title: Activation of TLR3 promotes the degeneration of retinal ganglion cells by upregulating the protein levels of JNK3.
abstract: OBJECTIVE
  To investigate whether activation of Toll-like receptor 3 (TLR3) promotes the degeneration of retinal ganglion cells (RGCs) by upregulating the protein levels of c-jun N-terminal kinase 3 (JNK3).
  
  
  METHODS
  Toll-like receptor 3-specific activator, Poly(I:C) (polyinosinic-polycytidylic acid), or PBS was injected into the vitreous humor of Thy1-YFP mice. At 24, 48, and 72 hours after treatments, degeneration of RGCs was assessed by using antibodies against brain-specific homeobox/POU domain protein 3a (Brn3a). A TLR3-specific inhibitor was injected into the vitreous humor with or without Poly(I:C). Western blot assays were performed to determine relative levels of TLR3, JNK3, pJNK3, and sterile alpha and HEAT/Armadillo motif-containing 1 (SARM1) proteins in retinal protein extracts, and immunohistochemistry assays were performed to determine their cellular localization in the retina. Mouse eyes were treated with Poly(I:C) or PBS along with MitoTracker Red, and colocalization of MitoTracker Red and JNK3 in the retinas was determined by using antibodies against JNK3.
  
  
  RESULTS
  Poly(I:C) activated TLR3 and upregulated its downstream target protein JNK3 but not SARM1 in the retina. Poly(I:C) activated TLR3 and upregulated JNK3 specifically in RGCs and promoted a significant degeneration of RGCs over a 72-hour time period. Toll-like receptor 3 upregulated the levels of JNK3 protein in the cytoplasm of RGCs, but not in the mitochondria. Toll-like receptor 3-specific inhibitor downregulated Poly(I:C)-mediated upregulation of JNK3 protein, and, in turn, significantly attenuated TLR3-induced degeneration of RGCs.
  
  
  CONCLUSIONS
  Results presented in this study show that the activation of TLR3 alone promotes the degeneration of RGCs by upregulating the protein levels of JNK3.
authors.affiliation: Laboratory of Ophthalmic Neurobiology, Eye Research Institute of Oakland University, Rochester, Michigan, United States.
authors.forename: Shravan K
authors.initials: SK
authors.lastname: Chintala
authors.affiliation: Laboratory of Ophthalmic Neurobiology, Eye Research Institute of Oakland University, Rochester, Michigan, United States.
authors.forename: Nahrain
authors.initials: N
authors.lastname: Putris
authors.affiliation: Laboratory of Ophthalmic Neurobiology, Eye Research Institute of Oakland University, Rochester, Michigan, United States.
authors.forename: Mason
authors.initials: M
authors.lastname: Geno
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D008268:Macular Degeneration / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D048057:Mitogen-Activated Protein Kinase 10 / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction; D051196:Toll-Like Receptor 3 / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: C519703:TLR3 protein, mouse; D051196:Toll-Like Receptor 3; D048057:Mitogen-Activated Protein Kinase 10
keywords: JNK3; RGCs; SARM1; Toll-like receptor 3