title: Increased tolerance to oxygen and glucose deprivation in astrocytes from Na(+)/H(+) exchanger isoform 1 null mice.
abstract: The ubiquitously expressed Na(+)/H(+) exchanger isoform 1 (NHE1) functions as a major intracellular pH (pH(i)) regulatory mechanism in many cell types, and in some tissues its activity may contribute to ischemic injury. In the present study, cortical astrocyte cultures from wild-type (NHE1(+/+)) and NHE1-deficient (NHE1(-/-)) mice were used to investigate the role of NHE1 in pH(i) recovery and ischemic injury in astrocytes. In the absence of HCO(3)(-), the mean resting pH(i) levels were 6.86 +/- 0.03 in NHE1(+/+) astrocytes and 6.53 +/- 0.04 in NHE1(-/-) astrocytes. Removal of extracellular Na(+) or blocking of NHE1 activity by the potent NHE1 inhibitor HOE-642 significantly reduced the resting level of pH(i) in NHE1(+/+) astrocytes. NHE1(+/+) astrocytes exhibited a rapid pH(i) recovery (0.33 +/- 0.08 pH unit/min) after NH(4)Cl prepulse acid load. The pH(i) recovery in NHE1(+/+) astrocytes was reversibly inhibited by HOE-642 or removal of extracellular Na(+). In NHE1(-/-) astrocytes, the pH(i) recovery after acidification was impaired and not affected by either Na(+)-free conditions or HOE-642. Furthermore, 2 h of oxygen and glucose deprivation (OGD) led to an approximately 80% increase in pH(i) recovery rate in NHE1(+/+) astrocytes. OGD induced a 5-fold rise in intracellular [Na(+)] and 26% swelling in NHE1(+/+) astrocytes. HOE-642 or genetic ablation of NHE1 significantly reduced the Na(+) rise and swelling after OGD. These results suggest that NHE1 is the major pH(i) regulatory mechanism in cortical astrocytes and that ablation of NHE1 in astrocytes attenuates ischemia-induced disruption of ionic regulation and swelling.
authors.affiliation: Department of Neurosurgery, University of Wisconsin Medical School, Madison, WI 53792, USA.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Kintner
authors.forename: Gui
authors.initials: G
authors.lastname: Su
authors.forename: Brett
authors.initials: B
authors.lastname: Lenart
authors.forename: Andy J
authors.initials: AJ
authors.lastname: Ballard
authors.forename: Jamie W
authors.initials: JW
authors.lastname: Meyer
authors.forename: Leong L
authors.initials: LL
authors.lastname: Ng
authors.forename: Gary E
authors.initials: GE
authors.lastname: Shull
authors.forename: Dandan
authors.initials: D
authors.lastname: Sun
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D005947:Glucose / Q000172:deficiency*; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout / Q000235:genetics; D009994:Osmolar Concentration; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
chemical_list: D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D012964:Sodium; D005947:Glucose