Reperfusion paradox: A novel mode of glial cell injury

Abstract

We have attempted to reconstruct in vitro the events that may occur in vivo during reperfusion injury after ischemia in the central nervous system. The phenomenon is induced by previous exposure to low calcium solutions ("calcium paradox") before the reperfusion episode. Intracellular calcium alterations during reperfusion of human astrocytoma U1242MG cells have been investigated with microspectrofluorimetry using the calcium-sensitive dye fura-2. Cells were perfused in calcium-free buffer solution for 30 min and then re-exposed to the control buffer solution (1.5 mM CaCl2). [Ca2+]i increased up to 3.5 times control levels during the reperfusion period. The mechanism of the increase was also investigated. Addition of TTX (2 microM) or choline chloride sodium substitution during perfusion with low calcium prevented the [Ca2+]i increase during reperfusion. Reperfusion increases in [Ca2+]i were exacerbated by low potassium in the perfusion medium, but unaltered by the calcium channel blockers cadmium (100 microM) and nickel (100 microM). In a similar manner, flunarizine (10 microM) and cadmium (100 microM) were unable to modify reperfusion [Ca2+]i alterations. Low sodium in the reperfusion medium produced significant increases in [Ca2+]i if preceded by low potassium and calcium perfusion. The viability of cells after 24 h of incubation after the insult produced by exposure to Ca(2+)-free media for 30 min was also investigated. Compared with control groups, the groups treated with Ca(2+)-free media for 30 min had a decreased number of surviving cells and morphological alterations indicative of cell pathology. The relative number of cytotoxic cells was increased by maneuvers (low potassium perfusion) that presumably blocked the Na/KATPase.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro ischemia promotes calcium influx and intracellular calcium release in hippocampal astrocytes

“…We also have shown that GABA promotes Ca*' influx via GABA, receptor-mediated depolarization (Fraser et al, 1995), suggesting that nonglutamatergic transmitters may contribute to the observed [Ca'+], response. Alternatively, internal Na+ accumulation Time (s) could lead to Ca2+ influx through reversal of the Na+-Ca2* exchange (Waxman et al, 1991;Kim-Lee et al, 1992).…”

Failure and function of intracellular pH regulation in acute hypoxic‐ischemic injury of astrocytes

“…Injury still occurred when reperfusion media retained the same low [Ca 2ϩ ] o as the HAIR solution (Bondarenko and Chesler, 2001a), excluding classical "calcium paradox" as a cause of glial death (Kimlee et al, 1992). Calcium entry was nonetheless implicated, since use of reperfusion media prepared with zero Ca 2ϩ /EGTA provided marked protection (Fig.…”

Glial calcium

“…1990) (van den Pol et al, 1992) (Hatton et al, 1992) (Glaum et al, 1990) (Supattapone et al, 1989) (Hart et al, 1989) (Jones et al, 1991) (Hart et al, 1989) (Ahmed et al, 1990) Y, quin-2 loaded cells in suspension; 2. quin-2 loaded cells attached to suhstrate; 3, fura-2 loaded cclls in suspension: 4, fura-2 loaded cells attached tu mhstrdte; 5. indu-l loaded cells in suspension; 6, indo-1 cells attached to substrate. Lee et al, 1992). The cytoplasmic Ca2+ of human astrocytoma U1242MG cells increases upon reperfusion with normal saline following exposure to Ca2+-free saline.…”