title: The Na+/HCO3-co-transporter is protective during ischemia in astrocytes.
abstract: The sodium bicarbonate co-transporter (NBC) is the major bicarbonate-dependent acid-base transporter in mammalian astrocytes and has been implicated in ischemic brain injury. A malfunction of astrocytes could have great impact on the outcome of stroke due to their participation in the formation of blood-brain barrier, synaptic transmission, and electrolyte balance in the human brain. Nevertheless, the role of NBC in the ischemic astrocyte death has not been well understood. In this work, we obtained skin biopsies from healthy human subjects and had their fibroblasts grown in culture and reprogrammed into human-induced pluripotent stem cells (hiPSCs). These hiPSCs were further differentiated into neuroprogenitor cells (NPCs) and then into human astrocytes. These astrocytes express GFAP and S100β and readily propagate calcium waves upon mechanical stimulation. Using pH-sensitive dye BCECF [2',7'-bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein] and qPCR technique, we have confirmed that these astrocytes express functional NBC including electrogenic NBC (NBCe). In addition, astrocytes exposed to an ischemic solution (IS) that mimics the ischemic penumbral environment enhanced both mRNA and protein expression level of NBCe1 in astrocytes. Using IS and a generic NBC blocker S0859, we have studied the involvement of NBC in IS-induced human astrocytes death. Our results show that a 30μM S0859 induced a 97.5±1.6% (n=10) cell death in IS-treated astrocytes, which is significantly higher than 43.6±4.5%, (n=10) in the control group treated with IS alone. In summary, a NBC blocker exaggerates IS-induced cell death, suggesting that NBC activity is essential for astrocyte survival when exposed to ischemic penumbral environment.
authors.affiliation: Departments of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States.
authors.forename: Hang
authors.initials: H
authors.lastname: Yao
authors.affiliation: Departments of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States.
authors.forename: Priti
authors.initials: P
authors.lastname: Azad
authors.affiliation: Departments of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States.
authors.forename: Huiwen W
authors.initials: HW
authors.lastname: Zhao
authors.affiliation: Departments of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States.
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.affiliation: Departments of Pediatrics, University of California San Diego, La Jolla, CA 92093, United States.
authors.forename: Orit
authors.initials: O
authors.lastname: Poulsen
authors.affiliation: Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA 92093, United States.
authors.forename: Beatriz C
authors.initials: BC
authors.lastname: Freitas
authors.affiliation: Department of Pediatrics/Rady Children's Hospital San Diego, Department of Cellular & Molecular Medicine, Stem Cell Program, La Jolla, CA 92093, United States.
authors.forename: Alysson R
authors.initials: AR
authors.lastname: Muotri
authors.affiliation: Departments of Pediatrics & Neuroscience, University of California-San Diego, La Jolla, CA 92093, United States; Rady Children's Hospital-San Diego, San Diego, CA 92123, United States. Electronic address: ghaddad@ucsd.edu.
authors.forename: Gabriel G
authors.initials: GG
authors.lastname: Haddad
mesh_terms: D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001549:Benzamides / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D057026:Induced Pluripotent Stem Cells / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D000066829:Neuroprotection / Q000187:drug effects / Q000502:physiology; D018696:Neuroprotective Agents / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters / Q000378:metabolism* / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D001549:Benzamides; D018696:Neuroprotective Agents; D012333:RNA, Messenger; C528718:S 0859 compound; C498898:SLC4A4 protein, human; D027982:Sodium-Bicarbonate Symporters; D013449:Sulfonamides
keywords: NBC; astrocytes; iPSCs; ischemia; penumbra