Calcium dependence of rapid astrocyte death induced by transient hypoxia, acidosis, and extracellular ion shifts

✍ Scribed by Alexander Bondarenko; Mitchell Chesler

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 140 KB
• Volume: 34
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/glia.1049

✦ Synopsis

Abstract

Exposure to hypoxic, acidic, ion‐shifted Ringer (HAIR) for 15–40 min has been shown to cause rapid astrocyte death upon reperfusion with normal media. The ion shifts of the HAIR solution included a rise in extracellular K^+^ (e.g., [K^+^]~o~) and a fall in [Na^+^]~o~, [Cl^−^]~o~, and [Ca^2+^]~o~, characteristic of ischemic‐traumatic brain insults. We investigated the ionic basis of the HAIR‐induced injury. After HAIR exposure, reperfusion in 0 Ca^2+^/EGTA media completely protected astrocytes. Preincubation of cells in BAPTA‐AM ester was also protective, indicating that the injury was triggered by Ca^2+^ influx during reperfusion. Neither nimodipine, CNQX, APV, nor TTX reduced injury. Astrocyte death could be blocked by 100 μM Ni^2+^ or 100 μM benzamil, suggesting involvement of Na^+^–Ca^2+^ exchange. KB‐R7943, which preferentially inhibits reverse Na^+^–Ca^2+^ exchange, also protected astrocytes. Elevation of [K^+^]~o~ was not necessary for astrocyte death. However, when [Na^+^]~o~ was maintained at 151 mM throughout the HAIR protocol, cell death was markedly reduced. We postulate that [Na^+^]~o~ shifts aid reversal of Na^+^–Ca^2+^ exchange by favoring cytosolic Na^+^ loading. Possible means of astrocytic Na^+^ accumulation are discussed. GLIA 34:143–149, 2001. © 2001 Wiley‐Liss, Inc.