Peptidase modulation of airway effects of neuropeptides.

SP and NKA are potent endogenous bronchoconstrictors, whereas VIP is a potent endogenous bronchodilator. There is abundant evidence that these neuropeptides are released in the lung in a variety of conditions and that they have the capacity to modulate the bronchoactivity of the same stimuli that release them. On many occasions, their bronchoactive effects are masked by their degradation at or near the site of their release. However, when the microenvironment is modified to decrease their cleavage, they can express enhanced physiologic effects. Although it appears that the human asthmatic lung may be an environment in which the effects of neuropeptides can be amplified, the role of neuropeptides in the pathogenesis of airway obstruction remains speculative.