Activation of NKCC1 by hyperosmotic stress in human tracheal epithelial cells involves PKC-δ and ERK

• Published in: Biochimica et biophysica acta 2002-02, Vol.1589 (1), p.77-88
• Main Authors: Liedtke, Carole M, Cole, Thomas S
• Format: Article
• Language: English
• Subjects: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid - pharmacology; Amiloride - analogs & derivatives; Amiloride - pharmacology; Bumetanide - pharmacology; Cell shrinkage; Cells, Cultured; Chlorine - analysis; Chlorine - metabolism; Cystic fibrosis; Enzyme Activation; Enzyme Inhibitors - pharmacology; Epithelial Cells - metabolism; Flavonoids - pharmacology; Humans; Hypertonicity; Mitogen-activated protein kinase; Mitogen-Activated Protein Kinases - antagonists & inhibitors; Mitogen-Activated Protein Kinases - metabolism; Na +-K +-2Cl − cotransport; Osmotic Pressure; Protein Kinase C - metabolism; Rubidium - metabolism; Sodium Chloride; Sodium-Potassium-Chloride Symporters - metabolism; Solute Carrier Family 12, Member 2; Sucrose; Trachea - metabolism
• ISSN: 0167-4889; 0006-3002; 1879-2596
• DOI: 10.1016/S0167-4889(01)00189-6

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 −(HCO 3 −) exchange carriers. Hyperosmolarity decreased intracellular volume ( V i) after 10 min from 7.8 to 5.4 μl/mg protein and increased intracellular Cl − (Cl − i) from 353 to 532 nmol/mg protein. Treatment with an α-adrenergic agent rapidly increased Cl − i and V i 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-δ 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-δ and ERK.