2001 Progress Report: Children's Exposure to Environmental Tobacco Smoke: Changes in Allergic ResponseEPA Grant Number: R826708C002
Subproject: this is subproject number 002 , established and managed by the Center Director under grant R826708
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Southern California Particle Center and Supersite
Center Director: Froines, John R.
Title: Children's Exposure to Environmental Tobacco Smoke: Changes in Allergic Response
Investigators: Gong, Henry , Diaz-Sanchez, David
Institution: University of California - Los Angeles
Current Institution: Rancho Los Amigos Medical Center , University of California - Los Angeles
EPA Project Officer: Callan, Richard
Project Period: January 1, 1998 through January 1, 2002
Project Period Covered by this Report: January 1, 2000 through January 1, 2001
Project Amount: Refer to main center abstract for funding details.
RFA: Centers for Children's Environmental Health and Disease Prevention Research (1998) RFA Text | Recipients Lists
Research Category: Children's Health , Health Effects , Health
The goal of this research project is to determine the effects of environmental tobacco smoke (ETS) on defined phases of the human allergic antibody response by establishing controlled human and animal models relating to ETS exposure. The specific objectives of this research project are to: (1) determine the mechanisms by which ETS alters the in vivo IgE antibody response in the human upper airway; (2) determine how exposure to ETS alters IgE-independent inflammatory responses in the human upper airway; and (3) test the hypothesis that the in vivo allergic antibody response caused by chronicexposure to ETS is controlled by genetic background and age.
We have focused on experiments to test our hypothesis that acute challenge with ETS will exacerbate the allergic response and compare ETS-induced nasal immune responses to ETS between adults and children.
We recruited 10 child volunteers between the ages of 11 and 14 with a history of allergic rhinitis. These subjects were nonsmokers but lived in a household where a member smoked. The children were advised of the health consequences of smoking and instructed to avoid smoke. The parents were instructed not to smoke in the vicinity of the child. At least 2 weeks later, the subjects were recalled. At this time, they performed a nasal lavage followed by ETS exposure. We have used our previously established human ETS exposure model performed in collaboration with Dr. Henry Gong at the Los Amigos Research and Education Institute. In this model, subjects are exposed to the sidestream smoke of five Kentucky reference cigarettes in a 2-hour period. The subjects performed nasal lavages at different times after exposure. Immunological changes manifest in the nasal lavages then were compared to results obtained from 10 allergic adults (aged 24 to 35 years) who underwent an identical procedure.
Production of antibody of the immunoglobulin E class (IgE) is the hallmark of allergy. Both children and adults responded to ETS in a similar fashion. In both groups, levels of total IgE measured in nasal lavages obtained 4 days after ETS challenge were significantly higher than baseline (preexposure) levels. In addition, there was a significant increase of IgG4 levels in both groups. The antibody IgG4 is thought to be coregulated with IgE. In contrast, there was no change from baseline in IgG or IgA (the predominant antibody class in mucosal immunity) levels following ETS challenge in either group. No significant difference was observed in either baseline IgE levels between adults and children or in the magnitude of the IgE increase following ETS challenge (mean = 4.4 ng/mL vs. 5.64 ng/mL, p > 0.05 unpaired t-test).
We have established previously that ETS exposure will not enhance significantly IL-4, IL-5, IL-13, or IFN-γ, but will result in increased production of the key proinflammatory cytokines, tumor necrosis factor-α (TNF-α), granulocyte macrophage-colony stimulating factor (GM-CSF) and IL-113. We have studied whether there is any qualitative or qualitative difference in the ability of ETS to induce production of these cytokines between children and adults. Immediately after exposure and 24 hours after ETS exposure, levels of TNF-α, GM-CSF, and IL-113 were significantly higher than at baseline in both groups. For all three cytokines, baseline levels were similar between children and adults; however, the magnitude of the response to ETS was significantly greater in children than in adults. Accordingly, 24 hours after ETS exposure, mean levels of TNF-α, GM-CSF, and IL-113 were 228 percent, 321 percent, and 122 percent higher, respectively, in children than in adults.
TNF-α, GM-CSF, and IL-113 are important cytokines in the recruitment and activation of inflammatory cells. We studied, therefore, whether the cellular response to ETS differed between children and adults. In both groups, total cell numbers were elevated in lavages performed immediately after or 24 hours after the ETS exposure compared to the preexposure baseline lavages. Although cell numbers increased 175 percent in adults 24 hours after ETS exposure, they increased by more than 361 percent in children.
Similar results were observed in the cellular subpopulations. For both groups, the total number of macrophages, neutrophils, and lymphocytes were all elevated significantly from baseline levels in lavages performed 24 hours after ETS. The magnitude of this increase, however, was more pronounced in children than in adults. The percentage of macrophages and lymphocytes in the total cell population also increased at this time. As a result, although macrophages constituted only 28 percent of the total cells before exposure, at 24 hours after ETS exposure they comprised 33 percent of the population in adults and 48 percent of the population in children.
We previously succeeded in establishing an animal model of chronic exposure to ETS using two strains. The BALB/c strain is a good IgE responder in response to allergen, whereas CB57/Black/6 is a poor responder. In both strains, we showed that ETS could increase antigen-specific IgE responses to an aerosolized protein. We have expanded on these studies. Others have shown that ETS augments allergic responses, but its role in atopic sensitization still is controversial. We studied whether ETS could initiate a Th2 response and thus induce primary allergic sensitization. Mice were exposed for 10 consecutive days to either 1 percent aerosolized ovalbumin (OVA), ETS (five cigarettes), or both ETS and OVA. C57/Black/6 mice receiving both ETS and OVA developed OVA-specific IgE and IgGl at 12, 14, and 25 days after the initial exposure, whereas those receiving OVA alone did not. Thirty days after the initial challenge (20 days after its completion), mice were reexposed to OVA. Bronchoalveolar lavage (BAL) performed 24 hours later revealed an influx of eosinophils in the group challenged initially with both ETS and OVA but not in those exposed to ETS alone or OVA alone. Increases in IL-5, GM-CSF, and IL-2 were observed in BAL from this OVA/ETS exposed group, whereas IFN-( levels were inhibited significantly. Thus, ETS induced not only increased allergic antibody production, but also promoted a Th2 cytokine environment and lung eosinophilia. These all are key end points and indicators of allergic airway disease in the mouse model.
The experiments all were performed in mice aged 8 weeks old. We have repeated them on mice aged 2-3 weeks old. In mice, both IgE and IgGl can bind to mast cells and cause anaphylaxis (in humans only IgE can do this). As in the older mice, OVA-specific IgG1 was detected at Day 12 in the young mice upon ETS plus OVA exposure, but were not observed in mice receiving OVA alone; however, these antibody levels were significantly higher than those observed in adult mice receiving the same treatment. In addition, the shift to a Th2 cytokine milieu was more marked in the younger mice, so that IL-4 and IL-5 levels in BAL performed after OVA rechallenge were significantly higher in the younger than in the older mice.
These experiments suggest that younger mice may be more susceptible to the effects of ETS. To confirm this and also to address dosimetry, we exposed both 8-week-old and 3-week-old BALB/c mice to different amounts of ETS. As noted above, exposure of either group to sidestream smoke from five cigarettes for 10 days promotes primary sensitization to an inhaled antigen (OVA). When wily exposure was reduced to smoke from three cigarettes prior to OVA inhalation, only one-sixth of the 8-week-old animals developed OVA-specific IgE; however, it was detectable in all of the 3-week-old mice. This effect was seen more strikingly in mice exposed to smoke from only one cigarette daily prior to OVA inhalation. Under these conditions, OVA-specific IgE was observed in none of the older mice but was detectable in five out of six of the younger mice.
Using the human and mouse models established in previous years, we have focused on the key issue of the role of age on the immune response to ETS. Our results show that the airway inflammatory response induced by ETS is more severe in children than in adults. This has important implications because it implies that children are more susceptible to ETS and that induction/exacerbation of allergic responses by ETS will be more severe in children. It is important to note that these studies are performed in the upper airways of nonasthmatic subjects. If similar results occurred in the lower airways, it is very likely that an increase in proinflammatory cytokines and inflammatory cells would result in aggravated asthmatic symptoms. This concept is supported by our mouse model studies. Our previous mice studies showed that ETS could both induce primary sensitization and exacerbate secondary (preestablished) allergic airway responses. The mice studies outlined here concur with the human studies and suggest that induction/enhancement of the allergic airway responses by ETS is more pronounced in the young. In addition, they suggest that far less ETS may be required to induce these changes in the young. These results have important health implications because they demonstrate for the first time, in both animal and human models, that ETS may pose a greater risk to children.
During the next year, we intend to continue our dosimetry studies in the mice. In addition, we will use whole body plethysmography to determine whether the airway changes we observe in response to ETS will result in increased airway hyprerresponsiveness. In addition, we will make use of the availability of mice whose gene for the aryl hydrocarbon receptor is absent (ahr-/- mice). Using our model on these animals and comparing to the CB57/Black/6 wild type will enable us to study the role of this chemical receptor on ETS-induced IgE responses. Using the human model, we will study whether ETS will alter expression of activation/contact signals that induce/augment ETS. We also will determine whether acute exposure to ETS can cause sensitization to a neo-allergen (i.e., if ETS can cause a de novo allergic response).
Journal Articles on this Report : 1 Displayed | Download in RIS Format
|Other subproject views:||All 4 publications||4 publications in selected types||All 4 journal articles|
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||Rumold R, Jyrala M, Diaz-Sanchez D. Secondhand smoke induces allergic sensitization in mice. Journal of Immunology 2001;167(8):4765-4770.||
Supplemental Keywords:children, health, air, exposure, susceptibility, tobacco smoke, allergen, air, health, atmospheric sciences, biology, children’s health, environmental chemistry, health risk assessment, risk assessments, genetic susceptibility, indoor air, airway disease, airway inflammation, allergen, allergic response, allergic rhinitis, assessment of exposure, asthma, biological response, childhood respiratory disease, children’s vulnerability, cigarette smoke, copollutant, cytokines, environmental hazard exposures, environmentally caused disease, exposure assessment, health effects, human exposure, indoor air quality, indoor environment, infants, pollen, respiratory problems, secondhand smoke, sensitive populations, susceptibility, tobacco, tobacco smoke,, RFA, Health, Scientific Discipline, Air, Environmental Chemistry, Health Risk Assessment, Risk Assessments, Susceptibility/Sensitive Population/Genetic Susceptibility, Allergens/Asthma, indoor air, Children's Health, Atmospheric Sciences, genetic susceptability, Biology, asthma, health effects, sensitive populations, cytokines, pollen, allergic rhinitis, infants, airway disease, biological response, respiratory problems, second hand smoke, exposure, children, Human Health Risk Assessment, airway inflammation, assessment of exposure, childhood respiratory disease, children's vulnerablity, susceptibility, tobacco, human exposure, cigarette smoke, environmentally caused disease, indoor air quality, allergic response, tobacco smoke, allergen, exposure assessment, indoor environment, copollutant, environmental hazard exposures
Progress and Final Reports:Original Abstract
Main Center Abstract and Reports:R826708 Southern California Particle Center and Supersite
Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R826708C001 Asthma in Children: A Community-based Intervention Project
R826708C002 Children's Exposure to Environmental Tobacco Smoke: Changes in Allergic Response
R826708C003 Respiratory Disease and Prevention Center