Short-chain 3-ketoceramides, strong apoptosis inducers against human leukemia HL-60 cells

Three short-chain 3-ketoceramides (compounds A, B, and C) were synthesized and their apoptotic activity against human leukemia HL-60 cells was evaluated. Ceramides act as a second messenger of the apoptotic signaling process. The allylic alcohol portion comprising the C-3, C-4, and C-5 carbons is essential for this function. The suggestion has been made that this alcohol moiety is oxidized in mitochondria to a carbonyl moiety, with the generation of reactive oxygen species. However, there is no established precedent for the apoptotic performance of 3-ketoceramides thus presumed. In this work, we have synthesized three different types of short-chain 3-ketoceramides, that is, (2 S, 4 E)-2-acetylamino-3-oxo-4-octadecen-1-ol ( A), (2 S, 4 E, 6 E)-2-acetylamino-3-oxo-4,6-octadecadien-1-ol ( B), and (2 S, 4 E)-2-acetylamino-1-methoxy-3-oxo-4-octadecene ( C), and demonstrated that these 3-ketoceramides are capable of inducing effective apoptosis in human leukemia HL-60 cells. In particular, the two monoenoic compounds, A and C, are far more powerful than the corresponding alcoholic analogue, N-acetyl- d- erythro-sphingosine. Observations of DNA fragmentation, caspase-3 activation, and cytochrome c release from mitochondria provide substantiated evidence for mitochondrial apoptosis and the effects of exogenous glutathione on these phenomena are also discussed.