Abstract
ATP-binding cassette (ABC) efflux transporters, including multidrug resistance protein 1 (Mdr1), breast cancer resistance protein (Bcrp), and multidrug resistance-associated proteins (Mrps) extrude chemicals from the brain. Although ABC transporters are critical for blood-brain barrier integrity, less attention has been placed on the regulation of these proteins in brain parenchymal cells such as microglia. Prior studies demonstrate that inflammation after lipopolysaccharide (LPS) treatment alters transporter expression in the livers of mice. Here, we sought to determine the effects of inflammation on the expression and function of transporters in microglia. To test this, the expression and function of ABC efflux transport proteins were quantified in mouse BV-2 microglial cells in response to activation with LPS. Intracellular retention of fluorescent rhodamine 123, Hoechst 33342, and calcein acetoxymethyl ester was increased in LPS-treated microglia, suggesting that the functions of Mdr1, Bcrp, and Mrps were decreased, respectively. LPS reduced Mdr1, Bcrp, and Mrp4 mRNA and protein expression between 40 and 70%. Conversely, LPS increased expression of Mrp1 and Mrp5 mRNA and protein. Immunofluorescent staining confirmed reduced Bcrp and Mrp4 and elevated Mrp1 and Mrp5 protein in activated microglia. Pharmacological inhibition of nuclear factor κB (NF-κB) transcriptional signaling attenuated down-regulation of Mdr1a mRNA and potentiated up-regulation of Mrp5 mRNA in LPS-treated cells. Together, these data suggest that LPS stimulates microglia and impairs efflux of prototypical ABC transporter substrates by altering mRNA and protein expression, in part through NF-κB signaling. Decreased transporter efflux function in microglia may lead to the retention of toxic chemicals and aberrant cell-cell communication during neuroinflammation.
Footnotes
This work was supported in part by the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases [Grant DK080774]; the National Institutes of Health National Institute of Environmental Health Sciences [Grants ES020522, ES015991, ES007148, ES005022]; and the National Institutes of Health National Institute of Neurological Disorders and Stroke [Grant NS072097].
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
ABBREVIATIONS:
- ABC
- ATP binding cassette
- Mdr
- multidrug resistance protein
- Mrp
- multidrug resistance-associated protein
- Bcrp
- breast cancer resistance protein
- LPS
- lipopolysaccharide
- NF-κB
- nuclear factor κB
- IκB
- inhibitor of κB
- Nrf2
- nuclear factor-e2 related factor 2
- TNFα
- tumor necrosis factor-α
- IL
- interleukin
- Nqo1
- NAD(P)H quinone oxidoreductase 1
- NSAID
- nonsteroidal anti-inflammatory drug
- AM
- acetoxymethyl ester
- PBS
- phosphate-buffered saline
- Rpl13a
- ribosomal protein l13a
- Gapdh
- glyceraldehyde-3-phosphate dehydrogenase
- qPCR
- quantitative polymerase chain reaction
- DMSO
- dimethyl sulfoxide
- BAY 11-7082
- 3-(4-methylphenylsulfonyl)-2-propenenitrile
- PSC833
- 6-[(2S,4R,6E)-4-methyl-2-(methylamino)-3-oxo-6-octenoic acid]-7-l-valine-cyclosporin A
- MK-571
- 5-(3-(2-(7-chloroquinolin-2-yl)ethenyl)phenyl)-8-dimethylcarbamyl-4,6-dithiaoctanoic acid sodium salt hydrate
- Ko143
- (3S,6S,12aS)-1,2,3,4,6,7,12,12a-octahydro-9-methoxy-6-(2-methylpropyl)-1,4-dioxopyrazino[1′,2′:1,6]pyrido[3,4-b]indole-3-propanoic acid 1,1-dimethylethyl ester hydrate.
- Received May 20, 2012.
- Accepted August 30, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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