title: Cytosolic phospholipase A2 alpha amplifies early cyclooxygenase-2 expression, oxidative stress and MAP kinase phosphorylation after cerebral ischemia in mice.
abstract: BACKGROUND
  The enzyme cytosolic phospholipase A2 alpha (cPLA2alpha) has been implicated in the progression of cerebral injury following ischemia and reperfusion. Previous studies in rodents suggest that cPLA2alpha enhances delayed injury extension and disruption of the blood brain barrier many hours after reperfusion. In this study we investigated the role of cPLA2alpha in early ischemic cerebral injury.
  
  
  METHODS
  Middle cerebral artery occlusion (MCAO) was performed on cPLA2alpha+/+ and cPLA2alpha-/- mice for 2 hours followed by 0, 2, or 6 hours of reperfusion. The levels of cPLA2alpha, cyclooxygenase-2, neuronal morphology and reactive oxygen species in the ischemic and contralateral hemispheres were evaluated by light and fluorescent microscopy. PGE2 content was compared between genotypes and hemispheres after MCAO and MCAO and 6 hours reperfusion. Regional cerebral blood flow was measured during MCAO and phosphorylation of relevant MAPKs in brain protein homogenates was measured by Western analysis after 6 hours of reperfusion.
  
  
  RESULTS
  Neuronal cPLA2alpha protein increased by 2-fold immediately after MCAO and returned to pre-MCAO levels after 2 hours reperfusion. Neuronal cyclooxygenase-2 induction and PGE2 concentration were greater in cPLA2alpha+/+ compared to cPLA2alpha-/- ischemic cortex. Neuronal swelling in ischemic regions was significantly greater in the cPLA2alpha+/+ than in cPLA2alpha-/- brains (+/+:2.2+/-0.3 fold vs. -/-:1.7+/-0.4 fold increase; P<0.01). The increase in reactive oxygen species following 2 hours of ischemia was also significantly greater in the cPLA2alpha+/+ ischemic core than in cPLA2alpha-/- (+/+:7.12+/-1.2 fold vs. -/-:3.1+/-1.4 fold; P<0.01). After 6 hours of reperfusion ischemic cortex of cPLA2alpha+/+, but not cPLA2alpha-/-, had disruption of neuron morphology and decreased PGE2 content. Phosphorylation of the MAPKs-p38, ERK 1/2, and MEK 1/2-was significantly greater in cPLA2a+/+ than in cPLA2alpha-/- ischemic cortex 6 hours after reperfusion.
  
  
  CONCLUSIONS
  These results indicate that cPLA2alpha modulates the earliest molecular and injury responses after cerebral ischemia and have implications for the potential clinical use of cPLA2alpha inhibitors.
authors.affiliation: The Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Koji
authors.initials: K
authors.lastname: Kishimoto
authors.forename: Rung-Chi
authors.initials: RC
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Judith A
authors.initials: JA
authors.lastname: Klaus
authors.forename: Kathleen K
authors.initials: KK
authors.lastname: Kibler
authors.forename: Sylvain
authors.initials: S
authors.lastname: Doré
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Koehler
authors.forename: Adam
authors.initials: A
authors.lastname: Sapirstein
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism / Q000503:physiopathology*; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism; D005260:Female; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D020244:Infarction, Middle Cerebral Artery / Q000503:physiopathology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D018384:Oxidative Stress; D010766:Phosphorylation; D015427:Reperfusion Injury / Q000503:physiopathology*
chemical_list: D051546:Cyclooxygenase 2; D020928:Mitogen-Activated Protein Kinases; D054513:Group IV Phospholipases A2; D015232:Dinoprostone