Fig. 7
SKI-II alone and combined with temozolomide (TMZ) reduces the levels of ceramide, and ceramide-derived metabolites. NCH82 cells were treated for 48 h with the vehicle control (DMSO), 48 µM TMZ, 2.66 µM SKI-II and the combination (TMZ + SKI-II) under normoxia (21% O2) and hypoxia (3% O2). Sphingolipids were quantified via liquid chromatography mass spectrometry. Data are normalized as fold change ratio of treatment to DMSO control values at 21% O2 and represent mean (+ SD) of n = 3 (Ceramide-1-Phosphate, n = 2). The framed panel Cer/dhSph shows the ratio of Cer (d18:1/16:0) to dihydrosphingosine and indicates that SKI-II affects the flux of the de novo synthesis of ceramide. The ratio was determined from the mean (+ SD) of n = 3. Two-way ANOVA followed by Tukey’s multiple comparisons test was performed for statistical analysis. Amount of sphingolipid present in DMSO control cells at 21% O2 (mean ± SD): C24-ceramide, 4791.2 ± 1790.9 nmol/g; C16-ceramide, 18,128.9 ± 8185.5 nmol/g; C16-ceramide-1-phosphate, 16,431 ± 221.3 nmol/g; sphingosine-1-phosphate, 81,925.5 ± 33,204.2 nmol/g; sphingosine, 656.6 ± 96.6 nmol/g; dihydrosphingosine, 283.1 ± 85.3 nmol/g; sphingomyelin 36:1,2, 975.1 ± 489.9 nmol/g; sphingomyelin 34:1,2, 35,030.9 ± 8629.9 nmol/g