The β-adrenergic system as a possible new target for pharmacologic treatment of neovascular retinal diseases

Targeted 8-arm PEG Nanosystems for Localization of Choroidal Neovascularization Macular Degeneration Model

8-arm PEG (polyethylene-glycol) is a highly promising nanoplatform due to its small size (<10 nm), ease-of-conjugation (many functionalized variants are readily available with "click-like" properties), biocompatibility, and optical inactivity. This study evaluates 8-arm PEG uptake into cells (in vitro) and localization and clearance in vasculature (in vivo) for targeting of choroidal neovascularization in mice, an animal model of macular degeneration. 8-arm PEG nanoparticles were labeled with fluorescein isothiocyanate (FITC) and functionalized in the absence or presence of pentameric Ar-Gly-Asp (RGD; 4 RGD motifs and a PGC linker), one of the most common peptide motifs used for active targeting. In vitro studies show that RGD-conjugated 8-arm PEG nanoparticles exhibit enhanced cellular uptake relative to non-RGD-conjugated control NPs at 34% ± 9%. Laser-induced choroidal neovascularization (CNV) was performed in a mouse model to measure 8-arm PEG localization and clearance to model macular degeneration lesions in vivo. It was determined that both RGD-conjugated and non-RGD-conjugated (nRGD) 8-arm PEG particles localized to CNV lesions, with a half-life around 24 h. In vivo experiments showed that RGD-conjugated nanoparticles exhibited enhanced localization by 15-20% relative to without RGD controls. Exhibiting a high rate of localization and fast clearance relative to larger nanoparticles, targeted 8-arm PEG nanoparticles with a conjugated RGD-peptide could be a promising modality for macular degeneration diagnosis and therapy.

Agonism of β3-Adrenoceptors Inhibits Pathological Retinal Angiogenesis in the Model of Oxygen-Induced Retinopathy

Purpose

In response to hypoxia, sympathetic fibers to the retina activate β-adrenoceptors (β-ARs) that play an important role in the regulation of vascular and neuronal functions. We investigated the role of β3-AR using the mouse model of oxygen-induced retinopathy (OIR).

Methods

Mouse pups were exposed to 75% oxygen at postnatal day 7 (PD7) followed by a return to room air at PD12. The β3-AR preferential agonist BRL37344 was subcutaneously administered once daily at different times after the return to room air. At PD17, the OIR mice underwent flash and pattern electroretinogram. After sacrifice, retinal wholemounts were used for vessel staining or immunohistochemistry for astrocytes, Müller cells, or retinal ganglion cells (RGCs). In retinal homogenates, the levels of markers associated with neovascularization (NV), the blood-retinal barrier (BRB), or astrocytes were determined by western blot, and quantitative reverse-transcription polymerase chain reaction was used to assess β3-AR messenger. Administration of the β3-AR antagonist SR59230A was performed to verify BRL37344 selectivity.

Results

β3-AR expression is upregulated in response to hypoxia, but its increase is prevented by BRL37344, which counteracts NV by inhibiting the pro-angiogenic pathway, activating the anti-angiogenic pathway, recovering BRB-associated markers, triggering nitric oxide production, and favoring revascularization of the central retina through recovered density of astrocytes that ultimately counteracts NV in the midperiphery. Vasculature rescue prevents dysfunctional retinal activity and counteracts OIR-associated retinal ganglion cell loss.

Conclusions

β3-AR has emerged as a crucial intermediary in hypoxia-dependent NV, suggesting a role of β3-AR agonists in the treatment of proliferative retinopathies.

β3-adREnoceptor Analysis in CORD Blood of Neonates (β3 RECORD): Study Protocol of a Pilot Clinical Investigation

Background and Objective: The embryo and the fetus develop in a physiologically hypoxic environment, where vascularization is sustained by HIF-1, VEGF, and the β-adrenergic system. In animals, β3-adrenoceptors (β3-ARs), up-regulated by hypoxia, favor global fetal wellness to such an extent that most diseases related to prematurity are hypothesized to be induced or aggravated by a precocious β3-AR down-regulation, due to premature exposure to a relatively hyperoxic environment. In animals, β3-AR pharmacological agonism is currently investigated as a possible new therapeutic opportunity to counteract oxygen-induced damages. Our goal is to translate the knowledge acquired in animals to humans. Recently, we have demonstrated that fetuses become progressively more hypoxemic from mid-gestation to near-term, but starting from the 33rd-34th week, oxygenation progressively increases until birth. The present paper aims to describe a clinical research protocol, evaluating whether the expression level of HIF-1, β3-ARs, and VEGF is modulated by oxygen during intrauterine and postnatal life, in a similar way to animals. Materials and Methods: In a prospective, non-profit, single-center observational study we will enroll 100 preterm (group A) and 100 full-term newborns (group B). We will collect cord blood samples (T0) and measure the RNA expression level of HIF-1, β3-ARs, and VEGF by digital PCR. In preterms, we will also measure gene expression at 48-72h (T1), 14 days (T2), and 30 days (T3) of life and at 40 ± 3 weeks of post-menstrual age (T4), regardless of the day of life. We will compare group A (T0) vs. group B (T0) and identify any correlations between the values obtained from serial samples in group A and the clinical data of the patients. Our protocol has been approved by the Pediatric Ethical Committee for Clinical Research of the Tuscany region (number 291/2022). Expected Results: The observation that in infants, the HIF-1/β3-ARs/VEGF axis shows similar modulation to that of animals could suggest that β3-ARs also promote fetal well-being in humans.

A promising case of preclinical-clinical translation: β-adrenoceptor blockade from the oxygen-induced retinopathy model to retinopathy of prematurity

Although compartmentalization of the eye seems to promote its experimental manipulation, drug penetration to its posterior part is severely limited by hard barriers thus hindering drug development for eye diseases. In particular, angiogenesis-related retinal diseases share common mechanisms and are responsible for the majority of cases of blindness. Their prevalence is globally increasing mostly because of the increased incidence of systemic pathologies in the adult. Despite the number of preclinical findings demonstrating the efficacy of novel treatments, therapy of retinal neovascular diseases still remains confined to intravitreal anti-vascular endothelial growth factor treatments with some extension to anti-inflammatory therapy. In the mare magnum of preclinical findings aimed to develop novel avenues for future therapies, most compounds, despite their efficacy in experimental models, do not seem to meet the criteria for their therapeutic application. In particular, the groove between preclinical findings and their clinical application increases instead of decreasing and the attempt to bridging the gap between them creates intense frustration and a sense of defeat. In this complex scenario, we will discuss here the role that overactivation of the sympathetic system plays in retinal vessel proliferation in response to hypoxia using the oxygen-induced retinopathy (OIR) model. The potential application of the beta-adrenoceptor (β-AR) blockade with propranolol to the treatment of retinopathy of prematurity will be also discussed in light of preclinical findings in the OIR model and clinical trials using propranolol in preterm infants either per os or as eye drops.

Effectiveness of Propranolol in Preventing Severe Retinopathy of Prematurity: A Comprehensive Systematic Review and Meta-Analysis

PURPOSE

To learn more about the effectiveness of oral propranolol as a therapeutic alternative for preterm newborns with pre-existing retinopathy of prematurity (ROP) as well as an early prevention method for ROP, one of the most common but avoidable causes of juvenile blindness.

STUDY DESIGN

Meta-analysis of relevant literature.

METHODS

A total of 3464 papers were identified, with 2873 from PubMed, 39 from Scopus, 67 from Medline, and 16 from Embase. After screening, finally, a total of 8 studies were deemed suitable for review. Following the PRISMA guidelines, published literature was systematically assessed up to May 10, 2023. Trials and observational studies were included in which beta blockage was used to prevent severe ROP (defined as stage ≥3 or requiring treatment). A total of 3646 papers were identified, with 2873 from PubMed, 39 from Scopus, 67 from Medline, and 16 from Embase. After screening, a total of 8 studies were deemed suitable for review.

RESULTS

The use of propranolol is linked to a lower risk of disease development in ROP compared to other therapies or control groups, according to the overall risk ratio of 0.59 (95% CI = 0.42, 0.82; P = .002, I2 = 41%). Additionally, the overall risk ratio for plus disease is 0.42 (95% CI = 0.23, 0.78; P = .006, I2 = 0%), for laser photocoagulation is 0.48 (95% CI = 0.31, 0.74; P = .001; I2 = 2%), and for intravitreal injection of VEGF is 0.43 (95% CI = 0.24, 0.74; P = 0.003, I2 = 0%), suggesting that use of propranolol may reduce the likelihood of developing a disease such as plus disease, requiring laser photocoagulation or necessitating intravitreal injection of vascular endothelial growth factor for ROP, respectively. No statistically significant heterogeneity was found in this study (P > .10, I2 = 50%). It can be concluded from this that the results of the chosen studies were sufficiently comparable and consistent.

CONCLUSION

This study showed that oral propranolol given as a preventive treatment in premature newborns successfully prevented severe ROP. Propranolol dosage and timing must now be carefully considered in the context of the study population, as these factors may have a major impact on the observed outcomes and treatment success.

The effect of combination therapy with intravitreal bevacizumab and topical timolol-dorzolamide eye drops on diabetic macular edema: a double-blind randomized controlled trial

BACKGROUND

The mainstay of treatment in diabetic macular edema (DME) is intravitreal administration of anti-vascular endothelial growth factors (anti-VEGFs). Aqueous depressants may enhance the effects of anti-VEGF agents by prolonging their clearance via aqueous outflow.

PURPOSE

To compare the anatomical and functional outcomes of treatment with intravitreal bevacizumab (IVB) and topical timolol-dorzolamide versus IVB alone.

METHOD

In this randomized placebo-controlled clinical trial, patients with center-involving DME (ci-DME) and best corrected visual acuity (BCVA) of 20/30 or less were enrolled and randomly allocated to two treatment arms. One group received three monthly IVB injections and timolol-dorzolamide eye drops twice a day (IVB + TD group); the other group received three monthly IVB injections and artificial tear drops as placebo (IVB group). Patients underwent ophthalmic evaluations and macular optical coherence tomography scans at baseline and 1 month after the third injection.

RESULT

Forty-six eyes from 46 patients with ci-DME were recruited. There was no intergroup difference regarding age, gender distribution, diabetic retinopathy stage, glycemic indices, BCVA, central macular thickness (CMT), or intraocular pressure at baseline. BCVA was significantly improved in the IVB + TD group (0.46 ± 0.18 to 0.36 ± 0.18 logarithm of the minimum angle of resolution [logMAR], p = 0.002), in contrast to IVB group (0.40 ± 0.17 to 0.35 ± 0.22 logMAR, p = 0.113). Similarly, the IVB + TD group showed a significant reduction in CMT (p < 0.001), unlike the IVB group (p = 0.086); and the CMT change in the former was greater than in the latter (- 0.57 ± 57.67 vs. - 25.52 ± 68.02 μm, p = 0.033).

CONCLUSION

Our findings support the short-term effectiveness of topical timolol-dorzolamide as adjunctive therapy to IVB injections in managing center-involving DME in terms of anatomical and visual outcomes.

TRIAL REGISTRATION

Clinicaltrials.gov NCT05083689 (October 19, 2021).

Inside the Biology of the β3-Adrenoceptor

Since the first discovery in 1989, the β3-adrenoceptor (β3-AR) has gained great attention because it showed the ability to regulate many physiologic and metabolic activities, such as thermogenesis and lipolysis in brown and white adipose tissue, respectively (BAT, WAT), negative inotropic effects in cardiomyocytes, and relaxation of the blood vessels and the urinary bladder. The β3-AR has been suggested as a potential target for cancer treatment, both in adult and pediatric tumors, since under hypoxia its upregulation in the tumor microenvironment (TME) regulates stromal cell differentiation, tumor growth and metastases, signifying that its agonism/antagonism could be useful for clinical benefits. Promising results in cancer research have proposed the β3-AR being targeted for the treatment of many conditions, with some drugs, at present, undergoing phase II and III clinical trials. In this review, we report the scientific journey followed by the research from the β3-Ars' discovery, with focus on the β3-Ars' role in cancer initiation and progression that elects it an intriguing target for novel antineoplastic approaches. The overview highlights the great potential of the β3-AR, both in physiologic and pathologic conditions, with the intention to display the possible benefits of β3-AR modulation in cancer reality.

Retinopathy of Prematurity-Targeting Hypoxic and Redox Signaling Pathways

Retinopathy of prematurity (ROP) is a proliferative vascular ailment affecting the retina. It is the main risk factor for visual impairment and blindness in infants and young children worldwide. If left undiagnosed and untreated, it can progress to retinal detachment and severe visual impairment. Geographical variations in ROP epidemiology have emerged over recent decades, attributable to differing levels of care provided to preterm infants across countries and regions. Our understanding of the causes of ROP, screening, diagnosis, treatment, and associated risk factors continues to advance. This review article aims to present the pathophysiological mechanisms of ROP, including its treatment. Specifically, it delves into the latest cutting-edge treatment approaches targeting hypoxia and redox signaling pathways for this condition.

Adrenoceptors in the Eye - Physiological and Pathophysiological Relevance

The autonomic nervous system plays a crucial role in the innervation of the eye. Consequently, it comes as no surprise that catecholamines and their corresponding receptors have been extensively studied and characterized in numerous ocular structures, including the cornea, conjunctiva, lacrimal gland, trabecular meshwork, uvea, and retina. These investigations have unveiled substantial clinical implications, particularly in the context of treating glaucoma, a progressive neurodegenerative disorder responsible for irreversible vision loss on a global scale. The primary therapeutic approaches for glaucoma frequently involve the modulation of α1-, α2-, and β-adrenoceptors, making them pivotal targets. In this chapter, we offer a comprehensive overview of the expression, distribution, and functional roles of adrenoceptors within various components of the eye and its associated structures. Additionally, we delve into the pivotal role of adrenoceptors in the pathophysiology of glaucoma. Furthermore, we provide a concise historical perspective on adrenoceptor research, examine the distinct contributions of individual adrenoceptor subtypes to the treatment of various ocular conditions, and propose potential future avenues of exploration in this field.

SYVN1 Promotes STAT3 Protein Ubiquitination and Exerts Antiangiogenesis Effects in Retinopathy of Prematurity Development

PURPOSE

SYVN1, a gene involved in endoplasmic reticulum-associated degradation, has been found to exert a protective effect by inhibiting inflammation in retinopathy. This study aimed to clarify whether SYVN1 is involved in the pathogenesis of retinopathy of prematurity (ROP) and its potential as a candidate for target therapy.

METHODS

Human retinal microvascular endothelial cells (hRMECs) and a mouse model of oxygen-induced retinopathy (OIR) were used to reveal the retinopathy development-associated protein expression and molecular mechanism. An adenovirus overexpressing SYVN1 or vehicle control was injected intravitreally at postnatal day 12 (P12), and the neovascular lesions were evaluated in retinal flatmounts with immunofluorescence staining, and hematoxylin and eosin staining at P17. Visual function was assessed by using electroretinogram (ERG).

RESULTS

Endogenous SYVN1 expression dramatically decreased in hRMECs under hypoxia and in ROP mouse retinas. SYVN1 regulated the signal transducer and activator of transcription 3 (STAT3)/vascular endothelial growth factor (VEGF) axis. SYVN1 overexpression promoted ubiquitination and degradation of STAT3, decreased the levels of phospho-STAT3, secretion of VEGF, and formation of neovascularization in hRMECs, which could be rescued by STAT3 activator treatment. In addition, SYVN1 overexpression prevented neovascularization and extended physiologic retinal vascular development in the retinal tissues of OIR mice without affecting retinal function.

CONCLUSIONS

SYVN1 has a protective effect against OIR, and the molecular mechanisms are partly through SYVN1-mediated ubiquitination of STAT3 and the subsequent downregulation of VEGF. These findings strongly support our assumption that SYVN1 confers ROP resistance and may be a potentially novel pharmaceutical target against proliferative retinopathy.

Evidence of vascular involvement in myopia: a review

The benign public perception of myopia (nearsightedness) as a visual inconvenience masks the severity of its sight-threatening consequences. Myopia is a significant risk factor for posterior pole conditions such as maculopathy, choroidal neovascularization and glaucoma, all of which have a vascular component. These associations strongly suggest that myopic eyes might experience vascular alterations prior to the development of complications. Myopic eyes are out of focus because they are larger in size, which in turn affects their overall structure and function, including those of the vascular beds. By reviewing the vascular changes that characterize myopia, this review aims to provide an understanding of the gross, cellular and molecular alterations identified at the structural and functional levels with the goal to provide an understanding of the latest evidence in the field of experimental and clinical myopia vascular research. From the evidence presented, we hypothesize that the interaction between excessive myopic eye growth and vascular alterations are tipping-points for the development of sight-threatening changes.

Intravitreal bevacizumab plus propranolol for neovascular age-related macular degeneration (the BEVALOL study): a phase I clinical trial

BACKGROUND

Given the persistently large public health impact of neovascular age-related macular degeneration (nARMD) despite many years of anti-VEGF therapy as the first-line treatment and the demonstrated ability of b-blockers to reduce neovascularization, a synergistic effect between an anti-VEGF agent and an intravitreal beta-blocker is important to investigate in the quest for therapeutic alternatives that maximize efficacy and/or reduce costs. The main purpose of this study is to investigate the safety of a 0.1 ml intravitreal injection of a combination of bevacizumab (1.25 mg/0.05 ml) and propranolol (50 g/0.05 ml) to treat nARMD.

METHODS

Prospective phase I clinical trial that included patients with nARMD. Comprehensive ophthalmic evaluation was performed at baseline and included Early Treatment Diabetic Retinopathy Study (ETDRS) best-corrected visual acuity (BCVA), biomicroscopy of the anterior and posterior segments, binocular indirect ophthalmoscopy, color fundus photography, spectral domain optical coherence tomography (OCT), OCT angiography (OCT-A), fluorescein angiography (Spectralis, Heidelberg), and full-field electroretinography (ERG). All eyes were treated with a 0.1 ml intravitreal injection of a combination of bevacizumab (1.25 mg/0.05 ml) and propranolol (50 g/0.05 ml) within 1 week of baseline evaluation. The patients were reexamined at weeks 4, 8 and 12, and clinical evaluation and SD-OCT were performed at all follow-up visits. Additional injections of combination bevacizumab (1.25 mg/0.05 ml) and propranolol (50 g/0.05 ml) were administered at weeks 4 and 8. At the final study evaluation (week 12), color fundus photography, OCT-A, fluorescein angiography, and full-field ERG were repeated.

RESULTS

Eleven patients (11 eyes) completed all study visits of the 12 week study. Full field ERG b-waves did not show significant (p < 0.05) changes at week 12 compared to baseline. During the 12 week follow-up period, none of the study eyes developed intraocular inflammation, endophthalmitis or intraocular pressure elevation more than 4 mmHg over baseline. Mean ± SE BCVA (logMAR) was 0.79 ± 0.09 at baseline and was significantly (p < 0.05) improved to 0.61 ± 0.10 at week 4; 0.53 ± 0.10 at week 8; and 0.51 ± 0.09 at week 12. Mean ± SE central subfield thickness (CST) (μm) was 462 ± 45 at baseline and was significantly (p < 0.05) lower at 4, 8 and 12 weeks (385 ± 37; 356 ± 29 and 341 ± 24, respectively).

CONCLUSIONS

In this 12 week trial of a combination of intravitreal bevacizumab and propranolol for treatment of nARMD, no adverse events or signals of ocular toxicity were observed. Further studies using this combination therapy are warranted. Trial Registration Project registered in Plataforma Brasil with CAAE number 28108920.0.0000.5440 and approved in ethics committee of Clinics Hospital of Ribeirao Preto Medicine School of São Paulo University-Ribeirão Preto, São Paulo, Brazil (appreciation number 3.999.989 gave the approval).

β-Adrenoreceptors as Therapeutic Targets for Ocular Tumors and Other Eye Diseases-Historical Aspects and Nowadays Understanding

β-adrenoreceptors (ARs) are members of the superfamily of G-protein-coupled receptors (GPCRs), and are activated by catecholamines, such as epinephrine and norepinephrine. Three subtypes of β-ARs (β₁, β₂, and β₃) have been identified with different distributions among ocular tissues. Importantly, β-ARs are an established target in the treatment of glaucoma. Moreover, β-adrenergic signaling has been associated with the development and progression of various tumor types. Hence, β-ARs are a potential therapeutic target for ocular neoplasms, such as ocular hemangioma and uveal melanoma. This review aims to discuss the expression and function of individual β-AR subtypes in ocular structures, as well as their role in the treatment of ocular diseases, including ocular tumors.

The β3 adrenoceptor in proliferative retinopathies: "Cinderella" steps out of its family shadow

In the retina, hypoxic condition leads to overgrowing leaky vessels resulting in altered metabolic supply that may cause impaired visual function. Hypoxia-inducible factor-1 (HIF-1) is a central regulator of the retinal response to hypoxia by activating the transcription of numerous target genes, including vascular endothelium growth factor, which acts as a major player in retinal angiogenesis. In the present review, oxygen urge by the retina and its oxygen sensing systems including HIF-1 are discussed in respect to the role of the beta-adrenergic receptors (β-ARs) and their pharmacologic manipulation in the vascular response to hypoxia. In the β-AR family, β1- and β2-AR have long been attracting attention because their pharmacology is intensely used for human health, while β3-AR, the third and last cloned receptor is no longer increasingly emerging as an attractive target for drug discovery. Here, β3-AR, a main character in several organs including the heart, the adipose tissue and the urinary bladder, but so far a supporting actor in the retina, has been thoroughly examined in respect to its function in retinal response to hypoxia. In particular, its oxygen dependence has been taken as a key indicator of β3-AR involvement in HIF-1-mediated responses to oxygen. Hence, the possibility of β3-AR transcription by HIF-1 has been discussed from early circumstantial evidence to the recent demonstration that β3-AR acts as a novel HIF-1 target gene by playing like a putative intermediary between oxygen levels and retinal vessel proliferation. Thus, targeting β3-AR may implement the therapeutic armamentarium against neovascular pathologies of the eye.

Use of β‑blockers and risk of age‑related macular degeneration among hypertensive patients: An insight from The National Health and Nutrition Examination Survey

Although age-related macular degeneration (AMD) is the leading cause of legal blindness, the treatment methods for AMD are limited. The aim of the present study was to examine the association between oral β-blockers (BBs) and the risk of developing AMD among hypertensive patients. For this purpose, a total of 3,311 hypertensive patients from the National Health and Nutrition Examination Survey were included in the study. The use of BBs and treatment duration data were collected using a self-reported questionnaire. AMD was diagnosed by gradable retinal images. Multivariate-adjusted survey-weighted univariate logistic regression was used to confirm the association between the use of BBs and the risk of developing AMD. The results revealed that the use of BBs exerted a beneficial effect (odds ratio (OR), 0.34; 95% confidence interval (95% CI, 0.13-0.92; P=0.04) in late-stage AMD in the multivariate adjusted model. When the BBs were classified into non-selective BBs and selective BBs, the protective effect in late-stage AMD was still observed in the non-selective BBs (OR, 0.20; 95% CI, 0.07-0.61; P<0.001). After accounting for treatment duration, long-term treatment with BBs (>6 years) was also found to reduce the risk of late-stage AMD (OR, 0.13; 95% CI, 0.03-0.63; P=0.01). In late-stage AMD, the long-term use of BBs was beneficial for geographic atrophy (OR, 0.07; 95% CI, 0.02-0.28; P<0.001). On the whole, the present study demonstrates that the use of non-selective BBs exerted a beneficial effect against the risk of late-stage AMD among hypertensive patients. Long-term treatment with BBs was also associated with lower risk of developing AMD. These findings may provide novel strategies for the management and treatment of AMD.

Changes of Beclin-1 and ULK1 in retina of mice model in oxygen-inducedretinopathy

Purpose

To observe the expression differences and potential effects of autophagy-related Beclin1 (mammalian Atg6) and Uncoordinated-51 like kinase 1 (ULK1) in the oxygen-induced retinopathy (OIR) model.

Materials and methods

Thirty-three C57BL/6 mice in OIR model group were exposed to 75 ​± ​0.5% oxygen from postnatal day-of-life 7 (P7) to P12, and were then brought into normal room environment (relative hypoxia stage) and raised to P17. Thirty-three control mice were kept in a normal room environment. The expression of autophagy in the retina tissue was assessed by Western blot analysis. The thickness and ultrastructural of retina were observed by light microscopy and transmission electron microscope (TEM) on P17.

Results

In the hyperoxia stage (P8-P11), the expression of Beclin1, ULK1 and Autophagy 5 (Atg5) in retina showed no significant difference between the OIR model group and the control group. In the relatively hypoxia stage (P14 to P17), however, the protein level of Beclin1, ULK1, and Bcl-2-associated X protein (Bax) were upregulated in the retina of the OIR model group, whereas B-cell lymphoma 2 (Bcl-2) was downregulated. The autophagosomes in the photoreceptors of retina in the OIR mice were observed. The inner-segment/out-segment (IS/OS) layer in OIR model group was thinner than that the control group on P17.

Conclusions

The expression of Beclin-1 and ULK1 in retina has changed in the OIR model, and the change of Beclin-1 and ULK1 expression is related to the change of oxygen concentration.

HIF-1-Dependent Induction of β3 Adrenoceptor: Evidence from the Mouse Retina

A major player in the homeostatic response to hypoxia is the hypoxia-inducible factor (HIF)-1 that transactivates a number of genes involved in neovessel proliferation in response to low oxygen tension. In the retina, hypoxia overstimulates β-adrenoceptors (β-ARs) which play a key role in the formation of pathogenic blood vessels. Among β-ARs, β3-AR expression is increased in proliferating vessels in concomitance with increased levels of HIF-1α and vascular endothelial growth factor (VEGF). Whether, similarly to VEGF, hypoxia-induced β3-AR upregulation is driven by HIF-1 is still unknown. We used the mouse model of oxygen-induced retinopathy (OIR), an acknowledged model of retinal angiogenesis, to verify the hypothesis of β3-AR transcriptional regulation by HIF-1. Investigation of β3-AR regulation over OIR progression revealed that the expression profile of β3-AR depends on oxygen tension, similar to VEGF. The additional evidence that HIF-1α stabilization decouples β3-AR expression from oxygen levels further indicates that HIF-1 regulates the expression of the β3-AR gene in the retina. Bioinformatics predicted the presence of six HIF-1 binding sites (HBS #1-6) upstream and inside the mouse β3-AR gene. Among these, HBS #1 has been identified as the most suitable HBS for HIF-1 binding. Chromatin immunoprecipitation-qPCR demonstrated an effective binding of HIF-1 to HBS #1 indicating the existence of a physical interaction between HIF-1 and the β3-AR gene. The additional finding that β3-AR gene expression is concomitantly activated indicates the possibility that HIF-1 transactivates the β3-AR gene. Our results are indicative of β3-AR involvement in HIF-1-mediated response to hypoxia.

Decoupling Oxygen Tension From Retinal Vascularization as a New Perspective for Management of Retinopathy of Prematurity. New Opportunities From β-adrenoceptors

Retinopathy of prematurity (ROP) is an evolutive and potentially blinding eye disease that affects preterm newborns. Unfortunately, until now no conservative therapy of active ROP with proven efficacy is available. Although ROP is a multifactorial disease, premature exposition to oxygen concentrations higher than those intrauterine, represents the initial pathogenetic trigger. The increase of oxygenation in a retina still incompletely vascularized promotes the downregulation of proangiogenic factors and finally the interruption of vascularization (ischemic phase). However, the increasing metabolic requirement of the ischemic retina induces, over the following weeks, a progressive hypoxia that specularly increases the levels of proangiogenic factors finally leading to proliferative retinopathy (proliferative phase). Considering non-modifiable the coupling between oxygen levels and vascularization, so far, neonatologists and ophthalmologists have "played defense", meticulously searching the minimum necessary concentration of oxygen for individual newborns, refining their diagnostic ability, adopting a careful monitoring policy, ready to decisively intervene only in a very advanced stage of disease progression. However, recent advances have demonstrated the possibility to pharmacologically modulate the relationship between oxygen and vascularization, opening thus the perspective for new therapeutic or preventive opportunities. The perspective of a shift from a defensive towards an attack strategy is now at hand.

Blocking Ocular Sympathetic Activity Inhibits Choroidal Neovascularization

Purpose: To investigate how modulating ocular sympathetic activity affects progression of choroidal neovascularization (CNV), a hallmark feature of wet age-related macular degeneration (AMD).

Methods: In the first of two studies, Brown Norway rats underwent laser-induced CNV and were assigned to one of the following groups: daily eye drops of artificial tears (n = 10; control group); daily eye drops of the β-adrenoreceptor agonist isoproterenol (n = 10); daily eye drops of the β-adrenoreceptor antagonist propranolol (n = 10); sympathetic internal carotid nerve (ICN) transection 6 weeks prior to laser-induced CNV (n = 10). In the second study, rats underwent laser-induced CNV followed by ICN transection at different time points: immediately after the laser injury (n = 6), 7 days after the laser injury (n = 6), and sham surgery 7 days after the laser injury (n = 6; control group). All animals were euthanized 14 days after laser application. CNV development was quantified with fluorescein angiography and optical coherence tomography (in vivo), as well as lesion volume analysis using 3D confocal reconstruction (postmortem). Angiogenic growth factor protein levels in the choroid were measured with ELISA.

Results: In the first study, blocking ocular sympathetic activity through pharmacological or surgical manipulation led to a 75% or 70% reduction in CNV lesion volume versus the control group, respectively (P < 0.001). Stimulating ocular sympathetic activity with isoproterenol also led to a reduction in lesion volume, but only by 27% versus controls (P < 0.05). VEGF protein levels in the choroid were elevated in the three treatment groups (P < 0.01). In the second study, fluorescein angiography and CNV lesion volume analysis indicated that surgically removing the ocular sympathetic supply inhibited progression of laser-induced CNV, regardless of whether ICN transection was performed on the same day or 7 days after the laser injury.

Conclusion: Surgical and pharmacological block of ocular sympathetic activity can inhibit progression of CNV in a rat model. Therefore, electrical block of ICN activity could be a potential bioelectronic medicine strategy for treating wet AMD.

Update in the Treatment of Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is an alteration in the development of the immature retina vascularization that frequently occurs in premature infants and is one of the leading causes of childhood blindness worldwide. In threshold stage retinopathy, laser photocoagulation is the standard treatment, particularly in those located in zone II. However, this therapy destroys parts of the retina and can lead to significant eye complications later in life. For this reason, in the last few years, antivascular endothelial growth factor agents are being used as monotherapy or as coadjuvant with laser, especially in retinopathy located in zone I. More recently, the administration of oral propranolol has been used as prevention and/or treatment of prethreshold retinopathy with encouraging results. This review provides an overview of the current evidence on newer treatment strategies for ROP. KEY POINTS: · Laser is the standard treatment in threshold retinopathy of prematurity (ROP).. · Prethreshold stages of the ROP have no treatment.. · Propranolol may prevent the progression of ROP..

β3-Adrenoceptor, a novel player in the round-trip from neonatal diseases to cancer: Suggestive clues from embryo

The role of the β-adrenoceptors (β-ARs) in hypoxia-driven diseases has gained visibility after the demonstration that propranolol promotes the regression of infantile hemangiomas and ameliorates the signs of retinopathy of prematurity (ROP). Besides the role of β2-ARs, preclinical studies in ROP have also revealed that β3-ARs are upregulated by hypoxia and that they are possibly involved in retinal angiogenesis. In a sort of figurative round trip, peculiarities typical of ROP, where hypoxia drives retinal neovascularization, have been then translated to cancer, a disease equally characterized by hypoxia-driven angiogenesis. In this step, investigating the role of β3-ARs has taken advantage of the assumption that cancer growth uses a set of strategies in common with embryo development. The possibility that hypoxic induction of β3-ARs may represent one of the mechanisms through which primarily embryo (and then cancer, as an astute imitator) adapts to grow in an otherwise hostile environment, has grown evidence. In both cancer and embryo, β3-ARs exert similar functions by exploiting a metabolic shift known as the Warburg effect, by acquiring resistance against xenobiotics, and by inducing a local immune tolerance. An additional potential role of β3-AR as a marker of stemness has been suggested by the finding that its antagonism induces cancer cell differentiation evoking that β3-ARs may help cancer to grow in a nonhospital environment, a strategy also exploited by embryos. From cancer, the round trip goes back to neonatal diseases for which new possible interpretative keys and potential pharmacological perspectives have been suggested.

The Anti-Inflammatory Effect of the β1-Adrenergic Receptor Antagonist Metoprolol on High Glucose Treated Human Microvascular Retinal Endothelial Cells

Hyperglycemia-induced impairment of the blood-retinal barrier represents the main pathological event in diabetic retinopathy that is elicited by a reduced cellular response to an accumulation of reactive oxygen species (ROS) and increased inflammation. The purpose of the study was to evaluate whether the selective β1-adrenoreceptor (β1-AR) antagonist metoprolol could modulate the inflammatory response to hyperglycemic conditions. For this purpose, human retinal endothelial cells (HREC) were treated with normal (5 mM) or high glucose (25 mM, HG) in the presence of metoprolol (10 μM), epinephrine (1 μM), or both compounds. Metoprolol prevented both the HG-induced reduction of cell viability (MTT assays) and the modulation of the angiogenic potential of HREC (tube formation assays) reducing the TNF-α, IL-1β, and VEGF mRNA levels (qRT-PCR). Moreover, metoprolol prevented the increase in phospho-ERK1/2, phospho-cPLA₂, COX2, and protein levels (Western blot) as well as counteracting the translocation of ERK1/2 and cPLA₂ (high-content screening). Metoprolol reduced ROS accumulation in HG-stimulated HREC by activating the anti-oxidative cellular response mediated by the Keap1/Nrf2/HO-1 pathway. In conclusion, metoprolol exerted a dual effect on HG-stimulated HREC, decreasing the activation of the pro-inflammatory ERK1/2/cPLA₂/COX2 axis, and counteracting ROS accumulation by activating the Keap1/Nrf2/HO-1 pathway.

INTRAVITREAL INJECTION OF PROPRANOLOL FOR THE TREATMENT OF RETINAL CAPILLARY HEMANGIOMA IN A CASE OF VON HIPPEL-LINDAU

PURPOSE

The purpose of this study was to evaluate the safety and efficacy of intravitreal propranolol for the management of retinal capillary hemangioma in a patient with Von Hippel-Lindau.

METHODS

Two intravitreal injections of 50 μg/0.05 mL propranolol were administered 6 weeks apart in the left eye of a 26-year-old patient with bilateral multiple retinal capillary hemangiomas. Safety and response to therapy were evaluated using electroretinogram, fluorescein angiography, and measurement of visual acuity. Laser photocoagulation was performed in the right eye.

RESULTS

One month after the second intravitreal injection of propranolol, fluorescein leakage decreased from the tumors located on the optic nerve head and in the inferonasal retinal periphery. Reduction of the retinal capillary hemangioma vascularity and enhancement of its fibrosis associated with the attenuation of the feeder vessel were also observed. Ophthalmic examination showed no adverse effect except for a mild transient vitreous haziness after each injection. Electroretinogram performed 4 weeks after the first injection revealed no retinal toxicity.

CONCLUSION

Intravitreal propranolol showed a therapeutic effect on retinal capillary hemangioma with no short-term adverse effects except a mild transient inflammatory response in a patient with Von Hippel-Lindau.

Intravitreal metoprolol for circumscribed choroidal hemangiomas: a phase I clinical trial

BACKGROUND

Choroidal hemangioma is a visual threatening condition for which treatments is neither uniform nor widely available. New management options are necessary. The purpose of this study is to assess the safety and early outcome of intravitreal metoprolol tartrate in five patients with CCH.

METHODS

Five eyes of five patients diagnosed with subfoveal or peripapillary CCH and unsuccessfully treated with intravitreal anti-VEGF agents were enrolled and received off-label intravitreal injections of metoprolol (50μg/0.05 ml). Baseline and follow-up evaluations included best-corrected visual acuity, intraocular pressure measurement, assessment of anterior chamber cellular score/flare and vitritis, retinography, fundus autofluorescence, and ERG. Patients were followed for a period of 30 days. Statistical analysis involved comparison of pre- and post-treatment findings using a paired t-test.

RESULTS

There was no significant difference in all ERG parameters regarding a- and b-wave amplitude and implicit time, and oscillatory potentials' maximal amplitude. There were no significant changes in visual acuity. None of the patients developed clinical signs of intraocular inflammation. The subretinal and/or intraretinal fluid improved in 3 out of 5 patients 4 weeks after the metoprolol injection.

CONCLUSIONS

Patients with CCH treated with a single injection of 50μg/0.05ml intravitreal metoprolol injections showed no signs of acute ocular toxicity. This pilot study did not assess long-term retinal toxicity, different concentrations, drug resistance, and complications from repeated-intravitreal injections.

Identification of candidate genes and pathways in retinopathy of prematurity by whole exome sequencing of preterm infants enriched in phenotypic extremes

Retinopathy of prematurity (ROP) is a vasoproliferative retinal disease affecting premature infants. In addition to prematurity itself and oxygen treatment, genetic factors have been suggested to predispose to ROP. We aimed to identify potentially pathogenic genes and biological pathways associated with ROP by analyzing variants from whole exome sequencing (WES) data of premature infants. As part of a multicenter ROP cohort study, 100 non-Hispanic Caucasian preterm infants enriched in phenotypic extremes were subjected to WES. Gene-based testing was done on coding nonsynonymous variants. Genes showing enrichment of qualifying variants in severe ROP compared to mild or no ROP from gene-based tests with adjustment for gestational age and birth weight were selected for gene set enrichment analysis (GSEA). Mean BW of included infants with pre-plus, type-1 or type 2 ROP including aggressive posterior ROP (n = 58) and mild or no ROP (n = 42) were 744 g and 995 g, respectively. No single genes reached genome-wide significance that could account for a severe phenotype. GSEA identified two significantly associated pathways (smooth endoplasmic reticulum and vitamin C metabolism) after correction for multiple tests. WES of premature infants revealed potential pathways that may be important in the pathogenesis of ROP and in further genetic studies.

Effect of Adjuvant Topical Dorzolamide-Timolol vs Placebo in Neovascular Age-Related Macular Degeneration: A Randomized Clinical Trial

Importance

Some eyes with neovascular age-related macular degeneration (AMD) have persistent exudation despite frequent intravitreal anti-vascular endothelial growth factor (VEGF) injections. Adjuvant therapies that further reduce edema may improve vision outcomes.

Objective

To compare the short-term effect of topical dorzolamide-timolol vs placebo in eyes with neovascular AMD that have persistent exudation following intravitreal anti-VEGF injections.

Design, Setting, and Participants

Randomized placebo-controlled clinical trial with enrollment from March 1, 2017, through October 30, 2018. Multicenter trial at 4 clinical sites in the United States. Sixty-three patients with neovascular AMD who had persistent exudation despite intravitreal anti-VEGF injections at 4-week, 5-week, or 6-week intervals.

Interventions

Patients were randomized to use dorzolamide-timolol or artificial tears for the study duration. They continued to receive the same anti-VEGF drug at the same interval as the 2 visits before enrollment for 3 additional study visits.

Main Outcomes and Measures

The primary outcome measure was change in mean central subfield thickness on optical coherence tomography from baseline to visit 3 (approximately 3 months). Secondary measures included change in mean maximum subretinal fluid height, mean maximum pigment epithelial detachment height, and mean visual acuity (VA).

Results

This trial included 52 patients. All 27 patients (100%) assigned to dorzolamide-timolol and 23 of 25 (92%) assigned to placebo were analyzed for the primary outcome. Mean (SD) age was 78.4 (7) years, and 34 of 50 patients (68%) were women. Mean (SD) injections were 20.5 (14) (range, 4-58) before enrollment. Mean (SD) baseline logMAR VA was 0.361 (0.26) (approximate Snellen equivalent, 20/50). Comparing the dorzolamide-timolol with placebo group from baseline to visit 3, mean (SD) change in central subfield thickness (primary outcome) was -36.6 (54) μm vs 1.7 (52.3) μm (difference, 30.8; 95% CI, 0.3-61.3; P = .04); secondary outcomes: maximum PED height was -39.1 (65) μm vs 1.1 (16) μm (difference, 39.6; 95% CI, 9.6-69.6; P = .01) and change in VA from baseline to visit 3 was -2.3 (5) vs 0.3 (1) letters (difference, 2.6 letters; 95% CI, -1.9 to 7.1 letters; P = .78).

Conclusions and Relevance

These findings suggest use of dorzolamide-timolol in patients with neovascular AMD with persistent exudation resulted in anatomic but not visual acuity improvements compared with placebo at approximately 3 months. Additional clinical trials with longer follow-up and larger sample sizes presumably would be needed to determine the role, if any, of dorzolamide-timolol in neovascular AMD.

Trial Registration

ClinicalTrials.gov Identifier: NCT03034772.

The Role of Adrenoceptors in the Retina

The retina is a part of the central nervous system, a thin multilayer with neuronal lamination, responsible for detecting, preprocessing, and sending visual information to the brain. Many retinal diseases are characterized by hemodynamic perturbations and neurodegeneration leading to vision loss and reduced quality of life. Since catecholamines and respective bindings sites have been characterized in the retina, we systematically reviewed the literature with regard to retinal expression, distribution and function of alpha₁ (α₁)-, alpha₂ (α₂)-, and beta (β)-adrenoceptors (ARs). Moreover, we discuss the role of the individual adrenoceptors as targets for the treatment of retinal diseases.

Novel Insights into Beta 2 Adrenergic Receptor Function in the rd10 Model of Retinitis Pigmentosa

Background: In retinitis pigmentosa (RP), inherited rod death is followed by cone loss and blindness. Why cones die is still a matter of consideration. Here, we investigate the pathogenic role of the sympathetic transmission in the rd10 mouse model of RP. Methods: Retinal levels of beta adrenergic receptor (BAR) 2 and norepinephrine (NE) were measured. After administration of the BAR1/2 blocker propranolol or the hypoxia-inducible factor (HIF)-1 activator dimethyloxalylglycine (DMOG), retinal levels of HIF-1α, BAR2 or proteins involved in BAR2 desensitization were also measured. In DMOG treated mice, expression and localization of BAR2, inflammatory markers and cone arrestin were determined. Finally, rd10 mice were subjected to electroretinogram (ERG) analysis to assess rod and cone function. Results: In the rd10 retina, BAR2 overexpression and NE accumulation were found, with BAR2 immunoreactivity localized to Müller cells. BAR2 overexpression was likely due to desensitization defects. Upregulated levels of BAR2 were drastically reduced by propranolol that also restored desensitization defects. Due to the low level of HIF-1 consequent to the hyperoxic environment in the rd10 retina, we hypothesized a link between HIF-1 and BAR2. HIF-1α stabilization with DMOG resulted in i. increased HIF-1α accumulation, ii. decreased BAR2 levels, iii. restored desensitization processes, iv. reduced expression of inflammatory markers and v. increased cone survival without improved retinal function. Conclusions: Our results support a pathogenic role of the sympathetic system in RP that might help to understand why rd10 mice show a positive response to BAR blockers.

Using Esterase Selectivity to Determine the In Vivo Duration of Systemic Availability and Abolish Systemic Side Effects of Topical β-Blockers

For disorders of the skin, eyes, ears, and respiratory tract, topical drugs, delivered directly to the target organ, are a therapeutic option. Compared with systemic oral therapy, the benefits of topical treatments include a faster onset of action, circumventing the liver first pass drug metabolism, and reducing systemic side effects. Nevertheless, some systemic absorption still occurs for many topical agents resulting in systemic side effects. One way to prevent these would be to develop drugs that are instantly degraded upon entry into the bloodstream by serum esterases. Because topical β-blockers are used in glaucoma and infantile hemeangioma and cause systemic side effects, the β-adrenoceptor system was used to test this hypothesis. Purified liver esterase reduced the apparent affinity of esmolol, an ester-containing β-blocker used in clinical emergencies, for the human β-adrenoceptors in a concentration and time-dependent manner. However, purified serum esterase had no effect on esmolol. Novel ester-containing β-blockers were synthesized and several were sensitive to both liver and serum esterases. Despite good in vitro affinity, one such compound, methyl 2-(3-chloro-4-(3-((2-(3-(3-chlorophenyl)ureido)ethyl)amino)-2-hydroxypropoxy)phenyl)acetate, had no effect on heart rate when injected intravenously into rats, even at 10 times the equipotent dose of esmolol and betaxolol that caused short and sustained reductions in heart rate, respectively. Thus, ester-based drugs, sensitive to serum esterases, offer a mechanism for developing topical agents that are truly devoid of systemic side effects. Furthermore, differential susceptibility to liver and serum esterases degradation may also allow the duration of systemic availability for other drugs to be fine-tuned.

Oral propranolol in prevention of severe retinopathy of prematurity: a systematic review and meta-analysis

OBJECTIVE

To systematically assess the efficacy of oral beta blockage treatment in primary (before established) and secondary (in threshold stages) prevention of severe retinopathy of prematurity (ROP) in premature infants born ≤32 weeks gestational age.

STUDY DESIGN

Following the PRISMA guidelines, published literature was systematically assessed up to April 27, 2018. Trials and observational studies, in which beta blockage was used to prevent severe ROP (defined as stage ≥3, or requiring treatment) were included. Meta-analyses including random effects models were conducted to determine the overall effect of oral beta blockage on prevention of ROP.

RESULTS

Six studies (five clinical trials and one observational study) including 461 infants met inclusion criteria using propranolol. The pooled relative risk (RR) of severe ROP in the primary and secondary prophylaxis groups were 0.65 (95% CI 0.43-0.98, NNT = 7) and 0.48 (95% CI 0.35-0.65, NNT = 6) in RCTs, respectively. The RR of severe ROP in one observational study was 0.21 (95% CI 0.08-0.55) with a NNT of 3. There were low heterogeneity and publication bias. Side effects occurred in 8.4% of participants on propranolol.

CONCLUSIONS

Systematic assessment of studies showed that prophylactic oral propranolol appeared to be effective in preventing severe ROP in premature infants ≤32 weeks gestational age. Additional well powered, multinational, randomized control trials reporting on long-term outcomes are needed.

Relationships Between Neurodegeneration and Vascular Damage in Diabetic Retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes and constitutes a major cause of vision impairment and blindness in the world. DR has long been described exclusively as a microvascular disease of the eye. However, in recent years, a growing interest has been focused on the contribution of neuroretinal degeneration to the pathogenesis of the disease, and there are observations suggesting that neuronal death in the early phases of DR may favor the development of microvascular abnormalities, followed by the full manifestation of the disease. However, the mediators that are involved in the crosslink between neurodegeneration and vascular changes have not yet been identified. According to our hypothesis, vascular endothelial growth factor (VEGF) could probably be the most important connecting link between the death of retinal neurons and the occurrence of microvascular lesions. Indeed, VEGF is known to play important neuroprotective actions; therefore, in the early phases of DR, it may be released in response to neuronal suffering, and it would act as a double-edged weapon inducing both neuroprotective and vasoactive effects. If this hypothesis is correct, then any retinal stress causing neuronal damage should be accompanied by VEGF upregulation and by vascular changes. Similarly, any compound with neuroprotective properties should also induce VEGF downregulation and amelioration of the vascular lesions. In this review, we searched for a correlation between neurodegeneration and vasculopathy in animal models of retinal diseases, examining the effects of different neuroprotective substances, ranging from nutraceuticals to antioxidants to neuropeptides and others and showing that reducing neuronal suffering also prevents overexpression of VEGF and vascular complications. Taken together, the reviewed evidence highlights the crucial role played by mediators such as VEGF in the relationship between retinal neuronal damage and vascular alterations and suggests that the use of neuroprotective substances could be an efficient strategy to prevent the onset or to retard the development of DR.

Sympathetic Effects of Internal Carotid Nerve Manipulation on Choroidal Vascularity and Related Measures

Purpose

To investigate specific effects of denervation and stimulation of the internal carotid nerve (ICN) on the choroid and retina.

Methods

Female Sprague Dawley rats underwent unilateral ICN transection (n = 20) or acute ICN electrical stimulation (n = 7). Rats in the denervation group were euthanized 6 weeks after nerve transection, and eyes were analyzed for changes in choroidal vascularity (via histomorphometry) or angiogenic growth factors and inflammatory markers (via ELISA). Rats in the stimulation group received acute ICN electrical stimulation with a bipolar cuff electrode over a range of stimulus amplitudes, frequencies, and pulse widths. Choroidal blood flow and pupil diameter were monitored before, during, and after stimulation.

Results

Six weeks after unilateral ICN transection, sympathectomized choroids exhibited increased vascularity, defined as the percentage of choroidal surface area occupied by blood vessel lumina. Vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR-2) protein levels in denervated choroids were 61% and 124% higher than in contralateral choroids, respectively. TNF-α levels in denervated retinas increased by 3.3-fold relative to levels in contralateral retinas. In animals undergoing acute ICN electrical stimulation, mydriasis and reduced choroidal blood flow were observed in the ipsilateral eye. The magnitude of the reduction in blood flow correlated positively with stimulus frequency.

Conclusions

Modulation of ICN activity reveals a potential role of the ocular sympathetic system in regulating endpoints related to neovascular diseases of the eye.

Landscape of microRNA in the aqueous humour of proliferative diabetic retinopathy as assessed by next-generation sequencing

BACKGROUND

The microRNAs (miRNA) have been found to play an important role in the pathogenesis of diabetic retinopathy. We try to explore the miRNA and piwi-interacting RNA (piRNA) profile in the aqueous humour of proliferative diabetic retinopathy (PDR) using next-generation sequencing (NGS).

METHODS

Aqueous humour samples were collected from nine PDR eyes and nine cataract control eyes, and NGS was performed. Quantitative polymerase chain reaction (qPCR) was used to validate the sequencing results. An oxygen-induced retinopathy (OIR) model was used to validate the angiogenesis related miRNA.

RESULTS

In total, 484 miRNAs were differently expressed between the PDR eyes and cataract control eyes, including 210 mature miRNAs and 274 novel miRNAs. Furthermore, eight miRNAs and 30 piRNAs were identified as the most differently expressed between the two groups (P > .85). This differential expression of miRNA was predicted to regulate Rho protein signal transduction, neurotransmitter uptake and histone lysine methylation. Relative expression patterns of miR-184, -150-5p and -93-5p were confirmed by qPCR. A reduced expression of miR-93-5p was confirmed in the OIR model.

CONCLUSIONS

This study comprehensively demonstrated the miRNA and piRNA expression profile of the aqueous humour of PDR eyes, which may serve as a potential biomarker and involved in the pathogenesis of PDR.

Everything You Always Wanted to Know about β3-AR * (* But Were Afraid to Ask)

The beta-3 adrenergic receptor (β₃-AR) is by far the least studied isotype of the beta-adrenergic sub-family. Despite its study being long hampered by the lack of suitable animal and cellular models and inter-species differences, a substantial body of literature on the subject has built up in the last three decades and the physiology of β₃-AR is unraveling quickly. As will become evident in this work, β₃-AR is emerging as an appealing target for novel pharmacological approaches in several clinical areas involving metabolic, cardiovascular, urinary, and ocular disease. In this review, we will discuss the most recent advances regarding β₃-AR signaling and function and summarize how these findings translate, or may do so, into current clinical practice highlighting β₃-AR’s great potential as a novel therapeutic target in a wide range of human conditions.

Efficacy of adjuvant topical timolol-dorzolamide with intravitreal bevacizumab injection in diabetic macular edema: A contralateral eye study

Purpose

To assess the efficacy of adjuvant topical timolol-dorzolamide with intravitreal bevacizumab (IVB) injection on anatomic and functional results in eyes affected with diabetic macular edema (DME).

Methods

In an interventional prospective contralateral pilot eye study at a third level referral academic facility, patients with bilateral DME who were treatment-naive were enrolled. Enrolled patients received a treatment plan of topical timolol-dorzolamide twice daily in the right eye. Three monthly bilateral IVB injections 1.25 mg/0.05 mL were also planned. Baseline central macular thickness (CMT) was measured by spectral-domain optical coherence tomography (SD-OCT), and clinical information such as best corrected visual acuity (BCVA) and intraocular pressure (IOP) were collected at enrollment and one month after the third injection.

Results

Eleven patients (seven females) with DME were included. BCVA and CMT improved in both eyes and IOP decreased in the right eye but did not change in the left eye. In repeated measures ANOVA analysis, the decrease in CMT and improvement in BCVA were significant in the right eye.

Conclusion

Our study suggested that adjuvant topical timolol-dorzolamide in combination with IVB may further reduce central macular thickness in eyes with DME.

β-Adrenoceptors as drug targets in melanoma: novel preclinical evidence for a role of β3 -adrenoceptors

Stress plays a role in tumourigenesis through catecholamines acting at β-adrenoceptors including β₁ -, β₂ - and β₃ -adrenoceptors, and the use of β-adrenoceptor antagonists seems to counteract tumour growth and progression. Preclinical evidence and meta-analysis data demonstrate that melanoma shows a positive response to β-adrenoceptor blockers and in particular to propranolol acting mainly at β₁ - and β₂ -adrenoceptors. Although evidence suggesting that β₃ -adrenoceptors may play a role as a therapeutic target in infantile haemangiomas has been recently reviewed, a comprehensive analysis of the data available from preclinical studies supporting a possible role of β₃ -adrenoceptors in melanoma was not available. Here, we review data from the literature demonstrating that propranolol may be effective at counteracting melanoma growth, and we provide preclinical evidence that β₃ -adrenoceptors may also play a role in the pathophysiology of melanoma, thus opening the door for further clinical assays trying to explore β₃ -adrenoceptor blockers as novel alternatives for its treatment. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.

Lisosan G Protects the Retina from Neurovascular Damage in Experimental Diabetic Retinopathy

Lisosan G (LG), a fermented powder obtained from whole grains, is a recognized antioxidant compound that improves the bioactivity and survival of different cell types. The purpose of this study was to investigate whether LG ameliorates both the neural and the vascular damage characterizing early stages of diabetic retinopathy (DR). The effects of LG were studied in cultured explants of mouse retinas challenged with oxidative stress (OS) or in retinas of streptozotocin (STZ)-treated rats. Apoptosis, vascular endothelial growth factor (VEGF) expression, OS markers, blood-retinal barrier (BRB) integrity, and inflammation were assessed, while retinal function was evaluated with electroretinogram (ERG). LG extensively inhibited apoptosis, VEGF expression, and OS both in retinal explants and in STZ rats. In addition, STZ rats treated with LG displayed an almost total BRB integrity, reduced levels of inflammatory markers and a partially restored visual function as evaluated with ERG. In summary, we demonstrated that LG exhibits antioxidant and anti-inflammatory effects that exert powerful protective actions against neural and vascular defects characteristic of DR. Therefore, LG-containing foods or supplements may be considered to implement DR treatments.

Catecholamines facilitate VEGF-dependent angiogenesis via β2-adrenoceptor-induced Epac1 and PKA activation

Chronic stress has been associated with the progression of cancer and antagonists for β-adrenoceptors (βAR) are regarded as therapeutic option. As they are also used to treat hemangiomas as well as retinopathy of prematurity, a role of endothelial β₂AR in angiogenesis can be envisioned. We therefore investigated the role of β₂AR-induced cAMP formation by analyzing the role of the cAMP effector molecules exchange factor directly activated by cAMP 1 (Epac1) and protein kinase A (PKA) in endothelial cells (EC). Epac1-deficient mice showed a reduced amount of pre-retinal neovascularizations in the model of oxygen-induced retinopathy, which is predominantly driven by vascular endothelial growth factor (VEGF). siRNA-mediated knockdown of Epac1 in human umbilical vein EC (HUVEC) decreased angiogenic sprouting by lowering the expression of the endothelial VEGF-receptor-2 (VEGFR-2). Conversely, Epac1 activation by β₂AR stimulation or the Epac-selective activator cAMP analog 8-p-CPT-2’-O-Me-cAMP (8-pCPT) increased VEGFR-2 levels and VEGF-dependent sprouting. Similar to Epac1 knockdown, depletion of the monomeric GTPase Rac1 decreased VEGFR-2 expression. As Epac1 stimulation induces Rac1 activation, Epac1 might regulate VEGFR-2 expression through Rac1. In addition, we found that PKA was also involved in the regulation of angiogenesis in EC since the adenylyl cyclase (AC) activator forskolin (Fsk), but not 8-pCPT, increased sprouting in Epac1-depleted HUVEC and this increase was sensitive to a selective synthetic peptide PKA inhibitor. In accordance, β₂AR- and AC-activation, but not Epac1 stimulation increased VEGF secretion in HUVEC.

Our data indicate that high levels of catecholamines, which occur during chronic stress, prime the endothelium for angiogenesis through a β₂AR-mediated increase in endothelial VEGFR-2 expression and VEGF secretion.

EFFECT OF INTRAOCULAR PRESSURE-LOWERING MEDICATIONS ON NEOVASCULAR AGE-RELATED MACULAR DEGENERATION TREATMENT OUTCOMES IN THE COMPARISON OF AGE-RELATED MACULAR DEGENERATION TREATMENT TRIALS

PURPOSE

To evaluate the effect of intraocular pressure-lowering medications on treatment outcomes in the Comparison of AMD Treatments Trials.

METHODS

Secondary analysis of Comparison of AMD Treatments Trials data. Medication logs were reviewed for continuous 2-year use of agents that increased aqueous outflow (Group A: topical prostaglandins) or suppressed aqueous production (Group B: topical beta blockers and carbonic anhydrase inhibitors). Eyes were excluded if mixed-mechanism intraocular pressure-lowering agents or medications from more than one group were taken. Anatomical and vision responses to treatment at years 1, 2, and over the entire 2-year period in each group were compared with controls (no intraocular pressure-lowering medications).

RESULTS

Inclusion criteria were met by 28 Group A patients, 19 Group B patients, and 857 controls. After 2 years, the control group had a mean visual acuity improvement of +6.3 letters from baseline, compared with +3.5 letters in Group A (P = 0.38), and +13.8 letters in Group B (P = 0.052). Mean retinal thickness change from baseline was -54.9 μm in controls, -80.6 μm in Group A (P = 0.26), and -96.8 μm in Group B (P = 0.13). Mean total thickness change from baseline was -163 μm in controls, -180 μm in Group A (P = 0.63), and -238 μm in Group B (P = 0.08). In longitudinal analysis with adjustment by their baseline values, anti-vascular endothelial growth factor treatment drug and regimen, Group B had more visual acuity improvement (difference of 2.6 letters, 95% confidence interval: -3.4-8.5 letters), more reduction in the retinal thickness (-17.9 μm, 95% confidence interval: -36.5 to 0.7 μm), and total thickness from baseline (mean difference of -54.7 μm, 95% confidence interval: -103 to 6.2 μm) compared with the control group.

CONCLUSION

Concurrent aqueous suppressant use during anti-vascular endothelial growth factor therapy for neovascular age-related macular degeneration was associated with a trend toward greater reductions in retinal and total thickness as well as improved visual outcomes over 2 years. A similar effect was not observed to the same extent with agents that increase aqueous outflow. Because of the small sample size and secondary analysis, these findings must be cautiously interpreted and perhaps serve as a basis for future prospective studies.

Beta-blockers for prevention and treatment of retinopathy of prematurity in preterm infants

BACKGROUND

Retinopathy of prematurity (ROP) is a vision-threatening disease of preterm neonates. The use of beta-adrenergic blocking agents (beta-blockers), which modulate the vasoproliferative retinal process, may reduce the progression of ROP or even reverse established ROP.

OBJECTIVES

To determine the effect of beta-blockers on short-term structural outcomes, long-term functional outcomes, and the need for additional treatment, when used either as prophylaxis in preterm infants without ROP, stage 1 ROP (zone I), or stage 2 ROP (zone II) without plus disease or as treatment in preterm infants with at least prethreshold ROP.

SEARCH METHODS

We searched the Cochrane Neonatal Review Group Specialized Register; CENTRAL (in the Cochrane Library Issue 7, 2017); Embase (January 1974 to 7 August 2017); PubMed (January 1966 to 7 August 2017); and CINAHL (January 1982 to 7 August 2017). We checked references and cross-references and handsearched abstracts from the proceedings of the Pediatric Academic Societies Meetings.

SELECTION CRITERIA

We considered for inclusion randomised or quasi-randomised clinical trials that used beta-blockers for prevention or treatment of ROP in preterm neonates of less than 37 weeks' gestational age.

DATA COLLECTION AND ANALYSIS

We used the standard methods of Cochrane and the Cochrane Neonatal Review Group. We used the GRADE approach to assess the quality of evidence.

MAIN RESULTS

We included three randomised trials (N = 366) in this review. Two of these studies were at high risk of bias. All studies reported on prevention of ROP and compared oral propranolol with placebo or no treatment. We found no trials assessing beta-blockers in infants with established stage 2 or higher ROP with plus disease.In one trial, study medication was started after one week of life, i.e. prior to the first ROP screening. The other two trials included preterm infants if they had stage 2 or lower ROP without plus disease. Based on the GRADE assessment, we considered evidence to be of low quality for the following outcomes: rescue treatment with anti-VEGF or laser therapy; and arterial hypotension or bradycardia requiring inotropic support. Evidence was of moderate quality for the following outcomes: progression to stage 2 with plus disease; progression to stage 3 ROP; and progression to stage 4 or 5 ROP.Meta-analysis of three trials (N = 366) suggested beneficial effects of oral beta-blockers on the risk of requiring anti-VEGF agents (typical risk ratio (RR) 0.32, 95% confidence interval (CI) 0.12 to 0.86; I² = 0%; typical risk difference (RD) -0.06, 95% CI -0.10 to -0.01; I² = 75%; number needed to treat for an additional beneficial outcome (NNTB) 18, 95% CI 14 to 84) and laser therapy (typical RR 0.54, 95% CI 0.32 to 0.89; typical RD -0.09, 95% CI -0.16 to -0.02; I² = 31%; NNTB 12, 95% CI 8 to 47). Meta-analysis of two trials (N = 161) demonstrated a beneficial effect of oral beta-blockers on progression to stage 3 ROP (typical RR 0.60, 95% CI 0.37 to 0.96; I² = 0%; typical RD -0.15, 95% CI -0.28 to -0.02; I² = 73%; NNTB 7, 95% CI 5 to 67). There was no significant effect of oral beta-blockers on progression to stage 2 ROP with plus disease or to stage 4 or 5 ROP. Although meta-analysis did not indicate a significant effect of beta-blockers on arterial hypotension or bradycardia, propranolol dosage in one study was reduced by 50% in infants of less than 26 weeks' gestational age due to severe hypotension, bradycardia, and apnoea in several participants. Analyses did not indicate significant effects of beta-blockers on complications of prematurity or mortality. None of the trials reported on long-term visual impairment.

AUTHORS' CONCLUSIONS

Limited evidence of low-to-moderate quality suggests that prophylactic administration of oral beta-blockers might reduce progression towards stage 3 ROP and decrease the need for anti-VEGF agents or laser therapy. The clinical relevance of those findings is unclear as no data on long-term visual impairment were reported. Adverse events attributed to oral propranolol at a dose of 2 mg/kg/d raise concerns regarding systemic administration of this drug for prevention of ROP at the given dose. There is insufficient evidence to determine the efficacy and safety of beta-blockers for prevention of ROP due to high risk of bias in two included trials and the lack of long-term functional outcomes. We would encourage researchers to conduct large, well-designed trials to confirm or refute the role of beta-blockers for prevention and treatment of ROP in preterm infants. Trials should report on long-term visual impairment. Researchers should consider dose-finding studies of systemic beta-blockers and topical administration of beta-blockers, in order to optimise drug delivery and minimise adverse events.

The Beta Adrenergic Receptor Blocker Propranolol Counteracts Retinal Dysfunction in a Mouse Model of Oxygen Induced Retinopathy: Restoring the Balance between Apoptosis and Autophagy

In a mouse model of oxygen induced retinopathy (OIR), beta adrenergic receptor (BAR) blockade has been shown to recover hypoxia-associated retinal damages. Although the adrenergic signaling is an important regulator of apoptotic and autophagic processes, the role of BARs in retinal cell death remains to be elucidated. The present study was aimed at investigating whether ameliorative effects of BAR blockers may occur through their coordinated action on apoptosis and autophagy. To this aim, retinas from control and OIR mice untreated or treated with propranolol, a non-selective BAR1/2 blocker, were characterized in terms of expression and localization of apoptosis and autophagy markers. The effects of propranolol on autophagy signaling were also evaluated and specific autophagy modulators were used to get functional information on the autophagic effects of BAR antagonism. Finally, propranolol effects on neurodegenerative processes were associated to an electrophysiological investigation of retinal function by recording electroretinogram (ERG). We found that retinas of OIR mice are characterized by increased apoptosis and decreased autophagy, while propranolol reduces apoptosis and stimulates autophagy. In particular, propranolol triggers autophagosome formation in bipolar, amacrine and ganglion cells that are committed to die by apoptosis in response to hypoxia. Also our data argue that propranolol, through the inhibition of the Akt-mammalian target of rapamycin pathway, activates autophagy which decreases retinal cell death. At the functional level, propranolol recovers dysfunctional ERG by recovering the amplitude of a- and b-waves, and oscillatory potentials, thus indicating an efficient restoring of retinal transduction. Overall, our results demonstrate that BAR1/2 are key regulators of retinal apoptosis/autophagy, and that BAR1/2 blockade leads to autophagy-mediated neuroprotection. Reinstating the balance between apoptotic and autophagic machines may therefore be viewed as a future goal in the treatment of retinopathies.

Retinal vasculature development in health and disease

Development of the retinal vasculature is based on highly coordinated signalling between different cell types of the retina, integrating internal metabolic requirements with external influences such as the supply of oxygen and nutrients. The developing mouse retinal vasculature is a useful model system to study these interactions because it is experimentally accessible for intra ocular injections and genetic manipulations, can be easily imaged and develops in a similar fashion to that of humans. Research using this model has provided insights about general principles of angiogenesis as well as pathologies that affect the developing retinal vasculature. In this review, we discuss recent advances in our understanding of the molecular and cellular mechanisms that govern the interactions between neurons, glial and vascular cells in the developing retina. This includes a review of mechanisms that shape the retinal vasculature, such as sprouting angiogenesis, vascular network remodelling and vessel maturation. We also explore how the disruption of these processes in mice can lead to pathology - such as oxygen induced retinopathy - and how this translates to human retinopathy of prematurity.

Neurodegeneration and Neuroinflammation in Diabetic Retinopathy: Potential Approaches to Delay Neuronal Loss

In spite of the extensive research the complex pathogenesis of diabetic retinopathy (DR) has not been fully elucidated. For many years it has been thought that diabetic retinopathy manifests only with microangiopathic lesions, which are totally responsible for the loss of vision in diabetic patients. In view of the current knowledge on the microangiopathic changes in the fundus of the eye, diabetic retinopathy is perceived as a neurodegenerative disease. Several clinical tools are available to detect neuronal dysfunction at early stages of diabetes. Many functional changes in the retina can be identified before vascular pathology develops, suggesting that they result from a direct effect of diabetes on the neural retina. In the course of diabetes there is a chronic loss of retinal neurons due to increased frequency of apoptosis. The neuronal apoptosis begins very early in the course of diabetes. This observation has led to suggestions that precautions against DR should be implemented immediately after diabetes is diagnosed. Neurodegeneration cannot be reversed; therefore treatments preventing neuronal cell loss in the retina need to be developed to protect diabetic patients. This review is an attempt to summarize what is currently known about the mechanisms of neuronal apoptosis in the context of diabetic retinopathy and vascular degeneration as well as about potential treatments of DR

Neurovascular cross talk in diabetic retinopathy: Pathophysiological roles and therapeutic implications

Diabetic retinopathy (DR) is the leading cause of blindness in the working-age population in developed countries, and its prevalence will increase as the global incidence of diabetes grows exponentially. DR begins with an early nonproliferative stage in which retinal blood vessels and neurons degenerate as a consequence of chronic hyperglycemia, resulting in vasoregression and persistent retinal ischemia, metabolic disequilibrium, and inflammation. This is conducive to overcompensatory pathological neovascularization associated with advanced proliferative DR. Although DR is considered a microvascular complication, the retinal microvasculature is intimately associated with and governed by neurons and glia; neurodegeneration, neuroinflammation, and dysregulation of neurovascular cross talk are responsible in part for vascular abnormalities in both early nonproliferative DR and advanced proliferative DR. Neuronal activity directly regulates microvascular dilation and blood flow in the process of neurovascular coupling. Retinal neurons also secrete guidance cues in response to injury, ischemia, or metabolic stress that may either promote or suppress vascular outgrowth, either alleviating or exacerbating DR, contingent on the stage of disease and retinal microenvironment. Neurodegeneration, impaired neurovascular coupling, and dysregulation of neuronal guidance cues are key events in the pathogenesis of DR, and correcting these events may prevent or delay development of advanced DR. The review discusses the mechanisms of neurovascular cross talk and its dysregulation in DR, and their potential therapeutic implications.

Effect of periocular injection of celecoxib and propranolol on ocular level of vascular endothelial growth factor in a diabetic mouse model

AIM

To investigate the effects of periocular injection of propranolol and celecoxib on ocular levels of vascular endothelial growth factor (VEGF) in a diabetic mouse model.

METHODS

Forty 4-6wk BALB-C male mice weighing 20-25 g were used. The study groups included: non-diabetic control (group 1), diabetic control (group 2), diabetic propranolol (group 3), and diabetic celecoxib (group 4). After induction of type 1 diabetes by streptozotocin, propranolol (10 µg) and celecoxib (200 µg dissolved in carboxymethylcellulose 0.5%) were injected periocularly. The ocular level of VEGF was measured in all the study groups using enzyme-linked immuno sorbent assay (ELISA) method.

RESULTS

Ocular VEGF level was significantly increased (1.25 fold) in the diabetic control group when compared to the non-diabetic group one week after induction with streptozotocin (P=0.002). Both periocular propranolol and celecoxib significantly reduced ocular VEGF levels (P=0.047 and P<0.001, respectively). The effect was more pronounced with celecoxib.

CONCLUSION

The periocular administration of propranolol and celecoxib can significantly reduce ocular VEGF levels in a diabetic mouse model.

Neuroprotection as a Therapeutic Target for Diabetic Retinopathy

Diabetic retinopathy (DR) is a multifactorial progressive disease of the retina and a leading cause of vision loss. DR has long been regarded as a vascular disorder, although neuronal death and visual impairment appear before vascular lesions, suggesting an important role played by neurodegeneration in DR and the appropriateness of neuroprotective strategies. Upregulation of vascular endothelial growth factor (VEGF), the main target of current therapies, is likely to be one of the first responses to retinal hyperglycemic stress and VEGF may represent an important survival factor in early phases of DR. Of central importance for clinical trials is the detection of retinal neurodegeneration in the clinical setting, and spectral domain optical coherence tomography seems the most indicated technique. Many substances have been tested in animal studies for their neuroprotective properties and for possible use in humans. Perhaps, the most intriguing perspective is the use of endogenous neuroprotective substances or nutraceuticals. Together, the data point to the central role of neurodegeneration in the pathogenesis of DR and indicate neuroprotection as an effective strategy for treating this disease. However, clinical trials to determine not only the effectiveness and safety but also the compliance of a noninvasive route of drug administration are needed.