title: Normotonic cell shrinkage induces apoptosis under extracellular low Cl conditions in human lymphoid and epithelial cells.
abstract: OBJECTIVE
  Sustained cell shrinkage is associated with apoptosis. Apoptotic volume decrease, which is known to be induced by release of osmolytes including Cl- ions, may be an essential event for apoptosis induction. Provided any anion channels and/or anion transporters are basally functioning, there is a possibility that imposition of a driving force for Cl- efflux per se results in sustained cell shrinkage and thereby induces apoptotic death. Here, this possibility was tested by reducing the extracellular Cl- concentration.
  
  
  METHODS
  Human lymphoid U937 and epithelial HeLa cells were provided for experiments after exposing to isotonic electrolyte solution which contains 146 or 1 mM Cl-. Measurements of mean cell volume, caspase-3 activity and cell viability were performed by a Coulter-type cell size analyzer, a fluorometric assay and a colorimetric assay, respectively.
  
  
  RESULTS
  After exposure to low Cl- solution in which most chloride was replaced with aspartate, gluconate, phosphate or methanesulphonate, both U937 and HeLa cells exhibited, for up to 60 min, shrinkage to a level (90-80%) significantly lower than that in control high Cl- solution. Reduction in cell viability started within 2 h and reached below 20% within 8 h after exposure to low Cl- solution. The cell death was found to be associated with caspase-3 activation and DNA fragmentation.
  
  
  CONCLUSIONS
  Exposure to isotonic low Cl- solution induced sustained shrinkage and thereafter apoptotic death in U937 and HeLa cells. Thus, it is suggested that sustained cell shrinkage per se provides a sufficient condition for apoptosis induction.
authors.affiliation: Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Maeno
authors.forename: T
authors.initials: T
authors.lastname: Shimizu
authors.forename: Y
authors.initials: Y
authors.lastname: Okada
mesh_terms: D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D048429:Cell Size; D018118:Chloride Channels / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D053938:DNA Fragmentation; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D045604:Extracellular Fluid / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007552:Isotonic Solutions; D008221:Lymphoid Tissue / Q000378:metabolism* / Q000473:pathology; D013997:Time Factors; D020298:U937 Cells
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D007552:Isotonic Solutions; D053148:Caspase 3