Maturation-dependent oligodendrocyte apoptosis caused by hyperoxia

Abstract

In the immature human brain, periventricular leukomalacia (PVL) is the predominant white matter injury underlying the development of cerebral palsy. PVL has its peak incidence during a well-defined period in human brain development (23-32 weeks postconceptional age) characterized by extensive oligodendrocyte migration and maturation. We hypothesized that the dramatic rise of oxygen tissue tension associated with mammalian birth and additional oxygen exposure of the preterm infant during intensive care may be harmful to immature oligodendrocytes (OLs). We therefore investigated the effects of hyperoxia on rat oligodendroglia cells in vitro and in vivo. Immature OLs (OLN-93), their progenitors [preoligodendrocytes (pre-OL)], and mature OLs were subjected to 80% hyperoxia (24-96 hr). Flow cytometry was used to assess cell death. Cell viability was measured by metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT). In addition, 6-day-old rat pups were subjected to 80% oxygen (24 hr) and then sacrificed, and their brains were processed for immunfluorescence staining. Apoptosis was detected at various stages (annexin-V, activated caspase-3) after 24-48 hr of incubation in 80% oxygen in pre- and immature OLs. Mature OLs were resistant to oxygen exposure. These results were confirmed by MTT assay. This cell death was blocked by administration of the pan-caspase inhibitor zVAD-fmk. Degeneration of OLs was confirmed in 7-day-old rat brains by positive staining for activated caspase-3. Hyperoxia triggers maturation-dependent apoptosis in immature and pre-OLs and involves caspase activation. This mechanism may be relevant to the white matter injury observed in infants born preterm.

Hyperoxia Causes Maturation-Dependent Cell Death in the Developing White Matter

“…Recently, we found that hyperoxia triggers maturationdependent apoptosis in immature (O4ϩO1ϩMBPϪ) and preOLs (O4ϩO1ϪMBPϪ), which is dependent on caspase activation (Gerstner et al, 2006). This study used the oligodendroglial cell line OLN-93 (Richter-Landsberg and Heinrich, 1996).…”

“…Hyperoxia has been implicated in the pathogenesis of bronchopulmonary dysplasia and retinopathy of prematurity (Saugstad, 2001;Chow et al, 2003). There is increasing evidence that hyperoxia may negatively influence brain maturation and development (Collins et al, 2001;Felderhoff-Mueser et al, 2004;Klinger et al, 2005;Gerstner et al, 2006). However, the mechanism of hyperoxia-induced injury and the identification of vulnerable cells in the human brain are still unknown.…”

Normobaric Hyperoxia Delays Perfusion/Diffusion Mismatch Evolution, Reduces Infarct Volume, and Differentially Affects Neuronal Cell Death Pathways after Suture Middle Cerebral Artery Occlusion in Rats

“…In light of decreased penumbral caspase-8 cleavage with NBO (Liu et al, 2006), it can be speculated that treatment with NBO only delays initiation of early stages of apoptosis but ultimately cannot prevent cell death (Wang and Lenardo, 2000). Potentially, reactive oxygen speciesmediated mitochondrial damage could lead to caspase-9 activation, leading to cell death through effector caspases such as caspase-6 (Gerstner et al, 2006;Lee and Choi, 2003;Wang and Lenardo, 2000); however, further studies are necessary to confirm these hypotheses.…”

The RNA-Binding Protein RBM3 Is Required for Cell Proliferation and Protects Against Serum Deprivation-Induced Cell Death

“…Cell cycle analysis including detection of apoptotic cells was performed as described previously (15). Data analysis was performed in WIN MDI 2.8 and the Cylchred program (see www.facslab.toxikologie.uni-mainz.de).…”