Effect Of Modification Of CYP2E1 On Acute Acrylonitrile Toxicity In Rats

Objective:Cytochrome P450 2E1 (CYP 2E1) plays a key role in the oxidative pathway of acrylonitrile (AN). The present study was designed to examine the effects of the inhibition or induction of CYP 2E1 activity on acute AN toxicity in rats.Methods:42 Sprague-Dawley rats were weighted and randomly assigned into six groups:normal control, acetone alone, AN alone, acetone+AN, DCE+AN and acetone+DCE+AN. All rats in the acetone, acetone+AN and acetone+DCE+AN groups were pretreated with acetone in their drinking water (1% v/v) for 1 week. In the two DCE-treated groups, DCE at a dose of 100 mg/kg was intraperitoneally injected at 2-2.5 h before AN administration. After all the pretreatments, AN was administered by intraperitoneal injection at a dose of 50 mg/kg. the rats were observed for cholinomimetic signs, labored breathing, convulsions and death. Cyanide concentrations in tissue homogenates were determined by microdiffusion. The level of CYP2E1 protein in liver microsomes was measured using Western blot. The CYP2E1 and Cytochrome c Oxidase (CcOx) activity were determined with spectrophotometer. The lipid peroxidation (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) activity in the brain were detected. Results:Pretreatment of acetone significantly increased hepatic CYP 2E1 activity and protein whereas DCE significantly decreased them. Behavioral observations showed that all AN-treated animals exhibited similar pattern of cholinomimetic signs. Time to onset of convulsions and death was shorter in acetone pretreatment groups. The convulsions occurred in all animals of the acetone+AN group at approximately 18 min, and two rats expired at 45 min after administration of AN alone. Compared with the AN, DCE+AN and acetone+DCE+AN groups, cyanide, an end metabolite of AN, was significantly increased both in brains and livers of rats in the acetone+AN group. The magnitude of increment in cyanide levels was about 9-fold in the liver of the acetone+ AN group compared with AN alone group. The CcOx activity in brains and livers of the AN and acetone+AN groups was significantly lower compared with the control and acetone groups. When rats were pretreated with DCE, CcOx activity in brains and livers were significantly increased in comparison with the control and acetone groups. MDA levels were significantly increased in both AN and DCE+AN groups compared with control group and a significant difference was observed between the acetone+AN and DCE+AN groups. Compared with control and acetone+AN groups, the GSH activities in the brain of rats of the AN and DCE+AN groups were significantly decreased. Compared with the control group, the SOD and CAT activities in rat pretreated with DCE were significantly decreased.Conclusion:These novel data show that (1) CYP 2E1 plays a key role in AN metabolism to cyanide, (2) higher expression of CYP 2E1 enhance the acute neurotoxicity of AN, and (3) the parent molecule contributed more to oxidative stress than metabolically-released cyanide.