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- Title
AMP-activated protein kinase regulates CO2-induced alveolar epithelial dysfunction in rats and human cells by promoting Na,K-ATPase endocytosis.
- Authors
Vadász, István; Dada, Laura A.; Briva, Arturo; Trejo, Humberto E.; Welch, Lynn C.; Jiwang Chen; Tóth, Péter T.; Lecuona, Emilia; Witters, Lee A.; Schumacker, Paul T.; Chandel, Navdeep S.; Seeger, Werner; Sznajder, Jacob I.; Vadász, István; Chen, Jiwang; Tóth, Péter T
- Abstract
Hypercapnia (elevated CO(2) levels) occurs as a consequence of poor alveolar ventilation and impairs alveolar fluid reabsorption (AFR) by promoting Na,K-ATPase endocytosis. We studied the mechanisms regulating CO(2)-induced Na,K-ATPase endocytosis in alveolar epithelial cells (AECs) and alveolar epithelial dysfunction in rats. Elevated CO(2) levels caused a rapid activation of AMP-activated protein kinase (AMPK) in AECs, a key regulator of metabolic homeostasis. Activation of AMPK was mediated by a CO(2)-triggered increase in intracellular Ca(2+) concentration and Ca(2+)/calmodulin-dependent kinase kinase-beta (CaMKK-beta). Chelating intracellular Ca(2+) or abrogating CaMKK-beta function by gene silencing or chemical inhibition prevented the CO(2)-induced AMPK activation in AECs. Activation of AMPK or overexpression of constitutively active AMPK was sufficient to activate PKC-zeta and promote Na,K-ATPase endocytosis. Inhibition or downregulation of AMPK via adenoviral delivery of dominant-negative AMPK-alpha(1) prevented CO(2)-induced Na,K-ATPase endocytosis. The hypercapnia effects were independent of intracellular ROS. Exposure of rats to hypercapnia for up to 7 days caused a sustained decrease in AFR. Pretreatment with a beta-adrenergic agonist, isoproterenol, or a cAMP analog ameliorated the hypercapnia-induced impairment of AFR. Accordingly, we provide evidence that elevated CO(2) levels are sensed by AECs and that AMPK mediates CO(2)-induced Na,K-ATPase endocytosis and alveolar epithelial dysfunction, which can be prevented with beta-adrenergic agonists and cAMP.
- Subjects
PROTEIN kinases; PHYSIOLOGICAL effects of carbon dioxide; ADENOSINE triphosphatase; ENDOCYTOSIS; CELL physiology; CELLULAR mechanics; HYPERCAPNIA; ABSORPTION (Physiology); CALCIUM antagonists; CALCIUM metabolism; ENZYME metabolism; ADRENERGIC beta agonists; ANIMAL experimentation; CARBON dioxide; COMPARATIVE studies; CYCLIC adenylic acid; EXTRACELLULAR fluid; ISOPROTERENOL; RESEARCH methodology; MEDICAL cooperation; PHOSPHOTRANSFERASES; PULMONARY alveoli; RATS; RESEARCH; RESPIRATORY mucosa; TRANSFERASES; EVALUATION research; CHELATING agents; CHEMICAL inhibitors; PHARMACODYNAMICS
- Publication
Journal of Clinical Investigation, 2008, Vol 118, Issue 2, p752
- ISSN
0021-9738
- Publication type
journal article
- DOI
10.1172/JCI29723