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Abnormal intraepithelial airway nerves in persistent unexplained cough?
F O'Connell1, D R Springall, A Moradoghli-Haftvani
1Department of Clinical Pharmacology, Royal Postgraduate Medical School, Hammersmith Hospital, London, United Kingdom.
American Journal of Respiratory and Critical Care Medicine
|December 1, 1995
Summary
Patients with idiopathic persistent nonproductive cough (PNPC) have heightened cough sensitivity. This is linked to increased calcitonin gene-related peptide (CGRP) in airway nerves, suggesting nerve abnormalities contribute to this cough reflex.
Area of Science:
- Pulmonology
- Neuroscience
- Pathology
Background:
- Idiopathic persistent nonproductive cough (PNPC) is linked to heightened cough sensitivity.
- This suggests an involvement of capsaicin-sensitive afferent airway nerves.
Purpose of the Study:
- To investigate cough sensitivity to capsaicin.
- To assess the density of airway nerves immunoreactive for PGP-9.5, CGRP, and SP in PNPC patients versus controls.
Main Methods:
- Measured cough sensitivity using inhaled capsaicin (C2 and C5 thresholds).
- Quantified nerve density in bronchial epithelium using PGP-9.5, CGRP, and SP immunoreactivity.
- Compared findings between 16 PNPC patients and 8 healthy controls.
Main Results:
- PNPC patients exhibited significantly lower capsaicin thresholds (higher sensitivity).
- CGRP-immunoreactive nerve density was significantly higher in the bronchial epithelium of PNPC patients compared to controls.
- No significant difference in SP-immunoreactive nerves was observed between groups.
Conclusions:
- Idiopathic PNPC is associated with increased cough sensitivity.
- Abnormal intraepithelial airway nerves, specifically those with increased CGRP, are present in PNPC patients.
- These nerve abnormalities may play a role in the pathophysiology of PNPC.