Synergistic depletion of astrocytic glutathione by glucose deprivation andperoxynitrite: Correlation with mitochondrial dysfunction and subsequent cell death
C. Ju et al., Synergistic depletion of astrocytic glutathione by glucose deprivation andperoxynitrite: Correlation with mitochondrial dysfunction and subsequent cell death, J NEUROCHEM, 74(5), 2000, pp. 1989-1998
Previously we reported that immunostimulated astrocytes were highly vulnera
ble to glucose deprivation. The augmented death was mimicked by the peroxyn
itrite (ONOO-)-producing reagent 3-morpholinosydnonimine (SIN-1). Here we s
how that glucose deprivation and ONOO- synergistically deplete intracellula
r reduced glutathione (GSH) and augment the death of astrocytes via formati
on of cyclosporin A-sensitive mitochondrial permeability transition (MPT) p
ore. Astrocytic GSH levels were only slightly decreased by glucose deprivat
ion or SIN-1 (200 mu M) alone. In contrast, a rapid and large depletion of
GSH was observed in glucose-deprived/SIN-1-treated astrocytes. The depletio
n of GSH occurred before a significant release of lactate dehydrogenase (a
marker of cell death). Superoxide dismutase and ONOO- scavengers completely
blocked the augmented death, indicating that the reaction of nitric oxide
with superoxide to form ONOO- was implicated. Furthermore, nitrotyrosine im
munoreactivity (a marker of ONOO-) was markedly enhanced in glucose-deprive
d/SIN-1-treated astrocytes. Mitochondrial transmembrane potential (MTP) was
synergistically decreased in glucose-deprived/SIN-1 treated astrocytes. Th
e glutathione synthase inhibitor L-buthionine-(S,R)-sulfoximine markedly de
creased the MTP and increased lactate dehydrogenase (LDH) releases in SIN-1
-treated astrocytes. Cyclosporin A, an MPT pore blocker, completely prevent
ed the MTP depolarization as well as the enhanced LDH releases in glucose-d
eprived/SIN-1-treated astrocytes.