Interleukin-1beta-dependent signaling between astrocytes and neurons depends critically on astrocytic calcineurin/NFAT activity.
Interleukin-1beta (IL-1beta) and the Ca(2+)/calmodulin-dependent protein phosphatase, calcineurin, have each been shown to play an important role in neuroinflammation. However, whether these signaling molecules interact to coordinate immune/inflammatory processes and neurodegeneration has not been investigated. Here, we show that exogenous application of IL-1beta (10 ng/ml) recruited calcineurin/NFAT (nuclear factor of activated T cells) activation in primary astrocyte-enriched cultures within minutes, through a pathway involving IL-1 receptors and L-type Ca(2+) channels. Adenovirus-mediated delivery of the NFAT inhibitor, VIVIT, suppressed the IL-1beta-dependent induction of several inflammatory mediators and/or markers of astrocyte activation, including tumor necrosis factor alpha, granulocyte/macrophage colony-stimulating factor, and vimentin. Expression of an activated form of calcineurin in one set of astrocyte cultures also triggered the release of factors that, in turn, stimulated NFAT activity in a second set of "naive" astrocytes. This effect was prevented when calcineurin-expressing cultures co-expressed VIVIT, suggesting that the calcineurin/NFAT pathway coordinates positive feedback signaling between astrocytes. In the presence of astrocytes and neurons, 48-h delivery of IL-1beta was associated with several excitotoxic effects, including NMDA receptor-dependent neuronal death, elevated extracellular glutamate, and hyperexcitable synaptic activity. Each of these effects were reversed or ameliorated by targeted delivery of VIVIT to astrocytes. IL-1beta also caused an NFAT-dependent reduction in excitatory amino acid transporter levels, indicating a possible mechanism for IL-1beta-mediated excitotoxicity. Taken together, the results have potentially important implications for the propagation and maintenance of neuroinflammatory signaling processes associated with many neurodegenerative conditions and diseases.
Sama
Michelle A
MA
Department of Molecular and Biomedical Pharmacology, Graduate Center for Gerontology, University of Kentucky, Lexington, Kentucky 40536, USA.
Mathis
Diana M
DM
Furman
Jennifer L
JL
Abdul
Hafiz Mohmmad
HM
Artiushin
Irina A
IA
Kraner
Susan D
SD
Norris
Christopher M
CM
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019703:Calcineurin / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D025461:Feedback, Physiological; D005786:Gene Expression Regulation / Q000187:drug effects; D050491:Glutamate Plasma Membrane Transport Proteins / Q000235:genetics; D053583:Interleukin-1beta / Q000378:metabolism* / Q000494:pharmacology; D050778:NFATC Transcription Factors / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D021381:Protein Transport; D011506:Proteins / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology
D020746:Calcium Channels, L-Type; D050491:Glutamate Plasma Membrane Transport Proteins; D053583:Interleukin-1beta; D050778:NFATC Transcription Factors; D011506:Proteins; D019703:Calcineurin