Abstract
In vivo studies have shown that interleukin (IL)-1α binds to and is transported across brain endothelial cells, whereas in vitro studies have shown that brain endothelial cells respond to IL and contain mRNA for the IL-type 1 receptor. However, these binding sites have yet to be characterized. Herein, we used murine brain microvessels to characterize the binding of IL labeled with 125I. Binding was temperature- and time-dependent with maximal binding after 4 h of incubation at 37°C. The amount of radioactivity determined by HPLC to represent intact 125I-labeled murine IL-1α at 4 h was ∼100% in the incubation fluid and 80 to 90% for radioactive material recovered from the incubated cells.Bmax was 0.955 fmol and theKd was 292 pM for human 125I-IL and binding was displaced by interleukin-1β and interleukin-1 receptor antagonist but not by tumor necrosis factor α. Binding was dependent on magnesium and glucose. Incubation with antibodies showed that the binding site was not identical with the IL-type 1 receptor but closely resembled the blood-brain barrier transporter. These results show that murine brain endothelial cells have specific binding sites for IL and that these sites more closely resemble the transporter than the type 1 receptor.
Footnotes
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Send reprint requests to: William A. Banks, VAMC, 915 N. Grand Blvd., St. Louis, MO 63106. E-mail: bankswa{at}slu.edu
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↵1 Supported by Veterans Affairs merit review and RO1 MH54979.
- Abbreviations:
- IL
- interleukin
- CNS
- central nervous system
- BBB
- blood-brain barrier
- I-hIL,125I-labeled human IL-1α
- I-mIL, 125I-labeled murine IL-1α
- %TB
- percent of total binding
- IL-1ra
- IL-1 receptor antagonist
- TNF-α
- tumor necrosis factor α
- R-B
- receptor blocking
- R-NB
- receptor nonblocking
- I-B
- IL blocking
- I-NB
- IL nonblocking
- Received March 30, 1999.
- Accepted July 12, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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