Mechanisms of Airway Hyperresponsiveness

Airway hyperresponsiveness is relevant to air pollution because its presence defines a sensitive segment of the population and because it can be a consequence of pollutant exposure. No unifying explanation for naturally occurring airway hyperresponsiveness can be supported by present experimental evidence. Nonetheless, a good deal has been learned about the normal control of airway narrowing and the derangements in normal control mechanisms that occur in association with airway injury and inflammation. Evidence to date suggests that different mechanisms may be involved in responses to different, and perhaps even to the same, inflammatory stimuli. In human subjects, there appears to be a wide range of sensitivity to the effects of ozone on airway responsiveness, but any physiological, biochemical, or genetic bases for ozone sensitivity remain to be determined.