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Nguyen T, Toussaint J, Xue Y, Raval C, Cancel L, Russell S, Shou Y, Sedes O, Sun Y, Yakobov R, Tarbell JM, Jan KM, Rumschitzki DS. Aquaporin-1 facilitates pressure-driven water flow across the aortic endothelium. Am J Physiol Heart Circ Physiol 2015; 308:H1051-64. [PMID: 25659484 PMCID: PMC4551120 DOI: 10.1152/ajpheart.00499.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 01/23/2015] [Indexed: 01/23/2023]
Abstract
Aquaporin-1, a ubiquitous water channel membrane protein, is a major contributor to cell membrane osmotic water permeability. Arteries are the physiological system where hydrostatic dominates osmotic pressure differences. In the present study, we show that the walls of large conduit arteries constitute the first example where hydrostatic pressure drives aquaporin-1-mediated transcellular/transendothelial flow. We studied cultured aortic endothelial cell monolayers and excised whole aortas of male Sprague-Dawley rats with intact and inhibited aquaporin-1 activity and with normal and knocked down aquaporin-1 expression. We subjected these systems to transmural hydrostatic pressure differences at zero osmotic pressure differences. Impaired aquaporin-1 endothelia consistently showed reduced engineering flow metrics (transendothelial water flux and hydraulic conductivity). In vitro experiments with tracers that only cross the endothelium paracellularly showed that changes in junctional transport cannot explain these reductions. Percent reductions in whole aortic wall hydraulic conductivity with either chemical blocking or knockdown of aquaporin-1 differed at low and high transmural pressures. This observation highlights how aquaporin-1 expression likely directly influences aortic wall mechanics by changing the critical transmural pressure at which its sparse subendothelial intima compresses. Such compression increases transwall flow resistance. Our endothelial and historic erythrocyte membrane aquaporin density estimates were consistent. In conclusion, aquaporin-1 significantly contributes to hydrostatic pressure-driven water transport across aortic endothelial monolayers, both in culture and in whole rat aortas. This transport, and parallel junctional flow, can dilute solutes that entered the wall paracellularly or through endothelial monolayer disruptions. Lower atherogenic precursor solute concentrations may slow their intimal entrainment kinetics.
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Affiliation(s)
- Tieuvi Nguyen
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Jimmy Toussaint
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - Yan Xue
- Department of Chemical Engineering, City College of the City University of New York, New York, New York; Biology Department, City College and GSUC of The City College of New York, New York, New York; and
| | - Chirag Raval
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Limary Cancel
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Stewart Russell
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Yixin Shou
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - Omer Sedes
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - Yu Sun
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - Roman Yakobov
- Department of Chemical Engineering, City College of the City University of New York, New York, New York
| | - John M Tarbell
- Department of Biomedical Engineering, City College of the City University of New York, New York, New York
| | - Kung-ming Jan
- Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, New York
| | - David S Rumschitzki
- Department of Chemical Engineering, City College of the City University of New York, New York, New York; Biology Department, City College and GSUC of The City College of New York, New York, New York; and Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, New York
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Shachar-Hill B, Hill AE, Powell J, Skepper JN, Shachar-Hill Y. Mercury-sensitive water channels as possible sensors of water potentials in pollen. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:5195-205. [PMID: 24098048 PMCID: PMC3830494 DOI: 10.1093/jxb/ert311] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The growing pollen tube is central to plant reproduction and is a long-standing model for cellular tip growth in biology. Rapid osmotically driven growth is maintained under variable conditions, which requires osmosensing and regulation. This study explores the mechanism of water entry and the potential role of osmosensory regulation in maintaining pollen growth. The osmotic permeability of the plasmalemma of Lilium pollen tubes was measured from plasmolysis rates to be 1.32±0.31×10(-3) cm s(-1). Mercuric ions reduce this permeability by 65%. Simulations using an osmotic model of pollen tube growth predict that an osmosensor at the cell membrane controls pectin deposition at the cell tip; inhibiting the sensor is predicted to cause tip bursting due to cell wall thinning. It was found that adding mercury to growing pollen tubes caused such a bursting of the tips. The model indicates that lowering the osmotic permeability per se does not lead to bursting but rather to thickening of the tip. The time course of induced bursting showed no time lag and was independent of mercury concentration, compatible with a surface site of action. The submaximal bursting response to intermediate mercuric ion concentration was independent of the concentration of calcium ions, showing that bursting is not due to a competitive inhibition of calcium binding or entry. Bursting with the same time course was also shown by cells growing on potassium-free media, indicating that potassium channels (implicated in mechanosensing) are not involved in the bursting response. The possible involvement of mercury-sensitive water channels as osmosensors and current knowledge of these in pollen cells are discussed.
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Affiliation(s)
| | - Adrian E. Hill
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge, UK
- * To whom correspondence should be addressed. E-mail:
| | - Janet Powell
- Multi-Imaging Centre, Cambridge University, Cambridge, UK
| | | | - Yair Shachar-Hill
- Department of Plant Biology, Plant Biology Building, Michigan State University, East Lansing, MI 48824-1312, USA
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Tan SW, Meiller JC, Mahaffey KR. The endocrine effects of mercury in humans and wildlife. Crit Rev Toxicol 2009; 39:228-69. [DOI: 10.1080/10408440802233259] [Citation(s) in RCA: 206] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Nesovic-Ostojic J, Cemerikic D, Dragovic S, Milovanovic A, Milovanovic J. Low micromolar concentrations of cadmium and mercury ions activate peritubular membrane K+ conductance in proximal tubular cells of frog kidney. Comp Biochem Physiol A Mol Integr Physiol 2008; 149:267-74. [DOI: 10.1016/j.cbpa.2007.12.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Revised: 12/20/2007] [Accepted: 12/20/2007] [Indexed: 11/26/2022]
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Barnes DM, Kircher EA. Effects of mercuric chloride on glucose transport in 3T3-L1 adipocytes. Toxicol In Vitro 2005; 19:207-14. [PMID: 15649634 DOI: 10.1016/j.tiv.2004.08.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2004] [Accepted: 08/23/2004] [Indexed: 11/17/2022]
Abstract
Mercury, as well as the other Group IIB metals, stimulates glucose transport in adipocytes. Here we characterize the action of mercury on adipocyte glucose transport and examine several potential mechanisms of action. Mercury exposure causes a modest (compared to insulin) 1.8-fold increase in glucose transport. This glucose transport corresponds with an increase in GLUT 1, but not GLUT 4 glucose transporters. Phosphorylation of p38 kinase and c-Jun N-terminal kinase (JNK) were examined as possible mediators of mercury induced GLUT 1 levels. Phosphorylation of p38 kinase, but not JNK, increased with mercury exposure. Activation of p38 and an increase in glucose transport corresponding to an increase in GLUT 1 are indicative the induction of a stress response, which can contribute to the induction of insulin resistance in adipocytes. However, inhibition of p38 by the p38 inhibitor SB203580 did not prevent mercury-mediated glucose uptake. While the magnitude of the action of mercury is modest, its effects were sustained over many days of exposure and impacted subsequent insulin-mediated glucose transport. Pre-treatment with HgCl2 decreased insulin-mediated glucose transport 1.3-fold suggesting that exposure to mercury may contribute to pathologies associated with glucose homeostasis.
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Affiliation(s)
- David M Barnes
- Department of Animal Sciences, University of Wisconsin, Madison, WI 53706, USA.
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Aduayom I, Denizeau F, Jumarie C. Multiple effects of mercury on cell volume regulation, plasma membrane permeability, and thiol content in the human intestinal cell line Caco-2. Cell Biol Toxicol 2005; 21:163-79. [PMID: 16328895 DOI: 10.1007/s10565-005-0157-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Accepted: 05/17/2005] [Indexed: 10/25/2022]
Abstract
In a previous study, we characterized Cd-Hg interactions for uptake in human intestinal Caco-2 cells. We pursued our investigations on metal uptake from metal mixtures, focusing on the effects of Hg on cellular homeostasis. A 4-fold higher equilibrium accumulation value of 0.3 micromol/L (203)Hg was measured in the presence of 100 micromol/L unlabeled Hg in the serum-free exposure medium without modification in the initial uptake rate. This phenomenon was eliminated at 4 degrees C. Mercury induced an increase in tritiated water and [(3)H]mannitol uptakes for exposure times greater than 20 min. Incubations for 20 min and 30 min with 100 micromol/L Hg and 2 mmol/L N-ethylmaleimide (NEM) resulted in a 34% and 50% reductions in cellular thiol staining, respectively, with additive effects. Lactate dehydrogenase leakage and live/dead assays confirmed the maintenance of cell membrane integrity in Hg- or NEM-treated cells. We conclude that Hg may alter membrane permeability and increase cell volume without any loss in cell viability. This phenomenon is sensitive to temperature and could involve Hg interaction with membrane thiols, possibly related to solute transport. During metal uptake from metal mixtures, Hg may thus promote the uptake of other toxic metals by increasing cell volume and consequently cell capacity.
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Affiliation(s)
- I Aduayom
- Département de Chimie, Université du Québec à Montréal, Canada
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Barnes DM, Sykes DB, Miller DS. Mercuric chloride acting through Mg stimulates protein synthesis in Xenopus oocytes. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2002; 65:617-629. [PMID: 11991634 DOI: 10.1080/152873902317349763] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In Xenopus laevis oocytes, addition of HgCl2 (Hg) to the medium rapidly stimulated incorporation of [35S]methionine (MET) into protein, increasing incorporation up to five-fold over control values. The action of inorganic mercury persisted after removal of Hg. Microinjection of HgCl2 into oocytes maintained in buffer also increased MET incorporation. However, no such stimulation was found when Hg was microinjected into oocytes maintained under oil, suggesting that Hg action was dependent on a cell-medium interaction. Removing medium Mg2+ decreased insulin- and Hg-stimulated methionine incorporation. Increasing medium Mg2+ from 1 mM to 10 mM increased Hg-stimulated methionine incorporation twofold. Hypotonic swelling of oocytes stimulated hexose transport but inhibited protein synthesis. Together these data indicate that inorganic mercury activates translation in the oocyte through an Mg-dependent mechanism, possibly increased Mg2+ influx.
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Affiliation(s)
- David M Barnes
- Department of Animal Sciences, University of Wisconsin, Madison 53706, USA.
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