CDDO-Me rescues dopaminergic MN9D cells by attenuating LPS-induced TNF production rather than by direct inhibition of TNF-induced death. (A) MN9D cells were incubated with conditioned medium (CM) from BV2 microglia cultures stimulated with 0, 10 or 100 ng/mL LPS alone or with the same concentrations of LPS plus 10 nM CDDO-Me; 200 ng/mL etanercept; or both CDDO-Me and etanercept. Survival of MN9D cells was evaluated after 2 days of incubation in the CM using an MTS viability assay (See Materials and Methods). (B) Differentiated MN9D dopaminergic cells were treated with 0, 1, 3, or 5 ng/mL TNF alone or with the same concentrations of TNF plus 10 nM or 100 nM CDDO-Me. Survival was evaluated after 3 days using an MTS viability assay. Results are expressed as mean ± SEM. Values were analyzed by one-way ANOVA followed by Tukey's post hoc, groups denoted by different letters are significantly different from each other at p < 0.05.