title: Excitotoxicity upregulates SARM1 protein expression and promotes Wallerian-like degeneration of retinal ganglion cells and their axons.
abstract: OBJECTIVE
  This study investigated the role of sterile alpha/Armadillo/Toll-Interleukin receptor homology domain 1 protein (SARM1) in Wallerian-like degeneration of retinal ganglion cells (RGCs) and their axons after inducing excitotoxicity.
  
  
  METHODS
  To induce excitotoxicity, kainic acid (KA) was injected into the vitreous humor of B6.Cg-Tg(Thy1-YFP)HJrs/J mice. Control mice received PBS. At 24, 48, and 72 hours after injection, degeneration of RGCs and their axons in the retina was determined by fundus imaging, and axonal degeneration in the optic nerves was determined by fluorescence microscopy. SARM1 protein levels were determined by Western blot analysis and SARM1 tissue localization was determined by immunohistochemistry. Causal role of SARM1 in KA-mediated degeneration of RGCs and their axons was determined by treating the eyes with KA along with Sarm1 silencer siRNA.
  
  
  RESULTS
  Fundus imaging and microscopic analysis indicated that KA promoted Wallerian-like degeneration of RGCs and axons in KA-treated eyes, but not in PBS-treated eyes. Quantitative analysis indicated a significant increase in degeneration of RGCs and their axons in KA-treated injected eyes, but not in PBS-treated eyes. Compared with low levels of SARM1 protein in retinal protein extracts, retinal cross sections, and optic nerve from PBS-treated eyes, SARM1 protein levels were increased in KA-treated eyes. Finally, treatment of eyes with KA along with a Sarm1 silencer siRNA attenuated KA-mediated degeneration of RGCs and their axons significantly.
  
  
  CONCLUSIONS
  Results presented in this study, for the first time, show that KA-mediated upregulation of SARM1 protein promotes Wallerian-like degeneration of RGCs and their axons.
authors.affiliation: Eye Research Institute of Oakland University, Rochester, Michigan 48309, USA.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Massoll
authors.forename: Wasym
authors.initials: W
authors.lastname: Mando
authors.forename: Shravan K
authors.initials: SK
authors.lastname: Chintala
mesh_terms: D000818:Animals; D017209:Apoptosis; D051186:Armadillo Domain Proteins / Q000378:metabolism*; D001369:Axons / Q000187:drug effects* / Q000473:pathology; D015153:Blotting, Western; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity*; D019084:Fluorescent Antibody Technique, Indirect; D020868:Gene Silencing; D058449:Intravitreal Injections; D007608:Kainic Acid / Q000633:toxicity*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D009900:Optic Nerve / Q000187:drug effects*; D034741:RNA, Small Interfering / Q000235:genetics; D012165:Retinal Ganglion Cells / Q000187:drug effects* / Q000473:pathology; D015854:Up-Regulation; D014855:Wallerian Degeneration / Q000209:etiology* / Q000378:metabolism / Q000473:pathology
chemical_list: D051186:Armadillo Domain Proteins; D003598:Cytoskeletal Proteins; D018690:Excitatory Amino Acid Agonists; D034741:RNA, Small Interfering; C543961:SARM1 protein, mouse; D007608:Kainic Acid