Disruption of endothelial glycocalyx after ischemic stroke onset: Activated scission activity of proHPSE by acrolein exposure

Infiltration of peripheral immune cells after blood-brain barrier (BBB) dysfunction causes severe inflammation after a stroke. Although the endothelial glycocalyx functions as a barrier to circulating cells, the relationship between stroke severity and glycocalyx dysfunction remains unclear. In this study, glycosaminoglycans (GAGs), a component of the endothelial glycocalyx, in ischemic stroke were studied using a photochemically induced thrombosis (PIT) mouse model. As results, decreased levels of heparan sulfate (HS) and chondroitin sulfate (CS) and increased activity of hyaluronidase 1 and heparanase (HPSE) were observed in ischemic brain tissues. HPSE expression in cerebral vessels increased after stroke onset and infarct volume greatly decreased after co-administration of N-acetylcysteine (NAC)+GAG oligosaccharides as compared to NAC administration alone. These results suggest that the endothelial glycocalyx was injured after the onset of stroke. Interestingly, scission activity of proHPSE produced by HBMEC/ciβ and HEK293 cells transfected with hHPSE1 cDNA were activated by acrolein exposure. We identified the ACR modified amino acid residues of proHPSE using nano LC-MS/MS, suggesting that ACR modification of Lys139 (6-kDa linker), and Lys107 and Lys161, located in the immediate vicinity of the 6-kDa linker, at least in part, is attributed to the activation of proHPSE. Since proHPSE, but not HPSE, localizes outside cells by binding with HS proteoglycans, ACR-modified proHPSE represents a promising target to protect the endothelial glycocalyx.