Ac-SDKP suppresses epithelial-mesenchymal transition in A549 cells via HSP27 signaling

The synthetic tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) has been shown to be a modulator of molecular aspects of the fibrosis pathway. This study reveals that Ac-SDKP exerts an anti-fibrotic effect on human type II alveolar epithelial cells (A549), which are a source of myofibroblasts once exposed to TGF-beta 1, by decreasing the expression of heat shock protein 27 (HSP27). We used A549 cells in vitro to detect morphological evidence of epithelial-mesenchymal transition (EMT) by phase-contrast microscopy. Immunocytochemical and western blot analysis determined the distributions of cytokeratin 8 (CK8), alpha-smooth muscle actin (alpha-SMA), and SNAI1. Confocal laser scanning microscopy revealed a colocalization of HSP27 and SHAH on TGF-beta 1-induced A549 cells. These results also demonstrated that A549 cells became spindle-like when exposed to TGF-beta 1. Coincident with these morphological changes, expression levels of CK8 and E-cad decreased, while those of vimentin and alpha-SMA increased. This process was accompanied by increases in levels of HSP27, SNAIL and type I and type III collagen. In vitro transfection experiments demonstrated that the inhibition of HSP27 in cultured A549 cells could decrease the expression of SHAH and alpha-SMA while increasing the expression of E-cad. A noticeable reduction in collagen types land III was also evident. Our results found that Ac-SDKP inhibited the transition of cultured A549 cells to myofibroblasts and attenuated collagen synthesis through modulating the expression of HSP27. (C) 2014 Elsevier Inc. All rights reserved.