Figure 3. HDACIs improve cell viability in MPP⁺ treated cells while maintaining histone hyperacetylation.

A) Changes in the percent of viable cells estimated by trypan blue exclusion following incubation of cells in MPP⁺ or MPP⁺/HDACI. SK-N-SH cells were treated with 100μM MPP⁺ while MES 23.5 cells were treated with 50μM MPP⁺. ^{a, α} Untreated vs. MPP⁺ p<0.0001; ^{b, β} MPP⁺ vs. NaB/MPP⁺ p<0.001; ^{c, γ}: MPP⁺ vs. VPA/MPP⁺ p<0.001; ^{d, δ}: MPP⁺ vs. SAHA/MPP⁺ p< 0.01. Incubation of cells with low level HDACIs did not prevent MPP⁺ mediated decreases in cell viability. B) HDACI-induced hyperacetylation of histone H3 on Lys9 was maintained in the presence of MPP⁺ (24hr incubation) in both SK-N-SH and MES 23.5 cells. C) Densitometric analysis of acetylated histone H3 Lys9: MPP⁺ vs. HDACI/MPP⁺ * p<05; ** p< 0.01; ^†p< 0.001.