(−)-Epicatechin, a Natural Flavonoid Compound, Protects Astrocytes Against Hemoglobin Toxicity via Nrf2 and AP-1 Signaling Pathways

Xi Lan, Xiaoning Han, Qian Li, Jian Wang

Research output: Contribution to journalArticle

Abstract

(−)-Epicatechin is a brain-permeable, natural product found at high concentrations in green tea and cocoa. Our previous research has shown that (−)-epicatechin treatment reduces hemorrhagic stroke injury via nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in vivo. However, the mechanism of action of this compound in modulation of oxidant stress and in protection against hemoglobin-induced astrocyte injury is unclear. Therefore, we explored the cellular and molecular mechanisms that underlie these protective effects in vitro. Mouse primary astrocytes isolated from wild-type mice and Nrf2 knockout (KO) mice were preconditioned with hemoglobin to simulate intracerebral hemorrhage (ICH) in vitro. Effects of (−)-epicatechin were measured by Western blotting, immunostaining, MTT assay, and reactive oxidant stress (ROS) assay. (−)-Epicatechin increased Nrf2 nuclear accumulation and cytoplasmic levels of superoxide dismutase 1 (SOD1) in wild-type astrocytes but did not increase SOD1 expression in Nrf2 knockout (KO) astrocytes. Furthermore, (−)-epicatechin treatment did not alter heme oxygenase 1 (HO1) expression in wild-type astrocytes after hemoglobin exposure, but it did decrease HO1 expression in similarly treated Nrf2 KO astrocytes. In both wild-type and Nrf2 KO astrocytes, (−)-epicatechin suppressed phosphorylated JNK and nuclear expression of JNK, c-jun, and c-fos, indicating that inhibition of activator protein-1 (AP-1) activity by (−)-epicatechin is Nrf2-independent. These novel findings indicate that (−)-epicatechin protects astrocytes against hemoglobin toxicity through upregulation of Nrf2 and inhibition of AP-1 activity. These cellular and molecular effects may partially explain the cerebroprotection as we previously observed for (−)-epicatechin in animal models of ICH.

LanguageEnglish (US)
Pages1-10
Number of pages10
JournalMolecular Neurobiology
DOIs
StateAccepted/In press - Nov 18 2016

Fingerprint

Catechin
Transcription Factor AP-1
Flavonoids
Astrocytes
Hemoglobins
Heme Oxygenase-1
Cerebral Hemorrhage
Oxidants
Wounds and Injuries
Tea
Biological Products
Knockout Mice
Up-Regulation
Animal Models
Western Blotting
Stroke
Brain

Keywords

  • (−)-Epicatechin
  • Heme oxygenase 1
  • Intracerebral hemorrhage
  • Nuclear factor erythroid 2-related factor 2
  • Reactive oxygen species

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience

Cite this

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title = "(−)-Epicatechin, a Natural Flavonoid Compound, Protects Astrocytes Against Hemoglobin Toxicity via Nrf2 and AP-1 Signaling Pathways",
abstract = "(−)-Epicatechin is a brain-permeable, natural product found at high concentrations in green tea and cocoa. Our previous research has shown that (−)-epicatechin treatment reduces hemorrhagic stroke injury via nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in vivo. However, the mechanism of action of this compound in modulation of oxidant stress and in protection against hemoglobin-induced astrocyte injury is unclear. Therefore, we explored the cellular and molecular mechanisms that underlie these protective effects in vitro. Mouse primary astrocytes isolated from wild-type mice and Nrf2 knockout (KO) mice were preconditioned with hemoglobin to simulate intracerebral hemorrhage (ICH) in vitro. Effects of (−)-epicatechin were measured by Western blotting, immunostaining, MTT assay, and reactive oxidant stress (ROS) assay. (−)-Epicatechin increased Nrf2 nuclear accumulation and cytoplasmic levels of superoxide dismutase 1 (SOD1) in wild-type astrocytes but did not increase SOD1 expression in Nrf2 knockout (KO) astrocytes. Furthermore, (−)-epicatechin treatment did not alter heme oxygenase 1 (HO1) expression in wild-type astrocytes after hemoglobin exposure, but it did decrease HO1 expression in similarly treated Nrf2 KO astrocytes. In both wild-type and Nrf2 KO astrocytes, (−)-epicatechin suppressed phosphorylated JNK and nuclear expression of JNK, c-jun, and c-fos, indicating that inhibition of activator protein-1 (AP-1) activity by (−)-epicatechin is Nrf2-independent. These novel findings indicate that (−)-epicatechin protects astrocytes against hemoglobin toxicity through upregulation of Nrf2 and inhibition of AP-1 activity. These cellular and molecular effects may partially explain the cerebroprotection as we previously observed for (−)-epicatechin in animal models of ICH.",
keywords = "(−)-Epicatechin, Heme oxygenase 1, Intracerebral hemorrhage, Nuclear factor erythroid 2-related factor 2, Reactive oxygen species",
author = "Xi Lan and Xiaoning Han and Qian Li and Jian Wang",
year = "2016",
month = "11",
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doi = "10.1007/s12035-016-0271-y",
language = "English (US)",
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T1 - (−)-Epicatechin, a Natural Flavonoid Compound, Protects Astrocytes Against Hemoglobin Toxicity via Nrf2 and AP-1 Signaling Pathways

AU - Lan,Xi

AU - Han,Xiaoning

AU - Li,Qian

AU - Wang,Jian

PY - 2016/11/18

Y1 - 2016/11/18

N2 - (−)-Epicatechin is a brain-permeable, natural product found at high concentrations in green tea and cocoa. Our previous research has shown that (−)-epicatechin treatment reduces hemorrhagic stroke injury via nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in vivo. However, the mechanism of action of this compound in modulation of oxidant stress and in protection against hemoglobin-induced astrocyte injury is unclear. Therefore, we explored the cellular and molecular mechanisms that underlie these protective effects in vitro. Mouse primary astrocytes isolated from wild-type mice and Nrf2 knockout (KO) mice were preconditioned with hemoglobin to simulate intracerebral hemorrhage (ICH) in vitro. Effects of (−)-epicatechin were measured by Western blotting, immunostaining, MTT assay, and reactive oxidant stress (ROS) assay. (−)-Epicatechin increased Nrf2 nuclear accumulation and cytoplasmic levels of superoxide dismutase 1 (SOD1) in wild-type astrocytes but did not increase SOD1 expression in Nrf2 knockout (KO) astrocytes. Furthermore, (−)-epicatechin treatment did not alter heme oxygenase 1 (HO1) expression in wild-type astrocytes after hemoglobin exposure, but it did decrease HO1 expression in similarly treated Nrf2 KO astrocytes. In both wild-type and Nrf2 KO astrocytes, (−)-epicatechin suppressed phosphorylated JNK and nuclear expression of JNK, c-jun, and c-fos, indicating that inhibition of activator protein-1 (AP-1) activity by (−)-epicatechin is Nrf2-independent. These novel findings indicate that (−)-epicatechin protects astrocytes against hemoglobin toxicity through upregulation of Nrf2 and inhibition of AP-1 activity. These cellular and molecular effects may partially explain the cerebroprotection as we previously observed for (−)-epicatechin in animal models of ICH.

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KW - (−)-Epicatechin

KW - Heme oxygenase 1

KW - Intracerebral hemorrhage

KW - Nuclear factor erythroid 2-related factor 2

KW - Reactive oxygen species

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