Activation of de Novo Synthetic Pathway of Ceramides is Responsible for the Initiation of Hydrogen Peroxide–induced Apoptosis in HI-60 Cells

Abstract

Sphingolipid metabolites in HL-60 cells were analyzed to gain an understanding of their roles in early events underlying hydrogen peroxide (H₂O₂)-induced apoptosis. Incubation of cells with H₂O₂ increased the intracellular levels of ceramides and sphinganine, but decreased those of ceramide 1-phosphates (ceramide 1‐P) and sphingosine. The levels of sphingomyelins and sphingomyelinase (SMase) activities were not affected by H₂O₂ treatment. These results were similar to the profiles induced by daunorubicin, an activator of serine palmitoyl CoA transferase (SPT), suggesting that H₂O₂ stimulated the de novo synthetic pathway of ceramides. L-cycloserine and fumonisin B₁ (FB₁), specific inhibitors of de novo ceramide biosynthesis, suppressed the elevation of ceramides and sphinganine induced by H₂O₂, which consequently reduced apoptotic cell death. Collectively, these results demonstrated that H₂O₂ increased the intracellular concentrations of ceramides via activation of a de novo biosynthetic pathway, and the enhanced ceramides might initiate apoptosis in HL-60 cells.

This work was supported in part by grants from Seoul Metropolitan City and in part by the intra-mural research program of the Korea Institute of Science and Technology.