Abrin induced oxidative stress mediated DNA damage in human leukemic cells and its reversal by N-acetylcysteine

Abrin is a plant glycoprotein toxin, classified as ribosome inactivating protein (RIP) due to its property of damaging ribosomes in an irreversible manner. Many RIPs have direct DNA damaging activity. The objective of the present study was to evaluate the oxidative stress and DNA damaging potential of abrin in U937 human myeloleukemic cells. Cells were treated with abrin at IC50 of 8 ng/ml for 24 h. Abrin induced a time dependent increase in reactive oxygen species and levels of antioxidant enzymes. There was significant depletion of reduced glutathione levels. DNA damage was assessed by comet assay in terms of percent head DNA, tail DNA, tail length and Olive tail moment. DNA damage was more pronounced at 4 and 8 h at IC50 concentration. Abrin at 4, 8, 16 and 32 ng/ml concentration induced significant DNA damage at 4 h. There was time dependent increase in levels of 8-OHdG in abrin treated cells indicating the oxidative stress mediated DNA damage. N-Acetylcysteine pretreatment at 10 nM for 1 h, considerably reversed the abrin induced DNA damage at 16 and 32 ng/ml. Our results clearly show oxidative DNA damage potential of abrin at low concentration.