VEGFD Protects Retinal Ganglion Cells and, consequently, Capillaries against Excitotoxic Injury.
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ABSTRACT:
SUBMITTER: Schluter A
PROVIDER: S-EPMC7005343 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Purpose:To analyze whether activation of endogenous wingless (Wnt)/?-catenin signaling in Müller cells is involved in protection of retinal ganglion cells (RGCs) following excitotoxic damage. Methods:Transgenic mice with a tamoxifen-dependent ?-catenin deficiency in Müller cells were injected with N-methyl-D-aspartate (NMDA) into the vitreous cavity of one eye to induce excitotoxic damage of the RGCs, while the contralateral eye received PBS only. Retinal damage was quantified by counting the total number of RGC axons in cross sections of optic nerves and measuring the thickness of the retinal layers on meridional sections. Then, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay was performed to identify apoptotic cells in retinas of both genotypes. Western blot analyses to assess the level of retinal ?-catenin and real-time RT-PCR to quantify the retinal expression of neuroprotective factors were performed. Results:Following NMDA injection of wild-type mice, a statistically significant increase in retinal ?-catenin protein levels was observed compared to PBS-injected controls, an effect that was blocked in mice with a Müller cell-specific ?-catenin deficiency. Furthermore, in mice with a ?-catenin deficiency in Müller cells, NMDA injection led to a statistically significant decrease in RGC axons as well as a substantial increase in TUNEL-positive cells in the RGC layer compared to the NMDA-treated controls. Moreover, in the retinas of the control mice a NMDA-mediated statistically significant induction of leukemia inhibitory factor (Lif) mRNA was detected, an effect that was substantially reduced in mice with a ?-catenin deficiency in Müller cells. Conclusions:Endogenous Wnt/?-catenin signaling in Müller cells protects RGCs against excitotoxic damage, an effect that is most likely mediated via the induction of neuroprotective factors, such as Lif.
| S-EPMC7058433 | biostudies-literature
Project description:Retinal neurodegeneration, characterized by retinal ganglion cell (RGC) death, is a leading cause of vision impairment and loss in blind diseases, such as glaucoma. Müller cells play crucial roles in maintaining retinal homeostasis. Thus, dysfunction of Müller cells has been implicated as one of the causes of retinal diseases. Yes-associated protein 1 (YAP), a nuclear effector of the Hippo pathway, regulates mammalian cell survival. In this study, we investigated the role of YAP in Müller cells during N-methyl-D-aspartic acid (NMDA)-induced excitotoxic RGC injury in rats. We found that YAP expression increased and was activated in Müller cells after NMDA-induced RGC injury. This YAP response was partly due to an increase in Yap mRNA levels, although it may be independent of the Hippo pathway and β-TrCP-mediated YAP degradation. Morphological analysis revealed that verteporfin, a selective YAP inhibitor, exacerbated NMDA-induced RGC degeneration, suggesting that YAP activation in Müller cells contributes to RGC survival in NMDA-treated retinas. Studies in the rat Müller cell line (rMC-1) demonstrated that overexpression of YAP increased the levels of Bcl-xL, while verteporfin decreased the levels of Bcl-xL and cell viability and increased the levels of cytochrome c released from mitochondria and cleaved caspase-3. Finally, we found that Bcl-xL expression increased slightly in NMDA-treated retinas, whereas intravitreal injection of verteporfin suppressed this increase. Our findings suggest that activated YAP in Müller cells protects against NMDA-induced RGC injury by upregulating Bcl-xL expression.
| S-EPMC11333228 | biostudies-literature
Project description:Loss of idiopathic retinal ganglion cells (RGCs) leads to irreversible vision defects and is considered the primary characteristic of glaucoma. However, effective treatment strategies in terms of RGC neuroprotection remain elusive. In the present study, the protective effects of resveratrol on RGC apoptosis, and the mechanisms underlying its effects were investigated, with a particular emphasis on the function of optic atrophy 1 (Opa1). In an ischemia/reperfusion (I/R) injury model, the notable thinning of the retina, significant apoptosis of RGCs, reduction in Opa1 expression and long Opa1 isoform to short Opa1 isoform ratios (L?Opa1/S?Opa1 ratio) were observed, all of which were reversed by resveratrol administration. Serum deprivation resulted in reductions in R28 cell viability, superoxide dismutase (SOD) activity, Opa1 expression and induced apoptosis, which were also partially reversed by resveratrol treatment. To conclude, results from the present study suggest that resveratrol treatment significantly reduced retinal damage and RGC apoptosis in I/R injury and serum deprivation models. In addition, resveratrol reversed the downregulated expression of Opa1 and reduced SOD activity. Mechanistically, resveratrol influenced mitochondrial dynamics by regulating the L?Opa1/S?Opa1 ratio. Therefore, these observations suggest that resveratrol may exhibit potential as a therapeutic agent for RGC damage in the future.
| S-EPMC7521588 | biostudies-literature
Project description:Glaucoma is a leading cause of blindness worldwide in individuals 60 years of age and older. Despite its high prevalence, the factors contributing to glaucoma progression are currently not well characterized. Glia-driven neuroinflammation and mitochondrial dysfunction play critical roles in glaucomatous neurodegeneration. Here, we demonstrated that elevated intraocular pressure (IOP) significantly decreased apolipoprotein A-I binding protein (AIBP; gene name Apoa1bp) in retinal ganglion cells (RGCs), but resulted in upregulation of TLR4 and IL-1β expression in Müller glia endfeet. Apoa1bp-/- mice had impaired visual function and Müller glia characterized by upregulated TLR4 activity, impaired mitochondrial network and function, increased oxidative stress and induced inflammatory responses. We also found that AIBP deficiency compromised mitochondrial network and function in RGCs and exacerbated RGC vulnerability to elevated IOP. Administration of recombinant AIBP prevented RGC death and inhibited inflammatory responses and cytokine production in Müller glia in vivo. These findings indicate that AIBP protects RGCs against glia-driven neuroinflammation and mitochondrial dysfunction in glaucomatous neurodegeneration and suggest that recombinant AIBP may be a potential therapeutic agent for glaucoma.
| S-EPMC7484594 | biostudies-literature
Project description:Diabetic retinopathy (DR) is a common complication of diabetes, for which hyperglycemia is a major etiological factor. It is known that retinal glia (Müller cells) and retinal ganglion cells (RGCs) are affected by diabetes, and there is evidence that DR is associated with neural degeneration. Dexamethasone is a glucocorticoid used to treat many inflammatory and autoimmune conditions, including several eye diseases like DR. Thus, our goal was to study the effect of dexamethasone on the survival of RGCs and Müller glial cells isolated from rat retinas and maintained in vitro under hyperglycemic conditions. The behavior of primary RGC cell cultures, and of mixed RGC and Müller cell co-cultures, was studied in hyperglycemic conditions (30 mM glucose), both in the presence and absence of Dexamethasone (1 μM). RGC and Müller cell survival was evaluated, and the conditioned media of these cultures was collected to quantify the inflammatory cytokines secreted by these cells using a multiplex assay. The role of IL-1β, IL-6 and TNFα in RGC death was also evaluated by adding these cytokines to the co-cultures. RGC survival decreased significantly when these cells were grown in high glucose conditions, reaching 54% survival when they were grown alone and only 33% when co-cultured with Müller glia. The analysis of the cytokines in the conditioned media revealed an increase in IL-1β, IL-6 and TNFα under hyperglycemic conditions, which reverted to the basal concentration in co-cultures maintained in the presence of dexamethasone. Finally, when these cytokines were added to co-cultures they appeared to have a direct effect on RGC survival. Hence, these cytokines could be implicated in the death of RGCs when glucose concentrations increase and dexamethasone might protect RGCs from the cell death induced in these conditions.
| S-EPMC6258116 | biostudies-literature
Project description:BackgroundSirtuins (Sirt), a family of nicotinamide adenine nucleotide (NAD) dependent deacetylases, are implicated in energy metabolism and life span. Among the known Sirt isoforms (Sirt1-7), Sirt3 was identified as a stress responsive deacetylase recently shown to play a role in protecting cells under stress conditions. Here, we demonstrated the presence of Sirt3 in neurons, and characterized the role of Sirt3 in neuron survival under NMDA-induced excitotoxicity.Methodology/principal findingsTo induce excitotoxic injury, we exposed primary cultured mouse cortical neurons to NMDA (30 µM). NMDA induced a rapid decrease of cytoplasmic NAD (but not mitochondrial NAD) in neurons through poly (ADP-ribose) polymerase-1 (PARP-1) activation. Mitochondrial Sirt3 was increased following PARP-1 mediated NAD depletion, which was reversed by either inhibition of PARP-1 or exogenous NAD. We found that massive reactive oxygen species (ROS) produced under this NAD depleted condition mediated the increase in mitochondrial Sirt3. By transfecting primary neurons with a Sirt3 overexpressing plasmid or Sirt3 siRNA, we showed that Sirt3 is required for neuroprotection against excitotoxicity.ConclusionsThis study demonstrated for the first time that mitochondrial Sirt3 acts as a prosurvival factor playing an essential role to protect neurons under excitotoxic injury.
| S-EPMC3046953 | biostudies-literature
Project description:Retinal ganglion cells (RGCs) undergo apoptosis after injury. c-Jun N-terminal kinase (JNK)-interacting protein 1 (JIP1) is a scaffold protein that is relevant to JNK activation and a key molecule known to regulate neuronal apoptosis. However, the specific role of JIP1 in the apoptosis of RGCs is currently undefined. Here, we used JIP1 gene knockout (KO) mice to investigate the importance of JIP1-JNK signaling in the apoptosis of RGCs in a rotenone-induced injury model. In adult JIP1 KO mice, the number and electrophysiological functions of RGCs were not different from those of wild-type (WT) mice. Ablation of JIP1 attenuated the activation of JNK and the cleavage of caspase-3 in the retina after rotenone injury and contributed to a lower number of TUNEL-positive RGCs, a greater percentage of surviving RGCs, and a significant reduction in the electrophysiological functional loss of RGCs when compared to those in WT controls. We also found that JIP1 was located in the neurites of primary RGCs, but accumulated in soma in response to rotenone treatment. Moreover, the number of TUNEL-positive RGCs, the level of activation of JNK and the rate of cleavage of caspase-3 were reduced in primary JIP1-deficient RGCs after rotenone injury than in WT controls. Together, our results demonstrate that the JIP1-mediated activation of JNK contributes to the apoptosis of RGCs in a rotenone-induced injury model in vitro and in vivo, suggesting that JIP1 may be a potential therapeutic target for RGC degeneration.
| S-EPMC6804425 | biostudies-literature
Project description:Glaucoma, a group of eye diseases, causes gradual loss of retinal ganglion cells (RGCs) and ultimately results in irreversible blindness. Studies of the underlying mechanisms of glaucoma and clinical trial are far from satisfactory. Results from a genome-wide association study have suggested that the CAV1/CAV2 locus is associated with glaucoma, but this association and its potential underlying mechanisms need to be confirmed and further explored. Here, we studied the function of caveolin-1 (Cav1) in an acute ocular hypertension glaucoma model. Cav1 deficiency caused an aggregated lesion in the retina. In addition, treatment with cavtratin, a membrane permeable Cav1 scaffolding domain peptide, enhanced RGC survival. After cavtratin treatment, microglial numbers decreased significantly, and the majority of them migrated from the inner retinal layer to the outer retinal layers. Furthermore, cavtratin promoted a change in the microglia phenotype from the neurotoxic pro-inflammatory M1 to the neuroprotective anti-inflammatory M2. In a molecular mechanism experiment, we found that cavtratin activated the phosphorylation of both AKT and PTEN in cultured N9 cells. Our data highlights the neuroprotective effect of Cav1 on acute ocular hypertension and suggests that Cav1 may serve as a novel therapeutic target for the treatment of glaucoma. We further propose that cavtratin is a therapeutic candidate for glaucoma clinical trials.
| S-EPMC5587691 | biostudies-literature
Project description:BackgroundBrain-derived neurotrophic factor (BDNF) protects retinal ganglion cells against ischemia in ocular degenerative diseases. We aimed to determine the effect of BDNF-AS on the ischemic injury of retinal ganglion cells.MethodsThe levels of BDNF and BDNF-AS were measured in retinal ganglion cells subjected to oxygen and glucose deprivation. The lentiviral vectors were constructed to either overexpress or knock out BDNF-AS. The luciferase reporter gene assay was used to determine whether BDNF-AS could target its seed sequence on BDNF mRNA. The methyl thiazolyl tetrazolium assay was used to determine cell viability, and TUNEL staining was used for cell apoptosis.ResultsThe levels of BDNF-AS were negatively correlated with BDNF in ischemic retinal ganglion cells. BDNF-AS directly targeted its complementary sequences on BDNF mRNA. BDNF-AS regulated the expression of BDNF and its related genes in retinal ganglion cells. Down-regulation of BDNF-AS increased cell viability and decreased the number of TUNEL-positive retinal ganglion cells under oxygen and glucose deprivation conditions.ConclusionInhibition of BDNF-AS protected retinal ganglion cells against ischemia by increasing the levels of BDNF.
| S-EPMC5147780 | biostudies-literature
Project description:BackgroundGlaucoma, the major cause of irreversible blindness worldwide, is characterized by progressive degeneration of retinal ganglion cells (RGCs). Current treatments for glaucoma only slow or partially prevent the disease progression, failing to prevent RGCs death and visual field defects completely. Glutamate excitotoxicity via N-methyl-D-aspartic acid (NMDA) receptors plays a vital role in RGCs death in glaucoma, which is often accompanied by oxidative stress and NLRP3 inflammasome activation. However, the exact mechanisms remain unclear.MethodsThe glutamate-induced R28 cell excitotoxicity model and NMDA-induced mouse glaucoma model were established in this study. Cell counting kit-8, Hoechst 33342/PI dual staining and lactate dehydrogenase release assay were performed to evaluate cell viability. Annexin V-FITC/PI double staining was used to detect apoptosis and necrosis rate. Reactive oxygen species (ROS) and glutathione (GSH) were used to detect oxidative stress in R28 cells. Levels of proinflammatory cytokines were measured by qRT-PCR. Transmission electron microscopy (TEM) was used to detect necroptotic morphological changes in RGCs. Retinal RGCs numbers were detected by immunofluorescence. Hematoxylin and eosin staining was used to detect retinal morphological changes. The expression levels of RIP1, RIP3, MLKL and NLRP3 inflammasome-related proteins were measured by immunofluorescence and western blotting.ResultsWe found that glutamate excitotoxicity induced necroptosis in RGCs through activation of the RIP1/RIP3/MLKL pathway in vivo and in vitro. Administration of the RIP3 inhibitor GSK872 and RIP1 inhibitor necrostatin-1 (Nec-1) prevented glutamate-induced RGCs loss, retinal damage, neuroinflammation, overproduction of ROS and a decrease in GSH. Furthermore, after suppression of the RIP1/RIP3/MLKL pathway by GSK872 and Nec-1, glutamate-induced upregulation of key proteins involved in NLRP3 inflammasome activation, including NLRP3, pro-caspase-1, cleaved-caspase-1, and interleukin-1β (IL-1β), was markedly inhibited.ConclusionsOur findings suggest that the RIP1/RIP3/MLKL pathway mediates necroptosis of RGCs and regulates NLRP3 inflammasome activation induced by glutamate excitotoxicity. Moreover, GSK872 and Nec-1 can protect RGCs from necroptosis and suppress NLRP3 inflammasome activation through inhibition of RIP1/RIP3/MLKL pathway, conferring a novel neuroprotective treatment for glaucoma.
| S-EPMC9608931 | biostudies-literature