Skf 525-A induces cocaine N-demethylase, ethoxyresorufin O-deethylase, and pentoxyresorufin O-dealkylase activities by induction of cytochrome p-450 2B in female B6C3F1 mice

Nevirapine modulation of paraoxonase-1 in the liver: An in vitro three-model approach

INTRODUCTION

Nevirapine is associated with severe hepatotoxicity, through the formation of reactive metabolites. Paraoxonase-1 (PON-1) is a promiscuous enzyme involved in the metabolism of xeno- and endobiotics and proposed as a biomarker of hepatotoxicity. The aim of this work was to explore the effects of nevirapine and its phase I metabolites, 2-hydroxy-nevirapine and 12-hydroxy-nevirapine, on PON-1 activities.

MATERIAL AND METHODS

2D and 3D primary cultures of rat hepatocytes, and also HepG2 2D cell cultures, were exposed to nevirapine, 2-hydroxy-nevirapine, and 12-hydroxy-nevirapine. The paraoxonase (POase), arylesterase (AREase) and lactonase (LACase) activities of PON-1 were quantified.

RESULTS

Effects of nevirapine and its metabolites were only observed in the 3D cell model. Both nevirapine and 12-hydroxy-nevirapine increased POase (p<0.05, p<0.01) and LACase activities (p<0.05, p<0.001). The AREase activity was increased only upon 12-hydroxy-nevirapine exposure (p<0.01). These modulatory effects were observed at 300μM concentrations of nevirapine and 12-hydroxy-nevirapine.

CONCLUSIONS

The formation of 12-hydroxy-nevirapine seems to be the main factor responsible for the increase of PON-1 activities induced by nevirapine exposure. This effect was only observed in the 3D model, suggesting that an in vivo-like system is necessary for this modulation to occur. The present data suggest that the 3D model is a more suitable in vitro model than the conventional ones to explore drug effects on PON-1.

Role of metabolism in 1-bromopropane-induced hepatotoxicity in mice

A possible role of metabolism in 1-bromopropane (1-BP)-induced hepatotoxicity was investigated in male ICR mice. The depletion of glutathione (GSH) by formation of GSH conjugates was associated with increased hepatotoxicity in 1-BP-treated mice. The formation of S-propyl and 2-hydroxypropyl GSH conjugates were identified in the liver following 1-BP treatment. In addition, the formation of reactive metabolites of 1-BP by certain cytochrome P-450 (CYP) may be involved in 1-BP-induced hepatotoxicity. The decreased content of hepatic GSH produced by 1-BP was associated not only with increased activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) but also with elevated levels of hepatic thiobarbituric acid-reactive substance (TBARS) in mice where metabolic enzymes were induced by pretreatment with phenobarbital. In addition, the hepatotoxicity induced by 1-BP was prevented by pretreatment with SKF-525A. Taken together, the formation of reactive metabolites by CYP and depletion of GSH may play important roles in hepatotoxicity induced by 1-BP.