| Objectives:In environmental air, respirable particulate matters as risk factors are threatening human health. PM2.5 is a fine particle with the size less than 2.5?m in diameter. After being inhaled, PM2.5 can directly enter the bronchi, deposit in the pulmonary alveoli, further interfere with pulmonary gas exchange. PM2.5 can seriously damage the alveoli and mucosa, causing bronchial asthma, chronic fibrosis of lung tissues, even lung cancer. EMT(epithelial mesenchymal transition)is a programmed biological process by which epithelial cells adopt a mesenchymal phenotype, and EMT of bronchial epithelial cells has been shown to play an important role in carcinogenesis and metastasis of lung cancer, organ fibrosis, and other pathological processes.The microfluidic chip technology has advantages over traditional analytical method in terms of lower cost, smaller size, simplification and higher sensitivity. Moreover, in the chip, the channels responsible for quantitative fluid input simulate blood vessels in vivo to supply fresh oxygen and nutrients to the incubating cells, and remove metabolic wastes, thereby mimicking the physiological milieu of the cell. In our study, microfluidic chip was utilized to study the effect of PM2.5 on EMT of human bronchial epithelial 16 HBE cells, which could contribute to PM2.5-induced lung cancer.Methods : The microfluidic chip system consisted of two parts, an upstream concentration gradient generator(CGG) module and downstream cell culture chamber modules. CGG contained two sample holes for injecting cell cultural medium and PM2.5 suspension, respectively. The flow of liquid through generator channels 1-4 generated four different concentration ratios(0:1:3:4) of PM2.5. The cell culture unit consisted of upper and lower layers with 4 chambers each. The lower layer chambers, in which the bronchial epithelial cells were incubated, were connected to the CGG through a channel. The upper incubation chambers were used for incubating macrophage. The microfluidic chip employed in this study accomplished the integration of a number of different assay steps including cell incubation, generation of four distinct concentrations of PM2.5 allowing the evaluation of its cellular effects on the survival rate of human bronchial epithelial cell line 16 HBE, monitoring chemotactic migration of macrophages, cell staining, and immuno-fluorescent analysis. The inner environment of the chip was controlled by automated regulation of the flow of liquid.This microfluidic chip was used to evaluate the effects of the air pollutant PM2.5 on EMT of human bronchial epithelial 16 HBE cells, as well as on alveolar macrophage chemotaxis. The effects of PM2.5 on inducing NF-κB, PI3 K, Snail and N-cadherin, and repressing E-cadherin in 16 HBE cells, and promoting macrophage chemotaxis were also studied.Results:In this study, the microfluidic chip was used to study the effects of different concentrations of and durations of PM2.5 exposed on EMT of the human pulmonary bronchial epithelial cell line 16 HBE. We found that cell survival rates decreased in a dose- and time-dependent manner when PM2.5 was exposed. The chemotactic migration of human alveolar macrophages was enhanced while the 16 HBE cells were treated with increasing concentrations of PM2.5. Furthermore, to response to the treatment of different concentrations of PM2.5 from 0μg/ml to 200μg/ml on the 16 HBE cells, the cellular levels of NF-κB PI3 K, Snail, N-cadherin and TGF-β were increased in a dose dependent manner, whereas that of E-cadherin decreased. Consistent with this, levels of TGF-β in the extracellular medium were increased after the treatment of 16 HBE cells with PM2.5.Conclusion:The results indicate that PM2.5 causes EMT in 16 HBE cells, and that this phenomenon may contribute to PM2.5-induced lung cancer. |
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