Transient receptor potential A1 channels: insights into cough and airway inflammatory disease.

Cough is a common symptom of diseases such as asthma and COPD and also presents as a disease in its own right. Treatment options are limited; a recent meta-analysis concluded that over-the-counter remedies are ineffective, and there is increasing concern about their use in children. Transient receptor potential cation channel, subfamily A, member 1 (TRPA1) channels are nonselective cation channels that are activated by a range of natural products (eg, allyl isothiocyanate), a multitude of environmental irritants (eg, acrolein, which is present in air pollution, vehicle exhaust, and cigarette smoke), and inflammatory mediators (eg, cyclopentenone prostaglandins). TRPA1 is primarily expressed in small-diameter, nociceptive neurons where its activation probably contributes to the perception of noxious stimuli. Inhalational exposure to irritating gases, fumes, dusts, vapors, chemicals, and endogenous mediators can lead to the development of cough. The respiratory tract is innervated by primary sensory afferent nerves, which are activated by mechanical and chemical stimuli. Recent data suggest that activation of TRPA1 on these vagal sensory afferents by these irritant substances could lead to central reflexes, including dyspnea, changes in breathing pattern, and cough, which contribute to the symptoms and pathophysiology of respiratory diseases.