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AMP‐activated protein kinase (AMPK)–dependent and –independent pathways regulate hypoxic inhibition of transepithelial Na + transport across human airway epithelial cells
Author(s) -
Tan CD,
Smolenski RT,
Harhun MI,
Patel HK,
Ahmed SG,
Wanisch K,
YáñezMuñoz RJ,
Baines DL
Publication year - 2012
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.2012.01993.x
Subject(s) - ampk , microbiology and biotechnology , protein kinase a , amp activated protein kinase , chemistry , epithelium , signal transduction , kinase , biology , biophysics , genetics
BACKGROUND AND PURPOSE Pulmonary transepithelial Na + transport is reduced by hypoxia, but in the airway the regulatory mechanisms remain unclear. We investigated the role of AMPK and ROS in the hypoxic regulation of apical amiloride‐sensitive Na + channels and basolateral Na + K + ATPase activity. EXPERIMENTAL APPROACH H441 human airway epithelial cells were used to examine the effects of hypoxia on Na + transport, AMP : ATP ratio and AMPK activity. Lentiviral constructs were used to modify cellular AMPK abundance and activity; pharmacological agents were used to modify cellular ROS. KEY RESULTS AMPK was activated by exposure to 3% or 0.2% O 2 for 60 min in cells grown in submerged culture or when fluid (0.1 mL·cm −2 ) was added to the apical surface of cells grown at the air–liquid interface. Only 0.2% O 2 activated AMPK in cells grown at the air–liquid interface. AMPK activation was associated with elevation of cellular AMP : ATP ratio and activity of the upstream kinase LKB1. Hypoxia inhibited basolateral ouabain‐sensitive I sc ( I ouabain ) and apical amiloride‐sensitive Na + conductance ( G Na+ ). Modification of AMPK activity prevented the effect of hypoxia on I ouabain (Na + K + ATPase) but not apical G Na+ . Scavenging of superoxide and inhibition of NADPH oxidase prevented the effect of hypoxia on apical G Na+ (epithelial Na + channels). CONCLUSIONS AND IMPLICATIONS Hypoxia activates AMPK‐dependent and ‐independent pathways in airway epithelial cells. Importantly, these pathways differentially regulate apical Na + channels and basolateral Na + K + ATPase activity to decrease transepithelial Na + transport. Luminal fluid potentiated the effect of hypoxia and activated AMPK, which could have important consequences in lung disease conditions.