Ocular pharmacological and biochemical profiles of 6-thioguanine: a drug repurposing study

Introduction

The purine analog 6-thioguanine (6TG), an old drug approved in the 60s to treat acute myeloid leukemia (AML), was tested in the diabetic retinopathy (DR) experimental in vivo setting along with a molecular modeling approach.

Methods

A computational analysis was performed to investigate the interaction of 6TG with MC1R and MC5R. This was confirmed in human umbilical vein endothelial cells (HUVECs) exposed to high glucose (25 mM) for 24 h. Cell viability in HUVECs exposed to high glucose and treated with 6TG (0.05-0.5-5 µM) was performed. To assess tube formation, HUVECs were treated for 24 h with 6TG 5 µM and AGRP (0.5-1-5 µM) or PG20N (0.5-1-5-10 µM), which are MC1R and MC5R antagonists, respectively. For the in vivo DR setting, diabetes was induced in C57BL/6J mice through a single streptozotocin (STZ) injection. After 2, 6, and 10 weeks, diabetic and control mice received 6TG intravitreally (0.5-1-2.5 mg/kg) alone or in combination with AGRP or PG20N. Fluorescein angiography (FA) was performed after 4 and 14 weeks after the onset of diabetes. After 14 weeks, mice were euthanized, and immunohistochemical analysis was performed to assess retinal levels of CD34, a marker of endothelial progenitor cell formation during neo-angiogenesis.

Results

The computational analysis evidenced a more stable binding of 6TG binding at MC5R than MC1R. This was confirmed by the tube formation assay in HUVECs exposed to high glucose. Indeed, the anti-angiogenic activity of 6TG was eradicated by a higher dose of the MC5R antagonist PG20N (10 µM) compared to the MC1R antagonist AGRP (5 µM). The retinal anti-angiogenic effect of 6TG was evident also in diabetic mice, showing a reduction in retinal vascular alterations by FA analysis. This effect was not observed in diabetic mice receiving 6TG in combination with AGRP or PG20N. Accordingly, retinal CD34 staining was reduced in diabetic mice treated with 6TG. Conversely, it was not decreased in diabetic mice receiving 6TG combined with AGRP or PG20N.

Conclusion

6TG evidenced a marked anti-angiogenic activity in HUVECs exposed to high glucose and in mice with DR. This seems to be mediated by MC1R and MC5R retinal receptors.

Changes in Circulating Acylated Ghrelin and Neutrophil Elastase in Diabetic Retinopathy

Background and Objectives: The role and the levels of ghrelin in diabetes-induced retinal damage have not yet been explored. The present study aimed to measure the serum levels of total ghrelin (TG), and its acylated (AG) and des-acylated (DAG) forms in patients with the two stages of diabetic retinopathy (DR), non-proliferative (NPDR) and proliferative (PDR). Moreover, the correlation between serum ghrelin and neutrophil elastase (NE) levels was investigated. Materials and Methods: The serum markers were determined via enzyme-linked immunosorbent assays in 12 non-diabetic subjects (CTRL), 15 diabetic patients without DR (Diabetic), 15 patients with NPDR, and 15 patients with PDR. Results: TG and AG serum levels were significantly decreased in Diabetic (respectively, p < 0.05 and p < 0.01 vs. CTRL), NPDR (p < 0.01 vs. Diabetic), and in PDR patients (p < 0.01 vs. NPDR). AG serum levels were inversely associated with DR abnormalities (microhemorrhages, microaneurysms, and exudates) progression (r = -0.83, p < 0.01), serum neutrophil percentage (r = -0.74, p < 0.01), and serum NE levels (r = -0.73, p < 0.01). The latter were significantly increased in the Diabetic (p < 0.05 vs. CTRL), NPDR (p < 0.01 vs. Diabetic), and PDR (p < 0.01 vs. PDR) groups. Conclusions: The two DR stages were characterized by decreased AG and increased NE levels. In particular, serum AG levels were lower in PDR compared to NPDR patients, and serum NE levels were higher in the PDR vs. the NPDR group. Together with the greater presence of retinal abnormalities, this could underline a distinctive role of AG in PDR compared to NPDR.

Multimodal Assessment of the Prognostic Role of Ectopic Inner Foveal Layers on Epiretinal Membrane Surgery

BACKGROUND

To perform a multimodal assessment of the ectopic inner foveal layers' (EIFL) prognostic role on idiopathic epiretinal membrane (ERM) surgery.

METHODS

We retrospectively followed-up for 12 months 27 patients who underwent ERM surgery and stratified them based on EIFL presence (group 1) or absence (group 2) at baseline. Central Retinal Thickness (CRT) and best-corrected visual acuity (BCVA) were compared pre- and post-operatively at 1, 4 and 12 months, whereas fixation stability (FS), macular sensitivity (MS) and multifocal electroretinogram (mfERG) responses were confronted at baseline and 12 months.

RESULTS

In group 1, BCVA improved at 4 and 12 months (MD = 0.14 (SE = 0.04); MD = 0.13 (SE = 0.05), respectively) as well as in group 2 (MD = 0.31 (SE = 0.07); MD = 0.41 (SE = 0.08), respectively). CRT did not change in group 1, whereas it decreased in group 2 at 4 and 12 months (MD = -73.13; SE = 23.56; MD = -76.20; SE = 23.56). MS showed no changes in both groups after surgery. FS did not change in group 1, whereas group 2 improved FS 2° (+8.91 ± 13.97) and FS 4° (+4.33 ± 3.84). MfERG P1 wave did not change in group 1, while in group 2 αP1-2, αP1-3 and αP1-4 improved postoperatively (27.97 ± 27.62; 12.51 ± 17.36; 10.49 ± 17.19, respectively).

CONCLUSIONS

Multimodal assessment confirmed that EIFL negatively affected ERM surgery outcomes.

Brolucizumab Intravitreal Injections for Wet Age-Related Macular Degeneration: Real-Life Study on a Cohort of Italian Patients

Background and Objectives: To report the real-life Brolucizumab therapeutical outcomes of treatment-naïve and non-treatment-naïve eyes with neovascular age-related macular degeneration (nAMD) and to analyze the incidence of therapy-related adverse events. Materials and Methods: A total of 56 eyes of 54 patients diagnosed with nAMD were retrospectively evaluated over a 3-month follow-up. Naïve eyes received a 3-month loading phase, whereas non-naïve eyes were treated with one intravitreal injection + ProReNata scheme. The main outcome measures were best-corrected visual acuity (BCVA) and central retinal thickness (CRT) change. In addition, patients were stratified on the basis of fluid accumulation site, whether intra-retinal (IRF), sub-retinal (SRF), or sub-retinal pigmented epithelium (SRPE), to separately assess the eventual BCVA change in each subgroup. Finally, the incidence of ocular adverse events was evaluated. Results: In naïve eyes, a significant improvement of BCVA (LogMar) was observed at all timepoints from baseline (1 month-Mean Difference (MD): -0.13; 2 months MD: -0.17; 3 months MD: -0.24). In non-naïve eyes, a significant mean change was observed at all timepoints, with the exception of 1-month follow-up (2 months MD: -0.08; 3 months MD: -0.05). CRT significantly changed in both groups at all timepoints at a similar pace within the first two months, with naïve eyes displaying a larger overall thickness decrease at the end of the follow-up (Group 1 = MD: -123.91 µm; Group 2 = MD: -110.33 µm). With respect to the location of the edema, a significant BCVA change was observed in naïve patients with fluid in all three sites at the end of the follow-up (SRPE = MD: -0.13 (p = 0.043); SR = MD: -0.15 (p = 0.019); IR = MD: -0.19 (p = 0.041). Non-naïve patients exhibited significant mean BCVA changes only with respect to SR and IR fluid presence (SRPE = MD: -0.13 (p = 0.152); SR = MD: -0.15 (p = 0.007); IR = MD: -0.06 (p = 0.011). One naïve patient experienced acute-onset anterior and intermediate uveitis which completely resolved after therapy. Conclusions: Brolucizumab was demonstrated to be a safe and efficient alternative in improving both the anatomical and functional parameters of eyes with nAMD in this small, uncontrolled, series of patients.

Inhibition of Galectins and the P2X7 Purinergic Receptor as a Therapeutic Approach in the Neurovascular Inflammation of Diabetic Retinopathy

Diabetic retinopathy (DR) is the most frequent microvascular retinal complication of diabetic patients, contributing to loss of vision. Recently, retinal neuroinflammation and neurodegeneration have emerged as key players in DR progression, and therefore, this review examines the neuroinflammatory molecular basis of DR. We focus on four important aspects of retinal neuroinflammation: (i) the exacerbation of endoplasmic reticulum (ER) stress; (ii) the activation of the NLRP3 inflammasome; (iii) the role of galectins; and (iv) the activation of purinergic 2X7 receptor (P2X7R). Moreover, this review proposes the selective inhibition of galectins and the P2X7R as a potential pharmacological approach to prevent the progression of DR.

Oral Administration of Vitamin D3 Prevents Corneal Damage in a Knock-Out Mouse Model of Sjögren's Syndrome

BACKGROUND

Vitamin D deficiency has been associated with dry eye development during Sjögren's syndrome (SS). Here, we investigated whether repeated oral vitamin D3 supplementation could prevent the corneal epithelium damage in an SS mouse model.

METHODS

30 female mouse knock-out for the thrombospondin 1 gene were randomized (six per group) in untreated mice euthanized at 6 weeks as negative control (C-) or at 12 weeks as the positive control for dry eye (C+). Other mice were sacrificed after 6 weeks of oral vitamin D3 supplementation in the drinking water (1000, 8000, and 20,000 IU/kg/week, respectively).

RESULTS

The C+ mice showed alterations in their corneal epithelial morphologies and thicknesses (p < 0.01 vs. C-), while the mice receiving 8000 (M) and 20,000 (H) IU/kg/week of vitamin D3 showed preservation of the corneal epithelium morphology and thickness (p < 0.01 vs. C+). Moreover, while the C+ mice exhibited high levels and activity of corneal tumor necrosis factor alpha converting enzyme (TACE), neovascularization and fibrosis markers; these were all reduced in the M and H mice.

CONCLUSIONS

Oral vitamin D3 supplementation appeared to counteract the negative effect of TACE on corneal epithelium in a mouse model of SS-associated dry eye.

Effects of the Calix[4]arene Derivative Compound OTX008 on High Glucose-Stimulated ARPE-19 Cells: Focus on Galectin-1/TGF-β/EMT Pathway

Diabetic retinopathy (DR) is a neurovascular disease characterized by the reduction of retina integrity and functionality, as a consequence of retinal pigment epithelial cell fibrosis. Although galectin-1 (a glycan-binding protein) has been associated with dysregulated retinal angiogenesis, no evidence has been reported about galectin-1 roles in DR-induced fibrosis. ARPE-19 cells were cultured in normal (5 mM) or high glucose (35 mM) for 3 days, then exposed to the selective galectin-1 inhibitor OTX008 (2.5–5–10 μM) for 6 days. The determination of cell viability and ROS content along with the analysis of specific proteins (by immunocytochemistry, Western blotting, and ELISA) or mRNAs (by real time-PCR) were performed. OTX008 5 μM and 10 μM improved cell viability and markedly reduced galectin-1 protein expression in cells exposed to high glucose. This was paralleled by a down-regulation of the TGF-β/, NF-kB p65 levels, and ROS content. Moreover, epithelial–mesenchymal transition markers were reduced by OTX008 5 μM and 10 μM. The inhibition of galectin-1 by OTX008 in DR may preserve retinal pigment epithelial cell integrity and functionality by reducing their pro-fibrotic phenotype and epithelial–mesenchymal transition phenomenon induced by diabetes.

Resolution of Inflammation in Retinal Disorders: Briefly the State

The most frequent retinal diseases, such as diabetic retinopathy, age-related macular degeneration and posterior uveitis, are underlined by oxidative stress or aging-induced retinal inflammation, which contributes to vision impairing or loss. Resolution of inflammation is emerging as a critical phase able to counteract the inflammatory process leading to the progression of retinal damage. Particularly, pro-resolving mediators (PMs) play a key role in the modulation of inflammatory exudates and could be considered a new target to be investigated in different inflammatory-autoimmune pathologies. Here, we highlight the most recent studies concerning the role of the main PMs (lipoxins, resolvins, prtectins, maresins and annexins) in retinal inflammation, in order to collect the best evidence in the field of inflammatory retinal damage resolution and to propose novel pharmacological approaches in the management of the most common retinal diseases.

Serum Iba-1, GLUT5, and TSPO in Patients With Diabetic Retinopathy: New Biomarkers for Early Retinal Neurovascular Alterations? A Pilot Study

Purpose

This study explored the possibility of highlighting early retinal neurovascular alterations of diabetic retinopathy (DR) by monitoring in DR patients the serum levels of microglial biomarkers ionized calcium-binding adapter molecule 1 (Iba-1), glucose transporter 5 (GLUT5), and translocator protein (TSPO), along with serum changes of the endothelial dysfunction marker arginase-1.

Methods

Serum markers were determined by enzyme-linked immunosorbent assay in 50 patients: 12 non-diabetic subjects, 14 diabetic patients without DR, 13 patients with non-proliferative DR (NPDR), and 11 patients with proliferative DR (PDR). The results were correlated with hyperreflective retinal spots (HRS), observed with optical coherence tomography (OCT).

Results

Although HRS were absent in diabetic patients without DR, NPDR patients showed an average of 4 ± 1 HRS, whereas the highest presence was detected in PDR patients, with 8 ± 1 HRS (P < 0.01 vs. NPDR). HRS were positively correlated (P < 0.01) with serum levels of arginase-1 (r = 0.91), Iba-1 (r = 0.96), GLUT5 (r = 0.94), and TSPO (r = 0.88). Moreover, serum proinflammatory cytokines and chemokines showed a positive correlation (P < 0.01) with HRS number and the serum markers analyzed.

Conclusions

Serum markers of microglial activation positively correlate with retinal HRS in NPDR and PDR patients.

Translational Relevance

These data corroborate the possibility of highlighting early retinal neurovascular changes due to diabetes by monitoring circulating microglial markers.

Inclusion of a degron reduces levelsof undesired inteins after AAV-mediated proteintrans-splicing in the retina

Split intein-mediated protein trans-splicing expands AAV transfer capacity, thus overcoming the limited AAV cargo. However, non-mammalian inteins persist as trans-splicing by-products, and this could raise safety concerns for AAV intein clinical applications. In this study, we tested the ability of several degrons to selectively decrease levels of inteins after protein trans-splicing and found that a version of E. coli dihydrofolate reductase, which we have shortened to better fit into the AAV vector, is the most effective. We show that subretinal administration of AAV intein armed with this short degron is both safe and effective in a mouse model of Stargardt disease (STGD1), which is the most common form of inherited macular degeneration in humans. This supports the use of optimized AAV intein for gene therapy of both STGD1 and other conditions that require transfer of large genes.

Fingolimod and Diabetic Retinopathy: A Drug Repurposing Study

This study aimed to investigate the interactions between fingolimod, a sphingosine 1-phosphate receptor (S1PR) agonist, and melanocortin receptors 1 and 5 (MCR1, MCR5). In particular, we investigated the effects of fingolimod, a drug approved to treat relapsing-remitting multiple sclerosis, on retinal angiogenesis in a mouse model of diabetic retinopathy (DR). We showed, by a molecular modeling approach, that fingolimod can bind with good-predicted affinity to MC1R and MC5R. Thereafter, we investigated the fingolimod actions on retinal MC1Rs/MC5Rs in C57BL/6J mice. Diabetes was induced in C57BL/6J mice through streptozotocin injection. Diabetic and control C57BL/6J mice received fingolimod, by oral route, for 12 weeks and a monthly intravitreally injection of MC1R antagonist (AGRP), MC5R antagonist (PG20N), and the selective S1PR1 antagonist (Ex 26). Diabetic animals treated with fingolimod showed a decrease of retinal vascular endothelial growth factor A (VEGFA) and vascular endothelial growth factor receptors 1 and 2 (VEGFR1 and VEGFR2), compared to diabetic control group. Fingolimod co-treatment with MC1R and MC5R selective antagonists significantly (p < 0.05) increased retinal VEGFR1, VEGFR2, and VEGFA levels compared to mice treated with fingolimod alone. Diabetic animals treated with fingolimod plus Ex 26 (S1PR1 selective blocker) had VEGFR1, VEGFR2, and VEGFA levels between diabetic mice group and the group of diabetic mice treated with fingolimod alone. This vascular protective effect of fingolimod, through activation of MC1R and MC5R, was evidenced also by fluorescein angiography in mice. Finally, molecular dynamic simulations showed a strong similarity between fingolimod and the MC1R agonist BMS-470539. In conclusion, the anti-angiogenic activity exerted by fingolimod in DR seems to be mediated not only through S1P1R, but also by melanocortin receptors.

Therapy of Age-related Exudative Macular Degeneration with Anti-vascular Endothelial Growth Factor Drugs: An Italian Real Life Study

Aim:

To evaluate the real utilization of ranibizumab and aflibercept in the daily management of patients with neovascular age-related macular degeneration (nAMD) treated at the Eye Clinic of Campania University L.Vanvitelli.

Background:

Therapy with anti-vascular endothelial growth factor represents the gold standard in wet age-related macular degeneration. There are nonreal life italian studies of this therapy in the literature.

Objective:

To analyze in our sample the post-therapy variations of best-corrected visual acuity (BCVA) and central retinal thickness (CRT) observed at the end of a 12-month follow-up period.

Methods:

This real-life study analyzes 109 patients that underwent monthly checks for the first 4 months and then every 2 months until the end of the 12-month follow-up. The sample was first analyzed in its entirety, subsequently subdivided into 3 groups based on baseline BCVA, age, and the number of intravitreal injections performed, in order to identify possible predictive elements of the anti-VEGF response.

Results:

On average, patients underwent 4.16 ± 1.58 intravitreal anti-VEGF injections in 1 year. At the end of the 12-month follow-up, the patients’ average BCVA increased from 33.01 letters to 33.75 letters (+0.74 ± 9,4 letters), while the average CRT decreased from 346.86 µm to 265.39 µm (-81.47 ± 121 µm).

Conclusion:

The study shows the efficacy of anti-VEGF therapy in the stabilization of BCVA in nAMD, confirming the differences in visual outcomes compared to clinical trials, mainly for economic-organizational reasons.

Autophagy: A Novel Pharmacological Target in Diabetic Retinopathy

Autophagy is the major catabolic pathway involved in removing and recycling damaged macromolecules and organelles and several evidences suggest that dysfunctions of this pathway contribute to the onset and progression of central and peripheral neurodegenerative diseases. Diabetic retinopathy (DR) is a serious complication of diabetes mellitus representing the main preventable cause of acquired blindness worldwide. DR has traditionally been considered as a microvascular disease, however this concept has evolved and neurodegeneration and neuroinflammation have emerged as important determinants in the pathogenesis and evolution of the retinal pathology. Here we review the role of autophagy in experimental models of DR and explore the potential of this pathway as a target for alternative therapeutic approaches.

Sex and Age-Related Differences in Neuroinflammation and Apoptosis in Balb/c Mice Retina Involve Resolvin D1

(1) Background: The pro-resolving lipid mediator Resolvin D1 (RvD1) has already shown protective effects in animal models of diabetic retinopathy. This study aimed to investigate the retinal levels of RvD1 in aged (24 months) and younger (3 months) Balb/c mice, along with the activation of macro- and microglia, apoptosis, and neuroinflammation. (2) Methods: Retinas from male and female mice were used for immunohistochemistry, immunofluorescence, transmission electron microscopy, Western blotting, and enzyme-linked immunosorbent assays. (3) Results: Endogenous retinal levels of RvD1 were reduced in aged mice. While RvD1 levels were similar in younger males and females, they were markedly decreased in aged males but less reduced in aged females. Both aged males and females showed a significant increase in retinal microglia activation compared to younger mice, with a more marked reactivity in aged males than in aged females. The same trend was shown by astrocyte activation, neuroinflammation, apoptosis, and nitrosative stress, in line with the microglia and Müller cell hypertrophy evidenced in aged retinas by electron microscopy. (4) Conclusions: Aged mice had sex-related differences in neuroinflammation and apoptosis and low retinal levels of endogenous RvD1.

Correlation Between Choriocapillaris Density and Retinal Sensitivity in Age-Related Macular Degeneration

Purpose

The purpose of this study was to investigate the relationship between perfusion of the choriocapillaris (CC) and retinal sensitivity in eyes with intermediate age-related macular degeneration (iAMD).

Methods

This prospective study included patients with iAMD and healthy controls. All enrolled subjects underwent optical coherence tomography angiography (OCT-A) in order to compute the percent perfused choriocapillaris area (PPCA). In patients with iAMD, microperimetry (MP) testing was performed in order to quantify: mean retinal sensitivity (MRS), over an area of 10 degrees; mean macular sensitivity (MMS), over the macular area scanned with OCT-A; and retinal sensitivity (RS) in each macular point.

Results

Eighteen eyes of 13 patients were included in the analysis. In addition, 18 eyes of 12 healthy subjects were enrolled as controls. No statistically significant difference (P value > 0.2) was observed in age between patients (73.9 ± 2.0 years) and controls (70.1 ± 2.8 years). We observed significantly lower values of PPCA between patients with iAMD and healthy controls (42.0% ± 3.8% vs. 66.4% ± 3.0%; -β = 23.8%; P value < 0.001). Among iAMD eyes, higher values of PPCA were significantly associated with higher values of MRS (P value = 0.002) and MMS (P value = 0.013). Finally, higher values of RS in each macular point analyzed with MP were significantly (P value < 0.001) associated with higher values of PPCA computed in circular regions of interest (ROIs) centered in each analyzed MP point with radii of 0.5 degrees and 1.0 degree.

Conclusions

Using OCT-A, we demonstrated a significant association between CC impairment and macular dysfunction, quantified by MP, in iAMD eyes.

Translational Relevance

OCT-A could be a useful tool for detecting CC alterations and to monitor disease progression.

Circulating miRNAs in diabetic retinopathy patients: Prognostic markers or pharmacological targets?

In this study we analyzed the expression of circulating miRNAs, in the serum of diabetic retinopathy (DR) patients. Five miRNAs (hsa-miR-195-5p, hsa-miR-20a-5p, hsa-miR-20b-5p, hsa-miR-27b-3p and hsa-miR-451a) were validated as biomarkers for stratification of DR stages, from the early non-proliferative (NPDR) to the late proliferative (PDR) phase. Furthermore, circulating levels of these miRNAs correlated with retinal hyper-reflective spots (HRS), assessed by optical coherence tomography (OCT). The number of HRS increased with worsening of DR stages. On the contrary, no significant vascular density differences between NPDR and PDR patients were detected by angio-OCT (OCTA). A post-hoc bioinformatics analysis associated these five miRNAs to target genes belonging to the "Tumor Necrosis Factor alfa signaling" pathway, and several molecules were predicted to modify miRNAs expression. In conclusion, correlation between specific circulating miRNAs and intraretinal hyper-reflective spots was demonstrated, confirming that these miRNAs were validated as prognostic biomarkers, and also as potential pharmacological targets, warranting further clinical evaluation to explore novel therapeutics for diabetic retinopathy.

Changes in Retinal Structure and Ultrastructure in the Aged Mice Correlate With Differences in the Expression of Selected Retinal miRNAs

Age and gender are two important factors that may influence the function and structure of the retina and its susceptibility to retinal diseases. The aim of this study was to delineate the influence that biological sex and age exert on the retinal structural and ultrastructural changes in mice and to identify the age-related miRNA dysregulation profiles in the retina by gender. Experiments were undertaken on male and female Balb/c aged 24 months (approximately 75–85 years in humans) compared to the control (3 months). The retinas were analyzed by histology, transmission electron microscopy, and age-related miRNA expression profile analysis. Retinas of both sexes showed a steady decline in retinal thickness as follows: photoreceptor (PS) and outer layers (p < 0.01 for the aged male vs. control; p < 0.05 for the aged female vs. control); the inner retinal layers were significantly affected by the aging process in the males (p < 0.01) but not in the aged females. Electron microscopy revealed more abnormalities which involve the retinal pigment epithelium (RPE) and Bruch’s membrane, outer and inner layers, vascular changes, deposits of amorphous materials, and accumulation of lipids or lipofuscins. Age-related miRNAs, miR-27a-3p (p < 0.01), miR-27b-3p (p < 0.05), and miR-20a-5p (p < 0.05) were significantly up-regulated in aged male mice compared to the controls, whereas miR-20b-5p was significantly down-regulated in aged male (p < 0.05) and female mice (p < 0.05) compared to the respective controls. miR-27a-3p (5.00 fold; p < 0.01) and miR-27b (7.58 fold; p < 0.01) were significantly up-regulated in aged male mice vs. aged female mice, whereas miR-20b-5p (−2.10 fold; p < 0.05) was significantly down-regulated in aged male mice vs. aged female mice. Interestingly, miR-27a-3p, miR-27b-3p, miR-20a-5p, and miR-20b-5p expressions significantly correlated with the thickness of the retinal PS layer (p < 0.01), retinal outer layers (p < 0.01), and Bruch’s membrane (p < 0.01). Our results showed that biological sex can influence the structure and function of the retina upon aging, suggesting that this difference may be underlined by the dysregulation of age-related mi-RNAs.

Two-year macular volume assessment in multiple sclerosis patients treated with fingolimod

BACKGROUND

Fingolimod (FNG) is associated with the development of symptomatic macular edema (ME) in a small subset of multiple sclerosis (MS) patients. By using spectral domain optical coherence tomography (SD-OCT), an increase in the total macular volume (TMV) was rarely detected during the first months of treatment.

OBJECTIVES

The objective of this study is to assess whether FNG treatment leads to long-term macular changes in a real-life setting.

METHODS

Sixty RRMS patients starting FNG, according to therapeutic indication, were enrolled at three Italian MS centers and followed for 2 years.

RESULTS

The mean TMV did not change between baseline and the follow-up. No patients experienced visual acuity drop during the follow-up.

CONCLUSIONS

Initiation of FNG in MS is associated with a modest, not significant, increase in macular volume followed by no further significant changes over 2 years, highlighting the good safety profile of such treatment in MS.

Bergmeister's papilla in a young patient with type 1 sialidosis: case report

Background

Sialidosis is a rare genetic lysosomal storage disorder caused by a deficit of neuraminidase enzyme activity. Patients with sialidosis present various neurological disorders such as: myoclonic epilepsy and hypotonia, often associated with visual impairment. A typical aspect of sialidosis is the finding of a macular cherry-red spot on ocular fundus examination. In this paper we describe a unilateral case of Bergmeister’s papilla (BP) in a young female patient suffering from type 1 sialidosis.

Case presentation

A 28-year-old young woman suffering from type 1 sialidosis, confirmed by previously described compound heterozigosity Leu91Arg and Gly328Ser on N-acetyl-alpha-neuraminidase − 1 (NEU1) gene, underwent an opthalmological examination at the Eye Clinic of the University of Campania L. Vanvitelli, for bilateral visual deterioration. The patient was suffering from myoclonic epilepsy with hypotonia and severe motor disability. Fundoscopic examination showed a typical macular cherry-red spot with retinal pigment epithelium dystrophy in the middle periphery, in both eyes. Furthermore, in the left eye (OS), a vitreous thickening was observed in the nasal sector of the optic disc, remnant of fetal vasculature on the optic disc (Bergmeister’s papilla). Optical coherence tomography (OCT) showed, in both eyes, a thickening of the ganglion cell layer (GCL) with a hyperreflective opacity as a cap on the left optic disc.

Conclusions

In our paper we have described, for the first time in literature, a case of BP in a patient with type 1 sialidosis. The detection of BP with thickening of the peripapillary vitreous by SD-OCT is useful in monitoring any vitreo-retinal change that could cause future visual deterioration.

Stabilization of HIF-1α in Human Retinal Endothelial Cells Modulates Expression of miRNAs and Proangiogenic Growth Factors

Retinal hypoxia is one of the causative factors of diabetic retinopathy and is also one of the triggers of VEGF release. We hypothesized that specific dysregulated miRNAs in diabetic retinopathy could be linked to hypoxia-induced damage in human retinal endothelial cells (HRECs). We investigated in HRECs the effects of chemical (CoCl₂) hypoxia on the expression of HIF-1α, VEGF, PlGF, and of a focused set of miRNAs. We found that miR-20a-5p, miR-20b-5p, miR-27a-3p, miR-27b-3p, miR-206-3p, miR-381-3p correlated also with expression of TGFβ signaling pathway genes in HRECs, challenged with chemical hypoxic stimuli. In conclusion, our data suggest that retinal angiogenesis would be promoted, at least under HIF-1α activation, by upregulation of PlGF and other factors such as miRNAs, VEGFA, and TGFβ1.

Intein-mediated protein trans-splicing expands adeno-associated virus transfer capacity in the retina

Retinal gene therapy with adeno-associated viral (AAV) vectors holds promises for treating inherited and noninherited diseases of the eye. Although clinical data suggest that retinal gene therapy is safe and effective, delivery of large genes is hindered by the limited AAV cargo capacity. Protein trans-splicing mediated by split inteins is used by single-cell organisms to reconstitute proteins. Here, we show that delivery of multiple AAV vectors each encoding one of the fragments of target proteins flanked by short split inteins results in protein trans-splicing and full-length protein reconstitution in the retina of mice and pigs and in human retinal organoids. The reconstitution of large therapeutic proteins using this approach improved the phenotype of two mouse models of inherited retinal diseases. Our data support the use of split intein-mediated protein trans-splicing in combination with AAV subretinal delivery for gene therapy of inherited blindness due to mutations in large genes.

Retinal and circulating miRNA expression patterns in diabetic retinopathy: An in silico and in vivo approach

BACKGROUND AND PURPOSE

Diabetic retinopathy, a secondary complication of diabetes mellitus, can lead to irreversible vision loss. Currently, no treatment is approved for early phases of diabetic retinopathy. Modifications of the expression pattern of miRNAs could be involved in the early retinal damage of diabetic subjects. Therefore, we aimed at identification of dysregulated miRNAs-mRNA interactions that might be biomarkers and pharmacological targets for diagnosis and treatment of early diabetic retinopathy.

METHODS

A focused set of miRNAs was predicted through a bioinformatic analysis accessing to Gene Expression Omnibus dataset and enrichment of information approach (GENEMANIA-Cytoscape). Identification of miRNAs-mRNA interactions was carried out with miRNET analysis. Diabetes was induced in C57BL6J mice by streptozotocin and samples analysed at 5 and 10 weeks after diabetes induction. Retinal ultrastructure of diabetic mice was analysed through electron microscopy. We used Real-time PCR, western blot analysis, elisa, and immunohistochemistry to study expression of miRNAs and possible targets of dysregulated miRNAs.

KEY RESULTS

We found that miR-20a-5p, miR-20a-3p, miR-20b, miR-106a-5p, miR-27a-5p, miR-27b-3p, miR-206-3p, and miR-381-3p were dysregulated in the retina and serum of diabetic mice. VEGF, brain-derived neurotrophic factor (BDNF), PPAR-α, and cAMP response element-binding protein 1 (CREB1) are targets of dysregulated miRNAs, which then modulated protein expression in diabetic retina. We found structural modifications in retinas from diabetic mice.

CONCLUSIONS AND IMPLICATIONS

Serum and retina of diabetic mice express eight dysregulated miRNAs, which modified the expression of VEGF, BDNF, PPAR-α, and CREB1, before vasculopathy in diabetic retinas.

Targeting and silencing of rhodopsin by ectopic expression of the transcription factor KLF15

The genome-wide activity of transcription factors (TFs) on multiple regulatory elements precludes their use as gene-specific regulators. Here we show that ectopic expression of a TF in a cell-specific context can be used to silence the expression of a specific gene as a therapeutic approach to regulate gene expression in human disease. We selected the TF Krüppel-like factor 15 (KLF15) based on its putative ability to recognize a specific DNA sequence motif present in the rhodopsin (RHO) promoter and its lack of expression in terminally differentiated rod photoreceptors (the RHO-expressing cells). Adeno-associated virus (AAV) vector-mediated ectopic expression of KLF15 in rod photoreceptors of pigs enables Rho silencing with limited genome-wide transcriptional perturbations. Suppression of a RHO mutant allele by KLF15 corrects the phenotype of a mouse model of retinitis pigmentosa with no observed toxicity. Cell-specific-context conditioning of TF activity may prove a novel mode for somatic gene-targeted manipulation.

Macular hole closure patterns associated with different internal limiting membrane flap techniques

PURPOSE

To compare the anatomic and functional outcome of two variants of the inverted internal limiting membrane (I-ILM) flap technique for idiopathic macular holes (IMH) larger than 400 µm.

METHODS

Twenty-seven consecutive patients undergoing PPV for IMH were randomly assigned to different variants of I-ILM technique: the Cover group included 14 patients in which the I-ILM was folded upside-down over the MH as a single layer while the Fill group enrolled 13 patients in which the I-ILM was folded within the MH in multiple layers.

RESULTS

MH closed in 12/14 Cover and in 13/13 Fill eyes (84.6 vs. 100%, p = 0.14; n.s.). Vision at 1 month was Snellen 0.44 ± 0.17 vs. 0.28 ± 0.21 (p = 0.05) and 0.48 ± 0.20 vs. 0.37 ± 0.25 (n.s.) at 3 months. IS/OS line interruption width was 463 ± 385 vs. 602 ± 210 µm, respectively, at 1 month (n.s.) and 602 ± 210 vs. 563 ± 209 µm at 3 months (n.s.). The Cover group showed outer retina cystic changes more often (p < 0.01). MH over 700 µm closed in 0/2 and in 2/2 cases, respectively, in the Cover and Fill groups (0.045).

CONCLUSIONS

Cover and Fill I-ILM techniques allowed similar closure rates and post-operative vision at 3 months. The Cover group showed better anatomical restoration and vision at 1 month while the Fill technique might be more efficient in closing larger MHs.

Melanocortin receptor agonists MCR1-5 protect photoreceptors from high-glucose damage and restore antioxidant enzymes in primary retinal cell culture

Retinal photoreceptors are particularly vulnerable to local high‐glucose concentrations. Oxidative stress is a risk factor for diabetic retinopathy development. Melanocortin receptors represent a family of G‐protein‐coupled receptors classified in five subtypes and are expressed in retina. Our previous data indicate that subtypes 1 and 5 receptor agonists exert a protective role on experimental diabetic retinopathy. This study focuses on their role in primary retinal cell cultures in high‐glucose concentrations. After eye enucleation from wild‐type male C57BL/6 mice, retinal cells were isolated, plated in high‐glucose concentration and treated with melanocortin receptors 1 and 5 agonists and antagonists. Immunocytochemical and biochemical analysis showed that treatment with melanocortin receptors 1 and 5 agonists reduced anti‐inflammatory cytokines and chemokines and enhanced manganese superoxide dismutase and glutathione peroxidase levels, preserving photoreceptor integrity. According with these evidences, we propose a major role of melanocortin receptors 1 and 5 on primary retinal cell response against high glucose or oxidative insults.

Rhodopsin targeted transcriptional silencing by DNA-binding

Transcription factors (TFs) operate by the combined activity of their DNA-binding domains (DBDs) and effector domains (EDs) enabling the coordination of gene expression on a genomic scale. Here we show that in vivo delivery of an engineered DNA-binding protein uncoupled from the repressor domain can produce efficient and gene-specific transcriptional silencing. To interfere with RHODOPSIN (RHO) gain-of-function mutations we engineered the ZF6-DNA-binding protein (ZF6-DB) that targets 20 base pairs (bp) of a RHOcis-regulatory element (CRE) and demonstrate Rho specific transcriptional silencing upon adeno-associated viral (AAV) vector-mediated expression in photoreceptors. The data show that the 20 bp-long genomic DNA sequence is necessary for RHO expression and that photoreceptor delivery of the corresponding cognate synthetic trans-acting factor ZF6-DB without the intrinsic transcriptional repression properties of the canonical ED blocks Rho expression with negligible genome-wide transcript perturbations. The data support DNA-binding-mediated silencing as a novel mode to treat gain-of-function mutations.

DOI:http://dx.doi.org/10.7554/eLife.12242.001

Proteins called transcription factors bind to sections of DNA known as regulatory elements to activate or deactivate nearby genes. In animals, transcription factors typically have two sections: a “DNA-binding domain” that attaches to DNA, and an “effector domain” that is responsible for interacting with other proteins to regulate the gene’s expression.

Rhodopsin is a gene that encodes the instructions needed to make a light-sensitive protein in the eyes of humans and other animals. Botta et al. have now used this gene as an example to investigate whether proteins that contain a DNA-binding domain – but not an effector domain – can repress gene expression.

The experiments show that only a small section of the regulatory elements in the human Rhodopsin gene is actually required for the gene to be expressed. Botta et al. designed an artificial protein – referred to as ZF6-DB – that is able to bind to this section of DNA. The binding of ZF6-DB to this short DNA section was sufficient to switch off a Rhodopsin gene in living pig cells, and, unlike conventional transcription factors, seemed to have minimal impact other genes.

Next, Botta et al. used a virus to insert both the gene that encodes ZF6-DB and a normal copy of Rhodopsin into pigs. In these animals, ZF6-DB switched off the existing copy of Rhodopsin, but not the inserted copy so the cells produced a working form of the light-sensitive protein. Further experiments were carried out in mice that have both a faulty version and a normal copy of the Rhodopsin gene. ZF6-DB switched off the faulty Rhodopsin gene, which allowed the normal Rhodopsin gene to work without any interference from the faulty copy.

Mutations in Rhodopsin can cause an eye disease that leads to severe loss of vision in humans. These new findings could now guide future efforts to develop treatments for people with this condition. It will also be important to investigate how ZF6-DB binds to the regulatory elements in the Rhodopsin gene and whether a similar strategy could be used to alter the expression of other genes.

DOI:http://dx.doi.org/10.7554/eLife.12242.002

Clinical and genetic features in Italian Bietti crystalline dystrophy patients

Aim

The aim of the study was to describe the clinical and genetic features of 15 Italian patients with Bietti crystalline dystrophy (BCD).

Methods

All study participants underwent a complete ophthalmological examination, including standard electroretinogram (ERG), optical coherence tomography, microperimetry, autofluorescence and multifocal electroretinogram. The 11 exons of the CYP4V2 gene were sequenced. The effect of mutations on protein function was estimated by a combination of web based programs.

Results

15 patients (eight women, 7 men, aged 29–60 years) with BCD were recruited into this study. Sequencing of CYP4V2 revealed nine sequence variants in four unrelated families and six isolated individuals with BCD. Seven of these variants were novel. Among the patients, even with the same genotype, considerable variability in phenotypic expression with different degrees of accumulation of the typical intraretinal crystalline deposits was detected. Moreover, we found that more than 50% of patients had recordable standard ERG responses and in two patients the responses were within normal limits after 20 years of symptom onset.

Conclusions

In conclusion, we have reported seven new mutations and illustrated the large range of genotypic and phenotypic variability in BCD, highlighting the lack of a clear genotype–phenotype correlation and underlining the existence of less severe clinical manifestations, probably linked to relatively mild mutations.

An atypical form of Bietti crystalline dystrophy

PURPOSE

To describe clinical and functional features of a patient with Bietti crystalline dystrophy and atypical electroretinogram responses.

METHODS

The patient underwent a thorough medical anamnesis, genetic counseling, peripheral blood draw for CYP4V2 gene analysis and electron microscopy, and a complete ophthalmological assessment including optical coherence tomography, indocyanine green angiography, microperimetry, full-field electroretinogram and multifocal electroretinogram.

RESULTS

The most striking features of the retina were deposits of yellowish-white glistening crystals and focal lobular areas of choriocapillary atrophy at the posterior pole and midperiphery. The full-field electroretinogram was normal and the multifocal electroretinogram showed extinguished central recordings. Mutation analysis revealed a homozygous c. 332T>C p.I111T mutation in exon 3 of the CYP4V2 gene. Typical cytoplasmic inclusions containing crystalline-like structure and large degenerative lysosomes were seen on electron microscopy of peripheral leukocytes.

CONCLUSION

Here we describe a patient with Bietti crystalline dystrophy with a CYP4V2 gene mutation and typical leukocyte inclusions who showed the classical retinal lesions but had a normal electroretinogram. This suggests the existence of less severe forms of BCD related to relatively mild CYP4V2 mutations.