Role of Na+-K+-Cl- cotransport and Na+/Ca2+ exchange in mitochondrial dysfunction in astrocytes following in vitro ischemia.

Na(+)-K(+)-Cl(-) cotransporter isoform 1 (NKCC1) and reverse mode operation of the Na(+)/Ca(2+) exchanger (NCX) contribute to intracellular Na(+) and Ca(2+) overload in astrocytes following oxygen-glucose deprivation (OGD) and reoxygenation (REOX). Here, we further investigated whether NKCC1 and NCX play a role in mitochondrial Ca(2+) (Ca(m)(2+)) overload and dysfunction. OGD/REOX caused a doubling of mitochondrial-releasable Ca(2+) (P < 0.05). When NKCC1 was inhibited with bumetanide, the mitochondrial-releasable Ca(2+) was reduced by approximately 42% (P < 0.05). Genetic ablation of NKCC1 also reduced Ca(m)(2+) accumulation. Moreover, OGD/REOX in NKCC1(+/+) astrocytes caused dissipation of the mitochondrial membrane potential (Psi(m)) to 42 +/- 3% of controls. In contrast, when NKCC1 was inhibited with bumetanide, depolarization of Psi(m) was attenuated significantly (66 +/- 10% of controls, P < 0.05). Cells were also subjected to severe in vitro hypoxia by superfusion with a hypoxic, acidic, ion-shifted Ringer buffer (HAIR). HAIR/REOX triggered a secondary, sustained rise in intracellular Ca(2+) that was attenuated by reversal NCX inhibitor KB-R7943. The hypoxia-mediated increase in Ca(m)(2+) was accompanied by loss of Psi(m) and cytochrome c release in NKCC1(+/+) astrocytes. Bumetanide or genetic ablation of NKCC1 attenuated mitochondrial dysfunction and astrocyte death following ischemia. Our study suggests that NKCC1 acting in concert with NCX causes a perturbation of Ca(m)(2+) homeostasis and mitochondrial dysfunction and cell death following in vitro ischemia.
AuthorsDouglas B Kintner, Jing Luo, Josiah Gerdts, Andy J Ballard, Gary E Shull, Dandan Sun
JournalAmerican journal of physiology. Cell physiology (Am J Physiol Cell Physiol) Vol. 292 Issue 3 Pg. C1113-22 (Mar 2007) ISSN: 0363-6143 [Print] United States
PMID17035299 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
Chemical References
  • Slc12a2 protein, mouse
  • Sodium-Calcium Exchanger
  • Sodium-Potassium-Chloride Symporters
  • Solute Carrier Family 12, Member 2
  • Animals
  • Astrocytes (metabolism)
  • Cell Hypoxia (physiology)
  • Cells, Cultured
  • Cerebral Cortex (physiology)
  • Membrane Potential, Mitochondrial (physiology)
  • Membrane Potentials (physiology)
  • Mice
  • Mice, Knockout
  • Mitochondria (physiology)
  • Reperfusion Injury (physiopathology)
  • Sodium-Calcium Exchanger (metabolism)
  • Sodium-Potassium-Chloride Symporters (metabolism)
  • Solute Carrier Family 12, Member 2

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