Minocycline and Diacetyl Minocycline Eye Drops Reduce Ocular Neovascularization in Mice

Purpose

To evaluate the efficacy of minocycline and a novel, modified minocycline analogue that lacks antimicrobial action, diacetyl minocycline (DAM), on choroidal neovascularization (CNV) in mice of both sexes.

Methods

CNV was induced via laser injury in female and male C57BL/6J mice. Minocycline, DAM, or saline was administered via topical eye drops twice a day for 2 weeks starting the day after laser injury. CNV volume was measured using immunohistochemistry labeling and confocal microscopy.

Results

Minocycline reduced lesion volume by 79% (P ≤ 0.0004) in female and male mice. DAM reduced lesion volume by 73% (P ≤ 0.001) in female and male mice. There was no significant difference in lesion volume between minocycline and DAM treatment groups or between female and male mice.

Conclusions

Both minocycline and DAM eye drops significantly reduced laser-induced CNV lesion volume in female and male mice. While oral tetracyclines have been shown to mitigate pathologic neovascularization in both preclinical studies and clinical trials, the present data are the first to suggest that tetracycline derivatives may be effective to reduce pathologic CNV when administered via topical eye drops. However, the action is unrelated to antimicrobial action. Targeted delivery of these medications via eye drops may reduce the potential for systemic side effects.

Translational Relevance

Topical administration of minocycline and/or DAM via eye drops may represent a novel therapeutic strategy for disorders involving pathologic CNV.

Discovery and Development of the Quininib Series of Ocular Drugs

The quininib series is a novel collection of small-molecule drugs with antiangiogenic, antivascular permeability, anti-inflammatory, and antiproliferative activity. Quininib was initially identified as a drug hit during a random chemical library screen for determinants of developmental ocular angiogenesis in zebrafish. To enhance drug efficacy, novel quininib analogs were designed by applying medicinal chemistry approaches. The resulting quininib drug series has efficacy in in vitro and ex vivo models of angiogenesis utilizing human cell lines and tissues. In vivo, quininib drugs reduce pathological angiogenesis and retinal vascular permeability in rodent models. Quininib acts as a cysteinyl leukotriene (CysLT) receptor antagonist, revealing new roles of these G-protein-coupled receptors in developmental angiogenesis of the eye and unexpectedly in uveal melanoma (UM). The quininib series highlighted the potential of CysLT receptors as therapeutic targets for retinal vasculopathies (e.g., neovascular age-related macular degeneration, diabetic retinopathy, and diabetic macular edema) and ocular cancers (e.g., UM).

Largazole Inhibits Ocular Angiogenesis by Modulating the Expression of VEGFR2 and p21

Ocular angiogenic diseases, characterized by abnormal blood vessel formation in the eye, are the leading cause of blindness. Although Anti-VEGF therapy is the first-line treatment in the market, a substantial number of patients are refractory to it or may develop resistance over time. As uncontrolled proliferation of vascular endothelial cells is one of the characteristic features of pathological neovascularization, we aimed to investigate the role of the class I histone deacetylase (HDAC) inhibitor Largazole, a cyclodepsipeptide from a marine cyanobacterium, in ocular angiogenesis. Our study showed that Largazole strongly inhibits retinal vascular endothelial cell viability, proliferation, and the ability to form tube-like structures. Largazole strongly inhibits the vessel outgrowth from choroidal explants in choroid sprouting assay while it does not affect the quiescent choroidal vasculature. Largazole also inhibits vessel outgrowth from metatarsal bones in metatarsal sprouting assay without affecting pericytes coverage. We further demonstrated a cooperative effect between Largazole and an approved anti-VEGF drug, Alflibercept. Mechanistically, Largazole strongly inhibits the expression of VEGFR2 and leads to an increased expression of cell cycle inhibitor, p21. Taken together, our study provides compelling evidence on the anti-angiogenic role of Largazole that exerts its function through mediating different signaling pathways.

PFKFB3: A Potential Key to Ocular Angiogenesis

The current treatment for ocular pathological angiogenesis mainly focuses on anti-VEGF signals. This treatment has been confirmed as effective despite the unfavorable side effects and unsatisfactory efficiency. Recently, endothelial cell metabolism, especially glycolysis, has been attracting attention as a potential treatment by an increasing number of researchers. Emerging evidence has shown that regulation of endothelial glycolysis can influence vessel sprouting. This new evidence has raised the potential for novel treatment targets that have been overlooked for a long time. In this review, we discuss the process of endothelial glycolysis as a promising target and consider regulation of the enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase as treatment for ocular pathological angiogenesis.

Calcitriol and non-calcemic vitamin D analogue, 22-oxacalcitriol, attenuate developmental and pathological choroidal vasculature angiogenesis ex vivo and in vivo

Aberrant ocular angiogenesis can underpin vision loss in leading causes of blindness, including neovascular age-related macular degeneration and proliferative diabetic retinopathy. Current pharmacological interventions require repeated invasive administrations, may lack efficacy and are associated with poor patient compliance and tachyphylaxis. Vitamin D has de novo anti-angiogenic properties. Here, our aim was to validate the ocular anti-angiogenic activity of biologically active vitamin D, calcitriol, and selected vitamin D analogue, 22-oxacalcitriol. Calcitriol induced a significant reduction in ex vivo mouse choroidal fragment sprouting. Viability studies in a human RPE cell line suggested non-calcemic vitamin D analogues including 22-oxacalcitriol have less off-target anti-proliferative activity compared to calcitriol and other analogues. Thereafter, the anti-angiogenic activity of 22-oxacalcitriol was demonstrated in an ex vivo mouse choroidal fragment sprouting assay. In zebrafish larvae, 22-oxacalcitriol was found to be anti-angiogenic, inducing a dose-dependent reduction in choriocapillaris development. Subcutaneously administered calcitriol failed to attenuate mouse retinal vasculature development. However, calcitriol and 22-oxacalcitriol administered intraperitoneally, significantly attenuated lesion volume in the laser-induced choroidal neovascularisation mouse model. In summary, calcitriol and 22-oxacalcitriol attenuate ex vivo and in vivo choroidal vasculature angiogenesis. Therefore, vitamin D may have potential as an interventional treatment for ophthalmic neovascular indications.

Mesoporous silica nanoparticles as a delivery system for improving antiangiogenic therapy

PURPOSE

Antiangiogenic drugs usually have short-acting efficacy and poor treatment compliance. The purpose of this study was to determine whether mesoporous silica nanoparticles (MSNs) could be utilized as a nanodrug delivery system for improving antiangiogenic therapy.

MATERIALS AND METHODS

MSN-encapsulated bevacizumab nanoparticles were prepared by the nanocasting strategy and characterized by Fourier transform infrared, transmission electron microscopy, and Brunauer-Emmett-Teller method. Encapsulation efficiency and drug loading efficiency of MSN-encapsulated bevacizumab nanoparticles were calculated. The pharmacokinetics, cytotoxicity, and tissue toxicity were evaluated in vitro and in vivo. The antiangiogenic effects of MSN-bevacizumab nanoparticles were evaluated in vitro and in vivo.

RESULTS

MSN encapsulation could prolong the residency of bevacizumab in vitreous/aqueous humor and maintain the long-lasting drug concentration. MSN-encapsulated bevacizumab nanoparticles did not show any obvious cytotoxicity and tissue toxicity. MSN-encapsulated bevacizumab nanoparticles were more effective than bevacizumab in suppressing vascular endothelial growth factor-induced endothelial cell proliferation, migration, and tube formation in vitro. MSN-encapsulated bevacizumab nanoparticles showed sustained inhibitory effects on corneal neovascularization and retinal neovascularization in vivo.

CONCLUSION

This study provides a novel strategy of encapsulating bevacizumab to protect and deliver it, which could increase the time between administration and formulation shelf-life. MSN-encapsulated bevacizumab is a promising drug delivery alternative of antiangiogenic therapy.

Phenotype-based Discovery of 2-[(E)-2-(Quinolin-2-yl)vinyl]phenol as a Novel Regulator of Ocular Angiogenesis

Retinal angiogenesis is tightly regulated to meet oxygenation and nutritional requirements. In diseases such as proliferative diabetic retinopathy and neovascular age-related macular degeneration, uncontrolled angiogenesis can lead to blindness. Our goal is to better understand the molecular processes controlling retinal angiogenesis and discover novel drugs that inhibit retinal neovascularization. Phenotype-based chemical screens were performed using the ChemBridge Diverset(TM)library and inhibition of hyaloid vessel angiogenesis in Tg(fli1:EGFP) zebrafish. 2-[(E)-2-(Quinolin-2-yl)vinyl]phenol, (quininib) robustly inhibits developmental angiogenesis at 4-10 μmin zebrafish and significantly inhibits angiogenic tubule formation in HMEC-1 cells, angiogenic sprouting in aortic ring explants, and retinal revascularization in oxygen-induced retinopathy mice. Quininib is well tolerated in zebrafish, human cell lines, and murine eyes. Profiling screens of 153 angiogenic and inflammatory targets revealed that quininib does not directly target VEGF receptors but antagonizes cysteinyl leukotriene receptors 1 and 2 (CysLT1-2) at micromolar IC50values. In summary, quininib is a novel anti-angiogenic small-molecule CysLT receptor antagonist. Quininib inhibits angiogenesis in a range of cell and tissue systems, revealing novel physiological roles for CysLT signaling. Quininib has potential as a novel therapeutic agent to treat ocular neovascular pathologies and may complement current anti-VEGF biological agents.