Sodium iodate induces ferroptosis in human retinal pigment epithelium ARPE-19 cells

Binghua Liu,Meng Yu,Libo He,Yang Liu,Arman Shah,Zihuai Tang,Ke Liu,Li Yang,Mengli Yan,Jinye Dang,Yuling Ying,Weiyan Wang

doi:10.1038/s41419-021-03520-2

Abstract

Sodium iodate (SI) is a widely used oxidant for generating retinal degeneration models by inducing the death of retinal pigment epithelium (RPE) cells. However, the mechanism of RPE cell death induced by SI remains unclear. In this study, we investigated the necrotic features of cultured human retinal pigment epithelium (ARPE-19) cells treated with SI and found that apoptosis or necroptosis was not the major death pathway. Instead, the death process was accompanied by significant elevation of intracellular labile iron level, ROS, and lipid peroxides which recapitulated the key features of ferroptosis. Ferroptosis inhibitors deferoxamine mesylate (DFO) and ferrostatin-1(Fer-1) partially prevented SI-induced cell death. Further studies revealed that SI treatment did not alter GPX4 (glutathione peroxidase 4) expression, but led to the depletion of reduced thiol groups, mainly intracellular GSH (reduced glutathione) and cysteine. The study on iron trafficking demonstrated that iron influx was not altered by SI treatment but iron efflux increased, indicating that the increase in labile iron was likely due to the release of sequestered iron. This hypothesis was verified by showing that SI directly promoted the release of labile iron from a cell-free lysate. We propose that SI depletes GSH, increases ROS, releases labile iron, and boosts lipid damage, which in turn results in ferroptosis in ARPE-19 cells.

Highlights

Introduction Theretinal pigment epithelium (RPE) layer consists of a single layer of neatly arranged and highly specialized cells located between the retinal photoreceptors and the choroid
At concentrations in the millimolar range that have been widely used for establishing degeneration models of retina[32], we found that sodium iodate (SI) induced the death of ARPE-19 cells in a time and concentration-dependent manner (Fig. 1A, Fig. S1)
The loss of membrane potential (MMP) can be induced by apoptosis, the similarity of Hoechst 33342 staining between control and SI-treated cells suggests that SI did not enhance apoptosis of ARPE-19 cells (Fig. 1E)

Summary

Introduction

Introduction TheRPE layer consists of a single layer of neatly arranged and highly specialized cells located between the retinal photoreceptors and the choroid. Oxidative stress can increase the level of ROS7, deplete ATP8, and promote plasma membrane leakage[8], DNA damage[9], and premature aging[10] in RPE cells. These lesions in turn obstruct the functionality of RPE cells, which leads to retinal degeneration. Many oxidative agents have been used to study the mechanism of retinal degeneration and evaluate treatments for retina protection. Despite the wide usage of SI to generate retinal degeneration models, the mechanism of SI-induced death of RPE cells is poorly understood. It was reported that SI treatment of RPE cells resulted in the aggregation of receptor-interacting protein kinase 3

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Results

Conclusion