Angiotensin II Formation Research Articles

Effect Of Astragalus Injection Combined With Aerobic Exercise On Myocardial Renin-angiotensin System In Diabetic Mice

PURPOSE: This investigation aimed at investigating the synergistic effect of Astragalus injection combined with aerobic exercise on myocardial renin-angiotensin system in diabetic mice,and clarify whether the myocardial disease of diabetic mice is improved. METHODS: 32 6-week-aged male db/db mice were randomly divided into 4 groups,Diabetes mellitus group, Astragalus injection group,Swimming group and Astragalus injection + swimming group.Monitor the amount of drinking water,body weight and blood glucose changes.The myocardial tissue was executed after 6 weeks and the ventricular mass index was calculated;detect the angiotensin II (Ang-II),angiotensin-converting enzyme (ACE) and angiotensin converting enzyme 2(ACE2) in each group of myocardium tissues. RESULTS: In addition to diabetic group, the ventricular mass index of each group was elevated (P<0.05).In addition to the diabetic group, the Ang-IIlevels of myocardial tissues were decreased (P<0.05).In addition to the diabetic group, the ACE and ACE2 levels averaged increased (P<0.05). CONCLUSIONS: Myocardial ACE,ACE2 enzyme activity is generally low, Ang-II content is also higher than other groups, and the decrease of enzyme activity will promote the increase of Ang-II content, indicating that renin-angiotensin system is overactivated, resulting in strong vasoconstriction and myocardial ischemia and hypoxia, and eventually lead to all kinds of cardiomyopathy. After the intervention of astragalus membranaceus or aerobic exercise, the activity of ACE,ACE2 enzyme was increased and the level of Ang-II content was also significantly suppressed. Astragalus membranaceus or aerobic exercise had a positive effect on renin-angiotensin system in myocardial tissue of diabetic mice, and played a protective role in the myocardium of diabetic mice. It was speculated that there was a great deal of inhibition on renin-angiotensin system in myocardium of diabetic mice. It may be achieved by increasing the enzyme activity of ACE2 to inhibit the formation of Ang-II in diabetic myocardial tissue. FUNDING: This study was supported by Jiangsu Province Graduate Research and Innovation Program(KYCX18_1719)

Expression and tissue distribution analysis of Angiotensin II in sheep (Ovis aries) skins associated with white and black coat colors

Angiotensin II (AngII) regulates pigment synthesis by tyrosinase in melanocytes. To evaluate the association between AngII and coat color formation, we detected the expression distribution of AngII in white and black sheep skins by LC-ESI-MS/MS, western blot, quantitative real-time-PCR (qPCR) and distribution of AngII by immunohistochemistry.Liquid chromatography-electrospray ionization tandem MS (LC-ESI-MS/MS) results showed that AngII was found in white and black skin tissues of sheep. Western blot results verified the LC-ESI-MS/MS results and suggested that AngII was expressed at significantly higher levels in black sheep skins compared with the white sheep skins. Quantitative real time PCR (qRT-PCR) results also revealed that the expression level of AngII mRNA was higher in black sheep skins than that in white sheep skins. Immunohistochemical analysis further demonstrated that AngII protein was localized in the hair bulb and outer root sheath of hair follicle in sheep. In summary, protein and transcripts exhibited the same expression pattern in white and black sheep skins. Furthermore, the expressions of AngII in the hair bulb and outer root sheath of black sheep were stronger than those in white sheep. These results suggested that AngII functions in sheep coat color regulation and offer a novel insight for further investigation on the role of AngII in the coat color formation in sheep.

Tonin Overexpression in Mice Diminishes Sympathetic Autonomic Modulation and Alters Angiotensin Type 1 Receptor Response.

Background: Tonin, a serine-protease that forms Angiotensin II (AngII) from angiotensinogen, is increased in failing human heart samples. Increased blood pressure (BP) and decreased heart rate (HR) variabilities are associated with higher risk of cardiovascular morbidity. Losartan has been used to reduce hypertension and, therefore, lowers the risk of fatal and non-fatal cardiovascular events. Determination of tonin's impact on BP and HR variabilities as well as the impact of losartan remain questions to be elucidated.Aim: Evaluation of cardiovascular autonomic profile in transgenic mice overexpressing the rat tonin enzyme TGM'(rton) and the impact of AT1 receptor blocker, losartan.Methods: Male C57BL/6 (WT) and TGM'(rTon) mice were cannulated for recording BP (Windaq, 4 MHz) for 30 min at baseline and 30 min after losartan injection (20 mg/kg). BP and HR variabilities were analyzed in time and frequency domain method. Low-frequency (LF) and high-frequency (HF) components were identified for sympathetic and parasympathetic modulations analysis. Ang I, AngII, and Ang1-7 were quantified by high performance liquid chromatography method. The total enzymatic activity for AngI, AngII, and Ang1-7 formation was evaluated in the heart and plasma by Liquid chromatography mass spectrometry (LC-MS/MS).Results: At the baseline TGM'(rTon) exhibited higher BP, lower cardiac LF, higher cardiac HF, lower LF/HF, and lower alpha index than wild type (WT). After losartan injection, TGM'(rTon) mice presented an additional decrease in cardiac LF and increase in HF in relation to baseline and WT. In the vasculature, losartan caused decreased in BP and LF of systolic BP in WT mice in relation to its baseline. A similar effect was observed in the BP of TGM'(rTon) mice; however, LF of systolic BP increased compared to baseline. Our data also indicates that AT1R receptor signaling has been altered in TGM’(rTon)mice. Interestingly, the dynamics of the renin-angiotensin system kinetics change, favoring production of Ang1-7.Conclusion: Autonomic evaluation of TGM’(rTon) mice indicates an unclear prognosis for diseases that affect the heart. HR variability in TGM’(rTon) mice indicates high risk of morbidity, and sympathetic and parasympathetic modulation indicate low risk of morbidity. The low risk of morbidity could be the biased production of Ang1-7 in the heart and circulation; however, the altered response of AT1R in the TGM’(rTon) remains to be elucidated, as well aswhether that signaling is pro-protection or pro-pathology.

Abstract P286: Modulation Way Classical and Alternatives of Renin Angiotensin System (RAS) in Mesangial Cells After Exposure to Fructose

Background: Our group demonstrated previously that rats subjected to a high fructose diet showed increased activity of kidney ACE.In order to understand the effect of fructose in the forming process of angiotensin II (AngII) and angiotensin 1-7 (Ang1-7) affecting the levels of these effectors, the aim of this study was to evaluate the activities of the RAS enzymes responsible for the formation of Ang1-7 and AngIIof immortalized human mesangial cells (IMCH)exposed to low and high concentration of fructose. Methods: IMCH were divided into control (low glucose medium), Fructose 5 mM(medium + 5 mM Fructose) and Fructose 30mM(medium + 30 mM Fructose) groups. The enzymatic activity of ACE, chymase, cathepsin D, Neutral Endopeptidase (NEP) and ACE2 were evaluated using Z-Phe-His-Leu,Abz-AIKFFSAQ-EDDnp, Abz-AIAFFSRQ-EDDnp,Abz(d)-Arg-Gly-Leu,Mca-APK (DNP) as substrates respectively. Data were analyzed using ANOVA one way. Results: Among the AngIIforming enzymes, fructose decreased ACE activity in cell lysate.Both fructose concentrations increased chymase in the culture medium. No effect was observed on the activity of cathepsin D. When evaluating the activities of peptidases forming Ang-1-7,NEP activity was increasedin culture medium.We did not detected differences in ACE2 activity. Conclusion: The results suggest fructose modulates renal and systemic RAS in IMCH acting in the classical andalternative pathways of AngII formation. Additionally this sugar was able to increase NEP activity, forming Ang-1-7. Quantitation of angiotensin remains necessary to better understand how the end effector is available in IMCH and evaluate possible effects on glomerular physiology.

Insight into the interactive residues between two domains of human somatic Angiotensin-converting enzyme and Angiotensin II by MM-PBSA calculation and steered molecular dynamics simulation

Angiotensin-converting enzyme (ACE), a membrane-bound zinc metallopeptidase, catalyzes the formation of Angiotensin-II (AngII) and the deactivation of bradykinin in the renin–angiotensin-aldosterone and kallikrein–kinin systems. As a hydrolysis product of ACE, AngII is regarded as an inhibitor and displays stronger competitive inhibition in the C-domain than the N-domain of ACE. However, the AngII binding differences between the two domains and the mechanisms behind AngII dissociation from the C-domain are rarely explored. In this work, molecular docking, Molecular Mechanics/Poisson–Boltzmann Surface Area calculation, and steered molecular dynamics (SMD) are applied to explore the structures and interactions in the binding or unbinding of AngII with the two domains of human somatic ACE. Calculated free energy values suggest that the C-domain–AngII complex is more stable than the N-domain–AngII complex, consistent with available experimental data. SMD simulation results imply that electrostatic interaction is dominant in the dissociation of AngII from the C-domain. Moreover, Gln106, Asp121, Glu123, and Tyr213 may be the key residues in the unbinding pathway of AngII. The simulation results in our work provide insights into the interactions between the two domains of ACE and its natural peptide inhibitor AngII at a molecular level. Moreover, the results provide theoretical clues for the design of new inhibitors.

Abstract 15597: Acute Venous Congestion Causes Angiotensin II formation via Angiotensin-Converting Enzyme Activation in Compensated Ambulatory Patients with Systolic Heart Failure

Background: Plasma levels of angiotensin II (AII) are increased in congestive states such as heart failure (HF). The current study examined i) whether venous congestion (VC) itself promotes AII formation, and ii) the contributions of angiotensin-converting enzyme (ACE) vs. other enzymes such as chymases to AII generation in patients with systolic HF. Methods: 42 ambulatory patients with NYHA functional class II or III, an LVEF &lt;40%, no evidence of VC on physical exam and on stable medical therapy were studied. To experimentally model VC, venous arm pressure was increased to 30 mmHg above baseline by inflating a pressure cuff around the dominant arm. Blood was sampled from test and control arm (lacking an inflated cuff) before and after 90 minutes of VC. Radioimmunoassay was used for plasma AII measurements.The effect of ACE inhibitor (ACEI) based therapy (N=29) vs. non-ACEI (N=13) was compared. Results: The age of the study cohort was 53±12 years, 29% were female, 31% had an ischemic etiology and the LVEF was 22±8%. Baseline AII levels were 3-times lower in the ACEI vs. non-ACEI group (24±10 vs. 76±40 pg/mL, P&lt;0.001). Plasma AII was significantly higher in the congested over control arm only in non-ACEI group after 90 minutes of VC (figure). No adverse event was observed during the test. Conclusions: Our study provides the first direct evidence that VC is sufficient to cause AII formation in compensated ambulatory HF patients on non-ACEI based therapy. ACEI treatment completely abolished this increase suggesting activation of ACE, rather than other enzymes such as chymases, to be the cause of volume-dependent AII formation in response to peripheral VC.

An evolving story of angiotensin-II-forming pathways in rodents and humans.

Lessons learned from the characterization of the biological roles of Ang-(1-7) [angiotensin-(1-7)] in opposing the vasoconstrictor, proliferative and prothrombotic actions of AngII (angiotensin II) created an underpinning for a more comprehensive exploration of the multiple pathways by which the RAS (renin-angiotensin system) of blood and tissues regulates homoeostasis and its altered state in disease processes. The present review summarizes the progress that has been made in the novel exploration of intermediate shorter forms of angiotensinogen through the characterization of the expression and functions of the dodecapeptide Ang-(1-12) [angiotensin-(1-12)] in the cardiac production of AngII. The studies reveal significant differences in humans compared with rodents regarding the enzymatic pathway by which Ang-(1-12) undergoes metabolism. Highlights of the research include the demonstration of chymase-directed formation of AngII from Ang-(1-12) in human left atrial myocytes and left ventricular tissue, the presence of robust expression of Ang-(1-12) and chymase in the atrial appendage of subjects with resistant atrial fibrillation, and the preliminary observation of significantly higher Ang-(1-12) expression in human left atrial appendages.

Stimulation of renal sodium transporters’ abundance and phosphorylation during chronic angiotensin II (AII) infusion requires intrarenal AII formation

The hypertensive response to AII infusion (400ng/kg/min for 14 d) is blunted in mice expressing normal systemic ACE levels but no kidney ACE (ACE 10/10) vs. WT mice: mean arterial pressure increased 28 mmHg in ACE 10/10 mice vs. 42 mmHg in WT mice (p&lt;0.001). Kidney AII content was also reduced 50% in AII infused ACE 10/10 vs. WT (p&lt;0.05), (Gonzalez‐Villalobos, 2011). We tested the hypothesis that the reduced hypertensive response to AII infusion in the ACE 10/10 mice was due to blunted increases in renal Na+ transporters’ abundance or phosphorylation (‐P) along the nephron. Na+ transporter abundance was measured in whole kidney homogenates by immunoblotting. Density values in AII infused mice were normalized to values in uninfused WT and ACE10/10 mice defined as 1.00. Sodium Transporters AII infused WT AII infused ACE 10/10 NHE3 1.03 ± .06 0.76 ± .11 NHE3‐P 0.99 ± .06 0.70 ± .02 NKCC 0.86 ± .03* 0.97 ± .03 NKCC‐P 2.87 ± .38* 1.01 ± .22 NCC 1.61 ± .15* 0.94 ± .10 NCC‐PS71 2.24 ± .91* 1.01 ± .29 β ENaC 0.93 ± .02 0.96 ± .07 p&lt; 0.05 AII vs. uninfused. Conclusions1) In WT, AII infusion significantly increases NCC, NCC‐P, NCC‐P/total, NKCC‐P, and NKCC‐P/total which may account for the hypertension. 2) In ACE 10/10, lacking intrarenal ACE, AII did not provoke any of these responses indicating that the increased abundance and –P of transporters, like the rise in BP, are dependent on AII stimulation of intrarenal RAS. DK0837854, R00DK083455‐03

ACE Inhibition in Anti-Thy1 Glomerulonephritis Limits Proteinuria but Does Not Improve Renal Function and Structural Remodeling

Background/Aims: ACE inhibitor (ACE-I) treatment effectively inhibits proteinuria and ameliorates the course of various renal diseases. In experimental glomerulonephritis, however, angiotensin II (AngII) infusion has also been shown to be renoprotective. We evaluated the long-term (28 days) course of anti-Thy1 glomerulonephritis in animals with suppressed AngII formation by ACE-I treatment. Methods: Brown Norway rats received perindopril (2.8 mg/kg/day, n = 12), dihydropyridine calcium-antagonist amlodipine (Ca-A; 13 mg/kg/day, n = 6) or were left untreated (n = 14). All animals were monitored for blood pressure, proteinuria, and creatinine clearance after anti-Thy1 injection. Renal histology was assessed at day 7 and 28. Results: Systolic blood pressure was equally reduced by ACE-I and Ca-A treatment. AngII suppression prevented development of proteinuria, but did not protect against glomerular microaneurysm formation or reduction in creatinine clearance. After resolution of the microaneurysms, animals with suppressed AngII production showed a modest increase in glomerulosclerosis and vasculopathic thickening of intrarenal vessels. Conclusions: In anti-Thy1 glomerulonephritis, suppression of AngII formation does not protect against the induction of glomerular damage and is associated with mild aggravation of adverse renal fibrotic remodeling. Proteinuria, however, is effectively prevented by ACE-I treatment. Ca-A treatment did not affect the course of glomerulonephritis, indicating that ACE-I effects are blood pressure independent.

Angiotensin-II-induced reactive oxygen species along the SFO-PVN-RVLM pathway: implications in neurogenic hypertension

Neurogenic hypertension has been the subject of extensive research worldwide. This review is based on the premise that some forms of neurogenic hypertension are caused in part by the formation of angiotensin-II (Ang-II)-induced reactive oxygen species along the subfornical organ-paraventricular nucleus of the hypothalamus-rostral ventrolateral medulla pathway (SFO-PVN-RVLM pathway). We will discuss the recent contribution of our laboratory and others regarding the mechanisms by which neurons in the SFO (an important circumventricular organ) are activated by Ang-II, how the SFO communicates with two other important areas involved in sympathetic activity regulation (PVN and RVLM) and how Ang-II-induced reactive oxygen species participate along the SFO-PVN-RVLM pathway in the pathogenesis of neurogenic hypertension.

The renin–angiotensin system and the gastrointestinal mucosa

The gastrointestinal (GI) tract is fundamental for the intake of fluid and electrolytes and accommodates a large proportion of bodily hemodynamics and host defence systems. Despite that the renin-angiotensin system (RAS) is a prominent regulatory system for fluid and electrolyte homeostasis its impact on GI physiology is only little explored. Recent data indicate that RAS is well expressed and active in the GI tract although exact physiological roles are to be settled. There are several reports showing influences by RAS and its key mediator angiotensin II (AngII) on intestinal epithelial fluid and electrolyte transport and data are accumulating, suggesting involvement in GI mucosal inflammation and carcinogenesis. Of particular interest is the increasing amount of experimental support for the involvement of AngII formation and actions via the AngII subtype 1 (AT1) receptor in the pathogenesis and treatment of inflammatory bowel disease. The picture of RAS in the GI tract is, however, far from complete. Because RAS is an important application area for reno-cardiovascular diseases, a number of pharmacological agents as well as research technologies already exist and can in the future be used for GI research. A marked expansion of knowledge concerning the role of RAS in GI physiology and pathophysiology is to be expected.

Urinary Renin Excretion is augmented in Chronic Angiotensin II‐infused Sprague‐Dawley Hypertensive Rats

Renin is upregulated in principal cells of the collecting ducts of angiotensin II (AngII)‐dependent hypertensive rats; however it remains unclear if increased distal nephron‐derived renin is secreted into the urine during AngII‐dependent hypertension. Urinary renin (uRen), angiotensinogen (uAGT) and AngII (uAngII) excretion was measured in chronic AngII‐infused male Sprague‐Dawley rats [80 ng/min, SC minipumps for 14 d, n=5] and control, sham‐operated rats [n=5]. Systolic blood pressures increased in the AngII rats by Day 5 and continued to increase throughout the study (Day 13; AngII: 175±10 vs. sham: 116±2 mm Hg). Although plasma renin activity was suppressed in the AngII‐infused rats (AngII: 0.3±0 vs. sham: 5.5±2 ng Ang I/ml/h); renin content in renal medullary tissues did not change (AngII: 10,564±1,476 vs. sham: 9,438±1,588 ng Ang I/h/mg; p=ns). Excretion of uAGT and uAngII increased in the AngII rats compared to sham rats, respectively [uAGT (AngII:1107±106 vs. sham:60±26 ng/day); uAngII (AngII: 3813±431 vs. sham: 2080±361 fmol/day). Importantly, uRen excretion rate at Day 13 was markedly increased in the AngII rats (AngII: 9±3 vs. sham: 1±1×10−5 Enzyme Units/day; p&lt;0.05). Augmented uRen and uAGT may contribute to increased intrarenal AngII formation in AngII‐dependent hypertensive rats.NIH [IdeA (P20‐RR‐017659‐06), Tulane‐BIRCWH (K12HD043451)]; and AHA (09PRE2209079 and 09BGIA2280440).

Contribution of Chymase-Dependent Angiotensin II Formation to the Progression of Tubulointerstitial Fibrosis in Obstructed Kidneys in Hamsters

Recent studies indicate a role of chymase in the regulation of angiotensin II (AngII) formation in cardiovascular and renal tissues. We investigated a possible contribution of chymase to AngII formation and to renal fibrosis in unilateral ureteral obstruction (UUO). Eight-week-old Syrian hamsters were subjected to UUO and treated with vehicle, the specific chymase inhibitor (CI) 4-[1-(4-methyl-benzo[b]thiophen-3-ylmethyl)-1H-benzimidazol-2-ylsulfanyl]-butyric acid (50 mg/kg, twice a day, p.o.), or the selective AT1-receptor blocker olmesartan (10 mg/kg per day, p.o.) for 14 days. UUO-induced renal interstitial fibrosis was associated with increases in renal mRNA levels of α-smooth muscle actin (SMA), type I collagen, and transforming growth factor (TGF)-β. The UUO hamsters showed markedly higher AngII contents and increased AT1-receptor mRNA level in the obstructed kidney than sham-operated ones. In contrast, angiotensin-converting enzyme (ACE) protein expression was significantly lower in UUO hamsters. In UUO hamsters, treatment with CI or olmesartan significantly decreased AngII levels in renal tissue and mRNA levels of α-SMA, type I collagen, and TGF-β and ameliorated tubulointerstitial injury. On the other hand, neither CI nor olmesartan changed systolic blood pressure, renal ACE, and AT1-receptor protein levels. These data suggest that chymase-dependent intrarenal AngII formation contributes to the pathogenesis of interstitial fibrosis in obstructed kidneys of hamsters.

Chymase Inhibitor Improves Renal Dysfunction Under Long-term Angiotensin-converting Enzyme Inhibition in Heart Failure

Impaired renal function is one of the predictors of mortality in heart failure (HF). Angiotensin-II (Ang-II) plays a deteriorational role in renal injury and half of renal Ang-II formation is mediated via chymase not ACE pathway. The interaction between the heart and the kidney is an important issue in the treatment of HF. Thus, we evaluated the concomitant therapeutic effects of an ACE inhibitor (ACEI, Enalapril) with a specific chymase inhibitor (ChyI, TEI) on cardiorenal function in dogs with tachycardia induced HF.

Anti-inflammatory Actions of Quinapril

The role of angiotensin II (Ang-II) in inflammation and the mechanisms through which it exerts this role are explored. Signaling through angiotensin stimulation of inflammatory cells often amplifies inflammation. Formation of Ang-II from tissue angiotensin-converting enzyme (ACE) has been shown to be of greater importance in the development and progression of inflammatory diseases than plasma ACE. Quinapril, which is a potent and selective inhibitor of both plasma and tissue ACE, has demonstrated anti-inflammatory properties in many disease states such as atherosclerosis, nephritis, scleroderma, diabetes and arthritis, and, thus, offers new therapeutic possibilities for disease treatment.

Human gastroepiploic artery has greater chymase activity than the internal thoracic artery

Recent reports have demonstrated that long-term patency of the gastroepiploic artery (GEA) in coronary artery bypass grafting (CABG) is less satisfactory compared with the internal thoracic artery (ITA). However, the reason has not been fully elucidated. Angiotensin II is known to play an important role in the development of intimal hyperplasia, we hypothesized that the GEA is different from the ITA with respect to angiotensin II-forming ability. Accordingly, we measured activities of angiotensin II-forming enzymes, angiotensin-converting enzyme (ACE) and chymase, in human GEA and ITA. Remnant of the GEAs and ITAs were obtained from 24 patients who underwent CABG in which both conduits were used simultaneously. Activities of ACE and chymase were measured by using the extract form the GEA or ITA. Sections of the GEA or ITA were immunohistochemically stained with anti-human chymase antibody. The ACE activity of the GEA (0.28+/-0.16 mU/mg protein) was greater than that of the ITA (0.18+/-0.11, p < 0.001). The chymase activity of the GEA (11.11+/-7.15 mU/mg protein) was also greater than that in the ITA (7.13+/-4.89, p < 0.001). The density of chymase-positive cells in the GEA (3.8+/-4.2 cells/mm2) was greater than that in the ITA (1.1+/-1.2, p < 0.01). Activities of both ACE and chymase were significantly greater in the GEA compared with the ITA. The GEA may be different from the ITA with respect to potential ability of angiotensin II-formation.

Captopril does not affect reflex increases in adrenal or lumbar sympathetic nerve activity to hypoglycemia in rats

Blockade of angiotensin II (ANGII) receptors or converting enzyme inhibition attenuates reflex increases in epinephrine during insulin-induced hypoglycemia. Because ANGII receptors are found in several sites within the central nervous system, the aim of this study was to examine whether acute captopril attenuates the reflex increase in adrenal preganglionic sympathetic nerve activity (SNA) induced by hypoglycemia. We infused vehicle (control) or insulin (30 U/kg IV) in anesthetized rats or in rats pretreated with captopril (Cap-insulin; 2.5 mg/kg, then 1 mg/kg per hour IV) while measuring hemodynamics and SNA from adrenal preganglionic, adrenal postganglionic, and lumbar sympathetic nerves. Hypoglycemia elicited similar adrenal preganglionic SNA increases in insulin-treated (260% ± 31% from 100% baseline) and Cap-insulin–treated (255% ± 34%) rats. Likewise, increases in adrenal postganglionic SNA and lumbar SNA were equivalent in the insulin and Cap-insulin groups. Hypoglycemia also elicited a tachycardia in insulin-treated rats that was attenuated in Cap-insulin–treated rats, and corresponding blood pressure decreases in insulin rats were enhanced in Cap-insulin–treated rats. Thus, blockade of ANGII formation by captopril did not affect hypoglycemia-induced activation of adrenal preganglionic SNA, indicating that the renin-angiotensin systems in the brain and spinal cord do not modulate increases in adrenal SNA during hypoglycemia.

ACE Inhibition Lowers Angiotensin-II-Induced Monocyte Adhesion to HUVEC by Reduction of p65 Translocation and AT1 Expression

Angiotensin-converting enzyme (ACE) inhibitors interfere with several key events of vascular inflammation resulting in impressive reductions in coronary vascular events. However, in human arteries ACE inhibitors block the production of angiotensin II (AngII) incompletely because of the involvement of alternative pathways in local AngII formation. Therefore, our study concentrated on the presumed modulation by ACE inhibition of local AngII-mediated inflammatory actions by a mechanism independent of blockage of AngII formation. We analyzed the effect of the ACE inhibitor ramiprilat on AngII-dependent cell adhesion molecule (CAM) expression and adhesion of monocytic THP-1 cells to endothelial cells. AngII induced upregulation of P-selectin, VCAM-1 and ICAM-1 on endothelial cells via activation of AT1, which was correlated with enhanced THP-1 adhesion in flow chamber assays. Both enhanced adhesion and adhesion molecule expression were significantly reduced by pretreatment with ramiprilat. Ramiprilat reduced AT1 expression on endothelial cells and decreased the AngII-induced p65 translocation into the nucleus. Diminished AT1 expression and adhesion molecule expression in response to ramiprilat treatment were partially reversed after incubation with a bradykinin 2 receptor antagonist, suggesting that elevated bradykinin levels under ACE inhibition may be involved in the beneficial effect of ACE inhibitors. Thus, modulation of the local AngII system by ramiprilat may at least in part contribute to the benefits of ACE inhibition in the treatment of atherosclerotic diseases.

Mast cell chymase in the ischemic kidney of severe unilateral renovascular hypertension

Chymase degrades angiotensin I (AI) to form angiotensin II (AII), probably constituting a bypass of the renin-angiotensin cascade. Chymase activity increases in some vascular diseases. In the kidney, an increase in chymase activity was reported in an animal model of ischemic kidney of renovascular hypertension (RVH); however, no such evidence has been provided in humans. We treated a 64-year-old patient with severe unilateral RVH and atherosclerosis, for whom removal of the ischemic kidney was the only option. Using immunohistochemical staining, we investigated chymase activity in the removed kidney and associated artery and vein. An increase in chymase activity, together with mast cells infiltrating the interstitium, was observed where interstitial fibrosis was seen. In the renal artery, where severe atherosclerosis was seen, and also in the vein, mast cell infiltration in the adventitia was accompanied by chymase. The captopril test showed an increase in serum aldosterone level, with a concomitant increase in plasma renin activity and decrease in blood pressure. Because the decrease in blood pressure implies a decrease in circulatory AII levels, it is plausible that in this patient, chymase had a role in AII formation in the adrenal gland to stimulate aldosterone secretion. Thus, by means of captopril, AI levels increased, and chymase may have produced AII in loci tissues, which, in turn, stimulated aldosterone secretion. This is the first report of an increase in chymase activity in the interstitium of an ischemic kidney and renal artery and vein in a patient with RVH and atherosclerosis.

Dietary salt restriction accelerates atherosclerosis in apolipoprotein E-deficient mice

Background: Whether a general reduction in salt intake reduces or actually enhances cardiovascular mortality in man remains an issue of controversy. Low sodium diets may lead to adverse side effects by stimulating the renin–angiotensin and sympathetic nervous systems. The present study was designed to investigate the effects of low dietary salt on atherosclerotic lesion progression in apolipoprotein E deficient (apoE −/−) mice. Methods and results: We fed 7-week-old apoE −/− mice on low (0.036% NaCl; n = 28) or regular (0.64% NaCl; n = 26) salt diets for 16 weeks. At the age of 23 weeks, the cross-section surface area of atherosclerotic plaques was measured in aortic root and thoracic aorta. Serum total cholesterol, triglycerides, plasma angiotensin levels and urinary protein/creatinine concentrations were assessed. Exposure to low salt caused significant increases in atherosclerotic lesion surface area in thoracic aorta, but did not alter lesion area in aortic root. Low-salt mice also had higher serum total cholesterol and higher plasma angiotensin II (ANG-II) concentrations. Atherosclerotic lesion area was correlated with ANG-II levels in low-salt but not in regular-salt animals, and with total cholesterol concentration in all mice. Mean arterial pressure was comparable in both groups. Conclusions: Dietary salt restriction accelerated atherosclerotic lesion formation in apoE −/− mice through a mechanism that is probably related to ANG-II formation. Whether these findings are relevant to human cardiovascular disease remains to be evaluated.