title: Conditional over-expression of RAGE by embryonic alveolar epithelium compromises the respiratory membrane and impairs endothelial cell differentiation.
abstract: BACKGROUND
  Receptors for advanced glycation end-products (RAGE) are cell surface receptors prominently expressed by lung epithelium. Previous research demonstrated that over-expression of RAGE by murine alveolar epithelial cells during embryogenesis caused severe lung hypoplasia and neonatal lethality. However, the effects of RAGE over-expression on adjacent matrix and endothelial cells remained unknown.
  
  
  METHODS
  RAGE transgenic (TG) mice were generated that conditionally over-expressed RAGE in alveolar type II cells when fed doxycycline (dox) from conception to E18.5. To evaluate effects on the basement membrane, immunostaining and immunoblotting were performed for collagen IV and MMP-9, a matrix metalloprotease capable of degrading basement membranes. To assess changes in vasculature, immunostaining, immunoblotting and qRT-PCR were performed for Pecam-1, a platelet endothelial cell adhesion marker also known as CD31. Lastly, to characterize potential regulatory mechanisms of endothelial cell differentiation, immunoblotting and qRT-PCR for FoxM1, a key endothelium-specific transcription factor of the Forkhead Box (Fox) family, were completed.
  
  
  RESULTS
  Qualitative immunostaining for collagen IV was less in RAGE TG mice compared to controls and immunoblotting revealed decreased collagen IV in the RAGE TG mouse lung. Additionally, elevated MMP-9 detected via immunostaining and immunoblotting implicated MMP-9 as a possible down stream effector in matrix destabilization mediated by RAGE signaling. Lastly, Pecam-1 assessment revealed a decrease in the prevalence of microvascular endothelial cells coincident with FoxM1 abrogation in RAGE TG mice compared to controls.
  
  
  CONCLUSIONS
  RAGE over-expression by alveolar epithelium weakened the basement membrane and associated matrix via increased MMP-9 activity. Furthermore, over-expression of RAGE inhibited FoxM1, suggesting that anomalous transcriptional control contributes to decreased endothelial cell prevalence in the TG mouse lung.
authors.forename: Duane R
authors.initials: DR
authors.lastname: Winden
authors.forename: Nicholas T
authors.initials: NT
authors.lastname: Ferguson
authors.forename: Benjamin R
authors.initials: BR
authors.lastname: Bukey
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Geyer
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Wright
authors.forename: Zac R
authors.initials: ZR
authors.lastname: Jergensen
authors.forename: Adam B
authors.initials: AB
authors.lastname: Robinson
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Stogsdill
authors.affiliation: Department of Physiology and Developmental Biology, Brigham Young University, 375A Widtsoe Building, 84602 Provo, UT, USA. paul_reynolds@byu.edu.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Reynolds
mesh_terms: D000818:Animals; D001485:Basement Membrane / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D003094:Collagen / Q000378:metabolism; D004727:Endothelium / Q000378:metabolism / Q000473:pathology*; D004848:Epithelium / Q000196:embryology / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D023421:Models, Animal; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000196:embryology* / Q000378:metabolism*; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*
chemical_list: D051858:Forkhead Transcription Factors; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic; D003094:Collagen; D020780:Matrix Metalloproteinase 9