论文部分内容阅读
Objective Glaucoma, the second leading cause of blindness, is a neurodegenerative disease that is characterized by optic nerve degeneration resulting from apoptotic death of retinal ganglion cells (RGCs).Although previous work has shown that ephrinB2/EphB2 signaling was upregulated in the optic nerve head of glaucomatous DBA/2J mice, the role of ephrinB/EphB signaling in glaucomatous retina is largely unknown.In the present work, we investigated the possible involvement of ephrinB/EphB signaling in the pathogenesis of RGCs death in a rat chronic ocular hypertension (COH) model.Methods COH model was reproduced by blocking episcleral veins.Immunohistochemistry and Western blot techniques were used to detect the expression of EphB1, EphB2, ephrinB 1, ephrinB2, phosphorylated EphB, phosphorylated ephrinB, and GluR2 in the retina.TUNEL staining was employed to detect RGCs apoptosis.The direct interaction between GluR2 and phosphorylated EphB or phosphorylated ephrinB was detected by co-immunoprecipitation (co-IP) assay.Results (1) In normal retina, EphB1 was mainly expressed in GFAP-positive Müller cells and EpbB2 was expressed in the ganglion cell layer (GCL) and the inner nuclear layer (INL), while their ligands ephrinB 1 and ephrinB2 were expressed in both Müller cells and neurons in the GCL.(2) In COH retina, the expression of EphB 1 was remarkably increased in Müiler cells, and the expression of ephrinB2 was increased in the endfeet of Müller cells and in neurons of the GCL, while ephrinB 1 and EphB2 almost kept unchanged.(3) Although total GluR2 proteins in the retinal extract hardly changed, the GluR2 proteins in the membrane component were significantly decreased in the COH rats.An intravitreal injection of EphB2-Fc, but not ephrinB2-Fc, induced a significant increase of TUNEL-positive signals in the normal retina, which was similar to the observation in the COH rats.Furthermore, injection of EphB2-Fc intravitreally could mimic the expression change of GluR2 in the COH rats.(4) Although the expression of both phosphorylated EphB and phosphorylated ephrinB were significantly enhanced in the retina of COH rats, co-IP experiments showed that phosphorylated ephrinB, but not phosphorylated EphB, has a direct interaction with GluR2 protein.Since GluR2-lacking AMPA receptors are highly Ca2+-permeant receptors, ephrinB2/EphB2 reverse signaling-induced GluR2 trafficking may contribute to RGCs apoptosis in the COH rats.Conclusion Elevated ephrinB/EphB reverse signaling regulates GluR2 trafficking in a rat experimental glaucomatous model, which plays an important role in RGCs apoptosis.