Bleomycin (BLM) Induces Epithelial-to-Mesenchymal Transition in Cultured A549 Cells via the TGF-β/Smad Signaling Pathway

Abstract

The epithelial-to-mesenchymal transition (EMT) is a crucial cellular event in wound healing, tissue repair, and cancer progression in adult tissues, with the interactions with numerous signals. In this study, we aimed to determine whether bleomycin (BLM), an agent that causes pulmonary fibrosis, induces the EMT of the alveolar epithelial cell line A549 and investigated the possible mechanisms. We examined the EMT involved changes in cell morphology, isoform switching of the fibroblast growth factor receptor 2 (FGFR2) by alternative splicing, and expression of the phenotypic markers including E-cadherin, vimentin, and α-SMA using RT-PCR, Western blotting, and immunofluorescence assays. A TGF-β/Smad inhibitor was used to determine whether coculture with BLM would inhibit the EMT of A549 cells. The results showed that BLM induced the EMT of A549 cells possibly via the TGF-β/Smad signaling pathway, evident from the decrease in the expression of E-cadherin and increase in the expression on vimentin.

Bleomycin induces epithelial-to-mesenchymal transition via bFGF/PI3K/ESRP1 signaling in pulmonary fibrosis

“…In previous studies, we demonstrated that bleomycin induces EMT partly through activating TGF-β/Smad/ESRP1 signaling [17,30]. However, the mechanism of bFGF in bleomycin-induced EMT is not clear.…”

“…Increased expression of mesenchymal cell markers (Vimentin, α-SMA etc.) and decreased expression of epithelial cell markers (E-cadherin and cytokeratin) were found in TGF-β1-treated alveolar epithelial cells, A549 cells and bronchial epithelial cells [17][18][19]. In addition to its effect on the activation of Smad2/3, TGF-β also participates in other non-Smad signaling pathways to induce EMT, such as PI3K/Akt, ERK1/2 and MAPK [20,21], and can also alter cell behavior independently by stimulating nonreceptor protein tyrosine kinases, small GTP-binding proteins and MAP kinases [22,23].…”

“…Among the numerous pulmonary fibrosis/EMT models, the most common and successful model is bleomycin-induced pulmonary fibrosis/EMT, both in vivo and in vitro [17,24,36]. Previous studies verified that BLM can induce EMT of A549 cells via the TGF-β1/Smad signaling pathway and can increase the expression of bFGF and TGF-β1 [28].…”

“…Studies have identified BLM-induced EMT via the TGF-β1/Smad signaling pathway [17]; however, the bFGF-PI3K/Akt signaling pathway in BLM-induced EMT has rarely been reported. Our findings suggesting that BLM treatment caused up-regulation of bFGF was involved in stimulation of lung fibrosis and EMT.…”

Withaferin A attenuates bleomycin‐induced scleroderma by targeting FoxO3a and NF‐κβ signaling: Connecting fibrosis and inflammation

“…Various evidences support TGF‐β1 to be the principle initiator, regulator, and propagator of fibrogenesis in scleroderma . BLM‐induced murine scleroderma is known to be associated with persistent activation of intracellular TGF‐β1/Smad signaling . Strong nuclear accumulation and phosphorylation of Smad2/3 takes place in resident skin fibroblasts following resolution of local inflammation.…”