Sensitivity of ara-C action to inhibitors of ceramide generation
| Treatment | Cotreatment | Ceramide levels | SAPK activity | Apoptosis |
|---|---|---|---|---|
| pmol/106 cells | % control | % total | ||
| Control | Vehicle | 94 ± 37 | 100 ± 7 | 3 ± 1 |
| ara-C | Vehicle | 335 ± 795-a | 345 ± 115-a | 36 ± 45-a |
| Control | Methoxysphingomyelin | 74 ± 22 | 77 ± 2 | 4 ± 2 |
| ara-C | Methoxysphingomyelin | 82 ± 215-b | 122 ± 155-b | 27 ± 65-a |
| Control | Fumonisin B1 | 86 ± 33 | 159 ± 285-a | 5 ± 2 |
| ara-C | Fumonisin B1 | 369 ± 675-b | 319 ± 105-a | 31 ± 45-a |
HL-60 cells in serum-free medium were pretreated for 90 min with neutral/acidic sphingomyelinase inhibitor 3-O-methoxysphingomyelin (25 μm), the ceramide synthase inhibitor fumonisin B1 (10 μm), or vehicle (0.01% MeOH in PBS) as indicated and then treated with ara-C (10 μm). Cells were prepared for quantification of cellular ceramide after 0.5 hr, determination of SAPK (JNK1/JNK2) activity after 2 hr, and assessment of apoptotic cell death after 6 hr as described in Experimental Procedures.