Molecular mechanism of chromium (VI) Induced Cytotoxicity and Apoptosis in L929 Mouse Fibroblasts

Document Type : Original Article

Authors

1 Zoology Dept. Faculty of science-Fayoum University

2 Fellow in Ain Shams Specialized Hospital, EM lab. Ain Shams University,Cairo, Egypt

Abstract

Several methods were used to investigate the mode of death of L929 mouse fibroblast cells in cultures treated with different concentrations of sodium Chromate. Drastic morphological alterations were showed; the cells have grown chaotic, lost their alignment and adherence to the dish surface, consequently they appeared almost round. The nuclei became bigger, later on fragmented into multi nuclei as indication to apoptosis.
Chromate inhibited the proliferation of L929 cells and led to the increase of free nucleosomes in the cell cytoplasm. The exposure of cells to Chromate for 24 and 48 hrs. led to the accumulation of the cells in G2 /M. the ratios were 66.5 and 84 % after 24 and 48 hrs. respectively. The cells in S phase remained unaffected for 24 hrs. and then extensively fall down, may be due to the induction of apoptosis. It was observed that a dose-dependent increase in caspase 3 and caspase 8 activities due to treatment with Chromate. These data are expressed as the fold increase in caspases activities as compared with the control.
Gel electrophoresis of DNA extracted from cells treated with Chromate for 48 h revealed the discontinuous “ladder" pattern of degradation. Such patterns of DNA degradation generally serve as a marker of apoptosis and indicate a preferential hydrolysis of DNA at the internucleosomal linker regions.
The conclusion of cytometric, microscopic, and biochemical data reported in this study fully supported that Cr (VI) induces genotoxic and cytotoxic effects including structural and functional DNA damage.

Keywords