Renal Angiotensin Research Articles

Cardiovascular effect of inflammation and nonsteroidal anti-inflammatory drugs on renin-angiotensin system in experimental arthritis.

A co-morbidity of inflammatory conditions is increased cardio-renal risks. Additionally, nonsteroidal anti-inflammatory drugs (NSAIDs) which are used to treat pain and inflammation are also associated with increase in such risks. We hypothesized that inflammation and NSAIDs impose the cardio-renal risk through the activation of the renin-angiotensin-system (RAS), a regulating pathway of the renal and cardiovascular homeostasis. We investigated the effect of adjuvant arthritis and NSAIDs on the RAS. Western blotting and ELISA were used to measure the RAS components. Inflammation caused significant imbalances in the cardiac and renal angiotensin converting enzymes, their biologically active angiotensin peptides (AngII and Ang1-7) and the target proteins involved in the peptide-receptor binding (AngII type 1 and type 2, and Ang1-7 receptor, Mas) toward cardio-renal toxicity. However, 7days treatment of arthritic animals with NSAIDs (rofecoxib, meloxicam, celecoxib and flurbiprofen) restored the constitutive balances, perhaps due to their anti-inflammatory properties. Inflammation exerts its cardio-renal effects by causing imbalance in the RAS. NSAIDs through their anti-inflammatory effect restore this imbalance. Thus, mechanisms other than imbalances in the RAS may be involved in the NSAIDs cardiotoxicity.

Does Androgen Withdrawal Reverse the Deleterious Cardiometabolic Effects Triggered by Hyperandrogenemia in PCOS?

IntroductionPolycystic Ovary Syndrome (PCOS), the most common endocrine disorder in young women, is characterized by hyperandrogenemia and ovarian dysfunction. PCOS is also frequently associated with increased incidence of cardiometabolic risk factors such as obesity, insulin resistance and hypertension. Several lines of evidence indicate that there is a positive association between circulating levels of androgens, obesity, insulin resistance and blood pressure (BP) in PCOS. We have previously reported that exposure of female rats to dihydrotestosterone (DHT) before puberty resembles many characteristics found in PCOS women: increase in food intake, body weight, fat/lean mass, BP and renal injury. The DHT‐mediated increase in BP was associated with activation of renal renin angiotensin system (RAS). In the present study, we tested the hypothesis that androgen withdrawal reverses the deleterious cardiometabolic effects triggered by hyperandrogenemia in PCOS.MethodsFemale SD rats, 4 wks. old, were randomized to DHT (7.5 mg/90 days) or placebo (n=10/grp). After 6 months, DHT pellets were discontinued (Ex‐DHT). During additional 6 months food intake, body weight and body composition (Echo‐MRI), insulin resistance (area under the curve (AUC) during oral glucose tolerance test) and QUICKI test (log of fasting glucose and insulin) were analyzed. At 12 months, mean arterial blood pressure (MAP), baseline and after administration of enalapril (RAS blocker, at 250 mg/L, drinking water), was measured by radiotelemetry for 5 days. At the end of the study: insulin, leptin, adiponectin, androgens, estrone and estradiol were measured by RIA and MS/MS. Renal gene expression of androgen receptor and RAS's components were quantified by qRT‐PCR.ResultsAfter 6 months DHT withdrawal, body weight (330 ± 9 vs. 265 ± 4 g, p<0.001), fat mass (44.60 ± 4.1 vs. 26.6 ± 1.5 g, p<0.001), lean mass (269.7 ± 6.6 vs. 222.1 ± 4.9 g, p<0.0001) and food intake were significantly higher in Ex‐DHT female rats. Fasting plasma insulin (29.8 ± 1.7 vs. 19.7±2.2 μIU/mL, p<0.05), leptin (1,917 ± 445 vs. 837 ± 100 pg/mL, p<0.05) and adiponectin (24.9 ± 1.5 vs. 20.2 ± 1.3 ng/mL, p<0.05) were increased in Ex‐DHT. AUC and QUICKI test were significantly higher in Ex‐DHT indicating insulin resistance. Plasma DHT (72.6 ± 5.0 vs. 105.4 ± 6.9 pg/mL, p<0.001) and testosterone (3.6 ± 0.2 vs. 5.9 ± 0.5 ng/dL, p<0.001) were decreased in Ex‐DHT. MAP was significantly higher in Ex‐DHT than placebo (122 ± 1 vs. 110 ± 1 mm Hg, p<0.001). Enalapril normalized MAP in Ex‐DHT rats. Renal injury, glomerular sclerosis were significantly higher in Ex‐DHT rats, and renal expression (qRT‐PCR) of androgen receptor, angiotensinogen and AT‐1 receptor were upregulated.In summary, despite normalization of hyperandrogenemia in PCOS, females still exhibit profound irreversible negative cardiometabolic effects previously triggered by androgens. Activation of renal RAS that persist after DHT withdrawal plays a major role in PCOS hypertension. These irreversible deleterious effects may be related to the renal androgen receptor upregulation.

PDI via Keap1/Nrf2 pathway Regulates Redox Balance, Renal AT1 Receptor Function and Blood Pressure

Oxidative stress is reported to play a vital role in the regulation of renal angiotensin AT1 receptor (AT1R) function and blood pressure (BP). This indicates that redox balance is crucial for normal AT1R function and BP. We tested a hypothesis that Protein Disulfide Isomerase (PDI), an enzyme that has diverse biological activity, via Keap1/Nrf2 pathway, regulates cellular redox homeostasis, AT1R function and blood pressure. To test the hypothesis, we treated adult Sprague Dawley (SD) rats with bacitracin, a PDI inhibitor for 14 days and determined various parameters. We found that bacitracin treated compared to vehicle treated rats, showed higher blood pressure. This was associated with greater diuresis and natriursis in response to AT1R blocker candesartan in bacitracin treated rats, indicating higher AT1R function in these rats. Moreover, bacitracin treated rats had higher oxidative stress and renal injury, as determined by measuring oxidative stress markers: urinary 8‐isoprostane, renal protein carbonyls and renal nitrotyrosine levels as well as urinary kidney injury molecule‐1 levels, respectively. This was associated with reduced antioxidant capacity and impaired Nrf2 transcription factor activity, involved in maintaining antioxidant capacity. Further, Kelch like ECH associated protein 1 (keap1) levels, an endogenous repressor of Nrf2, and tyrosine 216 phosphorylated GSK3β protein, which causes Nrf2 nuclear export were higher in bacitracin treated rats. Moreover, Nuclear Nrf2 levels in human kidney 2 cells treated with bacitracin also decreased compared to control cells. These data suggest that PDI via keap1/Nrf2 pathway regulates redox balance, AT1R function and BP in SD rats.Support or Funding InformationNIH/NIA, AG039856

Ovine uterine space restriction causes dysregulation of the renin–angiotensin system in fetal kidneys<sup><xref ref-type="fn" rid="afn1">†</xref></sup>

: To test the hypothesis that ovine USR is associated with dysregulation of the fetal renal RAS. : Multiparous pregnant ewes (n = 32), 16 with surgical bifurcated disconnection of one uterine horn to further reduce placental attachment sites, were studied. USR (n = 31) ovine fetuses were compared to nonspace restricted (NSR) singleton controls (n = 22) on gestational day (GD) 120 or GD130, term GD147. Fetal plasma was collected to evaluate plasma renin activity and iron indices. Fetal kidney AT 1 R, AT 2 R, and MASR proteins were assessed by Western immunoblotting and immunohistochemistry. : AT 1 R, AT 2 R, and MASR protein expression was higher in USR at GD130 than aged-matched NSR and USR at GD120, ( P < 0.05 all). AT 1 R and AT 2 R localization was homogenous throughout proximal and distal tubules in both USR and NSR at both gestational dates. MASR localization was punctate throughout renal cortical structures including tubules and glomeruli in both USR and NSR, shifted to intranuclear at GD130. Plasma renin activity was inversely related to plasma osmolarity ( P < 0.02) and was downregulated in USR at GD130 ( P < 0.05). : By late gestation, USR upregulated renal angiotensin receptor expression, an effect with potential functional implications.

Activation of Renal (Pro)Renin Receptor Contributes to High Fructose-Induced Salt Sensitivity.

A high-fructose diet is shown to induce salt-sensitive hypertension, but the underlying mechanism largely remains unknown. The major goal of the present study was to test the role of renal (pro)renin receptor (PRR) in this model. In Sprague-Dawley rats, high-fructose intake increased renal expression of full-length PRR, which were attenuated by allopurinol. High-fructose intake also upregulated renal mRNA and protein expression of sodium/hydrogen exchanger 3 and Na/K/2Cl cotransporter, as well as in vivo Na/K/2Cl cotransporter activity, all of which were nearly completely blocked by a PRR decoy inhibitor PRO20 or allopurinol treatment. Parallel changes were observed for indices of intrarenal renin-angiotensin-system including renal and urinary renin and angiotensin II levels. Radiotelemetry demonstrated that high-fructose or a high-salt diet alone did not affect mean arterial pressure, but the combination of the 2 maneuvers induced a ≈10-mm Hg increase of mean arterial pressure, which was blunted by PRO20 or allopurinol treatment. In cultured human kidney 2 cells, both fructose and uric acid increased protein expression of soluble PRR in a time- and dose-dependent manner; fructose-induced PRR upregulation was inhibited by allopurinol. Taken together, our data suggest that fructose via uric acid stimulates renal expression of PRR/soluble PRR that stimulate sodium/hydrogen exchanger 3 and Na/K/2Cl cotransporter expression and intrarenal renin-angiotensin system to induce salt-sensitive hypertension.

Renal tubular angiotensin converting enzyme is responsible for nitro-L-arginine methyl ester (L-NAME)-induced salt sensitivity

Renal parenchymal injury predisposes to salt-sensitive hypertension, but how this occurs is not known. Here we tested whether renal tubular angiotensin converting enzyme (ACE), the main site of kidney ACE expression, iscentral to the development of salt sensitivity in this setting. Two mouse models were used: it-ACE mice in whichACE expression is selectively eliminated from renal tubular epithelial cells; and ACE 3/9 mice, a compound heterozygous mouse model that makes ACE only in renal tubular epithelium from the ACE 9 allele, and in liver hepatocytes from the ACE 3 allele. Salt sensitivity was induced using a post L-NAME salt challenge. While bothwild-type and ACE 3/9 mice developed arterial hypertension following three weeks of high salt administration, it-ACE mice remained normotensive with low levels of renal angiotensin II. These mice displayed increased sodium excretion, lower sodium accumulation, and an exaggerated reduction in distal sodium transporters. Thus, in mice with renal injury induced by L-NAME pretreatment, renal tubular epithelial ACE, and not ACE expression by renal endothelium, lung, brain, or plasma, isessential for renal angiotensin II accumulation and salt-sensitive hypertension.

Klotho suppresses the renin-angiotensin system in adriamycin nephropathy.

Klotho protein interacts with the transforming growth factor β (TGF-β) receptor and Wnt, which contribute to the progression of renal disease, inhibiting their signals. Renal and circulating klotho levels are diminished in chronic kidney disease. Experiments were performed to assess whether supplementation of klotho protein could have protective effects on the kidney. Rats were injected with adriamycin (5 mg/kg) and divided into three groups: those treated with vehicle, those treated with klotho protein and those treated with klotho plus 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD). Rats without adriamycin treatment were used as a control. Adriamycin reduced the serum klotho concentration and renal expression of klotho and E-cadherin. Adriamycin also increased the renal expression of Wnt, TGF-β, and angiotensinogen, as well as the renal abundance of β-catenin and angiotensin II. Klotho supplementation suppressed adriamycin-induced elevations of β-catenin and angiotensin II with sustained Wnt expression. Combined treatment with klotho and TDZD reversed the klotho-induced improvements in the renal abundance of β-catenin and angiotensin II as well as the expression of TGF-β and angiotensinogen without affecting E-cadherin. Our data indicate that Wnt is involved in the pathogenesis of adriamycin nephropathy. Furthermore, klotho supplementation inhibited Wnt signaling, ameliorating renal angiotensin II. Finally, klotho protein appears to suppress epithelial-mesenchymal transition by inhibiting TGF-β and Wnt signaling.

Downregulation of angiotensin type 1 receptor and nuclear factor-κB by sirtuin 1 contributes to renoprotection in unilateral ureteral obstruction.

Activation of sirtuin 1 (Sirt1) attenuates unilateral ureteral obstruction (UUO)-induced inflammation and fibrosis, suggesting that Sirt1 may prevent tubulointerstitial fibrosis. In this study, we explored changes in the expression of Sirt1 in the kidneys of UUO-treated rats and evaluated the effects of Sirt1 activation or inhibition on renal pathology and mediators of UUO pathogenesis, especially angiotensin II and nuclear factor (NF)-κB, in rats and rat renal fibroblasts. Sirt1 expression increased in the obstructed kidney but not in the contralateral kidney and was mainly detected in tubulointerstitial cells. Resveratrol, a Sirt1 activator, decreased UUO-induced inflammation and fibrosis, while sirtinol, a Sirt1 inhibitor, enhanced UUO-induced inflammation. UUO increased renal angiotensin type 1 receptor (AT1R), NF-κB, monocyte chemotactic protein 1 (MCP-1), and fibronectin expression. Resveratrol attenuated these UUO-induced changes, whereas sirtinol enhanced them, with the exception of fibronectin. In renal fibroblasts, Sirt1 overexpression reduced AT1R and NF-κB levels, while Sirt1 knockdown had the opposite effects. Sirtinol increased the levels of AT1R, NF-κB, MCP-1, and connective tissue growth factor (CTGF), while resveratrol reduced AT1R levels. Our results suggested that Sirt1 inhibited AT1R and NF-κB expression in renal fibroblasts and that these mechanisms may play roles in alleviating UUO-induced damages.

High and Low Salt Intake during Pregnancy: Impact on Cardiac and Renal Structure in Newborns.

IntroductionPrevious studies from our laboratory demonstrated that dietary salt overload and salt restriction during pregnancy were associated with cardiac and renal structural and/or functional alterations in adult offspring. The present study evaluated renal and cardiac structure and the local renin-angiotensin system in newborns from dams fed high-, normal- or low-salt diets during pregnancy.MethodsFemale Wistar rats were fed low- (LS, 0.15% NaCl), normal- (NS, 1.3% NaCl) or high- (HS, 8% NaCl) salt diets during pregnancy. Kidneys and hearts were collected from newborns (n = 6-8/group) during the first 24 hours after birth to evaluate possible changes in structure using stereology. Protein expression of renin-angiotensin system components was evaluated using an indirect enzyme-linked immunosorbent assay (ELISA).ResultsNo differences between groups were observed in total renal volume, volume of renal compartments or number of glomeruli. The transverse diameter of the nuclei of cardiomyocytes was greater in HS than NS males in the left and right ventricles. Protein expression of the AT1 receptor was lower in the kidneys of the LS than in those of the NS and HS males but not females. Protein expression of the AT2 receptor was lower in the kidneys of the LS males and females than in those of the NS males and females.ConclusionHigh salt intake during pregnancy induced left and right ventricular hypertrophy in male newborns. Salt restriction during pregnancy reduced the expression of renal angiotensin II receptors in newborns.

The effects and mechanisms of benazepril and losartan on glomerular podocyte autophagy in aged spontaneously hypertensive rats

Objective To examine the effects of benazepril and losartan on glomerular podocyte autophagy in aged spontaneously hypertensive rats (SHRs) and investigate the underlying mechanisms of renal-protective effects of angiotensin-converting enzyme inhibitors (ACEI)/angiotensin receptor blockers (ARB). Methods Wistar-Kyoto rats (WKYs) were used as the normal control (NORM) group (2 ml physiological saline per day). SHRs were randomly divided into 4 groups: the CTRL group (2 ml physiological saline per day), the ACEI group (10 mg·kg-1·d-1), the ARB group (30 mg·kg-1·d-1) and the combined group (10 mg·kg-1·d-1 benazepril and 30 mg·kg-1·d-1), with six 18-month-old male rats in each group. The experiments were conducted during a 4-month period. Blood pressure was monitored regularly. At the end of the experiments, we measured the levels of urine protein, urine creatinine, serum creatinine (SCR), blood urea nitrogen (BUN), and serum and renal cortex angiotensin Ⅱ (AngII). Ultrastructural changes in the kidney were examined under light and transmission electron microscopy. The expressions of nephrin, LC3BII, Atg5 and p62 in the glomerulus were analyzed by Western blot analysis. Results After treatment, the blood pressure and the urine albumin/creatinine ratio of the four SHR groups were still significantly higher than those of the NORM group, but the blood pressure and the urine albumin/creatinine ratio of the ARB group and the combined group were significantly lower than those of the CTRL group (all P 0.05); The level of serum AngII of the combined group was significantly higher than that of the CTRL group 〔CTRL (0.08±0.00) μg/L, Combined (0.12±0.01) μg/L, P<0.05〕; The levels of cortex AngII of the four SHR groups were significantly lower than those of the NORM group, while the level of cortex AngII of the ARB group was significantly higher than that of the CTRL group (all P<0.05); Renal ultrastructural examination revealed shrunken glomeruli, fused or effaced epithelial cell foot processes, and focal atrophy of renal tubules in the four SHR groups. These pathological changes were more serious in the CTRL group but less so in the combined group. There were significantly more autophagosomes in the NORM group and the combined group than in the CTRL group (P<0.05). Compared with the NORM group, the expressions of nephrin, LC3BII, Atg5 and p62 in the CTRL group were suppressed significantly (P<0.05). The expressions of nephrin, LC3BII and Atg5 in the ACEI group and the expressions of nephrin, LC3BII, Atg5 and p62 in the ARB group and the combined group were higher than in the CTRL group (P<0.05). Conclusions ACEI/ARB can decrease the autophagic activity of glomerular podocytes. The renal-protective effects of ACEI/ARB may be mediated by glomerular podocyte autophagy, which is induced by AngII. Key words: Hypertension; Podocytes; Autophagy; Angiotensin-converting enzyme inhibitor; Angiotensin receptor antagonist

Low dose ouabain stimulates Na[sbnd]K ATPase α1 subunit association with angiotensin II type 1 receptor in renal proximal tubule cells

Our laboratory has recently demonstrated that low concentrations of ouabain increase blood pressure in rats associated with stimulation of NaK ATPase activity and activation of the Src signaling cascade in NHE1-dependent manner. Proteomic analysis of human kidney proximal tubule cells (HKC11) suggested that the Angiotensin II type 1 receptor (AT1R) as an ouabain-associating protein. We hypothesize that ouabain-induced stimulation of NaK ATPase activity is mediated through AT1R. To test this hypothesis, we examined the effect of ouabain on renal cell angiotensin II production, the effect of AT1R inhibition on ouabain-stimulated NKA activity, and the effect of ouabain on NKA-AT1R association. Ouabain increased plasma angiotensin II levels in rats treated with ouabain (1μg/kg body wt./day) for 9days and increased angiotensin II levels in cell culture media after 24h treatment with ouabain in human (HKC11), mouse (MRPT), and human adrenal cells. Ouabain 10pM stimulated NKA-mediated 86Rb uptake and phosphorylation of EGFR, Src, and ERK1/2. These effects were prevented by the AT1R receptor blocker candesartan. FRET and TIRF microscopy using Bodipy-labeled ouabain and mCherry-NKA or mCherry-AT1R demonstrated association of ouabain with AT1R and NKA. Further our FRET and TIRF studies demonstrated increased association between AT1R and NKA upon treatment with low dose ouabain. We conclude that ouabain stimulates NKA in renal proximal tubule cells through an angiotensin/AT1R-dependent mechanism and that this pathway contributes to cardiac glycoside associated hypertension.

20-Hydroxyeicosatetraenoic Acid (HETE)-dependent Hypertension in Human Cytochrome P450 (CYP) 4A11 Transgenic Mice

Male and female homozygous 129/Sv mice carrying four copies of the human cytochrome P450 4A11 gene (CYP4A11) under control of its native promoter (B-129/Sv-4A11(+/+)) develop hypertension (142 ± 8 versus 113 ± 7 mm Hg systolic blood pressure (BP)), and exhibit increased 20-hydroxyeicosatetraenoic acid (20-HETE) in kidney and urine. The hypertension is reversible by a low-sodium diet and by the CYP4A inhibitor HET0016. B-129/Sv-4A11(+/+) mice display an 18% increase of plasma potassium (p < 0.02), but plasma aldosterone, angiotensin II (ANGII), and renin activities are unchanged. This phenotype resembles human genetic disorders with elevated activity of the sodium chloride co-transporter (NCC) and, accordingly, NCC abundance is increased by 50% in transgenic mice, and NCC levels are normalized by HET0016. ANGII is known to increase NCC abundance, and renal mRNA levels of its precursor angiotensinogen are increased 2-fold in B-129/Sv-4A11(+/+), and blockade of the ANGII receptor type 1 with losartan normalizes BP. A pro-hypertensive role for 20-HETE was implicated by normalization of BP and reversal of renal angiotensin mRNA increases by administration of the 20-HETE antagonists 2-((6Z,15Z)-20-hydroxyicosa-6,15-dienamido)acetate or (S)-2-((6Z,15Z)-20-hydroxyicosa-6,15-dienamido)succinate. SGK1 expression is also increased in B-129/Sv-4A11(+/+) mice and paralleled increases seen for NCC. Losartan, HET0016, and 20-HETE antagonists each normalized SGK1 mRNA expression. These results point to a potential 20-HETE dependence of intrarenal angiotensinogen production and ANGII receptor type 1 activation that are associated with increases in NCC and SGK1 and identify elevated P450 4A11 activity and 20-HETE as potential risk factors for salt-sensitive human hypertension by perturbation of the renal renin-angiotensin axis.

Efficacy of lycopene on modulation of renal antioxidant enzymes, ACE and ACE gene expression in hyperlipidaemic rats.

Introduction:We aimed to evaluate the efficacy of lycopene on renal tissue antioxidant enzymes and angiotensin converting enzyme (ACE) gene expression and serum activity in diet-induced hyperlipidaemia.Methods:Thirty-two female Wistar albino rats (200–250 g weight), 5–6 months of age, were randomly selected and divided into four groups. Group I received normal diet; group II received 24 g high fat diet/100 g of daily diet; group III received 24 g high fat diet/100 g daily diet and 200 ml of lycopene extract (twice a week) for 8 weeks; and group IV received 200 ml oral lycopene extract twice a week for 8 weeks.Results:A marked increase was observed in plasma urea and creatinine levels, serum C-reactive protein, kidney weight, tissue renal malonyldialdehyde level, ACE gene expression and serum level, while a decrease catalase level among hyperlipidaemic rats was observed. Histologically, interstitial inflammation and proliferation was seen. Lycopene supplementation significantly decreased plasma urea and creatinine, serum ACE, renal tissue malonyldialdehyde level and C-reactive protein level, while it increased tissue antioxidant enzymes level and total protein. Tissue inflammation and proliferation was improved.Conclusions:This finding suggests that supplementation of lycopene is effective for renal antioxidant enzymes, ACE gene expression and ACE serum level in hyperlipidaemic rats.

Angiotensin type 2 receptor null mice express reduced levels of renal angiotensin II type 2 receptor/angiotensin (1-7)/Mas receptor and exhibit greater high-fat diet-induced kidney injury.

Introduction:Renin–angiotensin system (RAS) components exert diverse physiological functions and have been sub-grouped into deleterious angiotensin-converting enzyme (ACE)/angiotensin II (Ang II)/angiotensin type 1 receptor (AT1R) and protective ACE2/angiotensin (1-7) (Ang-(1-7))/Mas receptor (MasR) axes. We have reported that chronic activation of angiotensin type 2 receptor (AT2R) alters RAS components and provides protection against obesity-related kidney injury.Materials and methods:We utilized AT2R knockout (AT2KO) mice in this study and evaluated the renal expression of various RAS components and examined the renal injury after placing these mice on high fat diet (HFD) for 16 weeks.Results:The cortical ACE2 activity and MasR expression were significantly decreased in AT2KO mice compared to wild type (WT) mice. LC/MS analysis revealed an increase in renal Ang II levels and a decrease in Ang-(1-7) levels in AT2KO mice. Cortical expression of ACE and AT1R was increased but renin activity remained unchanged in AT2KO compared with WT mice. WT mice fed HFD exhibited increased systolic blood pressure, higher indices of kidney injury, mesangial matrix expansion score, and microalbuminuria, which were further increased in AT2KO mice.Conclusion:This study suggests that deletion of AT2R decreases the expression of the beneficial ACE2/Ang-(1-7)/MasR and increases the deleterious ACE/Ang II/AT1R axis of the renal RAS in mice. Further, AT2KO mice are more susceptible to HFD-induced renal injury.

Early postnatal treatment with soluble epoxide hydrolase inhibitor or 15-deoxy-Δ12,14-prostagandin J2 prevents prenatal dexamethasone and postnatal high saturated fat diet induced programmed hypertension in adult rat offspring

Prenatal dexamethasone (DEX) exposure, postnatal high-fat (HF) intake, and arachidonic acid pathway are closely related to hypertension. We tested whether a soluble epoxide hydrolase (SEH) inhibitor, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA) or 15-deoxy-Δ12,14-prostagandin J2 (15dPGJ2) therapy can rescue programmed hypertension in the DEX+HF two-hit model. Four groups of Sprague Dawley rats were studied: control, DEX+HF, AUDA, and 15dPGJ2. Dexamethasone (0.1mg/kg body weight) was intraperitoneally administered to pregnant rats from gestational day 16–22. Male offspring received high-fat diet (D12331, Research Diets) from weaning to 4 months of age. In AUDA group, mother rats received 25mg/L in drinking water during lactation. In the 15dPGJ2 group, male offspring received 15dPGJ2 1.5mg/kg BW by subcutaneous injection once daily for 1 week after birth. We found postnatal HF diet aggravated prenatal DEX-induced programmed hypertension, which was similarly prevented by early treatment with AUDA or 15dPGJ2. The beneficial effects of AUDA and 15d-PGJ2 therapy include inhibition of SEH, increases of renal angiotensin converting enzyme-2 (ACE2) and angiotensin II type 2 receptor (AT2R) protein levels, and restoration of nitric oxide bioavailability. Better understanding of the impact of arachidonic acid pathway in the two-hit model will help prevent programmed hypertension in children exposed to corticosteroids and postnatal HF intake.

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.

Role of the Collecting Duct Renin Angiotensin System in Regulation of Blood Pressure and Renal Function.

Recent evidence suggests that the renal tubular renin angiotensin system regulates urinary Na(+) and water excretion and blood pressure. Three key components of the tubular renin angiotensin system, namely renin, prorenin receptor, and angiotensin-II type 1 receptor, are localized to the collecting duct. This system may modulate collecting duct Na(+) and water reabsorption via angiotensin-II-dependent and angiotensin-II-independent pathways. Further, the system may be of greatest relevance in hypertensive states and particularly those characterized by high circulating angiotensin-II. In this review, we summarize the current knowledge on the synthesis, regulation, and function of collecting duct-derived renin angiotensin system components and examine recent developments with regard to regulation of blood pressure and renal fluid and Na(+) excretion.

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.

Antioxidant resveratrol restores renal sodium transport regulation in SHR.

Previously we have shown that in spontaneously hypertensive rats (SHR) renal angiotensin (Ang) II receptor (AT1R) upregulation leads to overstimulation of Na/K-ATPase by Ang II. There are reports that antioxidants can reduce oxidative stress and blood pressure (BP) in SHR, however the effect of these compounds on AT1R function remains to be determined. Therefore, we hypothesized that polyphenol antioxidant resveratrol would mitigate oxidative stress, normalize renal AT1R signaling, and reduce BP in SHR. SHR and wistar-kyoto (WKY) rats were treated with resveratrol for 8 weeks. Untreated SHR exhibited oxidative stress and enhanced renal proximal tubular Ang II-induced G-protein activation and Na/K-ATPase stimulation. Treatment of SHR with resveratrol mitigated oxidative stress, reduced BP, and normalized renal AT1R signaling. In SHR, nuclear expression of transcription factor NF-κB was increased while expression of Nrf2 was reduced. SHR also exhibited a significant decrease in renal antioxidant capacity and activities of phase II antioxidant enzymes. Resveratrol treatment of SHR abolished renal NF-κB activation, restored Nrf2-phase II antioxidant signaling and Ang II-mediated Na/K-ATPase regulation. These data show that in SHR, oxidative stress via activation of NF-κB upregulates AT1R–G-protein signaling resulting in overstimulation Na/K-ATPase which contributes to hypertension. Resveratrol, via Nrf2, activates phase II antioxidant enzymes, mitigates oxidative stress, normalizes AT1R–G-protein signaling and Na/K-ATPase regulation, and decreases BP in SHR.

High-fat diet amplifies renal renin angiotensin system expression, blood pressure elevation, and renal dysfunction caused by Ceacam1 null deletion.

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAMl), a substrate of the insulin receptor tyrosine kinase, regulates insulin action by promoting insulin clearance. Global null mutation of Ceacam1 gene (Cc1(-/-)) results in features of the metabolic syndrome, including insulin resistance, hyperinsulinemia, visceral adiposity, elevated blood pressure, and albuminuria. It also causes activation of the renal renin-angiotensin system (RAS). In the current study, we tested the hypothesis that high-fat diet enhances the expression of RAS components. Three-month-old wild-type (Cc1(+/+)) and Cc1(-/-) mice were fed either a regular or a high-fat diet for 8 wk. At baseline under regular feeding conditions, Cc1(-/-) mice exhibited higher blood pressure, urine albumin-to-creatinine ratio (UACR), and renal expression of angiotensinogen, renin/prorenin, angiotensin-converting enzyme, (pro)renin receptor, angiotensin subtype AT1 receptor, angiotensin II, and elevated PI3K phosphorylation, as detected by p85α (Tyr(508)) immunostaining, inflammatory response, and the expression of collagen I and collagen III. In Cc1(+/+) mice, high-fat diet increased blood pressure, UACR, the expression of angiotensin-converting enzyme and angiotensin II, PI3K phosphorylation, inflammatory response, and the expression of collagen I and collagen III. In Cc1(-/-) mice, high-fat intake further amplified these parameters. Immunohistochemical staining showed increased p-PI3K p85α (Tyr(508)) expression in renal glomeruli, proximal, distal, and collecting tubules of Cc1(-/-) mice fed a high-fat diet. Together, this demonstrates that high-fat diet amplifies the permissive effect of Ceacam1 deletion on renal expression of all RAS components, PI3K phosphorylation, inflammation, and fibrosis.