Clin Res Cardiol (2022). https://doi.org/10.1007/s00392-022-02002-5

Complement-mediated endothelial dysfunction through endothelial glycocalyx shedding and cell cortex stiffening in acute myocardial infarction

C. Vahldieck1, B. Fels1, C. Hamacher1, S. Loening1, T. Agdirlioglu2, J. Weil2, K. Kusche-Vihrog1

1Institut für Physiologie, Universitätsklinikum Schleswig-Holstein, Lübeck; 2Sana-Kliniken Lübeck GmbH, Lübeck;

Background The endothelial surface, namely the endothelial glycocalyx (eGC) and the underlying cell cortex (CTX) provide a vasoprotective barrier against vascular diseases. Their nanomechanical properties (i.e. stiffness or height) determine endothelial function in that they control the release of vasoactive substances such as nitric oxide (NO). Impairment of endothelial surface structures (eGC and CTX) can be seen as hallmark in cardiovascular diseases, such as acute myocardial infarction (AMI). During AMI the endothelial surface is attacked by several specific molecules, including components of the complement system. This study investigates the role of the anaphylatoxins C3a and C5a in inducing endothelial dysfunction in the context of AMI. Methods Human umbilical vein endothelial cells (HUVEC) were exposed to anaphylatoxins (C3a: 250 ng/ml and C5a: 50 ng/ml) for 24 hours and the nanomechanical properties of eGC and CTX were quantified using atomic force microscopy (AFM)-based nanoindentation as well as fluorescence staining (FS) of eGC and CTX components. Serum samples of patients (N=50) with first manifestation of AMI, as well as age and gender matched controls, were collected. C3a and C5a concentrations were quantified via ELISA. HUVEC were exposed to AMI serum samples with either HIGH (C3a: 1233 ± 260 ng/ml; C5a: 79 ± 22 ng/ml) or LOW (C3a: 379 ± 55 ng/ml; C5a: 21 ± 3 ng/ml) levels of anaphylatoxins.  In addition, complement receptor-antagonists were employed (C3aR-A: SB 290157; C5aR1-A: PMX53) and ex vivo endothelial cells derived from isolated aortae of complement-receptor-KO mice were evaluated. A full length recombinant Syndecan-1 was applied to recover eGC and CTX damage. Results Stimulation with anaphylatoxins caused an increase in cortical stiffness by 10% (C3a) and 11% (C5a) compared to the control group (p < 0.0001). Shedding (loss of height and softening) of the eGC was observed after complement stimulation for both anaphylatoxins (p < 0.001). Stimulation with AMI serum containing LOW or HIGH levels of anaphylatoxins led to a CTX stiffening and loss of eGC height compared to control group (C3a: CTR: 288 nm, LOW: 160 nm, HIGH: 114 nm / C5a: CTR: 265 nm, LOW: 156 nm, HIGH: 115 nm; p < 0.0001). Receptor-antagonists led to a full recovery after stimulation with anaphylatoxins. These results where supported in complement-receptor-KO mice. Syndecan-1-treatment prevented damage of the endothelial surface structures after AMI: CTX stiffness was lower by 8 % (untreated vs. Syndecan-1: 1.38 ± 0.08 vs. 1.27 ± 0.06 pN/nm), eGC was higher by 7 % (109 ± 15.1 vs. 117 ± 17.8 nm) and stiffer by 12 % (0.32 ± 0.03 vs. 0.36 ± 0.03 pN/nm). FS results were consistent with the results of AFM. Conclusion Our data identify the vascular endothelium as an important target of anaphylatoxins, as stimulation of endothelial cells with C3a and C5a led to endothelial impairment in a dose dependent manner, indicating endothelial dysfunction.  We conclude that AMI-induced damage of the endothelial surface is mediated by the C3a:C3aR/C5a:C5aR1-axis. Thus, anaphylatoxins or their receptors, could be important mediators of ischemia-induced endothelial damage and might represent important therapeutic targets. Of note, treatment with recombinant Syndecan-1 restored the nanomechanics properties of the endothelium after AMI. Syndecan-1 could thus be a promising novel approach to positively influence endothelial function in the context of AMI.

https://dgk.org/kongress_programme/jt2022/aP1498.html