title: Prenatal retinoic acid upregulates pulmonary gene expression of PI3K and AKT in nitrofen-induced pulmonary hypoplasia.
abstract: BACKGROUND
  The precise mechanism of pulmonary hypoplasia associated with congenital diaphragmatic hernia (CDH) still remains unclear. Recently, prenatal treatment with retinoic acid (RA) has been reported to stimulate alveologenesis in hypoplastic lungs in the nitrofen model of CDH. The serine/threonine protein kinase B (AKT) plays a key role in lung morphogenesis through epithelial-mesenchymal interaction in phosphatidylinositide 3-kinase (PI3K)-dependent manner. It has been reported that the lung morphogenesis in explants in mice is interfered by inhibitors of PI3K-AKT signaling pathway. Furthermore, we have recently shown that nitrofen inhibits PI3K-AKT signaling during mid-to-late lung morphogenesis in the nitrofen-induced hypoplastic lung. We hypothesized that prenatal administration of RA upregulates pulmonary gene expression of PI3K and AKT in the nitrofen-induced hypoplastic lung.
  
  
  METHODS
  Pregnant rats were exposed to either olive oil or nitrofen on day 9 of gestation (D9). 5 mg/kg of RA was given on D18, D19 and D20. The fetuses were harvested on D21, and fetal lungs were obtained and divided into four groups: control, control + RA, nitrofen, nitrofen + RA. The mRNA expression levels of PI3K and AKT were analyzed in each lung by real-time RT-PCR and statistically analyzed. Immunohistochemistry was also performed to evaluate protein expression of PI3K and AKT in the fetal lungs at D21.
  
  
  RESULTS
  The pulmonary gene expression levels of PI3K and AKT were significantly upregulated in nitrofen + RA group compared to nitrofen group and control + RA group (p < 0.05), whereas there were no significant differences between controls and control + RA group. Immunoreactivity of PI3K and AKT was markedly increased in nitrofen + RA lungs compared to nitrofen-induced hypoplastic lungs.
  
  
  CONCLUSIONS
  Upregulation of PI3K and AKT genes after prenatal treatment with RA in the nitrofen-induced hypoplastic lung suggests that RA may have a therapeutic potential in modulating lung alveologenesis by stimulating epithelial-mesenchymal interaction via PI3K-AKT signaling.
authors.affiliation: The Children's Research Centre, Our Lady's Children's Hospital, Dublin 12, Ireland.
authors.forename: Takashi
authors.initials: T
authors.lastname: Doi
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Elke
authors.initials: E
authors.lastname: Ruttenstock
authors.forename: Jens
authors.initials: J
authors.lastname: Dingemann
authors.forename: Prem
authors.initials: P
authors.lastname: Puri
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D005315:Fetal Diseases / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D005865:Gestational Age; D006548:Hernia, Diaphragmatic / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism; D007150:Immunohistochemistry; D008168:Lung / Q000196:embryology / Q000378:metabolism*; D009024:Morphogenesis / Q000187:drug effects / Q000235:genetics; D010647:Phenyl Ethers / Q000633:toxicity; D011247:Pregnancy; D011270:Pregnancy, Animal; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014212:Tretinoin / Q000494:pharmacology*; D015854:Up-Regulation
chemical_list: D010647:Phenyl Ethers; D012333:RNA, Messenger; D014212:Tretinoin; D051057:Proto-Oncogene Proteins c-akt; C007350:nitrofen