Insulin therapy restores impaired function and expression of P-glycoprotein in blood-brain barrier of experimental diabetes.
We aimed to investigate effects of insulin on function and expression of P-glycoprotein (P-GP) in the blood-brain barrier of streptozotocin (STZ)-induced diabetic rats. Brain-to-plasma concentration ratio of vincristine (VCR) in rats was used as an indicator of in vivo function of P-GP. Western blot and quantitative real time-polymerase chain reaction were used to determine protein levels of P-GP and its mdr1a/mdr1b mRNA levels, respectively, in cerebral cortex of rats. In vitro effects of insulin on function and expression of P-GP in primarily cultured rat brain microvessel endothelial cells (rBMECs) were evaluated using rhodamine 123 (Rho123) uptakes and Western blot, respectively. The results showed that 3- and 5-week insulin treatment alleviated the impaired efflux function, expression and mdr1a/mdr1b mRNA levels of P-GP in cerebral cortex of diabetic rats. The 3- and 5-week insulin treatments also significantly enhanced P-GP levels and mdr1a/mdr1b mRNA levels in the cerebral cortex of normal rats. Addition of insulin to the insulin-deficient diabetic rat serum normalized the impaired function and expression of P-GP in rBMECs cultured in diabetic rat serum. When incubated with normal culture medium containing different levels of insulin, the rBMECs exhibited the enhanced P-GP levels and the reduced Rho123 uptake in a concentration-dependent manner. So we may conclude that appropriate level of insulin plays an important role in maintaining the normal function of BBB through regulating the function and expression of P-GP in the diabetic and normal rats.
Liu
Haiyan
H
Center of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009, China.
Liu
Xiaodong
X
Jia
Lee
L
Liu
Yuchun
Y
Yang
Huiwen
H
Wang
Guangji
G
Xie
Lin
L
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics / Q000378:metabolism*; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy* / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D007328:Insulin / Q000627:therapeutic use*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014750:Vincristine / Q000097:blood / Q000493:pharmacokinetics; D000097202:ATP-Binding Cassette Sub-Family B Member 4
D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D012333:RNA, Messenger; D014750:Vincristine; D000097202:ATP-Binding Cassette Sub-Family B Member 4; C095122:multidrug resistance protein 3