Asthma and lower airway disease
Increased expression of bronchial epithelial transient receptor potential vanilloid 1 channels in patients with severe asthma

https://doi.org/10.1016/j.jaci.2013.09.016Get rights and content

Background

The airway epithelium is exposed to a range of physical and chemical irritants in the environment that are known to trigger asthma. Transient receptor potential (TRP) cation channels play a central role in sensory responses to noxious physical and chemical stimuli. Recent genetic evidence suggests an involvement of transient receptor potential vanilloid 1 (TRPV1), one member of the vanilloid subfamily of TRP channels, in the pathophysiology of asthma. The functional expression of TRPV1 on airway epithelium has yet to be elucidated.

Objective

In this study we examined the molecular, functional, and immunohistochemical expression of TRPV1 in asthmatic and healthy airways.

Methods

Bronchial biopsy specimens and bronchial brushings were obtained from healthy volunteers (n = 18), patients with mild-to-moderate asthma (n = 24), and patients with refractory asthma (n = 22). Cultured primary bronchial epithelial cells from patients with mild asthma (n = 4), nonasthmatic coughers (n = 4), and healthy subjects (n = 4) were studied to investigate the functional role of TRPV1.

Results

Quantitative immunohistochemistry revealed significantly more TRPV1 expression in asthmatic patients compared with healthy subjects, with the greatest expression in patients with refractory asthma (P = .001). PCR and Western blotting analysis confirmed gene and protein expression of TRPV1 in cultured primary bronchial epithelial cells. Patch-clamp electrophysiology directly confirmed functional TRPV1 expression in all 3 groups. In functional assays the TRPV1 agonist capsaicin induced dose-dependent IL-8 release, which could be blocked by the antagonist capsazepine. Reduction of external pH from 7.4 to 6.4 activated a capsazepine-sensitive outwardly rectifying membrane current.

Conclusions

Functional TRPV1 channels are present in the human airway epithelium and overexpressed in the airways of patients with refractory asthma. These channels might represent a novel therapeutic target for the treatment of uncontrolled asthma.

Section snippets

Methods

Full methodological details are provided in the Methods section in this article's Online Repository at www.jacionline.org.

Confirmation of TRPV1 expression in cultured human bronchial epithelial cells

Gene expression for multiple members of the TRPV family, including TRPV1 (but not TRPV5), was identified in PBECs from healthy control subjects (n = 3; Fig 1, A). TRPV1 protein was detected at its expected molecular mass of 95 kDa by using Western blotting in the same samples (Fig 1, B).

Microarray

Using gene expression microarray analysis of bronchial brush samples from the Leicester cohort, we found significantly greater TRPV1 expression in patients with severe asthma (median, 0.673; interquartile range

Discussion

In this study, for the first time, we have shown that TRPV1, which is primarily recognized as the major neuronal hot receptor,23, 24 is expressed and functional in human bronchial epithelium. In PBEC cultures we have shown that pharmacologic activation of the TRPV1 channel with capsaicin induces IL-8 release, which can be attenuated by pretreatment with the selective TRPV1 antagonist capsazepine.

Interestingly, TRPV1 expression in the airway was increased in asthmatic patients compared with that

References (38)

  • D. Sachs et al.

    Tumour necrosis factor-alpha, interleukin-1beta and interleukin-8 induce persistent mechanical nociceptor hypersensitivity

    Pain

    (2002)
  • L.J. Karai et al.

    Vanilloid receptor 1 regulates multiple calcium compartments and contributes to Ca2+-induced Ca2+ release in sensory neurons

    J Biol Chem

    (2004)
  • G. Chen et al.

    Discordant protein and mRNA expression in lung adenocarcinomas

    Mol Cell Proteomics

    (2002)
  • C. Szigeti et al.

    Disparate changes in the expression of transient receptor potential vanilloid type 1 receptor mRNA and protein in dorsal root ganglion neurons following local capsaicin treatment of the sciatic nerve in the rat

    Neuroscience

    (2012)
  • B.F. Bessac et al.

    Sensory detection and responses to toxic gases: mechanisms, health effects, and countermeasures

    Proc Am Thorac Soc

    (2010)
  • M.J. Doherty et al.

    Capsaicin responsiveness and cough in asthma and chronic obstructive pulmonary disease

    Thorax

    (2000)
  • T.J. Hathaway et al.

    Effects of inhaled capsaicin in heart-lung transplant patients and asthmatic subjects

    Am Rev Respir Dis

    (1993)
  • P. Paredi et al.

    Faster rise of exhaled breath temperature in asthma: a novel marker of airway inflammation?

    Am J Respir Crit Care Med

    (2002)
  • J.F. Hunt et al.

    Endogenous airway acidification. Implications for asthma pathophysiology

    Am J Respir Crit Care Med

    (2000)
  • Cited by (126)

    • The impact of temperature on the skin barrier and atopic dermatitis

      2023, Annals of Allergy, Asthma and Immunology
    View all citing articles on Scopus

    S.S. was supported by a grant from the Northern Ireland Chest Heart & Stroke Association, and L.P. was supported by a grant from the Higher Education Authority (North South Research Programme). Work in Leicester and Belfast was supported in part by grants from Genentech, South San Francisco, California.

    Disclosure of potential conflict of interest: L. P. McGarvey has been supported by one or more grants from the Northern Ireland Chest Heart & Stroke Association and from the Health Education Authority (North South Funding); is a member of advisory boards for Almirall, the NAPP, GlaxoSmithKline (GSK), and Boehringer Ingelheim; has consultancy arrangements with the Endpoint Adjudication Committee (served as Chairman and Committee Member), Boehringer Ingelheim, and GSK; has received one or more grants from or has one or more grants pending with Chiesi, the Laboratory Animal Science Association/NC3Rs, the British Heart Foundation, the Northern Ireland Chest Heart & Stroke Association, Royal Belfast Hospital (Sick Children Clinical Fellowship), Asthma UK, and the Research Forum for the Child International PhD studentships; and has received one or more payments for travel/accommodations/meeting expenses from Chiesi, Boehringer Ingelheim, and GSK. C. A. Butler has received one or more payments for travel/accommodations/meeting expenses from GSK. S. Stokesberry has been supported by one or more grants from the Northern Ireland Chest Heart & Stroke Association. L. Polley has been supported by an educational grant from the Higher Education Authority (North South Research Programme) and has received money from GSK (General Practice Education–Asthma Update [SIGN Guidelines]). J. Arron is employed by and has one or more patents (planned, pending, or issued) with Genentech and owns stock/stock options in Roche Holdings. D. Choy is employed by and owns stock/stock options in Genentech. P. Bradding has been supported by one or more grants from Genentech. M. Ennis has been supported by one or more grants from the Northern Ireland Chest Heart and Stroke Association and from the Higher Education Authority (North South Research Programme). L. G. Heaney has received one or more grants from or has one or more grants pending with GSK, MedImmune, Novartis UK, AstraZeneca, Genenetch, the Medical Research Council UK, the Northern Ireland Chest Heart & Stroke Association, Hoffmann la Roche UK, and Asthma UK/the Northern Ireland Chest Heart & Stroke Association; has received one or more payments for lecturing from or is on the speakers' bureau for GSK, Merck Sharpe & Dohme, Nycomed, Novartis, Genentech Inc and AstraZeneca; and has received one or more payments for travel/accommodations/meeting expenses from AstraZeneca, Chiesi, Novartis, and GSK. The rest of the authors declare that they have no relevant conflicts of interest.

    View full text