PM2.5 from traffic-related ambient air and wood smoke induces epithelial-mesenchymal transition in human bronchial epithelial cells

Abstract

Objective: To observe if arterial traffic ambient PM2.5 (TAPM2.5) and wood smoke PM2.5(WSPM2.5) exposure can induce epithelial-mesenchymal transition (EMT) in human bronchial cells (HBEC). Methods: PM2.5 was collected from an arterial traffic road and a typical southern kitchen, and then the collections were extracted by DMSO. The viability of HBEC was measured by Cell Counting Kit (CCK-8) after culture with PM2.5-DMSO extracts for 24 hours. The expressions of EMT markers, including E-cadherin, cytokeratin, α-smooth muscle actin (α-SMA), vimentin and collagen typeⅠ (COL-Ⅰ) in HBEC were assayed by cell immunofluorescence and Western blot analysis after exposed to two different sources of PM2.5-DMSO extracts for 14 days. Results: The cell viability of HBEC increased at low concentrations (1, 2, 10 μg/ml and 1, 5, 10 μg/ml, corresponding to [(118.4±13.7)%, (118.2±8.0)%, (123.0±19.6)% and (112.4±4.1)%, (120±5.4)%, (117.8±7.0)%, respectively, all P<0.05], and then declined at high levels [20, 100, 200 μg/ml and 15, 20, 30, 40 μg/ml, corresponding to (100.7±12.1)%, (53.4±15.3)%, (9.4±1.7)% and (106.8±10.0)%, (93.8±7.9)%, (60.9±9.5)%, (46.2±3.6)%, respectively, P values were 0.923, 0.000, 0.000 and 0.231, 0.278, 0.000, 0.000, respectively] in both TAPM2.5-DMSO and WSPM2.5-DMSO incubation. After exposure for 14 days, the cells lost their typical cobblestone-like shape which implied that EMT might occur. The same treatment caused decreased positive signals of E-cadherin and cytokeratin in a small proportion of the cells. The decreased expressions of cytokeratin were verified by Western blot (TAPM2.5 and WSPM2.5 were 0.063±0.109 and 0.039±0.313, P values were 0.033 and 0.030, respectively), while α-SMA was only significantly upregulated in the WSPM2.5-DMSO group (7.853±4.784, P=0.049). The expressions of E-cadherin decreased in both groups but not statistically significant in Western blot (0.862±0.096 and 0.817±0.212, P values were 0.228 and 0.117, respectively). Another marker of EMT, COL-I, markedly increased in both PM2.5 treatment groups (2.549±1.037 and 3.658±1.207, P values were 0.034 and 0.001). Conclusions: Both PM2.5 from arterial traffic ambient air and wood smoke could induce EMT in human bronchial epithelial cells, while WSPM2.5 appeared to have a more significant influence on EMT in HBEC.