title: Sustained Na+/H+ exchanger activation promotes gliotransmitter release from reactive hippocampal astrocytes following oxygen-glucose deprivation.
abstract: Hypoxia ischemia (HI)-related brain injury is the major cause of long-term morbidity in neonates. One characteristic hallmark of neonatal HI is the development of reactive astrogliosis in the hippocampus. However, the impact of reactive astrogliosis in hippocampal damage after neonatal HI is not fully understood. In the current study, we investigated the role of Na(+)/H(+) exchanger isoform 1 (NHE1) protein in mouse reactive hippocampal astrocyte function in an in vitro ischemia model (oxygen/glucose deprivation and reoxygenation, OGD/REOX). 2 h OGD significantly increased NHE1 protein expression and NHE1-mediated H(+) efflux in hippocampal astrocytes. NHE1 activity remained stimulated during 1-5 h REOX and returned to the basal level at 24 h REOX. NHE1 activation in hippocampal astrocytes resulted in intracellular Na(+) and Ca(2+) overload. The latter was mediated by reversal of Na(+)/Ca(2+) exchange. Hippocampal astrocytes also exhibited a robust release of gliotransmitters (glutamate and pro-inflammatory cytokines IL-6 and TNFα) during 1-24 h REOX. Interestingly, inhibition of NHE1 activity with its potent inhibitor HOE 642 not only reduced Na(+) overload but also gliotransmitter release from hippocampal astrocytes. The noncompetitive excitatory amino acid transporter inhibitor TBOA showed a similar effect on blocking the glutamate release. Taken together, we concluded that NHE1 plays an essential role in maintaining H(+) homeostasis in hippocampal astrocytes. Over-stimulation of NHE1 activity following in vitro ischemia disrupts Na(+) and Ca(2+) homeostasis, which reduces Na(+)-dependent glutamate uptake and promotes release of glutamate and cytokines from reactive astrocytes. Therefore, blocking sustained NHE1 activation in reactive astrocytes may provide neuroprotection following HI.
authors.affiliation: Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America ; Department of Waisman Center, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Pelin
authors.initials: P
authors.lastname: Cengiz
authors.affiliation: Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America ; Department of Waisman Center, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Kintner
authors.affiliation: Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America ; Department of Waisman Center, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Vishal
authors.initials: V
authors.lastname: Chanana
authors.affiliation: Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Hui
authors.initials: H
authors.lastname: Yuan
authors.affiliation: Department of Neurological Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Erinc
authors.initials: E
authors.lastname: Akture
authors.affiliation: Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America ; Department of Anesthesiology, Istanbul University, Cerrahpaşa Medical School, Turkey.
authors.forename: Pinar
authors.initials: P
authors.lastname: Kendigelen
authors.affiliation: Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Gulnaz
authors.initials: G
authors.lastname: Begum
authors.affiliation: Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Emin
authors.initials: E
authors.lastname: Fidan
authors.affiliation: Department of Neurological Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Kutluay
authors.initials: K
authors.lastname: Uluc
authors.affiliation: Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America ; Department of Waisman Center, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Peter
authors.initials: P
authors.lastname: Ferrazzano
authors.affiliation: Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Dandan
authors.initials: D
authors.lastname: Sun
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001692:Biological Transport; D002545:Brain Ischemia / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism; D016923:Cell Death; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D005947:Glucose / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism*; D051379:Mice; D018377:Neurotransmitter Agents / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D061251:Primary Cell Culture; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D027682:Cation Transport Proteins; D016207:Cytokines; D018377:Neurotransmitter Agents; C490997:Slc9a1 protein, mouse; D019831:Sodium-Calcium Exchanger; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D018698:Glutamic Acid; D012964:Sodium; D005947:Glucose; D010100:Oxygen; D002118:Calcium