Axonal/glial upregulation of EphB/ephrin-B signaling in mouse experimental ocular hypertension.
OBJECTIVE
To use a laser-induced ocular hypertension (LIOH) mouse model to examine the optic nerve head (ONH) expression of EphB/ephrin-B, previously shown to be upregulated in glaucomatous DBA/2J mice. To relate ephrin-B reverse signaling with states of axonal response to disease.


METHODS
LIOH was induced unilaterally in CD-1 mice by laser photocoagulation of limbal and episcleral veins. Intraocular pressure (IOP) was measured with a tonometer. EphB/ephrin-B mRNA expression was assessed by in situ hybridization on eyecup cryosections and real-time PCR. Cell specific markers were used to identify the cellular origin of EphB/ephrin-B expression. Activation of ephrin-B signaling was investigated with a phosphospecific antibody on cryosections and retinal whole-mounts.


RESULTS
Upregulation of EphB/ephrin-B expression occurred early within a day of IOP elevation. A transient increase of phosphorylation-dependent ephrin-B (pEB) reverse signaling was observed in ONH axons, microglia, and some astrocytes. Morphologically unaffected retinal ganglion cell (RGC) axons differed from axons with reactive aberrant trajectories by exhibiting increased pEB activation, whereas pEB levels in morphologically affected axons were comparable to those of controls.


CONCLUSIONS
An Eph-ephrin signaling network is activated at the ONH after LIOH in CD-1 mice, either before or coincident with the initial morphologic signs of RGC axon damage reported previously. Of note, ephrin-B reverse signaling was transiently upregulated in RGC axons at the ONH early in their response to IOP elevation but was downregulated in axons that had been damaged by glaucomatous injury and exhibited aberrant trajectories. Ephrin-B reverse signaling may mark RGC axons for damage or confer a protective advantage against injury.
Fu
Christine T
CT
Neuroscience Graduate Program, Department of Ophthalmology, University of California, San Francisco, San Francisco, California 94143, USA. cfu@vision.ucsf.edu
Tran
Tony
T
Sretavan
David
D
D000818:Animals; D001369:Axons / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D004195:Disease Models, Animal; D036389:Ephrin-B3 / Q000235:genetics* / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D007429:Intraocular Pressure; D017075:Laser Coagulation / Q000009:adverse effects; D051379:Mice; D009457:Neuroglia / Q000378:metabolism*; D009798:Ocular Hypertension / Q000209:etiology / Q000235:genetics* / Q000378:metabolism; D009898:Optic Disk / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D036081:Receptors, Eph Family / Q000235:genetics* / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D015854:Up-Regulation
D015415:Biomarkers; D036389:Ephrin-B3; D012333:RNA, Messenger; D036081:Receptors, Eph Family