Caspase-3 dependent, induction of barrier dysfunction and hyperpermeability in blood-brain barrier endothelial cells

BACKGROUND: Blood-brain barrier (BBB) dysfunction and associated microvascular hyperpermeability lead to brain edema and elevation of intracranial pressure in traumatic and ischemic brain injuries. Pro-inflammatory cytokines, interleukin (IL-1β) and tumor necrosis factor (TNF-α), are up-regulated in such conditions and serve as endogenous activators of caspase-3 and apoptosis. The objective of this study was to comparatively test how these cytokines regulate caspase-3-mediated BBB breakdown/hyperpermeability, and understand if these effects were cell death dependent. METHODS: Rat brain microvascular endothelial cells were exposed to IL-1β, TNF-α, or caspase-3 activator, staurosporine (STS). Blood-brain barrier integrity and functions were determined by monolayer permeability, tight junction integrity, and cytoskeletal integrity. The changes in mitochondrial reactive oxygen species (ROS) and caspase-3 activity were evaluated microscopically and fluorometrically, respectively. RESULTS: IL-1β, TNF-α, and STS induced caspase-3 activation, tight junction/cytoskeletal disorganization, and monolayer hyperpermeability. These effects were inhibited by a caspase-3 inhibitor, Z-DEVD-fmk. Treatments had no effect on ROS formation. DISCUSSION: This comparative study shows that, in BBB endothelial cells, IL-1β, TNF-α, and STS induce tight junction/cytoskeletal disorganization and hyperpermeability via Caspase-3 mediated breakdown of the tight junction proteins. Effects are independent of ROS formation, one of the significant factors that promote blood-brain barrier dysfunctions in neurological disorders.