Negative regulation of RhoA/Rho kinase by angiotensin II type 2 receptor in vascular smooth muscle cells: role in angiotensin II-induced vasodilation in stroke-prone spontaneously hypertensive rats

Role of Neural Circuits in Cognitive Impairment

Cognitive impairment refers to abnormalities in learning, memory and cognitive judgment, mainly manifested as symptoms such as decreased memory, impaired orientation and reduced computational ability. As the fundamental unit of information processing in the brain, neural circuits have recently attracted great attention due to their functions in regulating pain, emotion and behavior. Furthermore, a growing number of studies have suggested that neural circuits play an important role in cognitive impairment. Neural circuits can affect perception, attention and decision-making, they can also regulate language skill, thinking and memory. Pathological conditions crucially affecting the integrity and preservation of neural circuits and their connectivity will heavily impact cognitive abilities. Nowadays, technological developments have led to many novel methods for studying neural circuits, such as brain imaging, optogenetic techniques, and chemical genetics approaches. Therefore, neural circuits show great promise as a potential target in mitigating cognitive impairment. In this review we discuss the pathogenesis of cognitive impairment and the regulation and detection of neural circuits, thus highlighting the role of neural circuits in cognitive impairment. Hence, therapeutic agents against cognitive impairment may be developed that target neural circuits important in cognition.

Losartan and metabolite EXP3179 activate endothelial function without lowering blood pressure in AT2 receptor KO mice

BACKGROUND

We have documented profound release of nitric oxide (NO) and endothelium-derived hyperpolarization factor (EDHF) by angiotensin II (ANGII) receptor 1 (AT1) blocker (ARB) losartan and its unique metabolite EXP3179, a pleiotropic effect that may help rationalize the protective properties of ARBs. Since blood pressure (BP) lowering by ARBs likely require an ANGII-dependent switch from AT1 to ANGII receptor 2 (AT2) signaling, a receptor known to stimulate endothelial NO release, we investigated the contribution of AT1 and AT2 to losartan and EXP3179's endothelial function-activating properties.

EXPERIMENTAL APPROACH

Two AT1 ligands were used in an attempt to block the AT1-dependent endothelium-enhancing effects of EXP3179. AT2-null mice were used to evaluate the acute ex vivo and chronic in vivo effects of EXP3179 (20μM) and losartan (0.6 g/l), respectively, on endothelial function, BP and aortic stiffness.

KEY RESULTS

Ex vivo blockade of AT1 receptors did not attenuate EXP3179's effects on NO and EDHF-dependent endothelial function activation. We observed significant reductions in PE-induced contractility with EXP3179 in both WT and AT2 knockout (KO) aortic rings. In vivo, a 1-month chronic treatment with losartan did not affect pulse wave velocity (PWV) but decreased PE-induced contraction by 74.9 % in WT (p < 0.0001) and 47.3 % in AT2 KO (p < 0.05). Presence of AT2 was critical to losartan's BP lowering activity.

CONCLUSION

In contrast to BP lowering, the endothelial function-enhancing effects of losartan and EXP3179 are mostly independent of the classic ANGII/AT1/AT2 pathway, which sheds light on ARB pleiotropism.

Angiotensin II type 2 receptor-mediated dilation is greater in the cutaneous microvasculature of premenopausal women compared with men

Differential activation of the renin-angiotensin system (RAS) likely contributes to sex differences in cardiovascular outcomes in premenopausal women compared with age-matched men. Women demonstrate reduced activation of the vasoconstrictor angiotensin II type 1 receptors (AT1R) compared with men, and evidence suggests that women also likely have increased sensitivity of the vasodilatory angiotensin II type 2 receptors (AT2R). However, few in vivo studies have directly examined sex differences in AT2R-mediated dilation, or the balance between AT1R- and AT2R-mediated vascular responses in humans. Using the cutaneous microcirculation as a model, we hypothesized that AT2R-mediated dilation would be greater in premenopausal women compared with men, and that AT1R-blockade would augment AT2R-mediated dilation to a greater extent in men than in women. Twelve healthy women (22 ± 3 yr) and 12 men (23 ± 5 yr) had two intradermal microdialysis fibers placed in the ventral forearm for graded infusions of compound 21 (AT2R agonist; 10-12 to 10-8 M) in a control fiber site and a site treated with 43 µM losartan (AT1R antagonist). Red blood cell flux was measured continuously by laser-Doppler flowmetry, and cutaneous vascular conductance [CVC = flux/mean arterial pressure (MAP)] was normalized to maximum [%max; 28 mM sodium nitroprusside (SNP) + 43 °C]. Women had greater AT2R-mediated dilation compared with men (women: 25 ± 4 vs. men: 15 ± 2%max, P = 0.03). Local AT1R inhibition increased AT2R-mediated dilation in men (losartan: 26 ± 4 vs. control: 15 ± 2%max, P < 0.001) but had no effect in women (losartan: 27 ± 6 vs. control: 25 ± 4%max, P > 0.05). These data suggest that premenopausal women have a greater AT2R-mediated vasodilation response than men, and that AT1R activation inhibits AT2R-mediated dilation in men, but not in women.NEW & NOTEWORTHY Premenopausal women have greater protection against cardiovascular disease than age-matched men. However, the role of vasoconstrictor angiotensin II type 1 receptors (AT1R) and vasodilatory angiotensin II type 2 receptors (AT2R) in mediating these sex differences is unclear. Here, we demonstrate that women have greater AT2R-mediated vasodilation than men and that AT1R negates AT2R-mediated dilation in men, but not in women.

Restoring Angiotensin Type 2 Receptor Function Reverses PFOS-Induced Vascular Hyper-Reactivity and Hypertension in Pregnancy

Perfluorooctane sulfonic acid (PFOS) exposure during pregnancy induces hypertension with decreased vasodilatory angiotensin type-2 receptor (AT2R) expression and impaired vascular reactivity and fetal weights. We hypothesized that AT2R activation restores the AT1R/AT2R balance and reverses gestational hypertension by improving vascular mechanisms. Pregnant Sprague-Dawley rats were exposed to PFOS through drinking water (50 μg/mL) from gestation day (GD) 4-20. Controls received drinking water with no detectable PFOS. Control and PFOS-exposed rats were treated with AT2R agonist Compound 21 (C21; 0.3 mg/kg/day, SC) from GD 15-20. In PFOS dams, blood pressure was higher, blood flow in the uterine artery was reduced, and C21 reversed these to control levels. C21 mitigated the heightened contraction response to Ang II and enhanced endothelium-dependent vasorelaxation in uterine arteries of PFOS dams. The observed vascular effects of C21 were correlated with reduced AT1R levels and increased AT2R and eNOS protein levels. C21 also increased plasma bradykinin production in PFOS dams and attenuated the fetoplacental growth restriction. These data suggest that C21 improves the PFOS-induced maternal vascular dysfunction and blood flow to the fetoplacental unit, providing preclinical evidence to support that AT2R activation may be an important target for preventing or treating PFOS-induced adverse maternal and fetal outcomes.

The AT1/AT2 Receptor Equilibrium Is a Cornerstone of the Regulation of the Renin Angiotensin System beyond the Cardiovascular System

The AT₁ receptor has mainly been associated with the pathological effects of the renin-angiotensin system (RAS) (e.g., hypertension, heart and kidney diseases), and constitutes a major therapeutic target. In contrast, the AT₂ receptor is presented as the protective arm of this RAS, and its targeting via specific agonists is mainly used to counteract the effects of the AT₁ receptor. The discovery of a local RAS has highlighted the importance of the balance between AT₁/AT₂ receptors at the tissue level. Disruption of this balance is suggested to be detrimental. The fine tuning of this balance is not limited to the regulation of the level of expression of these two receptors. Other mechanisms still largely unexplored, such as S-nitrosation of the AT₁ receptor, homo- and heterodimerization, and the use of AT₁ receptor-biased agonists, may significantly contribute to and/or interfere with the settings of this AT₁/AT₂ equilibrium. This review will detail, through several examples (the brain, wound healing, and the cellular cycle), the importance of the functional balance between AT₁ and AT₂ receptors, and how new molecular pharmacological approaches may act on its regulation to open up new therapeutic perspectives.

Probiotics: functional food ingredients with the potential to reduce hypertension

Hypertension is an increasingly pressing public health concern across the globe. It can be triggered by a variety of factors such as age and diet, as well as the stress of modern life. The traditional treatment of hypertension includes calcium ion blockers, angiotensin II receptor inhibitors and β-receptor blockers, but these drugs have at least some side effects. Recent studies have revealed that intestinal flora plays a vital role in maintaining and promoting human health. This is due to the type and amount of probiotics present in the flora. Probiotics can reduce hypertension symptoms through four mechanisms: regulating vascular oxidative stress, producing short-chain fatty acids, restoring endothelial cell function, and reducing inflammation. It has been reported that certain functional foods, using probiotics as their raw material, can modify the composition of intestinal flora, thus regulating hypertension symptoms. Consequently, utilizing the probiotic function of probiotics in conjunction with the properties of functional foods to treat hypertension is a novel, side-effect-free treatment method. This study seeks to summarize the various factors that contribute to hypertension, the mechanism of probiotics in mitigating hypertension, and the fermented functional foods with probiotic strains, in order to provide a basis for the development of functional foods which utilize probiotics as their raw material and may have the potential to reduce hypertension.

The Proteome of Circulating Large Extracellular Vesicles in Diabetes and Hypertension

Hypertension and diabetes induce vascular injury through processes that are not fully understood. Changes in extracellular vesicle (EV) composition could provide novel insights. Here, we examined the protein composition of circulating EVs from hypertensive, diabetic and healthy mice. EVs were isolated from transgenic mice overexpressing human renin in the liver (TtRhRen, hypertensive), OVE26 type 1 diabetic mice and wild-type (WT) mice. Protein content was analyzed using liquid chromatography-mass spectrometry. We identified 544 independent proteins, of which 408 were found in all groups, 34 were exclusive to WT, 16 were exclusive to OVE26 and 5 were exclusive to TTRhRen mice. Amongst the differentially expressed proteins, haptoglobin (HPT) was upregulated and ankyrin-1 (ANK1) was downregulated in OVE26 and TtRhRen mice compared with WT controls. Conversely, TSP4 and Co3A1 were upregulated and SAA4 was downregulated exclusively in diabetic mice; and PPN was upregulated and SPTB1 and SPTA1 were downregulated in hypertensive mice, compared to WT mice. Ingenuity pathway analysis identified enrichment in proteins associated with SNARE signaling, the complement system and NAD homeostasis in EVs from diabetic mice. Conversely, in EVs from hypertensive mice, there was enrichment in semaphroin and Rho signaling. Further analysis of these changes may improve understanding of vascular injury in hypertension and diabetes.

Counter-regulatory renin-angiotensin system in hypertension: Review and update in the era of COVID-19 pandemic

Cardiovascular disease is the major cause of mortality and disability, with hypertension being the most prevalent risk factor. Excessive activation of the renin-angiotensin system (RAS) under pathological conditions, leading to vascular remodeling and inflammation, is closely related to cardiovascular dysfunction. The counter-regulatory axis of the RAS consists of angiotensin-converting enzyme 2 (ACE2), angiotensin (1-7), angiotensin (1-9), alamandine, proto-oncogene Mas receptor, angiotensin II type-2 receptor and Mas-related G protein-coupled receptor member D. Each of these components has been shown to counteract the effects of the overactivated RAS. In this review, we summarize the latest insights into the complexity and interplay of the counter-regulatory RAS axis in hypertension, highlight the pathophysiological functions of ACE2, a multifunctional molecule linking hypertension and COVID-19, and discuss the function and therapeutic potential of targeting this counter-regulatory RAS axis to prevent and treat hypertension in the context of the current COVID-19 pandemic.

The role of angiotensin II and relaxin in vascular adaptation to pregnancy

In brief

There is a pregnancy-induced vasodilation of blood vessels, which is known to have a protective effect on cardiovascular function and can be maintained postpartum. This review outlines the cardiovascular changes that occur in a healthy human and rodent pregnancy, as well as different pathways that are activated by angiotensin II and relaxin that result in blood vessel dilation.

Abstract

During pregnancy, systemic and uteroplacental blood flow increase to ensure an adequate blood supply that carries oxygen and nutrients from the mother to the fetus. This results in changes to the function of the maternal cardiovascular system. There is also a pregnancy-induced vasodilation of blood vessels, which is known to have a protective effect on cardiovascular health/function. Additionally, there is evidence that the effects of maternal vascular vasodilation are maintained post-partum, which may reduce the risk of developing high blood pressure in the next pregnancy and reduce cardiovascular risk later in life. At both non-pregnant and pregnant stages, vascular endothelial cells produce a number of vasodilators and vasoconstrictors, which transduce signals to the contractile vascular smooth muscle cells to control the dilation and constriction of blood vessels. These vascular cells are also targets of other vasoactive factors, including angiotensin II (Ang II) and relaxin. The binding of Ang II to its receptors activates different pathways to regulate the blood vessel vasoconstriction/vasodilation, and relaxin can interact with some of these pathways to induce vasodilation. Based on the available literature, this review outlines the cardiovascular changes that occur in a healthy human pregnancy, supplemented by studies in rodents. A specific focus is placed on vasodilation of blood vessels during pregnancy; the role of endothelial cells and endothelium-derived vasodilators will also be discussed. Additionally, different pathways that are activated by Ang II and relaxin that result in blood vessel dilation will also be reviewed.

The Angiotensin AT2 Receptor: From a Binding Site to a Novel Therapeutic Target

Discovered more than 30 years ago, the angiotensin AT2 receptor (AT2R) has evolved from a binding site with unknown function to a firmly established major effector within the protective arm of the renin-angiotensin system (RAS) and a target for new drugs in development. The AT2R represents an endogenous protective mechanism that can be manipulated in the majority of preclinical models to alleviate lung, renal, cardiovascular, metabolic, cutaneous, and neural diseases as well as cancer. This article is a comprehensive review summarizing our current knowledge of the AT2R, from its discovery to its position within the RAS and its overall functions. This is followed by an in-depth look at the characteristics of the AT2R, including its structure, intracellular signaling, homo- and heterodimerization, and expression. AT2R-selective ligands, from endogenous peptides to synthetic peptides and nonpeptide molecules that are used as research tools, are discussed. Finally, we summarize the known physiological roles of the AT2R and its abundant protective effects in multiple experimental disease models and expound on AT2R ligands that are undergoing development for clinical use. The present review highlights the controversial aspects and gaps in our knowledge of this receptor and illuminates future perspectives for AT2R research. SIGNIFICANCE STATEMENT: The angiotensin AT2 receptor (AT2R) is now regarded as a fully functional and important component of the renin-angiotensin system, with the potential of exerting protective actions in a variety of diseases. This review provides an in-depth view of the AT2R, which has progressed from being an enigma to becoming a therapeutic target.

Endothelial Cell Plasma Membrane Biomechanics Mediates Effects of Pro-Inflammatory Factors on Endothelial Mechanosensors: Vicious Circle Formation in Atherogenic Inflammation

Chronic low-grade vascular inflammation and endothelial dysfunction significantly contribute to the pathogenesis of cardiovascular diseases. In endothelial cells (ECs), anti-inflammatory or pro-inflammatory signaling can be induced by different patterns of the fluid shear stress (SS) exerted by blood flow on ECs. Laminar blood flow with high magnitude is anti-inflammatory, while disturbed flow and laminar flow with low magnitude is pro-inflammatory. Endothelial mechanosensors are the key upstream signaling proteins in SS-induced pro- and anti-inflammatory responses. Being transmembrane proteins, mechanosensors, not only experience fluid SS but also become regulated by the biomechanical properties of the lipid bilayer and the cytoskeleton. We review the apparent effects of pro-inflammatory factors (hypoxia, oxidative stress, hypercholesterolemia, and cytokines) on the biomechanics of the lipid bilayer and the cytoskeleton. An analysis of the available data suggests that the formation of a vicious circle may occur, in which pro-inflammatory cytokines enhance and attenuate SS-induced pro-inflammatory and anti-inflammatory signaling, respectively.

Emerging Role of Angiotensin AT2 Receptor in Anti-Inflammation: An Update

The hyperactive RAS and inflammation are closely associated. The angiotensin-II/AT1R axis of the RAS has been explored extensively for its role in inflammation and a plethora of pathological conditions. Understanding the role of AT2R in inflammation is an emerging area of research. The AT2R is expressed on a variety of immune and non-immune cells, which upon activation triggers the release of a host of cytokines and has multiple effects that coalesce to anti-inflammation and prevents maladaptive repair. The anti-inflammatory outcomes of AT2R activation are linked to its well-established signaling pathways involving formation of nitric oxide and activation of phosphatases. Collectively, these effects promote cell survival and tissue function. The consideration of AT2R as a therapeutic target requires further investigations.

New insights into RhoA/Rho-kinase signaling: a key regulator of vascular contraction

While Rho-signalling controlling vascular contraction is a canonical mechanism, with the modern approaches used in research, we are advancing our understanding and details into this pathway are often uncovered. RhoA-mediated Rho-kinase is the major regulator of vascular smooth muscle cells and a key player manoeuvring other functions in these cells. The discovery of new interactions, such as oxidative stress and hydrogen sulphide with Rho signalling are emerging addition not only in the physiology of the smooth muscle, but especially in the pathophysiology of vascular diseases. Likewise, the interplay between ageing and Rho-kinase in the vasculature has been recently considered. Importantly, in smooth muscle contraction, this pathway may also be affected by sex hormones, and consequently, sex-differences. This review provides an overview of Rho signalling mediating vascular contraction and focuses on recent topics discussed in the literature affecting this pathway such as ageing, sex differences and oxidative stress.

Cell signaling model for arterial mechanobiology

Arterial growth and remodeling at the tissue level is driven by mechanobiological processes at cellular and sub-cellular levels. Although it is widely accepted that cells seek to promote tissue homeostasis in response to biochemical and biomechanical cues—such as increased wall stress in hypertension—the ways by which these cues translate into tissue maintenance, adaptation, or maladaptation are far from understood. In this paper, we present a logic-based computational model for cell signaling within the arterial wall, aiming to predict changes in extracellular matrix turnover and cell phenotype in response to pressure-induced wall stress, flow-induced wall shear stress, and exogenous sources of angiotensin II, with particular interest in mouse models of hypertension. We simulate a number of experiments from the literature at both the cell and tissue level, involving single or combined inputs, and achieve high qualitative agreement in most cases. Additionally, we demonstrate the utility of this modeling approach for simulating alterations (in this case knockdowns) of individual nodes within the signaling network. Continued modeling of cellular signaling will enable improved mechanistic understanding of arterial growth and remodeling in health and disease, and will be crucial when considering potential pharmacological interventions.

Biological soft tissues are characterized by continuous production and removal of material, which endows them with a remarkable ability to adapt to changes in their biochemical and biomechanical environments. For arteries, mechanical stimuli result primarily from changes in blood pressure or flow, and biochemical changes are induced by multiple factors, including pharmacological intervention. In order to understand how arterial properties are maintained in health, or how they adapt or fail to adapt in disease, we must understand better how these diverse stimuli affect material turnover. Extracellular matrix is tightly regulated by mechano-sensing and mechano-regulation, and therefore cell signaling, thus we present a computational model of relevant signaling pathways within the vascular wall, with the aim of predicting changes in wall composition and function in response to three main inputs: pressure-induced wall stress, flow-induced wall shear stress, and exogenous angiotensin II. We obtain qualitative agreement with a range of experimental studies from the literature, and provide illustrative examples demonstrating how such models can be used to further our understanding of arterial remodeling.

Focal adhesion kinase, RhoA, and p38 mitogen-activated protein kinase modulates apoptosis mediated by angiotensin II AT2 receptors

Apoptosis plays an important role in cellular processes such as development, differentiation, and homeostasis. Although the participation of angiotensin II (Ang II) AT₂ receptors (AT ₂ R) in cellular apoptosis is well accepted, the signaling pathway involved in this process is not well established. We evaluated the participation of signaling proteins focal adhesion kinase (FAK), RhoA, and p38 mitogen-activated protein kinase (p38MAPK) in apoptosis induced by Ang II via AT ₂ R overexpressed in HeLa cells. Following a short stimulation time (120 to 240 minutes) with Ang II, HeLa-AT ₂ cells showed nuclear condensation, stress fibers disassembly and membrane blebbing. FAK, classically involved in cytoskeleton reorganization, has been postulated as an early marker of cellular apoptosis. Thus, we evaluated FAK cleavage, detected at early stimulation times (15 to 30 minutes). Apoptosis was confirmed by increased caspase-3 cleavage and enzymatic activity of caspase-3/7. Participation of RhoA was evaluated. HeLa-AT ₂ cells overexpressing RhoA wild-type (WT) or their mutants, RhoA V14 (constitutively active form) or RhoA N19 (dominant-negative form) were used to explore RhoA participation. HeLa-AT ₂ cells expressing the constitutively active variant RhoA V14 showed enhanced apoptotic features at earlier times as compared with cells expressing the WT variant. RhoA N19 expression prevented nuclear condensation/caspase activation. Inhibition of p38MAPK caused an increase in nuclear condensation and caspase-3/7 activation, suggesting a protective role of p38MAPK. Our results clearly demonstrated that stimulation of AT ₂ R induce apoptosis with participation of FAK and RhoA while p38MAPK seems to play a prosurvival role.

Angiotensin-(1-9) reduces cardiovascular and renal inflammation in experimental renin-independent hypertension

Hypertension-induced cardiovascular and renal damage can be mediated by activation of the renin-angiotensin-aldosterone system. There are different factors beyond renin-angiotensin-aldosterone system involved in hypertension and renal damage. Inflammation has emerged as an important mediator of hypertension and cardiovascular and kidney damage. Angiotensin-(1-9), a peptide of the renin-angiotensin system, counter-regulates both the physiological and pathological actions of angiotensin II. Recent data has shown that angiotensin-(1-9) protects the heart and blood vessels from adverse cardiovascular remodeling in experimental models of hypertension and/or heart failure and reduces cardiac fibrosis in stroke-prone, spontaneously hypertensive rats. These effects are mediated by the angiotensin II type 2 receptor (AT2R). However, it remains unknown whether angiotensin-(1-9) also has an anti-inflammatory effect. In the present study, we investigate whether angiotensin-(1-9) reduces inflammation and fibrosis in the heart, arteries, and kidney in a DOCA-salt hypertensive model and explore the mechanisms underlying the amelioration of end-organ damage. DOCA-salt hypertensive rats received: a) vehicle, b) angiotensin-(1-9), c) PD123319 (AT2R blocker), d) angiotensin-(1-9) plus A779 (a Mas receptor blocker) or e) angiotensin-(1-9) plus PD123319, and sham rats were used as a control. Our results showed that angiotensin-(1-9) decreased hypertension and increased vasodilation in DOCA-salt hypertensive rats. These actions were partially inhibited by PD123319. Moreover, angiotensin-(1-9) decreased diuresis, fibrosis, and inflammation. These beneficial effects were not mediated by Mas or AT2R blockers. We concluded that angiotensin-(1-9) protects against volume overload-induced hypertensive cardiovascular and kidney damage by decreasing inflammation in the heart, aortic wall, and kidney, through mechanisms independent of the Mas or AT2R.

Pressor response to angiotensin II is enhanced in aged mice and associated with inflammation, vasoconstriction and oxidative stress

Aging is commonly associated with chronic low-grade inflammation and hypertension but it is unknown whether a cause-effect relationship exists between them. We compared the sensitivity of young adult (8-12 w) and aged (23-31 mo) male C57Bl6J mice to develop hypertension in response to a slow-pressor dose of angiotensin II (Ang II; 0.28 mg/kg/d; 28 d). In young mice, the pressor response to Ang II was gradual and increased to 142±8 mmHg over 28 d. However, in aged mice, Ang II promptly increased SBP and reached 155±12 mmHg by 28 d. Aging increased renal but not brain expression of Ang II receptors (At1ar and At2r) and elevated AT1R:AT2R expression ratio in mesenteric artery. Maximal contractile responses of mesenteric arteries to Ang II were enhanced in aged mice and were not affected by L-NAME, indomethacin or tempol. Mesenteric arteries and thoracic aortae from aged mice exhibited higher Nox2-dependent superoxide production. Despite having higher renal expression of Nlrp3, Casp-1 and Il-1β, Ang II-induced hypertension (SBP: 139±7 mmHg) was unaffected by co-infusion of the NLRP3 inflammasome inhibitor, MCC950 (10 mg/kg/d; SBP: 145±10 mmHg). Thus, increased vascular AT1R:AT2R expression, rather than NLRP3 inflammasome activation, may contribute to enhanced responses to Ang II in aging.

Effects of natural peptides from food proteins on angiotensin converting enzyme activity and hypertension

Cardiovascular diseases are the leading cause of death. The underlying pathophysiology is largely contributed by an overactivation of the renin-angiotensin-aldosterone-system (RAAS). Herein, angiotensin II (AngII) is a key mediator not only in blood pressure control and vascular tone regulation, but also involved in inflammation, endothelial dysfunction, atherosclerosis, hypertension and congestive heart failure. Since more than three decades suppression of AngII generation by inhibition of the angiotensin-converting enzyme (ACE) or blockade of the AngII-receptor has shown clinical benefit by reducing hypertension, atherosclerosis and other inflammation-associated cardiovascular diseases. Besides pharmaceutical ACE-inhibitors some natural peptides derived from food proteins reduce in vitro ACE activity. Several animal studies and a few human clinical trials have shown antihypertensive effects of such peptides, which might be attractive as food additives to prevent age-related RAAS activation. However, their inhibitory potency on in vitro ACE activity does not always correlate with an antihypertensive impact. While some peptides with high inhibitory activity on ACE-activity in vitro show no antihypertensive effect in vivo, other peptides with only a moderate ACE inhibitory activity in vitro cause such effects. The explanation for this conflicting phenomenon between inhibitory activity and antihypertensive effect remains unclear to date. This review shall critically address the effects of natural peptides derived from different food proteins on the cardiovascular system and the possible underlying mechanisms. A central aspect will be to point to conceptual gaps in the current understanding of the action of these peptides with respect to in vivo blood pressure lowering effects.

Hypertensive nephropathy. Moving from classic to emerging pathogenetic mechanisms

Hypertensive kidney disease classically entails nephroangiosclerosis and hyalinosis with glomerular damage. However, in recent years, several evidences showed that high blood pressure also injures tubular cells, inducing epithelial-to-mesenchymal transition and tubulointerstitial fibrosis. Recently investigated mechanisms are also podocyte effacement and loss, which lead to denudation of the glomerular basement membrane and focal adhesion of the tufts to the Bowman's capsule, with reduced filtration and scars. Starting from the classic concept of nephroangiosclerosis, this review examines the recently emerged knowledge of new biochemical and molecular mechanisms underlying the kidney damage in hypertension and discusses how viable podocytes or podocyte-deriving proteins are promising tools for early diagnosis of renal remodelling in hypertension.

DL0805-2, a novel indazole derivative, relaxes angiotensin II-induced contractions of rat aortic rings by inhibiting Rho kinase and calcium fluxes

AIM

DL0805-2 [N-(1H-indazol-5-yl)-1-(4-methylbenzyl) pyrrolidine-3-carboxamide] is a DL0805 derivative with more potent vasorelaxant activity and lower toxicity. This study was conducted to investigate the vasorelaxant mechanisms of DL0805-2 on angiotensin II (Ang II)-induced contractions of rat thoracic aortic rings in vitro.

METHODS

Rat thoracic aortic rings and rat aortic vascular smooth muscle cells (VSMCs) were pretreated with DL0805-2, and then stimulated with Ang II. The tension of the aortic rings was measured through an isometric force transducer. Ang II-induced protein phosphorylation, ROS production and F-actin formation were assessed with Western blotting and immunofluorescence assays. Intracellular free Ca(2+) concentrations were detected with Fluo-3 AM.

RESULTS

Pretreatment with DL0805-2 (1-100 μmol/L) dose-dependently inhibited the constrictions of the aortic rings induced by a single dose of Ang II (10(-7) mol/L) or accumulative addition of Ang II (10(-10)-10(-7) mol/L). The vasodilatory effect of DL0805-2 was independent of endothelium. In the aortic rings, pretreatment with DL0805-2 (1, 3, and 10 μmol/L) suppressed Ang II-induced Ca(2+) influx and intracellular Ca(2+) mobilization, and Ang II-induced phosphorylation of two substrates of Rho kinase (MLC and MYPT1). In VSMCs, pretreatment with DL0805-2 (1, 3, and 10 μmol/L) also suppressed Ang II-induced Ca(2+) fluxes and phosphorylation of MLC and MYPT1. In addition, pretreatment with DL0805-2 attenuated ROS production and F-actin formation in the cells.

CONCLUSION

DL0805-2 exerts a vasodilatory action in rat aortic rings through inhibiting the Rho/ROCK pathway and calcium fluxes.

Understanding the mechanisms of angiotensin II signaling involved in hypertension and its long-term sequelae: insights from Bartter's and Gitelman's syndromes, human models of endogenous angiotensin II signaling antagonism

Angiotensin II (Ang II) plays a key role in hypertension, renal and cardiovascular pathophysiology via intracellular pathways that involve the activation of a multiplicity of signaling mechanisms. Although experimental and genetic animal models have been developed and used to explore Ang II signaling's role in hypertension, a complete understanding of the processes mediating Ang II signaling in hypertension in humans remains elusive. One impediment is that these animal models do not exhibit all the traits of human hypertension, making it impossible to extrapolate from them to humans. To overcome this issue, we have used patients with Bartter's and Gitelman's syndromes, a human model of endogenously blunted and blocked Ang II signaling that presents a constellation of clinical findings which manifest themselves as the opposite of hypertension. This article reviews the aspects of the pathophysiology of human hypertension and its short and long term sequelae, and uses the results of our studies in Bartter's and Gitelman's syndromes along with those of others to gain better insight and understanding of the role of Ang II signaling in these processes.

ACE2 and vasoactive peptides: novel players in cardiovascular/renal remodeling and hypertension

The renin-angiotensin system (RAS) is a key component of cardiovascular physiology and homeostasis due to its influence on the regulation of electrolyte balance, blood pressure, vascular tone and cardiovascular remodeling. Deregulation of this system contributes significantly to the pathophysiology of cardiovascular and renal diseases. Numerous studies have generated new perspectives about a noncanonical and protective RAS pathway that counteracts the proliferative and hypertensive effects of the classical angiotensin-converting enzyme (ACE)/angiotensin (Ang) II/angiotensin type 1 receptor (AT1R) axis. The key components of this pathway are ACE2 and its products, Ang-(1-7) and Ang-(1-9). These two vasoactive peptides act through the Mas receptor (MasR) and AT2R, respectively. The ACE2/Ang-(1-7)/MasR and ACE2/Ang-(1-9)/AT2R axes have opposite effects to those of the ACE/Ang II/AT1R axis, such as decreased proliferation and cardiovascular remodeling, increased production of nitric oxide and vasodilation. A novel peptide from the noncanonical pathway, alamandine, was recently identified in rats, mice and humans. This heptapeptide is generated by catalytic action of ACE2 on Ang A or through a decarboxylation reaction on Ang-(1-7). Alamandine produces the same effects as Ang-(1-7), such as vasodilation and prevention of fibrosis, by interacting with Mas-related GPCR, member D (MrgD). In this article, we review the key roles of ACE2 and the vasoactive peptides Ang-(1-7), Ang-(1-9) and alamandine as counter-regulators of the ACE-Ang II axis as well as the biological properties that allow them to regulate blood pressure and cardiovascular and renal remodeling.

Mechanistic approach to the pathophysiology of target organ damage in hypertension from studies in a human model with characteristics opposite to hypertension: Bartter's and Gitelman's syndromes

INTRODUCTION

Extensive studies using Bartter's/Gitelman's syndrome patients have provided insights into the angiotensin II (Ang II) signaling pathways involved in the regulation of vascular tone and cardiovascular-renal remodeling. The renin-angiotensin-aldosterone system is activated in these syndromes, however, patients do not develop hypertension and cardiovascular remodeling and clinically manifest conditions opposite to hypertension. The short- and the long-term signaling of Ang II remains an important matter of investigation to shed light on mechanisms responsible for the pathophysiology of hypertension and its long-term complications. The long-term signaling of Ang II is involved in the pathophysiology of cardiovascular-renal remodeling and inflammatory responses in which the balance between RhoA/Rho kinase pathway and NO system plays a crucial role.

METHODS AND RESULTS

In this brief review, the results of our studies in Bartter's and Gitelman's syndromes are reported on these processes.

CONCLUSIONS

The information obtained from these studies can clarify, confirm or be used to extend the biochemical mechanisms responsible for the pathophysiology of hypertension and its long-term complications and could offer further chances to identify additional potential significant targets of therapy.

Summertime dosage-dependent hypersensitivity to an angiotensin II receptor blocker

Background

Summertime dips in blood pressure (BP), both in normotensive and hypertensive subjects, are well known. However, the dips are small and are not related to particular forms or doses of antihypertensive medication. Nevertheless it is the practice in some quarters to decrease antihypertensive medication in summer, and/or to increase in winter. Large scale studies being inconclusive, there are calls for long-term examination of the relationship between environmental temperature and blood pressure in single individuals under medication.

Case presentation

While analyzing data from a subject whose BP had been controlled for a decade with the angiotensin-II receptor blocker losartan, an extreme, dosage-dependent, summertime dip came to light. Downward dosage adjustment appeared essential and may have prevented hypotension-related pathology.

Conclusion

The benefits of aggressive medication (the “J curve” phenomenon) being debated, the possibility of seasonal hypersensitivity, perhaps explicable in terms of differential signaling by countervailing receptors, should be taken into account when considering dosage adjustments in hypertensive subjects.

Identification of the Vasoconstriction-Inhibiting Factor (VIF), a Potent Endogenous Cofactor of Angiotensin II Acting on the Angiotensin II Type 2 Receptor

BACKGROUND

The renin-angiotensin system and especially the angiotensin peptides play a central role in blood pressure regulation. Here, we hypothesize that an as-yet unknown peptide is involved in the action of angiotensin II modulating the vasoregulatory effects as a cofactor.

METHODS AND RESULTS

The peptide with vasodilatory properties was isolated from adrenal glands chromatographically. The effects of this peptide were evaluated in vitro and in vivo, and the receptor affinity was analyzed. The plasma concentration in humans was quantified in patients with chronic kidney disease, patients with heart failure, and healthy control subjects. The amino acid sequence of the peptide from bovine adrenal glands was HSSYEDELSEVL EKPNDQAE PKEVTEEVSSKDAAE, which is a degradation product of chromogranin A. The sequence of the peptide isolated from human plasma was HSGFEDELSEVLENQSSQAELKEAVEEPSSKDVME. Both peptides diminished significantly the vasoconstrictive effect of angiotensin II in vitro. Therefore, we named the peptide vasoconstriction-inhibiting factor (VIF). The vasoregulatory effects of VIF are mediated by the angiotensin II type 2 receptor. VIF impairs angiotensin II-induced phosphorylation of the p38 mitogen-activated protein kinase pathway but not of extracellular-regulated kinase 1/2. The vasodilatory effects were confirmed in vivo. The plasma concentration was significantly increased in renal patients and patients with heart failure.

CONCLUSIONS

VIF is a vasoregulatory peptide that modulates the vasoconstrictive effects of angiotensin II by acting on the angiotensin II type 2 receptor. It is likely that the increase in VIF may serve as a counterregulatory effect to defend against hypertension. The identification of this target may help us to understand the pathophysiology of renal and heart failure and may form a basis for the development of new strategies for the prevention and treatment of cardiovascular disease.

Angiotensin II and Cardiovascular-Renal Remodelling in Hypertension: Insights from a Human Model Opposite to Hypertension

Insights into the Angiotensin II (Ang II) signalling pathways have been provided by extensive studies using Bartter's/Gitelman's syndromes patients. These syndromes are characterized by activation of the renin-angiotensin-aldosterone system but do not develop hypertension and cardiovascular remodelling, therefore represent a mirror image of hypertension and clinically manifest themselves as the opposite of hypertension. The short and the long-term signalling of Ang II remain an important matter of investigation to shed light on mechanisms responsible for the pathophysiology of hypertension and its long-term complications, such as cardiovascular remodelling and atherogenesis. In particular the long-term signalling of Ang II is involved in the pathophysiology of cardiovascular-renal remodelling, inflammatory and hypertrophic responses in which the relationship between RhoA/Rho kinase pathway and NO system plays a crucial role. This review reports the results of our studies in Bartter's and Gitelman's syndromes to get better insight these processes and the role of Ang II signaling. The information obtained from the studies in Bartter's/Gitelman's patients can, in fact, clarify, confirm or be used to gather more general data on the biochemical mechanisms responsible for the pathophysiology of hypertension and its long-term complications and could contribute to identify additional potential significant targets of therapy.

Increased level of p63RhoGEF and RhoA/Rho kinase activity in hypertensive patients

OBJECTIVE

p63RhoGEF, a guanine nucleotide exchange factor, has been reported 'in vitro' as key mediator of the angiotensin II-induced RhoA/Rho kinase activation leading to vasoconstriction and cardiovascular remodeling. We assessed p63RhoGEF gene and protein expression and RhoA/Rho kinase activity in essential hypertensive and Bartter's and Gitelman's syndrome patients, a human model opposite to hypertension; the latter have, in fact, increased plasma angiotensin II, activation of the renin-angiotensin system, yet normotension/hypotension, reduced peripheral resistance and lack of cardiovascular remodeling due to an endogenously blunted angiotensin II type 1 receptor signaling.

METHODS

Mononuclear cell p63RhoGEF gene and protein expression and the phosphorylation status of the myosin phosphatase target protein-1 (MYPT-1), marker of Rho kinase activity, were assessed in essential hypertensive patients, Bartter's/Gitelman's patients and healthy individuals by quantitative real-time PCR and western blot.

RESULTS

p63RhoGEF mRNA and protein level and MYPT-1 phosphorylation status were higher in hypertensive patients and lower in Bartter's/Gitelman's patients compared with healthy individuals: p63RhoGEF mRNA level: 0.59 ± 0.17 ΔΔCt vs. 0.37 ± 0.17 vs. 0.20 ± 0.19, analysis of variance (ANOVA): P <0.016; p63RhoGEF protein level 1.35 ± 0.14 vs. 1.09 ± 0.05 vs. 0.90 ± 0.09 densitometric units, ANOVA: P <0.0001; MYPT-1: 1.39 ± 0.34 vs. 1.01 ± 0.12 vs. 0.81 ± 0.06, ANOVA: P < 0.0001. p63RhoGEF mRNA was significantly correlated with both SBP and DBP in both hypertensive patients (R = 0.79, P < 0.02 and R = 0.78, P < 0.02) and in Bartter's syndrome/Gitelman's syndrome patients (R = 0.87, P < 0.001 and R = 0.86, P < 0.001), respectively.

CONCLUSION

Increased p63RhoGEF mRNA and protein level and Rho kinase activity are shown for the first time in essential hypertensive patients, whereas the opposite was found in Bartter's/Gitelman's patients, a human model opposite to hypertension. These results combined with other 'in-vitro' studies strongly support the crucial importance of p63RhoGEF in Ang II-mediated signaling involved in the regulation of blood pressure and its long-term complications in humans.

Recent insights and therapeutic perspectives of angiotensin-(1-9) in the cardiovascular system

Chronic RAS (renin-angiotensin system) activation by both AngII (angiotensin II) and aldosterone leads to hypertension and perpetuates a cascade of pro-hypertrophic, pro-inflammatory, pro-thrombotic and atherogenic effects associated with cardiovascular damage. In 2000, a new pathway consisting of ACE2 (angiotensin-converting enzyme2), Ang-(1-9) [angiotensin-(1-9)], Ang-(1-7) [angiotensin-(1-7)] and the Mas receptor was discovered. Activation of this novel pathway stimulates vasodilation, anti-hypertrophy and anti-hyperplasia. For some time, studies have focused mainly on ACE2, Ang-(1-7) and the Mas receptor, and their biological properties that counterbalance the ACE/AngII/AT1R (angiotensin type 1 receptor) axis. No previous information about Ang-(1-9) suggested that this peptide had biological properties. However, recent data suggest that Ang-(1-9) protects the heart and blood vessels (and possibly the kidney) from adverse cardiovascular remodelling in patients with hypertension and/or heart failure. These beneficial effects are not modified by the Mas receptor antagonist A779 [an Ang-(1-7) receptor blocker], but they are abolished by the AT2R (angiotensin type 2 receptor) antagonist PD123319. Current information suggests that the beneficial effects of Ang-(1-9) are mediated via the AT2R. In the present review, we summarize the biological effects of the novel vasoactive peptide Ang-(1-9), providing new evidence of its cardiovascular-protective activity. We also discuss the potential mechanism by which this peptide prevents and ameliorates the cardiovascular damage induced by RAS activation.

Angiotensin Type 2 Receptor Stimulation Increases Renal Function in Female, but Not Male, Spontaneously Hypertensive Rats

Accumulating evidence suggests that the protective pathways of the renin–angiotensin system are enhanced in women, including the angiotensin type 2 receptor (AT 2 R), which mediates vasodilatory and natriuretic effects. To provide insight into the sex-specific ability of pharmacological AT 2 R stimulation to modulate renal function in hypertension, we examined the influence of the AT 2 R agonist, compound 21 (100–300 ng/kg per minute), on renal function in 18- to 19-week-old anesthetized male and female spontaneously hypertensive rats. AT 2 R stimulation significantly increased renal blood flow in female hypertensive rats ( P Treatment <0.001), without influencing arterial pressure. For example, at 300 ng/kg per minute of compound 21, renal blood flow increased by 14.3±1.8% from baseline. Furthermore, at 300 ng/kg per minute of compound 21, a significant increase in urinary sodium excretion was observed in female hypertensive rats (+180±59% from baseline; P <0.05 versus vehicle-treated rats). This was seen in the absence of any major change in glomerular filtration rate, indicating that the natriuretic effects of AT 2 R stimulation were likely the result of altered renal tubular function. Conversely, we did not observe any significant effect of AT 2 R stimulation on renal hemodynamic or excretory function in male hypertensive rats. Finally, gene expression studies confirmed greater renal AT 2 R expression in female than in male hypertensive rats. Taken together, acute AT 2 R stimulation enhanced renal vasodilatation and sodium excretion without concomitant alterations in glomerular filtration rate in female hypertensive rats. Chronic studies of AT 2 R agonist therapy on renal function and arterial pressure in hypertensive states are now required to establish the suitability of AT 2 R as a therapeutic target for cardiovascular disease, particularly in women.

Vascular effects of a tripeptide fragment of novokinine in hypertensive rats: Mechanism of the hypotensive action

BACKGROUND

Activation of angiotensin AT2 receptors (AT2R) counteracts vasoconstrictor effects of AT1R stimulation and contributes to blood pressure control. We examined effects on mean arterial pressure (MAP) and renal hemodynamics of LKP, a tripeptide fragment of novokinine, an established AT2R agonist.

METHODS

Effects of intravenous LKP infusion and then superimposed losartan (AT1R antagonist) on MAP, total renal (RBF, Transonic probe) and renal medullary blood flows (laser-Doppler), and on renal excretion, were examined in anesthetized (1) Wistar rats with acute norepinephrine-induced hypertension, untreated or pretreated with AT2R antagonist (PD 123319) and (2) spontaneously hypertensive rats (SHR) maintained on standard or high-sodium (HS) diet.

RESULTS

In Wistar rats LKP decreased MAP (-4%, p<0.01) and increased renal medullary perfusion, these effects were abolished in rats pretreated with PD 123319 in which a post-LKP increase in MAP (+6%, p<0.02) occurred. LKP did not alter MAP in SHR; in those on HS diet RBF decreased (-14%, p<0.02), the response that was reverted by losartan. Addition of losartan always decreased or tended to decrease MAP.

CONCLUSIONS

LKP lowered MAP in norepinephrine-induced hypertension, probably via activation of AT2R. At reduced availability of AT2R, as in SHR, LKP appeared to bind to different receptors, possibly AT1, and induced systemic or renal vasoconstriction. Compared to the parent novokinine, a smaller LKP molecule might be easier absorbed after oral application and more useful in therapy.

Small Rho GTPases in the control of cell shape and mobility

Rho GTPases are a class of evolutionarily conserved proteins comprising 20 members, which are predominantly known for their role in regulating the actin cytoskeleton. They are primarily regulated by binding of GTP/GDP, which is again controlled by regulators like GEFs, GAPs, and RhoGDIs. Rho GTPases are thus far well known for their role in the regulation of actin cytoskeleton and migration. Here we present an overview on the role of Rho GTPases in regulating cell shape and plasticity of cell migration. Finally, we discuss the emerging roles of ubiquitination and sumoylation in regulating Rho GTPases and cell migration.

Angiotensin II type 2 receptor-mediated and nitric oxide-dependent renal vasodilator response to compound 21 unmasked by angiotensin-converting enzyme inhibition in spontaneously hypertensive rats in vivo

Angiotensin II type 2 receptor (AT2R)-mediated vasodilation has been demonstrated in different vascular beds in vitro and in perfused organs. In vivo studies, however, consistently failed to disclose renal vasodilator responses to compound 21, a selective AT2R agonist, even after angiotensin II type 1 receptor blockade. Here, we investigated in vivo whether angiotensin-converting enzyme inhibition, reducing endogenous angiotensin II levels, could unmask the effects of selective AT2R stimulation on blood pressure and renal hemodynamics in normotensive and hypertensive rats. After pretreatment with the angiotensin-converting enzyme inhibitor captopril, intravenous administration of compound 21 did not affect blood pressure and induced dose-dependent renal vasodilator responses in spontaneously hypertensive but not in normotensive rats. The D1 receptor agonist fenoldopam, used as positive control, reduced blood pressure and renal vascular resistance in both strains. The AT2R antagonist PD123319 and the nitric oxide synthase inhibitor L-NMMA (N(G)-monomethyl-L-arginine acetate) abolished the renal vasodilator response to compound 21 without affecting responses to fenoldopam. The cyclooxygenase inhibitor indomethacin partially inhibited the renal vascular response to compound 21, whereas the bradykinin B2 receptor antagonist icatibant was without effect. Angiotensin-converting enzyme inhibition unmasked a renal vasodilator response to selective AT2R stimulation in vivo, mediated by nitric oxide and partially by prostaglandins. AT2R may have a pathophysiological role to modulate renal hemodynamic effects of angiotensin II in the hypertensive state.

How does the angiotensin II type 1 receptor 'trump' the type 2 receptor in blood pressure control?

BACKGROUND

A kinetic model for the binding of angiotensin II (Ang II) to AT1 receptors (AT1Rs) in arterioles did suggest a novel mechanism of association rate amplification and facilitated Ang II diffusion in vivo.

AIM OF STUDY

To examine how this mechanism, acting on AT1R, will affect the stimulation of AT2R.

METHOD

The model distinguishes between the diffusion of plasma Ang II across the endothelium layer (thickness 10(-4) - 5 × 10(-4) cm) into the vascular smooth muscle (VSM) layer (5 × 10(-4) cm), and the diffusion of tissue Ang II from perivascular interstitium (thickness of micromilieu fluid layer at abluminal VSM surface 10(-6) - 10(-5) cm, i.e. 1 to 10 times the glycocalyx). Thus, Ang II concentration [Ang II] is taken to be 0 at the abluminal and adluminal VSM cell surfaces, respectively. Tissue Ang II is defined as originating from local generation and/or from the capillary circulation. [Ang II]/AT1R and [Ang II]/AT2R occupancy curves for the two directions of diffusion are constructed from the model-based calculations.

RESULTS

Ang II, at 10(-15)-10(-13) mol/ml (~1-100 pg/ml), is much less likely to react with vascular AT2R than AT1R, though it has similar affinity for the receptor types. With plasma [Ang II] = 10(-15)-10(-13) mol/ml, AT2R occupancy is less than 10% of maximum on endothelium, and virtually 0 on VSM, whereas AT1R occupancy on VSM is virtually 0 at plasma [Ang II] < 10(-14) mol/ml, and between 0 and 30% at plasma [Ang II] = 10(-13) mol/ml. With tissue [Ang II] = 10(-15)-10(-13) mol/ml, VSM AT2R occupancy is close to 0, whereas VSM AT1R occupancy is 40-60% in the absence of endocytotic AT1R down-regulation, and up to 70-90% in its presence.

CONCLUSION

The threshold concentration of Ang II needed for response is much higher for AT2R than for AT1R. Plasma Ang II rather than tissue Ang II is the agonist of AT2R, and the reverse applies to AT1R. Thus, AT2R stimulation may come into play only at unusually high circulating levels of Ang II.

Angiotensin II regulates the LARG/RhoA/MYPT1 axis in rat vascular smooth muscle in vitro

AIM

To identify a key protein that binds monomeric G protein RhoA and activates the RhoA/Rho kinase/MYPT1 axis in vascular smooth muscle cells (VSMCs) upon angiotensin II (Ang II) stimulation.

METHODS

Primary cultured VSMCs from Sprague-Dawley rats were transfected with siRNAs against leukemia-associated RhoGEF (LARG), and then treated with Ang II, losartan, PD123319, or Val(5)-Ang II. The target mRNA and protein levels were determined using qPCR and Western blot analysis, respectively. Rat aortic rings were isolated, and the isometric contraction was measured with a force transducer and recorder.

RESULTS

Stimulation with Ang II (0.1 μmol/L) for 0.5 h significantly increased the level of LARG mRNA in VSMCs. At 3, 6, and 9 h after the treatment with Ang II (0.1 μmol/L) plus AT(2) antagonist PD123319 (1 μmol/L) or with AT(1) agonist Val(5)-Ang II (1 μmol/L), the LARG protein, RhoA activity, and phosphorylation level of myosin phosphatase target subunit 1 (MYPT1) in VSMCs were significantly increased. Knockdown of LARG with siRNA reduced these effects caused by AT(1) receptor activation. In rat aortic rings pretreated with LARG siRNA, Ang II-induced contraction was diminished.

CONCLUSION

Ang II upregulates LARG gene expression and activates the LARG/RhoA/MYPT1 axis via AT(1), thereby maintaining vascular tone.

The vascular phenotypes in hypertension: Relation with the natural history of hypertension

The different vascular phenotypes found in hypertension comprise different aspects. They may be clinical, diagnostic, structural, mechanical, functional, cellular and extracellular, signaling and molecular, proteomic, and gene expression phenotypes. In this manuscript the emphasis will be on the various structure, mechanics, dysfunction, and cell and signaling changes that can be demonstrated in hypertension, and particularly in human hypertension. The phenotype relates to the natural history of hypertension, increasingly elucidated on the basis of cohort studies. The evolution from pre-hypertension to diastolic, systolic, and systo-diastolic hypertension may have a vascular substratum that could explain, in part, the prevalence of each of these phenotypes. The potential for intervention to prevent the passage from pre-hypertension to hypertension thanks to therapies that modulate the development of vascular remodeling is highlighted.

Fasudil improves the endothelial dysfunction in the aorta of spontaneously hypertensive rats

We investigated the effects of fasudil, a Rho kinase inhibitor, in the endothelial dysfunction of aortas from spontaneously hypertensive rats (SHRs). SHRs were divided in three groups; intraperitoneally (i.p.) vehicle-treated SHRs (SHR), SHRs treated with fasudil 3 mg/kg i.p. (Fas3), and SHRs treated with fasudil 10 mg/kg i.p. (Fas10). Vehicle-treated Wistar rats were used as normo-tensive control group. After a six-week-treatment, blood pressure and heart rate were measured by the tail cuff method. Afterwards animals were sacrificed and aortas were examined in vitro by organ bath studies to evaluate the contraction and relaxation ability. Rho kinase activity, myosin light chain (MLC), phosphorylated MLC (phospho-MLC), eNOS, phospho-eNOS protein expression and eNOS mRNA levels were evaluated. SHR demonstrated a significant hypercontractility and impaired relaxation compared to the control. Fasudil 10mg/kg significantly corrected the hypercontractility, restored the relaxation, and significantly decreased the mean arterial blood pressure, while no change observed in the systolic blood pressure. Rho kinase activity was significantly higher in the SHR, and was significantly inhibited by the high dose of fasudil. There was a slight up-regulation in the MLC, and phospho-MLC protein levels in the SHR. eNOS and phospho-eNOS protein levels were significantly lower in the SHR, and this abnormality was significantly normalized by fasudil treatment. No significant difference was observed in the eNOS gene expression. This study suggests that fasudil by inhibiting the Rho kinase activity normalizes the eNOS expression and phosphorylation and ameliorates the endothelial dysfunction induced by hypertension in the SHR model.

Rho GTPase regulation by miRNAs and covalent modifications

To date, most studies of Rho GTPase regulation have focused on the classic GTPase cycle - GTP binding and hydrolysis - controlled by guanine nucleotide exchange factors (GEFs), GTPase-activating proteins (GAPs) and GDP-dissociation inhibitors (GDIs). Recent investigations have unveiled important additional regulatory mechanisms: microRNA (miRNA) regulating post-transcriptional processing of Rho GTPase-encoding mRNAs; palmitoylation and nuclear targeting affecting intracellular distribution; post-translational phosphorylation, transglutamination and AMPylation impacting Rho GTPase signaling; and ubiquitination controlling Rho GTPase protein stability and turnover. These modes of regulation add to the complexity of the Rho GTPase signaling network and allow precise spatiotemporal control of individual Rho GTPases. This review discusses these 'unconventional' modes of regulation and their contribution to cellular function, focusing on post-transcriptional and post-translational events beyond the classic GTPase cycle regulatory model.

Protective Role of the ACE2/Ang-(1-9) Axis in Cardiovascular Remodeling

Despite reduction in cardiovascular (CV) events and end-organ damage with the current pharmacologic strategies, CV disease remains the primary cause of death in the world. Pharmacological therapies based on the renin angiotensin system (RAS) blockade are used extensively for the treatment of hypertension, heart failure, and CV remodeling but in spite of their success the prevalence of end-organ damage and residual risk remain still high. Novel approaches must be discovered for a more effective treatment of residual CV remodeling and risk. The ACE2/Ang-(1–9) axis is a new and important target to counterbalance the vasoconstrictive/proliferative RAS axis. Ang-(1–9) is hydrolyzed slower than Ang-(1–7) and is able to bind the Ang II type 2 receptor. We review here the current experimental evidence suggesting that activation of the ACE2/Ang-(1–9) axis protects the heart and vessels (and possibly the kidney) from adverse cardiovascular remodeling in hypertension as well as in heart failure.

Cannabinoid receptor type 1 (CB1) activation inhibits small GTPase RhoA activity and regulates motility of prostate carcinoma cells

The cannabinoid receptor type 1 (CB1) is a G protein-coupled receptor that is activated in an autocrine fashion by the endocannabinoids (EC), N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG). The CB1 and its endogenous and synthetic agonists are emerging as therapeutic targets in several cancers due to their ability to suppress carcinoma cell invasion and migration. However, the mechanisms that the CB1 regulates cell motility are not well understood. In this study, we examined the molecular mechanisms that diminish cell migration upon the CB1 activation in prostate carcinoma cells. The CB1 activation with the agonist WIN55212 significantly diminishes the small GTPase RhoA activity but modestly increases the Rac1 and Cdc42 activity. The diminished RhoA activity is accompanied by the loss of actin/myosin microfilaments, cell spreading, and cell migration. Interestingly, the CB1 inactivation with the selective CB1 antagonist AM251 significantly increases RhoA activity, enhances microfilament formation and cell spreading, and promotes cell migration. This finding suggests that endogenously produced EC activate the CB1, resulting in chronic repression of RhoA activity and cell migration. Consistent with this possibility, RhoA activity is significantly diminished by the exogenous application of AEA but not by 2-AG in PC-3 cells (cells with very low AEA hydrolysis). Pretreatment of cells with a monoacylglycerol lipase inhibitor, JZL184, which blocks 2-AG hydrolysis, decreases the RhoA activity. These results indicate the unique CB1 signaling and support the model that EC, through their autocrine activation of CB1 and subsequent repression of RhoA activity, suppress migration in prostate carcinoma cells.