Endothelial Dysfunction in Diabetic Retinopathy

Endogenous advanced glycation end products in the pathogenesis of chronic diabetic complications

Diabetes is a common metabolic illness characterized by hyperglycemia and is linked to long-term vascular problems that can impair the kidney, eyes, nerves, and blood vessels. By increasing protein glycation and gradually accumulating advanced glycation end products in the tissues, hyperglycemia plays a significant role in the pathogenesis of diabetic complications. Advanced glycation end products are heterogeneous molecules generated from non-enzymatic interactions of sugars with proteins, lipids, or nucleic acids via the glycation process. Protein glycation and the buildup of advanced glycation end products are important in the etiology of diabetes sequelae such as retinopathy, nephropathy, neuropathy, and atherosclerosis. Their contribution to diabetes complications occurs via a receptor-mediated signaling cascade or direct extracellular matrix destruction. According to recent research, the interaction of advanced glycation end products with their transmembrane receptor results in intracellular signaling, gene expression, the release of pro-inflammatory molecules, and the production of free radicals, all of which contribute to the pathology of diabetes complications. The primary aim of this paper was to discuss the chemical reactions and formation of advanced glycation end products, the interaction of advanced glycation end products with their receptor and downstream signaling cascade, and molecular mechanisms triggered by advanced glycation end products in the pathogenesis of both micro and macrovascular complications of diabetes mellitus.

Vitamin D3 preserves blood retinal barrier integrity in an in vitro model of diabetic retinopathy

The impairment of the blood retinal barrier (BRB) represents one of the main features of diabetic retinopathy, a secondary microvascular complication of diabetes. Hyperglycemia is a triggering factor of vascular cells damage in diabetic retinopathy. The aim of this study was to assess the effects of vitamin D₃ on BRB protection, and to investigate its regulatory role on inflammatory pathways. We challenged human retinal endothelial cells with high glucose (HG) levels. We found that vitamin D₃ attenuates cell damage elicited by HG, maintaining cell viability and reducing the expression of inflammatory cytokines such as IL-1β and ICAM-1. Furthermore, we showed that vitamin D₃ preserved the BRB integrity as demonstrated by trans-endothelial electrical resistance, permeability assay, and cell junction morphology and quantification (ZO-1 and VE-cadherin). In conclusion this in vitro study provided new insights on the retinal protective role of vitamin D₃, particularly as regard as the early phase of diabetic retinopathy, characterized by BRB breakdown and inflammation.

Elevated IgG and IgM Autoantibodies to Advanced Glycation End Products of Vascular Elastin in Hypertensive Patients with Type 2 Diabetes: Relevance to Disease Initiation and Progression

The increased glycation of elastin is an important factor in vascular changes in diabetes. Using the ELISA method, we determined serum levels of IgM and IgG autoantibodies to advanced glycation end products of vascular elastin (anti-AGE EL IgM and anti-AGE EL IgG) in 59 hypertensive patients with type 2 diabetes (T2D) and 20 healthy controls. Serum levels of matrix metalloproteinases-2 and -9 (MMP-2 and MMP-9) and the C-reactive protein (CRP) were also determined. The levels of anti-AGE EL IgM antibodies in the T2D group were similar to those in the control group, while those of anti-AGE EL IgG antibodies were significantly higher (p = 0.017). Significant positive correlations were found between the levels of anti-AGE EL IgM antibodies and MMP-2 (r = 0.322; p = 0.013) and between the levels of anti-AGE EL IgG antibodies and CRP (r = 0.265; p = 0.042). Our study showed that elevated anti-AGE EL IgG antibody levels may be an indicator of the enhanced AGE-modification and inflammatory-mediated destruction of vascular elastin in hypertensive patients with T2D. Anti-AGE EL IgM antibodies may reflect changes in vascular MMP-2 activity, and their elevated levels may be a sign of early vascular damage.

Effect of high glucose on glycosaminoglycans in cultured retinal endothelial cells and rat retina

INTRODUCTION

The endothelial glycocalyx regulates vascular permeability, inflammation, and coagulation, and acts as a mechanosensor. The loss of glycocalyx can cause endothelial injury and contribute to several microvascular complications and, therefore, may promote diabetic retinopathy. Studies have shown a partial loss of retinal glycocalyx in diabetes, but with few molecular details of the changes in glycosaminoglycan (GAG) composition. Therefore, the purpose of our study was to investigate the effect of hyperglycemia on GAGs of the retinal endothelial glycocalyx.

METHODS

GAGs were isolated from rat retinal microvascular endothelial cells (RRMECs), media, and retinas, followed by liquid chromatography-mass spectrometry assays. Quantitative real-time polymerase chain reaction was used to study mRNA transcripts of the enzymes involved in GAG biosynthesis.

RESULTS AND CONCLUSIONS

Hyperglycemia significantly increased the shedding of heparan sulfate (HS), chondroitin sulfate (CS), and hyaluronic acid (HA). There were no changes to the levels of HS in RRMEC monolayers grown in high-glucose media, but the levels of CS and HA decreased dramatically. Similarly, while HA decreased in the retinas of diabetic rats, the total GAG and CS levels increased. Hyperglycemia in RRMECs caused a significant increase in the mRNA levels of the enzymes involved in GAG biosynthesis (including EXTL-1,2,3, EXT-1,2, ChSY-1,3, and HAS-2,3), with these increases potentially being compensatory responses to overall glycocalyx loss. Both RRMECs and retinas of diabetic rats exhibited glucose-induced alterations in the disaccharide compositions and sulfation of HS and CS, with the changes in sulfation including N,6-O-sulfation on HS and 4-O-sulfation on CS.

High Glucose Aggravates Retinal Endothelial Cell Dysfunction by Activating the RhoA/ROCK1/pMLC/Connexin43 Signaling Pathway

Purpose

This research aims to explore the mechanism underlying the relationship between RhoA/ROCK signaling and Connexin43 (Cx43) in retinal endothelial cell dysfunction and to evaluate the protective effect of ROCK inhibitors against retinal endothelial cell dysfunction in diabetic retinopathy (DR) models.

Methods

TUNEL staining, hematoxylin and eosin staining, a retinal digestion assay, and Evans blue assay were conducted to explore the effect of fasudil in alleviating retinal dysfunction induced by DR. ELISA, the CCK-8 assay, and flow cytometry were conducted to study inflammation, viability, and apoptosis of mouse retinal microvascular endothelial cells treated with high glucose and ROCK inhibitors. The qRT–PCR and Western blotting were used to evaluate the expression of RhoA, ROCK1, ROCK2, MLC, pMLC, and Cx43. Co-immunoprecipitation was used to verify the interaction between pMLC and Cx43. Immunofluorescence and scrape-loading and dye transfer were used to evaluate the expression and function of Cx43.

Results

Marked endothelial cell dysfunction resulting from the activation of RhoA/ROCK1 signaling was found in in vivo and in vitro models of DR. Via interaction with pMLC, which is downstream of RhoA/ROCK1, a significant downregulation of Cx43 was observed in retinal endothelial cells. Treatment with ROCK inhibitors ameliorated retinal endothelial dysfunction in vitro. The ROCK inhibitor, fasudil, significantly alleviated retinal dysfunction as shown by a decrease of retinal acellular capillaries, an improvement of vascular permeability, and a reduction of cell apoptosis in vivo.

Conclusions

Our study highlights a novel mechanism that high glucose could activate RhoA/ROCK1/pMLC signaling, which targets the expression and localization of Cx43 and is responsible for cell viability, apoptosis, and inflammation, resulting in retinal endothelial cell injury. ROCK inhibitors markedly ameliorate endothelial cell dysfunction, suggesting their therapeutic potential for diabetic retinopathy.

Human umbilical cord-derived mesenchymal stem cells not only ameliorate blood glucose but also protect vascular endothelium from diabetic damage through a paracrine mechanism mediated by MAPK/ERK signaling

BACKGROUND

Endothelial damage is an initial step of macro- and micro-vasculature dysfunctions in diabetic patients, accounting for a high incidence of diabetic vascular complications, such as atherosclerosis, nephropathy, retinopathy, and neuropathy. However, clinic lacks effective therapeutics targeting diabetic vascular complications. In field of regenerative medicine, mesenchymal stem cells, such as human umbilical cord-derived MSCs (hucMSCs), have great potential in treating tissue damage.

METHODS

To determine whether hucMSCs infusion could repair diabetic vascular endothelial damage and how it works, this study conducted in vivo experiment on streptozotocin-induced diabetic rat model to test body weight, fasting blood glucose (FBG), serum ICAM-1 and VCAM-1 levels, histopathology and immunohistochemical staining of aorta segments. In vitro experiment was further conducted to determine the effects of hucMSCs on diabetic vascular endothelial damage, applying assays of resazurin staining, MTT cell viability, wound healing, transwell migration, and matrigel tube formation on human umbilical vein endothelial cells (HUVECs). RNA sequencing (RNAseq) and molecular experiment were conducted to clarify the mechanism of hucMSCs.

RESULTS

The in vivo data revealed that hucMSCs partially restore the alterations of body weight, FBG, serum ICAM-1 and VCAM-1 levels, histopathology of aorta and reversed the abnormal phosphorylation of ERK in diabetic rats. By using the conditioned medium of hucMSCs (MSC-CM), the in vitro data revealed that hucMSCs improved cell viability, wound healing, migration and angiogenesis of the high glucose-damaged HUVECs through a paracrine action mode, and the altered gene expressions of IL-6, TNF-α, ICAM-1, VCAM-1, BAX, P16, P53 and ET-1 were significantly restored by MSC-CM. RNAseq incorporated with real-time PCR and Western blot results clarified that high glucose activated MAPK/ERK signaling in HUVECs, while MSC-CM reversed the abnormal phosphorylation of ERK and overexpressions of MKNK2, ERBB3, MYC and DUSP5 in MAPK/ERK signaling pathway.

CONCLUSIONS

HucMSCs not only ameliorated blood glucose but also protected vascular endothelium from diabetic damage, in which MAPK/ERK signaling mediated its molecular mechanism of paracrine action. Our findings provided novel knowledge of hucMSCs in the treatment of diabetes and suggested a prospective strategy for the clinical treatment of diabetic vascular complications.

The potential effects and mechanisms of hispidulin in the treatment of diabetic retinopathy based on network pharmacology

Background

Diabetic retinopathy (DR), one of the most common and severe microvascular complication of diabetes mellitus (DM), is mainly caused by diabetic metabolic disorder. So far, there is no effective treatment for DR. Eriocauli Flos, a traditional Chinese herb, has been used in treating the ophthalmic diseases including DR. However, the active ingredients and molecular mechanisms of Eriocauli Flos to treat diabetic retinopathy remain elusive.

Methods

Here, the systems pharmacology model was developed via constructing network approach. 8 active components which were screened by oral bioavailability (OB ≥ 30%) and drug-likeness (DL ≥ 0.18) and 154 targets were selected from Eriocauli Flos through TCMSP database. Another 3593 targets related to DR were obtained from Genecards, OMIM, TTD, and Drugbank databases. The 103 intersecting targets of DR and Eriocauli Flos were obtained by Draw Venn Diagram. In addition, protein-protein interaction network was established from STRING database and the compound-target network was constructed by Cytoscape which screened top 12 core targets with cytoNCA module. Then the overlapping targets were analyzed by GO and KEGG enrichment. Moreover, two core targets were selected to perform molecular docking simulation. Subsequently, CCK8 assay, RT-PCR and Western blotting were applied to further reveal the mechanism of new candidate active component from Eriocauli Flos in high glucose-induced HRECs.

Results

The results showed that the overlapping targets by GO analysis were enriched in cellular response to chemical stress, response to oxidative stress, response to reactive oxygen species, reactive oxygen species metabolic process and so on. Besides, the overlapping targets principally regulated pathways such as AGE-RAGE signaling pathway in diabetic complications, lipid atherosclerosis, fluid shear stress and atherosclerosis, and PI3K-Akt signaling pathway. Molecular docking exhibited that VEGFA and TNF-α, had good bindings to the great majority of compounds, especially the compound hispidulin. In vitro, hispidulin ameliorated high-glucose induced proliferation by down-regulating the expression of p-ERK, p-Akt, and VEGFA; meanwhile inhibited the mRNA levels of TNF-α.

Conclusions

In this study, through network pharmacology analysis and experimental validation, we found that hispidulin maybe has a potential targeted therapy effect for DR by decreasing the expression of p-Akt, p-ERK, and VEGFA, which resulted in ameliorating the proliferation in HRECs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03593-2.

Three-dimensional spheroids of choroid-retinal vascular endothelial cells as an in-vitro model for diabetic retinopathy: Proof-of-concept investigation

Diabetic retinopathy (DR) is a primary microvascular complication of diabetes mellitus and a vision-threatening condition. Vascular endothelial growth factor (VEGF) induces neovascularization and causes metabolic damage to the retinal and choroidal vasculature in diabetic patients. Existing drug screening models and treatment strategies for DR need to be refined through the establishment of relevant pre-clinical models, which may enable development of effective and safe therapies. The present study discusses the development of an in-vitro three-dimensional (3D) spheroid model, using RF/6A choroid-retinal vascular endothelial cells, to closely mimic the in-vivo disease condition. Compact, reproducibly-sized, viable and proliferating RF/6A spheroids were fabricated, as confirmed by microscopy, live/dead assay, cell proliferation assay and histological staining. In-vitro angiogenesis was studied by evaluating individual effects of VEGF and an anti-VEGF monoclonal antibody, Bevacizumab, and their combination on cellular proliferation and 3D endothelial sprout formation. VEGF stimulated angiogenic sprouting while Bevacizumab demonstrated a dose-dependent anti-angiogenic effect, as determined from the cellular proliferation observed and extent and length of sprouting. These investigations validated the potential of RF/6A spheroids in providing an alternative-to-animal, pathophysiologically-relevant model to facilitate pre-clinical and biomedical research related to DR.

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Matrix-free three-dimensional RF/6A spheroids were developed and characterized.

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VEGF-induced sprouting in RF/6A spheroids mimicked in-vivo vascular angiogenesis.

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Bevacizumab showed clinically-relevant anti-angiogenic responses in spheroid model.

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Proof-of-concept for in-vitro diabetic retinopathy model was developed.

[Wogonoside alleviates high glucose-induced dysfunction of retinal microvascular endothelial cells and diabetic retinopathy in rats by up-regulating SIRT1]

OBJECTIVE

To investigate the effects of wogonoside on high glucose-induced dysfunction of human retinal microvascular endothelial cells (hRMECs) and streptozotocin (STZ)-induced diabetic retinopathy in rats and explore the underlying molecular mechanism.

METHODS

HRMECs in routine culture were treated with 25 mmol/L mannitol or exposed to high glucose (30 mmol/L glucose) and treatment with 10, 20, 30, 40 μmol/L wogonoside. CCK-8 assay and Transwell assay were used to examine cell proliferation and migration, and the changes in tube formation and monolayer cell membrane permeability were tested. ROS, NO and GSH-ST kits were used to evaluate oxidative stress levels in the cells. The expressions of IL-1β and IL-6 in the cells were examined with qRT-PCR and ELISA, and the protein expressions of VEGF, HIF-1α and SIRT1 were detected using Western blotting. We also tested the effect of wogonoside on retinal injury and expressions of HIF-1α, ROS, VEGF, TNF-α, IL-1β, IL-6 and SIRT1 proteins in rat models of STZ-induced diabetic retinopathy.

RESULTS

High glucose exposure caused abnormal proliferation and migration, promoted angiogenesis, increased membrane permeability (P < 0.05), and induced inflammation and oxidative stress in hRMECs (P < 0.05). Wogonoside treatment concentration-dependently inhibited high glucose-induced changes in hRMECs. High glucose exposure significantly lowered the expression of SIRT1 in hRMECs, which was partially reversed by wogonoside (30 μmol/L) treatment; interference of SIRT1 obviously attenuated the inhibitory effects of wogonoside against high glucose-induced changes in proliferation, migration, angiogenesis, membrane permeability, inflammation and oxidative stress in hRMECs. In rat models of STZ-induced diabetic retinopathy, wogonoside effectively suppressed retinal thickening (P < 0.05), alleviated STZ-induced retinal injury, and increased the expression of SIRT1 in the retinal tissues (P < 0.001).

CONCLUSION

Wogonoside alleviates retinal damage caused by diabetic retinopathy by up-regulating SIRT1 expression.

MG53 represses high glucose-induced inflammation and angiogenesis in human retinal endothelial cells by repressing the EGR1/STAT3 axis

BACKGROUND

Diabetic retinopathy (DR) is a vascular complication of diabetes mellitus that leads to visual injury and blindness. Both angiogenesis and inflammation play an important role in the pathogenesis of DR. Here we aimed to explore the mechanisms of mitsugumin 53 (MG53) in ameliorating the dysfunction induced by high glucose (HG) in humans retinal microvascular endothelial cells (HRECs).

METHODS

HRECs were subjected to HG in the presence or absence of MG53 overexpression. The effect of MG53 on cell viability and inflammatory response in HG-treated HRECs was measured using the Cell Counting Kit-8 and ELISAs, respectively. Expression of MG53, EGR1, p-STAT3, FGF2, TGFB1, and Angiopoietin-1 in HG-treated HRECs was quantified by western blot or quantitative real-time polymerase chain reaction.

RESULTS

HG significantly downregulated MG53 in HRECs, which reduced cell viability while inducing angiogenesis and inflammatory response. Upregulation of MG53 reversed these effects of HG. MG53 directly interacted with EGR1 and repressed its expression, which decreased phosphorylation of STAT3 and downregulated FGF2, TGFB1, and Angiopoietin-1. EGR1 up-regulation or STAT3 activation antagonized the protective effects of MG53.

CONCLUSION

MG53 alleviates HG-induced dysfunction in HRECs by repressing EGR1/STAT3 signaling. Thereby MG53 may have therapeutic potential in DR.

Recent Advances in KEAP1/NRF2-Targeting Strategies by Phytochemical Antioxidants, Nanoparticles, and Biocompatible Scaffolds for the Treatment of Diabetic Cardiovascular Complications

Significance: Modulation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated antioxidant response is a key aspect in the onset of diabetes-related cardiovascular complications. With this review, we provide an overview of the recent advances made in the development of Nrf2-targeting strategies for the treatment of diabetes, with particular attention toward the activation of Nrf2 by natural antioxidant compounds, nanoparticles, and oxidative stress-modulating biocompatible scaffolds. Recent Advances: In the past 30 years, studies addressing the use of antioxidant therapies to treat diabetes have grown exponentially, showing promising but yet inconclusive results. Animal studies and clinical trials on the Nrf2 pathway have shown promising results, suggesting that its activation can delay or reverse some of the cardiovascular impairments in diabetes. Critical Issues: Hyperglycemia- and oscillating glucose levels-induced reactive oxygen species (ROS) accumulation is progressively emerging as a central factor in the onset and progression of diabetes-related cardiovascular complications, including endothelial dysfunction, retinopathy, heart failure, stroke, critical limb ischemia, ulcers, and delayed wound healing. In this context, accumulating evidence suggests a central role for Nrf2-mediated antioxidant response, one of the most studied cellular defensive mechanisms against ROS accumulation. Future Directions: Innovative approaches such as tissue engineering and nanotechnology are converging toward targeting oxidative stress in diabetes. Antioxid. Redox Signal. 36, 707-728.

Cardiac autonomic neuropathy predicts diabetic retinopathy progression in Asian population with type 2 diabetes mellitus

PURPOSE

To investigate the role of cardiac autonomic neuropathy (CAN), vascular condition, and sensory function in diabetic retinopathy (DR) progression.

METHODS

This 3-year cohort study conducted in a community hospital included 4850 patients over 20 with type 2 diabetes mellitus. Participants were assessed in 2017 at baseline and were followed up in 2020. Patients were divided into two groups based on whether they had DR progression or not and were compared using the chi-square test or two-sample t-test. Beta coefficient and odds ratio (OR) with 95% confidence intervals were calculated using binary logistic regression. The receiver operating characteristic (ROC) curve of various independent variables for DR progression was provided with C-statistics.

RESULTS

Abnormal hemoglobin A1c (HbA1c) level/variation, estimated glomerular filtration rate, urine albumin-to-creatinine ratio, R-R interval variation, standard deviation of the average NN intervals, autonomic nervous system function, power of high-frequency (HF) bands, balance, cardio-ankle vascular index (CAVI), and warm stimulation (WS) were associated with DR progression. Average HbA1c, HF, and proliferative diabetic retinopathy were independent factors for patients developing DR progression. The top three areas under the curve of ROCs were HF + baseline DR grading, WS + baseline DR grading, and CAVI + baseline DR grading. These variable combinations were the most reliable predictors of DR progression.

CONCLUSION

CAN, abnormal vascular condition, and sensory function are associated with DR progression. The combination of HF, WS, and CAVI with baseline DR grading provides the most accurate predictive model for DR progression. Early detection of these factors is important to prevent DR progression.

A Hypothesis From Metabolomics Analysis of Diabetic Retinopathy: Arginine-Creatine Metabolic Pathway May Be a New Treatment Strategy for Diabetic Retinopathy

Diabetic retinopathy is one of the serious complications of diabetes, which the leading causes of blindness worldwide, and its irreversibility renders the existing treatment methods unsatisfactory. Early detection and timely intervention can effectively reduce the damage caused by diabetic retinopathy. Metabolomics is a branch of systems biology and a powerful tool for studying pathophysiological processes, which can help identify the characteristic metabolic changes marking the progression of diabetic retinopathy, discover potential biomarkers to inform clinical diagnosis and treatment. This review provides an update on the known metabolomics biomarkers of diabetic retinopathy. Through comprehensive analysis of biomarkers, we found that the arginine biosynthesis is closely related to diabetic retinopathy. Meanwhile, creatine, a metabolite with arginine as a precursor, has attracted our attention due to its important correlation with diabetic retinopathy. We discuss the possibility of the arginine-creatine metabolic pathway as a therapeutic strategy for diabetic retinopathy.

Contribution of Müller Cells in the Diabetic Retinopathy Development: Focus on Oxidative Stress and Inflammation

Diabetic retinopathy is a neurovascular complication of diabetes and the main cause of vision loss in adults. Glial cells have a key role in maintenance of central nervous system homeostasis. In the retina, the predominant element is the Müller cell, a specialized cell with radial morphology that spans all retinal layers and influences the function of the entire retinal circuitry. Müller cells provide metabolic support, regulation of extracellular composition, synaptic activity control, structural organization of the blood-retina barrier, antioxidant activity, and trophic support, among other roles. Therefore, impairments of Müller actions lead to retinal malfunctions. Accordingly, increasing evidence indicates that Müller cells are affected in diabetic retinopathy and may contribute to the severity of the disease. Here, we will survey recently described alterations in Müller cell functions and cellular events that contribute to diabetic retinopathy, especially related to oxidative stress and inflammation. This review sheds light on Müller cells as potential therapeutic targets of this disease.

Trimetazidine mitigates high glucose-induced retinal endothelial dysfunction by inhibiting PI3K/Akt/mTOR pathway-mediated autophagy

Trimetazidine (TMZ), as a metabolic regulator, has been widely testified to exhibit positive therapeutic effects on various disease models, but its role in diabetic retinopathy has not been reported. Therefore, this study was designed with the purpose of exploring the effects of TMZ on high-glucose (HG)-induced retinal endothelial dysfunction and its underlying mechanism. To establish DR model in vitro, 30 mM glucose was applied to induce human retinal endothelial cells (HRECs). Cell proliferation, invasion, and migration were examined by means of Cell Counting Kit-8, transwell, and wound healing assays, respectively. The tubule formation experiment was used to test the tubulogenesis ability and fluorescein isothiocyanate (FITC)-albumin was utilized to measure the permeability of monolayer HRECs. In addition, immunofluorescence and Western blot were employed to detect protein expression. Compared with the HG-induced group, TMZ concentration dependently inhibited the proliferation, migration, and angiogenesis of HG-induced HRECs, decreased the permeability of monolayer HRECs, and increased the protein expression levels of Claudin-5 and VE-cadherin. In addition, TMZ intervention increased the expression of p-PI3K, p-AKT, and p-mTOR but decreased the expression of LC3I, LC3II, and Beclin 1, which were then partially reversed by P13 K inhibitor (LY294002). Moreover, the autophagy agonist rapamycin (RAPA) was also testified to reverse the inhibitory effects of TMZ on the proliferation, migration, and angiogenesis of HG-induced HRECs. In summary, TMZ inhibited excessive autophagy by activating PI3K/Akt/mTOR pathway, thereby improving retinal endothelial dysfunction induced by HG.

Differentiation and Characterization of Human Pluripotent Stem Cell-Derived Cardiac Endothelial Cells for In Vitro Applications

Various protocols have been developed to generate endothelial cells for disease modeling, angiogenesis, vascular regeneration, and drug screening. These protocols often require cell sorting, as most differentiation strategies result in a heterogenous population of endothelial cells (ECs). For any given model system, one important consideration is choosing the appropriate EC subtype, as different EC populations have unique molecular signatures.Herein, we describe a protocol for cardiac EC differentiation and a protocol for endothelial cell characterization. This protocol is aimed at investigating differentiation efficiency by measuring endothelial lineage markers, CD31, VE-Cadherin, and VEGFR2 by flow cytometry. Collectively, these protocols comprise the tools required to generate cardiac ECs efficiently and reproducibly from different hPSC lines without the need for cell sorting. Our protocol adds to the panel of hPSCs for cardiac EC differentiation and addresses reproducibility concerns of hPSC-based experiments. The approaches described are also applicable for complex model generation where multiple cardiovascular cell types are involved and may assist in optimizing differentiations for different cell lineages, including cardiomyocytes, cardiac endothelial cells, and cardiac fibroblasts.

Runx1 regulates Tff1 expression to expedite viability of retinal microvascular endothelial cells in mice with diabetic retinopathy

Diabetic retinopathy (DR) represents a major complication of diabetes, and molecular mechanisms related to vascular dysfunction, particularly endothelial dysfunction, in DR remains unclear. In the present work, we generated a DR animal model using mice and a cell model in mouse retinal microvascular endothelial cells (mRMECs) to examine the role of Trefoil factor family 1 (Tff1) in DR. Tff1 was poorly expressed in DR mice and high glucose (HG)-treated mRMECs. Overexpression of Tff1 significantly attenuated streptozotocin-induced retinal proliferation and angiogenesis in DR mice and reduced the secretion of inflammatory factors. In HG-treated mRMECs, overexpression of Tff1 remarkably reduced the proliferation and angiogenesis of mRMECs. In further experiments, we found that Tff1 was transcriptionally repressed by Runt-related transcription factor 1 (Runx1) directly, and Tff1 expression was indirectly modulated by Runx1 via the core-binding factor subunit beta (CBF-β)/nuclear factor, erythroid 2/microRNA-423-5p axis and the CBF-β/estrogen receptor 1 (ESR1) axis. Moreover, Tff1 could inhibit the activation of NF-κB signaling pathway, which in turn attenuated retinal endothelial cell proliferation and angiogenesis. It was thus proposed that Runx1/Tff1/NF-κB axis may be a potential target for the treatment strategy of DR, and further studies are needed.

Circular RNA circZNF532 facilitates angiogenesis and inflammation in diabetic retinopathy via regulating miR-1243/CARM1 axis

BACKGROUND

Diabetic retinopathy (DR) is a serious complication of diabetes. Numerous reports have validated that circular RNAs (circRNAs) participate in DR progression. This study aimed to elucidate the role and potential mechanism of circRNA zinc finger protein 532 (circZNF532) in DR.

METHODS

The levels of circZNF532, miR-1243, and coactivator associated arginine methyltransferase 1 (CARM1) in DR patients and human retinal microvascular endothelial cells (hRMECs) were determined by quantitative real-time PCR and western blot. Colony formation assay, transwell assay, tube formation assay and enzyme-linked immunosorbent assay were used to assess the biological function of hRMECs. The binding relationship between miR-1243 and circZNF532/CARM1 was verified by dual-luciferase reporter and RNA immunoprecipitation assays.

RESULTS

circZNF532 and CARM1 levels were increased, while miR-1243 level was reduced in DR patients and high glucose (HG)-stimulated hRMECs. In terms of mechanism, miR-1243 competitively bound to circZNF532 and CARM1. Down-regulation of circZNF532 restrained HG-induced hRMECs proliferation, migration, invasion, angiogenesis and inflammation via regulating miR-1243. In addition, miR-1243 inhibited HG-triggered hRMECs progression via targeting CARM1.

CONCLUSION

circZNF532 facilitated HG-induced angiogenesis and inflammation in hRMECs via modulating the miR-1243/CARM1 pathway, suggesting that circZNF532 might be a potential biomarker for DR treatment.

Circ-ADAM9 Promotes High Glucose-Induced Retinal Pigment Epithelial Cell Injury in DR via Regulating miR-338-3p/CARM1 Axis

Background. Circular RNAs (circRNAs) have been reported to be involved in the regulation of retinal pigment epithelial (RPE) cell injury and are closely related to the development of diabetic retinopathy (DR). More research is needed to confirm the role and mechanism of circ-ADAM9 in DR progression. Methods. High glucose (HG)-induced RPE cells (ARPE-19) were used to mimic the hyperglycemia condition. The expression of circ-ADAM9, microRNA (miR)-338-3p, and coactivator-associated arginine methyltransferase 1 (CARM1) was measured using quantitative real-time PCR. Cell proliferation and apoptosis were determined using MTT assay, EdU assay, and flow cytometry. The protein expression of apoptosis markers and CARM1 was examined by the western blot analysis. Also, MDA level and SOD activity were determined to assess cell oxidative stress. In addition, the interaction between miR-338-3p and circ-ADAM9 or CARM1 was confirmed by dual-luciferase reporter assay and RIP assay. Results. The expression of circ-ADAM9 was upregulated in DR patients and HG-induced ARPE-19 cells. Silenced circ-ADAM9 could promote proliferation and inhibit inflammation, apoptosis, and oxidative stress in HG-induced ARPE9 cells. In terms of mechanism, circ-ADAM9 could sponge miR-338-3p to upregulate CARM1. The inhibitory effect of circ-ADAM9 knockdown on HG-induced ARPE9 cell injury could be reversed by an miR-338-3p inhibitor. As a target of miR-338-3p, CARM1 knockdown could alleviate HG-induced ARPE9 cells’ injury, and its overexpression also could reverse the negatively regulation of miR-338-3p on HG-induced ARPE9 cell injury. Conclusion. Circ-ADAM9 contributed to HG-induced ARPE9 cell injury by regulating miR-338-3p/CARM1 axis, which provided effective targets for DR treatment.

Plasma miR-21 as a potential predictor in prediabetic individuals with a positive family history of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a heritable metabolic perturbation, rapidly growing across the world. Primary recognition of susceptible individuals with a family history of type 2 diabetes (FHD) in the prediabetes stage could delay the onset of T2DM or reduce complications induced by diabetes. This study aims to evaluate the expression levels of miR-21, miR-126 as noninvasive predictive biomarkers in individuals with genetic predisposition and investigate the correlation of miRNAs and cardiometabolic risk factors. Our study demonstrated that miR-21 expression has a notable elevate in both groups of T2DM and pre-T2DM. miR-21 expression was distinguished in the pre-T2DM and T2DM from the nondiabetic individuals by ROC curve analysis with AUC of 0.77 (95% CI 0.65-0.90; p = 0.0004) and AUC of 0.78 (95% CI 0.64-0.92; p = 0.0042), respectively. The relative gene expression of miR-126 was nearly equal among groups. miR-21 expression was positively associated with glycosylated hemoglobin (HbA1c), fasting blood sugar (FBS), and triglyceride (TG) and might have diagnostic value for T2DM and pre-T2DM. This study has revealed that the expression level of miR-21 can be considered as a non-invasive and rapid tool for distinguishing pre-T2DM and T2DM counterparts from healthy individuals.

VEGF and eNOS genes polymorphism features in patients with diabetes mellitus with and without initial non-proliferative diabetic retinopathy

The endothelial NO synthase (eNOS) and vascular endothelial growth factor (VEGF) imbalance and the polymorphism of these genes may be the predisposition for diabetic retinopathy (DR) development and progression.The aim: to analyze VEGF (rs699947 and rs3025039) and eNOS (rs2070744) genes polymorphism and their combinations in patients with type 2 diabetes mellitus (DM2) with and without initial non-proliferative DR.Materials and methods. The study included 200 patients with type 2 diabetes (155 women and 45 men, age – 43–70 years): 111 people without and 89 people with DR. The polymorphism of the regulatory regions of VEGF (rs699947 and rs3025039) and eNOS (rs2070744) genes was studied using restriction fragment length polymorphism analysis and TaqMan Real-Time PCR by. Statistical processing was carried out using the software packages Statistica 10.0, SPSS Statistics 23 and the package of original programs for volumetric processing of bioinformation.Results. The VEGF-2578 heterozygosity and two complex genotypes – VEGF-2578CA:VEGF+936CC and NOS3-786CT:VEGF-2578CA:VEGF+936CC – signifi cantly decreased in patients with DR. The predisposition to early DR development to minor genotype of eNOS gene in the NOS3-786CC:VEGF+936CT complex and signifi cantly decreased the homozygous wild-type eNOS genotype in DM2 patients with ophthalmopathology were shown. NOS3-86TT:VEGF2578AA genotype signifi cantly decreased in group with retinopathy developing and the glycated hemoglobin high level.Conclusion. Along with the clinical risk factors for the development of DR in DM2, the genetic polymorphism of the regulatory regions of the genes analyzed by us has a signifi cant weight. When analyzing potential genetic markers, it is important to consider possible joint epistatic/hypostatic effects. The complex analysis of polymorphic gene can help early prognosis of the DR development.

Distinct Mechanisms of Human Retinal Endothelial Barrier Modulation In Vitro by Mediators of Diabetes and Uveitis

Ocular diseases such as diabetic retinopathy (DR) and uveitis are associated with injury to the blood–retinal barrier (BRB). Whereas high glucose (HG) and advanced glycation end products (AGE) contribute to DR, bacterial infections causing uveitis are triggered by endotoxins such as lipopolysaccharide (LPS). It is unclear how HG, AGE, and LPS affect human retinal endothelial cell (HREC) junctions. Moreover, tumor necrosis factor-α (TNFα) is elevated in both DR and ocular infections. In the current study, we determined the direct effects of HG, AGE, TNFα, and LPS on the expression and intracellular distribution of claudin-5, VE-cadherin, and β-catenin in HRECs and how these mediators affect Akt and P38 MAP kinase that have been implicated in ocular pathologies. In our results, whereas HG, AGE, and TNFα activated both Akt and P38 MAPK, LPS treatment suppressed Akt but increased P38 MAPK phosphorylation. Furthermore, while treatment with AGE and HG increased cell-junction protein expression in HRECs, LPS elicited a paradoxical effect. By contrast, when HG treatment increased HREC-barrier resistance, AGE and LPS stimulation compromised it, and TNFα had no effect. Together, our results demonstrated the differential effects of the mediators of diabetes and infection on HREC-barrier modulation leading to BRB injury.

The palliative effects of folic acid on retinal microvessels in diabetic retinopathy via regulating the metabolism of DNA methylation and hydroxymethylation

Diabetic retinopathy (DR) is one of the severe microvascular complications of diabetes. The protective effects of FA on retinal vascular endothelial cells against high glucose levels involve in multiple aspects in DR; however, the underlying mechanism is not fully elucidated. In present study, we investigated the transcriptome as well as genome-wide DNA methylation and hydroxymethylation signature in human retinal microvascular endothelial ACBRI 181 cells cultured within high glucose (HG) medium supplemented with or without FA by RNA-seq, MeDIP-seq, and hMeDIP-seq. Total 3308 differential expressed genes (DEGs) were involved in multiple biological processes and molecular functions containing angiogenesis, inflammation, S-adenosyl methionine metabolism, and hypoxia response. Moreover, the global DNA methylation and hydroxymethylation in ACBRI 181 cells with FA treatment were both compromised compared to HG. Combined with transcriptome data, four subclusters of DEGs with hyper- or hypomethylated promoters were further verified. Unexpectedly, promoters of these 487 genes all displayed a pattern of increased DNA hydroxymethylation. Furthermore, hyperglycemia rat model was established and administered with FA. The DNA methylation and hydroxymethylation changes of selected target genes COL1A1, ITGA7, MMP-14, and VEGFB confirmed by MeDIP-qPCR were consistent with the results in human ACBRI 181 cells. Finally, the presence of activated DNMT1 and TET2 induced by FA was determined in ACBRI 181 cells and hyperglycemia rat. Taken together, this research provided a resource of expression and epigenetic profiles in retinal microvascular endothelial cell, emphasizing a pharmacological mechanism of FA on DNA methylation and hydroxymethylation regulation in retinal microvessel cells of DR.

Association Between Prediabetes and Retinopathy: A Meta-Analysis

Diabetes confers an increased risk of microvascular complications, including retinopathy. However, whether prediabetes is also related to retinopathy has not been comprehensively examined. We performed a meta-analysis to evaluate the relationship between prediabetes and retinopathy. This meta-analysis included relevant observational studies from Medline, Embase, and Web of Science databases. A random-effect model after incorporation of the intra-study heterogeneity was selected to pool the results. Subgroup analyses were applied to evaluate the influences of study characteristics on relationship. Nine cross-sectional studies including 14 751 community dwelling adult participants were included; 3847 (26.1%) of them were prediabetic. Results showed that prediabetes was associated with a higher prevalence of retinopathy compared to normoglycemia [odds ratio (OR): 1.55, 95% confidence interval (CI): 1.10-2.20, p=0.01, I²=34%]. Sensitivity analysis by excluding one study at a time showed consistent result (OR: 1.35 to 1.73, p all<0.05). Subgroup analysis showed study characteristics such as definition of prediabetes, country of study, sample size, mean age of participants, or univariate or multivariate analyses may not significantly affect the association (p for subgroup difference all>0.05). Current evidence suggests that patients with prediabetes may be associated with higher prevalence of retinopathy as compared to those with normoglycemia. Although prospective cohort studies are needed to validate these findings, results of our meta-analysis highlighted the importance of early prevention of retinopathy in patients with prediabetes.

Hyperglycemia-induced effects on glycocalyx components in the retina

PURPOSE

Diabetic retinopathy is a vision-threatening complication of diabetes characterized by endothelial injury and vascular dysfunction. The loss of the endothelial glycocalyx, a dynamic layer lining all endothelial cells, contributes to several microvascular pathologies, including an increase in vascular permeability, leukocyte plugging, and capillary occlusion, and may drive the progression of retinopathy. Previously, a significant decrease in glycocalyx thickness has been observed in diabetic retinas. However, the effects of diabetes on specific components of the retinal glycocalyx have not yet been studied. Therefore, the aim of our study was to investigate changes in synthesis, expression, and shedding of retinal glycocalyx components induced by hyperglycemia, which could provide a novel therapeutic target for diabetic retinopathy.

METHODS

Primary rat retinal microvascular endothelial cells (RRMECs) were grown under normal glucose (5 mM) or high-glucose (25 mM) conditions for 6 days. The mRNA and protein levels of the glycocalyx components were examined using qRT-PCR and Western blot analysis, respectively. Further, mass spectrometry was used to analyze protein intensities of core proteins. In addition, the streptozotocin-induced Type 1 diabetic rat model was used to study changes in the expression of the retinal glycocalyx in vivo. The shedding of the glycocalyx was studied in both culture medium and in plasma using Western blot analysis.

RESULTS

A significant increase in the shedding of syndecan-1 and CD44 was observed both in vitro and in vivo under high-glucose conditions. The mRNA levels of syndecan-3 were significantly lower in the RRMECs grown under high glucose conditions, whereas those of syndecan-1, syndecan-2, syndecan-4, glypican-1, glypican-3, and CD44 were significantly higher. The protein expression of syndecan-3 and glypican-1 in RRMECs was reduced considerably following exposure to high glucose, whereas that of syndecan-1 and CD44 increased significantly. In addition, mass spectrometry data also suggests a significant increase in syndecan-4 and a significant decrease in glypican-3 protein levels with high glucose stimulation. In vivo, our data also suggest a significant decrease in the mRNA transcripts of syndecan-3 and an increase in mRNA levels of glypican-1 and CD44 in the retinas of diabetic rats. The diabetic rats exhibited a significant reduction in the retinal expression of syndecan-3 and CD44. However, the expression of syndecan-1 and glypican-1 increased significantly in the diabetic retina.

CONCLUSIONS

One of the main findings of our study was the considerable diversity of glucose-induced changes in expression and shedding of various components of endothelial glycocalyx, for example, increased endothelial and retinal syndecan-1, but decreased endothelial and retinal syndecan-3. This indicates that the reported decrease in the retinal glycocalyx in diabetes in not a result of a non-specific shedding mechanism. Moreover, mRNA measurements indicated a similar diversity, with increases in endothelial and/or retinal levels of syndecan-1, glypican-1, and CD44, but a decrease for syndecan-3, with these increases in mRNA potentially a compensatory reaction to the overall loss of glycocalyx.

Nuclear factor of activated T-cells (NFAT) regulation of IL-1β-induced retinal vascular inflammation

Chronic low-grade retinal inflammation is an essential contributor to the pathogenesis of diabetic retinopathy (DR). It is characterized by increased retinal cell expression and secretion of a variety of inflammatory cytokines; among these, IL-1β has the reputation of being a major driver of cytokine-induced inflammation. IL-1β and other cytokines drive inflammatory changes that cause damage to retinal cells, leading to the hallmark vascular lesions of DR; these include increased leukocyte adherence, vascular permeability, and capillary cell death. Nuclear factor of activated T-cells (NFAT) is a transcriptional regulator of inflammatory cytokines and adhesion molecules and is expressed in retinal cells. Consequently, it may influence multiple pathogenic steps early in DR. We investigated the NFAT-dependency of IL-1β-induced inflammation in human Müller cells (hMC) and human retinal microvascular endothelial cells (hRMEC). Our results show that an NFAT inhibitor, Inhibitor of NFAT-Calcineurin Association-6 (INCA-6), decreased IL-1β-induced expression of IL-1β and TNFα in hMC, while having no effect on VEGF, CCL2, or CCL5 expression. We also demonstrate that INCA-6 attenuated IL-1β-induced increases of IL-1β, TNFα, IL-6, CCL2, and CCL5 (inflammatory cytokines and chemokines), and ICAM-1 and E-selectin (leukocyte adhesion molecules) expression in hRMEC. INCA-6 similarly inhibited IL-1β-induced increases in leukocyte adhesion in both hRMEC monolayers in vitro and an acute model of retinal inflammation in vivo. Finally, INCA-6 rescued IL-1β-induced permeability in both hRMEC monolayers in vitro and an acute model of retinal inflammation in vivo. Taken together, these data demonstrate the potential of NFAT inhibition to mitigate retinal inflammation secondary to diabetes.

Extent and features of liver steatosis in vitro pave the way to endothelial dysfunction without physical cell-to-cell contact

BACKGROUND AND AIMS

Several chronic multifactorial diseases originate from energy unbalance between food intake and body energy expenditure, including non-alcoholic fatty liver disease (NAFLD), diabetes, and cardiovascular disorders. Vascular endothelium plays a central role in body homeostasis, and NAFLD is often associated with endothelial dysfunction (ED), the first step in atherosclerosis. Both sugars and fatty acids (FAs) are fuel sources for energy production, but their excess leads to liver steatosis which may trigger ED through a network of mechanisms which need to be clarified. Here, we investigated the crosstalk pathways between in vitro cultured steatotic hepatocytes (FaO) and endothelial cells (HECV) being mediated by soluble factors.

METHODS AND RESULTS

We employed the conditioned medium approach to test how different extent and features of hepatic steatosis distinctively affect endothelium leading to ED. The steatogenic media collected from steatotic hepatocytes were characterized by high triglyceride content and led to lipid accumulation and fat-dependent dysfunction in HECV cells. We found a parallelism between (i) extent of hepatocyte steatosis and level of lipid accumulation in HECV cells; (ii) type of hepatocyte steatosis (with macro- or microvesicular LDs) and extent of oxidative stress, lipid peroxidation, nitric oxide release and expression of ED markers in HECV cells.

CONCLUSIONS

The present findings seem to suggest that, in addition to triglycerides, other soluble mediators should be released by steatotic hepatocytes and may influence lipid accumulation and function of HECV cells. Further studies need to depict the exact profile of soluble factors involved in steatotic hepatocyte-endothelium crosstalk.

Characterization of a murine model of endothelial dysfunction induced by chronic intraperitoneal administration of angiotensin II

Endothelial dysfunction (ED) is a key factor for the development of cardiovascular diseases. Due to its chronic, life-threatening nature, ED only can be studied experimentally in animal models. Therefore, this work was aimed to characterize a murine model of ED induced by a daily intraperitoneal administration of angiotensin II (AGII) for 10 weeks. Oxidative stress, inflammation, vascular remodeling, hypertension, and damage to various target organs were evaluated in treated animals. The results indicated that a chronic intraperitoneal administration of AGII increases the production of systemic soluble VCAM, ROS and ICAM-1 expression, and the production of TNFα, IL1β, IL17A, IL4, TGFβ, and IL10 in the kidney, as well as blood pressure levels; it also promotes vascular remodeling and induces non-alcoholic fatty liver disease, glomerulosclerosis, and proliferative retinopathy. Therefore, the model herein proposed can be a representative model for ED; additionally, it is easy to implement, safe, rapid, and inexpensive.

Protective Effect of Effective Components of Coreopsis tinctoria Nutt on Retinopathy of db/db Diabetic Mice

Objective

Diabetic retinopathy (DR) is one of the main diabetic microvascular complications in clinical practice, which features a complicated mechanism and insignificant efficacy. Therefore, it is urgent to find effective drugs. Xinjiang Coreopsis tinctoria Nutt is a rare alpine wild plant with unique effects and extremely high medicinal value. Preliminary studies have shown that it can reduce elevated blood sugar, unhealthy lipids, and antioxidants. This study was intended to investigate the protective effect of the effective components of Coreopsis tinctoria Nutt on the retinopathy of db/db diabetic mice and provide experimental basis for exploring the efficacy of Coreopsis tinctoria Nutt and the development of new drugs for the treatment of DR.

Method

The db/db diabetic mouse models were used, and the effective components of Coreopsis tinctoria Nutt were obtained from Coreopsis tinctoria Nutt using macroporous resin enrichment method after alcohol extraction. These mice were divided into the normal group, model group, and high-dose Coreopsis tinctoria Nutt groups, the positive drug metformin group, and the metformin and Coreopsis tinctoria Nutt combination group. After these db/db type 2 diabetes mouse models were intervened for 10 weeks, their weight, blood sugar, glycosylated hemoglobin, serum MDA, SOD, and other indicators of each group were tested, and the expression changes of VEGF, ICAM1, PEDF, Bcl-2 in mouse retina were observed by immunohistochemistry method.

Result

The effective components of Coreopsis tinctoria Nutt were obtained using macroporous resin enrichment method after alcohol extraction, which were mainly comprised of chlorogenic acid, flavone mariside, mariside, dicaffeoyl quinic acid, and flavone oxanine, with a total content of 532.82 mg/g, and the total flavonoid content of 330 mg/g. The effective components of Coreopsis tinctoria Nutt significantly reduced blood sugar and glycosylated hemoglobin and improved oxidative stress levels in db/db diabetic mice. Meanwhile, they reduced the expression of VEGF and ICAM1 in retinopathy and increased the expression of Bcl-2 and PEDF. The combination of Coreopsis tinctoria Nutt and metformin has the most significant effect.

Conclusion

Coreopsis tinctoria Nutt can prevent and treat early diabetic retinopathy by affecting the expression of retinopathy-related factors.

Looking for In Vitro Models for Retinal Diseases

Retina is a layered structure of the eye, composed of different cellular components working together to produce a complex visual output. Because of its important role in visual function, retinal pathologies commonly represent the main causes of visual injury and blindness in the industrialized world. It is important to develop in vitro models of retinal diseases to use them in first screenings before translating in in vivo experiments and clinics. For this reason, it is important to develop bidimensional (2D) models that are more suitable for drug screening and toxicological studies and tridimensional (3D) models, which can replicate physiological conditions, for investigating pathological mechanisms leading to visual loss. This review provides an overview of the most common retinal diseases, relating to in vivo models, with a specific focus on alternative 2D and 3D in vitro models that can replicate the different cellular and matrix components of retinal layers, as well as injury insults that induce retinal disease and loss of the visual function.

Ocular Neurodegenerative Diseases: Interconnection between Retina and Cortical Areas

The possible interconnection between the eye and central nervous system (CNS) has been a topic of discussion for several years just based on fact that the eye is properly considered an extension of the brain. Both organs consist of neurons and derived from a neural tube. The visual process involves photoreceptors that receive light stimulus from the external environment and send it to retinal ganglionic cells (RGC), one of the cell types of which the retina is composed. The retina, the internal visual membrane of the eye, processes the visual stimuli in electric stimuli to transfer it to the brain, through the optic nerve. Retinal chronic progressive neurodegeneration, which may occur among the elderly, can lead to different disorders of the eye such as glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy (DR). Mainly in the elderly population, but also among younger people, such ocular pathologies are the cause of irreversible blindness or impaired, reduced vision. Typical neurodegenerative diseases of the CSN are a group of pathologies with common characteristics and etiology not fully understood; some risk factors have been identified, but they are not enough to justify all the cases observed. Furthermore, several studies have shown that also ocular disorders present characteristics of neurodegenerative diseases and, on the other hand, CNS pathologies, i.e., Alzheimer disease (AD) and Parkinson disease (PD), which are causes of morbidity and mortality worldwide, show peculiar alterations at the ocular level. The knowledge of possible correlations could help to understand the mechanisms of onset. Moreover, the underlying mechanisms of these heterogeneous disorders are still debated. This review discusses the characteristics of the ocular illnesses, focusing on the relationship between the eye and the brain. A better comprehension could help in future new therapies, thus reducing or avoiding loss of vision and improve quality of life.

Genetics of Diabetic Retinopathy, a Leading Cause of Irreversible Blindness in the Industrialized World

Diabetic retinopathy (DR) is a chronic complication of diabetes and a leading cause of blindness in the industrialized world. Traditional risk factors, such as glycemic control and duration of diabetes, are unable to explain why some individuals remain protected while others progress to a more severe form of the disease. Differences are also observed in DR heritability as well as the response to anti-vascular endothelial growth factor (VEGF) treatment. This review discusses various aspects of genetics in DR to shed light on DR pathogenesis and treatment. First, we discuss the global burden of DR followed by a discussion on disease pathogenesis as well as the role genetics plays in the prevalence and progression of DR. Subsequently, we provide a review of studies related to DR’s genetic contribution, such as candidate gene studies, linkage studies, and genome-wide association studies (GWAS) as well as other clinical and meta-analysis studies that have identified putative candidate genes. With the advent of newer cutting-edge technologies, identifying the genetic components in DR has played an important role in understanding DR incidence, progression, and response to treatment, thereby developing newer therapeutic targets and therapies.

Exposure to Porphyromonas gingivalis and Modifiable Risk Factors Modulate Risk for Early Diabetic Retinopathy

Purpose

We hypothesized that exposure to Porphyromonas gingivalis (Pg) increases the risk for early diabetic retinopathy (DR) and that the risk can be modulated.

Methods

We identified 116 early DR cases, and 116 non-DR controls were selected randomly by frequency matching for age, sex, race, and education from the US Third National Health and Nutrition Examination Survey. DR was assessed using non-mydriatic fundus photographs and graded by trained graders using the Modified Airlie House Classification scheme and the Early Treatment for Diabetic Retinopathy Study severity scale. Serum Pg immunoglobulin G (IgG) antibody (Ab) was measured in enzyme-linked immunosorbent assay units. Logistic regression was used to relate serum Pg IgG Ab levels to the risk for early DR.

Results

Per tenfold increase in Pg IgG Ab levels, there was an over 60% increased risk for early DR (odds ratio = 1.64; 95% confidence interval, 1.36–1.97), and a linear trend was noted for the estimated probabilities of early DR at various Pg IgG Ab levels (P for trend = 0.0053). The analysis also suggested that moderate alcohol consumption (less than 12 drinks in the past 12 months; P for interaction = 0.0003) and maintaining a normal serum glycated hemoglobulin level (HbA1c ≤ 5.7%; P for interaction < 0.0001) helped reduce the Pg-related DR risk.

Conclusions

The increased Pg-related DR risk could be alleviated by managing alcohol consumption and maintaining a normal blood glucose level.

Translational Relevance

Findings from this study provide new directions for developing novel therapeutics and prevention strategies for DR.

Systemic diseases and the cornea

There is a number of systemic diseases affecting the cornea. These include endocrine disorders (diabetes, Graves' disease, Addison's disease, hyperparathyroidism), infections with viruses (SARS-CoV-2, herpes simplex, varicella zoster, HTLV-1, Epstein-Barr virus) and bacteria (tuberculosis, syphilis and Pseudomonas aeruginosa), autoimmune and inflammatory diseases (rheumatoid arthritis, Sjögren's syndrome, lupus erythematosus, gout, atopic and vernal keratoconjunctivitis, multiple sclerosis, granulomatosis with polyangiitis, sarcoidosis, Cogan's syndrome, immunobullous diseases), corneal deposit disorders (Wilson's disease, cystinosis, Fabry disease, Meretoja's syndrome, mucopolysaccharidosis, hyperlipoproteinemia), and genetic disorders (aniridia, Ehlers-Danlos syndromes, Marfan syndrome). Corneal manifestations often provide an insight to underlying systemic diseases and can act as the first indicator of an undiagnosed systemic condition. Routine eye exams can bring attention to potentially life-threatening illnesses. In this review, we provide a fairly detailed overview of the pathologic changes in the cornea described in various systemic diseases and also discuss underlying molecular mechanisms, as well as current and emerging treatments.

Progress of Clinical Evaluation for Vascular Aging in Humans

Human society is experiencing a serious aging process. Age-related arteriosclerotic cardiovascular diseases (ASCVD) are the most common cause of deaths around the world and bring a huge burden on the whole society. Vascular aging-related pathological alterations of the vasculature play an important role in the pathogenesis of ASCVD and morbidity and mortality of older adults. In this review, we describe the progress of clinical evaluation of vascular aging in humans, including functional evaluation, structural assessment, and cellular molecular markers. The significance of detection for vascular aging is highlighted, and we call for close attention to the evaluation for a better quality of life in the elderly population.

RPS4Y1 Promotes High Glucose-Induced Endothelial Cell Apoptosis and Inflammation by Activation of the p38 MAPK Signaling

AIM

Endothelial dysfunction is a key pathological basis for diabetes mellitus complications, including diabetic nephropathy, diabetic retinopathy, and diabetic cardiomyopathy. This study aimed to reveal the functional role of ribosomal protein S4 Y-linked 1 (RPS4Y1) in endothelial dysfunction.

METHODS

Human umbilical vein endothelial cells (HUVECs) were subjected to high glucose. The expression of RPS4Y1 in cells was overexpressed or silenced by plasmid or siRNA transfection. MTT assay, flow cytometry, JC-1 probe, scratch test, tube formation, and ELISA were conducted to assess the effects of RPS4Y1 on cell. Western blot was performed to assay the downstream signaling of RPS4Y1. The inhibitors of p38, ERK, and Jnk were used to treat cells to validate the involvement of them in RPS4Y1-mediated endothelial dysfunction.

RESULTS

RPS4Y1 was upregulated in HUVECs in response to high glucose in both dose- and time-dependent manners. Overexpression of RPS4Y1 induced viability loss, apoptosis, and inflammation, but inhibited cell migration and tube formation. Silence of RPS4Y1 impacted these aspects in a contrary trend. The phosphorylation of p38 rather than ERK and Jnk was activated by RPS4Y1. In addition, the dysfunction of HUVECs mediated by RPS4Y1 was attenuated by SB203580 (a specific inhibitor of p38 signaling).

CONCLUSION

The highly expressed RPS4Y1 in endothelial cells may contribute to high glucose-induced dysfunction through regulating p38 MAPK signaling. RPS4Y1 might be a potential therapeutic target for treating diabetes mellitus complications.

An Overview of Vascular Dysfunction and Determinants: The Case of Children of African Ancestry

The balance between dilatory and constrictive factors is important as it keeps blood vessels in a homeostatic state. However, altered physiological processes as a result of obesity, hypertension, oxidative stress, and other cardiovascular risk factors may lead to vascular damage, causing an imbalance of vasoactive factors. Over time, the sustained imbalance of these vasoactive factors may lead to vascular dysfunction, which can be assessed by non-invasive methods, such as flow-mediated dilation, pulse wave velocity, flow-mediated slowing, retinal vessel analysis, peripheral vascular reactivity, and carotid intima-media thickness assessment. Although there is increasing prevalence of cardiovascular risk factors (obesity and hypertension) in children in sub-Saharan Africa, little is known about how this may affect vascular function. This review focuses on vasoactive factors implicated in vascular (dys)function, highlighting the determinants and consequences of vascular dysfunction. It further describes the non-invasive methods used for vascular (dys)function assessments and, last, describes the impact of cardiovascular risk factors on vascular dysfunction in children of African ancestry.