Dickkopf-1, the Wnt antagonist, is induced by acidic pH and mediates epithelial cellular senescence in human reflux esophagitis. Am J Physiol Gastrointest Liver Physiol 2014 Apr 01;306(7):G557-74
Date
02/01/2014Pubmed ID
24481601Pubmed Central ID
PMC3962590DOI
10.1152/ajpgi.00153.2013Scopus ID
2-s2.0-84900542202 (requires institutional sign-in at Scopus site) 25 CitationsAbstract
Squamous esophageal epithelium adapts to acid reflux-mediated injury by proliferation and differentiation via signal transduction pathways. Induction of the Wnt antagonist Dickkopf-1 (Dkk1) is involved in tissue repair during inflammation and cellular injury. In this study, we aimed to identify the biological role of Dkk1 in human reflux esophagitis with respect to cell growth and regulation of Wnt signaling. Esophageal biopsies from reflux-esophagitis patients (n = 15) and healthy individuals (n = 10) were characterized in terms of Dkk1 expression. The role of Dkk1 in response to acid-mediated epithelial injury was analyzed by cellular assays in vitro utilizing squamous esophageal epithelial cell lines (EPC1-hTERT, EPC2-hTERT, and HEEC). Dkk1 was significantly overexpressed in human reflux-esophagitis tissue compared with healthy esophageal mucosa at transcriptional and translational levels. After acute and chronic acid (pH 4) exposure, esophageal squamous epithelial cell lines expressed and secreted high levels of Dkk1 in response to stress-associated DNA injury. High extracellular levels of human recombinant Dkk1 inhibited epithelial cell growth and induced cellular senescence in vitro, as demonstrated by reduced cell proliferation, G0/G1 cell cycle arrest, elevated senescence-associated β-galactosidase activity, and upregulation of p16. Acid pulsing induced Dkk1-mediated senescence, which was directly linked to the ability of Dkk1 to antagonize the canonical Wnt/β-catenin signaling. In healthy esophageal mucosa, Dkk1 expression was associated with low expression of transcriptionally active β-catenin, while in reflux-esophagitis tissue, Dkk1 overexpression correlated with increased senescence-associated β-galactosidase activity and p16 upregulation. The data indicate that, in human reflux esophagitis, Dkk1 functions as a secreted growth inhibitor by suppressing Wnt/β-catenin signaling and promoting cellular senescence. These findings suggest a significant role for Dkk1 and cellular senescence in esophageal tissue homeostasis during reflux esophagitis.
Author List
Lyros O, Rafiee P, Nie L, Medda R, Jovanovic N, Schmidt J, Mackinnon A, Venu N, Shaker RAuthor
Reza Shaker MD Assoc Provost, Sr Assoc Dean, Ctr Dir, Chief, Prof in the Medicine department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AdultAged
Aged, 80 and over
Case-Control Studies
Cell Cycle Checkpoints
Cell Line
Cell Proliferation
Cellular Senescence
Cyclin-Dependent Kinase Inhibitor p16
Epithelial Cells
Esophagitis, Peptic
Esophagus
Female
Humans
Hydrogen-Ion Concentration
Intercellular Signaling Peptides and Proteins
Male
Middle Aged
Mucous Membrane
RNA Interference
Time Factors
Transfection
Up-Regulation
Wnt Signaling Pathway
Young Adult
beta Catenin
beta-Galactosidase