Browsing by Subject "Retina"
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Item ENDOTHELIN A RECEPTOR EXPRESSION IN RAT MODEL OF OCULAR HYPERTENSION(2013-04-12) McGrady, NolanPurpose: The endothelin system of peptides and their receptors have been implicated for their neurodegenerative role in glaucoma. The purpose of this study was to determine changes in ETA receptor expression in the retina in the Morrison's elevated IOP model of glaucoma in rats. Methods: IOP was elevated in the left eye of adult male retired breeder Brown Norway rats using the Morrison's model of glaucoma (by injection of hypertonic saline through episcleral veins) while the contralateral eye served as the corresponding control. The rats were maintained for two weeks following IOP elevation and sacrificed. Retinal sections were obtained from both the control and IOP-elevated eyes and analyzed for changes in ETA receptor expression using immunohistochemistry. ETA receptor immunostaining was co-localized with β-III-Tubulin, which is selectively expressed in retinal ganglion cells. Results: Rat eyes with IOP elevation showed an increase in immunostaining ETA receptor in several retinal layers including retinal ganglion cells, the inner plexiform layer, and the outer plexiform layer. An increased co-immunostaining of ETA receptors with β-III-Tubulin was observed both in retinal ganglion cells and inner plexiform layer. Conclusions: Elevated intraocular pressure results in an increase in ETA receptor expression. Increased endothelin receptor expression is associated with neurodegeneration in glaucoma.Item Functional optical coherence tomography at altitude: retinal microvascular perfusion and retinal thickness at 3,800 meters(American Physiological Society, 2022-07-01) Baker, Jacquie; Safarzadeh, Mohammad A.; Incognito, Anthony V.; Jendzjowsky, Nicholas G.; Foster, Glen E.; Bird, Jordan D.; Raj, Satish R.; Day, Trevor A.; Rickards, Caroline A.; Zubieta-DeUrioste, Natalia; Alim, Usman; Wilson, Richard J. A.Cerebral hypoxia is a serious consequence of several cardiorespiratory illnesses. Measuring the retinal microvasculature at high altitude provides a surrogate for cerebral microvasculature, offering potential insight into cerebral hypoxia in critical illness. In addition, although sex-specific differences in cardiovascular diseases are strongly supported, few have focused on differences in ocular blood flow. We evaluated the retinal microvasculature in males (n = 11) and females (n = 7) using functional optical coherence tomography at baseline (1,130 m) (day 0), following rapid ascent (day 2), and prolonged exposure (day 9) to high altitude (3,800 m). Retinal vascular perfusion density (rVPD; an index of total blood supply), retinal thickness (RT; reflecting vascular and neural tissue volume), and arterial blood were acquired. As a group, rVPD increased on day 2 versus day 0 (P < 0.001) and was inversely related to [Formula: see text] (R(2) = 0.45; P = 0.006). By day 9, rVPD recovered to baseline but was significantly lower in males than in females (P = 0.007). RT was not different on day 2 versus day 0 (P > 0.99) but was reduced by day 9 relative to day 0 and day 2 (P < 0.001). RT changes relative to day 0 were inversely related to changes in [Formula: see text] on day 2 (R(2) = 0.6; P = 0.001) and day 9 (R(2) = 0.4; P = 0.02). RT did not differ between sexes. These data suggest differential time course and regulation of the retina during rapid ascent and prolonged exposure to high altitude and are the first to demonstrate sex-specific differences in rVPD at high altitude. The ability to assess intact microvasculature contiguous with the brain has widespread research and clinical applications.NEW & NOTEWORTHY Measuring the retinal microvasculature at high altitude provides a surrogate for cerebral microvasculature, offering potential insight into consequence of cerebral hypoxia in critical illness. This study demonstrates dynamic regulation of the retina during rapid ascent and prolonged exposure to high altitude and is the first to demonstrate sex-specific differences in retinal microvasculature at high altitude. The ability to dynamically assess intact microvasculature contiguous with the brain has widespread research and clinical applications.Item PROTECTIVE EFFECT OF JNK INHIBITION IN RETINAL GANGLION CELLS AND IN RETINAL ISCHEMIA/REPERFUSION INJURY(2013-04-12) Kim, Byung-JinPurpose: The JNK (cJUN N-terminal kinase) signaling pathway plays an important role in various neuronal pathophysiologies. Using JNK inhibitor SP600125, we examined involvement of the JNK pathway in cultured retinal ganglion cell (RGC) death and in mouse retinal ischemia/reperfusion (I/R) injury. Methods: The in vitro effects of of several JNK inhibitors were evaluated in cultured adult rat retinal cells enriched in RGCs. Cytotoxicity was induced by glutamate or trophic factor withdrawal. Survival of RGCs was assessed by counting Thy-1 postive cells. Retinal I/R was induced in female C57BL/6J mice by raising the intraocular pressure to 120 mmHg for 60 min followed by reperfusion. SP600125 (5, 15, 30 mg/kg) was administered intraperitoneally once daily for 28 days starting at 2 h prior to injury. At various time points after I/R, phosphorylation of JNK and cJun was examined by immunoblotting of retinal proteins. The thickness of retinal layers and cell numbers in ganglion cell layer (GCL) were monitored using H&E stained retinal cross sections, and retinal function was measured by scotopic ERG. Results: SP600125 dose-dependently and significantly (p<0.05) completely protected against glutamate- and trophic factor withdrawal-induced cultured RGC cell death. In the I/R model, phosphorylation of JNK and cJun in retina was significantly (p<0.05) increased at 1 h after injury. I/R injury significantly (p<0.05) decreased the thickness of retinal layers, including whole retina (-23.2 ± 5.7%), inner plexiform layer (-38.0 ± 6.7%), and inner nuclear layer (-25.1 ± 7.4 %) and cell numbers in GCL (-30.0 ± 5.6%). Importantly, administration of all three doses of SP600125 protected against all these degenerative morphological changes (p<0.05). In addition, SP600125 administration also significantly (p<0.05) protected against I/R-induced reduction in b-wave amplitude at 3, 7, 14, 21 and 28 days after injury. Conclusions: Our results demonstrated involvement of the JNK pathway in retinal degeneration in both in vitro and in vivo models and suggest that JNK inhibitors may be a useful therapeutic strategy for neuroprotection in the retina.Item Proteomics-Based Identification of Retinal Protein Networks Impacted by Elevated Intraocular Pressure in the Hypertonic Saline Injection Model of Experimental Glaucoma(MDPI, 2023-08-26) Zaman, Khadiza; Nguyen, Vien; Prokai-Tatrai, Katalin; Prokai, LaszloElevated intraocular pressure is considered a major cause of glaucomatous retinal neurodegeneration. To facilitate a better understanding of the underlying molecular processes and mechanisms, we report a study focusing on alterations of the retina proteome by induced ocular hypertension in a rat model of the disease. Glaucomatous processes were modeled through sclerosing the aqueous outflow routes of the eyes by hypertonic saline injections into an episcleral vein. Mass spectrometry-based quantitative retina proteomics using a label-free shotgun methodology identified over 200 proteins significantly affected by ocular hypertension. Various facets of glaucomatous pathophysiology were revealed through the organization of the findings into protein interaction networks and by pathway analyses. Concentrating on retinal neurodegeneration as a characteristic process of the disease, elevated intraocular pressure-induced alterations in the expression of selected proteins were verified by targeted proteomics based on nanoflow liquid chromatography coupled with nano-electrospray ionization tandem mass spectrometry using the parallel reaction monitoring method of data acquisition. Acquired raw data are shared through deposition to the ProteomeXchange Consortium (PXD042729), making a retina proteomics dataset on the selected animal model of glaucoma available for the first time.Item ROLE OF C/EBP HOMOLOGOUS PROTEIN (CHOP) IN THE SURVIVAL OF RETINAL GANGLION CELLS AFTER RETINAL ISCHEMIA/REPERFUSION INJURY(2014-03) Nashine, Sonali; Kim, Byung-Jin; Clark, Abbot F.; Pang, Iok-HouGlaucoma is one of the leading causes of blindness and visual impairment, affecting 70 million people worldwide. A major characteristic of this disease is the irreversible death of retinal ganglion cells (RGCs), retinal neurons that transmit visual information from the eye to the brain. There is an unmet need to develop novel therapeutic strategies for glaucoma. One of the major causes of glaucoma is increased pressure inside the eye i.e., increased intraocular pressure. Increased IOP leads to obstruction of the central retinal artery. Obstruction of this artery leads to insufficient blood supply to the eye, which in turn prevents adequate supply of oxygen and nutrients to the eye, causing ischemia. All these events result in improper folding of proteins in the endoplasmic reticulum (ER). Unfolded or misfolded proteins in the ER lead to ER stress which is one of the major pathways of RGC death. C/EBP Homologous protein (CHOP) is a player in this pathway of cell death. We are studying the mechanisms of RGC death in mice. Our mouse model is called the ischemia/reperfusion (I/R) model. In this model, IOP is increased above the normal level for an hour. This prevents blood supply to the eye and leads to ischemia. After an hour, IOP is brought back to normal and blood supply is restored i.e., reperfusion, which causes considerable damage to the eye. Damage caused to the eye in this model simulates the mechanism of RGC death caused in glaucoma. The goal of our project is to investigate if the presence of CHOP in mice causes RGC death after ischemia/reperfusion injury. If it does, then we would study if the absence of CHOP in mice helps in the survival of RGCs. If absence of CHOP in mice is found to protect retinal ganglion cells, then results of the proposed study could lead to the development of a novel therapy for glaucoma. Purpose (a): Retinal ischemia/reperfusion (I/R) causes apoptotic death of retinal ganglion cells (RGC). CHOP is a pro-apoptotic protein and a unfolded protein response (UPR) marker that plays a role in ER-stress mediated apoptotic cell death. The purpose of this study was to investigate the role of CHOP in mouse RGC survival following retinal I/R injury. Methods (b): Retinal I/R was induced in adult C57BL/6J (WT) and CHOP-/- mice by cannulation of the anterior chamber of the left eye with a needle connected to a reservoir of saline. Intraocular pressure was increased to 120 mmHg for 60 min, after which the needle was withdrawn to restore retinal circulation. Uninjured right eyes served as controls. Expression of CHOP protein and other UPR markers (p-eIF2α and BiP) in WT mice post-I/R was studied using Western blot and immunohistochemistry. To compare RGC survival between WT and CHOP-/- mice, retinal flat mount staining with RGC marker, Brn3a was performed. Scotopic threshold response electroretinography (STR-ERG) was performed at 0.03 mcd.s/m2 light intensity to evaluate retinal function. Results (c): CHOP protein was up-regulated by 30 % in I/R injured eyes (1.30 ± 0.11 arbitrary units (a.u.)) compared to control eyes (1 ± 0.07 a.u.) in WT mice three days after I/R injury (p < 0.05). Protein levels of p-eIF2α and BiP also increased by 19% (I/R: 1.19 ± 0.15 a.u., Control: 1 ± 0.06 a.u.) and 11% (I/R: 1.11 ± 0.02 a.u., Control: 1 ± 0.03 a.u.) respectively (both p < 0.05). Co-localization of CHOP and Brn3a confirmed the up-regulation of CHOP specifically in the RGCs. In the uninjured control eyes, CHOP knockout did not affect baseline RGC density or STR-ERG amplitude. I/R injury decreased RGC densities and STR-ERG amplitudes in both WT and CHOP-/- mice. However, survival of RGCs in I/R-injured CHOP-/- mouse eyes (3337.1 ± 316.4 RGC/mm2) was 48% higher (p < 0.05) than that of I/R-injured WT mouse eyes (2248.7 ± 225.9 RGC/mm2) three days after I/R injury. STR-ERG amplitudes were 83 % higher in CHOP-/- I/R eyes (18.6 ± 1.1 μV) compared to WT I/R eyes (10.1 ± 0.9 μV) (p < 0.05). Conclusions (d): Absence of CHOP partially protects against the loss of RGCs and reduction in retinal function (STR-ERG) after I/R injury. These results indicate that CHOP and thus ER-stress play an important role in RGC apoptosis in retinal I/R injury.