The nervous system modulates the responses of the airways to inflammatory stimuli. The studies described here continue ongoing research into the role of substance P and other preprotachykinin (PPT)-A gene-encoded tachykinins in this modulation. The proposed work applies genetically altered murine systems to: 1. define the topographical organization and hierarchical connectivity of the airway's peptidergic sensory-motor network, 2. identify the cellular origin of the PPT-A tachykinins released in response to inflammatory stimuli and elucidate the contribution of three candidate cell types (sensory neurons, intrinsic ganglia, or hemopoietic cells) to the ensuing injury, and 3. establish whether over-expression of the PPT-A gene can in itself produce an inflammatory injury or requires a separate inflammatory stimulus.
Aim 1 will be accomplished by examining the expression of a fluorescent protein (ECFP) placed under the transcriptional control of the PPT-A 5' regulatory region in conjunction with tracking studies using pseudorabies virus as a retrograde trans-synaptic marker.
Aim 2 will be approached by a combination of selective chemical ablation of C-fibers by capsaicin and bone marrow reconstitution experiments in wild type mice and mice homozygous for targeted disruptions of the PPT-A and NK-1 receptor genes. The effects of these manipulations will then be compared in intact, inflamed (immune complex, Sendai virus, and stretch-induced), and denervated airways (selective C-fiber ablation and heterotopic tracheal transplantation).
Aim 3 will be achieved by analyzing the effects of transgenic manipulations of the PPT-A gene resulting either in ectopic constitutive overexpression of PPT-A in airway epithelial cells or in isotopic inducible over-expression of PPT-A in intact and inflamed airways (see above). Completion of these aims will improve our understanding of airway neurogenic injury and may help to develop therapeutic strategies to minimize tachykinin amplification of immune-mediated inflammation of the lungs and airways in disease processes such as bronchiolitis obliterans after lung transplantation or hyperoxic/stretch injury after mechanical ventilation.
