title: The speed of swelling kinetics modulates cell volume regulation and calcium signaling in astrocytes: A different point of view on the role of aquaporins.
abstract: Regulatory volume decrease (RVD) is a process by which cells restore their original volume in response to swelling. In this study, we have focused on the role played by two different Aquaporins (AQPs), Aquaporin-4 (AQP4), and Aquaporin-1 (AQP1), in triggering RVD and in mediating calcium signaling in astrocytes under hypotonic stimulus. Using biophysical techniques to measure water flux through the plasma membrane of wild-type (WT) and AQP4 knockout (KO) astrocytes and of an astrocyte cell line (DI TNC1) transfected with AQP4 or AQP1, we here show that AQP-mediated fast swelling kinetics play a key role in triggering and accelerating RVD. Using calcium imaging, we show that AQP-mediated fast swelling kinetics also significantly increases the amplitude of calcium transients inhibited by Gadolinium and Ruthenium Red, two inhibitors of the transient receptor potential vanilloid 4 (TRPV4) channels, and prevented by removing extracellular calcium. Finally, inhibition of TRPV4 or removal of extracellular calcium does not affect RVD. All together our study provides evidence that (1) AQP influenced swelling kinetics is the main trigger for RVD and in mediating calcium signaling after hypotonic stimulus together with TRPV4, and (2) calcium influx from the extracellular space and/or TRPV4 are not essential for RVD to occur in astrocytes.
authors.affiliation: Department of Bioscience, Biotechnology, and Biopharmaceutics, University of Bari "Aldo Moro,", Bari, Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Mola
authors.affiliation: Laboratory of Oncology, IRCCS Casa Sollievo Della Sofferenza, San Giovanni Rotondo, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Sparaneo
authors.affiliation: Department of Bioscience, Biotechnology, and Biopharmaceutics, University of Bari "Aldo Moro,", Bari, Italy.
authors.forename: Concetta Domenica
authors.initials: CD
authors.lastname: Gargano
authors.affiliation: Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Spray
authors.affiliation: Department of Bioscience, Biotechnology, and Biopharmaceutics, University of Bari "Aldo Moro,", Bari, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Svelto
authors.affiliation: Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA.|Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari "Aldo Moro,", Bari, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Frigeri
authors.affiliation: Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: Eliana
authors.initials: E
authors.lastname: Scemes
authors.affiliation: Department of Bioscience, Biotechnology, and Biopharmaceutics, University of Bari "Aldo Moro,", Bari, Italy.|Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: Grazia Paola
authors.initials: GP
authors.lastname: Nicchia
mesh_terms: D000818:Animals; D051398:Aquaporin 1 / Q000235:genetics / Q000378:metabolism; D051401:Aquaporin 4 / Q000235:genetics / Q000378:metabolism; D001253:Astrocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D018345:Mice, Knockout; D051381:Rats; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors / Q000378:metabolism; D014867:Water / Q000737:chemistry
chemical_list: C496020:AQP1 protein, human; C496030:AQP4 protein, human; C496031:Aqp4 protein, mouse; D051401:Aquaporin 4; D050916:TRPV Cation Channels; C486576:Trpv4 protein, mouse; C486577:Trpv4 protein, rat; D014867:Water; D051398:Aquaporin 1; D002118:Calcium
keywords: AQP1; AQP4; RVD; cell swelling; hypotonic stimulus