title: Role of AQP2 during apoptosis in cortical collecting duct cells.
abstract: BACKGROUND
  A major hallmark of apoptosis is cell shrinkage, termed apoptotic volume decrease, due to the cellular outflow of potassium and chloride ions, followed by osmotically obliged water. In many cells, the ionic pathways triggered during the apoptotic volume decrease may be similar to that observed during a regulatory volume decrease response under hypotonic conditions. However, the pathways involved in water loss during apoptosis have been largely ignored. It was recently reported that in some systems this water movement is mediated via specific water channels (aquaporins). Nevertheless, it is important to identify whether this is a ubiquitous aspect of apoptosis as well as to define the mechanisms involved. The aim of the present work was to investigate the role of aquaporin-2 during apoptosis in renal-collecting duct cells. We evaluated the putative relationship between aquaporin-2 expression and the activation of the ionic pathways involved in the regulatory volume response.
  
  
  RESULTS
  Apoptosis was induced by incubating cells with a hypertonic solution or with cycloheximide in two cortical collecting duct cell lines: one not expressing aquaporins and the other stably transfected with aquaporin-2. Typical features of apoptosis were evaluated with different approaches and the water permeability was measured by fluorescence videomicroscopy. Our results show that the rate of apoptosis is significantly increased in aquaporin-2 cells and it is linked to the rapid activation of volume-regulatory potassium and chloride channels. Furthermore, the water permeability of cells expressing aquaporin-2 was strongly reduced during the apoptotic process and it occurs before DNA degradation.
  
  
  CONCLUSIONS
  These results let us propose that under apoptotic stimulation aquaporin-2 would act as a sensor leading to a co-ordinated activation of specific ionic channels for potassium and chloride efflux, resulting in both more rapid cell shrinkage and more rapid achievement of adequate levels of ions necessary to activate the enzymatic apoptotic cascade.
authors: Laboratorio de Biomembranas, Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
authors: Pilar
authors: P
authors: Flamenco
authors: Luciano
authors: L
authors: Galizia
authors: Valeria
authors: V
authors: Rivarola
authors: Juan
authors: J
authors: Fernandez
authors: Paula
authors: P
authors: Ford
authors: Claudia
authors: C
authors: Capurro
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051399:Aquaporin 2 / Q000235:genetics / Q000378:metabolism*; D017609:Barium Compounds / Q000378:metabolism; D002460:Cell Line; D002463:Cell Membrane Permeability; D048429:Cell Size; D002712:Chlorides / Q000378:metabolism; D003513:Cycloheximide / Q000378:metabolism; D053938:DNA Fragmentation; D005905:Glyburide / Q000378:metabolism; D006801:Humans; D007473:Ion Channels / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism; D009994:Osmolar Concentration; D051381:Rats; D014867:Water / Q000378:metabolism
chemical_list: D051399:Aquaporin 2; D017609:Barium Compounds; D002712:Chlorides; D007473:Ion Channels; D014867:Water; C024986:barium chloride; D003513:Cycloheximide; D005905:Glyburide