Browsing by Author "Muniyandi, Anbukkarasi"

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    An improved method for murine laser-induced choroidal neovascularization lesion quantification from optical coherence tomography images
    (Elsevier, 2022-08-02) Jensen, Nathan R.; Lambert-Cheatham, Nathan; Hartman, Gabriella D.; Muniyandi, Anbukkarasi; Park, Bomina; Sishtla, Kamakshi; Corson, Timothy W.; Ophthalmology, School of Medicine
    Laser-induced choroidal neovascularization (L-CNV) in murine models is a standard method for assessing therapies, genetics, and mechanisms relevant to the blinding eye disease neovascular or "wet" age-related macular degeneration. The ex vivo evaluation of these lesions involves confocal microscopy analysis. In vivo evaluation via optical coherence tomography (OCT) has previously been established and allows longitudinal assessment of lesion development. However, to produce robust data, evaluation of many lesions may be required, which can be a slow, arduous process. A prior, manual method for quantifying these lesions as ellipsoids from orthogonal OCT images was effective but time consuming. We therefore developed an OCT lesion quantification that is simplified, streamlined, and less time-consuming.
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    Beyond VEGF: Targeting Inflammation and Other Pathways for Treatment of Retinal Disease
    (American Society for Pharmacology and Experimental Therapeutics, 2023) Muniyandi, Anbukkarasi; Hartman, Gabriella D.; Song, Yang; Mijit, Mahmut; Kelley, Mark R.; Corson, Timothy W.; Ophthalmology, School of Medicine
    Neovascular eye diseases include conditions such as retinopathy of prematurity, proliferative diabetic retinopathy, and neovascular age-related macular degeneration. Together, they are a major cause of vision loss and blindness worldwide. The current therapeutic mainstay for these diseases is intravitreal injections of biologics targeting vascular endothelial growth factor (VEGF) signaling. Lack of universal response to these anti-VEGF agents coupled with the challenging delivery method underscore a need for new therapeutic targets and agents. In particular, proteins that mediate both inflammatory and proangiogenic signaling are appealing targets for new therapeutic development. Here, we review agents currently in clinical trials and highlight some promising targets in preclinical and early clinical development, focusing on the redox-regulatory transcriptional activator APE1/Ref-1, the bioactive lipid modulator soluble epoxide hydrolase, the transcription factor RUNX1, and others. Small molecules targeting each of these proteins show promise for blocking neovascularization and inflammation. The affected signaling pathways illustrate the potential of new antiangiogenic strategies for posterior ocular disease. SIGNIFICANCE STATEMENT: Discovery and therapeutic targeting of new angiogenesis mediators is necessary to improve treatment of blinding eye diseases like retinopathy of prematurity, diabetic retinopathy, and neovascular age-related macular degeneration. Novel targets undergoing evaluation and drug discovery work include proteins important for both angiogenesis and inflammation signaling, including APE1/Ref-1, soluble epoxide hydrolase, RUNX1, and others.
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    PRMT5 is a therapeutic target in choroidal neovascularization
    (Nature, 2023) Muniyandi, Anbukkarasi; Martin, Matthew; Sishtla, Kamakshi; Motolani, Aishat; Sun, Mengyao; Jensen, Nathan R.; Qi, Xiaoping; Boulton, Michael E.; Prabhu, Lakshmi; Lu, Tao; Corson, Timothy W.; Ophthalmology, School of Medicine
    Ocular neovascular diseases including neovascular age-related macular degeneration (nvAMD) are widespread causes of blindness. Patients’ non-responsiveness to currently used biologics that target vascular endothelial growth factor (VEGF) poses an unmet need for novel therapies. Here, we identify protein arginine methyltransferase 5 (PRMT5) as a novel therapeutic target for nvAMD. PRMT5 is a well-known epigenetic enzyme. We previously showed that PRMT5 methylates and activates a proangiogenic and proinflammatory transcription factor, the nuclear factor kappa B (NF-κB), which has a master role in tumor progression, notably in pancreatic ductal adenocarcinoma and colorectal cancer. We identified a potent and specific small molecule inhibitor of PRMT5, PR5-LL-CM01, that dampens the methylation and activation of NF-κB. Here for the first time, we assessed the antiangiogenic activity of PR5-LL-CM01 in ocular cells. Immunostaining of human nvAMD sections revealed that PRMT5 is highly expressed in the retinal pigment epithelium (RPE)/choroid where neovascularization occurs, while mouse eyes with laser induced choroidal neovascularization (L-CNV) showed PRMT5 is overexpressed in the retinal ganglion cell layer and in the RPE/choroid. Importantly, inhibition of PRMT5 by PR5-LL-CM01 or shRNA knockdown of PRMT5 in human retinal endothelial cells (HRECs) and induced pluripotent stem cell (iPSC)-derived choroidal endothelial cells (iCEC2) reduced NF-κB activity and the expression of its target genes, such as tumor necrosis factor α (TNF-α) and VEGF-A. In addition to inhibiting angiogenic properties of proliferation and tube formation, PR5-LL-CM01 blocked cell cycle progression at G1/S-phase in a dose-dependent manner in these cells. Thus, we provide the first evidence that inhibition of PRMT5 impedes angiogenesis in ocular endothelial cells, suggesting PRMT5 as a potential therapeutic target to ameliorate ocular neovascularization.
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    Retinal Phenotyping of Ferrochelatase Mutant Mice Reveals Protoporphyrin Accumulation and Reduced Neovascular Response
    (ARVO, 2021-02-01) Sardar Pasha, S. P. B.; Shetty, Trupti; Lambert-Cheatham, Nathan A.; Sishtla, Kamakshi; Mathew, Deepa; Muniyandi, Anbukkarasi; Patwari, Neeta; Bhatwadekar, Ashay D.; Corson, Timothy W.; Ophthalmology, School of Medicine
    Purpose: Heme depletion, through inhibition of ferrochelatase (FECH), blocks retinal and choroidal neovascularization. Both pharmacologic FECH inhibition and a partial loss-of-function Fech mutation (Fechm1Pas) are associated with decreased neovascularization. However, the ocular physiology of Fechm1Pas mice under basal conditions has not been characterized. Here, we aimed to characterize the retinal phenotype of Fechm1Pas mice. Methods: We monitored retinal vasculature at postnatal day 17, 2 months, and 6 months in Fechm1Pas homozygotes, heterozygotes, and their wild-type littermates. We characterized Fech substrate protoporphyrin (PPIX) fluorescence in the eye (excitation = 403 nm, emission = 628 nm), retinal function by electroretinogram, visual acuity by optomotor reflex, and retinal morphology by optical coherence tomography and histology. We stained vasculature using isolectin B4 and fluorescein angiography. We determined endothelial sprouting of retinal and choroidal tissue ex vivo and bioenergetics of retinal punches using a Seahorse flux analyzer. Results: Fundi, retinal vasculature, venous width, and arterial tortuosity showed no aberrations. However, VEGF-induced retinal and choroidal sprouting was decreased in Fechm1Pas mutants. Homozygous Fechm1Pas mice had pronounced buildup of PPIX in the posterior eye with no damage to visual function, bioenergetics, and integrity of retinal layers. Conclusions: Even with a buildup of PPIX in the retinal vessels in Fechm1Pas homozygotes, the vasculature remains normal. Notably, stimulus-induced ex vivo angiogenesis was decreased in Fechm1Pas mutants, consistent with reduced pathologic angiogenesis seen previously in neovascular animal models. Our findings indicate that Fechm1Pas mice are a useful model for studying the effects of heme deficiency on neovascularization due to Fech blockade.
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    Small-molecule inhibitors of ferrochelatase are antiangiogenic agents
    (Elsevier, 2022-01-31) Sishtla, Kamakshi; Lambert-Cheatham, Nathan; Lee, Bit; Han, Duk Hee; Park, Jaehui; Sardar Pasha, Sheik Pran Babu; Lee, Sanha; Kwon, Sangil; Muniyandi, Anbukkarasi; Park, Bomina; Odell, Noa; Waller, Sydney; Park, Il Yeong; Lee, Soo Jae; Seo, Seung-Yong; Corson, Timothy W.; Ophthalmology, School of Medicine
    Activity of the heme synthesis enzyme ferrochelatase (FECH) is implicated in multiple diseases. In particular, it is a mediator of neovascularization in the eye and thus an appealing therapeutic target for preventing blindness. However, no drug-like direct FECH inhibitors are known. Here, we set out to identify small-molecule inhibitors of FECH as potential therapeutic leads using a high-throughput screening approach to identify potent inhibitors of FECH activity. A structure-activity relationship study of a class of triazolopyrimidinone hits yielded drug-like FECH inhibitors. These compounds inhibit FECH in cells, bind the active site in cocrystal structures, and are antiangiogenic in multiple in vitro assays. One of these promising compounds was antiangiogenic in vivo in a mouse model of choroidal neovascularization. This foundational work may be the basis for new therapeutic agents to combat not only ocular neovascularization but also other diseases characterized by FECH activity.
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    The Potential of Aqueous Humor Sampling in Diagnosis, Prognosis, and Treatment of Retinoblastoma
    (Association for Research in Vision and Ophthalmology (ARVO), 2024) Muniyandi, Anbukkarasi; Jensen, Nathan R.; Devanathan, Nirupama; Dimaras, Helen; Corson, Timothy W.; Pharmacology and Toxicology, School of Medicine
    Retinoblastoma (RB) is a rare malignant tumor that arises in the developing retina in one or both eyes of children. Pathogenic variants of the RB1 tumor suppressor gene drive the majority of germline and sporadic RB tumors. Considering the risk of tumor spread, the biopsy of RB tumor tissue is contraindicated. Advancement of chemotherapy has led to preservation of more eye globes. However, this has reduced access to tumor material from enucleation specimens. Recently, liquid biopsy of aqueous humor (AH) has advanced the RB tumor- or eye-specific genetic analysis. In particular, nucleic acid analysis of AH demonstrates the genomic copy number profiles and RB1 pathogenic variants akin to that of enucleated RB eye tissue. This advance reduces the previous limitation that genetic assessment of the primary tumor could be done only after enucleation of the eye. Additionally, nucleic acid evaluation of AH allows the exploration of the genomic landscape of RB tumors at diagnosis and during and after treatment. This review explores how AH sampling and AH nucleic acid analysis in RB patients assist in diagnosis, prognosis, and comprehending the pathophysiology of RB, which will ultimately benefit individualized treatment decisions to carefully manage this ocular cancer in children.