title: All-Trans Retinoic Acid Induces TGF-β2 in Intestinal Epithelial Cells via RhoA- and p38α MAPK-Mediated Activation of the Transcription Factor ATF2.
abstract: OBJECTIVE
  We have shown previously that preterm infants are at risk of necrotizing enterocolitis (NEC), an inflammatory bowel necrosis typically seen in infants born prior to 32 weeks' gestation, because of the developmental deficiency of transforming growth factor (TGF)-β2 in the intestine. The present study was designed to investigate all-trans retinoic acid (atRA) as an inducer of TGF-β2 in intestinal epithelial cells (IECs) and to elucidate the involved signaling mechanisms.
  
  
  METHODS
  AtRA effects on intestinal epithelium were investigated using IEC6 cells. TGF-β2 expression was measured using reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and Western blots. Signaling pathways were investigated using Western blots, transiently-transfected/transduced cells, kinase arrays, chromatin immunoprecipitation, and selective small molecule inhibitors.
  
  
  RESULTS
  AtRA-treatment of IEC6 cells selectively increased TGF-β2 mRNA and protein expression in a time- and dose-dependent fashion, and increased the activity of the TGF-β2 promoter. AtRA effects were mediated via RhoA GTPase, Rho-associated, coiled-coil-containing protein kinase 1 (ROCK1), p38α MAPK, and activating transcription factor (ATF)-2. AtRA increased phospho-ATF2 binding to the TGF-β2 promoter and increased histone H2B acetylation in the TGF-β2 nucleosome, which is typically associated with transcriptional activation.
  
  
  CONCLUSIONS
  AtRA induces TGF-β2 expression in IECs via RhoA- and p38α MAPK-mediated activation of the transcription factor ATF2. Further studies are needed to investigate the role of atRA as a protective/therapeutic agent in gut mucosal inflammation.
authors.affiliation: Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America; Department of Pediatrics, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America.
authors.forename: Kopperuncholan
authors.initials: K
authors.lastname: Namachivayam
authors.affiliation: Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America; Department of Pediatrics, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America.
authors.forename: Krishnan
authors.initials: K
authors.lastname: MohanKumar
authors.affiliation: Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America.
authors.forename: Dima
authors.initials: D
authors.lastname: Arbach
authors.affiliation: Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America.
authors.forename: Ramasamy
authors.initials: R
authors.lastname: Jagadeeswaran
authors.affiliation: Department of Pediatrics, University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Jain
authors.affiliation: Department of Pharmacology, University of Illinois at Chicago, Chicago, Illinois, United States of America.
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Natarajan
authors.affiliation: Department of Pharmacology, University of Illinois at Chicago, Chicago, Illinois, United States of America.
authors.forename: Dolly
authors.initials: D
authors.lastname: Mehta
authors.affiliation: Physiology & Experimental Medicine Program, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada; Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Jankov
authors.affiliation: Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States of America; Department of Pediatrics, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America; Department of Pharmacology, University of Illinois at Chicago, Chicago, Illinois, United States of America; Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America; Department of Community and Family Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America.
authors.forename: Akhil
authors.initials: A
authors.lastname: Maheshwari
mesh_terms: D051698:Activating Transcription Factor 2 / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D048308:Mitogen-Activated Protein Kinase 14 / Q000378:metabolism*; D010766:Phosphorylation; D051785:Smad Proteins / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*; D014212:Tretinoin / Q000494:pharmacology*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D051698:Activating Transcription Factor 2; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D014212:Tretinoin; D048308:Mitogen-Activated Protein Kinase 14; D020742:rhoA GTP-Binding Protein