Compromised regulation of the collecting duct ENaC activity in mice lacking AT<sub>1a</sub> receptor

Mamenko, Mykola; Zaika, Oleg; Tomilin, Viktor; Jensen, Vanessa; Pochynyuk, Oleh

doi:10.1002/jcp.26552

Cited by 11 publications

(16 citation statements)

References 46 publications

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“…ENaC activity was assessed using previously published procedures, detailed in Supplement. Female and male SD rats, bred and studied at Medical College of Georgia at Augusta University, were fed grain‐based vivarium chow (Teklad Irradiated Rodent Diet 8904) and studied under baseline conditions and after infusion of AngII as described in Protocol 1.…”

Section: Methodsmentioning

confidence: 99%

Electrolyte and transporter responses to angiotensin II induced hypertension in female and male rats and mice

et al. 2020

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Aim: Sexual dimorphisms are evident along the nephron: Females (F) exhibit higher ratios of renal distal to proximal Na + transporters' abundance, greater lithium clearance (C Li ) more rapid natriuresis in response to saline infusion and lower plasma [K + ] vs. males (M). During angiotensin II infusion hypertension (AngII-HTN) M exhibit distal Na + transporter activation, lower proximal and medullary loop transporters, blunted natriuresis in response to saline load, and reduced plasma [K + ]. This study aimed to determine whether responses of F to AngII-HTN mimicked those in M or were impacted by sexual dimorphisms evident at baseline. Methods: Sprague Dawley rats and C57BL/6 mice were AngII infused via osmotic minipumps 2 and 3 weeks, respectively, and assessed by metabolic cage collections, tail-cuff sphygmomanometer, semi-quantitative immunoblotting of kidney and patch-clamp electrophysiology. Results: In F rats, AngII-infusion increased BP to 190 mm Hg, increased phosphorylation of cortical NKCC2, NCC and cleavage of ENaC two to threefold, increased ENaC channel activity threefold and aldosterone 10-fold. K + excretion increased and plasma [K + ] decreased. Evidence of natriuresis in F included increased urine Na + excretion and C Li , and decreased medullary NHE3, NKCC2 and Na,K-ATPase abundance. In C57BL/6 mice, AngII-HTN increased abundance of distal Na + transporters, suppressed proximal-medullary transporters and reduced plasma [K + ] in both F and M. Conclusion: Despite baseline sexual dimorphisms, AngII-HTN provokes similar increases in BP, aldosterone, distal transporters, ENaC channel activation and K + loss accompanied by similar suppression of proximal and loop Na + transporters, natriuresis and diuresis in females and males. K E Y W O R D S angiotensin II, ENaC, female, potassium, proteinuria, sodium transport 2 of 12 | VEIRAS Et Al.

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Section: Methodsmentioning

confidence: 99%

Electrolyte and transporter responses to angiotensin II induced hypertension in female and male rats and mice

et al. 2020

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“…For patch-clamp analysis, C57BL/6 mice were fed with Na ϩ -deficient diet (Ͻ0.01% Na ϩ , TD.90228, Envigo) for 1 wk to increase ENaC activity in the cortical collecting duct (CCD). The procedure for CCD isolation has been previously described (43). Briefly, kidneys were cut into thin slices (Ͻ1 mm) and placed into ice-cold solution containing (in mmol/L) 150 NaCl, 5 KCl, 1 CaCl2, 2 MgCl2, 5 glucose, and 10 HEPES (pH 7.35).…”

Section: Methodsmentioning

confidence: 99%

PF-06869206 is a selective inhibitor of renal P_itransport: evidence from in vitro and in vivo studies

Thomas

Xue

Tomilin

et al. 2020

American Journal of Physiology-Renal Physiology

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Plasma phosphate (Pi) levels are tightly controlled, and elevated plasma Pi levels are associated with an increased risk of cardiovascular complications and death. Two renal transport proteins mediate the majority of Pi reabsorption, the Na+-phosphate cotransporters Npt2a and Npt2c, with Npt2a accounting for 70-80% of Pi reabsorption. The aim of this study was to determine the in vitro effects of a novel Npt2a inhibitor (Npt2a-I, PF-06869206) in opossum kidney (OK) cells as well as determine its selectivity in vivo in Npt2a knockout (Npt2a-/-) mice. In OK cells, Npt2a-I caused dose-dependent reductions of Na+-dependent Pi uptake (IC50: ~1.4 μmol/L), while the unselective Npt2 inhibitor phosphonoformic acid (PFA) resulted in a ~20% stronger inhibition of Pi uptake. The dose-dependent inhibitory effects were present after 24-hour incubation with both low and high Pi media. Michaelis-Menten kinetics in OK cells identified a ~2.4-fold higher Km for Pi in response to Npt2a inhibition with no significant change in apparent Vmax. Higher PTH concentrations decreased Pi uptake equivalent to the maximal inhibitory effect of Npt2a-I. In vivo, the Npt2a-I induced a dose-dependent increase in urinary Pi excretion in wild-type mice (ED50: ~23 mg/kg), which was completely absent in Npt2a-/- mice, alongside a lack of decrease in plasma Pi. Of note, the Npt2a-I-induced dose-dependent increase in urinary Na+ excretion was still present in Npt2a-/- mice, a response possibly mediated by an off-target acute inhibitory effect of the Npt2a-I on open probability of the epithelial Na+ channel, ENaC, in the cortical collecting duct.

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“…We recently showed that ClC-K2 activity in the intercalated cells is inversely related to dietary Cl − intake but not to aldosterone ( 45 ). Thus, it is plausible to propose that elevations of Ang II during volume depletion (which is also chloride depletion) increases ENaC-mediated sodium and pendrin/ClC-K2–dependent Cl − reabsorption by acting on principal and intercalated collecting duct cells, respectively ( 10 , 53 ). Furthermore, Ang II seems to be also critical to determine ClC-K2 expression.…”

Section: Discussionmentioning

confidence: 99%

“…Ang II augments chloride reabsorption in the collecting duct by stimulating apical Cl − /HCO 3 − exchange ( 10 ) and basolateral Cl − exit via ClC-K2 ( Figs. 1 and 3 ) in intercalated cells and increases the apical ENaC-mediated sodium entry in principal cells ( 14 , 53 ). In this regard, the lack of stimulatory effects of Ang II on K ir 4.1/5.1 ( Figs.…”

Section: Discussionmentioning

confidence: 99%

“…Although ROS-dependent redox-signaling processes contribute significantly to the normal cellular responses to Ang II, excessive ROS accumulation drives proinflammatory and profibrotic actions of Ang II contributing to endothelial dysfunction, fibrosis, and the development of hypertension ( 64 ). Indeed, we previously showed that Ang II increases ENaC activity by increasing ROS in the collecting duct principal cells ( 14 ) and this is an important mechanism for stimulation of ENaC-dependent Na + reabsorption in response to dietary sodium deficiency ( 53 ). However, chronic Ang II infusion stimulates ENaC activity far beyond the physiological range independently of aldosterone thus contributing to excessive volume retention and hypertension ( 13 ).…”

Section: Discussionmentioning

confidence: 99%

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Angiotensin II increases activity of the ClC-K2 Cl− channel in collecting duct intercalated cells by stimulating production of reactive oxygen species

Khayyat¹,

Zaika²,

Tomilin

et al. 2021

Journal of Biological Chemistry

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The renal collecting duct plays a critical role in setting urinary volume and composition, with principal cells transporting Na + and K + and intercalated cells mediating Cl − reabsorption. Published evidence implies Angiotensin II (Ang II) is a potent regulator of the collecting duct apical transport systems in response to systemic volume depletion. However, virtually nothing is known about Ang II actions on the basolateral conductance of principal and intercalated cells. Here, we combined macroscopic and single channel patch clamp recordings from freshly isolated mouse collecting ducts with biochemical and fluorescence methods to demonstrate an acute stimulation of the basolateral Cl − conductance and specifically the ClC-K2 Cl − channel by nanomolar Ang II concentrations in intercalated cells. In contrast, Ang II did not exhibit measurable effects on the basolateral conductance and on K ir 4.1/5.1 potassium channel activity in principal cells. Although both Ang II receptors AT 1 and AT 2 are expressed in collecting duct cells, we show that AT 1 receptors were essential for stimulatory actions of Ang II on ClC-K2. Moreover, AT 1 R −/− mice had decreased renal ClC-K2 expression. We further demonstrated that activation of NADPH oxidases is the major signaling pathway downstream of Ang II-AT 1 R that leads to stimulation of ClC-K2. Treatment of freshly isolated collecting ducts with Ang II led to production of reactive oxygen species on the same timescale as single channel ClC-K2 activation. Overall, we propose that Ang II-dependent regulation of ClC-K2 in intercalated cells is instrumental for stimulation of Cl − reabsorption by the collecting duct, particularly during hypovolemic states.

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Compromised regulation of the collecting duct ENaC activity in mice lacking AT_1a receptor

Cited by 11 publications

References 46 publications

Electrolyte and transporter responses to angiotensin II induced hypertension in female and male rats and mice

Electrolyte and transporter responses to angiotensin II induced hypertension in female and male rats and mice

PF-06869206 is a selective inhibitor of renal P_itransport: evidence from in vitro and in vivo studies

Angiotensin II increases activity of the ClC-K2 Cl− channel in collecting duct intercalated cells by stimulating production of reactive oxygen species

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Compromised regulation of the collecting duct ENaC activity in mice lacking AT1a receptor

Cited by 11 publications

References 46 publications

Electrolyte and transporter responses to angiotensin II induced hypertension in female and male rats and mice

Electrolyte and transporter responses to angiotensin II induced hypertension in female and male rats and mice

PF-06869206 is a selective inhibitor of renal Pitransport: evidence from in vitro and in vivo studies

Angiotensin II increases activity of the ClC-K2 Cl− channel in collecting duct intercalated cells by stimulating production of reactive oxygen species

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Compromised regulation of the collecting duct ENaC activity in mice lacking AT_1a receptor

PF-06869206 is a selective inhibitor of renal P_itransport: evidence from in vitro and in vivo studies