title: Dietary haem stimulates epithelial cell turnover by downregulating feedback inhibitors of proliferation in murine colon.
abstract: OBJECTIVE
  Colon cancer is a leading cause of cancer deaths in Western countries and is associated with diets high in red meat. Haem, the iron-porphyrin pigment of red meat, induces cytotoxicity of gut contents and damages the colon surface epithelium. Compensatory hyperproliferation leads to epithelial hyperplasia which increases the risk of colon cancer. The aim of this study was to identify molecules signalling from the surface epithelium to the crypt to initiate hyperproliferation upon stress induced by haem.
  
  
  METHODS
  C57Bl6/J mice (n=9/group) received a 'westernised' control diet (40 en% fat) with or without 0.5 μmol/g haem for 14 days. Colon mucosa was used to quantify cell proliferation and for microarray transcriptome analysis. Gene expression profiles of surface and crypt cells were compared using laser capture microdissection. Protein levels of potential signalling molecules were quantified.
  
  
  RESULTS
  Haem-fed mice showed epithelial hyperproliferation and decreased apoptosis, resulting in hyperplasia. Microarray analysis of the colon mucosa showed 3710 differentially expressed genes (false discovery rate (q) <0.01), with many involved in the cell cycle. Expression levels of haem- and stress-related genes showed that haem affected surface cells but did not directly affect crypt cells. Injured surface cells should therefore signal to crypt cells to induce compensatory hyperproliferation. Haem downregulated the inhibitors of proliferation, Wnt inhibitory factor 1, Indian Hedgehog and bone morphogenetic protein 2. Interleukin-15 was also downregulated. Haem upregulated amphiregulin, epiregulin and cyclo-oxygenase-2 mRNA in surface cells. Their protein/metabolite levels were, however, not increased as haem induced surface-specific inhibition of translation by increasing 4E-BP1.
  
  
  CONCLUSIONS
  Haem induces colonic hyperproliferation and hyperplasia by inhibiting the surface to crypt signalling of feedback inhibitors of proliferation.
authors.affiliation: Top Institute Food and Nutrition, Wageningen, The Netherlands. noortje.ijssennagger@wur.nl
authors.forename: Noortje
authors.initials: N
authors.lastname: IJssennagger
authors.forename: Anneke
authors.initials: A
authors.lastname: Rijnierse
authors.forename: Nicole
authors.initials: N
authors.lastname: de Wit
authors.forename: Denise
authors.initials: D
authors.lastname: Jonker-Termont
authors.forename: Jan
authors.initials: J
authors.lastname: Dekker
authors.forename: Michael
authors.initials: M
authors.lastname: Müller
authors.forename: Roelof
authors.initials: R
authors.lastname: van der Meer
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D003106:Colon / Q000166:cytology* / Q000378:metabolism; D003110:Colonic Neoplasms / Q000209:etiology; D019587:Dietary Supplements; D015536:Down-Regulation; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D025461:Feedback, Physiological; D015870:Gene Expression; D020869:Gene Expression Profiling; D006418:Heme / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000378:metabolism*; D061346:Laser Capture Microdissection; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020411:Oligonucleotide Array Sequence Analysis; D015398:Signal Transduction; D059467:Transcriptome
chemical_list: D006418:Heme