Inflammatory response and epithelial-mesenchymal transition based on the model of co-cultured alveolar epithelial cells and monocytes induced by lipopolysaccharide

Background: Epithelial cells and monocytes play the central roles in initiating and maintaining chronic inflammation. Co-culturing alveolar epithelial cells and monocytes could provide a useful in vitro model for investigating their biological function in chronic inflammation. Methods: Co-culture system of A549 and THP-1 cells in different ratio of 1/1,1/2,1/3, were established using Transwell. After 6,12,24,48h of LPS treatment, inflammation cytokine levels, EMT related indicators, and transcription factors activity were detected. Results: In LPS-treated group of A549 and THP-1 cells with ratio1/1, IL-6(at6,12,24, 48h), IL-1β(at6,48h), TNF-α(at6,24,48h), MMP-9(at24,48h), IL-23(at48h) were significantly increased, compared to control groups. Meanwhile, in LPS-treated group with ratio 1/2, IL-6(at6,12,24h), IL-1β(at48h), TNF-α(at6h), IL-23(at24,48h), MMP-9(at24,48h) levels were significantly increased, whereas significant increase of IL-6(at12h), TNF-α(at6h), IL-23(at24,48h), MMP-9(at24,48h)were observed in LPS-treated group with ratio 1/3, compared with their control group, respectively. In LPS-treated group with 1/1 ratio, α-SMAand COI-1 expression were elevated in A549 cells at 48 h, which indicated EMT of A549 cells were increased. In addition, STAT3, AP-1, NF-κB in LPS-induced A549 and THP-1 cells were obviously activated at different time-points, which might be contributed to the inflammatory response and EMT in A549 and THP-1cells. Conclusion:The co-culture system of A549 and THP-1 cells with ratio 1/1 was successfully established using LPS treatment for 48h, which provide a useful model for in vitro study of chronic inflammation.