Lipopolysaccharide-enhanced expression of interleukin-6 in dibutyryl cyclic AMP-differentiated rat C6 glioma.
Rat C6 glioma synthesizes a low basal level of interleukin-6 (IL-6). Stimulation with 10 micrograms/ml of lipopolysaccharide (LPS) and induction of differentiation with 1 mM N6,O2'-dibutyryl cyclic AMP (dbcAMP) for 48 h increased the secreted activity to 400 and 800 U/ml, respectively. An LPS stimulation of dbcAMP-differentiated cells strongly enhanced the secreted activity. Depending on the dbcAMP concentration, the cell number, and the stimulation time, the secreted IL-6 level increased up to 120,000 U/ml. After 48 h of costimulation with 10 micrograms/ml of LPS and 1 mM dbcAMP, northern blotting and immunoassay demonstrated an eightfold increase in IL-6 mRNA concentration and IL-6 immunoreactivity, whereas titration of the biological activity indicated a 100-fold increase in the secreted IL-6 activity. The enhanced secretion of IL-6 is correlated with the induction of differentiation. Chromatography on heparin-Sepharose and on DEAE-5PW separated the secreted activity into several fractions, indicating that they differ in heparin affinity and charge either by posttranslational modifications or by binding to a carrier protein. Each of the partially purified IL-6-like activities could be neutralized by an anti-murine IL-6 antibody. Our observations demonstrate that in vivo inflammatory signals can trigger astrocytes and their precursors to secrete substantially different levels of immunoregulatory cytokines depending on their degree of differentiation.
Slegers
H
H
Department Biochemie, Universitaire Instelling Antwerpen, Wilrijk, Belgium.
Joniau
M
M
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D005910:Glioma; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014407:Tumor Cells, Cultured
D015850:Interleukin-6; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D003994:Bucladesine