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.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, 720 Rutland Ave, Ross Bldg 370B, Baltimore, MD, 21205, USA.
authors.forename: Xi
authors.initials: X
authors.lastname: Lan
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, 720 Rutland Ave, Ross Bldg 370B, Baltimore, MD, 21205, USA.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Han
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, 720 Rutland Ave, Ross Bldg 370B, Baltimore, MD, 21205, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, 720 Rutland Ave, Ross Bldg 370B, Baltimore, MD, 21205, USA. jwang79@jhmi.edu.
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D002392:Catechin / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology*; D006454:Hemoglobins / Q000494:pharmacology*; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000187:drug effects; D018696:Neuroprotective Agents / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013482:Superoxide Dismutase / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000187:drug effects* / Q000378:metabolism
chemical_list: D005419:Flavonoids; D006454:Hemoglobins; D051267:NF-E2-Related Factor 2; D018696:Neuroprotective Agents; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; D002392:Catechin; D013482:Superoxide Dismutase
keywords: (−)-Epicatechin; Heme oxygenase 1; Intracerebral hemorrhage; Nuclear factor erythroid 2-related factor 2; Reactive oxygen species