Retinal Microvascular Dysfunction Research Articles

Ferroptosis Contributes to Microvascular Dysfunction in Diabetic Retinopathy

Ferroptosis is a new form of cell death characterized by iron-dependent lipid peroxidation. Whether ferroptosis is involved in retinal microvascular dysfunction under diabetic condition is not known. The expression of ferroptosis related genes in patients with proliferative diabetic retinopathy (PDR) and in diabetic mice was determined with RT-qPCR. Reactive oxygen species (ROS), iron content, lipid peroxidation products, and ferroptosis-associated proteins in the cultured human retinal microvascular endothelial cells (HRMECs) and in the retina of diabetic mice were examined. The association of ferroptosis with the functions of endothelial cells in vitro was evaluated. After administration of ferroptosis specific inhibitor Fer-1, the retinal microvasculature in diabetic mice was assessed. Characteristic change of ferroptosis associated marker including GPX4, FTH1, ACSL4, TFRC and COX2 were detected in the retinal fibrovascular membrane of PDR patients, cultured HRMECs and the retina of diabetic mice. Elevated levels of ROS, lipid peroxidation and iron content were found in the retina of diabetic mice and also in cultured HRMECs. Ferroptosis was found to be associated with HRMECs dysfunction under high glucose condition. Inhibition of ferroptosis with specific inhibitor Fer-1 in diabetic mice significantly reduced the severity of retinal microvasculopathy. Ferroptosis contributes to microvascular dysfunction in diabetic retinopathy, and inhibition of ferroptosis might be a promising strategy for the therapy of early-stage diabetic retinopathy.

Procyanidin B2 Protects TR-iBRB2 Cells Against Hyperglyc emia Stress by Attenuating Oxidative Stress and Inflammasome Activation via Regulation of Redoxosomes/NF-kB Signaling.

Microvascular dysfunction is a hallmark of diabetic retinopathy (DR), which may lead to visual impairment and blindness. Procyanidin B2 (PB2) is a subclass of flavonoids and is widely known due to its anti-oxidant and antiinflammatory effects. However, little is known about the effect of PB2 on hyperglycemia stress-induced retinal microvascular dysfunction. The purpose of this study was to investigate the effect of PB2 against hyperglycemia stress in rat retinal capillary endothelial cells (TR-iBRB2) as well as the underpinning mechanism. Cell viability was determined using MTT assay. ROS, NOX activity analysis, Western blot analysis, and immunofluorescence analysis were applied in the study. The results showed that PB2 pre-treatment significantly reduced high glucose- induced cytotoxicity in TR-iBRB2 cells by suppressing oxidative stress and inflammasome activation. Mechanistical study revealed that redoxosomes were formed and activated in TR-iBRB2 cells upon hyperglycemia stress, resulting in activation of NF- κB and thus induction of oxidative stress and inflammasomes activation. However, PB2 pre-treatment dose-dependently attenuated the above events, indicating the protective effect of PB2 against hyperglycemia stress was achieved by regulating redoxosomes/ NF-kB signaling. Our findings may contribute to the potential clinical use of PB2 in treating DR and suggest redoxosomes/NF-kB signaling may be a potential therapeutic target of this disease.

Impaired retinal micro-vascular function in patients with atrial fibrillation

BackgroundCardiovascular (CV) risk factors and CV diseases, in particular heart failure, are strongly associated with impaired microvascular retinal endothelial function. Whether atrial fibrillation (AF) contributes to vascular dysfunction is not clear. Therefore, the aim of this study was to investigate the impact of AF on retinal microvascular function. MethodsIn this study, vascular function was measured non-invasively with flicker-light induced vasodilatation of retinal arterioles (FIDart%). Patients with a history of AF and risk factors for heart failure (HF) or heart failure (n = 69; age 67.9 ± 9.2 years, 71% male, 35% HFrEF, 56% paroxysmal, 25% persistent, 19% permanent AF), as well as age, sex and ejection fraction matched patients with absent history of AF (n = 66; age 63.4 ± 10.6 years, 67% male, 47% HFrEF) were included. Patients with AF were further divided into those with paroxysmal AF (in sinus rhythm – AFSR: n = 38, age 71.4 ± 9.2, 73% male), and those with AF at the time of the study visit. ResultsRetinal microvascular function was impaired in patients with AF compared to patients without AF (FIDart% 1.1% [0.3–2.8] vs. 2.7% [1.3–5.1], p < 0.001). Patients currently in AF have poorer retinal microvascular function (FIDart% 0.8% [0.1–1.9) compared to patients with a history of AF but currently in SR at the time of retinal function measurement (1.5% [0.6–4.9] p = 0.017). In patients with AF, impaired retinal vascular function was independently associated with larger left atrial volume (mean 49.8 ± 18.4), even after correction for confounding factors in different models (SCR = -0. 251 to −0.256, p = 0.035–0.01). ConclusionsAF in patients with heart failure is associated with impaired vascular function, even if currently in sinus rhythm. The association of retinal microvascular dysfunction with left atrial volume, a surrogate for elevated cardiac filling pressures, may further highlight the important interplay between the vasculature and elevated filling pressures in the development of AF.

MiR-423-5p promotes Müller cell activation via targeting NGF signaling in diabetic retinopathy

AimsDiabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus and one of the major causes of visual impairment and blindness in industrialized countries. The early neuro-glial perturbations, especially retinal Müller cells (rMC) activation, intimately associated with the vascular alterations. MicroRNAs (miRNAs) have been reported to play critical roles in the progression of DR. Here, we aimed to further explore the role and underlying mechanism of miR-423-5p in Müller cell activation in streptozotocin (STZ)-induced diabetic mice and oxygen-induced retinopathy (OIR) model. Materials and methodsRetinal histology, optical coherence tomography (OCT) and biochemical markers were assessed. Key findingsOur data revealed that the expression of miR-423-5p was significantly increased under high-glucose environment. We also demonstrated that miR-423-5p overexpression markedly accelerated retinal vascular leakage, leukocytosis, and rMC activation. This response was ameliorated in animals pre-treated with the inhibition of miR-423-5p. Specifically, miR-423-5p bound to the nerve growth factor (NGF) 3′ UTR region to induce its silencing. NGF inhibition significantly promoted retinal microvascular dysfunction. SignificanceThese findings demonstrate that miR-423-5p is a critical miRNA that promotes microvascular dysfunction in DR.

EIF4A3-mediated circEHMT1 regulation in retinal microvascular endothelial dysfunction in diabetic retinopathy

Background and objectiveLiterature has reported that circular RNAs (circRNAs) are crucially associated with diabetic retinopathy (DR). Furthermore, circEHMT1 has been identified to maintain endothelial cell barrier function. This study aimed to investigate the mechanisms that regulate aberrant circEHMT1 expression and its role in the pathogenesis of DR. MethodsIn this study, retinal microvascular endothelial cells were exposed to a high glucose (HG) environment, and subsequently, tube formation and intercellular junction proteins were evaluated. Furthermore, the biological functions of circEHMT1 and its potential regulatory factor, eIF4A3, in microvascular endothelial cells under HG conditions were also assessed. In addition, the regulatory role of eIF4A3 on circEHMT1 expression was confirmed. Moreover, to elucidate the in vivo functions of eIF4A3 and circEHMT1, streptozotocin (STZ) was used to establish a DR model in rats. ResultsIt was revealed that HG condition decreased circEHMT1 and eIF4A3 expressions and reduced ZO-1, Claudin-5, and Occludin levels in retinal microvascular endothelial cells. Furthermore, it was observed that eIF4A3 could regulate the expression of circEHMT1. Overexpression of eIF4A3 or circEHMT1 under HG conditions improved endothelial cell injury and decreased tube-formation ability. Additionally, in the DR rat model, eIF4A3 overexpression restored circEHMT1 levels and ameliorated retinal vasculature changes. ConclusionAltogether, eIF4A3 regulates circEHMT1 expression, thereby affecting microvascular endothelial cell injury and tube formation. Further understanding the regulatory effect of eIF4A3 on circEHMT1 may provide novel therapeutic targets for DR.

MG132, Attenuates the Retinal Vascular Injury Through the Upregulation of Nrf2 Expression.

Purpose: This study clarifies the beneficial effects of MG132, a proteasomal inhibitor, on retinal vascular injury mediated by diabetes-induced oxidative stress through nuclear factor erythroid 2-related factor 2 (Nrf2). Methods: Diabetic rats and control animals were randomly assigned to receive MG132 or vehicle for 24 weeks, and human retinal endothelial cells (HRECs) were incubated with normal or high glucose with or without MG132. 26S proteasome activity in the rat retinas or cultured HRECs was measured using Suc-LLVY-7-amido-4-methylcoumarin. NADPH-quinone oxidoreduc-tase (NQO1), heme oxygenase (HO)-1, kelch-like ECH-associated protein 1 (Keap1) and Nrf2 were examined by Western blotting and real-time reverse transcription polymerase chain reaction. Cell apoptosis is measured through flow cytometry assay, mitochondrial reactive oxygen species (ROS) production, and retinal vascular leakage were assayed using CM-H2DCFDA fluorescent probes and Evans blue, respectively. Results: MG132 significantly inhibited the activation of 26S proteasome induced by diabetes or elevated glucose, and subsequently increased the expression of Nrf2, NQO1, and HO-1, and further reduced ROS accumulation. These changes were associated with a decrease of diabetes-induced retinal vascular leakage and retinal capillary cell apoptosis. Conclusions: MG132 decreases diabetes-induced 26S proteasome activation and exerts protective effects against retinal microvascular dysfunction in diabetic rats in association with the alleviation of retinal oxidative stress mediated by Nrf2.

Relationships of blood pressure and control with microvascular dysfunction in type 2 diabetes

BackgroundIn type 2 diabetes mellitus (T2D), cardiovascular risk factors including glycemic control differentially affect various microcirculatory beds. To date, studies comparing the impact of blood pressure (BP) on various microvascular beds in T2D are limited. We assessed the associations of BP and its control with neural, renal, and retinal microvascular dysfunction. MethodsThis was a cross-sectional study among 403 adults with T2D. Microvascular dysfunction was based on nephropathy (albumin-creatinine ratio ≥ 30 mg/g), neuropathy (vibration perception threshold ≥ 25 V and/or Diabetic Neuropathy Symptom score > 1), and retinopathy (based on retinal photography). Logistic regression was used to examine the associations of hypertension, systolic BP, and diastolic BP with microvascular dysfunction with adjustments for age, sex, diabetes duration, smoking pack years, HbA1c concentration, total cholesterol concentration, and BMI. ResultsThe mean age (± SD), proportion of females, and proportion of hypertensives were 56.35 (± 9.91) years, 75.7%, and 49.1%, respectively. In a fully adjusted model, hypertension was significantly associated with neuropathy [odds ratio 3.44, 95% confidence interval 1.96–6.04, P < 0.001] and nephropathy [2.05 (1.09–3.85), 0.026] but not for retinopathy [0.98 (0.42–2.31), 0.970]. Increasing Z-score systolic BP was significantly associated with nephropathy [1.43 (1.05–1.97), 0.025] but not for neuropathy [1.28 (0.98–1.67), 0.075] or retinopathy [1.27 (0.84–1.91), 0.261]. Increasing Z-score diastolic BP was significantly associated with nephropathy [1.81 (1.32 – 2.49), < 0.001] but not retinopathy [1.38 (0.92–2.05), 0.120] or neuropathy [0.86 (0.67–1.10), 0.230]. ConclusionOur study shows varying strengths of associations of hypertension, systolic BP, and diastolic BP with microvascular dysfunction in different microcirculatory beds. Hypertension prevention and/or control may be valuable in the prevention/treatment of microvascular disease, especially nephropathy, and neuropathy.

Association between albuminuria and retinal microvascular dysfunction in type 2 diabetes with and without hypertension

BackgroundStudies assessing the concordance of albuminuria and retinal microvascular dysfunction (RMD) in type 2 diabetes (T2D) have yielded inconsistent results. Similar to ethnicity, hypertension may be a potential explanatory variable. We compared the association between albuminuria and RMD in West Africans with T2D with and without hypertension. Materials and methodsThis was a cross-sectional study among 177 systematically sampled Ghanaians with T2D aged ≥ 35 years. Albuminuria was based on urinary albumin-creatinine ratio≥30 mg/g. Retinal images were analyzed and graded according to the Early Treatment Diabetic Retinopathy Study criteria. Logistic regression was used to examine the associations of albuminuria and RMD with adjustments for age, sex, socioeconomic status, diabetes duration, HbA1c, smoking, systolic blood pressure (BP), BMI, and total cholesterol. ResultsRMD was more prevalent in individuals with albuminuria than in those without albuminuria (41.7% vs. 24.0%, p = 0.026). In the fully adjusted model, albuminuria remained significantly associated with RMD (odds ratio 2.41[95% CI:1.00–5.80], p = 0.049); the association between albuminuria and RMD was more pronounced in individuals with hypertension (3.10 [1.01–9.50], 0.048) than without hypertension (1.70[0.33–8.77],0.523). In analyses stratified by BP control, albuminuria was significantly associated with RMD in individuals with suboptimal BP (2.76[1.07–7.14], 0.037) but not in individuals with optimal BP (0.24[0.00–17.04],0.512) ConclusionOur study shows positive associations between albuminuria and RMD among West Africans with T2D, with the strength of association, accentuated in individuals with hypertension/suboptimal BP. Future studies could further characterize the role of hypertension in the associations between albuminuria and RMD.

Retinal Microvascular Dysfunction Occurs Early and Similarly in Mild Alzheimer's Disease and Primary-Open Angle Glaucoma Patients.

To assess the similarities and differences in retinal microvascular function between mild Alzheimer's disease (AD) patients, early-stage primary open angle glaucoma (POAG) patients and healthy controls. Retinal vessel reactivity to flickering light was assessed in 10 AD, 19 POAG and 20 healthy age matched control patients by means of dynamic retinal vessel analysis (DVA, IMEDOS, GmbH, Jena, Germany) according to an established protocol. All patients additionally underwent BP measurements and blood analysis for glucose and lipid metabolism markers. AD and POAG patients demonstrated comparable alterations in retinal artery reactivity, in the form of an increased arterial reaction time (RT) to flicker light on the final flicker cycle (p = 0.009), which was not replicated by healthy controls (p &gt; 0.05). Furthermore, the sequential changes in RT on progressing from flicker one to flicker three were found to differ between healthy controls and the two disease groups (p = 0.001). AD and POAG patients demonstrate comparable signs of vascular dysfunction in their retinal arteries at the early stages of their disease process. This provides support for the concept of a common underlying vascular aetiology in these two neurodegenerative diseases.

Dopamine ameliorates hyperglycemic memory-induced microvascular dysfunction in diabetic retinopathy.

Dopamine is a neurotransmitter that mediates visual function in the retina and diabetic retinopathy (DR) is the most common microvascular complication of diabetes and the leading cause of blindness; however, the role of dopamine in retinal vascular dysfunction in DR remains unclear. Here, we report a mechanism of hyperglycemic memory (HGM)-induced retinal microvascular dysfunction and the protective effect of dopamine against the HGM-induced retinal microvascular leakage and abnormalities. We found that HGM induced persistent oxidative stress, mitochondrial membrane potential collapse and fission, and adherens junction disassembly and subsequent vascular leakage after blood glucose normalization in the mouse retinas. These persistent hyperglycemic stresses were inhibited by dopamine treatment in human retinal endothelial cells and by intravitreal injection of levodopa in the retinas of HGM mice. Moreover, levodopa supplementation ameliorated HGM-induced pericyte degeneration, acellular capillary and pericyte ghost generation, and endothelial apoptosis in the mouse retinas. Our findings suggest that dopamine alleviates HGM-induced retinal microvascular leakage and abnormalities by inhibiting persistent oxidative stress and mitochondrial dysfunction.

Retinal Microvascular Abnormalities and Systemic Arterial Stiffness Are the First Manifestation of Cardiovascular Abnormalities in Patients with Untreated Moderate to Severe Obstructive Sleep Apnoea and with Low to Intermediate Cardiovascular Risk-A Pilot Study.

This study aimed to investigate macro- and microvascular function parameters and their relationship with known markers of cardiovascular risk in patients with untreated moderate to severe obstructive sleep apnoea (OSA). Fourteen patients with moderate to severe OSA and fourteen controls were included in the present study. General assessments included BMI, systemic blood pressure (BP) and circulating markers for oxidative stress and endothelial function. Additional assessments included 24 h BP and heart rate monitoring, as well as the assessment of heart rate variability. Macro- and microvascular assessments included augmentation index, carotid intima-media thickness, brachial artery flow-mediated dilation, as well as various retinal microvascular function assessments, using the Dynamic Retinal Vessel Analyzer. All participants completed the Short Form Health Survey, Functional Outcomes of Sleep Questionnaire, and Epworth Sleepiness Scale. The results show that, in comparison to controls, BMI (p = 0.003) and AIx (p = 0.025) were significantly higher in the OSA group. There was, however, no significant difference between groups with regard to other measured systemic general, vascular and circulatory parameters (all p > 0.05). Nevertheless, the retinal microvascular function showed various alterations in the OSA patients, including a delayed reaction time in response to flicker (p = 0.047), as well as a decreased dilation amplitude (p = 0.004), dilation slope (p = 0.004), and post-flicker constriction (p = 0.015). In addition, the observed SlopeAD alterations correlated negatively with BMI values only in the OSA group (r = −0.46, p = 0.045). In conclusion, individuals with untreated moderate to severe OSA but without overt CVD, exhibit signs of increased arterial stiffness and retinal microvascular dysfunction, which can be early indicators for future vascular complications.

Hypertension and retinal microvascular dysfunction (HyperVasc): protocol of a randomised controlled exercise trial in patients with hypertension

IntroductionHypertension is a global healthcare burden that affects the structure and function of the macrocirculation and microcirculation and induces disease-specific end-organ damage. Vascular biomarkers are essential to timely diagnose this...

Oxysterols and Retinal Microvascular Dysfunction as Early Risk Markers for Cardiovascular Disease in Normal, Ageing Individuals.

The aim of the present paper is to assess the relationship between oxysterol levels and retinal microvascular function in individuals of various age groups, free of clinically evident diseases. Forty-two apparently healthy individuals were included in the present study (group 1: 19–30 years, group 2: 31–50 years, and group 3: 51–70 years). Retinal microvascular function was assessed using the dynamic retinal vessel analyzer (DVA, IMEDOS GmbH, Jena, Germany). Fasting plasma was obtained from all subjects and quantification of monohydroxy and dihydroxy oxysterols assessment was performed using LC-MS/MS following reverse phase chromatography. A Griess assay was used to evaluate the Nitric Oxide (NO) concentration in all individuals. The glutathione redox ratio was also analyzed by means of whole blood glutathione recycling assay. In all participants, the levels of 7-Ketocholesterol, 25-hydroxycholesterol and 7β-hydroxycholesterol correlated significantly and positively with the time to maximum arteriolar dilation. In addition, 25-hydroxycholesterol and 7β-hydroxycholesterol negatively correlated to the percentage of maximum arteriolar dilation. A negative correlation was observed for 27-hydroxycholesterol and 7β-hydroxycholesterol with microvascular arteriolar constriction. These results suggest that, with age, abnormal oxysterol levels correlate with early changes in microvascular bed function. This relationship could signal early risk for cardiovascular diseases (CVDs) in an ageing population.

IL-17A injury to retinal ganglion cells is mediated by retinal M\xfcller cells in diabetic retinopathy

Diabetic retinopathy (DR), the most common and serious ocular complication, recently has been perceived as a neurovascular inflammatory disease. However, role of adaptive immune inflammation driven by T lymphocytes in DR is not yet well elucidated. Therefore, this study aimed to clarify the role of interleukin (IL)-17A, a proinflammatory cytokine mainly produced by T lymphocytes, in retinal pathophysiology particularly in retinal neuronal death during DR process. Ins2Akita (Akita) diabetic mice 12 weeks after the onset of diabetes were used as a DR model. IL-17A-deficient diabetic mice were obtained by hybridization of IL-17A-knockout (IL-17A-KO) mouse with Akita mouse. Primarily cultured retinal Müller cells (RMCs) and retinal ganglion cells (RGCs) were treated with IL-17A in high-glucose (HG) condition. A transwell coculture of RGCs and RMCs whose IL-17 receptor A (IL-17RA) gene had been silenced with IL-17RA-shRNA was exposed to IL-17A in HG condition and the cocultured RGCs were assessed on their survival. Diabetic mice manifested increased retinal microvascular lesions, RMC activation and dysfunction, as well as RGC apoptosis. IL-17A-KO diabetic mice showed reduced retinal microvascular impairments, RMC abnormalities, and RGC apoptosis compared with diabetic mice. RMCs expressed IL-17RA. IL-17A exacerbated HG-induced RMC activation and dysfunction in vitro and silencing IL-17RA gene in RMCs abolished the IL-17A deleterious effects. In contrast, RGCs did not express IL-17RA and IL-17A did not further alter HG-induced RGC death. Notably, IL-17A aggravated HG-induced RGC death in the presence of intact RMCs but not in the presence of RMCs in which IL-17RA gene had been knocked down. These findings establish that IL-17A is actively involved in DR pathophysiology and particularly by RMC mediation it promotes RGC death. Collectively, we propose that antagonizing IL-17RA on RMCs may prevent retinal neuronal death and thereby slow down DR progression.

Retinal microvascular function predicts chronic kidney disease in patients with cardiovascular risk factors

Background and aimsEndothelial dysfunction is a precursor to atherosclerosis and is implicated in the coexistence between cardiovascular disease (CVD) and chronic kidney disease (CKD). We examined whether retinal microvascular dysfunction is present in subjects with renal impairment and predictive of long-term CKD progression in patients with CVD. MethodsIn a single centre prospective observational study, 253 subjects with coronary artery disease and CVD risk factors underwent dynamic retinal vessel analysis. Retinal microvascular dysfunction was quantified by measuring retinal arteriolar and venular dilatation in response to flicker light stimulation. Serial renal function assessment was performed over a median period of 9.3 years using estimated GFR (eGFR). ResultsFlicker light-induced retinal arteriolar dilatation (FI-RAD) was attenuated in patients with baseline eGFR <90 mL/min/1.73 m2, compared to those with normal renal function (eGFR ≥90 mL/min/1.73 m2) (1.0 [0.4–2.1]% vs. 2.0 [0.8–3.6]%; p < 0.01). In patients with normal renal function, subjects with the lowest FI-RAD responses exhibited the greatest annual decline in eGFR. In uni- and multivariable analysis, among subjects with normal renal function, a 1% decrease in FI-RAD was associated with an accelerated decline in eGFR of 0.10 (0.01, 0.15; p = 0.03) and 0.07 mL/min/1.73 m2 per year (0.00, 0.14; p = 0.06), respectively. FI-RAD was not predictive of CKD progression in subjects with baseline eGFR <90 mL/min/1.73 m2. ConclusionsRetinal arteriolar endothelial dysfunction is present in patients with CVD who have early-stage CKD, and serves as an indicator of long-term CKD progression in those with normal renal function.

Improvement of retinal microvascular function after initiation of lipid-lowering therapy with PCSK9 inhibitors – an observational study

Abstract Background Hypercholesterolemia is associated with endothelial dysfunction. While good evidence exists for the beneficial endothelial effects of first-line lipid-lowering drugs (statins), less is known on the new class of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors. This is particularly true for the differential effects on micro- and macrovascular endothelial function and arterial stiffness. Purpose The goal of this study was to study the change in retinal microvascular dysfunction, brachial artery endothelial function and arterial stiffness in high-risk cardiovascular risk patients before and after initiation of PCSK9 inhibitor therapy with alirocumab or evolocumab. Methods In this prospective observational study, cardiovascular high-risk patients with a clinical indication for PCSK9 inhibitors were included for the measurement of retinal microvascular function (flicker light-induced dilatation of retinal arterioles and venules, FIDart and FIDven respectively; retinal arteriovenous ratio, AVR), brachial artery flow-mediated dilatation (FMD) and arterial stiffness (pulse wave velocity, PWV; augmentation index, AI). Measurements were performed at baseline, after 3 months and after 12 months of PCSK9 inhibitor therapy. The primary endpoint was the change in FIDart after 12 months of therapy compared to baseline. Results We recruited 48 patients (mean age 57±11 years, 27% female, 81% coronary artery disease) which began treatment with alirocumab or evolocumab in our lipid outpatient clinic. 6 patients were excluded from the analysis (n=3 stopped due to side effects, n=1 stopped due to new metastatic cancer, n=1 moved abroad, n=1 no retinal vessel analysis possible). LDL cholesterol was reduced from 3.8±1.2 to 1.5±0.8 and 1.8±0.9 mmol/L at 3 and 12 months respectively (all p&amp;lt;0.001). There was no significant change in systolic blood pressure during therapy. The primary endpoint FIDart was significantly increased after 12 months of PCSK9 inhibitor therapy compared to baseline (3.4±2.3 vs. 2.6±1.6%, p=0.01). Among the secondary endpoints, augmentation index improved at 12 months vs. baseline (21±12 vs. 24±9%, p=0.03). No significant change was seen for FIDven, AVR, FMD and PWV after 3 and 12 months of therapy. Conclusion In cardiovascular high-risk patients, PCSK9 inhibition is associated with an improvement of retinal microvascular function and augmentation index after one year of therapy. No effects were seen for macrovascular parameters such as FMD or PWV in our cohort. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): University Hospital Zurich, AGLA Grant (sponsored by Amgen)

Analysis of the Peripapillary and Macular Regions Using OCT Angiography in Patients with Schizophrenia and Bipolar Disorder.

Purpose: To measure RNFL and vasculature around the optic disc and in the macula in patients with schizophrenia (SZ) and bipolar disorder (BD) using optical coherence tomography angiography (OCTA). Methods: 24 eyes of patients with SZ and 16 eyes of patients with BD as well as 30 eyes of healthy subjects were examined with OCTA. The radiant peripapillary capillary (RPC) density and RNFL thickness were measured in the peripapillary area. Moreover, macular thickness and vessel density were measured in both superficial and deep layers. Results: Significantly decreased values of vessel density in the macular deep vascular complex were found in the eyes of patients with SZ, compared to BD and the control group. The macular thickness in the whole vascular complex and in the fovea was significantly lower in SZ and BD group than in the control group. The radiant peripapillary vascular density and RNFL thickness were similar across groups. Conclusions: The retinal microvascular dysfunction occurs in the macula in patients with SZ and BD, but not around optic disc. OCTA can become an essential additional diagnostic tool in detection of psychiatric disorders.

Hydrogen Sulfide Is a Novel Protector of the Retinal Glycocalyx and Endothelial Permeability Barrier.

Significantly reduced levels of the anti-inflammatory gaseous transmitter hydrogen sulfide (H2S) are observed in diabetic patients and correlate with microvascular dysfunction. H2S may protect the microvasculature by preventing loss of the endothelial glycocalyx. We tested the hypothesis that H2S could prevent or treat retinal microvascular endothelial dysfunction in diabetes. Bovine retinal endothelial cells (BRECs) were exposed to normal (NG, 5.5 mmol/L) or high glucose (HG, 25 mmol/L) ± the slow-release H2S donor NaGYY4137 in vitro. Glycocalyx coverage (stained with WGA-FITC) and calcein-labeled monocyte adherence were measured. In vivo, fundus fluorescein angiography (FFA) was performed in normal and streptozotocin-induced (STZ) diabetic rats. Animals received intraocular injection of NaGYY4137 (1 μM) or the mitochondrial-targeted H2S donor AP39 (100 nM) simultaneously with STZ (prevention) or on day 6 after STZ (treatment), and the ratio of interstitial to vascular fluorescence was used to estimate apparent permeability. NaGYY4137 prevented HG-induced loss of BREC glycocalyx, increased monocyte binding to BRECs (p ≤ 0.001), and increased overall glycocalyx coverage (p ≤ 0.001). In rats, the STZ-induced increase in apparent retinal vascular permeability (p ≤ 0.01) was significantly prevented by pre-treatment with NaGYY4137 and AP39 (p < 0.05) and stabilized by their post-STZ administration. NaGYY4137 also reduced the number of acellular capillaries (collagen IV + /IB4-) in the diabetic retina in both groups (p ≤ 0.05). We conclude that NaGYY4137 and AP39 protected the retinal glycocalyx and endothelial permeability barrier from diabetes-associated loss of integrity and reduced the progression of diabetic retinopathy (DR). Hydrogen sulfide donors that target the glycocalyx may therefore be a therapeutic candidate for DR.

Carotid stiffness is associated with retinal microvascular dysfunction-The Maastricht study.

ObjectiveThis study investigated whether arterial stiffening is a determinant of subtle retinal microvascular changes that precede diabetic retinopathy.Research design and methodsThis study used cross‐sectional data from the Maastricht Study, a type 2 diabetes‐enriched population‐based cohort study. We used multivariable linear regression analysis to investigate, in individuals without and with type 2 diabetes, the associations of carotid distensibility coefficient and carotid‐femoral pulse wave velocity with retinal microvascular diameters and flicker light‐induced dilation and adjusted for cardiovascular and lifestyle risk factors.ResultsThe retinal microvascular diameter study population consisted of N = 2434 participants (51.4% men, mean ± SD age 59.8 ± 8.1 years, and 28.1% type 2 diabetes). No measures of arterial stiffness were significantly associated with microvascular diameters. Greater carotid distensibility coefficient (i.e., lower carotid stiffness) was significantly associated with greater retinal arteriolar flicker light‐induced dilation (per standard deviation, standardized beta [95% CI] 0.06 [0.00; 0.12]) and non‐significantly, but directionally similarly, associated with greater retinal venular flicker light‐induced dilation (0.04 [−0.02; 0.10]). Carotid‐femoral pulse wave velocity (i.e., aortic stiffness) was not associated with retinal microvascular flicker light‐induced dilation. The associations between carotid distensibility coefficient and retinal arteriolar and venular flicker light‐induced dilation were two‐ to threefold stronger in individuals with type 2 diabetes than in those without.ConclusionIn this population‐based study greater carotid, but not aortic, stiffness was associated with worse retinal flicker light‐induced dilation and this association was stronger in individuals with type 2 diabetes. Hence, carotid stiffness may be a determinant of retinal microvascular dysfunction.

Exosomal circEhmt1 Released from Hypoxia-Pretreated Pericytes Regulates High Glucose-Induced Microvascular Dysfunction via the NFIA/NLRP3 Pathway.

Diabetic retinopathy (DR) is a frequently occurring microvascular complication induced by long-term hyperglycemia. Pericyte-endothelial cell crosstalk is critical for maintaining vascular homeostasis and remodeling; however, the molecular mechanism underlying that crosstalk remains unknown. In this study, we explored the crosstalk that occurs between endothelial cells and pericytes in response to diabetic retinopathy. Pericytes were stimulated with cobalt chloride (CoCl2) to activate the HIF pathway. Hypoxia-stimulated pericytes were cocultured with high glucose- (HG-) induced endotheliocytes. Cell viability was determined using the CCK-8 assay. Western blot studies were performed to detect the expression of proteins associated with apoptosis, hypoxia, and inflammation. ELISA assays were conducted to analyze the release of IL-1β and IL-18. We performed a circRNA microarray analysis of exosomal RNAs expressed under normoxic or hypoxic conditions. A FISH assay was performed to identify the location of circEhmt1 in pericytes. Chromatin immunoprecipitation (CHIP) was used to identify the specific DNA-binding site on the NFIA-NLRP3 complex. We found that pericyte survival was negatively correlated with the angiogenesis activity of endotheliocytes. We also found that hypoxia upregulated circEhmt1 expression in pericytes, and circEhmt1 could be transferred from pericytes to endotheliocytes via exosomes. Moreover, circEhmt1 overexpression protected endotheliocytes against HG-induced injury in vitro. Mechanistically, circEhmt1 was highly expressed in the nucleus of pericytes and could upregulate the levels of NFIA (a transcription factor) to suppress NLRP3-mediated inflammasome formation. Our study revealed a critical role for circEhmt1-mediated NFIA/NLRP3 signaling in retinal microvascular dysfunction and suggests that signaling pathway as a target for treating DR.