Published ahead of print on May 14, 2003, doi:10.1165/rcmb.2002-0281OC Am. J. Respir. Cell Mol. Biol., Volume 29, Number 5, November 2003, 552-561 A more recent version of this article appeared on November 1, 2003
Submitted on December 2, 2002 Cell-cell communication in heterocellular cultures of alveolar epithelial cellsBrant E Isakson1,1 Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA, 2 Division of Pulmonary and Critical Care Medicine, University of Southern California Keck School of Medicine, Los Angeles, California, USA, 3 Wales Heart Research Institute, Department of Medical Biochemistry, University of Wales College of Medicine, Cardiff, Wales, United Kingdom, 4 Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA; Arizona Respiratory Center and Department of Physiology, University of Arizona, Tucson, Arizona, USA * To whom correspondence should be addressed. E-mail: sboitano{at}email.arizona.edu.
The mammalian alveolar epithelium is composed of alveolar type I (AT1) and alveolar type II (AT2) cells that together coordinate tissue function. We used a heterocellular culture model of AT1 and AT2 cells to determine pathways for intercellular signaling between these two phenotypes. Gap junction protein (connexin) profiles of AT1 and AT2 cells in heterocellular cultures were similar to those seen in rat lung alveolar sections. Dye coupling studies revealed functional gap junctions between and among each cell phenotype. Localized mechanical stimulation resulted in propagated changes of [Ca2+]i to AT1 or AT2 cells independent of the stimulated cell phenotype. Ca2+ communication that originated after AT1 cell stimulation was inhibited by gap junction blockers, but not by an inhibitor of extracellular nucleotide signaling (apyrase). Conversely, Ca2+ communication after stimulation of AT2 cells was not significantly reduced by gap junction inhibitors. However, apyrase significantly reduced Ca2+ communication from AT2 to AT1 cells, but not from AT2 to AT2 cells. In conclusion, AT1 and AT2 cells have unique connexin profiles that allow for functional coupling and distinct intercellular pathways for coordination of Ca2+ signaling.
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