Fig. 2.

PON1 gene expression in HEPG2 cells treated with PON1 short interfering RNA (siRNA) and aspirin. A: PON1 enzyme activity in the medium from nontransfected control HEPG2 cells and PON1 siRNA-treated cells. The cell-associated PON1 arylesterase activity was measured using 1 mM ρNPA as substrate, as assessed from the formation of ρNP at 410 nm. PON1 enzyme activity is expressed as percent of control; 100% corresponds to the activity in control nontransfected cells. B: Real-time PCR analysis shows that upon silencing the PON1 gene using PON1 siRNA in HEPG2 cells, 0.5 mM aspirin treatment fails to induce the expression of PON1. Cells treated with control siRNA were also maintained. The experimental set up, RNA extraction, and real-time PCR analysis are as described in Materials and Methods. Values are expressed as mean ± SD (n = 3). * P < 0.05; ** P < 0.01.