Phosphodiesterase 4 inhibition decreases MUC5AC expression induced by epidermal growth factor in human airway epithelial cells.
BACKGROUND
A common pathological feature of chronic inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease (COPD) is mucus hypersecretion. MUC5AC is the predominant mucin gene expressed in healthy airways and is increased in asthmatic and COPD patients. Recent clinical trials indicate that phosphodiesterase type 4 (PDE4) inhibitors may have therapeutic value for COPD and asthma. However, their direct effects on mucin expression have been scarcely investigated.


METHODS
MUC5AC mRNA and protein expression were examined in cultured human airway epithelial cells (A549) and in human isolated bronchial tissue stimulated with epidermal growth factor (EGF; 25 ng/ml). MUC5AC mRNA was measured by real time RT-PCR and MUC5AC protein by ELISA (cell lysates and tissue homogenates), Western blotting (tissue homogenates) and immunohistochemistry.


RESULTS
EGF increased MUC5AC mRNA and protein expression in A549 cells. PDE4 inhibitors produced a concentration dependent inhibition of the EGF induced MUC5AC mRNA and protein expression with potency values (-log IC(50)): roflumilast (approximately 7.5) > rolipram (approximately 6.5) > cilomilast (approximately 5.5). Roflumilast also inhibited the EGF induced expression of phosphotyrosine proteins, EGF receptor, and phospho-p38- and p44/42-MAPK measured by Western blot analysis in A549 cells. In human isolated bronchus, EGF induced MUC5AC mRNA and protein expression was inhibited by roflumilast (1 microM) as well as the MUC5AC positive staining shown by immunohistochemistry.


CONCLUSIONS
Selective PDE4 inhibition is effective in decreasing EGF induced MUC5AC expression in human airway epithelial cells. This effect may contribute to the clinical efficacy of this new drug category in mucus hypersecretory diseases.
Mata
M
M
Department of Pharmacology, Faculty of Medicine, University of Valencia, Spain.
Sarriá
B
B
Buenestado
A
A
Cortijo
J
J
Cerdá
M
M
Morcillo
E J
EJ
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D000368:Aged; D015153:Blotting, Western; D001980:Bronchi / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D004797:Enzyme-Linked Immunosorbent Assay; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055271:Mucin 5AC; D009077:Mucins / Q000378:metabolism*; D019000:Phosphotyrosine / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins; D020545:Respiratory Mucosa / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
C524678:MUC5AC protein, human; D055271:Mucin 5AC; D009077:Mucins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D019000:Phosphotyrosine; D004815:Epidermal Growth Factor; D000242:Cyclic AMP; D048051:p38 Mitogen-Activated Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4