Cooperation of NFkappaB and CREB to induce synergistic IL-6 expression in astrocytes.
Astrocytes are critical players in the innate immune response of the central nervous system. Upon encountering proinflammatory stimuli, astrocytes produce a plethora of inflammatory mediators. Here, we have investigated how beta(2)-adrenergic receptor activation modulates proinflammatory gene expression in astrocytes. We have observed that treatment of human 1321N1 astrocytes with the beta-adrenergic agonist isoproterenol synergistically enhanced TNF-alpha-induced expression of the cytokine IL-6. The effect of isoproterenol was cAMP-dependent and mediated by the beta(2)-adrenergic subtype. Using pharmacological inhibitors and siRNA we showed that protein kinase A (PKA) is an indispensable mediator of the synergy. Simultaneous induction with isoproterenol and TNF-alpha was moreover associated with combined recruitment of CREB and p65 to the native IL-6 promoter. The role of CREB and NFkappaB in promoting the synergy was corroborated using IL-6 promoter point mutants, as well as via siRNA-mediated silencing of CREB and NFkappaB. Interestingly, whereas CREB and NFkappaB usually compete for the limiting cofactor CREB binding protein (CBP), we detected enhanced recruitment of CBP at the IL-6 promoter in our system. The transcriptional synergy seems to be a gene specific process, occurring at the IL-6 and COX-2 gene, but not at other typical NFkappaB-dependent genes such as IL-8, ICAM-1 or VCAM-1. As astrocytic IL-6 overexpression has been associated with neuroinflammatory and neurodegenerative processes, our findings might have important physiological consequences.
Spooren
Anneleen
A
Department of Physiology, Ghent University, Belgium.
Kooijman
Ron
R
Lintermans
Béatrice
B
Van Craenenbroeck
Kathleen
K
Vermeulen
Linda
L
Haegeman
Guy
G
Gerlo
Sarah
S
D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D050882:CREB-Binding Protein / Q000378:metabolism; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics* / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051996:Transcription Factor RelA / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D017362:Cyclic AMP Response Element-Binding Protein; D015850:Interleukin-6; D016328:NF-kappa B; D012333:RNA, Messenger; D018343:Receptors, Adrenergic, beta-2; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol