Emodin abrogates peritoneal dialysis fluid induction of matrix protein synthesis and morphologic changes in human peritoneal mesothelial cells

Abstract

Peritoneal dialysis (PD) is recognised as a therapy for patients with end stage renal failure. Continuous prolonged exposure of the peritoneal membrane to unphysiologic PD solutions results in the activation of the mesothelium, with increased synthesis and secretion of pro-inflammatory/fibrotic mediators, and increased deposition of matrix proteins. We have recently shown that emodin, a natural anthraquinone can abrogate elevated glucose-induced matrix synthesis in human peritoneal mesothelial cells (HPMC). This study aims to investigate the modulatory role of emodin on HPMC morphology, matrix synthesis (fibronectin and collagen type I), and TGF-β1 and IL-1β secretion after stimulation with either spent non-infected or infected conventional PD fluids. HPMC were characterized by their cobblestone, polygonal morphology, and positive staining for vimentin and cytokeratin. HPMC cultured with either spent non-infected or infected PD fluids for 48h resulted in an elongated fibroblastic appearance. These transdifferentiated mesothelial cells were activated as demonstrated by their positive staining for smooth muscle actin. Activation of HPMC was accompanied by an increase in fibronectin, collagen type I, TGF-β1 and IL-1β secretion (210.5±12.5ng/μg cellular protein, 64.5±5.4ng/μg cellular protein, 3.9±0.5 pg/μg cellular protein, and 4.2pg/μg cellular protein respectively for non-infected PD fluid; 390.5±24.5ng/μg cellular protein, 108±12.9ng/μg cellular protein, 5.2±1.6 pg/μg cellular protein, and 7.9±2.7pg/μg cellular protein respectively for infected PD fluid (P<0.05 for all, infected vs non-infected, n=5). Co-incubation of HPMC with spent non-infected or infected PD fluids and emodin (20μg/ml) resulted in a reduction in activated mesothelial cells, with a significant number of cells reverting back to their polygonal, epithelial morphology. Furthermore, emodin significantly reduced matrix protein and cytokine/growth factor secretion to levels similar to basal conditions. Our preliminary results show that emodin may have therapeutic potential in preserving the structural integrity of the peritoneal membrane during long-term PD.