Apoptogenic activity and toxicity studies of a cytotoxic protein (BMP1) from the aqueous extract of common Indian toad (Bufo melanostictus Schneider) skin

Abstract

A protein (BMP1) was purified from common Indian toad (Bufo melanostictus, Schneider) skin through DEAE cellulose ion exchange chromatography and high performance liquid chromatography. The molecular weight of the BMP1 was found to be 79kDa. BMP1 (0.5 and 1mg/kg/day, i.p.) significantly decreased the number of viable Ehrlich ascites carcinoma (EAC) cells, thereby increased the lifespan of EAC bearing mice (p<0.001). MTT values reduced significantly with the treatment of BMP1 (0.5 and 1.0mg/kg/day, i.p. for 3 days) on EAC cells indicated its antiproliferative activity. This was also supported by flow-cytometric data on the cell cycle arrest at G1 in EAC cells. BMP1 (1mg/kg) reduced the solid tumor weight and volume of about three times further support the antiproliferative nature. Fluorescence and confocal microscopic study on EAC cells after BMP1 (0.5mg/kg/day, i.p. for 3 days) treatment indicated certain features of apoptosis, like nuclear fragmentation, membrane blebbing, and vacuolization of cells. DNA fragmentation was clearly observed in alkaline comet assay. Apoptosis induced by BMP1 was further confirmed through flow-cytometric analysis of annexin-V binding study, sub-G1 arrest in the cell cycle and found to be mediated through caspase 3 dependent pathway. LD50 of BMP1 was found to be 12.2mg/kg, i.p. in male Swiss albino mice. BMP1 treatment at 0.5mg/kg and 1.0mg/kg for 10 days did not alter any hematological and biochemical parameters in mice, but after 30 days of treatment produce significant rise in total leucocyte count, neutrophil percentage, serum urea, creatinine, GOT, LDH and decrease in lymphocyte percentage as compared to respective control. In conclusion, BMP1, a protein molecule isolated from Indian toad (B. melanostictus, Schneider) skin, showed antiproliferative and apoptogenic activity on EAC cancer cell with limited toxicity.