Imaging and characterization of stretch-induced ATP release from alveolar A549 cells

J Physiol. 2013 Mar 1;591(5):1195-215. doi: 10.1113/jphysiol.2012.244145. Epub 2012 Dec 17.


Abstract Mechano-transduction at cellular and tissue levels often involves ATP release and activation of the purinergic signalling cascade. In the lungs, stretch is an important physical stimulus but its impact on ATP release, the underlying release mechanisms and transduction pathways are poorly understood. Here, we investigated the effect of unidirectional stretch on ATP release from human alveolar A549 cells by real-time luciferin-luciferase bioluminescence imaging coupled with simultaneous infrared imaging, to monitor the extent of cell stretch and to identify ATP releasing cells. In subconfluent (<90%) cell cultures, single 1 s stretch (10-40%)-induced transient ATP release from a small fraction (1.5%) of cells that grew in number dose-dependently with increasing extent of stretch. ATP concentration in the proximity (150 μm) of releasing cells often exceeded 10 μm, sufficient for autocrine/paracrine purinoreceptor stimulation of neighbouring cells. ATP release responses were insensitive to the putative ATP channel blockers carbenoxolone and 5-nitro-2-(3-phenylpropyl-amino) benzoic acid, but were inhibited by N-ethylmaleimide and bafilomycin. In confluent cell cultures, the maximal fraction of responding cells dropped to <0.2%, but was enhanced several-fold in the wound/scratch area after it was repopulated by new cells during the healing process. Fluo8 fluorescence experiments revealed two types of stretch-induced intracellular Ca(2+) responses, rapid sustained Ca(2+) elevations in a limited number of cells and delayed secondary responses in neighbouring cells, seen as Ca(2+) waves whose propagation was consistent with extracellular diffusion of released ATP. Our experiments revealed that a single >10% stretch was sufficient to initiate intercellular purinergic signalling in alveolar cells, which may contribute to the regulation of surfactant secretion and wound healing.

Publication types

  • Research Support, Non-U.S. Gov't
  • Video-Audio Media

MeSH terms

  • Adenosine Triphosphate / metabolism*
  • Alveolar Epithelial Cells / drug effects
  • Alveolar Epithelial Cells / metabolism*
  • Alveolar Epithelial Cells / pathology
  • Autocrine Communication* / drug effects
  • Calcium Signaling
  • Cell Line, Tumor
  • Cell Proliferation
  • Diffusion
  • Genes, Reporter
  • Humans
  • Image Processing, Computer-Assisted
  • Infrared Rays
  • Luminescent Measurements
  • Mechanotransduction, Cellular* / drug effects
  • Microscopy, Fluorescence
  • Paracrine Communication* / drug effects
  • Pulmonary Stretch Receptors / metabolism*
  • Pulmonary Surfactant-Associated Proteins / metabolism
  • Purinergic P2 Receptor Antagonists / pharmacology
  • Receptors, Purinergic P2 / drug effects
  • Receptors, Purinergic P2 / metabolism
  • Time Factors
  • Transfection
  • Wound Healing


  • Pulmonary Surfactant-Associated Proteins
  • Purinergic P2 Receptor Antagonists
  • Receptors, Purinergic P2
  • Adenosine Triphosphate