Cystic Fibrosis Transmembrane Conductance Regulator in Sarcoplasmic Reticulum of Airway Smooth Muscle. Implications for Airway Contractility.
BACKGROUND
An asthma-like airway phenotype has been described in people with cystic fibrosis (CF). Whether these findings are directly caused by loss of CF transmembrane conductance regulator (CFTR) function or secondary to chronic airway infection and/or inflammation has been difficult to determine.


OBJECTIVE
Airway contractility is primarily determined by airway smooth muscle. We tested the hypothesis that CFTR is expressed in airway smooth muscle and directly affects airway smooth muscle contractility.


METHODS
Newborn pigs, both wild type and with CF (before the onset of airway infection and inflammation), were used in this study. High-resolution immunofluorescence was used to identify the subcellular localization of CFTR in airway smooth muscle. Airway smooth muscle function was determined with tissue myography, intracellular calcium measurements, and regulatory myosin light chain phosphorylation status. Precision-cut lung slices were used to investigate the therapeutic potential of CFTR modulation on airway reactivity.


RESULTS
We found that CFTR localizes to the sarcoplasmic reticulum compartment of airway smooth muscle and regulates airway smooth muscle tone. Loss of CFTR function led to delayed calcium reuptake following cholinergic stimulation and increased myosin light chain phosphorylation. CFTR potentiation with ivacaftor decreased airway reactivity in precision-cut lung slices following cholinergic stimulation.


CONCLUSIONS
Loss of CFTR alters porcine airway smooth muscle function and may contribute to the airflow obstruction phenotype observed in human CF. Airway smooth muscle CFTR may represent a therapeutic target in CF and other diseases of airway narrowing.
1 Department of Internal Medicine.|2 Department of Molecular Physiology and Biophysics.
Daniel P
DP
Cook
1 Department of Internal Medicine.
Michael V
MV
Rector
1 Department of Internal Medicine.
Drake C
DC
Bouzek
1 Department of Internal Medicine.
Andrew S
AS
Michalski
1 Department of Internal Medicine.
Nicholas D
ND
Gansemer
1 Department of Internal Medicine.
Leah R
LR
Reznikov
1 Department of Internal Medicine.
Xiaopeng
X
Li
1 Department of Internal Medicine.
Mallory R
MR
Stroik
1 Department of Internal Medicine.
Lynda S
LS
Ostedgaard
1 Department of Internal Medicine.
Mahmoud H
MH
Abou Alaiwa
3 Department of Anesthesiology and.|4 Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.
Michael A
MA
Thompson
3 Department of Anesthesiology and.|4 Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.
Y S
YS
Prakash
5 Department of Emergency Medicine, Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Boston, Massachusetts; and.
Ramaswamy
R
Krishnan
6 Department of Pathology.
David K
DK
Meyerholz
7 Department of Pathology and Laboratory Medicine, James Hogg Research Centre/St. Paul's Hospital, University of British Columbia, Vancouver, British Columbia, Canada.
Chun Y
CY
Seow
1 Department of Internal Medicine.|2 Department of Molecular Physiology and Biophysics.|8 Department of Biomedical Engineering, and.|9 Pappajohn Biomedical Institute, University of Iowa, Iowa City, Iowa.
David A
DA
Stoltz
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D008168:Lung / Q000503:physiopathology; D023421:Models, Animal; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000503:physiopathology*; D012519:Sarcoplasmic Reticulum / Q000502:physiology*; D013552:Swine
D019005:Cystic Fibrosis Transmembrane Conductance Regulator
airways; cystic fibrosis; pig; porcine