scholarly journals Role of caveolin 1 in AT1a receptor-mediated uptake of angiotensin II in the proximal tubule of the kidney

2014 ◽  
Vol 307 (8) ◽  
pp. F949-F961 ◽  
Author(s):  
Xiao C. Li ◽  
Victor Gu ◽  
Elise Miguel-Qin ◽  
Jia L. Zhuo

Caveolin 1 (CAV-1) functions not only as a constitutive scaffolding protein of caveolae but also as a vesicular transporter and signaling regulator. In the present study, we tested the hypothesis that CAV-1 knockout (CAV-1 KO) inhibits ANG II type 1 [AT1 (AT1a)] receptor-mediated uptake of ANG II in the proximal tubule and attenuates blood pressure responses in ANG II-induced hypertension. To determine the role of CAV-1 in mediating the uptake of FITC-labeled ANG II, wild-type (WT) mouse proximal convoluted tubule cells were transfected with CAV-1 small interfering (si)RNA for 48 h before AT1 receptor-mediated uptake of FITC-labeled ANG II was studied. CAV-1 siRNA knocked down CAV-1 expression by >90% ( P < 0.01) and inhibited FITC-labeled ANG II uptake by >50% ( P < 0.01). Moreover, CAV-1 siRNA attenuated ANG II-induced activation of MAPK ERK1/2 and Na+/H+ exchanger 3 expression, respectively ( P < 0.01). To determine whether CAV-1 regulates ANG II uptake in the proximal tubule, Alexa 488-labeled ANG II was infused into anesthetized WT and CAV-1 KO mice for 60 min (20 ng/min iv). Imaging analysis revealed that Alexa 488-labeled ANG II uptake was decreased by >50% in CAV-1 KO mice ( P < 0.01). Furthermore, Val5-ANG II was infused into WT and CAV-1 KO mice for 2 wk (1.5 mg·kg−1·day−1 ip). Basal systolic pressure was higher, whereas blood pressure and renal excretory and signaling responses to ANG II were attenuated, in CAV-1 KO mice ( P < 0.01). We concluded that CAV-1 plays an important role in AT1 receptor-mediated uptake of ANG II in the proximal tubule and modulates blood pressure and renal responses to ANG II.

2014 ◽  
Vol 307 (2) ◽  
pp. F222-F233 ◽  
Author(s):  
Xiao C. Li ◽  
Jia L. Zhuo

The present study tested the hypothesis that the multiligand endocytic receptor megalin is partially involved in the uptake of ANG II and downstream signaling responses in mouse proximal tubule cells (mPCT) by interacting with AT1a receptors. mPCT cells of wild-type (WT) and AT1a receptor-deficient (AT1a-KO) mice were treated with vehicle, the AT1 receptor blocker losartan (10 μM), or a selective megalin small interfering (si) RNA for 48 h. The uptake of fluorescein (FITC)-labeled ANG II (10 nM, 37°C) and downstream signaling responses were analyzed by fluorescence imaging and Western blotting. AT1a receptors and megalin were abundantly expressed in mPCT cells, whereas AT1a receptors were absent in AT1a-KO mPCT cells ( P < 0.01). In WT mPCT cells, FITC-ANG II uptake was visualized at 30 min in the cytoplasm and in the nuclei 1 h after exposure. Losartan alone completely blocked the uptake of FITC-ANG II, whereas megalin siRNA inhibited only 30% of the response ( P < 0.01). The remaining FITC-ANG II uptake in the presence of megalin siRNA was completely abolished by losartan. ANG II induced threefold increases in phosphorylated MAP kinases ERK1/2 and a onefold increase in phosphorylated sodium and hydrogen exchanger 3 (NHE3) proteins, which were also blocked by losartan and megalin-siRNA. By contrast, losartan and megalin siRNA had no effects on these signaling proteins in AT1a-KO mPCT cells. We conclude that the uptake of ANG II and downstream MAP kinases ERK1/2 and NHE3 signaling responses in mPCT cells are mediated primarily by AT1a receptors. However, megalin may also play a partial role in these responses to ANG II.


2019 ◽  
Vol 51 (4) ◽  
pp. 97-108 ◽  
Author(s):  
Xiao C. Li ◽  
Xiaowen Zheng ◽  
Xu Chen ◽  
Chunling Zhao ◽  
Dongmin Zhu ◽  
...  

The sodium (Na+)/hydrogen (H+) exchanger 3 (NHE3) and sodium-potassium adenosine triphosphatase (Na+/K+-ATPase) are two of the most important Na+ transporters in the proximal tubules of the kidney. On the apical membrane side, NHE3 primarily mediates the entry of Na+ into and the exit of H+ from the proximal tubules, directly and indirectly being responsible for reabsorbing ~50% of filtered Na+ in the proximal tubules of the kidney. On the basolateral membrane side, Na+/K+-ATPase serves as a powerful engine driving Na+ out of, while pumping K+ into the proximal tubules against their concentration gradients. While the roles of NHE3 and Na+/K+-ATPase in proximal tubular Na+ transport under in vitro conditions are well recognized, their respective contributions to the basal blood pressure regulation and angiotensin II (ANG II)-induced hypertension remain poorly understood. Recently, we have been fortunate to be able to use genetically modified mouse models with global, kidney- or proximal tubule-specific deletion of NHE3 to directly determine the cause and effect relationship between NHE3, basal blood pressure homeostasis, and ANG II-induced hypertension at the whole body, kidney and/or proximal tubule levels. The purpose of this article is to review the genetic and genomic evidence for an important role of NHE3 with a focus in the regulation of basal blood pressure and ANG II-induced hypertension, as we learned from studies using global, kidney- or proximal tubule-specific NHE3 knockout mice. We hypothesize that NHE3 in the proximal tubules is necessary for maintaining basal blood pressure homeostasis and the development of ANG II-induced hypertension.


2021 ◽  
Vol 12 ◽  
Author(s):  
Francisco J. Valenzuela-Melgarejo ◽  
Constanza Lagunas ◽  
Fabiola Carmona-Pastén ◽  
Kevins Jara-Medina ◽  
Gustavo Delgado

Hypertension can be induced by the disruption of factors in blood pressure regulation. This includes several systems such as Neurohumoral, Renin-angiotensin-aldosterone, the Circadian clock, and melatonin production, which can induce elevation and non-dipping blood pressure. Melatonin has a supraphysiological role as a chronobiotic agent and modulates vascular system processes via pro/antiangiogenic factors, inflammation, the immune system, and oxidative stress regulation. An elevation of melatonin production is observed during pregnancy, modulating the placenta and fetus’s physiological functions. Their impairment production can induce temporal desynchronization of cell proliferation, differentiation, or invasion from trophoblast cells results in vascular insufficiencies, elevating the risk of poor fetal/placental development. Several genes are associated with vascular disease and hypertension during pregnancy via impaired inflammatory response, hypoxia, and oxidative stress, such as cytokines/chemokines IL-1β, IL-6, IL-8, and impairment expression in endothelial cells/VSMCs of HIF1α and eNOS genes. Pathological placentas showed differentially expressed genes (DEG), including vascular genes as CITED2, VEGF, PL-II, PIGF, sFLT-1, and sENG, oncogene JUNB, scaffolding protein CUL7, GPER1, and the pathways of SIRT/AMPK and MAPK/ERK. Additionally, we observed modification of subunits of NADPH oxidase and extracellular matrix elements, i.e., Glypican and Heparanase and KCa channel. Mothers with a low level of melatonin showed low production of proangiogenic factor VEGF, increasing the risk of preeclampsia, premature birth, and abortion. In contrast, melatonin supplementation can reduce systolic pressure, prevent oxidative stress, induce the activation of the antioxidants system, and lessen proteinuria and serum level of sFlt-1. Moreover, melatonin can repair the endothelial damage from preeclampsia at the placenta level, increasing PIGF, Nrf-2, HO-1 production and reducing critical markers of vascular injury during the pregnancy. Melatonin also restores the umbilical and uterine blood flow after oxidative stress and inhibits vascular inflammation and VCAM-1, Activin-A, and sEng production. The beneficial effects of melatonin over pathological pregnancies can be partially observed in normal pregnancies, suggesting the dual role of/over placental physiology could contribute to protection and have therapeutic applications in vascular pathologies of pregnancies in the future.


2013 ◽  
Vol 304 (8) ◽  
pp. R588-R598 ◽  
Author(s):  
Xiao C. Li ◽  
Jia L. Zhuo

The role of intracellular ANG II in proximal tubules of the kidney remains poorly understood. We tested the hypothesis that proximal tubule-dominant transfer of AT1a receptors in the cortex mediates intracellular ANG II-induced blood pressure responses in AT1a receptor-deficient (Agtr1a-/-) mice. A GFP-tagged AT1a receptor, AT1aR/GFP, and an enhanced cyan fluorescent intracellular ANG II fusion protein, ECFP/ANG II, were expressed in proximal tubules of Agtr1a-/- mouse kidneys via the adenoviral transfer using a sodium and glucose cotransporter 2 promoter. Transfer of AT1aR/GFP alone or with ECFP/ANG II induced proximal tubule-dominant expression of AT1aR/GFP and/or ECFP/ANG II with a peak response at 2 wk. No significant AT1aR/GFP and/or ECFP/ANG II expression was observed in the glomeruli, medulla, or extrarenal tissues. Transfer of AT1aR/GFP alone, but not ECFP/ANG II, increased systolic blood pressure by 12 ± 2 mmHg by day 14 ( n = 9, P < 0.01). However, cotransfer of AT1aR/GFP with ECFP/ANG II increased blood pressure by 18 ± 2 mmHg ( n = 12, P < 0.01). Twenty-four hour urinary sodium excretion was decreased by day 7 with proximal tubule-dominant transfer of AT1aR/GFP alone ( P < 0.01) or with AT1aR/GFP and ECFP/ANG II cotransfer ( P < 0.01). These responses were associated with twofold increases in phosphorylated ERK1/2, lysate, and membrane NHE-3 proteins in freshly isolated proximal tubules ( P < 0.01). By contrast, transfer of control CMV-GFP (a recombinant human adenovirus type 5 expresses enhanced green fluorescent protein under the control of a cytomegalovirus (CMV) promoter), ECFP/ANG II, or a scrambled control ECFP/ANG IIc alone in proximal tubules had no effect on all indices. These results suggest that AT1a receptors and intracellular ANG II in proximal tubules of the kidney play an important physiological role in blood pressure regulation.


1991 ◽  
Vol 261 (5) ◽  
pp. F741-F745
Author(s):  
E. A. Walters ◽  
L. Rome ◽  
R. G. Luke ◽  
J. H. Galla

Chloride-depletion alkalosis (CDA) has been characterized by hypereninemia. To determine whether angiotensin II (ANG II) has an important role in its maintenance or correction, anesthetized alkalotic rats, chloride depleted by peritoneal dialysis, were infused with 5% dextrose and saralasin (1 microgram.kg-1.min-1) (SAR) or vehicle (SAR-C), 5% dextrose and pretreatment with enalapril (1-1.5 mg/kg) (ENP) or vehicle (ENP-C), or 80 mM Cl solution with ANG II (20 micrograms/min) (ANG) or vehicle (ANG-C). Rats infused with 5% dextrose showed no differences in the magnitude of the alkalosis, inulin clearance, or urinary total CO2 excretion; both SAR and ENP were associated with decreased blood pressure. In SAR, tCO2 delivery out of late proximal convoluted tubule did not differ from that in SAR-C. Rats infused with 80 mM Cl corrected CDA similarly (delta plasma [Cl] - ANG-C + 6 +/- 1, ANG + 5 +/- 1 mM; P = not significant). These data suggest that, although ANG II can importantly influence vascular tone and early proximal tubule bicarbonate reabsorption, it does not have an important role in the renal maintenance or correction of acute CDA.


2009 ◽  
Vol 9 ◽  
pp. 522-535 ◽  
Author(s):  
Marc Dilauro ◽  
Kevin D. Burns

Angiotensin-(1-7) (Ang-[1-7]) is a heptapeptide member of the renin-angiotensin system (RAS), and acts as a vasodilator and antagonist of angiotensin II (Ang II) in the vasculature. The role of Ang-(1-7) in regulating kidney function is not well understood. Within the kidneys, Ang-(1-7) is generated by angiotensin-converting enzyme 2 (ACE2)–mediated degradation of Ang II, sequential cleavage of the precursor angiotensin I (Ang I) by ACE2 and ACE, or the actions of brush-border membrane peptidases on Ang I. Ang-(1-7) mediates its effects via binding to kidney Mas receptors, although some actions may occur via Ang II AT1or AT2receptors.In vitrostudies suggest that Ang-(1-7) is an intrarenal vasodilator. Ang-(1-7) has been reported to induce either natriuresis/diuresis or sodium and water retention, via modulation of sodium transporters in the proximal tubule and loop of Henle, and collecting duct water transport. In the proximal tubule, Ang-(1-7) antagonizes growth-promoting signaling pathways via activation of a protein tyrosine phosphatase, whereas in mesangial cells, Ang-(1-7) stimulates cell growth via activation of mitogen-activated protein kinases. The phenotype of the Mas gene knockout mouse suggests that Ang-(1-7)–signaling events exert cardiovascular protection by regulating blood pressure, and by limiting production of reactive oxygen species and extracellular matrix proteins. Ang-(1-7) also protects against renal injury in the renal wrap hypertension model, independent of effects on blood pressure. In diabetic nephropathy, however, the role of Ang-(1-7) on disease progression remains unclear. In summary, Ang-(1-7) and its receptor Mas have emerged as important components of the intrarenal RAS. The signaling and downstream effects of Ang-(1-7) in the kidney are complex and appear to be cell specific. The body of evidence suggests that Ang-(1-7) is protective against endothelial dysfunction or Ang II–stimulated proximal tubular injury, although the overall effects on glomerular function require further study.


1957 ◽  
Vol 188 (2) ◽  
pp. 371-374 ◽  
Author(s):  
Sol Rothman ◽  
Douglas R. Drury

The blood pressure responses to various drugs were investigated in renal hypertensive, cerebral hypertensive and normotensive rabbits. Hexamethonium bromide and Dibenamine reduced the blood pressures of renal and cerebral hypertensives. Effects in the normal were insignificant. The cerebral hypertensive's blood pressure was slightly affected by benzodioxane. Blood pressure was not reduced at all in the other groups. Blood pressure of the renal hypertensive rabbit was greatly reduced by Veriloid and dihydroergocornine. Blood pressures of cerebral and normal animals were affected to a lesser degree. The results suggest that maintenance of hypertension in the cerebral hypertensive rabbit depends on an overactive sympathetic nervous system, possibly due to the release of medullary pressor centers from inhibitory impulses originating in higher centers; whereas, the maintenance of hypertension in the renal hypertensive rabbit may be attributed to an increased reactivity of the peripheral vasculature to a normal sympathetic tone.


2007 ◽  
Vol 292 (2) ◽  
pp. F861-F867 ◽  
Author(s):  
Melvin R. Hayden ◽  
Nazif A. Chowdhury ◽  
Shawna A. Cooper ◽  
Adam Whaley-Connell ◽  
Javad Habibi ◽  
...  

TG(mRen2)27 (Ren2) transgenic rats overexpress the mouse renin gene, with subsequent elevated tissue ANG II, hypertension, and nephropathy. The proximal tubule cell (PTC) is responsible for the reabsorption of 5–8 g of glomerular filtered albumin each day. Excess filtered albumin may contribute to PTC damage and tubulointerstitial disease. This investigation examined the role of ANG II-induced oxidative stress in PTC structural remodeling: whether such changes could be modified with in vivo treatment with ANG type 1 receptor (AT1R) blockade (valsartan) or SOD/catalase mimetic (tempol). Male Ren2 (6–7 wk old) and age-matched Sprague-Dawley rats were treated with valsartan (30 mg/kg), tempol (1 mmol/l), or placebo for 3 wk. Systolic blood pressure, albuminuria, N-acetyl-β-d-glucosaminidase, and kidney tissue malondialdehyde (MDA) were measured, and ×60,000 transmission electron microscopy images were used to assess PTC microvilli structure. There were significant differences in systolic blood pressure, albuminuria, lipid peroxidation (MDA and nitrotyrosine staining), and PTC structure in Ren2 vs. Sprague-Dawley rats (each P < 0.05). Increased mean diameter of PTC microvilli in the placebo-treated Ren2 rats ( P < 0.05) correlated strongly with albuminuria ( r2 = 0.83) and moderately with MDA ( r2 = 0.49), and there was an increase in the ratio of abnormal forms of microvilli in placebo-treated Ren2 rats compared with Sprague-Dawley control rats ( P < 0.05). AT1R blockade, but not tempol treatment, abrogated albuminuria and N-acetyl-β-d-glucosaminidase; both therapies corrected abnormalities in oxidative stress and PTC microvilli remodeling. These data indicate that PTC structural damage in the Ren2 rat is related to the oxidative stress response to ANG II and/or albuminuria.


Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Kevin D Comeau ◽  
Pierre Paradis ◽  
Ernesto L Schiffrin

Background: We recently demonstrated that γδ T cells participate in the pathogenesis of hypertension. Evidence also suggests that memory T cells may develop during an initial hypertensive episode, sensitizing mice to develop hypertension to further mild hypertensive challenges. However, whether memory γδ T cells develop and play a role in hypertension remains unknown. Our objective is to determine if memory γδ T cells sensitize mice to develop hypertension in response to a mild hypertensive challenge. Methods: Ten-12-week-old C57BL/6J mice were exposed or not to a hypertensive challenge (490 ng/kg/min angiotensin II (Ang II), SC) for two weeks, followed by a two-week washout period, and then infused with a subpressor dose of Ang II (140 ng/kg/min Ang II, SC) for two weeks. Blood pressure was measured via telemetry and central, effector, and resident memory γδ T cells were profiled by flow cytometry. Results: Mice exposed to the first hypertensive challenge had a higher systolic blood pressure than the sham group at the end of the subpressor hypertensive challenge (149±6 vs. 122±3 mmHg, P <0.001). After 14-days of Ang II infusion, effector memory γδ T cells increased 5.2-fold in the mesenteric artery perivascular adipose tissue (PVAT, 1.25±0.37% vs. 0.24±0.12%, P <0.05), and 1.8-fold in the mesenteric lymph nodes (mLN, 1.49±0.03% vs. 0.82±0.15%, P <0.05) compared to sham treated mice. After repeated Ang II infusion, central memory γδ T cells decreased by 57% in the aortic PVAT (6.79±1.46% vs. 15.69±2.87%, P <0.05), and by 22% in the mLN (0.18±0.01% vs. 0.23±0.01%, P <0.05) compared to control mice. Conclusion: An initial exposure to a hypertensive stimulus sensitizes mice to develop hypertension to a subsequent subpressor hypertensive challenge and results in the development of memory γδ T cells.


Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Takuto Nakamura ◽  
Masanobu Yamazato ◽  
Akio Ishida ◽  
Yusuke Ohya

Objective: Aminopeptidase A (APA) have important role in conversion of Ang II to Ang III. Intravenous APA administration lowers blood pressure in hypertensive rats. In contrast, APA inhibition in the brain lowers blood pressure in hypertensive rats. Therefore APA might have different role on cardiovascular regulation. However, a role of APA and Ang III on cardiovascular regulation especially in the brain has not been fully understood. Our purpose of present study was to investigate a role of APA and Ang III in the brain on cardiovascular regulation in conscious state. Method: 12-13 weeks old Wistar Kyoto rat (WKY) and 12-16 weeks old spontaneously hypertensive rat (SHR) were used. i) APA distribution in the brain was evaluated by immunohistochemistry. Protein expression of APA was evaluated by Western blotting. Enzymatic activity of APA was evaluated using L-glutamic acid γ-(4-nitroanilide) as a substrate. ii) WKY received icv administration of Ang II 25ng/2μL and Ang III 25ng/2μL. We recorded change in mean arterial pressure (MAP) in conscious and unrestraied state and measured induced drinking time. iii) SHR received icv administeration of recombinant APA 400ng/4μL. We recorded change in MAP in conscious and unrestraied state and measured induced drinking time. Result: i) APA was diffusely immunostained in the cells of brain stem including cardiovascular regulatory area such as rostral ventrolateral medulla. Protein expression and APA activity in the brain were similar between WKY (n=3) and SHR (n=3).ii) Icv administration of Ang II increased MAP by 33.8±3.8 mmHg and induced drinking behavior for 405±90 seconds (n=4). Icv administration of Ang III also increased MAP by 24.7±2.4 mmHg and induced drinking behavior for 258±62 seconds (n=3). These vasopressor activity and induced drinking behavior was completely blocked by pretretment of angiotensin receptor type 1 blocker.iii) Icv administration of APA increased MAP by 10.0±1.7 mmHg (n=3). Conclusion: These results suggested that Ang III in the brain increase blood pressure by Angiotensin type 1 receptor dependent mechanism and APA in the brain may involved in blood pressure regulation as a vasopressor enzyme.


Sign in / Sign up

Export Citation Format

Share Document