title: Alpha-Defensin 5 Expression is Regulated by microRNAs in the Caco-2 Intestinal Epithelial Cell Line.
abstract: BACKGROUND
  In inflammatory bowel disease (IBD), an inappropriate immune response leads to chronic mucosal inflammation. This response may be partly due to dysregulation of defensins, which are endogenously produced antimicrobial peptides. This study determined whether microRNAs (miRNAs) regulate α-defensin 5 (DEFA5), which could further implicate both in IBD pathogenesis.
  
  
  METHODS
  Induction of DEFA5 mRNA and protein expression was determined in Caco-2 cells. Anin silicoanalysis identified putative miRNA binding sites of DEFA5. Expression of these miRNAs was assessed in Caco-2 cells. Regulation of DEFA5 expression by these miRNAs was measured by luciferase assays. Caco-2 cells were transfected with miR-124 and miR-924 mimics, and DEFA5 mRNA and protein expression was measured.
  
  
  RESULTS
  DEFA5 mRNA and protein expression was inducible in Caco-2 cells. Fifteen putative miRNA binding sites were found in DEFA5. The expression of miR-124 and miR-924 decreased following induction. Transfection of a luciferase construct containing the DEFA5 miRNA binding sites resulted in a decrease in luciferase activity compared to transfection of the empty vector. Transfection of a reporter construct containing mismatched miRNA binding sites resulted in restoration of luciferase activities. Transfection of miRNA mimics decreased DEFA5 mRNA expression and protein expression.
  
  
  CONCLUSIONS
  miR-124 and miR-924 negatively regulate DEFA5 mRNA and protein expression. These data implicate miRNAs in intestinal innate immune regulation and IBD pathogenesis.
authors.affiliation: Johns Hopkins School of Medicine, USA.
authors.forename: Donald R B
authors.initials: DR
authors.lastname: Miles
authors.affiliation: University of Chicago, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Shen
authors.affiliation: University of Chicago, USA.
authors.forename: Alice Y
authors.initials: AY
authors.lastname: Chuang
authors.affiliation: University of Chicago, USA.
authors.forename: Fenshi
authors.initials: F
authors.lastname: Dong
authors.affiliation: University of Texas, Southwestern Medical Center, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Wu
authors.affiliation: University of Texas, Southwestern Medical Center, USA.
authors.forename: John
authors.initials: J
authors.lastname: Kwon
keywords: Defensin; Inflammatory bowel disease; MicroRNA regulation