Effect of the methylation enzyme inhibitors of 5-aza-2-deoxycytidine on the TGF-beta/smad signal transduction pathway in human keloid fibroblasts

Abstract

To investigate the effect of 5-aza-2-deoxycytidine on the TGF-beta/smad signal transduction pathway in human keloid fibroblasts (KFSs). Firstly, immunohistochemical method was used to detect the positive expression rate of phospho-smad2 and phospho-smad3 in the specimens of 15 cases of keloid and 15 cases of normal skin. The keloid fibroblasts were cultured in vitro with 5-aza-2-deoxycytidine(experimental group) or with DMEM (control group). The effect of 5-aza-2-deoxycytidine on the cell cycle and apoptosis of fibroblasts was analysed with flow cytometry ( FCM). Transforming growth factor (TGF)-beta1, Smad7, phospho-smad2 and phospho-smad3 were analyzed by Western Blot, and Immunofluorescence. It was found that the positive expression of phospho-smad2 and phospho-smad3 in keloid were higher than those in normal skin. The FCM showed that the proportion of cells in G0/G1 stage was increased, and so does the proportion of apoptosis cells in keloid fibroblasts intervened by 5-aza-2-deoxycytidine. The expression of TGF-beta1, phospho-smad2 and phospho-smad3 protein were significantly suppressed while the expression of smad7 protein increased in keloid fibroblasts with 5-aza-2-deoxycytidine. In addition, 5-aza-2-deoxycytidine reversed phosphorylation and nuclear translocation of smad2 and smad3. 5-aza-2-deoxycytidine, methylase inhibitors, inhibits cell proliferation and promotes apoptosis of KFSs, which may be associated with the suppression of TGF-beta/smad signal pathway.