Background: Placental multidrug resistance?associated protein 2 (MRP2), encoded by ABCC2 gene in human, plays a significant role in regulating drugs transplacental transfer rates. Studies on placental MRP2 regulation could provide more therapeutic targets for individualized and safe pharmacotherapy during pregnancy. Currently, the roles of epigenetic mechanisms in regulating placental drug transporters are still unclear. This study aimed to investigate the effect of histone deacetylases (HDACs) inhibition on MRP2 expression in the placental trophoblast cell line and to explore whether HDAC1/2/3 are preliminarily involved in this process. Methods: The human choriocarcinoma?derived trophoblast cell line (Bewo cells) was treated with the HDAC inhibitors?trichostatin A (TSA) at different concentration gradients of 0.5, 1.0, 3.0, and 5.0 μmol/L. Cells were harvested after 24 and 48 h treatment. Small interfering RNA (siRNA) specific for HDAC1/HDAC2/HDAC3 or control siRNA was transfected into cells. Total HDAC activity was detected by colorimetric assay kits. HDAC1/2/3/ABCC2 messenger RNA(mRNA) and protein expressions were determined by real?time quantitative polymerase chain reaction and West?blot analysis, respectively. Immunofluorescence for MRP2 protein expression was visualized and assessed using an immunofluorescence microscopy and ImageJ software, respectively. Results:TSA could inhibit total HDAC activity and HDAC1/2/3 expression in company with increase of MRP2 expression in Bewo cells.Reduction of HDAC1 protein level was noted after 24 h of TSAincubation at 1.0, 3.0, and 5.0 μmol/L (vs. vehicle group, all P < 0.001), accompanied with dose?dependent induction of MRP2 expression (P = 0.045 for 1.0 μmol/L, P = 0.001 for 3.0 μmol/L, and P < 0.001 for 5.0 μmol/L), whereas no significant differences in MRP2 expression were noted after HDAC2/3 silencing.Fluorescent micrograph images of MRP2 protein were expressed on the cell membrane. The fluorescent intensities of MRP2 in the control, HDAC2, and HDAC3 siRNA?transfected cells were week, and no significant differences were noticed among these three groups (all P > 0.05). However, MRP2 expression was remarkably elevated in HDAC1 siRNA?transfected cells, which displayed an almost 3.19?fold changes in comparison with the control siRNA?transfected cells (P < 0.001). Conclusions:HDACs inhibition could up?regulate placental MRP2 expression in vitro,and HDAC1 was probably to be involved in this process.