Breakdown of the Gut Barrier in Patients with Multiple Organ Dysfunction Syndrome is Attenuated by Continuous Blood Purification: Effects on Tight Junction Structural Proteins

Abstract

Breakdown of the gut barrier increases intestinal permeability and allows movement of intraluminal contents across the mucosa, which can lead to distant organ injury and multiple organ dysfunction syndrome (MODS). Intestinal permeability is associated with alterations in cellular tight junctions involving the structural proteins occludin and zonula occludens-1 (ZO-1). The aim of this study was to investigate the effect of continuous blood purification (CBP) on gut barrier function in patients with MODS. Serum diamine oxidase (DAO) and endotoxin, epithelial monolayer permeability, and transepithelial electrical resistance (TER) were used as markers for the assessment of gut barrier function in 22 patients with MODS who underwent continuous venovenous hemofiltration (CWH) for 24 hours. Blood samples were taken from patients at 0, 6, 12, and 24 hours during CWH therapy. Serum DAO and endotoxin were determined by spectrophotography. Permeability and TER were assessed using Caco-2 cell monolayers. Occludin and ZO-1 protein levels were analyzed by immunoblotting and immunofluorescence staining. And inducible nitric oxide synthase (iNOS) mRNA levels and nitric oxide (NO) production were determined by real-time PCR and spectrophotography, respectively. Gut barrier dysfunction was evident in patients with MODS compared with normal controls. Serum DAO, endotoxin levels, and epithelial permeability were elevated, while TER was decreased in patients with MODS, and this change was more pronounced in nonsurvivors. Breakdown and reorganization of occludin and ZO-1 away from tight junctions was found in all MODS patients. After CBP treatment, APACHE II and MODS scores improved significantly. Serum DAO and endotoxin levels and epithelial permeability also diminished, while TER increased in all patients; CBP significantly attenuated breakdown and reorganization of tight junction proteins, and also attenuated the inflammation-induced increase in iNOS mRNA expression and NO production. Breakdown of gut barrier function is present in patients with MODS and may be correlated with poor outcomes in the disease. CBP can not only improve the general conditions, as measured by the APACHE II score, but also improve gut barrier dysfunction by attenuating the breakdown and reorganization of occludin and ZO-1. This beneficial effect of CBP on gut barrier dysfunction is associated with down-regulation of iNOS.