Browsing by Subject "Retinal ganglion cells"
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Item In vitro and in vivo neuroprotective effects of cJun N-terminal kinase inhibitors on retinal ganglion cells(BioMed Central Ltd., 2016-04-21) Kim, Byung-Jin; Silverman, Sean M.; Liu, Yang; Wordinger, Robert J.; Pang, Iok-Hou; Clark, Abbot F.BACKGROUND: The c-Jun N-terminal kinase (JNK) signaling pathway plays an important role in neuronal pathophysiology. Using JNK inhibitors, we examined involvement of the JNK pathway in cultured rat retinal ganglion cell (RGC) death and in mouse retinal ischemia/reperfusion (I/R) injury of the visual axis. The in vitro effects of JNK inhibitors were evaluated in cultured adult rat retinal cells enriched in RGCs. Retinal I/R was induced in C57BL/6J mice through elevation of intraocular pressure to 120 mmHg for 60 min followed by reperfusion. SP600125 was administered intraperitoneally once daily for 28 days. Phosphorylation of JNK and c-Jun in the retina was examined by immunoblotting and immunohistochemistry. The thickness of retinal layers and cell numbers in the ganglion cell layer (GCL) were examined using H&E stained retinal cross sections and spectral domain optical coherence tomography (SD-OCT). Retinal function was measured by scotopic flash electroretinography (ERG). Volumetric measurement of the superior colliculus (SC) as well as VGLUT2 and PSD95 expression were studied. RESULTS: JNK inhibitors SP600125 and TAT-JNK-III, dose-dependently and significantly (p < 0.05) protected against glutamate excitotoxicity and trophic factor withdrawal induced RGC death in culture. In the I/R model, phosphorylation of JNK (pJNK) in the retina was significantly (p < 0.05) increased after injury. I/R injury significantly (p < 0.05) decreased the thickness of retinal layers, including the whole retina, inner plexiform layer, and inner nuclear layer and cell numbers in the GCL. Administration of SP600125 for 28 days protected against all these degenerative morphological changes (p < 0.05). In addition, SP600125 significantly (p < 0.05) protected against I/R-induced reduction in scotopic ERG b-wave amplitude at 3, 7, 14, 21 and 28 days after injury. SP600125 also protected against the I/R-induced losses in volume and levels of synaptic markers in the SC. Moreover, the protective effects of SP600125 in the retina and SC were also detected even with only 7 days (Days 1-7 after I/R) of SP600125 treatment. CONCLUSIONS: Our results demonstrate the important role the JNK pathway plays in retinal degeneration in both in vitro and in vivo models and suggest that JNK inhibitors may be a useful therapeutic strategy for neuroprotection of RGCs in the retina.Item INCREASED EXPRESSION OF ENDOTHELIN B RECEPTORS PRECEDES RETINAL GANGLION CELL DEATH IN A RODENT MODEL OF GLAUCOMA(2013-04-12) Minton, Alena Z.Purpose: Endothelin B (ETB) receptors have been shown to be involved in the pathogenesis of glaucoma. However, the precise sequence of molecular events involving ETB receptor expression and retinal ganglion cell death is not completely understood. This study was aimed at investigating whether the expression of ETB receptors precedes retinal ganglion cell loss in vivo in the Morrison's elevated intraocular pressure (IOP) model of glaucoma in rats. Methods: Intraocular pressure (IOP) was elevated in one eye of retired breeders Brown Norway rats using the Morrison's method (injection of hypertonic saline through episcleral veins), while the contralateral eye served as control. Retinas were collected after 1 and 2 weeks of IOP elevation, sectioned and stained for ETB receptor expression by immunohistochemistry. In a separate set of experiments, retired breeders Brown Norway rats were used for retrograde labeling of retinal ganglion cells (RGCs) with Fluoro-gold. Following retrograde labeling, IOP was elevated in one eye using the Morrison's method, while the contralateral eye served as control. After IOP was elevated, rats were maintained for 2 weeks and sacrificed. Fluoro-gold labeled retinas were isolated, flat-mounted, and images taken using a Zeiss LSM-510 confocal microscope. Fluoro-gold-labeled RGCs were counted in three eccentricities from the optic nerve head. In addition, optic nerves were isolated from Brown Norway rats following 2 weeks of IOP elevation, sectioned and stained using p-phenylenediamine. Confocal images were taken and morphology of optic nerve axons was compared. Results: Immunohistochemical analysis of retinal sections showed no appreciable change in ETB receptor immunostaining following 1 week of IOP elevation. However, IOP elevation for 2 weeks produced increased expression of ETB receptor in the RGCs, inner plexiform layer (IPL) and inner nuclear layer (INL). In addition, IOP elevation for 2 weeks resulted in 25% loss of RGCs in the first eccentricity, while no significant loss was seen in the second and third eccentricities. Moreover, there was no appreciable damage observed in the optic nerve axons after 2 weeks of IOP elevation. Conclusions: Early increase in expression of ETB receptors (at 2 weeks of IOP elevation) could contribute to RGC loss and damage to the optic nerve axons.