IL-1ß promotes transendothelial migration of PBMCs by upregulation of the FN/α5ß1 signalling pathway in immortalised human brain microvascular endothelial cells.

ABSTRACT

Neuroinflammation is often associated with pathological changes in the function of the blood-brain barrier (BBB) caused by disassembly of tight and adherens junctions that under physiological conditions are important for the maintenance of the BBB integrity. Consequently, in inflammation the BBB becomes dysfunctional, facilitating leukocyte traversal of the barrier and accumulation of immune cells within the brain. The extracellular matrix (ECM) also contributes to BBB integrity but the significance of the main ECM receptors, the ß1 integrins also expressed on endothelial cells, is less well understood. To evaluate whether ß1 integrin function is affected during inflammation and impacts barrier function, we used a transformed human brain microvascular endothelial cell (THBMEC)-based Interleukin 1ß (IL-1ß)-induced inflammatory in vitro BBB model. We demonstrate that IL-1ß increases cell-matrix adhesion and induces a redistribution of active ß1 integrins to the basal surface. In particular, binding of α5ß1 integrin to its ligand fibronectin is enhanced and α5ß1 integrin-dependent signalling is upregulated. Additionally, localisation of the tight junction protein claudin-5 is altered. Blockade of the α5ß1 integrin reduces the IL-1ß-induced transendothelial migration of peripheral blood mononuclear cells (PBMCs). These data imply that IL-1ß-induced inflammation not only destabilizes tight junctions but also increases α5ß1 integrin-dependent cell-matrix adhesion to fibronectin.