Dexamethasone protects the glycocalyx on the kidney microvascular endothelium during severe acute pancreatitis

Abstract

Objective: This study demonstrated that dexamethasone (DEX) protects the endothelial glycocalyx from damage induced by the inflammatory stimulus tumor necrosis factor-α (TNF-α) during severe acute pancreatitis (SAP), and improves the renal microcirculation.

Methods: Ninety mice were evenly divided into 3 groups (Sham, SAP, and SAP+DEX). The SAP mice model was established by ligature of pancreatic duct and intraperitoneal injection of cerulein. Renal perfusion and function, and morphological changes of the glycocalyx were evaluated by laser Doppler velocimetry, electron microscopy, and histopathology (hematoxylin and eosin (H&E) staining), respectively. Serum levels of syndecan-1 and TNF-α were assessed by enzyme-linked immunosorbent assay (ELISA). The protective effects of dexamethasone on the glycocalyx and renal microcirculation were evaluated.

Results: Significantly high levels of serum TNF-α were detected 3 h after the onset of SAP. These levels might induce degradation of the glycocalyx and kidney hypoperfusion, resulting in kidney microcirculation dysfunction. The application of dexamethasone reduced the degradation of the glycocalyx and improved perfusion of kidney.

Conclusions: Dexamethasone protects the endothelial glycocalyx from inflammatory degradation possibly initiated by TNF-α during SAP. This is might be a significant discovery that helps to prevent tissue edema and hypoperfusion in the future.

Keywords: Severe acute pancreatitis (SAP); Acute kidney injury (AKI); Glycocalyx; Dexamethasone; Tumor necrosis factor-α (TNF-α).

Fig. 1

Pathological changes in the pancreas in SAP mice The SAP mouse model was successfully established by ligature of pancreatic duct and intraperitoneal injection of cerulein, and confirmed by histological analysis following staining of pancreas tissue with hematoxylin and eosin (H&E; magnification: 20×). (a) Sham group, normal pancreatic structures without necrosis and inflammatory cell infiltrations. (b) SAP group, extensive necrosis accompanied by interstitial tissue edema, inflammatory infiltration, and hemorrhages in the pancreas. (c) Pancreas injury scores (Schmidt score) were significantly higher in the SAP group than in the Sham group (P<0.001, n=8). Data were expressed as mean±standard deviation

Fig. 2

Histological and laboratory assessment of renal injury in the early stage of SAP The H&E-staining images (magnification: 20×) showed the evidences of renal tubular damage in accordance with the high levels of serum creatinine in the early stages of SAP, which was reduced by administration of dexamethasone. (a) Sham group, normal kidney structure without tubular necrosis. (b) SAP+DEX group, dexamethasone treatment resulted in an attenuation of kidney injury. (c) SAP group, several injurious changes were observed on the renal tubulars during SAP. (d) The tubular damage score in the mice of SAP group was significantly higher than that in the Sham mice (P<0.001, n=8), and the score was reduced by dexamethasone treatment (P<0.01, n=8). (e) Serum creatinine levels indicated similar elevations at each time point from 6 to 48 h after onset of SAP (^# P<0.01, n=8), which were attenuated by administration of dexamethasone (^* P<0.05, n=8). Data were expressed as mean±standard deviation

Fig. 3

Changes in kidney perfusion in the early stage of SAP SAP caused a reduction of perfusion in the kidneys of mice from the SAP and SAP+DEX groups at each time point from 6 to 48 h after onset of SAP compared to those in the Sham group (^* P<0.05, ^# P<0.01, n=8). The perfusion of the kidney in the mice from the SAP+DEX group was significantly higher than that in mice from the SAP group (^* P<0.05, n=8). Data were expressed as mean±standard deviation

Fig. 4

Degradation of the endothelial glycocalyx in the kidney during SAP Damage to the glycocalyx was observed by electron microscopic analysis (magnification: 40 000×). (a) Sham group, normal glycocalyx lining on the surface of endothelial cells. (b) SAP+DEX group, the glycocalyx was slightly damaged after DEX treatment. (c) SAP group, the glycocalyx was seriously damaged 48 h after onset of SAP. (d) The thickness of the glycocalyx in the mice from SAP group was significantly lower than that in mice from the Sham group (P<0.01, n=8), which showed attenuation after application of dexamethasone (P<0.05, n=8). Data were expressed as mean±standard deviation

Fig. 5

Serum levels of syndecan-1 and TNF-α in the early stage of SAP SAP caused elevation of TNF-α in serum, which resulted in shedding of syndecan-1 from the endothelial glycocalyx into the vascular lumen. (a) Levels of syndecan-1 were remarkably increased at each time point from 3 to 48 h after onset of SAP (^# P<0.01, n=8), and were reduced by applying dexamethasone at each time point from 6 to 48 h after onset of SAP (^* P<0.05, n=8). (b) Levels of TNF-α were remarkably elevated with SAP (^# P<0.01, n=8), and were reduced by applying dexamethasone (^* P=0.05, n=8). Data were expressed as mean±standard deviation