Brivanib, a multitargeted small‐molecule tyrosine kinase inhibitor, suppresses laser‐induced CNV in a mouse model of neovascular AMD

Olink Profiling of Aqueous Humor Identifies Novel Biomarkers for Wet Age-Related Macular Degeneration

Metabolic dysfunction is recognized as a contributing factor in the pathogenesis of wet age-related macular degeneration (wAMD). However, the specific metabolism-related proteins implicated in wAMD remain elusive. In this study, we assessed the expression profiles of 92 metabolism-related proteins in aqueous humor (AH) samples obtained from 44 wAMD patients and 44 cataract control patients. Our findings revealed significant alterations in the expression of 60 metabolism-related proteins between the two groups. Notably, ANGPTL7 and METRNL displayed promising diagnostic potential for wAMD, as evidenced by area under the curve values of 0.88 and 0.85, respectively. Subsequent validation studies confirmed the upregulation of ANGPTL7 and METRNL in the AH of wAMD patients and in choroidal neovascularization (CNV) models. Functional assays revealed that increased ANGPTL7 and METRNL played a pro-angiogenic role in endothelial biology by promoting endothelial cell proliferation, migration, tube formation, and spouting in vitro. Moreover, in vivo studies revealed the pro-angiogenic effects of ANGPTL7 and METRNL in CNV formation. In conclusion, our findings highlight the association between elevated ANGPTL7 and METRNL levels and wAMD, suggesting their potential as novel predictive and diagnostic biomarkers for this condition. These results underscore the significance of ANGPTL7 and METRNL in the context of wAMD pathogenesis and offer new avenues for future research and therapeutic interventions.

Research progress of VEGFR small molecule inhibitors in ocular neovascular diseases

Angiogenesis is the biological process in which existing blood vessels generate new ones and it is essential for body growth and development, wound healing, and granulation tissue formation. Vascular endothelial growth factor receptor (VEGFR) is a crucial cell membrane receptor that binds to VEGF to regulate angiogenesis and maintenance. Dysregulation of VEGFR signaling can lead to several diseases, such as cancer and ocular neovascular disease, making it a crucial research area for disease treatment. Currently, anti-VEGF drugs commonly used in ophthalmology are mainly four macromolecular drugs, Bevacizumab, Ranibizumab, Conbercept and Aflibercept. Although these drugs are relatively effective in treating ocular neovascular diseases, their macromolecular properties, strong hydrophilicity, and poor blood-eye barrier penetration limit their efficacy. However, VEGFR small molecule inhibitors possess high cell permeability and selectivity, allowing them to traverse and bind to VEGF-A specifically. Consequently, they have a shorter duration of action on the target, and they offer significant therapeutic benefits to patients in the short term. Consequently, there is a need to develop small molecule inhibitors of VEGFR to target ocular neovascularization diseases. This review summarizes the recent developments in potential VEGFR small molecule inhibitors for the targeted treatment of ocular neovascularization diseases, with the aim of providing insights for future studies on VEGFR small molecule inhibitors.

JP1, a polypeptide specifically targeting integrin αVβ3, ameliorates choroidal neovascularization and diabetic retinopathy in mice

Anti-vascular endothelial growth factor (VEGF) drugs have revolutionized the treatment of neovascular eye diseases, but responses are incomplete in some patients. Recent evidence shows that integrins are involved in the pathogenesis of neovascular age-related macular degeneration and diabetic retinopathy. JP1, derived from an optimized seven-amino-acid fragment of JWA protein, is a polypeptide specifically targeting integrin αVβ3. In this study we evaluated the efficacy of JP1 on laser-induced choroidal neovascularization (CNV) and retinal vascular leakage. CNV mice received a single intravitreal (IVT) injection of JP1 (10, 20, 40 µg) or ranibizumab (RBZ, 10 µg). We showed that JP1 injection dose-dependently inhibited laser-induced CNV; the effect of RBZ was comparable to that of 20 µg JP1; a combined IVT injection of JP1 (20 μg) and RBZ (5 μg) exerted a synergistic effect on CNV. In the 3rd month after streptozotocin injection, diabetic mice receiving IVT injection of JP1 (40 µg) or RBZ (10 µg) once a week for 4 weeks showed significantly suppressed retinal vascular leakage. In both in vivo and in vitro experiments, JP1 counteracted oxidative stress and inflammation via inhibiting ROS/NF-κB signaling in microglial cells, and angiogenesis via modulating MEK1/2-SP1-integrin αVβ3 and TRIM25-SP1-MMP2 axes in vascular endothelial cells. In addition, intraperitoneal injection of JP1 (1, 5 or 10 mg) once every other day for 3 times also dose-dependently inhibited CNV. After intraperitoneal injection of FITC-labeled JP1 (FITC-JP1) or FITC in laser-induced CNV mice, the fluorescence intensity in the CNV lesion was markedly increased in FITC-JP1 group, compared with that in FITC group, confirming that JP1 could penetrate the blood-retinal barrier to target CNV lesion. We conclude that JP1 can be used to design novel CNV-targeting therapeutic agents that may replace current invasive intraocular injections.

Emerging therapeutic strategies for unmet need in neovascular age-related macular degeneration

Neovascular age-related macular degeneration (nAMD) is a major cause of visual impairment and blindness. Anti-vascular endothelial growth factor (VEGF) agents, such as ranibizumab, bevacizumab, aflibercept, brolucizumab and faricimab have revolutionized the clinical management of nAMD. However, there remains an unmet clinical need for new and improved therapies for nAMD, since many patients do not respond optimally, may lose response over time or exhibit sub-optimal durability, impacting on real world effectiveness. Evidence is emerging that targeting VEGF-A alone, as most agents have done until recently, may be insufficient and agents that target multiple pathways (e.g., aflibercept, faricimab and others in development) may be more efficacious. This article reviews issues and limitations that have arisen from the use of existing anti-VEGF agents, and argues that the future may lie in multi-targeted therapies including alternative agents and modalities that target both the VEGF ligand/receptor system as well as other pathways.

Role of protein phosphorylation in cell signaling, disease, and the intervention therapy

Protein phosphorylation is an important post-transcriptional modification involving an extremely wide range of intracellular signaling transduction pathways, making it an important therapeutic target for disease intervention. At present, numerous drugs targeting protein phosphorylation have been developed for the treatment of various diseases including malignant tumors, neurological diseases, infectious diseases, and immune diseases. In this review article, we analyzed 303 small-molecule protein phosphorylation kinase inhibitors (PKIs) registered and participated in clinical research obtained in a database named Protein Kinase Inhibitor Database (PKIDB), including 68 drugs approved by the Food and Drug Administration of the United States. Based on previous classifications of kinases, we divided these human protein phosphorylation kinases into eight groups and nearly 50 families, and delineated their main regulatory pathways, upstream and downstream targets. These groups include: protein kinase A, G, and C (AGC) and receptor guanylate cyclase (RGC) group, calmodulin-dependent protein kinase (CaMK) group, CMGC [Cyclin-dependent kinases (CDKs), Mitogen-activated protein kinases (MAPKs), Glycogen synthase kinases (GSKs), and Cdc2-like kinases (CLKs)] group, sterile (STE)-MAPKs group, tyrosine kinases (TK) group, tyrosine kinase-like (TKL) group, atypical group, and other groups. Different groups and families of inhibitors stimulate or inhibit others, forming an intricate molecular signaling regulatory network. This review takes newly developed new PKIs as breakthrough point, aiming to clarify the regulatory network and relationship of each pathway, as well as their roles in disease intervention, and provide a direction for future drug development.

Recent Advances in Age-Related Macular Degeneration Therapies

Age-related macular degeneration (AMD) was described for the first time in the 1840s and is currently the leading cause of blindness for patients over 65 years in Western Countries. This disease impacts the eye’s posterior segment and damages the macula, a retina section with high levels of photoreceptor cells and responsible for the central vision. Advanced AMD stages are divided into the atrophic (dry) form and the exudative (wet) form. Atrophic AMD consists in the progressive atrophy of the retinal pigment epithelium (RPE) and the outer retinal layers, while the exudative form results in the anarchic invasion by choroidal neo-vessels of RPE and the retina. This invasion is responsible for fluid accumulation in the intra/sub-retinal spaces and for a progressive dysfunction of the photoreceptor cells. To date, the few existing anti-AMD therapies may only delay or suspend its progression, without providing cure to patients. However, in the last decade, an outstanding number of research programs targeting its different aspects have been initiated by academics and industrials. This review aims to bring together the most recent advances and insights into the mechanisms underlying AMD pathogenicity and disease evolution, and to highlight the current hypotheses towards the development of new treatments, i.e., symptomatic vs. curative. The therapeutic options and drugs proposed to tackle these mechanisms are analyzed and critically compared. A particular emphasis has been given to the therapeutic agents currently tested in clinical trials, whose results have been carefully collected and discussed whenever possible.

3D-Cultured Vascular-Like Networks Enable Validation of Vascular Disruption Properties of Drugs In Vitro

Vascular-disrupting agents are an interesting class of anticancer compounds because of their combined mode of action in preventing new blood vessel formation and disruption of already existing vasculature in the immediate microenvironment of solid tumors. The validation of vascular disruption properties of these drugs in vitro is rarely addressed due to the lack of proper in vitro angiogenesis models comprising mature and long-lived vascular-like networks. We herein report an indirect coculture model of human umbilical vein endothelial cells (HUVECs) and human dermal fibroblasts (HDFs) to form three-dimensional profuse vascular-like networks. HUVECs embedded and sandwiched in the collagen scaffold were cocultured with HDFs located outside the scaffold. The indirect coculture approach with the vascular endothelial growth factor (VEGF) producing HDFs triggered the formation of progressively maturing lumenized vascular-like networks of endothelial cells within less than 7 days, which have proven to be viably maintained in culture beyond day 21. Molecular weight-dependent Texas red-dextran permeability studies indicated high vascular barrier function of the generated networks. Their longevity allowed us to study the dose-dependent response upon treatment with the three known antiangiogenic and/or vascular disrupting agents brivanib, combretastatin A4 phosphate (CA4P), and 6´-sialylgalactose (SG) via semi-quantitative brightfield and qualitative confocal laser scanning microscopic (CLSM) image analysis. Compared to the reported data on in vivo efficacy of these drugs in terms of antiangiogenic and vascular disrupting effects, we observed similar trends with our 3D model, which are not reflected in conventional in vitro angiogenesis assays. High-vascular disruption under continuous treatment of the matured vascular-like network was observed at concentrations ≥3.5 ng·ml⁻¹ for CA4P and ≥300 nM for brivanib. In contrast, SG failed to induce any significant vascular disruption in vitro. This advanced model of a 3D vascular-like network allows for testing single and combinational antiangiogenic and vascular disrupting effects with optimized dosing and may thus bridge the gap between the in vitro and in vivo experiments in validating hits from high-throughput screening. Moreover, the physiological 3D environment mimicking in vitro assay is not only highly relevant to in vivo studies linked to cancer but also to the field of tissue regeneration.

Non-neglectable therapeutic options for age-related macular degeneration: A promising perspective from traditional Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Age-related macular degeneration (AMD) is a chronic neurodegenerative disease which causes irreversible central vision loss among the elderly population. Traditional Chinese Medicine (TCM), including formulas, acupuncture and herbs, has been used in the treatment of AMD for thousands of years and is currently used by many AMD patients around the world.

AIM OF THE REVIEW

A comprehensive, in-depth literature review examining the use of TCM in the treatment of AMD has yet to be compiled. This review will improve current knowledge relating to the use of TCM and will open new avenues of exploration in developing new drugs for the treatment of AMD.

METHODS

A literature search of the PubMed database, Web of Science, Google Scholar and China National Knowledge Infrastructure (CNKI) was performed using relevant terms and keywords related to TCM in the treatment of AMD. Related books, PhD and master's theses were also researched.

RESULTS

The TCM-based interpretation of AMD has been used to establish a theoretical foundation for understanding the effect of TCM formulas and acupuncture on AMD. The possible mechanism of action of common Chinese herbs has also been discussed in detail.

CONCLUSION

TCM is a promising treatment option of AMD patients. However, lack of rigorous scientific evidence has limited the impact and uptake of TCM therapy. Future research should focus on improving understanding of the mechanism of action and bioactive components of TCM therapies.

Zebrafish Model in Ophthalmology to Study Disease Mechanism and Drug Discovery

Visual impairment and blindness are common and seriously affect people’s work and quality of life in the world. Therefore, the effective therapies for eye diseases are of high priority. Zebrafish (Danio rerio) is an alternative vertebrate model as a useful tool for the mechanism elucidation and drug discovery of various eye disorders, such as cataracts, glaucoma, diabetic retinopathy, age-related macular degeneration, photoreceptor degeneration, etc. The genetic and embryonic accessibility of zebrafish in combination with a behavioral assessment of visual function has made it a very popular model in ophthalmology. Zebrafish has also been widely used in ocular drug discovery, such as the screening of new anti-angiogenic compounds or neuroprotective drugs, and the oculotoxicity test. In this review, we summarized the applications of zebrafish as the models of eye disorders to study disease mechanism and investigate novel drug treatments.

Zebrafish as an Animal Model for Ocular Toxicity Testing: A Review of Ocular Anatomy and Functional Assays

Xenobiotics make their way into organisms from diverse sources including diet, medication, and pollution. Our understanding of ocular toxicities from xenobiotics in humans, livestock, and wildlife is growing thanks to laboratory animal models. Anatomy and physiology are conserved among vertebrate eyes, and studies with common mammalian preclinical species (rodent, dog) can predict human ocular toxicity. However, since the eye is susceptible to toxicities that may not involve a histological correlate, and these species rely heavily on smell and hearing to navigate their world, discovering visual deficits can be challenging with traditional animal models. Alternative models capable of identifying functional impacts on vision and requiring minimal amounts of chemical are valuable assets to toxicology. Human and zebrafish eyes are anatomically and functionally similar, and it has been reported that several common human ocular toxicants cause comparable toxicity in zebrafish. Vision develops rapidly in zebrafish; the tiny larvae rely on visual cues as early as 4 days, and behavioral responses to those cues can be monitored in high-throughput fashion. This article describes the comparative anatomy of the zebrafish eye, the notable differences from the mammalian eye, and presents practical applications of this underutilized model for assessment of ocular toxicity.

Blocking VEGF signaling augments interleukin-8 secretion via MEK/ERK/1/2 axis in human retinal pigment epithelial cells

AIM

To identify proangiogenic factors engaged in neovascular age-related macular degeneration (AMD) except vascular endothelial growth factor (VEGF) from human retinal pigment epithelial (hRPE) cells and investigate the underlying mechanisms.

METHODS

VEGF receptor 2 (VEGFR2) in ARPE-19 cells was depleted by siRNA transfection or overexpressed through adenovirus infection. The mRNA and the protein levels of interleukin-8 (IL-8) in ARPE-19 cells were measured by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay respectively. The protein levels of AKT, p-AKT, MEK, p-MEK, ERK1/2, p-ERK1/2, JNK, p-JNK, p38 and p-p38 were detected by Western blotting. A selective chemical inhibitor, LY3214996, was employed to inhibit phosphorylation of ERK1/2. Cell viability was determined by MTT assay.

RESULTS

Knockdown of VEGFR2 in ARPE-19 cells robustly augmented IL-8 production at both the mRNA and the protein levels. Silencing VEGFR2 substantially enhanced phosphorylation of MEK and ERK1/2 while exerted no effects on phosphorylation of AKT, JNK and p38. Inhibiting ERK1/2 phosphorylation by LY3214996 reversed changes in VEGFR2 knockdown-induced IL-8 upregulation at the mRNA and the protein levels with no effects on cell viability. VEGFR2 overexpression significantly reduced IL-8 generation at the mRNA and the protein levels.

CONCLUSION

Blockade of VEGF signaling augments IL-8 secretion via MEK/ERK1/2 axis and overactivation of VEGF pathway decreases IL-8 production in hRPE cells. Upregulated IL-8 expression after VEGF signaling inhibition in hRPE cells may be responsible for being incompletely responsive to anti-VEGF remedy in neovascular AMD, and IL-8 may serve as an alternative therapeutic target for neovascular AMD.

Experimental Models in Neovascular Age Related Macular Degeneration

Neovascular age-related macular degeneration (vAMD), characterized by the neo-vascularization of the retro-foveolar choroid, leads to blindness within few years. This disease depends on angiogenesis mediated by the vascular endothelial growth factor A (VEGF) and to inflammation. The only available treatments consist of monthly intravitreal injections of antibodies directed against VEGF or VEGF/VEGFB/PlGF decoy receptors. Despite their relative efficacy, these drugs only delay progression to blindness and 30% of the patients are insensitive to these treatments. Hence, new therapeutic strategies are urgently needed. Experimental models of vAMD are essential to screen different innovative therapeutics. The currently used in vitro and in vivo models in ophthalmic translational research and their relevance are discussed in this review.

APOE2 promotes the development and progression of subretinal neovascularization in age-related macular degeneration via MAPKs signaling pathway

Background

Neovascular age-related macular degeneration (nvAMD) is one of the main pathological features of wet AMD. Apolipoprotein E2 is involved in the formation of nvAMD but the molecular mechanism has not been reported.

Methods

The APOE alleles in AMD patients were detected by genotyping. Mouse models were divided into 4 groups according to transfection different gene segments and laser-induced treatment. APOE2, VEGF, PDGF-BB, b-FGF and inflammatory cytokines (including p-NF-κB, TNF-α, IL-1β and IL-6) were tested by ELISA in mice retinal lysate. The formation of nvAMD in the indicated treatment groups at 3rd, 7th and 14th day after laser-induced damage were detected by FFA. Besides, qRT-PCR was used to determine the mRNA levels of p38, JNK and ERK in ARPE-19 cells. Finally, the inflammatory cytokines and MAPK proteins (including P38, p-P38, JNK, p-JNK, ERK and p-ERK) were detected by western blot.

Results

The statistics of APOE alleles showed that APOE2 allele carriers were more likely to nvAMD. VEGF, PDGF-BB, b-FGF and related inflammatory cytokines were up-regulated significantly after treatment with APOE2, which were reduced after silencing the MAPK family genes, however. Further, the expression levels of neovascular growth factors and inflammatory cytokines were highly consistent between mouse models and ARPE-19 cells. Besides, the phosphorylation levels of p38, JNK and ERK were affected by APOE2.

Conclusion

nvAMD was affected directly by the overexpression of VEGF, PDGF-BB and b-FGF, which were regulated by APOE2 through activating MAPKs pathway.

Establishing a mouse model of choroidal neovascularization to study the therapeutic effect of levotinib and its mechanism

Objective

To study the therapeutic effect and mechanism of levotinib on choroidal neovascularization (CNV) in mice.

Methods

45 healthy C57BL/6 mice were selected and randomly divided into three groups: control group (group A), model group (group B) and levotinib group (group C). The model of CNV in mice was established. The fluorescence leakage of choroidal lesions in mice was observed by fundus fluorescein angiography. The morphological changes of retinal vessels in mice were observed by retinal slice preparation, the pathological changes of eyeball tissues in mice were observed by hematoxylin-eosin (HE) staining, the expression of vascular endothelial growth factor (VEGF) in mice retina was detected by real-time quantitative fluorescence PCR, and the protein expression of VEGF in mice retina was detected by Western blotting.

Result

On the 7th, 14th and 21st day after modeling, compared with group B, the fluorescence leakage area of group C mice was significantly reduced, and the difference was statistically significant (P < 0.05). The morphology of retinal vessels in group A was normal. In group B, the retinal vessels showed large areas of ischemia without perfusion and abundant neovascularization clusters and capillaries. Compared with group B, the morphology of retinal vessels in group C was significantly improved. Group A mice had normal eyeball structure, group B mice had visible spindle-like damage to the inner and outer retina, while group C mice had significantly less spindle-like damage than group B. Compared with group A, group B mice had significantly higher expression of retinal VEGF and the difference was statistically significant (P < 0.05), but compared with group B mice, the expression of VEGF in the retina of mice in group C was significantly decreased, and the difference was statistically significant (P < 0.05). Compared with group A, the expression of VEGF in retina of group B mice was significantly increased, and the difference was statistically significant (P < 0.05). Compared with group B, the expression of VEGF in retina of group C mice was significantly decreased, and the difference was statistically significant (P < 0.05).

Conclusion

Levatinib has obvious therapeutic effect on CNV, which may be achieved by inhibiting the high expression of VEGF in CNV.

Cabozantinib, a Multityrosine Kinase Inhibitor of MET and VEGF Receptors Which Suppresses Mouse Laser-Induced Choroidal Neovascularization

Choroidal neovascularization (CNV) is a leading cause of blindness in the elderly in developed countries and is particularly associated with age-related macular degeneration (AMD). Cabozantinib (CBZ) hinders the activation of multiple receptor tyrosine kinases involved in tumor angiogenesis, such as hepatocyte growth factor receptor (MET) and vascular endothelial growth factor receptor 2 (VEGFR2). We aimed to investigate the role and mechanism of CBZ in a mouse laser-induced CNV model. In zebrafish embryos, CBZ perturbed intersegmental vessel (ISV) formation without obvious neurodevelopment impairment. In the mouse laser-induced CNV model, phosphorylated hepatocyte growth factor receptor (p-MET) and phosphorylated vascular endothelial growth factor receptor 2 (p-VEGFR2) were increased in the CNV region. CBZ intravitreal injection or oral gavage alleviated CNV leakage and the CNV lesion area without obvious intraocular toxicity, as well as disturbed the phosphorylation of MET and VEGFR2. Additionally, CBZ downregulated the expression of the hepatocyte growth factor (HGF) with no effect on the expression of the vascular endothelial growth factor (VEGF). CBZ downregulated HGF, p-MET, and p-VEGFR2 expressions in vitro, as well as inhibited the proliferation, migration, and tube formation of b-End3 cells. In summary, CBZ alleviates mouse CNV formation possibly via inhibiting the activation of MET and VEGFR2. The findings provide a novel potential therapy method for CNV patients.