dizocilpine-maleate and Retinal-Diseases

B-N-methylamino-L-alanine (BMAA), a cyanotoxin produced by most cyanobacteria, has been proposed to cause long term damages leading to neurodegenerative diseases, including Amyotrophic Lateral Sclerosis/Parkinsonism Dementia complex (ALS/PDC) and retinal pathologies. Previous work has shown diverse mechanisms leading to BMAA-induced degeneration; however, the underlying mechanisms of toxicity affecting retina cells are not fully elucidated. We here show that BMAA treatment of rat retina neurons in vitro induced nuclear fragmentation and cell death in both photoreceptors (PHRs) and amacrine neurons, provoking mitochondrial membrane depolarization. Pretreatment with the N-Methyl-D-aspartate (NMDA) receptor antagonist MK-801 prevented BMAA-induced death of amacrine neurons, but not that of PHRs, implying activation of NMDA receptors participated only in amacrine cell death. Noteworthy, BMAA stimulated a selective axonal outgrowth in amacrine neurons, simultaneously promoting growth cone destabilization. BMAA partially decreased the viability of Müller glial cells (MGC), the main glial cell type in the retina, induced marked alterations in their actin cytoskeleton and impaired their capacity to protect retinal neurons. BMAA also induced cell death and promoted axonal outgrowth in differentiated rat pheochromocytoma (PC12) cells, implying these effects were not limited to amacrine neurons. These results suggest that BMAA is toxic for retina neurons and MGC and point to the involvement of NMDA receptors in amacrine cell death, providing new insight into the mechanisms involved in BMAA neurotoxic effects in the retina.

Topics: Amino Acids, Diamino; Animals; Animals, Newborn; Cell Survival; Cyanobacteria Toxins; Dizocilpine Maleate; DNA Fragmentation; Ependymoglial Cells; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Membrane Potential, Mitochondrial; Rats; Rats, Wistar; Reactive Oxygen Species; Receptors, N-Methyl-D-Aspartate; Retinal Diseases; Retinal Neurons

In this study, we examined the effect of SUN N8075, a radical scavenger with neuroprotective properties, on murine retinal damage induced by intravitreous injection of N-methyl-d-aspartate (NMDA) or high-intraocular pressure (IOP). In both models, systemic administration of SUN N8075 decreased the cell loss in the ganglion cell layer (GCL) after retinal damage occurred. Moreover, SUN N8075 reduced the number of apoptotic cells and the expression of an oxidative stress marker in GCL in the NMDA model. These findings suggest that SUN N8075 has a neuroprotective effect against retinal damage, presumably via the radical scavenging effect.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aniline Compounds; Animals; Cell Death; Deoxyguanosine; Disease Models, Animal; Dizocilpine Maleate; In Situ Nick-End Labeling; Mice; N-Methylaspartate; Neurons; Neuroprotective Agents; Ocular Hypertension; Piperazines; Retina; Retinal Diseases; Time Factors

A new experimental glaucoma model was developed by using an ex vivo rat retinal preparation to examine the effects of elevated hydrostatic pressure on retinal morphology and glutamine synthetase (GS) activity.. Ex vivo rat retinas were exposed to elevated hydrostatic pressure for 24 hours in the presence of glutamate or glutamate receptor antagonists and examined histologically. GS activity was assessed by colorimetric assay.. Pressure elevation induced axonal swelling in the nerve fiber layer. Axonal swelling was prevented by a combination of non-N-methyl-d-aspartate (non-NMDA) receptor antagonist and an NMDA receptor antagonist, indicating that the damage results from activation of both types of glutamate receptor. When glial function was preserved, the typical changes induced by glutamate consisted of reversible Müller cell swelling resulting from excessive glial glutamate uptake. The irreversible Müller cell swelling in hyperbaric conditions may indicate that pressure disrupts glutamate metabolism. Indeed, elevated pressure inhibited GS activity. In addition, glutamate exposure after termination of pressure exposure exhibited apparent Müller cell swelling.. These results suggest that the neural degeneration observed during pressure elevation is caused by impaired glial glutamate metabolism after uptake.

Topics: Animals; Axons; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Fluorescent Antibody Technique, Indirect; Glial Fibrillary Acidic Protein; Glutamate-Ammonia Ligase; Glutamic Acid; Hydrostatic Pressure; Male; Optic Disk; Optic Nerve Diseases; Rats; Rats, Sprague-Dawley; Receptors, Glutamate; Retinal Diseases; Retinal Ganglion Cells

Loss of retinal ganglion cells occurs in a variety of pathological conditions, including central retinal artery occlusion, diabetes and glaucoma. Using an experimental model of retinal ischemia induced by transiently raise the intraocular pressure (IOP), In this study, we report the original observation that ischemic retinal ganglion cells death is associated with the transient deactivation of the pro-survival kinase Akt and activation of GSK-3beta followed, during reperfusion, by a longer lasting, PI3K-dependent, activation of Akt and phosphorylation of GSK-3beta. Under these experimental conditions, retinal ischemia induced the expression of Bad, a pro-apoptotic protein, member of the Bcl-2 family. The detrimental effects yielded by the ischemic stimulus were minimized by intravitreal administration of the NMDA receptor antagonist, MK801, that reduced the expression of Bad and significantly increased Akt phosphorylation. In conclusion, our present results contribute to unravel the mechanisms underlying retinal damage by high IOP-induced transient ischemia in rat. In addition, these data implicate the pro-survival PI3K/Akt pathway and the observed reduced expression of Bad in the neuroprotection afforded by MK801.

Topics: Analysis of Variance; Androstadienes; Animals; bcl-Associated Death Protein; Cell Death; Chromones; Dizocilpine Maleate; Enzyme Inhibitors; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Intraocular Pressure; Ischemia; Male; Morpholines; Oncogene Protein v-akt; Proto-Oncogene Proteins c-bcl-2; PTEN Phosphohydrolase; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Reperfusion Injury; Retinal Diseases; Serine; Signal Transduction; Time Factors; Wortmannin

Glutamate is thought to participate in a variety of retinal degenerative disorders. However, when exposed to glutamate at concentrations up to 1 mM, ex vivo rat retinas typically exhibit Müller cell swelling, but not excitotoxic neuronal damage. This Müller cell swelling is reversible following glutamate washout, indicating that the glial edema is not required for glutamate-induced neuronal injury. It is unclear whether glutamate directly induces the Müller cell swelling or whether a metabolite of glutamate such as glutamine acts as an osmolyte to generate the cellular edema. To examine this issue, ex vivo rat retinas were exposed to 1 mM glutamate or 1 mM glutamine and were evaluated histologically. Glutamate was also combined with 1 mM ammonia or with methionine sulfoximine (MSO), an inhibitor of glutamine synthetase, the enzyme that catalyzes the synthesis of glutamine from glutamate and ammonia. Glutamate-mediated Müller cell swelling was blocked by co-administration of ammonia and the reversibility of Müller cell swelling was inhibited by MSO administered following glutamate exposure. Glutamine alone failed to induce Müller cell swelling. These results indicate that glutamate-mediated Müller cell swelling is unlikely to result from glutamine accumulation. Rather, conversion of glutamate to glutamine in a reaction involving ammonia helps reverse Müller cell swelling following exposure to exogenous glutamate.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Ammonia; Animals; Cell Death; Cell Size; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Glutamate-Ammonia Ligase; Glutamic Acid; Glutamine; Hypothermia; Methionine Sulfoximine; Neurons; Rats; Rats, Sprague-Dawley; Retina; Retinal Diseases; Tissue Fixation

Excessive activation of poly(ADP-ribose) polymerase (PARP), a nuclear enzyme that is activated by DNA damage, leads to neuronal cell death through depletion of ATP. The purpose of this study was to determine whether inhibition of PARP has some neuroprotective effects on the N-methyl-D-aspartate (NMDA)-induced functional and morphological injury to the rabbit retina.. Visually evoked potentials (VEPs) were recorded at different times after an intravitreal injection of NMDA (200, 660, and 2000 nmol) alone, or NMDA with 3-aminobenzamide (ABA, 200 nmol), a PARP inhibitor, or with MK-801 (200 nmol), an NMDA antagonist. The physiological changes were followed for 2 weeks, after which the eyes were enuculeated and prepared for histological examinations.. Intravitreal injections of NMDA reduced the amplitudes of rabbit VEPs and the number of cells in the retinal ganglion cell layer in a dose-dependent manner. No significant changes could be detected in the bright-flash electroretinograms (ERGs). Simultaneous injection of MK-801 (200 nmol) significantly diminished the changes induced by intravitreal NMDA. 3-Aminobenzamide (ABA) (200 nmol) also suppressed these changes, but its effects were less than those of MK-801.. NMDA-induced retinal damage can be detected by VEPs, and PARP inhibition has some neuroprotective effects on the NMDA-induced retinal damage.

Topics: Animals; Benzamides; Cell Count; Cytoprotection; Dizocilpine Maleate; Dose-Response Relationship, Drug; Electroretinography; Enzyme Activation; Enzyme Inhibitors; Evoked Potentials, Visual; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Immunoenzyme Techniques; Injections; N-Methylaspartate; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Rabbits; Retina; Retinal Diseases; Retinal Ganglion Cells; Vitreous Body

Following transient retinal ischemia, there is neuronal cell death, breakdown of the blood-retinal barrier, activation of microglia and infiltration by hematogenous cells. The early appearance of cyclooxygenase-2 (COX-2) following an ischemic event may be responsible for signaling some of the responses that lead to neurodegeneration. We have determined the time courses of changes in protein levels and cellular localizations of COX-2 in the rat retina after transient ischemia. In the normal rat retina, COX-2 immunoreactivity was present in neurons in the INL and ganglion cell layer (GCL). Six to 12 hr after ischemia, COX-2 immunoreactivity was upregulated/induced in horizontal cells, amacrine cells, retinal ganglion cells, displaced amacrine cells of the INL and GCL, and Müller cells. The NMDA-receptor antagonist, MK801, blocked the increased COX-2 protein level and COX-2 immunoreactivity in neurons of the INL and GCL, but did not affect the induction of COX-2 in Müller cells after ischemia. The selective COX-2 inhibitor, SC-58236, prevented apoptotic cell death and was neuroprotective against loss of retinal ganglion cells after ischemia. Following transient ischemia, the selective COX-2 inhibitor did not prevent breakdown of the blood-retinal barrier or activation of microglia. However, the selective COX-2 inhibitor reduced infiltration of hematogenous cells into the retina. These results suggest that the early, increased activity of COX-2 signals neurodegenerative events following retinal ischemia.

Topics: Animals; Blood-Retinal Barrier; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Immunohistochemistry; In Situ Nick-End Labeling; Ischemia; Isoenzymes; Male; Microglia; Prostaglandin-Endoperoxide Synthases; Pyrazoles; Rats; Rats, Wistar; Retinal Diseases; Retinal Ganglion Cells; Retinal Vessels; Sulfonamides; Up-Regulation

The aim of this study was to examine whether the antioxidant alpha-lipoic acid protects retinal neurons from ischemia-reperfusion injury. Rats were injected intraperitoneally with either vehicle or alpha-lipoic acid (100 mg/kg) once daily for 11 days. On the third day, ischemia was delivered to the rat retina by raising the intraocular pressure above systolic blood pressure for 45 min. The electroretinogram was measured prior to ischemia and 5 days after reperfusion. Rats were killed 5 or 8 days after reperfusion and the retinas were processed for immunohistochemistry and for determination of mRNA levels by RT-PCR. Ischemia-reperfusion caused a significant reduction of the a- and b-wave amplitudes of the electroretinogram, a decrease in nitric oxide synthase and Thy-1 immunoreactivities, a decrease of retinal ganglion cell-specific mRNAs and an increase in bFGF and CNTF mRNA levels. All of these changes were clearly counteracted by alpha-lipoic acid. Moreover, in mixed rat retinal cultures, alpha-lipoic acid partially counteracted the loss of GABA-immunoreactive neurons induced by anoxia. The results of the study demonstrate that alpha-lipoic acid provides protection to the retina as a whole, and to ganglion cells in particular, from ischemia-reperfusion injuries. alpha-Lipoic acid also displayed negligible affinity for voltage-dependent sodium and calcium channels.

Topics: Anesthetics, Local; Animals; Antioxidants; Binding, Competitive; Brain-Derived Neurotrophic Factor; Calcium; Calcium Channel Blockers; Cells, Cultured; Ciliary Neurotrophic Factor; Diltiazem; Dizocilpine Maleate; DNA Primers; Dose-Response Relationship, Drug; Drug Interactions; Electroretinography; Fibroblast Growth Factors; Glial Fibrillary Acidic Protein; Glyceraldehyde-3-Phosphate Dehydrogenases; N-Methylaspartate; Nifedipine; Rats; Reperfusion Injury; Retinal Diseases; Reverse Transcriptase Polymerase Chain Reaction; Rhodopsin; RNA, Messenger; Sodium; Tetrodotoxin; Thioctic Acid; Thy-1 Antigens; Veratridine

Two types of experiment were performed to examine the role of interleukin-1beta in ischemia-induced damage in the rat retina. In the in vivo study, enzyme-linked immunosorbent assay was used to investigate the expression of immunoreactive interleukin-1beta in the rat retina following a hypertension-induced ischemia/reperfusion, while the effect of a recombinant human interleukin-1 receptor antagonist or an anti-interleukin-1beta neutralizing antibody on the ischemia-induced damage was examined histologically. A transient increase in the expression of immunoreactive interleukin-1beta was observed in the retina 3-12 hr after reperfusion, and morphometric evaluation at 7 days after the ischemia showed a decrease in cell numbers in the ganglion cell layer and a decreased thickness of the inner plexiform layer with no change in the other retinal layers. Intravitreal injection of interleukin-1 receptor antagonist (1 or 10 ng per eye) or anti-interleukin-1beta antibody (50 or 500 ng per eye) 5 min before the onset of the ischemia reduced the damage. In the in vitro study, interleukin-1 receptor antagonist (500 ng ml(-1)) significantly reduced glutamate-induced neurotoxicity in rat cultured retinal neurons. These results suggest that interleukin-1 plays an important role in mediating ischemic and excitotoxic damage in the retina, and that interleukin-1 inhibitors may be therapeutically useful against neuronal injury caused by optic nerve or retinal diseases such as glaucoma and central retinal artery or vein occlusion.

Topics: Analysis of Variance; Animals; Cell Count; Cell Survival; Cells, Cultured; Choroid Plexus; Dizocilpine Maleate; Enzyme-Linked Immunosorbent Assay; Ganglia, Sensory; Glutamic Acid; Interleukin-1; Male; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Retina; Retinal Diseases

Accumulated evidence has shown that apoptosis and necrosis contribute to neuronal death after ischemia. The present study was performed to study the temporal and spatial patterns of neuronal necrosis and apoptosis after ischemia in retina and to outline mechanisms underlying necrosis and apoptosis.. Retinal ischemia was induced by increasing intraocular pressure to a range of 160 mm Hg to 180 mm Hg for 90 minutes in adult rats. The patterns of neuronal cell death were determined using light and electron microscopy and were visualized by TdT-dUTP nick-end labeling (TUNEL). The mRNA expression profile of p53 was examined using reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization histochemistry. Immunohistochemistry was performed using anti-p53, anti-microtubule associated protein-2, and anti-glial fibrillary acidic protein antibodies.. Within 4 hours after ischemia, neurons in the inner nuclear cell layer (INL) and ganglion cell layer (GCL) underwent marked necrosis, made apparent by swelling of the cell body and mitochondria, early fenestration of the plasma membrane, and irregularly scattered condensation of nuclear chromatin. After 3 days, the INL and GCL neurons showed further degeneration through apoptosis marked by cell body shrinkage, aggregation, and condensation of nuclear chromatin. Apoptotic neurons were also observed sparsely in the outer nuclear cell layer. Intravitreal injections of MK-801 prevented early neuronal degeneration after ischemia. Of note, mRNA and protein levels of p53, the tumor suppressor gene known to induce apoptosis, were increased in the retinal areas undergoing apoptosis 1 to 3 days after ischemic injury.. Ischemia produces the N-methyl-D-aspartate-mediated necrosis and slowly evolving apoptosis of neurons in the retina. The latter may depend on the expression of the p53 proapoptosis gene.

Topics: Animals; Apoptosis; Dizocilpine Maleate; DNA Primers; Excitatory Amino Acid Antagonists; Glial Fibrillary Acidic Protein; In Situ Hybridization; In Situ Nick-End Labeling; Ischemia; Male; Microtubule-Associated Proteins; Necrosis; Nerve Degeneration; Neurons; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Retina; Retinal Diseases; Retinal Vessels; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tumor Suppressor Protein p53

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 injection of dizocilpine (MK-801) or Nomega-nitro-L-arginine methyl ester (L-NAME) prior to ischemia ameliorated retinal injury. These results suggest that activation of NO synthase following NMDA receptor stimulation is involved in ischemia-induced retinal injury.

Topics: Animals; Body Temperature; Dizocilpine Maleate; Enzyme Inhibitors; Ischemia; Male; Neuroprotective Agents; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Retina; Retinal Diseases; Retinal Vessels

Laser photocoagulation treatment of the central retina is often complicated by an immediate side effect of visual impairment, caused by the unavoidable laser-induced destruction of the normal tissue lying adjacent to the lesion and not affected directly by the laser beam. Furthermore, accidental laser injuries are at present untreatable. A neuroprotective therapy for salvaging the normal tissue might enhance the benefit obtained from treatment and allow safe perifoveal photocoagulation. We have developed a rat model for studying the efficacy of putative neuroprotective compounds in ameliorating laser-induced retinal damage. Four compounds were evaluated: the corticosteroid methylprednisolone, the glutamate-receptor blocker MK-801, the anti-oxidant enzyme superoxide dismutase, and the calcium-overload antagonist flunarizine. The study was carried out in two steps: in the first, the histopathological development of retinal laser injuries was studied. Argon laser lesions were inflicted in the retinas of 18 pigmented rats. The animals were killed after 3, 20 or 60 days and their retinal lesions were evaluated under the light microscope. The laser injury mainly involved the outer layers of the retina, where it destroyed significant numbers of photoreceptor cells. Over time, evidence of two major histopathological processes was observed: traction of adjacent normal retinal cells into the central area of the lesion forming an internal retinal bulging, and a retinal pigmented epithelial proliferative reaction associated with subretinal neovascularization and invasion of the retinal lesion site by phagocytes. The neuroprotective effects of each of the four compounds were verified in a second step of the study. For each drug tested, 12 rats were irradiated with argon laser inflictions: six of them received the tested agent while the other six were treated with the corresponding vehicle. Twenty days after laser exposure, the rats were killed and their lesions were subjected to image-analysis morphometry. The extent of retinal destruction was assessed by measuring the lesion diameter and the amount of photoreceptor cell loss in the outer nuclear layer. Methylprednisolone and MK-801 were shown to ameliorate laser-induced retinal damage, whereas both superoxide dismutase and flunarizine were ineffective. Furthermore, MK-801 diminished the proliferative reaction of the retinal pigment epithelial cells. On the basis of our results we suggest that the pigmented rat model

Topics: Animals; Calcium Channel Blockers; Cell Division; Dizocilpine Maleate; Flunarizine; Laser Coagulation; Male; Methylprednisolone; Neuroprotective Agents; Photoreceptor Cells; Rats; Rats, Inbred Strains; Retina; Retinal Diseases; Superoxide Dismutase; Time Factors