title: Altered glycaemia differentially modulates efflux transporter expression and activity in hCMEC/D3 cell line.
abstract: The unique phenotype of blood-brain barrier (BBB) endothelium is partly maintained by abundant expression of ATP-binding cassette superfamily of efflux transporters that strictly restrict the CNS access to toxic substances including xenobiotics in circulation. Previously, we have shown that diabetes-related altered glycemic conditions differentially affect and compromise BBB integrity. However, the impact of diabetes on BBB efflux transporters is less understood. In this study, we examined the effects of single or repeated episodes of hypo-and hyperglycemia on major BBB efflux transporters expression/function in human cerebromicrovascular endothelial cell line (hCMEC/D3). Cells were exposed to normal (5.5 mM), hypo (2.2 mM) or hyper (25 or 35 mM)-glycemic media containing D-glucose for 12h (acute) or two 3h episodes/day of hypo- or hyperglycemia with an intercalated 2h normalglycemic exposure for 3 days ("glycemic variability", see Methods). Acute hypoglycemic exposure (12h) up-regulated BBB endothelial mRNA and protein expression of P-glycoprotein, BCRP and other multidrug resistance associated proteins (MRP1 and 4) paralleled by an increase in transporter-specific efflux activity (∼ 2-fold vs. control). Although, 12h hyperglycemia did not affect the efflux transporter expression (except for MRP4), a significant increase in BCRP activity was observed. By contrast, DNA microarray data revealed that repeated hyperglycemic episodes (but not hypoglycemia) significantly up-regulate P-glycoprotein expression and activity. Thus, this study suggests a differential impact of altered glycemic conditions on major BBB drug efflux transporters expression/function, sensitive to the length of exposure (acute vs. repeated), with an implication for altered CNS drug disposition in diabetic population.
authors.affiliation: Center for Blood-Brain Barrier Research, Department of Pharmaceutical Sciences, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA.
authors.forename: Ravi K
authors.initials: RK
authors.lastname: Sajja
authors.affiliation: Center for Blood-Brain Barrier Research, Department of Pharmaceutical Sciences, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA. Electronic address: luca.cucullo@ttuhsc.edu.
authors.forename: Luca
authors.initials: L
authors.lastname: Cucullo
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D001812:Blood-Brain Barrier / Q000378:metabolism; D002460:Cell Line; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D006943:Hyperglycemia / Q000378:metabolism; D007003:Hypoglycemia / Q000378:metabolism; D055806:Microvessels / Q000166:cytology / Q000378:metabolism; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D005947:Glucose; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; C073492:ABCC4 protein, human; C116614:ABCG2 protein, human; C421109:multidrug resistance-associated protein 1
keywords: Alternative; BBB; Diabetes; Drug resistance; Glycemic variability; Hypoglycemia; Transcriptome; Transporter