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

Abstract

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.

• Authors: Douglas B Kintner, Jing Luo, Josiah Gerdts, Andy J Ballard, Gary E Shull, Dandan Sun
• Journal: American 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
• PMID: 17035299 (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

Topics

• 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