title: Mild stretch activates cPLA2 in alveolar type II epithelial cells independently through the MEK/ERK and PI3K pathways.
abstract: Alveolar epithelial type II cells (AT II) in which lung surfactant synthesis and secretion take place, are subjected to low magnitude stretch during normal breathing. The aim of the study was to explore the effect of mild stretch on phospholipase A(2) (PLA(2)) activation, an enzyme known to be involved in surfactant secretion. In A549 cells (a model of AT II cells), we showed, using a fluorometric assay, that stretch triggers an increase of total PLA(2) activity. Western blot experiments revealed that the cytosolic isoform cPLA(2) is rapidly phosphorylated under stretch, in addition to a modest increase in cPLA(2) mRNA levels. Treatment of A549 cells with selective inhibitors of the MEK/ERK pathway significantly attenuated the stretch-induced cPLA(2) phosphorylation. A strong interaction of cPLA(2) and pERK enzymes was demonstrated by immunoprecipitation. We also found that inhibition of PI3K pathway attenuated cPLA(2) activation after stretch, without affecting pERK levels. Our results suggest that low magnitude stretch can induce cPLA(2) phosphorylation through the MEK/ERK and PI3K-Akt pathways, independently.
authors.affiliation: Biochemistry Laboratory, Chemistry Department, University of Ioannina, 45110, Ioannina, Greece.
authors.forename: Eleftheria
authors.initials: E
authors.lastname: Letsiou
authors.forename: Ei
authors.initials: E
authors.lastname: Kitsiouli
authors.forename: George
authors.initials: G
authors.lastname: Nakos
authors.forename: Marilena E
authors.initials: ME
authors.lastname: Lekka
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D002070:Butadienes / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D005470:Fluorometry; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D054510:Phospholipases A2, Cytosolic / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013314:Stress, Mechanical; D013997:Time Factors; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D002070:Butadienes; D002118:Calcium; D004791:Enzyme Inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases; D005419:Flavonoids; D054513:Group IV Phospholipases A2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D009570:Nitriles; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D054510:Phospholipases A2, Cytosolic; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin; C113580:U 0126; C535150:MAPK1 protein, human; C516389:PLA2G4A protein, human; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one