VPA increased nuclear translocation of NF-κB. (A) Nuclear translocation of NF-κB by VPA. NPCs cellular proteins were fractionated into nucleus and cytoplasmic fraction as described in materials and methods. The levels of NF-κB in each fraction were measured by Western blot. The level of NF-κB in nucleus was increased, whereas that in cytoplasm was not changed. (B) Densitometric quantification of NF-κB p65 and NF-κB p50 in nuclear fraction (n = 3). (C) Translocation of NF-κB p65 was confirmed by immuncytochemical staining. NPCs were co-stained with NF-κB p65 and DAPI. Arrows indicate nuclear localization of NF-κB p65. (D, E) An inhibitor of NF-κB, TDZD-8, was pre-treated 1 hour before VPA treatment and nuclear translocation of NF-κB p65 and Bcl-XL expression was determined as above (n = 3). Results are mean ± S.E.M. **P < 0.01 and ***P < 0.001 vs. control. Scale bar represents 50 μm.