Abstract:
Background Carbon black was classified as a possible carcinogen to human by the International Agency for Research on Cancer (IARC) in 1996, but the mechanism by which it causes adverse health effects is still not fully understood. Oxidative stress is usually considered as one of the mechanisms involved, which might further trigger some biological events like organelle dysfunction or apoptosis.
Objective This study is designed to investigate the effects of carbon black on oxidative stress, mitochondria, lysosomes, and apoptosis in human bronchial epithelial cells, aiming to understand the pathophysiological mechanism by which carbon black induces adverse health outcomes.
Methods In vitro cultured human bronchial epithelial cells Beas-2B in logarithmic growth phase were prepared for the following experiments. One control group and four carbon black groups (25, 50, 100, and 200 μg/mL) were set for cell viability assay, and one control group, three carbon black groups (25, 50, and 100 μg/mL), and one N-acety-L-cysteine (NAC, 2 mmol/L) + 50 μg/mL carbon black group for the rest assays. After exposure to designed concentrations of carbon black for 24 h, the cell viability was determined by CCK-8; the intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and lysosomal pH were detected by high content screening system with specific molecular probes; the apoptosis rate was examined by flow cytometry.
Results The cell viabilities of the 50, 100, and 200 μg/mL carbon black groups were decreased significantly compared with the control group (Ps < 0.05). The intracellular ROS, lysosomal pH, and apoptosis rates were increased while the MMP levels were decreased in the 50 and 100 μg/mL carbon black groups compared with the control group (Ps < 0.05). The intracellular ROS, lysosomal pH, and apoptosis rate were decreased while the MMP level was increased in the NAC + 50 μg/mL carbon black group compared with the 50 μg/mL carbon black group (Ps < 0.05).
Conclusion Carbon black exposure could induce oxidative stress in human bronchial epithelial cells, and oxidative stress could subsequently cause a decrease in MMP and an increase in lysosomal pH; such organelle dysfunction might further trigger cell apoptosis.
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