Transcriptome Analysis of Human Reninomas as an Approach to Understanding Juxtaglomerular Cell Biology.

Renin, a key component in the regulation of blood pressure in mammals, is produced by the rare and highly specialized juxtaglomerular cells of the kidney. Chronic stimulation of renin release results in a recruitment of new juxtaglomerular cells by the apparent conversion of adjacent smooth muscle cells along the afferent arterioles. Because juxtaglomerular cells rapidly dedifferentiate when removed from the kidney, their developmental origin and the mechanism that explains their phenotypic plasticity remain unclear.

A novel mouse model of advanced diabetic kidney disease.

Currently available rodent models exhibit characteristics of early diabetic nephropathy (DN) such as hyperfiltration, mesangial expansion, and albuminuria yet features of late DN (hypertension, GFR decline, tubulointerstitial fibrosis) are absent or require a significant time investment for full phenotype development. Accordingly, the aim of the present study was to develop a mouse model of advanced DN with hypertension superimposed (HD mice). Mice transgenic for human renin cDNA under the control of the transthyretin promoter (TTRhRen) were employed as a model of angiotensin-dependent hypertension.

Differences in cell-type-specific responses to angiotensin II explain cardiac remodeling differences in C57BL/6 mouse substrains.

Despite indications that hearts from the C57BL/6N and C57BL/6J mouse substrains differ in terms of their contractility and their responses to stress-induced overload, no information is available about the underlying molecular and cellular mechanisms. We tested whether subacute (48 hours) and chronic (14 days) administration of angiotensin II (500 ng/kg per day) had different effects on the left ventricles of male C57BL/6J and C57BL/6N mice. Despite higher blood pressure in C57BL/6J mice, chronic angiotensin II induced fibrosis and increased the left ventricular weight/body weight ratio and cardiac expression of markers of left ventricular hypertrophy to a greater extent in C57BL/6N mice.

General lysosomal hydrolysis can process prorenin accurately.

Renin, an aspartyl protease that catalyzes the rate-limiting step of the renin-angiotensin system, is first synthesized as an inactive precursor, prorenin. Prorenin is activated by the proteolytic removal of an amino terminal prosegment in the dense granules of the juxtaglomerular (JG) cells of the kidney by one or more proteases whose identity is uncertain but commonly referred to as the prorenin-processing enzyme (PPE). Because several extrarenal tissues secrete only prorenin, we tested the hypothesis that the unique ability of JG cells to produce active renin might be explained by the existence of a PPE whose expression is restricted to JG cells.

Effects of a domain-selective ACE inhibitor in a mouse model of chronic angiotensin II-dependent hypertension.

The somatic isozyme of ACE (angiotensin I-converting enzyme) comprises two distinct zinc-dependent catalytic domains with different substrate specificities for angiotensin I (cleaved selectively by the C-domain) and bradykinin (cleaved equally efficiently by both the N- and C-domains). Classical ACEIs (ACE inhibitors) target both domains, with side effects such as cough and angio-oedema being attributed, in part, to N-domain inhibition, probably through bradykinin accumulation. We questioned whether a novel C-domain-selective ACEI (lisW-S) has anti-hypertensive effects without influencing bradykinin status.

Where hypertension happens.

Essential hypertension, which accounts for 90%-95% of all cases of hypertension seen in the clinic, is also referred to as idiopathic hypertension, because we simply don't understand the cause(s). Although many theories have been advanced, in the current issue of the JCI, Gonzalez-Villalobos et al. present further evidence implicating the intrarenal renin-angiotensin system and take us one step further by proposing a mechanism underlying this pathology.

The interaction between prorenin, renin and the (pro)renin receptor: time to rethink the role in hypertension.

Purpose Of Review: Elevated prorenin levels are seen in diabetics with microvascular disease. The discovery of a receptor capable of binding renin and prorenin [(P)RR] and triggering an intracellular signal in the laboratory setting raised the expectation that prorenin might be directly responsible for these vascular disorders. However, there has been substantial disagreement concerning the signaling properties of renin and prorenin and it has been impossible to inactivate the (P)RR gene in mouse to define its function.

Local angiotensin II aggravates cardiac remodeling in hypertension.

Angiotensin II (ANG II) contributes to hypertension, cardiac hypertrophy, fibrosis, and dysfunction; however, it is difficult to separate the cardiac effect of ANG II from its hemodynamic action in vivo. To overcome the limitations, we used transgenic mice with cardiac-specific expression of a transgene fusion protein that releases ANG II from cardiomyocytes (Tg-ANG II) and treated them with deoxycorticosterone acetate (DOCA)-salt to suppress their systemic renin-angiotensin system. Using this unique model, we tested the hypothesis that cardiac ANG II, acting on the angiotensin type 1 receptor (AT(1)R), increases inflammation, oxidative stress, and apoptosis, accelerating cardiac hypertrophy and fibrosis.

The angiotensin-converting enzyme 2/angiogenesis-(1-7)/Mas axis confers cardiopulmonary protection against lung fibrosis and pulmonary hypertension.

Rationale: An activated vasoconstrictive, proliferative, and fibrotic axis of the renin angiotensin system (angiotensin-converting enzyme [ACE]/angiotensin [Ang]II/AngII type 1 receptor) has been implicated in the pathophysiology of pulmonary fibrosis (PF) and pulmonary hypertension (PH). The recent discovery of a counterregulatory axis of the renin angiotensin system composed of ACE2/Ang-(1-7)/Mas has led us to examine the role of this vasoprotective axis on such disorders.

Objectives: We hypothesized that Ang-(1-7) treatment would exert protective effects against PF and PH.

Deleterious combined effects of salt-loading and endothelial cell restricted endothelin-1 overexpression on blood pressure and vascular function in mice.

Background: We previously showed that young transgenic mice overexpressing preproendothelin-1 specifically in endothelial cells had hypertrophic remodeling, endothelial dysfunction, increased vascular NADPH oxidase activity, and inflammation in mesenteric small arteries without blood pressure (BP) elevation compared to nontransgenic wild-type littermates. To assess the consequences of salt-loading and the role of endothelin receptors, we investigated the effects of these on vascular structure, function, and oxidative stress in mesenteric arteries in salt-loaded transgenic mice treated with endothelin receptor antagonists.

Methods: Ten-month-old male transgenic and wild-type littermates were salt-loaded (4% NaCl) and treated with endothelin subtype A receptor antagonist (ET(A)RA, ABT-627, 5 mg/kg per day), endothelin subtype B receptor antagonist (ET(B)RA; A-192621, 30 mg/kg per day), or ET(A)/BRA (bosentan, 100 mg/kg per day) for 4 weeks.

Cathepsin B is not the processing enzyme for mouse prorenin.

Renin, an aspartyl protease that catalyzes the rate-limiting step in the renin-angiotensin system (RAS), is proteolytically activated by a second protease [referred to as the prorenin processing enzyme (PPE)] before its secretion from the juxtaglomerular cells of the kidney. Although several enzymes are capable of activating renin in vitro, the leading candidate for the PPE in the kidney is cathepsin B (CTSB) due to is colocalization with the renin precursor (prorenin) in juxtaglomerular cell granules and because of its site-selective activation of human prorenin both in vitro and in transfected tissue culture cell models. To verify the role of CTSB in prorenin processing in vivo, we tested the ability of CTSB-deficient (CTSB-/-) mice to generate active renin.

Circulating rather than cardiac angiotensin-(1-7) stimulates cardioprotection after myocardial infarction.

Background: Angiotensin (Ang)-(1-7) attenuates the development of heart failure. In addition to its local effects on cardiovascular tissue, Ang-(1-7) also stimulates bone marrow, which harbors cells that might complement the therapeutic effect of Ang-(1-7). We studied the effects of Ang-(1-7) either produced locally in the heart or subcutaneously injected during the development of heart failure induced by myocardial infarction (MI) and explored the role of cardiovascular progenitor cells in promoting the effects of this heptapeptide.

Attenuation of isoproterenol-induced cardiac fibrosis in transgenic rats harboring an angiotensin-(1-7)-producing fusion protein in the heart.

Objective: It has been shown that Ang-(1-7) has cardioprotective actions. To directly investigate the effects of Ang-(1-7) specifically in the heart, we generated and characterized transgenic (TG) rats which express an Ang-(1-7)-producing fusion protein driven by the alpha-MHC promoter.

Methods And Results: After microinjection of the transgene into fertilized rat zygotes, we obtained four different transgenic lines.

Physiological genomics identifies estrogen-related receptor alpha as a regulator of renal sodium and potassium homeostasis and the renin-angiotensin pathway.

Estrogen-related receptor alpha (ERRalpha) is an orphan nuclear receptor highly expressed in the kidney, an organ playing a central role in blood pressure regulation through electrolyte homeostasis and the renin-angiotensin system. Physiological analysis revealed that, relative to wild-type mice, ERRalpha null mice are hypotensive despite significant hypernatremia, hypokalemia, and slight hyperreninemia. Using a combination of genome-wide location analysis and expression profiling, we demonstrate that ERRalpha regulates the expression of channels involved in renal Na(+) and K(+) handling (Scnn1a, Atp1a1, Atp1b1) and altered in Bartter syndrome (Bsnd, Kcnq1).

Functional and structural characterization of a dense core secretory granule sorting domain from the PC1/3 protease.

Several peptide hormones are initially synthesized as inactive precursors. It is only on entry of these prohormones and their processing proteases into dense core secretory granules (DCSGs) that the precursors are cleaved to generate their active forms. Prohormone convertase (PC)1/3 is a processing protease that is targeted to DCSGs.

Chronic increases in circulating prorenin are not associated with renal or cardiac pathologies.

Elevated levels of circulating prorenin, the precursor of renin, have been reported to precede the appearance of microvascular complications in diabetes mellitus. Although several studies using animal models have attempted to address the link between elevated prorenin and the tissue remodeling and damage associated with both hypertension and diabetes mellitus, the results have been contradictory, and the mechanism whereby prorenin might contribute to these pathologies remains a subject of debate. To directly test the role of prorenin in these pathologies, we generated transgenic mice with selective increases (13- to 66-fold) in circulating native or active site-mutated prorenin.

Angiotensin(1-7) blunts hypertensive cardiac remodeling by a direct effect on the heart.

Angiotensin-converting enzyme 2 (ACE2) converts the vasopressor angiotensin II (Ang II) into angiotensin (1-7) [Ang(1-7)], a peptide reported to have vasodilatory and cardioprotective properties. Inactivation of the ACE2 gene in mice has been reported by one group to result in an accumulation of Ang II in the heart and an age-related defect in cardiac contractility. A second study confirmed the role of ACE2 as an Ang II clearance enzyme but failed to reproduce the contractility defects previously reported in ACE2-deficient mice.

Reduced isoproterenol-induced renin-angiotensin changes and extracellular matrix deposition in hearts of TGR(A1-7)3292 rats.

We investigated the expression of specific extracellular matrix (ECM) proteins in cardiac hypertrophy induced by isoproterenol in TGR(A1-7)3292 rats. Additionally, changes in circulating and tissue renin-angiotensin system (RAS) were analyzed. Left ventricles (LV) were used for quantification of collagen type I, III, and fibronectin using immunofluorescence-labeling techniques.

Vascular inflammation in absence of blood pressure elevation in transgenic murine model overexpressing endothelin-1 in endothelial cells.

Objective: We previously showed that in transgenic mice with endothelium-targeted overexpression of human preproendothelin-1, mesenteric resistance arteries exhibited vascular remodeling, endothelial dysfunction and increased oxidative stress early in life in the absence of significant elevation of blood pressure. To further characterize this model, the role of vascular inflammation was investigated in young male transgenic and wild-type littermate mice.

Methods And Results: Systemic and local inflammatory markers in mesenteric arteries were assessed by Luminex-based enzyme-linked immunosorbent assay technique, confocal microscopy, electrophoretic mobility shift assay and western blotting in 10-week old male transgenic and wild-type mice.

Renal redox-sensitive signaling, but not blood pressure, is attenuated by Nox1 knockout in angiotensin II-dependent chronic hypertension.

We demonstrated previously that, in mice with chronic angiotensin II-dependent hypertension, gp91phox-containing NADPH oxidase is not involved in the development of high blood pressure, despite being important in redox signaling. Here we sought to determine whether a gp91phox homologue, Nox1, may be important in blood pressure elevation and activation of redox-sensitive pathways in a model in which the renin-angiotensin system is chronically upregulated. Nox1-deficient mice and transgenic mice expressing human renin (TTRhRen) were crossed, and 4 genotypes were generated: control, TTRhRen, Nox1-deficient, and TTRhRen Nox1-deficient.

Angiotensin II controls occludin function and is required for blood brain barrier maintenance: relevance to multiple sclerosis.

The blood-brain barrier (BBB) restricts molecular and cellular trafficking between the blood and the CNS. Although astrocytes are known to control BBB permeability, the molecular determinants of this effect remain unknown. We show that angiotensinogen (AGT) produced and secreted by astrocytes is cleaved into angiotensin II (AngII) and acts on type 1 angiotensin receptors (AT1) expressed by BBB endothelial cells (ECs).