Tight junction protein expression from peritoneal dialysis effluent

Background: We hypothesized that tight junction (TJ) proteins may have a role in paracellular transport of solute and water in peritoneal dialysis (PD) patients. Previous studies on TJ proteins in PD patients have used only cultured human peritoneal mesothelial cells (HPMCs). This study was undertaken to test whether TJ proteins are directly identified from PD effluent and whether their expressions are associated with functional parameters of PD. Methods: Dialysis effluents were collected from 40 patients undergoing PD, after the peritoneal equilibration test (PET). Different molecular sizes of Amicon Ultra-15 Centrifugal Filter Units were used to concentrate and purify proteins in PD effluents, and immunoblot analyses for occludin, ZO-1, and claudins were carried out to test for their existence and relationships with peritoneal clearance or results of the PET. Results: Immunoblotting from PD effluents revealed discrete bands of occludin (∼65 kDa), ZO-1 (∼215 kDa), claudin-1 (∼22 kDa), and claudin-15 (∼22 kDa) in all 40 patients. The peritoneal creatinine clearance inversely correlated with the protein expression of claudin-1 (r= −0.369, p= .019), and the dialysate-to-plasma creatinine ratio at 4 h PET correlated with occludin (r = 0.396, p= .011) and inversely correlated with claudin-15 (r= −0.393, p= .012). Conclusion: In PD patients, expression of peritoneal TJ proteins can be estimated from the dialysis effluent and may be used as novel peritoneal biomarkers.