Western blots for RARβ, RXRα, Sp1, and Sp3 in nuclear proteins extracted from HUVECs treated with native LDL, ox-LDL, native PAPC, or ox-PAPC. HUVECs were incubated with or without 200 μg protein/mL native LDL (n-LDL) or ox-LDL (A), or 50 μg/mL native PAPC (n-PAPC) or ox-PAPC (B) for various times, and nuclear proteins were extracted from the cells. Nuclear proteins (5 μg) were subjected to SDS-PAGE under nonreducing conditions and transferred to a nitrocellulose membrane. The membrane was incubated with polyclonal antibody to RARβ, RXRα, or Sp3, or with monoclonal antibody to Sp1. Detection of RARβ, RXRα and Sp3, and Sp1 were carried out using HRP–conjugated sheep anti–rabbit IgG and HRP-conjugated sheep anti–mouse IgG, respectively, with detection using chemiluminescence and exposure of X-ray film.