SorLA in astrocytes regulates blood-brain barrier integrity

Abstract

The brain`s homeostasis depends heavily on the integrity of the blood-brain barrier (BBB). Astrocytes are an essential part of the BBB in modulating and maintaining the barrier properties of the brain endothelial cells (BECs). Despite decades of research, the elements of glial regulation are not fully elucidated. SorLA/SorL1/LR11, a multifunctional receptor, is the most composite member of the Vps10p domain receptor family. In this study, we characterize the expression and function of SorLA in the cells of the BBB. The applied in vitro approaches describe BBB functions in primary cells isolated from wild-type and Sorl1−/− knock-out rats. Here, we present that Sorl1 gene is highly expressed in wild-type astrocytes but not in BECs and pericytes. Furthermore, we show that SorLA in astrocytes is an important regulator of the BBB’s tightness. The primary rat BBB models where astrocytes lack SorLA protein proved leaky, which correlated well with the decrease in claudin-5 tight junction protein in BECs. Meanwhile, other junctional proteins, i.e., occludin and zonula occludens-1 are unaffected. Collectively, these data suggest that the absence of SorLA in astrocytes affects the tight junctions of BECs, thereby disturbing the BBB. Our results add another layer to understanding astrocyte-endothelial interactions in the healthy and diseased BBB.