title: Ischemia-induced stimulation of Na-K-Cl cotransport in cerebral microvascular endothelial cells involves AMP kinase.
abstract: Increased blood-brain barrier (BBB) Na-K-Cl cotransporter activity appears to contribute to cerebral edema formation during ischemic stroke. We have shown previously that inhibition of BBB Na-K-Cl cotransporter activity reduces edema and infarct in the rat middle cerebral artery occlusion (MCAO) model of ischemic stroke. We have also shown that the BBB cotransporter is stimulated by the ischemic factors hypoxia, aglycemia, and arginine vasopressin (AVP), although the mechanisms responsible are not well understood. AMP-activated protein kinase (AMPK), a key mediator of cell responses to stress, can be activated by a variety of stresses, including ischemia, hypoxia, and aglycemia. Previous studies have shown that the AMPK inhibitor Compound C significantly reduces infarct in mouse MCAO. The present study was conducted to evaluate the possibility that AMPK participates in ischemic factor-induced stimulation of the BBB Na-K-Cl cotransporter. Cerebral microvascular endothelial cells (CMEC) were assessed for Na-K-Cl cotransporter activity as bumetanide-sensitive (86)Rb influx. AMPK activity was assessed by Western blot analysis and immunofluorescence methods using antibodies that detect total versus phosphorylated (activated) AMPK. We found that hypoxia (7% and 2% O(2)), aglycemia, AVP, and oxygen-glucose deprivation (5- to 120-min exposures) increase activation of AMPK. We also found that Compound C inhibition of AMPK reduces hypoxia-, aglycemia-, and AVP-induced stimulation of CMEC Na-K-Cl cotransporter activity. Confocal immunofluorescence of perfusion-fixed rat brain slices revealed the presence of AMPK, both total and phosphorylated kinase, in BBB in situ of both control and ischemic brain. These findings suggest that ischemic factor stimulation of the BBB Na-K-Cl cotransporter involves activation of AMPK.
authors.affiliation: Department of Physiology and Membrane Biology, University of California, Davis, CA 95616, USA.
authors.forename: Breanna K
authors.initials: BK
authors.lastname: Wallace
authors.forename: Shahin
authors.initials: S
authors.lastname: Foroutan
authors.forename: Martha E
authors.initials: ME
authors.lastname: O'Donnell
mesh_terms: D000263:Adenylate Kinase / Q000378:metabolism*; D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000201:enzymology*; D015153:Blotting, Western; D002034:Bumetanide / Q000494:pharmacology; D002417:Cattle; D015687:Cell Hypoxia; D002478:Cells, Cultured; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000172:deficiency; D020244:Infarction, Middle Cerebral Artery / Q000201:enzymology*; D008297:Male; D055806:Microvessels / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D047428:Protein Kinase Inhibitors; D011720:Pyrazoles; D011743:Pyrimidines; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; C516138:dorsomorphin; D001127:Arginine Vasopressin; D000263:Adenylate Kinase; D005947:Glucose