title: Cleaning up after ICH: the role of Nrf2 in modulating microglia function and hematoma clearance.
abstract: As a consequence of intracerebral hemorrhage (ICH), blood components enter brain parenchyma causing progressive damage to the surrounding brain. Unless hematoma is cleared, the reservoirs of blood continue to inflict injury to neurovascular structures and blunt the brain repair processes. Microglia/macrophages (MMΦ) represent the primary phagocytic system that mediates the cleanup of hematoma. Thus, the efficacy of phagocytic function by MMΦ is an essential step in limiting ICH-mediated damage. Using primary microglia to model red blood cell (main component of hematoma) clearance, we studied the role of transcription factor nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), a master-regulator of antioxidative defense, in the hematoma clearance process. We showed that in cultured microglia, activators of Nrf2 (i) induce antioxidative defense components, (ii) reduce peroxide formation, (iii) up-regulate phagocytosis-mediating scavenger receptor CD36, and (iv) enhance red blood cells (RBC) phagocytosis. Through inhibiting Nrf2 or CD36 in microglia, by DNA decoy or neutralizing antibody, we documented the important role of Nrf2 and CD36 in RBC phagocytosis. Using autologous blood injection ICH model to measure hematoma resolution, we showed that Nrf2 activator, sulforaphane, injected to animals after the onset of ICH, induced CD36 expression in ICH-affected brain and improved hematoma clearance in rats and wild-type mice, but expectedly not in Nrf2 knockout (KO) mice. Normal hematoma clearance was impaired in Nrf2-KO mice. Our experiments suggest that Nrf2 in microglia play an important role in augmenting the antioxidative capacity, phagocytosis, and hematoma clearance after ICH.
authors.affiliation: Stroke Program - Department of Neurology, University of Texas Health Science Center, Medical School at Houston, Houston, Texas, USA.
authors.forename: Xiurong
authors.initials: X
authors.lastname: Zhao
authors.forename: Guanghua
authors.initials: G
authors.lastname: Sun
authors.forename: Shun-Ming
authors.initials: SM
authors.lastname: Ting
authors.forename: Shen
authors.initials: S
authors.lastname: Song
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Edwards
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Aronowski
mesh_terms: D000818:Animals; D001921:Brain / Q000473:pathology; D018955:CD36 Antigens / Q000096:biosynthesis; D002452:Cell Count; D002478:Cells, Cultured; D002543:Cerebral Hemorrhage / Q000378:metabolism* / Q000473:pathology; D006861:Hydrogen Peroxide / Q000378:metabolism; D006873:Hydroquinones / Q000494:pharmacology; D017879:Isothiocyanates / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D017628:Microglia / Q000378:metabolism*; D050984:NF-E2 Transcription Factor, p45 Subunit / Q000235:genetics / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects; D013454:Sulfoxides
chemical_list: D018955:CD36 Antigens; D006873:Hydroquinones; D017879:Isothiocyanates; D050984:NF-E2 Transcription Factor, p45 Subunit; D013454:Sulfoxides; D006861:Hydrogen Peroxide; C018855:2-tert-butylhydroquinone; C016766:sulforaphane
keywords: Nrf2; hematoma; intracerebral hemorrhage; microglia; phagocytosis; sulforaphane