title: Role of ERK map kinase and CRM1 in IL-1beta-stimulated release of HMGB1 from cortical astrocytes.
abstract: Reactive astrocytes are traditionally thought to impede brain plasticity after stroke. However, we previously showed that reactive astrocytes may also contribute to stroke recovery, partly via the release of a nuclear protein called high-mobility group box 1 (HMGB1). Here, we investigate the mechanisms that allow stimulated astrocytes to release HMGB1. Exposure of rat primary astrocytes to IL-1beta for 24 h elicited a dose-dependent HMGB1 response. Immunostaining and western blots of cell lysates showed increased intracellular levels of HMGB1. Western blots confirmed that IL-1beta induced a release of HMGB1 into astrocyte conditioned media. MAP kinase signaling was involved. Levels of phospho-ERK were increased by IL-1beta, and the MEK/ERK inhibitor U0126 decreased HMGB1 upregulation in the stimulated astrocytes. Since HMGB1 is a nuclear protein, the role of the nuclear protein exporter, chromosome region maintenance 1 (CRM1), was assessed as a candidate mechanism for linking MAP kinase signaling to HMGB1 release. IL-1beta increased CRM1 expression in concert with a translocation of HMGB1 from nucleus into cytoplasm. Blockade of IL-1beta-stimulated HMGB1 release with the ERK inhibitor U0126 was accompanied by a downregulation of CRM1. Our findings reveal that IL-1beta stimulates the release of HMGB1 from activated astrocytes via ERK MAP kinase and CRM1 signaling. These data suggest a novel pathway by which inflammatory cytokines may enhance the ability of reactive astrocytes to release prorecovery mediators after stroke.
authors.affiliation: Neuroprotection Research Laboratory, Departments of Radiology and Neurology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA.
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Hayakawa
authors.forename: Ken
authors.initials: K
authors.lastname: Arai
authors.forename: Eng H
authors.initials: EH
authors.lastname: Lo
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D002070:Butadienes / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D024243:HMGB1 Protein / Q000378:metabolism*; D053583:Interleukin-1beta / Q000494:pharmacology*; D028884:Karyopherins / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D000097606:Exportin 1 Protein
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D024243:HMGB1 Protein; D053583:Interleukin-1beta; D028884:Karyopherins; D020929:Mitogen-Activated Protein Kinase Kinases; D009570:Nitriles; D018160:Receptors, Cytoplasmic and Nuclear; D000097606:Exportin 1 Protein; C104200:Hbp1 protein, rat; C113580:U 0126; C038753:leptomycin B