Lipopolysaccharide-induced IL-12 expression in the central nervous system and cultured astrocytes and microglia.
We examined whether the cytokine IL-12 could be induced locally in the brain or in glial cell cultures following LPS treatment. In the brain, expression of IL-12 p35 mRNA was constitutive and did not alter following i.p. injection of LPS. In contrast, IL-12 p40 mRNA was only detectable in the brain of mice given two staggered injections of LPS. Dual labeling in situ analysis revealed IL-12 p40 RNA-positive cells scattered throughout the brain parenchyma, with a small number of these cells being identified as astrocytes, while the majority of IL-12 p40 RNA-expressing cells appeared to be microglia. In cultured microglia or astrocytes, LPS and to a much lesser degree IL-1beta, but not IFN-gamma or TNF-alpha, induced the expression of IL-12 p40 mRNA. Numerous glial fibrillary acidic protein-immunopositive cells colabeled for IL-12 p40 RNA; indicating that LPS-stimulated astrocytes expressed IL-12 in vitro. Immunoblot analysis of lysates from LPS-treated astrocytes revealed the presence of multiple species of 40, 43, 75, and 120 kDa containing the IL-12 p40 protein. Finally, secretion of the IL-12 p75 heterodimer was detectable by ELISA from astrocytes treated with LPS plus IFN-gamma, but not with LPS alone. The findings indicate that IL-12 gene expression can be activated in the brain, with the resident glial cells being a prodigious source of this cytokine. The localized production of IL-12 may have a significant impact on the development of cell-mediated immune responses within the central nervous system.
Stalder
A K
AK
Department of Neuropharmacology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Pagenstecher
A
A
Yu
N C
NC
Kincaid
C
C
Chiang
C S
CS
Hobbs
M V
MV
Bloom
F E
FE
Campbell
I L
IL
D000818:Animals; D001253:Astrocytes / Q000276:immunology / Q000378:metabolism*; D001921:Brain / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D001923:Brain Chemistry / Q000235:genetics; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D005904:Glial Fibrillary Acidic Protein / Q000737:chemistry / Q000235:genetics; D017403:In Situ Hybridization; D018664:Interleukin-12 / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D013154:Spleen / Q000187:drug effects / Q000276:immunology / Q000378:metabolism
D005904:Glial Fibrillary Acidic Protein; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018664:Interleukin-12