Phosphodiesterase 6 subunits are expressed and altered in idiopathic pulmonary fibrosis.
BACKGROUND
Idiopathic Pulmonary Fibrosis (IPF) is an unresolved clinical issue. Phosphodiesterases (PDEs) are known therapeutic targets for various proliferative lung diseases. Lung PDE6 expression and function has received little or no attention. The present study aimed to characterize (i) PDE6 subunits expression in human lung, (ii) PDE6 subunits expression and alteration in IPF and (iii) functionality of the specific PDE6D subunit in alveolar epithelial cells (AECs).


RESULTS
PDE6 subunits expression in transplant donor (n = 6) and IPF (n = 6) lungs was demonstrated by real-time quantitative (q)RT-PCR and immunoblotting analysis. PDE6D mRNA and protein levels and PDE6G/H protein levels were significantly down-regulated in the IPF lungs. Immunohistochemical analysis showed alveolar epithelial localization of the PDE6 subunits. This was confirmed by qRT-PCR from human primary alveolar type (AT)II cells, demonstrating the down-regulation pattern of PDE6D in IPF-derived ATII cells. In vitro, PDE6D protein depletion was provoked by transforming growth factor (TGF)-β1 in A549 AECs. PDE6D siRNA-mediated knockdown and an ectopic expression of PDE6D modified the proliferation rate of A549 AECs. These effects were mediated by increased intracellular cGMP levels and decreased ERK phosphorylation.


CONCLUSIONS
Collectively, we report previously unrecognized PDE6 expression in human lungs, significant alterations of the PDE6D and PDE6G/H subunits in IPF lungs and characterize the functional role of PDE6D in AEC proliferation.
Nikolova
Sevdalina
S
University of Giessen Lung Centre, Giessen, Germany.
Guenther
Andreas
A
Savai
Rajkumar
R
Weissmann
Norbert
N
Ghofrani
Hossein A
HA
Konigshoff
Melanie
M
Eickelberg
Oliver
O
Klepetko
Walter
W
Voswinckel
Robert
R
Seeger
Werner
W
Grimminger
Friedrich
F
Schermuly
Ralph T
RT
Pullamsetti
Soni S
SS
D054707:Cyclic Nucleotide Phosphodiesterases, Type 6 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000201:enzymology*; D007150:Immunohistochemistry; D008168:Lung / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D012333:RNA, Messenger / Q000032:analysis; D014018:Tissue Distribution
D012333:RNA, Messenger; C517432:PDE6D protein, human; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; C517433:PDE6G protein, human