Figure 5From: Neutral sphingomyelinase 2 modulates cytotoxic effects of protopanaxadiol on different human cancer cells PPD exerted its cytotoxic effects on cancer cells through activation of neutral sphingomyelinase 2. (A) K562 cells were exposed to PPD at 0 (DMSO) and 25 μM for 24 hr. They were stained with BODIPY-Cholesterol ester or BODIPY-C12-SM, then examined using confocal microscopy. (B) K562 cells were exposed to PPD at 0, 12.5, 25 and 50 μM for 6 or 16 hr, then levels of different ceramides were analyzed using LC-MS/MS. K562 (C) and HT29 (D) cells were preincubated with neutral sphingomyelinase (nSMase) inhibitor GW4869 for 1 hr, exposed to PPD at 0, 25 and 50 μM for 48 hr and evaluated for cell viabilities using WST-1 assay. Inhibition studies with GW4869 were repeated three times with similar results. K562 (E) and HT29 (F) cells were transfected with nSMase 2 siRNA 1141725, exposed to PPD at 0, 6.25, 12.5, 25 and 50 μM for 48 hr and evaluated for cell viabilities using WST-1 assay. Inhibition studies with siRNA transfections were repeated twice with similar results. *, p < 0.05; **, p < 0.01; ***, p < 0.001 for control (vehicle) are considered as significant.Back to article page