Programmed cell death of retinal ganglion cells during experimental glaucoma (original) (raw)
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Journal of Neurotrauma, 1999
We have investigated time course and characteristics of retinal ganglion cell (RGC) death after partial optic nerve injury. In situ end labeling of DNA fragments with the terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine (dUTP)-biotin nick end labeling (TUNEL) method revealed the presence of apoptotic cells on as early as 5 days postcrush with a very high number of TUNEL-positive cells 1 week postinjury. At the ultrastructural level, features of apoptosis were clearly present in the ganglion cell layer at this time point. Moreover, TUNEL-positive cells could be identified as retinal ganglion cells by retrograde labeling with fiuorogold. In addition, DNA laddering characteristic for apoptosis was found 1 week postinjury. A considerable number of TUNELlabeled cells was still found after 2 weeks postinjury. Retinal whole mounts prepared at postlesion days 2-5, however, revealed that many cell bodies with ruptured membranes as evidenced by nucleosomal Sytox staining were present. These cells were also identified as retinal ganglion cells by retrograde labeling with fiuorogold. Moreover, at this early stages of RGC degeneration necrotic cellular profiles could be detected by electron microscopic analysis. Thus, evidence is provided that necrosis and apoptosis follow a distinctly different time course after partial optic nerve injury.
The molecular basis of retinal ganglion cell death in glaucoma
Glaucoma is a group of diseases characterized by progressive optic nerve degeneration that results in visual field loss and irreversible blindness. A crucial element in the pathophysiology of all forms of glaucoma is the death of retinal ganglion cells (RGCs), a population of CNS neurons with their soma in the inner retina and axons in the optic nerve. Strategies that delay or halt RGC loss have been recognized as potentially beneficial to preserve vision in glaucoma; however, the success of these approaches depends on an in-depth understanding of the mechanisms that lead to RGC dysfunction and death. In recent years, there has been an exponential increase in valuable information regarding the molecular basis of RGC death stemming from animal models of acute and chronic optic nerve injury as well as experimental glaucoma. The emerging landscape is complex and points at a variety of molecular signals e acting alone or in cooperation e to promote RGC death. These include: axonal transport failure, neurotrophic factor deprivation, toxic pro-neurotrophins, activation of intrinsic and extrinsic apoptotic signals, mitochon-drial dysfunction, excitotoxic damage, oxidative stress, misbehaving reactive glia and loss of synaptic connectivity. Collectively, this body of work has considerably updated and expanded our view of how RGCs might die in glaucoma and has revealed novel, potential targets for neuroprotection.
Experimental Eye Research, 2006
Glaucoma is a chronic and progressive optic nerve neuropathy involving the death of retinal ganglion cells (RGCs). Elevated intraocular pressure (IOP) is considered to be the major risk factor associated with the development of this neuropathy. The objective of the present study was to compare the effects on RGC survival of three different experimental methods to induce chronic elevation of IOP in rats. These methods were: (i) injections of latex microspheres into the eye anterior chamber; (ii) injections into the anterior chamber of a mixture of microspheres plus hydroxypropylmethylcellulose (HPM) and (iii) cauterization of three episcleral veins. The IOP of right (control) and left (glaucomatous) eyes was measured with an applanation tonometer in awake animals. Thirteen to 30 weeks later, RGCs were retrogradely labeled with 3% fluorogold. Subsequently, we analyzed the density of RGCs, as well as the major axis length and area of RGC soma resulting from the application of each method. A significant increase in IOP was found following application of each of the three methods. Cell death was evident in the glaucomatous eyes as compared to controls. However, no statistical differences were found between the extent of cell death associated with each of the three methods. IOP increase also induced a significant increase in the size of the soma of the remaining RGCs. In conclusion, the three methods used to increase IOP induce a similar degree of RGC death. Moreover, the extent of cell death was similar when the retinas were maintained under conditions of elevated IOP for 24 weeks in comparison to 13 weeks.
Regulation of cell death and survival pathways in experimental glaucoma
Experimental Eye Research, 2007
This study investigates cell death and survival pathways in experimental glaucoma using the translimbal photocoagulation laser model. Glaucoma was induced unilaterally in 79 Wistar rats and all eyes developed elevated intraocular pressure. The involvement of caspase-3, p-AKT and members of the MAP kinase pathway was evaluated by immunohistochemistry and Western blotting. We found that protein levels of caspase-3 were elevated from day 15 to day 30 ( p < 0.05). All investigated members of the MAP kinase pathway were significantly activated. P-SAPK/ JNK activation began on day 2, reaching a 6-fold elevation by day 30 ( p < 0.05). The p-P38 level was elevated on days 2 and 8 ( p < 0.05), followed by a decrease to baseline on day 15. The level of p-ATF-2, the substrate of P38, was significantly elevated at all time points tested, up to day 30 ( p < 0.05). P-ERK was detected early ( p < 0.05) on day 1, returning to normal on day 15. The pro-survival protein p-Akt, a member of the PI3-kinase survival pathway, was also detected early on day 1 ( p < 0.05) returning to baseline on day 8 and remaining unchanged up to 64 days. We conclude that retinal ganglion cell death in glaucoma involves activation, at different time points, of multiple pro-apoptotic pathways (the MAP kinase pathway and the caspase family) and pro-survival (PI-3 Kinase/ Akt and p-ERK).
Bio-tactics for neuroprotection of retinal ganglion cells in the treatment of glaucoma
Life Sciences, 2020
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Caspase inhibitors block the retinal ganglion cell death following optic nerve transection
Molecular Brain Research, 1999
Retinal ganglion cells die by apoptosis following axotomy. The molecular mechanisms of the retinal ganglion cell death are not well understood. In the present study using RT-PCR and in situ hybridization techniques we demonstrated that levels of mRNA for Bcl-2 and Bcl-x decreased after axotomy. Bax levels remained high until 4 days after axotomy, decreased by day 7 and remained low up to day 10. CPP32 levels increased at day 7 and remained high after optic nerve cut. We studied whether inhibitors of CPP32rcaspase would save Ž. Ž the axotomy induced ganglion cell death. DEVD-CHO Ac-Asp-Glu-Val-aspartic acid aldehyde and DEVD-FMK Z-Asp-Glu-Val-Asp-. FMK , caspase inhibitors, when administered intraocularly at the time of optic nerve cut, at days 3 and 7 protect about 30-35% the ganglion cells from death. We further demonstrated that the number of reactive microglia decrease in the retina when the inhibitors were given as compared with retina where no inhibitors were given. The present data offers new avenues for studying the complex interactions between the retinal ganglion cell death and the activation of resident microgliarmacrophages.
Molecular vision, 2013
The pathogenesis of retinal ganglion cell loss in glaucoma remains incompletely understood. Current evidence suggests that the optic nerve (ON) head and axons are the main site of injury in glaucoma. This study compares changes in prosurvival and proapoptotic gene expression in ONs with those in retinas in three models of ocular injury, specifically ON transection (ONTX), N-methyl-D-aspartate (NMDA) retinal toxicity, and experimental glaucoma. Rats (n=240) were divided into three models (ONTX, NMDA retinal toxicity, and experimental glaucoma). The experimental model was induced unilaterally and the contralateral eye served as control. Rats were sacrificed at 4-5 different time points specific for each model. ONs and retinas were isolated for real-time PCR investigation of expression of selected genes. Immunohistochemistry localized changes in inhibitor of apoptosis (IAP)-1 and X-linked IAP (XIAP) proteins in retinas and ONs. Colocalization was measured using Imaris colocalization so...
Age-dependent susceptibility of the retinal ganglion cell layer to cell death.
Abstract PURPOSE: The purpose of this study was to determine the susceptibility of the retinal ganglion cell layer (GCL) to apoptosis after optic nerve transection and excitotoxic stimulus and to investigate the regulation of apoptosis in the GCL during development. The authors also sought to determine the role played by caspases in cell death and their expression during development. METHODS: TdT-mediated dUTP nick end labeling (TUNEL) was used to identify cells undergoing apoptosis during mouse retinal development from postnatal day (P)3 to P5 and in retinal explant sections under various conditions. The expression of active caspases was determined by immunohistochemistry (IHC) using an antibody that detects the cleaved large subunit. IHC was also used to detect the expression levels of procaspase-3, procaspase-9, and Apaf-1 in P6 and P60 whole eye sections. Retinal ganglion cells at ages P6 and P60 were purified by immunopanning, total RNA was extracted, and mRNA levels of the above proteins were determined by semiquantitative PCR. RESULTS: After optic nerve transection, a significant number of TUNEL-positive cells were seen 24 hours after lesion in P6 retinas. This death was caspase dependent, as shown by IHC and caspase inhibition with zVAD-fmk. In contrast, adult GCL was resistant to apoptosis under these conditions. Similarly, after excitotoxic stimulus, the GCL of the P6 retinas underwent apoptosis at 6 hours and was caspase dependent, whereas adult GCL was resistant. Developmental apoptosis in the GCL between P2 and P6 was shown to involve caspase-3 and caspase-9. Significant downregulation of Apaf-1 and caspase-3 was detected in the P60 GCL at both the mRNA and the protein levels. CONCLUSIONS: Adult GCL is more resistant to apoptosis than neonatal GCL after ON transection and excitotoxic stimulus. The expression of caspase-3 and Apaf-1 is significantly reduced in adult GCL. The authors suggest that age-dependent susceptibility to apoptosis may be caused by this reduced expression.
An optic nerve crush injury murine model to study retinal ganglion cell survival
Journal of visualized experiments : JoVE, 2011
Injury to the optic nerve can lead to axonal degeneration, followed by a gradual death of retinal ganglion cells (RGCs), which results in irreversible vision loss. Examples of such diseases in human include traumatic optic neuropathy and optic nerve degeneration in glaucoma. It is characterized by typical changes in the optic nerve head, progressive optic nerve degeneration, and loss of retinal ganglion cells, if uncontrolled, leading to vision loss and blindness. The optic nerve crush (ONC) injury mouse model is an important experimental disease model for traumatic optic neuropathy, glaucoma, etc. In this model, the crush injury to the optic nerve leads to gradual retinal ganglion cells apoptosis. This disease model can be used to study the general processes and mechanisms of neuronal death and survival, which is essential for the development of therapeutic measures. In addition, pharmacological and molecular approaches can be used in this model to identify and test potential thera...
Alternative Programs of Cell Death in Developing Retinal Tissue
Journal of Biological Chemistry, 2003
We examined cell death in developing retinal tissue, following inhibition of protein synthesis, which kills undifferentiated post-mitotic cells. Ultrastructural features were found of both apoptosis and autophagy. Only approximately half of the degenerating cells were either terminal dUTP nick-end labeling (TUNEL)-positive or reacted with antibodies specific for activated caspases-3 or-9. Bongkrekic acid completely inhibited any appearance of cell death, whereas inhibitors of autophagy, caspases-9 or-3, prevented only TUNEL-positive cell death. Interestingly, inhibition of caspase-6 blocked TUNEL-negative cell death. Simultaneous inhibition of caspases-9 and-6 prevented cell death almost completely, but degeneration dependent on autophagy/ caspase-9 still occurred under inhibition of both caspases-3 and-6. Thus, inhibition of protein synthesis induces in the developing retina various post-translational, mitochondria-dependent pathways of cell death. Autophagy precedes sequential activation of caspases-9 and-3, and DNA fragmentation, whereas, in parallel, caspase-6 leads to a TUNEL-negative form of cell death. Additional mechanisms of cell death may be engaged upon selective caspase inhibition.