title: Synapse loss regulated by matrix metalloproteinases in traumatic brain injury is associated with hypoxia inducible factor-1alpha expression.
abstract: The present study assessed the role of matrix metalloproteinase-2 (MMP-2) and -9 in synapse loss after traumatic brain injury (TBI) and the role of hypoxia inducible factor-1alpha (HIF-1alpha), a transcription factor up-regulated during hypoxia, in the regulation of MMP-2 and -9 expression post-TBI. Adult male Sprague-Dawley rats (n=6 per group, 400 g-425 g) were injured using Marmarou's closed-head acceleration impact model and allowed to survive for 1, 4, 24 and 48 h. In another set of experiments, 30 min after TBI, animals were treated with Minocycline (inhibitor of MMPs), or 2-Methoxyestradiol (2ME2, inhibitor of HIF-1alpha) and sacrificed at 4 h after injury. Relative amounts of synaptophysin, a presynaptic vesicular protein, HIF-1alpha, as well as MMP-2 and -9 were assessed by real-time PCR and Western blotting. Activity levels of MMP-2 and -9 were determined by zymography. Synaptophysin expression was significantly (p<0.05) decreased at 1 h through 48 h after TBI. A significant increase in gene and protein expressions of HIF-1alpha, MMP-2 and -9, as well as enzyme activity of MMP-2 and -9 at the same time points was also detected. Inhibition of either MMPs or HIF-1alpha significantly reversed the TBI-induced decrease in synaptophysin. Inhibition of HIF-1alpha reduced expression of MMP-2 and -9. This study showed an early detection of a correlation between synaptic loss and MMP expression after TBI. The data also supports a role for HIF-1alpha in the MMP regulatory cascade in synapse loss after TBI, suggesting potential targets for reducing loss of synaptic terminals.
authors.affiliation: Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI, USA.
authors.forename: Jamie Y
authors.initials: JY
authors.lastname: Ding
authors.affiliation: Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI, USA.
authors.forename: Christian W
authors.initials: CW
authors.lastname: Kreipke
authors.affiliation: Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Schafer
authors.affiliation: Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Schafer
authors.affiliation: Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI, USA.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Speirs
authors.affiliation: Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI, USA. Electronic address: jrafols@med.wayne.edu.
authors.forename: José A
authors.initials: JA
authors.lastname: Rafols
mesh_terms: D000077584:2-Methoxyestradiol; D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D001930:Brain Injuries / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D015870:Gene Expression; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism*; D061965:Matrix Metalloproteinase Inhibitors; D008911:Minocycline / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000473:pathology / Q000502:physiology*; D016708:Synaptophysin / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D061965:Matrix Metalloproteinase Inhibitors; D012333:RNA, Messenger; D016708:Synaptophysin; D004958:Estradiol; D000077584:2-Methoxyestradiol; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D008911:Minocycline