CHOP deletion and anti-neuroinflammation treatment with hesperidin synergistically attenuate NMDA retinal injury in mice

Kota Sato,Taimu Sato,Michiko Ohno-Oishi,Mikako Ozawa,Shigeto Maekawa,Yukihiro Shiga,Takeshi Yabana,Masayuki Yasuda,Noriko Himori,Kazuko Omodaka,Kosuke Fujita,Koji M Nishiguchi,Shi Ge,Toru Nakazawa

doi:10.1016/j.exer.2021.108826

Kota Sato, Taimu Sato + Show 12 more

Open Access

https://doi.org/10.1016/j.exer.2021.108826

Copy DOI

Journal: Experimental Eye Research	Publication Date: Nov 6, 2021
Citations: 22	License type: cc-by

Affiliation: Tohoku University, Nagoya University

Abstract

Glaucoma is a leading cause of blindness worldwide and is characterized by degeneration associated with the death of retinal ganglion cells (RGCs). It is believed that glaucoma is a group of heterogeneous diseases with multifactorial pathomechanisms. Here, we investigate whether anti-inflammation treatment with an ER stress blockade can selectively promote neuroprotection against NMDA injury in the RGCs. Retinal excitotoxicity was induced with an intravitreal NMDA injection. Microglial activation and neuroinflammation were evaluated with Iba1 immunostaining and cytokine gene expression. A stable HT22 cell line transfected with an NF-kB reporter was used to assess NF-kB activity after hesperidin treatment. CHOP-deficient mice were used as a model of ER stress blockade. Retinal cell death was evaluated with a TUNEL assay. As results, in the NMDA injury group, Iba1-positive microglia increased 6 h after NMDA injection. Also at 6 h, pro-inflammatory cytokines and chemokine increased, including TNFα, IL-1b, IL-6 and MCP-1. In addition, the MCP-1 promoter-driven EGFP signal, which we previously identified as a stress signal in injured RGCs, also increased; hesperidin treatment suppressed this inflammatory response and reduced stressed RGCs. In CHOP-deficient mice that received an NMDA injection, the gene expression of pro-inflammatory cytokines, chemokines, markers of active microglia, and inflammatory regulators was greater than in WT mice. In WT mice, hesperidin treatment partially prevented retinal cell death after NMDA injury; this neuroprotective effect was enhanced in CHOP-deficient mice. These findings demonstrate that ER stress blockade is not enough by itself to prevent RGC loss due to neuroinflammation in the retina, but it has a synergistic neuroprotective effect after NMDA injury when combined with an anti-inflammatory treatment based on hesperidin.

Highlights

Glaucoma has become the most frequent cause of irreversible blindness worldwide
These findings demonstrate that ER stress blockade is not enough by itself to prevent retinal ganglion cells (RGCs) loss due to neuroinflammation in the retina, but it has a synergistic neuroprotective effect after N-methyl- D-aspartate (NMDA) injury when combined with an anti-inflammatory treatment based on hesperidin
Memantine has been found to prevent RGC loss in a high-intraocular pressure (IOP) model of glaucoma [12]. These findings indicate that NMDA receptors are involved in RGC loss in glaucoma even when IOP is not elevated, making it important to clarify the pathomechanism of excitotoxicity to prevent RGC death

Summary

Introduction

Glaucoma has become the most frequent cause of irreversible blindness worldwide It is characterized by a progressive loss of retinal ganglion cells (RGCs) that results in characteristic visual field defects[1]. Studies of in vitro human samples and in vivo animal models have provided some evidence of the triggers that cause RGC loss. These include many well-known contributors to the pathogenesis of RGC death, and include such events and molecules as oxidative stress[3][4], a low level of ocular blood flow[5], genetics[6], excessive calpain activation[7], glutamate excitotoxicity[8], and neuroinflammation[9].

Methods

Results

Conclusion