Fig. 1.

A synergistic effect was observed with the combination of vorinostat and tadalafil on histone 3 acetylation. a Western blot analysis showing histone 3 acetylation (AcH3-K9) levels in primary neuronal culture treated with vorinostat or tadalafil for 2 h (*p ≤ 0.05). Actin was used for normalization. b Western blot analysis showing AcH3-K9 levels in primary neuronal culture treated with vorinostat and different concentrations of tadalafil for 2 h (*p ≤ 0.05, ***p ≤ 0.001). Actin was used for normalization. c–e Detection of cellular AcH3-K9 was assayed using SHSY-5Y cells and AlphaLisa technology. SHSY-5Y cells were treated with vorinostat or tadalafil in c and d or the combination in e for 2 h (**p ≤ 0.01, ***p ≤ 0.001). Histone 3 (H3) was used for normalization. In all figures, data are represented as mean ± SEM expressed as fold change versus control vehicle-treated cultures (n = 3–4 per condition). f Scheme showing a possible synergistic effect with HDAC and PDE inhibition. Ac acetyl, HDAC histone deacetylase, HAT histone acetyl transferase, CRE cAMP responsive element, CREB CRE-binding protein, CBP CREB-binding protein, P phospho, PDE phosphodiesterase.