title: Toll-like receptor 9 mediated responses in cardiac fibroblasts.
abstract: Altered cardiac Toll-like receptor 9 (TLR9) signaling is important in several experimental cardiovascular disorders. These studies have predominantly focused on cardiac myocytes or the heart as a whole. Cardiac fibroblasts have recently been attributed increasing significance in mediating inflammatory signaling. However, putative TLR9-signaling through cardiac fibroblasts remains non-investigated. Thus, our aim was to explore TLR9-signaling in cardiac fibroblasts and investigate the consequence of such receptor activity on classical cardiac fibroblast cellular functions. Cultivated murine cardiac fibroblasts were stimulated with different TLR9 agonists (CpG A, B and C) and assayed for the secretion of inflammatory cytokines (tumor necrosis factor α [TNFα], CXCL2 and interferon α/β). Expression of functional cardiac fibroblast TLR9 was proven as stimulation with CpG B and -C caused significant CXCL2 and TNFα-release. These responses were TLR9-specific as complete inhibition of receptor-stimulated responses was achieved by co-treatment with a TLR9-antagonist (ODN 2088) or chloroquine diphosphate. TLR9-stimulated responses were also found more potent in cardiac fibroblasts when compared with classical innate immune cells. Stimulation of cardiac fibroblasts TLR9 was also found to attenuate migration and proliferation, but did not influence myofibroblast differentiation in vitro. Finally, results from in vivo TLR9-stimulation with subsequent fractionation of specific cardiac cell-types (cardiac myocytes, CD45+ cells, CD31+ cells and cardiac fibroblast-enriched cell-fractions) corroborated our in vitro data and provided evidence of differentiated cell-specific cardiac responses. Thus, we conclude that cardiac fibroblast may constitute a significant TLR9 responder cell within the myocardium and, further, that such receptor activity may impact important cardiac fibroblast cellular functions.
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway; Faculty of Medicine, University of Oslo, Oslo, Norway; Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Ingrid Kristine
authors.initials: IK
authors.lastname: Ohm
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway.
authors.forename: Katrine
authors.initials: K
authors.lastname: Alfsnes
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway; Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Maria
authors.initials: M
authors.lastname: Belland Olsen
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway; Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Trine
authors.initials: T
authors.lastname: Ranheim
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway; Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Sandanger
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway; Faculty of Medicine, University of Oslo, Oslo, Norway.
authors.forename: Tuva Børresdatter
authors.initials: TB
authors.lastname: Dahl
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway; Faculty of Medicine, University of Oslo, Oslo, Norway; Section of Clinical Immunology and Infectious Diseases, Oslo University Hospital Rikshospitalet, Oslo, Norway; K.G. Jebsen Inflammatory Research Center, University of Oslo, Oslo, Norway.
authors.forename: Pål
authors.initials: P
authors.lastname: Aukrust
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway; Center for Heart Failure Research, University of Oslo, Oslo, Norway; Department of Cardiology, Oslo University Hospital Rikshospitalet, Oslo, Norway.
authors.forename: Alexandra Vanessa
authors.initials: AV
authors.lastname: Finsen
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway; Faculty of Medicine, University of Oslo, Oslo, Norway; Center for Heart Failure Research, University of Oslo, Oslo, Norway; K.G. Jebsen Inflammatory Research Center, University of Oslo, Oslo, Norway.
authors.forename: Arne
authors.initials: A
authors.lastname: Yndestad
authors.affiliation: Research Institute of Internal Medicine, Oslo University Hospital Rikshospitalet, Oslo, Norway; Center for Heart Failure Research, University of Oslo, Oslo, Norway; Department of Cardiology, Oslo University Hospital Rikshospitalet, Oslo, Norway; K.G. Jebsen Cardiac Research Center, University of Oslo, Oslo, Norway.
authors.forename: Leif Erik
authors.initials: LE
authors.lastname: Vinge
mesh_terms: D000818:Animals; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism*; D009841:Oligonucleotides / Q000494:pharmacology; D015398:Signal Transduction; D051217:Toll-Like Receptor 9 / Q000378:metabolism*
chemical_list: D016207:Cytokines; D009841:Oligonucleotides; D051217:Toll-Like Receptor 9