Vascular Renin-angiotensin System Research Articles

Pea-derived tripeptide LRW fails to reduce blood pressure in spontaneously hypertensive rats due to its low gastrointestinal stability and transepithelial permeability

Leu-Arg-Trp (LRW), a pea-derived tripeptide, is an isomer of Ile-Arg-Trp (IRW), an egg-derived tripeptide possessing various health benefits including antihypertensive activity. Since LRW and IRW are structural analogs, we hypothesized that LRW can significantly reduce blood pressure in spontaneously hypertensive rats. LRW showed a more potent in vitro ACE-inhibitory activity (IC50 value of 0.45 ± 0.06 μM) than that of IRW (1.65 ± 0.14 μM); molecular docking results also verified that LRW could form a more stable complex with ACE than that of IRW. In addition, LRW could inhibit tumor necrosis factor alpha-induced endothelial inflammation in similar manners to IRW. However, oral administration of LRW at a dose of 15 mg/kg/day body weight over 12 days did not cause any blood pressure reduction (p > 0.05). Subsequent tissue analyses revealed no changes in the vascular renin-angiotensin system components and vascular inflammation, which are the primary targets of IRW, indicating that LRW might not be able to reach the blood circulation and exert in vivo efficacies. Furthermore, LRW demonstrated significantly lower gastrointestinal stability (p < 0.001) and lower permeability (p < 0.001) across human Caco-2 cell monolayers than those of IRW. These findings indicated the low oral bioavailability of LRW which might underlie its failure in reducing blood pressure in vivo.

Effects of the Hormonal Replacement Therapy with Estrogen and Progestins on the Vascular Renin-Angiotensin System of Ovariectomized Rats

Effects of the Hormonal Replacement Therapy with Estrogen and Progestins on the Vascular Renin-Angiotensin System of Ovariectomized Rats

Spike protein 1 of SARS‐CoV‐2 induces an immune and inflammatory response and increases expression of ACE2 in human endothelial cells

Introduction Interferon (IFN) alpha (IFNα) and lambda3 (IFNλ3) constitute the first line of immunity against viral infection by increasing expression of interferon-stimulated genes (ISGs). Both are produced in SARS-CoV-2 infection and have been considered therapeutically in COVID-19. In epithelial cells IFNs have been shown to influence the expression of angiotensin-converting enzyme 2 (ACE2), the receptor for S-protein (S1P) of SARS-CoV-2. ACE2 is part of the vascular renin angiotensin system and may be important in COVID-19-associated endotheliitis. Whether SP1 influences immune responses in endothelial cells unknown. We investigated effects of SP1 on ACE2 expression and immune responses in human endothelial cells. Methods Culturedhuman Microvascular, Lymphatic, Aortic and Pulmonary Endothelial Cells (MEC, LEC, AEC, and PEC respectively) were stimulated with SP1 of SARS-CoV-2 (1µg/106 cells), IFNα (100ng/mL) or IFNλ3 (100IU/mL). Because ACE2, metalloproteinase domain 17 (ADAM17) and type II transmembrane serine protease (TMPRSS2) are important for SARS-CoV-2 infection, cells were treated with inhibitors of ADAM17 (marimastat, 3.8nM and TAPI-1, 100nM), ACE2 (MLN4760, 440pM), and TMPRSS2 (camostat, 50µM). Expression of ISGs (ISG15, IFIT1, and MX1) was investigated by real-time PCR (5h), cytokine by ELISA and protein expression by immunoblotting (24h). Results AEC, LEC, MEC, and PEC stimulated with SP1 exhibited increased expression of ISGs: ISG15 (1.9-2.3-fold), IFIT1 (2.0-7.9-fold), MX1 (3.1-5.8-fold), indicating activation of the IFN pathway. MEC and LEC exhibited higher responses to IFNα activation. MEC (ISG15: 16-fold, IFIT1: 21-fold, MX1: 31-fold) and LEC (ISG15: 48-fold, IFIT1: 105-fold, MX1: 134-fold). Only MEC exhibited ISG expression induced by IFNλ3 (ISG15: 1.7-fold, IFIT1: 1.9-fold, MX1: 1.7-fold) (P<0.05). IL-6 production was increased in MEC stimulated with IFNα (1230pg/mL) and IFNλ3 (1124pg/mL) vs control (591pg/mL). Marimastat, but not camostat or MLN4760 inhibited SP1 effects. IFNα induced IL-6 production in AEC and PEC (178pg/mL vs control 109pg/mL). No changes in IL-6 were observed in LEC. IFNα increased expression of the short form of ACE2 (75kDa) (63%), ADAM17 (36%), and TMPRSS2 (65%) in MECs. This was associated with increased activation of pro-inflammatory pathways with increased phosphorylation of Stat1 (134%), Stat2 (102%), ERK1/2 (42%). IFNλ3 also increased phosphorylation of Stat2 (60%) and ERK1/2 (75%). In MEC, phosphorylation of the eNOS activation motif Ser1177 was reduced by IFNLα and (40%) and IFNλ3 (40%). Conclusions In human endothelial cells from multiple vascular beds, SP1, IFNα and IFNλ3 induced an immune response characterised by increased ISG expression and IL-6 production, processes that involve ADAM17. These effects were associated with increased expression of the short form of ACE2 and activation of pro-inflammatory pathways. Our novel findings demonstrate that SP-1 induces an endothelial immune and inflammatory response that may be important in endotheliitis associated with COVID-19.

Chronic Intermittent Hypobaric Hypoxia Decreases High Blood Pressure by Stabilizing the Vascular Renin-Angiotensin System in Spontaneously Hypertensive Rats.

Background and AimsPrevious studies have demonstrated the anti-hypertensive effect of chronic intermittent hypobaric hypoxia (CIHH) in hypertensive rats. The present study investigated the anti-hypertensive effect of CIHH in spontaneously hypertensive rats (SHR) and the role of the renin-angiotensin system (RAS) in anti-hypertensive effect of CIHH.MethodsFifteen-week-old male SHR and WKY rats were divided into four groups: the SHR without CIHH treatment (SHR-CON), the SHR with CIHH treatment (SHR-CIHH), the WKY without CIHH treatment (WKY-CON), and the WKY with CIHH treatment (WKY-CIHH) groups. The SHR-CIHH and WKY-CIHH rats underwent 35-days of hypobaric hypoxia simulating an altitude of 4,000 m, 5 h per day. Arterial blood pressure and heart rate were recorded by biotelemetry, and angiotensin (Ang) II, Ang1–7, interleukin (IL)-6, tumor necrosis factor-alpha (TNF)-α, and IL-10 in serum and the mesenteric arteries were measured by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, respectively. The microvessel tension recording technique was used to determine the contraction and relaxation of the mesenteric arteries. Hematoxylin and eosin and Masson’s staining were used to observe vascular morphology and fibrosis. Western blot was employed to detect the expression of the angiotensin-converting enzyme (ACE), ACE2, AT1, and Mas proteins in the mesenteric artery.ResultsThe biotelemetry result showed that CIHH decreased arterial blood pressure in SHR for 3–4 weeks (P < 0.01). The ELISA and immunohistochemistry results showed that CIHH decreased Ang II, but increased Ang1–7 in serum and the mesenteric arteries of SHR. In the CIHH-treated SHR, IL-6 and TNF-α decreased in serum and the mesenteric arteries, and IL-10 increased in serum (P < 0.05–0.01). The microvessel tension results revealed that CIHH inhibited vascular contraction with decreased Ang1–7 in the mesenteric arteries of SHR (P < 0.05–0.01). The staining results revealed that CIHH significantly improved vascular remodeling and fibrosis in SHR. The western blot results demonstrated that CIHH upregulated expression of the ACE2 and Mas proteins, and downregulated expression of the ACE and AT1 proteins (P < 0.05–0.01).ConclusionCIHH decreased high blood pressure in SHR, possibly by inhibiting RAS activity, downregulating the ACE-Ang II-AT1 axis and upregulating the ACE2-(Ang1-7)-Mas axis, which resulted in antagonized vascular remodeling and fibrosis, reduced inflammation, and enhanced vascular relaxation.

High sucrose intake during gestation increases angiotensin II type 1 receptor-mediated vascular contractility associated with epigenetic alterations in aged offspring rats

Accruing evidence have confirmed that the fetal programming in response to adverse environmental in utero factors plays essential roles in the pathogenesis of hypertension in later life. High sugar intake has been accepted worldwide in everyday life diet and becomes the critical public health issue. Our previous studies indicated that intake of high sucrose (HS) during pregnancy could change the vascular reactivity and dipsogenic behavior closely associated with abnormal renin-angiotensin system (RAS), to increase the risk of hypertension in adult offspring. In the present study, we tested the hypothesis that maternal HS intake in pregnancy may further deteriorate the Ang II-induced cardiovascular responses in the aged offspring. HS intake was provided to pregnant rats throughout the gestation. Blood pressure (BP) in conscious state and vascular contractility in vitro were measured in 22-month-old aged offspring rats. In addition, mRNA and protein expressions and epigenetic changes of Ang II type 1 receptor (AT1R) gene in blood vessels were determined with the methods of real-time RT-PCR, Western blotting, and Chromatin Immunoprecipitation Assay (CHIP). Results showed that, in the aged offspring, maternal HS intake during gestation would cause the elevation of basal BP which could be diminished by losartan. Although the circulatory Ang II was not changed, levels of local Ang II were significantly increased in blood vessels. In addition, prenatal HS exposure would significantly enhance the AT1R-mediated vasoconstrictions in both aorta and mesenteric arteries of the aged offspring. Moreover, in the aged offspring of prenatal HS exposure, mRNA and protein expressions of AT1R gene in both large and small blood vessels were significantly increased, which should be closely associated with the changes of epigenetic mechanisms such as histone modifications. Collectively, we proposed that maternal HS intake during gestation would cause abnormal BP responses mediated via the enhancement of vascular RAS, together with the increased expression of AT1R gene related to the its epigenetic changes, which would actually lead to the overt phenotype of hypertension in the aged offspring.

Modulation of Vascular ACE by Oxidative Stress in Young Syrian Cardiomyopathic Hamsters: Therapeutic Implications.

Increased vascular angiotensin-converting enzyme (ACE) activity and oxidative stress are present in young Syrian cardiomyopathic hamsters (SCH) before the clinical manifestation of heart failure (HF). The developmental time-course of these alterations and their potential interactions, however, are still unknown. We evaluated mRNA and protein levels of ACE, endothelial nitric oxide synthase (eNOS), and inducible nitric oxide synthase (iNOS) in the vasculature of SCH from one to four months of age. Total RNA and proteins were quantified with real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot, respectively. The role of nitric oxide (NO) on vascular ACE activity was also assessed. ACE mRNA and protein levels were up-regulated in SCH at two months of age compared with controls (CT) (p < 0.05). At this two-month stage, eNOS protein levels were lower in SCH (87%) than in CT (100%) (p < 0.05), although iNOS protein levels increased significantly (482%) compared to CT (100%; p < 0.05). In addition, ACE mRNA expression and activity were modulated by NO at two months of age. Thus, the combination of low eNOS and high iNOS protein levels may underlie vascular renin-angiotensin system (RAS) over-activation. Altogether, these factors may contribute to the development of endothelial dysfunction and vascular hyper-reactivity in the early stages of heart failure, and eventually trigger cardiac deterioration in this animal model of HF.

Nitric oxide up-regulates endothelial expression of angiotensin II type 2 receptors

Increasing vascular NO levels following up-regulation of endothelial nitric oxide synthase (eNOS) is considered beneficial in cardiovascular disease. Whether such beneficial effects exerted by increased NO-levels include the vascular renin–angiotensin system remains elucidated. Exposure of endothelial cells originated from porcine aorta, mouse brain and human umbilical veins to different NO-donors showed that expression of the angiotensin-II-type-2-receptor (AT2) mRNA and protein is up-regulated by activation of soluble guanylyl cyclase, protein kinase G and p38 mitogen-activated protein kinase without changing AT2 mRNA stability. In mice, endothelial-specific overexpression of eNOS stimulated, while chronic treatment with the NOS-blocker l-nitroarginine inhibited AT2 expression. The NO-induced AT2 up-regulation was associated with a profound inhibition of angiotensin-converting enzyme (ACE)-activity. In endothelial cells this reduction of ACE-activity was reversed by either the AT2 antagonist PD 123119 or by inhibition of transcription with actinomycin D. Furthermore, in C57Bl/6 mice an acute i.v. bolus of l-nitroarginine did not change AT2-expression and ACE-activity suggesting that inhibition of ACE-activity by endogenous NO is crucially dependent on AT2 protein level. Likewise, three weeks of either voluntary or forced exercise training increased AT2 expression and reduced ACE-activity in C57Bl/6 but not in mice lacking eNOS suggesting significance of this signaling interaction for vascular physiology. Finally, aortic AT2 expression is about 5 times greater in female as compared to male C57Bl/6 and at the same time aortic ACE activity is reduced in females by more than 50%. Together these findings imply that endothelial NO regulates AT2 expression and that AT2 may regulate ACE-activity.

Auto-inhibitory regulation of angiotensin II functionality in hamster aorta during the early phases of dyslipidemia

Emerging data point the crosstalk between dyslipidemia and renin-angiotensin system (RAS). Advanced dyslipidemia is described to induce RAS activation in the vasculature. However, the interplay between early dyslipidemia and the RAS remains unexplored. Knowing that hamsters and humans have a similar lipid profile, we investigated the effects of early and advanced dyslipidemia on angiotensin II-induced contraction. Cumulative concentration-response curves for angiotensin II (1.0pmol/l to 1.0µmol/l) were obtained in the hamster thoracic aorta. We also investigated the modulatory action of NAD(P)H oxidase on angiotensin II-induced contraction using ML171 (Nox-1 inhibitor, 0.5µmol/l) and VAS2870 (Nox-4 inhibitor, 5µmol/l). Early dyslipidemia was detected in hamsters treated with a cholesterol-rich diet for 15 days. Early dyslipidemia decreased the contraction induced by angiotensin II and the concentration of Nox-4-derived hydrogen peroxide. Advanced dyslipidemia, observed in hamsters treated with cholesterol-rich diet for 30 days, restored the contractile response induced by angiotensin II by compensatory mechanism that involves Nox-4-mediated oxidative stress. The hyporresponsiveness to angiotensin II may be an auto-inhibitory regulation of the angiotensinergic function during early dyslipidemia in an attempt to reduce the effects of the upregulation of the vascular RAS during the advanced stages of atherogenesis. The recovery of vascular angiotensin II functionality during the advanced phases of dyslipidemia is the result of the upregulation of redox-pro-inflammatory pathway that might be most likely involved in atherogenesis progression rather than in the recovery of vascular function. Taken together, our findings show the early phase of dyslipidemia may be the most favorable moment for effective atheroprotective therapeutic interventions.

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

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.

Inhibition of the vascular renin‐angiotensin system preserves nitric oxide‐mediated vasodilation in human adipose arterioles after transient high pressure stress (676.9)

Increased intraluminal pressure converts the mediator of flow mediated dilation (FMD) from nitric oxide (NO) to hydrogen peroxide (H2O2) in human adipose arterioles. We hypothesized that inhibition of the local renin‐angiotensin system (RAS) would preserve NO‐mediated dilation after acute high pressure (HP) stress. Microvessels were dissected from surgically discarded adipose tissue, cannulated onto glass pipettes, pressurized to 60 mmHg, and constricted with endothelin‐1. Vasodilation to incremental increases in flow was measured followed by exposure to an intraluminal pressure of 150 mmHg for 30 minutes ± the ACE inhibitor captopril (10 µM), the AT1R antagonist losartan (10 µM), or the ACE2 activator DIZE (10 µM). In untreated vessels, PEG‐catalase reduced maximum FMD (24±6.1% vs. 62±5.6%, p&lt;0.05) following exposure to HP, whereas L‐NAME had no effect (72±5.9% vs. 62±5.6%). When HP was generated in the presence of losartan, captopril, or DIZE, L‐NAME inhibited FMD (19±6.8%; 43±20.3%; 14±15.6% respectively; p&lt;0.05 vs. control). These results indicate that the vascular RAS is activated by increased intraluminal pressure, and plays a role in switching the mechanism of FMD from an NO‐mediated response to one mediated by H2O2.

GPER activation ameliorates vascular remodeling in salt‐sensitive mRen2.Lewis rats (867.7)

The mRen2.Lewis female rat is an estrogen‐ and salt‐sensitive model of hypertension which may reflect the higher pressure and salt sensitivity associated with menopause. In salt‐loaded mRen2.Lewis, activation of the novel estrogen receptor GPER reduces renal hypertrophy, proteinuria, and oxidative stress but not blood pressure (Lindsey et al. 2011). The current study hypothesized that vascular remodeling is also improved by GPER activation in the absence of changes in blood pressure. Intact mRen2.Lewis females were fed a normal (0.5% Na+) or high salt diet (4% Na+) for 10 weeks and treated with vehicle or the selective GPER agonist G‐1 for the last two weeks of the study. Systolic blood pressure was measured by tail cuff plethysmography, and aortic sections were mounted on a wire myograph or formalin‐fixed for histological analysis. Systolic blood pressure increased with the high salt diet (137 ± 2 mmHg, n=7 to 224 ± 8, n=9; P&lt;0.001) and remained unchanged with G‐1 (216 ± 4, n=9; P&gt;0.05). While aortic reactivity to phenylephrine and acetylcholine were not different between groups (P&gt;0.05), chronic G‐1 treatment reduced vasoconstriction to angiotensin II (P&lt;0.05) and enhanced G‐1 vasorelaxation ex vivo (P&lt;0.01) in both endothelium‐intact and denuded aortic rings. Analysis of aortic sections revealed that while the high salt diet significantly increased the media to lumen ratio (0.43 ± 0.02, n=6 vs. 0.83 ± 0.05, n=7; P&lt;0.001), two‐week G‐1 treatment partially reversed the salt effect (0.62 ± 0.02, n=6, P&lt;0.005). We conclude that GPER exerts vascular protective actions in the aorta of salt‐loaded mRen2.Lewis females independently of blood pressure. The anti‐remodeling actions of this novel estrogen receptor may be effective in postmenopausal cardiovascular disease by targeting the vascular renin‐angiotensin system.Grant Funding Source: Supported by NIH (HL56973, HL51952, HL103974) and the American Heart Association (25515E, 3080005)

Abstract 132: Roles of Angiotensin (1-7) And Angiotensin II Type 2 Receptor on Intracranial Aneurysmal Rupture

Background and Purpose: Angiotensin (Ang) 1-7 is emerging as a new key player of the vascular renin-angiotensin system. Ang (1-7) generated from either Ang I or Ang II, acts to oppose the vasoconstrictor and proinflammatory actions of Ang II. However, which receptor Ang (1-7) activates still remains unclear. It has been suggested that Ang (1-7) mediates its effect via Mas receptor (MasR), although some suggest that it may also act at Ang II type 2 receptor (AT2R). Therefore, we hypothesized that Ang (1-7) has protective effect against aneurysmal rupture via MasR or AT2R. We tested this hypothesis by using our own established mouse model of intracranial aneurysm. Methods: Intracranial aneurysms were induced in male mice using a combination of a single injection of elastase into the cerebrospinal fluid and the deoxycorticosterone acetate (DOCA) salt hypertension (Figure 1). Six days after aneurysm induction, we started 2-week treatment with vehicle or Ang (1-7). MasR antagonist (A779) or AT2R antagonist (PD123319) was added to Ang (1-7) treatment. We induced aneurysms to AT2R knockout mice and treated them with vehicle or Ang (1-7) with the same protocol mentioned above. Aneurysmal rupture was detected by neurological symptoms and confirmed by the presence of intracranial aneurysms with subarachnoid hemorrhage. Results: Ang (1-7) reduced the incidence of ruptured aneurysms and rupture rate. AT2R antagonist but not MasR antagonist reversed the reduced rupture rate by Ang (1-7) (Figure 2, 3). To confirm whether the effect of Ang (1-7) is through the AT2R, we administered Ang (1-7) to AT2R knockout mice. Although there was no significant difference between wild type and AT2R knockout mice, Ang (1-7) was not effective against aneurysmal rupture in AT2R knockout mice (Figure 4, 5). Conclusion: Our results indicate that Ang (1-7) is protective against intracranial aneurysmal rupture and that its protective effect is exerted via AT2R rather than MasR.

Is the renin–angiotensin system actually hypertensive?

The historical view of the renin-angiotensin system (RAS) is that of an endocrine hypertensive system that is controlled by renin and mediated via the action of angiotensin II on its type 1 receptor. Numerous new angiotensins (Ang) and receptors have been described, the majority being hypotensive and natriuretic, namely Ang-(1-7) and its receptor rMas. Renin and its precursor (pro-renin) can bind their common receptor. In addition to the production of Ang II, this receptor triggers intracellular effects. Given the control of renin production by intracellular calcium, calcium homeostasis is of particular importance. Ang-(1-12), which is not controlled by renin, is converted to several different angiotensin peptides and is a new pathway of the RAS. Local RAS enzymes produce or transform the different hyper- or hypotensive angiotensin within vessels and organs, but also in blood through circulating forms of the enzymes. In the kidney, a powerful local vascular RAS allows for the independence of renal vascularization from systemic control. Moreover, the kidney also contains an independent urinary RAS, which counterbalances the systemic RAS and coordinates proximal and distal sodium reabsorption. The systemic and local effects of renal RAS cannot be analyzed without taking into account the antagonistic effect of renalase. Our concept of RAS needs to evolve to take into account its dual potentiality (hyper- or hypotensive).

Peroxisome Proliferator-Activated Receptor-γ Mutations Responsible for Lipodystrophy With Severe Hypertension Activate the Cellular Renin–Angiotensin System

Inactivating peroxisome proliferator-activated receptor-γ (PPARγ) mutations lead to a syndrome of familial partial lipodystrophy (FPLD3) associated with early-onset severe hypertension. PPARγ can repress the vascular renin-angiotensin system (RAS) and angiotensin II receptor 1 expression. We evaluated the relationships between PPARγ inactivation and cellular RAS using FPLD3 patients' cells and human vascular smooth muscle cells expressing mutant or wild-type PPARγ. Approach and Results- We identified 2 novel PPARG mutations, R165T and L339X, located in the DNA and ligand-binding domains of PPARγ, respectively in 4 patients from 2 FPLD3 families. In cultured skin fibroblasts and peripheral blood mononuclear cells from the 4 patients and healthy controls, we compared markers of RAS activation, oxidative stress, and inflammation, and tested the effect of modulators of PPARγ and angiotensin II receptor 1. We studied the impact of the 2 mutations on the transcriptional activity of PPARγ and on the vascular RAS in transfected human vascular smooth muscle cells. Systemic RAS was not altered in patients. However, RAS markers were overexpressed in patients' fibroblasts and peripheral blood mononuclear cells, as in vascular cells expressing mutant PPARγ. Angiotensin II-mediated mitogen-activated protein kinase activity increased in patients' fibroblasts, consistent with RAS constitutive activation. Patients' cells also displayed oxidative stress and inflammation. PPARγ activation and angiotensin II receptor 1 mRNA silencing reversed RAS overactivation, oxidative stress, and inflammation, arguing for a role of angiotensin II receptor 1 in these processes. Two novel FPLD3-linked PPARG mutations are associated with a defective transrepression of cellular RAS leading to cellular dysfunction, which might contribute to the specific FPLD3-linked severe hypertension.

Asymmetric Dimethylarginine Reduces Nitric Oxide Donor-Mediated Dilation of Arterioles by Activating the Vascular Renin-Angiotensin System and Reactive Oxygen Species

Introduction: We tested the hypothesis that asymmetric dimethylarginine (ADMA) interferes with other mechanisms in addition to inhibition of nitric oxide synthase (NOS). Thus, in skeletal muscle arterioles, in the presence of ADMA, we investigated the dilator effect of an NO donor and increases in flow and aimed to elucidate the underlying mechanisms, including the role of oxidative stress, which is known to reduce the bioavailability of NO. Methods and Results: In isolated rat gracilis skeletal muscle arterioles (∼160 µm at 80 mm Hg), ADMA (similarly to pyrogallol) reduced dilations to sodium nitroprusside (SNP), which was significantly prevented by the presence of superoxide dismutase (SOD) and catalase (CAT): SNP 10^–8M; control: 43.2 ± 3%, ADMA: 4.9 ± 1%, ADMA + SOD/CAT: 30.2 ± 9% (p < 0.05). Also, ADMA reduced basal diameter and flow-induced dilations, which were not restored by L-arginine, but prevented by SOD/CAT and by inhibition of NAD(P)H oxidase (but not xanthine oxidase) and by an angiotensin-converting enzyme inhibitor or an angiotensin type 1 receptor blocker (ARB). ADMA increased the production of reactive oxygen species detected by lucigenin-enhanced chemiluminescence, which was significantly inhibited by SNP or ARB. Conclusion: We suggest that by activating the vascular renin-angiotensin-NAD(P)H oxidase pathway, ADMA elicits oxidative stress, which interferes with the bioavailability of NO and consequently reduces NO-mediated dilations.

The Vascular Renin Angiotensin System Contributes to Endothelial Dysfunction Induced by Acute High Pressure in Human Adipose Microvessels

We have previously shown that transient elevations in intraluminal pressure reduce endothelium‐dependent vasodilation, but the mechanism of this impairment is unknown. Since the renin‐angiotensin system (RAS) is activated by barostress, we hypothesized that the pressure‐induced endothelial dysfunction is mediated by local generation of angiotensin II (ANG II). Arterioles (100–200 μm) from discarded surgical adipose specimens were cannulated onto glass micropipettes, pressurized to 60 mmHg and constricted with endothelin‐1. Vasodilation to acetylcholine (ACh; 10−9 – 10−4 M) or papaverine (10−9 – 10−4 M) was assessed before and after the vessel had been exposed to an intraluminal pressure of 150 mmHg for 30 minutes. Dilation to ACh was significantly reduced in vessels exposed to 150 mmHg of pressure, while the response to papaverine was unaffected. The pressure‐induced endothelial dysfunction was prevented by incubating the vessels with PEG‐SOD (100 U/mL), the angiotensin type 1 receptor antagonist losartan (1 μM), or the angiotensin converting enzyme inhibitor captopril (1 μM). The acute high pressure did not affect vessel sensitivity to ANG II (10−11 – 10−7M). We conclude that local generation of ANG II by the vascular RAS plays a causative role in pressure‐induced endothelial dysfunction, possibly by increasing vascular superoxide. This study was supported by NHLBI grants HL‐094971 and HL‐080704.

Increased urinary protein excretion in the “normal” range is associated with increased renin-angiotensin system activity

Increased levels of albuminuria and proteinuria, both linked to augmented renin-angiotensin system (RAS) activity, are associated with adverse kidney and cardiovascular events. However, the relationship between variations in urinary albumin excretion (UAE) and total protein excretion (UTPE) in the normal range and RAS activity is unclear. We examined the association between UAE and UTPE and the hemodynamic response to angiotensin II (ANG II) challenge, a well-accepted indirect measure of RAS activity, in healthy individuals with normal UAE and UTPE. Forty subjects (15 men, 25 women; age 38 ± 2 yr; UAE, 3.32 ± 0.55 mg/day; UTPE, 56.8 ± 3.6 mg/day) were studied in high-salt balance. Blood pressure (BP), arterial stiffness determined by applanation tonometry, and circulating RAS components were measured at baseline and in response to graded ANG II infusion. The primary outcome was the BP response to ANG II challenge at 30 and 60 min. UAE was associated with a blunted diastolic BP response to ANG II infusion (30 min, P = 0.005; 60 min, P = 0.17), a relationship which remained even after adjustment (30 min, P < 0.001; 60 min, P = 0.035). Similar results were observed with UTPE (30 min, P = 0.031; 60 min, P = 0.001), even after multivariate analysis (30 min, P = 0.008; 60 min, P = 0.001). Neither UAE nor UTPE was associated with systolic BP, circulating RAS components, or arterial stiffness responses to ANG II challenge. Among healthy individuals with UAE and UTPE in the normal range, increased levels of these measures were independently associated with a blunted diastolic BP response to ANG II, indicating increased vascular RAS activity, which is known to be deleterious to both renal and cardiac function.

822 NOVEL APPROACHES TO PREVENTION OF CHRONIC KIDNEY DISEASE IN PATIENTS WITH METABOLIC SYNDROME

Metabolic syndrome (MS) is a major public health threat. Individuals with MS are at increased risk for development of chronic kidney disease (CKD). Despite effective medical interventions that have targeted vascular renin-angiotensin system (RAS) blockade the prevalence of CKD remains considerably high. Few studies have directly compared the reno- protective effects of Angiotensin II-receptor blockers and Angiotensin-converting- enzyme inhibitors (ACE) in patients with MS. The aim of the present study was to compare the renoprotective effects of Angiotensin II-receptor blockers and Angiotensin-converting-enzyme inhibitors (ACE) in patients with MS and early nephropathy. In this prospective three year study, we randomly assigned 123 patients (mean age 45.8±11.7 years, range 31-57 years, 72 male and 51 female) with metabolic syndrome and early nephropathy to receive either the ACE inhibitor Quinapril (Accupro, Pfizer International, 20mg daily, 43 subjects) or Angiotensin II- receptor blocker Valsartan (Diovan, Novartis, 160 mg daily, in 41 subjects) or in combination Valsartan / Quinapril (160 mg/20 mg daily, in 39 subjects). The endpoint was the change in the glomerular filtration rate (GFR) (determined by measuring the plasma Clearance of Creatinine) between the baseline value and the last available value during the three-year treatment. After three years, indices of GFR increased by 4.2 ml/min/1.73m² in Quinapril-treated patients, compared with - 4.7 ml/min/1.73m² in Valsartan-treated subjects, and - 7.1 ml /min/ 1.73m² in Valsartan /Quinapril group (p<0.01). The results indicated that Valsartan was not superior to Quinapril, but the renoprotective effects of the combined therapy with Valsartan/Quinapril significantly improved after three years. © 2011 Bull. Georg. Natl. Acad. Sci.

Mechanism underlying the efficacy of combination therapy with losartan and hydrochlorothiazide in rats with salt-sensitive hypertension

Although thiazide diuretics are commonly used to supplement angiotensin receptor blockers for treatment of hypertension, the mechanism underlying the therapeutic effects of this drug combination remains unclear. We investigated the antihypertensive and cardioprotective effects of combination therapy with losartan (LOS) and hydrochlorothiazide (HCTZ), in comparison with those of either drug alone, in Dahl salt-sensitive hypertensive rats. Rats fed a high-salt diet from 6 weeks of age were treated with LOS, HCTZ, both drugs (COMB) and vehicle from 6 to 11 weeks. The salt-induced increase in systolic blood pressure was attenuated moderately by LOS and to a greater extent by HCTZ and COMB. Left ventricular (LV) hypertrophy and fibrosis, diastolic dysfunction, as well as angiotensin-converting enzyme and angiotensin II type 1A (AT(1A)) receptor gene expression were attenuated similarly by LOS and HCTZ and more so by COMB. LOS downregulated expression of the AT(1A) receptor gene, without affecting that of the AT(2) receptor gene, in the aorta. In contrast, neither HCTZ nor COMB affected aortic expression of the AT(1A) receptor gene, but both markedly upregulated that of the AT(2) receptor gene. The salt-induced decrease in the plasma concentration of nitric oxide metabolites was attenuated substantially by LOS and abolished by both HCTZ and COMB. In conclusion, the combination of LOS and HCTZ attenuated hypertension, as well as LV remodeling and diastolic dysfunction, more effectively than did LOS or HCTZ alone in rats with salt-sensitive hypertension. Modulation of the cardiac and vascular renin-angiotensin system may have contributed to these beneficial effects of the drug combination.

Aortic elastic properties are impaired in patients with Graves’ ophtalmopathy

Aortic elastic properties have been shown to be an important predictor of cardiovascular morbidity and mortality. Hyperthyroidism was shown to be an important cause of impaired aortic elastic properties both due to the direct effect of the thyroid hormones on the aorta and also due to modulating effects of thyroid hormones on the vascular renin angiotensin system. However, there is no study investigating the aortic elastic properties in Graves's patients who were euthyroid. The goal of the present study was to investigate the aortic elastic properties of patients with Graves' Ophtalmopathy (GO) who had been euthyroid for at least 3 months. A cross-sectional study was performed on 47 GO patients and 27 controls. Aortic-diastolic and aortic-systolic diameters, aortic strain, aortic distensibility, and aortic stiffness indices were calculated from the diameter of the thoracic aorta as measured by transthoracic echocardiography. The aortic stiffness index was markedly increased (31 ± 26 vs. 17 ± 8.9; p = 0.015) and aortic strain was markedly reduced (20.3 ± 10 % vs. 25.9 ± 12 %; p = 0.046) in the GO group relative to the control group. Aortic distensibility was statistically significantly decreased in the GO group as compared to the control group (9.5 ± 5.7 10(-3)/kPa vs. 13.5 ± 7.1 10(-3)/kPa; p = 0.022). Weak correlations were detected between GO severity and aortic distensibility (r = -0.333, p = 0.011) as well as the aortic stiffness index (r = 0.266, p = 0.044). Aortic elastic properties were impaired in patients with GO. Therefore, patients with GO, especially those with severe manifestations of the condition, should be followed closely with regard to the occurrence of future cardiovascular events.