siRNA-mediated knockdown of Nrf2 results in down-regulation of HO-1–mediated expression and sensitization to TNF-induced cell death. THP-1 cells and HL60 cells were transfected with 30 nM of either control siRNA or Nrf2 siRNA for 24 hours before treatment for 4 hours or 24 hours with TNF (10 ng/mL) alone or in conjunction with 30 minutes preincubated BAY 11-7082 (10 μM). (A) Protein was extracted and Nrf2 or β-actin levels measured by Western blot analysis. (B) mRNA extracts were prepared from the 4-hour-treated cells, reverse transcribed, and HO-1 or IL-1β mRNA expression detected by real-time PCR. (C) Cell number was assessed by MTS assay from 24-hour–TNF-treated cells. Values indicate mean plus or minus SEM from 3 independent experiments (*statistical significance, P < .01, between the different treatment groups).