PI3K/Akt signaling regulates epithelial-mesenchymal transition of peritoneal mesothelial cells in peritoneal dialysis

Objective To investigate the role of PI3K/Akt signaling in the regulation of epithelial-mesenchymal transition (EMT) of peritoneal mesothelial cells (PMCs) in peritoneal dialysis in vitro and in vivo. Methods The level of Phosphorylated serine/threonine kinase Akt and the expression of EMT associated gene and protein, including ZO-1, Vimentin and FN, were measured in mice EMT model. In vitro study, phosphorylation level and nuclear translocation of Akt, ZO - 1 and Vimentin expression induced by TGF - β1 in human peritoneal mesothelial cells (HPMCs) were also observed. Moreover, HPMCs were pre-treated by one of PI3K/Akt inhibitor, LY294002, or transfected with dominant-negative Akt plasmid to inhibit PI3K/Akt signaling, then analyzed its effect on Zo-1 and Vimentin expression induced by TGF-β1. Results Compared with the control, thickened parietal peritoneum and remarkable decrease in mRNA and protein of the epithelial marker ZO-1, and notable increased in the expression of mesenchymal markers Vimentin and FN were observed in PD mice (all P＜0.01). Moreover, the phosphorylation of Akt also significantly increased under above condition (P＜ 0.01). In vitro study, with the stimulation of TGF-β1, the expression of Zo-1 was down-regulated, while the expression of Vimentin increased (all P＜0.01). In addition, TGF-β1 remarkably increased pAkt in HPMCs (all P＜0.01) in dose-dependent. However, LY294002 and DN-Akt dramatically inhibited the vimentin expression in HPMCs induced by TGF-β1 after inhibition of pAkt. On the other hand, the expression of ZO - 1 also was restored (P＜0.01). Conclusion PI3K/Akt signaling is involved in EMT of peritoneal mesothelial cells in peritoneal dialysis, and may be a new target for the prevention and treatment of peritoneal fibrosis during PD.