Cell protective mechanism of valproic acid in lethal hemorrhagic shock

BackgroundWe have demonstrated that valproic acid (VPA), a histone deacetylase inhibitor, can improve animal survival after hemorrhagic shock and protect neurons from hypoxia-induced apoptosis. This study investigated whether VPA treatment works through the β-catenin survival pathways.MethodsWistar-Kyoto rats underwent hemorrhagic shock (60% blood loss) followed by treatment with or without VPA (300 mg/kg). Brains were harvested after 1, 6, and 24 hours and analyzed for acetylated histone-H3 at lysine-9 (Ac-H3K9), acetylated and total β-catenin, and Bcl-2 by Western blot. In addition, primary neurons dissociated from E18 rat embryos were exposed to hypoxia (0.5% O2) for 16 hours with or without VPA (1 mmol/L) and analyzed using confocal microscopy.ResultsAfter treatment of hemorrhaged animals with VPA, acetylated β-catenin was found in both the cytosol and nucleus, along with Ac-H3K9. Bcl-2 transcript increased after 1 hour followed by an increase in Bcl-2 protein at 6 hours. Confocal imaging demonstrated that after VPA treatment, β-catenin translocated into the nucleus and colocalized with Ac-H3K9.ConclusionVPA treatment acetylates H3K9 and β-catenin and enhances translocation of β-catenin into the nucleus, where it colocalizes with Ac-H3K9 and stimulates the transcription of survival gene bcl-2. This finding suggests that VPA protects cells after severe insult through the β-catenin survival pathway.