[Role of circ_000681 in cadmium-induced DNA damage on human bronchial epithelial cells]

Objective: To investigate the role of circ_000681 in DNA damage caused by cadmium chloride exposure in human bronchial epithelial cells (16HBE cells), and to provide scientific evidence for clarifying the molecular mechanism of respiratory system diseases caused by metal cadmium exposure and exploring early molecular markers. Methods: In April 2022, 16HBE cells were used as the research object, and a cell DNA damage model induced by cadmium chloride was constructed. The experiment consisted of a control group (0 μmol/L) and four different dose cadmium chloride exposure groups (2.5, 5, 10, 20 μmol/L), and treated 16HBE cells with each group for 24 h and 48 h respectively. Comet assay was used to analyze the changes in Olive tail moment; Western blot was used to detect the expression of phosphorylated histone H2AX (γ-H2AX), and to identify the degree of cell DNA damage. Real-time fluorescence quantitative PCR was used to detect the expression of significantly differentially expressed circular RNA (circRNA) in cadmium chloride-induced DNA damage. The circ_000681 knockdown and overexpression sequences were constructed, transfected into 16HBE cells, and combined with cadmium chloride exposure. The DNA damage indicators of the cells were analyzed using the above methods to clarify the role of circ_000681 in cadmium chloride-induced DNA damage in 16HBE cells. Data statistics were performed using one-way analysis of variance and Student's t-test. Results: After 24 h and 48 h of exposure to different doses of cadmium chloride (2.5, 5, 10, 20 μmol/L) in 16HBE cells, compared with the control group, the Olive tail moment and γ-H2AX protein expression levels in each dose group were significantly increased (P<0.05). Compared with the control group, after 24 h of exposure to cadmium chloride at 2.5, 5, 10, and 20 μmol/L, the expression level of circ_000681 was significantly decreased (P<0.05). Compared with the 5 μmol/L cadmium chloride exposure group alone, the Olive tail moment and γ-H2AX protein expression in the knockdown circ_000681 combined with 5 μmol/L cadmium chloride exposure group were increased (P<0.05), while the Olive tail moment and γ-H2AX protein expression in the overexpression circ_000681 combined with 5 μmol/L cadmium chloride exposure group were decreased (P<0.05) . Conclusion: Overexpression of circ_000681 may inhibit DNA damage in bronchial epithelial cells caused by cadmium chloride exposure.