Continuous Blood Purification Ameliorates Endothelial Hyperpermeability in SAP Patients with MODS by Regulating Tight Junction Proteins via ROCK

Abstract

Excessive activation of inflammatory mediator cascade during severe acute pancreatitis (SAP) is a major cause of multiple organ dysfunction and is associated with a high mortality. Recently, more and more studies have shown that continuous blood purification (CBP) could improve the prognosis of patients with multiple organ dysfunction syndrome (MODS), but the exact mechanism is still unclear. Many researchers have found that the disruption of tight junction barrier was an important factor for endothelial hyperpermeability, which played a key role in the pathogenesis of MODS. Previously, we found CBP could attenuate endothelial hyperpermeability in SAP patients with lung injury through regulating cytoskeleton reorganization mediated by RhoA/ROCK. However, the effect of CBP on the change of tight junction proteins in SAP patients with MODS was still unknown. This study aimed to investigate the role of tight junctions in endothelial hyperpermeability in SAP patients with MODS using an in vitro model, and the effect of CBP on tight junction barrier. Before CBP and after CBP, blood samples were collected to observe hepatic and renal function, and arterial blood gas, while the APACHE II score was calculated to evaluate the severity of patients. To test whether RhoA/ROCK signaling pathway was involved, human umbilical vein endothelial cells (HUVECs) were exposed to serum samples taken from patients at specific time points during CBP, or preincubated with ROCK inhibitor, Y-27632, followed by treatment with serum. Then, the changes in endothelial cell permeability and the expression and distribution of tight junction proteins occludin and claudin-1 were observed. Compared with before CBP, the APACHE II score, serum creatinine and alanine aminotransferase decreased significantly, while PaO2/FiO2 increased significantly after CBP. Meanwhile, endothelial permeability induced by serum from patients significantly increased, while the expression of tight junction proteins occludin and claudin-1 significantly decreased, and severe disruption of occludin and claudin-1 was found in these cells. However, pretreated with Rho-kinase inhibitor, Y-27632 could lessen all of these abnormalities, and in a dose-dependent way. Endothelial hyperpermeability, the abnormal expression and distribution of occludin and claudin-1 were attenuated in HUVECs treated with serum from patients after CBP treatment. The abnormality of tight junctions mediated by ROCK was an important mechanism for endothelial hyperpermeability induced by serum from SAP patients with MODS. CBP could ameliorate the disorganization and redistribution of tight junction proteins, hence improve the endothelial permeability.