Oligodendroglial cells in culture effectively dispose of exogenous hydrogen peroxide: comparison with cultured neurones, astroglial and microglial cells

Abstract

To investigate the antioxidative capacities of oligodendrocytes, rat brain cultures enriched for oligodendroglial cells were prepared and characterized. These cultures contained predominantly oligodendroglial cells as determined by immunocytochemical staining for the markers galactocerebroside and myelin basic protein. If oligodendroglial cultures were exposed to exogenous hydrogen peroxide (100 lM), the peroxide disappeared from the incubation medium following first order kinetics with a half-time of approximately 18 min. Normalization of the disposal rate to the protein content of the cultures by calculation of the specific hydrogen peroxide detoxification rate constant revealed that the cells in oligodendroglial cultures have a 60% to 120% higher specific capacity to dispose of hydrogen peroxide than cultures enriched for astroglial cells, microglial cells or neurones. Oligodendroglial cultures contained specific activities of 133.5 ± 30.4 nmol · min )1 · mg protein )1 and 27.5 ± 5.4 nmol · min )1 · mg protein )1 of glutathione peroxidase and glutathione reductase, respectively. The specific rate constant of catalase in these cultures was 1.61 ± 0.54 min )1 · mg protein )1 . Comparison with data obtained by identical methods for cultures of astroglial cells, microglial cells and neurones revealed that all three of the enzymes which are involved in hydrogen peroxide disposal were present in oligodendroglial cultures in the highest specific activities. These results demonstrate that oligodendroglial cells in culture have a prominent machinery for the disposal of hydrogen peroxide, which is likely to support the protection of these cells in brain against peroxides when produced by these or by surrounding brain cells. Keywords: astrocytes, glutathione, microglia, neurones, oligodendrocytes, oxidative stress. In mammalian cells, reactive oxygen species (ROS) like peroxides and radicals are continuously generated during aerobic metabolism and, consequently, have to be detoxified continuously. These processes appear to be especially important for the brain, since oxidative stress has been connected with neurodegenerative diseases, i.e. Parkinson's disease and Alzheimer's disease (Bains and Shaw 1997;Schulz et al. 2000). Several studies demonstrate that the tripeptide glutathione (GSH) plays an important role in the detoxification of reactive oxygen species in brain and that neuronal damage induced by insults which have been discussed to act by generation of ROS is substantially increased if brain glutathione levels are reduced (for an overview see Bains and Shaw 1997;Cooper 1997;Dringen 2000;Schulz et al. 2000).During detoxification of radicals and peroxides, GSH is involved in two types of reactions (Halliwell and Gutteridge 1999; Dringen 2000): (i) GSH reacts nonenzymatically with radicals such as the superoxide radical anion, nitric oxide or the hydroxyl radical; and (ii) GSH is the electron donor for the reduction of peroxides in the reactions catalyzed by glutathione peroxidases (GPx). The final product...

Astrocytes, but Not Microglia, Rapidly Sense H2O2 via STAT6 Phosphorylation, Resulting in Cyclooxygenase-2 Expression and Prostaglandin Release

“…Because the extent of oxidative stress depends on cellular antioxidant capacity, we first determined the variance resulting from differences in plated cell numbers and antioxidant enzyme distribution between astrocytes and microglia. In line with previous reports (43,44), the total antioxidant capacities of the two cell types did not differ significantly (data not shown). Thus, difference in the cellular distribution of enzymes involved in phosphorylation/dephosphorylation and redox signaling between the two cell types might be responsible for this differential sensitivity.…”

“…The decrease in the extent of phosphorylation evident at later times was attributable to destruction of H 2 O 2 by astroglial cells. Exogenously added H 2 O 2 is taken up by such cells via a process characterized by first-order kinetics, with the time taken to achieve 50% of the ultimate uptake depending on both cell type and cell numbers (43,44). To minimize the impact of astroglial uptake and destruction of H 2 O 2 on peroxide levels, as well as to exclude indirectly propagating signals, we chose to confine the H 2 O 2 (0.5 mM) treatment time to only 10 min; the peroxide was then washed away.…”

Glutathione Peroxidase-Catalase Cooperativity Is Required for Resistance to Hydrogen Peroxide by Mature Rat Oligodendrocytes

“…Recently, both glutathione peroxidase and catalase, the two main enzymes involved in H 2 O 2 detoxification, have been shown to be implicated in the disposal of exogenous H 2 O 2 by astrocytes (Dringen and Hamprecht, 1997). Both have been found in the brain (De Marchena et al, 1974;Gaunt and de Duve, 1976;Brannan et al, 1981) and in astrocytes and oligodendrocytes (Dringen and Hamprecht, 1997;Hirrlinger et al, 2002). Catalase is known to be of special importance when the clearance of H 2 O 2 in high concentrations is required.…”

“…Catalase is known to be of special importance when the clearance of H 2 O 2 in high concentrations is required. More recently, a higher capacity for the degradation of H 2 O 2 has been demonstrated in myelin basic protein (MBP) expressing oligodendrocytes than in astrocytes, microglia, or neu-rons (Hirrlinger et al, 2002). However, the developmental variation in the vulnerability of OLs to H 2 O 2 has not been investigated.…”

Poly(ADP-ribose) polymerase-1 protects neurons against apoptosis induced by oxidative stress

“…[1][2][3][4] Furthermore, accumulation of DNA strand breaks is a contributing factor to neurodegeneration during oxidative stress and other conditions such as exposure to alkylating agents 5,6 and aging. 7 To repair damaged DNA, most eukaryotic cells -except yeast -express poly(ADP-ribose) polymerase-1 ((PARP-1); EC 2.4.2.30), 8 a nuclear enzyme that rapidly binds to DNA strand breaks leading to the formation of long, branched poly(ADP-ribose) polymers using NAD þ as substrate.…”