Selective Isoprostane-Induced Death of Oligodendrocyte and Endothelial Cells from Newborn • 1886

Oxidant stress contributes to hypoxic-ischemic encephalopathy including periventricular leukomalacia (PVL). Peroxidation may reduce O₂ delivery to brain and cause cell death such as that of oligodendrocytes (Olg) seen in PVL. Isoprostanes are major products of peroxidation. So far the only property attributed to these agents has been vasoconstriction including in brain. Because peroxides can kill cells, we hypothesized that this cell death may be reproduced at least in part by the stable peroxidation products, 8-iso-PGE₂ and 8-iso-PGF_2α (abundant isoprostanes). The effects of these isoprostanes on cell survival was tested on primary cultures of neonatal (1 day old) rat brain Olg precursor (A₂B₅ positive) and mature cells (galactocerebroside positive), as well as on cerebrovascular endothelial cells (Factor VIII positive) of newborn pig (1 day old); cell viability was tested by MTT assay and propydium iodide exclusion. 8-iso-PGE₂, but not 8-iso-PGF_2α, caused a 35-40% concentration-dependent (EC₅₀≅0.5 μM) death rate of Olg precursors after 48 h exposure, whereas these two isoprostanes had no effect on mature Olg; H₂O₂ (100 μM) also caused 35-40% Olg precursor death rate. A 6 h exposure to 8-iso-PGE₂ also lead to 25-30% death rate of Olg precursors 48 h later. In contrast to Olg, on endothelial cells 8-iso-PGF_2α(EC_50≅1 nM), but not 8-iso-PGE₂, caused 15-20% death rate after 6-48 h exposure to the isoprostane. Nuclear and DNA fragmentation (respectively by DAPI staining and laddering on agarose) were not significantly augmented by isoprostanes, and suggests that apoptosis may not be a principal process of cell death. Finally, to test if isoprostanes can cause endothelial cell death in vivo, 8-iso-PGF_2α(1 μM) was injected intravitreally in one eye of rat pups (7 days old) and revealed vasoobliteration 48 h later; saline-treated contralateral eye was unaffected. Selective isoprostanes cause death of specific cell types, and may contribute to oxidant stress-induced injuries such as hypoxic-ischemic encephalopathies and retinopathies.