Characterization of interleukin-1alpha binding to mouse brain endothelial cells.
In vivo studies have shown that interleukin (IL)-1alpha 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 (125)I. Binding was temperature- and time-dependent with maximal binding after 4 h of incubation at 37 degrees C. The amount of radioactivity determined by HPLC to represent intact (125)I-labeled murine IL-1alpha at 4 h was approximately 100% in the incubation fluid and 80 to 90% for radioactive material recovered from the incubated cells. B(max) was 0.955 fmol and the K(d) was 292 pM for human (125)I-IL and binding was displaced by interleukin-1beta and interleukin-1 receptor antagonist but not by tumor necrosis factor alpha. 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.
Banks
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Geriatrics Research Educational and Clinical Center, Veterans Affairs Medical Center-St. Louis and Division of Geriatrics, Department of Internal Medicine, Saint Louis University, Missouri, USA.
D000818:Animals; D000906:Antibodies / Q000276:immunology; D001665:Binding Sites / Q000502:physiology; D001812:Blood-Brain Barrier / Q000502:physiology*; D001921:Brain / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D016207:Cytokines / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D051379:Mice; D008833:Microcirculation / Q000502:physiology; D011485:Protein Binding; D013696:Temperature; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D000906:Antibodies; D016207:Cytokines; D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D008274:Magnesium; D005947:Glucose