Submitted on October 28, 2003
Accepted on March 25, 2004
Proximal Airway Mucous Cells of Ovalbumin Sensitized and Challenged Brown Norway Rats Accumulate the Neuropeptide Calcitonin Gene-Related Peptide (CGRP)
Shawnessy D. Larson1, Charles G. Plopper1, Greg Baker1, Brian K. Tarkington2, Kendra C. Decile1, Kent Pinkerton1, James K. Mansoor3, Dallas M. Hyde4, and Edward S. Schelegle1*
1 Department of Anatomy, Physiology and Cell Biology, University of California, Davis, CA, USA
2 California National Primate Research Center, University of California, Davis, CA, USA
3 Department of Physical Therapy, University of Pacific, Stockton, CA, USA
4 Department of Anatomy, Physiology and Cell Biology, University of California, Davis, CA, USA; California National Primate Research Center, University of California, Davis, CA, USA
* To whom correspondence should be addressed. E-mail: esschelegle{at}ucdavis.edu.
Mucous cell hypersecretion and increased neuropeptide production play a role in the exacerbation of symptoms associated with asthma. The source of these neuropeptides have been confined to the contributions of small afferent nerves or possibly neuroendocrine cells. We tested
the hypothesis that repeated exposure to allergen would alter the sources and abundance of neuropeptides in airways. Right middle lobes from rats (8 weeks old) exposed to 2.5% ovabumin (OVA) for 5 episodes (30 minutes each) or filtered air (FA) were inflation fixed with
paraformaldehyde. The lobes were dissected to expose the airway tree, permeablized with dimethyl sulfoxide, incubated in antibody to rat calcitonin gene-related peptide (CGRP), followed with a fluorochrome labelled second antibody. CGRP positive structures were imaged
via confocal microscopy. Airways were later embedded in plastic and sectioned for cell identification. In animals challenged with OVA, CGRP positive cells, not neuroendocrine or neuronal in origin (confirmed by a lack of PGP 9.5 signal), were recorded along the axial path.
In section, this fluorescent signal was localized to granules within epithelial cells. AB/PAS staining of these same sections positively identify these cells as mucous cells. Mucous cells of animals not challenged with OVA were not positive for CGRP. We conclude that episodic patterns of allergen exposure results in the accumulation of CGRP within mucous cells creating a new source for the release of this neuropeptide within the airway.
