Dh Lee

Soluble Nogo-66 receptor prevents synaptic dysfunction and rescues retinal ganglion cell loss in chronic glaucoma.

PURPOSE Myelin inhibitory proteins inhibit axon growth and synaptic function by binding to the Nogo-66 receptor (NgR)1 in the central nervous system. Glaucoma is a progressive neuropathy characterized by loss of vision as a result of retinal ganglion cell (RGC) death. Synaptic degeneration is thought to be an early pathology of neurodegeneration in glaucoma and precedes RGC loss. The authors aimed to examine whether the NgR1 antagonist promotes synaptic recovery and RGC survival in glaucoma. METHODS Experimental ocular hypertension model was induced in adult rats with laser coagulation of the episcleral and limbal veins. NgR1 antagonist, soluble NgR1 (sNgR-Fc) was administrated to examine their effect on synaptic recovery and RGC survival. Expression of c-Fos, a neuronal connectivity marker, in the retinas was investigated using immunohistochemistry. RESULTS NgR1 was expressed in RGCs and upregulated after intraocular pressure elevation. Treatment with sNgR-Fc significantly reduced RGC loss at 2 and 4 weeks after the induction of ocular hypertension and also promoted RGC survival after optic nerve transection. There was no RGC loss at 5 days but there was significant synaptic degeneration as measured by c-Fos. Administration of sNgR-Fc attenuated synaptic degeneration at 5 days, and at 2 and 4 weeks. CONCLUSIONS These data suggest that synaptic degeneration may be an initial molecular mechanism for neurodegeneration in glaucoma and appropriate NgR1 antagonism may delay the progression of the disease.

Soluble NgR Fusion Protein Modulates the Proliferation of Neural Progenitor Cells via the Notch Pathway

NogoA, myelin-associated glycoprotein (MAG) and oligodendrocyte myelin glycoprotein are CNS myelin molecules that bind to the neuronal Nogo-66 receptor (NgR) and inhibit axon growth. The NgR antagonist, soluble NgR1-Fc protein (sNgR-Fc), facilitates axon regeneration by neutralizing the inhibitory effects of myelin proteins in experimental models of CNS injury. Here we aim to investigate the effect of sNgR-Fc on the proliferation of neural progenitor cells (NPCs). The hippocampus cells of embryonic rats were isolated and cultured in vitro. The expression of nestin, βIII-Tubulin, GFAP and Nogo-A on these cells was observed using immunocytochemistry. In order to investigate the effect on proliferation of NPCs, sNgR-Fc, MAG-Fc chimera and Notch1 blocker were added respectively. The total cell number for the proliferated NPCs was counted. BrdU was applied and the rate of proliferating cells was examined. The level of Notch1 was analyzed using Western blotting. We identified that NogoA is expressed in NPCs. sNgR-Fc significantly enhanced the proliferation of NPCs in vitro as indicated by BrdU labeling and total cell count. This proliferation effect was abolished by the administration of MAG suggesting specificity. In addition, we demonstrate that sNgR-Fc is a potent activator for Notch1 and Notch1 antagonist reversed the effect of sNgR-Fc on NPC proliferation. Our results suggest that sNgR-Fc may modulate Nogo activity to induce NPC proliferation via the Notch pathway.