title: Activation of NKCC1 by hyperosmotic stress in human tracheal epithelial cells involves PKC-delta and ERK.
abstract: Hyperosmotic stress activates Na+-K+-2Cl- cotransport (NKCC1) in secretory epithelia of the airways. NKCC1 activation was studied as uptake of 36Cl or 86Rb in human tracheal epithelial cells (HTEC). Application of hypertonic sucrose or NaCl increased bumetanide-sensitive ion uptake but did not affect Na+/H+ and Cl-/OH-(HCO3-) exchange carriers. Hyperosmolarity decreased intracellular volume (Vi) after 10 min from 7.8 to 5.4 microl/mg protein and increased intracellular Cl- (Cl-i) from 353 to 532 nmol/mg protein. Treatment with an alpha-adrenergic agent rapidly increased Cl-i and Vi in a bumetanide-sensitive manner, indicating uptake of ions by NKCC1 followed by osmotically obligated water. These results indicate that HTEC act as osmometers but lose intracellular water slowly. Hyperosmotic stress also increased the activity of PKC-delta and of the extracellular signal-regulated kinase ERK subgroup of the MAPK family. Activity of stress-activated protein kinase JNK was not affected by hyperosmolarity. PD-98059, an inhibitor of the ERK cascade, reduced ERK activity and bumetanide-sensitive 36Cl uptake. PKC inhibitors blocked activation of ERK indicating that PKC may be a downstream activator of ERK. The results indicate that hyperosmotic stress activates NKCC1 and this activation is regulated by PKC-delta and ERK.
authors.affiliation: Cystic Fibrosis Center, Departments of Pediatrics, and Physiology and Biophysics, Pediatric Pulmonology, Case Western Reserve University, BRB, Room 824, 2109 Adelbert Rd., Cleveland, OH 44106-4948, USA. cx17@po.cwru.edu
authors.forename: Carole M
authors.initials: CM
authors.lastname: Liedtke
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Cole
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D002713:Chlorine / Q000032:analysis / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009997:Osmotic Pressure; D011493:Protein Kinase C / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism; D012965:Sodium Chloride; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism*; D064506:Solute Carrier Family 12, Member 2; D013395:Sucrose; D014132:Trachea / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; C578877:SLC12A2 protein, human; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D002034:Bumetanide; C048793:methylisopropylamiloride; D012965:Sodium Chloride; D002713:Chlorine; D013395:Sucrose; D000584:Amiloride; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D012413:Rubidium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one