BACKGROUND:The risks for infants and young children receiving inhaled corticosteroid (ICS) therapy are largely unknown. Recent clinical studies indicate that ICS therapy in pre-school children with symptoms of asthma result in decreased symptoms without influencing the clinical disease course, but potentially affect postnatal growth and development. The current study employs a primate experimental model to identify the risks posed by ICS therapy.OBJECTIVE:To (1) establish whether ICS therapy in developing primate lungs reverses pulmonary pathobiology associated with allergic airway disease (AAD) and (2) define the impact of ICS on postnatal lung growth and development in primates.METHODS:Infant rhesus monkeys were exposed, from 1 through 6 months, to filtered air (FA) with house dust mite allergen and ozone using a protocol that produces AAD (AAD monkeys), or to FA alone (Control monkeys). From three through 6 months, the monkeys were treated daily with ICS (budesonide) or saline.RESULTS:Several AAD manifestations (airflow restrictions, lavage eosinophilia, basement membrane zone thickening, epithelial mucin composition) were reduced with ICS treatment, without adverse effects on body growth or adrenal function; however, airway branching abnormalities and intraepithelial innervation were not reduced. In addition, several indicators of postnatal lung growth and differentiation: vital capacity, inspiratory capacity, compliance, non-parenchymal lung volume and alveolarization, were increased in both AAD and Control monkeys that received ICS treatment.CONCLUSIONS AND CLINICAL RELEVANCE:Incomplete prevention of pathobiological changes in the airways and disruption of postnatal growth and differentiation of airways and lung parenchyma in response to ICS pose risks for developing primate lungs. These responses also represent two mechanisms that could compromise ICS therapy's ability to alter clinical disease course in young children.

Cough is the most common symptom for which individuals seek medical attention and spend health-care dollars. Despite the burden induced by cough, the current treatments for cough are only partially effective. Delineating the sites and mechanisms in the cough central network for changes in the cough reflex could lead to new therapeutic strategies and drug target sites for more effective treatments. The first synaptic target in the CNS for the cough-related sensory input is the secondorder neurons in the nucleus tractus solitarius (NTS); these neurons reorganize the primary sensory information into a coherent output. The NTS neurons have been shown to undergo neuroplasticity under a variety of conditions, such as respiratory disorders, stress, and exposures to environmental pollutants. The NTS contains a rich innervation of substance P immunoreactive nerve terminals, suggesting that substance P might be important in altered cough reflex response. This chapter summarizes our current findings on the role of substance P in enhanced cough reflex as well as the potential NTS targets for the action of substance P.

TAB3-PD-02 Background: Epidemiologic studies have demonstrated beneficial effects of foods rich in antioxidants or antioxidant supplements on ventilatory function, respiratory symptoms, and atopy in children and adults. One plausible mechanism by which vitamin levels may influence health is through immunomodulation. Objective: To determine whether concentrations of vitamins C and E in cord blood are associated with alterations in immune parameters at birth. Methods: Mothers delivering in 2 districts in the Czech Republic between 1994 and 1998 were enrolled in the Immune Biomarker Study. Cord blood samples (n = 1397) were analyzed by flow cytometry to determine lymphocyte phenotypes (T lymphocytes: CD3+, CD4+, CD8+; B lymphocytes: CD19+; and natural killer cells: CD16+CD56+). Cord IgE was determined by Carrier-Polymer-System and maternal IgE by nephelometry for 463 births. Vitamin C was determined using spectrophotometry (n = 763) and vitamin E by high pressure liquid chromatography with UV detection (n = 642). Multiple linear regression was used to quantify the relations between vitamins C and E and lymphocyte proportions adjusting for questionnaire information (lifestyle, sociodemographic, reproductive) as well as delivery and meteorologic variables. Elevated cord serum IgE (>0.9 IU/mL) was predicted by multiple logistic regression models adjusting for district, year of birth, and elevated levels of maternal IgE (>100 IU/mL) as a proxy for maternal atopy (other covariates were not predictive). Results: Mean cord blood levels (μg/mL, ± SD) for vitamins E and C were 3.2 ± 2.0 and 13.9 ± 4.8, respectively. For a 1-μg (about half the SD)/mL increase in cord vitamin E, the percentage of cord CD19+ cells decreased −2.8% (95% CI, −5.4% to −0.3%) in a model adjusted for 45-day average ambient temperature. Models alternatively adjusting for 3-day temperature showed similar results. Associations were attenuated after control for season of delivery. Other lymphocyte subsets were not associated with cord vitamin E levels. For a 1-μg/mL increase in cord vitamin E, the odds of having an elevated cord IgE increased slightly (OR = 1.3; 95% CI, 1.0 to 1.6). Adjustment for maternal atopy, a strong predictor of cord IgE, had no impact here. Vitamin C levels were not associated with lymphocytes or IgE. Conclusion: Fetal vitamin E levels may affect the relative production of B cells and the concentrations of circulating IgE at birth. Other seasonal factors, such as pollen exposures or additional nutritional factors, may confound the association with lymphocytes. Further work is needed to clarify the independent and joint effects of these exposures.

SM4-PD-06 Background: The mechanisms by which ambient air pollutants influence health may include immunomodulation. We previously demonstrated differences in the distribution of cord lymphocyte immunophenotypes with chronic and short-term exposure to PM2.5 and PAH in mothers infant pairs in the Czech Republic. Others have observed acute effects, ie, a decrease in absolute numbers of T lymphocytes in peripheral blood, following nitrogen dioxide exposure in chamber studies. Objective: To determine whether maternal exposure to outdoor nitrogen oxide pollution in the 2 weeks prior to delivery is related to systemic immunologic alterations in the fetus, as measured in cord blood. Methods: Cord blood samples were analyzed by flow cytometer (FACSort) to determine immunophenotypes (T lymphocytes: CD3+, CD4+ subsets, CD8+, B lymphocytes: CD19+, and natural killer cells: CD16+CD56+) for 1397 births in the Czech Republic between 1994 and 1998. Daily 24-hour average concentrations of nitrogen oxides (nitrogen oxide [NO], nitrogen dioxide [NO2], and total nitrogen oxides [NOx]), fine particulate matter (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) were measured at 2 centrally located monitors. Missing data were imputed using standard algorithms. For each pollutant, we evaluated the 14-day average ambient concentration preceding the date of birth in relation to cord blood lymphocyte proportions, using multiple linear regression models adjusted for potential confounders. Information on covariates was collected by interview with the mother. Results: All pairwise Spearman correlation coefficients ranged from 0.51 to 0.66. For a 30 μg/m3 (corresponding to 2 standard deviations) increase in average NO2 exposure in the 14 days before birth, the fraction of NK cells decreased by −2.70% [CI (confidence interval) −5.29, −0.06] when adjusting for 3-day average temperature before delivery. Models adjusting for 45-day average temperature yielded greater estimates: −4.38% [CI −7.39, −1.38]. In models adjusting for season of birth as well as 3 day-average temperature the decrease in NK cell fractions was slightly smaller −2.30% [CI −5.12, −0.52]. Other lymphocyte subsets changed only negligibly. Models addressing NO and NOx exposure showed similar results. Conclusion: These results suggest that exposure to nitrogen oxide pollution shortly before birth may affect fetal production of NK cells relative to other lymphocytes. The relative contribution of nitrogen oxides versus other seasonal factors requires further investigation. In other work, we found that PAHs and PM2.5 were associated with decreases in T lymphocytes and increases in B lymphocytes, but not with changes in NK cell fractions, suggesting that the present findings are not due to confounding by co-pollutants. Possible interactions cannot be ruled out.

Asthma is a worldwide health problem that affects 300 million people, as estimated by the World Health Organization. A key question in light of this statistic is: “what is the most appropriate laboratory animal model for human asthma?”The present authors used stereological methods to assess airways in adults and during post-natal development, and their response to inhaled allergens to compare rodents and nonhuman primates to responses in humans.An epithelial–mesenchymal trophic unit was defined in which all of the compartments interact with each other. Asthma manifests itself by altering not only the epithelial compartment but also other compartments (e.g.interstitial, vascular, immunological and nervous). All of these compartments show significant alteration in an airway generation-specific manner in rhesus monkeys but are limited to the proximal airways in mice. The rhesus monkey model shares many of the key features of human allergic asthma including the following: 1) allergen-specific immunoglobulin (Ig)E and skin-test positivity; 2) eosinophils and IgE+ cells in airways; 3) a T-helper type 2 cytokine profile in airways; 4) mucus cell hyperplasia; 5) subepithelial fibrosis; 6) basement membrane thickening; and 7) persistent baseline hyperreactivity to histamine or methacholine.In conclusion, the unique responses to inhaled allergens shown in rhesus monkeys make it the most appropriate animal model of human asthma.

ISEE-281 Introduction: The prevalence of atopy in children is increasing. One hypothesis suggests that modern lifestyle tends to shift the immune response away from the Th1 system that protects against infections, and towards the Th2 system response that favours atopy. Two factors have been proposed to cause this shift: increasing exposure to new environmental toxicants and declining exposure to infectious agents or their by-products. Aim: This study examined early childhood development of atopic disease in relation to both respiratory infection in the first six months of life and family history of atopy. Separate and combined effects were examined. Methods: This project is a longitudinal study of early childhood morbidity. 7502 births formed the initial cohort, comprising 90% of deliveries in Teplice and Prachatice district. Socio-demographic information was obtained by interviewing the mother. At birth, 1492 were studied for immune factors, and of these children, 693 born 1997–1998 were followed up at 4.5 years of age. Paediatricians provided information about all illnesses, including the date of the visit and diagnoses coded by the International Classification of Diseases, 10th edition (ICD-10). Families were administered questionnaires regarding exposure to cigarette smoke, breastfeeding, pets and history of parental allergy. Atopic diseases diagnosed after the first 6 months of life included: allergic asthma (ICD10 codes -J45), atopic eczema (ICD10 codes-L20 and L27), and allergic rhinoconjunctivitis (ICD10 codes- J30). Respiratory infections (ICD10 codes-J00-J06, J20-J22) occurring during the first 6 months of a child's life constituted the exposure of interest. Possible genetic predisposition for atopy is defined as one or both parents having a history of allergy. Regression analyses were conducted using Generalized Estimating Equations (GEE) and relative risks and associated 95% confidence intervals were obtained. Results: The relative risk for atopy in children with a family history of atopy who were not diagnosed with respiratory infections during the first 6 months of life was 1.83 (95% CI=“1.24–2.69”), whereas among children with family history of atopy who were diagnosed with respiratory infections, it was 1.40 (95% CI=“0.92” – 2.13). Children without atopic heredity who were diagnosed with respiratory infections showed a relative risk of 1.14 (95% ci=“0.77” – 1.68). The comparison group was children without atopic diseases who were not diagnosed with respiratory infections in the first six months of life. Other factors that appeared to protect against the development of atopic diseases were pets at home, low maternal education and Romani ethnicity. Conclusion: Our findings suggest that having an atopic parent puts children at higher risk for development of atopy, but that some protection is provided by early life exposure to infections. Heterogeneity by genetic predisposition may be key to understanding early life priming of the immune system.

Effects of air pollution on morbidity and mortality may be mediated by alterations in immune competence. In this study we examined short-term associations of air pollution exposures with lymphocyte immunophenotypes in cord blood among 1,397 deliveries in two districts of the Czech Republic. We measured fine particulate matter < 2.5 μm in diameter (PM2.5) and 12 polycyclic aromatic hydrocarbons (PAHs) in 24-hr samples collected by versatile air pollution samplers. Cord blood samples were analyzed using a FACSort flow cytometer to determine phenotypes of CD3+ T-lymphocytes and their subsets CD4+ and CD8+, CD19+ B-lymphocytes, and natural killer cells. The mothers were interviewed regarding sociodemographic and lifestyle factors, and medical records were abstracted for obstetric, labor and delivery characteristics. During the period 1994 to 1998, the mean daily ambient concentration of PM2.5 was 24.8 μg/m3 and that of PAHs was 63.5 ng/m3. In multiple linear regression models adjusted for temperature, season, and other covariates, average PAH or PM2.5 levels during the 14 days before birth were associated with decreases in T-lymphocyte phenotype fractions (i.e., CD3+ CD4+, and CD8+), and a clear increase in the B-lymphocyte (CD19+) fraction. For a 100-ng/m3 increase in PAHs, which represented approximately two standard deviations, the percentage decrease was −3.3% [95% confidence interval (CI), −5.6 to −1.0%] for CD3+, −3.1% (95% CI, −4.9 to −1.3%) for CD4+, and −1.0% (95% CI, −1.8 to −0.2%) for CD8+ cells. The corresponding increase in the CD19+ cell proportion was 1.7% (95% CI, 0.4 to 3.0%). Associations were similar but slightly weaker for PM2.5. Ambient air pollution may influence the relative distribution of lymphocyte immunophenotypes of the fetus.

ISEE-153 Introduction: Ambient air pollution increases asthma severity in children, and appears to increase infant mortality, but few studies have addressed early childhood morbidity or the effects from hydrocarbons. In this study, exposures to polycyclic aromatic hydrocarbons (PAHs) and fine particulate matter (PM2.5) in two regions of the Czech Republic were evaluated in relation to incidence of lower respiratory illnesses in early childhood. Methods: A birth cohort, comprising 20% of deliveries between May 1994 and March 1999 in two districts in the Czech Republic, was enrolled. Mothers completed questionnaires about their pregnancy, socio-demographic characteristics, and home environment. Children were followed up at either three or 4.5 years of age (depending on birth year) for collection of pediatric data. Lower respiratory illnesses (LRI) were defined as physician diagnoses for one of twelve ICD (International Classification of Diseases, Tenth Revision) codes. Additionally, acute bronchitis (J20) was examined separately. Parents completed questionnaires regarding indoor air pollution sources, breastfeeding, day care, and other factors potentially related to respiratory illnesses. Analyses were conducted on 1133 children with complete data, covering 1.5 million child-days of observation. Fine and coarse particulates and PAHs were captured using a Versatile Air Pollution Sampler. Daily measurements were made during five winter months of the year, and scheduled third or sixth day measurements were taken in the remaining months. Generalized linear models were used to quantify relationships between each exposure and LRI, and to control for multiple individual risk factors. Rate ratios were estimated using GEE to adjust for repeated measures on the same child and to accommodate time-varying exposures. All associations were estimated for a 100 ng/m3 incremental increase in PAHs or a 25 μg/m3 incremental increase in PM 2.5. Results: Adjusting for multiple covariates, the incidence of LRI, especially bronchitis, increased sharply as average concentrations of PAHs or PM 2.5 over the previous 7 days rose. Between birth and two years, an increment of 100 ng/m3 PAHs and of 25 μg/m3 in PM 2.5 resulted in rate ratios (RRs) of 1.3, 95% ci=[1.2, 1.4] and 1.2 [1.1, 1.3], respectively, for LRI and 1.4 [1.2, 1.5], and 1.3 [1.1, 1.4], respectively, for bronchitis. From two to 4.5 years of age, bronchitis RRs were 1.8 [1.5, 2.2] and 1.4 [1.2, 1.7] for PAHs and PM 2.5, respectively. Adjustment for temperature attenuated results, but RRs remained statistically distinguishable from the null. For instance, adjusted for 3-day average temperature, RRs in the older age group were 1.5 [1.2, 1.8] for PAHs. Conclusion: Increased incidences of LRI generally and especially bronchitis, from birth through the first 4.5 years of life, was associated with weekly average ambient concentrations of PAHs and PM 2.5. The effects are especially strong above two years of age, and are robust to adjustment for ambient temperatures.

ISEE-235 Introduction: The mechanisms by which ambient air pollutants influence health may include immune alteration. We previously demonstrated differences in the distribution of cord lymphocyte immunophenotypes with chronic and short-term air pollution exposure. Aim: To determine whether air pollution exposure in critical gestational time windows is asssociated with alterations in distribution of lymphocyte immunophenotypes and immunoglobulin E (IgE) at birth. Methods: Cord blood samples were analyzed by FACSort flow cytometer to determine phenotypes (T-lymphocytes: CD3+, subsets CD4+, CD8+, B-lymphocytes: CD19+, and natural killer cells) for 1397 births in the Czech Republic, between 1994 and 1998. Cord IgE was determined by CAP system, and mothers' IgE by nephelometry, for a subgroup of 463, born between 1994 and 1996. Fine particulate matter (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) were measured in 24-hour samples. Exposures to average PAHs or PM 2.5 during four different time windows was evaluated, two weeks before to two weeks after the last menstrual period (LMP), weeks four to eight post-LMP, weeks 24–28 post-LMP, and weeks 32–36 post-LMP. Multiple linear regression, adjusting for potential confounders, was used to quantify the relation between pollutants and lymphocyte proportions. Elevated cord serum IgE (>0.9 IU/ml) was predicted by multiple logistic regression models adjusted for district, year of birth; and in further models for maternal atopy (>100 IU IgE/ml). Results: For a 100 ng/m3 increase in average PAH exposure 4–8 weeks post-LMP, the risk of elevated cord IgE decreased, OR (odds ratio) =0.60 [95%CI (confidence interval) 0.40, 0.89], while exposure 24–28 weeks post-LMP was associated with increased risk, OR =1.35 [95%CI 0.95, 1.90]. After adjustment for mothers' atopy, a strong predictor of cord IgE, protection from elevated IgE for exposure 4–8 weeks post-LMP declined, OR=0.52, [95%CI 0.34, 0.80] and risk for elevated IgE associated with exposure 24–28 weeks post-LMP OR= 1.60 [95%CI 1.10, 2.34] rose. Effects of PM 2.5 were similar. For a 100 ng/m3 increase in average PAH exposure in the pre-conception window, in models adjusted for temperature and season prior to conception, the percentage of CD3+ cells increased by 3.4% (95%CI= 1.2%, 5.7%); CD4+ cells increased by 3.5% (95%CI= 1.4%, 5.6%); CD19+ cells decreased −2.1% (95%CI= −3.4%, −0.8%) and NK cells decreased −1.2% (95%CI= −3.3, 0.8). Controlling for acute pollution did not change these results. For PAH exposures in weeks 32–36 weeks adjusted for season, the percentage of CD3+ cells decreased −2.5% (95%CI= −4.6%, −0.4%, −4.6 %), the percentage of CD4+ cells −2.1% (95%CI= −3.9%, −0.3%) and the percentage of CD19+ cells increased by 2.2% (95%CI= 0.3%, 4.1%). Conclusion: These results suggest exposure to pollutants during critical time windows in gestation may, by some mechanism, impact on foetal development, so as to alter the relative production of lymphocyte phenotypes and IgE at birth. Genetic factors appear to modify these effects in IgE.

Rationale Infants exposed to environmental tobacco smoke (ETS) have more severe respiratory syncytial virus (RSV) bronchiolitis. RSV bronchiolitis is associated with elevated cysteinyl leukotrienes and ETS exposure is associated with a Th2 phenotype, which may ultimately result in a greater production of cysteinyl leukotrienes. Cysteinyl leukotrienes can produce bronchoconstriction, edema, and mucus secretion, hallmarks of bronchiolitis. We hypothesized that infants hospitalized with RSV bronchiolitis who were exposed to ETS would have higher cysteinyl leukotrienes in their urine. Methods Urine was collected from infants ≤24 months of age admitted with RSV bronchiolitis. Patients were excluded if they had asthma, chronic lung or heart disease, or immunodeficiency. The urine was analyzed with an enzyme immunoassay for leukotriene E4 (LTE4), liquid chromatography with tandem mass spectophotometry for cotinine, a metabolite of nicotine, and colorometric technique for creatinine. Results None of the caretakers reported that the infant was exposed to smoke in the home. However, 6 of 23 infants had a urinary cotinine/creatinine ratio of >30ng/mg indicating exposure to ETS. LTE4 was 134% higher in infants exposed to ETS (P=0.005, single factor ANOVA). Among the infants exposed to ETS, cotinine/creatinine ratio correlated with LTE4 (r2=0.82, P=0.01). Conclusions ETS exposure may worsen RSV bronchiolitis by enhancing production of cysteinyl leukotrienes.

Nerves and neuroendocrine cells located within the airway epithelium are ideally situated to sample a changing airway environment, to transmit that information to the central nervous system, and to promote trophic interactions between epithelial and mesenchymal cellular and acellular components. We tested the hypothesis that the environmental stresses of ozone (O(3)) and house dust mite allergen (HDMA) in atopic infant rhesus monkeys alter the distribution of airway nerves. Midlevel bronchi and bronchioles from 6-month-old infant monkeys that inhaled filtered air (FA), house dust mite allergen HDMA, O(3), or HDMA + O(3) for 11 episodes (5 days each, 0.5 ppm O(3), 8 h/day followed by 9 days recovery) were examined using immunohistochemistry for the presence of Protein gene product 9.5 (PGP 9.5), a nonspecific neural indicator, and calcitonin gene-related peptide (CGRP). Along the axial path between the sixth and the seventh intrapulmonary airway generations, there were small significant (P < 0.05) decrements in the density of epithelial nerves in monkeys exposed to HDMA or O(3), while in monkeys exposed to HDMA + O(3) there was a greater significant (P < 0.05) reduction in epithelial innervation. In animals exposed to O(3) or HDMA + O(3) there was a significant increase in the number of PGP 9.5 positive/CGRP negative cells that were anchored to the basal lamina and emitted projections in primarily the lateral plain and often intertwined with projections and cell bodies of other similar cells. We conclude that repeated cycles of acute injury and repair associated with the episodic pattern of ozone and allergen exposure alter the normal development of neural innervation of the epithelial compartment and the appearance of a new population of undefined PGP 9.5 positive cells within the epithelium.

Children raised with extended exposure to environmental tobacco smoke (ETS) experience increased cough and wheeze. This study was designed to determine whether extended ETS exposure enhances citric acid-induced cough and bronchoconstriction in young guinea pigs via a neurokinin-1 (NK-1) receptor mechanism at the first central synapse of lung afferent neurons, the nucleus tractus solitarius. Guinea pigs were exposed to ETS from 1 to 6 weeks of age. At 5 weeks of age, guide cannulae were implanted bilaterally in the medial nucleus tractus solitarius at a site that produced apnea in response to the glutamate agonist D,L-homocysteic acid. At 6 weeks of age, either vehicle or a NK-1 receptor antagonist, SR 140333, was injected into the nucleus tractus solitarius of the conscious guinea pigs who were then exposed to citric acid aerosol. ETS exposure significantly enhanced citric acid-induced cough by 56% and maximal Penh (a measure of airway obstruction) by 43%, effects that were attenuated by the NK-1 receptor antagonist in the nucleus tractus solitarius. We conclude that in young guinea pigs extended exposure to ETS increases citric acid-induced cough and bronchoconstriction in part by an NK-1 receptor mechanism in the nucleus tractus solitarius.

RATIONALE: Children raised with exposure to environmental tobacco smoke experience increased cough and wheeze.This study was designed to determine if extended environmental tobacco smoke exposure enhances citric-acid induced cough and bronchoconstriction in young guinea pigs via a neurokinin-1 (NK-1) receptor mechanism at the first central synapse of lung afferent neurons, the nucleus tractus solitarius.METHODS: Guinea pigs were exposed to environmental tobacco smoke (1 mg/m 3 total suspended particulates) from 1 to 6 weeks of age.At 5 weeks of age, guide cannulae were implanted bilaterally in the medial nucleus tractus solitarius at a site that produced apnea in response to the glutamate agonist, D,L-homocysteic acid.At 6 weeks of age, either vehicle or a neurokinin-1 receptor antagonist, SR-140333 was injected into the nucleus tractus solitarius of the conscious guinea pigs who were then exposed to citric acid aerosol (n=7 to 10 each group).Statistical analysis was by ANOVA with post hoc analysis consisting of a series of Sheffe contrast tests among the treatment groups as appropriate.RESULTS: Environmental tobacco smoke exposure significantly enhanced citric acid-induced cough by 56% (P=0.03) and maximal Penh (a measure of airway obstruction) by 43% (P<0.02),effects that were attenuated by the neurokinin-1 receptor antagonist in the nucleus tractus solitarius (P=0.0003 for cough and P=0.03 for Penh).CONCLUSIONS: We conclude that in young guinea pigs, extended exposure to environmental tobacco smoke increases citric acid-induced cough and bronchoconstriction in part by an neurokinin-1 receptor mechanism in the nucleus tractus solitarius.

Cough is associated with plasticity of putative cough afferent fibres, but whether plasticity in the brainstem network contributes is less well understood. A key site in the CNS network is the nucleus tractus solitarius (NTS), the first synaptic contact of the primary afferent fibres. We sought to develop a conscious guinea pig model to detect enhanced cough, to focus on the NTS as a potential site for plasticity, and to test a role for substance P in the NTS since the neuropeptide has been implicated in plasticity of the vagal afferent fibres. Guinea pigs were exposed to second-hand tobacco smoke (SHS) or filtered air (FA) from 1–6 weeks of age. At 5 weeks, cannulae were implanted in the NTS. At 6 weeks, either vehicle or a neurokinin 1 (NK-1) receptor antagonist was injected into the NTS of the conscious guinea pigs who were then exposed to citric acid aerosol. SHS exposure significantly enhanced citric acid-induced cough (56%, P<0.05), an effect attenuated by NTS NK-1 receptor blockade (P<0.05). The findings suggest that one possible mechanism for plasticity in cough is related to substance P effects in the NTS. Future studies will be required to investigate the possible mechanisms underlying the role of substance P as well as other mechanisms in generating SHS-induced cough.

Substance P modulates the reflex regulation of respiratory function by its actions both peripherally and in the CNS, particularly in the nucleus tractus solitarii (NTS), the first central site for synaptic contact of the lung and airway afferent fibres. There is considerable evidence that the actions of substance P in the NTS augment respiratory reflex output, but the precise effects on synaptic transmission have not yet been determined. Therefore, we determined the effects of substance P on synaptic transmission at the first central synapses by using whole-cell voltage clamping in an NTS slice preparation. Studies were performed on second-order neurons in the slice anatomically identified as receiving monosynaptic input from sensory nerves in the lungs and airways. This was done by the fluorescent labelling of terminal boutons after 1,1'-dioctadecyl-3,3,3',3'-tetra-methylindocarbo-cyanine perchlorate (DiI) was applied via tracheal instillation. Substance P (1.0, 0.3 and 0.1 microM) significantly decreased the amplitude of excitatory postsynaptic currents (eEPSCs) evoked by stimulation of the tractus solitarius, in a concentration-dependent manner. The decrease was accompanied by an increase in the paired-pulse ratio of two consecutive eEPSCs, and a decrease in the frequency, but not the amplitude, of spontaneous EPSCs and miniature EPSCs, findings consistent with a presynaptic site of action. The effects were consistently and significantly attenuated by a neurokinin-1 (NK1) receptor antagonist (SR140333, 3 muM). The data suggest a new site of action for substance P in the NTS (NK1 receptors on the central terminals of sensory fibres) and a new mechanism (depression of synaptic transmission) for regulating respiratory reflex function.

Twenty-four infant rhesus monkeys (30 days old) were exposed to 11 episodes of filtered air (FA), house dust mite allergen aerosol (HDMA), ozone (O3), or HDMA + O3 (5 days each followed by 9 days of FA). Ozone was delivered for 8 h/day at 0.5 ppm. Twelve of the monkeys were sensitized to house dust mite allergen (Dermatophagoides farinae) at ages 14 and 28 days by subcutaneous inoculation (SQ) of HDMA in alum and intraperitoneal injection of heat-killed Bordetella pertussis cells. Sensitized monkeys were exposed to HDMA aerosol for 2 h/day on days 3-5 of either FA (n = 6) or O3 (n = 6) exposure. Nonsensitized monkeys were exposed to either FA (n = 6) or O3 (n = 6). During the exposure regimen, parameters of allergy (i.e., serum IgE, histamine, and eosinophilia), airways resistance, reactivity, and structural remodeling were evaluated. Eleven repeated 5-day cycles of inhaling 0.5 ppm ozone over a 6-month period had only mild effects on the airways of nonsensitized infant rhesus monkeys. Similarly, the repeated inhalation of HDMA by HDMA-sensitized infant monkeys resulted in only mild airway effects, with the exception of a marked increase in proximal airway and terminal bronchiole content of eosinophils. In contrast, the combined cyclic inhalation of ozone and HDMA by HDMA sensitized infants monkeys resulted in a marked increase in serum IgE, serum histamine, and airways eosinophilia. Furthermore, combined cyclic inhalation of ozone and HDMA resulted in even greater alterations in airway structure and content that were associated with a significant elevation in baseline airways resistance and reactivity. These results suggest that ozone can amplify the allergic and structural remodeling effects of HDMA sensitization and inhalation.