Induction of apoptosis by novel synthesized acylamides of human lymphocytes

To investigate a pathway to apoptosis which may involve ceramides and to elucidate the minimum structure which leads to apoptosis, we synthesized several novel acylamides. Although the four synthesized compounds were different in structure from C2-ceramide, they caused Jurkat cells to undergo apoptosis. The most effective of them was N-myristoyl-D-alaninol (D-MA), as shown by DNA fragmentation (detected with propidium iodide) and a decrease in the mitochondrial transmembrane potential (DeltaPsi(m)) (detected with rhodamine 123). Nevertheless, peripheral blood leukocytes exhibited no change after D-MA exposure, like after C2-ceramide or anti-Fas antibody treatment. The DNA fragmentation and DeltaPsi(m) caused by D-MA were blocked by a caspase-3 specific inhibitor as in the case of anti-Fas antibody stimulation. Quantification of ceramides by metabolic labeling with [(14)C]palmitic acid and HPTLC showed no increases in the ceramide levels on stimulation with D-MA, C2-ceramide or anti-Fas antibodies. Furthermore, D-MA had an apoptosis-inducing effect on an anti-Fas-resistant subline of Jurkat cells. These data suggest that D-MA may cause apoptosis of Jurkat cells without distinct ceramide formation and that this apoptotic pathway is very comparable, i.e. not identical, to that induced by anti-Fas antibodies.