Induction of interleukin-1 beta-converting enzyme (ICE) in murine microglia by lipopolysaccharide.
Interleukin-1beta (IL-1beta) synthesized in the brain is thought to be involved in the behavioral response to LPS. In this study, we examined in microglia the ability of LPS to induce interleukin-1 beta-converting enzyme (ICE), the protease responsible for processing proIL-1beta to its mature biologically active form. The murine microglial cell line, N13, and primary microglia which had been previously isolated from brains of 2-d-old endotoxin-responsive C3H/HeOuJ mice and endotoxin-resistant C3H/HeJ mice, were cultured in the presence of various concentrations of LPS. Oligonucleotide primers for ICE and GAPDH were used in RT-PCR to determine the levels of ICE mRNA in microglia. ICE mRNA was constitutively expressed in N13 cells and primary microglia from both C3H/HeOuJ and C3H/HeJ mice. Upon exposure to LPS, ICE mRNA levels were markedly elevated in N13 cells and in microglia from C3H/HeOuJ mice, but not in microglia from endotoxin-resistant C3H/HeJ mice. Western immunoblotting was used to determine if the increase in ICE mRNA induced by LPS was accompanied by an increase in ICE protein. A modest increase in immunoreactivity for the p45 ICE precursor protein was evident in N13 cells and primary microglia from C3H/HeOuJ mice following exposure to LPS. Because corticosteroids inhibit the synthesis and secretion of IL-1beta, in a second experiment microglia were treated with LPS in the presence of dexamethasone (0, 10 and 100 microM). Dexamethasone inhibited the LPS-induced increase in ICE mRNA and protein in microglia from C3H/HeOuJ mice. These results indicate that LPS stimulates microglia to express ICE. That dexamethasone inhibited the expression of ICE, suggests that corticosteroids regulate the secretion of IL-1beta by microglial cells, in part, by regulating the expression of ICE.
Yao
J
J
Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
Johnson
R W
RW
D000818:Animals; D001921:Brain / Q000166:cytology / Q000201:enzymology; D020170:Caspase 1; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000096:biosynthesis*; D017931:DNA Primers; D003907:Dexamethasone / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D004926:Escherichia coli; D007375:Interleukin-1 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D008809:Mice, Inbred C3H; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects
D017931:DNA Primers; D007375:Interleukin-1; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D003907:Dexamethasone; D003546:Cysteine Endopeptidases; D020170:Caspase 1