Role of endothelial TRPA1 expression in blood-brain barrier dysfunction

BACKGROUND: Transient Receptor Potential Ankyrin 1 (TRPA1) is a cation channel receptor that regulate calcium homeostasis among other cations. Calcium dyshomeostasis known to disrupt the blood-brain barrier (BBB). In the brains of Alzheimer's disease (AD) transgenic mice, increased levels of TRPA1 was associated with increased levels of amyloid-β (Aβ) and neuroinflammation. TRPA1 expressed in the endothelial cells of the BBB. The objective of this work is to investigate the effect of BBB-endothelium TRPA1 activation on the BBB tightness and function. METHOD: We performed in vitro and in vivo studies, Western blot, calcium assay, immunostaining. RESULT: We performed in vitro studies using the mouse brain endothelial cell line bEnd3. First, we determined the expression of TRPA1 in bEnd3 by western blot and immunocytochemistry. Results confirmed TRPA1 expression in bEnd3. In addition, TRPA1 function was evaluated by monitoring calcium influx; the addition of the TRPA1 antagonist A-967079 significantly reduced calcium influx in bEnd3, while the addition of Aβ42 oligomers to the cells increased intracellular calcium levels, which was blocked by the co-addition of the TRPA1 antagonist suggesting that Aβ induces calcium influx via TRPA1. When tested in vivo in 5XFAD mouse model for AD by western blot, we found that TRPA1 levels were significantly higher in brain homogenates when compared to wild-type (WT) mouse brains. Furthermore, the cerebrovascular levels of TRPA1 were significantly higher in 5XFAD compared to WT, which were also associated with BBB disruption as determined by increased IgG extravasation. CONCLUSION: Our data suggests that endothelium-TRPA1 could contribute to BBB disruption by increasing calcium influx.