Molekulare Mechanismen von Heparanase-2 bei der endothelialen Inflammation und der Albuminurie
Zusammenfassung der Projektergebnisse
In our research project we analyzed molecular mechanisms regulating the glycocalyx as well as endothelial cell function in the proteinuric state and tested the hypothesis that a novel molecule, heparanase-2 (hpa-2), interferes with both, the degradation of the glycocalyx and endothelial cell function, thereby preventing or ameliorating proteinuria. We were able to delineate the role of heparanase-2 in the pathophysiology of proteinuric nephropathy and to outline a novel treatment strategies for this disease. Over the last decade we have learnt that the endothelium is not a passive cellular layer of the vessel wall but has important functions in the communication between the blood and the vessel wall. Most importantly, several important functions such as vascular permeability, vasodilation and -constriction, the regulation of inflammation via adhesion molecules and cytokines as well as coagulation and the complement system are important mechanisms regulated by the endothelial cells. The endothelium is covered with a thick layer of heavily glycosylated proteins, a structure which has been called the glycocalyx. The glycocalyx is situated at the luminal side of all blood vessels and covers the surface receptors and other membrane-bound molecules of the endothelium. The volume of the glycocalyx depends on the balance between biosynthesis and the enzymatic or shear-dependent shedding of its components. The glycocalyx is a negatively charged, organized mesh of membranous glycoproteins, with core proteoglycans of the syndecan and glypican family carrying highly sulfated, linear glycosaminoglycan attachments (mostly of the heparan, chondroitin, and dermatan sulfate families). Hyaluronic acid and the negatively charged heparan sulphate proteoglycans are its major constituents. Heparanase is the only known mammalian endoglycosidase capable of degrading heparan sulfate (HS) glycosaminoglycan. Heparanase cleaves the glycosidic bond within the HS chain at selective sites releasing saccharide products with appreciable size (5–7 kDa) that can still associate with protein ligands and modulate their biological potency. Heparanase plays such an important role in inflammation but also in tumor progression and metastasis it is a promising therapeutic target. Classically, the main target of heparanase inhibitors has been aimed at the enzymatic function of the protein;however, recent approaches have also used the potential of targeting the non-enzymatic pro-adhesion activity. However, there are still few heparanase inhibitors available. The recent cloning of a novel family member of heparanases, namely heparanase-2, and the unexpected finding that it inhibits heparanase activity offers the opportunity to study this endogenous molecule and its effects in the context of renal disease and proteinuria. The aim of our research project was to analyze the functional role of hpa-2 in renal disease and its possible role in the pathogenesis of endothelial cell function and albuminuria has not been investigated so far. We studied the molecular function of heparanase-2 (hpa-2) and tested 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 facos (VEGF, FGF), and (4) thereby prevents renal and vascular damage under pathological conditions such as diabetes and sepsis. For this purpose, we have used (1) a newly developed animal model for proteinuria in the zebrafish, and (2) a novel microcirculation system for endothelial cells.
Projektbezogene Publikationen (Auswahl)
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Heparanase-2 protects from LPS-mediated endothelial injury by inhibiting TLR4 signalling. Scientific Reports, 9(1).
Kiyan, Yulia; Tkachuk, Sergey; Kurselis, Kestutis; Shushakova, Nelli; Stahl, Klaus; Dawodu, Damilola; Kiyan, Roman; Chichkov, Boris & Haller, Hermann
