Soluble (pro)renin receptor in preeclampsia and diabetic pregnancies.

Women with preexisting or gestational diabetes mellitus have an increased risk for developing preeclampsia. Diabetes and pregnancy are both characterized by very high prorenin levels and renin-angiotensin system activation. Prorenin bound to the (pro)renin receptor has enzymatic activity. We hypothesized that soluble (pro)renin receptor levels are elevated in high-risk pregnancies. Third trimester maternal blood samples from complicated pregnancies (n = 165), (preeclampsia [n = 76], diabetes mellitus [type I diabetes, n = 35; type II diabetes, n = 11; gestational diabetes mellitus, n = 43]), and healthy pregnancies (n = 49) were analyzed for prorenin, renin, and soluble (pro)renin receptor. There were no significant differences in prorenin or renin levels between the study groups in a multivariate model. In the group of women with gestational diabetes, soluble (pro)renin receptor concentrations were significantly higher compared with healthy pregnancies or preeclampsia. Soluble (pro)renin receptor did not correlate with renin or prorenin levels for any of the study groups. Our results show that soluble (pro)renin receptor is dysregulated in pregnancies affected by diabetes mellitus, but not in preeclampsia. Alterations in circulating soluble (pro)renin receptor are unrelated to renin/prorenin in pregnancy, but may be of pathophysiological relevance in diabetic pregnancies in a renin-angiotensin system-independent manner.

New role for the (pro)renin receptor in T-cell development.

The (pro)renin receptor (PRR) was originally thought to be important for regulating blood pressure via the renin-angiotensin system. However, it is now emerging that PRR has instead a generic role in cellular development. Here, we have specifically deleted PRR from T cells. T-cell-specific PRR-knockout mice had a significant decrease in thymic cellularity, corresponding with a 100-fold decrease in the number of CD4(+) and CD8(+) thymocytes, and a large increase in double-negative (DN) precursors. Gene expression analysis on sorted DN3 thymocytes indicated that PRR-deficient thymocytes have perturbations in key cellular pathways essential at the DN3 stage, including transcription and translation. Further characterization of DN T-cell progenitors leads us to propose that PRR deletion affects thymocyte survival and development at multiple stages; from DN3 through to DN4, double-positive, and single-positive CD4 and CD8. Our study thus identifies a new role for PRR in T-cell development.

Heterozygous de-novo mutations in ATP1A3 in patients with alternating hemiplegia of childhood: a whole-exome sequencing gene-identification study.

BACKGROUND: Alternating hemiplegia of childhood (AHC) is a rare neurological disorder characterised by early-onset episodes of hemiplegia, dystonia, various paroxysmal symptoms, and developmental impairment. Almost all cases of AHC are sporadic but AHC concordance in monozygotic twins and dominant transmission in a family with a milder phenotype have been reported. Thus, we aimed to identify de-novo mutations associated with this disease. METHODS: We recruited patients with clinically characterised AHC from paediatric neurology departments in Germany and with the aid of a parental support group between Sept, 2004, and May 18, 2012. We used whole-exome sequencing of three proband-parent trios to identify a disease-associated gene and then tested whether mutations in the gene were also present in the remaining patients and their healthy parents. We analysed genotypes and characterised their associations with the phenotypic spectrum of the disease. FINDINGS: We studied 15 female and nine male patients with AHC who were aged 8-35 years. ATP1A3 emerged as the disease-associated gene in AHC. Whole-exome sequencing showed three heterozygous de-novo missense mutations. Sequencing of the 21 remaining affected individuals identified disease-associated mutations in ATP1A3 in all patients, including six de-novo missense mutations and one de-novo splice-site mutation. Because ATP1A3 is also the gene associated with rapid-onset dystonia-parkinsonism (DYT12, OMIM 128235) we compared the genotypes and phenotypes of patients with AHC in our cohort with those of patients with rapid-onset dystonia-parkinsonism reported in the scientific literature. We noted overlapping clinical features, such as abrupt onset of dystonic episodes often triggered by emotional stress, a rostrocaudal (face to arm to leg) gradient of involvement, and signs of brainstem dysfunction, as well as clearly differentiating clinical characteristics, such as episodic hemiplegia and quadriplegia. INTERPRETATION: Mutation analysis of the ATP1A3 gene in patients who met clinical criteria for AHC allows for definite genetic diagnosis and sound genetic counselling. AHC and rapid-onset dystonia-parkinsonism are allelic diseases related to mutations in ATP1A3 and form a phenotypical continuum of a dystonic movement disorder. FUNDING: Eva Luise and Horst Köhler Foundation for Humans with Rare Diseases.

Renin- and prorenin-induced effects in rat vascular smooth muscle cells overexpressing the human (pro)renin receptor: does (pro)renin-(pro)renin receptor interaction actually occur?

Renin/prorenin binding to the (pro)renin receptor ([P]RR) results in direct (angiotensin-independent) second-messenger activation in vitro, whereas in vivo studies in rodents overexpressing prorenin (≈400-fold) or the (P)RR do not support such activation. To solve this discrepancy, DNA synthesis, extracellular signal-regulated kinase 1/2 phosphorylation, and plasminogen-activator inhibitor 1 release were evaluated in wild-type and human (P)RR-overexpressing vascular smooth muscle cells after their incubation with 1 to 80 nmol/L of (pro)renin. Human prorenin (4 nmol/L, ie, ≈800-fold above normal) + angiotensinogen increased DNA synthesis in human (P)RR cells only in an angiotensin II type 1 receptor-dependent manner. Prorenin at this concentration also increased plasminogen-activator inhibitor 1 release via angiotensin. Prorenin alone at 4 nmol/L was without effect, but at 20 nmol/L (≈4000-fold above normal) it activated extracellular signal-regulated kinase 1/2 directly (ie, independent of angiotensin). Renin at concentrations of 1 nmol/L (≈2000-fold above normal) and higher directly stimulated DNA synthesis, extracellular signal-regulated kinase 1/2 phosphorylation, and plasminogen-activator inhibitor 1 release in wild-type and human (P)RR cells, and similar effects were seen for rat renin, indicating that they were mediated via the rat (P)RR. In conclusion, angiotensin generation depending on prorenin-(P)RR interaction may occur in transgenic rodents overexpressing prorenin several 100-fold. Direct (pro)renin-induced effects via the (P)RR require agonist concentrations that are far above the levels in wild-type and transgenic rats. Therefore, only prorenin (and not [P]RR) overexpression will result in an angiotensin-dependent phenotype, and direct renin-(P)RR interaction is unlikely to ever occur in nonrenin-synthesizing organs.

Prorenin receptor is essential for podocyte autophagy and survival.

The prorenin receptor (PRR) is highly expressed in podocytes, but its role in the maintenance of podocyte function is unknown. Here we generated podocyte-specific PRR-knockout mice and found that these animals died between 2 to 3 wk after birth. Within 14 d, PRR-knockout mice developed nephrotic syndrome, albuminuria with podocyte foot-process fusion, and cytoskeletal changes. Podocyte-specific PRR deletion also led to disturbed processing of multivesicular bodies and enrichment of autophagosomal (LC3) and lysosomal (LAMP2) markers, indicating a functional block in autophagosome-lysosome fusion and an overload of the proteasomal protein-degradation machinery. In vitro, PRR knockdown and pharmacologic blockade of vacuolar H(+)-ATPases, which associate with the PRR, increased vesicular pH, led to accumulation of LC3-positive and LAMP2-positive vesicles and altered the cytoskeleton. Taken together, these results suggest that the PRR is essential for podocyte function and survival by maintaining autophagy and protein-turnover machinery. Furthermore, PRR contributes to the control of lysosomal pH, which is important for podocyte survival and cytoskeletal integrity.

The (pro)renin receptor and the mystic HRP--is there a role in cardiovascular disease?

In 2002, Nguyen et al. cloned the (pro)renin receptor ((P)RR). Two years later, Suzuki, Ichihara and colleagues provided a concept to inhibit the (P)RR through HRP. This decapeptide mimics a sequence of the prorenin prosegment and functions thereby as a decoy peptide. They showed that HRP prevented diabetic nephropathy in rodents and ameliorated renal and cardiac damage in spontaneously hypertensive rats. We tested HRP and the human renin inhibitor aliskiren in transgenic rats overexpressing the human renin and angiotensinogen genes (dTGR). Only aliskiren, but not HRP, was able to ameliorate target organ damage in this model. HRP had also no effect on target organ damage in renovascular hypertensive rats. In vitro studies showed that HRP did not inhibit (pro)renin binding and signaling. More confusing was the fact that HRP bound to cells lacking (P)RR on their surface. We believe that HRP does not act as a competitive antagonist for the (P)RR and promotes its action via an alternative mechanism. Elucidating this mechanism could offer further opportunities, in terms of (pro)renin research.

Lack of cardiac fibrosis in a new model of high prorenin hyperaldosteronism.

The aim of the present study was to test the hypothesis that elevation of prorenin in plasma is sufficient to induce cardiac fibrosis. Normotensive cyp1a1ren-2 transgenic rats with normal plasma prorenin and aldosterone levels were given 0.125% indole-3-carbinol (I3C) orally for a period of 12 wk. Plasma prorenin and aldosterone levels were determined in 4-wk intervals, and cardiac marker enzymes for hypertrophy, fibrosis, and oxidative stress as well as cardiac pathology were investigated. In I3C-treated cyp1a1 ren-2 transgenic rats, plasma prorenin concentrations were >100-fold elevated (> or = 7.1 + or - 2.6 microg ANG I.ml(-1).h(-1) vs. < or = 0.07 + or - 0.1; P < 0.001), whereas active renin levels were suppressed (0.09 + or - 0.02 vs. 0.2 + or - 0.1; P < 0.05). Aldosterone concentrations were elevated three- to fourfold for a period of >4 wk (574 + or - 51 vs. 160 + or - 68 pg/ml; P < 0.01). After 12 wk of I3C, rats exhibited moderate cardiac hypertrophy (heart weight/body weight 2.5 + or - 0.04 vs. 3.1 + or - 0.1 mg/g; P < 0.01). There was a slight increase in mRNA contents of endothelin 1 (1.21 + or - 0.08 vs. 0.75 + or - 0.007; P < 0.001), NADP oxidase-2 (1.03 + or - 0.006 vs. 0.76 + or - 0.04; P < 0.001), transforming growth factor-beta (0.99 + or - 0.06 vs. 0.84 + or - 0.04; P < 0.05), collagen type I (1.32 + or - 0.32 vs. 0.94 + or - 0.18; P < 0.05), and intercellular adhesion molecule-1 (1.12 + or - 0.12 vs. 0.84 + or - 0.08; P < 0.05). These genes are known to be stimulated by the renin-angiotensin system. There were no histological signs of fibrosis in the heart. We found that prorenin and aldosterone alone are not sufficient to induce considerable cardiac fibrosis in the absence of sodium load.

The putative (pro)renin receptor blocker HRP fails to prevent (pro)renin signaling.

The prorenin/renin receptor is a recently discovered component of the renin-angiotensin system. The effects of aliskiren, a direct inhibitor of human renin, were compared with the handle region decoy peptide (HRP), which blocks the prorenin/renin receptor, in double-transgenic rats overexpressing the human renin and angiotensinogen genes. After 7 wk, all aliskiren-treated rats were alive, whereas mortality was 40% in vehicle-treated and 58% in HRP-treated rats. Aliskiren but not the HRP reduced BP and normalized albuminuria, cystatin C, and neutrophil gelatinase-associated lipocalin, a marker of renal tubular damage, to the levels of nontransgenic controls. In vitro, human renin and prorenin induced extracellular signal-regulated kinase 1/2 phosphorylation, independent of angiotensin II (AngII), in vascular smooth muscle cells. Preincubation with the HRP or aliskiren did not prevent renin- and prorenin-induced extracellular signal-regulated kinase 1/2 phosphorylation, whereas the MAP kinase kinase (MEK1/2) inhibitor PD98059 prevented both. In conclusion, renin inhibition but not treatment with the HRP protects against AngII-induced renal damage in double-transgenic rats. In addition, the in vitro data do not support the use of the HRP to block AngII-independent prorenin- or renin-mediated effects.

Prorenin and renin-induced extracellular signal-regulated kinase 1/2 activation in monocytes is not blocked by aliskiren or the handle-region peptide.

The recently cloned (pro)renin receptor [(P)RR] mediates renin-stimulated cellular effects by activating mitogen-activated protein kinases and promotes nonproteolytic prorenin activation. In vivo, (P)RR is said to be blocked with a peptide consisting of 10 amino acids from the prorenin prosegment called the "handle-region" peptide (HRP). We tested whether human prorenin and renin induce extracellular signal-regulated kinase (ERK) 1/2 activation and whether the direct renin inhibitor aliskiren or the HRP inhibits the receptor. We detected the (P)RR mRNA and protein in isolated human monocytes and in U937 monocytes. In U937 cells, we found that both human renin and prorenin induced a long-lasting ERK 1/2 phosphorylation despite angiotensin II type 1 and 2 receptor blockade. In contrast to angiotensin II-ERK signaling, renin and prorenin signaling did not involve the epidermal growth factor receptor. A mitogen-activated protein kinase kinase 1/2 inhibitor inhibited both renin and prorenin-induced ERK 1/2 phosphorylation. Neither aliskiren nor HRP inhibited binding of (125)I-renin or (125)I-prorenin to (P)RR. Aliskiren did not inhibit renin and prorenin-induced ERK 1/2 phosphorylation and kinase activity. Fluorescence-activated cell sorter analysis showed that, although fluorescein isothiocyanate-labeled HRP bound to U937 cells, HRP did not inhibit renin or prorenin-induced ERK 1/2 activation. In conclusion, prorenin and renin-induced ERK 1/2 activation are independent of angiotensin II. The signal transduction is different from that evoked by angiotensin II. Aliskiren has no (P)RR blocking effect and did not inhibit ERK 1/2 phosphorylation or kinase activity. Finally, we found no evidence that HRP affects renin or prorenin binding and signaling.