FIGURE 3.

Nano-SiO₂ exposure induces global DNA hypomethylation in human bronchial epithelial cells. 16HBE cells were treated with 10 μg/ml Nano-SiO₂ for 8, 16, or 32 passages and BEAS-2B cells were treated with 40 μg/ml Nano-SiO₂ for 15, 30, or 45 passages. (A,B) Immunofluorescence assay was performed to detect 5-mC levels in 16HBE and BEAS-2B cells. 5-mC was visualized by immunostaining with the antibodies against 5-mC (green) and nuclei were visualized by staining with DAPI (blue). Quantification of relative fluorescence intensity was shown on the right. (C) The levels of 5-mdC normalized to that of cytosine were shown in percentage. The data are presented as mean ± SD (n = 3). *p < 0.05, compared with the control group (P0). A549, an epithelial cell line derived from human lung carcinoma, was used as a positive control.