Blood-retinal Barrier Research Articles

Finerenone, a Non-Steroidal Mineralocorticoid Receptor Antagonist, Reduces Vascular Injury and Increases Regulatory T-Cells: Studies in Rodents with Diabetic and Neovascular Retinopathy.

Vision loss in diabetic retinopathy features damage to the blood-retinal barrier and neovascularization, with hypertension and the renin-angiotensin system (RAS) having causal roles. We evaluated if finerenone, a non-steroidal mineralocorticoid receptor (MR) antagonist, reduced vascular pathology and inflammation in diabetic and neovascular retinopathy. Diabetic and hypertensive transgenic (mRen-2)27 rats overexpressing the RAS received the MR antagonist finerenone (10 mg/kg/day, oral gavage) or the angiotensin-converting enzyme inhibitor perindopril (10 mg/kg/day, drinking water) for 12 weeks. As retinal neovascularization does not develop in diabetic rodents, finerenone (5 mg/kg/day, i.p.) was evaluated in murine oxygen-induced retinopathy (OIR). Retinal vasculopathy was assessed by measuring gliosis, vascular leakage, neovascularization, and VEGF. Inflammation was investigated by quantitating retinal microglia/macrophages, pro-inflammatory mediators, and anti-inflammatory regulatory T-cells (Tregs). In diabetes, both treatments reduced systolic blood pressure, gliosis, vascular leakage, and microglial/macrophage density, but only finerenone lowered VEGF, ICAM-1, and IL-1ß. In OIR, finerenone reduced neovascularization, vascular leakage, and microglial density, and increased Tregs in the blood, spleen, and retina. Our findings, in the context of the FIDELIO-DKD and FIGARO-DKD trials reporting the benefits of finerenone on renal and cardiovascular outcomes in diabetic kidney disease, indicate the potential of finerenone as an effective oral treatment for diabetic retinopathy.

Optimizing treatment for diabetic macular edema during cataract surgery.

Diabetic macular edema (DME) causes visual impairment in diabetic retinopathy (DR). Diabetes mellitus is a global epidemic and diabetic individuals are at risk of developing DR. Approximately 1 in 10 diabetic patients suffers from DME, which is the commonest cause of vision-threatening DR at primary-care screening. Furthermore, diabetes predisposes to a higher frequency and a younger onset of cataract, which further threatens vision in DME patients. Although cataract extraction is an effective cure, vision may still deteriorate following cataract surgery due to DME progression or recurrence, of which the risks are significantly higher than for patients without concurrent or previous history of DME at the time of operation. The management of pre-existing DME with visually significant cataract is a clinical conundrum. Deferring cataract surgery until DME is adequately treated is not ideal because of prolonged visual impairment and maturation of cataract jeopardizing surgical safety and monitoring of DR. On the other hand, the progression or recurrence of DME following prompt cataract surgery is a profound disappointment for patients and ophthalmic surgeons who had high expectations for postoperative visual improvement. Prescription of perioperative anti-inflammatory eye drops is effective in lowering the risk of new-onset DME after cataract surgery. However, management of concurrent DME at the time of cataract surgery is much more challenging because DME is unlikely to resolve spontaneously even with the aid of anti-inflammatory non-steroidal or steroid eye drops. A number of clinical trials using intravitreal injection of corticosteroids and anti-vascular endothelial growth factor (anti-VEGF) as first-line therapy have demonstrated safety and efficacy to treat DME. These drugs have also been administered perioperatively for the prevention of DME worsening in patients undergoing cataract surgery. This article reviews the scientific evidence to guide ophthalmologists on the efficacy and safety of various therapies for managing patients with DME who are particularly vulnerable to cataract surgery-induced inflammation, which disintegrates the blood-retinal barrier and egression of fluid in macular edema.

Microglia: The breakthrough to treat neovascularization and repair blood-retinal barrier in retinopathy.

Microglia are the primary resident retinal macrophages that monitor neuronal activity in real-time and facilitate angiogenesis during retinal development. In certain retinal diseases, the activated microglia promote retinal angiogenesis in hypoxia stress through neurovascular coupling and guide neovascularization to avascular areas (e.g., the outer nuclear layer and macula lutea). Furthermore, continuously activated microglia secrete inflammatory factors and expedite the loss of the blood-retinal barrier which causes irreversible damage to the secondary death of neurons. In this review, we support microglia can be a potential cellular therapeutic target in retinopathy. We briefly describe the relevance of microglia to the retinal vasculature and blood-retinal barrier. Then we discuss the signaling pathway related to how microglia move to their destinations and regulate vascular regeneration. We summarize the properties of microglia in different retinal disease models and propose that reducing the number of pro-inflammatory microglial death and conversing microglial phenotypes from pro-inflammatory to anti-inflammatory are feasible for treating retinal neovascularization and the damaged blood-retinal barrier (BRB). Finally, we suppose that the unique properties of microglia may aid in the vascularization of retinal organoids.

Dengue fever ophthalmic manifestations: A review and update.

Dengue fever, the most common arbovirus disease, affects an estimated 390 million people annually. Dengue virus (DENV) is an RNA virus of the Flaviviridae family with four different serotypes. Dengue haemorrhagic fever is the deadliest form of dengue infection and is characterised by thrombocytopaenia, hypotension, and the possibility of multi-system organ failure. The mechanism hypothesised for DENV viral replication is intrinsic antibody-dependent enhancement, which refers to Fcγ receptor-mediated viral amplification. This hypothesis suggests that the internalisation of DENV through the Fcγ receptor inhibits antiviral genes by suppressing type-1 interferon-mediated antiviral responses. DENV NS1 antibodies can promote the release of various inflammatory mediators in the nuclear transcription factor pathway (NF-κB-dependent), including monocyte chemoattractant protein (MCP)-1, interleukin (IL)-6, and IL-8. As a result, MCP-1 increases ICAM-1 expression and facilitates leukocyte transmigration. In addition, anti-DENV NS1 antibodies induce endothelial cell apoptosis via a nitric oxide-regulated pathway. A chain reaction involving pre-existing DENV heterotypic antibodies and innate immune cells causes dysfunction in complement system activity and contributes to the action of autoantibodies and anti-endothelial cells, resulting in endothelial cell dysfunction, blood-retinal barrier breakdown, haemorrhage, and plasma leakage. A spectrum of ocular diseases associated with DENV infection, ranging from haemorrhagic to inflammatory manifestations, has been reported in the literature. Although rare, ophthalmic manifestations can occur in both the anterior and posterior segments and are usually associated with thrombocytopenia. The most common ocular complication is haemorrhage. However, ophthalmic complications, such as anterior uveitis and vasculitis, suggest an immune-mediated pathogenesis.

Ebola virus disrupts the inner blood-retinal barrier by induction of vascular endothelial growth factor in pericytes.

Ebola virus (EBOV) causes severe hemorrhagic fever in humans with high mortality. In Ebola virus disease (EVD) survivors, EBOV persistence in the eyes may break through the inner blood-retinal barrier (iBRB), leading to ocular complications and EVD recurrence. However, the mechanism by which EBOV affects the iBRB remains unclear. Here, we used the in vitro iBRB model to simulate EBOV in retinal tissue and found that Ebola virus-like particles (EBO-VLPs) could disrupt the iBRB. Cytokine screening revealed that EBO-VLPs stimulate pericytes to secrete vascular endothelial growth factor (VEGF) to cause iBRB breakdown. VEGF downregulates claudin-1 to disrupt the iBRB. Ebola glycoprotein is crucial for VEGF stimulation and iBRB breakdown. Furthermore, EBO-VLPs caused iBRB breakdown by stimulating VEGF in rats. This study provides a mechanistic insight into that EBOV disrupts the iBRB, which will assist in developing new strategies to treat EBOV persistence in EVD survivors.

Vitamin D Receptor Expression Limits the Angiogenic and Inflammatory Properties of Retinal Endothelial Cells.

The integrity of retinal endothelial cell (EC) is essential for establishing and maintaining the retinal blood barrier to ensure proper vision. Vitamin D is a hormone with known protective roles in EC function. The majority of vitamin D action is mediated through the vitamin D receptor (VDR). VDR is a nuclear receptor whose engagement by vitamin D impacts the expression of many genes with important roles in regulation of angiogenesis and inflammation. Although many studies have investigated vitamin D-VDR action in cardiovascular protection and tumor angiogenesis, its impact on retinal EC function and regulation of ocular angiogenesis and inflammation is exceedingly limited. We previously showed calcitriol, the active form of vitamin D, is a potent inhibitor of retinal neovascularization in vivo and retinal EC capillary morphogenesis in vitro. Here, using retinal EC prepared from wild-type (Vdr+/+) and VDR-deficient (Vdr-/-) mice, we show that retinal EC express VDR and its expression is induced by calcitriol. The lack of VDR expression had a significant impact on endothelial cell-cell and cell-matrix interactions. Vdr-/- retinal EC proliferated at a slower rate and were more adherent and less migratory. They also exhibited increased expression levels of inflammatory markers driven in part by sustained activation of STAT1 and NF-κB pathways and were more sensitive to oxidative challenge. These changes were attributed, in part, to down-regulation of endothelial nitric oxide synthetase, enhanced hepcidin expression, and increased intracellular iron levels. Taken together, our results indicate that VDR expression plays a fundamental role in maintaining the proper angiogenic and inflammatory state of retinal EC.

Intraocular neutralizing antibodies against aflibercept in patients with age related macular degeneration

PurposeTo detect immunoglobulins in aqueous humour of AMD patients after repeated administration of intravitreal aflibercept.Patients and methodsTwenty-one patients (age: 77.85 ± 9.21 years) previously treated with intravitreal aflibercept due to wet type age-related macular degeneration (AMD group) and 18 age-matched control subjects (age: 69.75 ± 12.67 years) were included in this study. Patients in the AMD group received a mean of 5 intravitreal injections (min: 1 max: 17) prior to the cataract surgery. Samples of aqueous humour (50 μl) were obtained by anterior chamber paracentesis as the first step of routine cataract surgery. The IgG content of the samples was analysed by an in-house developed ELISA system.ResultsA significant increase in nonspecific IgG levels in the AMD group was detected compared to the control group (13.37 ± 6.65 vs. 9.44 ± 6.55 μg/ml; p = 0.03). In 11 patients, intraocular anti-aflibercept immunoglobulins could be detected (0.05 ± 0.01 μg/ml) which was significantly higher than the limit of detection for anti-aflibercept (0.04 μg/ml; p = 0.001). No correlation was found between the number of injections or the type of CNV and the aqueous level of anti-aflibercept (r = 0.02; p = 0.95).ConclusionAccording to our results, penetration of non-specific systemic antibodies through the impaired blood-retinal barrier is higher in patients with neovascular AMD than in subjects with an intact structural barrier. Evaluation of neutralizing antibodies to anti-VEGF agents in the aqueous humour can lead us to understanding tachyphylaxis and changes in intraocular immune mechanisms due to AMD.

Protective Effects of Human Pericyte-like Adipose-Derived Mesenchymal Stem Cells on Human Retinal Endothelial Cells in an In Vitro Model of Diabetic Retinopathy: Evidence for Autologous Cell Therapy.

Diabetic retinopathy (DR) is characterized by morphologic and metabolic alterations in endothelial cells (ECs) and pericytes (PCs) of the blood-retinal barrier (BRB). The loss of interendothelial junctions, increased vascular permeability, microaneurysms, and finally, EC detachment are the main features of DR. In this scenario, a pivotal role is played by the extensive loss of PCs. Based on previous results, the aim of this study was to assess possible beneficial effects exerted by adipose mesenchymal stem cells (ASCs) and their pericyte-like differentiated phenotype (P-ASCs) on human retinal endothelial cells (HRECs) in high glucose conditions (25 mM glucose, HG). P-ASCs were more able to preserve BRB integrity than ASCs in terms of (a) increased transendothelial electrical resistance (TEER); (b) increased expression of adherens junction and tight junction proteins (VE-cadherin and ZO-1); (c) reduction in mRNA levels of inflammatory cytokines TNF-α, IL-1β, and MMP-9; (d) reduction in the angiogenic factor VEGF and in fibrotic TGF-β1. Moreover, P-ASCs counteracted the HG-induced activation of the pro-inflammatory phospho-ERK1/2/phospho-cPLA2/COX-2 pathway. Finally, crosstalk between HRECs and ASCs or P-ASCs based on the PDGF-B/PDGFR-β axis at the mRNA level is described herein. Thus, P-ASCs might be considered valuable candidates for therapeutic approaches aimed at countering BRB disruption in DR.

Relationship between Glycosylated Haemoglobin Levels and Macular Thickness on Optical Coherence Tomography in Type 2 Diabetic Patients: A Cross-sectional Study

Introduction: Diabetic Macular Oedema (ME) is the main cause of poor visual acuity due to the breakdown of the inner and/or outer Blood Retinal Barrier (BRB). This can occur at any stage of Diabetic Retinopathy (DR) due to increased vascular permeability from retinal capillaries, as well as from microaneurysms and Intraretinal Microvascular Abnormalities (IRMAs). A high level of Glycosylated Haemoglobin (HbA1c) is a well known risk factor for diabetic ME. Aim: To evaluate the relationship between glycosylated Haemoglobin (Hb) and macular thickness on Optical Coherence Tomography (OCT) in patients with Type 2 Diabetes Mellitus (T2DM). Materials and Methods: A cross-sectional study was in the Department of Ophthalmology at RL Jalappa Hospital, Kolar, Karnataka, India. The study duration was one year and eight months, conducted from January 2021 to September 2022. A total of 162 eyes of 81 patients with Diabetes Mellitus (DM) were included. Patients were assessed for age, gender, duration of diabetes, subfield macular thickness, total macular volume as measured by Optical Coherence Tomography (OCT), and HbA1c levels. Pearson’s correlation and paired t-test were used to identify the mean difference between paired data. A p-value <0.05 was considered statistically significant. Results: Out of 81 patients, 52 (64.2%) were males and 29 (35.8%) were females, with a mean age of 59.36±8.98 years (range 40-81 years) and a duration of diabetes of 14.61±4.2 years. The mean HbA1c level was 8.18±1.47% (range 5.5-12.1). A significant positive correlation was observed between central subfield thickness and total macular volume with HbA1c among both eyes (p-value=0.001). This correlation was more prominent in patients with HbA1c values >8% compared to those with HbA1c values <8% (p-value=0.001). Additionally, a positive correlation was observed between duration of diabetes and right central macular thickness (p-value=0.046) and HbA1c levels (p-value=0.027). Age did not have a major influence on central subfield thickness and total macular volume, but it did show a positive Pearson’s correlation with HbA1c levels (p-value=0.008). Conclusion: A significant positive correlation was observed between central subfield thickness and total macular volume in both eyes with HbA1c levels. Patients with HbA1c levels >8% and a longer duration of diabetes exhibited increased macular thickness and total macular volume as measured by OCT, which was also observed in patients with severe non proliferative DR and proliferative DR.

Untargeted Analysis of Lipids Containing Very Long Chain Fatty Acids in Retina and Retinal Tight Junctions.

Several recent studies suggest that C24-C38 very long chain fatty acids (VLCFA) play an important role in vision, and decreased levels of retina VLCFA have been associated with vision disorders including the onset and progression of diabetic retinopathy in animal models. Traditional methods for VLCFA analysis lack the sensitivity and specificity needed to enable detailed characterization of VLCFA incorporation into complex lipids in tissues and subcellular components. To assess whether decreased VLCFA in diabetic retina are directly implicated in diabetes-induced breakdown of the blood-retinal barrier, we demonstrated the utility of performing untargeted lipid analysis via Orbitrap high resolution/accurate mass MS and MS/MS-based shotgun lipidomics to identify structural lipids containing VLCFA substituents. This comprehensive and highly sensitive approach to untargeted lipid identification enabled us to characterize low-abundance sphingolipids containing very long chain fatty acids from isolated retinal tight junction complexes, as well as VLCFA-containing phospholipids in retinal tissues. To facilitate future biochemical and physiological studies of the roles of VLCFA in blood-retina barrier integrity and maintenance of vision, this chapter describes steps to isolate tight junction complexes from a cell culture model of the outer blood-retinal barrier and perform untargeted Orbitrap high resolution/accurate mass-based lipid analysis to identify VLCFA in tight junctions and retina tissue.

A Comprehensive Review of Diabetic Retinopathy and Diabetic Macular Edema from an Ayurveda Point of View

Introduction: Diabetes and other related disorders, such as hypertension, are involved in diabetic retinopathy (DR), a chronic, progressive disease of the retinal microvasculature that threatens vision. The retinal pre-capillary arterioles, capillaries, and venules are impacted by DR. Hyperglycemia damages capillary walls, endothelial cells, retinal cells, and capillary pericytes. It also thickens the capillary basement membrane. The blood-retina barrier is broken down by microangiopathy, which can result in retinal edema, bleeding, lipid leakage (hard exudates), micro-aneurysms, hemorrhages, ischemia, and intraretinal microvascular abnormalities. Materials and Methods: Ayurveda classical texts along with the internet sources such as Google Scholar and PubMed were reviewed upon to collect the literature available as per the aims of the present article. Discussion and Conclusion: In Ayurveda, DR can be understood as Pramehajanya Timira. Due to prolonged uncontrolled hyperglycemia, two types of pathology in Madhumeha: Dhatukshayajanya and Avaranajanya play a crucial role in the development of DR. Dhatus are expelled from the body in Dhatukshaya, which leads to several pathogenic events and the development of DME. Attipravritti, Sanga, Siragranthi, and Vimarga Gamana are the four varieties of Srotodusti that are known to be important in the development of DR and macular edema.

Opium and Opioid Receptors: From the Ancient Times to a Possible Novel Therapeutic Target for Diabetic Retinopathy

Opium prescriptions date from the Sumerian era about 8,000 years ago, and they were commonly abused among wounded soldiers during the American Civil and Prussian French wars. With the isolation of morphine in 1805 by Setürner, the synthesis of morphine by Tschudi in 1952 and the manufacturing of synthetic derivatives called opioids, a new era of research began. In normal conditions, the endogenous opioid levels are elevated under stress conditions as a part of adaptive response. This mechanism implies in b-endorphin release, not only from the hypothalamus but also by immune circulating cells as lymphocytes. This system is powerful against pain, ischemic insult and oxidative imbalance protecting the tissues. The recognition of opioid receptors, particularly the delta subtype in retinal tissue, has broadened the potential for clinical applications. In the eye, opioid receptors were demonstrated to be present in optic nerve head, ganglion cells and pigmented epithelium cells. As such, studies have revealed that opioid receptors play a role in the pathogenesis of DR preserving the outer blood retinal barrier and also acting as a retinal neuroprotective agent. In this scenario, the modulation of the opioid receptor in the retina might become an attractive therapeutic target in the treatment of this devastating complication. Thus, this review assesses recent and scarce findings on this topic which deserves to be further investigated

Therapeutic effect of ultra-long-lasting human C-peptide delivery against hyperglycemia-induced neovascularization in diabetic retinopathy.

Rationale: Neovascularization is a hallmark of the late stages of diabetic retinopathy (DR) leading to blindness. The current anti-DR drugs have clinical disadvantages including short circulation half-lives and the need for frequent intraocular administration. New therapies with long-lasting drug release and minimal side effects are therefore needed. We explored a novel function and mechanism of a proinsulin C-peptide molecule with ultra-long-lasting delivery characteristics for the prevention of retinal neovascularization in proliferative diabetic retinopathy (PDR). Methods: We developed a strategy for ultra-long intraocular delivery of human C-peptide using an intravitreal depot of K9-C-peptide, a human C-peptide conjugated to a thermosensitive biopolymer, and investigated its inhibitory effect on hyperglycemia-induced retinal neovascularization using human retinal endothelial cells (HRECs) and PDR mice. Results: In HRECs, high glucose conditions induced oxidative stress and microvascular permeability, and K9-C-peptide suppressed those effects similarly to unconjugated human C-peptide. A single intravitreal injection of K9-C-peptide in mice resulted in the slow release of human C-peptide that maintained physiological levels of C-peptide in the intraocular space for at least 56 days without inducing retinal cytotoxicity. In PDR mice, intraocular K9-C-peptide attenuated diabetic retinal neovascularization by normalizing hyperglycemia-induced oxidative stress, vascular leakage, and inflammation and restoring blood-retinal barrier function and the balance between pro- and anti-angiogenic factors. Conclusions: K9-C-peptide provides ultra-long-lasting intraocular delivery of human C-peptide as an anti-angiogenic agent to attenuate retinal neovascularization in PDR.

Retracted: Endostatin Inhibits Blood-Retinal Barrier Breakdown in Diabetic Rats by Increasing the Expression of ICAM-1 and VCAM-1 and Decreasing the Expression of VEGF.

[This retracts the article DOI: 10.1155/2022/5105866.].

PS-BPB06-8: THE NON-STEROIDAL MINERALOCORTICOID RECEPTOR ANTAGONIST, FINERENONE, REDUCES VASCULAR PATHOLOGY AND INFLAMMATION IN PRE-CLINICAL DIABETIC RETINOPATHY

Objective: Diabetic retinopathy is the leading cause of vision loss in the working population across the globe. Diabetes has devastating effects on the retinal vasculature, and can lead to vision-threatening vascular leakage, odema, and neovascularization. Current treatments such as anti-vascular endothelial growth factor (VEGF) are administered directly into the eye late in the disease process but are ineffective in about 50% of patients. Hypertension is a risk factor for the development of diabetic retinopathy and the renin-angiotensin aldosterone system contributes to disease pathogenesis. Here we aimed to determine if finerenone, a non-steroidal mineralocorticoid receptor (MR) antagonist, reduced vascular pathology and inflammation in animal models of diabetic retinopathy. Methods: To study diabetic retinopathy, streptozotocin diabetes was induced in female hypertensive transgenic Ren-2 rats overexpressing renin in extra-renal tissues. Diabetic Ren-2 rats were randomised to receive finerenone (10 mg/kg/day) by oral gavage or the angiotensin converting enzyme inhibitor perindopril (10 mg/kg/day) in drinking water for 12 weeks. As retinal neovascularization does not develop in diabetic rodents, the oxygen-induced retinopathy (OIR) model was studied. Litters of C57BL/6J mice were exposed to high oxygen (75%) between postnatal days 7 to 12 and then room air until postnatal day 18. Mouse pups were randomised to be OIR controls, or treated with finerenone (5 mg/kg/day) by intraperitoneal injection between postnatal days 7 to 18. Comparisons were made to mice exposed to room air. Damage to the blood-retinal barrier was evaluated by measuring the gliosis of macroglial Müller cells which confer barrier properties, vascular leakage (albumin ELISA), neovascularization, and the expression of VEGF. Inflammation was evaluated by the quantitation of retinal microglia and the expression of pro-inflammatory mediators. Results: Systolic blood pressure was similar between untreated non-diabetic (174.2 ± 6.3 mmHG) and diabetic (184.2 ± 8.5 mmHG) Ren-2 rats. Finerenone (138.5 ± 5.01 mmHG, P < 0.0001) and perindopril (106 ± 2.9 mmHG, P < 0.0001) reduced systolic blood pressure compared to untreated diabetic rats. In diabetic rats, finerenone reduced the gliosis of retinal Müller cells, vascular leakage, microglial density and the expression of VEGF, ICAM-1 and IL-1β;. In diabetic rats, perindopril did not reduce retinal VEGF levels, microglial density and the expression of pro-inflammatory mediators. In OIR mice, finerenone reduced retinal neovascularization, vascular leakage and microglial density. Conclusion: Our findings placed in the context of the FIDELIO-DKD trial reporting the benefits of finerenone on renal and cardiovascular outcomes in diabetic kidney disease, indicate the potential of finerenone to be an effective orally administered treatment for diabetic retinopathy.

Inflammation in diabetic retinopathy: possible roles in pathogenesis and potential implications for therapy.

Diabetic retinopathy, characterized as a microangiopathy and neurodegenerative disease, is the leading cause of visual impairment in diabetic patients. Many clinical features observed in diabetic retinopathy, such as capillary occlusion, acellular capillaries and retinal non-perfusion, aggregate retinal ischemia and represent relatively late events in diabetic retinopathy. In fact, retinal microvascular injury is an early event in diabetic retinopathy involving multiple biochemical alterations, and is manifested by changes to the retinal neurovascular unit and its cellular components. Currently, intravitreal anti-vascular endothelial growth factor therapy is the first-line treatment for diabetic macular edema, and benefits the patient by decreasing the edema and improving visual acuity. However, a significant proportion of patients respond poorly to anti-vascular endothelial growth factor treatments, indicating that factors other than vascular endothelial growth factor are involved in the pathogenesis of diabetic macular edema. Accumulating evidence confirms that low-grade inflammation plays a critical role in the pathogenesis and development of diabetic retinopathy as multiple inflammatory factors, such as interleukin-1β, monocyte chemotactic protein-1 and tumor necrosis factor -α, are increased in the vitreous and retina of diabetic retinopathy patients. These inflammatory factors, together with growth factors such as vascular endothelial growth factor, contribute to blood-retinal barrier breakdown, vascular damage and neuroinflammation, as well as pathological angiogenesis in diabetic retinopathy, complicated by diabetic macular edema and proliferative diabetic retinopathy. In addition, retinal cell types including microglia, Müller glia, astrocytes, retinal pigment epithelial cells, and others are activated, to secrete inflammatory mediators, aggravating cell apoptosis and subsequent vascular leakage. New therapies, targeting these inflammatory molecules or related signaling pathways, have the potential to inhibit retinal inflammation and prevent diabetic retinopathy progression. Here, we review the relevant literature to date, summarize the inflammatory mechanisms underlying the pathogenesis of diabetic retinopathy, and propose inflammation-based treatments for diabetic retinopathy and diabetic macular edema.

CGMP signaling: a potential therapeutic target for neurodegeneration in glaucoma?

cGMP signaling: a potential therapeutic target for neurodegeneration in glaucoma?

Molecular genetics in diagnosis of Coats disease: combination of oligogenic variants associated with different forms of hereditary retinal dystrophy

Coats disease (OMIM 300216) is a form of hereditary retinal dystrophy, which occurs due to congenital abnormality of retinal vessels and features unilateral exudative vitreoretinopathy. Coats disease mostly occurs sporadically; its genetic cause is still undetermined. Molecular genetic research including whole exome sequencing by the NGS method was used to define a genetic cause of the observed phenotype. Two heterozygous variants in different genomic loci associated with other forms of hereditary retinal dystrophy were detected, a rare variant in the HMCN1 gene c.9571C>T, p.(Arg3191Cys), and a known pathogenic variant in the NPHP4 gene c.2930C>T, p.(Thr977Met). The HMCN1 gene is responsible for dominant age-related macular degeneration (OMIM 603075), pathogenic variants in the NPHP4 gene cause recessive Senior-Løken syndrome 4 (OMIM 266900). These genes encode the proteins that are involved in the regulation of integrity of the blood-retinal barrier in the vascular endothelium (NPHP4) and retinal pigment epithelium (HMCN1). The identified mutation in the NPHP4 gene could lead to decreased function of the NPHP4 protein and contribute to the development of retinal degeneration, potentially of oligogenic nature.

Retinal TRP channels: Cell-type-specific regulators of retinal homeostasis and multimodal integration.

Transient receptor potential (TRP) channels are a widely expressed family of 28 evolutionarily conserved cationic ion channels that operate as primary detectors of chemical and physical stimuli and secondary effectors of metabotropic and ionotropic receptors. In vertebrates, the channels are grouped into six related families: TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP. As sensory transducers, TRP channels are ubiquitously expressed across the body and the CNS, mediating critical functions in mechanosensation, nociception, chemosensing, thermosensing, and phototransduction. This article surveys current knowledge about the expression and function of the TRP family in vertebrate retinas, which, while dedicated to transduction and transmission of visual information, are highly susceptible to non-visual stimuli. Every retinal cell expresses multiple TRP subunits, with recent evidence establishing their critical roles in paradigmatic aspects of vertebrate vision that include TRPM1-dependent transduction of ON bipolar signaling, TRPC6/7-mediated ganglion cell phototransduction, TRP/TRPL phototransduction in Drosophila and TRPV4-dependent osmoregulation, mechanotransduction, and regulation of inner and outer blood-retina barriers. TRP channels tune light-dependent and independent functions of retinal circuits by modulating the intracellular concentration of the 2nd messenger calcium, with emerging evidence implicating specific subunits in the pathogenesis of debilitating diseases such as glaucoma, ocular trauma, diabetic retinopathy, and ischemia. Elucidation of TRP channel involvement in retinal biology will yield rewards in terms of fundamental understanding of vertebrate vision and therapeutic targeting to treat diseases caused by channel dysfunction or over-activation.

The rs1800469 T/T and rs1800470 C/C genotypes of the TGFB1 gene confer protection against diabetic retinopathy in a Southern Brazilian population.

The transforming growth factor beta 1 (TGFB1) is a pro-inflammatory cytokine that plays a key role in the mechanisms of angiogenesis and breakdown of the blood-retina barrier, which are implicated in the pathogenesis of diabetic retinopathy (DR). Polymorphisms in the TGFB1 gene have been associated with DR; however, results are still contradictory. Therefore, the aim of this study was to investigate the potential association between two TGFB1 polymorphisms and DR. This study included 992 patients with diabetes mellitus (DM): 546 patients with DR (cases) and 446 patients without DR and with ≥10 years of DM (controls). The TGFB1 rs1800469 and rs1800470 polymorphisms were genotyped by real-time PCR. Frequency of rs1800469 T/T genotype was higher in controls compared to DR cases (18.3% vs. 12.7%, P= 0.022). This genotype remained associated with protection for DR, adjusting for covariables (OR= 0.604; 95% CI 0.395 - 0.923; P= 0.020, recessive model). The rs1800470 C/C genotype was observed in 25.4% of the controls and 18.0% of the cases (P= 0.015); thus, being associated with protection against DR under the recessive model (OR= 0.589; 95% CI 0.405 - 0.857; P= 0.006), adjusting for covariables. In conclusion, the TGFB1 rs1800469 and rs1800470 polymorphisms are associated with protection against DR in DM patients from Southern Brazil.