Oxidative stress-induced metabolic alterations in rat brain astrocytes studied by multinuclear NMR spectroscopy

Oxidative stress in cultured astrocytes exerted by 30-min treatment with 50-200 microM H(2)O(2) caused time- and concentration-dependent effects on cellular metabolism. These changes were accompanied by alterations in cellular morphology. Using (31)P nuclear magnetic resonance (NMR) spectroscopy, the data demonstrate that the energy status of the cells was greatly affected directly after the stress, as indicated by the loss of high energy phosphates, i.e., phosphocreatine (PCr) and nucleoside triphosphates (NTP). Oxidative stress also involves a dysregulation of the osmotic control in astrocytes, which is accompanied by a dramatic loss of myo-inositol, taurine, and hypotaurine, as monitored by (1)H and (13)C NMR spectroscopy. While the energy state of the cells was essentially restored during a 7-hr recovery period, the changes in osmolyte concentrations lasted longer and went on throughout the recovery period. Even after 24-hr recovery, organic osmolyte concentrations were still below the control levels. (13)C NMR spectra of astrocyte cell extracts also demonstrated an enhanced glucose metabolism via the pentose phosphate pathway (PPP) and a reduced glycolysis. Additionally, the appearance of (13)C glutamate points to a distortion of glutamine synthetase (GS), leading to the accumulation of glutamate. Glycolysis as well as GS activity were back to control levels after 7 hr recovery. Thus, in contrast to the energy metabolism, osmoregulatory processes and complex glucose metabolism was impaired not only directly after oxidative stress, but occurred with a later onset during a 2-hr recovery period, and cells only slowly recovered during the next 24 hr.