Effect of Dual Endothelin Receptor Antagonist on a Retinal Degeneration Animal Model by Regulating Choroidal Microvascular Morphology.

Xiaowei Zhu,Yuanbin Li,Qing Zhou,Ying Xu,Xiaowei Sun,Naiyang Li,Xuming Lin

doi:10.1155/2021/5688300

Abstract

Objective Clinical studies have found that increasing levels of plasma endothelin-1 (ET-1) might inhibit choroidal blood flow (BF) and promote choroidal vasoconstriction. This study was designed to investigate ET-1 levels and its effect on choroidal microvascular morphology in a retinitis pigmentosa (RP) animal model. Methods Mice with retinal degeneration (rd10) were intragastrically administered bosentan, a dual endothelin receptor antagonist. We detected plasma ET-1 levels using an enzyme-linked immunosorbent assay (ELISA) kit at P14, P21, and P28 and evaluated ET-1 expression in RPE/choroid/sclera complexes using western blot and whole mount immunofluorescence staining at P28. Retinal thickness was measured using hematoxylin and eosin (H&E) staining at P28. At the same time, we also estimated choroidal microvascular densities using vascular luminal casting with a scanning electron microscope (SEM). Results Plasma ET-1 levels were increased significantly in rd10 mice at P21 (65.48 ± 24.83 pg/ml) and P28 (85.89 ± 20.23 pg/ml) compared with C57BL/6J mice at P21 (33.52 ± 16.33 pg/ml) and P28 (42.38 ± 17.53 pg/ml); the expression of ET-1 was also upregulated in RPE/choroid/sclera complexes at P28. Bosentan inhibited ET-1 expression in plasma (P < 0.05) and RPE/choroid/sclera complexes at P28 in rd10 mice. Choroidal microvascular densities were decreased in rd10 mice, and bosentan could weaken these changes. Conclusion Plasma and local ET-1 was elevated in an animal model of RP, suggesting that it likely participates in the pathological progression of retinal degeneration and may thus provide a new intervention target. ET-1 blockade might exert its protective effect by elevating choroidal microvascular density via inhibition of ET-1.

Highlights

Retinitis pigmentosa (RP), a common cause of blindness in working age people [1], is a well-known hereditary disease with >200 gene variations; it is characterized by nyctalopia and concentric visual-field defects [2, 3]
All mice were maintained in specific pathogen-free (SPF) laboratories at Yantai Yuhuangding Hospital (YYH; Yantai, China), and 34 C57 mice and 46 rd10 mice were used in this experiment. is study was approved by the Animal Ethics Committee of YYH and was performed in accordance with the Association for Research in Vision and Ophthalmology (ARVO) Statement for the Use of Animals in Ophthalmic and Vision Research. ere were three groups in this study: a C57BL/6J control group, a rd10 group that received phosphate-buffered saline (PBS) intragastrically (i.g.), and a rd10+bosentan group that received 100 mg/kg bosentan
Plasma levels of ET-1 were increased in rd10 mice, while those in C57 mice remained relatively stable from P14 to P28 (Figure 1(a))

Summary

Introduction

Retinitis pigmentosa (RP), a common cause of blindness in working age people [1], is a well-known hereditary disease with >200 gene variations; it is characterized by nyctalopia (night blindness) and concentric visual-field defects [2, 3]. ET-1, which is mainly secreted by vascular endothelial cells (ECs), can constrict vessels, promote the proliferation of vascular smooth-muscle cells, and remodel vasculature It mediates these physiological functions mainly through two subtype receptors of ETA and ETB, which are expressed in human and animal choroids [9, 10]. Bosentan was a nonpeptide orally active dual ETA and ETB antagonist chemically named 4-tert-butyl-N-[6-(2-hydroxyethoxy)-5-(2-methoxyphenoxy)-2-(2-pyrimidinyl)-4-pyrimidinyl] benzenesulfonamide mainly used as a first-line treatment option for pulmonary artery hypertension [13]. For this reason, we assumed that ET-1 may participate in the pathological progress of RP and ET-1 blockade using bosentan might slow it down by regulating the choroidal BF

Methods

Results

Conclusion