Renin Expression Research Articles

Regulation of Renin-Angiotensin System Activity and Blood Pressure by Vascular Smooth Muscle Cullin-3

Mutations in the ubiquitin ligase scaffold protein Cullin 3 (CUL3) in smooth muscle cells (SMCs) cause vascular dysfunction, arterial stiffness, and severe hypertension. We hypothesized that conditional deletion of CUL3 in SMCs causes severe hypertension through a renin-angiotensin system (RAS)-dependent mechanism. Mice carrying a conditional allele of CUL3 were bred to mice expressing a tamoxifen-inducible CRE-recombinase driven by a smooth muscle promoter (ISM-CRE, control). Tamoxifen was administered to generate smooth muscle CUL3 knockout (S-CUL3KO). Primary aortic SMCs were used to elucidate the contribution of CUL3 to intracellular angiotensin II-mediated calcium flux. Calcium response in SMCs was analyzed via ratiometric confocal fluorescent microscopyS-CUL3KO mice demonstrated hypertension following three weeks of tamoxifen, mean arterial pressure (MAP) was 108±1 vs. 140±1 mmHg (ISM-CRE vs. S-CUL3KO). Aorta from S-CUL3KO mice exhibited impaired vasorelaxation to acetylcholine (ACh, max relaxation: 84±4% vs. 16±9%, p<0.05) and sodium nitroprusside (SNP, max relaxation: 95±3% vs. 56±9%, p<0.05). Captopril administration (7 days) markedly reduced MAP to 84±0.3 mmHg and improved vasorelaxation in response to both ACh (72±6%) and SNP (91±4%) in S-CUL3KO mice, suggesting RAS-dependency of the hypertension. Additionally, candesartan treatment (7 days) substantially decreased MAP from 138±1 to 96±3 mmHg suggesting that hypertension in S-CUL3KO group is angiotensin type-1 receptor mediated. Q-PCR and RNAScope analyses demonstrated no difference in renin expression in the kidney between the S-CUL3KO and control mice suggesting a blunting of the baroreceptor mechanism regulating renin mRNA expression. Equilibrium angiotensin II plasma levels in both groups were not different (2517±352 and 2379±549 pmol/L, p>0.05). Preliminary data demonstrated that acute application of 10 μM of angiotensin II to S-CUL3KO SMCs resulted in a sustained increase in intracellular calcium which was abolished by a preincubation with 2 μM of candesartan.Our data suggest that CUL3 may play a vital role in baroreceptor mechanism in the kidney and regulate angiotensin II response in SMCs which are essential for responding to changes in perfusion pressure. Ultimately, understanding CUL3 target proteins may benefit the development of novel treatments for hypertension. R35 HL144807 (to CDS). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

An Evolutionarily Conserved Olfactory Receptor Is Required for Sex Differences in Blood Pressure

Olfactory receptor 558 (Olfr558) is expressed in the kidney where its functional role is unknown. Using RNAScope, we find that Olfr558 localizes to vascular smooth muscle, including the renal afferent arteriole. Thus, we measured blood pressure (BP) in Olfr558 wild-type (WT) and knockout (KO) mice. Systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP) were measured in whole-body Olfr558 wild-type (WT) and knockout (KO) via telemetry. It is known that males have a higher BP than premenopausal females in both humans and mice; indeed, we find Olfr558WT males (M) have higher BP than females (F, n=7-9 per group), including MAP (M:101.0±1.6 vs. F:89.0±0.9 mmHg, p<0.0001), SBP (M:113±2 vs. F:102±1mmHg, p=0.0025), and DBP (M: 89±2 vs. F:75±01mmHg, p<0.0001). However, sex differences in BP are entirely absent in Olfr558 KO (MAP M: 96±2 vs. F: 95±1mmHg; SBP M: 110±2 vs. F: 108±2mmHg; DBP M: 81±2 vs. F: 82±2mmHg). Of note, other sex differences (body weight) are intact in KO, and KO males and females are fertile. To characterize this phenotype, renin expression was analyzed by qPCR, plasma renin activity (PRA) was measured by ELISA, and vasoreactivity was examined ex vivo by wire myography (responses to potassium chloride (KCl), phenylephrine (PE), acetylcholine (Ach), and sodium nitroprusside (SNP) in aortic and mesenteric rings). In male KOs (n=10-12), there was a decrease in kidney renin mRNA (0.4±0.1 vs WT: 1±0.1 p=0.001) and PRA (201±21 vs WT: 402±15, p=0.001); these parameters were unchanged in female KOs. Male KO aortic rings exhibit less constriction to PE, male KO mesenterics exhibit more relaxation to SNP, and female KO aortic rings exhibit more constriction to KCl. In females, pulse wave velocity (PWV) and tensile testing revealed that KO females have increased PWV (KO: 4.6±0.4 vs WT: 3.2±0.2 m/s, p=0.0069, n=8-11), but no changes in tensile testing. The human ortholog of Olfr558, OR51E1, was previously identified as a locus associated with DBP. Using UK Biobank data (N~450k), we find that a rare OR51E1 missense variant has a statistically significant sex interaction effect with DBP ( p=0.015), increasing DBP (+6.28mmHg) in women but decreasing it (-4.77mmHg) in men (similar to the phenotype in M and F Olfr558 KO mice). Finally, we express OR51E1 variants in HEK 293T cells and characterize how two different clinically relevant OR51E1 variants influence OR51E1 signaling. In sum, our findings demonstrate that an evolutionarily conserved olfactory receptor is required for sex differences in BP. Olfr558 regulates BP in males via renin and vascular reactivity, but via arterial stiffness in females. Funding: R56DK107726 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Enhanced Intrarenal pro-renin and salt sensitive hypertension in a mouse model of Type-1 diabetes

Hypertension affects up to 50% of patients with type 1 diabetes. Despite aggressive anti-hypertensive therapy, at least 30% of diabetic patients develop chronic kidney disease. Renin is the rate-limiting enzyme in the activation of the RAS and is essential for blood pressure control. Renin is expressed in Juxtaglomerular (JG) cells, as an immature pro-peptide (pro-renin), and then stored as active renin. In diabetic humans, plasma pro-renin is enhanced while renin remains unchanged or low. We hypothesize that intrarenal renin and pro-renin are enhanced in type 1 diabetes, which could potentially contribute to hypertension and diabetic nephropathy. We used the Akita mice strain, one of the few mouse models of diabetes mellitus that shows features of the human disease including hypertension and kidney damage. We found that Akita mice had higher blood pressure as measured by tailcuff (mmHg: C57=109±2.8; Aki=120.6±2.5;p<0.05, n=6), plasma glucose (in mM: C57=7.71±23.9; Aki=23.2±2.3; p<0.01; n=4) and proteinuria (mg/24hrs: C57 18.2±3.1; Aki: 29.4±3.3; p<0.05; n=5) when compared to C57 (control). In addition, plasma renin was not changed in Akita mice (n=6; p= NS). Histological staining of kidney cuts with a renin antibody (recognizes both renin and pro-renin) showed overall decreased total renin expression in Akita mice (O.D C57: 46.6±1.5; Akita=30.7±3.5). Surprisingly, Western Blots of renal cortical lysates and JG cells showed that pro-renin (43-45 kDa) expression was 79±21% higher in male Akita diabetic mice (p<0.05), demonstrating increased intra-renal pro-renin in Akita. The mechanism driving the increase in pro-renin is unknown. We previously showed that ROS potently stimulate renin release from JG cells. We found that Akita mice have increased urinary isoprostanes, supporting higher kidney ROS (ng/24hrs: C57:3.5±0.6 Aki=6.0±0.8 p<0.05; n=5). We measured H202 levels by transducing primary JG cells in culture with the fluorescent H202 protein sensor HyPer and found that JG cells isolated from Akita mice had higher baseline levels of H202 (C57= 100, Akita=117±7%, p<0.05). An activated intrarenal RAS contributes to salt sensitive hypertension, and at least one third of diabetic patients are salt-sensitive. It is not known whether diabetic Akita mice are salt sensitive. Therefore, we tested the effect of a high salt diet on blood pressure in Akita and C57 mice measured by radiotelemetry. High salt increased systolic blood pressure (SBP) in Akita (from 109±5 to 138±6 mmHg, p<0.001) but not in control C57 (from 104±2 to 117±6 mmHg, NS). We conclude that intrarenal renin and pro-renin is enhanced in Akita mice which also exhibit salt sensitive hypertension. The mechanism may involve elevated superoxide and H202 levels within JG cells stimulating pro-renin expression and release. AHA-SDG; NIH-NIDDK-RO3 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A systems biology approach identifies the role of dysregulated PRDM6 in the development of hypertension.

Genetic variants in the third intron of the PRDM6 gene have been associated with BP traits in multiple GWAS. By combining fine mapping, massively parallel reporter assays, and gene editing, we identified super enhancers that drive the expression of PRDM6 and are partly regulated by STAT1 as the causal variants for hypertension. The heterozygous disruption of Prdm6 in mice expressing Cre recombinase under the control of mouse smooth muscle cell protein 22-α promoter (Prdm6fl/+ SM22-Cre) exhibited a markedly higher number of renin-producing cells in the kidneys at E18.5 compared with WT littermates and developed salt-induced systemic hypertension that was completely responsive to the renin inhibitor aliskiren. Strikingly, RNA-Seq analysis of the mouse aortas identified a network of PRDM6-regulated genes that are located in GWAS-associated loci for blood pressure, most notably Sox6, which modulates renin expression in the kidney. Accordingly, the smooth muscle cell-specific disruption of Sox6 in Prdm6fl/+ SM22-Cre mice resulted in a dramatic reduction of renin. Fate mapping and histological studies also showed increased numbers of neural crest-derived cells accompanied by increased collagen deposition in the kidneys of Prdm6fl/+ Wnt1Cre-ZsGreen1Cre mice compared with WT mice. These findings establish the role of PRDM6 as a regulator of renin-producing cell differentiation into smooth muscle cells and as an attractive target for the development of antihypertensive drugs.

Regulation of Renin Expression by Β1-Integrin in As4.1 Juxtaglomerular Line Cells

(1) Background: Renal dysfunction and hypertension are mutually aggravating factors; however, the details of their interaction remain unclear. In a study using renal tissue from diabetic rats, we found that β1-integrin, a cell-substrate adhesion molecule, is specifically phosphorylated in juxtaglomerular cells that secrete renin, a blood pressure regulator. (2) Methods: A mouse juxtaglomerular cell line (As4.1 cells) was used for the following experiments: drug-induced promotion of β1-integrin phosphorylation/dephosphorylation; knockdown of β1-integrin and the cell adhesion molecule connexin-40 (a candidate for the main body of baroreceptor); and pressurization to atmospheric pressure + 100 mmHg. culture in hypotonic liquid medium. The expression of renin under these conditions was measured by qRT-PCR. (3) Results: Phosphorylation of β1-integrin suppressed the expression of renin, while dephosphorylation conversely promoted it. β1-integrin and connexin-40 knockdown both promoted the expression of renin. Pneumatic pressurization and hypotonic medium culture both decreased the expression of renin, which was restored by the knockdown of β1-integrin. (4) Conclusions: β1-integrin plays an inhibitory role in the regulation of the expression of renin, which may be controlled by phosphorylation and dephosphorylation. It is hypothesized that β1-integrin and other adhesion factors regulate the expression of renin by altering the sensitivity of baroreceptors on the plasma membrane.

Effects of Vitamin D on Cardiovascular Risk and Oxidative Stress.

Vitamin D has been primarily studied as an important factor influencing bone and calcium metabolism. Metabolites of vitamin D are essential for whole-body calcium homeostasis, maintaining serum calcium levels within a narrow range by regulating this process in the bones and gut. Nevertheless, its deficiency is also related to increased risk of type 2 diabetes mellitus (T2DM), metabolic syndrome (MS), and cardiovascular disease (CVD)-with increased visceral adipose tissue and body mass index (BMI), as well as the frequently associated hypercholesterolemia. It has been reported that vitamin D levels are inversely related to cardiovascular (CV) risk in men and women. However, the effects of vitamin D on distinct outcomes in women and the dose of supplementation needed to improve clinical endpoints have not been established. 25-Hydroxyvitamin D [25(OH)D] reduces systemic inflammatory mediators in CVD and favors the release of anti-inflammatory cytokines from the immune system. In addition, 25(OH)D can be primarily converted into calcitriol (1,25-dihydroxycholecalciferol [1,25(OH)2D]) in the kidneys through the action of the 1-α-hydroxylase enzyme. Calcitriol, through the downregulation mechanism of renin expression, renin-angiotensin-aldosterone system (RAAS) activity, and its interaction with the vitamin D receptor, can bring CV benefits. The calcitriol form also lowers parathyroid hormone (PTH) levels by indirectly causing a reduction in aldosterone and mineralocorticoid synthesis. Elevated plasma aldosterone is related to endothelial dysfunction and CVD in hypovitaminosis D status. Vitamin D supplementation may benefit certain risk groups, as it improves metabolic variables, reducing oxidative stress and CV outcomes. More studies are needed to define interventions with vitamin D in men and women.

Activation of Mas and pGCA receptor pathways protects renal epithelial cell damage against oxidative-stress-induced injury

Over-activation of the renin-angiotensin-aldosterone system (RAAS) is a leading cause of cardio-renal complications. Oxidative stress is one of the major contributing factors in the over-activation of RAAS. Angiotensin-converting enzyme2/Angiotensin1–7/MasR and natriuretic peptide/particulate guanylyl cyclase receptor-A pathways play a key role in cardiorenal disease protection. Even though individual activation of these pathways possesses cardiorenal protective effects. However, the dual activation of these pathways under stress conditions and the underlying mechanism has not been explored. The study aimed to investigate whether activation of these pathways by dual-acting peptide (DAP) shows a protective effect in-vitro in oxidative stress-induced renal epithelial cells. Oxidative stress was induced in renal epithelial NRK-52E cells with H2O2. Co-treatment with Ang 1–7, BNP, and DAP was given for 30 min. AT1, MasR, and pGCA expression were measured by RT-PCR. The markers of oxidative stress and apoptosis were measured by confocal microscopy and FACS analysis. A significant increase in AT1, renin, α-SMA, and NFk-β expression and a significant decrease in MasR and pGCA expression was observed in H2O2-induced cells. DAP improved H2O2-induced pathological changes in NRK-52E cells. The effect of DAP was superior to that of Ang1–7 and BNP alone. Interestingly, MasR and pGCA inhibitors could block the effect of DAP in H2O2-induced cells. DAP shows superior anti-RAAS activity, and it is effective against H2O2-induced oxidative stress, apoptosis, fibrosis, and inflammation compared to Ang1–7 and BNP alone. The protective effect is mediated by the dual activation of MasR and pGCA.

Role of Vitamin D Deficiency in the Pathogenesis of Cardiovascular and Cerebrovascular Diseases

Deficiency in vitamin D (VitD), a lipid-soluble vitamin and steroid hormone, affects approximately 24% to 40% of the population of the Western world. In addition to its well-documented effects on the musculoskeletal system, VitD also contributes importantly to the promotion and preservation of cardiovascular health via modulating the immune and inflammatory functions and regulating cell proliferation and migration, endothelial function, renin expression, and extracellular matrix homeostasis. This brief overview focuses on the cardiovascular and cerebrovascular effects of VitD and the cellular, molecular, and functional changes that occur in the circulatory system in VitD deficiency (VDD). It explores the links among VDD and adverse vascular remodeling, endothelial dysfunction, vascular inflammation, and increased risk for cardiovascular and cerebrovascular diseases. Improved understanding of the complex role of VDD in the pathogenesis of atherosclerotic cardiovascular diseases, stroke, and vascular cognitive impairment is crucial for all cardiologists, dietitians, and geriatricians, as VDD presents an easy target for intervention.

Экспрессия ренина и ангиотензинпревращающего фермента 2 в матке и плаценте при иммунозависимых и ассоциированных с преэклампсией спонтанных абортах у мышей

Introduction. Spontaneous abortion and preeclampsia (PE) are the most common pregnancy abnormalities in humans. The renin-angiotensin-aldosterone system (RAAS) and the immune system are among the first to recognize pregnancy and play key roles in its maintenance. RAAS dysfunction is one of the causes of insufficient trophoblast invasion and defect in spiral artery remodeling, which both cause PE. Apart from circulating RAAS components, there are local ones, including uteroplacental ones. The study aimed to analyze the renin and angiotensin-converting enzyme 2 (ACE2) expression in the placenta and uterus in PE-associated spontaneous and immune-dependent abortions in mice. Materials and methods. We reached the physiological pregnancy model by ♀CBA × ♂Balb/c mating (control group); spontaneous PE-associated abortions were ♀CBA × ♂DBA/2. Induced abortions were caused by intraperitoneal β-heptylglycoside muramyldipeptide administration to CBA females fertilized by Balb/c males on gestation days (GDs) 5 and 7. Mice were removed from the experiment on GD 14 after the placenta has completely formed. We performed immunohistochemistry (IHC) of the uterus and placenta using rabbit monoclonal antibodies to renin and ACE2 and evaluated the distribution of the renin- and ACE2-positive cells and the intensity of IHC reaction. Results. Compared to the physiological pregnancy model and immune abortion groups, the spontaneous abortion/PE group was characterized by reduced renin expression in trophoblast giant cells (TGC) and its absence in placental vascular endothelium. We noted increased renin expression in the myometrium and its vascular endothelium in the spontaneous abortion/PE and immune-dependent abortion groups. ACE2 expression in TGC and glycogen cells and placental vascular endothelium was lower in spontaneous/PE and immune-dependent abortions than in the physiological pregnancy group. In contrast, higher ACE2 expression was observed in the myometrium and its vascular endothelium in the abortion groups compared to the controls. Conclusion. Reduced renin expression in TGC and its absence in the placental vascular endothelium of spontaneous abortions/PE group reflects trophoblast invasion disorder characteristic of PE. The detected changes in ACE2 expression in the myometrium in pregnancy failure and PE may represent a systemic compensatory mechanism, which does not exclude the negative effects of renin. Keywords: preeclampsia, pregnancy failure, uterus, placenta, renin-angiotensin-aldosterone system

PS-BPB10-2: MOLECULAR INSIGHT INTO SALT-SENSITIVITY; THE ROLE OF ATF3 AND THE GENERATION OF TUBULAR SPECIFIC KO MICE. (1)

Objectives: Current research including ours suggested pivotal roles of expressions of and regulations of tubular ion transporters for developments of sodium sensitivity and hypertension. Orlov et al. demonstrated using rat cardiomyocytes three different genes which are activated according to the elevation of intra-cellular Na ion concentration. (2015) To elucidate detailed biological roles of these genes in tubules, we performed current experiments. Methods: We tested expressions of three genes for cDNA from kidneys of Nedd4 2 C2 KO mice using quantitative RT PCR methods. Subsequently, we performed crossbreeding experiments between floxed target gene mice (generous gift from Prof. Kitamura, Tokyo Medical and Dental University) and Ksp-cre mice (Jackson Laboratory), which cre-recombinase expresses specifically along urinary tubules to generate mice with cre+, flox/flox genotype. Results: We found expressions of Atf3 are significantly changed due to oral sodium intake and diuretics treatment in Nedd4–2 C2 KO mice. We successfully generated mice with cre+, Atf3 flox/flox mice for current experiments. Under normal salt diet, we could not find any significant differences between cre + and minus mice in terms of systolic blood pressure, water intake, urine volume, urinary sodium excretions, urinary pH, and urinary osmotic pressures using metabolic cage experiments. We found, under high salt intake, gene expressions of both classic renin and tubular alternative renin are significantly suppressed for 30 to 70% in KO mice by quantitative RT PCR and immunohistochemistry imaging. Conclusions: Tubular epithelial Atf3 genes are involved in regulations of renin gene expressions in accordance with intracellular Na ion concentrations. Therefore, there are possibilities that tubular specific Atf3 KO mice shows blood pressure change under various salt intake and diuretics treatment.

PS-BPB10-3: MOLECULAR INSIGHT INTO SALT-SENSITIVITY; THE ROLE OF ATF3 AND THE GENERATION OF TUBULAR SPECIFIC KO MICE. (2)

Objective: Atf3 is transcriptionally activated according to intracellular Na concentrations. We found about 1.6 fold to 2.5 fold gene expression enhancements in kidney of Nedd4 2 C2 KO mice due to oral salt intakes and diuretics treatments. Aim of this study is to elucidate significance of Atf3 gene for salt-sensitivity by dietary salt loading and furosemide treatment for tubular specific Atf3 KO mice examining blood pressure, body weight, urine volume, water intake with genetic analyses. Methods: We performed metabolic cage experiments for male Ksp-cre (minus) Atf3 flox/flox mice (N = 5) and male Ksp-cre (+) Atf3 flox/flox mice (N = 10) with 7–8 wks old for subsequent protocol. After 1 week habituation period, experiments were done for 3 days normal salt intake, 5 days high salt intake, and 5 days high salt intake with furosemide treatment (40 mg/kg, ip), respectively. We measured blood pressure by tail cuff methods at day 0, day 8, and day 12. During experimental periods, body weight, water intake and urine volumes are measured daily. Results: We could not find significant differences among body weight, water intake and urine volume between two groups. After high oral salt intake and intra-peritoneal furosemide injection, we found blood pressure of cre (+) Atf3 flox/flox mice were significantly higher than cre (minus) Atf 3 flox/flox mice. (p < 0.001, 119.6 ± 1.4 mmHg vs 112.8 mmHg) Additionally, we found significant expression change of both classic renin and alternative renin in tubules between two groups by quantitative RT PCR and immunohisto chemistry imaging for kidney. Conclusions: Tubular-specific Atf3 KO mice have elevated blood pressure sensitive to salt and furosemide treatment. Because furosemide treatment might induce enhancement of intra-cellular Na ion concentration, Atf3 gene is responsible for adaptations for intra-cellular Na concentration change through tubular renin expressions.

Genetic Deletion of AT1a Receptor or Na+/H+ Exchanger 3 Selectively in the Proximal Tubules of the Kidney Attenuates Two-Kidney, One-Clip Goldblatt Hypertension in Mice.

The roles of angiotensin II (Ang II) AT1 (AT1a) receptors and its downstream target Na+/H+ exchanger 3 (NHE3) in the proximal tubules in the development of two-kidney, 1-clip (2K1C) Goldblatt hypertension have not been investigated previously. The present study tested the hypothesis that deletion of the AT1a receptor or NHE3 selectively in the proximal tubules of the kidney attenuates the development of 2K1C hypertension using novel mouse models with proximal tubule-specific deletion of AT1a receptors or NHE3. 2K1C Goldblatt hypertension was induced by placing a silver clip (0.12 mm) on the left renal artery for 4 weeks in adult male wild-type (WT), global Agtr1a−/−, proximal tubule (PT)-specific PT-Agtr1a−/− or PT-Nhe3−/− mice, respectively. As expected, telemetry blood pressure increased in a time-dependent manner in WT mice, reaching a maximal response by Week 3 (p < 0.01). 2K1C hypertension in WT mice was associated with increases in renin expression in the clipped kidney and decreases in the nonclipped kidney (p < 0.05). Plasma and kidney Ang II were significantly increased in WT mice with 2K1C hypertension (p < 0.05). Tubulointerstitial fibrotic responses were significantly increased in the clipped kidney (p < 0.01). Whole-body deletion of AT1a receptors completely blocked the development of 2K1C hypertension in Agtr1a−/− mice (p < 0.01 vs. WT). Likewise, proximal tubule-specific deletion of Agtr1a in PT-Agtr1a−/− mice or NHE3 in PT-Nhe3−/− mice also blocked the development of 2K1C hypertension (p < 0.01 vs. WT). Taken together, the present study provides new evidence for a critical role of proximal tubule Ang II/AT1 (AT1a)/NHE3 axis in the development of 2K1C Goldblatt hypertension.

Exercise Training Prevents High Fructose-Induced Hypertension and Renal Damages in Male Dahl Salt-Sensitive Rats.

High-fructose diet (HFr) causes metabolic syndrome, and HFr-induced hypertension and renal damage are exaggerated in Dahl salt-sensitive (DS) rats. Exercise training (Ex) has antihypertensive and renal protective effects in rats fed HFr; however, there has been little discussion about the DS rats, which exhibit metabolic disturbances. This study thus examined the effects of Ex on DS rats fed HFr. Male DS rats were divided into three groups. The control group was fed a control diet, and both the HFr group and the HFr-Ex group were fed an HFr (60% fructose). The HFr-Ex group also underwent treadmill running (20 m·min -1 , 60 min·d -1 , 5 d·wk -1 ). After 12 wk, renal function, histology, and renin-angiotensin system were examined. HFr increased blood pressure, urinary albumin, and creatinine clearance, and Ex inhibited these increases. HFr induced glomerular sclerosis, podocyte injury, afferent arteriole thickening, and renal interstitial fibrosis, and Ex ameliorated them. HFr reduced plasma renin activity, and Ex further reduced the activity. HFr also increased the expression of angiotensinogen, renin, angiotensin-converting enzyme (ACE), and angiotensin II type 1 receptor, and Ex restored the ACE expression to the control levels. HFr decreased the expression of ACE2, angiotensin II type 2 receptor, and Mas receptor, and Ex restored the ACE2 and Mas receptor expressions to the control levels and further decreased the angiotensin II type 2 receptor expression. HFr increased the ACE activity and decreased the ACE2 activity, and Ex restored these activities to the control levels. Ex prevents HFr-induced hypertension and renal damages in DS rats. The changes in renal renin-angiotensin system may be involved in the mechanism of the antihypertensive and renal protective effects of Ex.

Activation of Piezo1 downregulates renin in juxtaglomerular cells and contributes to blood pressure homeostasis

BackgroundThe synthesis and secretion of renin in juxtaglomerular (JG) cells are closely regulated by the blood pressure. To date, however, the molecular identity through which JG cells respond to the blood pressure remains unclear.ResultsHere we discovered that Piezo1, a mechanosensitive ion channel, was colocalized with renin in mouse kidney as well as As4.1 cells, a commonly used JG cell line. Activation of Piezo1 by its agonist Yoda1 induced an intracellular calcium increase and downregulated the expression of renin in these cells, while knockout of Piezo1 in JG cells abolished the effect of Yoda1. Meanwhile, mechanical stress using microfluidics also induced an intracellular calcium increase in wildtype but not Piezo1 knockout JG cells. Mechanistically, we demonstrated that activation of Piezo1 upregulated the Ptgs2 expression via the calcineurin-NFAT pathway and increased the production of Ptgs2 downstream molecule PGE2 in JG cells. Surprisingly, we discovered that increased PGE2 could decreased the renin expression through the PGE2 receptor EP1 and EP3, which inhibited the cAMP production in JG cells. In mice, we found that activation of Piezo1 significantly downregulated the renin expression and blood pressure in wildtype but not adeno-associated virus (AAV)-mediated kidney specific Piezo1 knockdown mice.ConclusionsIn summary, these results revealed that activation of Piezo1 could downregulate the renin expression in JG cells and mice, subsequently a reduction of blood pressure, highlighting its therapeutic potential as a drug target of the renin-angiotensin system.

Abstract 11064: Role of Renin-Angiotensin System Axis in Human Abdominal Aortic Aneurysm

Introduction: Renin-Angiotensin System (RAS) regulates the cardiovascular system and has been implicated in the development of abdominal aortic aneurysm (AAA). RAS modulates function via balancing the ACE/Chymase/AngII-AT1 receptor and ACE-2/Ang(1-7)-Mas receptor axis. Preferential activation of the ACE/Chymase/AngII-AT1 receptor pathway of the RAS contributes to dysregulation of cardiovascular system and disease while the Ang(1-7)-MasR axis contributes to anti-inflammatory pathways. Therefore, identifying the RAS axis mechanism involved in growth, progression, or the risk of rupture in AAA humans could bring a novel treatment perspective. Hypothesis: We hypothesize that in the AAA, the local RAS is altered such as it favours the ACE/AngII/AT1R axis while decreasing the ACE-2/Ang(1-7)/MasR pathway, with consequent AAA development. Objective: We sought to investigate the expression of RAS components in the AAA human aorta. Methods: Aorta tissue from AAA patients (n=21) was collected during the AAA conventional repair surgery, and aorta control aortas were obtained from organ donors (Control, n=11). Protein expression of renin, chymase, ACE, ACE-2 AT1, AT2, and MAS receptors was analyzed by Western Blotting. Results: Our AAA cohort consisted mostly males (76.6% AAA vs. 63.6% Control, p=0.68), smokers or ex-smokers (90.4% AAA vs. 36.3% Control, p=0.002) and most of them had hypertension(71.4% AAA vs. 36.3% Control, p=0.07). Analysis of protein expression in the AAA group showed that ACE and AT1 receptors were upregulated compared with Control (p=0.05; p=0.02, respectively,), while chymase expression was decreased in AAA compared to the control (p=0.03). Additionally, the AAA group showed downregulation in ACE-2 and AT2 compared with Control (respectively, p=0.01, p=0.03). There was no significant difference in the expression of renin and MAS receptors between groups (p=0.52, p=0.41, respectively,). Conclusions: Our data show that the ACE/AT1R axis was upregulated while ACE-2 and AT2 receptors were downregulated in the AAA aorta. Our results implicate local RAS in AAA development and warrant further studies.

Regulatory Effect of Vitamin D on Renin Expression at Maternal-Fetal Interface

To investigate the regulatory effect and mechanism of vitamin D on the local renin-angiotensin system at maternal-fetal interface in the pathological process of preeclampsia (PE). The mRNA and protein expression of renin in decidua of normal pregnancy and PE placentas was determined by RT-PCR and Western blot. Normal decidual tissues were treated with active and inactive vitamin D for 48 h in vitro and the expressions of renin and vitamin D deactivating enzyme CYP24A1 were determined by RT-PCR and Western blot. Normal decidual stromal cells and glandular epithelial cells were isolated and purified, and identified by immunocytochemical staining. RT-PCR was used to examine the mRNA of vdr, cyp27 b1, cyp24 a1, and renin in the two types of cells and in decidual tissue, and the mRNA products were subjected to gel electrophoresis. These two cell types were treated with active and inactive vitamin D in vitro and the expressions of renin and vitamin D deactivating enzyme CYP24A1 were determined by RT-PCR and Western blot. Decidual gland epithelial cells were treated with protein kinase A (PKA) activator forskolin or inhibitor H89 to explore the interaction between PKA pathway and vitamin D in the regulation of renin expression. The expression of renin in PE decidua was significantly higher than that of normal control at transcriptional and translational levels ( P<0.05). Vitamin D treatment could significantly down-regulate the expression of renin in normal decidua tissues ( P<0.05), while it significantly up-regulated CYP24A1 expression ( P<0.001). Decidual stromal cells and gland epithelial cells were successfully isolated from decidual tissue. Compared with that in decidual stromal cells, the mRNA level of vitamin D-related molecules in gland epithelial cells was more similar to that in decidual tissue. Active or inactive vitamin D treatment significantly inhibited the expression of renin in glandular epithelial cells ( P<0.05), but the expression of renin in decidual stromal cells was not affected. However, the treatment of active or inactive vitamin D in these two kinds of cells significantly increased the expression of CYP24A1 ( P<0.001). Active vitamin D could significantly inhibit the upregulation of renin by PKA agonist forskolin, and could inhibit the expression of renin through synergy with PKA inhibitor H89. The expression of renin in placental decidua is up-regulated in patients with PE, and the activation of local renin-angiotensin system at the maternal-fetal interface may be involved in the pathogenesis of PE. Vitamin D can specifically down-regulate renin expression in human decidual gland epithelial cells by competing with the PKA pathway. Vitamin D supplementation may have potential value for clinical intervention of PE.

Effects of maternal fructose intake on the offspring's kidneys.

Fructose overload is associated with cardiovascular and metabolic disorders. During pregnancy, these alterations may affect the maternal environment and predispose offspring to diseases. Aims: To evaluate the renal morphology and function of offspring of dams that received fructose overload during pregnancy and lactation. Methods: Female Wistar rats were divided into the control (C) and fructose (F) groups. C received food and water ad libitum, and F received food and d-fructose solution (20%) ad libitum. The d-fructose offer started 1 week before mating and continued during pregnancy and lactation. The progeny were designated as control (C) or fructose (F); after weaning, half of the F received water to drink (FW), and half received d-fructose (FF). Blood pressure (BP) and renal function were evaluated. The expression of sodium transporters (NHE3-exchanger, NKCC2 and NCC-cotransporters, and ENaC channels) and markers of renal dysfunction, including ED1 (macrophage), eNOS, 8OHdG (oxidative stress), renin, and ACE 1 and 2, were evaluated. CEUA-UNIFESP: 2757270117. The FF group presented with reduced glomerular filtration rate and urinary osmolarity, increased BP, proteinuria, glomerular hypertrophy, macrophage infiltration, and increased expression of transporters (NHE3, NCC, and ENaC), 8OHdG, renin, and ACE1. The FW group did not show increased BP and renal functional alterations; however, it presented glomerular hypertrophy, macrophage infiltration, and increased expression of the transporters (NHE3, NKCC2, NCC, and ENaC), renin, and ACE1. These data suggest that fructose overload during fetal development alters renal development, resulting in the increased expression of renin, ACE1, and sodium transporters, thus predisposing to hypertension and renal dysfunction.

Abstract P332: The Hypertension Induced By Clozapine Is Related With Increased Renal Sodium Transporters In Mice

Introduction: Hypertension is caused by multi-factors, and the pathogenesis is linked to, generally, the increases in the protein expressions and functions of renal sodium transport proteins along the nephron. One of the major side effects of clozapine (common antipsychotic drug) is hypertension. The mechanism is unknown. Hypothesis: the pathogenesis of the clozapine-induced hypertension is associated with increases of renal sodium transport proteins. Methods: we examined the blood pressures (BP) and protein expressions of major sodium transport proteins profiled along the renal tubules in the C57Bl6/J male mice (9 weeks old, n=4-5/group) treated with clozapine at three doses of 5,10 and 20 mg/ kg for 1 week via intraperitoneal injection. Result: blood pressures (tail-cuff, BP98A, softron, Japan) were higher in clozapine at 20mg/kg/day than vehicle (SBP: 130±1.64 vs 109±1.39, DBP: 87 ±4.12 vs 69±2.10 mmHg, n=5/group) and not altered at 5 &amp; 10 mg/kg/day. There were no differences in BW, serum/urine creatinine and electrolytes except for a slight increase in serum sodium at dose of 20 mg/kg (152.8±0.71 vs 150.6±0.40, mmol/L).In renal homogenates, total protein abundance of NaPi2 (western blotting,199±26% of vehicle) NKCC2(184±20), NCC(213±14),and ENaC-α(217±47),were higher at 20 mg/kg than vehicle. No increases were found in protein expressions of NHE3, αNKA, ENaC-β and ENaC-γ. The expressions of renin, AT1R and ACE at 20mg/kg were similar between groups while ACE2 was decreased (42±10). No increases were found in protein expressions of pNKCC2 in 5&amp;10mg/kg(100±50,45±15); NCC was increased at 5 mg/kg (175±9); α NKA was increased in 5mg/kg (216±5) and 10mg/kg (163±2) groups.In plasma membrane enriched fraction (17k), NKCC2(204±43) and ENaC-α(381±28)were higher at 20 mg/kg than vehicle. In intracellular membrane enriched fraction (200k), NKCC2(521±127) was higher than vehicle. Phosphorylated NKCC2 was increased in renal homogenates(331±35),17k(427±87) 200k(521±127) but WNK4 was not changed. Conclusions: increases of renal sodium transport proteins, mainly pNKCC2 and NKCC2, contribute to the dose-related increase of BP in mice treated with clozapine and may play an important role in the pathogenesis of the clozapine-induced hypertension.

Abstract 091: Does Smooth Muscle Cullin-3 Regulate The Renin-angiotensin System?

Cullin-3 (CUL3) is a scaffold protein involved in the formation and function of the CUL3-RING E3 ubiquitin ligase complex. Loss of smooth muscle CUL3 promotes vascular dysfunction, arterial stiffness, and severe hypertension (HTN). We hypothesized that conditional deletion of CUL3 in smooth muscle cells causes severe HTN through a renin-angiotensin system (RAS)-dependent mechanism. Mice carrying a conditional allele of CUL3 were bred to mice expressing a tamoxifen-inducible CRE-recombinase driven by a smooth muscle promoter (ISM-CRE, control). Tamoxifen was administered to generate smooth muscle CUL3 knockout (S-CUL3KO). Three weeks after tamoxifen, mean arterial pressure (MAP) was 140±1 vs. 108±1 mmHg (S-CUL3KO vs. ISM-CRE). Aorta from S-CUL3KO mice exhibited impaired acetylcholine-induced vasorelaxation (ACh, max relaxation: 19±11% vs. 84±5%, p&lt;0.05). S-CUL3KO mice also manifested impaired vasorelaxation to sodium nitroprusside (SNP, max relaxation: 15±12% vs. 96±2%, p&lt;0.05). Captopril administration (7 days) markedly reduced MAP to 84±0.3 mmHg and improved vasorelaxation in response to both ACh (72±6%) and SNP (87±4%) in S-CUL3KO mice, suggesting RAS-dependency of the HTN. Q-PCR analyses and RNAScope showed no difference in renin expression in the kidney between the S-CUL3KO and control mice suggesting a blunting of the baroreceptor mechanism regulating renin. In preliminary studies, lamin A/C, a crucial component of the nuclear mechanotransducer controlling expression of renin, displayed a trend to increased protein expression in S-CUL3KO animals (6±2 vs. 2±1 normalized RFU, p=0.12). Similarly, expression of connexin 40, a component responsible renin signal transduction in the renin cells, was significantly higher in S-CUL3KO mice (8±1 vs. 3±1 normalized RFU, p&lt;0.05). Our data suggest that CUL3 may play a vital role in baroreceptor mechanism in the renin cells via regulation of components of the baroreflex sensor (connexin 40) and transducer (lamin A/C) which are essential for responding to changes in perfusion pressure. Hence, understanding CUL3 target proteins and the mechanism of the impaired baroreceptor mechanism is beneficial in developing new treatments of hypertension.

Abstract P234: Arterial Hypertension, Insulin Resistance And Depressive-like Behavior In Crtc1 -deficient Mice

Background: Epidemiological evidence has demonstrated a link between cardiovascular disease, metabolic syndrome and depression. Whether this association is causal and what mechanisms may be involved is still unknown. Studies in humans and mice suggest that alterations of the CREB-BDNF pathway can contribute to the development of both, eating disorders and major depressive disorders. Mice deficient in the CREB-regulated transcriptional coactivator 1 (Crtc1) have been shown to become overweight and display depressive-like behavior. Here, we investigated whether Crtc1 -deficient mice concomitantly exhibit a hypertensive, insulin resistant and depression-like phenotype. Methods: Mean arterial blood pressure and heart rate were measured by radiotelemetry in unrestrained Crtc1 -deficient mice (KO) and wildtype littermates (WT). Renal renin expression was quantified by qPCR. Insulin resistance was determined by the i.p. glucose tolerance test, and depressive-like behavior was assessed by the soiled bedding preference test. Results: Crtc1 -deficient mice had higher arterial blood pressures (dark: KO 117±2 mm Hg, WT 107±2 mm Hg, p&lt;0.05; light: KO 102±2 mm Hg, WT 94±2 mm Hg, p&lt;0.05, 1-way ANOVA, n=8-11) and heart rates (dark: KO 593±11 bpm, WT 596±7 bpm; light: KO 529±12 bpm, WT 494±8 bpm, p&lt;0.05, 1-way ANOVA, n=8-11). Relative renin mRNA expression was not different between genotypes (KO 0.86±0.07, WT 1.00±0.10, n=10). Glucose tolerance was significantly impaired in Crtc1 -deficient mice (maximum plasma glucose concentrations KO 423±27 mg/dl, WT 295±27 mg/dl, p&lt;0.0001, 2-way ANOVA, n=9). In the soiled bedding preference test, male Crtc1 -deficient mice exhibited a lack of preference for female-soiled bedding over clean bedding (female vs. clean KO 75.3±11.2 s vs 79.0±11.0 s, WT 119.5±13.5 s vs. 51.5±10.5 s, n=2-3). Conclusions: Crtc1 might be a molecular component of a pathway that connects arterial hypertension, metabolic syndrome and depression.