Retina Of Diabetic Rats Research Articles

Paquinimod attenuates retinal injuries by suppressing the S100A9/TLR4 signaling in an experimental model of diabetic retinopathy

Diabetic retinopathy (DR), the most common ocular complication of diabetes mellitus (DM), has exhibited an increase in incidence over the past decade. S100 calcium-binding protein A9 (S100A9) plays a significant role in inflammation and cancer. Toll-like receptor 4 (TLR4), a transmembrane receptor, initiates signaling cascades upon ligand binding. S100A9 activates TLR4, and their involvement in various diseases is well-established. We found elevated S100A9/TLR4 pathway proteins in the vitreous of DR patients. Bioinformatics analysis revealed differential gene expression related to this pathway. These proteins were also detected in diabetic rat retinas and induced structural damage. Paquinimod, an S100A9 inhibitor, decreased pathway protein expression and reduced retinal damage. Our study validates the S100A9/TLR4 pathway in diabetic retinas and suggests its potential as a therapeutic target for DR. Targeting S100A9 could offer a novel approach to prevention and treatment.

Melatonin Attenuates Diabetic Retinopathy by Regulating EndMT of Retinal Vascular Endothelial Cells via Inhibiting the HDAC7/FOXO1/ZEB1 Axis

ABSTRACTDiabetic retinopathy (DR) is characterized as a microvascular disease. Nonproliferative diabetic retinopathy (NPDR) presents with alterations in retinal blood flow and vascular permeability, thickening of the basement membrane, loss of pericytes, and formation of acellular capillaries. Endothelial–mesenchymal transition (EndMT) of retinal microvessels may play a critical role in advancing NPDR. Melatonin, a hormone primarily secreted by the pineal gland, is a promising therapeutic for DR. This study explored the EndMT in retinal microvessels of NPDR and its related mechanisms. The effect of melatonin on the retina of diabetic rats was evaluated by electroretinogram (ERG) and histopathologic slide staining. Furthermore, the effect of melatonin on human retinal microvascular endothelial cells (HRMECs) was detected by EdU incorporation assay, scratch assay, transwell assay, and tube formation test. Techniques such as RNA‐sequencing, overexpression or knockdown of target genes, extraction of cytoplasmic and nuclear protein, co‐immunoprecipitation (co‐IP), and multiplex immunofluorescence facilitated the exploration of the mechanisms involved. Our findings reveal, for the first time, that melatonin attenuates diabetic retinopathy by regulating EndMT of retinal vascular endothelial cells via inhibiting the HDAC7/FOXO1/ZEB1 axis. Collectively, these results suggest that melatonin holds potential as a therapeutic strategy to reduce retinal vascular damage and protect vision in NPDR.

Tocotrienol-rich fraction (TRF) protects against retinal cell apoptosis and preserves visual behavior in rats with streptozotocin-induced diabetic retinopathy

BackgroundTocotrienol is a vitamin E analogue that is known to exert anti-inflammatory and antioxidant effects. Hence, in the current study, the effects of TRF on the expression of pro- and anti-apoptotic proteins in the streptozotocin-induced diabetic rat retinas were investigated. The effect of TRF on the visual behaviour of rats was also studied.MethodsDiabetes was induced in rats by intraperitoneal injection of streptozotocin and was confirmed by a blood sugar level of at least 20 mmol/L, 48 h, post-injection. Diabetic rats were divided into a group treated with vehicle (DV) and the other treated with TRF (100 mg/kg; DT). A group of non-diabetic rats treated with vehicle (N) served as the control group. All treatments were administered orally for 12 weeks. Rats were then subjected to an assessment of general behaviour in an open field arena and a two-chamber mirror test to assess their visual behaviour. At the end of the experimental period, rats were sacrificed, and their retinas were isolated to measure the expression of pro- (Casp3, Bax) and anti-apoptotic (Bcl2) markers using RT-qPCR and ELISA. TUNEL staining was used to detect the apoptotic retinal cells.ResultsTreatment with TRF lowered the retinal expression of Casp3 protein by 2.26-folds (p < 0.001) and Bax protein by 2.18-fold (p < 0.001) compared to vehicle-treated rats. The retinal anti-apoptotic protein Bcl2 expression was 1.87-fold higher in DT compared to DV rats (p < 0.001). Accordingly, the Bax/Bcl2 ratio in the TRF-treated group was significantly greater in DT compared to DV rats. Retinal Casp3, Bax, and Bcl2 gene expression, as determined by RT-qPCR, also showed changes corresponding to protein expression. In the open field test, DV rats showed greater anxiety-related behaviour than group N, while the behaviour of DT rats was similar to the N group of rats. DT rats and group N rats preferred the inverse mirror chamber over the mirror-containing chamber in the two-mirror chamber test (p < 0.01).ConclusionOral TRF therapy for 12 weeks lowers retinal cell apoptosis by decreasing pro- and increasing anti-apoptotic markers. The preservation of visual behaviour in a two-chamber mirror test supported these retinal molecular alterations in diabetic rats.

Knockdown of fibrillin-1 suppresses retina-blood barrier dysfunction by inhibiting vascular endothelial apoptosis under diabetic conditions.

To investigate the effects of fibrillin-1 (FBN1) deletion on the integrity of retina-blood barrier function and the apoptosis of vascular endothelial cells under diabetic conditions. Streptozotocin (STZ)-induced diabetic mice were used to simulate the diabetic conditions of diabetic retinopathy (DR) patients, and FBN1 expression was detected in retinas from STZ-diabetic mice and controls. In the Gene Expression Omnibus (GEO) database, the GSE60436 dataset was selected to analyze FBN1 expressions in fibrovascular membranes from DR patients. Using lentivirus to knock down FBN1 levels, vascular leakage and endothelial barrier integrity were detected by Evans blue vascular permeability assay, fluorescein fundus angiography (FFA) and immunofluorescence labeled with tight junction marker in vivo. High glucose-induced monkey retinal vascular endothelial cells (RF/6A) were used to investigate effects of FBN1 on the cells in vitro. The vascular endothelial barrier integrity and apoptosis were detected by trans-endothelial electrical resistance (TEER) assay and flow cytometry, respectively. FBN1 mRNA expression was increased in retinas of STZ-induced diabetic mice and fibrovascular membranes of DR patients (GSE60436 datasets) using RNA-seq approach. Besides, knocking down of FBN1 by lentivirus intravitreal injection significantly inhibited the vascular leakage compared to STZ-DR group by Evans blue vascular permeability assay and FFA detection. Expressions of tight junction markers in STZ-DR mouse retinas were lower than those in the control group, and knocking down of FBN1 increased the tight junction levels. In vitro, 30 mmol/L glucose could significantly inhibit viability of RF/6A cells, and FBN1 mRNA expression was increased under 30 mmol/L glucose stimulation. Down-regulation of FBN1 reduced high glucose (HG)-stimulated retinal microvascular endothelial cell permeability, increased TEER, and inhibited RF/6A cell apoptosis in vitro. The expression level of FBN1 increases in retinas and vascular endothelial cells under diabetic conditions. Down-regulation of FBN1 protects the retina of early diabetic rats from retina-blood barrier damage, reduce vascular leakage, cell apoptosis, and maintain vascular endothelial cell barrier function.

Exploring Neuroprotective Effects of Topical Brimonidine in Experimental Diabetic Retinopathy.

Diabetic retinopathy is a leading cause of blindness worldwide, characterized by neurovascular dysfunction. This study aimed to investigate the impact of brimonidine, a selective adrenoceptor agonist, on diabetic retinal neurodegeneration, recognizing the critical role of neurodegeneration in diabetic retinopathy. Streptozotocin-induced diabetes was established in adult male Sprague-Dawley rats to mimic diabetic retinopathy. Rats, except non-diabetic control rats, received topical applications of 0.15% brimonidine tartrate (treatment group) or balanced salt solution (diabetic control group) twice daily following diabetes induction. Each group comprised six randomly assigned animals. Retinal samples were analyzed using immunofluorescence staining, apoptosis assay, and western blot. Topical brimonidine treatment reduced apoptosis of retinal ganglion cells at 8 weeks after induction of diabetes (p<0.05). Glial activation induced by diabetes was reduced by brimonidine treatment. Immunoblot and immunofluorescence assay revealed that the decrease in phospho- protein kinase B (AKT) level resulting from diabetes was also attenuated by brimonidine (p<0.05). Furthermore, brimonidine alleviated the decrease in anti-apoptotic proteins [BCL2 apoptosis regulator (BCL2) and BCL-xl] induced by diabetes (p<0.05). Elevation of phospho-p38 mitogen-activated protein kinase (p38MAPK) and p53 in diabetic rats were reduced by brimonidine (p<0.05). Additionally, brimonidine treatment attenuated the upregulation of the pro-apoptotic molecule BCL-2 associated X in retinas of diabetic rats (p<0.05). These findings suggest that topical brimonidine treatment may protect retinal ganglion cells in experimental diabetes by modulating the AKT pathway and reducing pro-apoptotic p38MAPK levels. This presents a potential neuroprotective approach in diabetes, offering the advantage of localized treatment without the added burden of oral medication.

GMFB/AKT/TGF-β3 in Müller cells mediated early retinal degeneration in a streptozotocin-induced rat diabetes model.

Retinal degeneration, characterized by Müller cell gliosis and photoreceptor apoptosis, is considered an early event in diabetic retinopathy (DR). Our previous study proposed that GMFB may mediate diabetic retinal degeneration. This study identified GMFB as a sensitive and functional gliosis marker for DR. Compared to the wild type (WT) group, Gmfb knockout (KO) significantly improved visual function, attenuated gliosis, reduced the apoptosis of neurons, and decreased the mRNA levels of tumor necrosis factor α (Tnf-α) and interleukin-1β (Il-1β) in diabetic retinas. Tgf-β3 was enriched by hub genes using RNA sequencing in primary WT and KO Müller cells. Gmfb KO significantly upregulated the transforming growth factor (TGF)-β3 protein level via the AKT pathway. The protective effect of TGF-β3 in the vitreous resulted in significantly improved visual function and decreased the number of apoptotic cells in the diabetic retina. The protection of Gmfb KO in primary Müller cells against high glucose (HG)-induced photoreceptor apoptosis was partially counteracted by TGF-β3 antibody and administration of TGFBR1/2 inhibitors. Nuclear receptor subfamily 3 group C member 1 (NR3C1) binds to the promoter region of Gmfb and regulates Gmfb mRNA at the transcriptional level. NR3C1 was increased in the retinas of early diabetic rats but decreased in the retinas of late diabetic rats. N'-[(1E)-(3-Methoxyphenyl)Methylene]-3-Methyl-1H-Pyrazole-5-Carbohydrazide (DS-5) was identified as an inhibitor of GMFB, having a protective role in DR. We demonstrated that GMFB/AKT/TGF-β3 mediated early diabetic retinal degeneration in diabetic rats. This study provides a novel therapeutic strategy for treating retinal degeneration in patients with DR.

Moringa oleifera extract ameliorates diabetic retinopathy via NF-κB and VCAM-1 pathway in streptozotocin induced diabetic rats

Diabetes is a major cause of mortality and morbidity worldwide, leading to various complications, including diabetic retinopathy (DR), which can result in vision impairment and blindness. DR involves the disruption of the blood retinal barrier (BRB) and the development of neovascularization due to high blood sugar levels. Inflammatory cytokines and cell adhesion molecules play a role in this process, with NF-κB and its down regulators, such as ICAM-1 and VCAM-1, being key players. Moringa oleifera (MO), a plant with medicinal properties, is being investigated for its prospective effect in preventing and treating DR. This study explores the effects of Moringa oleifera extract on streptozotocin (STZ) induced diabetic rats with DR. Molecular docking studies indicate that components of Moringa oleifera extract, namely Quercetin and Myrecetin, strongly bind to key targets involved in DR.To induce DR, rats were given STZ, and after 8 weeks, various factors were evaluated. The results show that MO extract significantly reduces blood glucose levels compared to the diabetes group. Additionally, the extract decreases the expression of VEGF, an angiogenic mediator, and reduces the levels of TNF-α and Total Antioxidant Capacity (TAC), markers of inflammation, in the retinas of diabetic rats. Histopathological analyses reveal improvements in the retinal blood vessels of MO-treated animals compared to the diabetes group. The extract also reduces the overexpression of NF-κB and VCAM-1 in the retina. These findings suggest that MO may be useful in managing diabetic retinopathy by inhibiting angiogenic mediators and regulating NF-κB and VCAM-1.

Beneficial effects of protocatechuic acid on diabetic retinopathy in streptozocin-induced diabetic rats.

To determine the effects of protocatechuic acid (PCA) on streptozocin-induced diabetic retinopathy (DR) in rats. Wistar rats were given a 50 mg/kg intraperitoneal injection of streptozocin to induce diabetes. Animals were assigned randomly one of four groups (8 rats per group): control, diabetic, diabetic plus PCA (25 mg/kg·d), and diabetic plus PCA (50 mg/kg·d). After inducing diabetes, treatments were started one week later and continued for eight weeks. After the experiment, the rats were sacrificed, and their retinas were taken for biochemical and molecular analysis. PCA administration diminished the blood glucose and glycated haemoglobin levels relative to the diabetic group. In diabetic rats, PCA lowered elevated levels of advanced glycosylated end products (AGEs) and receptor for AGEs (RAGE). In the retina of diabetic rats, PCA effectively decreased inflammatory cytokine, nuclear factor-κB, tumour necrosis factor-α, interleukin-1β, and vascular endothelial growth factor, and increased antioxidant markers glutathione, superoxide dismutase, and catalase. The protective benefits of PCA against DR may be attributable to its suppression of the AGEs and RAGE and its antioxidant and anti-inflammatory properties.

Changes and related factors of blood CCN1 levels in diabetic patients.

To study the differences in blood cellular communication network factor 1 (CCN1) levels between patients with diabetes mellitus (DM) and healthy individuals and to explore the relationship between CCN1 and diabetic retinopathy (DR). Plasma CCN1 levels were detected using ELISA in 50 healthy controls, 74 patients with diabetes without diabetic retinopathy (DM group), and 69 patients with diabetic retinopathy (DR group). Correlations between CCN1 levels and age, body mass index, mean arterial pressure, hemoglobin A1c, and other factors were analyzed. The relationship between CCN1 expression and DR was explored using logistic regression after adjusting for confounding factors. Blood mRNA sequencing analysis was performed for all subjects, and the molecular changes that may be related to CCN1 were explored. The retinal vasculature of streptozotocin-induced diabetic rats was examined using fundus fluorescein angiography; in addition, retinal protein expression was examined using western blotting. Plasma CCN1 levels in patients with DR were significantly higher than in the control and DM groups; however, no significant differences were observed between healthy controls and patients with DM. CCN1 levels negatively correlated with body mass index and positively correlated with the duration of diabetes and urea levels. It was observed that high (OR 4.72, 95% CI: 1.10-20.25) and very high (OR 8.54, 95% CI: 2.00-36.51) levels of CCN1 were risk factors for DR. Blood mRNA sequencing analysis revealed that CCN1-related pathways were significantly altered in the DR group. The expression of hypoxia-, oxidative stress-, and dephosphorylation-related proteins were elevated, while that of tight junction proteins were reduced in the retinas of diabetic rats. Blood CCN1 levels are significantly elevated in patients with DR. High and very high levels of plasma CCN1 are risk factors for DR. Blood CCN1 level may be a potential biomarker for diagnosis of DR. The effects of CCN1 on DR may be related to hypoxia, oxidative stress, and dephosphorylation.

Thymoquinone Attenuates Retinal Expression of Mediators and Markers of Neurodegeneration in a Diabetic Animal Model.

Diabetic retinopathy (DR) is a slow eye disease that affects the retina due to a long-standing uncontrolled diabetes mellitus. Hyperglycemia-induced oxidative stress can lead to neuronal damage leading to DR. The aim of the current investigation is to assess the protective effects of thymoquinone (TQ) as a potential compound for the treatment and/or prevention of neurovascular complications of diabetes, including DR. Diabetes was induced in rats by the administration of streptozotocin (55 mg/kg intraperitoneally, i.p.). Subsequently, diabetic rats were treated with either TQ (2 mg/kg i.p.) or vehicle on alternate days for three weeks. A healthy control group was also run in parallel. At the end of the treatment period, animals were euthanized, and the retinas were collected and analyzed for the expression levels of brain-derived neurotrophic factor (BDNF), tyrosine hydroxylase (TH), nerve growth factor receptor (NGFR), and caspase-3 using Western blotting techniques in the retina of diabetic rats and compared with the normal control rats. In addition, dichlorofluorescein (DCF) levels in the retina were assessed as a marker of reactive oxygen species (ROS), and blood-retinal barrier breakdown (BRB) was examined for vascular permeability. The systemic effects of TQ treatments on glycemic control, kidney and liver functions were also assessed in all groups. Diabetic animals treated with TQ showed improvements in the liver and kidney functions compared with control diabetic rats. Normalization in the levels of neuroprotective factors, including BDNF, TH, and NGFR, was observed in the retina of diabetic rats treated with TQ. In addition, TQ ameliorated the levels of apoptosis regulatory protein caspase-3 in the retina of diabetic rats and reduced disruption of the blood-retinal barrier, possibly through a reduction in reactive oxygen species (ROS) generation. These findings suggest that TQ harbors a significant potential to limit the neurodegeneration and retinal damage that can be provoked by hyperglycemia in vivo.

Effects of noopept on ocular, pancreatic and renal histopathology in streptozotocin induced prepubertal diabetic rats

ABSTRACT Diabetes mellitus (DM) is a chronic disease at all ages including childhood and puberty. Failure to treat DM can cause retinopathy, nephropathy and neuropathy. Endocrine and metabolic changes during the pubertal period complicate management of DM. Noopept is a cognitive enhancer that exhibits antidiabetic properties. We investigated the effect of noopept on the histopathology of the cornea, retina, kidney and pancreas in pubertal diabetic rats. We allocated 60 prepubertal male rats randomly into six groups of 10: untreated control (C), DM control (DC), noopept control (NC), DM + noopept (D + N), DM + insulin (D + I) and DM + insulin + noopept (D + I + N). DM was induced by streptozotocin in the DC, D + N, D + I and D + I + N groups. Noopept was administered to the NC, D + N and D + I + N groups; insulin was administered to the D + I and D + I + N groups for 14 days. On day 18 of the experiment, animals were sacrificed and eyes, kidneys and pancreata were excised for histological investigation. Renal tubule diameter and corneal and retinal thickness were increased significantly in DC groups compared to the control group. The D + I, D + N and D + I + N groups exhibited fewer DM induced pathological changes than the DC group. The D + I + N group exhibited no significant differences in renal tubule diameter and corneal and retinal thickness compared to the DC group. Our findings suggest that noopept is protective against DM end organ complications in streptozotocin induced diabetic pubertal rats.

A comparative study between the possible protective role of melatonin versus its combination with adipose derived-mesenchymal stem cells on experimentally induced diabetic retinopathy in adult male albino rats (Histological and immunohistochemical study)

ABSTRACT Diabetes mellitus is a metabolic disorder that can cause numerous ocular issues as well as long-term effects. In our study, we evaluate the effect of melatonin on the diabetic retinal alterations in male albino rats to the effect of melatonin combined with stem cells. 50 adult male rats were equally divided into four groups control, diabetic, melatonin, and melatonin plus stem cells. STZ, 65 mg/kg in phosphate buffered was administered intraperitoneally as a bolus to diabetic group of rats. After inducing diabetes, melatonin (10 mg/kg b.wt./day) was administered orally to the melatonin group for 8 weeks. The stem cell and melatonin group got the same dosage of melatonin as the prior group. They received an intravenous injection of (3?×?106 cell) adipose-derived MSC suspended in phosphate-buffered saline at same time of melatonin ingestion. Animals from all groups had their fundics examined. Following the injection of stem cells, samples of rat retina were collected for light and electron microscopy analyses. H&E and immunohistochemically stained sections revealed a slight improvement in group (III). At the same time, group (IV) results were comparable to those of the control group, which was supported by the findings of an electron microscope. Neovascularization was visible on fundus examination in group (II), whereas it was less noticeable in group (III) and group IV. Melatonin mildly improved the histological structure of the retina in diabetic rats, and when it was combined with adipose-derived MSC, it considerably improved the diabetic alterations.

Inhibition of NF-κB ameliorates aberrant retinal glia activation and inflammatory responses in streptozotocin-induced diabetic rats.

To determine the anti-inflammatory effects of IMD-0354, a specific NF-κB blocker, on glial cells in rats with streptozotocin (STZ)-induced diabetic retinopathy (DR). The following four groups of rats were used: control, control + IMD-0354, STZ, and STZ + IMD-0354. After six weeks of STZ injection, diabetic rats and nondiabetic control rats received IMD-0354 (30 mg/kg) or an equal volume of 4% dimethyl sulfoxide (DMSO) in phosphate-buffered saline intraperitoneally for six consecutive weeks. The following four groups of primary rat retinal microglia and Müller cells were used: control (5 mM), control + IMD-0354, high glucose (20 mM), and high glucose + IMD-0354. The effects of IMD-0354 on nuclear factor-κB (NF-κB) activation, oxidative stress strength, expression of inflammatory cytokines and VEGF (vascular endothelial growth factor), activation of glial cells, and apoptosis of neuron cells were evaluated by immunohistochemistry, oxidative stress assays, western blot, enzyme linked immunosorbent assay (ELISA) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining respectively. Nuclear translocation of NF-κB was markedly increased in diabetic rat retina and high glucose treated glial cells. Systemic administration of IMD-0354 significantly inhibited NF-κB activation in both diabetic rat retina and high glucose treated glial cells, ameliorated oxidative injury, inflammatory responses, VEGF production and glial cell activation, and protected neurons from apoptosis. Our findings indicated that NF-κB activation is acritical step in the abnormal reactivity of glial cells in STZ-induced diabetic rats. Inhibition effect of IMD-0354 on NF-κB activation may represent a promising therapeutic strategy for DR via a variety of mechanisms, including inflammation reduction and glial cells regulation.

Study on the Antioxidant Effect of Tanshinone IIA on Diabetic Retinopathy and Its Mechanism Based on Integrated Pharmacology.

To explore the effect of tanshinone IIA on diabetic retinopathy (DR) and its mechanism. GeneCards and OMM databases were used to mine DR-related genes. The chemical structure of tanshinone IIA was searched by PubChem, and the potential target was predicted by PharmMapper. Cystape 3.8.2 was used to visualize and analyze the tanshinone IIA-DR protein interaction network. DAVID ver 6.8 data were used to perform enrichment analysis of the tanshinone IIA-DR protein interaction network. Then animal experiments were carried out to further explore the mechanism of tanshinone IIA in the treatment of DR. Male SD rats were intraperitoneally injected with streptozotocin to establish a diabetes model and were randomly divided into a model group, a low-dose tanshinone IIA group and a high-dose group. Normal rats served as the control group. Hematoxylin-eosin (HE) staining was used to observe the structural changes of the retina; the SOD, GSH-Px, and MDA levels in the retina were detected by the xanthine oxidase method; the expression of VEGF, IL-1β, IL-6, TNF-α, and caspase-3 mRNA were detected by qRT-PCR; and the Bcl-2, Bax, and VEGFA proteins were determined by the western blot. A total of 213 tanshinone IIA potential targets and 223 DR-related genes were obtained. The enrichment analysis showed that tanshinone IIA may regulate hypoxia, oxidative stress, positive regulation of ERK1 and ERK2 cascade, steroid hormone-mediated signaling pathway, inflammatory response, angiogenesis, VEGF signaling pathway, apoptosis, PI3K-Akt signaling pathway, TNF signaling pathway, and biological processes and signaling pathways. The structure of the retina in the normal control group was clear, the retina in the model group was not clear, the nerve fiber layer was edema, the retinal cell layers of the tanshinone IIA low-dose group are arranged neatly, the inner and outer nuclear layers are slightly disordered, and the tanshinone IIA low-dose group was large. The structure of the mouse retina was further improved compared with the low-dose tanshinone IIA group. Compared with the model group, the retinal tissue SOD and GSH-PX of rats in the tanshinone IIA group increased, and the MDA level decreased (P < 0.05). Compared with the model group, the expression of VEGF, IL-1β, IL-6, TNF-α, and caspase-3 mRNA in the retina of tanshinone IIA groups was significantly reduced (P < 0.01). Compared with the model group, the Bcl-2 protein in the tanshinone IIA groups increased, while the Bax and VEGFA proteins decreased (P < 0.05). Tanshinone IIA may improve the morphological performance of the retina of diabetic rats and inhibit DR, the mechanism of which may be anti-inflammatory, antiangiogenesis, etc.

FBXW7 alleviates hyperglycemia-induced endothelial oxidative stress injury via ROS and PARP inhibition

Diabetic retinopathy (DR) and other diabetic vascular complications are the leading cause of death and disability in patients with suboptimum glycemic control. In the pathogenesis of diabetic vascular diseases, hyperglycemia-induced oxidative stress, DNA damage, and poly-ADP-ribose-polymerase (PARP) hyperactivation play important roles in endothelial cell impairment. Adipose differentiation-related protein FBXW7 was reported to regulate PGC-1α stability and mitochondrial homeostasis. Here, we investigated the role and mechanism of FBXW7 in repairing endothelial oxidative stress injuries under hyperglycemic conditions. FBXW7 promoted the hampered activity of homologous recombination and non-homologues end joining pathway for repairing DNA double-strand breaks damage, an initiating factor for PARP hyperactivation and diabetic vascular complications. The abundant mobilization of DNA damage repair mediated by FBXW7 suppressed PARP activation, leading to downregulation of PARP expression and activity in both human endothelial cells and diabetic rat retinas. This provided a new method for PARP inhibition, superior to PARP inhibitors for treating diabetic vascular complication. Furthermore, FBXW7 rescued downregulated NAD+ levels and ameliorated mitochondrial dysfunction, thereby reducing superoxide production under hyperglycemic conditions. These effects reversed oxidative injury and vascular leakage in diabetic rat retina, providing a potential future treatment strategy.

NGF Prevents Loss of TrkA/VEGFR2 Cells, and VEGF Isoform Dysregulation in the Retina of Adult Diabetic Rats.

Among the factors involved in diabetic retinopathy (DR), nerve growth factor (NGF) and vascular endothelial growth factor A (VEGFA) have been shown to affect both neuronal survival and vascular function, suggesting that their crosstalk might influence DR outcomes. To address this question, the administration of eye drops containing NGF (ed-NGF) to adult Sprague Dawley rats receiving streptozotocin (STZ) intraperitoneal injection was used as an experimental paradigm to investigate NGF modulation of VEGFA and its receptor VEGFR2 expression. We show that ed-NGF treatment prevents the histological and vascular alterations in STZ retina, VEGFR2 expression decreased in GCL and INL, and preserved the co-expression of VEGFR2 and NGF-tropomyosin-related kinase A (TrkA) receptor in retinal ganglion cells (RGCs). The WB analysis confirmed the NGF effect on VEGFR2 expression and activation, and showed a recovery of VEGF isoform dysregulation by suppressing STZ-induced VEGFA121 expression. Reduction in inflammatory and pro-apoptotic intracellular signals were also found in STZ+NGF retina. These findings suggest that ed-NGF administration might favor neuroretina protection, and in turn counteract the vascular impairment by regulating VEGFR2 and/or VEGFA isoform expression during the early stages of the disease. The possibility that an increase in the NGF availability might contribute to the switch from the proangiogenic/apoptotic to the neuroprotective action of VEGF is discussed.

Differential Expression and Localization of ADAMTS Proteinases in Proliferative Diabetic Retinopathy.

We analyzed the expression of ADAMTS proteinases ADAMTS-1, -2, -4, -5 and -13; their activating enzyme MMP-15; and the degradation products of proteoglycan substrates versican and biglycan in an ocular microenvironment of proliferative diabetic retinopathy (PDR) patients. Vitreous samples from PDR and nondiabetic patients, epiretinal fibrovascular membranes from PDR patients, rat retinas, retinal Müller glial cells and human retinal microvascular endothelial cells (HRMECs) were studied. The levels of ADAMTS proteinases and MMP-15 were increased in the vitreous from PDR patients. Both full-length and cleaved activation/degradation fragments of ADAMTS proteinases were identified. The amounts of versican and biglycan cleavage products were increased in vitreous from PDR patients. ADAMTS proteinases and MMP-15 were localized in endothelial cells, monocytes/macrophages and myofibroblasts in PDR membranes, and ADAMTS-4 was expressed in the highest number of stromal cells. The angiogenic activity of PDR membranes correlated significantly with levels of ADAMTS-1 and -4 cellular expression. ADAMTS proteinases and MMP-15 were expressed in rat retinas. ADAMTS-1 and -5 and MMP-15 levels were increased in diabetic rat retinas. HRMECs and Müller cells constitutively expressed ADAMTS proteinases but not MMP-15. The inhibition of NF-κB significantly attenuated the TNF-α-and-VEGF-induced upregulation of ADAMTS-1 and -4 in a culture medium of HRMECs and Müller cells. In conclusion, ADAMTS proteinases, MMP-15 and versican and biglycan cleavage products were increased in the ocular microenvironment of patients with PDR.

Capsaicin ameliorates diabetic retinopathy by inhibiting poldip2-induced oxidative stress

BackgroundOxidative stress and the resultant hyperpermeability play a vital role in the pathogenesis of diabetic retinopathy (DR). Poldip2 has been implicated in H2O2 production, but the effects of capsaicin on poldip2 have not been reported. MethodsDiabetic Sprague-Dawley (SD) rats induced with STZ were treated with capsaicin or AAV9-poldip2-shRNA, and human retinal microvascular endothelial cells (HRMECs) were treated with capsaicin or poldip2 siRNA. ResultsCurrent data indicated that the expression of PPARγ, poldip2, Nox4, VCAM-1, HIF-1α, and VEGF increased in rat retinas with DR and in HRMECs treated with high glucose. The production of ROS or H2O2 in the tissues, serum, and cells increased, and the paracellular permeability of cultured HRMECs with high glucose significantly increased. In addition, overt hyperpermeability of retinal microvessels and increased retinal neovascularization in diabetic rats were observed. However, capsaicin treatment inhibited these increases and suppressed the expression of PPARγ by enhancing its phosphorylation and ubiquitination in the retinas of DR rats. Poldip2 knockdown in HRMECs or its silencing in the retina of DR rats concomitantly led to reduced levels of Nox4, VCAM-1, HIF-1α, VEGF, ROS, and H2O2, and the paracellular permeability of HRMECs or the hyperpermeability of retinal microvessels in diabetic rat retinas decreased. Similarly, after PPARγ knockdown in HRMECs, poldip2, Nox4, HIF-1α, VEGF, ROS, and H2O2 decreased, and the monolayer paracellular permeability was reduced accordingly. ConclusionCapsaicin may ameliorate diabetic retinopathy by activating TRPV1 and suppressing the PPARγ-poldip2-Nox4 pathway.

NADH-Cytochrome B5 reductase 2 suppresses retinal vascular dysfunction through regulation of vascular endothelial growth factor A in diabetic retinopathy

Diabetic retinopathy (DR) is a progressive vascular complication of diabetes mellitus (DM) and is related to retinal vascular abnormalities. NADH-Cytochrome B5 Reductase 2 (CBR2) has been implicated in angiogenesis, but the effect of CBR2 on angiogenesis and endothelial cell biological behavior in DR remains unclear. Here, we aimed to explore the effect of CBR2 on retinal vascular dysfunction under diabetic conditions. The histological analyses were performed to explore the effect of CBR2 on pathological change in streptozotocin (STZ)-induced diabetic rat retinas. The effect of CBR2 on endothelial cell function was explored by CCK-8, scratch wound, transwell, tube formation, and immunofluorescence assays in high glucose (HG)-stimulated human retinal microvascular endothelial cells (HRMECs). CBR2 expression was significantly downregulated in DM rat retinas and HG-stimulated HRMECs. Intravitreal injection of CBR2-expressing lentivirus under diabetic conditions reduced retinal angiogenesis, acellular capillary formation, and pericyte loss, along with decreased expression of hypoxia-inducible factor-1α (HIF-1α), cluster of differentiation 31 (CD31), and vascular endothelial growth factor A (VEGFA) in vivo. Moreover, CBR2 overexpression inhibited cell growth and tube formation and led to decreased expression of HIF-1α and VEGFA in HG-induced HRMECs. Interestingly, the repressive effects of CBR2 on cell proliferation, migration, and tube formation under HG conditions were strongly reversed when VEGFA was overexpressed. Overall, the key findings of our study suggested that CBR2 might alleviate retinal vascular dysfunction and abnormal endothelial proliferation during the process of DR by regulating VEGFA, providing a piece of potent evidence for DR therapy.

N-Methyl-D-Aspartic Acid Receptor-Mediated Vasodilation Is Attenuated in the Retinas of Diabetic Rats

Purpose Activation of N-methyl-d-aspartic acid (NMDA) receptors enhances nitric oxide (NO) production in retinal neuronal cells, and in turn, NO released from neuronal cells induces glial cell-mediated dilation of retinal arterioles in rats. The purpose of this study was to examine how neuronal cell-dependent, glial cell-mediated vasodilation is impacted in diabetic rat retinas. Methods Diabetes was induced in 6-week-old male Wistar rats by combining streptozotocin injection and D-glucose feeding. Two weeks later, the dilator function of retinal arterioles was assessed. Results Compared with non-diabetic rats, the dilator responses of retinal arterioles induced by intravitreal injection of NMDA and NOR3, an NO donor, were reduced in diabetic rats. Following the blockade of large-conductance Ca2+-activated K+ (BKCa) channels with iberiotoxin, no significant difference in the retinal vasodilator response to NOR3 was observed between non-diabetic and diabetic rats. Intravitreal injection of 14,15-epoxyeicosatrienoic acid, a vasodilatory factor released from glial cells, dilated retinal arterioles, and the response was diminished by diabetes. Conclusion These findings suggest that the impaired BKCa channel function in vascular cells is responsible for the diminished neuronal cell-dependent, glial cell-mediated dilation of retinal arterioles during the early stage of diabetes.