Protective effect of thymoquinone against cyclophosphamide-induced genotoxic damage in human lymphocytes

OBJECTIVE: Protective effect of thymoquinone (TQ) against the cytotoxic and genotoxic effects of cyclophosphamide (CP) was assessed in human peripheral blood lymphocyte culture. METHODS: Mitotic indices were determined as endpoints of cytotoxicity, while sister chromatid exchanges (SCE) served as endpoints of genotoxicity. Firstly, the genotoxic effect of 0.16 µg/ml of CP was tested and CP was detected as genotoxic. In the second set, CP group was treated with 20 µM and 40 µM TQ. RESULTS: TQ reduced the SCE frequencies, suggesting its protective action on human lymphocytes in vitro against the CP induced genotoxic damage. CONCLUSIONS: Our results suggest that TQ produces a protective mechanism against CP-induced genetic damage, and suggest a role of DNA strand breaks in the genotoxicity (Tab. 1, Fig. 1, Ref. 19).