title: Toll-like receptor 7 preconditioning induces robust neuroprotection against stroke by a novel type I interferon-mediated mechanism.
abstract: OBJECTIVE
  Systemic administration of Toll-like receptor (TLR) 4 and TLR9 agonists before cerebral ischemia have been shown to reduce ischemic injury by reprogramming the response of the brain to stroke. Our goal was to explore the mechanism of TLR-induced neuroprotection by determining whether a TLR7 agonist also protects against stroke injury.
  
  
  METHODS
  C57Bl/6, TNF(-/-), interferon (IFN) regulatory factor 7(-/-), or type I IFN receptor (IFNAR)(-/-) mice were subcutaneously administered the TLR7 agonist Gardiquimod (GDQ) 72 hours before middle cerebral artery occlusion. Infarct volume and functional outcome were determined after reperfusion. Plasma cytokine responses and induction of mRNA for IFN-related genes in the brain were measured. IFNAR(-/-) mice also were treated with the TLR4 agonist (lipopolysaccharide) or the TLR9 agonist before middle cerebral artery occlusion and infarct volumes measured.
  
  
  RESULTS
  The results show that GDQ reduces infarct volume as well as functional deficits in mice. GDQ pretreatment provided robust neuroprotection in TNF(-/-) mice, indicating that TNF was not essential. GDQ induced a significant increase in plasma IFNα levels and both IRF7(-/-) and IFNAR(-/-) mice failed to be protected, implicating a role for IFN signaling in TLR7-mediated protection.
  
  
  CONCLUSIONS
  Our studies provide the first evidence that TLR7 preconditioning can mediate neuroprotection against ischemic injury. Moreover, we show that the mechanism of protection is unique from other TLR preconditioning ligands in that it is independent of TNF and dependent on IFNAR.
authors.affiliation: Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR 97239, USA.
authors.forename: Philberta Y
authors.initials: PY
authors.lastname: Leung
authors.forename: Susan L
authors.initials: SL
authors.lastname: Stevens
authors.forename: Amy E B
authors.initials: AE
authors.lastname: Packard
authors.forename: Nikola S
authors.initials: NS
authors.lastname: Lessov
authors.forename: Tao
authors.initials: T
authors.lastname: Yang
authors.forename: Valerie K
authors.initials: VK
authors.lastname: Conrad
authors.forename: Noortje N A M
authors.initials: NN
authors.lastname: van den Dungen
authors.forename: Roger P
authors.initials: RP
authors.lastname: Simon
authors.forename: Mary P
authors.initials: MP
authors.lastname: Stenzel-Poore
mesh_terms: D000634:Aminoquinolines / Q000627:therapeutic use*; D000818:Animals; D001921:Brain / Q000098:blood supply*; D020520:Brain Infarction / Q000473:pathology; D007093:Imidazoles / Q000627:therapeutic use*; D050839:Interferon Regulatory Factor-7 / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D019194:Ischemic Preconditioning / Q000379:methods*; D008297:Male; D008562:Membrane Glycoproteins / Q000819:agonists*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D023421:Models, Animal; D018696:Neuroprotective Agents / Q000627:therapeutic use*; D053633:Receptor, Interferon alpha-beta / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D020521:Stroke / Q000503:physiopathology / Q000517:prevention & control*; D051199:Toll-Like Receptor 7 / Q000819:agonists*; D014409:Tumor Necrosis Factor-alpha / Q000172:deficiency / Q000235:genetics / Q000502:physiology
chemical_list: D000634:Aminoquinolines; D007093:Imidazoles; D050839:Interferon Regulatory Factor-7; D008562:Membrane Glycoproteins; D018696:Neuroprotective Agents; C477038:Tlr7 protein, mouse; D051199:Toll-Like Receptor 7; D014409:Tumor Necrosis Factor-alpha; C546771:gardiquimod; D053633:Receptor, Interferon alpha-beta