Apoptotic Death Of Retinal Cells Research Articles

Calcium-permeable α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid Receptors Trigger Neuronal Nitric-oxide Synthase Activation to Promote Nerve Cell Death in an Src Kinase-dependent Fashion

In the retina information decoding is dependent on excitatory neurotransmission and is critically modulated by AMPA glutamate receptors. The Src-tyrosine kinase has been implicated in modulating neurotransmission in CNS. Thus, our main goal was to correlate AMPA-mediated excitatory neurotransmission with the modulation of Src activity in retinal neurons. Cultured retinal cells were used to access the effects of AMPA stimulation on nitric oxide (NO) production and Src phosphorylation. 4-Amino-5-methylamino-2',7'-difluorofluorescein diacetate fluorescence mainly determined NO production, and immunocytochemistry and Western blotting evaluated Src activation. AMPA receptors activation rapidly up-regulated Src phosphorylation at tyrosine 416 (stimulatory site) and down-regulated phosphotyrosine 527 (inhibitory site) in retinal cells, an effect mainly mediated by calcium-permeable AMPA receptors. Interestingly, experiments confirmed that neuronal NOS was activated in response to calcium-permeable AMPA receptor stimulation. Moreover, data suggest NO pathway as a key regulatory signaling in AMPA-induced Src activation in neurons but not in glial cells. The NO donor SNAP (S-nitroso-N-acetyl-DL-penicillamine) and a soluble guanylyl cyclase agonist (YC-1) mimicked AMPA effect in Src Tyr-416 phosphorylation, reinforcing that Src activation is indeed modulated by the NO pathway. Gain and loss-of-function data demonstrated that ERK is a downstream target of AMPA-induced Src activation and NO signaling. Furthermore, AMPA stimulated NO production in organotypic retinal cultures and increased Src activity in the in vivo retina. Additionally, AMPA-induced apoptotic retinal cell death was regulated by both NOS and Src activity. Because Src activity is pivotal in several CNS regions, the data presented herein highlight that Src modulation is a critical step in excitatory retinal cell death.

Intravenously Administered Anti-recoverin Antibody Alone Does Not Pass through the Blood-Retinal Barrier

PurposeCancer-associated retinopathy is a paraneoplastic retinal degeneration which may primarily result from auto-immune mediated apoptosis. It has been hypothesized that high titer of auto-antibodies are able to cross the blood-retinal barrier (BRB) and to enter retinal cells to activate apoptotic pathway which has been already well-established. However, it still remains to be elucidated whether auto-antibodies could cross BRB in the retina. Herein, we demonstrated that intravenously administrated anti-recoverin antibodies could not pass through BRB and not lead to retinal cell death.MethodsAnti-recoverin antibody was intravenously injected to C57BL/6 mice, which were sacrificed 1 and 7 days to obtain eye. Vascular endothelial growth factor was intravitreally injected to induce BRB breakdown, which was confirmed by fluorescein angiography and western blotting for zonula occludens (ZO)-1, ZO-2 and occludin. To investigate the location of anti-recoverin antibody in the retina, immunofluorescein was performed. The retinal toxicity of intravenous anti-recoverin antibody was evaluated by histological examination and transferase-mediated dUTP nick-end labeling. Immunofluorescein staining for glial fibrillary acidic protein was done to address glial activation as well.ResultsIntravenously administrated anti-recoverin antibodies were exclusively distributed on retinal vessels which were co-localized with CD31, and led to neither increase of glial fibrillary acidic protein expression, as an indicator of retinal stress, nor apoptotic retinal cell death. Moreover, even in the condition of vascular endothelial growth factor-induced BRB breakdown, anti-recoverin antibodies could not migrate across BRB and still remained on retinal vessels without retinal cytotoxicity.ConclusionsOur results suggest that high titer of intravascular anti-recoverin antibodies could not penetrate into the retina by themselves, and BRB breakdown mediated by dysregulation of tight junction might not be sufficient to allow anti-recoverin antibodies to pass through BRB.

Zebrafish Rpgr is required for normal retinal development and plays a role in dynein-based retrograde transport processes

Mutations in the human RPGR gene cause one of the most common and severe forms of inherited retinal dystrophy, but the function of its protein product remains unclear. We have identified two genes resembling human RPGR (ZFRPGR1, ZFRPGR2) in zebrafish (Danio rerio), both of which are expressed within the nascent and adult eye as well as more widely during development. ZFRPGR2 appears to be functionally orthologous to human RPGR, because it encodes similar protein isoforms (ZFRPGR2(ORF15), ZFRPGR2(ex1-17)) and causes developmental defects similar to other ciliary proteins, affecting gastrulation, tail and head development after morpholino-induced knockdown (translation suppression). These defects are consistent with a ciliary function and were rescued by human RPGR but not by RPGR mutants causing retinal dystrophy. Unlike mammals, RPGR knockdown in zebrafish resulted in both abnormal development and increased cell death in the dysplastic retina. Developmental abnormalities in the eye included lamination defects, failure to develop photoreceptor outer segments and a small eye phenotype, associated with increased cell death throughout the retina. These defects could be rescued by expression of wild-type but not mutant forms of human RPGR. ZFRPGR2 knockdown also resulted in an intracellular transport defect affecting retrograde but not anterograde transport of organelles. ZFRPGR2 is therefore necessary both for the normal differentiation and lamination of the retina and to prevent apoptotic retinal cell death, which may relate to its proposed role in dynein-based retrograde transport processes.

How it appears: electron microscopic evaluation of internal limiting membrane specimens obtained during brilliant blue G assisted macular hole surgery

The intravitreal application of the novel dye, brilliant blue G (BBG), has recently been suggested to facilitate macular hole and epiretinal membrane surgery because BBG has been shown to selectively...

Resveratrol prevents antibody-induced apoptotic death of retinal cells through upregulation of Sirt1 and Ku70

BackgroundTo determine whether resveratrol, a natural plant-derived drug, has protective effects against antibody-induced apoptosis of retinal cells in vitro and to provide insights on the mechanism of resveratrol protection.FindingsE1A.NR3 retinal cells pretreated with 40 μM resveratrol were grown in the presence of anti-recoverin (Rec-1), anti-enolase (Enol-1) antibodies, and normal purified immunoglobulins. When the cells were exposed to resveratrol before treatment with Enol-1 or Rec-1 antibodies, 30–55% more cells survived compared to the resveratrol-untreated cells. Western blotting showed a reduction in proapoptotic protein Bax in the cytoplasm and mitochondria of resveratrol-treated cells. Resveratrol-pretreated cells also showed a significant decrease in intracellular calcium and an inhibition of caspase-3 activity as compared to the untreated cells. Sirt1 expression was greatly reduced in the cells grown in the presence of Rec-1 and Enol-1, but it increased about five times in the resveratrol-pretreated cells. Immunocytochemistry revealed that Sirt1 expression in the cytoplasm and nucleus was colocalized with Ku70 expression in resveratrol-treated cells, suggesting possible interaction with each other in the cell. The pattern of the Ku70 cellular localization also overlapped with the Bax cellular localization in treated and untreated cells.ConclusionIn vitro protection of retinal cells from apoptosis by resveratrol occurred through multiple early molecular events, such as reduction of intracellular calcium levels, down-regulation of Bax, up-regulation of Sirt1 and Ku70 activities, and inhibition of caspase-3 activity. These findings will help designing future in vivo and pre-clinical treatments for autoimmune retinopathies.

The role of clusterin in retinal development and free radical damage

Aim:To assess the role of clusterin in retinal vascular development and in free radical damage in vivo and in vitro.Methods:The expression of clusterin, von Willebrand factor (vWF), flk-1, heat shock...

Naturally occurring rhodopsin mutation in the dog causes retinal dysfunction and degeneration mimicking human dominant retinitis pigmentosa.

Rhodopsin is the G protein-coupled receptor that is activated by light and initiates the transduction cascade leading to night (rod) vision. Naturally occurring pathogenic rhodopsin (RHO) mutations have been previously identified only in humans and are a common cause of dominantly inherited blindness from retinal degeneration. We identified English Mastiff dogs with a naturally occurring dominant retinal degeneration and determined the cause to be a point mutation in the RHO gene (Thr4Arg). Dogs with this mutant allele manifest a retinal phenotype that closely mimics that in humans with RHO mutations. The phenotypic features shared by dog and man include a dramatically slowed time course of recovery of rod photoreceptor function after light exposure and a distinctive topographic pattern to the retinal degeneration. The canine disease offers opportunities to explore the basis of prolonged photoreceptor recovery after light in RHO mutations and determine whether there are links between the dysfunction and apoptotic retinal cell death. The RHO mutant dog also becomes the large animal needed for preclinical trials of therapies for a major subset of human retinopathies.