title: Autophagy activation in the injured photoreceptor inhibits fas-mediated apoptosis.
abstract: OBJECTIVE
  To examine the activation of autophagy and its relationship to Fas-mediated photoreceptor apoptosis during experimental retinal detachment.
  
  
  METHODS
  Retina-retinal pigment epithelium (RPE) separation was created in Brown-Norway rats by subretinal injection of 1% hyaluronic acid and the intraretinal levels of the autophagy proteins LC3 and Atg5, the time course of LC3-I to LC3-II conversion, and the activation of cathepsins B and D were assayed with Western blot analysis and immunohistochemistry. We measured the ability of a Fas-activating antibody to induce LC3-I to LC3-II conversion in 661W cells, and the in vivo effect of Met12, a small molecule inhibitor of the Fas receptor, on LC3-I to LC3-II conversion and Atg5 expression. Autophagy activation was inhibited using 3-methyladenine (3-MA) or siRNA knockdown of Atg5 and the effect on apoptosis was measured using a caspase 8 activity assay, caspase 8 immunoblots, and photoreceptor TUNEL staining.
  
  
  RESULTS
  Retina-RPE separation resulted in a Fas-dependent activation of autophagy, with increased Atg5 levels and intraphotoreceptor conversion of LC3-I to LC3-II. Detached retinas had increased levels of autophagosome-associated lysosomal proteases, cathepsins B and D. Inhibition of autophagy by 3-MA or siAtg5 accelerated the time course of caspase 8 activation and photoreceptor TUNEL staining.
  
  
  CONCLUSIONS
  Autophagy activation occurs in the photoreceptors after retina-RPE separation. This appears to be, at least in part, dependent on Fas receptor activation, and plays a role in regulating the level of photoreceptor apoptosis.
authors.affiliation: Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan 48105-0714, USA.
authors.forename: Cagri G
authors.initials: CG
authors.lastname: Besirli
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Chinskey
authors.forename: Qiong-Duan
authors.initials: QD
authors.lastname: Zheng
authors.forename: David N
authors.initials: DN
authors.lastname: Zacks
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D000071187:Autophagy-Related Protein 5; D015153:Blotting, Western; D053181:Caspase 8 / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism; D002402:Cathepsin D / Q000378:metabolism; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D007150:Immunohistochemistry; D008297:Male; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D020419:Photoreceptor Cells, Vertebrate; D020033:Protein Isoforms / Q000378:metabolism; D011506:Proteins / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D011914:Rats, Inbred BN; D012163:Retinal Detachment / Q000503:physiopathology*; D013997:Time Factors; D019014:fas Receptor / Q000378:metabolism*
chemical_list: D000225:Adenine; D000071187:Autophagy-Related Protein 5; D053181:Caspase 8; D002401:Cathepsin B; D002402:Cathepsin D; D008869:Microtubule-Associated Proteins; D020033:Protein Isoforms; D011506:Proteins; D034741:RNA, Small Interfering; D019014:fas Receptor; C545865:Atg5 protein, rat; C526109:Anxa3 protein, rat; C025946:3-methyladenine; C505528:Casp8 protein, rat; C533916:Ctsb protein, rat; C533924:Ctsd protein, rat