title: Irradiation alters MMP-2/TIMP-2 system and collagen type IV degradation in brain.
abstract: OBJECTIVE
  Blood-brain barrier (BBB) disruption is one of the major consequences of radiation-induced normal tissue injury in the central nervous system. We examined the effects of whole-brain irradiation on matrix metalloproteinases (MMPs)/tissue inhibitors of metalloproteinases (TIMPs) and extracellular matrix (ECM) degradation in the brain.
  
  
  METHODS
  Animals received either whole-brain irradiation (a single dose of 10 Gy γ-rays or a fractionated dose of 40 Gy γ-rays, total) or sham-irradiation and were maintained for 4, 8, and 24 h following irradiation. mRNA expression levels of MMPs and TIMPs in the brain were analyzed by real-time reverse transcriptase-polymerase chain reaction (PCR). The functional activity of MMPs was measured by in situ zymography, and degradation of ECM was visualized by collagen type IV immunofluorescent staining.
  
  
  RESULTS
  A significant increase in mRNA expression levels of MMP-2, MMP-9, and TIMP-1 was observed in irradiated brains compared to that in sham-irradiated controls. In situ zymography revealed a strong gelatinolytic activity in the brain 24 h postirradiation, and the enhanced gelatinolytic activity mediated by irradiation was significantly attenuated in the presence of anti-MMP-2 antibody. A significant reduction in collagen type IV immunoreactivity was also detected in the brain at 24 h after irradiation. In contrast, the levels of collagen type IV were not significantly changed at 4 and 8 h after irradiation compared with the sham-irradiated controls.
  
  
  CONCLUSIONS
  The present study demonstrates for the first time that radiation induces an imbalance between MMP-2 and TIMP-2 levels and suggests that degradation of collagen type IV, a major ECM component of BBB basement membrane, may have a role in the pathogenesis of brain injury.
authors.affiliation: School of Biomedical Engineering and Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA.
authors.forename: Won Hee
authors.initials: WH
authors.lastname: Lee
authors.forename: Junie P
authors.initials: JP
authors.lastname: Warrington
authors.forename: William E
authors.initials: WE
authors.lastname: Sonntag
authors.forename: Yong Woo
authors.initials: YW
authors.lastname: Lee
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism / Q000528:radiation effects*; D002540:Cerebral Cortex / Q000378:metabolism / Q000528:radiation effects; D024141:Collagen Type IV / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D016371:Cranial Irradiation / Q000009:adverse effects* / Q000379:methods; D005109:Extracellular Matrix / Q000378:metabolism / Q000528:radiation effects; D005260:Female; D005455:Fluorescent Antibody Technique / Q000379:methods; D018093:Gelatinases / Q000378:metabolism / Q000528:radiation effects; D006624:Hippocampus / Q000378:metabolism / Q000528:radiation effects; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000378:metabolism; D011833:Radiation Injuries, Experimental / Q000209:etiology / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D060888:Real-Time Polymerase Chain Reaction; D013997:Time Factors; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*
chemical_list: D024141:Collagen Type IV; D012333:RNA, Messenger; C560823:TIMP2 protein, human; D019716:Tissue Inhibitor of Metalloproteinase-2; D018093:Gelatinases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9