Changes in blood-brain barrier permeability and ultrastructure, and protein expression in a rat model of cerebral hypoperfusion

Cerebral hypoperfusion involved a reduction in cerebral blood flow, leading to neuronal dysfunction, microglial activation and white matter degeneration. The effects on the blood-brain barrier (BBB) however, have not been well-documented. Here, two-vessel occlusion model was adopted to mimic the condition of cerebral hypoperfusion in Sprague-Dawley rats. The BBB permeability to high and low molecular weight exogenous tracers i.e. Evans blue dye and sodium fluorescein respectively, showed marked extravasation of the Evans blue dye in the frontal cortex, posterior cortex and thalamus-midbrain at day 1 following induction of cerebral hypoperfusion. Transmission electron microscopy revealed brain endothelial cell and astrocyte damages including increased pinocytotic vesicles and formation of membrane invaginations in the endothelial cells, and swelling of the astrocytes' end-feet. Investigation on brain microvessel protein expressions using two-dimensional (2D) gel electrophoresis coupled with LC-MS/MS showed that proteins involved in mitochondrial energy metabolism, transcription regulation, cytoskeleton maintenance and signaling pathways were differently expressed. The expression of aconitate hydratase, heterogeneous nuclear ribonucleoprotein, enoyl Co-A hydratase and beta-synuclein were downregulated, while the opposite observed for calreticulin and enhancer of rudimentary homolog. These findings provide insights into the BBB molecular responses to cerebral hypoperfusion, which may assist development of future therapeutic strategies.