University of Toronto, Leslie Dan Faculty of Pharmacy

Toronto, Ontario, Canada

JOE M. & EULA C. LAWRENCE RESEARCH PROJECT

Effect of soluble epoxide hydrolase loss on a dry AMD-like
phenotype

The long-term goal is to find new therapeutic approaches for age-related macular degeneration, a disease characterized by abnormal blood vessel growth and retinal pigment epithelium (RPE) dysfunction. The specific goal of the current project is to explore soluble epoxide hydrolase (sEH), an enzyme identified by Dr. Corson’s laboratory to be important for abnormal new blood vessel growth and more recently for inflammation. Dr. Corson will use a mouse model lacking sEH in the RPE to assess its importance for dry AMD.

Plans for 2024

The goal for 2024 is to use this mouse model to explore whether loss of sEH in the RPE protects eyes against a dry AMD-like oxidative stress stimulus. We will delete (or not) sEH in the mouse RPE, then expose mice to sodium iodate, a chemical that causes retinal degeneration due to oxidative stress, with similarity to dry AMD. Dr. corson will assess whether mice with sEH loss are protected by assessing the structure of the retina and visual function by electroretinogram.

Specific Aims:
Aim 1: Assess the effect of RPE-specific sEH knockout on sodium iodate-induced retinal degeneration. We will expose our novel RPE-specific, inducible sEH knockout (KO) mice to NaIO3, which induces oxidative-stress mediated retinal degeneration with some features of dry AMD. We will assess these KO mice in comparison to uninduced controls by optical coherence tomography (OCT), fundus photography, fluorescein angiography (FA), electroretinogram (ERG), histology, and immunohistochemistry.

Progress in 2023

In previous years of RRF funding, Dr. Corson found sEH as a target of SH-11037, a chemical his laboratory developed that blocks blood vessel growth. We showed that sEH is present at high levels in human and mouse eyes with AMD-like features. His lab found that sEH inhibitors can block new blood vessel growth in the eye and we characterized the molecular mechanism of how SH-11037 inhibits sEH, and identified factors that increase its levels in the eye. The team assessed our library of novel chemicals to build a “structure activity relationship” for blocking sEH function. They showed differential expression in sEH between the sexes, found that depletion of sEH with a genetic tool we developed reduces inflammatory signals, and revealed RPE as a major source of this protein. They further explored whether sEH regulates the permeability of blood vessels in culture, finding that sEH inhibition can decrease leakiness of blood vessels. In 2023, Dr. Corson’s lab developed a mouse model in which sEH can be specifically “turned off” in the RPE cells where it is highly expressed. Importantly, sEH loss does not cause obvious defects in the eye.

2023 Publications

Progress in 2022

Role of soluble epoxide hydrolase in blood-retinal barrier function

In previous years of RRF funding, Dr. Corson developed a potent chemical called SH-11037, and tested this in combination with standard anti-VEGF therapy. His team found sEH as a cellular target of SH-11037, and showed that sEH is present at high levels in human and mouse eyes with AMD-like features. Likewise, they found that known sEH inhibitors can block new blood vessel growth in the eye and we characterized the molecular mechanism of how SH11037 inhibits sEH, including identifying factors that increase its levels in the eye. Assessment of their library of novel chemicals and found candidates that perform as well as SH11037 at blocking sEH, helping to build a “structure activity relationship” for blocking sEH function. They showed differential expression in sEH between the sexes, found that depletion of sEH with a genetic tool we developed reduces inflammatory signals, and revealed RPE as a major source of this protein. In 2022, we explored whether sEH regulates the permeability of blood vessels in culture, finding that sEH inhibition can decrease leakiness of blood vessels, one of the pathological features of wet AMD.

Specific Aims: Aim 1: Test the effects of sEH inhibition on EC and RPE barrier function. Human RPE cells and ocular ECs will be cultured as monolayers in the Electric Cell-substrate Impedance Sensing (ECIS) Z-Theta system, which measures monolayer permeability by impedance. They will be exposed to barrier-disrupting stimuli: oxidative and inflammatory signals for RPE and VEGF for ECs, then treated with sEH inhibitors and barrier function assessed. For further validation, cells with siRNA knockdown of sEH will also be tested.

Progress in 2021

Localization and lipid modulation of soluble epoxide hydrolase in choroidal neovascularization

In previous years of RRF funding, Dr. Corson’s team developed a potent chemical called SH-11037, and tested this in combination with standard anti-VEGF therapy. They found sEH as a cellular target of SH-11037, and showed that sEH is present at high levels in human and mouse eyes with AMD-like features. They also found that known sEH inhibitors can block new blood vessel growth in the eye and characterized the molecular mechanism of how SH11037 inhibits sEH, including identifying factors that increase its levels in the eye. The lab team assessed their library of novel chemicals and found candidates that perform as well as SH11037 at blocking sEH, helping to build a “structure activity relationship” for blocking sEH function. We showed differential expression in sEH between the sexes, and found that depletion of sEH with a genetic tool we developed reduces inflammatory signals. In 2021, we resolved a controversy on which cells express sEH in the eye, revealing RPE as a major source of this protein.

Progress in 2020

Effects of sex differences in soluble epoxide hydrolase expression on choroidal neovascularization

The specific goal of the 2020 project was to understand how the levels of soluble epoxide hydrolase (sEH), an enzyme identified to be important for abnormal new blood vessel growth, differ between the sexes, and how this influences the therapeutic effectiveness of sEH inhibitors.

Specific Aims: Aim 1: Examine sex differences in sEH expression and pharmacological response to sEH inhibitors. In a pilot study, male mice exhibited higher sEH expression in their eyes than females leading to the postulation that sex-specific expression of sEH could lead to differential response to sEH inhibition for new blood vessel growth.  Dr. Corson’s laboratory will assess the effects of sex differences in sEH expression on the therapeutic effects of sEH inhibition by genetic and chemical means.  They will explore downstream signaling in response to sEH inhibition.

Progress in 2019

Characterization of soluble expoxide hydrolase as a marker of choroidal neovascularization

 A major avenue for the treatment of diseases such as retinopathy of prematurity (ROP), proliferative diabetic retinopathy and wet age-related macular degeneration (AMD) is to stop the growth of new blood vessels in the eye, and there is a critical need to find new targets that could be effective in treating these blinding eye diseases.  Dr. Corson studies the mechanisms of a class of molecules called homoisoflavonoids, derived from medicinal plants, with potent effects on blocking blood vessel growth in mouse models of AMD and ROP.

His goal in 2019 was to find the cellular factors that promote high levels of sEH in new blood vessel growth in humans and mice. Dr. Corson’s work showed that sEH can be induced by cellular factors like stress, low oxygen levels, and high glucose known to be associated with eye disease, and in human wet AMD, that the light-sensing and pigmented cells of the retina increase sEH.   His research revealed that known sEH inhibitors can block new blood vessel growth in the eye, and his team characterized the molecular mechanism of the process.

Specific Aim: 1. Define factors that induce sEH overexpression in neovascularization. The working hypothesis for this aim is that proangiogenic stimuli – VEGF-A, TNF-α, endoplasmic reticulum (ER) stress and/or hypoxia – will enhance the expression and activity of sEH in photoreceptor cells, retinal pigment epithelial cells, and/or retinal and choroidal endothelial cells. sEH levels in treated cells will be assessed by qRTPCR and immunoblot, followed by sEH activity assays and luciferase assays. In addition, we will determine which retinal cell types in human eyes express sEH under normal and wet AMD conditions by co-immunostaining human sections with retinal cell type markers.

Progress in 2018

Screening homoisoflavonoids as soluble epoxide inhibitors for choroidal neovascularization

In prior years of RRF funding, Dr. Corson developed a potent chemical called SH-11037, and tested this in combination with anti-VEGF therapy. We found sEH as a cellular target of SH-11037, and showed that sEH is present at high levels in human and mouse eyes with AMD-like features. We found that known sEH inhibitors can block new blood vessel growth in the eye, that a substrate (input) of sEH was antiangiogenic, and we characterized the molecular mechanism of how SH-11037 inhibits sEH. In 2018, we assessed our library of novel chemicals and found candidates that perform as well as SH-11037 at blocking sEH, helping to build a “structure activity relationship” for blocking sEH function.

Progress in 2017

Role of epoxy lipid metabolism in choroidal neovascularization

Dr. Corson previously developed a potent “homoisoflavonoid” chemical called SH-11037, and tested this in combination with anti-VEGF therapy. His team found sEH as a cellular target of SH-11037, and showed that sEH is present at high levels in human and mouse eyes with AMD-like features. In 2017, they showed that a substrate (input) of sEH was antiangiogenic, characterized the molecular mechanism of how SH11037 inhibits sEH, showed this inhibition occurs in eye tissue, confirmed that the rod photoreceptor cells are the site of increased sEH in eyes undergoing angiogenesis, and found that known sEH inhibitors can block new blood vessel growth in the eye.

Progress in 2016

“Soluble epoxide hydrolase: a therapeutic target in choroidal neovascularization?”

Homoisoflavonoids are a small class of natural products that Dr. Corson has pursued as antiangiogenic leads. In particular, he focused on a target of SH-11037 that he identified, soluble epoxide hydrolase (sEH), hypothesizing that sEH is required for choroidal neovascularization. He has completed the Aim 1 of assessing sEH expression in murine and human choroidal neovascularization, and most of Aim 2, inhibiting sEH in the context of choroidal neovascularization. It will be important to determine what aspects of sEH function are important for blood vessel growth, and how this enzyme is linked to signaling in the cell.  This work will lay the groundwork for future efforts to target sEH for the treatment of wet AMD and related retinal diseases of abnormal blood vessel growth.

Progress in 2015

“Synergistic effects of a novel antiangiogenic molecule”

Dr. Corson’s laboratory tested their most potent synthetic homoisoflavanone, SH-11037, in combination with anti-VEGF therapy. It showed efficacy comparable to the standard anti-VEGF treatment in the laser-induced choroidal neovascularization (L-CNV) mouse model, which models some of the features of wet AMD. SH-11037 could synergize with anti-VEGF, reducing the amount of each drug needed for an effect. Importantly, they saw no short-or long-term toxicity in the eyes of adult mice with SH-11037 injected into their eyes. They have begun to tease apart how SH-11037 works to block blood vessel growth, and have identified an enzyme called soluble epoxide hydrolase (sEH) as a target of SH-11037. It will be important to assess if sEH is found at high levels in CNV, and if blocking its function can decrease L-CNV.

Corson Lab Group at 2015 ARVO (L to R): Mehdi Shadmand, Michael O’Hare, Rania Sulaiman, Tim Corson, Halesha Basavarajappa

Progress in 2014

“Testing a novel Antiangiogenic molecule in a mouse model of retinopathy of prematurity”

Dr. Corson further investigated a class of natural products, homoisoflavonoids, as antiangiogenic molecules. He synthesized a naturally occurring, antiangiogenic homoisoflavanone called Cremastranone derived from a medicinal orchid species and a novel isomer, both of which showed antiangiogenic activity in vitro.  He has tested a novel, more potent derivative of Cremastranone called SH-11037 in the oxygen-induced retinopathy (OIR) model of ROP. It showed efficacy comparable to the standard anti-VEGF treatment. Importantly, he saw no short- or long-term toxicity in the eyes of adult mice intravitreally injected with SH-11037, and the compound was also effective in the laser-induced choroidal neovascularization (L-CNV) mouse model. Dr. Corson has begun to tease apart how SH-11037 works to block blood vessel growth.

Corson laboratory staff

Progress in 2013

Dr. Corson investigated a class of natural products, homoisoflavonoids, as antiangiogenic molecules. He synthesized a novel isomer (SH-11052) of a naturally occurring, antiangiogenic homoisoflavanone derived from a medicinal orchid species and showed Antiangiogenic activity of SH-11052 in vitro. In the course of these studies, Dr. Corson’s laboratory developed a compound SH-11037, a novel therapeutic lead based on the natural product, but with improved efficacy and specificity. SH-11037 potently and specifically blocks human retinal microvascular endothelial cell (HRMVEC) proliferation, migration, and tube formation in vitro by a molecular mechanism distinct from other homoisoflavonoids, but has little cytotoxic effect on other ocular cell lines and does not promote apoptosis. In a small pilot experiment, SH-11037 showed antiangiogenic activity in the oxygen-induced retinopathy (OIR) model of ROP.