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Blaustein MP, Hamlyn JM. Sensational site: the sodium pump ouabain-binding site and its ligands. Am J Physiol Cell Physiol 2024; 326:C1120-C1177. [PMID: 38223926 PMCID: PMC11193536 DOI: 10.1152/ajpcell.00273.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 12/22/2023] [Accepted: 01/10/2024] [Indexed: 01/16/2024]
Abstract
Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
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2
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Mohammed EN, Soliman AM, Mohamed AS. Modulatory effect of
Ovothiol‐A
on myocardial infarction induced by epinephrine in rats. J Food Biochem 2022; 46:e14296. [DOI: 10.1111/jfbc.14296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 05/17/2022] [Accepted: 05/26/2022] [Indexed: 11/26/2022]
Affiliation(s)
| | - Amel M. Soliman
- Zoology Department, Faculty of Science Cairo University Giza Egypt
| | - Ayman S. Mohamed
- Zoology Department, Faculty of Science Cairo University Giza Egypt
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3
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Xian W, Wu J, Li Q, Du X, Wang N, Chen D, Gao W, Cao J. CXCR3 alleviates renal ischemia‑reperfusion injury via increase of Tregs. Mol Med Rep 2021; 24:541. [PMID: 34080653 PMCID: PMC8170869 DOI: 10.3892/mmr.2021.12180] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 03/19/2021] [Indexed: 12/26/2022] Open
Abstract
Increasing evidence has demonstrated that regulatory T cells (Tregs) suppress innate immunity, as well as protect the kidneys from ischemia‑reperfusion injury (IRI) and offer a potentially effective strategy to prevent or alleviate renal IRI. The present study explored whether C‑X‑C motif chemokine receptor 3 (CXCR3) alleviated renal IRI by increasing Tregs. Male C57BL/6J mice were divided into sham‑surgery, IRI, CXCR3 overexpression (OE‑CXCR3)+IRI, PC61+IRI and OE‑CXCR3+PC61+IRI groups. Histopathological examination of the kidney was carried out using hematoxylin‑eosin and Masson staining. The levels of serum creatinine (Scr) and blood urea nitrogen (BUN) were measured. Blood and kidney levels of IL‑6, TNF‑α, C‑C motif chemokine ligand (CCL)‑2 and IL‑10 were detected by ELISA and western blotting. The levels of superoxide dismutase (SOD), glutathione peroxidase (GSH‑Px) and malondialdehyde (MDA) in kidney tissues were also measured to assess oxidative stress. The population of Tregs in the kidney was assessed using flow cytometry. The results demonstrated that administration of OE‑CXCR3 to IRI mice significantly decreased the levels of Scr, BUN, IL‑6, TNF‑α, CCL‑2 and MDA, increased the levels of IL‑10, SOD and GSH‑Px, and mitigated the morphologic injury and fibrosis induced by IR compared with the IRI group. In addition, administration of OE‑CXCR3 induced significant reductions in the expression levels of fibrosis‑related markers, including fibronectin and type IV collagen, and increased the number of Tregs. These roles of OE‑CXCR3 were significantly neutralized following deletion of Tregs with PC61 (anti‑CD25 antibody). Together, the present study demonstrated that injection of OE‑CXCR3 lentiviral vectors into animal models can alleviate renal IRI by increasing the number of Tregs. The results may be a promising approach for the treatment of renal IRI.
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Affiliation(s)
- Wenjing Xian
- Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Jiali Wu
- Department of Anesthesiology, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, P.R. China
| | - Qingshu Li
- Department of Pathology, Molecular and Cancer Research Center, Chongqing Medical University, Chongqing 400016, P.R. China
| | - Xunsong Du
- Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Na Wang
- Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Daiyu Chen
- Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Wuxi Gao
- Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Jun Cao
- Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
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4
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Citterio L, Bianchi G, Scioli GA, Glorioso N, Bigazzi R, Cusi D, Staessen JA, Cavuto S, Ferrandi M, Lanzani C, Li X, Lau LF, Chiang CE, Wang TD, Wang KL, Ferrari P, Manunta P. Antihypertensive treatment guided by genetics: PEARL-HT, the randomized proof-of-concept trial comparing rostafuroxin with losartan. THE PHARMACOGENOMICS JOURNAL 2021; 21:346-358. [PMID: 33649520 PMCID: PMC8159753 DOI: 10.1038/s41397-021-00214-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 01/14/2021] [Accepted: 01/27/2021] [Indexed: 12/22/2022]
Abstract
We compared a standard antihypertensive losartan treatment with a pharmacogenomics-guided rostafuroxin treatment in never-treated Caucasian and Chinese patients with primary hypertension. Rostafuroxin is a digitoxigenin derivative that selectively disrupts the binding to the cSrc-SH2 domain of mutant α-adducin and of the ouabain-activated Na-K pump at 10-11 M. Of 902 patients screened, 172 were enrolled in Italy and 107 in Taiwan. After stratification for country and genetic background, patients were randomized to rostafuroxin or losartan, being the difference in the fall in office systolic blood pressure (OSBP) after 2-month treatment the primary endpoint. Three pharmacogenomic profiles (P) were examined, considering: P1, adding to the gene variants included in the subsequent P2, the variants detected by post-hoc analysis of a previous trial; P2, variants of genes encoding enzymes for endogenous ouabain (EO) synthesis (LSS and HSD3B1), EO transport (MDR1/ABCB1), adducin (ADD1 and ADD3); P3, variants of the LSS gene only. In Caucasians, the group differences (rostafuroxin 50 μg minus losartan 50 mg in OSBP mmHg) were significant both in P2 adjusted for genetic heterogeneity (P2a) and P3 LSS rs2254524 AA [9.8 (0.6-19.0), P = 0.038 and 13.4 (25.4-2.5), P = 0.031, respectively]. In human H295R cells transfected with LSS A and LSS C variants, the EO production was greater in the former (P = 0.038); this difference was abolished by rostafuroxin at 10-11 M. Chinese patients had a similar drop in OSBP to Caucasians with losartan but no change in OSBP with rostafuroxin. These results show that genetics may guide drug treatment for primary hypertension in Caucasians.
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Affiliation(s)
- Lorena Citterio
- Genomics of Renal Diseases and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Università Vita Salute San Raffaele, Milano, Italy.,Università Vita Salute San Raffaele, Milan, Italy
| | | | - Giuseppe A Scioli
- Hypertension and Cardiovascular Prevention Center, Ospedale Ferdinando Veneziale, Isernia, Italy
| | - Nicola Glorioso
- Hypertension and Related Diseases Center, Department of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | | | - Daniele Cusi
- Institute of Biomedical Technologies Milano National Research Council of Italy (CNR), Segrate, Milano, Italy.,Bio4Dreams Scientific Unit, Bio4Dreams-Business Nursery for Life Sciences, Milano, Italy
| | - Jan A Staessen
- Research Unit Hypertension and Cardiovascular Epidemiology KU Leuven Department of Cardiovascular Sciences, University of Leuven, Leuven, Belgium
| | - Silvio Cavuto
- Clinical Trials and Statistics Unit, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy
| | | | - Chiara Lanzani
- Genomics of Renal Diseases and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Università Vita Salute San Raffaele, Milano, Italy.,Università Vita Salute San Raffaele, Milan, Italy
| | | | - Lit-Fui Lau
- Zhaoke (Guangzhou) Ophthalmology Pharmaceutical Limited, Guangzhou, China
| | - Chern-En Chiang
- General Clinical Research Center, Taipei Veterans General Hospital and National Yang-Ming University, Taipei, Taiwan
| | - Tzung-Dau Wang
- Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Kang-Ling Wang
- General Clinical Research Center, Taipei Veterans General Hospital and National Yang-Ming University, Taipei, Taiwan
| | | | - Paolo Manunta
- Genomics of Renal Diseases and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Università Vita Salute San Raffaele, Milano, Italy.,Università Vita Salute San Raffaele, Milan, Italy
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5
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Blaustein MP, Hamlyn JM. Ouabain, endogenous ouabain and ouabain-like factors: The Na + pump/ouabain receptor, its linkage to NCX, and its myriad functions. Cell Calcium 2020; 86:102159. [PMID: 31986323 DOI: 10.1016/j.ceca.2020.102159] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Revised: 01/01/2020] [Accepted: 01/03/2020] [Indexed: 12/12/2022]
Abstract
In this brief review we discuss some aspects of the Na+ pump and its roles in mediating the effects of ouabain and endogenous ouabain (EO): i) in regulating the cytosolic Ca2+ concentration ([Ca2+]CYT) via Na/Ca exchange (NCX), and ii) in activating a number of protein kinase (PK) signaling cascades that control a myriad of cell functions. Importantly, [Ca2+]CYT and the other signaling pathways intersect at numerous points because of the influence of Ca2+ and calmodulin in modulating some steps in those other pathways. While both mechanisms operate in virtually all cells and tissues, this article focuses primarily on their functions in the cardiovascular system, the central nervous system (CNS) and the kidneys.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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6
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Iatrino R, Lanzani C, Bignami E, Casamassima N, Citterio L, Meroni R, Zagato L, Zangrillo A, Alfieri O, Fontana S, Macrina L, Delli Carpini S, Messaggio E, Brioni E, Dell’Antonio G, Manunta P, Hamlyn JM, Simonini M. Lanosterol Synthase Genetic Variants, Endogenous Ouabain, and Both Acute and Chronic Kidney Injury. Am J Kidney Dis 2019; 73:504-512. [DOI: 10.1053/j.ajkd.2018.10.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 10/20/2018] [Indexed: 01/25/2023]
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7
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Simonini M, Casanova P, Citterio L, Messaggio E, Lanzani C, Manunta P. Reply: "Comment on: Endogenous Ouabain and Related Genes in the Translation from Hypertension to Renal Diseases". Int J Mol Sci 2019; 20:ijms20030542. [PMID: 30696018 PMCID: PMC6387140 DOI: 10.3390/ijms20030542] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 01/17/2019] [Indexed: 12/31/2022] Open
Affiliation(s)
- Marco Simonini
- Genomics of Renal Disease and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Università Vita Salute San Raffaele, 20132 Milan, Italy.
| | - Paola Casanova
- Genomics of Renal Disease and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Università Vita Salute San Raffaele, 20132 Milan, Italy.
| | - Lorena Citterio
- Genomics of Renal Disease and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Università Vita Salute San Raffaele, 20132 Milan, Italy.
| | - Elisabetta Messaggio
- Genomics of Renal Disease and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Università Vita Salute San Raffaele, 20132 Milan, Italy.
| | - Chiara Lanzani
- Genomics of Renal Disease and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Università Vita Salute San Raffaele, 20132 Milan, Italy.
| | - Paolo Manunta
- Genomics of Renal Disease and Hypertension Unit, IRCCS San Raffaele Scientific Institute, Università Vita Salute San Raffaele, 20132 Milan, Italy.
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8
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Liu C, Lou M, Ding Y, Wang Y, Huang Y, Shao D, Chen W. Ouabain-induced apoptosis and inhibition of viability of tubulointerstitial cells by regulating NKA/pSrc/pERK/pAkt/pS6k/caspase 3 may contribute to lupus nephritis development. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2018; 11:2305-2313. [PMID: 31938342 PMCID: PMC6958254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 03/14/2018] [Indexed: 06/10/2023]
Abstract
This study aimed to investigate the underlying molecular mechanism of ouabain-induced apoptosis and inhibited viability of tubulointerstitial cells in lupus nephritis (LN). Serum ouabain expression in 21 LN patients and 20 healthy controls (HCs) was detected by ELISA. Na-K-ATPase α1 (NKA) expression in kidney tissue from 21 LN patients and 6 controls who underwent nephrectomy was determined by immunohistochemistry assay. HK-2 cells were treated by ouabain with concentration 0 nM (control), 0.1 nM, 1 nM, 10 nM, 100 nM and 1000 nM for 72 h; MTT assay was performed at 24 h, 48 h and 72 h to detect cells viability, AV/PI assay was conducted at 24 h to detect the cell apoptosis. NKA expression was detected by immunofluorescence assay and western blot (WB) while pSrc, pERK, pAkt, pS6K and caspase 3 expression was detected by WB after 100 nM ouabain treatment. Serum ouabain was elevated in LN patients compared to HCs, while kidney NKA was reduced in LN patients compared with controls. HK-2 cell viability by MTT assay was decreased while cell apoptosis by AV/PI was increased at each time point after ouabain 0.1 nM, 1 nM, 10 nM, 100 nM and 1000 nM treatment compared to control group. Both immunofluorescence and WB disclosed that NKA expression was decreased at 12 h and 24 h compared to 0 h after 100 nM ouabain treatment. Moreover, pSrc, pERK, pAkt, pS6K and caspase 3 expressions were elevated after 100 nM ouabain treatment. In conclusion, ouabain may contribute to LN etiology by inhibiting human proximal tubular cell viability and promoting cells apoptosis through regulating NKA, pSrc, pERK, pAkt, pS6K and caspase 3.
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Affiliation(s)
- Changxuan Liu
- Division of Nephrology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430014, China
| | - Meiyu Lou
- Division of Nephrology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430014, China
| | - Yu Ding
- Key Laboratory for Molecular Diagnosis of Hubei Province, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430014, China
| | - Yin Wang
- Division of Nephrology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430014, China
| | - Yunfang Huang
- Division of Nephrology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430014, China
| | - Danni Shao
- Division of Nephrology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430014, China
| | - Wenli Chen
- Division of Nephrology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430014, China
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9
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Blaustein MP. The pump, the exchanger, and the holy spirit: origins and 40-year evolution of ideas about the ouabain-Na + pump endocrine system. Am J Physiol Cell Physiol 2017; 314:C3-C26. [PMID: 28971835 DOI: 10.1152/ajpcell.00196.2017] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Two prescient 1953 publications set the stage for the elucidation of a novel endocrine system: Schatzmann's report that cardiotonic steroids (CTSs) are all Na+ pump inhibitors, and Szent-Gyorgi's suggestion that there is an endogenous "missing screw" in heart failure that CTSs like digoxin may replace. In 1977 I postulated that an endogenous Na+ pump inhibitor acts as a natriuretic hormone and simultaneously elevates blood pressure (BP) in salt-dependent hypertension. This hypothesis was based on the idea that excess renal salt retention promoted the secretion of a CTS-like hormone that inhibits renal Na+ pumps and salt reabsorption. The hormone also inhibits arterial Na+ pumps, elevates myocyte Na+ and promotes Na/Ca exchanger-mediated Ca2+ gain. This enhances vasoconstriction and arterial tone-the hallmark of hypertension. Here I describe how those ideas led to the discovery that the CTS-like hormone is endogenous ouabain (EO), a key factor in the pathogenesis of hypertension and heart failure. Seminal observations that underlie the still-emerging picture of the EO-Na+ pump endocrine system in the physiology and pathophysiology of multiple organ systems are summarized. Milestones include: 1) cloning the Na+ pump isoforms and physiological studies of mutated pumps in mice; 2) discovery that Na+ pumps are also EO-triggered signaling molecules; 3) demonstration that ouabain, but not digoxin, is hypertensinogenic; 4) elucidation of EO's roles in kidney development and cardiovascular and renal physiology and pathophysiology; 5) discovery of "brain ouabain", a component of a novel hypothalamic neuromodulatory pathway; and 6) finding that EO and its brain receptors modulate behavior and learning.
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Affiliation(s)
- Mordecai P Blaustein
- Departments of Physiology and Medicine, University of Maryland School of Medicine , Baltimore, Maryland
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Abstract
Acute kidney injury (AKI) is characterized by an acute decline in renal function and is associated to increased mortality rate, hospitalization time, and total health-related costs. The severity of this ‘fearsome’ clinical complication might depend on, or even be worsened by, the late detection of AKI, when the diagnosis is based on the elevation of serum creatinine (SCr). For these reasons, in recent years a great number of new tools, biomarkers and predictive models have been proposed to clinicians in order to improve diagnosis and prevent the development of AKI. The purpose of this narrative paper is to review the current state of the art in prediction and early detection of AKI and outline future challenges.
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Affiliation(s)
- Simona Pozzoli
- Chair of Nephrology - IRCCS San Raffaele Scientific Institute, Genomics of Renal Diseases and Hypertension Unit, Università Vita Salute San Raffaele, Via Olgettina 60, 20132, Milan, Italy
| | - Marco Simonini
- Chair of Nephrology - IRCCS San Raffaele Scientific Institute, Genomics of Renal Diseases and Hypertension Unit, Università Vita Salute San Raffaele, Via Olgettina 60, 20132, Milan, Italy.
| | - Paolo Manunta
- Chair of Nephrology - IRCCS San Raffaele Scientific Institute, Genomics of Renal Diseases and Hypertension Unit, Università Vita Salute San Raffaele, Via Olgettina 60, 20132, Milan, Italy
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11
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On the Many Actions of Ouabain: Pro-Cystogenic Effects in Autosomal Dominant Polycystic Kidney Disease. Molecules 2017; 22:molecules22050729. [PMID: 28467389 PMCID: PMC5688955 DOI: 10.3390/molecules22050729] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 04/19/2017] [Accepted: 04/30/2017] [Indexed: 02/07/2023] Open
Abstract
Ouabain and other cardenolides are steroidal compounds originally discovered in plants. Cardenolides were first used as poisons, but after finding their beneficial cardiotonic effects, they were rapidly included in the medical pharmacopeia. The use of cardenolides to treat congestive heart failure remained empirical for centuries and only relatively recently, their mechanisms of action became better understood. A breakthrough came with the discovery that ouabain and other cardenolides exist as endogenous compounds that circulate in the bloodstream of mammals. This elevated these compounds to the category of hormones and opened new lines of investigation directed to further study their biological role. Another important discovery was the finding that the effect of ouabain was mediated not only by inhibition of the activity of the Na,K-ATPase (NKA), but by the unexpected role of NKA as a receptor and a signal transducer, which activates a complex cascade of intracellular second messengers in the cell. This broadened the interest for ouabain and showed that it exerts actions that go beyond its cardiotonic effect. It is now clear that ouabain regulates multiple cell functions, including cell proliferation and hypertrophy, apoptosis, cell adhesion, cell migration, and cell metabolism in a cell and tissue type specific manner. This review article focuses on the cardenolide ouabain and discusses its various in vitro and in vivo effects, its role as an endogenous compound, its mechanisms of action, and its potential use as a therapeutic agent; placing especial emphasis on our findings of ouabain as a pro-cystogenic agent in autosomal dominant polycystic kidney disease (ADPKD).
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