title: Glucocorticoid receptor-mediated suppression of activator protein-1 activation and matrix metalloproteinase expression after spinal cord injury.
abstract: Post-traumatic inflammatory reaction may contribute to progressive tissue damage after spinal cord injury (SCI). Two key transcription factors, nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1), are activated in inflammation. An increase in NF-kappaB binding activity has been shown in the injured spinal cord. We report activation of AP-1 after SCI. Electrophoretic mobility shift assay showed that AP-1 binding activity increased after SCI, starting at 1 hr, peaking at 8 hr, and declining to basal levels by 7 d. Methylprednisolone (MP) is the only therapeutic agent approved by the Food and Drug Administration for treating patients with acute traumatic SCI. MP reduced post-traumatic AP-1 activation. RU486, a glucocorticoid receptor (GR) antagonist, reversed MP inhibition of AP-1 activation. Immunostaining showed an increase in the expression of the Fos-B and c-Jun components of AP-1 in the injured cord. A c-fos antisense oligodeoxynucleotide (ODN) inhibited AP-1, but not NF-kappaB, activation after SCI. AP-1 and NF-kappaB can transactivate genes encoding matrix metalloproteinase-1 (MMP-1) and MMP-9. Western blotting and immunostaining show increased expression of MMP-1 and MMP-9 in the injured cord. MP inhibited MMP-1 and MMP-9 expression after SCI. RU486 reversed this MP effect. The c-fos antisense ODN, however, failed to suppress MMP-1 or MMP-9 expression. These findings demonstrate that MP may suppress post-traumatic inflammatory reaction by inhibiting both the AP-1 and NF-kappaB transcription cascades via a GR mechanism. Expression of inflammatory genes such as MMP-1 and MMP-9 that are transactivated jointly by AP-1 and NF-kappaB may not be suppressed by inhibiting only AP-1 activity.
authors.affiliation: Department of Neurology and Center for the Study of Nervous System Injury, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: G M
authors.initials: GM
authors.lastname: Kim
authors.forename: S H
authors.initials: SH
authors.lastname: Ahmed
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: P
authors.initials: P
authors.lastname: Yan
authors.forename: X M
authors.initials: XM
authors.lastname: Xu
authors.forename: C Y
authors.initials: CY
authors.lastname: Hsu
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D015153:Blotting, Western; D004195:Disease Models, Animal; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology; D006727:Hormone Antagonists / Q000494:pharmacology; D007150:Immunohistochemistry; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D008775:Methylprednisolone / Q000494:pharmacology; D015735:Mifepristone / Q000494:pharmacology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013119:Spinal Cord Injuries / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D005938:Glucocorticoids; D006727:Hormone Antagonists; D016328:NF-kappa B; D018696:Neuroprotective Agents; D016376:Oligonucleotides, Antisense; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D011965:Receptors, Glucocorticoid; D018808:Transcription Factor AP-1; D015735:Mifepristone; D020780:Matrix Metalloproteinase 9; D020781:Matrix Metalloproteinase 1; D008775:Methylprednisolone