Insulin-like Growth Factor-I signaling mechanisms, type I collagen and alpha smooth muscle actin in human fetal lung fibroblasts.
Bronchial wall remodeling is a major morbidity component in oxidant injury in bronchopulmonary dysplasia (BPD) and asthma.


OBJECTIVE
IGF-1 enhances alpha smooth muscle expression and collagen synthesis in developing lung fibroblasts leading to fibrosis through nuclear NF-(k)B -dependent transcription. We studied NF-(k)B dependent transcription by transfecting HFLF with a NF-(k)B responsive promoter driving the luciferase gene and treating with IGF-1 (100 ng/mL) and measuring luciferase activity. We exposed cells to the PI-3 kinase inhibitor or the Erk1/2 inhibitor one hr before stimulating with IGF-1. We also used IGF-1 receptor antibody to inhibit the action of IGF-1 and studied its effect on alpha-sma and type I collagen. IGF-1 treatment significantly increased luciferase activity. This was attenuated by PI-3 kinase and MAP-Kinase inhibitors. Western blot analysis showed PI-3 kinase mediates IGF-1 activation of NF-(k)B independent of I(K)B phosphorylation. We found an up-regulation of phospho NF-kB in the nuclear extract compared with total NFKB showing that IGF-1 regulates NF-(k)B transcriptional activity downstream of NF-(k)B nuclear translocation. IGF-1-induced increase in alpha-sma expression and type-I collagen was significantly inhibited by pretreatment with LY294002 and IGF-1 receptor antibody. IGF-1 cell signaling leading to collagen synthesis in fetal lung fibroblasts is mediated by PI3 Kinase acting through NF-(k)B in HFLF.
Chetty
Anne
A
Department of Pediatric Pulmonary, Floating Hospital for Children, New England Medical Center, Boston, MA 02111, USA. achetty@tufts-nemc.org
Cao
Gong-Jee
GJ
Nielsen
Heber C
HC
D000199:Actins / Q000032:analysis / Q000378:metabolism*; D000906:Antibodies / Q000494:pharmacology; D002867:Chromones / Q000494:pharmacology; D024042:Collagen Type I / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D005333:Fetus / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000494:pharmacology* / Q000502:physiology; D008168:Lung / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009130:Muscle, Smooth / Q000737:chemistry / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000235:genetics; D014158:Transcription, Genetic
D000199:Actins; D000906:Antibodies; D002867:Chromones; D024042:Collagen Type I; D048049:Extracellular Signal-Regulated MAP Kinases; D007334:Insulin-Like Growth Factor I; D009025:Morpholines; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one