International Journal of Molecular Sciences

Research

Jump to: Review

19 pages, 3015 KiB

Open AccessArticle

Metabolic Syndrome and Salt-Sensitive Hypertension in Polygenic Obese TALLYHO/JngJ Mice: Role of Na/K-ATPase Signaling

by Yanling Yan, Jiayan Wang, Muhammad A. Chaudhry, Ying Nie, Shuyan Sun, Jazmin Carmon, Preeya T. Shah, Fang Bai, Rebecca Pratt, Cameron Brickman, Komal Sodhi, Jung Han Kim, Sandrine Pierre, Deepak Malhotra, Gary O. Rankin, Zi-jian Xie, Joseph I. Shapiro and Jiang Liu

Int. J. Mol. Sci. 2019, 20(14), 3495; https://doi.org/10.3390/ijms20143495 - 16 Jul 2019

Cited by 11 | Viewed by 4698

Abstract

We have demonstrated that Na/K-ATPase acts as a receptor for reactive oxygen species (ROS), regulating renal Na⁺ handling and blood pressure. TALLYHO/JngJ (TH) mice are believed to mimic the state of obesity in humans with a polygenic background of type 2 diabetes. [...] Read more.

We have demonstrated that Na/K-ATPase acts as a receptor for reactive oxygen species (ROS), regulating renal Na⁺ handling and blood pressure. TALLYHO/JngJ (TH) mice are believed to mimic the state of obesity in humans with a polygenic background of type 2 diabetes. This present work is to investigate the role of Na/K-ATPase signaling in TH mice, focusing on susceptibility to hypertension due to chronic excess salt ingestion. Age-matched male TH and the control C57BL/6J (B6) mice were fed either normal diet or high salt diet (HS: 2, 4, and 8% NaCl) to construct the renal function curve. Na/K-ATPase signaling including c-Src and ERK1/2 phosphorylation, as well as protein carbonylation (a commonly used marker for enhanced ROS production), were assessed in the kidney cortex tissues by Western blot. Urinary and plasma Na⁺ levels were measured by flame photometry. When compared to B6 mice, TH mice developed salt-sensitive hypertension and responded to a high salt diet with a significant rise in systolic blood pressure indicative of a blunted pressure-natriuresis relationship. These findings were evidenced by a decrease in total and fractional Na⁺ excretion and a right-shifted renal function curve with a reduced slope. This salt-sensitive hypertension correlated with changes in the Na/K-ATPase signaling. Specifically, Na/K-ATPase signaling was not able to be stimulated by HS due to the activated baseline protein carbonylation, phosphorylation of c-Src and ERK1/2. These findings support the emerging view that Na/K-ATPase signaling contributes to metabolic disease and suggest that malfunction of the Na/K-ATPase signaling may promote the development of salt-sensitive hypertension in obesity. The increased basal level of renal Na/K-ATPase-dependent redox signaling may be responsible for the development of salt-sensitive hypertension in polygenic obese TH mice. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

14 pages, 2415 KiB

Open AccessArticle

Testis-Specific Isoform of Na/K-ATPase (ATP1A4) Interactome in Raft and Non-Raft Membrane Fractions from Capacitated Bovine Sperm

by Gayathri D. Rajamanickam, John P. Kastelic and Jacob C. Thundathil

Int. J. Mol. Sci. 2019, 20(13), 3159; https://doi.org/10.3390/ijms20133159 - 28 Jun 2019

Cited by 11 | Viewed by 3471

Abstract

The plasma membrane of sperm contains highly dynamic lipid microdomains (rafts), which house signaling proteins with a role in regulating capacitation. We reported that ATP1A4, the testis-specific isoform of Na/K-ATPase, interacted with caveolin-1, Src, epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinases [...] Read more.

The plasma membrane of sperm contains highly dynamic lipid microdomains (rafts), which house signaling proteins with a role in regulating capacitation. We reported that ATP1A4, the testis-specific isoform of Na/K-ATPase, interacted with caveolin-1, Src, epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinases 1/2 (ERK1/2) in raft and non-raft domains of the plasma membrane of bovine sperm during capacitation. The objective of the present study was to use a proteomic approach to characterize the ATP1A4 interactome in rafts and non-rafts from capacitated bovine sperm. The non-raft interactome included hexokinase 1, plakophilin 1, desmoglein 1, 14-3-3 protein ζ/δ, cathepsin D and heat shock protein beta1 proteins exclusively, whereas glutathione S-transferase and annexin A2 were unique to raft interactome. However, a disintegrin and metalloprotease 32 (ADAM 32), histone H4, actin, acrosin, serum albumin and plakoglobin were identified in both raft and non-raft fractions of capacitated sperm. Based on gene ontology studies, these differentially interacted proteins were implicated in cell–cell adhesion, signal transduction, fertilization, metabolism, proteolysis and DNA replication, in addition to acting as transport/carrier and cytoskeletal proteins. Overall, we identified proteins not previously reported to interact with ATP1A4; furthermore, we inferred that ATP1A4 may have a role in sperm capacitation. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

24 pages, 1404 KiB

Open AccessArticle

Gene and Protein Expression Profile of Selected Molecular Targets Mediating Electrophysiological Function in Pgc-1α Deficient Murine Atria

by Karan R. Chadda, Charlotte E. Edling, Haseeb Valli, Shiraz Ahmad, Christopher L.-H. Huang and Kamalan Jeevaratnam

Int. J. Mol. Sci. 2018, 19(11), 3450; https://doi.org/10.3390/ijms19113450 - 2 Nov 2018

Cited by 8 | Viewed by 3569

Abstract

Increases in the prevalence of obesity, insulin resistance, and metabolic syndrome has led to the increase of atrial fibrillation (AF) cases in the developed world. These AF risk factors are associated with mitochondrial dysfunction, previously modelled using peroxisome proliferator activated receptor-γ (PPARγ) coactivator-1 [...] Read more.

Increases in the prevalence of obesity, insulin resistance, and metabolic syndrome has led to the increase of atrial fibrillation (AF) cases in the developed world. These AF risk factors are associated with mitochondrial dysfunction, previously modelled using peroxisome proliferator activated receptor-γ (PPARγ) coactivator-1 (Pgc-1)-deficient murine cardiac models. We explored gene and protein expression profiles of selected molecular targets related to electrophysiological function in murine Pgc-1α^−/− atria. qPCR analysis surveyed genes related to Na⁺-K⁺-ATPase, K⁺ conductance, hyperpolarisation-activated cyclic nucleotide-gated (Hcn), Na⁺ channels, Ca²⁺ channels, and indicators for adrenergic and cholinergic receptor modulation. Western blot analysis for molecular targets specific to conduction velocity (Na_v1.5 channel and gap junctions) was performed. Transcription profiles revealed downregulation of molecules related to Na⁺-K⁺-ATPase transport, Hcn-dependent pacemaker function, Na⁺ channel-dependent action potential activation and propagation, Ca²⁺ current generation, calsequestrin-2 dependent Ca²⁺ homeostasis, and adrenergic α_1D dependent protection from hypertrophic change. Na_v1.5 channel protein expression but not gap junction expression was reduced in Pgc-1α^−/− atria compared to WT. Na_v1.5 reduction reflects corresponding reduction in its gene expression profile. These changes, as well as the underlying Pgc-1α^−/− alteration, suggest potential pharmacological targets directed towards either upstream PGC-1 signalling mechanisms or downstream ion channel changes. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Graphical abstract

14 pages, 4647 KiB

Open AccessArticle

Dietary Sodium Restriction Reduces Arterial Stiffness, Vascular TGF-β-Dependent Fibrosis and Marinobufagenin in Young Normotensive Rats

by Yulia N. Grigorova, Wen Wei, Natalia Petrashevskaya, Valentina Zernetkina, Ondrej Juhasz, Rachel Fenner, Christian Gilbert, Edward G. Lakatta, Joseph I. Shapiro, Alexei Y. Bagrov and Olga V. Fedorova

Int. J. Mol. Sci. 2018, 19(10), 3168; https://doi.org/10.3390/ijms19103168 - 15 Oct 2018

Cited by 29 | Viewed by 3975

Abstract

High salt (HS) intake stimulates the production of marinobufagenin (MBG), an endogenous steroidal Na/K-ATPase ligand, which activates profibrotic signaling. HS is accompanied by a blood pressure (BP) increase in salt-sensitive hypertension, but not in normotensive animals. Here, we investigated whether HS stimulates MBG [...] Read more.

High salt (HS) intake stimulates the production of marinobufagenin (MBG), an endogenous steroidal Na/K-ATPase ligand, which activates profibrotic signaling. HS is accompanied by a blood pressure (BP) increase in salt-sensitive hypertension, but not in normotensive animals. Here, we investigated whether HS stimulates MBG production and activates transforming growth factor-beta (TGF-β) profibrotic signaling in young normotensive rats, and whether these changes can be reversed by reducing salt to a normal salt (NS) level. Three-month old male Sprague–Dawley rats received NS for 4 and 8 weeks (0.5% NaCl; NS4 and NS8), or HS for 4 and 8 weeks (4% NaCl; HS4 and HS8), or HS for 4 weeks followed by NS for 4 weeks (HS4/NS4), n = 8/group. Systolic BP (SBP), pulse wave velocity (PWV), MBG excretion, aortic collagen 1α2, collagen 4α1 and TGF-β, Smad2, Smad3, Fli-1 mRNA, and total collagen abundance were measured at baseline (BL), and on weeks 4 and 8. Statistical analysis was performed using one-way ANOVA. SBP was not affected by HS (125 ± 5 and 126 ± 6 vs. 128 ± 7 mmHg, HS4 and HS8 vs. BL, p > 0.05). HS increased MBG (164 ± 19 vs. 103 ± 19 pmol/24 h/kg, HS4 vs. BL, p < 0.05) and PWV (3.7 ± 0.2 vs. 2.7 ± 0.2 m/s, HS4 vs. NS4, p < 0.05). HS8 was associated with a further increase in MBG and PWV, with an increase in aortic Col1a2 80%), Col4a1 (50%), Tgfb1 (30%), Smad2 (30%) and Smad3 (45%) mRNAs, and aortic wall collagen (180%) vs. NS8 (all p < 0.05). NS following HS downregulated HS-induced factors: in HS4/NS4, the MBG level was 91 ± 12 pmol/24 h/kg (twofold lower than HS8, p < 0.01), PWV was 3.7 ± 0.3 vs. 4.7 ± 0.2 m/s (HS4/NS4 vs. HS8, p < 0.05), aortic wall Tgfb1, Col1a2, Col4a1, Smad2, Smad3 mRNAs, and collagen abundance were reversed by salt reduction to the BL levels (p < 0.05). HS was associated with an activation of TGF-β signaling, aortic fibrosis and aortic stiffness accompanied by an MBG increase in the absence of SBP changes in young normotensive rats. The reduction of dietary salt following HS decreased MBG, PWV, aortic wall collagen and TGF-β. Thus, HS-induced aortic stiffness in normotensive animals occurred in the context of elevated MBG, which may activate SMAD-dependent TGF-β pro-fibrotic signaling. This data suggests that a decrease in salt consumption could help to restore aortic elasticity and diminish the risk of cardiovascular disease by reducing the production of the pro-fibrotic factor MBG. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Graphical abstract

22 pages, 6552 KiB

Open AccessArticle

Telocinobufagin and Marinobufagin Produce Different Effects in LLC-PK1 Cells: A Case of Functional Selectivity of Bufadienolides

by Luciana S. Amaral, Jainne Martins Ferreira, Danilo Predes, José Garcia Abreu, François Noël and Luis Eduardo M. Quintas

Int. J. Mol. Sci. 2018, 19(9), 2769; https://doi.org/10.3390/ijms19092769 - 14 Sep 2018

Cited by 14 | Viewed by 4249

Abstract

Bufadienolides are cardiotonic steroids (CTS) identified in mammals. Besides Na⁺/K⁺-ATPase inhibition, they activate signal transduction via protein–protein interactions. Diversity of endogenous bufadienolides and mechanisms of action may indicate the presence of functional selectivity and unique cellular outcomes. We evaluated [...] Read more.

Bufadienolides are cardiotonic steroids (CTS) identified in mammals. Besides Na⁺/K⁺-ATPase inhibition, they activate signal transduction via protein–protein interactions. Diversity of endogenous bufadienolides and mechanisms of action may indicate the presence of functional selectivity and unique cellular outcomes. We evaluated whether the bufadienolides telocinobufagin and marinobufagin induce changes in proliferation or viability of pig kidney (LLC-PK1) cells and the mechanisms involved in these changes. In some experiments, ouabain was used as a positive control. CTS exhibited an inhibitory IC₅₀ of 0.20 (telocinobufagin), 0.14 (ouabain), and 3.40 μM (marinobufagin) for pig kidney Na⁺/K⁺-ATPase activity and concentrations that barely inhibited it were tested in LLC-PK1 cells. CTS induced rapid ERK1/2 phosphorylation, but corresponding proliferative response was observed for marinobufagin and ouabain instead of telocinobufagin. Telocinobufagin increased Bax:Bcl-2 expression ratio, sub-G0 cell cycle phase and pyknotic nuclei, indicating apoptosis. Src and MEK1/2 inhibitors blunted marinobufagin but not telocinobufagin effect, which was also not mediated by p38, JNK1/2, and PI3K. However, BIO, a GSK-3β inhibitor, reduced proliferation and, as telocinobufagin, phosphorylated GSK-3β at inhibitory Ser9. Combination of both drugs resulted in synergistic antiproliferative effect. Wnt reporter activity assay showed that telocinobufagin impaired Wnt/β-catenin pathway by acting upstream to β-catenin stabilization. Our findings support that mammalian endogenous bufadienolides may exhibit functional selectivity. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Graphical abstract

18 pages, 2372 KiB

Open AccessArticle

K⁺ and Rb⁺ Affinities of the Na,K-ATPase α₁ and α₂ Isozymes: An Application of ICP-MS for Quantification of Na⁺ Pump Kinetics in Myofibers

by Hesamedin Hakimjavadi, Cory A. Stiner, Tatiana L. Radzyukevich, Jerry B. Lingrel, Natalie Norman, Julio A. Landero Figueroa and Judith A. Heiny

Int. J. Mol. Sci. 2018, 19(9), 2725; https://doi.org/10.3390/ijms19092725 - 12 Sep 2018

Cited by 5 | Viewed by 3726

Abstract

The potassium affinities of Na,K-ATPase isozymes are important determinants of their physiological roles in skeletal muscle. This study measured the apparent K⁺ and Rb⁺ affinities of the Na,K-ATPase α₁ and α₂ isozymes in intact, dissociated myofibers obtained from WT [...] Read more.

The potassium affinities of Na,K-ATPase isozymes are important determinants of their physiological roles in skeletal muscle. This study measured the apparent K⁺ and Rb⁺ affinities of the Na,K-ATPase α₁ and α₂ isozymes in intact, dissociated myofibers obtained from WT and genetically altered mice (α₁^S/Sα₂^R/R and skα₂^−/−). It also validates a new method to quantify cations in intact, dissociated myofibers, using inductively coupled plasma mass spectrometry (ICP-MS). Our findings were that: (1) The extracellular substrate sites of Na,K-ATPase bind Rb⁺ and K⁺ with comparable apparent affinities; however; turnover rate is reduced when Rb⁺ is the transported ion; (2) The rate of Rb⁺ uptake by the Na,K-ATPase is not constant but declines with a half-time of approximately 1.5 min; (3) The apparent K⁺ affinity of the α₂ isozymes for K⁺ is significantly lower than α₁. When measured in intact fibers of WT and α₁^S/Sα₂^R/R mice in the presence of 10 µM ouabain; the K_1/2,K of α₁ and α₂ isozymes are 1.3 and 4 mM, respectively. Collectively, these results validate the single fiber model for studies of Na,K-ATPase transport and kinetic constants, and they imply the existence of mechanisms that dynamically limit pump activity during periods of active transport. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

15 pages, 2549 KiB

Open AccessArticle

Uremic Toxins Activates Na/K-ATPase Oxidant Amplification Loop Causing Phenotypic Changes in Adipocytes in In Vitro Models

by David E. Bartlett, Richard B. Miller, Scott Thiesfeldt, Hari Vishal Lakhani, Tilak Khanal, Rebecca D. Pratt, Cameron L. Cottrill, Rebecca L. Klug, Nathaniel Seth Adkins, Paul C. Bown, D. Blaine Nease, Joseph I. Shapiro and Komal Sodhi

Int. J. Mol. Sci. 2018, 19(9), 2685; https://doi.org/10.3390/ijms19092685 - 10 Sep 2018

Cited by 16 | Viewed by 4194

Abstract

Background: Oxidant stress plays a key role in the development of chronic kidney disease (CKD). Experimental CKD leads to accumulation of uremic toxins (UT) in the circulation resulting in increased ROS production, which in turn, is known to activate the Na/K-ATPase/ROS amplification loop. [...] Read more.

Background: Oxidant stress plays a key role in the development of chronic kidney disease (CKD). Experimental CKD leads to accumulation of uremic toxins (UT) in the circulation resulting in increased ROS production, which in turn, is known to activate the Na/K-ATPase/ROS amplification loop. Studies in a murine model of obesity have shown that increased oxidative stress in plasma is due to increased ROS and cytokine production from dysfunctional adipocytes. Therefore, we hypothesized that adipocytes exposed to UTs will activate the Na/K-ATPase oxidant amplification loop causing redox imbalance and phenotypic alterations in adipocytes. We also aimed to demonstrate that the Na/K-ATPase signaling antagonist, pNaKtide, attenuates these pathophysiological consequences. Methods: In the first set of experiments, 3T3-L1 murine pre-adipocytes were treated with varying concentrations of UTs, indoxyl sulfate (IS) (50, 100 and 250 µM) and p-cresol (50, 100 and 200 µM), with or without pNaKtide (0.7 µM) for five days in adipogenic media, followed by Oil Red O staining to study adipogenesis. RT-PCR analysis was performed to study expression of adipogenic, apoptotic and inflammatory markers, while DHE staining evaluated the superoxide levels in UT treated cells. In a second set of experiments, visceral fat was obtained from the West Virginian population. MSCs were isolated and cultured in adipogenic media for 14 days, which was treated with indoxyl sulfate (0, 25, 50 and 100 µM) with or without pNaKtide (1 µM). MSC-derived adipocytes were evaluated for morphological and molecular analysis of the above markers. Results: Our results demonstrated that 3T3-L1 cells and MSCs-derived adipocytes, treated with UTs, exhibited a significant decrease in adipogenesis and apoptosis through activation of the Na/K-ATPase/ROS amplification loop. The treatment with pNaKtide in 3T3-L1 cells and MSC-derived adipocytes negated the effects of UTs and restored cellular redox in adipocytes. We noted a varying effect of pNaKtide, in adipocytes treated with UTs, on inflammatory markers, adipogenic marker and superoxide levels in 3T3-L1 cells and MSC-derived adipocytes. Conclusions: This study demonstrates for the first time that the Na/K-ATPase/ROS amplification loop activated by elevated levels of UTs has varying effect on phenotypic alterations in adipocytes in various in vitro models. Thus, we propose that, if proven in humans, inhibition of Na/K-ATPase amplification of oxidant stress in CKD patients may ultimately be a novel way to combat adipocyte dysfunction and metabolic imbalance in these patients. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Graphical abstract

14 pages, 2415 KiB

Open AccessArticle

Telocinobufagin, a Novel Cardiotonic Steroid, Promotes Renal Fibrosis via Na⁺/K⁺-ATPase Profibrotic Signaling Pathways

by David J. Kennedy, Fatimah K. Khalaf, Brendan Sheehy, Malory E. Weber, Brendan Agatisa-Boyle, Julijana Conic, Kayla Hauser, Charles M. Medert, Kristen Westfall, Philip Bucur, Olga V. Fedorova, Alexei Y. Bagrov and W. H. Wilson Tang

Int. J. Mol. Sci. 2018, 19(9), 2566; https://doi.org/10.3390/ijms19092566 - 29 Aug 2018

Cited by 20 | Viewed by 3836

Abstract

Cardiotonic steroids (CTS) are Na⁺/K⁺-ATPase (NKA) ligands that are elevated in volume-expanded states and associated with cardiac and renal dysfunction in both clinical and experimental settings. We test the hypothesis that the CTS telocinobufagin (TCB) promotes renal dysfunction in [...] Read more.

Cardiotonic steroids (CTS) are Na⁺/K⁺-ATPase (NKA) ligands that are elevated in volume-expanded states and associated with cardiac and renal dysfunction in both clinical and experimental settings. We test the hypothesis that the CTS telocinobufagin (TCB) promotes renal dysfunction in a process involving signaling through the NKA α-1 in the following studies. First, we infuse TCB (4 weeks at 0.1 µg/g/day) or a vehicle into mice expressing wild-type (WT) NKA α-1, as well as mice with a genetic reduction (~40%) of NKA α-1 (NKA α-1^+/−). Continuous TCB infusion results in increased proteinuria and cystatin C in WT mice which are significantly attenuated in NKA α-1^+/− mice (all p < 0.05), despite similar increases in blood pressure. In a series of in vitro experiments, 24-h treatment of HK2 renal proximal tubular cells with TCB results in significant dose-dependent increases in both Collagens 1 and 3 mRNA (2-fold increases at 10 nM, 5-fold increases at 100 nM, p < 0.05). Similar effects are seen in primary human renal mesangial cells. TCB treatment (100 nM) of SYF fibroblasts reconstituted with cSrc results in a 1.5-fold increase in Collagens 1 and 3 mRNA (p < 0.05), as well as increases in both Transforming Growth factor beta (TGFb, 1.5 fold, p < 0.05) and Connective Tissue Growth Factor (CTGF, 2 fold, p < 0.05), while these effects are absent in SYF cells without Src kinase. In a patient study of subjects with chronic kidney disease, TCB is elevated compared to healthy volunteers. These studies suggest that the pro-fibrotic effects of TCB in the kidney are mediated though the NKA-Src kinase signaling pathway and may have relevance to volume-overloaded conditions, such as chronic kidney disease where TCB is elevated. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

18 pages, 3048 KiB

Open AccessArticle

The Na,K-ATPase-Dependent Src Kinase Signaling Changes with Mesenteric Artery Diameter

by Lin Zhang, Christian Aalkjaer and Vladimir V. Matchkov

Int. J. Mol. Sci. 2018, 19(9), 2489; https://doi.org/10.3390/ijms19092489 - 23 Aug 2018

Cited by 9 | Viewed by 3925

Abstract

Inhibition of the Na,K-ATPase by ouabain potentiates vascular tone and agonist-induced contraction. These effects of ouabain varies between different reports. In this study, we assessed whether the pro-contractile effect of ouabain changes with arterial diameter and the molecular mechanism behind it. Rat mesenteric [...] Read more.

Inhibition of the Na,K-ATPase by ouabain potentiates vascular tone and agonist-induced contraction. These effects of ouabain varies between different reports. In this study, we assessed whether the pro-contractile effect of ouabain changes with arterial diameter and the molecular mechanism behind it. Rat mesenteric small arteries of different diameters (150–350 µm) were studied for noradrenaline-induced changes of isometric force and intracellular Ca²⁺ in smooth muscle cells. These functional changes were correlated to total Src kinase and Src phosphorylation assessed immunohistochemically. High-affinity ouabain-binding sites were semi-quantified with fluorescent ouabain. We found that potentiation of noradrenaline-sensitivity by ouabain correlates positively with an increase in arterial diameter. This was not due to differences in intracellular Ca²⁺ responses but due to sensitization of smooth muscle cell contractile machinery to Ca²⁺. This was associated with ouabain-induced Src activation, which increases with increasing arterial diameter. Total Src expression was similar in arteries of different diameters but the density of high-affinity ouabain binding sites increased with increasing arterial diameters. We suggested that ouabain binding induces more Src kinase activity in mesenteric small arteries with larger diameter leading to enhanced sensitization of the contractile machinery to Ca²⁺. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

8 pages, 1338 KiB

Open AccessArticle

Antibody to Marinobufagenin Reverses Placenta-Induced Fibrosis of Umbilical Arteries in Preeclampsia

by Olga V. Fedorova, Valentina V. Ishkaraeva, Yulia N. Grigorova, Vitaly A. Reznik, Nikolai I. Kolodkin, Irina E. Zazerskaya, Valentina Zernetkina, Natalia I. Agalakova, Natalia I. Tapilskaya, C. David Adair, Edward G. Lakatta and Alexei Y. Bagrov

Int. J. Mol. Sci. 2018, 19(8), 2377; https://doi.org/10.3390/ijms19082377 - 13 Aug 2018

Cited by 16 | Viewed by 3948

Abstract

Background: Previous studies implicated cardiotonic steroids, including Na/K-ATPase inhibitor marinobufagenin (MBG), in the pathogenesis of preeclampsia (PE). Immunoneutralization of heightened MBG by Digibind, a digoxin antibody, reduces blood pressure (BP) in patients with PE, and anti-MBG monoclonal antibody lessens BP in a rat [...] Read more.

Background: Previous studies implicated cardiotonic steroids, including Na/K-ATPase inhibitor marinobufagenin (MBG), in the pathogenesis of preeclampsia (PE). Immunoneutralization of heightened MBG by Digibind, a digoxin antibody, reduces blood pressure (BP) in patients with PE, and anti-MBG monoclonal antibody lessens BP in a rat model of PE. Recently, we demonstrated that MBG induces fibrosis in cardiovascular tissues via a mechanism involving inhibition of Fli-1, a nuclear transcription factor and a negative regulator of collagen-1 synthesis. Objectives and Methods: We hypothesized that in PE, elevated placental MBG levels are associated with development of fibrosis in umbilical arteries. Eleven patients with PE (mean BP 124 ± 4 mmHg; age 29 ± 2 years; 39 weeks gest. age) and 10 gestational age-matched normal pregnant subjects (mean BP 92 ± 2 mmHg; controls) were enrolled in the clinical study. Results: PE was associated with a higher placental (0.04 ± 0.01 vs. 0.49 ± 0.11 pmol/g; p < 0.01) and plasma MBG (0.5 ± 0.1 vs. 1.6 ± 0.5 nmol/L; p < 0.01), lower Na/K-ATPase activity in erythrocytes (2.7 ± 0.2 vs. 1.5 ± 0.2 µmol Pi/mL/hr; p < 0.01), 9-fold decrease of Fli-1 level and 2.5-fold increase of collagen-1 in placentae (p < 0.01) vs. control. Incubation of umbilical arteries from control patients with 1 nmol/L MBG was associated with four-fold decrease in Fli-1 level and two-fold increase in collagen-1 level vs. those incubated with placebo (p < 0.01), i.e., physiological concentration of MBG mimicked effect of PE in vitro. Collagen-1 abundance in umbilical arteries from PE patients was 4-fold higher than in control arteries, and this PE-associated fibrosis was reversed by monoclonal anti-MBG antibody ex vivo. Conclusion: These results demonstrate that elevated placental MBG level is implicated in the development of fibrosis of the placenta and umbilical arteries in PE. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

12 pages, 1628 KiB

Open AccessArticle

Quantum Modeling: A Bridge between the Pumping and Signaling Functions of Na/K-ATPase

by Weiguang Wang and Joseph I. Shapiro

Int. J. Mol. Sci. 2018, 19(8), 2347; https://doi.org/10.3390/ijms19082347 - 9 Aug 2018

Cited by 1 | Viewed by 3789

Abstract

Although the signaling function of Na/K-ATPase has been studied for decades, the chasm between the pumping function and the signaling function of Na/K-ATPase is still an open issue. This article explores the relationship between ion pumping and signaling with attention to the amplification [...] Read more.

Although the signaling function of Na/K-ATPase has been studied for decades, the chasm between the pumping function and the signaling function of Na/K-ATPase is still an open issue. This article explores the relationship between ion pumping and signaling with attention to the amplification of oxidants through this signaling function. We specifically consider the Na/K-ATPase with respect to its signaling function as a superposition of different states described for its pumping function. We then examine how alterations in the relative amounts of these states could alter signaling through the Src-EGFR-ROS pathway. Using assumptions based on some experimental observations published by our laboratories and others, we develop some predictions regarding cellular oxidant stress. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

15 pages, 2851 KiB

Open AccessArticle

Regulation of Neuronal Na,K-ATPase by Extracellular Scaffolding Proteins

by Thomas Liebmann, Nicolas Fritz, Markus Kruusmägi, Linda Westin, Kristoffer Bernhem, Alexander Bondar, Anita Aperia and Hjalmar Brismar

Int. J. Mol. Sci. 2018, 19(8), 2214; https://doi.org/10.3390/ijms19082214 - 29 Jul 2018

Cited by 10 | Viewed by 5300

Abstract

Neuronal activity leads to an influx of Na⁺ that needs to be rapidly cleared. The sodium-potassium ATPase (Na,K-ATPase) exports three Na⁺ ions and imports two K⁺ ions at the expense of one ATP molecule. Na,K-ATPase turnover accounts for the majority [...] Read more.

Neuronal activity leads to an influx of Na⁺ that needs to be rapidly cleared. The sodium-potassium ATPase (Na,K-ATPase) exports three Na⁺ ions and imports two K⁺ ions at the expense of one ATP molecule. Na,K-ATPase turnover accounts for the majority of energy used by the brain. To prevent an energy crisis, the energy expense for Na⁺ clearance must provide an optimal effect. Here we report that in rat primary hippocampal neurons, the clearance of Na⁺ ions is more efficient if Na,K-ATPase is laterally mobile in the membrane than if it is clustered. Using fluorescence recovery after photobleaching and single particle tracking analysis, we show that the ubiquitous α1 and the neuron-specific α3 catalytic subunits as well as the supportive β1 subunit of Na,K-ATPase are highly mobile in the plasma membrane. We show that cross-linking of the β1 subunit with polyclonal antibodies or exposure to Modulator of Na,K-ATPase (MONaKA), a secreted protein which binds to the extracellular domain of the β subunit, clusters the α3 subunit in the membrane and restricts its mobility. We demonstrate that clustering, caused by cross-linking or by exposure to MONaKA, reduces the efficiency in restoring intracellular Na⁺. These results demonstrate that extracellular interactions with Na,K-ATPase regulate the Na⁺ extrusion efficiency with consequences for neuronal energy balance. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

11 pages, 4071 KiB

Open AccessArticle

Characterization of a Long Non-Coding RNA, the Antisense RNA of Na/K-ATPase α1 in Human Kidney Cells

by Xiaoming Fan, Usman M. Ashraf, Christopher A. Drummond, Huilin Shi, Xiaolu Zhang, Sivarajan Kumarasamy and Jiang Tian

Int. J. Mol. Sci. 2018, 19(7), 2123; https://doi.org/10.3390/ijms19072123 - 21 Jul 2018

Cited by 3 | Viewed by 4214

Abstract

Non-coding RNAs are important regulators of protein-coding genes. The current study characterized an antisense long non-coding RNA, ATP1A1-AS1, which is located on the opposite strand of the Na/K-ATPase α1 gene. Our results show that four splice variants are expressed in human adult [...] Read more.

Non-coding RNAs are important regulators of protein-coding genes. The current study characterized an antisense long non-coding RNA, ATP1A1-AS1, which is located on the opposite strand of the Na/K-ATPase α1 gene. Our results show that four splice variants are expressed in human adult kidney cells (HK2 cells) and embryonic kidney cells (HEK293 cells). These variants can be detected in both cytosol and nuclear fractions. We also found that the inhibition of DNA methylation has a differential effect on the expression of ATP1A1-AS1 and its sense gene. To investigate the physiological role of this antisense gene, we overexpressed the ATP1A1-AS1 transcripts, and examined their effect on Na/K-ATPase expression and related signaling function in human kidney cells. The results showed that overexpression of the ATP1A1-AS1-203 transcript in HK2 cells reduced the Na/K-ATPase α1 (ATP1A1) gene expression by approximately 20% (p < 0.05), while reducing the Na/K-ATPase α1 protein synthesis by approximately 22% (p < 0.05). Importantly, overexpression of the antisense RNA transcript attenuated ouabain-induced Src activation in HK2 cells. It also inhibited the cell proliferation and potentiated ouabain-induced cell death. These results demonstrate that the ATP1A1-AS1 gene is a moderate negative regulator of Na/K-ATPase α1, and can modulate Na/K-ATPase-related signaling pathways in human kidney cells. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

Review

Jump to: Research

12 pages, 1362 KiB

Open AccessReview

The Na/K-ATPase Signaling: From Specific Ligands to General Reactive Oxygen Species

by Rebecca D. Pratt, Cameron R. Brickman, Cameron L. Cottrill, Joseph I. Shapiro and Jiang Liu

Int. J. Mol. Sci. 2018, 19(9), 2600; https://doi.org/10.3390/ijms19092600 - 1 Sep 2018

Cited by 43 | Viewed by 4712

Abstract

The signaling function of the Na/K-ATPase has been established for 20 years and is widely accepted in the field, with many excellent reports and reviews not cited here. Even though there is debate about the underlying mechanism, the signaling function is unquestioned. This [...] Read more.

The signaling function of the Na/K-ATPase has been established for 20 years and is widely accepted in the field, with many excellent reports and reviews not cited here. Even though there is debate about the underlying mechanism, the signaling function is unquestioned. This short review looks back at the evolution of Na/K-ATPase signaling, from stimulation by cardiotonic steroids (also known as digitalis-like substances) as specific ligands to stimulation by reactive oxygen species (ROS) in general. The interplay of cardiotonic steroids and ROS in Na/K-ATPase signaling forms a positive-feedback oxidant amplification loop that has been implicated in some pathophysiological conditions. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Graphical abstract

20 pages, 6213 KiB

Open AccessReview

Cardiotonic Steroids and the Sodium Trade Balance: New Insights into Trade-Off Mechanisms Mediated by the Na⁺/K⁺-ATPase

by Fatimah K. Khalaf, Prabhatchandra Dube, Amal Mohamed, Jiang Tian, Deepak Malhotra, Steven T. Haller and David J. Kennedy

Int. J. Mol. Sci. 2018, 19(9), 2576; https://doi.org/10.3390/ijms19092576 - 30 Aug 2018

Cited by 32 | Viewed by 5455

Abstract

In 1972 Neal Bricker presented the “trade-off” hypothesis in which he detailed the role of physiological adaptation processes in mediating some of the pathophysiology associated with declines in renal function. In the late 1990’s Xie and Askari published seminal studies indicating that the [...] Read more.

In 1972 Neal Bricker presented the “trade-off” hypothesis in which he detailed the role of physiological adaptation processes in mediating some of the pathophysiology associated with declines in renal function. In the late 1990’s Xie and Askari published seminal studies indicating that the Na⁺/K⁺-ATPase (NKA) was not only an ion pump, but also a signal transducer that interacts with several signaling partners. Since this discovery, numerous studies from multiple laboratories have shown that the NKA is a central player in mediating some of these long-term “trade-offs” of the physiological adaptation processes which Bricker originally proposed in the 1970’s. In fact, NKA ligands such as cardiotonic steroids (CTS), have been shown to signal through NKA, and consequently been implicated in mediating both adaptive and maladaptive responses to volume overload such as fibrosis and oxidative stress. In this review we will emphasize the role the NKA plays in this “trade-off” with respect to CTS signaling and its implication in inflammation and fibrosis in target organs including the heart, kidney, and vasculature. As inflammation and fibrosis exhibit key roles in the pathogenesis of a number of clinical disorders such as chronic kidney disease, heart failure, atherosclerosis, obesity, preeclampsia, and aging, this review will also highlight the role of newly discovered NKA signaling partners in mediating some of these conditions. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

9 pages, 933 KiB

Open AccessReview

Na/K-ATPase Signaling and Cardiac Pre/Postconditioning with Cardiotonic Steroids

by Pauline V. Marck and Sandrine V. Pierre

Int. J. Mol. Sci. 2018, 19(8), 2336; https://doi.org/10.3390/ijms19082336 - 9 Aug 2018

Cited by 14 | Viewed by 5942

Abstract

The first reports of cardiac Na/K-ATPase signaling, published 20 years ago, have opened several major fields of investigations into the cardioprotective action of low/subinotropic concentrations of cardiotonic steroids (CTS). This review focuses on the protective cardiac Na/K-ATPase-mediated signaling triggered by low concentrations of [...] Read more.

The first reports of cardiac Na/K-ATPase signaling, published 20 years ago, have opened several major fields of investigations into the cardioprotective action of low/subinotropic concentrations of cardiotonic steroids (CTS). This review focuses on the protective cardiac Na/K-ATPase-mediated signaling triggered by low concentrations of ouabain and other CTS, in the context of the enduring debate over the use of CTS in the ischemic heart. Indeed, as basic and clinical research continues to support effectiveness and feasibility of conditioning interventions against ischemia/reperfusion injury in acute myocardial infarction (AMI), the mechanistic information available to date suggests that unique features of CTS-based conditioning could be highly suitable, alone /or as a combinatory approach. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

13 pages, 799 KiB

Open AccessReview

Na⁺, K⁺-ATPase Signaling and Bipolar Disorder

by David Lichtstein, Asher Ilani, Haim Rosen, Noa Horesh, Shiv Vardan Singh, Nahum Buzaglo and Anastasia Hodes

Int. J. Mol. Sci. 2018, 19(8), 2314; https://doi.org/10.3390/ijms19082314 - 7 Aug 2018

Cited by 45 | Viewed by 6881

Abstract

Bipolar disorder (BD) is a severe and common chronic mental illness characterized by recurrent mood swings between depression and mania. The biological basis of the disease is poorly understood and its treatment is unsatisfactory. Although in past decades the “monoamine hypothesis” has dominated [...] Read more.

Bipolar disorder (BD) is a severe and common chronic mental illness characterized by recurrent mood swings between depression and mania. The biological basis of the disease is poorly understood and its treatment is unsatisfactory. Although in past decades the “monoamine hypothesis” has dominated our understanding of both the pathophysiology of depressive disorders and the action of pharmacological treatments, recent studies focus on the involvement of additional neurotransmitters/neuromodulators systems and cellular processes in BD. Here, evidence for the participation of Na⁺, K⁺-ATPase and its endogenous regulators, the endogenous cardiac steroids (ECS), in the etiology of BD is reviewed. Proof for the involvement of brain Na⁺, K⁺-ATPase and ECS in behavior is summarized and it is hypothesized that ECS-Na⁺, K⁺-ATPase-induced activation of intracellular signaling participates in the mechanisms underlying BD. We propose that the activation of ERK, AKT, and NFκB, resulting from ECS-Na⁺, K⁺-ATPase interaction, modifies neuronal activity and neurotransmission which, in turn, participate in the regulation of behavior and BD. These observations suggest Na⁺, K⁺-ATPase-mediated signaling is a potential target for drug development for the treatment of BD. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

7 pages, 228 KiB

Open AccessReview

The Antiviral Effects of Na,K-ATPase Inhibition: A Minireview

by Luciano Amarelle and Emilia Lecuona

Int. J. Mol. Sci. 2018, 19(8), 2154; https://doi.org/10.3390/ijms19082154 - 24 Jul 2018

Cited by 46 | Viewed by 6233

Abstract

Since being first described more than 60 years ago, Na,K-ATPase has been extensively studied, while novel concepts about its structure, physiology, and biological roles continue to be elucidated. Cardiac glycosides not only inhibit the pump function of Na,K-ATPase but also activate intracellular signal [...] Read more.

Since being first described more than 60 years ago, Na,K-ATPase has been extensively studied, while novel concepts about its structure, physiology, and biological roles continue to be elucidated. Cardiac glycosides not only inhibit the pump function of Na,K-ATPase but also activate intracellular signal transduction pathways, which are important in many biological processes. Recently, antiviral effects have been described as a novel feature of Na,K-ATPase inhibition with the use of cardiac glycosides. Cardiac glycosides have been reported to be effective against both DNA viruses such as cytomegalovirus and herpes simplex and RNA viruses such as influenza, chikungunya, coronavirus, and respiratory syncytial virus, among others. Consequently, cardiac glycosides have emerged as potential broad-spectrum antiviral drugs, with the great advantage of targeting cell host proteins, which help to minimize resistance to antiviral treatments, making them a very promising strategy against human viral infections. Here, we review the effect of cardiac glycosides on viral biology and the mechanisms by which these drugs impair the replication of this array of different viruses. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

13 pages, 1098 KiB

Open AccessReview

The Role of Na/K-ATPase Signaling in Oxidative Stress Related to Aging: Implications in Obesity and Cardiovascular Disease

by David E. Bartlett, Richard B. Miller, Scott Thiesfeldt, Hari Vishal Lakhani, Joseph I. Shapiro and Komal Sodhi

Int. J. Mol. Sci. 2018, 19(7), 2139; https://doi.org/10.3390/ijms19072139 - 23 Jul 2018

Cited by 41 | Viewed by 6111

Abstract

Aging has been associated with a series of pathophysiological processes causing general decline in the overall health of the afflicted population. The cumulative line of evidence suggests an important role of oxidative stress in the development and progression of the aging process and [...] Read more.

Aging has been associated with a series of pathophysiological processes causing general decline in the overall health of the afflicted population. The cumulative line of evidence suggests an important role of oxidative stress in the development and progression of the aging process and metabolic abnormalities, exacerbating adipocyte dysfunction, cardiovascular diseases, and associated complications at the same time. In recent years, robust have established the implication of Na/K-ATPase signaling in causing oxidative stress and alterations in cellular mechanisms, in addition to its distinct pumping function. Understanding the underlying molecular mechanisms and exploring the possible sources of pro-oxidants may allow for developing therapeutic targets in these processes and formulate novel intervention strategies for patients susceptible to aging and associated complications, such as obesity and cardiovascular disease. The attenuation of oxidative stress with targeted treatment options can improve patient outcomes and significantly reduce economic burden. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Graphical abstract

20 pages, 2857 KiB

Open AccessReview

Gene Level Regulation of Na,K-ATPase in the Renal Proximal Tubule Is Controlled by Two Independent but Interacting Regulatory Mechanisms Involving Salt Inducible Kinase 1 and CREB-Regulated Transcriptional Coactivators

by Mary Taub

Int. J. Mol. Sci. 2018, 19(7), 2086; https://doi.org/10.3390/ijms19072086 - 18 Jul 2018

Cited by 7 | Viewed by 5466

Abstract

For many years, studies concerning the regulation of Na,K-ATPase were restricted to acute regulatory mechanisms, which affected the phosphorylation of Na,K-ATPase, and thus its retention on the plasma membrane. However, in recent years, this focus has changed. Na,K-ATPase has been established as a [...] Read more.

For many years, studies concerning the regulation of Na,K-ATPase were restricted to acute regulatory mechanisms, which affected the phosphorylation of Na,K-ATPase, and thus its retention on the plasma membrane. However, in recent years, this focus has changed. Na,K-ATPase has been established as a signal transducer, which becomes part of a signaling complex as a consequence of ouabain binding. Na,K-ATPase within this signaling complex is localized in caveolae, where Na,K-ATPase has also been observed to regulate Inositol 1,4,5-Trisphosphate Receptor (IP3R)-mediated calcium release. This latter association has been implicated as playing a role in signaling by G Protein Coupled Receptors (GPCRs). Here, the consequences of signaling by renal effectors that act via such GPCRs are reviewed, including their regulatory effects on Na,K-ATPase gene expression in the renal proximal tubule (RPT). Two major types of gene regulation entail signaling by Salt Inducible Kinase 1 (SIK1). On one hand, SIK1 acts so as to block signaling via cAMP Response Element (CRE) Binding Protein (CREB) Regulated Transcriptional Coactivators (CRTCs) and on the other hand, SIK1 acts so as to stimulate signaling via the Myocyte Enhancer Factor 2 (MEF2)/nuclear factor of activated T cell (NFAT) regulated genes. Ultimate consequences of these pathways include regulatory effects which alter the rate of transcription of the Na,K-ATPase β1 subunit gene atp1b1 by CREB, as well as by MEF2/NFAT. Full article

(This article belongs to the Special Issue The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie)

► Show Figures

Figure 1

Journal Menu

Journal Browser

The 20th Anniversary of the Discovery of the Scaffolding Function of the Sodium Pump by Dr. Zijian Xie

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (20 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI