title: Extracellular ATP induces cell death in human intestinal epithelial cells.
abstract: BACKGROUND
  Extracellular ATP is an endogenous signaling molecule released by various cell types and under different stimuli. High concentrations of ATP released into the extracellular medium activate the P2X7 receptor in most inflammatory conditions. Here, we seek to characterize the effects of ATP in human intestinal epithelial cells and to evaluate morphological changes in these cells in the presence of ATP.
  
  
  METHODS
  We treated human intestinal epithelial cells with ATP and evaluated the effects of this nucleotide by scanning and transmission electron microscopy analysis and calcium measurements. We used flow cytometry to evaluate apoptosis. We collected human intestinal explants for immunohistochemistry, apoptosis by the TUNEL approach and caspase-3 activity using flow cytometry analyses. We also evaluated the ROS production by flow cytometry and NO secretion by the Griess technique.
  
  
  RESULTS
  ATP treatment induced changes characteristic of cell death by apoptosis and autophagy but not necrosis in the HCT8 cell line. ATP induced apoptosis in human intestinal explants that showed TUNEL-positive cells in the epithelium and in the lamina propria. The explants exhibited a significant increase of caspase-3 activity when the colonic epithelial cells were incubated with IFN-gamma followed by ATP as compared to control cells. In addition, it was found that antioxidants were able to inhibit both the ROS production and the apoptosis induced by ATP in epithelial cells.
  
  
  CONCLUSIONS
  The activation of P2X7 receptors by ATP induces apoptosis and autophagy in human epithelial cells, possibly via ROS production, and this effect might have implications for gut inflammatory conditions.
authors.affiliation: Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Carolina O
authors.initials: CO
authors.lastname: Souza
authors.forename: Giani F
authors.initials: GF
authors.lastname: Santoro
authors.forename: Vanessa R
authors.initials: VR
authors.lastname: Figliuolo
authors.forename: Hayandra Ferreira
authors.initials: HF
authors.lastname: Nanini
authors.forename: Heitor S P
authors.initials: HS
authors.lastname: de Souza
authors.forename: Morgana Teixeira Lima
authors.initials: MT
authors.lastname: Castelo-Branco
authors.forename: Alessandra Alves
authors.initials: AA
authors.lastname: Abalo
authors.forename: Mauricio M
authors.initials: MM
authors.lastname: Paiva
authors.forename: Claudia M L M
authors.initials: CM
authors.lastname: Coutinho
authors.forename: Robson
authors.initials: R
authors.lastname: Coutinho-Silva
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D003106:Colon / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007078:Ileal Neoplasms / Q000378:metabolism / Q000473:pathology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009336:Necrosis; D009569:Nitric Oxide / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D000255:Adenosine Triphosphate; D007770:L-Lactate Dehydrogenase; D053148:Caspase 3; D002118:Calcium