ABSTRACT
Long term peritoneal dialysis (PD) is often associated with peritoneal fibrosis. The aim of this study was to explore the effect of emodin on PD-related peritoneal fibrosis and its related cellular and molecular mechanism. PD-related peritoneal fibrosis rats and cultured rat peritoneal mesothelial cells were recruited in the experiment. PD-related peritoneal fibrosis was induced by intraperitoneal injection of lactate-buffered solution containing 4.25% glucose. The peritoneal equilibrium test (PET) was performed at the end of 2 weeks, 4 weeks, and 6 weeks, respectively. HE staining and Masson staining were used for histopathological evaluation. Enzyme linked immunosorbent assay (ELISA) was used to measure the plasma N-terminal procollagen III propeptide (PIIINP) level. Real-time PCR technique was used to detect the mRNA levels of Notch1, Jagged-1, and Hes-1 in peritoneal tissue. Western blot was applied to identify the protein levels of Notch1, Jagged-1, Hes-1, and Notch intracellular domain (NICD). In vitro, Notch1 overexpressing or knockdown rat peritoneal mesothelial cells were established and Western blot was used to examine the effect of emodin on the expressions of Hes-1 and Hey. Compared with the control group, HE staining revealed that PD rats suffered from decreasing in mesothelial cells, or detaching from surface of parietal peritoneum, accompanied by infiltration of inflammatory cells; Masson staining result showed thickened peritonea (P < 0.01), and the collagen deposition in the parietal peritoneum was increased; also, PIIINP level in plasma was elevated (P < 0.01). Treatment of the PD rats with emodin increased mesothelial cells in peritoneal tissue, and decreased the peritoneal thickness (P < 0.01), collagen depositions, as well as the plasma PIIINP level (P < 0.05). The expressions of Notch1, Jagged-1, Hes-1 and NICD in peritoneal tissue were also attenuated (P < 0.05 or P < 0.01). In cultured rat peritoneal mesothelial cells, compared with emodin group, emodin further inhibited the expressions of Hes-1 and Hey induced by Notch1-overexpression (P < 0.05), but not the expressions of Hes-1 and Hey induced by Notch1-knockdown (P > 0.05). Therefore, the activation of Notch pathway may be involved in the pathological process of PD-induced peritoneal fibrosis. Emodin may ameliorate the PD-related peritoneal fibrosis through inhibiting the activation of Notch pathway.