title: 40- to 100-kD protein(s) of Helicobacter pylori stimulate DNA synthesis in epithelial cell lines without affecting apoptosis.
abstract: BACKGROUND
  Previous in vitro studies have demonstrated that water extracts and sonicates of Helicobacter pylori increase DNA synthesis in a small intestinal epithelial cell line. The aim of this study was to identify mitogenic factor(s) in a water extract of a H. pylori strain and to examine their effects on DNA synthesis and apoptosis in vitro.
  
  
  METHODS
  IEC-6 and FHs 74 cells were incubated for 24 h with different dilutions of a water extract of H. pylori (cytotoxic strain 88-23) or with 6 protein fractions obtained by gel filtration. Cells were labeled with tritiated thymidine and processed for autoradiography. DNA synthesis was evaluated by the labeling index (LI%). The proportion of IEC-6 cells undergoing apoptosis and/or necrosis was evaluated by flow cytometry using fluorescein isothiocyanate (FITC)-labeled annexin-V and propidium iodide. In vitro caspase activity was also determined as an alternative method for detection of apoptosis.
  
  
  RESULTS
  The water extract of H. pylori 88-23 markedly increased DNA synthesis in both epithelial cell lines (p < 0.01). A marked stimulation of DNA synthesis was also observed in IEC-6 cells incubated with fraction II- containing proteins of a molecular weight ranging between 40 and 100 kD (p < 0.01). A lesser stimulation of DNA synthesis was observed in cells incubated with higher concentrations of the other protein fractions (p < 0.01). Neither the water extract of H. pylori 88-23 nor the protein fraction II (40-100 kD) induced apoptosis in IEC-6 cells.
  
  
  CONCLUSIONS
  A water extract of H. pylori 88-23 and a protein fraction containing proteins with molecular weights of 40-100 kD stimulate DNA synthesis in a rat and human small intestinal cell line. Apoptosis was unaffected by the water extract and by protein fraction II, which indicate that the H. pylori-derived mitogen(s) have the capacity to directly enhance epithelial cell proliferation in vitro.
authors.affiliation: Division of Internal Medicine, Section of Gastroenterology and Hepatology, Karolinska Institutet, Danderyd Hospital, Stockholm, Sweden.
authors.forename: V
authors.initials: V
authors.lastname: Neopikhanov
authors.forename: A
authors.initials: A
authors.lastname: Samali
authors.forename: K
authors.initials: K
authors.lastname: Wreiber
authors.forename: L
authors.initials: L
authors.lastname: Engstrand
authors.forename: A
authors.initials: A
authors.lastname: Uribe
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D001426:Bacterial Proteins / Q000494:pharmacology*; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival; D004247:DNA / Q000096:biosynthesis*; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005434:Flow Cytometry; D016480:Helicobacter pylori / Q000737:chemistry*; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D008970:Molecular Weight; D051381:Rats
chemical_list: D017304:Annexin A5; D001426:Bacterial Proteins; D004247:DNA; D020169:Caspases