Long-term exposure of indoxyl sulfate induces mesothelial-to-mesenchymal transition of peritoneal mesothelial cells via β-catenin-involved signaling pathway.

BACKGROUND

Long-term peritoneal dialysis (PD) leads to peritoneal injury, with mesothelial-to-mesenchymal transition (MMT) potentially serving as an initial and reversible stage of this process. Indoxyl sulfate (IS), a protein-bound uremic toxin that accumulates in patients with declining renal function, is known to be associated with epithelial-mesenchymal transition (EMT) in proximal renal tubular cells. However, its effects on peritoneal mesothelial cells, which serve as the first-line barrier during PD, have not yet been investigated.

OBJECTIVES

This study aimed to evaluate whether IS induces MMT in human peritoneal mesothelial cells during PD through the β-catenin signaling pathway.

MATERIAL AND

METHODS

A human peritoneal mesothelial cell line (HMrSV5) was used for this in vitro study. Cells were treated with IS or combined with β-catenin inhibitor ICG-001, and high glucose PD fluid (PDF) served as a positive control. Morphology, proliferation and adhesion were assessed, while the expression of β-catenin and α-smooth muscle actin (α-SMA) as mesenchymal markers, along with E-cadherin as a mesothelial marker, were analyzed at both RNA and protein levels using real-time polymerase chain reaction (PCR) and western blot, respectively.

RESULTS

The number of viable and adherent cells was significantly increased in the IS and PDF groups compared to the control (p < 0.05). Treatment with ICG-001 significantly reduced both viable and adherent cell numbers compared to cells treated with IS or PDF alone (p < 0.05). At the RNA level, IS treatment significantly decreased E-cadherin expression (p = 0.002) while significantly increasing β-catenin (p = 0.001) and α-SMA (p = 0.002) expression compared to the control group. These changes were reversed by ICG-001 treatment. Protein expression showed similar trends.

CONCLUSIONS

Indoxyl sulfate induces MMT in human peritoneal mesothelial cells, and these changes can be reversed by the specific β-catenin inhibitor ICG-001. This suggests that IS may be considered as another inducer of MMT during PD through the β-catenin signaling pathway.