Tamoxifen protects photoreceptors in the sodium iodate model.

Because the selective estrogen receptor modulator tamoxifen was shown to be retina-protective in the light damage and rd10 models of retinal degeneration, the purpose of this study was to test whether tamoxifen is retina-protective in a model where retinal pigment epithelium (RPE) toxicity appears to be the primary insult: the sodium iodate (NaIO3) model. C57Bl/6J mice were given oral tamoxifen (in the diet) or the same diet lacking tamoxifen, then given an intraperitoneal injection of NaIO3 at 25 mg/kg. The mice were imaged a week later using optical coherence tomography (OCT). ImageJ with a custom macro was utilized to measure retinal thicknesses in OCT images. Electroretinography (ERG) was used to measure retinal function one week post-injection. After euthanasia, quantitative real-time PCR (qRT-PCR) was performed. Tamoxifen administration partially protected photoreceptors. There was less photoreceptor layer thinning in OCT images of tamoxifen-treated mice. qRT-PCR revealed, in the tamoxifen-treated group, less upregulation of antioxidant and complement factor 3 mRNAs, and less reduction in the rhodopsin and short-wave cone opsin mRNAs. Furthermore, ERG results demonstrated preservation of photoreceptor function for the tamoxifen-treated group. Cone function was better protected than rods. These results indicate that tamoxifen provided structural and functional protection to photoreceptors against NaIO3. RPE cells were not protected. These neuroprotective effects suggest that estrogen-receptor modulation may be retina-protective. The fact that cones are particularly protected is intriguing given their importance for human visual function and their survival until the late stages of retinitis pigmentosa. Further investigation of this protective pathway could lead to new photoreceptor-protective therapeutics.

Sphingolipid biosynthetic inhibitor L-Cycloserine prevents oxidative-stress-mediated death in an in vitro model of photoreceptor-derived 661W cells.

Oxidative stress plays a pivotal role in the pathogenesis of several neurodegenerative diseases. Retinal degeneration causes irreversible death of photoreceptor cells, ultimately leading to vision loss. Under oxidative stress, the synthesis of bioactive sphingolipid ceramide increases, triggering apoptosis in photoreceptor cells and leading to their death. This study investigates the effect of L-Cycloserine, a small molecule inhibitor of ceramide biosynthesis, on sphingolipid metabolism and the protection of photoreceptor-derived 661W cells from oxidative stress. The results demonstrate that treatment with L-Cycloserine, an inhibitor of Serine palmitoyl transferase (SPT), markedly decreases bioactive ceramide and associated sphingolipids in 661W cells. A nontoxic dose of L-Cycloserine can provide substantial protection of 661W cells against H2O2-induced oxidative stress by reversing the increase in ceramide level observed under oxidative stress conditions. Analysis of various antioxidant, apoptotic and sphingolipid pathway genes and proteins also confirms the ability of L-Cycloserine to modulate these pathways. Our findings elucidate the generation of sphingolipid mediators of cell death in retinal cells under oxidative stress and the potential of L-Cycloserine as a therapeutic candidate for targeting ceramide-induced degenerative diseases by inhibiting SPT. The promising therapeutic prospect identified in our findings lays the groundwork for further validation in in-vivo and preclinical models of retinal degeneration.

Pharmacological inhibition of MERTK induces in vivo retinal degeneration: a multimodal imaging ocular safety assessment.

The receptor tyrosine kinase, MERTK, plays an essential role in homeostasis of the retina via efferocytosis of shed outer nuclear segments of photoreceptors. The Royal College of Surgeons rat model of retinal degeneration has been linked to loss-of-function of MERTK, and together with the MERTK knock-out mouse, phenocopy retinitis pigmentosa in humans with MERTK mutations. Given recent efforts and interest in MERTK as a potential immuno-oncology target, development of a strategy to assess ocular safety at an early pre-clinical stage is critical. We have applied a state-of-the-art, multi-modal imaging platform to assess the in vivo effects of pharmacological inhibition of MERTK in mice. This involved the application of mass spectrometry imaging (MSI) to characterize the ocular spatial distribution of our highly selective MERTK inhibitor; AZ14145845, together with histopathology and transmission electron microscopy to characterize pathological and ultra-structural change in response to MERTK inhibition. In addition, we assessed the utility of a human retinal in vitro cell model to identify perturbation of phagocytosis post MERTK inhibition. We identified high localized total compound concentrations in the retinal pigment epithelium (RPE) and retinal lesions following 28 days of treatment with AZ14145845. These lesions were present in 4 of 8 treated animals, and were characterized by a thinning of the outer nuclear layer, loss of photoreceptors (PR) and accumulation of photoreceptor outer segments at the interface of the RPE and PRs. Furthermore, the lesions were very similar to that shown in the RCS rat and MERTK knock-out mouse, suggesting a MERTK-induced mechanism of PR cell death. This was further supported by the observation of reduced phagocytosis in the human retinal cell model following treatment with AZ14145845. Our study provides a viable, translational strategy to investigate the pre-clinical toxicity of MERTK inhibitors but is equally transferrable to novel chemotypes.

Pharmacological Inhibition of the VCP/Proteasome Axis Rescues Photoreceptor Degeneration in RHOP23H Rat Retinal Explants.

Rhodopsin (RHO) misfolding mutations are a common cause of the blinding disease autosomal dominant retinitis pigmentosa (adRP). The most prevalent mutation, RHOP23H, results in its misfolding and retention in the endoplasmic reticulum (ER). Under homeostatic conditions, misfolded proteins are selectively identified, retained at the ER, and cleared via ER-associated degradation (ERAD). Overload of these degradation processes for a prolonged period leads to imbalanced proteostasis and may eventually result in cell death. ERAD of misfolded proteins, such as RHOP23H, includes the subsequent steps of protein recognition, targeting for ERAD, retrotranslocation, and proteasomal degradation. In the present study, we investigated and compared pharmacological modulation of ERAD at these four different major steps. We show that inhibition of the VCP/proteasome activity favors cell survival and suppresses P23H-mediated retinal degeneration in RHOP23H rat retinal explants. We suggest targeting this activity as a therapeutic approach for patients with currently untreatable adRP.

Myosin 1f-mediated activation of microglia contributes to the photoreceptor degeneration in a mouse model of retinal detachment.

Photoreceptor death and neurodegeneration is the leading cause of irreversible vision loss. The inflammatory response of microglia plays an important role in the process of neurodegeneration. In this study, we chose retinal detachment as the model of photoreceptor degeneration. We found Myosin 1f was upregulated after retinal detachment, and it was specifically expressed in microglia. Deficiency of myosin 1f protected against photoreceptor apoptosis by inhibiting microglia activation. The elimination of microglia can abolish the protective effect of myosin 1f deficiency. After stimulation by LPS, microglia with myosin 1f deficiency showed downregulation of the MAPK and AKT pathways. Our results demonstrated that myosin 1f plays a crucial role in microglia-induced neuroinflammation after retinal injury and photoreceptor degeneration by regulating two classic inflammatory pathways and thereby decreasing the expression of inflammatory cytokines. Knockout of myosin 1f reduces the intensity of the immune response and prevents cell death of photoreceptor, suggesting that myosin 1f can be inhibited to prevent a decline in visual acuity after retinal detachment.

Does ganciclovir exert retinal toxicity after multiple continuous intravitreal injections?

BACKGROUND: The objective of this study is to report a case of acute retinal necrosis in which abnormalities in visual function did not correspond to retinal anatomical outcomes. CASE PRESENTATION: A 39-year-old female diagnosed with acute retinal necrosis underwent repeated (nine rounds) intravitreal ganciclovir injection (3 mg/0.1 ml) into the left eye, one injection every 2 weeks. During the therapy, the patient noticed her visual acuity declining gradually. The best corrected visual acuity in the left eye was 20/33. The visual field showed massive visual damage. There was no posterior necrotizing involvement, no macular edema or exudation, and only slight abnormity of the interdigitation zone in the fovea area was visible on OCT. Angio-OCT revealed normal capillary density of three retinal capillary and choriocapillaris layers. The visually evoked potential was normal. The photopic single-flash response showed a declined amplitude of a-wave and b-wave. The amplitudes of photopic 30 Hz flicker were decreased. Multifocal electroretinography revealed macular dysfunction. CONCLUSION: Ganciclovir-associated photoreceptor damage may induce abnormalities in retinal function in response to multiple continuous intravitreal ganciclovir injections at a relatively high dosage (3 mg/0.1 ml).

Pigment epithelium-derived factor (PEDF) and derived peptides promote survival and differentiation of photoreceptors and induce neurite-outgrowth in amacrine neurons.

Pigment epithelium-derived factor (PEDF) is a cytoprotective protein for the retina. We hypothesize that this protein acts on neuronal survival and differentiation of photoreceptor cells in culture. The purpose of the present study was to evaluate the neurotrophic effects of PEDF and its fragments in an in vitro model of cultured primary retinal neurons that die spontaneously in the absence of trophic factors. We used Wistar albino rats. Cell death was assayed by immunofluorescence and flow cytometry through TUNEL assay, propidium iodide, mitotracker, and annexin V. Immunofluorescence of cells for visualizing rhodopsin, CRX, and antisyntaxin under confocal microscopy was performed. Neurite outgrowth was also quantified. Results show that PEDF protected photoreceptor precursors from apoptosis, preserved mitochondrial function and promoted polarization of opsin enhancing their developmental process, as well as induced neurite outgrowth in amacrine neurons. These effects were abolished by an inhibitor of the PEDF receptor or receptor-derived peptides that block ligand/receptor interactions. While all the activities were specifically conferred by short peptide fragments (17 amino acid residues) derived from the PEDF neurotrophic domain, no effects were triggered by peptides from the PEDF antiangiogenic region. The observed effects on retinal neurons imply a specific activation of the PEDF receptor by a small neurotrophic region of PEDF. Our findings support the neurotrophic PEDF peptides as neuronal guardians for the retina, highlighting their potential as promoters of retinal differentiation, and inhibitors of retinal cell death and its blinding consequences. Cover Image for this issue: https://doi.org/10.1111/jnc.15089.

Alterations of Lipidomes in Rat Photoreceptor Degeneration Induced by N-Methyl-N-nitrosourea.

To investigate alterations of lipidomes in the progress of photoreceptor degeneration induced by N-methyl-N-nitrosourea (MNU) in a rat model, retinal lipid molecular species in adult Sprague-Dawley (SD) rats at 1, 3, and 7 days after MNU administration and age-matched controls were analyzed by the shotgun lipidomics technology. Moreover, total fatty acid levels in retinal, liver, and plasma samples of different groups were determined with gas chromatography. Generally, at day 1, the levels of ethanolamine plasmalogen species in retinas were markedly elevated after treatment with MNU, while the contents of other phospholipids and sphingolipids in the retina were not significantly changed than those of the control group. The compositions of almost all of unsaturated fatty acids in the retina increased significantly at day 1 after MNU administration. At day 7, the MNU treatment group has significant increases in lipid species in the retina. However, the majority of lipids containing docosahexaenoic acid (DHA, 22:6n-3) and docosapentaenoic acid (22:5n-6) declined, especially di-DHA phospholipids were dramatically reduced in the retina. In contrast, similar alterations did not occur in plasma or the liver after MNU treatment. These results suggested that at the early stage of photoreceptor degeneration, lipidome remodeling in the retina might involve protection of photoreceptor from apoptosis and continue their transduction of light. However, at the late stage of photoreceptor apoptosis, increases in comprehensive lipid species occurred, likely due to the myelination of the retina. Finally, the deficiency of DHA in photoreceptor degeneration could exacerbate the influence of myelination on retinal function. We further investigated the effects of unsaturated fatty acids on neuronal apoptosis. The preliminary experiments confirmed our observation from lipidomics analysis that unsaturated fatty acids can protect neurons from apoptosis. Collectively, our study suggests that increased levels of DHA should be protective from photoreceptor degeneration.

A potential role for somatostatin signaling in regulating retinal neurogenesis.

Neuropeptides have been reported to regulate progenitor proliferation and neurogenesis in the central nervous system. However, these studies have typically been conducted using pharmacological agents in ex vivo preparations, and in vivo evidence for their developmental function is generally lacking. Recent scRNA-Seq studies have identified multiple neuropeptides and their receptors as being selectively expressed in neurogenic progenitors of the embryonic mouse and human retina. This includes Sstr2, whose ligand somatostatin is transiently expressed by immature retinal ganglion cells. By analyzing retinal explants treated with selective ligands that target these receptors, we found that Sstr2-dependent somatostatin signaling induces a modest, dose-dependent inhibition of photoreceptor generation, while correspondingly increasing the relative fraction of primary progenitor cells. These effects were confirmed by scRNA-Seq analysis of retinal explants but abolished in Sstr2-deficient retinas. Although no changes in the relative fraction of primary progenitors or photoreceptor precursors were observed in Sstr2-deficient retinas in vivo, scRNA-Seq analysis demonstrated accelerated differentiation of neurogenic progenitors. We conclude that, while Sstr2 signaling may act to negatively regulate retinal neurogenesis in combination with other retinal ganglion cell-derived secreted factors such as Shh, it is dispensable for normal retinal development.

Minocycline decreases CCR2-positive monocytes in the retina and ameliorates photoreceptor degeneration in a mouse model of retinitis pigmentosa.

Retinal inflammation accelerates photoreceptor cell death caused by retinal degeneration. Minocycline, a semisynthetic broad-spectrum tetracycline antibiotic, has been previously reported to rescue photoreceptor cell death in retinal degeneration. We examined the effect of minocycline on retinal photoreceptor degeneration using c-mer proto-oncogene tyrosine kinase (Mertk)-/-Cx3cr1GFP/+Ccr2RFP/+ mice, which enabled the observation of CX3CR1-green fluorescent protein (GFP)- and CCR2-red fluorescent protein (RFP)-positive macrophages by fluorescence. Retinas of Mertk-/-Cx3cr1GFP/+Ccr2RFP/+ mice showed photoreceptor degeneration and accumulation of GFP- and RFP-positive macrophages in the outer retina and subretinal space at 6 weeks of age. Mertk-/-Cx3cr1GFP/+Ccr2RFP/+ mice were intraperitoneally administered minocycline. The number of CCR2-RFP positive cells significantly decreased after minocycline treatment. Furthermore, minocycline administration resulted in partial reversal of the thinning of the outer nuclear layer and decreased the number of apoptotic cells, as assessed by the TUNEL assay, in Mertk-/-Cx3cr1GFP/+Ccr2RFP/+ mice. In conclusion, we found that minocycline ameliorated photoreceptor cell death in an inherited photoreceptor degeneration model due to Mertk gene deficiency and has an inhibitory effect on CCR2 positive macrophages, which is likely to be a neuroprotective mechanism of minocycline.

SAHA is neuroprotective in in vitro and in situ models of retinitis pigmentosa.

PURPOSE: Recent reports linking HDAC6 to mitochondrial turnover and neurodegeneration led us to hypothesize that an inhibitor such as Vorinostat (suberoylanilide hydroxamic acid, SAHA) may reduce mitochondrial damage found in retinitis pigmentosa (RP), a progressive neurodegenerative disease of the eye. Here we tested the efficacy of SAHA for its ability to protect photoreceptors in in-vitro and in-situ models of RP. As the stressor, we focused on calcium overload. Calcium is one of the main drivers of cell death, and is associated with rod loss in the rd1 mouse retina, which harbors a mutation in the Pde6b gene similar to that found in human patients suffering from autosomal recessive RP. METHOD: Murine photoreceptor cell line (661W) were exposed to agents that led to calcium stress. Cell survival and redox capacity were measured using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, real-time changes in cellular metabolism were assessed using the Seahorse Biosciences XF24 analyzer, and mitochondrial fission-fusion using imaging. In-situ, neuroprotection was assessed in RPE/retina organ cultures of the rd1 mouse. SAHA effects on cell survival were compared in 661W cells with those of the specific HDAC6 inhibitor tubastatin A, and those on protein acetylation by Western blotting. RESULTS: In stressed 661W cells, SAHA was found to increase cell survival that was associated with improved mitochondrial respiration and reduced mitochondrial fission. The protective effects of SAHA were also observed on photoreceptor cell survival in whole retinal organ explants of the rd1 mouse. Even though tubastatin A was ineffective in increasing cell survival in 661W cells, HDAC6 activity was confirmed in 661W cells after SAHA treatment with protein acetylation specific for HDAC6, defined by an increase in tubulin, but not histone acetylation. CONCLUSIONS: SAHA was found to protect mitochondria from damage, and concomitantly reduced photoreceptor cell death in cell and organ cultures. The lack of activity of tubastatin A suggests that there must be an additional mechanism of action involved in the protective mechanism of SAHA that is responsible for its neuroprotection. Overall, SAHA may be a useful treatment for the prevention of photoreceptor degeneration associated with human RP. The results are discussed in the context of the effects of inhibitors that target different classes and members of the HDAC family and their effects on rod versus cone survival.

Oral Ursodeoxycholic Acid Crosses the Blood Retinal Barrier in Patients with Retinal Detachment and Protects Against Retinal Degeneration in an Ex Vivo Model.

Rhegmatogenous retinal detachment (RD) is a threatening visual condition and a human disease model for retinal degenerations. Despite successful reattachment surgery, vision does not fully recover, due to subretinal fluid accumulation and subsequent photoreceptor cell death, through mechanisms that recapitulate those of retinal degenerative diseases. Hydrophilic bile acids are neuroprotective in animal models, but whether they can be used orally for retinal diseases is unknown. Ursodeoxycholic acid (UDCA) being approved for clinical use (e.g., in cholestasis), we have evaluated the ocular bioavailability of oral UDCA, administered to patients before RD surgery. The level of UDCA in ocular media correlated with the extent of blood retinal barrier disruption, evaluated by the extent of detachment and the albumin concentration in subretinal fluid. UDCA, at levels measured in ocular media, protected photoreceptors from apoptosis and necrosis in rat retinal explants, an ex vivo model of RD. The subretinal fluid from UDCA-treated patients, collected during surgery, significantly protected rat retinal explants from cell death, when compared to subretinal fluid from control patients. Pan-transcriptomic analysis of the retina showed that UDCA upregulated anti-apoptotic, anti-oxidant, and anti-inflammatory genes. Oral UDCA is a potential neuroprotective adjuvant therapy in RD and other retinal degenerative diseases and should be further evaluated in a clinical trial.

IGFBPs mediate IGF-1's functions in retinal lamination and photoreceptor development during pluripotent stem cell differentiation to retinal organoids.

Development of the retina is regulated by growth factors, such as insulin-like growth factors 1 and 2 (IGF-1/2), which coordinate proliferation, differentiation, and maturation of the neuroepithelial precursors cells. In the circulation, IGF-1/2 are transported by the insulin growth factor binding proteins (IGFBPs) family members. IGFBPs can impact positively and negatively on IGF-1, by making it available or sequestering IGF-1 to or from its receptor. In this study, we investigated the expression of IGFBPs and their role in the generation of human retinal organoids from human pluripotent stem cells, showing a dynamic expression pattern suggestive of different IGFBPs being used in a stage-specific manner to mediate IGF-1 functions. Our data show that IGF-1 addition to culture media facilitated the generation of retinal organoids displaying the typical laminated structure and photoreceptor maturation. The organoids cultured in the absence of IGF-1, lacked the typical laminated structure at the early stages of differentiation and contained significantly less photoreceptors and more retinal ganglion cells at the later stages of differentiation, confirming the positive effects of IGF-1 on retinal lamination and photoreceptor development. The organoids cultured with the IGFBP inhibitor (NBI-31772) and IGF-1 showed lack of retinal lamination at the early stages of differentiation, an increased propensity to generate horizontal cells at mid-stages of differentiation and reduced photoreceptor development at the later stages of differentiation. Together these data suggest that IGFBPs enable IGF-1's role in retinal lamination and photoreceptor development in a stage-specific manner.

Inhibition of PARP activity improves therapeutic effect of ARPE-19 transplantation in RCS rats through decreasing photoreceptor death.

Photoreceptor (PR) dysfunction or death is the key pathological change in retinal degeneration (RD). The death of PRs might be due to a primary change in PRs themselves or secondary to the dysfunction of the retinal pigment epithelium (RPE). Poly(ADP-ribose) polymerase (PARP) was reported to be involved in primary PR death, but whether it plays a role in PR death secondary to RPE dysfunction has not been determined. To clarify this question and develop a new therapeutic approach, we studied the changes in PAR/PARP in the RCS rat, a RD model, and tested the effect of PARP intervention when given alone or in combination with RPE cell transplantation. The results showed that poly(ADP-ribosyl)ation of proteins was increased in PRs undergoing secondary death in RCS rats, and this result was confirmed by the observation of similar changes in sodium iodate (SI)-induced secondary RD in SD rats. The increase in PAR/PARP was highly associated with increased apoptotic PRs and decreased visual function, as represented by lowered b-wave amplitudes on electroretinogram (ERG). Then, as we expected, when the RCS rats were treated with subretinal injection of the PARP inhibitor PJ34, the RD process was delayed. Furthermore, when PJ34 was given simultaneously with subretinal ARPE-19 cell transplantation, the therapeutic effects were significantly improved and lasted longer than those of ARPE-19 or PJ34 treatment alone. These results provide a potential new approach for treating RD.

Photoreceptive Ganglion Cells Drive Circuits for Local Inhibition in the Mouse Retina.

Intrinsically photosensitive retinal ganglion cells (ipRGCs) exhibit melanopsin-dependent light responses that persist in the absence of rod and cone photoreceptor-mediated input. In addition to signaling anterogradely to the brain, ipRGCs signal retrogradely to intraretinal circuitry via gap junction-mediated electrical synapses with amacrine cells (ACs). However, the targets and functions of these intraretinal signals remain largely unknown. Here, in mice of both sexes, we identify circuitry that enables M5 ipRGCs to locally inhibit retinal neurons via electrical synapses with a nonspiking GABAergic AC. During pharmacological blockade of rod- and cone-mediated input, whole-cell recordings of corticotropin-releasing hormone-expressing (CRH+) ACs reveal persistent visual responses that require both melanopsin expression and gap junctions. In the developing retina, ipRGC-mediated input to CRH+ ACs is weak or absent before eye opening, indicating a primary role for this input in the mature retina (i.e., in parallel with rod- and cone-mediated input). Among several ipRGC types, only M5 ipRGCs exhibit consistent anatomical and physiological coupling to CRH+ ACs. Optogenetic stimulation of local CRH+ ACs directly drives IPSCs in M4 and M5, but not M1-M3, ipRGCs. CRH+ ACs also inhibit M2 ipRGC-coupled spiking ACs, demonstrating direct interaction between discrete networks of ipRGC-coupled interneurons. Together, these results demonstrate a functional role for electrical synapses in translating ipRGC activity into feedforward and feedback inhibition of local retinal circuits.SIGNIFICANCE STATEMENT Melanopsin directly generates light responses in intrinsically photosensitive retinal ganglion cells (ipRGCs). Through gap junction-mediated electrical synapses with retinal interneurons, these uniquely photoreceptive RGCs may also influence the activity and output of neuronal circuits within the retina. Here, we identified and studied an electrical synaptic circuit that, in principle, could couple ipRGC activity to the chemical output of an identified retinal interneuron. Specifically, we found that M5 ipRGCs form electrical synapses with corticotropin-releasing hormone-expressing amacrine cells, which locally release GABA to inhibit specific RGC types. Thus, ipRGCs are poised to influence the output of diverse retinal circuits via electrical synapses with interneurons.

PJ34 Protects Photoreceptors from Cell Death by Inhibiting PARP-1 Induced Parthanatos after Experimental Retinal Detachment.

PURPOSE: Our previous study discoveredreactive oxygen species (ROS) and apoptosis inducing factor (AIF) increased after retinal detachment. Parthanatos is a cell death form involving ROS and AIF, which is induced by poly (ADP-ribose) polymerase-1 (PARP-1). Therefore, we investigated whether PJ34 (a PARP-1 inhibitor) could inhibit parthanatos and protect the photoreceptors from cell death after retinal detachment (RD). METHODS: Experimental retinal detachment modelswere created in Sprague-Dawley rats by subretinal injection of sodium hyaluronate.PJ34 orDMSO were introduced into subretinal space at RD induction, respectively. The structure of retinas and the morphology of photoreceptors were observed by hematoxylin eosin (H&E) staining and transmission electron microscope (TEM). Parthanatos related proteins (PARP-1, PAR,AIF) were detected by Western blot. The vision-dependent behavior of rat was tested by Morris water maze. RESULTS: H&E staining and TEM results indicated that the structure and outer nuclear layer (ONL) thickness of retinas were preserved, and the photoreceptors death decreasedwith PJ34 treatment. Western blot showed that the expression of PARP-1, PAR and AIF were decreased withPJ34 treatment. In addition, administration of PJ34 also improved the vision-dependent behavior of rat. CONCLUSIONS: These findings suggested that PJ34 is a potential therapeutic agent that attenuated photoreceptor parthanatos death in retinal detachment through inhibition of PARP-1/AIF pathway.

Evolution of oxidative stress, inflammation and neovascularization in the choroid and retina in a subretinal lipid induced age-related macular degeneration model.

Oxidative stress, inflammation and neovascularization are the key pathological events that are implicated in human age-related macular degeneration (AMD). There are a limited number of animal models available for evaluating and developing new therapies. Most models represent late exudative or neovascular AMD (nAMD) but there is a relative paucity of models that mimic early events in AMD. The purpose of this study is to characterize the evolution of oxidative stress, inflammation, retinal degeneration and neovascularization in a rat model of AMD, created by subretinal injection of human lipid hydroperoxide (HpODE) that found in the sub-macular region in aged and AMD patients. Subretinal HpODE induced retinal pigment epithelium (RPE) and retinal degeneration resulting in loss of RPE cells, photoreceptors and retinal thinning. RPE degeneration and atrophy were detected by day 5, followed by neural tissue degeneration at day 12 with robust TUNEL positive cells. Western blot analysis confirmed an increase in pro-apoptotic Bak protein at day 12 in retinal tissues. Oxidative damage biomarkers (4-hydroxynonenal, malondialdehyde, 8-hydroxy-2'-deoxyguanosine, and nitrotyrosine) increased in retinal tissue from days 5-12. Müller glial activation was observed in the HpODE injected area at day 5 followed by its remodeling and migration in the outer retina by day 20. RT-qPCR analysis further indicated upregulation of pro-inflammatory genes (TNF-α, IL-1ß and IL-6) both in retinal and RPE/choroidal tissue as early as day 2 and persisted until day 12. Upregulation of oxidative stress markers such as NADPH oxidase (NOX and DOUX family) was detected early in retinal tissue by day 2 followed by its upregulation in choroidal tissue at day 5. Neovascularization was demonstrated from day 12 to day 20 post HpODE injection in choroidal tissue. The results from this study indicate that subretinal HpODE induces advanced AMD phenotypes comprising many aspects of both dry/early and late) and neovascular/late AMD as observed in humans. Within 3 weeks via oxidative damage, upregulation of reactive oxygen species and pro-inflammatory genes, pro-apoptotic Bak and pro-angiogenic VEGF upregulation occurs leading to CNV formation. This experimental model of subretinal HpODE is an appropriate model for the study of AMD and provides an important platform for translational and basic research in developing new therapies particularly for early/dry AMD where currently no viable therapies are available.

Neuroprotective effects and mechanisms of action of nicotinamide mononucleotide (NMN) in a photoreceptor degenerative model of retinal detachment.

Currently, no pharmacotherapy has been proven effective in treating photoreceptor degeneration in patients. Discovering readily available and safe neuroprotectants is therefore highly sought after. Here, we investigated nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD+), in a retinal detachment (RD) induced photoreceptor degeneration. NMN administration after RD resulted in a significant reduction of TUNEL+ photoreceptors, CD11b+ macrophages, and GFAP labeled glial activation; a normalization of protein carbonyl content (PCC), and a preservation of the outer nuclear layer (ONL) thickness. NMN administration significantly increased NAD+ levels, SIRT1 protein expression, and heme oxygenase-1 (HO-1) expression. Delayed NMN administration still exerted protective effects after RD. Mechanistic in vitro studies using 661W cells revealed a SIRT1/HO-1 signaling as a downstream effector of NMN-mediated protection under oxidative stress and LPS stimulation. In conclusion, NMN administration exerts neuroprotective effects on photoreceptors after RD and oxidative injury, suggesting a therapeutic avenue to treating photoreceptor degeneration.

Recent Developments in the Treatment of Wet Age-related Macular Degeneration.

Age-related macular degeneration (AMD) is the most common cause of irreversible blindness and visual impairment in individuals over the age of 50 years in western societies. More than 25 million people currently suffer from this illness in the world, with an additional 500 000 every year, approximately. It is a multifactorial ocular disease that affects the maculae due to a late-onset progressive neurodegeneration and dysfunction of photoreceptors and retinal pigment epithelium (RPE). There are many subtypes of AMD but basically two broad forms: the nonneovascular (dry, nonexudative) and neovascular (wet, exudative). Exudative AMD is the less common form (about 15%) but tends to progress more rapidly. At the moment, wet AMD is treated primarily on the basis of anti-vascular endothelial growth factor (VEGF) agents, which have led to massive improvement in the prognosis of the disease since they were first introduced. This article focuses on the latest treatment approaches to neovascular AMD. An extensive literature review was performed in order to illustrate the effectiveness of current and future anti-VEGF agents as well as the landmark clinical studies that have been carried out to establish these drugs as a gold standard in the therapy of wet AMD.