Aquaporin-1: a potential target for age-related macular degeneration

Abstract

Purpose : Age-related macular degeneration (AMD) is a leading cause of central vision loss, which involves lesions in the Bruch’s membrane/RPE (retinal pigment epithelium) layer and abnormal neovascularization that originates from the choroid. Despite success with anti-VEGF (vascular endothelial growth factor) therapy, a significant number of patients do not respond with appreciable clinical improvements, which justifies the need for the discovery of novel targets that modulate angiogenic processes. Recent evidence indicates that water channel protein Aquaporin-1 (AQP1) is involved in angiogenesis. Our purpose is to validate the role of AQP1 in retina/choroid angiogenesis using the AQP1 inhibitor that we recently identified in in vitro and ex vivo models for angiogenesis.

Methods : Immunohistochemistry was performed to detect the expression of AQP1 in retina/choroid tissue from normal and laser-induced choroidal neovascularization (CNV) mice using AQP1 monoclonal antibody. Transwell migration assay was performed using primary human retinal endothelial cells and choroidal sprouting assay was performed using choroid explants isolated from postnatal day 3 C56/BL6 mouse pups. VEGF, VEGF-antibody and Linifanib were used as the reference compounds.

Results : AQP1 was expressed in sclera, RPE/choroid and outer retina but not in the inner retina. Expression of AQP1 was upregulated in lesions of RPE/choroid in laser-induced CNV mice compared to RPE/choroid from normal mice. AQP1 inhibitor reduced retinal endothelial cell migration rate and choroidal sprouting in a dose dependent manner. Cell migration was decreased by 82 ± 3.4% (n=3, mean SD) in the presence of 1.0 µM AQP1 inhibitor Whereas, AQP1 inhibitor blocked choroidal angiogenesis with an IC₅₀ value of 1.4 ± 0.075 µM (n = 6, mean SEM), which is agreeable with the reported IC₅₀ value of 2.7 µM for this compound in a cell based water channel activity.

Conclusions : We observed upregulation of AQP1 in the lesions of retina/choroid during neovascularization compared to normal mice. Further, results obtained using AQP1 inhibitor suggests that AQP1 is involved in human retinal endothelial cell migration and new vessel formation in mouse choroid. Based on these observations we postulate that inhibition of AQP1 will have marked effect on retina/choroid angiogenesis and can serve as potential/effective target for modulation of neovascularization in AMD.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.