Glomerular Endothelial Glycocalyx Constitutes a Barrier to Protein Permeability

Abstract

Glycocalyx, composed of glycoproteins including proteoglycans, coats the luminal surface of the glomerular capillaries. Human heparanase degrades heparan sulphate glycosaminoglycans and is upregulated in proteinuric states. In this study, we analyze the structure of the human glomerular endothelial cell glycocalyx in vitro and examine its functional relevance, especially after treatment with human heparanase. Electron microscopy of conditionally immortalized glomerular endothelial cells revealed a 200-nm thick glycocalyx over the plasma membrane, which was also demonstrated by confocal microscopy. Neuraminidase treatment removed the majority of glycocalyx, reduced trans-endothelial electrical resistance by 59%, and increased albumin flux by 207%. Heparinase III and human heparanase specifically cleaved heparan sulphate: this caused no change in trans-endothelial electrical resistance, but increased the albumin passage across the monolayers by 40% and 39%, respectively. Therefore, we have characterized the glomerular endothelial cell glycocalyx and have shown that it contributes to the barrier to flux of albumin across the cell layer. These results suggest an important role for this glycocalyx in the restriction of glomerular protein passage in vivo and suggest ways in which human heparanase levels may be linked to proteinuria in clinical disease.

A Biliary HCO3 − Umbrella Constitutes A Protective Mechanism Against Bile Acid–Induced Injury in Human Cholangiocytes

“…7 A glycocalyx influences the permeation of charged proteins over the endothelial wall. 53,54 The striking effect of desialylation of the glycocalyx by neuraminidase treatment on pH-dependent cholangiocyte toxicity induced by CDC and GCDC, but not TCDC, supports the idea that polar, negatively charged bile salts are prohibited from entering cholangiocytes and from inducing cell death. We assume that this protective effect of the intact glycocalyx is the result of local stabilization of the biliary HCO À 3 umbrella, enabling the deprotonation of bile acids to bile salts in the close vicinity to the membrane.…”

Maintenance of Endothelial Guanosine Triphosphate Cyclohydrolase I Ameliorates Diabetic Nephropathy

“…It has recently been reported that GEnCs are covered by an ESL, containing glycocalyx and cell coat, which extends into the fenestrae. 30,31 The ESL covers the cellular surface and is composed of large amounts of glycoprotein, such as heparan sulfate proteoglycan. 32 Because of the presence of sulfated sugar chains in heparan sulfate proteoglycan, the ESL possesses a highly negative charge and thereby regulates vascular permeability.…”

The association between therapeutic outcomes and VEGF G-1154A and C-936T gene polymorphisms in patients with glomerulonephritis

“…7 The fenestrated endothelium in glomeruli, glomerular basement membrane, and podocytes form a physical barrier against transition of macromolecules such as albumin and the other proteins in plasma. 8,9 Given the role of VEGF in enhancing microvascular permeability, it is estimated that VEGF may regulate glomerular permeability. There is a close relationship between the distribution of fenestrae and rise in VEGF expression.…”