Grantee Research Project Results

2002 Progress Report: Children's Exposure to Environmental Tobacco Smoke: Changes in Allergic Response

EPA 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: Great Lakes Air Center for Integrative Environmental Research
Center Director: Harkema, Jack
Title: Children's Exposure to Environmental Tobacco Smoke: Changes in Allergic Response
Investigators: Gong, Henry , Diaz-Sanchez, David
Institution: Rancho Los Amigos Medical Center , University of California - Los Angeles
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1998 through January 1, 2002
Project Period Covered by this Report: January 1, 2001 through January 1, 2002
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 , Human Health

Objective:

Allergic rhinitis (hay fever) is a common illness involving the nose, throat, and eyes. Persons with this allergic condition of their upper airway often have allergic reactions in their lungs (asthma) as well. These reactions are caused by the presence of a particular antibody called immunoglobulin E (IgE) which reacts to foreign allergy material (e.g., pollen). The severity of allergic symptoms normally correlates with the levels of these antibodies. Several studies have compared antibody levels in children of smoking parents to those of non-smokers. Some have concluded that exposure to second-hand tobacco smoke (i.e., passive smoking) can increase the likelihood of producing IgE, while others have not been able to show such a link. These types of studies are complicated by other factors such as differences in lifestyle between the two groups being compared and the difficulties of accurately measuring smoke exposure.

The purpose of this new study is to investigate the ability of environmental tobacco smoke (ETS) to alter the amount and types of IgE and other mediators (cytokines). Investigators will do this by taking a new direct approach. They will measure levels of these agents in the nasal secretions of adults and children before and after controlled experimental exposure to tobacco smoke in an environmentally controlled chamber. (All children will be from homes where parents smoke.) Some subjects will also be exposed to a common environmental allergen (ragweed pollen) with and without associated exposure to low levels of tobacco smoke (equivalent to one day's exposure for a child living with a smoking parent).

The investigators will, therefore, determine if exposure to tobacco smoke plus pollen produces greater amounts of IgE and mediators in the nose than exposure to pollen alone. These experiments will also demonstrate whether children are more susceptible to tobacco smoke than adults. Similar studies will be performed in rats to address genetic and age-related questions that cannot be easily studied in humans. Overall, these studies will be important in determining the potential role of secondhand smoke in causing or exacerbating allergic disease.

Progress Summary:

Studies and Results

Specific Aim #1: Investigators will determine the mechanisms by which ETS alters the in vivo IgE antibody response in the human upper airway.

As with other inhaled pollutants, ETS is thought to exert major effects through the production of reactive oxygen species (ROS). Antioxidants have been shown to reduce the allergic inflammatory effects of chemicals present in ETS in vitro. Glutathione-S-Transferases (GSTS) are a family of enzymatic antioxidants involved in metabolism of ROS and detoxification of chemicals present in ETS. Functional polymorphisms in the GST genes are very common in the population (up to 50%) and are candidates for modulating individual susceptibility to the adjuvant effects of ETS on allergic inflammation. Investigators tested the effects of GSTM1 and GSTTI null genotypes, (which results in an absence of these enzymes) and GSTP1 codon 105 variants (which determines GSTP1 activity) on the ETS adjuvant effect. They have used their previously established human ETS exposure model performed in collaboration with Dr. Gong at the Los Amigos Research and Education Institute. In this model subjects are exposed to the side-stream smoke of five Kentucky Reference cigarettes in a two-hour period. Nineteen ragweed allergen sensitive subjects were challenged intranasally with allergen following 2 hours exposure to either clean air or ETS. As they have previously reported exposure to ETS prior to allergen challenge significantly enhanced ragweed-specific IgE levels in nasal ravages obtained 4 days after exposure. In collaboration with Dr. Gilliland (Project 2) and the Molecular Biology Core we determined GST genotypes using DNA from buccal cell specimens.

Individuals with either a GSTM1 present or the GSTP1 vallO5 variant genotypes showed markedly reduced ETS enhancement of the nasal response to allergen. In subjects with the GSTM1 null genotype, allergen specific-IgE levels were 26 fold higher following ETS/allergen exposure than clean air/allergen exposure. In contrast subjects with GSTM1 present genotype showed only a 4 fold in Acreage. A similar significantly larger increase in IgE was observed in subjects with GSTP1 val105 variant genotypes compared with subjects with wildtype GSTP1 genotype. The same pattern was observed in histamine levels obtained 10 mins after allergen challenge. ETS potentiated the response to a significantly greater degree in subjects with the GSTM1 null and GSTP1 wild type genotypes. None of the GSTs modified the allergic response following allergen challenge alone. G8TT1 genotype was not associated with allergic response following ETS.

Aim #2): Investigators will determine how exposure to ETS alters IQE-independent inflammatory responses in the human upper airway.

Investigators have previously established that ETS will synergise with allergen to produce a local Th2 cytokine milieu. This cytokine response is characteristic of an enhanced allergic response and is critical to allergic inflammation. Following challenge of allergic subjects with allergen alone they observed little or no change in nasal cytokine levels. In contrast if allergen-challenge was performed following ETS exposure, there was a rise in IL-4, IL-5 and IL-13 levels in nasal washes obtained 24 hours later. In contrast, IFN-Y levels were riot significantly changed by ETS plus allergen exposure. They tested the hypothesis that the increased responsiveness to ETS in IgE production in individuals with certain GST genotypes was due to regulation of cytokines by these natural antioxidants. Although an increase in IL-4 and a decrease in INF-Y were associated with GSTM1 null and GSTP1 wild type genotype, the changes did not achieve statistical significance. This may be because of the limited number of subjects used.

They have also previously shown that eosinophil influx in the nasal mucosa is significantly greater if allergen challenge followed ETS exposure. Thus while less than 1% of total cells were identified as eosinophils in baseline ravages, and 19% eosinophils were measured 24 hours after allergen challenge, this number rose to 32% following ETS plus allergen exposure. Investigators hypothesized that this is due to changes in chemokine levels. They have obtain nasal ravages from subjects before and 1, 6 and 14 hours after exposure to either ETS/allergen or clean air/allergen. These samples are currently being measured for levels of RANTES, GM-CSF, IL-8, MIP-1alpha and MCP-1. These are CC and CXC chemokines implicated in eosinophil and lymphocyte attraction and activation.

Aim #3) Investigators will test the hypothesis that the in vivo allergic antibody response due to chronic exposure to ETS is controlled by genetic back-ground and age.

We have previously succeeded in establishing an animal model of chronic exposure to ETS using two strains (a poor and a good IgE responder) and shown that ETS could increase antigen-specific IgE responses to an aerosolized protein in both. This model is characterized by increased eosinophils in BAL fluid and increased IL-4 levels. We tested the hypothesis that this key TH2 promoting cytokine is responsible for both the humural and cellular responses observed in our model. Therefore, we compared untreated mice to mice treated with i.p. injections of a IL-4 receptor antagonist. This antagonist blocks the binding of both IL4 and IL-13. As before untreated BALB/c mice exposed to 10 days exposure of ETS+ aerosolized OVA made significantly more OVA-IGE than those exposed to OVA alone. However, in mice treated with 10µg IL-4R antagonist given immediately prior to each ETS exposure, there was no enhancement of OVA-IGE by ETS, thus OVA-IGE in OVA or OVA+ETS exposed animals were the same. Furthermore, eosinophil enhancement by ETS was significantly inhibited in the antagonist-treated animals.

Significance

Investigators results studying GST polymorphisms and their relationships to responsiveness to ETS have important public health consequences. These results suggest that GSTM1 and GSTP1 genotypes, common polymorphisms in the population, powerfully modify the adjuvant effect of ETS on allergic inflammation in the upper respiratory track. Therefore there may be a large susceptible population for enhanced adjuvant effects of ETS exposure which may be identified by genotyping for antioxidant genes. Their murine model results advance our understanding of how ETS modulates the immune system. Not surprisingly IgE enhancement by ETS is critically dependent on activation of the IL-4receptor. Of importance, is the finding that enhancement of lung eosinophilia by ETS is also dependent on this process.

Future Activities:

Investigators have shown that ETS has the potential to exacerbate on-going allergic diseases and presumably increase severity of allergic disease. During this next year of support they intend to further study the importance of genotype on susceptibility to the adjuvant effects of ETS. They believe that the association between IL-4/ INF- levels and GST genotypes although not statistical significant is real. They believe that the study at the moment is under-powered. They therefore, propose to increase the number of subjects studied to test this assertion. During this same time they will make use of the availability of mice whose gene for a key natural antioxidant is absent (NQO14' mice).

Journal Articles:

No journal articles submitted with this report: View all 4 publications for this subproject

Supplemental Keywords:

Allergens, Biochemistry, Children's Health, Human Health Risk Assessment, age-related differences, air pollutants, airway disease, airway inflammation, environmental tobacco smoke, genetics, susceptibility., RFA, Health, Scientific Discipline, Air, Environmental Chemistry, Health Risk Assessment, Risk Assessments, Susceptibility/Sensitive Population/Genetic Susceptibility, Allergens/Asthma, Children's Health, genetic susceptability, indoor air, Atmospheric Sciences, Biology, asthma, health effects, sensitive populations, infants, cytokines, allergic rhinitis, pollen, airway disease, exposure, respiratory problems, second hand smoke, biological response, children, Human Health Risk Assessment, airway inflammation, human exposure, susceptibility, tobacco, children's vulnerablity, assessment of exposure, childhood respiratory disease, cigarette smoke, environmentally caused disease, indoor air quality, tobacco smoke, allergic response, allergen, copollutant, exposure assessment, indoor environment, toxics

Relevant Websites:

The link to University of Southern California is:
https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/outlinks.centers

Progress and Final Reports:

Original Abstract

1998

1999

2000 Progress Report

Final Report

Main Center Abstract and Reports:

R826708    Great Lakes Air Center for Integrative Environmental Research

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