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Published on: August 15, 2012
Lipopolysaccharide-activated microglia lower P-glycoprotein function in brain microvascular endothelial cells
Junichi Matsumoto1, Shinya Dohgu, Fuyuko Takata
1Department of Pharmaceutical Care and Health Sciences, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan.
Abstract:
P-glycoprotein, an efflux transporter that is highly expressed at the blood-brain barrier (BBB), is involved in the traffic of several compounds across the BBB. BBB disruption under pathological conditions is observed in parallel with microglial activation. Previous studies of the interaction between rat brain endothelial cells (RBECs) and microglia have shown that lipopolysaccharide (LPS) activated microglia increase the permeability of RBECs through a mechanism involving NADPH oxidase. In this study, to investigate whether LPS-activated microglia are linked to P-gp dysfunction at the BBB, we examined the effect of LPS on P-gp function in a coculture system with RBECs and rat microglia. When LPS at a concentration showing no effect on the RBEC monolayer was added for 6h to the abluminal side of the RBEC monolayer and RBEC/microglia cocultures, cellular accumulation of the P-gp substrate rhodamine 123, in RBECs, was increased by LPS in the RBEC/microglia coculture. This increased accumulation of rhodamine 123 in RBECs was blocked by diphenyleneiodoniumchloride, an NADPH oxidase inhibitor. P-gp expression on RBECs was not influenced by treatment with LPS in either RBEC monolayers or RBEC/microglia cocultures. These findings suggest that activated microglia induce P-gp dysfunction at the BBB through an NADPH oxidase-dependent pathway.
Insights
Activated microglia impair blood-brain barrier (BBB) P-glycoprotein (P-gp) function via NADPH oxidase, increasing substance accumulation in brain endothelial cells. This dysfunction occurs without altering P-gp expression levels.
Area of Science:
- Neuroscience
- Pharmacology
- Cell Biology
Background:
- P-glycoprotein (P-gp) is a key efflux transporter at the blood-brain barrier (BBB), regulating compound traffic.
- Microglial activation and BBB disruption often occur concurrently under pathological conditions.
- Previous research indicates lipopolysaccharide (LPS)-activated microglia increase endothelial cell permeability via NADPH oxidase.
Purpose of the Study:
- To investigate the link between LPS-activated microglia and P-glycoprotein (P-gp) dysfunction at the BBB.
- To examine the effect of LPS on P-gp function in a rat brain endothelial cell (RBEC)/microglia coculture system.
Main Methods:
- Utilized a coculture system of RBECs and rat microglia.
- Applied LPS to the abluminal side of RBEC monolayers and cocultures.
- Assessed cellular accumulation of the P-gp substrate rhodamine 123.
- Investigated the role of NADPH oxidase using its inhibitor, diphenyleneiodoniumchloride.
Main Results:
- LPS treatment in RBEC/microglia cocultures significantly increased rhodamine 123 accumulation in RBECs.
- This increased accumulation was effectively blocked by diphenyleneiodoniumchloride, indicating NADPH oxidase involvement.
- LPS did not alter P-gp expression levels in either RBEC monolayers or cocultures.
Conclusions:
- Activated microglia induce P-glycoprotein (P-gp) dysfunction at the blood-brain barrier (BBB).
- This dysfunction is mediated through an NADPH oxidase-dependent pathway.
- P-gp expression remains unaffected, suggesting a functional impairment rather than a change in transporter quantity.
