Carcinogen metabolizing enzymes: modulation of their activities in liver, lung and stomach by thymoquinone.

Background : Thymoquinone (TQ), the bioactive constituent of black seed ( Nigella sativa), has been shown to inhibit the growth of various human cancerous cells both in vitro and in vivo. Aim:To characterize the effects of thymoquinone on the activity of phase I and phase II carcinogen metabolizing enzymes in rats. Materials and Methods : Phase I enzymes, namely the cytochrome P450 enzymes CYP1A1 and CYP2E1, and phase II enzymes, including UDP-glucuronyltransferase (UGT) and glutathioneS-transferase (GST), were studied in the liver, lung and stomach of female Swiss albino rats. The animals were divided into two groups (10 rats/group), a control group treated wit h corn oil and a TQ-treated group receiving oral (gavage) thymoquinone at a dose of 10 mg/kg/day for 15 consecutive days. Animals were then sacrificed on day 16. Tissue homogenates of liver, lung and stomach were prepared to evaluate the activities of both phase I and phase II selected enzymes. Results:Thymoquinone treatment induced significant modulation of the selected phase I and phase II enzymes in a tissue -specific manner. Our results revealed statistically significant reductions in the activities of CYP1A1 enzyme (46%, 60% and 57% in liver, lung and stomach respectively) versus the control group. Similarly, CYP2E1 activities OriginalResearch Article