Deterioration of glomerular endothelial surface layer induced by oxidative stress is implicated in altered permeability of macromolecules in Zucker fatty rats

Abstract

Aims/hypothesisThe glomerular endothelial layer is coated by the endothelial surface layer (ESL), which is suggested to play a role in regulation of the permselectivity of macromolecules. Production of heparanase, a degrading enzyme of the ESL, is induced by reactive oxygen species (ROS). We hypothesised that oxidative stress could cause deterioration of the glomerular ESL by induction of heparanase, resulting in increased glomerular permeability.MethodsMale Zucker fatty (ZF) rats with albuminuria and Zucker lean (ZL) rats were used in this study. Some of the ZF rats were treated with the angiotensin II receptor blocker, irbesartan. We determined the amount of ESL by wheat germ agglutinin staining and heparan sulphate proteoglycan production by western blot analysis. Glomerular hyperfiltration of macromolecules was visualised using in vivo microscopy. We used 2′,7′-dichlorofluorescein diacetate-derived chemiluminescence staining to assess ROS production, and heparanase production and expression were determined by western blot analysis and quantitative real-time polymerase chain reaction respectively.ResultsBy 18 weeks of age, ZF rats had developed albuminuria. The glomerular endothelial cell glycocalyx was significantly decreased in ZF compared with ZL rats. Glomerular filtration and the permeability of macromolecules were increased in ZF, but not in ZL rats. Glomerular ROS and heparanase production were significantly increased in ZF compared with ZL rats. These changes in ZF rats were reversed by irbesartan treatment.Conclusions/interpretationIncreased oxidative stress induces glomerular ESL deterioration in part through increased heparanase levels, resulting in exacerbation of glomerular permselectivity and development of albuminuria.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-010-1810-0) contains supplementary material, which is available to authorised users.

Targeted Glomerular Angiopoietin-1 Therapy for Early Diabetic Kidney Disease

“…39 The endothelial glycocalyx also plays a critical role in the function of the filtration barrier. 40,41 We visualized the glycocalyx using wheat germ agglutinin 40,42 but did not observe any changes in the three groups of animals studied. This contrasts with the suggested role of Angpt1 in increasing glycocalyx thickness observed in isolated glomeruli of normal healthy animals.…”

The Renal Endothelium in Diabetic Nephropathy

“…55 Albuminuria in Zucker fatty rats is accompanied by a significant glycocalyx decrease, which at least in part is related to ROS-induced increased heparanase levels. 56 The effect of diabetes on the glycocalyx of sublingual and retinal capillaries in relation to microalbuminuria was also evaluated in humans. In type I diabetic patients, glycocalyx volume decreased in a stepwise fashion from controls, diabetics without microalbuminuria to diabetics with microalbuminuria.…”

Maintenance of Endothelial Guanosine Triphosphate Cyclohydrolase I Ameliorates Diabetic Nephropathy

“…We have demonstrated that the glomerular ESL is implicated in the regulation of glomerular wall permeability and that ROS-induced deterioration of the ESL exacerbates glomerular permeability in Zucker fatty rats. 24 Salmon et al reported that loss of endothelial glycocalyx is associated to albuminuria with vascular dysfunction. 33 Furthermore, Gil et al reported that the deletion of the heparanase gene, the predominant enzyme that degrades heparan sulfate, protects diabetic mice from diabetic nephropathy.…”

“…24 A very small volume of filtered 70-kD FITC-labeled dextran was detected in the Bowman's capsule space of WT mice ( Figure 4A and Supplemental Video 1) but a massive leakage of this dextran was seen in Ins2 +/Akita mice ( Figure 4B and Supplemental Video 2). The leakage level of this dextran, however, was ameliorated in GCHtg/Ins2 +/Akita mice ( Figure 4C and Supplemental Video 3).…”