Induction of Growth Arrest and DNA Damage-Inducible Genes in Human Hepatoma HepG2 Cells by 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD)

To investigate the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD) on DNA damage and expression of DNA damage-inducible genes in human hepatoma HapG2 cells. Cell survival was measured using MTT metabolic viability assay. Single cell gel assay was applied to determine the DNA damage .The level of gene expression was measured by reverse transcription-polymerase chain reaction . The cell survival decreased from 94% to 69% after 24 h treatment with TCDD of varying concentration ranging 0.5-20 nM. The cell survival decreased to 85% and 71% respectively after 12 h and 24 h treatment with 10 nM. with DNA damage gradually elevated . At 48 h treatment , the cell survival further decreased to 67% and DNA damage became most serious .At 24 h after treatment, GADD135 gene expression increased with 10 nM. TCDD respectively .However , P38MAPK, P53, GADD34, GADD45 four genes expression were inhibited in 24 h treatment period ,then recovered gradually after treatment . These findings indicate that TCDD-mediated oxidative stress activated p38 MAPK to induce three GADD genes, in this study, we investigated the effect of TCDD on expression of GADD34S GADD45 and GADD135 genes using human HepG2. 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD) could lead to DNA damage and expression level change of genes involved in nucleotide excision repair in human hepatoma HapG2 cells.