Probucol up-regulates paraoxonase 1 expression in hepatocytes of hypercholesterolemic rabbits

Paraoxonase 1 (PON1), an HDL-associated enzyme, has anti-oxidative property. Probucol, a hydrophobic antioxidant drug, inhibits progression of atherosclerosis and post-angioplasty restenosis. However, the mechanism by which probucol affects atherosclerosis is not completely understood. Sixteen rabbits fed with high cholesterol diet for 8 weeks were randomly divided into two groups: (1) starch group (n = 8): maintained high cholesterol diet plus starch (500 mg/kg/d) for 6 weeks; (2) probucol group (n = 8): the same cholesterol diet plus probucol (500 mg/kg/d) for 6 weeks. Control group (n = 8) was fed with normal diet for 14 weeks. The classic in-situ two-step perfusion of the liver with collagenase IV was used to isolate the parenchymal hepatocytes. The total activity of superoxide dismutase (SOD) and malondialdehyde (MDA) and PON1 concentrations in serum were measured after 0, 8, and 14 weeks of feeding. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect the mRNA expression of PON1. Compared with control group, rabbits fed with high cholesterol diet showed higher levels of serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), all of which were significantly reduced by probucol. Probucol significantly decreased the MDA concentration but was ineffective on SOD activity. High cholesterol diet decreased serum PON1 concentration and down-regulated PON1 mRNA expression in hepatocytes. Probucol significantly increased serum PON1 level and up-regulated the mRNA expression of PON1 as compared with starch group (0.65 +/- 0.06 versus 0.46 +/- 0.05, P = 0.001). The PON1 concentration is negatively associated with MDA concentration (r = -0.86, P = 0.003) but not with the level of HDL-C. In conclusion, probucol decreased MDA concentration, and increased PON1 serum level as well as mRNA expression in hepatocytes, which may help us to understand its antioxidant and anti-atherogenic effects.