Intrarenal Renin-angiotensin System Research Articles

Androgens, the kidney, and COVID-19: an opportunity for translational research.

Coronavirus disease 2019 (COVID-19) has reached pandemic proportions, affecting millions of people worldwide. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative agent of COVID-19. Epidemiological reports have shown that the severity of SARS-CoV-2 infection is associated with preexisting comorbidities such as hypertension, diabetes mellitus, cardiovascular diseases, and chronic kidney diseases, all of which are also risk factors for acute kidney injury (AKI). The kidney has emerged as a key organ affected by SARS-CoV-2. AKI is associated with increased morbidity and mortality in patients with COVID-19. Male sex is an independent predictor for AKI, and an increased death rate has been reported in male patients with COVID-19 worldwide. The mechanism(s) that mediate the sex discrepancy in mortality due to COVID-19 remain(s) unknown. Angiotensin-converting enzyme (ACE)2 is the receptor for SARS-CoV-2. Alterations in the ACE-to-ACE2 ratio have been implicated in renal diseases. This perspective aims to discuss data that suggest that androgens, via alterations in the intrarenal renin-angiotensin system, impair renal hemodynamics, predisposing patients to AKI during COVID-19 infection, which could explain the higher mortality observed in men with COVID-19. Clinicians should ensure early and effective cardiometabolic control for all patients to ameliorate the compensatory elevation of ACE2 and alterations in the ACE-to-ACE2 ratio. A better understanding of the role of androgens in SARS-CoV-2-associated AKI and mortality is imperative. The kidney could constitute a key organ that may explain the sex disparities of the higher mortality and worst outcomes associated with COVID-19 in men.

Urinary angiotensin converting enzyme 2 and disease activity in pediatric IgA nephropathy.

Background : Our previous studies demonstrated that the intrarenal renin-angiotensin system (RAS) status was activated in pediatric patients with chronic glomerulonephritis. In the present study, we tested the hypothesis that angiotensin-converting enzyme 2 (ACE2) expression in the kidney is associated with the development of pediatric IgA nephropathy. Methods : We analyzed urinary ACE2 levels and ACE2 expression in the kidney tissues of pediatric patients with IgA nephropathy treated with RAS blockade. Paired tests were used to analyze changes from the first to the second biopsy. Results : Urinary ACE2 levels were significantly decreased after RAS blockade treatment, accompanied by decreased ACE2 expression levels in kidney tissues, urinary protein levels and mesangial hypercellularity scores. Urinary ACE2 levels at the first biopsy were positively correlated with the ACE2 expression levels. Conclusions : These data suggest that urinary ACE2 is associated with ACE2 expression in the diseased kidney, which correlates with the pathogenesis of IgA nephropathy in pediatric patients. J. Med. Invest. 68 : 292-296, August, 2021.

Effect of Vitamin D on Urinary Angiotensinogen Level in Early Diabetic Nephropathy.

Background:Urinary angiotensinogen (UAGT) is supposed to be a marker of activation of the intrarenal renin– angiotensin system (RAS) system in early diabetic nnephropathy (EDN). Vitamin D has been studied as a negative regulator of the circulating and tissue RAS activity, so its supplementation may prevent the progression of diabetic nephropathy (DN). This study was planned to assess the RAS activation and effect of vitamin D supplementation in EDN progression by estimating the UAGT level.Methods:A total of 103 EDN subjects were randomized in two groups to receive either cholecalciferol (54) or matching placebo (49) in a double-blind manner. All were subjected to routine investigations, urinary albumin-to-creatinine ratio (UACR), UAGT, vitamin D, and intact parathyroid hormone (iPTH) at the 0 and 6 months. A total 40 healthy controls were also included for assessment of the same investigations at 0 month.Results:Significant reduction of UACR, UAGT, and iPTH level were corroborated with an increase in 25(OH) vitamin D level from 0 to 6 months (all four P < 0.001). After 6 months, the median [interquartile range (IQR)] of UAGT and UACR levels was significantly lower in the cholecalciferol group as compared to placebo group (p < 0.001 and P = 0.04, respectively). The median UAGT level was significantly higher in patients with EDN (cholecalciferol & placebo Group) than control group at 0 month (p = 0.001).Conclusion:Significantly higher UAGT levels in EDN supports the role of intrarenal RAS activation. A significant decrease in UAGT level in the cholecalciferol group supports the beneficial role of vitamin D supplementation in the progression of EDN.

Effect of sodium bicarbonate supplementation on the renin-angiotensin system in patients with chronic kidney disease and acidosis: a randomized clinical trial

BackgroundAcidosis-induced kidney injury is mediated by the intrarenal renin-angiotensin system, for which urinary renin is a potential marker. Therefore, we hypothesized that sodium bicarbonate supplementation reduces urinary renin excretion in patients with chronic kidney disease (CKD) and metabolic acidosis.MethodsPatients with CKD stage G4 and plasma bicarbonate 15–24 mmol/l were randomized to receive sodium bicarbonate (3 × 1000 mg/day, ~ 0.5 mEq/kg), sodium chloride (2 × 1,00 mg/day), or no treatment for 4 weeks (n = 15/arm). The effects on urinary renin excretion (primary outcome), other plasma and urine parameters of the renin-angiotensin system, endothelin-1, and proteinuria were analyzed.ResultsForty-five patients were included (62 ± 15 years, eGFR 21 ± 5 ml/min/1.73m2, plasma bicarbonate 21.7 ± 3.3 mmol/l). Sodium bicarbonate supplementation increased plasma bicarbonate (20.8 to 23.8 mmol/l) and reduced urinary ammonium excretion (15 to 8 mmol/day, both P < 0.05). Furthermore, a trend towards lower plasma aldosterone (291 to 204 ng/L, P = 0.07) and potassium (5.1 to 4.8 mmol/l, P = 0.06) was observed in patients receiving sodium bicarbonate. Sodium bicarbonate did not significantly change the urinary excretion of renin, angiotensinogen, aldosterone, endothelin-1, albumin, or α1-microglobulin. Sodium chloride supplementation reduced plasma renin (166 to 122 ng/L), and increased the urinary excretions of angiotensinogen, albumin, and α1-microglobulin (all P < 0.05).ConclusionsDespite correction of acidosis and reduction in urinary ammonium excretion, sodium bicarbonate supplementation did not improve urinary markers of the renin-angiotensin system, endothelin-1, or proteinuria. Possible explanations include bicarbonate dose, short treatment time, or the inability of urinary renin to reflect intrarenal renin-angiotensin system activity.Graphic abstract

High blood pressure induced by vitamin D deficiency is associated with renal overexpression and hyperphosphorylation of Na+-K+-2Cl- cotransporter type 2.

Clinical and epidemiological studies have suggested a correlation between vitamin D deficiency (VDD) and high blood pressure (BP). This study aimed to test the hypothesis that high BP induced by VDD is associated with altered expression and covalent modification of apical sodium transporters along the nephron. The contributions of the intrarenal renin-angiotensin system (RAS) and oxidative stress were also investigated. Male Wistar rats were fed a vitamin D-free (n = 26) or standard diet (n = 25) for 30 days. BP was recorded using noninvasive and invasive procedures. The expression levels of total and phosphorylated apical sodium transporters in rat renal cortex and medulla were evaluated by immunoblotting. Intrarenal RAS components were assessed by immunoblotting and ELISA. Renal oxidative stress was analyzed by measuring the concentrations of thiobarbituric acid reactive substances and reduced glutathione. Higher BP levels in VDD rats than controls were accompanied by overexpression and hyperphosphorylation of renal cortical and medullary Na+-K+-2Cl- cotransporter type 2, enhanced levels of phosphorylated Na+/H+ exchanger type 3, and reduced expression levels of total and phosphorylated Na+/Cl- cotransporter. Changes in intrarenal RAS induced by VDD vs. controls included the marked elevation of medullary renin expression, higher expression of cortical angiotensinogen, higher urinary angiotensinogen excretion, and higher cortical and medullary angiotensin II content. VDD rats displayed higher thiobarbituric acid reactive substances/glutathione ratios in the renal cortex and medulla than controls. These results suggest that the molecular mechanisms underlying the effects of VDD on BP may include the upregulation of Na+-K+-2Cl- cotransporter type 2 and activation of intrarenal RAS and oxidative stress.

Low Nitric Oxide Bioavailability Increases Renin Production in the Collecting Duct.

In the kidney, the stimulation of renin production by the collecting duct (CD-renin) contributes to the development of hypertension. The CD is a major nephron segment for the synthesis of nitric oxide (NO), and low NO bioavailability in the renal medulla is associated with hypertension. However, it is unknown whether NO regulates renin production in the CD. To test the hypothesis that low intrarenal NO levels stimulate the production of CD-renin, we first examined renin expression in the distal nephron segments of CD-eNOS deficient mice. In these mice, specific CD-renin immunoreactivity was increased compared to wild-type littermates; however, juxtaglomerular (JG) renin was not altered. To further assess the intracellular mechanisms involved, we then treated M-1 cells with either 1 mM L-NAME (L-arginine analog), an inhibitor of NO synthase activity, or 1 mM NONOate, a NO donor. Both treatments increased intracellular renin protein levels in M-1 cells. However, only the inhibition of NOS with L-NAME stimulated renin synthesis and secretion as reflected by the increase in Ren1C transcript and renin protein levels in the extracellular media, respectively. In addition, NONOate induced a fast mobilization of cGMP and intracellular renin accumulation. These response was partially prevented by guanylyl cyclase inhibition with ODQ (1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1]. Accumulation of intracellular renin was blocked by protein kinase G (PKG) and protein kinase C (PKC) inhibitors. Our data indicate that low NO bioavailability increases CD-renin synthesis and secretion, which may contribute to the activation of intrarenal renin angiotensin system.

Time Course Changes in Urinary Angiotensinogen and Circulating N-Terminal Pro-B-Type Natriuretic Peptide in Patients Hospitalized with Acute Heart Failure.

Objective Home care is important in patients with heart failure (HF) in order to maintain their quality of life. A biomarker that can be measured noninvasively is needed to optimize the home care of patients with HF. Urinary angiotensinogen (uAGT) is an indicator of the intrarenal renin-angiotensin system activity, which may be augmented in HF. We hypothesized that uAGT might be a urinary biomarker in HF. Methods We measured uAGT by an enzyme-linked immunosorbent assay and uAGT normalized by urinary creatinine (uCr)-designated uAGT/uCr-at admission and discharge in 45 patients hospitalized for HF. Results We found that both uAGT/uCr [median (interquartile range): 65.5 (17.1-127.7) μg/g Cr at admission; 12.1 (6.0-37.0) μg/g Cr at discharge; p<0.01] and N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels [5,422 (2,280-9,907) pg/mL at admission; 903 (510-1,729) pg/mL at discharge; p<0.01] significantly decreased between admission and discharge along with an improvement in patient's clinical status [New York Heart Association scores: 3 (3-4) at admission; 1 (1-1) at discharge; p<0.01]. The generalized least squares model revealed that the time course changes in uAGT/uCr also correlated with those in NT-proBNP levels between admission and readmission in five patients readmitted for HF. Conclusion The results indicated that the time course changes in uAGT/uCr correlated with those in the NT-proBNP levels in patients with HF who showed a clinical improvement. Further investigation and development of a kit for the rapid measurement of uAGT are needed to evaluate the clinical utility of uAGT as a biomarker in HF.

Effect of urinary angiotensinogen and high-salt diet on blood pressure in patients with chronic kidney disease: results from the Korean Cohort Study for Outcome in Patients with Chronic Kidney Disease (KNOW-CKD).

Background/AimsThis study aimed to investigate whether urinary angiotensinogen (UAGT) excretion was associated with elevated blood pressure in patients with chronic kidney disease (CKD) and to evaluate the relationship among blood pressure, intra-renal renin-angiotensin system (RAS) activity, and dietary sodium in patients with CKD.MethodsParticipants from the Korean Cohort Study for Outcome in Patients with Chronic Kidney Disease (KNOW-CKD) were included. Of the total cohort of 2,238 individuals with CKD, we included 1,955 participants who underwent complete 24-hour urinary sodium (24-hour UNa) analysis. They were categorized into three groups according to three tertiles of their 24-hour UNa, reflecting daily salt intake. To measure intra-renal RAS activity, the UAGT excretion was assayed with an enzyme-linked immunosorbent assay.ResultsElevated 24-hour UNa levels, logarithm of UAGT-to-creatinine ratio (UAGT/Cr), increased waist-to-hip ratio, and decreased estimated glomerular filtration rate were the risk factors for increased systolic blood pressure. Systolic blood pressure showed a positive correlation with 24-hour UNa levels and logarithm of UAGT/Cr.ConclusionsUAGT and urinary sodium excretion are independent determinants of systolic blood pressure in patients with CKD. These findings suggest that increased systolic blood pressure in CKD patients is associated with both increased dietary sodium levels and intra-renal RAS activity. The risk of elevated systolic blood pressure in the 3rd tertile of both the UAGT/Cr and 24-hour UNa groups was about 2.3 times higher than that in the reference group.

Maternal Adenine-Induced Chronic Kidney Disease Programs Hypertension in Adult Male Rat Offspring: Implications of Nitric Oxide and Gut Microbiome Derived Metabolites.

Maternal chronic kidney disease (CKD) during pregnancy causes adverse fetal programming. Nitric oxide (NO) deficiency, gut microbiota dysbiosis, and dysregulated renin-angiotensin system (RAS) during pregnancy are linked to the development of hypertension in adult offspring. We examined whether maternal adenine-induced CKD can program hypertension and kidney disease in adult male offspring. We also aimed to identify potential mechanisms, including alterations of gut microbiota composition, increased trimethylamine-N-oxide (TMAO), reduced NO bioavailability, and dysregulation of the RAS. To construct a maternal CKD model, female Sprague-Dawley rats received regular chow (control group) or chow supplemented with 0.5% adenine (CKD group) for 3 weeks before pregnancy. Mother rats were sacrificed on gestational day 21 to analyze placentas and fetuses. Male offspring (n = 8/group) were sacrificed at 12 weeks of age. Adenine-fed rats developed renal dysfunction, glomerular and tubulointerstitial damage, hypertension, placental abnormalities, and reduced fetal weights. Additionally, maternal adenine-induced CKD caused hypertension and renal hypertrophy in adult male offspring. These adverse pregnancy and offspring outcomes are associated with alterations of gut microbiota composition, increased uremic toxin asymmetric and symmetric dimethylarginine (ADMA and SDMA), increased microbiota-derived uremic toxin TMAO, reduced microbiota-derived metabolite acetate and butyrate levels, and dysregulation of the intrarenal RAS. Our results indicated that adenine-induced maternal CKD could be an appropriate model for studying uremia-related adverse pregnancy and offspring outcomes. Targeting NO pathway, microbiota metabolite TMAO, and the RAS might be potential therapeutic strategies to improve maternal CKD-induced adverse pregnancy and offspring outcomes.

Salt-sensitive hypertension in chronic kidney disease: distal tubular mechanisms.

Chronic kidney disease (CKD) causes salt-sensitive hypertension that is often resistant to treatment and contributes to the progression of kidney injury and cardiovascular disease. A better understanding of the mechanisms contributing to salt-sensitive hypertension in CKD is essential to improve these outcomes. This review critically explores these mechanisms by focusing on how CKD affects distal nephron Na+ reabsorption. CKD causes glomerulotubular imbalance with reduced proximal Na+ reabsorption and increased distal Na+ delivery and reabsorption. Aldosterone secretion further contributes to distal Na+ reabsorption in CKD and is not only mediated by renin and K+ but also by metabolic acidosis, endothelin-1, and vasopressin. CKD also activates the intrarenal renin-angiotensin system, generating intratubular angiotensin II to promote distal Na+ reabsorption. High dietary Na+ intake in CKD contributes to Na+ retention by aldosterone-independent activation of the mineralocorticoid receptor mediated through Rac1. High dietary Na+ also produces an inflammatory response mediated by T helper 17 cells and cytokines increasing distal Na+ transport. CKD is often accompanied by proteinuria, which contains plasmin capable of activating the epithelial Na+ channel. Thus, CKD causes both local and systemic changes that together promote distal nephron Na+ reabsorption and salt-sensitive hypertension. Future studies should address remaining knowledge gaps, including the relative contribution of each mechanism, the influence of sex, differences between stages and etiologies of CKD, and the clinical relevance of experimentally identified mechanisms. Several pathways offer opportunities for intervention, including with dietary Na+ reduction, distal diuretics, renin-angiotensin system inhibitors, mineralocorticoid receptor antagonists, and K+ or H+ binders.

The interaction partners of (pro)renin receptor in the distal nephron.

The (pro)renin receptor (PRR), a key regulator of intrarenal renin-angiotensin system (RAS), is predominantly presented in podocytes, proximal tubules, distal convoluted tubules, and the apical membrane of collecting duct A-type intercalated cells, and plays a crucial role in hypertension, cardiovascular disease, kidney disease, and fluid homeostasis. In addition to its well-known renin-regulatory function, increasing evidence suggests PRR can also act in a variety of intracellular signaling cascades independently of RAS in the renal medulla, including Wnt/β-catenin signaling, cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2 ) signaling, and the apelinergic system, and work as a component of the vacuolar H+ -ATPase. PRR and these pathways regulate the expression/activity of each other that controlling blood pressure and renal functions. In this review, we highlight recent findings regarding the antagonistic interaction between PRR and ELABELA/apelin, the mutually stimulatory relationship between PRR and COX-2/PGE2 or Wnt/β-catenin signaling in the renal medulla, and their involvement in the regulation of intrarenal RAS thereby control blood pressure, renal injury, and urine concentrating ability in health and patho-physiological conditions. We also highlight the latest progress in the involvement of PRR for the vacuolar H+ -ATPase activity.

Chronotherapy with a Renin-angiotensin System Inhibitor Ameliorates Renal Damage by Suppressing Intrarenal Renin-angiotensin System Activation.

Objective The intrarenal renin-angiotensin system (RAS) is activated in chronic kidney disease (CKD) patients and is not suppressed at night in CKD patients showing nocturnal hypertension, contributing to renal damage. Furthermore, changes in RAS inhibitor administration from morning to evening, namely chronotherapy, ameliorates renal damage at night. We attempted to clarify whether or not chronotherapy ameliorates renal damage by suppressing the intrarenal RAS activity. Methods We recruited 34 CKD patients with RAS inhibitors in the morning. We conducted ambulatory blood pressure (BP) monitoring and urine collection and evaluated urinary albumin (Alb) and angiotensinogen (AGT), which are surrogate markers for intrarenal RAS activity during the day and at night, respectively. The same experiments were conducted after changing the administration time. The ratio of values associated with morning versus evening dosing was defined as the morning to evening (M/E) ratio. Results The M/E ratio of urinary Alb had a significant and positive relationship with that of urinary AGT during the day and at night in all CKD patients. However, no significant relationships were found between the M/E ratios of urinary Alb and AGT using multiple linear regression analyses. Conversely, there was a significant and positive relationship between the M/E ratios of urinary Alb and AGT at night but not during the day in CKD patients whose estimated glomerular filtration rate was <45 mL/min/1.73 m2 and whose night-to-day ratio of systolic BP was >0.90, even after adjustment. Conclusion This study indicated that chronotherapy with RAS inhibitors improved the renal damage via intrarenal RAS suppression, especially in CKD patients with an impaired renal function and nocturnal hypertension.

Intrarenal Renin Angiotensin System Imbalance During Postnatal Life Is Associated With Increased Microvascular Density in the Mature Kidney.

Environmental stress during early life is an important factor that affects the postnatal renal development. We have previously shown that male rats exposed to maternal separation (MatSep), a model of early life stress, are normotensive but display a sex-specific reduced renal function and exacerbated angiotensin II (AngII)-mediated vascular responses as adults. Since optimal AngII levels during postnatal life are required for normal maturation of the kidney, this study was designed to investigate both short- and long-term effect of MatSep on (1) the renal vascular architecture and function, (2) the intrarenal renin-angiotensin system (RAS) components status, and (3) the genome-wide expression of genes in isolated renal vasculature. Renal tissue and plasma were collected from male rats at different postnatal days (P) for intrarenal RAS components mRNA and protein expression measurements at P2, 6, 10, 14, 21, and 90 and microCT analysis at P21 and 90. Although with similar body weight and renal mass trajectories from P2 to P90, MatSep rats displayed decreased renal filtration capacity at P90, while increased microvascular density at both P21 and P90 (p < 0.05). MatSep increased renal expression of renin, and angiotensin type 1 (AT1) and type 2 (AT2) receptors (p < 0.05), but reduced ACE2 mRNA expression and activity from P2-14 compared to controls. However, intrarenal levels of AngII peptide were reduced (p < 0.05) possible due to the increased degradation to AngIII by aminopeptidase A. In isolated renal vasculature from neonates, Enriched Biological Pathways functional clusters (EBPfc) from genes changed by MatSep reported to modulate extracellular structure organization, inflammation, and pro-angiogenic transcription factors. Our data suggest that male neonates exposed to MatSep could display permanent changes in the renal microvascular architecture in response to intrarenal RAS imbalance in the context of the atypical upregulation of angiogenic factors.

Endogenous Activation of Glucagon-Like Peptide-1 Receptor Contributes to Blood Pressure Control: Role of Proximal Tubule Na+/H+ Exchanger Isoform 3, Renal Angiotensin II, and Insulin Sensitivity.

The pharmacological administration of GLP-1R (glucagon-like peptide-1 receptor) agonists reduces blood pressure (BP) in type 2 diabetes mellitus and nondiabetic patients. This study tested the hypothesis that endogenous GLP-1R signaling influences the regulation of BP. To this end, SHRs (spontaneously hypertensive rats) and Wistar rats were treated with the GLP-1R antagonist Ex9 (exendin-9) or vehicle for 4 weeks. Rats receiving the GLP-1R agonist Ex4 (exenatide) were used as an additional control. We found that blockade of baseline GLP-1R signaling by Ex9 increased systolic BP in both SHR and Wistar rats, compared with vehicle-treated animals, while Ex4 only reduced systolic BP in SHR. Higher systolic BP induced by Ex9 was accompanied by reduced lithium clearance and lower levels of NHE3 (Na+/H+ exchanger isoform 3) phosphorylation at the serine 552, indicative of increased proximal tubule sodium reabsorption. Additionally, urinary AGT (angiotensinogen) and renal cortical concentration of Ang II (angiotensin II) were enhanced by Ex9. Conversely, Ex4 decreased both urinary AGT and cortical Ang II but exclusively in SHRs. Moreover, both SHR and Wistar rats treated with Ex9 displayed hyperinsulinemia as compared with vehicle-treated rats, whereas Ex4 reduced fasting insulin concentration in SHR. Collectively, these results suggest that endogenous GLP-1R signaling exerts a physiologically relevant effect on BP control, which may be attributable, in part, to its tonic actions on the proximal tubule NHE3-mediated sodium reabsorption, intrarenal renin-angiotensin system, and insulin sensitivity. The possible role of impaired GLP-1R signaling in the pathogenesis of hypertension warrants further investigation.

Abstract P031: Reduced Augmentation Of The Intrarenal Renin-angiotensin System (ras), Lower Systolic Blood Pressure, And Preserved Renal Function In Female Compared To Male Rats With Unilateral Renal Artery Stenosis

Despite growing evidence of sex differences in the progression of hypertension, there are no guidelines that differentiate treatment between men and women. Intrarenal renin-angiotensin system (RAS) activation and tissue injury in 2-kidney, 1-clip (2K1C) hypertensive rats have been characterized in previous studies of male but not female rats. To evaluate possible sex differences in response to renovascular hypertension, urinary angiotensinogen (uAGT) excretion, systolic blood pressure (BP), urinary protein excretion, and renal function were assessed in female rats.Female (n=8) and male (n=6) rats underwent placement of a 0.2 mm clip on the left renal artery to simulate unilateral renal artery stenosis. BP was measured by tail-cuff plethysmography, and clearance studies were conducted in anesthetized rats to assess renal function. Urine protein concentration was determined by pyrogallol red method. uAGT was measured by ELISA as an index of intrarenal RAS activity. Systolic BP increased from 120±1 to 176±8 mmHg, and urinary protein excretion reached 20.2±5.6 mg/day in female rats. Although uAGT excretion increased from 13.2±7.7 ng/day to 74.1±29.9 ng/day in female rats, male rats had a significantly higher uAGT excretion of 1572.6±750 ng/day. Nonclipped kidneys exhibited more uAGT excretion compared to clipped kidneys, consistent with previous findings in males. Although 2K1C female rats demonstrate significantly lower renal function than sham females, they show more preserved renal function than male rats. Female rats also demonstrate significantly lower increases in systolic BP and urinary protein excretion compared to male rats. The data support substantial sex-dependent differences in renal responses to unilateral renal artery stenosis. The results show substantial increases in systolic BP, uAGT, and urinary protein excretion and decreased renal function after renal artery clipping in females, but the magnitude of the changes is markedly lower than in males. Nonclipped kidneys of both sexes exhibit greater uAGT excretion than clipped kidneys. Notably, females show less augmentation of the intrarenal RAS compared to male rats in renovascular hypertension.

Abstract P033: PRESSOR, NATRIURETIC, AND RENAL RESPONSES IN ANGIOTENSIN II-INDUCED HYPERTENSION IN MALE AND FEMALE WILD-TYPE AND PROXIMAL TUBULE-SPECIFIC AT 1A RECEPTOR KNOCKOUT MICE

Dysregulation of intrarenal renin-angiotensin system is one of the key factors of human hypertension, but the mechanisms involved remain incompletely understood. To determine the roles of AT 1a receptors in the proximal tubules of the kidney, we infused angiotensin II (Ang II) for 2 weeks (40 ng / min, i.p.) in adult male and female wild-type C57BL/6J and mutant mice with deletion of AT 1a receptors in the proximal tubules (PT- Agtr1a -/- ), and treated with or without the AT 1 receptor blocker losartan (20 mg/kg/day, p.o.) (n=8 per group). The pressor response, 24 h urinary Na + excretion, glomerular and tubulointerstitial injury were compared between male and female wild-type and PT- Agtr1a -/- mice. Basal systolic, diastolic, and mean arterial blood pressure were about 13 ± 3 mmHg lower in male and female PT- Agtr1a -/- mice ( P &lt;0.01), but no differences were observed between male and female wild-type or PT- Agtr1a -/- mice. In response to Ang II, both male and female wild-type and PT- Agtr1a -/- mice developed hypertension ( P &lt;0.01), and the net pressor response were similar in male and female wild-type and PT- Agtr1a -/- mice (n.s.). However, absolute blood pressure was about 12 ± 3 mmHg lower in male and female PT- Agtr1a -/- mice ( P &lt;0.01 vs. wild-type). Ang II-induced hypertension increased the natriuretic response in both male and female wild-type and PT- Agtr1a -/- mice ( P &lt;0.01), but there were no significant differences between male and female wild-type and PT- Agtr1a -/- mice (n.s). Losartan did not increase the natriuretic responses further in all animals. Furthermore, Ang II-induced hypertension was associated with significant increases in glomerular and tubulointerstitial injury in male and female wild-type mice ( P &lt;0.01), which were attenuated in male and female PT- Agtr1a -/- mice ( P &lt;0.01). LOS treatment attenuated Ang II-induced hypertension and decreased Ang II-induced glomerular and tubulointerstitial injury in male and female wild-type and PT- Agtr1a -/- mice ( P &lt;0.01). Taken together, we demonstrated that intratubular AT 1 (AT 1a ) receptors in the proximal tubules of the kidney plays a key role in maintaining basal blood pressure homeostasis and overall body salt and fluid balance, and the development of Ang II-induced hypertension and kidney injury.

(Pro)renin receptor decoy peptide PRO20 protects against adriamycin-induced nephropathy by targeting the intrarenal renin-angiotensin system.

Adriamycin (ADR) administration in susceptible rodents such as the BALB/c mouse strain produces injury to the glomerulus mimicking human chronic kidney disease due to primary focal segmental glomerulosclerosis. The goal of the present study was to use this model to investigate antiproteinuric actions of the (pro)renin receptor decoy inhibitor PRO20. BALB/c mice were pretreated for 1 day with PRO20 at 500 μg·kg-1·day-1 via an osmotic minipump followed by a single injection of vehicle or ADR (10 mg/kg) via the tail vein. Albuminuria and renal function were analyzed at the fourth week post-ADR administration. ADR-treated mice exhibited severe proteinuria, hypoalbuminemia and hyperlipidemia, glomerulosclerosis, podocyte loss, tubulointerstitial fibrosis, and oxidative stress, accompanied by elevated urinary neutrophil gelatinase-associated lipocalin and kidney injury molecule-1, all of which were significantly attenuated by PRO20. Urinary and renal renin activity and angiotensin II were elevated by ADR and suppressed by PRO20. In parallel, urinary and renal H2O2 levels and renal NADPH oxidase 4 (Nox4) and transient receptor potential channel C6 (TRPC6) expression in response to ADR were all similarly suppressed. Taken together, the results of the present study provide the first evidence that PRO20 can protect against podocyte damage and interstitial fibrosis in ADR nephropathy by preventing activation of the intrarenal renin-angiotensin system and upregulation of Nox4 and TRPC6 expression. PRO20 may have a potential application in the treatment of ADR nephropathy.

P1002EFFECT OF VITAMIN D ON URINARY ANGIOTENSIOGEN LEVEL IN EARLY DIABETIC NEPHROPATHY

Abstract Background and Aims UrinaryAngiotensinogen (UAGT) is supposed to be a marker of activation of intrarenalreninangiotensin system (RAS) system in early Diabetic Nephropathy (DN). Vitamin D has been studied as a negative regulator of the circulating and tissue RAS activity; so its supplementation may prevent progression of DN. This study was planned to assess the RAS activation and effect of vitamin D supplementation in early diabetic nephropathy progression by estimatingUAGT level. Method A total of 730 Diabetic subjects were screened for early DN based on Inclusion criteria(eGFR ≥ 120ml/min/1.73m2 with unrestricted ACR value eGFR of 60- 120 mL/min/1.73m2 and ACR 30-300mg) and Exclusion criteria(on ACE I or ARB, eGFR&amp;lt;60ml/min/1.73m2, Hypercalcemia (&amp;gt;11.5mg%), UTI, Pregnancy, Hypertension, HbA1c (&amp;gt;8.0 %), vitamin D supplementation during the last 6 month).Of them 103 included subjects were underwent randomization to receive either Cholecalciferol(54) or matching Placebo(49) in a double blind method. All were subjected to routine investigations, urinary albumin: creatinine (UACR), UAGT, serum 25(OH)vitamin D, and intact parathyroid hormone (iPTH) at the zero and six months. A total 40 healthy controls without any comorbidity were also includedfor assessment of same investigations at zero month. Comparative results at zero months of all three groups were analyzed. Results The change in levels of UACR (mg/g), UAGT (ng/ml), vitamin D (ng/ml) and iPTH(pg/ml)in Cholecalciferol group from zero to six month were [Median (IQR)] : 12.50 (-24.82 to -5.95); p&amp;lt;0.001, -6.60 (-20.91 to -2.63);p&amp;lt;0.001, 5.75 (2.07-9.70); p&amp;lt;0.001, -5.35 (-11.55 to -3.67) ;p&amp;lt;0.001, respectively. After six months, median (IQR) of UAGT and UACR levels were significantly lower in the Cholecalciferol group as compared to Placebo group (p&amp;lt;0.001 and p= 0.04 respectively).Significant reduction of UACR (mg/g) and UAGT (ng/ml) level corroborating with increase in 25(OH) vitamin D(ng/ml) levelfrom zero to six months (all three p&amp;lt;0.001). There was significant correlation of vitamin D3 level with UAGT (r value: -0.255 &amp; p value: 0.009) and UACR level (r value: -0.28&amp; p value: &amp;lt;0.01). The median UAGT level was significantly higher in patients with early DN (Cholecalciferol&amp;Placebo Group) than Control Group at zero month (p =0.001). Conclusion Significantly higher UAGT levels in early DN supports role of intrarenal RAS activation. Significant decrease in UAGT level in cholecalciferol group supports beneficial role of vitamin D supplementation in progression of early DN.

Intrarenal renin-angiotensin system in hypertensive patients with localized kidney cancer.

e17069 Background: In the last decade, the relationship between arterial hypertension and the risk of developing kidney cancer has been pointed out. Some studies have shown that the metabolic imbalance of the components of the renal renin-angiotensin system (RAS) is associated with the development and progression of kidney cancer. Aim: To study the state of RAS in tumor and peritumoral tissues in hypertensive patients with kidney cancer. Methods: In patients with localized kidney cancer T1N0M0 and grade I-II arterial hypertension without special treatment (n = 40; KC + AH) in the samples of tumor (TT), peritumoral (PTT) and histologically unchanged tissue (HUT), the levels of angiotensin 1 and 2, 1-7 (AT1 and AT2, AT (1-7)) of angiotensin-converting enzymes (ACE and ACE2) were determined by ELISA. The comparison group consisted of patients with RC without impaired blood pressure (n = 55, KC). Results: In patients with KC, the level of AT1 is 1.5 times higher (p &lt; 0.05), and AT2 is 1.6 times higher (p &lt; 0.05) in TT against the background of unchanged content in PTT compared with HUT. The level of ACE is higher than HUT by 2.7 times, ACE2 - by 1.6 times (in all cases p &lt; 0.05), and in PTT it is identical in HUT. In patients with KC + AH, the level of AT1 and AT2 in the TT is 1.8 times higher (p &lt; 0.05) and 2.1 times (p &lt; 0.01), respectively, the content of AT(1-7) is 1.6 times (p &lt; 0.01). In PTT, AT1 is 1.6 times higher (p &lt; 0.01) and AT2 is 1.9 times higher (p &lt; 0.05), significantly lower than only AT2 in the TT (1.2 times at p &lt; 0, 05). The level of AT(1-7) in the PTT is identical to the values in the GNT. The content of ACE and ACE2 in TT is 3.6 and 2.9 times higher, respectively, and in PTT is identical to that in TT. Correlation analysis revealed a reliable direct relationship in the studied groups for all parameters, while in the PTT of hypertensive patients, the relationship between the average blood pressure and the RAS peptide content had a higher tightness. Conclusions: An increase in the levels of angiotensin 1 and 2, angiotensin-converting enzymes ACE and ACE2 in the tumor tissues and peritumoral tissue in patients with localized kidney cancer, regardless of the presence of arterial hypertension at initially higher values in hypertensive patients, was shown. The presence of arterial hypertension in patients with KC changes the metabolism of local RAS in peritumoral tissue and is associated with an increase in the correlation between changes in the components of RAS and arterial hypertension.

Maternal high-fructose intake induces hypertension through activating histone codes on the (pro)renin receptor promoter

High-fructose intake induces hypertension via the renal expression of (pro)renin receptor (PRR) that stimulates the expression of sodium/hydrogen exchanger 3, Na/K/2Cl cotransporter 2, and genes of the intrarenal renin-angiotensin system. We hypothesize that maternal high-fructose intake induces hypertension in subsequent generation offspring through activating histone codes on the PRR promoter.Mice dams were offered 20% fructose solution during pregnancy and lactation, while the subsequent 1st to 4th generation offspring were raised without fructose. Blood pressure was measured via tail-cuff method. The mRNA and protein expression were determined using quantitative real-time polymerase chain reaction and western blotting, respectively. Histone modification was evaluated using a chromatin immunoprecipitation assay.Maternal high-fructose intake statistically significantly increased blood pressure in the 1st and 2nd generations of offspring compared to the control group. Expression levels of sodium transporters and PRR were increased in the kidneys of the 1st to 3rd generation offspring. Increased enrichment of active histone codes such as H3Ac and H3K4me2 but decreased enrichment of repressive histone codes such as H3K9me3 and H3K27me3 on the PRR promoter were observed in the 1st to 3rd not the 4th generation. Moreover, there was increased the mRNA expression for histone acetyltransferase and methyl transferases for H3K4 in the 1st and 2nd generation offspring compared to the control group.This study implicates that maternal high-fructose intake induces hypertension in multigenerational offspring through activating histone codes on the PRR promoter.