12-Lipoxygenase plays a key role in cell death caused by glutathione depletion and arachidonic acid in rat oligodendrocytes

Oxidative injury to premyelinating oligodendrocytes (preOLs) in developing white matter has been implicated in the pathogenesis of periventricular leukomalacia, the lesion underlying most cases of cerebral palsy in premature infants. In this study, we investigated the pathways of OL death induced by intracellular glutathione (GSH) depletion. We found that the lipoxygenase (LOX) inhibitors AA-861 and BMD-122 (N-benzyl-N-hydroxy-5-phenylpentamide; BHPP), but not the cyclooxygenase (COX) inhibitor indomethacin, fully protected the cells from GSH depletion caused by cystine deprivation. Arachidonic acid (AA), the substrate for 12-LOX, potentiated the toxicity of mild cystine deprivation and at higher concentration was itself toxic. This toxicity was also blocked by 12-LOX inhibitors. Consistent with a role for 12-LOX in the cell death pathway, 12-LOX activity increased following cystine deprivation in OLs. Blocking 12-LOX with AA-861 effectively inhibited the accumulation of reactive oxygen species (ROS) induced by cystine deprivation. These data suggest that, in OLs, intracellular GSH depletion leads to activation of 12-LOX, ROS accumulation and cell death. Mature OLs were more resistant than preOLs to cystine deprivation. The difference in sensitivity was not due to a difference in 12-LOX activity but rather appeared to be related to the presence of stronger antioxidant defense mechanisms in mature OLs. These results suggest that 12-LOX activation plays a key role in oxidative stress-induced OL death.