In the retina, the mineralocorticoid receptor is expressed in retinal and choroidal vessels and in cells from neural and glial origins. Like in the brain, the major ligand of the mineralocorticoid ...receptor is cortisol, and the mineralocorticoid/glucocorticoid receptor balance regulates the activation of the MR pathway. Experimental mineralocorticoid receptor pathway activation using either pharmacological agents or transgenic manipulation favours retinal and choroidal pathology. In various models of retinal diseases, such as glaucomatous neuropathy, retinopathy of prematurity, ischaemic retinopathies, diabetic retinopathy and choroidal neovascularization, mineralocorticoid receptor antagonism exerts beneficial effects, demonstrating its potential in the treatment of major blinding retinal diseases. But specific formulations are required to optimize the bioavailability of mineralocorticoid receptor antagonists in various compartments of the eye, and molecular biomarkers of mineralocorticoid receptor pathway activation remain to be identified in humans to select patients amenable to clinical trials.
LINKED ARTICLES
This article is part of a themed issue on Emerging Fields for Therapeutic Targeting of the Aldosterone‐Mineralocorticoid Receptor Signaling Pathway. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.13/issuetoc
•Luxturna, a viral gene therapy product, is approved for rare Leber’s congenital amaurosis.•Ocular gene therapies are now being developed for non-inherited retinal disorders.•Specificities of viral ...and non-viral vectors as well as future challenges to face are discussed.
Ocular gene therapy has entered into clinical practice. Although viral vectors are currently the best option to replace and/or correct genes, the optimal method to deliver these treatments to the retinal pigment epithelial (RPE) cells and/or photoreceptor cells remains to be improved to increase transduction efficacy and reduce iatrogenic risks. Beyond viral-mediated gene replacement therapies, nonviral gene delivery approaches offer the promise of sustained fine-tuned expression of secreted therapeutic proteins that can be adapted to the evolving stage of the disease course and can address more common nongenetic retinal diseases, such as age-related macular degeneration (AMD). Here, we review current gene therapy strategies for ocular diseases, with a focus on clinical stage products.
Ageing and alteration of the functions of the retinal pigment epithelium (RPE) are at the origin of lost of vision seen in age‐related macular degeneration (AMD). The RPE is known to be vulnerable to ...high‐energy blue light. The white light‐emitting diodes (LED) commercially available have relatively high content of blue light, a feature that suggest that they could be deleterious for this retinal cell layer. The aim of our study was to investigate the effects of “white LED” exposure on RPE. For this, commercially available white LEDs were used for exposure experiments on Wistar rats. Immunohistochemical stain on RPE flat mount, transmission electron microscopy and Western blot were used to exam the RPE. LED‐induced RPE damage was evaluated by studying oxidative stress, stress response pathways and cell death pathways as well as the integrity of the outer blood–retinal barrier (BRB). We show that white LED light caused structural alterations leading to the disruption of the outer blood–retinal barrier. We observed an increase in oxidized molecules, disturbance of basal autophagy and cell death by necrosis. We conclude that white LEDs induced strong damages in rat RPE characterized by the breakdown of the BRB and the induction of necrotic cell death.
Aims
Glucocorticoid intake is a well‐established risk factor for central serous chorioretinopathy that belongs to the pachychoroid spectrum disease (PSD). The study aimed to assess the prevalence of ...PSD and analyse the choroidal phenotype in patients with Cushing syndrome.
Methods
A cross‐sectional study was performed in Ophtalmopôle hôpital Cochin, Paris, France, with a systematic evaluation of hospitalized patients with Cushing syndrome, between November 2017 and July 2018. 56 eyes from 28 Cushing syndrome patients and 56 eyes of 28 age and gender‐matched, and close spherical equivalent healthy participants were included. All patients underwent a complete ophthalmic examination including Enhanced‐Depth Imaging (EDI)‐Optical Coherence Tomography (OCT). Measures of subfoveal, 1000 µm nasal and 1000 µm temporal choroidal thicknesses were realized, and the presence of choroidal pachyvessels was evaluated. Hormonal tests evaluated the corticotropic axis.
Results
The number of eyes with PSD was significantly higher in Cushing syndrome patients as compared to controls (21.4% versus 3.6%, p = 0.004). In Cushing patients’ eyes, 17.9% had a pachychoroid pigment epitheliopathy (PPE) and 3.6% had a polypoidal choroidal vasculopathy. Pachyvessels were more common in Cushing syndrome patients than in healthy subjects (71.4% versus 42.9%, p = 0.002). Mean subfoveal choroidal thickness was 331 ± 110 µm in Cushing patients, with no statistical difference between the two groups. There was no correlation between choroidal thickness and urinary and salivary cortisol levels.
Conclusion
Patients with Cushing syndrome have a higher prevalence of PDS. An ophthalmologic specialized follow‐up of these patients with EDI‐OCT could detect chorioretinal abnormalities and adapt the surveillance of these patients.
Central serous chorioretinopathy (CSCR) is a major cause of vision threat among middle-aged male individuals. Multimodal imaging led to the description of a wide range of CSCR manifestations, and ...highlighted the contribution of the choroid and pigment epithelium in CSCR pathogenesis. However, the exact molecular mechanisms of CSCR have remained uncertain. The aim of this review is to recapitulate the clinical understanding of CSCR, with an emphasis on the most recent findings on epidemiology, risk factors, clinical and imaging diagnosis, and treatments options. It also gives an overview of the novel mineralocorticoid pathway hypothesis, from animal data to clinical evidences of the biological efficacy of oral mineralocorticoid antagonists in acute and chronic CSCR patients. In rodents, activation of the mineralocorticoid pathway in ocular cells either by intravitreous injection of its specific ligand, aldosterone, or by over-expression of the receptor specifically in the vascular endothelium, induced ocular phenotypes carrying many features of acute CSCR. Molecular mechanisms include expression of the calcium-dependent potassium channel (KCa2.3) in the endothelium of choroidal vessels, inducing subsequent vasodilation. Inappropriate or over-activation of the mineralocorticoid receptor in ocular cells and other tissues (such as brain, vessels) could link CSCR with the known co-morbidities observed in CSCR patients, including hypertension, coronary disease and psychological stress.
The role of vascular endothelial growth factor (VEGF), including in retinal vascular diseases, has been well studied, and pharmacological blockade of VEGF is the gold standard of treatment for ...neovascular age‐related macular degeneration, retinal vein occlusion and diabetic macular oedema. Placental growth factor (PGF, previously known as PlGF), a homologue of VEGF, is a multifunctional peptide associated with angiogenesis‐dependent pathologies in the eye and non‐ocular conditions. Animal studies using genetic modification and pharmacological treatment have demonstrated a mechanistic role for PGF in pathological angiogenesis. Inhibition decreases neovascularization and microvascular abnormalities across different models, including oxygen‐induced retinopathy, laser‐induced choroidal neovascularization and in diabetic mice exhibiting retinopathies. High levels of PGF have been found in the vitreous of patients with diabetic retinopathy. Despite these strong animal data, the exact role of PGF in pathological angiogenesis in retinal vascular diseases remains to be defined, and the benefits of PGF‐specific inhibition in humans with retinal neovascular diseases and macular oedema remain controversial. Comparative effectiveness research studies in patients with diabetic retinal disease have shown that treatment that inhibits both VEGF and PGF may provide superior outcomes in certain patients compared with treatment that inhibits only VEGF. This review summarizes current knowledge of PGF, including its relationship to VEGF and its role in pathological angiogenesis in retinal diseases, and identifies some key unanswered questions about PGF that can serve as a pathway for future basic, translational and clinical research.
Atrophic age‐related macular degeneration (AMD) is associated with the subretinal accumulation of mononuclear phagocytes (MPs). Their role in promoting or inhibiting retinal degeneration is unknown. ...We here show that atrophic AMD is associated with increased intraocular CCL2 levels and subretinal CCR2+ inflammatory monocyte infiltration in patients. Using age‐ and light‐induced subretinal inflammation and photoreceptor degeneration in Cx3cr1 knockout mice, we show that subretinal Cx3cr1 deficient MPs overexpress CCL2 and that both the genetic deletion of CCL2 or CCR2 and the pharmacological inhibition of CCR2 prevent inflammatory monocyte recruitment, MP accumulation and photoreceptor degeneration in vivo. Our study shows that contrary to CCR2 and CCL2, CX3CR1 is constitutively expressed in the retina where it represses the expression of CCL2 and the recruitment of neurotoxic inflammatory CCR2+ monocytes. CCL2/CCR2 inhibition might represent a powerful tool for controlling inflammation and neurodegeneration in AMD.
The eyes of patients with atrophic AMD feature high CCL2 and CCR2+ monocytes. This is modeled in Cx3cr1 KO mice in which Ccl2 and Ccr2 deletion, CCR2 inhibition and monocyte depletion diminished subretinal inflammation and photoreceptor degeneration.
Background and Purpose
The respective impact and interplay between ABC (P‐glycoprotein/P‐gp/Abcb1a, BCRP/ABCG2, MRP/ABCC) and SLC transporter functions at the blood–brain barrier (BBB) and ...blood–retinal barriers (BRB) are incompletely understood.
Experimental Approach
We measured the initial cerebral and retinal distribution of selected ABC substrates by in situ carotid perfusion using P‐gp/Bcrp knockout mice and chemical ABC/SLC modulation strategies. P‐gp, Bcrp, Mrp1 and Mrp4 were studied by confocal retina imaging.
Key Results
Chemical or physical disruption of P‐gp increased 3H‐verapamil transport by ~10‐fold at the BBB and ~1.5‐fold at the BRB. 3H‐Verapamil transport involved influx‐mediated by an organic cation clonidine‐sensitive/diphenhydramine‐sensitive proton antiporter at both barriers; this effect was unmasked when P‐gp was partially or fully inhibited/disrupted at the BBB. Studies of 3H‐mitoxantrone and 3H‐zidovudine transport suggested, respectively, that Bcrp efflux was less involved at the BRB than BBB, whereas Mrps were significantly and similarly involved at both barriers. Confocal imaging showed that P‐gp and Bcrp were expressed in intra‐retinal vessels (inner BRB/iBRB) but absent from the blood/basal membrane of cells of the retinal pigment epithelium (outer BRB/oBRB/RPE) where, in contrast, Mrp1 and Mrp4 were localized.
Conclusions and Implications
P‐gp, Bcrp, Mrp1 and Mrp4 are differentially expressed at the outer and inner BRB, resulting in an altered ability to limit substrate distribution at the retina as compared with the BBB. 3H‐Verapamil distribution is not P‐gp‐specific and involves a proton antiporter at both the BBB and BRB. However, this transport is concealed by P‐gp at the BBB, but not at the BRB, where P‐gp activity is reduced.
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•The current phototoxicity threshold for rodents is overestimated by a factor 50.•Low doses of LED light induce caspase-independent apoptosis.•The entire spectral composition of white ...light plays a role in its phototoxicity.•Addition of red light to white light reduces the loss of photoreceptors.•Low doses of light induce significant damage to the RPE.
Nowadays artificial light highly increases human exposure to light leading to circadian rhythm and sleep perturbations. Moreover, excessive exposure of ocular structures to photons can induce irreversible retinal damage. Meta-analyses showed that sunlight exposure influences the age of onset and the progression of Age-related macular degeneration (AMD), the leading cause of blindness in people over fifty-year old. Currently, the blue-light hazard (BLH) curve is used in the evaluation of the phototoxicity of a light source for domestic lighting regulations.
Here, we analyze the phototoxicity threshold in rats and investigate the role played by the light spectrum, assessing the relevance of the use of the BLH-weighting to define phototoxicity.
We exposed albino rats to increasing doses of blue and white light, or to lights of different colors to evaluate the impact of each component of the white light spectrum on phototoxicity. Cellular mechanisms of cell death and cellular stress induced by light were analyzed.
Our results show that the phototoxicity threshold currently accepted for rats is overestimated by a factor of 50 when considering blue light and by a factor of 550 concerning white light. This is the result of the toxicity induced by green light that increases white light toxicity by promoting an inflammatory response. The content of green in white light induces 8 fold more invasion of macrophages in the retina than the content of blue light. Moreover, the use of BLH-weighting does not evaluate the amount of red radiations contained in white light that mitigates damage by inhibiting the nuclear translocation of L-DNase II and reducing by 33% the number of TUNEL-positive cells.
These findings question the current methods to determine the phototoxicity of a light source and show the necessity to take into account the entire emission spectrum. As current human phototoxicity thresholds were estimated with the same methods used for rats, our results suggest that they might need to be reconsidered.
To evaluate the relative efficacy and safety profile of bevacizumab versus ranibizumab intravitreal injections for the treatment of neovascular age-related macular degeneration (AMD).
Multicenter, ...prospective, noninferiority, double-masked, randomized clinical trial performed in 38 French ophthalmology centers. The noninferiority limit was 5 letters.
Patients aged ≥50 years were eligible if they presented with subfoveal neovascular AMD, with best-corrected visual acuity (BVCA) in the study eye of between 20/32 and 20/320 measured on the Early Treatment of Diabetic Retinopathy Study chart and a lesion area of less than 12 optic disc areas (DA).
Patients were randomly assigned to intravitreal administration of bevacizumab (1.25 mg) or ranibizumab (0.50 mg). Hospital pharmacies were responsible for preparing, blinding, and dispensing treatments. Patients were followed for 1 year, with a loading dose of 3 monthly intravitreal injections, followed by an as-needed regimen (1 injection in case of active disease) for the remaining 9 months with monthly follow-up.
Mean change in visual acuity at 1 year.
Between June 2009 and November 2011, 501 patients were randomized. In the per protocol analysis, bevacizumab was noninferior to ranibizumab (bevacizumab minus ranibizumab +1.89 letters; 95% confidence interval CI, -1.16 to +4.93, P < 0.0001). The intention-to-treat analysis was concordant. The mean number of injections was 6.8 in the bevacizumab group and 6.5 in the ranibizumab group (P = 0.39). Both drugs reduced the central subfield macular thickness, with a mean decrease of 95 μm for bevacizumab and 107 μm for ranibizumab (P = 0.27). There were no significant differences in the presence of subretinal or intraretinal fluid at final evaluation, dye leakage on angiogram, or change in choroidal neovascular area. The proportion of patients with serious adverse events was 12.6% in the bevacizumab group and 12.1% in the ranibizumab group (P = 0.88). The proportion of patients with serious systemic or ocular adverse events was similar in both groups.
Bevacizumab was noninferior to ranibizumab for visual acuity at 1 year with similar safety profiles. Ranibizumab tended to have a better anatomic outcome. The results are similar to those of previous head-to-head studies.
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