title: The protein kinase C activator phorbol myristate acetate decreases brain edema by aquaporin 4 downregulation after middle cerebral artery occlusion in the rat.
abstract: The protein kinase C activator phorbol 12-myristate 13-acetate (PMA) is known to interact with aquaporin 4 (AQP 4), a water-selective transporting protein that is abundant in astrocytes, and has experimentally been found to decrease osmotically-induced cell swelling. The purpose of this study was to examine whether PMA reduces brain edema following focal ischemia induced by middle cerebral artery (MCA) occlusion by modulation of AQP4 expression. Male Sprague-Dawley rats were randomly assigned to either sham surgery (n = 6), or a continuous intravenous infusion of vehicle (1% dimethylsulfoxide), followed by MCA occlusion (n = 18), and administration of PMA at 50 microg/kg (n = 6) or at 200 microg/kg (n = 6) starting 60 min before or 30 min (200 microg/kg; n = 6) or 60 min (200 microg/kg; n = 6) after MCA occlusion. Cerebral blood flow was monitored with laser Doppler over the MCA territory, and confirmed a 70% reduction during occlusion. After a 2-h period of ischemia and 2 h of reperfusion, the animals were sacrificed for assessment of brain water content and sodium and potassium concentration. AQP4 expression was assessed by immunoblotting and quantified by densitometry (n = 24). Statistical analysis was performed by ANOVA followed by Tukey's post-hoc test. PMA treatment at 200 microg/kg significantly reduced brain water concentration in the infarcted area when started 60 min before or 30 min after occlusion (p < 0.001 and p = 0.022, respectively), and prevented the subsequent sodium shift (p < 0.05). PMA normalized the AQP4 upregulation in ischemia (p = 0.021). A downregulation of AQP4 in the ischemic area paralleling the reduction in brain edema formation following PMA treatment suggests that the effect was mediated by AQP4 modulation.
authors.affiliation: Department of Neurosurgery, Virginia Commonwealth University Medical Center, Richmond, Virginia 23298-0508, USA.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Fazzina
authors.forename: Angela M
authors.initials: AM
authors.lastname: Amorini
authors.forename: Christina R
authors.initials: CR
authors.lastname: Marmarou
authors.forename: Shinji
authors.initials: S
authors.lastname: Fukui
authors.forename: Kenji
authors.initials: K
authors.lastname: Okuno
authors.forename: Jana G
authors.initials: JG
authors.lastname: Dunbar
authors.forename: Renee
authors.initials: R
authors.lastname: Glisson
authors.forename: Anthony
authors.initials: A
authors.lastname: Marmarou
authors.forename: Andrea
authors.initials: A
authors.lastname: Kleindienst
mesh_terms: D000818:Animals; D051401:Aquaporin 4 / Q000096:biosynthesis / Q000187:drug effects*; D001929:Brain Edema / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002545:Brain Ischemia / Q000188:drug therapy / Q000209:etiology / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000187:drug effects; D015536:Down-Regulation; D015151:Immunoblotting; D020244:Infarction, Middle Cerebral Artery / Q000150:complications / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D018696:Neuroprotective Agents / Q000494:pharmacology*; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D051401:Aquaporin 4; D018696:Neuroprotective Agents; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate