Paraoxon targets CES1 protein in intact THP1 cells. Intact THP-1 cells were exposed to 10 μM paraoxon for 24 h. Control cells were exposed to vehicle only. THP-1 cell lysates were subjected to native gel electrophoresis (25 μg protein in each lane). The gel was stained with a mixture of α,β-naphthyl acetate to detect esterase activity. Lanes 1, 2, and 3 contain THP-1 cell lysate from paraoxon-treated cells and lanes 4, 5, and 6 contain THP-1 cell lysate from control cells. The migration positions of CES1 and CES2 proteins are as indicated.