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Interleukin‐1‐β and Tumor Necrosis Factor‐α Increase Peripheral‐Type Benzodiazepine Binding Sites in Cultured Polygonal Astrocytes
Author(s) -
Oh Young J.,
Francis Jonathan W.,
Markelonis George J.,
Oh Tae H.
Publication year - 1992
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1992.tb10955.x
Subject(s) - astrocyte , tumor necrosis factor alpha , receptor , binding site , ligand (biochemistry) , neuroglia , in vitro , biology , medicine , chemistry , microbiology and biotechnology , endocrinology , central nervous system , biochemistry
Peripheral‐type benzodiazepine binding sites (PTBBS) are markedly increased in the injured CNS. Astrocytes appear to be the primary cell type which express increased PTBBS. Because certain cytokines within the injured CNS are potent mitogens for astrocytes, we examined the effects of two such cytokines, interleukin (IL)‐1β and tumor necrosis factor (TNF), on PTBBS in cultured astrocytes using [ 3 H]Ro 5‐4864 as the specific ligand. Purified cultures of either polygonal or process‐bearing astrocytes were prepared from neonatal rat cerebral hemispheres. At a concentration of 1.8 n M , specific binding of the radioactive ligand to polygonal astrocytes reached equilibrium within 60 min and was half‐maximal by 5–10 min. By contrast, specific binding to process‐bearing astrocytes barely exceeded background levels. IL‐1 and TNF increased PTBBS within polygonal astrocytes in both dose‐ and time‐dependent manners. At 10–50 ng/ml, IL‐1β and TNF‐α elevated [ 3 H]Ro 5–4864 binding in polygonal astrocyte cultures 65 and 87%, respectively, above the level in control cultures. However, no changes in PTBBS were seen within polygonal astrocytes after IL‐2 treatment. Scatchard analysis of saturation binding experiments suggested that the increase in PTBBS promoted by TNF was due to an increased number of binding sites present in polygonal astrocytes and not due to an increase in receptor affinity. Binding data suggested that PTBBS within cultures of process‐bearing astrocytes were virtually absent irrespective of the treatment. These in vitro data suggest that certain cytokines found in the injured brain may be involved in up‐regulating PTBBS within a particular subtype of astrocyte.