In the present study, we found that VPA, a pan-HDAC inhibitor, can inhibit the expression of HDAC1, HDAC2, HDAC6, SIRT1 and SIRT2 in the cortex and hippocampus of AD mice as well as in the AD cell model (Fig. 1, Fig. S2, Fig. 8, Additional file 1: Fig. S9). The gene discussed is HDAC9; the disease is Alzheimer disease.