title: The MUC13 cell-surface mucin protects against intestinal inflammation by inhibiting epithelial cell apoptosis.
abstract: OBJECTIVE
  The MUC13 transmembrane mucin is highly and constitutively expressed in the small and large intestine. Although MUC13 polymorphisms have been associated with human inflammatory bowel diseases and susceptibility to Escherichia coli infection in pigs, the biological functions of MUC13 are unknown. This study aimed to explore whether MUC13 modulates intestinal inflammation.
  
  
  METHODS
  Muc13(-/-) mice were generated, phenotyped and challenged with the colitis-inducing agent, dextran sodium sulphate (DSS). Colitis was assessed by clinical symptoms and intestinal histopathology. Intestinal epithelial cell apoptosis and proliferation, macrophage infiltration and cytokine production were also quantified. Apoptosis of human LS513 intestinal epithelial cells in response to apoptotic agents, including DSS, was also measured, following knockdown of MUC13 with siRNA.
  
  
  RESULTS
  Muc13(-/-) mice were viable, fertile and developed normally, with no spontaneous intestinal pathology except mild focal neutrophilic inflammation in the small and large intestines of old mice. In response to DSS challenge, Muc13(-/-) mice developed more severe acute colitis, as reflected by increased weight loss, rectal bleeding, diarrhoea and histological colitis scores compared with wild-type mice. Increased numbers of F4/80(+) macrophages in inflamed mucosa of Muc13(-/-) mice were accompanied by increased expression of intestinal IL-1β and TNFα mRNA. Muc13(-/-) mice had significantly increased intestinal epithelial cell apoptosis within 3 days of DSS exposure. LS513 cells were more susceptible to DSS, actinomycin-D, ultraviolet irradiation and TRAIL-induced apoptosis when MUC13 was knocked down by siRNA.
  
  
  CONCLUSIONS
  These novel findings indicate a protective role for Muc13 in the colonic epithelium by inhibiting toxin-induced apoptosis and have important implications for intestinal infections, inflammatory diseases and the development of intestinal cancer.
authors.affiliation: Immunity, Infection and Inflammation Program, Mater Medical Research Institute and The University of Queensland, Mater Health Services, South Brisbane, Queensland, Australia.
authors.forename: Yong H
authors.initials: YH
authors.lastname: Sheng
authors.forename: Rohan
authors.initials: R
authors.lastname: Lourie
authors.forename: Sara K
authors.initials: SK
authors.lastname: Lindén
authors.forename: Penny L
authors.initials: PL
authors.lastname: Jeffery
authors.forename: Deborah
authors.initials: D
authors.lastname: Roche
authors.forename: Thu V
authors.initials: TV
authors.lastname: Tran
authors.forename: Chin W
authors.initials: CW
authors.lastname: Png
authors.forename: Nigel
authors.initials: N
authors.lastname: Waterhouse
authors.forename: Philip
authors.initials: P
authors.lastname: Sutton
authors.forename: Timothy H J
authors.initials: TH
authors.lastname: Florin
authors.forename: Michael A
authors.initials: MA
authors.lastname: McGuckin
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism / Q000502:physiology*; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D049109:Cell Proliferation; D003092:Colitis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D016207:Cytokines / Q000502:physiology; D016264:Dextran Sulfate / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000378:metabolism / Q000503:physiopathology; D007413:Intestinal Mucosa / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D017737:Macrophages, Peritoneal / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009077:Mucins / Q000378:metabolism / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D000954:Antigens, Surface; D016207:Cytokines; C063487:Ly64 protein, mouse; D009077:Mucins; D004815:Epidermal Growth Factor; D016264:Dextran Sulfate