Radiation-induced apoptosis of oligodendrocytes and its association with increased ceramide and down-regulated protein kinase B/Akt activity.

Purpose: Oligodendrocytes are cells responsible for myelination in the central nervous system and have been shown to undergo radiation‐induced apoptosis. The roles of ceramide and protein kinase B/Akt (PKB/Akt) were assessed in radiation‐induced apoptosis of oligodendrocytes in vitro.Materials and methods: Primary cultures of oligodendrocytes were established from neonatal rat brains and cell identity was assessed by immunohistochemistry. Apoptosis was assessed histologically according to its specific morphologic features using 4′,6‐diaminido‐2‐phenylindole, and by transferase‐mediated deoxynucleotidyl transferase nick end‐labelling staining. The ceramide level was measured using a diacyglycerol kinase assay, and PKB/Akt activity was determined using immunoblotting and a protein kinase assay.Results: Ionizing radiation, C2‐ceramide or wortmannin induced apoptosis in oligodendrocytes but not astrocytes. A rapid increase in ceramide was observed in oligodendrocytes after ionizing radiation. Monensin, an inh...