Hydrogen sulfide causes vanilloid receptor 1‐mediated neurogenic inflammation in the airways

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Abstract
Hydrogen sulfide (H2S) is described as a mediator of diverse biological effects, and is known to produce irritation and injury in the lung following inhalation. Recently, H2S has been found to cause contraction in the rat urinary bladder via a neurogenic mechanism. Here, we studied whether sodium hydrogen sulfide (NaHS), used as donor of H2S, produces responses mediated by sensory nerve activation in the guinea‐pig airways. NaHS evoked an increase in neuropeptide release in the airways that was significantly attenuated by capsaicin desensitization and by the transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine. In addition, NaHS caused an atropine‐resistant contraction of isolated airways, which was completely prevented by capsaicin desensitization. Furthermore, NaHS‐induced contraction was reduced by TRPV1 antagonism (ruthenium red, capsazepine and SB366791), and was abolished by pretreatment with the combination of tachykinin NK1 (SR140333) and NK2 (SR48968) receptor antagonists. In anesthetized guinea‐pigs, intratracheal instillation of NaHS increased the total lung resistance and airway plasma protein extravasation. These two effects were reduced by TRPV1 antagonism (capsazepine) and tachykinin receptors (SR140333 and SR48968) blockade. Our results provide the first pharmacological evidence that H2S provokes tachykinin‐mediated neurogenic inflammatory responses in guinea‐pig airways, and that this effect is mediated by stimulation of TRPV1 receptors on sensory nerves endings. This novel mechanism may contribute to the irritative action of H2S in the respiratory system. British Journal of Pharmacology (2005) 145, 1123–1131. doi:10.1038/sj.bjp.0706277; published online 6 June 2005