Penetration of verapamil across blood brain barrier following cerebral ischemia depending on both paracellular pathway and P-glycoprotein transportation.

BACKGROUND: Blood brain barrier (BBB) dysfunction is a common facet of cerebral ischemia, and the alteration of drug transporter, P-glycoprotein (P-gp), has been documented. AIMS: This study explores influence of damaged BBB and elevated P-gp on cerebral verapamil penetration after ischemia both in vivo and in vitro.
METHODS: Middle cerebral artery occlusion (MCAO) induced ischemia/reperfusion (I/R) of rats, and Na(2)S(2)O(4) induced hypoxia/reoxygenation (H/R) damage of rat brain mirovessel endothelial cells (RBMECs) respectively, served as BBB breakdown model in vivo and in vitro. Evans-Blue (EB) extravagation and (125)I-albumin were used to quantify BBB dysfunction; UPLC-MS/MS analytical method was performed to determine accurately the concentration of verapamil in brain tissue and cell. Flow cytometry, immunohistochemistry and western blotting were applied to evaluate transport function and protein expression of P-gp.
RESULTS: Overexpressed ICAM-1 and MMP-9 mediated BBB dysfunction after ischemia, which induced EB leakage and (125)I-albumin uptake increase. Enhanced accumulation of verapamil in brain tissue, but intracellular concentration reduced evidently after H/R injury. Transcellular transportation of verapamil elevated when P-gp function or expression was inhibited after H/R injury.
CONCLUSION: These data indicated that BBB penetration of verapamil under ischemia condition was not only depending on BBB breakdown, but also regulated by P-gp.