Continuous exposure to bright light upregulates bFGF and CNTF expression in the rat retina.
OBJECTIVE
To examine mRNA expression of neurotrophic factors in the retina after exposure to bright light.


METHODS
Male adult Sprague-Dawley rats were exposed to light of 115-130 ft-c. Retinas were collected after 1, 2, 4 or 7 days of exposure. Northern blot analysis was performed to determine mRNA levels for the following factors and their receptors: basic fibroblast growth factor (bFGF), ciliary neurotrophic factor (CNTF), acidic fibroblast growth factor (aFGF), brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1) and glial fibrillary acidic protein (GFAP). Expression of bFGF, CNTF and GFAP was localized by in situ hybridization.


RESULTS
Exposure to light of 115-130 ft-c resulted in a substantial increase in bFGF and CNTF expression that persisted during the entire 7-day period of exposure. The peak expression of bFGF was almost 9-fold at day 2. The increase in CNTF mRNA reached a maximum of 6-fold at day 4. A small increase (50%) in IGF-1 mRNA was also seen at day 4. Among the receptors, an elevation of 3-fold in FGF receptor 1 (FGFR-1) was observed at day 2. There was also a small increase (70%) in IGF-1 receptor (IGF-1R) at day 2. In addition, the expression of GFAP showed a rapid elevation of about 8-fold by day 1 and 9-fold by day 2, and 18-fold by day 4. There was, however, no significant alteration in the expression of aFGF and BDNF. In situ hybridizations showed that the elevation of bFGF, CNTF and GFAP occurred across the entire retina with especially prominent increases over specific layers for each gene.


CONCLUSIONS
Continuous exposure to bright light upregulates bFGF, CNTF, FGFR-1 and GFAP expression in the rat retina. The pattern of induced expression closely resembles that induced by mechanical injury, implying a common underlying mechanism.
Wen
R
R
Department of Ophthalmology, University of Pennsylvania, School of Medicine, Philadelphia 19104, USA. rwen@mail.med.upenn.edu
Cheng
T
T
Song
Y
Y
Matthes
M T
MT
Yasumura
D
D
LaVail
M M
MM
Steinberg
R H
RH
D000818:Animals; D015152:Blotting, Northern; D020934:Ciliary Neurotrophic Factor; D016222:Fibroblast Growth Factor 2 / Q000235:genetics / Q000378:metabolism*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006133:Growth Substances / Q000235:genetics / Q000378:metabolism; D017403:In Situ Hybridization; D008027:Light; D008297:Male; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011833:Radiation Injuries, Experimental / Q000209:etiology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000378:metabolism / Q000528:radiation effects*; D012162:Retinal Degeneration / Q000209:etiology / Q000378:metabolism; D015854:Up-Regulation
D020934:Ciliary Neurotrophic Factor; D005904:Glial Fibrillary Acidic Protein; D006133:Growth Substances; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D016222:Fibroblast Growth Factor 2