The transcription factor c-jun is activated in retinal ganglion cells in experimental rat glaucoma

• Published in: Experimental eye research Vol. 80; no. 5; pp. 663 - 670
• Main Authors: Levkovitch-Verbin, Hana, Quigley, Harry A., Martin, Keith R.G., Harizman, Noga, Valenta, Danielle F., Pease, Mary Ellen, Melamed, Shlomo
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-05-2005
• Subjects: Activating Transcription Factor 2; Animals; Axotomy; Blotting, Western - methods; c-jun; Cyclic AMP Response Element-Binding Protein - analysis; Cyclic AMP Response Element-Binding Protein - metabolism; glaucoma; Glaucoma - metabolism; Immunohistochemistry - methods; JNK; JNK Mitogen-Activated Protein Kinases - analysis; JNK Mitogen-Activated Protein Kinases - metabolism; Lasers; MAP Kinase Kinase 4; Mitogen-Activated Protein Kinase Kinases - analysis; Mitogen-Activated Protein Kinase Kinases - metabolism; Models, Animal; Optic Nerve - pathology; Optic Nerve Injuries - metabolism; Optic Nerve Injuries - pathology; optic nerve transection; Phosphorylation; Proto-Oncogene Proteins c-jun - analysis; Proto-Oncogene Proteins c-jun - metabolism; Rats; Rats, Wistar; retinal ganglion cells; Retinal Ganglion Cells - chemistry; Retinal Ganglion Cells - metabolism; Trabeculectomy; Transcription Factors - analysis; Transcription Factors - metabolism; c-jun; retinal ganglion cells; glaucoma; optic nerve transection; JNK
• ISSN: 0014-4835; 1096-0007
• DOI: 10.1016/j.exer.2004.11.016

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 RGCs
mm
−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.