Photoreceptor protection against light damage by AAV-mediated overexpression of heme oxygenase-1.
OBJECTIVE
To investigate whether overexpression of the cytoprotective gene heme oxygenase-1 (HO-1) in photoreceptors by gene delivery attenuates cellular injury caused by intense light damage and to document the possible mechanisms of protection.


METHODS
Recombinant adeno-associated virus type 5 (rAAV5) expressing the mouse HO-1 gene (mHO-1) was delivered to cyclic-light reared Sprague-Dawley (SD) rats by subretinal injection. Three weeks after transfer of HO-1 gene, animals were subjected to 2-hour intense light exposure then were returned to darkness. Expression of HO-1, p53, p38, and cellular FLICE inhibitory protein (c-FLIP) at different times after intense light damage was evaluated by Western blot analysis. HO-1 transgene expression, along with expression of c-fos and bcl-2, was analyzed by immunohistochemistry. In addition, the protective effects of HO-1 were evaluated by determining the morphology of the retina. Finally, apoptosis in photoreceptors was measured using TdT-dUTP terminal nick-end labeling (TUNEL) 24 hours after photic injury.


RESULTS
Exogenous administration of HO-1 by gene transfer led to HO-1 transgene expression in photoreceptors. Protection of retina by HO-1 overexpression is evident from the partially preserved retina structure and attenuated apoptosis in photoreceptors after photic injury. Concurrently, overexpression of HO-1 was associated with a decrease in the expression of c-fos and p53, an increase in the activation of p38 and bcl-2, and preserved the expression of c-FLIP.


CONCLUSIONS
Overexpression of HO-1 in photoreceptors protected themselves from subsequent cellular damage caused by intense light exposure. The anti-apoptotic mechanisms of HO-1 may be related to the induction of p38, bcl-2, and c-FLIP and to the suppression of c-fos and p53.
Department of Ophthalmology, Chang Gung Memorial Hospital [corrected] Taoyuan, Taiwan.
Ming-Hui
MH
Sun
Jong-Hwei Su
JH
Pang
Show-Li
SL
Chen
Ping-Chang
PC
Kuo
Kuan-Jen
KJ
Chen
Ling-Yuh
LY
Kao
Ju-Yun
JY
Wu
Ken-Kuo
KK
Lin
Yeou-Ping
YP
Tsao
D000818:Animals; D015153:Blotting, Western; D053181:Caspase 8 / Q000378:metabolism; D000229:Dependovirus / Q000235:genetics*; D019084:Fluorescent Antibody Technique, Indirect; D015971:Gene Expression Regulation, Enzymologic; D005822:Genetic Vectors; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics* / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D008027:Light / Q000009:adverse effects*; D008297:Male; D020419:Photoreceptor Cells, Vertebrate / Q000528:radiation effects* / Q000648:ultrastructure; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011833:Radiation Injuries, Experimental / Q000209:etiology / Q000235:genetics* / Q000517:prevention & control*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012162:Retinal Degeneration / Q000209:etiology / Q000235:genetics / Q000517:prevention & control; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
D019253:Proto-Oncogene Proteins c-bcl-2; D016760:Proto-Oncogene Proteins c-fos; D016159:Tumor Suppressor Protein p53; D006419:Heme Oxygenase (Decyclizing); C491523:Hmox1 protein, rat; D048051:p38 Mitogen-Activated Protein Kinases; D053181:Caspase 8