Benzo (a) pyrene-loaded gypsum dust induced apoptosis of human bronchial epithelial cells through the AHR signaling pathway

Abstract

Abstract Objective To determine the molecular mechanism of human bronchial epithelial cell apoptosis induced by adsorption of organic matter in an air pollutant, solid gypsum dust. Methods Benzo (a) pyrene (BaP) was mixed with gypsum dust at a specific ratio (1 µg/g), and human bronchial epithelium (16HBE) cells were selected as the target of infection. Cell survival rate was detected by the CCK8 method and their morphology was observed by Wright-Giemsa staining. Flow cytometry was used to detect apoptosis and the mRNA expression levels of Ahr, Nrf2, Bax, and Bcl-2 were detected by qRT-PCR. The protein expression levels of Ahr, Bax and Bcl-2 were detected by Western blot, while the expression levels of Ahr, Nrf2, Bax and Bcl-2 were detected after pretreatment with geldanamycin. Results Compared with gypsum or BaP alone, the 16HBE cells exposed to BaP-loaded gypsum dust had a significantly reduced survival rate that showed a concentration dependent trend. The mRNA expression of Ahr, Bax, and Bcl-2 and the protein levels of Ahr, Bax, and Bcl-2 were increased significantly (P<0.01). However, after geldanamycin pretreatment, the expression of Ahr, Nrf2, Bax, and Bcl-2 (P<0.01) and protein expression levels of Ahr, Bax and Bcl-2 were decreased significantly (P<0.01). Conclusions BaP-loaded gypsum dust increases apoptosis of 16HBE cells by reducing the effective dose of BaP. Our results suggest that the mechanism of apoptosis may involve activation of the AHR signaling pathway. However, the corresponding mechanism of this synergistic effect requires further study.