Asthma is characterized by episodic bronhoconstriction, chronic lung inflammation, and airway hyperreactivity to constricting stimuli. Airway inflammation in asthma is thought to be a critical factor in the pathogenesis of the disease, but the molecular mechanisms underlying the inflammation that develops in asthma are not known. Airborne pollutants, including ozone, have been reported to worsen asthma and associated inflammation, but the mechanisms by which pollutants contribute to the pathology of asthma are not known. Since there are many potential inflammatory mediator involved, it has not been possible to establish in vivo which molecules are playing a mechanistic role in the development of the disease. The studies proposed here will examine sensory neuropeptides known a tachykinins that can act as inflammatory mediators. Tachykinins include the neuropeptides substance P and neurokinin A, which exert their effects by binding to neurokinin receptors. Levels of the tachykinin substance P are increased in asthmatic lung, and substance P is released in humans after allergen or ozone exposure. The central hypothesis to be tested here is that tachykinin neuropeptides released from sensory nerve endings are key mediators in the development of allergen- and ozone-induced airway inflammation. The hypothesis will be tested by using transgenic and gene knock-out technology to manipulate the amount of sensory nerve fibers that innervate the lungs of mice. The inflammation that develops in the lungs of these genetically altered mice after exposure to allergen or ozone, or a combination of the two agents, will be measured by histological, biochemical, and cytological methods. Our hypothesis predicts that mice releasing increased amounts of tachykinins will be unusually susceptible to allergen-and ozone-induced airway inflammation and that mice releasing reduced amounts of tachykinins will be resistant tot he development of inflammation. The propose experiments will allow a determination of whether ozone and allergen act synergistically to produce inflammation and whether tachykinins are involved in the action of these agents, either individually or in combination. In addition, the molecules through which tachykinins exert their effects will be examined in the genetically manipulated mice. For example, neurokinin receptor antagonists will be used to characterize receptor subtypes mediating neurogenic inflammation in mice that release increased amounts of tachykinins. Molecular biological and biochemical methods will also be used to determine whether expression of cytokine mRNAs and protein products are altered in mice releasing increased or reduced amounts of tachykinins. This novel approach employing genetically manipulated mice will provide valuable mechanistic information concerning inflammation induced by tachykinins in airway disease.
| Graham, R M; Friedman, M; Hoyle, G W (2001) Sensory nerves promote ozone-induced lung inflammation in mice. Am J Respir Crit Care Med 164:307-13 |
| Hoyle, G W; Graham, R M; Finkelstein, J B et al. (1998) Hyperinnervation of the airways in transgenic mice overexpressing nerve growth factor. Am J Respir Cell Mol Biol 18:149-57 |
| Hoyle, G W; Brody, A R (1996) Gene expression in rodent model of environmental lung disease. Ann N Y Acad Sci 796:162-72 |
