Advanced oxidation protein products trigger apoptosis and block epithelial-to-mesenchymal transition in crypt epithelial cells.

ABSTRACT

Advanced oxidation protein products (AOPPs) are uremic toxins. The present study aimed to investigate the effects of AOPPs on the epithelial mesenchymal transition (EMT) and apoptosis of rat crypt epithelial cells, and to assess the signaling pathways involved. The oxidized rat serum albumin was obtained by sodium hypochlorite modification as AOPPs, and the rat serum albumin (RSA) without sodium hypochlorite modification was set as the control. Different concentrations of AOPPs or RSA were incubated with rat crypt epithelial cells (IEC-6 cells). After culturing for 48 and 72 h, apoptosis was detected by flow cytometry. IEC-6 cells were divided into three groups A normal group, an AOPPs group and an RSA group. Three groups of cells were collected following treatment for 2 h, and the phosphorylation levels of Akt and p65 NF-κB were detected by western blotting. After 72 h of treatment, the cells were collected and the apoptotic rate was detected by flow cytometry. The expression of EMT-related proteins was detected by reverse transcription-quantitative polymerase chain reaction and western blotting. The apoptotic rate of IEC-6 cells increased with the concentration of AOPPs, and the apoptotic rate of the AOPPs group was higher than that of the RSA group. The expression of fibronectin, snail, slug and collagen I in the AOPPs group was lower than that in the RSA group, while the expression of E-cadherin was not significantly different between the two groups. In addition, the expression of fibronectin, snail, slug and collagen I genes in the AOPPs-treated group was equal to or lower than that in the normal group. Compared with the normal group, the Akt phosphorylation level was decreased and the p65 phosphorylation level was increased in the AOPPs- or RSA-treated groups. Compared with the AOPPs-treated group, Akt and p65 phosphorylation levels in RSA-treated group were slightly higher. In conclusion, AOPPs trigger apoptosis and inhibit the EMT of rat crypt epithelial cells, which may be associated with the inhibition of Akt phosphorylation and the promotion of p65 phosphorylation.