Renin-angiotensin System Status Research Articles

Human soluble prorenin receptor expressed in mouse renal collecting duct shows sex-specific effect on cardiorenal function.

Soluble prorenin receptor (sPRR), a component of the renin-angiotensin system (RAS), has been identified as a plasma biomarker for hypertension and cardiovascular diseases in humans. Despite studies showing that sPRR in the kidney is produced by tubular cells in the renal collecting duct (CD), its biological actions modulating cardiorenal function in physiological conditions remain unknown. Therefore, the objective of our study was to investigate whether CD-derived human sPRR (HsPRR) expression influences cardiorenal function and examine sex and circadian differences. Thus, we investigated the status of the intrarenal RAS, water and electrolyte balance, renal filtration capacity, and blood pressure (BP) regulation in CD-HsPRR and control (CTL) mice. CD-HsPRR mice were generated by breeding human sPRR-Myc-tag mice with Hoxb7/Cre mice. Renal sPRR expression increased in CD-HsPRR mice, but circulating sPRR and RAS levels were unchanged compared with CTL mice. Only female littermates expressing CD-HsPRR showed 1) increased 24-h BP, 2) an impaired BP response to an acute dose of losartan and attenuated angiotensin II (ANG II)-induced hypertension, 3) reduced angiotensin-converting enzyme activity and ANG II content in the renal cortex, and 4) decreased glomerular filtration rate, with no changes in natriuresis and kaliuresis despite upregulation of the β-subunit of the epithelial Na+ channel in the renal cortex. These cardiorenal alterations were displayed only during the active phase of the day. Taken together, these data suggest that HsPRR could interact with ANG II type 1 receptors mediating sex-specific, ANG II-independent renal dysfunction and a prohypertensive phenotype in a sex-specific manner.NEW & NOTEWORTHY We successfully generated a humanized mouse model that expresses human sPRR in the collecting duct. Collecting duct-derived human sPRR did not change circulating sPRR and RAS levels but increased daytime BP in female mice while showing an attenuated angiotensin II-dependent pressor response. These findings may aid in elucidating the mechanisms by which women show uncontrolled BP in response to antihypertensive treatments targeting the RAS, improving approaches to reduce uncontrolled BP and chronic kidney disease incidences in women.

COVID-19 as a viral functional ACE2 deficiency disorder with ACE2 related multi-organ disease

SARS-CoV-2, the agent of COVID-19, shares a lineage with SARS-CoV-1, and a common fatal pulmonary profile but with striking differences in presentation, clinical course, and response to treatment. In contrast to SARS-CoV-1 (SARS), COVID-19 has presented as an often bi-phasic, multi-organ pathology, with a proclivity for severe disease in the elderly and those with hypertension, diabetes and cardiovascular disease. Whilst death is usually related to respiratory collapse, autopsy reveals multi-organ pathology. Chronic pulmonary disease is underrepresented in the group with severe COVID-19. A commonality of aberrant renin angiotensin system (RAS) is suggested in the at-risk group. The identification of angiotensin-converting-enzyme 2 (ACE2) as the receptor allowing viral entry to cells precipitated our interest in the role of ACE2 in COVID-19 pathogenesis.We propose that COVID-19 is a viral multisystem disease, with dominant vascular pathology, mediated by global reduction in ACE2 function, pronounced in disease conditions with RAS bias toward angiotensin-converting-enzyme (ACE) over ACE2. It is further complicated by organ specific pathology related to loss of ACE2 expressing cells particularly affecting the endothelium, alveolus, glomerulus and cardiac microvasculature. The possible upregulation in ACE2 receptor expression may predispose individuals with aberrant RAS status to higher viral load on infection and relatively more cell loss. Relative ACE2 deficiency leads to enhanced and protracted tissue, and vessel exposure to angiotensin II, characterised by vasoconstriction, enhanced thrombosis, cell proliferation and recruitment, increased tissue permeability, and cytokine production (including IL-6) resulting in inflammation. Additionally, there is a profound loss of the “protective” angiotensin (1–7), a vasodilator with anti-inflammatory, anti-thrombotic, antiproliferative, antifibrotic, anti-arrhythmic, and antioxidant activity. Our model predicts global vascular insult related to direct endothelial cell damage, vasoconstriction and thrombosis with a disease specific cytokine profile related to angiotensin II rather than “cytokine storm”. Our proposed mechanism of lung injury provides an explanation for early hypoxia without reduction in lung compliance and suggests a need for revision of treatment protocols to address vasoconstriction, thromboprophylaxis, and to minimize additional small airways and alveolar trauma via ventilation choice. Our model predicts long term sequelae of scarring/fibrosis in vessels, lungs, renal and cardiac tissue with protracted illness in at-risk individuals. It is hoped that our model stimulates review of current diagnostic and therapeutic intervention protocols, particularly with respect to early anticoagulation, vasodilatation and revision of ventilatory support choices.

Losartan prevents the elevation of blood pressure in adipose-PRR deficient female mice while elevated circulating sPRR activates the renin-angiotensin system.

Deletion of the prorenin receptor (PRR) in adipose tissue elevates systolic blood pressure (SBP) and the circulating soluble form of PRR (sPRR) in male mice fed a high-fat (HF) diet. However, sex differences in the contribution of adipose-PRR and sPRR to the regulation of the renin-angiotensin system (RAS) in key organs for blood pressure control are undefined. Therefore, we assessed blood pressure and the systemic and intrarenal RAS status in adipose-PRR knockout (KO) female mice. Blockade of RAS with losartan blunted SBP elevation in HF diet-fed adipose-PRR KO mice. ANG II levels were significantly increased in the renal cortex of HF diet-fed adipose-PRR KO female mice, but not systemically. HF diet-fed adipose-PRR KO mice exhibited higher vasopressin levels, water retention, and lower urine output than wild-type (WT) mice. The results also showed that deletion of adipose-PRR increased circulating sPRR and total hepatic sPRR contents, suggesting the liver as a major source of elevated plasma sPRR in adipose-PRR KO mice. To mimic the elevation of circulating sPRR and define the direct contribution of systemic sPRR to the regulation of the RAS and vasopressin, C57BL/6 female mice fed a standard diet were infused with recombinant sPRR. sPRR infusion increased plasma renin levels, renal and hepatic angiotensinogen expression, and vasopressin. Together, these results demonstrate that the deletion of adipose-PRR induced an elevation of SBP likely mediated by an intrarenal ANG II-dependent mechanism and that sPRR participates in RAS regulation and body fluid homeostasis via its capacity to activate the RAS and increase vasopressin levels. NEW & NOTEWORTHY The elevation of systolic blood pressure appears to be primarily mediated by cortical ANG II in high-fat diet-fed adipose-prorenin receptor knockout female mice. In addition, our data support a role for soluble prorenin receptor in renin-angiotensin system activation and vasopressin regulation.

A2830 Serum soluble (pro)renin receptor concentration is correlated with organ dysfunctions in patients with primary aldosteronism

Objectives: Primary aldosteronism (PA) is characterized by autonomous production of aldosterone by adrenal lesions and leads to hypertension. It is known that excess of aldosterone causes organ dysfunctions, but the underlying mechanism to cause organ dysfunctions still remains undetermined. (Pro)renin receptor[(P)RR] binds to both renin and its precursor prorenin to activate tissue renin-angiotensin system (RAS). (P)RR is cleaved by furin to generate soluble (pro)renin receptor [s(P)RR], and thus blood s(P)RR concentration is a candidate biomarker reflecting the status of the tissue RAS. In this study, we investigated the relationships between serum s(P)RR concentration and indices of organ dysfunctions in PA patients. Methods: We examined serum s(P)RR concentration in PA patients who were either without antihypertensive medications or were treated only with calcium channel blockers. We also evaluated the relationships between serum s(P)RR concentration and indices of organ dysfunctions such as high-sensitivity CRP (hsCRP), cardio-ankle vascular index (CAVI), eGFR, and BNP. Results: A total of 124 patients (76 males, 54.9 ± 12.2 y.o.) were enrolled. Serum s(P)RR concentration was significantly positively correlated with hsCRP (r = 0.44, p < 0.05), CAVI (r = 0.39, p < 0.05), and BNP (r = 0.25, p < 0.05), and was significantly negatively associated with eGFR (r = 0.42, p < 0.05). Plasma aldosterone concentration (PAC) did not show significant relationships with these indices. Conclusion: In PA patients, serum s(P)RR concentration but not PAC showed associations with organ dysfunctions. Increased tissue RAS may be associated with the cause of organ dysfunctions in these patients. Further investigations are needed to clarify the underlying mechanisms by which serum s(P)RR concentrations are associated with organ dysfunctions.

Urinary angiotensinogen level is increased in renal transplant recipients with masked hypertension and is correlated with left ventricular mass index and albuminuria in these patients.

Activation of the local renin-angiotensin system (RAS) is an independent risk factor for the development of proteinuria and left ventricular hypertrophy (LVH) more commonly seen in masked hypertensives. It has been reported that urinary angiotensinogen (UAGT) level provides a specific index of the intrarenal RAS status. The aim of this study was to evaluate the association between UAGT and left ventricular mass index (LVMI) and urinary albumin-creatinine ratio (UACR) in renal transplant recipients (RTRs) with masked hypertension (HT). A total of 116 non-diabetic-treated hypertensive RTRs were included in this study. The patients were divided into two groups: masked hypertensives and controlled hypertensives. Forty-two (36.2%) of RTRs had masked HT. Mean UACR and LVMI levels were higher in RTRs with masked HT than in RTRs with controlled HT (P<0.001). UAGT level was also higher in masked hypertensives compared to controlled hypertensives (P<0.001). Multivariable regression analysis showed that UAGT was positively correlated with UACR (β=0.024, P=0.001) and LVMI (β=0.082, P=0.001) in masked hypertensives. Consequently, masked HT was considerably frequent (36.2%) in treated hypertensive RTRs and high UAGT levels accompanied by high albuminuria and LVMI levels were seen in these patients. Overproduction of the UAGT may play a pivotal role in the development of LVH and proteinuria in masked hypertensives.

PS 02-47 RELATIONSHIPS BETWEEN SERUM SOLUBLE (PRO)RENIN RECEPTOR LEVELS AND OBESITY- OR METABOLISM-RELATED FACTORS IN ESSENTIAL HYPERTENSIVE PATIENTS

Objective: (Pro)renin receptor[(P)RR] is a single trans-membrane receptor that binds to both renin and its precursor prorenin to activate tissue renin-angiotensin system (RAS). (P)RR is cleaved by furin to generate soluble (pro)renin receptor [s(P)RR], which is secreted into the extracellular space. Blood s(P)RR level is a candidate biomarker reflecting the status of the tissue RAS, and we have reported serum s(P)RR levels are associated with renal function. Metabolic factors contribute to progression of end organ damages in hypertensive patients. Therefore, in this study, we investigated the relationships between serum s(P)RR levels and obesity- or metabolism-related factors in patients with essential hypertension. Design and Method: We measured serum s(P)RR levels and assessed the relationships between serum s(P)RR levels and background factors including endocrine or metabolic factors such as body mass index (BMI), abdominal circumference, blood glucose, Insulin, HbA1c, HOMA-R, HOMA-β, LDL-cholesterol (C), HDL-C, triglyceride (TG), adrenocorticotrophic hormone (ACTH), cortisol, visceral fat area (VFA), and subcutaneous fat area (SFA) (Dual impedance method). Results: A total of 300 patients (135 males) were enrolled. The mean value for age was 57 ± 14 y.o., BMI 24.8 ± 4.8 Kg/m2, abdominal circumference 89.4 ± 10.9 cm, blood pressure 142 ± 17/86 ± 13 mmHg, HbA1c 5.8 ± 0.9%, HOMA-R 2.46 ± 2.58%, HOMA-β 89.6 ± 56.6%, VFA 92.3 ± 38.5 cm2, SFA 191.9 ± 82.9 cm2, and serum s(P)RR level 21.5 ± 5.8 ng/mL. Serum s(P)RR levels were significantly positively correlated with BMI (r = 0.174, p = 0.009), abdominal circumference (r = 0.162, p = 0.040), HbA1c (r = 0.194, p = 0.003), TG (r = 0.261, p < 0.001), cortisol (r = 0.243, p = 0.002), and were significantly negatively correlated with HDL-C (r = −0.201, p < 0.005). Serum s(P)RR levels showed a positive correlation with VFA (r = 0.263, p = 0.037), but not with SFA. Conclusions: In patients with essential hypertension, serum s(P)RR levels were shown to be associated with obesity- or metabolism-related factors, suggesting that the expression of (P)RR may have a role in metabolic disorders such as obesity.

PS 02-46 URINARY SOLUBLE (PRO)RENIN RECEPTOR EXCRETION ASSOCIATED WITH URINE pH

Objective: (Pro)renin receptor[(P)RR] binds to renin and its precursor prorenin to activate tissue renin-angiotensin system (RAS). (P)RR is cleaved by furin to generate soluble (P)RR [s(P)RR], which is secreted into the extracellular space, and ATP6AP2 protein, which is an accessory protein of vacuolar-type H+-ATPase (V-ATPase) and plays an essential role in controlling intracellular vesicular acid environment. It has been reported that (P)RR may have a role in transporting H+ to the urine in the collecting duct. Although blood s(P)RR level has been recognized as a biomarker reflecting the status of tissue RAS, the significance of urinary s(P)RR excretion has not been determined. Therefore, the present study was undertaken to investigate the characteristics of urinary s(P)RR excretion. Design and Method: Urinary s(P)RR excretion was measured by ELISA and relationships between urinary s(P)RR excretion and background factors were investigated in 126 (58 males, 51 ± 16 y.o) subjects. Relationships between changes in urine pH and urinary s(P)RR excretion by treatment with vitamin C, which reduces urine pH, for 14 days were investigated. Results: The mean urinary s(P)RR excretion was 2.32 ± 3.77 ng/gCre. Urinary s(P)RR excretion was significantly positively and negatively related with urine pH (r = 0.376, p < 0.001) and uric acid (r = -0.237, p = 0.026), respectively. Multiple regression analysis testing urine pH, eGFR, uric acid, and serum s(P)RR, as independent variables revealed that only urine pH was significantly positively associated with urine s(P)RR excretion. Changes in urine pH and urinary s(P)RR excretion by vitamin C treatment were significantly positively related (r = 0.899, p = 0.015). Conclusions: Urinary s(P)RR excretion showed an independent association with urine pH. It can be speculated that urine (P)RR excretion is elevated due to increased (P)RR expression in tubules resulting from V-ATPase activation to compensate decreased urine pH, although this presumption needs to be estimated by further investigations.

Role of the intrarenal renin-angiotensin system in the progression of renal disease.

The intrarenal renin-angiotensin system (RAS) has many well-documented pathophysiologic functions in both blood pressure regulation and renal disease development. Angiotensin II (Ang II) is the major bioactive product of the RAS. It induces inflammation, renal cell growth, mitogenesis, apoptosis, migration, and differentiation. In addition, Ang II regulates the gene expression of bioactive substances and activates multiple intracellular signaling pathways that are involved in renal damage. Activation of the Ang II type 1 (AT1) receptor pathway results in the production of proinflammatory mediators, intracellular formation of reactive oxygen species, cell proliferation, and extracellular matrix synthesis, which in turn facilities renal injury. Involvement of angiotensinogen (AGT) in intrarenal RAS activation and development of renal disease has previously been reported. Moreover, studies have demonstrated that the urinary excretion rates of AGT provide a specific index of the intrarenal RAS status. Enhanced intrarenal AGT levels have been observed in experimental models of renal disease, supporting the concept that AGT plays an important role in the development and progression of renal disease. In this review, we focus on the role of intrarenal RAS activation in the pathophysiology of renal disease. Additionally, we explored the potential of urinary AGT as a novel biomarker of intrarenal RAS status in renal disease.

Overexpression of Intrarenal Renin-Angiotensin System in Human Acute Tubular Necrosis

Background/Aims: Acute tubular necrosis (ATN), a leading cause of acute kidney injury (AKI), is associated with decreased survival and increased progression of chronic kidney disease. A barrier to improving the clinical outcomes is the incomplete understanding of the pathogenesis of AKI. Our objective is to test the hypothesis that intrarenal renin-angiotensin system (RAS) is overexpressed in patients with ATN and could be an indicator of ATN severity. Methods: A transversal study was conducted in patients with biopsy-proven ATN. Intrarenal expression of angiotensinogen and angiotensin II, and urinary angiotensinogen were measured. Results: Patients with ATN demonstrated upregulation of intrarenal RAS, evidenced by upregulation of intrarenal angiotensinogen and angiotensin II. Patients with ATN also have elevated urinary angiotensinogen level that correlated with the overexpressed intrarenal RAS. Moreover, this increase in intrarenal RAS expression and urinary angiotensinogen was associated with the extent of acute tubular injury and urinary albumin excretion, respectively. Conclusions: We demonstrate that the intrarenal RAS is upregulated in patients with ATN and is associated with the severity of ATN. Urinary angiotensinogen reflects intrarenal RAS status, and is of value to assess the severity of ATN.

Abstract MP03: Relationships between Serum Soluble (Pro)Renin Receptor Levels and Endocrine or Metabolic Factors in Patients with Essential Hypertension

Background: (Pro)renin receptor[(P)RR] is a single trans-membrane receptor that binds to both renin and its precursor prorenin to activate tissue renin-angiotensin system (RAS). (P)RR is cleaved by furin to generate soluble (pro)renin receptor [s(P)RR], which is secreted into the extracellular space. Blood s(P)RR level is a candidate biomarker reflecting the status of the tissue RAS, and we have reported that serum s(P)RR levels are associated with renal function. Endocrine or metabolic factors contribute to progression of endorgan damages in hypertensive patients. Therefore, in the present study, we investigated the relationships between serum s(P)RR levels and endocrine or metabolic factors in patients with essential hypertension. Methods: We measured serum s(P)RR levels and assessed the relationships between serum s(P)RR levels and background factors including endocrine or metabolic factors such as age, body mass index (BMI), abdominal circumference, hemoglobin, uric acid, HbA1c, LDL-cholesterol (C), HDL-C, triglyceride (TG), high-sensitivity (hs) CRP, plasma renin activity, aldosterone concentration, noradrenaline, adrenaline, thyroid stimulating hormone, free T3, and free T4 in essential hypertensive patients. Results: A total of 302 patients (138 males) were enrolled. The mean value for age was 57±12 y.o., BMI was 24.9±5.1 Kg/m2, blood pressure was 140±16/85±12 mmHg, hemoglobin was 14.0±1.3 g/dl, estimated glomerular filtration rate (eGFR) was 75.2±20.6 ml/min/1.73 m2, HbA1c was 5.7±0.7%, and serum s(P)RR level was 21.0±5.8 ng/ml. Serum s(P)RR levels were significantly positively correlated with age (r=0.209, p&lt;0.0005), abdominal circumference (r=0.177, p&lt;0.05), HbA1c (r=0.219, p&lt;0.001), TG (r=0.180, p&lt;0.01), hs CRP (r=0.162, p&lt;0.05), free T3 (r=0.521, p&lt;0.01), and free T4 (r=0.523, p&lt;0.005), and were significantly negatively correlated with hemoglobin (r=-0.243, p&lt;0.05), eGFR (r=-0.272, p&lt;0.0001), and HDL-C (r=-0.199, p&lt;0.005). Conclusion: In patients with essential hypertension, serum s(P)RR levels were shown to be associated with endocrine or metabolic factors in addition to renal function, suggesting serum s(P)RR level as a useful biomarker that reflects the status of endocrine or metabolic disorders.

Abstract P146: Serum Soluble (Pro)Renin Receptor Levels in Patients Undergoing Hemodialysis

Background: The (pro)renin receptor [(P)RR] plays an important role in regulating the tissue renin-angiotensin system (RAS) through the non-proteolytic activation of prorenin, the precursor of renin. (P)RR is cleaved by furin to generate soluble (P)RR [s(P)RR], which is secreted into the extracellular space, and serum s(P)RR has been reported to reflect the status of tissue RAS. Hemodialysis (HD) patients have poor prognosis due to increased prevalence of cardiovascular diseases resulting from severe atherosclerosis. It is speculated that activation of tissue RAS by (P)RR may be associated with this condition, it remains speculative. In the present study, we investigated the relationships between serum s(P)RR levels and background factors including indices of atherosclerosis in HD patients. Methods: Serum s(P)RR levels were measured in 258 maintenance HD patients and these values were compared with 25 subjects with normal renal function. Western blot analysis was done using HD waste water samples, and clearance of s(P)RR through the membrane of dialyzer was examined. Furthermore, relationships between serum s(P)RR levels and background factors were assessed in HD patients. Results: Serum s(P)RR levels were significantly higher in HD patients (30.4±6.1 ng/ml) than those in subjects with normal renal function (16.5±4.3, P&lt;0.0001). s(P)RR was detected in HD waste water by Western blot analysis, and the clearance of s(P)RR and creatinine were 56.9±33.5 and 147.6±9.50 ml/min, respectively. Serum (P)RR levels were significantly higher in those with ankle-brachial index (ABI) of &lt; 0.9, an indicator of severe stenosis or obstruction of lower limb arteries, than those of ≧0.9 (32.2±5.9 and 30.1±6.2 ng/ml, respectively; P&lt;0.05). The association between low ABI and high serum s(P)RR levels were observed even after the correction with age, history of smoking, HbA1c, and LDL-C. Conclusions: Serum s(P)RR levels are significantly higher in HD patients when compared with subjects with normal renal function, although s(P)RR are dialyzed to some extent. High serum s(P)RR levels may be associated with atherosclerosis independent of other risk factors, suggesting that serum s(P)RR could be used as a marker for atherosclerotic condition in HD patients.

Changes in urinary angiotensinogen posttreatment in pediatric IgA nephropathy patients.

Recently, we demonstrated that urinary angiotensinogen (AGT) levels are increased and reflect intrarenal renin-angiotensin system (RAS) status in pediatric patients with chronic glomerulonephritis. Therefore, this study was performed to test the hypothesis that urinary AGT (UAGT) levels provide a specific index of intrarenal RAS status associated with RAS blockade treatment in pediatric IgA nephropathy (IgAN) patients. We measured plasma and UAGT levels and urinary transforming growth factor beta (TGF-β) levels, after which we performed immunohistochemical analysis of AGT, angiotensin II (Ang II), and TGF-β in 24 pediatric IgAN patients treated with RAS blockades for 2 years. Paired tests were used to analyze the changes from baseline to study end. Although there was no change in plasma AGT levels, UAGT and TGF-β levels were significantly decreased after RAS blockade, which was accompanied by the expression levels of AGT, Ang II, and TGF-β, as well as the magnitude of glomerular injury. Baseline UAGT levels positively correlated with diastolic blood pressure, urinary protein levels, scores for mesangial hypercellularity, and the expression levels of AGT, Ang II, and TGF-β in renal tissues. These data indicate that UAGT is a useful biomarker of intrarenal RAS activation, which is associated with glomerular injury during RAS blockade in pediatric IgAN patients.

Abstract 559: Augmented Urinary Angiotensinogen in Young Type-1 Diabetic Subjects Correlates with Hemoglobin A1c and Urinary 8-Isoprostane

Previous studies indicate that the intrarenal renin-angiotensin system (RAS) is activated in type-1 diabetes mellitus (T1DM) experimental animal models and human subjects, and is reflected by augmentation of urinary angiotensinogen (uAGT) excretion rate. Studies were performed to evaluate uAGT in young patients with short duration diabetes mellitus (DM) and its relationships with HbA1c and urinary 8-isoprostane excretion rate. Blood and urine samples were collected from 77 young (15±1 years) patients (44 male, 33 female) with short duration T1DM treated only with insulin and 36 (17 male, 19 female) control subjects. Serum glucose levels were 85±4 mg/dl in control subjects and 192±11 mg/dl in DM patients. Urinary Alb/Cr and uPro/Cr ratios were not significantly different in DM patients compared to control (8.6±.9 vs 9.7±.6 and 51±8 vs 62±14 mg/g). However, the uAGT/Cr ratios were significantly elevated in the DM patients (6.8±.8 vs 16.5±1.5 ug/g). Correlation analysis demonstrated highly significant relationships (P&lt;.0001) between uAGT/Cr and HbA1c (R=.44) and urinary 8-isoprostane excretion rate (R=.52) in the DM patients. These results indicate that, even in young non-albuminuric patients with relatively short duration of DM, uAGT excretion rates are increased, suggesting early activation of the intrarenal RAS, and are correlated with HbA1c and urinary 8-isoprostane levels indicative of increased reactive oxygen species. Accordingly, uAGT levels may serve as an early marker of an activated intrarenal RAS and provide a specific index of renal RAS status potentially useful in monitoring clinical response to therapy.

Serum soluble (pro)renin receptor levels in patients with essential hypertension

The (pro)renin receptor ((P)RR) is expressed in several tissues including kidney, heart and brain, and is thought to regulate the tissue renin-angiotensin system (RAS) through the non-proteolytic activation of prorenin. (P)RR is cleaved by furin to generate soluble (P)RR (s(P)RR), which is secreted into the extracellular space. s(P)RR is a candidate biomarker reflecting the status of the tissue RAS. Here, we investigated the relationship between background factors and serum s(P)RR levels. We measured s(P)RR levels in 122 patients with essential hypertension (EH) and assessed the relationships between background factors and s(P)RR levels. Serum s(P)RR levels were 19.0±4.9 ng ml(-1). Single regression analyses showed that age (r=0.251, P<0.01), serum creatinine levels (r=0.229, P<0.05) and urinary angiotensinogen excretion (r=0.196, P<0.05) were positively correlated with s(P)RR levels, whereas estimated glomerular filtration rate (eGFR; r=-0.337, P<0.001) were negatively correlated. Multiple regression analyses of age, blood pressure (BP), hemoglobin A1c (HbA1c) and s(P)RR levels revealed that age and s(P)RR levels were negatively correlated with the eGFR (P<0.05). In patients with EH, serum s(P)RR levels correlated positively with renal function independent of age, BP and HbA1c. These findings support s(P)RR as a useful biomarker that reflects the status of the tissue RAS.

Abstract 631: Big Angiotensin-25 (Bang-25): A Novel Glycosylated Angiotensin-related Peptide Isolated From Human Urine

The renin-angiotensin system (RAS) plays key roles in the regulation of blood pressure and body fluid dynamics. It is now recognized that a wide variety of tissues and organs, including the heart, vasculature, kidney and nervous system, among others, contain a local tissue RAS, which exerts autocrine/paracrine effects and acts independently of the systemic RAS. In 2006, we isolated and characterized proangiotensin-12, a component of the tissue RAS in rat small intestine. Similar angiotensin-related peptides had never been reported in humans. When we screened human urine gel filtration fractions for bioactive peptides using an antibody raised against the N-terminal portion of Angiotensin II (Ang II), we found a highly immunoreactive peptide with an apparent molecular weight of about 5,000. Therefore, we purified this peptide from 5.5 L of human urine using ion-exchange, gel-filtration, and affinity chromatography, and finally reverse-phase high-performance liquid chromatography (RP-HPLC) steps. We isolated and identified a novel Aogen-derived peptide, Big angiotensin-25 (Bang-25), which is composed of 25 amino acids and is N-glycosylated on its 14th amino acid (Asn) and has a cysteine linked to its 18th amino acid (Cys). We then assessed the distribution of Bang-25 in tissues by immunostaining with an antiserum raised against the C-terminal portion of the peptide. We found that Bang-25 was abundantly expressed in a number of human tissues, including kidney, heart, adrenal gland, pancreas and placenta. In the kidney, Bang-25 is localized predominantly to podocytes. Then, compared with angiotensinogen, Bang-25 is rapidly cleaved by chymase to Ang II, but is resistant to cleavage by renin. In the present study, we have isolated and identified a novel Angiotensin-derived peptide, Bang-25, which is composed of 25 amino acids and is N-glycosylated on its 14th amino acid (Asn) and has a cysteine linked to its 18th amino acid (Cys). The identification of Bang-25 suggests the existence of a RAS processing cascade different from the renin-catalyzed cleavage of Angiotensin to Ang I, and provides a potential target for assessing tissue RAS status and for the development of new therapeutic approaches to related diseases.

Abstract 548: Reduced Urinary Angiotensinogen Excretion in Preeclampsia

Objective: Preeclampsia (preE) is a hypertensive disorder of pregnancy. We reported the suppression of circulatory renin-angiotensin system (RAS) in a rat model of preE. Urinary angiotensinogen has been considered as an indicator of intrarenal angiotensin status in hypertension. Little is known about the urinary angiotensinogen in preE. This study evaluates the level of urinary excretion of angiotensinogen in preE to assess the RAS status. Methods: Normal pregnant (n=57) and preE (n=32) patients were recruited from Scott &amp; White Hospital and had their blood drawn between 21 to 40 weeks of pregnancy. Criteria for diagnosis of preE included blood pressure &gt;140/90 mm Hg and proteinuria &gt;300 mg of protein/24h. Two groups of rats were used: normal pregnant (n=10) and preE rats (n=10) which were given weekly injections of desoxycorticosterone acetate and 0.9% saline to drink. Urinary angiotensinogen levels and the plasma AngII levels were assayed by ELISA. The kidney expression of (pro)renin receptor, AT 1 receptor, AT 2 receptor, and renin for the two groups of rats was measured by western blot. Results are expressed as means with SD and comparisons made using Student’s t test with p&lt;0.05 considered significant. Results: In preE patients, the mean urinary excretion of angiotensinogen (2.0 ± 1.1 ng/mg creatinine) differed (p&lt;0.05) from that in patients with normal pregnancy (2.7 ± 1.5 ng/mg creatinine). The urinary excretion of angiotensinogen (PreE: 1.5 ± 0.3, NP: 2. 3 ± 0.4 nmol/day) also differed (p&lt;0.05) in preE rats compared to NP. The plasma concentration of Ang II for preE rats (25 ± 3 fmol/ml) differed (p&lt;0.05) compared to NP rats (39 ± 5 fmol/ml). The kidney expression of (pro)renin receptor was downregulated (p=0.008), while the AT 1 receptor was upregulated (p=0.01) in preE rats compared to NP. However, the kidney expression of AT 2 receptor (1.0 vs 1.1) and renin (1.0 vs 1.4) were similar in NP and PDS rats (p=0.63 and p=0.12, respectively). Conclusions: We demonstrated that urinary excretion of angiotensinogen is reduced in both patients with preE and in a rat model of preE. The kidney expression of RAS components was either downregulated or remained unchanged in preE rats. This finding indicates that preE is an Ang-II independent form of systemic hypertension.

A Link between the Intrarenal Renin Angiotensin System and Hypertension in Autosomal Dominant Polycystic Kidney Disease

Background/Aims: Early onset of hypertension and its consequences account for the great majority of deaths in patients with autosomal dominant polycystic kidney disease (ADPKD). Renin-angiotensin system (RAS) components have been shown in ADPKD kidneys independent of systemic RAS. Thus, we examined the urinary angiotensinogen (UAGT) levels as a biomarker of intrarenal RAS status in ADPKD patients with/without hypertension and healthy subjects. Methods: Eighty-four ADPKD patients (43 with hypertension and 41 without hypertension) and 40 healthy controls were studied cross-sectionally. Patients with glomerular filtration rate <60 ml/min were excluded from the study. Hypertension was diagnosed with ambulatory blood pressure monitoring. Urinary and plasma concentration of angiotensinogen, spot urine microprotein and creatinine (UCre) levels were recorded for each participant. Results: UAGT/UCre levels were higher in hypertensive ADPKD patients (23.7 ± 8.4) compared with normotensive ADPKD patients (16.6 ± 5.2) and healthy controls (6.9 ± 3.3; p < 0.001). In univariate analysis, UAGT correlated with systolic blood pressure, diastolic blood pressure (DBP) and proteinuria. The independence of these correlations was analyzed in a regression model, and UAGT was shown to be significantly predicted by proteinuria and DBP. Conclusion: Intrarenal RAS activation which is monitored by UAGT levels clinically may be a harbinger of hypertension and kidney disease in ADPKD patients.

A Clinical Link Between Peroxisome Proliferator-Activated Receptor γ and the Renin–Angiotensin System

A mechanistic link between peroxisome proliferator-activated receptor γ (PPARγ) and the renin–angiotensin system (RAS) has been previously proposed, but clinical evidence supporting the relationship is incomplete. In the current issue of Arteriosclerosis, Thrombosis, and Vascular Biology , Caron-Debarle et al show that 4 patients with familial partial lipodystrophy associated with early-onset severe hypertension carry mutations in PPARγ that impair its ability to act as a ligand-activated transcription factor. Cells isolated from these patients, and cells transfected with the same mutations in PPARγ, exhibit activation of the cellular RAS, increased production of reactive oxygen species (ROS), and markers of inflammation, all of which are dependent on the angiotensin-II (Ang-II) AT1 receptor (AT1R). This translational study further supports a role for PPARγ as a regulator of blood pressure through its ability to modulate the RAS. See accompanying article on page 829 PPARγ is a ligand-activated transcription factor and target of the thiazolidinedione (TZD) class of antidiabetes mellitus medications. PPARγ is best recognized for its role in adipogenesis, but is also a regulator of systemic metabolism as evidenced by the pleiotropic abnormalities (lipodystrophy, insulin-resistance, and metabolic syndrome) caused by PPARγ mutations.1–3 Clinical studies of TZD use in type 2 diabetes mellitus, including the PROactive (PROspective pioglitAzone Clinical Trial In macroVascular Events) trial, documented improved endothelial function and modest, but significant reductions in blood pressure.4 Some of the same mutations that cause lipodystrophy and diabetes mellitus also cause severe hypertension and preeclampsia in human patients3 and in knock-in mice.5,6 Evidence suggests that PPARγ activity in the vascular endothelium and smooth muscle are important regulators of endothelial function, smooth muscle contraction, and systemic blood pressure.7,8 Data suggesting a role for PPARγ in regulating blood pressure led many to search for downstream …

Augmented intrarenal and urinary angiotensinogen in hypertension and chronic kidney disease

Activated intrarenal renin-angiotensin system plays a cardinal role in the pathogenesis of hypertension and chronic kidney disease. Angiotensinogen is the only known substrate for renin, which is the rate-limiting enzyme of the renin-angiotensin system. Because the levels of angiotensinogen are close to the Michaelis-Menten constant values for renin, angiotensinogen levels as well as renin levels can control the renin-angiotensin system activity, and thus, upregulation of angiotensinogen leads to an increase in the angiotensin II levels and ultimately increases blood pressure. Recent studies using experimental animal models have documented the involvement of angiotensinogen in the intrarenal renin-angiotensin system activation and development of hypertension. Enhanced intrarenal angiotensinogen mRNA and/or protein levels were observed in experimental models of hypertension and chronic kidney disease, supporting the important roles of angiotensinogen in the development and the progression of hypertension and chronic kidney disease. Urinary excretion rates of angiotensinogen provide a specific index of the intrarenal renin-angiotensin system status in angiotensin II-infused rats. Also, a direct quantitative method has been developed recently to measure urinary angiotensinogen using human angiotensinogen enzyme-linked immunosorbent assay. These data prompted us to measure urinary angiotensinogen in patients with hypertension and chronic kidney disease, and investigate correlations with clinical parameters. This short article will focus on the role of the augmented intrarenal angiotensinogen in the pathophysiology of hypertension and chronic kidney disease. In addition, the potential of urinary angiotensinogen as a novel biomarker of the intrarenal renin-angiotensin system status in hypertension and chronic kidney disease will be also discussed.

Angiotensinogen Expression Is Enhanced in the Progression of Glomerular Disease

Intrarenal renin-angiotensin system (RAS) activation plays a critical role in the development and progression of renal injury. In the kidney, all of the RAS components are present and intrarenal angiotensin II (Ang II) is formed by multiple independent mechanisms. Angiotensinogen (AGT) is the only known substrate for renin that is a rate-limiting enzyme of the RAS. Recently, enhanced intrarenal AGT levels have been shown to reflect the intrarenal RAS status in hypertension, chronic glomerular disease and diabetic nephropathy. In this review, we focus on AGT expression of the diseased glomeruli in the progression of glomerular disease. An anti-glomerular basement membrane nephritis rat model developed progressive proteinuria and glomerular crescent formation, accompanied by increased macrophage infiltration and glomerular expression of AGT and Ang II. The addition of Ang II type 1 receptor blocker to CC-chemokine recaptor 2 antagonist markedly attenuated the induction of macrophage infiltration, AGT and Ang II, and reduced glomerular crescent formation. Next, the levels of glomerular AGT expression and marker of reactive oxygen species in Zucker diabetic fatty (ZDF) obese rats were higher than those in ZDF lean rats. Hydrogen peroxide (H(2)O(2)) induced an increase in the AGT expression in primary rat mesangial cells. Furthermore, the H(2)O(2)-induced upregulation of AGT was inhibited by a mitogen-activated protein kinase kinase and a c-Jun N-terminal kinase inhibitor. These data suggest the potential contribution of enhanced AGT expression in glomeruli to the intrarenal RAS activation for the development of glomerular disease.