D1.314 - Endothelial glycocalyx shedding in IgE- and IgG-mediated anaphylaxis

A growing body of evidence points to the relevance of the endothelium in anaphylaxis. This cellular monolayer is protected by a dynamic and malleable structure of proteoglycans and glycosaminoglycans termed as the endothelial glycocalyx (eGCX). Its injury has already been associated with endothelial dysfunction. In addition, eGCX disruption leads to the release of circulating biomarkers reflecting endothelial damage. Our previous studies demonstrated eGCX shedding during anaphylaxis in a mouse model of active systemic anaphylaxis. However, the impact of immunological pathways on the eGCX, specifically IgE- and IgG-mediated mechanisms, remains unclear. Therefore, the aim of this study was to evaluate eGCX alterations during anaphylaxis through distinct IgE- and IgG- independent pathways. 

eGCX structure was evaluated in aortic tissue from mouse models of passive systemic anaphylaxis (IgE-PSA and IgG-PSA) 20 minutes after challenge. Transmission electron microscopy (TEM) was used to measure eGCX area and thickness. Plasma levels of Endocan (ESM-1), a marker of eGCX disruption, were measured by ELISA. Human aortic endothelial cells (HAEC) were in vitro incubated with mediators of anaphylaxis (histamine, platelet-activating factor (PAF), or a combination of them) for 2h. Then, TEM was performed to evaluate in vitro eGCX integrity. 

IgE-PSA and IgG-PSA mouse aortas showed a significant reduction of eGCX surface area and thickness after challenge. At that time, ESM-1 plasma levels were considerably increased in both IgE- and IgG-anaphylactic mice and positively correlated with the severity of the reaction in both PSA models. Furthermore, eGCX area and thickness were significantly diminished in HAEC after incubation with vasoactive mediators. No additive effect was observed when histamine and PAF were added together.

Our data show that eGCX shedding, and specifically ESM-1, is a key mediator during both IgE- and IgG-PSA and correlates with the reaction severity in mice. Moreover, in vitro findings demonstrate that histamine and PAF activate mechanisms that disrupt the eGCX, indicating its potential as a therapeutic target in human anaphylaxis.