Intracellular glutathione plays important roles in pyrrolizidine alkaloids-induced growth inhibition on hepatocytes

Pyrrolizidine alkaloids (PAs) are well-known natural hepatotoxins distributed widely in thousands of plants in the world. Adonifoline (Adon), senecionine (Sene) and monocrotaline (Mono) are retronecine-type PAs, and the present study is designed to observe the effects of intracellular glutathione on toxicity of these three PAs in human normal liver L-02 cells. The ratio of cellular reduced glutathione (GSH) and oxidized glutathione (GSSG) was assayed after L-02 cells were incubated with these three PAs for various times. Results showed that Adon, Sene and Mono all significantly decreased the ratio of GSH/GSSG in L-02 cells in the time- and concentration-dependent manner. The results of 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) and trypan blue staining assay showed that these three PAs all significantly decreased cell viability in L-02 cells when pretreated with 10 μM BSO (L-Buthionine-S-R-Sulfoximine) for 24 h to deplete intracellular GSH. Further results showed that anti-oxidant compounds such as NAC (N-Acetyl-Cysteine) and GSH could rescue the cytotoxicity caused by these three PAs with BSO pretreatment. Taken together, those results suggest that intracellular GSH plays important roles in regulating the cytotoxicity induced by PAs.