In Vitro Effects of Dexamethasone on Human Serum Paraoxonase-I PON1 Activity

Dexamethasone has successfully been used for treatment of some inflammatory diseases. Here, we evaluated the in vitro effects of dexamethasone on the activity of human serum paraoxonase hPON1 . PON1 enzyme was purified using simple chromatographic methods: DEAE-Sephadex anion exchanger and Sephadex G 200 gel filtration chromatography from human serum. hPON1 was purified approx. 225-fold with a final specific activity of 4867.3 U x mg-1 proteins and with a purity up to 39.8%. Dexamethasone dose-dependently decreased in vitro hPON1 activity. IC50 value for dexamethasone was determined as 1.106. Inhibition constant Ki was estimated as 3.284 ± 0.394 mM from Lineweaver-Burk graph. Inhibition type of dexamethasone was determined as noncompetitive. Our results show that dexamethasone inhibits hPON1 activity under in vitro conditions.