Systemic and Ocular Adverse Events with Intravitreal Anti-VEGF Therapy Used in the Treatment of Diabetic Retinopathy: a Review

Dual anti-angiogenic and anti-inflammatory action of tRNA-Cys-5-0007 in ocular vascular disease

BACKGROUND

Intravitreal injections of angiogenesis inhibitors have proved efficacious in the majority of patients with ocular angiogenesis. However, one-fourth of all treated patients fail to derive benefits from intravitreal injections. tRNA-derived small RNA (tsRNA) emerges as a crucial class of non-coding RNA molecules, orchestrating key roles in the progression of human diseases by modulating multiple targets. Through our prior sequencing analyses and bioinformatics predictions, tRNA-Cys-5-0007 has shown as a potential regulator of ocular angiogenesis. This study endeavors to elucidate the precise role of tRNA-Cys-5-0007 in the context of ocular angiogenesis.

METHODS

Quantitative reverse transcription PCR (qRT-PCR) assays were employed to detect tRNA-Cys-5-0007expression. EdU assays, sprouting assays, transwell assays, and Matrigel assays were conducted to elucidate the involvement of tRNA-Cys-5-0007 in endothelial angiogenic effects. STZ-induced diabetic model, OIR model, and laser-induced CNV model were utilized to replicate the pivotal features of ocular vascular diseases and evaluate the influence of tRNA-Cys-5-0007 on ocular angiogenesis and inflammatory responses. Bioinformatics analysis, luciferase activity assays, RNA pull-down assays, and in vitro studies were employed to elucidate the anti-angiogenic mechanism of tRNA-Cys-5-0007. Exosomal formulation was employed to enhance the synergistic anti-angiogenic and anti-inflammatory efficacy of tRNA-Cys-5-0007.

RESULTS

tRNA-Cys-5-0007 expression was down-regulated under angiogenic conditions. Conversely, tRNA-Cys-5-0007 overexpression exhibited anti-angiogenic effects in retinal endothelial cells, as evidenced by reduced proliferation, sprouting, migration, and tube formation abilities. In diabetic, laser-induced CNV, and OIR models, tRNA-Cys-5-0007 overexpression led to decreased ocular vessel leakage, inhibited angiogenesis, and reduced ocular inflammation. Mechanistically, these effects were attributed to the targeting of vascular endothelial growth factor A (VEGFA) and TGF-β1 by tRNA-Cys-5-0007. The utilization of an exosomal formulation further potentiated the synergistic anti-angiogenic and anti-inflammatory efficacy of tRNA-Cys-5-0007.

CONCLUSIONS

Concurrent targeting of tRNA-Cys-5-0007 for anti-angiogenic and anti-inflammatory therapy holds promise for enhancing the effectiveness of current anti-angiogenic therapy.

Systemic Arterial and Venous Thrombotic Events Associated With Anti-Vascular Endothelial Growth Factor Injections: A Meta-Analysis

PURPOSE

To compare the risk of systemic arteriovenous thrombotic events between intravitreal anti-vascular endothelial growth factor (anti-VEGF) and sham injections.

DESIGN

Random-effects meta-analysis.

METHODS

A systematic search was performed on OVID MEDLINE, Embase, and Cochrane Library from January 2005 to August 2023. Our inclusion criteria were randomized controlled trials (RCTs) reporting on systemic arteriovenous events for standard dose intravitreal anti-VEGF agents for any indication.

RESULTS

A total of 20 RCTs reporting on 12,833 eyes were included. There was no significant difference in the risk of any thrombotic event between bevacizumab 1.25 mg and ranibizumab 0.5 mg (Risk ratio (RR) = 0.96, 95% CI = 0.52-1.75, P = .89). There was no significant difference between bevacizumab and ranibizumab when restricting to arterial thrombotic events (RR= 0.88, 95% CI = 0.60-1.30, P = .53) or venous thrombotic events (RR = 1.99, 95% CI =86 0.68-5.82], P = .21). The risk of arterial thrombotic events was similar between aflibercept and bevacizumab (RR = 1.11, 95% CI = 0.60-2.07, P = .74), between aflibercept and ranibizumab (RR= 0.77, 95% CI = 0.49-1.21, P = .26), between brolucizumab and aflibercept (RR= 0.67, 95% CI = 0.32-1.38, P = .27), and between aflibercept and faricimab (RR = 0.96, 95% CI = 0.43-2.17, P = .93). Compared to sham, neither dose of ranibizumab (0.5 mg or 0.3 mg) showed a higher risk of arterial thrombotic events.

CONCLUSIONS

There was a similar risk of systemic arteriovenous thrombotic adverse events between anti-VEGF agents and between ranibizumab and sham injections.

Enhanced Ocular Delivery of Beva via Ultra-Small Polymeric Micelles for Noninvasive Anti-VEGF Therapy

Pathological ocular neovascularization resulting from retinal ischemia constitutes a major cause of vision loss. Current anti-VEGF therapies rely on burdensome intravitreal injections of Bevacizumab (Beva). Herein ultrasmall polymeric micelles encapsulating Beva (P@Beva) are developed for noninvasive topical delivery to posterior eye tissues. Beva is efficiently loaded into 11 nm micelles fabricated via self-assembly of hyperbranched amphiphilic copolymers. The neutral, brush-like micelles demonstrate excellent drug encapsulation and colloidal stability. In vitro, P@Beva enhances intracellular delivery of Beva in ocular cells versus free drug. Ex vivo corneal and conjunctival-sclera-choroidal tissues transport after eye drops are improved 23-fold and 7.9-fold, respectively. Anti-angiogenic bioactivity is retained with P@Beva eliciting greater inhibition of endothelial tube formation and choroid sprouting over Beva alone. Remarkably, in an oxygen-induced retinopathy (OIR) model, topical P@Beva matching efficacy of intravitreal Beva injection, is the clinical standard. Comprehensive biocompatibility verifies safety. Overall, this pioneering protein delivery platform holds promise to shift paradigms from invasive intravitreal injections toward simplified, noninvasive administration of biotherapeutics targeting posterior eye diseases.

Posterior eye delivery of angiogenesis-inhibiting RNA nanoparticles via subconjunctival injection

Neovascularization contributes to various posterior eye segment diseases such as age-related macular degeneration and diabetic retinopathy. RNA nanoparticles were demonstrated previously to enter the corneal and retinal cells after subconjunctival injection for ocular delivery. In the present study, antiangiogenic aptamers (anti-vascular endothelial growth factor (VEGF) and anti-angiopoietin-2 (Ang2) aptamers) were conjugated to RNA nanoparticles. The objectives were to investigate the clearance and distribution of these angiogenesis-inhibiting RNA nanoparticles after subconjunctival injection in vivo and their antiangiogenic effects for inhibiting ocular neovascularization in vitro. The results in the whole-body fluorescence imaging study showed that the clearance of RNA nanoparticles was size-dependent with no significant differences between RNA nanoparticles with and without the aptamers except for pRNA-3WJ. The distribution study of RNA nanoparticles by confocal microscopy of the dissected eye tissues in vivo indicated cell internalization of the larger RNA nanoparticles in the retina and retinal pigment epithelium after subconjunctival injection, and the larger nanoparticles with aptamers showed higher levels of cell internalization than those without. In the cell proliferation assay in vitro, RNA nanoparticles with multiple aptamers had higher antiangiogenic effects. With both longer retention time and high antiangiogenic effect, SQR-VEGF-Ang2 could be a promising RNA nanoparticle for posterior eye delivery.

Exploration of potential novel drug targets for diabetic retinopathy by plasma proteome screening

The aim of this study is to identify novel potential drug targets for diabetic retinopathy (DR). A bidirectional two-sample Mendelian randomization (MR) analysis was performed using protein quantitative trait loci (pQTL) of 734 plasma proteins as the exposures and clinically diagnosed DR as the outcome. Genetic instruments for 734 plasma proteins were obtained from recently published genome-wide association studies (GWAS), and external plasma proteome data was retrieved from the Icelandic Decoding Genetics Study and UK Biobank Pharma Proteomics Project. Summary-level data of GWAS for DR were obtained from the Finngen Consortium, comprising 14,584 cases and 202,082 population controls. Steiger filtering, Bayesian co-localization, and phenotype scanning were used to further verify the causal relationships calculated by MR. Three significant (p < 6.81 × 10-5) plasma protein-DR pairs were identified during the primary MR analysis, including CFH (OR = 0.8; 95% CI 0.75-0.86; p = 1.29 × 10-9), B3GNT8 (OR = 1.09; 95% CI 1.05-1.12; p = 5.9 × 10-6) and CFHR4 (OR = 1.11; 95% CI 1.06-1.16; p = 1.95 × 10-6). None of the three proteins showed reverse causation. According to Bayesian colocalization analysis, CFH (coloc.abf-PPH4 = 0.534) and B3GNT8 (coloc.abf-PPH4 = 0.638) in plasma shared the same variant with DR. All three identified proteins were validated in external replication cohorts. Our research shows a cause-and-effect connection between genetically determined levels of CFH, B3GNT8 and CFHR4 plasma proteins and DR. The discovery implies that these proteins hold potential as drug target in the process of developing drugs to treat DR.

Therapeutic Effects of Anti-Inflammatory and Anti-Oxidant Nutritional Supplementation in Retinal Ischemic Diseases

Appropriate nutrients are essential for cellular function. Dietary components can alter the risk of systemic metabolic diseases, including cardiovascular diseases, cancer, diabetes, and obesity, and can also affect retinal diseases, including age-related macular degeneration, diabetic retinopathy, and glaucoma. Dietary nutrients have been assessed for the prevention or treatment of retinal ischemic diseases and the diseases of aging. In this article, we review clinical and experimental evidence concerning the potential of some nutritional supplements to prevent or treat retinal ischemic diseases and provide further insights into the therapeutic effects of nutritional supplementation on retinopathies. We will review the roles of nutrients in preventing or protecting against retinal ischemic diseases.

Dose-Related Side Effects of Intravitreal Injections of Humanized Anti-Vascular Endothelial Growth Factor in Rats: Glial Cell Reactivity and Retinal Ganglion Cell Loss

Purpose

In a previous study, we documented that the Intravitreal injections (IVIs) of bevacizumab in rats caused a retinal inflammatory response. We now study whether the IVI of other humanized anti-VEGF: ranibizumab and aflibercept also cause an inflammatory reaction in the rat retina and if it depends on the dose administered. Finally, we study whether this reaction affects retinal ganglion cell (RGC) survival.

Methods

Albino Sprague-Dawley rats received a single IVI of 5 µL of PBS or ranibizumab or aflibercept at the concentration used in clinical practice (10 µg/µL or 40 µg/µL) or at a lower concentration (0.38 µg/µL and 1.5 µg/µL) calculated to obtain within the rat eye the same concentration as in the human eye in clinical practice. Others received a single 5 µL IVI of a polyclonal goat anti-rat VEGF (0.015 µg/µL) or of vehicle (PBS). Animals were processed 7 days or 1 month later. Retinal whole mounts were immunolabeled for the detection of microglial, macroglial, RGCs, and intrinsically photosensitive RGCs (ipRGCs). Fluorescence and confocal microscopy were used to examine retinal changes, and RGCs and ipRGCs were quantified automatically or semiautomatically, respectively.

Results

All the injected substances including the PBS induced detectable side effects, namely, retinal microglial cell activation and retinal astrocyte hypertrophy. However, there was a greater microglial and macroglial response when the higher concentrations of ranibizumab and aflibercept were injected than when PBS, the antibody anti-rat VEGF and the lower concentrations of ranibizumab or aflibercept were injected. The higher concentration of ranibizumab and aflibercept resulted also in significant RGC death, but did not cause appreciable ipRGC death.

Conclusions

The IVI of all the substances had some retinal inflammatory effects. The IVI of humanized anti-VEGF to rats at high doses cause important side effects: severe inflammation and RGC death, but not ipRGC death.

Influence of serial intravitreal injections on measures of dry eye: A systemic review and meta-analysis

PURPOSE

The aim of this study was to evaluate the long-term effects of serial intravitreal injections (IVI) on measures of dry eye.

METHODS

The PubMed, EMBASE, and Cochrane databases were searched according to the PROSPERO protocol (CRD42023455727). Studies evaluating the influence of serial IVI on the ocular surface compared with untreated fellow eyes were included. The measures of dry eye after IVI were used as outcome variables. The results are presented as mean difference (MD) with a corresponding 95% confidence interval (CI).

RESULTS

A total of 4 studies with 259 participants were included in this meta-analysis. Significant increases in ocular surface disease index (OSDI) scores (MD 10.26, 95 % CI 5.05 to 15.46, p ＜ 0.01) and tear film osmolarity (TOsm; MD 4.40, 95 % CI 0.87 to 7.92, p = 0.01) were observed in the IVI treated eyes compared to the untreated fellow eyes. There was no significant difference between the groups with respect to fluorescein tear film break-up time (TBUT; p = 0.05), average non-invasive tear film break-up time (NITBUT; p = 0.94), first NITBUT (p = 0.78) and Schirmer test (p = 0.94).

CONCLUSION

Repeated IVI of anti-VEGF agents with preoperative povidone-iodine application was associated with increased OSDI scores and TOsm, while no significant difference was found in fluorescein TBUT, average NITBUT, first NITBUT and Schirmer test. The ocular surface may partially recover after the procedures, but IVI still has deleterious effects on the ocular surface.

Exosomal noncoding RNA: A potential therapy for retinal vascular diseases

Exosomes are extracellular vesicles that can contain DNA, RNA, proteins, and metabolites. They are secreted by cells and play a regulatory role in various biological responses by mediating cell-to-cell communication. Moreover, exosomes are of interest in developing therapies for retinal vascular disorders because they can deliver various substances to cellular targets. According to recent research, exosomes can be used as a strategy for managing retinal vascular diseases, and they are being investigated for therapeutic purposes in eye conditions, including glaucoma, dry eye syndrome, retinal ischemia, diabetic retinopathy, and age-related macular degeneration. However, the role of exosomal noncoding RNA in retinal vascular diseases is not fully understood. Here, we reviewed the latest research on the biological role of exosomal noncoding RNA in treating retinal vascular diseases. Research has shown that noncoding RNAs, including microRNAs, circular RNAs, and long noncoding RNAs play a significant role in the regulation of retinal vascular diseases. Furthermore, through exosome engineering, the expression of relevant noncoding RNAs in exosomes can be controlled to regulate retinal vascular diseases. Therefore, this review suggests that exosomal noncoding RNA could be considered as a biomarker for diagnosis and as a therapeutic target for treating retinal vascular disease.

A real-world disproportionality analysis of anti-VEGF drugs from the FDA Adverse Event Reporting System

BACKGROUND

The association between anti-vascular endothelial growth factor (VEGF) drugs and ocular adverse events (AEs) has been reported, but large real-world studies of their association with systemic AEs are still lacking.

METHODS

A disproportionality analysis of reports from the FDA Adverse Event Reporting System from January 2004 to September 2021 was conducted to detect the significant ADR signals with anti-VEGF drugs (including aflibercept, bevacizumab, brolucizumab, pegaptanib, and ranibizumab).

RESULTS

A total of 2980 reported cases with 7125 drug-AEs were included. Five drugs were all associated with eye disorders, and pegaptanib and ranibizumab were also associated with cardiac disorders. For ranibizumab, pegaptanib, bevacizumab and aflibercept, the proportions of cardiac AEs were 8.57%, 5.62%, 3.43% and 3.20%, respectively, and the proportions of central nervous AEs were 8.81%, 7.41, 5.86% and 5.68%, respectively. In multiple comparisons, ranibizumab was significantly higher than bevacizumab and aflibercept in the proportion of cardiac AEs (P < 0.001), and ranibizumab was significantly higher than aflibercept in central nervous AEs (P < 0.001).

CONCLUSIONS

Our findings support the associations between anti-VEGF drugs and ocular AEs, cardiac AEs, and central nervous AEs. After intravitreal injection, attention should not only be paid to ocular symptoms, but also to systemic symptoms.

The Treatment of Diabetic Retinal Edema with Intravitreal Steroids: How and When

Diabetic macular edema (DME) is a common complication of diabetes mellitus and a leading cause of visual impairment worldwide. It is defined as the diabetes-related accumulation of fluid, proteins, and lipids, with retinal thickening, within the macular area. DME affects a significant proportion of individuals with diabetes, with the prevalence increasing with disease duration and severity. It is estimated that approximately 25-30% of diabetic patients will develop DME during their lifetime. Poor glycemic control, hypertension, hyperlipidemia, diabetes duration, and genetic predisposition are recognized as risk factors for the development and progression of DME. Although the exact pathophysiology is still not completely understood, it has been demonstrated that chronic hyperglycemia triggers a cascade of biochemical processes, including increased oxidative stress, inflammation, activation of vascular endothelial growth factor (VEGF), cellular dysfunction, and apoptosis, with breakdown of the blood-retinal barriers and fluid accumulation within the macular area. Early diagnosis and appropriate management of DME are crucial for improving visual outcomes. Although the control of systemic risk factors still remains the most important strategy in DME treatment, intravitreal pharmacotherapy with anti-VEGF molecules or steroids is currently considered the first-line approach in DME patients, whereas macular laser photocoagulation and pars plana vitrectomy may be useful in selected cases. Available intravitreal steroids, including triamcinolone acetonide injections and dexamethasone and fluocinolone acetonide implants, exert their therapeutic effect by reducing inflammation, inhibiting VEGF expression, stabilizing the blood-retinal barrier and thus reducing vascular permeability. They have been demonstrated to be effective in reducing macular edema and improving visual outcomes in DME patients but are associated with a high risk of intraocular pressure elevation and cataract development, so their use requires an accurate patient selection. This manuscript aims to provide a comprehensive overview of the pathology, epidemiology, risk factors, physiopathology, clinical features, treatment mechanisms of actions, treatment options, prognosis, and ongoing clinical studies related to the treatment of DME, with particular consideration of intravitreal steroids therapy.

PFKFB3 in neovascular eye disease: unraveling mechanisms and exploring therapeutic strategies

BACKGROUND

Neovascular eye disease is characterized by pathological neovascularization, with clinical manifestations such as intraocular exudation, bleeding, and scar formation, ultimately leading to blindness in millions of individuals worldwide. Pathologic ocular angiogenesis often occurs in common fundus diseases including proliferative diabetic retinopathy (PDR), age-related macular degeneration (AMD), and retinopathy of prematurity (ROP). Anti-vascular endothelial growth factor (VEGF) targets the core pathology of ocular angiogenesis.

MAIN BODY

In recent years, therapies targeting metabolism to prevent angiogenesis have also rapidly developed, offering assistance to patients with a poor prognosis while receiving anti-VEGF therapy and reducing the side effects associated with long-term VEGF usage. Phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a key enzyme in targeted metabolism, has been shown to have great potential, with antiangiogenic effects and multiple protective effects in the treatment of neovascular eye disease. In this review, we summarize the mechanisms of common types of neovascular eye diseases; discuss the protective effect and potential mechanism of targeting PFKFB3, including the related inhibitors of PFKFB3; and look forward to the future exploration directions and therapeutic prospects of PFKFB3 in neovascular eye disease.

CONCLUSION

Neovascular eye disease, the most common and severely debilitating retinal disease, is largely incurable, necessitating the exploration of new treatment methods. PFKFB3 has been shown to possess various potential protective mechanisms in treating neovascular eye disease. With the development of several drugs targeting PFKFB3 and their gradual entry into clinical research, targeting PFKFB3-mediated glycolysis has emerged as a promising therapeutic approach for the future of neovascular eye disease.

Clinical efficacy of subthreshold micropulse laser combined with anti-VEGF drugs in the treatment of diabetic macular edema: A meta-analysis

BACKGROUND

To systematically evaluate the efficacy and safety of subthreshold micropulse laser (SML) combined with anti-vascular endothelial growth factor (VEGF) drugs for the treatment of diabetic macular edema (DME).

METHODS

The randomized controlled trials on SML combined with anti-VEGF drugs for DME were retrieved from China National Knowledge Infrastructure, Wan Fang Data, VIP Data, Sino Med (China Biomedical Literature Database), PubMed, Web of Science, The Cochrane Library, and Embase by computer from inception to April 19, 2022. The observation group was treated with SML combined with anti-VEGF drugs, while the control group was treated with anti-VEGF agents alone or SML. And the references of the included literature were manually searched. The Meta-analysis was performed using Revman 5.4 and STATA SE 15.

RESULTS

This study finally included 15 randomized controlled trials involving 891 eyes for Meta-analysis. The results showed that there was no statistically significant difference between the 2 groups in best-corrected visual acuity at 1, 3, 6, 9, and 12 months after treatment. There was no statistical difference between the 2 groups in central macular thickness (CMT) at 1, 3, and 6 months after treatment (P > .05). CMT in the observation group was lower than that in the control group at 9 and 12 months (P < .05). There was no statistical difference between the 2 groups in total macular volume at 3, 6, 9, and 12 months in CMT (P > .05). The number of anti-VEGF drugs injections in the observation was lower than that in the control group (P < .05). The occurrence of complications between the 2 groups was not statistically significant difference (P > .05).

CONCLUSION

SML in combination with anti-VEGF drugs in patients with DME are comparable in reducing the number of anti-VEGF drugs injections and CMT, thereby reducing the financial burden on patients. It does not differ in best-corrected visual acuity and total macular volume.

New concepts drive the development of delivery tools for sustainable treatment of diabetic complications

Diabetic complications, especially diabetic retinopathy, diabetic nephropathy and painful diabetic neuropathy, account for a large portion of patients with diabetes and display rising global prevalence. They are the leading causes of blindness, kidney failure and hypersensitivity to pain caused by diabetes. Current approved therapeutics against the diabetic complications are few and exhibit limited efficacy. The enhanced cell-specificity, stability, biocompatibility, and loading capacity of drugs are essential for the mitigation of diabetic complications. In the article, we have critically discussed the recent studies over the past two years in material sciences and biochemistry. The insightful concepts in these studies drive the development of novel nanoparticles and mesenchymal stem cells-derived extracellular vesicles to meet the need for treatment of diabetic complications. Their underlying biochemical principles, advantages and limitations have been in-depth analyzed. The nanoparticles discussed in the article include double-headed nanodelivery system, nanozyme, ESC-HCM-B system, soft polymer nanostars, tetrahedral DNA nanostructures and hydrogels. They ameliorate the diabetic complication through attenuation of inflammation, apoptosis and restoration of metabolic homeostasis. Moreover, mesenchymal stem cell-derived extracellular vesicles efficiently deliver therapeutic proteins to the retinal cells to suppress the angiogenesis, inflammation, apoptosis and oxidative stress to reverse diabetic retinopathy. Collectively, we provide a critical discussion on the concept, mechanism and therapeutic applicability of new delivery tools to treat these three devastating diabetic complications.

Regression of Neovascularization after Panretinal Photocoagulation Combined with Anti-VEGF Injection for Proliferative Diabetic Retinopathy-A Review

Proliferative diabetic retinopathy (PDR) poses a significant therapeutic problem that often results in severe visual loss. Panretinal photocoagulation (PRP) has long been a mainstay treatment for this condition. Conversely, intravitreal anti-VEGF therapy has served as an alternative treatment for PDR. This review aimed to evaluate the effects of PRP combined with anti-VEGF therapy on the regression of neovascularization (NV), including functional outcomes and incidence of complications. The MEDLINE database was searched for articles evaluating regression of NV using a combination of the following terms: "proliferative diabetic retinopathy", "anti-VEGF", "panretinal photocoagulation", and "combined treatment". The search yielded a total of 22 articles. The analysis of their results indicated PRP combined with ant-VEGF therapy as superior over PRP alone in the management of PDR. Combination treatment yields better and faster regression of NV and a lower incidence of serious complications, such as vitreous hemorrhage and the need for pars plana vitrectomy. Nevertheless, complete regression of NV is not achieved in a significant proportion of patients. Further research is needed to establish the most effective schedule for intravitreal injections as an adjunct to PRP. The current literature shows that in some cases, cessation of anti-VEGF injection in combination treatment for PDR can lead to relapse of NV.

PACAP-ADNP axis prevents outer retinal barrier breakdown and choroidal neovascularization by interfering with VEGF secreted from retinal pigmented epitelium cells

During diabetic retinopathy (DR) progression, the retina undergoes various metabolic changes, including hypoxia-signalling cascade induction in the cells of retinal pigmented epithelium (RPE). The overexpression of hypoxic inducible factors causes transcription of many target genes including vascular endothelial growth factor (VEGF). The RPE cells form the outer blood retinal barrier (oBRB), a specialized structure that regulates ions and metabolites flux into the retina to maintain a suitable quality of its extracellular microenvironment. VEGF worsens retinal condition since its secretion from the basolateral compartment of RPE cells compromises the barrier's integrity and induces choroidal neovascularization. In this work, we hypothesized that PACAP prevents the damage to oBRB and controls choroidal neovascularization through the induction of ADNP. Firstly, we demonstrated that ADNP is expressed in Streptozotocin (STZ)-induced diabetic animals. To validate our hypothesis, we cultured endothelial cells (H5V) forming vessels-like structures, in a conditioned medium (CM) derived from ARPE-19 cells exposed to hyperglycaemic/hypoxic insult, containing a known VEGF concentration. The involvement of PACAP-ADNP axis on oBRB integrity was evaluated through the measurement of trans-epithelial-electrical resistance and permeability assay performed on ARPE cell monolayer cultured in CM and by analysing the expression of two tight junction forming proteins, ZO1 and occludin. By culturing H5V in CM, we demonstrated that PACAP-ADNP axis counteracted vessels-like structures formation promoted by VEGF. In conclusion, the results suggested a primary role of PACAP/ADNP axis in preventing oBRB damage and in controlling aberrant choroidal neovascularization induced by VEGF secreted from RPE cells exposed to hyperglycaemia/hypoxic insult in DR.

1,8-Cineole ameliorates diabetic retinopathy by inhibiting retinal pigment epithelium ferroptosis via PPAR-γ/TXNIP pathways

1,8-Cineole, the main component of volatile oil in aromatic plants, has diverse pharmacological properties, including antioxidant, anti-inflammatory, and anti-cancer properties. Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus (DM). Here, we investigated the protective effect of 1,8-cineole on DR and found that 1,8-cineole treatment could alter the expression of several genes in both high glucose (HG)-induced ARPE-19 cells and retinal tissues of DM mice, as well as inhibit ferroptosis. Subsequent investigations into the molecular mechanisms underlying this inhibition revealed that expression of thioredoxin-interacting protein (TXNIP) was significantly upregulated while that of peroxisome proliferator-activated receptor γ (PPAR-γ) was significantly downregulated in HG-induced ARPE-19 cells, and treatment with 1,8-cineole could effectively reverse these changes. Treatment with a PPAR-γ pharmacological agonist (rosiglitazone), alone or combined with 1,8-cineole, significantly inhibited the transcription of TXNIP and ferroptosis in HG-induced ARPE-19 cells. Conversely, pretreatment with GW9662, a PPAR-γ inhibitor, upregulated the transcription and expression of TXNIP in HG-induced ARPE-19 cells; 1,8-cineole failed to reverse this upregulated expression. To explore these relationships, we constructed a PPAR-γ adenovirus shRNA to elucidate the effect of 1,8-cineole on the negative regulation of TXNIP by PPAR-γ. Taken together, the present findings indicate that HG-induced ferroptosis in retinal tissue plays an essential role in the pathogenesis of DR, which can be ameliorated by 1,8-cineole.

Vaccinium as Potential Therapy for Diabetes and Microvascular Complications

Diabetes mellitus is one of the most critical global health concerns, with a fast-growing prevalence. The incidence of diabetic vascular complications is also rapidly increasing, exacerbating the burden on individuals with diabetes and the consumption of public medical resources. Despite the overall improvements in the prevention, diagnosis, and treatment of diabetic microvascular complications in recent years, safe and effective alternative or adjunctive therapies are urgently needed. The mechanisms underlying diabetic vascular complications are complex, with hyperglycemia-induced oxidative stress and inflammation being the leading causes. Therefore, glycemic control, antioxidation, and anti-inflammation are considered the main targets for the treatment of diabetes and its vascular comorbidities. Vaccinium L. (Ericaceae) is a genus of plants enriched with polyphenolic compounds in their leaves and fruits. Vaccinium and its extracts have demonstrated good bioactivity in reducing blood glucose, oxidative stress, and inflammation, making them excellent candidates for the management of diabetes and diabetic vascular complications. Here, we review recent preclinical and clinical studies on the potential effect of Vaccinium on ameliorating diabetes and diabetic complications, particularly diabetic kidney disease and diabetic retinopathy.

Antioxidant Phytochemicals as Potential Therapy for Diabetic Complications

The global prevalence of diabetes continues to increase partly due to rapid urbanization and an increase in the aging population. Consequently, this is associated with a parallel increase in the prevalence of diabetic vascular complications which significantly worsen the burden of diabetes. For these diabetic vascular complications, there is still an unmet need for safe and effective alternative/adjuvant therapeutic interventions. There is also an increasing urge for therapeutic options to come from natural products such as plants. Hyperglycemia-induced oxidative stress is central to the development of diabetes and diabetic complications. Furthermore, oxidative stress-induced inflammation and insulin resistance are central to endothelial damage and the progression of diabetic complications. Human and animal studies have shown that polyphenols could reduce oxidative stress, hyperglycemia, and prevent diabetic complications including diabetic retinopathy, diabetic nephropathy, and diabetic peripheral neuropathy. Part of the therapeutic effects of polyphenols is attributed to their modulatory effect on endogenous antioxidant systems. This review attempts to summarize the established effects of polyphenols on endogenous antioxidant systems from the literature. Moreover, potential therapeutic strategies for harnessing the potential benefits of polyphenols for diabetic vascular complications are also discussed.

The role of aldosterone in the pathogenesis of diabetic retinopathy

Aldosterone, as a mineralocorticoid of adrenal origin, has effects that are not limited to the urinary tract. As an important regulator in Vasoactive hormone pathways, aldosterone may play an effect in the pathogenesis of diabetic retinopathy (DR) through the regulation of oxidative stress, vascular regulation, and inflammatory mechanisms. This implies that mineralocorticoids, including aldosterone, have great potential and value for the diagnosis and treatment of DR. Because early studies did not focus on the intrinsic association between mineralocorticoids and DR, targeted research is still in its infancy and there are still many obstacles to its application in the clinical setting. Recent studies have improved the understanding of the effects of aldosterone on DR, and we review them with the aim of exploring possible mechanisms for the treatment and prevention of DR.