Synergistic Protection by Isoquercitrin and Quercetin against Glutamate-Induced Oxidative Cell Death in HT22 Cells via Activating Nrf2 and HO-1 Signaling Pathway: Neuroprotective Principles and Mechanisms of Dendropanax morbifera Leaves.

Hye-Jin Park,Seung-Hoon Baek,Min-Duk Seo,Chul Young Kim,Ha-Neul Kim

doi:10.3390/antiox10040554

Hye-Jin Park, Seung-Hoon Baek + Show 3 more

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https://doi.org/10.3390/antiox10040554

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Journal: Antioxidants	Publication Date: Apr 2, 2021
Citations: 29	License type: CC BY 4.0

Affiliation: Ajou University, Hanyang University

Abstract

Dendropanax morbifera leaves (DML) have long been used as traditional medicine to treat diverse symptoms in Korea. Ethyl acetate-soluble extracts of DML (DMLE) rescued HT22 mouse hippocampal neuronal cells from glutamate (Glu)-induced oxidative cell death; however, the protective compounds and mechanisms remain unknown. Here, we aimed to identify the neuroprotective ingredients and mechanisms of DMLE in the Glu-HT22 cell model. Five antioxidant compounds were isolated from DMLE and characterized as chlorogenic acid, hyperoside, isoquercitrin, quercetin, and rutin by spectroscopic methods. Isoquercitrin and quercetin significantly inhibited Glu-induced oxidative cell death by restoring intracellular reactive oxygen species (ROS) levels and mitochondrial superoxide generation, Ca2+ dysregulation, mitochondrial dysfunction, and nuclear translocation of apoptosis-inducing factor. These two compounds significantly increased the expression levels of nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) in the presence or absence of Glu treatment. Combinatorial treatment of the five compounds based on the equivalent concentrations in DMLE showed that significant protection was found only in the cells cotreated with isoquercitrin and quercetin, both of whom showed prominent synergism, as assessed by drug–drug interaction analysis. These findings suggest that isoquercitrin and quercetin are the active principles representing the protective effects of DMLE, and these effects were mediated by the Nrf2/HO-1 pathway.

Highlights

Glutamate (Glu)-induced oxidative cell death has been implicated in diverse neurological disorders, such as stroke, traumatic brain injury, epilepsy, and neurodegenerative diseases [1,2,3,4]
Isoquercitrin or quercetin significantly increased nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) levels by approximately 2-fold in a concentration-dependent manner. This was consistently found with I/Q and DMLE but not in NAC. These findings suggest that the activation of the Nrf2/HO-1 pathway may be associated with the protective effects of isoquercitrin or quercetin, which can be differentiated from those of NAC
Based on the HPLC and combinatory treatment assays, we found that isoquercitrin and quercetin are responsible for the protective effects of DMLE

Summary

Introduction

Glutamate (Glu)-induced oxidative cell death has been implicated in diverse neurological disorders, such as stroke, traumatic brain injury, epilepsy, and neurodegenerative diseases [1,2,3,4]. The pathological stimuli on the central nervous system induce the accumulation of extracellular Glu in glutamatergic synapses, thereby killing neuronal cells via excitotoxicity [5]. Glu receptors (GluRs) and cystine/Glu antiporters (system xc− ) are the major responders that initiate excitotoxicity [6]. Cytosolic release of Ca2+ from the endoplasmic reticulum (ER). It reverses the action of xc− to facilitate the export of cystine and import of Glu and leads to the inhibition of glutathione (GSH) synthesis.

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