The transcription factor c-jun is activated in retinal ganglion cells in experimental rat glaucoma.
This study investigates the role of the MAP kinase pathway including c-jun, ATF-2 and JNK in glaucomatous eyes of rats and in optic nerve transection. Glaucoma was induced in one eye of 51 adult Wistar rats by laser treatment to the trabecular meshwork. Eighteen further rats underwent unilateral optic nerve transection. We studied the transcription factor c-jun, its activated form, phospho-c-jun, the transcription factor p-ATF-2, and the enzyme JNK by immunohistochemistry. The activation of p-c-jun was also investigated using western blot analysis. Treated and control eyes were compared in a masked way at multiple time points after injury. We found a statistically significant increase in immunolabelling for c-jun and phospho-c-jun in retinal ganglion cells (RGCs) from 1 day to 4 weeks after intraocular pressure (IOP) elevation. At 1 and 2 days after the laser treatment, a mean of 2.9+/-3.3 RGCsmm(-1) were positive for c-jun (n=12, p=0.005, t-test), increasing to a mean of 13.4+/-7.5 cells mm(-1) at 1 week (n=18, p=0.00005), and decreasing to 2.3+/-2.0 cells mm(-1) at 2 weeks (n=5, p=0.04) and 0.1+/-0.1 cells mm(-1) at 2 months. Few of the 47 control eyes had any labelling for c-jun or phospho-c-jun, while between 80 and 100% of elevated IOP eyes showed positivity during the first 2 weeks of experimental glaucoma. After optic nerve transection, c-jun and phospho-c-jun were also significantly activated at 1, 2 and 9 days (p<0.03, t-test). Western blot analysis demonstrated significantly increased phospho-c-jun amounts in both transected and glaucomatous eyes compared to control fellow eyes 1 week following treatment. JNK was not significantly activated in glaucoma or optic nerve transection. P-ATF-2 was not significantly activated in glaucoma, but was significantly increased 2 days after optic nerve transection. We conclude that the process leading to RGC death in experimental glaucoma and after optic nerve transection involves the activation of c-jun at the RGC layer. C-jun is activated more gradually in glaucoma then after optic nerve transection.
Levkovitch-Verbin
Hana
H
Sam Rothberg Molecular Biology Lab, Goldschleger Eye Institute, Sheba Medical Center, Tel-Aviv University, Tel-Hashomer 52621, Israel. halevko@hotmail.com
Quigley
Harry A
HA
Martin
Keith R G
KR
Harizman
Noga
N
Valenta
Danielle F
DF
Pease
Mary Ellen
ME
Melamed
Shlomo
S
D051698:Activating Transcription Factor 2; D000818:Animals; D019771:Axotomy; D015153:Blotting, Western / Q000379:methods; D017362:Cyclic AMP Response Element-Binding Protein / Q000032:analysis / Q000378:metabolism; D005901:Glaucoma / Q000378:metabolism*; D007150:Immunohistochemistry / Q000379:methods; D048031:JNK Mitogen-Activated Protein Kinases / Q000032:analysis / Q000378:metabolism; D007834:Lasers; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000032:analysis / Q000378:metabolism; D023421:Models, Animal; D009900:Optic Nerve / Q000473:pathology; D020221:Optic Nerve Injuries / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D016755:Proto-Oncogene Proteins c-jun / Q000032:analysis* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012165:Retinal Ganglion Cells / Q000737:chemistry* / Q000378:metabolism; D014130:Trabeculectomy; D014157:Transcription Factors / Q000032:analysis / Q000378:metabolism
D051698:Activating Transcription Factor 2; C497107:Atf2 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases