title: MEK-1/2 inhibition reduces branching morphogenesis and causes mesenchymal cell apoptosis in fetal rat lungs.
abstract: The roles of the mitogen-activated protein (MAP) kinases extracellular signal-regulated kinases-1 and -2 (ERK-1/2) in fetal lung development have not been extensively characterized. To determine if ERK-1/2 signaling plays a role in fetal lung branching morphogenesis, U-0126, an inhibitor of the upstream kinase MAP ERK kinase (MEK), was added to fetal lung explants in vitro. Morphometry as measured by branching, area, perimeter, and complexity were significantly reduced in U-0126-treated lungs. At the same time, U-0126 treatment reduced ERK-1/2, slightly increased p38 kinase, but did not change c-Jun NH(2)-terminal kinase activities, indicating that U-0126 specifically inhibited the ERK-1/2 enzymes. These changes were associated with increased apoptosis as measured by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and immunofluorescent labeling of anti-active caspase-3 in the mesenchyme of explants after U-0126 treatment compared with the control. Mitosis characterized by immunolocalization of proliferating cell nuclear antigen was found predominantly in the epithelium and was reduced in U-0126-treated explants. Thus U-0126 causes specific inhibition of ERK-1/2 signaling, diminished branching morphogenesis, characterized by increased mesenchymal apoptosis, and decreased epithelial proliferation in fetal lung explants.
authors.affiliation: Pediatric Surgical Research Laboratories, Pediatric Surgical Services, and the Department of Surgery, Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Kling
authors.forename: Hans K
authors.initials: HK
authors.lastname: Lorenzo
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Trbovich
authors.forename: T Bernard
authors.initials: TB
authors.lastname: Kinane
authors.forename: Patricia K
authors.initials: PK
authors.lastname: Donahoe
authors.forename: Jay J
authors.initials: JJ
authors.lastname: Schnitzer
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002070:Butadienes / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D046508:Culture Techniques; D005314:Embryonic and Fetal Development / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005333:Fetus / Q000166:cytology / Q000502:physiology; D008168:Lung / Q000196:embryology*; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D008648:Mesoderm / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D009570:Nitriles / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D051381:Rats
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; C113580:U 0126; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases