Effects of phosphodiesterase 4 inhibition on bleomycin-induced pulmonary fibrosis in mice.
BACKGROUND
Pulmonary fibrosis (PF) is a group of devastating and largely irreversible diseases. Phosphodiesterase (PDE) 4 is involved in the processes of remodeling and inflammation, which play key role in tissue fibrosis. The aim of the study was, therefore, to investigate the effect of PDE4 inhibition in experimental model of PF.


METHODS
PF was induced in C57BL/6N mice by instillation of bleomycin. Pharmacological inhibition of PDE4 was achieved by using cilomilast, a selective PDE4 inhibitor. Changes in either lung inflammation or remodeling were evaluated at different stages of experimental PF. Lung inflammation was assessed by bronchoalveolar lavage fluid (BALF) differential cell count and reverse transcription quantitative polymerase chain reaction (RT-qPCR) for inflammatory cytokines. Changes in tissue remodeling were evaluated by pulmonary compliance measurement, quantified pathological examination, measurement of collagen deposition and RT-qPCR for late remodeling markers. Survival in all groups was analyzed as well.


RESULTS
PDE4 inhibition significantly reduced the total number of alveolar inflammatory cells in BALF of mice with bleomycin-induced PF at early fibrosis stage (days 4 and 7). Number of macrophages and lymphocytes, but not neutrophils, was significantly reduced as well. Treatment decreased lung tumor necrosis factor (TNF)-alpha mRNA level and increased mRNA level of interleukin (IL)-6 but did not influence IL-1 beta. At later stage (days 14 and 24) cilomilast improved lung function, which was shown by increase in lung compliance. It also lowered fibrosis degree, as was shown by quantified pathological examination of Hematoxilin-Eosin stained lung sections. Cilomilast had no significant effect on the expression of late remodeling markers such as transforming growth factor (TGF)-beta1 and collagen type Ia1 (COL(I)alpha1). However, it tended to restore the level of lung collagen, assessed by SIRCOL assay and Masson's trichrome staining, and to improve the overall survival.


CONCLUSIONS
Selective PDE4 inhibition suppresses early inflammatory stage and attenuates the late stage of experimental pulmonary fibrosis.
Udalov
Sergey
S
University of Giessen, Department of Internal Medicine, Giessen, Germany.
Dumitrascu
Rio
R
Pullamsetti
Soni S
SS
Al-tamari
Hamza M
HM
Weissmann
Norbert
N
Ghofrani
Hossein A
HA
Guenther
Andreas
A
Voswinckel
Robert
R
Seeger
Werner
W
Grimminger
Friedrich
F
Schermuly
Ralph T
RT
D000818:Animals; D001761:Bleomycin / Q000009:adverse effects*; D002264:Carboxylic Acids / Q000494:pharmacology; D024042:Collagen Type I / Q000378:metabolism; D000090602:Collagen Type I, alpha 1 Chain; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000378:metabolism; D003509:Cyclohexanecarboxylic Acids; D004195:Disease Models, Animal; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009570:Nitriles / Q000494:pharmacology; D058988:Phosphodiesterase 4 Inhibitors; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011014:Pneumonia / Q000139:chemically induced / Q000378:metabolism / Q000517:prevention & control; D011658:Pulmonary Fibrosis / Q000139:chemically induced* / Q000378:metabolism / Q000517:prevention & control*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D002264:Carboxylic Acids; D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D003509:Cyclohexanecarboxylic Acids; D053583:Interleukin-1beta; D015850:Interleukin-6; D009570:Nitriles; D058988:Phosphodiesterase 4 Inhibitors; D010726:Phosphodiesterase Inhibitors; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D001761:Bleomycin; C433247:Cilomilast; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4
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