Adenosine-induced expression of interleukin-6 in astrocytes through protein kinase A and NF-IL-6.
In various neurologic diseases, astrocytes express interleukin-6 (IL-6), which is an endogenous pyrogen, a neuroprotective factor, and a regulator of the blood-brain barrier. The expression of IL-6 in astrocytes is stimulated by extracellular adenosine through A(2B) receptors. To investigate the signaling cascade that induces IL-6 gene transcription further, we transfected primary mouse astrocytes with a reporter gene construct, in which luciferase expression is directed by the human IL-6 promoter. Expression of PKI, an inhibitor of protein kinase A (PKA), interfered with IL-6 transcription indicating that PKA mediates the effect of adenosine. The CAAT box of the IL-6 promoter is necessary for the stimulation by adenosine as a mutation in this element reduced the stimulation by adenosine. Indeed, the cAMP agonist forskolin increased the binding of the transcription factors NF-IL-6 and C/EBPdelta to the CAAT box of the IL-6 promoter in nuclear extracts of astrocytes. Inhibition of the de novo synthesis of NF-IL-6 by cycloheximide or an antisense oligonucleotide reduced the enhancement of NF-IL-6 binding to the CAAT box and inhibited stimulation of IL-6 transcription by forskolin. In addition, overexpression of NF-IL-6 induced IL-6 transcription. This suggests that adenosine induces the de novo synthesis of NF-IL-6 through activation of PKA and thereby stimulates transcription of IL-6 in astrocytes.
Schwaninger
M
M
Department of Neurology, University of Heidelberg, Germany. markus.schwaninger@med.uni-heidelberg.de
Petersen
N
N
Prinz
S
S
Sallmann
S
S
Neher
M
M
Spranger
M
M
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence / Q000235:genetics; D022762:CCAAT-Enhancer-Binding Proteins; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000819:agonists; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics*; D051379:Mice; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology; D014018:Tissue Distribution; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D015533:Transcriptional Activation / Q000502:physiology; D014162:Transfection
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000241:Adenosine