Epithelial-mesenchymal transition of A549 cells is enhanced by co-cultured with THP-1 macrophages under hypoxic conditions

Epithelial-mesenchymal transition (EMT) is associated with pulmonary fibrosis, including idiopathic pulmonary fibrosis (IPF). In this study, we investigated EMT of human pulmonary epithelial-derived cells (A549). A549 cells was either cultured by itself or co-cultured with THP-1 macrophages under normoxic (21% O-2) and hypoxic (2% O-2) conditions. We evaluated the presence of EMT by determining the expression of EMT markers, E-cadherin, vimentin, and fibronectin. To determine the role of TGF-beta 1 and IL-1 beta in EMT of the A549 cells, we analyzed the effects of blocking their activity with TGF-beta 1 inhibitor or IL-1 beta neutralizing antibody respectively. The A549 cells presented EMT when they were co-cultured with THP-1 macrophages. The EMT of the A549 cells co-cultured with THP-1 macrophages was exacerbated under hypoxia. In addition, the EMT were prevented by the addition of TGF-beta 1 type I receptor kinase inhibitor. The hypoxic condition increased the mRNA levels of TGF-beta 1 in A549 cells and THP-1 macrophages and that of IL-1 beta in THP-1 macrophages when each cells were co-cultured. Anti-IL-1 beta neutralizing antibody attenuated TGF-beta 1 secretion in co-culture media under hypoxic conditions. Thus, the IL-1 beta from THP-1 macrophages up-regulated the TGF-beta 1 from A549 cells and THP-1 macrophages, and then the TGF-beta 1 from both cells induced and promoted the EMT of A549 cells when they were co-cultured under hypoxia. Together, these results demonstrate that the interaction between type II pneumocytes and macrophages under hypoxia is necessary for the development of pulmonary fibrosis. 2014 Elsevier Inc. All rights reserved.