P-Cresylsulfate, the Protein-Bound Uremic Toxin, Increased Endothelial Permeability Partly Mediated by Src-Induced Phosphorylation of VE-Cadherin

Abstract

The goal of our study was to investigate the impact of p-cresylsulfate (PCS) on the barrier integrity in human umbilical vein endothelial cell (HUVEC) monolayers and the renal artery of chronic kidney disease (CKD) patients. We measured changes in the transendothelial electrical resistance (TEER) of HUVEC monolayers treated with PCS (0.1–0.2 mM) similar to serum levels of CKD patients. A PCS dose (0.2 mM) significantly decreased TEER over a 48-h period. Both PCS doses (0.1 and 0.2 mM) significantly decreased TEER over a 72-h period. Inter-endothelial gaps were observed in HUVECs following 48 h of PCS treatment by immunofluorescence microscopy. We also determined whether PCS induced the phosphorylation of VE-cadherin at tyrosine 658 (Y658) mediated by the phosphorylation of Src. Phosphorylated VE-cadherin (Y658) and phosphorylated Src levels were significantly higher when the cells were treated with 0.1 and 0.2 mM PCS, respectively, compared to the controls. The endothelial barrier dysfunction in the arterial intima in CKD patients was evaluated by endothelial leakage of immunoglobulin G (IgG). Increased endothelial leakage of IgG was related to the declining kidney function in CKD patients. Increased endothelial permeability induced by uremic toxins, including PCS, suggests that uremic toxins induce endothelial barrier dysfunction in CKD patients and Src-mediated phosphorylation of VE-cadherin is involved in increased endothelial permeability induced by PCS exposure.

Endothelial Damage, Inflammation and Immunity in Chronic Kidney Disease

“…PCS also exhibits a role in endothelial activation, through increased expression of ICAM-1, MCP-1 and TF, which promotes adhesion of leukocytes to the endothelium. It inhibits proliferation, viability, and repair capabilities impairing nitric oxide (NO) signaling or increasing its permeability [ 167 ]. TMAO, a gut metabolite derived from the fermentation of dietary choline/phosphatidylcholine, L-carnitine or betaine, also induces endothelial damage, with activation of NALP3 inflammasome [ 168 ], cellular inflammation, ROS production, and has been associated with atherothrombosis [ 169 ].…”

How do Uremic Toxins Affect the Endothelium?

“…Uremic toxins contribute to structural damage of the endothelial monolayer, which results in increased permeability. In CKD patients, studies have detected disruptions to the structure of the endothelial monolayer in renal arteries [ 13 , 75 ]. Loss of endothelial integrity and enhanced permeability are also seen in the aortic endothelium of nephrectomized rats, an animal model of CKD [ 76 , 77 ].…”

“…Loss of endothelial integrity and enhanced permeability are also seen in the aortic endothelium of nephrectomized rats, an animal model of CKD [ 76 , 77 ]. In vitro, PCS, IS, and uremic serum reduced the transendothelial electrical resistance (TEER), which indicates an increase in endothelial permeability [ 75 , 78 , 79 ]. In this regard, studies have also found that uremic toxins induced F-actin cytoskeletal remodeling in endothelial cells, leading to changes in cell morphology [ 13 , 79 , 80 ].…”

“…In vitro studies have shown that uremic toxins lead to the rupture of cell-cell junctions, especially related to vascular endothelial (VE)-cadherin and zonula occludens-1 (ZO-1) proteins [ 13 , 75 , 78 , 79 ]. VE-cadherin is a transmembrane protein that belongs to adherent junctions and plays a crucial role in cell–cell interaction [ 81 , 82 ].…”

“…Our group have demonstrated a decrease in the expression of VE-cadherin and ZO-1 in endothelial cells exposed to inorganic phosphate and uremic serum, while no change in expression was observed when cells were exposed to PCS and IS [ 13 ]. However, Chen et al [ 75 ] recently demonstrated that PCS increased phosphorylation of VE-cadherin at tyrosine 658 (Y658) in HUVECs. In a similar manner, Assefa et al [ 78 ] found that IS increased VE-cadherin phosphorylation in bovine aortic endothelial cells (BAECs).…”