Endothelial C3a receptor mediates vascular inflammation and blood-brain barrier permeability during aging
Nicholas E. Propson, … , Jörg Köhl, Hui Zheng
Nicholas E. Propson, … , Jörg Köhl, Hui Zheng
Published September 29, 2020
Citation Information: J Clin Invest. 2021;131(1):e140966. https://doi.org/10.1172/JCI140966.
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Research Article Aging

Endothelial C3a receptor mediates vascular inflammation and blood-brain barrier permeability during aging

Abstract

Dysfunction of immune and vascular systems has been implicated in aging and Alzheimer disease; however, their interrelatedness remains poorly understood. The complement pathway is a well-established regulator of innate immunity in the brain. Here, we report robust age-dependent increases in vascular inflammation, peripheral lymphocyte infiltration, and blood-brain barrier (BBB) permeability. These phenotypes were subdued by global inactivation and by endothelial cell–specific ablation of C3ar1. Using an in vitro model of the BBB, we identified intracellular Ca2+ as a downstream effector of C3a/C3aR signaling and a functional mediator of vascular endothelial cadherin junction and barrier integrity. Endothelial C3ar1 inactivation also dampened microglia reactivity and improved hippocampal and cortical volumes in the aging brain, demonstrating a crosstalk between brain vasculature dysfunction and immune cell activation and neurodegeneration. Further, prominent C3aR-dependent vascular inflammation was also observed in a tau-transgenic mouse model. Our studies suggest that heightened C3a/C3aR signaling through endothelial cells promotes vascular inflammation and BBB dysfunction and contributes to overall neuroinflammation in aging and neurodegenerative disease.

Authors

Nicholas E. Propson, Ethan R. Roy, Alexandra Litvinchuk, Jörg Köhl, Hui Zheng

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Figure 3

CD8+ T cells are preferentially recruited and infiltrate the aged brain.

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CD8+ T cells are preferentially recruited and infiltrate the aged brain....
(A) Schematic for flow cytometry analysis of dissociated infiltrating cells in the 20-month-old brain or spleen using antibody staining against CD45, CD11b, CD3ε, CD19, CD8a, and CD4. TC, T cells; BC, B cells. (B) Quantification of flow cytometry analysis showed predominantly CD3+ T cells in the brain compared with the spleen, which showed predominantly CD19+ B cells (n = 7/group). (C) Quantification of T cells showed the predominant subtype enriched in the brain was CD8+ T cells compared with CD4+ T cells in the spleen (n = 7/group). (D) Representative immunostaining of 2-month-old and 20-month-old brain tissue using anti-CD8a and anti–Col IV to determine regional immune cell infiltration within the brain. (E) Magnified image from D highlighting the infiltrated cell types that were counted for analysis. (F) Quantification of regional distribution of CD8+ T cell infiltrates in 4 major brain regions (n = 4/group, 2 tissue sections per mouse). CTX, cortex; THAL, thalamus; CPu, caudate putamen; HPC,hippocampus. (G) Representative images of 3 distinct stages of infiltration observed in all brain regions: perivascular residence (left panel), extravasation (middle panel), and parenchymal surveillance (right panel). Data in B and C represent the mean ± SEM. Analysis was done using 1-way ANOVA with Tukey’s post hoc test (***P < 0.001). Data in F are violin plots displaying medians and quartile ranges. Analysis was done using 2-way ANOVA with Holm-Sidak post hoc test (*P < 0.05, ***P < 0.001). Scale bars: 100 μm (D), 50 μm (E), 10 μm (G).