Interleukin (IL)-1 regulates ozone-enhanced tracheal smooth muscle responsiveness by increasing substance P (SP) production in intrinsic airway neurons of ferret

Abstract

Exposure to ozone induces airway hyperresponsiveness (AHR) mediated partly by SP released from nerve terminals of intrinsic airway neurons. Our recent studies showed that IL-1, an important multifunctional proinflammatory cytokine, increases synthesis and release of SP from intrinsic airway neurons. The purpose of this study is to investigate the possible involvement of endogenous IL-1 in modulating neural responses associated with ozone-enhanced airway responsiveness. Ferrets were exposed to 2 ppm ozone or filtered air for 3 hrs. IL-1 in the bronchoalveolar lavage (BAL) fluid was significantly increased in ozone-exposed animals and responses of tracheal smooth muscle to methacholine (MCh) and electrical field stimulation (EFS) were elevated significantly. Both the SP nerve fiber density in tracheal smooth muscle and the number of SP-containing neurons in airway ganglia were significantly increased following ozone exposure. Pretreatment with IL-1 receptor antagonist (IL-1 Ra) significantly diminished ozone-enhanced airway responses to EFS as well as ozone-increased SP in the airway. To selectively investigate intrinsic airway neurons, segments of ferret trachea were maintained in culture conditions for 24 hrs to eliminate extrinsic contributions from sensory nerves. The segments were then exposed to 2 ppm ozone in vitro for 3 hrs. The changes of ozone-induced airway responses to MCh and EFS, and the SP levels in airway neurons paralleled those observed with in vivo ozone exposure. The ozone-enhanced airway responses and neuronal SP levels were inhibited by pretreatment with IL-1 Ra. These findings show that IL-1 is released during ozone exposure enhances airway responsiveness by modulating SP expression in airway neurons.

Sensory Neural Responses to Ozone Exposure during Early Postnatal Development in Rat Airways

“…Irritant exposure during this developmental phase may be a predisposing factor to the pathogenic mechanisms leading to neurogenic inflammation (41). In ferret, we have shown that increased SP innervation after O 3 exposure is associated with increased airway smooth muscle responsiveness (31,42,43). In rat, SP contracts airway smooth muscle and increases vascular permeability (13,40).…”

Pulmonary exposure of rats to ultrafine titanium dioxide enhances cardiac protein phosphorylation and substance P synthesis in nodose ganglia

“…The nodose ganglia were then frozen in isopentane, cooled with liquid nitrogen, and stored in airtight bags at -80 C. Immunocytochemical procedures for localisation of substance P immunoreactive neurons were similar to those described previously (Wu et al 2008). Briefly, cryostat sections (12 mm thickness) of nodose ganglia were mounted on gelatin-coated coverslips, dried briefly at room temperature and then incubated with rabbit anti-substance P antiserum (Peninsula, Belmont, CA, USA) at a dilution of 1:100 for 60 min in a humidified chamber at 37 C. The coverslips were rinsed with a PBS-Tx containing 1% bovine serum albumin (PBS-Tx + BSA) three times, for 5 min per rinse.…”

“…The quantitative measurement of fluorescence intensity in nodose ganglia was similar to as describedpreviously (Wu et al 2008). Briefly, we recorded images using an AX70 microscope (Olympus America, Melville, NY, USA) with the SPOT 2 digital camera (Diagnostics Instruments, Sterling Heights, MI, USA).…”

Tissue Optical Clearing, Three-Dimensional Imaging, and Computer Morphometry in Whole Mouse Lungs and Human Airways

“…This allowed us to easily quantify a very sparsely and unevenly distributed set of structures-the instrinsic airway ganglia-which in previous studies required laborious tissue sampling (22,(36)(37)(38). We also pushed the limit of our technique by quantifying a rarer subset (15% total ganglia) that expresses substance P, which is implicated in lung disease and airway hyperresponsiveness (38,39). This low sampling probability of substance P may explain contradictory findings of the presence of substance P in human intrinsic ganglia (36,37).…”