Effects Of Nano-Fe₃O₄ And Cadmium On DNA Damage In Human Hepatoma(HepG2) Cells

As the physical and chemical properties of nanoparticles are greatly different from large particles, the characters and intension of their biologic effect will change. With the development of nanotechnology, people will be exposed to more and more nanomaterials and pay more attention to the biological security of nanomaterials. Nanomaterials have massive interface and strong adsorption ability. Thus nanomaterials can adsorb mental ions or organic compounds efficiently. Because of nanomaterials'special surface effect, they will combine with existed pollutants after they enter the environment. Cadmium, which can induce DNA damage and cause carcinoma, aberration and mutation, is one kind of industrial and environmental heavy mental pollutants. There is no research on the health impact of carcinogen cadmium chlorides combined with nanomaterials. Research on the health impact of combined environmental pollutants and nanomaterials will be helpful to understand the accurate health effect of nanomaterials.This paper mainly discuss the effect of nano-Fe₃O₄ and cadmium chlorides on growth arrest and DNA damage-inducible gene (GADD)153 expression and DNA single-strand breaks, chromosome damage and apoptosis in human hepatoma(HepG2) cells by a series of in vitro experiments, which were used to explore the DNA damage and apoptosis effect of nano-Fe₃O₄ combined with cadmium chlorides in order to provide experiment evidences to the health impact of nanoparticles. Part 1The effect of nano-Fe₃O₄ and CdCl2 on GADD153 promoter and GADD153 gene expression level in HepG2 cells was studied in this part. Mice GADD153 promoter was inserted into pGL3-Basic. This recombinant GADD153-luc plasmid was transfected into HepG2 to get the recombinant HepG2 cells. If the cells are exposed to DNA damage factors and induced DNA damage, the GADD153 promoter will be activated, and following luciferase will express. The recombinant cells and normal cells are exposed to 16 groups which were made up of 4 groups of nano-Fe₃O₄ with different concentration (0g/L, 0.002g/L, 0.01g/L, 0.05g/L)×4 groups of CdCl2 with different concentration (0μmol/L, 0.2μmol/L, 1μmol/L, 5μmol/L). Nano-Fe₃O₄ increased the luciferase expression without significancy. CdCl2 increased the luciferase expression significantly. Nano-Fe₃O₄ and CdCl2 have synergistic effect on the expression of luciferase. The results of RT-PCR showed that when CdCl2 was 1μmol/l and 5μmol/l, nano-Fe₃O₄ enhanced the increase of GADD153 gene expression level. The results suggested that nano-Fe₃O₄ and CdCl2 have synergistic effect on GADD153 promoter's expression and nano-Fe₃O₄ can enhance the expression of GADD153 gene induced by CdCl2.Part 2In this part it was invested that DNA single-strand breaks, chromosome damage and apoptosis induce by nano-Fe₃O₄ and CdCl2 via single cell gel electrophoresis (SCGE), cytokinesis-blocked micronucleus (CBMN) test, propidium iodide-FITC in vitro. There are 3 groups of nano-Fe₃O₄ with different concentration (0g/L, 0.01g/L, 0.05g/L)×3 groups of CdCl2 with different concentration (0μmol/L, 1μmol/L, 5μmol/L) and the cells were exposed to 9 groups of compounds. CdCl2 can induce DNA single-strand breaks and micronuclei formation and percentage of apoptosis. Nano-Fe₃O₄ can induce DNA single-strand breaks without significancy and can not induce micronuclei formation and percentage of apoptosis. Nano-Fe₃O₄ can aggravate the effect of CdCl2 on DNA single-strand breaks and chromosome damage in HepG2 cells. They showed synergistic effects on DNA single-strand breaks after the data were statistic analyzed. The results suggest that when nano-Fe₃O₄ coexist with CdCl2,CdCl2 play a dominant role on DNA damage,and nano-Fe₃O₄ can enhance the damage by synergistic effect or other mechanism.