Natural product inhibitors of ocular angiogenesis

Phytochemicals From Salvia substolonifera With Anti-Angiogenic Properties and Substolide H Decreased Oxygen-Induced Retinal Neovascularization

Retinal neovascularization is a pathological feature of ischemic retinopathy. Current therapeutic approaches are limited, and additional treatment options are needed. This study aims to discover lead compounds from Salvia substolonifera that inhibit angiogenesis. As a result, an undescribed norditerpene lactone, substolide H (3), and eight known compounds (1, 2, and 4-9) have been isolated. The structure was elucidated using synthetic spectroscopy and electron circular dichroism. Compounds 2, 3, 5, 7, and 9 inhibited human umbilical vein endothelial cells (HUVEC) proliferation with IC50 values of 26.47, 6.10, 43.27, 36.81, and 35.11 µM, respectively. Compounds 2, 3, and 7 inhibited HUVEC migration with IC50 values of 12.48, 8.37, and 7.63 µM, respectively. Further studies have shown that the substolide H (3) suppresses tube formation in human umbilical vein endothelial cells and that intravitreous administration suppresses retinal neovascularization in oxygen-induced retinopathy mice. Turning to its mechanism of action, we have shown that the anti-angiogenic effect of the substolide H may be through the downregulation of vascular endothelial growth factor expression and the phosphorylation of VEGFR2, ERK1/2, and protein kinase B. Our study represents the first report of these anti-angiogenic compounds from this plant, and substolide H may be a potential candidate for the treatment of retinal neovascularization.

Therapeutic potential of elema-1,3,7(11),8-tetraen-8,12-lactam from Curcuma wenyujin on diabetic retinopathy via anti-inflammatory and anti-angiogenic pathways

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine, the causes of diabetic retinopathy (DR) are blood stasis and heat. Curcuma wenyujin Y. H. Chen & C. Ling and its extracts have the effects of promoting blood circulation to remove blood stasis, clearing the heart, and cooling the blood, and have been used in the treatment of DR. Elema-1,3,7 (11),8-tetraen-8,12-lactam (Ele), an N-containing sesquiterpene isolated from this plant. However, the anti-inflammatory and anti-angiogenic effects of Ele and its therapeutic potential in DR are still unknown.

AIM OF THE STUDY

To evaluate the anti-inflammatory and anti-angiogenic effects of Ele and its therapeutic potential in DR.

MATERIALS AND METHODS

In vitro, anti-inflammatory and anti-angiogenic effects were assessed using TNF-α or VEGF-stimulated HUVECs. Protein expression was analyzed using Western blotting. ICAM-1 and TNF-α mRNA expressions were analyzed using real-time quantitative RT-PCR. The therapeutic potential in DR was assessed using both animal models of STZ-induced diabetes and oxygen-induced retinopathy. The retinal vascular permeability was measured using Evans blue, and the quantitation of retinal leukostasis using FITC-coupled Con A. The retinal neovascular tufts were analyzed using fluorescein angiography and counting pre-retinal vascular lumens.

RESULTS

Ele inhibited NF-κB pathway, and ICAM-1, TNF-α mRNA expression in TNF-α- stimulated HUVECs. It also inhibits the multistep process of angiogenesis by inhibiting the phosphorylation of VEGFR2 and its downstream signaling kinases Src, Erk1/2, Akt, and mTOR in VEGF-stimulated HUVECs. Intravitreal injection of Ele can significantly reduce retinal microvascular leakage, leukostasis, and expression of ICAM-1, TNF-α in diabetic rats and inhibits oxygen-induced retinal neovascularization and VEGFR2 phosphorylation in OIR mice.

CONCLUSIONS

Ele has anti-inflammatory and anti-angiogenic effects through inhibiting NF-κB and VEGFR2 signaling pathways, and it may be a potential drug candidate for DR.

Pharmacological modulation of Sonic Hedgehog signaling pathways in Angiogenesis: A mechanistic perspective

The Sonic hedgehog (SHh) signaling pathway is an imperative operating network that helps in regulates the critical events during the development processes like multicellular embryo growth and patterning. Disruptions in SHh pathway regulation can have severe consequences, including congenital disabilities, stem cell renewal, tissue regeneration, and cancer/tumor growth. Activation of the SHh signal occurs when SHh binds to the receptor complex of Patch (Ptc)-mediated Smoothened (Smo) (Ptc-smo), initiating downstream signaling. This review explores how pharmacological modulation of the SHh pathway affects angiogenesis through canonical and non-canonical pathways. The canonical pathway for angiogenesis involves the activation of angiogenic cytokines such as fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), placental growth factor (PGF), hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF), stromal cell-derived factor 1α, transforming growth factor-β1 (TGF-β1), and angiopoietins (Ang-1 and Ang-2), which facilitate the process of angiogenesis. The Non-canonical pathway includes indirect activation of certain pathways like iNOS/Netrin-1/PKC, RhoA/Rock, ERK/MAPK, PI3K/Akt, Wnt/β-catenin, Notch signaling pathway, and so on. This review will provide a better grasp of the mechanistic approach of SHh in mediating angiogenesis, which can aid in the suppression of certain cancer and tumor growths.

Highly water-soluble diacetyl chrysin ameliorates diabetes-associated renal fibrosis and retinal microvascular abnormality in db/db mice

BACKGROUND/OBJECTIVES

Chronic or intermittent hyperglycemia is associated with the development of diabetic complications. Oxidative stress and inflammation can be altered by hyperglycemia in diverse tissues, including kidneys and eyes, and play a pivotal role in diabetic complications. Our previous studies showed that the water-insoluble 5,7-dihydroxyflvone chrysin effectively combats diabetic damages incurred in diabetic kidneys and retinas. The current study employed the newly-synthesized 5.7-di-O-acetylchrysin, having higher solubility than chrysin, to compare the effects on diabetes-associated renal fibrosis and abnormal retinal neovascularization.

MATERIALS/METHODS

In the in vivo study, db/db mice as animal models of type 2 diabetes were orally administrated 10 mg/kg BW diacetylchrysin, daily for 10 weeks.

RESULTS

Unlike chrysin, oral administration of 10 mg/kg diacetylchrysin did not lower the blood glucose level and 24 h urine volume in db/db mice. Nevertheless, the urinary albumin excretion was markedly reduced. The administration of diacetylchrysin also diminished the deposition of collagen fibers in diabetic glomeruli and tubules by suppressing the induction of connective tissue growth factor and collagen IV in diabetic kidneys. Supplying diacetylchrysin enhanced the membrane type-1 matrix metalloproteinase (MMP) expression reduced in diabetic kidneys, while the tissue inhibitor of MMP-2 induction was attenuated in diacetylchrysin-challenged diabetic kidneys. In addition, supplementing diacetylchrysin to diabetic mice ameliorated renal injury due to glomerulosclerosis and tubular interstitial fibrosis. Furthermore, the reduced retinal inductions of Zonula occludens-1 and vascular endothelial cadherin in db/db mice were elevated in the retinal tissues of diacetylchrysin-treated animals. Oral administration of diacetylchrysin curtailed the induction of vascular endothelial growth factor (VEGF) and VEGF receptor 2 in db/db mice, ultimately retarding diabetes-associated retinal neovascularization. Additionally, the retinal formation of acellular capillaries with leaky vessels was reduced in diacetylchrysin-treated db/db mice.

CONCLUSION

Diacetylchrysin may act as a potent pro-health agent for treating renal fibrosis-associated diabetic nephropathy and retinal neovascularization-associated diabetic retinopathy.

Antiangiogenic Pterocarpan and Flavonoid Constituents of Erythrina lysistemon

The roots of Erythrina lysistemon, growing in Egypt, yielded 24 flavonoid compounds, including 17 pterocarpans, two isoflavanones, one flavanone, two isoflavans, one 2-arylbenzofuran, and an isoflava-3-ene. Nine pterocarpans have not been reported previously (7-9, 11-14, 19, and 20), and 11 are reported here for the first time from this species. Structures were established using HRESIMS, NMR, and circular dichroism techniques. Selected compounds were tested for their ability to block the growth of human retinal endothelial cells and antiangiogenic activity in vitro. The isoflavonoids 5 and 6, and the pterocarpans 1, 2, 4, 20, and 22 demonstrated selective antiproliferative activities on endothelial cells compared to a nonendothelial cell type, with concentration-dependent antiangiogenic effects in vitro against HRECs, a cell type relevant to neovascular eye diseases.

Anticancer potential of oroxylin A: from mechanistic insight to synergistic perspectives

Oroxylin A (OA), a well-known constituent of the root of Scutellariae plants, has been used in ethnomedicine already for centuries in treating various neoplastic disorders. However, only recent molecular studies have revealed the different mechanisms behind its action, demonstrating antiproliferative, anti-inflammatory, and proapoptotic effects, restricting also the spread of cancer cells to distant organs. A variety of cellular targets and modulated signal transduction pathways regulated by OA have been determined in diverse cells derived from different malignant tissues. In this review article, these anticancer activities are thoroughly described, representing OA as a potential lead structure for the design of novel more potent anticancer medicines. In addition, co-effects of this natural compound with conventional anticancer agents are analyzed and the advantages provided by nanotechnological methods for more efficient application of OA are discussed. In this way, OA might represent an excellent example of using ethnopharmacological knowledge for designing modern medicines.

Quercetin: an effective polyphenol in alleviating diabetes and diabetic complications

Various studies, especially in recent years, have shown that quercetin has beneficial therapeutic effects in various human diseases, including diabetes. Quercetin has significant anti-diabetic effects and may be helpful in lowering blood sugar and increasing insulin sensitivity. Quercetin appears to affect many factors and signaling pathways involved in insulin resistance and the pathogenesis of type 2 of diabetes. TNFα, NFKB, AMPK, AKT, and NRF2 are among the factors that are affected by quercetin. In addition, quercetin can be effective in preventing and ameliorating the diabetic complications, including diabetic nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy, and affects the key mechanisms involved in the pathogenesis of these complications. These positive effects of quercetin may be related to its anti-inflammatory and anti-oxidant properties. In this article, after a brief review of the pathogenesis of insulin resistance and type 2 diabetes, we will review the latest findings on the anti-diabetic effects of quercetin with a molecular perspective. Then we will review the effects of quercetin on the key mechanisms of pathogenesis of diabetes complications including nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy. Finally, clinical trials investigating the effect of quercetin on diabetes and diabetes complications will be reviewed.

Recent Developments of Nanostructures for the Ocular Delivery of Natural Compounds

Ocular disorders comprising various diseases of the anterior and posterior segments are considered as the main reasons for blindness. Natural products have been identified as potential treatments for ocular diseases due to their anti-oxidative, antiangiogenic, and anti-inflammatory effects. Unfortunately, most of these beneficial compounds are characterised by low solubility which results in low bioavailability and rapid systemic clearance thus requiring frequent administration or requiring high doses, which hinders their therapeutic applications. Additionally, the therapeutic efficiency of ocular drug delivery as a popular route of drug administration for the treatment of ocular diseases is restricted by various anatomical and physiological barriers. Recently, nanotechnology-based strategies including polymeric nanoparticles, micelles, nanofibers, dendrimers, lipid nanoparticles, liposomes, and niosomes have emerged as promising approaches to overcome limitations and enhance ocular drug bioavailability by effective delivery to the target sites. This review provides an overview of nano-drug delivery systems of natural compounds such as thymoquinone, catechin, epigallocatechin gallate, curcumin, berberine, pilocarpine, genistein, resveratrol, quercetin, naringenin, lutein, kaempferol, baicalin, and tetrandrine for ocular applications. This approach involves increasing drug concentration in the carriers to enhance drug movement into and through the ocular barriers.

Rhodopsin as a Molecular Target to Mitigate Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a group of hereditary degenerative diseases affecting 1 of 4000 people worldwide and being the most prevalent cause of visual handicap among working populations in developed countries. These disorders are mainly related to the abnormalities in the rod G protein-coupled receptor (GPCR), rhodopsin reflected in the dysregulated membrane trafficking, stability and phototransduction processes that lead to progressive loss of retina function and eventually blindness. Currently, there is no cure for RP, and the therapeutic options are limited. Targeting rhodopsin with small molecule chaperones to improve the folding and stability of the mutant receptor is one of the most promising pharmacological approaches to alleviate the pathology of RP. This review provides an update on the current knowledge regarding small molecule compounds that have been evaluated as rhodopsin modulators to be considered as leads for the development of novel therapies for RP.

Oxidative Stress and Cellular Senescence: The Key Tumor-promoting Factors in Colon Cancer and Beneficial Effects of Polyphenols in Colon Cancer Prevention

Background:

Colon cancer is the third leading cause of cancer-related deaths worldwide. Colon tumorigenesis is a sequential process called “Adenoma-carcinoma sequence”. The alimentary habits, obesity, heavy alcohol consumption, inflammatory bowel diseases, family history of colon cancer, oxidative stress, and cellular senescence are the major risk factor influencing colon cancer development. Senescence contributes to the aging process as well as the development and progression of colon cancer. However, the precise mechanism underlying the aging-related progress of colon cancer is yet to be answered. Recent studies proposed that the senescent cell secretes Senescence-Associated Secretory Phenotype (SASP) includes pro-inflammatory cytokines, interleukins, growth factors, and proteases actively involved in the creation of pro-tumorigenic microenvironment.

Objective:

This review aims to provide an overview of ROS influence cellular senescence and colon cancer development as well as summarize the antioxidant and antiaging activity of natural flavonoids. Many of the studies had reported that pro-aging genes suppress cancer and various ‘markers’ are used to identify senescent cells in vitro and in vivo. The SASP of the cells may act as a link between senescence and cancer.

Conclusion:

This review facilitates a better understanding and might contribute to diagnostic and prognostic systems as well as to find out the novel and targeted therapeutic approaches. Additionally, we focused on the potential role of natural flavonoids in colon cancer therapies and highlighting the flavonoid-based treatments as innovative immunomodulatory strategies to inhibit the growth of colon cancer.

Pharmacological basis and new insights of deguelin concerning its anticancer effects

Deguelin is a rotenoid of the flavonoid family, which can be extracted from Lonchocarpus, Derris, or Tephrosia. It possesses the inhibition of cancer cell proliferation by inducing apoptosis through regulating the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling pathway, the NF-κB signaling pathway, the Wnt signaling pathway, the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway and epidermal growth factor receptor (EGFR) signaling, activating the p38 mitogen-activated protein kinase (MAPK) pathway, repression of Bmi1, targeting cyclooxygenase-2 (COX-2), targeting galectin-1, promotion of glycogen synthase kinase-3β (GSK3β)/FBW7-mediated Mcl-1 destabilization and targeting mitochondria via down-regulating Hexokinases II-mediated glycolysis, PUMA-mediation, which are some crucial molecules which modulate closely cancer cell growth and metastasis. Deguelin inhibits tumor cell propagation and malignant transformation through targeting angiogenesis, targeting lymphangiogenesis, targeting focal adhesion kinase (FAK), inhibiting the CtsZ/FAK signaling pathway, targeting epithelial-mesenchymal transition (EMT), the NF-κB signaling pathway, regulating NIMA-related kinase 2 (NEK2). In addition, deguelin possesses other biological activities, such as targeting cell cycle arrest, modulation of autophagy, inhibition of hedgehog pathway, inducing differentiation of mutated NPM1 acute myeloid leukemia etc. Therefore, deguelin is a promising chemopreventive agent for cancer therapy.

Inhibition of APE1/Ref-1 for Neovascular Eye Diseases: From Biology to Therapy

Proliferative diabetic retinopathy (PDR), neovascular age-related macular degeneration (nvAMD), retinopathy of prematurity (ROP) and other eye diseases are characterized by retinal and/or choroidal neovascularization, ultimately causing vision loss in millions of people worldwide. nvAMD and PDR are associated with aging and the number of those affected is expected to increase as the global median age and life expectancy continue to rise. With this increase in prevalence, the development of novel, orally bioavailable therapies for neovascular eye diseases that target multiple pathways is critical, since current anti-vascular endothelial growth factor (VEGF) treatments, delivered by intravitreal injection, are accompanied with tachyphylaxis, a high treatment burden and risk of complications. One potential target is apurinic/apyrimidinic endonuclease 1/reduction-oxidation factor 1 (APE1/Ref-1). The multifunctional protein APE1/Ref-1 may be targeted via inhibitors of its redox-regulating transcription factor activation activity to modulate angiogenesis, inflammation, oxidative stress response and cell cycle in neovascular eye disease; these inhibitors also have neuroprotective effects in other tissues. An APE1/Ref-1 small molecule inhibitor is already in clinical trials for cancer, PDR and diabetic macular edema. Efforts to develop further inhibitors are underway. APE1/Ref-1 is a novel candidate for therapeutically targeting neovascular eye diseases and alleviating the burden associated with anti-VEGF intravitreal injections.

VEGF Detection via Simplified FLISA Using a 3D Microfluidic Disk Platform

Fluorescence-linked immunosorbent assay (FLISA) is a commonly used, quantitative technique for detecting biochemical changes based on antigen–antibody binding reactions using a well-plate platform. As the manufacturing technology of microfluidic system evolves, FLISA can be implemented onto microfluidic disk platforms which allows the detection of trace biochemical reactions with high resolutions. Herein, we propose a novel microfluidic system comprising a disk with a three-dimensional incubation chamber, which can reduce the amount of the reagents to 1/10 and the required time for the entire process to less than an hour. The incubation process achieves an antigen–antibody binding reaction as well as the binding of fluorogenic substrates to target proteins. The FLISA protocol in the 3D incubation chamber necessitates performing the antibody-conjugated microbeads’ movement during each step in order to ensure sufficient binding reactions. Vascular endothelial growth factor as concentration with ng mL⁻¹ is detected sequentially using a benchtop process employing this 3D microfluidic disk. The 3D microfluidic disk works without requiring manual intervention or additional procedures for liquid control. During the incubation process, microbead movement is controlled by centrifugal force from the rotating disk and the sedimentation by gravitational force at the tilted floor of the chamber.

An updated patent review of Akt inhibitors (2016-present)

Introduction: Akt is a widely known serine threonine kinase involved in a series of critical cellular pathways like cell survival and proliferation. With the development of small-molecule Akt inhibitors, new strategies such as covalent, peptide-based, and PROTAC (Proteolysis Targeting Chimera) strategies have also been used the design of Akt inhibitors. On the other hand, due to the specificity of the Akt pathway, the use of Akt modulators in combination therapy and immunotherapy has been disclosed in the past 5 years.Areas covered: This review focuses on the patent literature covering small-molecule inhibitors of Akt kinase and their applications from 2016-present.Expert opinion: Although Akt inhibitors' progress has been somewhat slow over the past five years, new strategies still provide new opportunities for the development of Akt inhibitors. Combination with Akt pathway inhibitors for tumor therapy has also been widely disclosed in patents in the last 5 years. Notably, combination strategies of Akt inhibitors and immunotherapy have started to emerge in recent years. While the clinical indications of Akt modulators should not be limited to anti-cancer, it is still worth trying the treatment of other diseases. Within the next years, current drug development around Akt inhibitors should be fascinating.

Licarin A as a Novel Drug for Inflammatory Eye Diseases

Purpose: This study investigated the safety and therapeutic efficacy of licarin A (LCA) in the treatment of intraocular inflammation. Methods: In vitro safety of LCA in retinal pigmented epithelial cells (ARPE-19) and human embryonic stem cell derived-retinal pigmented epithelial cells (hES-RPE) was evaluated using CellTiter-Blue^® kit. The chorioallantoic membrane (CAM) assay was used to investigate LCA safety and antiangiogenic activity. In vivo safety of intravitreal LCA was accomplished by clinical examination (including assessment of intraocular pressure), electroretinography (ERG), and histopathology. Uveitis was induced in rats by subcutaneous and intravitreal injection of bacillus Calmette-Guérin (BCG) antigen of Mycobacterium bovis. Intraocular inflammation was graded by slit-lamp and fundus examination, ERG, and histopathology. Results: LCA was safe to cells and to the CAM at concentration below 12.0 μM. LCA significantly reduced the percentage of blood vessels in the CAM. Retinal safety and anti-inflammatory efficacy of intravitreal injection of LCA 6.0 μM were confirmed through clinical, functional, and histopathological evaluation. Significant reduction of inflammatory cytokines (tumor necrosis factor-α and interleukin-6) was also found, when compared to untreated animals. Conclusion: The results suggest that LCA is a potential new drug for the treatment of inflammatory eye disease.

Glycyrrhizin micelle as a genistein nanocarrier: Synergistically promoting corneal epithelial wound healing through blockage of the HMGB1 signaling pathway in diabetic mice

The purpose of this study was to explore the feasibility of targeting the HMGB1 signaling pathway to treat diabetic keratopathy with a dipotassium glycyrrhizinate-based micelle ophthalmic solution encapsulating genistein (DG-Gen), and to evaluate whether these dipotassium glycyrrhizinate (DG) micelles could synergistically enhance the therapeutic effect of encapsulated genistein (Gen). An optimized DG-Gen ophthalmic solution was fabricated with a Gen/DG weight of ratio 1:15, and this formulation featured an encapsulation efficiency of 98.96 ± 0.82%, and an average particle size of 29.50 ± 2.05 nm. The DG-Gen ophthalmic solution was observed to have good in vivo ocular tolerance and excellent in vivo corneal permeation, and to remarkably improve in vitro antioxidant activity. Ocular topical application of the DG-Gen ophthalmic solution significantly prompted corneal re-epithelialization and nerve regeneration in diabetic mice, and this efficacy might be due to the inhibition of HMGB1 signaling through down-regulation of HMGB1 and its receptors RAGE and TLR4, as well as inflammatory factor interleukin (IL)-6 and IL-1β. In conclusion, these data showed that HMGB1 signaling is a potential regulation target for the treatment of diabetic keratopathy, and novel DG-micelle formulation encapsulating active agents such as Gen could synergistically cause blockage of HMGB1 signaling to prompt diabetic corneal and nerve wound healing.

Potential of mesenchymal stem cells as topical immunomodulatory cell therapies for ocular surface inflammatory disorders

Ocular surface inflammatory disorders (OSIDs) are a group of highly prevalent, heterogeneous diseases that display a variety of aetiologies and symptoms and are risk factors for serious complications, including ocular and cornea impairment. Corneal inflammation is a common factor of all OSIDs, regardless of their cause or symptoms. Current medications include over-the-counter lubricating eye drops, corticosteroids, and ciclosporin, which either do not treat the corneal inflammation or have been associated with multiple side effects leading to alternative treatments being sought. Regenerative medicine cell therapies, particularly mesenchymal stem cells (MSCs), have shown great promise for immunosuppression and disease amelioration across multiple tissues, including the cornea. However, for successful development and clinical translation of MSC therapy for OSIDs, significant problems must be addressed. This review aims to highlight considerations, including whether the source of MSC isolation impacts the efficacy and safety of the therapy, in addition to assessing the feasibility of MSC topical application to the cornea and ocular surface through analysis of potential scaffolds and cell carriers for application to the eye. The literature contains limited data assessing MSCs incorporated into scaffolds for corneal administration, thus here we highlight the necessity of further investigations to truly exploit the potential of an MSC-based cell therapy for the treatment of OSIDs.

Antiangiogenic Activity of Flavonoids: A Systematic Review and Meta-Analysis

Abstract: An imbalance of angiogenesis contributes to many pathologies such as cancer, arthritis and retinopathy, hence molecules that can modulate angiogenesis are of considerable therapeutic importance. Despite many reports on the promising antiangiogenic properties of naturally occurring flavonoids, no flavonoids have progressed to the clinic for this application. This systematic review and meta-analysis therefore evaluates the antiangiogenic activities of a wide range of flavonoids and is presented in two sections. The first part of the study (Systematic overview) included 402 articles identified by searching articles published before May 2020 using ScienceDirect, PubMed and Web of Science databases. From this initial search, different classes of flavonoids with antiangiogenic activities, related pathologies and use of in vitro and/or in/ex vivo angiogenesis assays were identified. In the second part (Meta-analysis), 25 studies concerning the antiangiogenic evaluation of flavonoids using the in vivo chick chorioallantoic membrane (CAM) assay were included, following a targeted search on articles published prior to June 2020. Meta-analysis of 15 out of the 25 eligible studies showed concentration dependent antiangiogenic activity of six compared subclasses of flavonoids with isoflavones, flavonols and flavones being the most active (64 to 80% reduction of blood vessels at 100 µM). Furthermore, the key structural features required for the antiangiogenic activity of flavonoids were derived from the pooled data in a structure activity relationship (SAR) study. All in all, flavonoids are promising candidates for the development of antiangiogenic agents, however further investigations are needed to determine the key structural features responsible for their activity.

Pharmacological Potential of Small Molecules for Treating Corneal Neovascularization

Under healthy conditions, the cornea is an avascular structure which allows for transparency and optimal visual acuity. Its avascular nature is maintained by a balance of proangiogenic and antiangiogenic factors. An imbalance of these factors can result in abnormal blood vessel proliferation into the cornea. This corneal neovascularization (CoNV) can stem from a variety of insults including hypoxia and ocular surface inflammation caused by trauma, infection, chemical burns, and immunological diseases. CoNV threatens corneal transparency, resulting in permanent vision loss. Mainstay treatments of CoNV have partial efficacy and associated side effects, revealing the need for novel treatments. Numerous natural products and synthetic small molecules have shown potential in preclinical studies in vivo as antiangiogenic therapies for CoNV. Such small molecules include synthetic inhibitors of the vascular endothelial growth factor (VEGF) receptor and other tyrosine kinases, plus repurposed antimicrobials, as well as natural source-derived flavonoid and non-flavonoid phytochemicals, immunosuppressants, vitamins, and histone deacetylase inhibitors. They induce antiangiogenic and anti-inflammatory effects through inhibition of VEGF, NF-κB, and other growth factor receptor pathways. Here, we review the potential of small molecules, both synthetics and natural products, targeting these and other molecular mechanisms, as antiangiogenic agents in the treatment of CoNV.

FTO regulates ocular angiogenesis via m6A-YTHDF2-dependent mechanism

Pathological ocular angiogenesis commonly results in visual impairment or even blindness. Unveiling the mechanisms of pathological angiogenesis is critical to identify the regulators and develop effective targeted therapies. Here, we used corneal neovascularization (CNV) model to investigate the mechanism of pathological ocular angiogenesis. We show that N⁶-methyladenosine (m⁶A) mRNA demethylation mediated by fat mass- and obesity-associated protein (FTO) could regulate endothelial cell (EC) function and pathological angiogenesis during CNV. FTO levels are increased in neovascularized corneas and ECs under pathological conditions. In vitro silencing of FTO in ECs results in reduced cellular proliferation, migration, and tube formation under both basal and pathological conditions. Furthermore, FTO silencing attenuates suture-induced CNV in vivo. Mechanically, FTO silencing in ECs could increase m⁶A methylation levels in critical pro-angiogenic genes, such as FAK, leading to decreased RNA stability and increased RNA decay through m⁶A reader YTHDF2. Our study demonstrates that FTO regulates pathological ocular angiogenesis by controlling EC function in an m⁶A-YTHDF2-dependent manner.

Aucuba japonica extract inhibits retinal neovascularization in a mouse model of oxygen-induced retinopathy, with its bioactive components preventing VEGF-induced retinal vascular hyperpermeability

Neovascularization in the retina is common pathophysiology of diabetic retinal microvasculopathy and exudative macular degeneration. Our study assessed the inhibitory activity of an ethanol-based extract of Aucuba japonica (AJE) on abnormal angiogenesis in the retina with a hyperoxia-induced neovascular retinopathy model. The inhibitory effects of aucubin, quercetin, and kaempferol, bioactive compounds, from A. japonica, on retinal vascular hyperpermeability were also examined. On the 7th postnatal day (P7), the C57BL/6 pups were exposed to a hyperoxic environment with 75% oxygen to develop the experimental angiogenesis in retinas. On the 12th postnatal day (P12), the pups were then returned to the normal atmospheric pressure of oxygen. From P12 to P16, the administration was intraperitoneal. The dose per day was 250 mg per kg weight. Retinal neovascularization was measured with retinal flat mounts prepared on P17. We also measured the vascular leakage mediated by the vascular endothelial growth factor (VEGF) in retinas. Mice treated with AJE had markedly smaller neovascular lesions, in comparison with vehicle-administered mice. AJE downregulated the expression of both VEGF protein and mRNA. In addition, aucubin, quercetin, and kaempferol ameliorated VEGF-induced retinal vascular leakage. The results of our study suggest that AJE is a potent antiangiogenic substance. AJE could also serve as a therapeutic agent for abnormal growth of vessels in the retina in patients with ischemic retinopathy. The bioactive compounds of AJE may be responsible for its antiangiogenic abilities.

Bufadienolides and anti-angiogenic homoisoflavonoids from Rhodocodon cryptopodus, Rhodocodon rotundus and Rhodocodon cyathiformis

BACKGROUND

Homoisoflavonoids have been shown to have potent anti-proliferative activities in endothelial cells over other cell types and have demonstrated a strong antiangiogenic potential in vitro and in vivo in animal models of ocular neovascularization. Three species of Rhodocodon (Scilloideaea subfamily of the Asparagaceae family), endemic to Madagascar, R. cryptopodus, R. rotundus and R. cyathiformis, were investigated.

PURPOSE

To isolate and test homoisoflavonoids for their antiangiogenic activity against human retinal microvascular endothelial cells (HRECs), as well as specificity against other ocular cell lines.

METHODS

Plant material was extracted at room temperature with EtOH. Compounds were isolated using flash column chromatography and were identified using NMR and CD spectroscopy and HRESIMS. Compounds were tested for antiproliferative effects on primary human microvascular retinal endothelial cells (HRECs), ARPE19 retinal pigment epithelial cells, 92-1 uveal melanoma cells, and Y79 retinoblastoma cells. HRECs exposed to compounds were also tested for migration and tube formation ability.

RESULTS

Two homoisoflavonoids, 3S-5,7-dihydroxy-(3'-hydroxy-4'-methoxybenzyl)-4-chromanone (1) and 3S-5,7-dihydroxy-(4'-hydroxy-3'-methoxybenzyl)-4-chromanone (2), were isolated along with four bufadienolides. Compound 1 was found to be non-specifically antiproliferative, with GI50 values ranging from 0.21-0.85 μM across the four cell types, while compound 2 showed at least 100-fold specificity for HRECs over the other tested cell lines. Compound 1, with a 3S configuration, was 700 times more potent that the corresponding 3R enantiomer recently isolated from a Massonia species.

CONCLUSION

Select homoisoflavonoids have promise as antiangiogenic agents that are not generally cytotoxic.

Structure based modification of chalcone analogue activates Nrf2 in the human retinal pigment epithelial cell line ARPE-19

Oxidative stress-induced degeneration of retinal pigment epithelial (RPE) cells is known to be a key contributor to the development of age-related macular degeneration (AMD). Activation of the nuclear factor-(erythroid-derived 2)-related factor-2 (Nrf2)-mediated cellular defense system is believed to be a valid therapeutic approach. In the present study, we designed and synthesized a novel chalcone analogue, 1-(2,3,4-trimethoxyphenyl)-2-(3,4,5-trimethoxyphenyl)-acrylketone (Tak), as a Nrf2 activator. The potency of Tak was measured in RPE cells by the induction of the Nrf2-dependent antioxidant genes HO-1, NQO-1, GCLc, and GCLm, which were regulated through the Erk pathway. We also showed that Tak could protect RPE cells against oxidative stress-induced cell death and mitochondrial dysfunction. Furthermore, by modifying the α, β unsaturated carbonyl entity in Tak, we showed that the induction of antioxidant genes was abolished, indicating that this unique feature in Tak was responsible for the Nrf2 activation. These results suggest that Tak is a potential candidate for clinical application against AMD.

CCAAT/Enhancer-Binding Protein β Mediates Oxygen-Induced Retinal Neovascularization via Retinal Vascular Damage and Vascular Endothelial Growth Factor

OBJECTIVE

To evaluate the role of CCAAT/enhancer-binding protein β (C/EBP β (C/EBP.

METHODS

Rats with OIR were exposed to alternating hypoxic and hyperopic conditions for 14 days. Then, the rats with OIR were assigned randomly to groups that received intravitreal injections of either shRNA lentiviral particles targeting C/EBP β (C/EBP β (C/EBP β (C/EBP β (C/EBP β (C/EBP β (C/EBP.

RESULTS

In OIR rats, the expression levels of C/EBP β (C/EBP P < 0.01). The p-C/EBP β (C/EBP β (C/EBP β (C/EBP β (C/EBP β (C/EBP P < 0.01). The p-C/EBP β (C/EBP β (C/EBP β (C/EBP P < 0.01). The p-C/EBP.

CONCLUSIONS

C/EBP β shRNA inhibits RNV in OIR. A potential mechanism may be that the activity of C/EBP β increases with its overexpression, which in turn aggravates the amount of the retinal vascular damage and promotes transcription of VEGF. C/EBP β might be a new therapeutic target for preventing RNV.β (C/EBP β (C/EBP β (C/EBP.

Curcumolide, a unique sesquiterpenoid from Curcuma wenyujin displays anti-angiogenic activity and attenuates ischemia-induced retinal neovascularization

BACKGROUND

Targeting vascular endothelial growth factor is a common treatment strategy for neovascular eye disease, a leading cause of visual impairment and blindness. However, these approaches are limited or carry various complications. Therefore, there is an urgent need for the development of unique therapeutic approaches.

PURPOSE

To investigate the anti-angiogenic effects of curcumolide and its mechanism of action.

METHODS /STUDY DESIGNS

In this study, we examine the effects of curcumolide on the process of vasculature formation, including cell proliferation, migration, tube formation and apoptosis in vitro using human umbilical vascular endothelial cells (HUVECs). We also assess the anti-angiogenic effects of curcumolide in vivo using a mouse model of oxygen induced retinopathy (OIR). The mechanism of anti-angiogenic effects was investigated by measuring the expression level of various signaling proteins and the molecular docking simulations.

RESULTS

Intravitreal injection of curcumolide reduced the formation of retinal neovascular tufts and VEGFR2 phosphorylation in the murine OIR model at concentrations administered without definite cellular and retinal toxicities. Curcumolide suppressed VEGF-induced HRMECs proliferation, migration and tube formation in a dose-dependent manner. Meanwhile, it promoted caspase-dependent apoptosis. Curcumolide also inhibited VEGF-induced phosphorylation of VEGFR-2 tyrosine kinase, and suppressed downstream protein kinases of VEGFR2, including Src, FAK, ERK, AKT, and mTOR in HRMECs. In silico study revealed that curcumolide bound with ATP-binding sites of the VEGFR2 kinase unit by the formation of a hydrogen bond and hydrophobic interactions.

CONCLUSION

Curcumolide has anti-angiogenic activity in HUVECs and in a murine OIR model of ischemia-induced retinal neovascularization, and it might be a potential drug candidate for the treatment of proliferative diabetic retinopathy.

Prospect of natural products in glioma: A novel avenue in glioma management

Glioma is one of the most perplexing cancers because of its infiltrating nature, molecular signaling, and location in central nervous system. Blood-brain barrier acts as a natural barrier to the glioma making it difficult to access by conventional chemotherapy. Clinicians are using natural compounds or their derivatives for several diseases including different cancers. However, the feasibility of using natural compounds in glioma is not explored in details. Natural compounds can act over a wide variety of signaling pathways such as survival and metabolic pathways and induce cell death. Some of the natural agents have additional benefits of crossing biological barriers such as blood-brain barrier with ease having few or no impact on the surrounding healthy cells. All of these benefits make natural compounds a prospective candidate for the glioma management. This article evaluates the benefits of using natural compounds for glioma therapy and their possible mechanism of actions. We have discussed the natural compounds assessed currently for glioma therapy and proposed a few novel natural compounds with potential antiglioma effect based on their mechanism of action.

Mouse Pharmacokinetics and in Vitro Metabolism of (±)-Cremastranone

The objective of this study was to characterize pharmacokinetics and metabolism of (±)-cremastranone (CMT) in mouse. Plasma concentrations of CMT following a single oral dose (10 mg/kg) were all below quantitation limit throughout 24-h time course, indicating poor oral bioavailability. Its plasma levels declined rapidly, with a half-life (t_1/2) of 1.5 ± 0.3 min following a single intravenous dose (5 mg/kg). They were below the quantitation limit after 15 min post-dosing. CMT showed a high plasma clearance (CL_p) of 7.73 ± 3.09 L/h/kg. Consistently, CMT was metabolized rapidly, with a t_1/2 < 1 min when it was incubated with liver or intestine S9 fractions of mouse and human in the presence of cofactors for CYP450, uridine 5'-diphosphate (UDP)-glucuronosyltransferase (UGT), and sulfotransferase (ST). Further studies showed that CMT was metabolized by CYP450, UGT, and ST in vitro in liver S9 fractions of mouse and human, with UGT being the major enzyme responsible for its rapid metabolism. CMT was metabolized by UGT and ST in intestine S9 fractions of mouse and human. Mono-demethylated (M1), mono-glucuronide (M2), and mono-sulfate (M3 and M4) metabolites were tentatively identified in vitro. In conclusion, the pharmacokinetics of CMT is suboptimal as a systemic agent, especially as an oral therapy, due to its extensive metabolism. This report provides possible structural modifications to design CMT derivatives with better pharmacokinetic properties.

Synthesis of Either C2- or C4'-Alkylated Derivatives of Honokiol and Their Biological Evaluation for Anti-inflammatory Activity

Honokiol, a biphenolic neolignan isolated from Magnolia officinalis, was reported to have a promising anti-inflammatory activity for the treatment of various diseases. There are many efforts on the synthesis and structure-activity relationship of honokiol derivatives. However, regioselective O-alkylation of honokiol remains a challenge and serves as a tool to provide not only some derivatives but also chemical probes for target identification and mode of action. In this study, we examined the reaction condition for regioselective O-alkylation, in which C2 and C4'-alkylated analogs of honokiol were synthesized and evaluated for inhibitory activity on nitric oxide production and cyclooxygenase-2 expression. Furthermore, we successfully synthesized a potential photoaffinity probe consisting of biotin and benzophenone based on a C4'-alkylated derivative.

The Antiangiogenic Activity of Naturally Occurring and Synthetic Homoisoflavonoids from the Hyacinthaceae ( sensu APGII)

Excessive blood vessel formation in the eye is implicated in wet age-related macular degeneration, proliferative diabetic retinopathy, neovascular glaucoma, and retinopathy of prematurity, which are major causes of blindness. Small molecule antiangiogenic drugs are strongly needed to supplement existing biologics. Homoisoflavonoids have been previously shown to have potent antiproliferative activities in endothelial cells over other cell types. Moreover, they demonstrated a strong antiangiogenic potential in vitro and in vivo in animal models of ocular neovascularization. Here, we tested the antiangiogenic activity of a group of naturally occurring homoisoflavonoids isolated from the family Hyacinthaceae and related synthetic compounds, chosen for synthesis based on structure-activity relationship observations. Several compounds showed interesting antiproliferative and antiangiogenic activities in vitro on retinal microvascular endothelial cells, a disease-relevant cell type, with the synthetic chromane, 46, showing the best activity (GI50 of 2.3 × 10-4 μM).

Dietary Polyphenols in Age-Related Macular Degeneration: Protection against Oxidative Stress and Beyond

Age-related macular degeneration (AMD) is a multifactorial disease of the retina featured by degeneration and loss of photoreceptors and retinal pigment epithelium (RPE) cells with oxidative stress playing a role in its pathology. Although systematic reviews do not support the protective role of diet rich in antioxidants against AMD, dietary polyphenols (DPs) have been reported to have beneficial effects on vision. Some of them, such as quercetin and cyanidin-3-glucoside, can directly scavenge reactive oxygen species (ROS) due to the presence of two hydroxyl groups in their B ring structure. Apart from direct ROS scavenging, DPs can lower oxidative stress in several other pathways. Many DPs induce NRF2 (nuclear factor, erythroid 2-like 2) activation and expression of phase II enzymes that are under transcriptional control of this factor. DPs can inhibit A2E photooxidation in RPE cells, which is a source of oxidative stress. Anti-inflammatory action of DPs in RPE cells is associated with regulation of various interleukins and signaling pathways, including IL-6/JAK2 (Janus kinase 2)/STAT3. Some DPs can improve impaired cellular waste clearance, including AMD-specific deficient phagocytosis of the Aβ42 peptide and autophagy.

Health Benefits of Polyphenols and Carotenoids in Age-Related Eye Diseases

Oxidative stress and inflammation play a critical role in the initiation and progression of age-related ocular abnormalities as cataract, glaucoma, diabetic retinopathy, and macular degeneration. Therefore, phytochemicals with proven antioxidant and anti-inflammatory activities, such as carotenoids and polyphenols, could be of benefit in these diseases. We searched PubMed and Web of Science databases for original studies investigating the benefits of different carotenoids and polyphenols in age-related ophthalmic diseases. Our results showed that several polyphenols (such as anthocyanins, Ginkgo biloba, quercetin, and resveratrol) and carotenoids (such as lutein, zeaxanthin, and mezoxanthin) have shown significant preventive and therapeutic benefits against the aforementioned conditions. The involved mechanisms in these findings include mitigating the production of reactive oxygen species, inhibiting the tumor necrosis factor-α and vascular endothelial growth factor pathways, suppressing p53-dependent apoptosis, and suppressing the production of inflammatory markers, such as interleukin- (IL-) 8, IL-6, IL-1a, and endothelial leucocyte adhesion molecule-1. Consumption of products containing these phytochemicals may be protective against these diseases; however, adequate human data are lacking. This review discusses the role and mechanisms of polyphenols and carotenoids and their possible synergistic effects on the prevention and treatment of age-related eye diseases that are induced or augmented by oxidative stress and inflammation.

Antiangiogenic Activity and Cytotoxicity of Triterpenoids and Homoisoflavonoids from Massonia pustulata and Massonia bifolia

The Hyacinthaceae family (sensu APGII), with approximately 900 species in around 70 genera, plays a significant role in traditional medicine in Africa as well as across Europe and the Middle and Far East. The dichloromethane extract of the bulbs of Massonia pustulata (Hyacinthaceae sensu APGII) yielded two known homoisoflavonoids, (R)-5-hydroxy-3-(4-hydroxybenzyl)-7-methoxy-4-chromanone 1: and 5-hydroxy-3-(4-hydroxybenzyl)-7-methoxy-4-chromone 2: and four spirocyclic nortriterpenoids, eucosterol 3: , 28-hydroxyeucosterol 4: and two previously unreported triterpenoid derivatives, (17S,23S)-17α,23-epoxy-3β,22β,29-trihydroxylanost-8-en-27,23-olide 5: , and (17S, 23S)-17α,23-epoxy-28,29-dihydroxylanost-8-en-3-on-27,23-olide 6: . Compounds 1, 2, 3: , and 5: were assessed for cytotoxicity against CaCo-2 cells using a neutral red uptake assay. Compounds 1, 2: , and 5: reduced cell viability by 70% at concentrations of 30, 100, and 100 µM, respectively. Massonia bifolia yielded three known homoisoflavonoids, (R)-(4'-hydroxy)-5-hydroxy-7-methoxy-4-chromanone 1: , (R)-(4'-hydroxy)-5,7-dihydroxy-4-chromanone 7: and (R)-(3'-hydroxy-4'-methoxy)-5,7-dihydroxy-4-chromanone 9: , two previously unreported homoisoflavonoids, (E)-3-benzylidene-(3',4'-dihydroxy)-5-hydroxy-7-methoxy-4-chromanone 8: and (R)-(3',4'-dihydroxy)-5-hydroxy-7-methoxy-4-chromanone 10,: and a spirocyclic nortriterpenoid, 15-deoxoeucosterol 11: . Compounds 1, 1AC, 7, 8, 9,: and 10: were screened for antiangiogenic activity against human retinal microvascular endothelial cells. Some compounds showed dose-dependent antiproliferative activity and blocked endothelial tube formation, suggestive of antiangiogenic activity.

Theme trends and knowledge structure on choroidal neovascularization: a quantitative and co-word analysis

Background

The distribution pattern and knowledge structure of choroidal neovascularization (CNV) was surveyed based on literatures in PubMed.

Methods

Published scientific papers about CNV were retrieved from Jan 1st, 2012 to May 31st, 2017. Extracted MeSH terms were analyzed quantitatively by using Bibliographic Item Co-Occurrence Matrix Builder (BICOMB) and high-frequency MeSH terms were identified. Hierarchical cluster analysis was conducted by SPSS 19.0 according to the MeSH term-source article matrix. High-frequency MeSH terms co-occurrence matrix was constructed to support strategic diagram and social network analysis (SNA).

Results

According to the searching strategy, all together 2366 papers were included, and the number of annual papers changed slightly from Jan 1st, 2012 to May 31st, 2017. Among all the extracted MeSH terms, 44 high-frequency MeSH terms were identified and hotspots were clustered into 6 categories. In the strategic diagram, clinical drug therapy, pathology and diagnosis related researches of CNV were well developed. In contrast, the metabolism, etiology, complications, prevention and control of CNV in animal models, and genetics related researches of CNV were relatively immature, which offers potential research space for future study. As for the SNA result, the position status of each component was described by the centrality values.

Conclusions

The studies on CNV are relatively divergent and the 6 research categories concluded from this study could reflect the publication trends on CNV to some extent. By providing a quantitative bibliometric research across a 5-year span, it could help to depict an overall command of the latest topics and provide some hints for researchers when launching new projects.

Ferrochelatase is a therapeutic target for ocular neovascularization

Ocular neovascularization underlies major blinding eye diseases such as “wet” age‐related macular degeneration (AMD). Despite the successes of treatments targeting the vascular endothelial growth factor (VEGF) pathway, resistant and refractory patient populations necessitate discovery of new therapeutic targets. Using a forward chemical genetic approach, we identified the heme synthesis enzyme ferrochelatase (FECH) as necessary for angiogenesis in vitro and in vivo. FECH is overexpressed in wet AMD eyes and murine choroidal neovascularization; siRNA knockdown of Fech or partial loss of enzymatic function in the Fech^m1Pas mouse model reduces choroidal neovascularization. FECH depletion modulates endothelial nitric oxide synthase function and VEGF receptor 2 levels. FECH is inhibited by the oral antifungal drug griseofulvin, and this compound ameliorates choroidal neovascularization in mice when delivered intravitreally or orally. Thus, FECH inhibition could be used therapeutically to block ocular neovascularization.

Ruta graveolens water extract inhibits cell-cell network formation in human umbilical endothelial cells via MEK-ERK1/2 pathway

Angiogenesis is a process encompassing several steps such as endothelial cells proliferation, differentiation and migration to form a vascular network, involving different signal transduction pathways. Among these, ERK1/2 signaling mediates VEGF-dependent signaling pathway. Here we report that the water extract of Ruta graveolens (RGWE), widely known as a medicinal plant, is able to impair in a dose-dependent manner, cell network formation without affecting cell viability. Biochemical analysis showed that the major component of RGWE is rutin, unable to reproduce RGWE effect. We found that RGWE inhibits ERK1/2 phosphorylation and that this event is crucial in cell network formation since the transfection of HUVEC with a constitutively active MEK (caMEK), the ERK1/2 activator, induces a robust cell network formation as compared to untransfected and/or mock transfected cells and, more importantly, caMEK transfected cells became unresponsive to RGWE. Moreover, RGWE inhibits VEGF and nestin gene expression, necessary for vessel formation, and the caMEK transfection induces their higher expression. In conclusion, we report that RGWE is able to significantly impair vessels network formation without affecting cell viability, preventing ERK1/2 activation and, in turn, down-regulating VEGF and nestin expression. These findings point to RGWE as a potential therapeutic tool capable to interfere with pathologic angiogenesis.

Quercetin Mitigates Inflammatory Responses Induced by Vascular Endothelial Growth Factor in Mouse Retinal Photoreceptor Cells through Suppression of Nuclear Factor Kappa B

Retinal vascular endothelial growth factor (VEGF) increased by neovascularization is well known as a pathogenic factor in ocular neovascular diseases. However, it is still unclear how retinal neurons are damaged by VEGF. The aims of this study are to demonstrate the inflammatory protein expression regulated by VEGF using mouse photoreceptor-derived cells and the protective effect of quercetin against VEGF-induced inflammatory response. Expression and phosphorylation of protein and expression of mRNA were detected by immunoblot and reverse transcriptase polymerase chain reaction. VEGF-induced degradation of limiting membrane and translocation of nuclear factor kappa B (NF-κB) were analyzed by immunocytochemistry. VEGF treatment activated angiogenic signaling pathway in photoreceptor cells. In addition, adhesion molecules and matrix metalloproteinases were increased in VEGF-treated photoreceptor cells. All these events were reversed by quercetin. Zona occludins-1 and β-catenin decreased by VEGF were recovered by quercetin. NF-κB signaling pathway regulated by VEGF through phosphorylations of mitogen-activated protein kinases (MAPK) and protein kinase B (Akt) was suppressed by quercetin. These results suggest that quercetin suppressed VEGF-induced excessive inflammatory response in retinal photoreceptor cells by inactivation of NF-κB signals through inhibition of MAPKs and Akt. These data may provide a basic information for development of pharmaceuticals or nutraceuticals for treatment of retinal diseases caused by excessive VEGF.

Cancer chemoprevention revisited: Cytochrome P450 family 1B1 as a target in the tumor and the microenvironment

Cancer chemoprevention is the use of synthetic, natural or biological agents to prevent or delay the development or progression of malignancies. Intriguingly, many phytochemicals with anti-inflammatory and anti-angiogenic effects, recently proposed as chemoprevention strategies, are inhibitors of Cytochrome P450 family 1B1 (CYP1B1), an enzyme overexpressed in a wide variety of tumors and associated with angiogenesis. In turn, pro-inflammatory cytokines were reported to boost CYP1B1 expression, suggesting a key role of CYP1B1 in a positive loop of inflammatory angiogenesis. Other well-known pro-tumorigenic activities of CYP1B1 rely on metabolic bioactivation of xenobiotics and steroid hormones into their carcinogenic derivatives. In contrast to initial in vitro observations, in vivo studies demonstrated a protecting role against cancer for the other CYP1 family members (CYP1A1 and CYP1A2), suggesting that the specificity of CYP1 family inhibitors should be carefully taken into account for developing potential chemoprevention strategies. Recent studies also proposed a role of CYP1B1 in multiple cell types found within the tumor microenvironment, including fibroblasts, endothelial and immune cells. Overall, our review of the current literature suggests a positive loop between inflammatory cytokines and CYP1B1, which in turn may play a key role in cancer angiogenesis, acting on both cancer cells and the tumor microenvironment. Strategies aiming at specific CYP1B1 inhibition in multiple cell types may translate into clinical chemoprevention and angioprevention approaches.

Evolving multidimensional pharmacological approaches to CNV therapy in AMD

PURPOSE

The leading cause of severe visual loss world-wide is age-related macular degeneration. Although anti-Vascular Endothelial Growth Factor agents have significantly led to the initial pharmacologic reversal of vision loss in many cases of exudative macular degeneration, there still has been recurrence of choroidal neovascularization, and/or the onset of chorioretinal atrophy with fibrosis.

MATERIALS AND METHODS

In this review we discuss the status of anti- Vascular Endothelial Growth Factor in age-related macular degeneration and describe different studies focused on new potential therapeutic targets beyond anti- Vascular Endothelial Growth Factor.

RESULTS

Further investigations have elicited that Vascular Endothelial Growth Factor is only one of many angiogenic, and pro-inflammatory factors that bring about the growth and leakage of active choroidal neovascularization. Various new multifaceted strategies, including inhibitors to down-stream targets of endothelial cell division, such as TNP-470, may lead to a more permanent inactivation of choroidal neovascularization.

CONCLUSIONS

Based on the accumulated results in the treatment of age-related macular degeneration, it is hoped that the appropriate combination of anti-Vascular Endothelial Growth Factor agents with longer-acting and multidimensional pharmaceuticals, such as Methionine Aminopeptidase-2 inhibitors, will more effectively control choroidal neovascularization, prevent atrophy and fibrosis, and reduce the burden of frequent intraocular injections in age-related macular degeneration.

Angiostatic actions of capsicodendrin through selective inhibition of VEGFR2-mediated AKT signaling and disregulated autophagy

Angiogenesis is the formation of new blood vessels from existing vasculature critical for embryonic development and vascular remodeling. Its dysregulation underlies numerous pathologic states ranging from ischemia to tumor growth and as such identifying new targeted- therapies is of significant interest for angiogenesis-based medicine. Here we evaluated the potential angiostatic properties of capsicodendrin (CPCD), a natural compound isolated from Cinnamosma macrocarpa, a plant belonging to the Malagasy Cinnamosma. CPCD potently inhibits endothelial proliferation, migration and capillary tube formation at nanomolar to low micromolar concentrations without inducing cytotoxic effects. We show that CPCD directly inactivates VEGFR2 and downstream AKT signaling, thereby strongly inducing autophagy as determined by increased expression of beclin1, autophagy-related gene (Atg) 3, Atg5 and LC3 cleavage. Ectopic AKT overexpression counteracts the inhibitory effects of CPCD on proliferation and capillary tubule formation. Importantly, CPCD treatment in vivo inhibits sprouting angiogenesis as evidenced by strongly reduced intersegmental vessel (ISV) sprouting and subintestinal vessel (SIV) formation during zebrafish embryonic development, and correlates with increased presence of LC3II along the ISVs despite overall reduced vasculature. These findings demonstrate CPCD as a potent inhibitor of the VEGFR2/AKT pathway at nanomolar concentrations and inducer of autophagy-related angiostatic effects.

Homoisoflavonoids as potential antiangiogenic agents for retinal neovascularization

A number of people worldwide have been suffering from ocular neovascularization that may be treated by a variety of drugs but these may possess adverse effects. Therefore, small antiangiogenic molecules with higher potency and lower toxic effects are intended. However, homoisoflavonoids of natural origin show the potential antiangiogenic effect in ocular neovascularization. These homoisoflavonoids are judged quantitatively in terms of statistical validation through multi-chemometric modeling approaches for the betterment and refinement of their structures required for higher antiangiogenic activity targeted to ocular neovascularization. These approaches may be utilized to design better antiangiogenic homoisoflavonoids.

EDIL3 knockdown inhibits retinal angiogenesis through the induction of cell cycle arrest in vitro

Pathological retinal angiogenesis is one of the most common causes of blindness, with limited treatment options being currently available. Epidermal growth factor (EGF)-like repeat and discoidin I-like domain-containing protein 3 (EDIL3) has been reported to serve an important role in embryonic vasculogenesis and tumor angiogenesis; however, its implication in retinal angiogenesis has yet to be elucidated. The present study aimed to investigate the putative roles of EDIL3 in retinal endothelial cells. RNA interference was used to disrupt the expression of EDIL3 in human retinal endothelial cells (HRECs) in vitro, and the resulting effects were examined. Cell proliferation was assessed using cell counting kit-8 reagent, Cell migration was investigated using a transwell chamber and a tube formation assay was used to study angiogenic capability in vitro. Flow cytometry was used to detect the cell cycle distribution and western blotting was used to study protein expression. The present results demonstrated that silencing EDIL3 expression significantly impaired the proliferative, migratory and tube forming capabilities of HRECs. Furthermore, EDIL3 knockdown was revealed to induce cell cycle arrest at the G₁ phase. Western blot analysis suggested that the possible mechanisms underlying the antiproliferative effects of EDIL3 silencing may involve the inhibition of EGF receptor-mediated pathways, and the suppression of cyclin D1 and cyclin E1 expression in HRECs. In conclusion, the findings of the present study suggested that EDIL3 may be implicated in retinal angiogenesis, and may have potential as a novel therapeutic target for the treatment of pathological angiogenesis.

Apigenin Inhibits Human SW620 Cell Growth by Targeting Polyamine Catabolism

Apigenin is a nonmutagenic flavonoid that has antitumor properties. Polyamines are ubiquitous cellular polycations, which play an important role in the proliferation and differentiation of cancer cells. Highly regulated pathways control the biosynthesis and degradation of polyamines. Ornithine decarboxylase (ODC) is the rate-limiting enzyme in the metabolism, and spermidine/spermine-N1-Acetyl transferase (SSAT) is the rate-limiting enzyme in the catabolism of polyamines. In the current study, the effect of increasing concentrations of apigenin on polyamine levels, ODC and SSAT protein expression, mRNA expression, cell proliferation and apoptosis, and the production of reactive oxygen species (ROS) was investigated in SW620 colon cancer cells. The results showed that apigenin significantly reduced cell proliferation, decreased the levels of spermidine and spermine, and increased previously downregulated putrescine contents. Apigenin also enhanced SSAT protein and mRNA levels and the production of reactive oxygen species in SW620 cells, though it had no significant effect on the levels of ODC protein or mRNA. Apigenin appears to decrease the proliferation rate of human SW620 cells by facilitating SSAT expression to induce polyamine catabolism and increasing ROS levels to induce cell apoptosis.

Dietary Compound Chrysin Inhibits Retinal Neovascularization with Abnormal Capillaries in db/db Mice

Diabetic retinopathy (DR) develops in a significant proportion of patients with chronic diabetes, characterized by retinal macular edema and abnormal retinal vessel outgrowth leading to vision loss. Chrysin, a naturally-occurring flavonoid found in herb and honeycomb, has anti-inflammatory, antioxidant, and anti-cancer properties. This study sought to determine the protective effects of chrysin on retinal neovascularization with abnormal vessels and blood-retinal barrier (BRB) breakdown in 33 mM glucose-exposed human retinal endothelial cells and in db/db mouse eyes. High glucose caused retinal endothelial apoptotic injury, which was inhibited by submicromolar chrysin. This compound diminished the enhanced induction of HIF-1α, vascular endothelial growth factor (VEGF), and VEGF receptor-2 (VEGFR2) in high glucose-exposed retinal endothelial cells. Consistently, oral administration of 10 mg/kg chrysin reduced the induction of these proteins in db/db mouse eye tissues. In addition, chrysin restored the decrement of VE-cadherin and ZO-1 junction proteins and PECAM-1 in hyperglycemia-stimulated retinal endothelial cells and diabetic mouse retina, possibly maintaining tight cell-cell interactions of endothelial cells and pericytes. Anti-apoptotic chrysin reduced the up-regulation of Ang-1, Ang-2, and Tie-2 crucial to retinal capillary occlusion and BRB permeability. Furthermore, orally treating chrysin inhibited acellular capillary formation, neovascularization, and vascular leakage observed in diabetic retinas. These observations demonstrate, for the first time, that chrysin had a capability to encumber diabetes-associated retinal neovascularization with microvascular abnormalities and BRB breakdown.