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 type Ⅰ (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,allP＜ 0.05],and then declined at high levels [20,100,200 iμ g/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 decreasedexpressions of cytokeratin were verified by Western blot (TAPM2.5 and WSPM2.5 were 0.063 ± 0.109 and0.039 ± 0.313,P values were 0.033 and 0.030,respectively),while α-SMA was only significantlyupregulated in the WSPM2.5-DMSO group (7.853 ± 4.784,P =0.049).The expressions of E-cadherindecreased 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.