AMP-activated protein kinase regulates CO2-induced alveolar epithelial dysfunction in rats and human cells by promoting Na,K-ATPase endocytosis

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.

  • Vadasz, I.
  • Dada, L. A.
  • Briva, A.
  • Trejo, H. E.
  • Welch, L. C.
  • Chen, J.
  • Toth, P. T.
  • Lecuona, E.
  • Witters, L. A.
  • Schumacker, P. T.
  • Chandel, N. S.
  • Seeger, W.
  • Sznajder, J. I.


  • AMP-Activated Protein Kinases
  • Adrenergic beta-Agonists/pharmacology
  • Animals
  • Calcium/antagonists & inhibitors/metabolism
  • Calcium-Calmodulin-Dependent Protein Kinase Kinase/antagonists &
  • inhibitors/genetics/metabolism
  • Carbon Dioxide/*metabolism
  • Chelating Agents/pharmacology
  • Cyclic AMP/pharmacology
  • *Endocytosis/drug effects/genetics
  • Extracellular Fluid/metabolism
  • Humans
  • Hypercapnia/*enzymology
  • Isoproterenol/pharmacology
  • Multienzyme Complexes/*metabolism
  • Protein Kinase C/metabolism
  • Protein-Serine-Threonine Kinases/*metabolism
  • Pulmonary Alveoli/enzymology
  • Rats
  • Rats, Sprague-Dawley
  • Respiratory Mucosa/enzymology
  • Sodium-Potassium-Exchanging ATPase/*metabolism
Publication details
DOI: 10.1172/JCI29723
Journal: J Clin Invest
Pages: 752-62
Number: 2
Work Type: Original
Access number: 18188452
See publication on PubMed