Hypoxia/reoxygenation-induced damage to mitochondrial activity is determined by glutathione threshold in astroglia-rich cell cultures

It has been shown that astrocytes play an important role during ischemia/reperfusion and in neurodegenerative diseases by supporting neuronal functions, but the effect of these pathophysiological conditions on this particular cell type is still unclear. Here, we investigated the ischemia / reperfusion- induced damage to astroglia-rich cells. For that purpose, we studied the effects of substrate deprivation and hypoxia/reoxygenation on total cellular glutathione contents, and mitochondrial function. Substrate deprivation as well as increasing time of cultivation in vitro (from 2 to 4 weeks) induced a decrease in the total glutathione content. Three qualitative distinct concentration ranges of the glutathione pool with respect to the effect of hypoxia/reoxygenation on the glutathione content were found: (i) high glutathione levels above 40 nmol per mg protein remained unchanged during hypoxia/reoxygenation. (ii) Hypoxia/reoxygenation was accompanied by higher glutathione levels in comparison to controls at intermediate initial glutathione concentrations of about 20 up to 40 nmol per mg protein. (iii) Below an initial glutathione threshold concentration of about 20 nmol per mg protein, hypoxia/reoxygenation led to a stronger decrease of glutathione levels in comparison to controls. Decrease of mitochondrial respiratory chain activity during hypoxia/reoxygenation only occurred at low initial glutathione concentrations below 20 nmol per mg protein. Our data emphasize the important role of glutathione with respect to the defense of mitochondria against oxidative stress in astroglia cells during hypoxia/ reoxygenation. (C) 2002 Elsevier Science B.V. All rights reserved.