Renal Renin-angiotensin-aldosterone System Research Articles

Increasing angiotensin-converting enzyme 1 regulated by histone 3 lysine 27 hyperacetylation in high-fat diet-induced hypertensive rat kidney.

Obesity is a key risk factor of hypertension. Angiotensin-converting enzyme 1 (ACE1) is a key enzyme involved in the renin-angiotensin-aldosterone system (RAAS), which contributes to obesity-related hypertension (OrHTN). Emerging evidence has shown that histone acetylation is also involved in OrHTN. As kidney is an effector organ that activates the RAAS by secreting renin after hypertension occurs, this study aimed to explore the regulatory role of histone acetylation on renal RAAS expression. Nineteen male Wistar rats were randomly divided into a control group ( n = 9, fed normal chow) and a high-fat diet (HFD) group ( n = 10, fed HFD for 16 weeks). The renal transcriptome and histone acetylation spectrum was analyzed by RNA sequencing and tandem mass spectrometry and was further confirmed by RT-qPCR, western blot, and immunohistochemistry. Then, chromatin immunoprecipitation (ChIP)-qPCR analysis was performed for the detection of DNA-protein interaction. After 16-week HFD, the rats became obese with increased plasma triglyceride and high blood pressure. Increased ACE1 and histone 3 lysine 27 acetylation (H3K27ac) expression levels were found in OrHTN rat kidneys. The following ChIP-qPCR analysis illustrated that the upregulation of ACE1 transcription was mediated by increased H3K27ac. H3K27ac could be an important histone acetylation site that activates renal ACE1 in HFD-induced hypertensive rats.

Nocturnal hypoxemia severity influences the effect of CPAP therapy on renal renin-angiotensin-aldosterone system activity in humans with obstructive sleep apnea.

Nocturnal hypoxemia (NH) in obstructive sleep apnea (OSA) is associated with renal renin-angiotensin-aldosterone system (RAAS) up-regulation and loss of kidney function. Continuous positive airway pressure (CPAP) therapy is associated with RAAS down-regulation, though the impact of NH severity remains unknown. We sought to determine whether NH severity alters the effect of CPAP on renal hemodynamics and RAAS activity in humans. Thirty sodium-replete, otherwise healthy, OSA participants (oxygen desaturation index ≥ 15 h-1) with NH (SpO2 < 90% ≥ 12%/night) were studied pre- and post-CPAP (>4 h/night∙4 weeks). NH severity was characterized as moderate (mean SpO2[MSpO2] ≥ 90%; N = 15) or severe (MSpO2 < 90%; N = 15). Glomerular filtration rate (GFR), renal plasma flow (RPF), and filtration fraction (FF) were measured at baseline and in response to angiotensin-II (3 ng/kg/min∙30 min, 6 ng/kg/min∙30 min), a marker of RAAS activity. Pre-CPAP, baseline renal hemodynamics did not differ by NH severity. Pre-CPAP, severe NH participants demonstrated blunted GFR (Δ30 min, -9 ± 4 vs 1 ± 3 mL/min, p = 0.021; Δ60 min, -5 ± 5 vs 8 ± 5 mL/min, p = 0.017) and RPF (Δ30 min, -165 ± 13 vs -93 ± 19 mL/min, p = 0.003; Δ60 min, -208 ± 18 vs -112 ± 22 mL/min, p = 0.001; moderate vs severe) responses to angiotensin-II. Post-CPAP, severe NH participants demonstrated maintained GFR (112 ± 5 vs 108 ± 3 mL/min, p = 0.9), increased RPF (664 ± 35 vs 745 ± 34 mL/min, p = 0.009), reduced FF (17.6 ± 1.4 vs 14.9 ± 0.6%, p = 0.009), and augmented RPF responses to Angiotensin-II (Δ30 min, -93 ± 19 vs -138 ± 16 mL/min, p = 0.009; Δ60 min, -112 ± 22 vs -175 ± 20 mL/min, p = 0.001; pre- vs post-CPAP), while moderate participants were unchanged. Correction of severe, but not moderate, NH with CPAP therapy was associated with improved renal hemodynamics and decreased renal RAAS activity in humans with OSA.

The relationship between urinary renin-angiotensin system markers, renal function, and blood pressure in adolescents with type 1 diabetes.

The relationship between the renal renin-angiotensin aldosterone system (RAAS) and cardiorenal pathophysiology is unclear. Our aims were to assess 1) levels of urinary RAAS components and 2) the association between RAAS components and HbA1c, the urine albumin/creatinine ratio (ACR), estimated glomerular filtration rate (eGFR), and blood pressure (BP) in otherwise healthy adolescents with type 1 diabetes mellitus (TID) vs. healthy controls (HC). Urinary angiotensinogen and angtionsin-converting enzyme (ACE) 2 levels, activity of ACE and ACE2, BP, HbA1c, ACR, and eGFR were measured in 65 HC and 194 T1D from the Adolescent Type 1 Diabetes Cardio-Renal Intervention Trial (AdDIT). Urinary levels of all RAAS components were higher in T1D vs. HC (P < 0.0001). Higher HbA1c was associated with higher urinary angiotensinogen, ACE2, and higher activity of ACE and ACE2 (P < 0.0001, P = 0.0003, P = 0.003, and P = 0.007 respectively) in T1D. Higher ACR (within the normal range) was associated with higher urinary angiotensinogen (P < 0.0001) and ACE activity (P = 0.007), but not with urinary ACE2 activity or ACE2 levels. These observations were absent in HC. Urinary RAAS components were not associated with BP or eGFR in T1D or HC. Otherwise healthy adolescents with T1D exhibit higher levels of urinary RAAS components compared with HC. While levels of all urinary RAAS components correlate with HbA1c in T1D, only urinary angiotensinogen and ACE activity correlate with ACR, suggesting that these factors reflect an intermediary pathogenic link between hyperglycemia and albuminuria within the normal range.

Maternal corticosterone exposure in the mouse programs sex-specific renal adaptations in the renin-angiotensin-aldosterone system in 6-month offspring.

Short‐term maternal corticosterone (Cort) administration at mid‐gestation in the mouse reduces nephron number in both sexes while programming renal and cardiovascular dysfunction in 12‐month male but not female offspring. The renal renin–angiotensin–aldosterone system (RAAS), functions in a sexually dimorphic manner to regulate both renal and cardiovascular physiology. This study aimed to identify if there are sex‐specific differences in basal levels of the intrarenal RAAS and to determine the impact of maternal Cort exposure on the RAAS in male and female offspring at 6 months of age. While intrarenal renin concentrations were higher in untreated females compared to untreated males, renal angiotensin II concentrations were higher in males than females. Furthermore, basal plasma aldosterone concentrations were greater in females than males. Cort exposed male but not female offspring had reduced water intake and urine excretion. Cort exposure increased renal renin concentrations and elevated mRNA expression of Ren1, Ace2, and Mas1 in male but not female offspring. In addition, male Cort exposed offspring had increased expression of the aldosterone receptor, Nr3c2 and renal sodium transporters. In contrast, Cort exposure increased Agtr1a mRNA levels in female offspring only. This study demonstrates that maternal Cort exposure alters key regulators of renal function in a sex‐specific manner at 6 months of life. These finding likely contribute to the disease outcomes in male but not female offspring in later life and highlights the importance of renal factors other than nephron number in the programming of renal and cardiovascular disease.

High maternal sodium intake alters sex-specific renal renin-angiotensin system components in newborn Wistar offspring.

This study aimed to evaluate the systemic and renal renin-angiotensin-aldosterone system (RAAS) at birth in male and female offspring and in mothers fed a high sodium diet (HSD) before and during gestation. Female Wistar rats were fed a HSD (8.0% NaCl) or a normal sodium diet (1.3% NaCl) from 8 weeks of age until delivery of their first litter. Maternal body weight, tail blood pressure, and food and water intake were evaluated. The litter sizes were assessed, and the body and kidney weights of the offspring were measured. Both mothers and offspring were euthanized immediately following the birth of the pups to evaluate plasma renin activity (PRA), renal renin content (RRC), renal angiotensin-converting enzyme (ACE) activity, renal angiotensin (Ang) II content, serum aldosterone (ALDO) levels, and renal cortical and medullary renin messenger RNA expression. In mothers in the HSD group, water intake and kidney mass were higher, whereas renal ACE activity, Ang II, PRA, ALDO and RRC were decreased. In the offspring of HSD-fed dams, the body and kidney mass were lower in both genders, renal ACE activity was lower in females and renal Ang II was lower in males. PRA, RRC, renin gene expression and ALDO levels did not differ between the groups of offspring. The data presented herein showed that a maternal HSD during pregnancy induces low birth weight and a sex-specific response in the RAAS in offspring.

Tenofovir during pregnancy in rats: a novel pathway for programmed hypertension in the offspring.

To evaluate the occurrence of systemic and renal abnormalities in the offspring of Wistar rats exposed to tenofovir disoproxil fumarate (DF) during pregnancy. Female Wistar rats received a standard diet, with or without addition of tenofovir DF (100 mg/kg diet), 1 week before mating and during pregnancy. Offspring from the tenofovir DF group were placed with an untreated foster mother during breastfeeding and compared with offspring from rats maintained on a standard diet during mating and pregnancy (control). Control and tenofovir DF were followed up at 3 and 6 months of age. Monthly body weight and systolic blood pressure (SBP), glomerular counts, renal function, biochemical parameters, angiotensin II, renal renin angiotensin aldosterone system (RAAS) and renal sodium transporters were analysed. Tenofovir DF offspring showed lower birth weight compared with the control group. After the third month, growth among the tenofovir DF group experienced a rapid catch-up. SBP increased progressively after the second month of age in the tenofovir DF group. Nephron number did not differ between the groups; however, the tenofovir DF group showed glomerular structural changes. Plasma aldosterone was higher in the tenofovir DF group, associated with a significant increase in renal expression of RAAS. The tenofovir DF rats showed up-regulation of renal sodium transporters and consequently lower urinary sodium excretion. This is the first demonstration using an experimental model that maternal exposure to tenofovir DF during gestation results in overactivation of RAAS, up-regulation of renal sodium transporters and hypertension in the offspring.

The renin–angiotensin–aldosterone system in pre-eclampsia: the delicate balance between good and bad

Pregnancy demands major changes of the cardiovascular system, and this involves, among others, activation of the RAAS (renin-angiotensin-aldosterone system), allowing an aldosterone-dependent increase in volume. Remarkably, a relative resistance to the pressor response of AngII (angiotensin II) develops simultaneously to prevent the increase in blood pressure that would normally accompany RAAS activation. The increase in volume, the degree of RAAS activation and the diminished pressor response to AngII are less pronounced in pre-eclampsia. However, animal models displaying excessive RAAS activation also result in a pre-eclampsia-like syndrome, and the aldosterone/renin ratio is elevated in pre-eclampsia compared with a normal pregnancy. New insights into the pathogenesis of pre-eclampsia have revealed a major role for VEGF (vascular endothelial growth factor), VEGF-inactivating sFlt-1 (soluble fms-like tyrosine kinase-1) and AT1 (angiotensin II type 1) receptor autoantibodies. The last mentioned activate AT(1) receptors, thereby potentially suppressing circulating renin and aldosterone. VEGF, both directly and indirectly (by increasing capillary density), affects adrenal aldosterone synthesis. The present review summarizes all of the recent findings regarding RAAS regulation in pre-eclampsia compared with normal pregnancy, concluding that factors such as sFlt-1 and AT(1) receptor autoantibodies disturb the delicate balance that normally results in a volume increase and a diminished vasoconstrictor response to AngII in pregnant women. It is possible that there are non-parallel changes in the circulating and renal RAAS in pre-eclampsia, which are potentially reflected by the urinary levels of renin.

Maternal high-sodium intake alters the responsiveness of the renin–angiotensin system in adult offspring

AimsThe goal of the current study was to evaluate the impact of maternal sodium intake during gestation on the systemic and renal renin–angiotensin–aldosterone-system (RAAS) of the adult offspring. Main methodsFemale Wistar rats were fed high- (HSD-8.0% NaCl) or normal-sodium diets (NSD-1.3% NaCl) from 8weeks of age until the delivery of their first litter. After birth, the offspring received NSD. Tail-cuff blood pressure (TcBP) was measured in the offspring between 6 and 12weeks of age. At 12weeks of age, the offspring were subjected to either one week of HSD or low sodium diet (LSD-0.16% NaCl) feeding to evaluate RAAS responsiveness or to acute saline overload to examine sodium excretory function. Plasma (PRA) and renal renin content (RRC), serum aldosterone (ALDO) levels, and renal cortical and medullary renin mRNA expression levels were evaluated at the end of the study. Key findingsTcBP was higher among dams fed HSD, but no TcBP differences were observed among the offspring. Male offspring, however, exhibited increased TcBP after one week of HSD feeding, and this effect was independent of maternal diet. Increased RAAS responsiveness to the HSD and LSD was also observed in male offspring. The baseline levels of PRA, ALDO, and cortical and medullary renin gene expression were lower but the RRC levels were higher among HSD-fed male offspring (HSDoff). Conversely, female HSDoff showed reduced sodium excretion 4h after saline overload compared with female NSDoff. SignificanceHigh maternal sodium intake is associated with gender-specific changes in RAAS responsiveness among adult offspring.

Uremic Toxins Induce Kidney Fibrosis by Activating Intrarenal Renin–Angiotensin–Aldosterone System Associated Epithelial-to-Mesenchymal Transition

BackgroundUremic toxins are considered to have a determinant pathological role in the progression of chronic kidney disease. The aim of this study was to define the putative pathological roles of the renal renin–angiotensin–aldosterone system (RAAS) and renal tubular epithelial-to-mesenchymal transition (EMT) in kidney fibrosis induced by (indoxyl sulfate) IS and (p-cresol sulfate) PCS.MethodsMouse proximal renal tubular cells (PKSV-PRs) treated with IS or PCS were used. Half-nephrectomized B-6 mice were treated with IS or PCS for 4 weeks. In the losartan treatment study, the study animal was administrated with IS+losartan or PCS+losartan for 4 weeks.ResultsIS and PCS significantly activated the intrarenal RAAS by increasing renin, angiotensinogen, and angiotensin 1 (AT1) receptor expression, and decreasing AT2 receptor expression in vitro and in vivo. IS and PCS significantly increased transforming growth factor-β1 (TGF-β1) expression and activated the TGF-β pathway by increasing Smad2/Smad2-P, Smad3/Smad3-P, and Smad4 expression. The expression of the EMT-associated transcription factor Snail was increased by IS and PCS treatment. IS and PCS induced the phenotype of EMT-like transition in renal tubules by increasing the expression of fibronectin and α-smooth muscle actin and decreasing the expression of E-cadherin. Losartan significantly attenuated the expression of TGF-β1 and Snail, and decreased kidney fibrosis induced by IS and PCS in vivo.ConclusionActivating the renal RAAS/TGF-β pathway has an important pathological role in chronic kidney injury caused by IS and PCS. IS and PCS may increase Snail expression and induce EMT-like transition.

Urinary renin, but not angiotensinogen or aldosterone, reflects the renal renin–angiotensin–aldosterone system activity and the efficacy of renin–angiotensin–aldosterone system blockade in the kidney

To study which renin-angiotensin-aldosterone system (RAAS) component best reflects renal RAAS activity. We measured urinary and plasma renin, prorenin, angiotensinogen, aldosterone, albumin and creatinine in 101 diabetic and nondiabetic patients with or without hypertension. Plasma prorenin was elevated in diabetic patients. Urinary prorenin was undetectable. Urinary albumin and renin were higher in diabetic patients. Men had higher plasma renin/prorenin levels, and lower plasma angiotensinogen levels than women. Plasma creatinine and albumin were also higher in men. Urinary RAAS components showed no sexual dimorphism, whereas urinary creatinine and albumin were higher in men. Angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor blockers increased plasma renin and decreased plasma angiotensinogen, without altering plasma aldosterone. In contrast, in urine, these drugs decreased renin and aldosterone without affecting angiotensinogen. When analyzing all patients together, urinary angiotensinogen excretion closely mimicked that of albumin, whereas urinary angiotensinogen and albumin levels both were 0.05% or less of their concomitant plasma levels. This may reflect the identical glomerular filtration and tubular handling of both proteins, which have a comparable molecular weight. In contrast, urinary renin excretion did not correlate with urinary albumin excretion, and the urinary/plasma concentration ratio of renin was more than 200 times the ratio of albumin, despite its comparable molecular weight. Urinary aldosterone excretion closely followed urinary creatinine excretion. The increased urinary renin levels in diabetes and the decreased urinary renin levels following RAAS blockade, occurring independently of changes in plasma renin, reflect the activated renal RAAS in diabetes and the success of RAAS blockade in the kidney, respectively. Urinary renin, therefore, more closely reflects renal RAAS activity than urinary angiotensinogen or aldosterone.

L/N-type calcium channel blocker cilnidipine ameliorates proteinuria and inhibits the renal renin–angiotensin–aldosterone system in deoxycorticosterone acetate-salt hypertensive rats

Cilnidipine, an N/L-type calcium channel blocker, has been reported to inhibit sympathetic nerve activity and has a greater renoprotective effect than L-type calcium channel blockers. To investigate the hypothesis that cilnidipine might ameliorate advanced hypertensive nephropathy and inhibit the renal renin-angiotensin-aldosterone system, cilnidipine (1 mg per kg per day) or amlodipine (1 mg per kg per day) was administered to uninephrectomized deoxycorticosterone (DOCA)-salt hypertensive rats (DOCA-salt) for 4 weeks by gavage. Although the blood pressure in the DOCA-salt group was higher than that of control, neither cilnidipine nor amlodipine had any effect on the increase in blood pressure in the DOCA-salt group. The DOCA (40 mg per kg per week, subcutaneously (s.c.)) and salt (1% NaCl in drinking water) treatment significantly aggravated the levels of urinary protein excretion and creatinine clearance and increased glomerulosclerosis and collagen deposition in the tubulointerstitial area of the kidney. These effects were attenuated by cilnidipine treatment. Reverse transcription-polymerase chain reaction analysis revealed that the renal expression of mRNA for collagen I/IV and transforming growth factor-β was enhanced in the DOCA-salt group and that the overexpression of these molecules was suppressed by cilnidipine. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-derived superoxide production in the kidney and urinary norepinephrine excretion, which were enhanced in the DOCA-salt group, were suppressed by cilnidipine. Cilnidipine also decreased the activity and expression of angiotensin-converting enzyme (ACE) and the aldosterone concentration in the renal homogenate. Although neither cilnidipine nor amlodipine had any effect on the increased blood pressure in the DOCA-salt group, these renal changes were not induced by treatment with amlodipine. In conclusion, cilnidipine inhibited renal dysfunction, sympathetic nerve activity and renal renin-angiotensin-aldosterone system in the DOCA-salt group.

Candesartan Differentially Regulates Epithelial Sodium Channel in Cortex Versus Medulla of Streptozotocin-Induced Diabetic Rats

Diabetes is associated with an activated renal renin-angiotensin-aldosterone system (RAAS) and it was shown that streptozotocin (STZ)-induced diabetic rats had increased whole kidney protein levels of the epithelial sodium channel subunits (α-, β- and γ-ENaC). However, the role of the RAAS on the regional, i.e., cortical versus medullary, regulation of ENaC is unclear. Male Sprague-Dawley rats were injected with STZ (intravenous, 65 mg/kg·bw, n=12/group). After 14 days, half of them received drinking water with candesartan (2 mg/kg·bw/day), an angiotensin-II type-1 receptor (AT1R) antagonist, for one week. In the medulla, i.e., inner stripe of the outer medulla (ISOM), base and/or tip of the inner medulla, immunoblotting revealed increased protein abundances of α1 Na-K-ATPase and ENaC subunits with diabetes (200-600% of controls), which were not reversed by candesartan. In fact, candesartan increased all ENaC subunits and α1 Na-K-ATPase in the ISOM and/or base in control rats. In contrast, in the cortex, diabetes did not increase these proteins. However, candesartan reduced cortical β- and γ-ENaC regardless of diabetic state. In summary, diabetes-induced increases in ENaC were seen preferentially in the medulla. These changes appeared to be due to a mechanism clearly distinct from AT1R activation, because they were not abolished by candesartan. In fact, candesartan treatment tended to increase some of these medullary proteins, perhaps in compensation for increased NaCl load. In contrast, cortical β- and γ-ENaC were reduced by candesartan regardless of diabetic state suggesting their regulation by AT1R at this site; however this did not appear to be a site of diabetes-induced ENaC up-regulation.

Spironolactone exhibits direct renoprotective effects and inhibits renal renin–angiotensin–aldosterone system in diabetic rats

Aldosterone itself has been reported to participate in mediating renal injury, and it was confirmed that the aldosterone synthase CYP11B2 gene, protein, and aldosterone production are locally present in the kidney. To test the hypothesis that a mineralocorticoid receptor antagonist might ameliorate diabetic nephropathy and the inhibition of renal CYP11B2 expression might be associated with these renoprotective effects, spironolactone (50 mg/kg/day) was administered by gavage to uninephrectomized diabetic rats for 3 weeks. Streptozotocin (55 mg/kg, i.v.) significantly increased urinary protein excretion and collagen deposition in glomerular and tubulointerstitial areas in the kidney, which were attenuated by spironolactone treatment. RT-PCR and Western blot analysis revealed that the expression of mRNA for collagen I/IV, transforming growth factor-β, NADPH oxidase and mineralocorticoid receptor and the mineralocorticoid receptor protein in the kidney was enhanced in the uninephrectomized diabetic rat kidney and that the overexpression of these molecules was suppressed by spironolactone. Renal angiotensin converting enzyme was activated and overexpressed in diabetic rats, and spironolactone inhibited these changes. We demonstrated that spironolactone prevented the streptozotocin-induced increase in the renal CYP11B2 mRNA content. Controlling blood glucose level with insulin also attenuated the renal expression of mRNA for CYP11B2. On the other hand, the treatment of spironolactone in the present study did not affect blood glucose level or blood pressure in uninephrectomized streptozotocin-induced diabetic rats. These results suggest that spironolactone exerted renoprotective effects in uninephrectomized streptozotocin-induced diabetic rats and inhibited local renin–angiotensin–aldosterone system, such as the ACE expression and the hyperglycemia-induced overexpression of CYP11B2, in the kidney.

Renal Response to Angiotensin II is Blunted in Sodium-sensitive Normotensive Men

In hypertension, sodium sensitivity (SS) of blood pressure is associated with renal hemodynamic abnormalities related to increased activity of the renal renin-angiotensin aldosterone system (RAAS). The renal mechanisms of SS in normotensives are unknown. Therefore, we studied whether SS is related to renal hemodynamics and renal responsiveness to angiotensin II (AngII) in young healthy adults. Blood pressure (mean arterial pressure (MAP)) and renal function were measured in 34 healthy men after 1-week low-sodium diet (LS; 50 mmol Na(+)/24 h), 1-week high-sodium diet (HS; 200 mmol Na(+)/24h), and 1-week HS-ACEi (enalapril 20 mg/day). The responses of effective renal plasma flow (ERPF; (131)I-Hippuran clearance) to graded infusion of AngII were assessed during each condition. The sodium-induced change in MAP ranged from -7 to +14 mm Hg. SS (a sodium-induced increase in MAP >3 mm Hg) was present in 13 subjects. ERPF was lower in SS subjects during LS and during HS-ACEi. The AngII-induced decrease in ERPF was blunted in SS on LS (-25 +/- 6 vs. -29 +/- 7% in sodium-resistant (SR) subjects, P < 0.05) and on HS (-30 +/- 5 vs. -35 +/- 6%, P < 0.05). The blunting was corrected by angiotensin-converting enzyme inhibitors (ACEi) (-36 +/- 6 vs. -37 +/- 7%). SS normotensive subjects have a blunted renal response to exogenous AngII. This is ameliorated by ACEi, supporting a role for inappropriately high intrarenal RAAS activity. As these findings cannot be attributed to subclinical renal hypertensive damage, high intrarenal RAAS activity and altered renal hemodynamics may be primary phenomena underlying SS.