TNF and ceramide (but not dihydro-Ceramide) reduce viability of neurally differentiated MN9D dopaminergic (DA) cells. A, Dose-dependent cytotoxic cell death in diff-MN9D cells treated with TNF for 72 hrs. All values represent group means +/− SEM, n = 3–4. One-way ANOVA with Tukey’s post-hoc; * denotes p < 0.05, ** denotes p < 0.01, and *** denotes p < 0.001 compared to vehicle (DMSO, 1%); for comparison between doses # denotes p < 0.05, n.s. denotes not significant. B, Dose-dependent C2-Ceramide-induced cytotoxic death in diff-MN9D cells. Cells were treated with ceramide (C2-Cer), or with equal concentrations of C2-dihydroceramide (C2-DH-Cer) as a negative control. All values represent group means +/− SEM, n = 3–4. Two-way ANOVA with Tukey’s post-hoc test for comparing C2-Cer conditions to C2-DH-Cer conditions where **denotes p < 0.01, *** denotes p < 0.001. One-way ANOVA to test for dose-dependent cell death in C2-Cer conditions where # denotes p < 0.05, ### denotes p < 0.001 relative to vehicle or different C2-Cer conditions as indicated.