Airway expression of Transient Receptor Potential (TRP) Vanniloid-1 and Ankyrin-1 channels is not increased in patients with Idiopathic Pulmonary Fibrosis

PLoS One. 2017 Nov 17;12(11):e0187847. doi: 10.1371/journal.pone.0187847. eCollection 2017.

Abstract

Dry cough is a common symptom described in patients with Idiopathic Pulmonary Fibrosis (IPF) and impairs quality of life. The exact mechanisms causing cough in IPF remain unclear, however evidence suggests altered cough neurophysiology and sensitisation plays a role; IPF patients have an enhanced cough reflex sensitivity to inhaled capsaicin. The Transient Receptor Potential Vanniloid-1 channel (TRPV-1) has a role in the cough reflex and airway expression is increased in patients with chronic cough. The Ankyrin-1 receptor (TRPA-1) is often co-expressed. It was hypothesised that, like chronic cough patients, IPF patients have increased airway TRP receptor expression. Bronchial biopsies were obtained from 16 patients with IPF, 11 patients with idiopathic chronic cough and 8 controls without cough. All other causes of cough were rigorously excluded. Real-time quantitative Polymerase Chain Reaction was used to detect TRPV-1 and TRPA-1 mRNA expression with Immunohistochemistry demonstrating protein expression. Mean TRPV-1 and TRPA-1 gene expression was higher in IPF patients compared with controls, but the difference did not reach statistical significance. Immunostaining supported these findings. This study suggests that structural up-regulation of central airway TRP receptors is not the key mechanism for cough in IPF patients. It is probable that IPF cough results from altered neuronal sensitivity at multiple levels of the cough pathway.

MeSH terms

  • Aged
  • Ankyrins / metabolism*
  • Case-Control Studies
  • Cough / complications
  • Female
  • Humans
  • Idiopathic Pulmonary Fibrosis / complications
  • Idiopathic Pulmonary Fibrosis / metabolism*
  • Idiopathic Pulmonary Fibrosis / physiopathology
  • Male
  • Middle Aged
  • Respiratory Function Tests
  • Reverse Transcriptase Polymerase Chain Reaction
  • TRPV Cation Channels / genetics
  • TRPV Cation Channels / metabolism*

Substances

  • ANK1 protein, human
  • Ankyrins
  • TRPV Cation Channels
  • TRPV1 protein, human

Grants and funding

The funding was entirely from Institutional Lung Research Endowment funds. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.