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Cough Reflex Testing With Inhaled Capsaicin and TRPV1 Activation in Asthma and Comorbid Conditions


M Couto,1,2 A de Diego,3 M Perpiñá,3 L Delgado,1,2 A Moreira1,2

1Serviço de Imunoalergologia, Centro Hospitalar São João, EPE, Porto, Portugal
2Laboratório de Imunologia, Faculdade de Medicina da Universidade do Porto, Porto, Portugal
3Servicio de Neumologia, Hospital Universitario La Fe, Valencia, Spain

J Investig Allergol Clin Immunol 2013; Vol. 23(5): 289-301



A high parasympathetic tone leading to bronchoconstriction and neurogenic inflammation is thought to have a major role in the pathogenesis of asthma. Transient receptor potential vanilloid 1 (TRPV1) is the hub of almost all neuronal inflammatory signaling pathways. A critical determinant of neurogenic inflammation, TRPV1 functions as a sensor for detecting irritants in the lung by transmitting noxious stimuli to the central nervous system and inducing the release of a variety of proinflammatory neuropeptides at the peripheral terminals.
Challenge with inhaled capsaicin, an exogenous agonist of TRPV1, has been used to measure the sensitivity of the cough reflex. However, inhalation of capsaicin is also associated with parasympathetic bronchoconstriction, mucus hypersecretion, vasodilatation, and the sensation of dyspnea. Therefore, inhaled capsaicin challenge is expected to have other potential applications in asthma and comorbid conditions, such as rhinitis and gastroesophageal refl ux disease, both of which produce cough. Capsaicin challenge has established itself as a useful objective method for evaluating airway hypersensitivity; however, it is potentially valuable in many other situations, which will be reviewed in this paper.

Key words: Asthma. Airway sensory hyperreactivity. Capsaicin. Cough. Gastroesophageal reflux. Rhinitis. Transient receptor potential vanilloid 1.