Effect of atorvastatin on paraoxonase1 (PON1) and oxidative status

It has been proposed that paraoxonase1 (PON1), a high density lipoprotein (HDL)-associated esterase/lactonase, has antiatherosclerotic properties. The activity of PON1 is influenced by PON1 polymorphisms. However, the influence of PON1 polymorphisms on PON1 activity and oxidative stress in response to lipid-lowering drugs remains poorly understood. The objective of the present study was to investigate the effects of atorvastatin on PON1 activity and oxidative status. The influence of PON1 polymorphisms on PON1 activity and oxidative status in response to atorvastatin treatment was also evaluated. In total, 22 hypercholesterolemic patients were treated with atorvastatin at a dose of 10 mg/day for 3 months. Lipid profile, lipid oxidation markers (malondialdehyde (MDA), conjugated diene (CD), total peroxides (TP)), total antioxidant substance (TAS), oxidative stress index (OSI), and paraoxonase1 activity were determined before and after treatment. L55M, Q192R, and T(-107)C PON1 polymorphisms were also determined. Atorvastatin treatment significantly reduced the levels of total cholesterol (24.5%), low density lipoprotein (LDL) cholesterol (25.4%), triglycerides (24.4%), CD (4.4%), MDA (15.2%), TP (13.0%) and OSI (24.0%), and significantly increased the levels of TAS (27.3%), and PON1 activity (14.0%). Interestingly, the increase in PON1 activity and the reduction in oxidative stress in response to atorvastatin were influenced only by the PON1 T-107C polymorphism. Atorvastatin treatment improved the lipid profile, lipid oxidation, and oxidative/antioxidative status markers including the activity of PON1 towards paraoxon. These beneficial effects may be attributed to the antioxidant properties of statins and the increase in PON1 activity. The increase in PON1 activity was enhanced by the PON1 T-107C polymorphism.     

Different profiles of hepatic alkoxyresorufin O‐dealkylase activities in small rodents

The aims of the present study were to determine cytochrome P450 enzyme activity in six strains of experimental rodents (n = 5/sex/species): ICR, C57BL/6 and DBA/2 mice; Sprague Dawley and Wistar rats; and Dunkin Hartley guinea pigs. After animals were treated with the typical inducers β‐naphthoflavone (BNF), dexamethasone (DEX) and phenobarbital (PB), the levels of O‐dealkylation of ethoxyresorufin (EROD), methoxyresorufin (MROD), pentoxyresorufin (PROD) and benzyloxyresorufin (BROD) activity were determined using responsive catalytic reactions to study CYP1A1, CYP1A2 and CYP2B, respectively. A maximal induction of EROD and MROD was found in BNF‐treated animals from all strains (2.4‐ to 15.1‐fold) except DBA/2 (0.9‐ to 1.8‐fold). C57BL/6 mice had the strongest BNF‐induced EROD (15.1‐fold) and MROD (8.3‐fold) activities. No differences in BNF‐induced EROD and MROD activities were observed between males and females. However, the EROD activity of Wistar rats and the MROD activity of Sprague Dawley rats were higher in males than females. DEX induced PROD activity only in mice (1.3‐ to 7.1‐fold), but not in rats and guinea pigs (0.2‐ to 1.1‐fold). However, induction of BROD activity was found in DEX‐treated mice and rats (1.5 to 12.5‐fold), but not in guinea pigs (0.3 to 0.4‐fold). PB caused a significant elevation of PROD (1.7‐ to 10.4‐fold) and BROD (31‐ to 13.2‐fold) activities in all the animals. PB‐induced BROD activity was higher in females than males in Sprague Dawley rats. These observations strongly suggest that the choice of experimental animal strain, species and inducer is of critical importance for studies of drug metabolism and interaction. Copyright © 2012 John Wiley & Sons, Ltd.     

Decreased paraoxonase 1 activity and increased oxidative stress in low lead-exposed workers

Paraoxonase 1 (PON1) has been proposed as an antioxidant enzyme. Although lead-inhibited PON1 activity has been demonstrated mostly based on in vitro experiments, it is uncertain whether this phenomenon is relevant in pathogenesis of lead-induced oxidative stress in the lead exposure. We examined associations of blood lead levels (BLL) and PON1 activity along with oxidative stress parameters in lead exposure workers. We determined malondialdehyde (MDA), conjugated diene (CD), total peroxides (TP), total antioxidant status (TAS), the oxidative stress index (OSI), and PON1 activity in earthenware factory workers (n = 60) and control subjects (n = 65). The lead-exposed group significantly increased lipid peroxidation parameters and OSI compared to the control group (p < 0.001). The lead-exposed group had significantly decreased PON1 activity and TAS levels compared to the control group (p < 0.001). Multiple linear regression analysis revealed that BLL were significantly correlated with decreased TAS (r = -0.496) and PON1 activity (r = -0.434), but with increased CD (r = 0.694), TP (r = 0.614), MDA (r = 0.788), and OSI (r = 0.722). Interestingly, BLL at 10 μg/dL significantly decreased PON1 activity and increased oxidative stress parameters with insignificant changes in other biochemical and hematological parameters. Altogether, the reduction of PON1 activity may associate in an imbalance in pro-oxidants and antioxidants, leading to oxidative damage in lead-exposed workers even at low BLL.