siRNA transfection was conducted as previously described.‍(23 (link)) Silencer select pre-designed siRNA for Nrf2 and negative control siRNA were purchased from Ambion (Life Technologies, Carlsbad, CA). The target sequences for the Nrf2 siRNAs were 5-GAAUGGUCCUAAAACACCATT-3 (sense) and 5-UGGUGUUUUAGGACCAUUCTG-3 (antisense). Reverse transfection of siRNAs into HepG2 cells was performed using Lipofectamine RNAiMAX (Invitrogen) according to the manufacturer’s instructions. Each siRNA was diluted with Opti-MEM I Reduced Serum Medium (Gibco, Carlsbad, CA), and Lipofectamine RNAiMAX was added to 6-well plate. After 20 min of incubation at room temperature (23–25°C), a suspension of 2.5 × 10‍5 cells/well was added to obtain a final siRNA concentration of 10 μM. After 48 h of incubation, the medium was replaced with fresh medium with or without 6 μM identified peptide. Cells were harvested for 24 h to measure HO-1 and Nrf2 expression. The efficiency of Nrf2 knockdown was confirmed by real-time PCR.