Liedtke Carole M, Cole Thomas S
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.
Biochim Biophys Acta. 2002 Feb 13;1589(1):77-88. 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-(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.
高渗应激可激活气道分泌上皮细胞中的钠-钾-2氯协同转运体（NKCC1）。通过检测人气管上皮细胞（HTEC）对³⁶Cl或⁸⁶Rb的摄取来研究NKCC1的激活情况。应用高渗蔗糖或氯化钠可增加布美他尼敏感的离子摄取，但不影响钠/氢和氯/氢氧根（碳酸氢根）交换载体。高渗作用10分钟后，细胞内体积（Vi）从7.8微升/毫克蛋白降至5.4微升/毫克蛋白，细胞内氯离子（Cl-i）从353纳摩尔/毫克蛋白增加至532纳摩尔/毫克蛋白。用α-肾上腺素能药物处理可迅速以布美他尼敏感的方式增加Cl-i和Vi，表明NKCC1摄取离子后伴有渗透性结合水。这些结果表明，HTEC起到了渗透压感受器的作用，但细胞内水分流失缓慢。高渗应激还增加了蛋白激酶C-δ（PKC-δ）以及丝裂原活化蛋白激酶（MAPK）家族细胞外信号调节激酶ERK亚组的活性。应激激活蛋白激酶JNK的活性不受高渗作用影响。ERK级联反应抑制剂PD-98059可降低ERK活性以及布美他尼敏感的³⁶Cl摄取。PKC抑制剂可阻断ERK的激活，表明PKC可能是ERK的下游激活剂。结果表明，高渗应激可激活NKCC1，且这种激活受PKC-δ和ERK调节。
