scholarly journals Activation of the Hypoxia-Inducible Factor Pathway Inhibits Epithelial Sodium Channel-Mediated Sodium Transport in Collecting Duct Principal Cells

2021 ◽  
pp. ASN.2021010046
Author(s):  
Eva Dizin ◽  
Valerie Olivier ◽  
Isabelle Roth ◽  
Ali Sassi ◽  
Grégoire Arnoux ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Knockout Mice ◽  
Sodium Transport ◽  
Sodium Intake ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Sodium Reabsorption ◽  
Active Sodium ◽  
Principal Cells ◽  
Hif Pathway

Background Active sodium reabsorption is the major factor influencing renal oxygen consumption and production of reactive oxygen species (ROS). Increased sodium reabsorption uses more oxygen, which may worsen medullary hypoxia and produce more ROS via enhanced mitochondrial ATP synthesis. Both mechanisms may activate the hypoxiainducible factor (HIF) pathway. Because the collecting duct is exposed to low oxygen pressure and variations of active sodium transport, we assessed whether the HIF pathway controls epithelial sodium channel (ENaC)-dependent sodium transport. Methods We investigated HIF's effect on ENaC expression in mpkCCDcl4 cells (a model of collecting duct principal cells) using real-time PCR and Western blot and ENaC activity by measuring amiloride-sensitive current. We also assessed the effect of hypoxia and sodium intake on abundance of kidney sodium transporters in wild-type and inducible kidney tubule-specific Hif1α knockout mice. Results In cultured cells, activation of the HIF pathway by dimethyloxalylglycine or hypoxia inhibited sodium transport and decreased expression of βENaC and γENaC, as well as of Na,K-ATPase. HIF1α silencing increased βENaC and γENaC expression and stimulated sodium transport. A constitutively active mutant of HIF1α produced the opposite effect. Aldosterone and inhibition of the mitochondrial respiratory chain slowly activated the HIF pathway, suggesting that ROS may also activate HIF. Decreased γENaC abundance induced by hypoxia in normal mice was abolished in Hif1α knockout mice. Similarly, Hif1α knockout led to increased γENaC abundance under high sodium intake. Conclusions This study reveals that γENaC expression and activity are physiologically controlled by the HIF pathway, which may represent a negative feedback mechanism to preserve oxygenation and/or prevent excessive ROS generation under increased sodium transport.

scholarly journals Interaction between Epithelial Sodium Channel γ-Subunit and Claudin-8 Modulates Paracellular Sodium Permeability in Renal Collecting Duct

2020 ◽  
Vol 31 (5) ◽  
pp. 1009-1023 ◽  
Author(s):  
Ali Sassi ◽  
Yubao Wang ◽  
Alexandra Chassot ◽  
Olga Komarynets ◽  
Isabelle Roth ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Knockout Mice ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Paracellular Permeability ◽  
Sodium Reabsorption ◽  
Kidney Tubule ◽  
Sodium Permeability ◽  
Tubular Lumen ◽  
Renal Collecting Duct

BackgroundWater and solute transport across epithelia can occur via the transcellular or paracellular pathways. Tight junctions play a key role in mediating paracellular ion reabsorption in the kidney. In the renal collecting duct, which is a typical absorptive tight epithelium, coordination between transcellular sodium reabsorption and paracellular permeability may prevent the backflow of reabsorbed sodium to the tubular lumen along a steep electrochemical gradient.MethodsTo investigate whether transcellular sodium transport controls tight-junction composition and paracellular permeability via modulating expression of the transmembrane protein claudin-8, we used cultured mouse cortical collecting duct cells to see how overexpression or silencing of epithelial sodium channel (ENaC) subunits and claudin-8 affect paracellular permeability. We also used conditional kidney tubule–specific knockout mice lacking ENaC subunits to assess the ENaC’s effect on claudin-8 expression.ResultsOverexpression or silencing of the ENaC γ-subunit was associated with parallel and specific changes in claudin-8 abundance. Increased claudin-8 abundance was associated with a reduction in paracellular permeability to sodium, whereas decreased claudin-8 abundance was associated with the opposite effect. Claudin-8 overexpression and silencing reproduced these functional effects on paracellular ion permeability. Conditional kidney tubule–specific ENaC γ-subunit knockout mice displayed decreased claudin-8 expression, confirming the cell culture experiments' findings. Importantly, ENaC β-subunit or α-subunit silencing or kidney tubule–specific β-ENaC or α-ENaC knockout mice did not alter claudin-8 abundance.ConclusionsOur data reveal the specific coupling between ENaC γ-subunit and claudin-8 expression. This coupling may play an important role in preventing the backflow of reabsorbed solutes and water to the tubular lumen, as well as in coupling paracellular and transcellular sodium permeability.

Vasopressin-mediated regulation of epithelial sodium channel abundance in rat kidney

2000 ◽  
Vol 279 (1) ◽  
pp. F46-F53 ◽  
Author(s):  
Carolyn A. Ecelbarger ◽  
Gheun-Ho Kim ◽  
James Terris ◽  
Shyama Masilamani ◽  
Carter Mitchell ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Sodium Transport ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Epithelial Sodium Channel ◽  
Sodium Reabsorption ◽  
Acute Administration ◽  
Brattleboro Rats ◽  
Water Restriction ◽  
Short Term

Sodium transport is increased by vasopressin in the cortical collecting ducts of rats and rabbits. Here we investigate, by quantitative immunoblotting, the effects of vasopressin on abundances of the epithelial sodium channel (ENaC) subunits (α, β, and γ) in rat kidney. Seven-day infusion of 1-deamino-[8-d-arginine]-vasopressin (dDAVP) to Brattleboro rats markedly increased whole kidney abundances of β- and γ-ENaC (to 238% and 288% of vehicle, respectively), whereas α-ENaC was more modestly, yet significantly, increased (to 142% of vehicle). Similarly, 7-day water restriction in Sprague-Dawley rats resulted in significantly increased abundances of β- and γ- but no significant change in α-ENaC. Acute administration of dDAVP (2 nmol) to Brattleboro rats resulted in modest, but significant, increases in abundance for all ENaC subunits, within 1 h. In conclusion, all three subunits of ENaC are upregulated by vasopressin with temporal and regional differences. These changes are too slow to play a major role in the short-term action of vasopressin to stimulate sodium reabsorption in the collecting duct. Long-term increases in ENaC abundance should add to the short-term regulatory mechanisms (undefined in this study) to enhance sodium transport in the renal collecting duct.

scholarly journals Regulation of the epithelial sodium channel by accessory proteins

2003 ◽  
Vol 371 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Kelly GORMLEY ◽  
Yanbin DONG ◽  
Giuseppe A. SAGNELLA
Keyword(s):  
Blood Pressure ◽  
Cystic Fibrosis ◽  
Sodium Channel ◽  
Sodium Transport ◽  
Genetic Disorders ◽  
Epithelial Sodium Channel ◽  
Sodium Balance ◽  
Sodium Reabsorption ◽  
Channel Activity ◽  
Cellular Mechanisms

The epithelial sodium channel (ENaC) is of fundamental importance in the control of sodium fluxes in epithelial cells. Modulation of sodium reabsorption through the distal nephron ENaC is an important component in the overall control of sodium balance, blood volume and thereby of blood pressure. This is clearly demonstrated by rare genetic disorders of sodium-channel activity (Liddle's syndrome and pseudohypoaldosteronism type 1), associated with contrasting effects on blood pressure. The mineralocorticoid aldosterone is a well-established modulator of sodium-channel activity. Considerable insight has now been gained into the intracellular signalling pathways linking aldosterone-mediated changes in gene transcription with changes in ion transport. Activating pathways include aldosterone-induced proteins and especially the serum- and glucocorticoid-inducible kinase (SGK) and the small G-protein, K-Ras 2A. Targeting of the ENaC for endocytosis and degradation is now emerging as a major mechanism for the down-regulation of channel activity. Several proteins acting in concert are an intrinsic part of this process but Nedd4 (neural precursor cell expressed developmentally down-regulated 4) is of central importance. Other mechanisms known to interact with ENaC and affect sodium transport include channel-activating protease 1 (CAP-1), a membrane-anchored protein, and the cystic fibrosis transmembrane regulator. The implications of research on accessory factors controlling ENaC activity are wide-ranging. Understanding cellular mechanisms controlling ENaC activity may provide a more detailed insight not only of ion-channel abnormalities in cystic fibrosis but also of the link between abnormal renal sodium transport and essential hypertension.

scholarly journals Apelin-13 Decreases Epithelial Sodium Channel (ENaC) Expression and Activity in Kidney Collecting Duct Cells

2022 ◽  
Vol 56 (1) ◽  
pp. 1-12
Keyword(s):  
Sodium Channel ◽  
Collecting Duct ◽  
Water Channel ◽  
Epithelial Sodium Channel ◽  
Sodium Balance ◽  
Principal Cells ◽  
Wide Range ◽  
Expression And Activity ◽  
Epithelial Sodium Channel Enac

BACKGROUND/AIMS: Apelin and its G protein-coupled receptor APLNR (also known as APJ) are widely expressed within the central nervous system and peripheral organs including heart, lung and kidney. Several studies have shown that the apelin/APJ system is involved in various important physiological processes such as energy metabolism, cardiovascular functions and fluid homeostasis. In the kidney, the apelin/APJ system performs a wide range of activities. We recently demonstrated that apelin antagonises the hydro-osmotic effect of vasopressin on aquaporin-2 water channel (AQP-2) expression by reducing its mRNA and protein levels in collecting duct principal cells. The central role of these cells in water and sodium transport is governed by AQP-2 and the epithelial sodium channel (ENaC). The coordination of these channels is essential for the control of extracellular fluid volume, sodium homeostasis and blood pressure. This study aimed at investigating the role of apelin in the regulation of sodium balance in the distal nephron, and more specifically its involvement in modulating the expression and activity of ENaC in collecting duct principal cells. METHODS: mpkCCD cells were incubated in the presence of aldosterone and treated with or without apelin-13. Transepithelial Na+ current was measured and the changes in ENaC expression determined by RT-PCR and immunoblotting. RESULTS: Our data show that apelin-13 reduces the transepithelial sodium amiloride-sensitive current in collecting duct principal cells after 8h and 24h treatment. This effect was associated with a decrease in αENaC subunit expression and mediated through the ERK pathway as well as SGK1 and Nedd4-2. CONCLUSION: Our findings indicate that apelin is involved in the fine regulation of sodium balance in the renal collecting duct by opposing the effects of aldosterone, likely by activation of ENaC ubiquitination.

Regulation of blood pressure, the epithelial sodium channel (ENaC), and other key renal sodium transporters by chronic insulin infusion in rats

2006 ◽  
Vol 290 (5) ◽  
pp. F1055-F1064 ◽  
Author(s):  
Jian Song ◽  
Xinqun Hu ◽  
Shahla Riazi ◽  
Swasti Tiwari ◽  
James B. Wade ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Sodium Channel ◽  
Insulin Infusion ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Kidney Cortex ◽  
Sodium Reabsorption ◽  
Cortical Collecting Duct ◽  
Sprague Dawley ◽  
Epithelial Sodium Channel Enac

Hyperinsulinemia is associated with hypertension. Dysregulation of renal distal tubule sodium reabsorption may play a role. We evaluated the regulation of the epithelial sodium channel (ENaC) and the thiazide-sensitive Na-Cl cotransporter (NCC) during chronic hyperinsulinemia in rats and correlated these changes to blood pressure as determined by radiotelemetry. Male Sprague-Dawley rats (∼270 g) underwent one of the following three treatments for 4 wk ( n = 6/group): 1) control; 2) insulin-infused plus 20% dextrose in drinking water; or 3) glucose water-drinking (20% dextrose in water). Mean arterial pressures were increased by insulin and glucose (mmHg at 3 wk): 98 ± 1 (control), 107 ± 2 (insulin), and 109 ± 3 (glucose), P < 0.01. Insulin (but not glucose) increased natriuretic response to benzamil (ENaC inhibitor) and hydrochlorothiazide (NCC inhibitor) on average by 125 and 60%, respectively, relative to control rats, suggesting increased activity of these reabsorptive pathways. Neither insulin nor glucose affected the renal protein abundances of NCC or the ENaC subunits (α, β, and γ) in kidney cortex, outer medulla, or inner medulla in a major way, as determined by immunoblotting. However, insulin and to some extent glucose increased apical localization of these subunits in cortical collecting duct principal cells, as determined by immunoperoxidase labeling. In addition, insulin decreased cortical “with no lysine” kinase (WNK4) abundance (by 16% relative to control), which may have increased NCC activity. Overall, insulin infusion increased blood pressure, and NCC and ENaC activity in rats. Increased apical targeting of ENaC and decreased WNK4 expression may be involved.

scholarly journals Conditional Transgenic Mice for Studying the Role of the Glucocorticoid Receptor in the Renal Collecting Duct

Endocrinology ◽  
2008 ◽  
Vol 150 (5) ◽  
pp. 2202-2210 ◽  
Author(s):  
Aurélie Nguyen Dinh Cat ◽  
Antoine Ouvrard-Pascaud ◽  
François Tronche ◽  
Maud Clemessy ◽  
Daniel Gonzalez-Nunez ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Glucocorticoid Receptor ◽  
Sodium Channel ◽  
Leucine Zipper ◽  
Collecting Duct ◽  
Extracellular Volume ◽  
Epithelial Sodium Channel ◽  
Sodium Reabsorption ◽  
Renal Collecting Duct

The mineralocorticoid receptor (MR) is a major regulator of renal sodium reabsorption and body fluid homeostasis. However, little is known about glucocorticoid receptor (GR)-dependent renal effects. Glucocorticoids may activate both receptors, so it is difficult to distinguish between MR- and GR-mediated effects in vivo. To overcome this complexity, we used a transgenic mouse model allowing conditional GR overexpression (doxycycline inducible TetON system, Hoxb7 promoter) in the renal collecting duct (CD) to identify GR-regulated genes involved in sodium transport in the CD. In microdissected cortical CD, induction of GR expression led (after 2 d of doxycycline) to increased α-epithelial sodium channel and glucocorticoid-induced leucine zipper and decreased abundance of with-no-lysine kinase 4 transcripts, without modification of Na,K-ATPase, serum- and glucocorticoid-kinase-1, or MR expression. No changes occurred in the upstream distal and connecting tubules [distal convoluted tubule (DCT), connecting tubule (CNT)]. Sodium excretion was unaltered, but the urinary aldosterone concentration was reduced, suggesting compensation of transitory extracellular volume expansion that subsequently disappeared. At steady state, i.e. after 15 d of doxycycline administration, transcript abundance remained altered in the CD, whereas mirror changes appeared in the DCT and CNT. Plasma aldosterone or glucocorticoids and blood pressure were all unaffected. These experiments show that: 1) GR, in addition to MR, controls epithelial sodium channel- and glucocorticoid-induced leucine zipper expression in vivo in the CD; 2) with-no-lysine kinase 4 is negatively controlled by GR; and 3) the DCT and CNT compensate for these alterations to maintain normal sodium reabsorption and blood pressure. These results suggest that enhanced GR expression may contribute to enhanced sodium retention in some pathological situations.

scholarly journals Epithelial Sodium Channel Is a Key Mediator of Growth Hormone-Induced Sodium Retention in Acromegaly

Endocrinology ◽  
2008 ◽  
Vol 149 (7) ◽  
pp. 3294-3305 ◽  
Author(s):  
Peter Kamenicky ◽  
Say Viengchareun ◽  
Anne Blanchard ◽  
Geri Meduri ◽  
Philippe Zizzari ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Sodium Transport ◽  
Epithelial Sodium Channel ◽  
Janus Kinase ◽  
Sodium Reabsorption ◽  
Sodium Retention ◽  
Signal Transducer ◽  
Distal Nephron ◽  
Igf I ◽  
Gc Rats

Acromegalic patients present with volume expansion and arterial hypertension, but the renal sites and molecular mechanisms of direct antinatriuretic action of GH remain unclear. Here, we show that acromegalic GC rats, which are chronically exposed to very high levels of GH, exhibited a decrease of furosemide-induced natriuresis and an increase of amiloride-stimulated natriuresis compared with controls. Enhanced Na+,K+-ATPase activity and altered proteolytic maturation of epithelial sodium channel (ENaC) subunits in the cortical collecting ducts (CCDs) of GC rats provided additional evidence for an increased sodium reabsorption in the late distal nephron under chronic GH excess. In vitro experiments on KC3AC1 cells, a murine CCD cell model, revealed the expression of functional GH receptors and IGF-I receptors coupled to activation of Janus kinase 2/signal transducer and activator of transcription 5, ERK, and AKT signaling pathways. That GH directly controls sodium reabsorption in CCD cells is supported by: 1) stimulation of transepithelial sodium transport inhibited by GH receptor antagonist pegvisomant; 2) induction of α-ENaC mRNA expression; and 3) identification of signal transducer and activator of transcription 5 binding to a response element located in the α-ENaC promoter, indicative of the transcriptional regulation of α-ENaC by GH. Our findings provide the first evidence that GH, in concert with IGF-I, stimulates ENaC-mediated sodium transport in the late distal nephron, accounting for the pathogenesis of sodium retention in acromegaly.

scholarly journals Iron Inhibits the Translation and Activity of the Renal Epithelial Sodium Channel

Biology ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 123
Author(s):  
Abdel A. Alli ◽  
Ling Yu ◽  
Ewa Wlazlo ◽  
Sadat Kasem ◽  
Mohammed F. Gholam ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Knockout Mice ◽  
Collecting Duct ◽  
Iron Chelation ◽  
Epithelial Sodium Channel ◽  
Renal Tubules ◽  
Local Responses ◽  
Collecting Duct Cells ◽  
Expression And Activity

Hypertension is associated with an increased renal expression and activity of the epithelial sodium channel (ENaC) and iron deficiency. Distal tubules absorb iron, causing perturbations that may influence local responses. In this observational study, we investigated the relationship between iron content and ENaC expression and activity using two cell lines and hepcidin knockout mice (a murine model of iron overload). We found that iron did not transcriptionally regulate ENaC in hepcidin knockout mice or in vitro in collecting duct cells. However, the renal tubules of hepcidin knockout mice have a lower expression of ENaC protein. ENaC activity in cultured Xenopus 2F3 cells and mpkCCD cells was inhibited by iron, which could be reversed by iron chelation. Thus, our novel findings implicate iron as a regulator of ENaC protein and its activity.

scholarly journals Prostaglandin E2 stimulates the epithelial sodium channel (ENaC) in cultured mouse cortical collecting duct cells in an autocrine manner

2020 ◽  
Vol 152 (8) ◽  
Author(s):  
Morag K. Mansley ◽  
Christian Niklas ◽  
Regina Nacken ◽  
Kathrin Mandery ◽  
Hartmut Glaeser ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Sodium Channel ◽  
Sodium Transport ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Prostaglandin E ◽  
Cortical Collecting Duct ◽  
Transepithelial Sodium Transport ◽  
Epithelial Sodium Channel Enac

Prostaglandin E2 (PGE2) is the most abundant prostanoid in the kidney, affecting a wide range of renal functions. Conflicting data have been reported regarding the effects of PGE2 on tubular water and ion transport. The amiloride-sensitive epithelial sodium channel (ENaC) is rate limiting for transepithelial sodium transport in the aldosterone-sensitive distal nephron. The aim of the present study was to explore a potential role of PGE2 in regulating ENaC in cortical collecting duct (CCD) cells. Short-circuit current (ISC) measurements were performed using the murine mCCDcl1 cell line known to express characteristic properties of CCD principal cells and to be responsive to physiological concentrations of aldosterone and vasopressin. PGE2 stimulated amiloride-sensitive ISC via basolateral prostaglandin E receptors type 4 (EP4) with an EC50 of ∼7.1 nM. The rapid stimulatory effect of PGE2 on ISC resembled that of vasopressin. A maximum response was reached within minutes, coinciding with an increased abundance of β-ENaC at the apical plasma membrane and elevated cytosolic cAMP levels. The effects of PGE2 and vasopressin were nonadditive, indicating similar signaling cascades. Exposing mCCDcl1 cells to aldosterone caused a much slower (∼2 h) increase of the amiloride-sensitive ISC. Interestingly, the rapid effect of PGE2 was preserved even after aldosterone stimulation. Furthermore, application of arachidonic acid also increased the amiloride-sensitive ISC involving basolateral EP4 receptors. Exposure to arachidonic acid resulted in elevated PGE2 in the basolateral medium in a cyclooxygenase 1 (COX-1)–dependent manner. These data suggest that in the cortical collecting duct, locally produced and secreted PGE2 can stimulate ENaC-mediated transepithelial sodium transport.

Sign in / Sign up

Export Citation Format

Share Document