© 2003 American Thoracic Society DOI: 10.1165/rcmb.4635 Airway Smooth Muscle Cells Express Functional Neurokinin-1 Receptors and the Nerve-Derived Preprotachykinin-A GeneRegulation by Passive SensitizationResearch Centre, Sacré-Coeur Hospital of Montreal, Respiratory Diseases Unit, Université de Montréal; and Meakins-Christie Laboratories, Department of Medicine, McGill University, Montreal, Quebec, Canada. Address correspondence to: Dr. K. Maghni, Laboratory of Neuroimmunology of Asthma, Research Centre, Sacré-Coeur Hospital, 5400 Gouin Blvd., Montreal, PQ, H4J 1C5 Canada. E-mail: maghnik{at}medclin.umontreal.ca
Preprotachykinin-A (PPT-A) gene-derived neuropeptides, namely substance P (SP) and neurokinin (NK)A, and their receptors participate in allergen-induced airway responses. Whether airway smooth muscle cells (ASMC) may react directly to SP through expression of the NK-1 receptor or express the gene for the synthesis of SP, the PPT-A gene, is unknown. We demonstrated using reverse transcription–polymerase chain reaction that tracheal SMC (TSMC) from atopic Brown Norway rats contained mRNA transcripts for the full-length isoform of the NK-1 receptor. Flow cytometric analysis indicated that the NK-1 receptor was expressed on the surface of TSMC. This receptor was functional as demonstrated by calcium mobilization in response to SP stimulation. The expression of the NK-1 receptor was not altered in passively sensitized TSMC in response to antigenic stimulation, although this stimulation increased the expression of the chemokine RANTES (regulated on activation, normal T cells expressed and secreted). Using different sets of PCR primers, we showed that TSMC also express the ß,
Abbreviations: airway smooth muscle, ASM • ASM cells, ASMC • Brown Norway, BN • fetal bovine serum, FBS • Hanks' buffered saline solution, HBSS • immunoglobulin, Ig • neurokinin, NK • ovalbumin, OVA • preprotachykinin-A, PPT-A • regulated on activation, normal T cells expressed and secreted, RANTES • reverse transcription–polymerase chain reaction, RT-PCR • smooth muscle cells, SMC • substance P, SP • tracheal SMC, TSMC This article has been cited by other articles:
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, and its alternative splicing product 
, and possibly the 
mRNA transcript isoforms of the PPT-A gene. Gene sequencing of the PCR-amplified ß isoform confirmed that it is a transcript product of the rat PPT-A gene, and the production of SP by TSMC was confirmed by enzyme immunoassay. We also showed the ß isoform increased after cell stimulation with rat sera, whether sensitized or not. In conclusion, both the PPT-A gene and NK-1 receptors are expressed by TSMC, which suggests the possibility of autocrine neuropeptidergic mechanisms in these cells. However, these mechanisms are not upregulated by passive sensitization. 
