title: The Extracellular IFI16 Protein Propagates Inflammation in Endothelial Cells Via p38 MAPK and NF-κB p65 Activation.
abstract: The nuclear interferon-inducible-16 (IFI16) protein acts as DNA sensor in inflammasome signaling and as viral restriction factor. Following Herpesvirus infection or UV-B treatment, IFI16 delocalizes from the nucleus to the cytoplasm and is eventually released into the extracellular milieu. Recently, our group has demonstrated the occurrence of IFI16 in sera of systemic-autoimmune patients that hampers biological activity of endothelia through high-affinity membrane binding. As a continuation, we studied the activity of endotoxin-free recombinant IFI16 (rIFI16) protein on primary endothelial cells. rIFI16 caused dose/time-dependent upregulation of IL-6, IL-8, CCL2, CCL5, CCL20, ICAM1, VCAM1, and TLR4, while secretion of IL-6 and IL-8 was amplified with lipopolysaccharide synergy. Overall, cytokine secretion was completely inhibited in MyD88-silenced cells and partially by TLR4-neutralizing antibodies. By screening downstream signaling pathways, we found that IFI16 activates p38, p44/42 MAP kinases, and NF-kB. In particular, activation of p38 is an early event required for subsequent p44/42 MAP kinases activity and cytokine induction indicating a key role of this kinase in IFI16 signaling. Altogether, our data conclude that extracellular IFI16 protein alone or by synergy with lipopolysaccharide acts like Damage-associated molecular patterns propagating "Danger Signal" through MyD88-dependent TLR-pathway.
authors.affiliation: 1 Department of Translational Medicine, University of Eastern Piedmont , Novara, Italy .|2 Interdisciplinary Research Center of Autoimmune Diseases (IRCAD) , Novara, Italy .|3 Division of Rheumatology, Department of Medicine, University of Wisconsin-Madison , Wisconsin.
authors.forename: Mandar
authors.initials: M
authors.lastname: Bawadekar
authors.affiliation: 4 Department of Public Health and Pediatric Sciences, University of Turin , Medical School, Turin, Italy .
authors.forename: Marco
authors.initials: M
authors.lastname: De Andrea
authors.affiliation: 1 Department of Translational Medicine, University of Eastern Piedmont , Novara, Italy .|2 Interdisciplinary Research Center of Autoimmune Diseases (IRCAD) , Novara, Italy .
authors.forename: Irene
authors.initials: I
authors.lastname: Lo Cigno
authors.affiliation: 1 Department of Translational Medicine, University of Eastern Piedmont , Novara, Italy .
authors.forename: Gianluca
authors.initials: G
authors.lastname: Baldanzi
authors.affiliation: 1 Department of Translational Medicine, University of Eastern Piedmont , Novara, Italy .|2 Interdisciplinary Research Center of Autoimmune Diseases (IRCAD) , Novara, Italy .
authors.forename: Valeria
authors.initials: V
authors.lastname: Caneparo
authors.affiliation: 1 Department of Translational Medicine, University of Eastern Piedmont , Novara, Italy .
authors.forename: Andrea
authors.initials: A
authors.lastname: Graziani
authors.affiliation: 4 Department of Public Health and Pediatric Sciences, University of Turin , Medical School, Turin, Italy .
authors.forename: Santo
authors.initials: S
authors.lastname: Landolfo
authors.affiliation: 1 Department of Translational Medicine, University of Eastern Piedmont , Novara, Italy .|2 Interdisciplinary Research Center of Autoimmune Diseases (IRCAD) , Novara, Italy .
authors.forename: Marisa
authors.initials: M
authors.lastname: Gariglio
mesh_terms: D057134:Antibodies, Neutralizing / Q000494:pharmacology; D016207:Cytokines / Q000096:biosynthesis / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D058847:Inflammasomes / Q000187:drug effects* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D010750:Phosphoproteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051996:Transcription Factor RelA / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism
chemical_list: D057134:Antibodies, Neutralizing; D016207:Cytokines; D058847:Inflammasomes; D008070:Lipopolysaccharides; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051996:Transcription Factor RelA; C076700:IFI16 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases