The central nervous system is isolated from the circulatory system by the blood-brain barrier (BBB). Hijacking BBB crossing mechanisms represents the ideal route for drug delivery to the brain. Specialized tight-junctions (TJs), constituted of transmembrane proteins called claudins, connect contiguous cells of the barrier and regulate paracellular traffic of hydrophilic solutes. While the selectivity properties of the TJs are critical in protecting the brain, they are also a major hindrance to direct drug delivery strategies. An intriguing route to overcome the obstacle is to modulate TJ function in a non-disruptive manner. So far, however, this has been hampered by lack of a detailed molecular description of the TJs.
By using computational and experimental techniques, we aim to develop novel molecular tools to efficiently control BBB permeability. We have recently obtained highly refined, full atom structural models of tetrameric and octameric TJ pore architectures, based on computational modeling and Molecular Dynamics simulations (Alberini et al., Plos One 2017). We are now exploiting these models to dissect the structural details underlying pore selectivity. Experimentally, we have set up a trans-well system that recapitulates the compartmentalization between vasculature, astrocytes and neurons, and addresses the transport of various substances and nanoparticles by using fluorescent or radioactive labels, as well as live measurements of BBB integrity and functionality by electrophysiological and imaging techniques. Optogenetic tools will be developed to tune BBB permeability by perturbing claudin-claudin interactions.