C3a Mediates Endothelial Barrier Disruption in Brain-Derived, but Not Retinal, Human Endothelial Cells
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Philipps-Universität Marburg
Abstract
Neuromyelitis optica spectrum disorder (NMOSD) is associated with pathological aquaporin-4
immunoglobulin G (AQP4-IgG), which cause brain damage. However, the impact of AQP4-IgG
on retinal tissue remains unclear. Additionally, dysregulated complement anaphylatoxins C3a and
C5a, known to modulate the endothelial barrier, are implicated in NMOSD. This study evaluates
the susceptibility of human brain microvascular endothelial cells (HBMEC) and human retinal
endothelial cells (HREC) to C3a- and C5a-mediated stress using real-time cell barrier analysis,
immunocytochemical staining, qPCR and IgG transmigration assays. The findings reveal that C3a
induced a concentration-dependent paracellular barrier breakdown and increased transcellular
permeability in HBMEC, while HREC maintained barrier integrity under the same conditions. C5a
attenuated C3a-induced disruption in HBMEC, indicating a protective role. Anaphylatoxin treatment
elevated transcript levels of complement component C3 and increased C5 gene and protein expression
in HREC, with no changes observed in HBMEC. In HBMEC, C5a treatment led to a transient
upregulation of C3a receptor (C3AR) mRNA and an early decrease in C5a receptor 1 (C5AR1) protein
detection. Conversely, HREC exhibited a late increase in C5aR1 protein levels. These results indicate
that the retinal endothelial barrier is more stable under anaphylatoxin-induced stress compared to
the brain, potentially offering better protection against paracellular AQP4-IgG transport.