Renal NOXA1/NOX1 Signaling Regulates Epithelial Sodium Channel and Sodium Retention in Angiotensin II-induced Hypertension

It is well demonstrated that activation of renal PRR ([pro]renin receptor) contributes to AngII (angiotensin II)-induced hypertension. Relatively, less is known for the function of sPRR (soluble PRR), the extracellular domain of PRR, primarily generated by S1P (site-1 protease) and furin. Moreover, the relationship between PRR/sPRR and the renin-angiotensin system (RAS) has been debated. In the present study, we used CRISPR/Cas9 strategy to generate mice with mutagenesis of the overlapping cleavage site for both proteases in PRR (termed as PRR R279V/L282V ) to examine the phenotype during AngII infusion with particular emphasis on circulating and intrarenal renin status. PRR R279V/L282V mice exhibited a reduction of sPRR level in plasma by ≈53% and in the kidney by ≈82%, were fertile, and had no gross developmental abnormalities. At basal condition, PRR R279V/L282V mice had drastically suppressed renin levels from plasma, urine, and the kidney as compared to wild-type controls. The hypertensive response of PRR R279V/L282V to AngII infusion was blunted in parallel with attenuated response of intrarenal renin and renal medullary α-epithelial sodium channel expression. By using Ussing chamber technique, primary collecting duct cells from PRR R279V/L282V mice exhibited blunted response of epithelial sodium channel activity to AngII as compared to wild-type cells. Together, these results represent strong evidence favoring sPRR as a mediator of AngII-induced hypertension and a master regulator of renin expression. Therefore, PRR should be considered as an integrative member of the RAS.

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Experimental nephrotic syndrome leads to proteolytic activation of the epithelial sodium channel (ENaC) in the mouse kidney

AJP Renal Physiology ◽

10.1152/ajprenal.00199.2021 ◽

2021 ◽

Author(s):

Bernhard N. Bohnert ◽

Daniel Essigke ◽

Andrea Janessa ◽

Jonas C Schneider ◽

Matthias Wörn ◽

...

Keyword(s):

Nephrotic Syndrome ◽

Sodium Channel ◽

Serine Protease ◽

Cleavage Site ◽

Mineralocorticoid Receptor ◽

Epithelial Sodium Channel ◽

Sodium Retention ◽

Cleavage Sites ◽

Proteolytic Activation ◽

Epithelial Sodium Channel Enac

Proteolytic activation of the renal epithelial sodium channel ENaC involves cleavage events in its α- and γ-subunits and is thought to mediate sodium retention in nephrotic syndrome (NS). However, detection of proteolytically processed ENaC in kidney tissue from nephrotic mice has been elusive so far. We used a refined Western blot technique to reliably discriminate full-length α- and γ-ENaC and their cleavage products after proteolysis at their proximal and distal cleavage sites (designated from the N-terminus), respectively. Proteolytic ENaC activation was investigated in kidneys from mice with experimental NS induced by doxorubicin or inducible podocin deficiency with or without treatment with the serine protease inhibitor aprotinin. Nephrotic mice developed sodium retention and increased expression of fragments of α- and γ-ENaC cleaved at both the proximal and more prominently at the distal cleavage site, respectively. Treatment with aprotinin but not with the mineralocorticoid receptor antagonist canrenoate prevented sodium retention and upregulation of the cleavage products in nephrotic mice. Increased expression of cleavage products of α- and γ-ENaC was similarly found in healthy mice treated with a low salt diet, sensitive to mineralocorticoid receptor blockade. In human nephrectomy specimens, γ-ENaC was found in the full-length form and predominantly cleaved at its distal cleavage site. In conclusion, murine experimental NS leads to aprotinin-sensitive proteolytic activation of ENaC at both proximal and more prominently distal cleavage sites of its α- and γ-subunit, most likely by urinary serine protease activity or proteasuria.

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Cyclosporine stimulates the renal epithelial sodium channel by elevating cholesterol

AJP Renal Physiology ◽

10.1152/ajprenal.90647.2008 ◽

2009 ◽

Vol 296 (2) ◽

pp. F284-F290 ◽

Cited By ~ 21

Author(s):

Jing Wang ◽

Zhi-Ren Zhang ◽

Chu-Fang Chou ◽

You-You Liang ◽

Yuchun Gu ◽

...

Keyword(s):

Sodium Channel ◽

Epithelial Sodium Channel ◽

Disulfonic Acid ◽

Severe Side Effect ◽

Open Probability ◽

A6 Cells ◽

Induced Hypertension ◽

Microscopy Data ◽

Abca1 Protein ◽

Epithelial Sodium Channel Enac

Cyclosporine A (CsA) is an efficient immunosuppressant used for reducing allograft rejection but with a severe side effect of causing hypertension. We hypothesize that the renal epithelial sodium channel (ENaC) may participate in CsA-induced hypertension. In the present study, we used the patch-clamp cell-attached configuration to examine whether and how CsA stimulates ENaC in A6 distal nephron cells. The data showed that CsA significantly increased ENaC open probability. Since CsA is an inhibitor of the ATP-binding cassette A1 (ABCA1) transporter, we employed 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS), another ABCA1 inhibitor, and found that DIDS mimicked the effects of CsA on ENaC basal and cholesterol-induced activity but without any additive effect if combined with CsA. CsA and DIDS also had an identical effect on reduced ENaC activity caused by cholesterol extraction. ABCA1 protein was detected in A6 cells by Western blot analysis. Confocal microscopy data showed that both CsA and DIDS facilitated A6 cells to uptake cholesterol. Since enhanced ENaC activity is known to cause hypertension, these data together suggest that CsA may cause hypertension by stimulating ENaC through a pathway associated with inhibition of ABCA1 and consequent elevation of cholesterol in the cells.

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Hyperaldosteronemia and Activation of the Epithelial Sodium Channel Are Not Required for Sodium Retention in Puromycin-Induced Nephrosis

Journal of the American Society of Nephrology ◽

10.1681/asn.2005040363 ◽

2005 ◽

Vol 16 (12) ◽

pp. 3642-3650 ◽

Cited By ~ 51

Author(s):

Stéphane Lourdel ◽

Johannes Loffing ◽

Guillaume Favre ◽

Marc Paulais ◽

Antoine Nissant ◽

...

Keyword(s):

Sodium Channel ◽

Epithelial Sodium Channel ◽

Sodium Retention

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Plasminogen Deficiency and Amiloride Mitigate Angiotensin II–Induced Hypertension in Type 1 Diabetic Mice Suggesting Effects Through the Epithelial Sodium Channel

Journal of the American Heart Association ◽

10.1161/jaha.120.016387 ◽

2020 ◽

Vol 9 (23) ◽

Author(s):

Henrik Andersen ◽

Maria Høj Hansen ◽

Kristian B. Buhl ◽

Mette Stæhr ◽

Ulla G. Friis ◽

...

Keyword(s):

Diabetes Mellitus ◽

Blood Pressure ◽

Angiotensin Ii ◽

Sodium Channel ◽

Arterial Blood Pressure ◽

Epithelial Sodium Channel ◽

Diabetic Mice ◽

Wild Type ◽

Arterial Blood ◽

Prorenin Receptor

Background Diabetic nephropathy is a common diabetes mellitus complication associated with hypertension, proteinuria, and excretion of urinary plasmin that activates the epithelial sodium channel, ENaC, in vitro . Here we hypothesized that the deletion of plasminogen and amiloride treatment protect against hypertension in diabetes mellitus. Methods and Results Male plasminogen knockout (plasminogen‐deficient [Plg −/− ]) and wild‐type mice were rendered diabetic with streptozotocin. Arterial blood pressure was recorded continuously by indwelling catheters before and during 10 days of angiotensin II infusion (ANGII; 30–60 ng/kg per minute). The effect of amiloride infusion (2 mg/kg per day, 4 days) was tested in wild‐type, diabetic ANGII‐treated mice. Streptozotocin increased plasma and urine glucose concentrations and 24‐hour urine albumin and plasminogen excretion. Diabetic Plg −/− mice displayed larger baseline albuminuria and absence of urine plasminogen. Baseline mean arterial blood pressure did not differ between groups. Although ANGII elevated blood pressure in wild‐type, diabetic wild‐type, and Plg −/− control mice, ANGII did not change blood pressure in diabetic Plg −/− mice. Compared with ANGII infusion alone, wild‐type ANGII‐infused diabetic mice showed blood pressure reduction upon amiloride treatment. There was no difference in plasma renin, ANGII, aldosterone, tissue prorenin receptor, renal inflammation, and fibrosis between groups. Urine from wild‐type mice evoked larger amiloride‐sensitive current than urine from Plg −/− mice with or without diabetes mellitus. Full‐length γ‐ENaC and α‐ENaC subunit abundances were not changed in kidney homogenates, but the 70 kDa γ‐ENaC cleavage product was increased in diabetic versus nondiabetic mice. Conclusions Plasmin promotes hypertension in diabetes mellitus with albuminuria likely through the epithelial sodium channel.

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Association of Urinary Plasminogen-Plasmin with Edema and Epithelial Sodium Channel Activation in Patients with Nephrotic Syndrome

American Journal of Nephrology ◽

10.1159/000501059 ◽

2019 ◽

Vol 50 (2) ◽

pp. 92-104 ◽

Cited By ~ 3

Author(s):

Jun-Liang Chen ◽

Li Wang ◽

Xing-Mei Yao ◽

Ying-Jun Zang ◽

Yi Wang ◽

...

Keyword(s):

Nephrotic Syndrome ◽

Sodium Channel ◽

Influencing Factor ◽

Fractional Excretion ◽

Epithelial Sodium Channel ◽

Pathophysiological Mechanism ◽

Sodium Retention ◽

Edema Formation ◽

Fractional Excretion Of Sodium ◽

Serial Samples

Background: Previous animal experiments and small human studies suggest that urinary plasmin can activate the epithelial sodium channel (ENaC) and contribute to sodium retention in nephrotic syndrome (NS), but this however is not well studied in clinical settings, and its relevance to edema formation is not well characterized in humans. We have investigated the association between urinary plasmin and clinical phenotypes in a large group of patients with NS from multiple etiologies, aiming to assess the role of urinary plasmin in sodium handling and edema formation. Methods: Two hundred and three NS patients with urine and blood samples were divided into mild and severe symptom groups based on their edema severity. Twenty six of them had serial samples collected during the course of immunosuppressive therapy. The plasminogen-plasmin level and other key parameters were assayed, and their association with clinical manifestations were analyzed. Results: One hundred and one of the 203 patients had renal biopsies performed, the results of which had included all the common types of primary NS and various types of secondary NS. Quantitative comparison and multivariate logistic regression analysis identified urinary plasminogen-plasmin to creatinine ratio (uPLG-PL/C), serum albumin, D-Dimer, and cardiac dysfunction history, but not albuminuria or 24-h urine protein, as independent risk factors for edema (p < 0.01). In patients who were treated and had serial samples, a decrease in uPLG-PL/C was identified as an independent influencing factor of edema remission (p < 0.01). Finally, the urinary fractional excretion of sodium (FENa) in patients was inversely correlated with the fractional excretion of potassium (FEK; p< 0.001), and FEK/FENa ratio was positively correlated with uPLG-PL/C (p < 0.001), suggesting a close association between uPLG-PL and ENaC activation. Conclusions: Our study identifies uPLG-PL abundance as an independent influencing factor of edema in adult NS patients, and supports the conclusion that plasmin-dependent ENaC activation is an important pathophysiological mechanism of sodium retention and edema formation in humans with NS.

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Sex and Age Result in Differential Regulation of the Renal Thiazide-Sensitive NaCl Cotransporter and the Epithelial Sodium Channel in Angiotensin II-Infused Mice

American Journal of Nephrology ◽

10.1159/000252776 ◽

2009 ◽

Vol 30 (6) ◽

pp. 554-562 ◽

Cited By ~ 17

Author(s):

Swasti Tiwari ◽

Lijun Li ◽

Shahla Riazi ◽

Veerendra K. Madala Halagappa ◽

Carolyn M. Ecelbarger

Keyword(s):

Angiotensin Ii ◽

Sodium Channel ◽

Epithelial Sodium Channel ◽

Differential Regulation ◽

Nacl Cotransporter

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Renal Natriuretic Peptide Receptor-C Deficiency Attenuates NaCl Cotransporter Activity in Angiotensin II–Induced Hypertension

Hypertension ◽

10.1161/hypertensionaha.120.15636 ◽

2021 ◽

Vol 77 (3) ◽

pp. 868-881

Author(s):

Shuai Shao ◽

Xiao-Dong Li ◽

Yuan-Yuan Lu ◽

Shi-Jin Li ◽

Xiao-Hui Chen ◽

...

Keyword(s):

Blood Pressure ◽

Angiotensin Ii ◽

Natriuretic Peptide ◽

Elevated Blood Pressure ◽

Natriuretic Peptide Receptor ◽

Sodium Retention ◽

Ang Ii ◽

Elevated Blood ◽

Peptide Receptor ◽

Induced Hypertension

Genome-wide association studies have identified that NPR-C (natriuretic peptide receptor-C) variants are associated with elevation of blood pressure. However, the mechanism underlying the relationship between NPR-C and blood pressure regulation remains elusive. Here, we investigate whether NPR-C regulates Ang II (angiotensin II)-induced hypertension through sodium transporters activity. Wild-type mice responded to continuous Ang II infusion with an increased renal NPR-C expression. Global NPR-C deficiency attenuated Ang II–induced increased blood pressure both in male and female mice associated with more diuretic and natriuretic responses to a saline challenge. Interestingly, Ang II increased both total and phosphorylation of NCC (NaCl cotransporter) abundance involving in activation of WNK4 (with-no-lysine kinase 4)/SPAK (Ste20-related proline/alanine-rich kinase) which was blunted by NPR-C deletion. NCC inhibitor, hydrochlorothiazide, failed to induce natriuresis in NPR-C knockout mice. Moreover, low-salt and high-salt diets–induced changes of total and phosphorylation of NCC expression were normalized by NPR-C deletion. Importantly, tubule-specific deletion of NPR-C also attenuated Ang II–induced elevated blood pressure, total and phosphorylation of NCC expression. Mechanistically, in distal convoluted tubule cells, Ang II dose and time-dependently upregulated WNK4/SPAK/NCC kinase pathway and NPR-C/Gi/PLC/PKC signaling pathway mediated NCC activation. These results demonstrate that NPR-C signaling regulates NCC function contributing to sodium retention-mediated elevated blood pressure, which suggests that NPR-C is a promising candidate for the treatment of sodium retention-related hypertension.

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