title: Protective effect of melatonin against transient global cerebral ischemia-induced neuronal cell damage via inhibition of matrix metalloproteinase-9.
abstract: OBJECTIVE
  Melatonin possesses various pharmacological effects including neuroprotective effects against brain ischemia. Post-ischemic increases in matrix metalloproteinase-9 (MMP-9) expression and activity mainly contribute to neuronal damage by degradation of the extracellular matrix. This study was designed to examine whether melatonin has a neuroprotective effect and an influence on MMP-9 in transient global brain ischemia.
  
  
  METHODS
  Mice were subjected to 20 min of global brain ischemia and sacrificed 72h later. Melatonin (30 mg/kg) was administered 30 min before and 2h after ischemia as well as once daily until sacrifice.
  
  
  RESULTS
  Hippocampal pyramidal cell damage after ischemia was significantly decreased by melatonin. As observed by zymography, melatonin inhibited the increase of MMP-9 activity after ischemia. In the brain sections, the increased gelatinase activity was mainly observed in the hippocampus after ischemia and melatonin also reduced gelatinase activity. The laminin and NeuN expression levels were reduced in the hippocampal CA1 and CA2 regions after ischemia, and melatonin reduced laminin degradation and neuronal loss. A TUNEL assay demonstrated that there were TUNEL-positive cells in the hippocampus and the number of TUNEL-positive cells was significantly decreased by melatonin. There was no difference in the ischemia-induced hippocampal neuronal damage between the vehicle- and melatonin-treated groups of MMP-9 knock-out mice.
  
  
  CONCLUSIONS
  These data demonstrate that melatonin suppressed the occurrence of neuronal injury, which might be partly due to its inhibitory effects on MMP-9 in addition to its anti-oxidative effects. MMP-9 may be an important key target of melatonin in neuroprotection against global ischemia.
authors.affiliation: Department of Anesthesiology, College of Medicine, Dongguk University, Gyeongju, South Korea; Department of Pharmacology, School of Medicine and Brain Research Institute, Keimyung University, Daegu 704-701, South Korea.
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Pharmacology, School of Medicine and Brain Research Institute, Keimyung University, Daegu 704-701, South Korea. Electronic address: srlee@kmu.ac.kr.
authors.forename: Seong-Ryong
authors.initials: SR
authors.lastname: Lee
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D018093:Gelatinases / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000473:pathology; D020287:In Situ Nick-End Labeling; D002546:Ischemic Attack, Transient / Q000473:pathology / Q000517:prevention & control*; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors / Q000494:pharmacology*; D008550:Melatonin / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D061965:Matrix Metalloproteinase Inhibitors; D018696:Neuroprotective Agents; D018093:Gelatinases; D020780:Matrix Metalloproteinase 9; D008550:Melatonin
keywords: Global cerebral ischemia; Matrix metalloproteinase; Melatonin