Figure 4

TNF- induced decreases in mitochondrial membrane potential were attenuated by SMase inhibitors. A, Treatment of diff-MN9D cells for 18 hrs with 5 or 10 μM C2-Cer or 5 ng/mL TNF comprised mitochondrial membrane potential. TMRM cytofluorescence was normalized to CCCP + Veh or CCCP + TNF, as CCCP uncouples mitochondrial membranes. Pre-treatment with the SMase inhibitors Desipramine or GW4869 attenuated the TNF-induced decreases in mitochondrial membrane potential. All values represent group means +/− SEM, n = 3–4. One-way ANOVA with Tukey’s post test; * denotes p < 0.05, *** denotes p < 0.001 compared to ‘Veh’; # denotes p < 0.05 compared to TNF alone. B, Treatment of diff-MN9D cells for 18 hrs with 5 or 10 μM C2-Cer or 5 ng/mL TNF induced cytotoxicity as measured by LDH release. Pre-treatment with SMase inhibitors (Desipramine or GW4869) attenuated TNF-induced cytotoxicity; the TNF inhibitor (etanercept) was used as a positive control. All values represent group means +/− SEM, n = 3–4. One-way ANOVA with Tukey’s post test; ### denotes p < 0.001 compared to vehicle; *** denotes p < 0.001 compared to TNF alone.