title: Up-regulation of MUC2 and IL-1β expression in human colonic epithelial cells by Shigella and its interaction with mucins.
abstract: BACKGROUND
  The entire gastrointestinal tract is protected by a mucous layer, which contains complex glycoproteins called mucins. MUC2 is one such mucin that protects the colonic mucosa from invading microbes. The initial interaction between microbes and mucins is an important step for microbial pathogenesis. Hence, it was of interest to investigate the relationship between host (mucin) and pathogen interaction, including Shigella induced expression of MUC2 and IL-1β during shigellosis.
  
  
  METHODS
  The mucin-Shigella interaction was revealed by an in vitro mucin-binding assay. Invasion of Shigella dysenteriae into HT-29 cells was analyzed by Transmission electron microscopy. Shigella induced mucin and IL-1β expression were analyzed by RT-PCR and Immunofluorescence.
  
  
  RESULTS
  The clinical isolates of Shigella were found to be virulent by a congo-red binding assay. The in vitro mucin-binding assay revealed both Shigella dysenteriae and Shigella flexneri have binding affinity in the increasing order of: guinea pig small intestinal mucin<guinea pig colonic mucin< Human colonic mucin. Invasion of Shigella dysenteriae into HT-29 cells occurs within 2 hours. Interestingly, in Shigella dysenteriae infected conditions, significant increases in mRNA expression of MUC2 and IL-1β were observed in a time dependent manner. Further, immunofluorescence analysis of MUC2 shows more positive cells in Shigella dysenteriae treated cells than untreated cells.
  
  
  CONCLUSIONS
  Our study concludes that the Shigella species specifically binds to guinea pig colonic mucin, but not to guinea pig small intestinal mucin. The guinea pig colonic mucin showed a greater binding parameter (R), and more saturable binding, suggesting the presence of a finite number of receptor binding sites in the colonic mucin of the host. In addition, modification of mucins with TFMS and sodium metaperiodate significantly reduced mucin-bacterial binding; suggesting that the mucin-Shigella interaction occurs through carbohydrate epitopes on the mucin backbones. Overproduction of MUC2 may alter adherence and invasion of Shigella dysenteriae into human colonic epithelial cells.
authors.affiliation: Department of Biochemistry, University of Madras, Guindy Campus, Chennai, Tamilnadu, India.
authors.forename: Radhakrishnan
authors.initials: R
authors.lastname: Prakash
authors.forename: Subramaniya
authors.initials: S
authors.lastname: Bharathi Raja
authors.forename: Halagowder
authors.initials: H
authors.lastname: Devaraj
authors.forename: Sivasitambaram Niranjali
authors.initials: SN
authors.lastname: Devaraj
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003106:Colon / Q000166:cytology / Q000378:metabolism*; D017931:DNA Primers; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D055262:Mucin-2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012762:Shigella dysenteriae / Q000472:pathogenicity / Q000502:physiology*; D015854:Up-Regulation; D014774:Virulence
chemical_list: D017931:DNA Primers; D053583:Interleukin-1beta; C524625:MUC2 protein, human; D055262:Mucin-2
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