High-fat diet causes endothelial dysfunction in the mouse ophthalmic artery.

Obesity is a significant health concern that leads to impaired vascular function and subsequent abnormalities in various organs. The impact of obesity on ocular blood vessels, however, remains largely unclear. In this study, we examined the hypothesis that obesity induced by high-fat diet produces vascular endothelial dysfunction in the ophthalmic artery. Mice were subjected to a high-fat diet for 20 weeks, while age-matched controls were maintained on a standard diet. Reactivity of isolated ophthalmic artery segments was assessed in vitro. Reactive oxygen species (ROS) were quantified in cryosections by dihydroethidium (DHE) staining. Redox gene expression was determined in ophthalmic artery explants by real-time PCR. Furthermore, the expression of nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2), the receptor for advanced glycation end products (RAGE), and of the lectin-like oxidized low-density-lipoprotein receptor-1 (LOX-1) was determined in cryosections using immunofluorescence microscopy. Ophthalmic artery segments from mice on a high-fat diet exhibited impaired vasodilation responses to the endothelium-dependent vasodilator acetylcholine, while endothelium-independent responses to nitroprusside remained preserved. DHE staining intensity in the vascular wall was notably stronger in mice on a high-fat diet. Messenger RNA expression for NOX2 was elevated in the ophthalmic artery of mice subjected to high fat diet. Likewise, immunostainings revealed increased expression of NOX2 and of RAGE, but not of LOX-1. These findings suggest that a high-fat diet triggers endothelial dysfunction by inducing oxidative stress in the ophthalmic artery via involvement of RAGE and NOX2.

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

ß-adrenoreceptors (ARs) are members of the superfamily of G-protein-coupled receptors (GPCRs), and are activated by catecholamines, such as epinephrine and norepinephrine. Three subtypes of ß-ARs (ß1, ß2, and ß3) have been identified with different distributions among ocular tissues. Importantly, ß-ARs are an established target in the treatment of glaucoma. Moreover, ß-adrenergic signaling has been associated with the development and progression of various tumor types. Hence, ß-ARs are a potential therapeutic target for ocular neoplasms, such as ocular hemangioma and uveal melanoma. This review aims to discuss the expression and function of individual ß-AR subtypes in ocular structures, as well as their role in the treatment of ocular diseases, including ocular tumors.

Lysed Erythrocyte Membranes Promote Vascular Calcification.

BACKGROUND: Intraplaque hemorrhage promotes atherosclerosis progression, and erythrocytes may contribute to this process. In this study we examined the effects of red blood cells on smooth muscle cell mineralization and vascular calcification and the possible mechanisms involved. METHODS: Erythrocytes were isolated from human and murine whole blood. Intact and lysed erythrocytes and their membrane fraction or specific erythrocyte components were examined in vitro using diverse calcification assays, ex vivo by using the murine aortic ring calcification model, and in vivo after murine erythrocyte membrane injection into neointimal lesions of hypercholesterolemic apolipoprotein E-deficient mice. Vascular tissues (aortic valves, atherosclerotic carotid artery specimens, abdominal aortic aneurysms) were obtained from patients undergoing surgery. RESULTS: The membrane fraction of lysed, but not intact human erythrocytes promoted mineralization of human arterial smooth muscle cells in culture, as shown by Alizarin red and van Kossa stain and increased alkaline phosphatase activity, and by increased expression of osteoblast-specific transcription factors (eg, runt-related transcription factor 2, osterix) and differentiation markers (eg, osteopontin, osteocalcin, and osterix). Erythrocyte membranes dose-dependently enhanced calcification in murine aortic rings, and extravasated CD235a-positive erythrocytes or Perl iron-positive signals colocalized with calcified areas or osteoblast-like cells in human vascular lesions. Mechanistically, the osteoinductive activity of lysed erythrocytes was localized to their membrane fraction, did not involve membrane lipids, heme, or iron, and was enhanced after removal of the nitric oxide (NO) scavenger hemoglobin. Lysed erythrocyte membranes enhanced calcification to a similar extent as the NO donor diethylenetriamine-NO, and their osteoinductive effects could be further augmented by arginase-1 inhibition (indirectly increasing NO bioavailability). However, the osteoinductive effects of erythrocyte membranes were reduced in human arterial smooth muscle cells treated with the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide or following inhibition of NO synthase or the NO receptor soluble guanylate cyclase. Erythrocytes isolated from endothelial NO synthase-deficient mice exhibited a reduced potency to promote calcification in the aortic ring assay and after injection into murine vascular lesions. CONCLUSIONS: Our findings in cells, genetically modified mice, and human vascular specimens suggest that intraplaque hemorrhage with erythrocyte extravasation and lysis promotes osteoblastic differentiation of smooth muscle cells and vascular lesion calcification, and also support a role for erythrocyte-derived NO.

Potential of Sulodexide in the Treatment of Diabetic Retinopathy and Retinal Vein Occlusion.

Retinal vascular diseases, such as diabetic retinopathy or retinal vein occlusion, are common causes of severe vision loss. Central to the pathophysiology of these conditions are endothelial dysfunction, inflammation, capillary leakage, ischemia, and pathological neoangiogenesis. Capillary damage leads to leakage and the development of macular edema, which is associated with vision loss and requires complex treatment. Sulodexide, a glycosaminoglycan composed of heparan sulfate and dermatan sulfate with high oral bioavailability, exhibits several favorable pharmacologic properties, including antithrombotic, anti-inflammatory, and endothelium-protective effects. Additionally, treatment with sulodexide has been associated with the reduction of oxidative stress and decreased expression of angiogenic growth factors, such as vascular endothelial growth factor. This review aims to provide an overview of the pharmacological properties, mechanisms of action, and therapeutic effects of sulodexide. Furthermore, its potential for clinical application in venous and diabetic diseases, such as venous thromboembolism, chronic venous insufficiency, peripheral artery disease, or diabetic nephropathy, is summarized. We also present experimental and clinical studies evaluating the potential of sulodexide in ocular conditions and discuss its therapeutic implications for the treatment of retinal vascular diseases.

Diabetic Retinopathy: New Treatment Approaches Targeting Redox and Immune Mechanisms.

Diabetic retinopathy (DR) represents a severe complication of diabetes mellitus, characterized by irreversible visual impairment resulting from microvascular abnormalities. Since the global prevalence of diabetes continues to escalate, DR has emerged as a prominent area of research interest. The development and progression of DR encompass a complex interplay of pathological and physiological mechanisms, such as high glucose-induced oxidative stress, immune responses, vascular endothelial dysfunction, as well as damage to retinal neurons. Recent years have unveiled the involvement of genomic and epigenetic factors in the formation of DR mechanisms. At present, extensive research explores the potential of biomarkers such as cytokines, molecular and cell therapies, antioxidant interventions, and gene therapy for DR treatment. Notably, certain drugs, such as anti-VEGF agents, antioxidants, inhibitors of inflammatory responses, and protein kinase C (PKC)-ß inhibitors, have demonstrated promising outcomes in clinical trials. Within this context, this review article aims to introduce the recent molecular research on DR and highlight the current progress in the field, with a particular focus on the emerging and experimental treatment strategies targeting the immune and redox signaling pathways.

Short-Term Clinical Outcomes of Patients with Diabetic Macular Edema Following a Therapy Switch to Faricimab.

Background: With this study, we investigate the short-term clinical outcomes of patients affected by diabetic macular edema (DME) after switching to intravitreal Faricimab (IVF) in a real-world setting. Methods: We conducted a retrospective chart review on all patients treated for DME with IVF who showed insufficient responses to prior anti-VEGF therapy. Data collected included baseline patient demographics, medical history, best-corrected visual acuity (BCVA), central retinal thickness (CRT) and central retinal volume (CRV). We analyzed functional and structural measures before and after IVF, compared baseline demographics and treatment factors between Faricimab-responders and reduced-responders and assessed influencing factors of the follow-up BCVA and CRT. Results: This study included 25 eyes from 16 patients. After switching to IVF, the mean BCVA showed no significant improvement, changing from 59.4 ± 13.4 Early Treatment of Diabetic Retinopathy Study (ETDRS) letters at baseline to 61.4 ± 12.8 ETDRS letters at follow-up (p = 0.26). CRT significantly reduced from 414.4 ± 126.3 µm to 353.3 ± 131.1 µm (p < 0.011), and the 3 mm CRV significantly decreased from 2.8 ± 0.5 mm3 to 2.6 ± 0.6 mm3 (p < 0.012). Seven patients met the responder criteria, exhibiting an improvement of at least 5 ETDRS letters and a simultaneous CRT reduction of at least 30 µm. Further analysis showed that higher BCVA at baseline (p < 0.001) was associated with better BCVA following IVF, while higher baseline CRT (p < 0.003), a higher number of prior anti-VEGF agents (p < 0.034) and prior corticosteroid injections (p < 0.019) were associated with greater CRT at follow-up. Conclusions: Following the initial IVF injection series, we observed a clear improvement of anatomical measures. No functional improvement was observed, although visual acuity remained stable. Higher baseline BCVA was associated with better post-IVF BCVA, while higher baseline CRT, a greater number of prior anti-VEGF agents and prior corticosteroid injections were linked to higher CRT post-IVF.

Cardio-ocular syndrome: Retinal microvascular changes in acutely decompensated heart failure.

AIMS: To investigate the changes in retinal microvasculature by contemporary imaging techniques during episodes of acute decompensated heart failure (ADHF) and following recompensation compared to age-matched controls without known cardiac or retinal disease. METHODS AND RESULTS: Adult patients hospitalized with a primary diagnosis of ADHF, regardless of left ventricular ejection fraction (LVEF) and treated with a minimum dose of 40 mg of intravenous furosemide or equivalent were included. Transthoracic echocardiography was conducted in all patients. Eye examinations were performed out within the initial 24 h after admission and after recompensation before discharge. All eyes underwent a general examination, including a best corrected visual acuity test, dilated fundoscopy, spectral-domain optical coherence tomography (OCT) as well as OCT angiography (OCT-A). In addition, 40 participants without documented cardiac or retinal diseases served as controls. Forty patients with ADHF (mean age 78.9 ± 8.8 years; 32% female) with a mean LVEF of 43 ± 12.8% were included. All patients were treated with intravenous diuretics for a median of 4.3 ± 2.8 days. There was a significant reduction in N-terminal pro-B-type natriuretic peptide from baseline up to discharge (10 396 [interquartile range 6410] vs. 6380 [interquartile range 3933] pg/ml, p ≤ 0.001) and inferior vena cava diameters (2.13 ± 0.4 vs. 1.63 ± 0.3 cm, p = 0.003). Compared to the control group, patients with ADHF showed on admission impaired visual acuity (0.15 ± 0.1 vs. 0.35 ± 0.1 logMAR, p < 0.001), reduced macular vessel density (18.0 ± 1.9 vs. 14.3 ± 3.6 mm/mm2, p < 0.001) and perfusion density (42.6 ± 3.2 vs. 35.2 ± 9.7%, p < 0.001). After recompensation, the mean overall vessel density and mean overall perfusion density were markedly increased at discharge (14.3 ± 3.6 vs. 19.7 ± 2.6 mm/mm2, p = 0.001, and 35.2 ± 9.7 vs. 39.2 ± 6.5%, p = 0.005, respectively). The mean diameter of the superior temporal retinal vein at admission was significantly larger compared to the control group (136 ± 19 vs. 124 ± 22 µm, p = 0.008) and decreased significantly to 122 ± 15 µm at discharge (p < 0.001). CONCLUSION: This analysis revealed a remarkable reversible change in retinal microvasculature after ADHF. This could provide a valuable evidence for use of OCT-A in the assessment of overall microperfusion and haemodynamic status in patients with acute heart failure.

Oxidative Stress: A Suitable Therapeutic Target for Optic Nerve Diseases?

Optic nerve disorders encompass a wide spectrum of conditions characterized by the loss of retinal ganglion cells (RGCs) and subsequent degeneration of the optic nerve. The etiology of these disorders can vary significantly, but emerging research highlights the crucial role of oxidative stress, an imbalance in the redox status characterized by an excess of reactive oxygen species (ROS), in driving cell death through apoptosis, autophagy, and inflammation. This review provides an overview of ROS-related processes underlying four extensively studied optic nerve diseases: glaucoma, Leber's hereditary optic neuropathy (LHON), anterior ischemic optic neuropathy (AION), and optic neuritis (ON). Furthermore, we present preclinical findings on antioxidants, with the objective of evaluating the potential therapeutic benefits of targeting oxidative stress in the treatment of optic neuropathies.

Measurement of Retrobulbar Blood Flow and Vascular Reactivity-Relevance for Ocular and Cardiovascular Diseases.

Abnormal retrobulbar hemodynamics have been linked to the development of various ocular diseases, including glaucoma, age-related macular degeneration, and diabetic retinopathy. Additionally, altered retrobulbar blood flow has been observed in patients with severe cardiovascular diseases, including carotid artery occlusion, stroke, heart failure, and acute coronary syndrome. Due to the complex and intricate anatomy of retrobulbar blood vessels and their location behind the eyeball, measurement of retrobulbar blood flow and vascular reactivity, as well as the interpretation of the findings, are challenging. Various methods, such as color Doppler imaging, computed tomography angiography or magnetic resonance imaging, have been employed to assess retrobulbar blood flow velocities in vivo. Color Doppler imaging represents a fast and non-invasive method to measure retrobulbar blood flow velocities in vivo. While no information about vessel diameter can be gained performing this method, computed tomography angiography and magnetic resonance imaging provide information about vessel diameter and detailed information on the anatomical course. Additionally, ex vivo studies, such as myography, utilizing genetically modified animal models may provide high optical resolution for functional vascular investigations in these small vessels. To our best knowledge, this is the first review, presenting a detailed overview of methods aiming to evaluate retrobulbar blood flow and vascular reactivity in both humans and laboratory animals. Furthermore, we will summarize the disturbances observed in retrobulbar blood flow in retinal, optic nerve, and cardiovascular diseases.

Oxidative stress in the eye and its role in the pathophysiology of ocular diseases.

Oxidative stress occurs through an imbalance between the generation of reactive oxygen species (ROS) and the antioxidant defense mechanisms of cells. The eye is particularly exposed to oxidative stress because of its permanent exposure to light and due to several structures having high metabolic activities. The anterior part of the eye is highly exposed to ultraviolet (UV) radiation and possesses a complex antioxidant defense system to protect the retina from UV radiation. The posterior part of the eye exhibits high metabolic rates and oxygen consumption leading subsequently to a high production rate of ROS. Furthermore, inflammation, aging, genetic factors, and environmental pollution, are all elements promoting ROS generation and impairing antioxidant defense mechanisms and thereby representing risk factors leading to oxidative stress. An abnormal redox status was shown to be involved in the pathophysiology of various ocular diseases in the anterior and posterior segment of the eye. In this review, we aim to summarize the mechanisms of oxidative stress in ocular diseases to provide an updated understanding on the pathogenesis of common diseases affecting the ocular surface, the lens, the retina, and the optic nerve. Moreover, we discuss potential therapeutic approaches aimed at reducing oxidative stress in this context.

Sulodexide Prevents Hyperglycemia-Induced Endothelial Dysfunction and Oxidative Stress in Porcine Retinal Arterioles.

Diabetes mellitus may cause severe damage to retinal blood vessels. The central aim of this study was to test the hypothesis that sulodexide, a mixture of glycosaminoglycans, has a protective effect against hyperglycemia-induced endothelial dysfunction in the retina. Functional studies were performed in isolated porcine retinal arterioles. Vessels were cannulated and incubated with highly concentrated glucose solution (HG, 25 mM D-glucose) +/- sulodexide (50/5/0.5 µg/mL) or normally concentrated glucose solution (NG, 5.5 mM D-glucose) +/- sulodexide for two hours. Endothelium-dependent and endothelium-independent vasodilatation were measured by videomicroscopy. Reactive oxygen species (ROS) were quantified by dihydroethidium (DHE) fluorescence. Using high-pressure liquid chromatography (HPLC), the intrinsic antioxidant properties of sulodexide were investigated. Quantitative PCR was used to determine mRNA expression of regulatory, inflammatory, and redox genes in retinal arterioles, some of which were subsequently quantified at the protein level by immunofluorescence microscopy. Incubation of retinal arterioles with HG caused significant impairment of endothelium-dependent vasodilation, whereas endothelium-independent responses were not affected. In the HG group, ROS formation was markedly increased in the vascular wall. Strikingly, sulodexide had a protective effect against hyperglycemia-induced ROS formation in the vascular wall and had a concentration-dependent protective effect against endothelial dysfunction. Although sulodexide itself had only negligible antioxidant properties, it prevented hyperglycemia-induced overexpression of the pro-oxidant redox enzymes, NOX4 and NOX5. The data of the present study provide evidence that sulodexide has a protective effect against hyperglycemia-induced oxidative stress and endothelial dysfunction in porcine retinal arterioles, possibly by modulation of redox enzyme expression.

Methods to measure blood flow and vascular reactivity in the retina.

Disturbances of retinal perfusion are involved in the onset and maintenance of several ocular diseases, including diabetic retinopathy, glaucoma, and retinal vascular occlusion. Hence, knowledge on ocular vascular anatomy and function is highly relevant for basic research studies and for clinical judgment and treatment. The retinal vasculature is composed of the superficial, intermediate, and deep vascular layer. Detection of changes in blood flow and vascular diameter especially in smaller vessels is essential to understand and to analyze vascular diseases. Several methods to evaluate blood flow regulation in the retina have been described so far, but no gold standard has been established. For highly reliable assessment of retinal blood flow, exact determination of vessel diameter is necessary. Several measurement methods have already been reported in humans. But for further analysis of retinal vascular diseases, studies in laboratory animals, including genetically modified mice, are important. As for mice, the small vessel size is challenging requiring devices with high optic resolution. In this review, we recapitulate different methods for retinal blood flow and vessel diameter measurement. Moreover, studies in humans and in experimental animals are described.

Colocalization of Erythrocytes and Vascular Calcification in Human Atherosclerosis: A Systematic Histomorphometric Analysis.

Background Intimal calcification typically develops in advanced atherosclerosis, and microcalcification may promote plaque progression and instability. Conversely, intraplaque hemorrhage and erythrocyte extravasation may stimulate osteoblastic differentiation and intralesional calcium phosphate deposition. The presence of erythrocytes and their main cellular components (membranes, hemoglobin, and iron) and colocalization with calcification has never been systematically studied. Methods and Results We examined three types of diseased vascular tissue specimens, namely, degenerative aortic valve stenosis ( n = 46), atherosclerotic carotid artery plaques ( n = 9), and abdominal aortic aneurysms ( n = 14). Biomaterial was obtained from symptomatic patients undergoing elective aortic valve replacement, carotid artery endatherectomy, or aortic aneurysm repair, respectively. Serial sections were stained using Masson-Goldner trichrome, Alizarin red S, and Perl's iron stain to visualize erythrocytes, extracelluar matrix and osteoid, calcium phosphate deposition, or the presence of iron and hemosiderin, respectively. Immunohistochemistry was employed to detect erythrocyte membranes (CD235a), hemoglobin or the hemoglobin scavenger receptor (CD163), endothelial cells (CD31), myofibroblasts (SMA), mesenchymal cells (osteopontin), or osteoblasts (periostin). Our analyses revealed a varying degree of intraplaque hemorrhage and that the majority of extravasated erythrocytes were lysed. Osteoid and calcifications also were frequently present, and erythrocyte membranes were significantly more prevalent in areas with calcification. Areas with extravasated erythrocytes frequently contained CD163-positive cells, although calcification also occurred in areas without CD163 immunosignals. Conclusion Our findings underline the presence of extravasated erythrocytes and their membranes in different types of vascular lesions, and their association with areas of calcification suggests an active role of erythrocytes in vascular disease processes.