OBJECTIVETo investigate oxidative stress and mitochondria-related cell apoptosis induced by silica dust in human normal bronchial epithelial 16HBE cells.

METHODSCell viability, lactate dehydrogenase (LDH), superoxide dismutase (SOD), cell apoptotic rate, the expression level of Bax and Bcl-2 mRNA were measured after 16HBE cells were exposed to 37.5, 75, 150, 300 µg/mL respirable silica dust (diameter<2 µm, d50=1 µm)for 24 h in vitro. Reactive oxygen species (ROS)were tested after 16HBE cells were exposed to silica dust at above concentrations for 1.5, 3, 6, 12 h, respectively.

RESULTSDose-dependent decreases of cell viability and the activity of SOD were observed when silica concentrations increased. The activity of LDH increased when silica concentrations elevated. Compared with the control group, cell viability significantly reduced in 75, 150, 300 µg/mL silica-treated groups (P<0.05). The activity of LDH significantly increased in 150, 300 µg/mL silica-treated groups when compared with the control group (P<0.05). The activity of SOD in all silica-treated groups were significantly lower in comparison with controls (P<0.05). Intracellular ROS levels reached peak values at 1.5 h of silica exposure and gradually dropped to the base level at 12 h. The relationship between ROS levels and silica exposure were dose-response at 1.5 h, 3 h and 6 h of exposure (P<0.05). Similar dose-dependent increase were observed for apoptotic rate and silica exposure (P<0.05). The expression levels of Bcl-2 mRNA decreased, and the expression levels of Bax mRNA increased when silica concentrations increased. The results showed that significantly positive correlations between ROS level and apoptotic rate (r=0.892,P<0.05)or the expression level of Bax mRNA (r=0.850,P<0.05). There was a negative correlation between ROS level and the expression level of Bcl-2 mRNA (r=-0.703,P<0.05).

CONCLUSIONSilica dust could induce cytotoxicity, oxidative stress and mitochondria-related cell apoptosis in 16HBE cells. Oxidative stress may play role in the processes of mitochondria-related apoptosis.

Apoptosis ; Cell Survival ; Cells, Cultured ; Dust ; Epithelial Cells ; cytology ; drug effects ; Humans ; L-Lactate Dehydrogenase ; metabolism ; Mitochondria ; Oxidative Stress ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; Reactive Oxygen Species ; metabolism ; Silicon Dioxide ; toxicity ; Superoxide Dismutase ; metabolism ; bcl-2-Associated X Protein ; metabolism

Dust ; Humans ; Inflammation ; metabolism ; Intercellular Signaling Peptides and Proteins ; metabolism ; Silicon Dioxide ; adverse effects ; Silicosis ; metabolism

China ; Humans ; Pneumoconiosis ; diagnosis