Protective effect of thymoquinone against lead-induced antioxidant defense system alteration in rat liver.

Alteration of the antioxidant system may be related to lead (Pb) hepatotoxicity. This study was carried out to investigate the possible beneficial effect of thymoquinone (TQ), the major active ingredient of volatile oil of Nigella sativa seeds, against Pb-induced liver antioxidant defense system impairment. Adult male rats were randomized into four groups: control group received no treatment, Pb group was exposed to 2000 ppm of Pb acetate in drinking water, Pb-TQ group was cotreated with Pb plus TQ (5 mg/kg/day, per os) and TQ group receiving only TQ. All treatments were applied for five weeks. TQ alone did not induce any significant changes in the enzymatic and non-enzymatic antioxidant status. By contrast, Pb exposure significantly decreased not only reduced glutathione level, but also superoxide dismutase, glutathione peroxidase, catalase and glutathione reductase activities in the liver tissue. Interestingly, when coadministrated with Pb, TQ significantly improved the affected antioxidant parameters. In conclusion, our results indicate a protective effect of TQ against Pb-induced liver antioxidant capacity impairment and suggest that this component might be a clinically promising alternative in Pb hepatotoxicity.