scholarly journals High intraluminal pressure via H2O2 upregulates arteriolar constrictions to angiotensin II by increasing the functional availability of AT1 receptors

2008 ◽  
Vol 295 (2) ◽  
pp. H835-H841 ◽  
Author(s):  
Zsolt Bagi ◽  
Nora Erdei ◽  
Akos Koller
Keyword(s):  
High Pressure ◽  
Angiotensin Ii ◽  
Renin Angiotensin System ◽  
Intraluminal Pressure ◽  
Ang Ii ◽  
At1 Receptors ◽  
Angiotensin System ◽  
Dose Dependent

Previously, we found that high intraluminal pressure leads to production of reactive oxygen species (ROS) and also upregulates several components of the renin-angiotensin system in the wall of small arteries. We hypothesized that acute exposure of arterioles to high intraluminal pressure in vitro via increasing ROS production enhances the functional availability of type 1 angiotensin II (Ang II) receptors (AT1 receptors), resulting in sustained constrictions. In arterioles (∼180 μm) isolated from rat skeletal muscle, Ang II elicited dose-dependent constrictions, which decreased significantly by the second application [maximum (max.): from 59% ± 4% to 26% ± 5% at 10−8 M; P < 0.05] in the presence of 80 mmHg of intraluminal pressure. In contrast, if the arterioles were exposed to high intraluminal pressure (160 mmHg for 30 min), Ang II-induced constrictions remained substantial on the second application (max.: 51% ± 3% at 10−8 M). In the presence of Tiron and polyethylene glycol (PEG)-catalase, known to reduce the level of superoxide anion and hydrogen peroxide (H2O2), second applications of Ang II evoked similarly reduced constrictions, even after high-pressure exposure (29% ± 4% at 10−8 M). Furthermore, when arterioles were exposed to H2O2 (for 30 min, 10−7 M, at normal 80 mmHg pressure), Ang II-induced constrictions remained substantial on second applications (59% ± 5% at 10−8 M). These findings suggest that high pressure, likely via inducing H2O2 production, increases the functional availability of AT1 receptors and thus enhances Ang II-induced arteriolar constrictions. We propose that in hypertension–regardless of etiology–high intraluminal pressure, via oxidative stress, enhances the functional availability of AT1 receptors augmenting Ang II-induced constrictions.

scholarly journals The vascular renin-angiotensin system contributes to blunted vasodilation induced by transient high pressure in human adipose microvessels

2014 ◽  
Vol 307 (1) ◽  
pp. H25-H32 ◽  
Author(s):  
Matthew J. Durand ◽  
Shane A. Phillips ◽  
Michael E. Widlansky ◽  
Mary F. Otterson ◽  
David D. Gutterman
Keyword(s):  
Polyethylene Glycol ◽  
Enzyme Inhibitor ◽  
Renin Angiotensin System ◽  
Intraluminal Pressure ◽  
Ang Ii ◽  
Angiotensin System ◽  
Renin Angiotensin ◽  
Pressure Sensitive ◽  
Endothelial Denudation

Increased intraluminal pressure can reduce endothelial function in resistance arterioles; however, the mechanism of this impairment is unknown. The purpose of this study was to determine the effect of local renin-angiotensin system inhibition on the pressure-induced blunting of endothelium-dependent vasodilation in human adipose arterioles. Arterioles (100–200 μm) were dissected from fresh adipose surgical specimens, cannulated onto glass micropipettes, pressurized to an intraluminal pressure of 60 mmHg, and constricted with endothelin-1. Vasodilation to ACh was assessed at 60 mmHg and again after a 30-min exposure to an intraluminal pressure of 150 mmHg. The vasodilator response to ACh was significantly reduced in vessels exposed to 150 mmHg. Exposure of the vessels to the superoxide scavenger polyethylene glycol-SOD (100 U/ml), the ANG II type 1 receptor antagonist losartan (10−6 mol/l), or the angiotensin-converting enzyme inhibitor captopril (10−5 mol/l) prevented the pressure-induced reduction in ACh-dependent vasodilation observed in untreated vessels. High intraluminal pressure had no effect on papaverine-induced vasodilation or ANG II sensitivity. Increased intraluminal pressure increased dihydroethidium fluorescence in cannulated vessels, which could be prevented by polyethylene glycol-SOD or losartan treatment and endothelial denudation. These data indicate that high intraluminal pressure can increase vascular superoxide and reduce nitric oxide-mediated vasodilation via activation of the vascular renin-angiotensin system. This study provides evidence showing that the local renin-angiotensin system in the human microvasculature may be pressure sensitive and contribute to endothelial dysfunction after acute bouts of hypertension.

Angiotensin II downregulates ACE2-mediated enhancement of MMP-2 activity in human cardiofibroblasts

2013 ◽  
Vol 91 (6) ◽  
pp. 435-442 ◽  
Author(s):  
Tang-Ching Kuan ◽  
Mu-Yuan Chen ◽  
Yan-Chiou Liao ◽  
Li Ko ◽  
Yi-Han Hong ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Signaling Pathway ◽  
Renin Angiotensin System ◽  
Ang Ii ◽  
Angiotensin System ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Lentiviral Infection ◽  
And Control

Angiotensin converting enzyme II (ACE2) is a component of the renin-angiotensin system (RAS) that negatively regulates angiotensin II (Ang II). Ang II, in turn, affects the expression of matrix metalloproteinases (MMPs) to induce heart remodeling. The specific mechanisms by which ACE2 regulates MMP-2, however, remain unclear. The aim of this study was to investigate the regulatory relationships between Ang II, ACE2, and MMP-2. ACE2 expression was upregulated and downregulated in human cardiofibroblasts (HCFs) by lentiviral infection. Effects on MMP-2 activity, shed ACE2 activity, extracellular signal-regulated kinase (ERK) signaling pathway, and ADAM metallopeptidase domain 17 (ADAM17) expression were assessed. ACE2 increased MMP-2 activity, and Ang II inhibited this effect through the Ang II type-1 receptor (AT1R) and ERK1/2 signaling pathway. Ang II also reduced the effect of ACE2 on ERK1/2 levels, the activity of shed ACE2, and adam17 expression in HCFs. Additionally, these Ang II-mediated reductions could be attenuated by AT1R antagonist valsartan. In conclusion, these data help to clarify how ACE2 and Ang II interact to regulate MMP-2 and control tissue remodeling in heart disease.

Central and peripheral renin-angiotensin systems in ouabain-induced hypertension

2006 ◽  
Vol 291 (2) ◽  
pp. H624-H630 ◽  
Author(s):  
Warren J. Cheung ◽  
Mary-Anne H. Kent ◽  
Esraa El-Shahat ◽  
Hongwei Wang ◽  
Junhui Tan ◽  
...  
Keyword(s):  
Renin Angiotensin System ◽  
Mrna Levels ◽  
Ang Ii ◽  
Peripheral Tissues ◽  
Angiotensin System ◽  
Subcutaneous Infusion ◽  
Renin Angiotensin ◽  
Blood Pressures

Chronic subcutaneous infusion of ouabain causes hypertension via central pathways involving angiotensin type 1 (AT1) receptor stimulation. The present study assessed plasma and tissue ANG I and II levels as well as AT1 receptor and angiotensin-converting enzyme (ACE) mRNA levels and binding densities by real-time PCR and in vitro autoradiography in relevant brain nuclei and peripheral tissues (heart and kidney) in rats at 1 and/or 2 wk after start of ouabain infusion at 50 μg/day. After 2 wk (but not after 1 wk), blood pressures significantly increased (+15 mmHg). At 2 wk, plasma ANG I and II levels were markedly suppressed by ouabain. In contrast, in the heart and kidneys, ANG I levels were not affected, and ANG II levels tended to decrease, whereas in the hypothalamus ANG II content clearly increased. At 1 wk, no changes in ACE and AT1 receptor densities were seen. After 2 wk, there were significant decreases in AT1 receptor mRNA and densities in the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), and paraventricular nucleus (PVN). ACE densities decreased only in the OVLT and SFO, but ACE mRNA showed more variable responses (decrease in OVLT vs. increase in PVN). In the kidneys, at 2 wk both AT1 receptor and ACE densities were decreased, but mRNA abundance did not change. The heart showed no significant changes. The increase in hypothalamic ANG II content and associated decreases in central AT1 receptor and ACE densities support the involvement of the brain renin-angiotensin system in the central hypertensive mechanism of action of ouabain.

Control of intestinal absorption by the renin-angiotensin system

1985 ◽  
Vol 249 (1) ◽  
pp. G3-G15 ◽  
Author(s):  
N. R. Levens
Keyword(s):  
Intestinal Absorption ◽  
Renin Angiotensin System ◽  
Sympathetic Nerves ◽  
Ang Ii ◽  
Volume Depletion ◽  
Angiotensin System ◽  
Dual Action ◽  
Dose Dependent

In vivo angiotensin II (ANG II) exerts a dose-dependent dual action upon intestinal absorption. At low doses, ANG II stimulates sodium (Na) and water absorption from all intestinal areas. At high doses, ANG II inhibits absorption. The stimulation of jejunal absorption in response to ANG II is secondary to the release of norepinephrine (NE) from enteric sympathetic nerves. ANG II may act either within the brain or at the sympathetic nerve terminal to liberate NE. In contrast, the inhibition of absorption in response to ANG II is due to enteric prostaglandin production. At the present time it is unclear whether the changes in absorption in response to ANG II in vivo are due to changes in transport processes or secondary to alterations in enteric hemodynamics. ANG II also exerts a dose-dependent dual action on intestinal ion and water absorption in vitro. The mechanisms responsible for changes in absorption in vitro are unknown. However, since enteric sympathetic nerves are severed from their ganglia, it is unlikely that ANG II stimulates absorption in isolated preparations through release of NE. ANG II exerts a major control over intestinal absorption following volume depletion. The hormone controls colonic absorption through release of aldosterone and directly influences jejunal absorption via enteric sympathetic nerves. ANG II may control ileal absorption following volume depletion. All components of the renin-angiotensin system are present within the intestine. Furthermore, ANG II-like immunoreactivity is present within enteric nerves. The role of locally formed ANG II in the control of intestinal absorption has not been studied. Models illustrating the effect of ANG II on intestinal absorption are discussed.

Preovulatory changes in the angiotensin II system in bovine follicles

2013 ◽  
Vol 25 (3) ◽  
pp. 539 ◽  
Author(s):  
Lucas C. Siqueira ◽  
Joabel T. dos Santos ◽  
Rogério Ferreira ◽  
Robson Souza dos Santos ◽  
Adelina M. dos Reis ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Granulosa Cells ◽  
Renin Angiotensin System ◽  
Mrna Levels ◽  
Ang Ii ◽  
Hormone Production ◽  
Angiotensin System ◽  
Renin Angiotensin ◽  
Theca Cells

The present study evaluated whether the gonadotrophin surge modulates components of the renin–angiotensin system and whether angiotensin II (Ang II) plays a role in the production of hormones by follicular cells during the ovulatory process. In Experiment 1, cows were ovariectomised at various times (0, 3, 6, 12 and 24h) after GnRH injection to obtain preovulatory follicles. The concentration of Ang II in follicular fluid increased after GnRH and reached a peak at 24h, concomitant with the peak of angiotensinogen (AGT) mRNA expression in granulosa cells. AGT mRNA was not expressed in theca cells. Ang II receptor type 2 and angiotensin-converting enzyme mRNA levels were transiently upregulated in theca cells. In Experiment 2, an in vitro culture was used to determine whether Ang II could modulate hormone production by healthy dominant follicles. In the absence of LH, Ang II did not alter hormonal production by either theca or granulosa cells. Ang II plus LH increased progesterone and prostaglandin secretion by granulosa cells. In summary, the renin–angiotensin system is actively controlled during the preovulatory period and Ang II amplifies the stimulatory effects of LH on the secretion of progesterone and prostaglandins by granulosa cells.

A Review of Angiotensin Receptor Blocker-based Therapies at all Levels of Cardiovascular Risk

2011 ◽  
Vol 7 (4) ◽  
pp. 254 ◽  
Author(s):  
Giuliano Tocci ◽  
Lorenzo Castello ◽  
Massimo Volpe ◽  
◽  
◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Ventricular Hypertrophy ◽  
Renin Angiotensin System ◽  
Left Ventricular ◽  
Clinical Settings ◽  
Angiotensin Ii Receptor ◽  
Angiotensin System ◽  
Receptor Blockers ◽  
Artery Disease

The renin–angiotensin system (RAS) has a key role in the maintenance of cardiovascular homeostasis, and water and electrolyte metabolism in healthy subjects, as well as in several diseases including hypertension, left ventricular hypertrophy and dysfunction, coronary artery disease, renal disease and congestive heart failure. These conditions are all characterised by abnormal production and activity of angiotensin II, which represents the final effector of the RAS. Over the last few decades, accumulating evidence has demonstrated that antihypertensive therapy based on angiotensin II receptor blockers (ARBs) has a major role in the selective antagonism of the main pathological activities of angiotensin II. Significant efforts have been made to demonstrate that blocking the angiotensin II receptor type 1 (AT1) subtype receptors through ARB-based therapy results in proven benefits in different clinical settings. In this review, we discuss the main benefits of antihypertensive strategies based on ARBs in terms of their efficacy, safety and tolerability.

scholarly journals A novel role for miR-133a in centrally mediated activation of the renin-angiotensin system in congestive heart failure

2017 ◽  
Vol 312 (5) ◽  
pp. H968-H979 ◽  
Author(s):  
Neeru M. Sharma ◽  
Shyam S. Nandi ◽  
Hong Zheng ◽  
Paras K. Mishra ◽  
Kaushik P. Patel
Keyword(s):  
Heart Failure ◽  
Congestive Heart Failure ◽  
Paraventricular Nucleus ◽  
Renin Angiotensin System ◽  
Luciferase Reporter ◽  
Mrna Levels ◽  
Ang Ii ◽  
Angiotensin System ◽  
Renin Angiotensin

An activated renin-angiotensin system (RAS) within the central nervous system has been implicated in sympathoexcitation during various disease conditions including congestive heart failure (CHF). In particular, activation of the RAS in the paraventricular nucleus (PVN) of the hypothalamus has been recognized to augment sympathoexcitation in CHF. We observed a 2.6-fold increase in angiotensinogen (AGT) in the PVN of CHF. To elucidate the molecular mechanism for increased expression of AGT, we performed in silico analysis of the 3′-untranslated region (3′-UTR) of AGT and found a potential binding site for microRNA (miR)-133a. We hypothesized that decreased miR-133a might contribute to increased AGT in the PVN of CHF rats. Overexpression of miR-133a in NG108 cells resulted in 1.4- and 1.5-fold decreases in AGT and angiotensin type II (ANG II) type 1 receptor (AT1R) mRNA levels, respectively. A luciferase reporter assay performed on NG108 cells confirmed miR-133a binding to the 3′-UTR of AGT. Consistent with these in vitro data, we observed a 1.9-fold decrease in miR-133a expression with a concomitant increase in AGT and AT1R expression within the PVN of CHF rats. Furthermore, restoring the levels of miR-133a within the PVN of CHF rats with viral transduction resulted in a significant reduction of AGT (1.4-fold) and AT1R (1.5-fold) levels with a concomitant decrease in basal renal sympathetic nerve activity (RSNA). Restoration of miR-133a also abrogated the enhanced RSNA responses to microinjected ANG II within the PVN of CHF rats. These results reveal a novel and potentially unique role for miR-133a in the regulation of ANG II within the PVN of CHF rats, which may potentially contribute to the commonly observed sympathoexcitation in CHF. NEW & NOTEWORTHY Angiotensinogen (AGT) expression is upregulated in the paraventricular nucleus of the hypothalamus through posttranscriptional mechanism interceded by microRNA-133a in heart failure. Understanding the mechanism of increased expression of AGT in pathological conditions leading to increased sympathoexcitation may provide the basis for the possible development of new therapeutic agents with enhanced specificity.

scholarly journals Intracrine angiotensin II functions originate from noncanonical pathways in the human heart

2016 ◽  
Vol 311 (2) ◽  
pp. H404-H414 ◽  
Author(s):  
Carlos M. Ferrario ◽  
Sarfaraz Ahmad ◽  
Jasmina Varagic ◽  
Che Ping Cheng ◽  
Leanne Groban ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Functional Significance ◽  
Vascular Remodeling ◽  
Human Heart ◽  
Renin Angiotensin System ◽  
Ang Ii ◽  
Extended Form ◽  
Angiotensin I ◽  
Angiotensin System ◽  
Ras Genes

Although it is well-known that excess renin angiotensin system (RAS) activity contributes to the pathophysiology of cardiac and vascular disease, tissue-based expression of RAS genes has given rise to the possibility that intracellularly produced angiotensin II (Ang II) may be a critical contributor to disease processes. An extended form of angiotensin I (Ang I), the dodecapeptide angiotensin-(1–12) [Ang-(1–12)], that generates Ang II directly from chymase, particularly in the human heart, reinforces the possibility that an alternative noncanonical renin independent pathway for Ang II formation may be important in explaining the mechanisms by which the hormone contributes to adverse cardiac and vascular remodeling. This review summarizes the work that has been done in evaluating the functional significance of Ang-(1–12) and how this substrate generated from angiotensinogen by a yet to be identified enzyme enhances knowledge about Ang II pathological actions.

Angiotensin II effects on microvascular diameters of in vitro blood-perfused juxtamedullary nephrons

1986 ◽  
Vol 251 (4) ◽  
pp. F610-F618 ◽  
Author(s):  
P. K. Carmines ◽  
T. K. Morrison ◽  
L. G. Navar
Keyword(s):  
Angiotensin Ii ◽  
Constant Pressure ◽  
Ang Ii ◽  
Experimental Conditions ◽  
Vasoactive Hormones ◽  
Juxtamedullary Nephron ◽  
Single Nephron ◽  
Afferent Arterioles ◽  
Dose Dependent

The purpose of this study was to determine the specific renal microvascular segments that are functionally responsive to angiotensin II (ANG II) and other vasoactive hormones. Experiments were performed on juxtamedullary tissue from captopril-treated rats during perfusion with blood at a constant pressure of 110 mmHg. Epifluorescence videomicroscopy was utilized to measure diameters of arcuate and interlobular arteries (ART), mid- (MA) and late- (LA) afferent arterioles, and efferent arterioles (EA). Norepinephrine (700 nM) significantly decreased, and sodium nitroprusside (380 nM) increased, inside diameters of all segments. Topical application of ANG II (0.01 to 1 nM) induced significant reductions in diameters of all vessel segments: ART, 17.5 +/- 2.0%; MA, 19.6 +/- 2.5%; LA, 13.5 +/- 1.5%; and EA, 16.9 +/- 2.7%. The preglomerular response to ANG II was blocked by saralasin (10 microM) and, in most cases, was dose dependent; however, an initial hypersensitivity to low ANG II doses (30% decrease in diameter) was exhibited by 38% of the preglomerular vessels studied. Under these experimental conditions, single-nephron glomerular filtration rate decreased significantly in response to 0.01 nM ANG II exposure. These observations demonstrate that physiological concentrations of ANG II can elicit receptor-dependent and reversible vasoconstriction of the juxtamedullary nephron microvasculature at both pre- and postglomerular sites.

Angiotensin II-induced thirst, but not sodium appetite, via AT1 receptors in organum cavum prelamina terminalis

1995 ◽  
Vol 268 (6) ◽  
pp. R1401-R1405 ◽  
Author(s):  
M. el Ghissassi ◽  
S. N. Thornton ◽  
S. Nicolaidis
Keyword(s):  
Angiotensin Ii ◽  
Salt Intake ◽  
High Sensitivity ◽  
Ang Ii ◽  
Nacl Solution ◽  
At1 Receptors ◽  
Sodium Appetite ◽  
Specific Antagonist

The angiotensin receptor specificity, with respect to fluid intake, of the organum cavum prelamina terminalis (OCPLT), a recently discovered discrete forebrain structure with high sensitivity to angiotensin II (ANG II), was investigated. ANG II (10 ng) microinjected into the OCPLT significantly increased water consumption but did not induce intake of a hypertonic (3%) NaCl solution. Losartan, an ANG II type 1 (AT1) receptor-specific antagonist, produced dose-related (1-100 ng) inhibition of ANG II-induced drinking. The ANG II type 2 receptor-specific antagonist CGP-42112A was ineffective. Intake of the 3% NaCl solution in response to microinjection of either of the antagonists into the OCPLT was never observed. These findings suggest that water intake produced by microinjection of ANG II into the OCPLT is mediated by AT1 receptors uniquely and that, in contrast to other regions of the brain, these receptors do not induce salt intake when stimulated by ANG II.

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