Molecular mechanisms of heparanase-2 (hpa-2) in endothelial cell activation, inflammation and albuminuria

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The endothelium is covered with a layer of heavily glycosylated glycoproteins called the glycocalyx. The endothelial glycocalyx plays an important role in many physiological glomerular mechanisms and damage to the glycocalyx results in renal disease and proteinuria. Proteoglycans can be regulated by heparanase, the only known mammalian endoglycosidase capable of degrading heparan sulfate (HS) glycosaminoglycan. Enzymatic degradation of HS by heparanase profoundly affects numerous physiological and pathological processes, including morphogenesis, neovascularization, tumorigenesis as well as immune reactivity and inflammation. Recently, a novel heparanase, hpa-2 has been cloned. Most importantly, Hpa2c inhibits heparanase enzymatic activity, likely due to its high affinity to heparin and HS and its ability to associate physically with heparanase. However, the functional role of hpa-2 in renal disease and its possible role in the pathogenesis of endothelial cell function and albuminuria have not been investigated so far. We therefore want to study the molecular function of heparanase-2 (hpa-2) and test the hypothesis that hpa-2 (1) prevents the shedding of the endothelial glycocalyx by heparanase-1, (2) antagonizes and reduces the intracellular effects of heparanase-1, (3) reduces the intracelluar signaling and effector mechanisms of cytokines and growth factors (VEGF, FGF), and (4) thereby prevents renal and vascular damage under pathological conditions such as diabetes and sepsis. For this purpose, we will use (1) a newly developed animal model for proteinuria in the zebrafish, (2) a novel microcirculation system for endothelial cells, and we have established (3) novel staining techiques for glycocalyx and (4) viral transfection of hpa-2 in mouse models of renal disease. Our research is not only improtnat for the understanding of endothelial glycocalyx and ist regulation but may also lead to novel treatment strategies in diabetic nephropathy and sepsis.