The Interplay between Cofilin and Phospho-Cofilin: Its Role in Maintaining Blood Brain Barrier Integrity

The blood brain barrier (BBB) is a continuous, non-fenestrated vessel system that tightly regulates the movement of molecules, ions, and cells between the blood and the central nervous system. Endothelial cells are the major constituents of the BBB and these cells are linked to each other through intercellular contact points composed of tight junctions, adherent junctions and gap junctions. These three types of junctions are connected to the intracellular actin cytoskeleton via various adaptor proteins. Thus, the actin cytoskeleton plays a crucial role in regulating the stability of endothelial cell contacts and vascular permeability. Shear stress, growth factors, and Wnt/β-catenin pathway modulators contribute to maintaining endothelial cell integrity by controlling actin dynamics under homeostatic conditions. Interestingly, the downstream signaling of the aforementioned factors converges at Rac1, which mediates cortical actin stabilization, stress fiber destabilization and junctional complex stabilization by controlling subcellular cofilin dynamics. However, Rac1 is not the only modulator of cofilin activity; many other agents activated during inflammatory, ischemic, and excitotoxic conditions can disturb homeostatic cofilin dynamics and induce BBB disruption. Therefore, in this review, we discuss organization of the actin cytoskeleton in BBB endothelial cells and how interactions between the actin cytoskeleton and junctional complexes are maintained during homeostatic conditions. Furthermore, we discuss how an imbalance in subcellular cofilin dynamics can contribute to BBB disruption and highlight Rac1 as a potential target that can be exploited to preserve BBB stability.