Grantee Research Project Results

2000 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, 1999 through January 1, 2000
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:

The objective 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 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 12E-independent inflammatory responses in the human upper airway; and (3) test the hypothesis that the in vivo allergic antibody response caused by chronic exposure to ETS is controlled by genetic background and age.

Progress Summary:

Objective 1

We have focused on experiments to determine how ETS interacts with allergen and demonstrated our hypothesis that acute challenge with ETS will exacerbate allergen-induced nasal allergic responses.

We recruited 10 volunteers with a positive skin test to short ragweed and a history of allergic rhinitis.  The antigen used in our challenge studies, short ragweed, is not present in the Los Angeles area.  This enabled us to use subjects who have been sensitized to short ragweed and who were not exposed naturally to it during the duration of the study.  Subjects were challenged by spraying the nose with increasing doses of short ragweed Amb a I starting at 10 AU and increasing in 10-fold steps until symptoms (sneezing/runny nose and ocular itching) were apparent; this was defined as an “active dose” of allergen for that subject.  For these studies, the active dose varied between subjects from 10,000 AU to 10 AU.  After a span of at least 4 weeks, the subjects were recalled and challenged with their active dose of allergen following 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.

Production of antibody of the IgE is the hallmark of allergy.  Ragweed-specific IgE levels measured in nasal lavages performed 4 days after exposure to ragweed plus ETS were significantly higher than following challenge with ragweed alone (mean = 58.4 U/mL vs. 2.2 U/mL, p < 0.001 paired t-test).  Similarly, ragweed specific-IgG4 levels were enhanced by ETS exposure (mean = 26.7 U/mL vs. 5.6 U/mL).  ETS also potentiated levels of total IgE and lgG4.  Although total IgA levels following ETS plus ragweed exposure were higher than after ragweed alone, ragweed-specific IgA was unchanged.

Histamine levels were measured in nasal lavages performed before and 10 minutes following allergen challenge.  As expected, in these ragweed allergic subjects, challenge with ragweed caused a significant rise in histamine levels from baseline levels (3.8 nM vs. 0.6 nM, p < 0.01); however, this increased more than four-fold to 16.1 nM when subjects were exposed with ETS immediately before allergen.  When the above experiments were repeated, with exposure to carbon black (elemental carbon devoid essentially of chemicals) instead of ETS, no increase in histamine levels was apparent.

Objective 2

We have established that ETS will synergize 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, we 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.  The levels of these cytokines were significantly greater at this time than following challenge with allergen alone (e.g., IL-5 mean = 4.8 pg/mL vs. 0.3 pu/mL, p < 0.01).  In contrast, IFN-g levels were not changed significantly by ETS plus allergen exposure.  ETS exposure alone did not enhance significantly IL-4, IL-5, IL-I 3, or IFN-g in lavages obtained 24 hours later, although the key proinflammatory cytokines tumor necrosis factor-α (TNF-α), and interleukine I p were both significantly higher than at baseline at this time.

IL-5 is a known activator and inducer of eosinophils.  We therefore predicted that ETS should augment recruitment of eosinophils into the nasal environment.  Nasal lavages were performed on nine allergic adults before and after exposure to both allergen plus ETS and to allergen alone.  As expected, allergen-challenge alone increased eosinophil numbers and its percentage in the total cell Gong/Diaz-Sanchez population.  This eosinophil influx was significantly greater if allergen challenge followed ETS exposure.  Thus, although less than 1 percent of total cells were identified as eosinophils in baseline lavages, and 19 percent eosinophils were measured 24 hours after allergen challenge, this number rose to 32 percent following ETS plus allergen exposure.  We had established previously that following exposure to ETS alone, the total number of macrophages, neutrophils, and lymphocytes all were elevated compared to baseline levels.  Additionally, the percentage of macrophages and lymphocytes in the total cell population also increased at this time.

Objective 3

Last year, we had established successfully an animal model of chronic exposure to ETS using BALB/c mice.  This year, we have extended these findings to the CB57/Black/6 mouse.  Additionally, we have commenced studies on the effect of age on ETS-induced IgE responses.

The CB57/Black/6 strain of mice is known to be a poor IgE responder in response to allergen.  Groups of six female mice were challenged with ovalbumin (OVA), ETS, or both.  The ability of these animals to mount total and allergen-specific IgE response were then determined from blood samples taken from the tail.  In mice, both IgE and IgG1 are “allergic antibodies”—that is, they are capable of inducing anaphylaxis.  In our model, mice receiving OVA alone did not produce either OVA-specific IgE or IgG1 at any time.  In contrast, animals receiving both ETS and OVA had significantly elevated levels of both total IgE and IgG1 and OVA-specific IgE and IgG1, 12 days after the initial exposure.

These experiments all were performed in mice aged 6-8 weeks old.  We have repeated the experiments on mice aged 2-3 weeks old.  OVA-specific IgG1 was detected at Day 12 in mice upon ETS plus OVA exposure, but was not observed in mice receiving OVA alone.  The levels of these antibodies were significantly higher than that observed in adult mice receiving the same treatment; however, no OVA-specific IgE could be detected.

Significance

The results demonstrate that ETS can synergize with allergen to exacerbate the allergic response in humans.  They demonstrate that ETS augments allergen-driven antibody responses in both human and murine models.  In addition, they provide for a putative mechanism by showing that ETS can aid in the formation of a Th2 cytokine response that is critical to the establishment of allergic inflammation, which is central to diseases such as rhinitis and asthma.  The establishment of a murine model on a CB57/Black/6 strain background will allow us to answer genetic questions because mice with knockouts to a variety of genes are available on this background.  Furthermore, the experiments on different aged mice suggest that the effects of ETS also are relevant and indeed may be of greater importance in the young.  These results have important health implications because they demonstrate for the first time in humans a direct causal effect of ETS on the allergic response.

Future Activities:

We have shown that ETS has the potential to exacerbate ongoing allergic diseases and, presumably, to increase severity of allergic disease.  During this next year of support, we intend to determine if acute exposure to ETS can cause sensitization to a neo-allergen (i.e., if ETS can cause a de novo allergic response).  These planned studies will therefore address whether passive smoking has the potential to increase the prevalence of allergic diseases.  During this same time, we will extend our human model to examine the role of age and the differences in responses between adults and children.  We will make use of the availability of mice whose gene for the arvl hydrocarbon receptor is absent (ahr mice).  Using our model on these animals and comparing results to the CB57/Black/6 wild-type mouse will enable us to study the role of this chemical receptor on ETS-induced IgE responses.

Journal Articles:

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

Supplemental Keywords:

children, health, air, exposure, susceptibility, tobacco smoke, allergen, air, 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, 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, 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:

http://www.usc.edu/schools/medicine/research/centers_programs/cehc Exit

Progress and Final Reports:

Original Abstract

1998

1999

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