Up-regulation of AMP-activated Kinase by Dysfunctional Cystic Fibrosis Transmembrane Conductance Regulator in Cystic Fibrosis Airway Epithelial Cells Mitigates Excessive Inflammation

Kenneth R Hallows,Adam C Fitch,Christine A Richardson,Paul R Reynolds,John P Clancy,Pierre C Dagher,Lee A Witters,Jay K Kolls,Joseph M Pilewski

doi:10.1074/jbc.m511029200

Abstract

AMP-activated kinase (AMPK) is a ubiquitous metabolic sensor that inhibits the cystic fibrosis (CF) transmembrane conductance regulator (CFTR). To determine whether CFTR reciprocally regulates AMPK function in airway epithelia and whether such regulation is involved in lung inflammation, AMPK localization, expression, and activity and cellular metabolic profiles were compared as a function of CFTR status in CF and non-CF primary human bronchial epithelial (HBE) cells. As compared with non-CF HBE cells, CF cells had greater and more diffuse AMPK staining and had greater AMPK activity than their morphologically matched non-CF counterparts. The cellular [AMP]/[ATP] ratio was higher in undifferentiated than in differentiated non-CF cells, which correlated with AMPK activity under these conditions. However, this nucleotide ratio did not predict AMPK activity in differentiating CF cells. Inhibiting channel activity in non-CF cells did not affect AMPK activity or metabolic status, but expressing functional CFTR in CF cells reduced AMPK activity without affecting cellular [AMP]/[ATP]. Therefore, lack of functional CFTR expression and not loss of channel activity in CF cells appears to up-regulate AMPK activity in CF HBE cells, presumably through non-metabolic effects on upstream regulatory pathways. Compared with wild-type CFTR-expressing immortalized CF bronchial epithelial (CFBE) cells, DeltaF508-CFTR-expressing CFBE cells had greater AMPK activity and greater secretion of tumor necrosis factor-alpha and the interleukins IL-6 and IL-8. Further pharmacologic AMPK activation inhibited inflammatory mediator secretion in both wild type- and DeltaF508-expressing cells, suggesting that AMPK activation in CF airway cells is an adaptive response that reduces inflammation. We propose that therapies to activate AMPK in the CF airway may be beneficial in reducing excessive airway inflammation, a major cause of CF morbidity.

Highlights

Cystic fibrosis (CF),2 the most common lethal genetic disease among Caucasians, is caused by mutations in the cystic fibrosis transmembrane
To determine whether the presence of functional CFTR in the airway epithelium is involved in the regulation of AMPK function, we initially examined the effects of mutant versus normal CFTR on the localization, amount, and activity of AMPK and on cellular metabolic profiles in polarized primary human bronchial epithelial (HBE) cells derived from CF patients versus patients with other non-CF lung diseases or normal donors
Because we have previously shown that CFTR is regulated by AMPK in lung epithelial cells [20], this study was undertaken to further examine the potential interregulation of CFTR and AMPK in the airway and the potential role of AMPK in CF lung disease

Summary

Introduction

Cystic fibrosis (CF),2 the most common lethal genetic disease among Caucasians, is caused by mutations in the cystic fibrosis transmembrane. To determine whether CFTR reciprocally regulates AMPK function in airway epithelia and whether such regulation is involved in lung inflammation, AMPK localization, expression, and activity and cellular metabolic profiles were compared as a function of CFTR status in CF and non-CF primary human bronchial epithelial (HBE) cells.

Results

Conclusion