The TLR3 ligand polyI: C downregulates connexin 43 expression and function in astrocytes by a mechanism involving the NF-kappaB and PI3 kinase pathways.
Toll-like receptor 3 (TLR3) is a component of the innate immune response that responds to dsRNA viruses and virus replication intermediates. In this study we show that activation of astrocytes with the dsRNA mimetic polyinosinic-cytidylic acid (pI:C) results in loss of expression of connexin43 (Cx43) mRNA and protein while upregulating the expression of the ionotropic P2 receptor P2X(4)R. Analysis of the signaling pathways involved failed to demonstrate a role for the p38 MAP kinase, ERK, or JNK signaling pathways whereas an inhibitor of the PI3 kinase/Akt pathway effectively blocked the action of pI:C. Using adenoviral vectors containing a super-repressor of NF-kappaB (NF-kappaB SR) construct or a dominant negative interferon regulatory factor 3 (dnIRF3) construct showed that inhibition of both transcription factors also blocked the effects of pI:C. To explore the functional consequences of pI:C activation we used a pore-forming assay for P2X(4)R activity and a scrape loading assay for gap junction intercellular communication (GJIC). No pore-forming activity consistent with functional P2X(4)R expression was detected in either control or activated astrocytes. In contrast, robust Lucifer yellow transfer indicative of GJIC was detected in resting cells that was lost following pI:C activation. The dnIRF3 construct failed to restore GJIC whereas the NF-kappaB SR or the NF-kappaB inhibitor BAY11-7082 and the PI3K inhibitor LY294002 all significantly reversed the effect of pI:C on GJ connectivity. We conclude that activation of the innate immune response in astrocytes is associated with functional loss of GJIC through a pathway involving NF-kappaB and PI3 kinase.
Zhao
Yongmei
Y
Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10464, USA.
Rivieccio
Mark A
MA
Lutz
Sarah
S
Scemes
Eliana
E
Brosnan
Celia F
CF
D001253:Astrocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D002450:Cell Communication / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D018031:Connexin 43 / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017629:Gap Junctions / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D007369:Interferon Inducers / Q000494:pharmacology; D050838:Interferon Regulatory Factor-3 / Q000235:genetics; D016328:NF-kappa B / Q000276:immunology* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011070:Poly I-C / Q000494:pharmacology; D012327:RNA Virus Infections / Q000276:immunology; D012328:RNA Viruses / Q000235:genetics; D012330:RNA, Double-Stranded / Q000235:genetics / Q000276:immunology; D018048:Receptors, Purinergic P2 / Q000276:immunology / Q000378:metabolism; D058848:Receptors, Purinergic P2X4; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D051196:Toll-Like Receptor 3 / Q000819:agonists / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics / Q000276:immunology
D018031:Connexin 43; D004791:Enzyme Inhibitors; C494232:IRF3 protein, human; D007369:Interferon Inducers; D050838:Interferon Regulatory Factor-3; D016328:NF-kappa B; C548226:P2RX4 protein, human; D012330:RNA, Double-Stranded; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; C495344:TLR3 protein, human; D051196:Toll-Like Receptor 3; D019869:Phosphatidylinositol 3-Kinases; D011070:Poly I-C