Acid fibroblast growth factor preserves blood-brain barrier integrity by activating the PI3K-Akt-Rac1 pathway and inhibiting RhoA following traumatic brain injury.

The blood-brain barrier (BBB) plays important roles in the recovery of traumatic brain injury (TBI) which is a major factor contributing to cerebral edema. Acid fibroblast growth factor (aFGF) contributes to maintain vascular integrity and restores nerve function. However, whether aFGF protects BBB following TBI remains unknown. The purpose of this study was to determine whether exogenous aFGF preserves BBB integrity by activating the PI3K-Akt-Rac1 pathway and inhibiting RhoA after TBI. BBB permeability was assessed using evans blue dye and fluorescein isothiocyanate dextran fluorescence. Neurofunctional tests, such as the garcia test, were conducted in a blinded fashion, and protein expression was evaluated via western blotting and immunofluorescence staining. Our results showed that aFGF improved neurofunctional deficits, preserved BBB integrity, and up-regulated tight junction proteins and adherens junction proteins 24 h after experimental TBI. However, the PI3K/Akt inhibitor LY294002 reversed the protective effects of aFGF on neurofunctional deficits and junction protein expression and significantly suppressed p-Akt and GTP-Rac1 activity. Furthermore, aFGF administration significantly decreased GTP-RhoA expression in the treated group compared with the vehicle group, while PI3K/Akt inhibition increased GTP-RhoA expression. Similar results were observed in vitro, as aFGF exerted protective effects on endothelial cell integrity by up-regulating junction proteins and PI3K-Akt-Rac1 pathway and down-regulating RhoA expression under oxygen-glucose deprivation/reoxygenation (OGD) conditions. These data suggest that exogenous aFGF reduces RhoA activity in part by activating the PI3K-Akt-Rac1 signaling pathway, thus improving neurofunctional deficits and preserving BBB integrity after TBI.