngII) with and without simvastatin (Sim) and found that Sim decreased AngII-induced protein content, [3H] leucine uptake, and atrial natriuretic factor (ANF) promoter activity. These effects were associated with decreases in cell size, membrane Rho activity, superoxide anion (O2*-) production, and intracellular oxidation, and were reversed with L-mevalonate or geranylgeranylpyrophosphate, but not with farnesylpyrophosphate or cholesterol. Treatments with the Rho inhibitor C3 exotoxin and with cell-permeable superoxide dismutase also decreased AngII-induced O2*- production and myocyte hypertrophy. Overexpression of the dominant-negative Rho mutant N17Rac1 completely inhibited AngII-induced intracellular oxidation and ANF promoter activity, while N19RhoA partially inhibited it, and N17Cdc42 had no effect. Indeed, Sim inhibited cardiac hypertrophy and decreased myocardial Rac1 activity and O2*- production in rats treated with AngII infusion or subjected to transaortic constriction. These findings suggest that statins prevent the development of cardiac hypertrophy through an antioxidant mechanism involving inhibition of Rac1.

Increased AT(1) receptor heterodimers in preeclampsia mediate enhanced angiotensin II responsiveness.

Abstract: Several examples of functional G-protein-coupled receptor heterodimers have been identified. However, it is not known whether receptor heterodimerization is involved in the pathogenesis of human disorders. Here we show that in preeclamptic hypertensive women, a significant increase in heterodimerization occurs between the AT(1)-receptor for the vasopressor angiotensin II and the B(2)-receptor for the vasodepressor bradykinin. AT(1)-B(2)-receptor heterodimerization in preeclampsia correlated with a 4-5-fold increase in B(2)-receptor protein levels. Expression of the AT(1)-B(2) heterodimer increased the responsiveness to angiotensin II and conferred resistance in AT(1)-receptors to inactivation by reactive oxygen species raised in normotensive and preeclamptic pregnancies. We suggest that AT(1)-B(2) heterodimers contribute to angiotensin II hypersensitivity in preeclampsia. Moreover, we identify preeclampsia as the first disorder associated with altered G-protein-coupled receptor heterodimerization.

Angiotensin II type 1 receptor blockers.

Abstract: In the 1970s, a series of observations demonstrated that angiotensin II has deleterious effects on the heart and kidney and that patients with high levels of plasma renin activity are at a higher risk of developing stroke or myocardial infarction than those with low plasma renin activity.1 2 Thereafter, the development of pharmacological probes that block the renin-angiotensin system helped define the contribution of this system to blood pressure control and to the pathogenesis of diseases such as hypertension, congestive heart failure, and chronic renal failure. Thus, the concept of treating hypertension and congestive heart failure by a specific blockade of the renin-angiotensin system was first established with the use of saralasin, a nonselective peptidic antagonist of angiotensin II receptors.3 4 5 6 7 8 9 With saralasin, it became possible to demonstrate that angiotensin II receptor blockade, alone or in combination with salt depletion, lowers blood pressure in hypertensive patients and improves systemic hemodynamics in patients with congestive heart failure.3 4 5 6 7 8 9 10 However, saralasin had many drawbacks. Because it is a peptide, it had to be administered intravenously. This characteristic limited its use to hours or a few days at maximum. In addition, at higher doses, saralasin had some partial agonist, angiotensin II–like effects. The next major breakthrough in the understanding of the renin-angiotensin system was triggered by the development of orally active angiotensin-converting enzyme (ACE) inhibitors.10 11 12 13 14 15 Studies performed with these agents rapidly confirmed and reinforced the seminal clinical observations made with saralasin. ACE inhibitors are now recognized as an important therapeutic step to control blood pressure in hypertensive patients and to reduce morbidity and mortality in patients with congestive heart failure.16 In addition, because of their ability to lower proteinuria, ACE inhibitors have …

Angiotensin II and Renal Fibrosis

Abstract: Angiotensin (Ang) II, the main peptide of the renin angiotensin system (RAS), is a renal growth factor, inducing hyperplasia/hypertrophy depending on the cell type. This vasoactive peptide activates mesangial and tubular cells and interstitial fibroblasts, increasing the expression and synthesis of extracellular matrix proteins. Some of these effects seem to be mediated by the release of other growth factors, such as TGF-beta. In experimental models of kidney damage, renal RAS activation, cell proliferation, and upregulation of growth factors and matrix production were described. In some of these models, blockade of Ang II actions by ACE inhibitors and angiotensin type 1 (AT(1)) antagonists prevents proteinuria, gene expression upregulation, and fibrosis, as well as inflammatory cell infiltration. Interestingly, Ang II could also be involved in the fibrotic process because of its behavior as a proinflammatory cytokine, participating in various steps of the inflammatory response: Ang II (1) activates mononuclear cells and (2) increases proinflammatory mediators (cytokines, chemokines, adhesion molecules, nuclear factor kappaB). Finally, Ang II also regulates matrix degradation. These data show that drugs controlling this complex vasoactive peptide are probably one of the best ways of avoiding fibrosis in progressive renal diseases.

HMG-CoA Reductase Inhibitors Improve Endothelial Dysfunction in Normocholesterolemic Hypertension via Reduced Production of Reactive Oxygen Species

Abstract: —3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) significantly reduce cardiovascular mortality associated with hypercholesterolemia. There is evidence that statins exert beneficial effects in part through direct effects on vascular cells independent of lowering plasma cholesterol. We characterized the effect of a 30-day treatment with atorvastatin in normocholesterolemic, spontaneously hypertensive rats (SHR). Systolic blood pressure was significantly decreased in atorvastatin-treated rats (184±5 versus 204±6 mm Hg for control). Statin therapy improved endothelial dysfunction, as assessed by carbachol-induced vasorelaxation in aortic segments, and profoundly reduced angiotensin II–induced vasoconstriction. Angiotensin type 1 (AT 1 ) receptor, endothelial cell NO synthase (ecNOS), and p22phox mRNA expression were determined with quantitative reverse transcription–polymerase chain reaction. Atorvastatin treatment downregulated aortic AT 1 receptor mRNA expression to 44±12% of control and reduced mRNA expression of the essential NAD(P)H oxidase subunit p22phox to 63±7% of control. Aortic AT 1 receptor protein expression was consistently decreased. Vascular production of reactive oxygen species was reduced to 62±12% of control in statin-treated SHR, as measured with lucigenin chemiluminescence assays. Accordingly, treatment of SHR with the AT 1 receptor antagonist fonsartan improved endothelial dysfunction and reduced vascular free-radical release. Moreover, atorvastatin caused an upregulation of ecNOS mRNA expression (138±7% of control) and an enhanced ecNOS activity in the vessel wall (209±46% of control). Treatment of SHR with atorvastatin causes a significant reduction of systolic blood pressure and a profound improvement of endothelial dysfunction mediated by a reduction of free radical release in the vasculature. The underlying mechanism could in part be based on the statin-induced downregulation of AT 1 receptor expression and decreased expression of the NAD(P)H oxidase subunit p22phox, because AT 1 receptor activation plays a pivotal role for the induction of this redox system in the vessel wall.

Elevated Circulating Level of Ghrelin in Cachexia Associated With Chronic Heart Failure Relationships Between Ghrelin and Anabolic/Catabolic Factors

Abstract: Background Ghrelin is a novel growth hormone (GH)-releasing peptide, isolated from the stomach, that may also cause a positive energy balance by stimulating food intake and inducing adiposity. We sought to investigate the pathophysiology of ghrelin in the cachexia associated with chronic heart failure (CHF). Methods and Results Plasma ghrelin was measured in 74 patients with CHF and 12 control subjects, together with potentially important anabolic and catabolic factors, such as GH and tumor necrosis factor (TNF-α). Patients with CHF were divided into two groups, those with cachexia (n=28) and those without cachexia (n=46). Plasma ghrelin did not significantly differ between all CHF patients and controls (181±10 versus 140±14 fmol/mL, P=NS). However, plasma ghrelin was significantly higher in CHF patients with cachexia than in those without cachexia (237±18 versus 147±10 fmol/mL, P<0.001). Circulating GH, TNF-α, norepinephrine, and angiotensin II were also significantly higher in CHF patients with cachexia...

Proinflammatory actions of angiotensins.

Abstract: Many experimental data have suggested that the renin-angiotensin system participates in immune and inflammatory responses. Angiotensin II is involved in several steps of the inflammatory process: mononuclear cells respond to angiotensin II stimulation (cell proliferation and chemotaxis); angiotensin II regulates the recruitment of proinflammatory cells into the site of injury (mediated by the expression of vascular permeability factors, adhesion molecules and chemokines by resident cells); inflammatory cells can produce angiotensin II, and might therefore contribute to the perpetuation of tissue damage. In this review, we summarize the proinflammatory properties of angiotensin II, to demonstrate the novel role of this vasoactive peptide as a true cytokine. We will show the information obtained as a result of the pharmacological blockade of the renin angiotensin system, which has demonstrated that this system is involved in immune and inflammatory diseases. In this aspect, we discuss the molecular mechanism of angiotensin II-induced tissue damage, as well as its contribution to the pathogenesis of several diseases, including atherosclerosis, hypertension and renal damage, showing that angiotensin II plays an active role in the inflammatory response of these diseases.

IGF-1 overexpression inhibits the development of diabetic cardiomyopathy and angiotensin II-mediated oxidative stress.

Abstract: Stimulation of the local renin-angiotensin system and apoptosis characterize the diabetic heart. Because IGF-1 reduces angiotensin (Ang) II and apoptosis, we tested whether streptozotocin-induced diabetic cardiomyopathy was attenuated in IGF-1 transgenic mice (TGM). Diabetes progressively depressed ventricular performance in wild-type mice (WTM) but had no hemodynamic effect on TGM. Myocyte apoptosis measured at 7 and 30 days after the onset of diabetes was twofold higher in WTM than in TGM. Myocyte necrosis was apparent only at 30 days and was more severe in WTM. Diabetic nontransgenic mice lost 24% of their ventricular myocytes and showed a 28% myocyte hypertrophy; both phenomena were prevented by IGF-1. In diabetic WTM, p53 was increased in myocytes, and this activation of p53 was characterized by upregulation of Bax, angiotensinogen, Ang type 1 (AT 1 ) receptors, and Ang II. IGF-1 overexpression decreased these biochemical responses. In vivo accumulation of the reactive O 2 product nitrotyrosine and the in vitro formation of H 2 O 2 -˙OH in myocytes were higher in diabetic WTM than TGM. Apoptosis in vitro was detected in myocytes exhibiting high H 2 O 2 -˙OH fluorescence, and apoptosis in vivo was linked to the presence of nitrotyrosine. H 2 O 2 -˙OH generation and myocyte apoptosis in vitro were inhibited by the AT 1 blocker losartan and the O 2 scavenger Tiron. In conclusion, IGF-1 interferes with the development of diabetic myopathy by attenuating p53 function and Ang II production and thus AT 1 activation. This latter event might be responsible for the decrease in oxidative stress and myocyte death by IGF-1.

Vasoactive Drugs Influence Aortic Augmentation Index Independently of Pulse-Wave Velocity in Healthy Men

Abstract: Aortic augmentation index, a measure of central systolic blood pressure augmentation arising mainly from pressure-wave reflection, increases with vascular aging. The augmentation index is influenced by aortic pulse-wave velocity (related to aortic stiffness) and by the site and extent of wave reflection. To clarify the relative influence of pulse-wave velocity and wave reflection on the augmentation index, we studied the association between augmentation index, pulse-wave velocity, and age and examined the effects of vasoactive drugs to determine whether altering vascular tone has differential effects on pulse-wave velocity and the augmentation index. We made simultaneous measurements of the augmentation index and carotid-to-femoral pulse-wave velocity in 50 asymptomatic men aged 19 to 74 years at baseline and, in a subset, during the administration of nitroglycerin, angiotensin II, and saline vehicle. The aortic augmentation index was obtained by radial tonometry (Sphygmocor device, PWV Medical) with the use of an inbuilt radial to aortic transfer function. In multiple regression analysis, the aortic augmentation index was independently correlated only with age (R=0.58, P<0.0001). Nitroglycerin (3 to 300 microg/min IV) reduced the aortic augmentation index from 4.8+/-2.3% to -11.9+/-5.3% (n=10, P<0.002). Angiotensin II (75 to 300 ng/min IV) increased the aortic augmentation index from 9.3+/-2.4% to 18.3+/-2.9% (n=12, P<0.001). These drugs had small effects on aortic pulse-wave velocity, producing mean changes from baseline of <1 m/s (each P<0.05). In healthy men, vasoactive drugs may change aortic augmentation index independently from aortic pulse-wave velocity.

Angiotensin II–Induced Hypertension Accelerates the Development of Atherosclerosis in ApoE-Deficient Mice

Abstract: Background—Angiotensin II may contribute to the development and progression of atherosclerotic lesions because of its growth and proinflammatory effects. We sought to determine whether angiotensin II–induced hypertension would augment and accelerate the development of atherosclerotic lesions in apoE-deficient mice. Methods and Results—Angiotensin II (0.7 mg · kg−1 · d−1 SC) was administered to apoE-deficient mice via osmotic minipumps. The animals were placed on either standard chow or an atherogenic diet. After 8 weeks, the mean atherosclerotic lesion area in the descending thoracic and abdominal aortas of animals on a standard chow diet was 0.4±0.1% compared with 5.2±1.2% in those animals maintained on an atherogenic diet (P<0.0001). In angiotensin II–treated animals on standard chow, the mean lesion area was increased to 11.0±2.3%, which was further increased to 69.9±9.4% (P<0.0001) in angiotensin II–treated animals on an atherogenic diet. Similar findings were obtained when tissues from the ascending ...

Angiotensin II Blockade Reverses Myocardial Fibrosis in a Transgenic Mouse Model of Human Hypertrophic Cardiomyopathy

Abstract: Background—Hypertrophic cardiomyopathy (HCM), the most common cause of sudden cardiac death in the young, is characterized by cardiac hypertrophy, myocyte disarray, and interstitial fibrosis. We propose that hypertrophy and fibrosis are secondary to the activation of trophic and mitotic factors and, thus, potentially reversible. We determined whether the blockade of angiotensin II, a known cardiotrophic factor, could reverse or attenuate interstitial fibrosis in a transgenic mouse model of human HCM. Methods and Results—We randomized 24 adult cardiac troponin T (cTnT-Q92) mice, which exhibit myocyte disarray and interstitial fibrosis, to treatment with losartan or placebo and included 12 nontransgenic mice as controls. The mean dose of losartan and the mean duration of therapy were 14.2±5.3 mg · kg–1 · d–1 and 42±9.6 days, respectively. Mean age, number of males and females, and heart/body weight ratio were similar in the groups. Collagen volume fraction and extent of myocyte disarray were increased in th...

Inhibition of geranylgeranylation reduces angiotensin II-mediated free radical production in vascular smooth muscle cells: involvement of angiotensin AT1 receptor expression and Rac1 GTPase.

Abstract: 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) may exert pleiotropic effects on vascular cells independent of lowering plasma cholesterol. To elucidate the molecular mechanisms involved in these effects, we investigated the impact of statins on production of reactive oxygen species (ROS) in rat aortic vascular smooth muscle cells (VSMC). Exposure of VSMC to angiotensin II caused production of ROS via angiotensin AT1 receptor activation. Pretreatment with atorvastatin inhibited angiotensin II-induced ROS production. Atorvastatin decreased AT1 receptor mRNA levels in a time- and concentration-dependent manner and consistently reduced AT1 receptor density. l-Mevalonate but not hydroxy-cholesterol reversed the inhibitory effect of atorvastatin on AT1 receptor transcript levels. Inhibition of geranylgeranyl-transferase but not of farnesyl-transferase mimicked the effect of atorvastatin on AT1 receptor gene expression. Atorvastatin did not decrease AT1 receptor gene transcription but did reduce the half-life of the AT1 receptor mRNA. AT1 receptor activation by angiotensin II increased the expression of the GTPase rac1, enhanced rac1 GTP-binding activity, and increased the geranylgeranyl-dependent translocation of rac1 to the cell membrane. In contrast, statins inhibited rac1 activity and membrane translocation. Consequently, specific inhibition of rac1 with Clostridium sordellii lethal toxin blocked angiotensin II-induced production of free radicals. Finally, treatment of rats with atorvastatin caused down-regulation of aortic AT1 receptor mRNA expression and reduced aortic superoxide production in vivo. Cholesterol-independent down-regulation of AT1 receptor gene expression and inhibition of rac1, leading to decreased ROS production, demonstrates a novel regulatory mechanism of statins that may contribute to the beneficial effects of these drugs beyond lowering of plasma cholesterol.

Comparative effect of ace inhibition and angiotensin II type 1 receptor antagonism on bioavailability of nitric oxide in patients with coronary artery disease: role of superoxide dismutase.

Abstract: Background—Flow-dependent, endothelium-mediated vasodilation (FDD) and activity of extracellular superoxide dismutase (EC-SOD), the major antioxidative enzyme of the arterial wall, are severely impaired in patients with coronary artery disease (CAD). We hypothesized that both ACE inhibitor (ACEI) and angiotensin II type 1 receptor antagonist (AT1-A) increase bioavailability of nitric oxide (NO) by reducing oxidative stress in the vessel wall, possibly by increasing EC-SOD activity. Methods and Results—Thirty-five patients with CAD were randomized to 4 weeks of ACEI (ramipril 10 mg/d) or AT1-A (losartan 100 mg/d). FDD of the radial artery was determined by high-resolution ultrasound before and after intra-arterial N-monomethyl-l-arginine (L-NMMA) to inhibit NO synthase and before and after intra-arterial vitamin C to determine the portion of FDD inhibited by oxygen free radicals. EC-SOD activity was determined after release from endothelium by heparin bolus injection. FDD was improved after ramipril and lo...