bFGF Protects Against Oxygen Glucose Deprivation/Reoxygenation-Induced Endothelial Monolayer Permeability via S1PR1-Dependent Mechanisms

Blood-brain barrier (BBB) disruption is a common pathological feature of many neurological disorders including stroke and brain trauma, therefore is an important therapeutic target for treatment of these diseases. Basic fibroblast growth factor (bFGF) as a member of FGF superfamily plays critical roles in angiogenesis, neurogenesis, and neuron survival. We recently showed that recombinant bFGF protects against BBB disruption in traumatic brain injury in mice. In this study, we further investigated the mechanisms of recombinant bFGF in BBB protection by measuring the permeability of cultured endothelial cell monolayer induced by oxygen-glucose deprivation and reoxygenation (OGD/R). We found that recombinant bFGF significantly decreased OGD/R-induced permeability of primary human brain microvascular endothelial cell (HBMEC) monolayer and preserved OGD/R-induced decreases of trans-endothelial electrical resistance (TEER). Western blot and immunocytochemistry showed that bFGF significantly rescued OGD/R-induced downregulation of junction proteins ZO-1, occludin, and VE-cadherin. We further show that the BBB protective effect of bFGF is via FGF receptor 1 (FGFR1) activation as FGFR1 inhibitor can block this protection effect. Moreover, we revealed that the BBB protection effect of bFGF is at least partially through rescuing the OGD/R-induced downregulation of sphingosine-1-phosphate receptor 1 (S1PR1) protein, as S1PR1 inhibitor or SIPR1 small interfering RNA blocked the BBB protective effect of bFGF, whereas S1PR1 agonist alone has comparable BBB protection effect of bFGF. These findings will improve our understanding of the protective effect and mechanisms of bFGF on BBB and propose bFGF as a potential therapeutic agent against BBB damage in neurological disorders.