Loss of Retinal Ganglion Cells Following Retinal Ischemia: The Role of Inducible Nitric Oxide Synthase (original) (raw)
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Nitric oxide produced during ischemia improves functional recovery in the rabbit retina
NeuroReport, 1996
Many investigators have reported that the soluble gas nitric oxide (NO) is released during periods of ischemia (i.e. low energy supply due to oxygen and glucose deprivation) in the central nervous system (CNS). Although many studies continue to address the role of NO during ischemia, little is known about functional recovery of the CNS following this insult. The significance of this report is that it suggests that NO released during ischemia is beneficial for, and improves, the subsequent functional recovery in the retina of the rabbit (i.e. a model of the mammalian CNS). Moreover, it further hints that the mechanisms for this protective effect is at least partially independent on the effect of NO on blood vessels supplying the tissue.
Retinal Ganglion Cell Death Induced by Retinal Ischemia
Survey of Ophthalmology, 2001
We have investigated in adult Sprague-Dawley rats the neuroprotective effects of two ␣-2-selective agonists [AGN 191,103 (AGN) and brimonidine tartrate (BMD)] on retinal ganglion cell (RGC) survival after transient retinal ischemia. RGCs were labelled with Fluorogold (FG) applied to both superior colliculi. Seven days later, 90 min of retinal ischemia were induced in the left eyes by ligature of the ophthalmic vessels (LOV). In one group of animals, vehicle or AGN (0.01 mg/kg) were administered systemically 1 hr before ischemia. In another group of animals, two 5 l drops of vehicle, AGN (0.05%) or BMD (0.1%) were administered topically in the left eye 1 hr before ischemia. The animals were processed 7 or 21 days later. RGC survival was estimated by counting FG-labelled cells in 12 standard areas of each retina. In control retinas of systemically pretreated animals, mean densities of labelled RGCs were 2372 Ϯ 49 cells/mm 2 (mean Ϯ SEM; n ϭ 6). In experimental retinas of systemically pretreated animals, mean RGC densities had decreased 7 days after ischemia to 53% (n ϭ 6) or 81% (n ϭ 6) of control in the groups treated with vehicle or AGN, respectively. Twenty-one days after ischemia, mean RGC densities had decreased to 38% (n ϭ 6) or 79% (n ϭ 6) of control in the groups treated with vehicle or AGN, respectively. In control retinas of topically pretreated animals, mean densities of labelled RGCs were 2208 Ϯ 29 cells/mm 2 (n ϭ 6). In experimental retinas of topically pretreated animals, mean RGC densities had decreased 7 days after ischemia to 54% (n ϭ 6), 95% (n ϭ 6) or 96% (n ϭ 6) of control in the groups treated with vehicle, AGN or BMD, respectively. These results indicate that pretreatment with a single systemic or topical dose of AGN or BMD can prevent completely the early rapid phase of RGC loss and abolish the delayed RGC loss observed after 90 min of retinal ischemia induced by ligature of the ophthalmic vessels.
Experimental Eye Research, 2006
Profound morphologic and functional protection against retinal ischemic injury can be achieved if the tissue is 'preconditioned' one day earlier with a brief, noninjurious ischemic challenge. To begin to address the mechanistic basis of this 'ischemic tolerance', we used genetic and pharmacologic approaches to test the hypothesis that nitric oxide (NO) derived from one of the three NO synthase (NOS) isoforms was responsible for triggering the adaptive response to brief preconditioning ischemia. Retinae of adult mice were preconditioned with 5-min preconditioning ischemia and subjected to 45-min injurious ischemia 24 hr later. Some animals were treated with the constitutive NOS inhibitor L-nitroarginine (5 mg/kg, i.p.) 1 hr before preconditioning. Retinal layer thicknesses and cell counts were determined one week postischemia in 5-mm thin sections, and flash electroretinograms were obtained at 1 and 7 days postischemia. We confirmed that ischemic preconditioning afforded morphologic and functional protection in the strains of wild-type mice studied. Histopathologic analyses of inducible NOS (iNOS) knockout mice revealed that ischemic preconditioning was completely effective, whereas ischemic tolerance was not achieved in the retinae of endothelial NOS (eNOS) and neuronal NOS (nNOS) knockout mice. The participation of the constitutive NOS enzymes in preconditioning-induced tolerance was confirmed by the finding that administration of the NOS inhibitor L-NA to wild-type mice prior to ischemic preconditioning blocked the development of ischemic tolerance. These cross-validating genetic and pharmacologic findings indicate that NO derived from both eNOS and nNOS is a required molecular signal in the adaptive response to ischemic preconditioning in the retina. q (J.M. Gidday).
Roles of constitutive nitric oxide synthase in postischemic rat retina
Investigative ophthalmology & visual science, 1999
Nitric oxide is a reactive species that could be protective or destructive to the retina depending on the stage of the evolving ischemic process. This study was conducted to obtain a better understanding of the roles of constitutive nitric oxide synthase (cNOS) during reperfusion after ischemia in rat retina. Retinal ischemia was induced for 60 minutes in Sprague-Dawley rats by ligating the optic nerve. Gene expression for endothelial and neuronal nitric oxide synthases (eNOS and nNOS) was studied by reverse transcription-polymerase chain reaction (RT-PCR). To inhibit cNOS, NG-nitro-L-arginine (L-NNA) was injected intraperitoneally four times (every 6 hours) beginning 2 hours after reperfusion, for a total dose of 80 mg/kg. Retinal damage was assessed by the rate of a- and b-wave recovery on electroretinograms and by the thickness of the retinal layers. Retinal circulation and vessel diameter were evaluated by the dye-dilution technique. After ischemia ended, eNOS mRNA initially dec...
The Role of Nitric Oxide and cGMP in Somatostatin's Protection against Retinal Ischemia
Investigative Ophthalmology & Visual Science, 2008
PURPOSE. To investigate whether nitric oxide (NO) and/or cGMP protects the retina from chemical ischemia and underlie somatostatin's neuroprotective effects. METHODS. Eyecups of female Sprague-Dawley rats were incubated with PBS or the chemical ischemia mixture [iodoacetic acid (5 mM)/sodium cyanate (25 mM)] in the absence or presence of (1) arginine (0.05-2.0 mM), the substrate of nitric oxide synthase (NOS); (2) the NO donors sodium nitroprusside (SNP; 0.25-4.0 mM), 3-morpholinosydnonimine (SIN-1; 0.1, 0.3, 1.0 mM), SIN-1 (0.1 mM)/L-cysteine (5 mM, peroxynitrite scavenger), and NONOate (1, 5, 10 ⌴, slow NO releaser); (3) 8-Br-cGMP (0.1, 0.5, 1.0 mM); (4) BIM23014 (sst 2 receptor agonist; 1 M), alone or in the presence of (5) the NOS inhibitor N ␥-monomethyl-L-arginine (NMMA; 0.5 mM); or (6) the guanylyl cyclase inhibitors 1H-[1,2,4]oxadiazolol [4,3-a]quinoxalin-1-one (ODQ;100 M) and NS2028 (50 M) for 60 minutes, at 5%CO 2 /air in 37°C. The effect of SIN-1 (0.1, 0.3, 1.0, or 3.0 mM) on the retina was also examined. Subsequently, the eyecups were fixed and sectioned for choline acetyltransferase (ChAT) immunoreactivity and TUNEL staining. RESULTS. Arginine and SNP had no effect on the chemical ischemia-induced toxicity. SIN-1, NONOate, and 8-Br-cGMP produced a concentration-dependent protective effect, as shown by ChAT immunoreactivity. TUNEL staining also confirmed the neuroprotective effect of these agents. L-Cysteine partially reduced the SIN-1-induced protective effect. SIN-1 alone was toxic only at the highest concentration used (3 mM). NMMA, ODQ, and NS2028 reversed the protective effect of BIM23014. CONCLUSIONS. The results suggest that a NO/peroxynitrite/ cGMP mechanism may be important in the protection of the retina from ischemic insult. Furthermore, the NO/sGC/cGMP pathway is involved in the neuroprotective effects of sst 2 ligands against retinal ischemia.
Inhibition of NMDA receptors and nitric oxide synthase reduces ischemic injury of the retina
European Journal of Pharmacology, 1998
This study was performed to examine the roles of body temperature, NMDA receptors and nitric oxide NO synthase in post-ischemic retinal injury in rats. Cell loss in the ganglion cell layer and thinning of the inner plexiform layer were observed 7 days after ischemia. Cell loss in the ganglion cell layer but not thinning of the inner plexiform layer was reduced by hypothermia during ischemia. Intravenous Ž .
Loss of Inner Retinal Neurons After Retinal Ischemia in Rats
Investigative Ophthalmology & Visual Science, 2014
PURPOSE. Ischemia is a risk factor for eye diseases like ocular vein occlusion or glaucoma. To investigate effects of ischemia-reperfusion (I/R) a lot of different animal models are used, studying one or two different cell types, which creates heterogeneity of data. The aim of this study was to investigate the function and morphology of the whole retina and different retinal cell types in an I/R model. METHODS. I/R was induced by elevating the intraocular pressure in the right eyes of rats. Twenty-one days after ischemia, electroretinogram measurements were performed. Changes in layer thickness were investigated. Changes of RGC, amacrine-, rod bipolar-, and glia cells as well as presence of apoptosis were analyzed immunohistologically. RESULTS. A-wave-and b-wave amplitudes were decreased; histology showed a reduction of RGC-and inner plexiform layer thickness and a 29% loss of RGCs occurred in ischemic eyes (P ¼ 0.016). An increase of apoptotic cells was detected in the GCL and INL of ischemic retinas (P < 0.05). Also, a loss of cholinergic amacrine cells (control: 11 6 1 cells/mm, I/R: 4 6 1 cells/mm, P < 0.001), but no change in rod bipolar cell numbers was noted. CONCLUSIONS. Our study allowed a comparison of the effects of I/R for different retinal cell types. Cells in the outer retina seemed to be more resistant to ischemic damage compared with cells of the inner retina. We hypothesize that a degenerative process, like a secondary wave of apoptosis, occurs 21 days after I/R, causing progressive damage in the retina.
Neuroscience, 2002
AbstractöIn adult Sprague^Dawley rats we have investigated retinal ganglion cell survival after transient intervals of retinal ischemia of 30, 45, 60, 90 or 120 min duration, induced by ligature of the ophthalmic vessels. Animals were killed 5, 7, 14, 21, 30, 60, 90 or 180 days later and densities of surviving retinal ganglion cells were estimated in retinal whole mounts by counting cells labelled with diAsp. This dye was applied, 3 days prior to death, to the ocular stump of the intraorbitally transected optic nerve. We found that retinal ganglion cell loss after retinal ischemia proceeds for di¡erent lengths of time. All the ischemic intervals induced loss of retinal ganglion cells whose severity and duration was related to the length of the ischemic interval. Following 30 or 45 min of ischemia, cell loss lasted 14 days and caused the death of 46 or 50%, respectively, of the population of retinal ganglion cells. Sixty, 90 or 120 min of retinal ischemia were followed by a period of cell loss that lasted up to 90 days and caused the death of 75%, 87% or 99%, respectively, of the population of retinal ganglion cells.
Survey of Ophthalmology
We have investigated in adult Sprague-Dawley rats the neuroprotective effects of two alpha-2-selective agonists [AGN 191,103 (AGN) and brimonidine tartrate (BMD)] on retinal ganglion cell (RGC) survival after transient retinal ischemia. RGCs were labelled with Fluorogold (FG) applied to both superior colliculi. Seven days later, 90 min of retinal ischemia were induced in the left eyes by ligature of the ophthalmic vessels (LOV). In one group of animals, vehicle or AGN (0.01 mg/kg) were administered systemically 1 hr before ischemia. In another group of animals, two 5 microl drops of vehicle, AGN (0.05%) or BMD (0.1%) were administered topically in the left eye 1 hr before ischemia. The animals were processed 7 or 21 days later. RGC survival was estimated by counting FG-labelled cells in 12 standard areas of each retina. In control retinas of systemically pretreated animals, mean densities of labelled RGCs were 2372 +/- 49 cells/mm(2) (mean +/- SEM; n = 6). In experimental retinas of...