Upregulated VEGF and Robo4 correlate with the reduction of miR-15a in the development of diabetic retinopathy

USP5 facilitates diabetic retinopathy development by stabilizing ROBO4 via deubiquitination

Ubiquitin-specific proteases (USPs) have been proved to play important roles in the progression of diabetic retinopathy. In this study, we explored the role of USP5 and its possible mechanisms in diabetic retinopathy development. Cell proliferation, apoptosis, inflammation and oxidative stress were determined using CCK-8 assay, EdU staining assay, flow cytometry, and ELISA, respectively. The mRNA and protein expression of ROBO4 and USP5 were measured through RT-qPCR and western blot, respectively. Co-IP and deubiquitination assay were conducted to evaluate the interaction between ROBO4 and USP5. The results showed that high glucose (HG) stimulation significantly led to HRPE cell damage as described by suppressing proliferation, and promoting oxidative stress, inflammation and apoptosis. ROBO4 was markedly increased in diabetic retinopathy plasma samples and HG-triggered HRPE cells. Depletion of ROBO4 could alleviate HG-caused HRPE cell damage. USP5 was also significantly elevated in diabetic retinopathy plasma samples and HG-triggered HRPE cells. USP5 overexpression aggravated HG-induced HRPE cell damage. USP5 stabilized ROBO4 through deubiquitination. Moreover, USP5 knockdown decreased ROBO4 expression to mitigate HG-triggered cell damage in HRPE cells. USP5 stabilized ROBO4 via deubiquitination to repress cell proliferation, and facilitate inflammation, cell apoptosis and oxidative stress in HG-treated HRPE cells, thereby promoting the development of diabetic retinopathy.

Endothelial Robo4 suppresses endothelial-to-mesenchymal transition induced by irradiation and improves hematopoietic reconstitution

Bone marrow ablation is routinely performed before hematopoietic stem cell transplantation (HSCT). Hematopoietic stem and progenitor cells (HSPCs) require a stable bone marrow microenvironment to expand and refill the peripheral blood cell pool after ablation. Roundabout guidance receptor 4 (Robo4) is a transmembrane protein exclusive to endothelial cells and is vital in preserving vascular integrity. Hence, the hypothesis is that Robo4 maintains the integrity of bone marrow endothelial cells following radiotherapy. We created an endothelial cell injury model with γ-radiation before Robo4 gene manipulation using lentiviral-mediated RNAi and gene overexpression techniques. We demonstrate that Robo4 and specific mesenchymal proteins (Fibronectin, Vimentin, αSma, and S100A4) are upregulated in endothelial cells exposed to irradiation (IR). We found that Robo4 depletion increases the expression of endoglin (CD105), an auxiliary receptor for the transforming growth factor (TGF-β) family of proteins, and promotes endothelial-to-mesenchymal transition (End-MT) through activation of both the canonical (Smad) and non-canonical (AKT/NF-κB) signaling pathways to facilitate Snail1 activation and its nuclear translocation. Endothelial Robo4 overexpression stimulates the expression of immunoglobulin-like adhesion molecules (ICAM-1 and VCAM-1) and alleviates irradiation-induced End-MT. Our coculture model showed that transcriptional downregulation of endothelial Robo4 reduces HSPC proliferation and increases HSC quiescence and apoptosis. However, Robo4 overexpression mitigated the damaged endothelium's suppressive effects on HSC proliferation and differentiation. These findings indicate that by controlling End-MT, Robo4 preserves microvascular integrity after radiation preconditioning, protects endothelial function, and lessens the inhibitory effect of damaged endothelium on hematopoietic reconstitution.

Gene augmentation for autosomal dominant retinitis pigmentosa using rhodopsin genomic loci nanoparticles in the P23H+/- knock-in murine model

Gene therapy for autosomal dominant retinitis pigmentosa (adRP) is challenged by the dominant inheritance of the mutant genes, which would seemingly require a combination of mutant suppression and wild-type replacement of the appropriate gene. We explore the possibility that delivery of a nanoparticle (NP)-mediated full-length mouse genomic rhodopsin (gRho) or human genomic rhodopsin (gRHO) locus can overcome the dominant negative effects of the mutant rhodopsin in the clinically relevant P23H+/--knock-in heterozygous mouse model. Our results demonstrate that mice in both gRho and gRHO NP-treated groups exhibit significant structural and functional recovery of the rod photoreceptors, which lasted for 3 months post-injection, indicating a promising reduction in photoreceptor degeneration. We performed miRNA transcriptome analysis using next generation sequencing and detected differentially expressed miRNAs as a first step towards identifying miRNAs that could potentially be used as rhodopsin gene expression enhancers or suppressors for sustained photoreceptor rescue. Our results indicate that delivering an intact genomic locus as a transgene has a greater chance of success compared to the use of the cDNA for treatment of this model of adRP, emphasizing the importance of gene augmentation using a gDNA that includes regulatory elements.

The role of TET2-mediated ROBO4 hypomethylation in the development of diabetic retinopathy

BACKGROUND

In diabetic retinopathy, increasing evidence points to a link between the pathogenesis of retinal microangiopathy and the endothelial cell-specific factor roundabout4 (ROBO4). According to earlier research, specificity protein 1 (SP1) enhances the binding to the ROBO4 promoter, increasing Robo4 expression and hastening the progression of diabetic retinopathy. To determine if this is related to aberrant epigenetic modifications of ROBO4, we examined the methylation level of the ROBO4 promoter and the corresponding regulatory mechanism during the course of diabetic retinopathy and explored the effect of this mechanism on retinal vascular leakage and neovascularization.

METHODS

The methylation level of CpG sites in the ROBO4 promoter was detected in human retinal endothelial cells (HRECs) cultured under hyperglycemic conditions and retinas from streptozotocin-induced diabetic mice. The effects of hyperglycemia on DNA methyltransferase 1, Tet methylcytosine dioxygenase 2 (TET2), 5-methylcytosine, 5-hydroxymethylcytosine, and the binding of TET2 and SP1 to the ROBO4 promoter, as well as the expression of ROBO4, zonula occludens 1 (ZO-1) and occludin were examined. Short hairpin RNA was used to suppress the expression of TET2 or ROBO4 and the structural and functional changes in the retinal microvascular system were assessed.

RESULTS

In HRECs cultured under hyperglycemic conditions, the ROBO4 promoter methylation level decreased. Hyperglycemia-induced TET2 overexpression caused active demethylation of ROBO4 by oxidizing 5-methylcytosine to 5-hydroxymethylcytosine, which enhanced the binding of SP1 to ROBO4, increased the expression of ROBO4, and decreased the expression of ZO-1 and occludin, leading to the abnormalities in monolayer permeability, migratory ability and angiogenesis of HRECs. The above pathway was also demonstrated in the retinas of diabetic mice, which caused leakage from retinal capillaries and neovascularization. Inhibition of TET2 or ROBO4 expression significantly ameliorated the dysfunction of HRECs and retinal vascular abnormalities.

CONCLUSIONS

In diabetes, TET2 can regulate the expression of ROBO4 and its downstream proteins by mediating active demethylation of the ROBO4 promoter, which accelerates the development of retinal vasculopathy. These findings suggest that TET2-induced ROBO4 hypomethylation is a potential therapeutic target, and anti- TET2/ROBO4 therapy is anticipated to emerge as a novel strategy for early intervention and delayed progression of diabetic retinopathy.

Inhibition of KCTD10 Affects Diabetic Retinopathy Progression by Reducing VEGF and Affecting Angiogenesis

Aim

We purposed to evaluate the KCTD10 effects of angiogenesis in diabetic retinopathy (DR).

Methods

We induced a DR cell model using high glucose (HG) treatment of HRECs and ARPE-19 cells. A DR rat was established by injecting streptozotocin. Small interference RNA targeted KCTD10 (si-KCTD10) was used to mediate KCTD10 inhibition in cell and animal models. The roles of KCTD10 on cell viability, apoptosis, angiogenesis, and related proteins (VEGF and HIF-1α) were observed by RT-qPCR, Western blot, CCK-8 assay, TUNEL staining, tube formation assay, ELISA, and immunohistochemistry assay.

Results

KCTD10 expression was upregulated in DR cells and retinal tissue of DR rats. Treatment of the cells with si-KCTD10 increased cell viability and decreased apoptosis and angiogenesis in DR cells. Inhibition of KCTD10 could reduce the expression of VEGF and HIF-1α in DR cells. Furthermore, KCTD10 inhibition reduced VEGF levels in the retinal tissue of DR rats.

Conclusion

This work showed that inhibition of KCTD10 relieved angiogenesis in DR.

Polyphenols target miRNAs as a therapeutic strategy for diabetic complications

MiRNAs are a large group of non-coding RNAs which participate in different cellular pathways like inflammation and oxidation through transcriptional, post-transcriptional, and epigenetic regulation. In the post-transcriptional regulation, miRNA interacts with the 3'-UTR of mRNAs and prevents their translation. This prevention or dysregulation can be a cause of pathological conditions like diabetic complications. A huge number of studies have revealed the association between miRNAs and diabetic complications, including diabetic nephropathy, cardiomyopathy, neuropathy, retinopathy, and delayed wound healing. To address this issue, recent studies have focused on the use of polyphenols as selective and safe drugs in the treatment of diabetes complications. In this article, we will review the involvement of miRNAs in diabetic complications' occurrence or development. Finally, we will review the latest findings on targeting miRNAs by polyphenols like curcumin, resveratrol, and quercetin for diabetic complications therapy.

Lycium barbarum polysaccharides attenuates high glucose-induced diabetic retinal angiogenesis by rescuing the expression of miR-15a-5p in RF/6A cells

ETHNOPHARMACOLOGICAL RELEVANCE

Lycium barbarum L., a classical traditional Chinese Medicine, has long been used to treat ocular diseases. Lycium barbarum polysaccharides (LBP) is an effective component of Lycium barbarum L. with a wide range of pharmacological activities. This research aims to investigate the inhibition of high glucose-induced angiogenesis by LBP in RF/6A cells.

MATERIALS AND METHODS

A high-glucose-induced angiogenesis model was established using monkey retinal vascular endothelial (RF/6A) cells. Different dosages administration times of LBP and glucose concentrations were tested. Under the optimized conditions, RF/6A cells were treated with LBP for 48 h, followed by another 48-h culture in high glucose (25 mmol/L) medium. The effect and mechanism of LBP were investigated following the treatment.

RESULTS

The expression of miR-15a-5p and miR-15a-3p in RF/6A cells decreased significantly after 48 h of 25 or 50 mmol/L high glucose treatment. The expression of miR-15a-5p was higher than that of miR-15a-3p. Mimic-miR-15a-5p or 600 mg/L LBP could increase the apoptosis of cells and the total length of vascular branches. The expression of VEGFA, VEGFR2, and ANG2 proteins was reduced, while the expression of ANG1 protein was elevated. Expression of ASM mRNA and protein was also inhibited.

CONCLUSIONS

LBP attenuates diabetic retinal angiogenesis by rescuing the expression of miR-15a-5p in RF/6A cells.

Inhibitory effect of miR‑182‑5p on retinal neovascularization by targeting angiogenin and BDNF

Retinal neovascularization (RNV) is a type of serious vision-threating disease, commonly induced by hypoxia of ischemic retinopathy, which happens in various ocular diseases including diabetic retinopathy and retinopathy of prematurity. In clinical work, anti-VEGF therapy is the preferred strategy for treating RNV. However, not all cases are sensitive to anti-VEGF injection. It is urgent and necessary to develop novel targets for inhibiting neovascularization in ocular diseases. Angiogenin (ANG) and brain-derived neurotrophic factor (BDNF) are implicated in angiogenesis, although their regulation and effects in RNV remain to be elucidated. microRNA (miRNA) is a type of small non-coding RNA, which can modulate targets by degrading transcripts or inhibiting protein translation. In the present study, miRNA-mediated modulation of ANG and BDNF was explored in an oxygen-induced retinopathy mouse model and human retinal microvascular endothelial cells (HRECs) under hypoxia. The results showed that downregulation of miR-182-5p and upregulation of ANG and BDNF were found in vivo and in vitro. Overexpression of miR-182-5p suppressed the expression of ANG and BDNF significantly in HRECs under hypoxia. In addition, knockdown of ANG and BDNF by miR-182-5p transfection significantly improved hypoxia-induced HRECs dysfunctions, including enhancing cell viability, reducing cell migration and improved tube integrity. In conclusion, miRNA-dependent regulation on ANG and BDNF indicates a critical role in hypoxia-induced retinal microvascular response. miR-182-5p-based therapy can influence the expression of ANG and BDNF, which demonstrates the potential for treating RNV diseases.

Dysregulation of miR-374a is involved in the progression of diabetic retinopathy and regulates the proliferation and migration of retinal microvascular endothelial cells

Clinical relevance: microRNAs (miRNAs) have been reported to be involved in the progression of various diseases.Background: This study evaluated the expression and clinical value of miR-374a in diabetic retinopathy (DR) patients and analysed the effects of miR-374a on the progression of DR.Methods: Subjects were divided into four groups: healthy control, type 2 diabetes mellitus without DR (NDR), proliferation DR (PDR) and non-proliferation DR (NPDR). Real-time polymerase chain reaction (qRT-PCR) was detected in the serum miR-374a levels of the subjects. The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of miR-374a in DR patients. Pearson correlation was used to analyse the correlation between miRNA and clinical indicators of patients. High glucose (HG) in treatment of human retinal microvascular endothelial cells (HRMECs). The effects of miR-374a on cell proliferation and migration induced by HG were detected.Results: Serum miR-374a was progressively accelerated in patients with NDR, NPDR and PDR than in healthy controls. Moreover, miR-374a can significantly distinguish between NDR and DR patients. Among DR patients, miR-374a can differentiate PDR patients from NPDR patients. Serum miR-374a was positively correlated with diabetes duration, fasting plasma glucose (FPG), glycosylated haemoglobin (HbA1c), and homoeostasis model assessment of insulin resistance (HOMA-IR) in DR patients. HG-induced proliferation and migration of HRMECs was inhibited by reduction of miR-374a.Conclusion: Dysregulation of miR-374a is involved in the progression of DR and serves a regulatory role in retinal, which can be used as a promising diagnostic biomarker for DR.

MicroRNA-135b-5p promotes endothelial cell proliferation and angiogenesis in diabetic retinopathy mice by inhibiting Von Hipp-el-Lindau and elevating hypoxia inducible factor α expression

OBJECTIVE

This study was performed to investigate the effect of microRNA-135b-5p (miR-135b-5p) on endothelial cell proliferation and angiogenesis in diabetic retinopathy (DR) mice with the involvement of Von Hipp-el-Lindau protein (VHL) and hypoxia-inducible factor 1 α (HIF1α).

METHODS

A DR mouse model was established. The loss- and gain-of-function approaches were conducted to figure out the roles of miR-135b-5p and VHL in vascular hyperplasia, inflammation and apoptosis in DR mice. Endothelial cells were extracted from DR mice and transfected with miR-135b-5p- and VHL-related oligonucleotides and plasmids to decode their functions in cell viability, migration, and tube formation in DR. miR-135b-5p, VHL and HIF-1α expression in mouse retinal tissues and endothelial cells were detected. The targeting connection between miR-135b-5p and VHL was tested.

RESULTS

Elevated miR-135b-5p and HIF-1α, as well as declined VHL existed in DR. Declined miR-135b-5p or overexpressed VHL impaired vascular hyperplasia, inflammation and apoptosis, and decreased HIF-1α expression in DR mice. Repressed miR-135b-5p or up-regulated VHL inhibited viability, migration and tube formation of endothelial cells in DR. miR-135b-5p targeted VHL.

CONCLUSION

MiR-135b-5p inhibits VHL and elevates HIF1α expression, thereby promoting endothelial cell proliferation and angiogenesis in DR mice.

MicroRNA-34a promotes apoptosis of retinal vascular endothelial cells by targeting SIRT1 in rats with diabetic retinopathy

MiR-34a is associated with diabetic retinopathy (DR). This article aims to demystify the role of miR-34a in DR. We established a DR model by streptozocin injection. Rat retinal vascular endothelial cells (RVECs) were treated with high glucose (HG) to induce DR. The pathological changes of retinal tissues and blood-retinal vascular barrier permeability of DR rats were assessed by HE staining and Evans-Blue leak test. The expression of gene and protein was evaluated by quantitative real-time PCR or western blot. MTT assay and flow cytometry were performed to detect proliferation and apoptosis. The relationship between miR-34a and SIRT1 was evaluated using luciferase reporter assay. MiR-34a was up-regulated and SIRT1 was down-regulated in retinal tissues of DR rats and HG-induced RVECs. MiR-34a silencing improved DR by regulating apoptosis and VEGF expression in DR rats. Furthermore, miR-34a interacted with SIRT1 and suppressed SIRT1 expression. MiR-34a overexpression inhibited proliferation and promoted apoptosis of RVECs, which was effectively abolished by SIRT1 up-regulation. In summary, our data demonstrate that miR-34a promotes apoptosis of RVECs by targeting SIRT1 in DR rats. Our findings suggest that miR-34a/SIRT1 axis could be a valuable target for DR therapies.

MiR-221/SIRT1/Nrf2 signal axis regulates high glucose induced apoptosis in human retinal microvascular endothelial cells

Background

Diabetic retinopathy (DR) is a serious symptom associated with diabetes and could cause much suffer to patients. MiR-221, SIRT1 and Nrf2 were associated with apoptosis and proliferation and their expression were altered in DR patients. However, their roles and regulatory mechanisms in human retinal microvascular endothelial cells (hRMEC) were not clear.

Methods

Expression of mRNA was detected by qRT-PCR. Protein expression was detected by Western blot. Interaction between miR-221 and SIRT1 was predicted by bioinformatics analysis and validated by dual-luciferase reporter assay. We analyzed the viability and apoptosis of hRMEC by MTT assay and FACS assay, respectively.

Results

High glucose (HG) treatment enhanced expression of miR-221 and inhibited expression of SIRT1 and Nrf2. MiR-221 overexpression promoted apoptosis under HG condition. Moreover, miR-221 directly interacted with mRNA of SIRT1 and inhibited SIRT1 expression in hRMEC, through which miR-221 inhibited Nrf2 pathway and induced apoptosis of hRMEC.

Conclusion

Our data demonstrated that miR-221/SIRT1/Nrf2 signal axis could promote apoptosis in hRMEC under HG conditions. This finding could provide theoretical support for future studies and may contribute to development of new treatment options to retard the process of DR development.

MiR-130a alleviated high-glucose induced retinal pigment epithelium (RPE) death by modulating TNF-α/SOD1/ROS cascade mediated pyroptosis

High-glucose induced retinal pigment epithelium (RPE) death by triggering oxidative stress, however, the underlying mechanisms are still not fully delineated. In this study, the RPE cell line ARPE-19 were treated with different concentrations of glucose, the results showed that high-glucose (50 mM) inhibited cell proliferation, promoted cell apoptosis and reactive oxygen species (ROS) production in a time-dependent manner. Notably, we found that high-glucose (50 mM) increased the expression levels of Caspase-1, Gasdermin D, NLRP3, IL-1β and IL-18 in ARPE-19 cells, which indicated that high-glucose triggered pyroptotic cell death. Further results validated that both ROS scavenger N-acetyl cysteine (NAC) and pyroptosis inhibitor necrosulfonamide (NSA) reversed the effects of high-glucose (50 mM) on ARPE-19 cell proliferation, apoptosis and pyroptosis. In addition, high-glucose (50 mM) significantly decreased the levels of miR-130a and superoxide dismutase (SOD) 1, and promoted tumor necrosis factor (TNF)-α expressions in ARPE-19 cells. Interestingly, upregulation of miR-130a increased SOD1 levels in a TNF-α dependent manner. Furthermore, overexpression of miR-130a abrogated the effects of high-glucose (50 mM) on the above cell functions, which were all reversed by either upregulating TNF-α or knocking down SOD1 in ARPE-19 cells. Taken together, upregulation of miR-130a alleviated the cytotoxic effects of high-glucose (50 mM) on ARPE-19 cells by regulating TNF-α/SOD1/ROS axis mediated pyroptotic cell death.

LncRNA TDRG1-Mediated Overexpression of VEGF Aggravated Retinal Microvascular Endothelial Cell Dysfunction in Diabetic Retinopathy

Purpose

Diabetic retinopathy (DR), a neurovascular disease, is one of the leading causes of blindness in working-age adults. Long noncoding RNAs (lncRNAs) have attracted attention as indicators for DR. This study aimed to characterize the role of lncRNA human testis development-related gene 1 (TDRG1) and its modulation of vascular endothelial growth factor (VEGF) in deteriorating DR.

Methods

Tissue samples were obtained from patients with epiretinal membranes (EMs) or proliferative DR, and human retinal microvascular endothelial cells (HRECs) were cultured with high-glucose medium to mimic DR as the in vitro model. The expression of lncRNA TDRG1 and VEGF was determined by immunofluorescence staining, Western blotting, and RT-qPCR. Transfection of small-interfering RNA was conducted to knock down target gene expression. HREC functions were evaluated by cell viability, fluorescein isothiocyanate (FITC)-dextran extravasation, migration, and tube formation assays under different conditions.

Results

LncRNA TDRG1 and VEGF were found to be co-expressed and significantly upregulated in fibrovascular membranes (FVMs) from DR patients compared to those from EM patients. In the in vitro model, hyperglycemic treatment markedly increased the expression of lncRNA TDRG1 and VEGF at the mRNA and protein levels, which promoted cell proliferation and migration, enhanced permeability, and disrupted tube formation of HRECs. However, knockdown of lncRNA TDRG1 or VEGF notably decreased the expression of VEGF and reversed the impaired functions of high-glucose-treated HRECs.

Conclusions

LncRNA TDRG1 promoted microvascular cell dysfunction via upregulating VEGF in the progression of DR and may serve as a potential therapeutic target in DR treatment.

Regulatory mechanisms of Robo4 and their effects on angiogenesis

Roundabout4 (Robo4) is a transmembrane receptor that belongs to the Roundabout (Robo) family of axon guidance molecules. Robo4 is an endothelial-specific receptor that participates in endothelial cell migration, proliferation, and angiogenesis and the maintenance of vasculature homeostasis. The purpose of this review is to summarize and analyze three main mechanisms related to the expression and function of Robo4 during developmental and pathological angiogenesis. In this review, static shear stress and the binding of transcription factors such as E26 transformation-specific variant 2 (ETV2) and Slit3 induce Robo4 expression and activate Robo4 during tissue and organ development. Robo4 interacts with Slit2 or UNC5B to maintain vascular integrity, while a disturbed flow and the expression of transcription factors in inflammatory or neoplastic environments alter Robo4 expression levels, although these changes have uncertain functions. Based on the mechanisms described above, we discuss the aberrant expression of Robo4 in angiogenesis-related diseases and propose antiangiogenic therapies targeting the Robo4 signaling pathway for the treatment of ocular neovascularization lesions and tumors. Finally, although many problems related to Robo4 signaling pathways remain to be resolved, Robo4 is a promising and potentially valuable therapeutic target for treating pathological angiogenesis and developmental defects in angiogenesis.