2006 Progress Report: Mechanisms of Particulate-Induced Allergic Asthma

EPA Grant Number: R832139C003
Subproject: this is subproject number 003 , established and managed by the Center Director under grant R832139
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Johns Hopkins Center for Childhood Asthma in the Urban Environment
Center Director: Breysse, Patrick N.
Title: Mechanisms of Particulate-Induced Allergic Asthma
Investigators: Wills-Karp, Marsha
Institution: The Johns Hopkins University
EPA Project Officer: Callan, Richard
Project Period: November 1, 2003 through October 31, 2008 (Extended to October 31, 2010)
Project Period Covered by this Report: November 1, 2005 through October 31, 2006
RFA: Centers for Children's Environmental Health and Disease Prevention Research (2003) RFA Text |  Recipients Lists
Research Category: Children's Health , Health Effects , Health

Objective:

The overall goal of the proposal was to establish a causal relationship between particulate matter (PM) exposure and asthma morbidity and to determine the mechanisms by which PM elicits these effects.

The primary objective of this project is to establish a causal relationship between PM exposure and asthma morbidity and to determine the mechanisms by which exposure enhances asthma morbidity. We have determined that a single (0.5 mg/mouse) intratracheal dose of particulate matter collected in urban Baltimore induces significant increases in airway hyperresponsiveness. The increase in AHR was preceded by dramatic increases in BAL granulocytes particularly, eosinophils. These physiological changes were associated with an early Th2 cytokine pattern (IL-5, IL-13, eotaxin), which shifted toward a Th1 pattern as AHR and granulocytes returned to normal levels. We concluded from these studies that ambient PM induces asthma-like parameters in naive mice suggesting that PM exposure may contribute to increases in asthma prevalence.

As we have recently identified complement as a susceptibility gene for asthma in a murine model, we evaluated its role in PM-induced AHR. The responses to PM exposure were compared in complement factor 3 (C3) deficient mice and their wild type controls. Interestingly, C3 deficient mice did not develop AHR, while the wild type mice developed significant AHR in response to particulate exposure. Immunostaining of lung sections with a fluorescently labeled anti-C3 antibody revealed that C3 was deposited along the epithelial surface and in the smooth muscle layer. Thus, complement deposition may be a common mechanism by which airborne particles elicit allergic airway responses.

The specific aims of the proposal were the following:

  1. To determine the relationship between exposure to airborne indoor PM and asthma morbidity, we will compare the biological effects or PM collected in homes of children with mild and severe asthma stratified for the presence of smokers in the home using the development of asthma symptoms in mice as a readout system.
  2. To determine the interaction with genetic factors, environmental exposure to allergens, and environmental PM exposures which contribute to asthma morbidity, we will examine the biological effects of exposure to indoor urban Baltimore PM in non-allergic strains of mice.
  3. To determine the role of complement factor 3 in mediating urban indoor PM-induced inflammation and/or exacerbations of allergic asthmatic symptoms, we will compare the biological effects of PM exposure in C3 deficient and wildtype mice.

Progress Summary:

As we have previously shown that PM induces the development of Th2-mediated allergic airway responses, we sought to determine whether AUB exposure activated the major antigen presenting cell in the lung, the dendritic cell. Interestingly, we have found that PM induces significant elevations in the numbers of lung derived myeloid DC as compared to the plasmacytoid subset. As we and others have previously shown that myeloid DC are immunogenic and induce allergic responses, whereas, plasmactyoid DCs confer tolerance to the development of allergic responses, these studies suggest that PM exposure may enhance allergic responses by altering the balance of immunogenic to tolerogenic DCs present in the lung. In order to begin determining the mechanisms by which AUB may activate mDCs, we hypothesized that AUB may induce changes in the airway epithelium which lead to the recruitment and activation of mDCs. To test this hypothesis, we asked whether AUB-conditioned supernatants influence the activation or cytokine production of DCs. Specifically, we cultured mDCs isolated from the bone marrow (BMDDC) of A/J mice and measured the production of the Th1-directing cytokine, IL-12 and the Th2-directing cytokines, IL-6. Interestingly, we find that AUB-conditioned epithelial supernatants preferentially induce the production of the Th2-directing cytokine, IL-6. These results suggest that AUB may induce the production of factors by the airway epithelium that activate DCs to provide Th2 promoting signals to T cells. To determine whether this effect differs from direct effects of AUB on DCs, we cultured BMDDC with AUB, and assessed IL-6 and IL-12 production. We found that direct exposure of BMDDC to AUB induces significant elevations in both cytokines suggesting that direct AUB exposure of DC would lead to a mixed Th1/Th2 response. Thus, our studies suggest that AUB induces changes in the airway epithelial that skew the immune response towards a Th2 response. The nature of these factors and the mechanisms by which AUB induces these factors remain unknown.

To begin to determine the potential mechanism by which AUB may induce cytokine production in the airway epithelium, we evaluated the expression of toll receptors in AUB-exposed primary tracheal epithelial cells. We find that AUB exposure upregulates TLR2 mRNA levels, but not TLR4 mRNA. To assess the contribution of TLR2 to AUB-induced cytokine production, we harvested epithelial cells from wildtype and TLR2 KO mice. Interestingly, TLR2 deficiency had no effect on epithelial cytokine production. As PM has been shown to induce oxidative stress pathways, we asked whether anti-oxidant treatment of epithelial cells would alter their ability to make proinflammatory cytokines. Indeed, treatment with NAC, a potent anti-oxidant, dose-dependently inhibited AUB-induced cytokine production. Consistent with a role for oxidative stress pathways, we also find that AUB significantly upregulates expression of the compensatory anti-oxidant transcription factor, Nrf2. These results suggest that AUB activation of airway epithelial cells occurs at least in part through oxidative stress pathways. Studies are currently underway: 1) to identify the AUB-induced epithelial mediator(s) that influence DC cytokine production;2) to further elucidate the exact mechanisms by which AUB-induces oxidative stress pathways;and 3) to determine the influence of AUB-induced epithelial conditioning on the ability of DCs to regulate T cell differentiation in vitro and in vivo.

Future Activities:

Our plans over the next year include further study of the ability of both outdoor and indoor particulates to induce allergic airway responses. Specifically, we will:

  1. Identify the AUB-induced epithelial mediator(s) that influence DC cytokine production;
  2. Further elucidate the exact mechanisms by which AUB-induces oxidative stress pathways in the airway epithelium;
  3. Determine the influence of AUB-induced epithelial conditioning on the ability of DCs to regulate T cell differentiation in vitro and in vivo;
  4. Compare the effects of AUB on DC and epithelial cell function in both susceptible and resistant strains of mice;
  5. Examine the effects of PM collected from homes in inner city Baltimore on allergic airway responses in mice. Specifically, we plan to collect PM by similar means as the AUB from indoor sources in inner city homes. A comparison of different sources of the PM may provide further information regarding the biologically active components of the PM.


Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other subproject views: All 18 publications 18 publications in selected types All 18 journal articles
Other center views: All 113 publications 113 publications in selected types All 110 journal articles
Type Citation Sub Project Document Sources
Journal Article Guajardo JR, Schleifer KW, Daines MO, Ruddy RM, Aronow BJ, Wills-Karp M, Hershey GK. Altered gene expression profiles in nasal respiratory epithelium reflect stable versus acute childhood asthma. Journal of Allergy and Clinical Immunology 2005;115(2):243-251. R832139 (2007)
R832139C003 (2006)
  • Abstract from PubMed
  • Full-text: Journal of Allergy and Clinical Immunology HTML
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  • Abstract: Journal of Allergy and Clinical Immunology
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  • Other: Journal of Allergy and Clinical Immunology PDF
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  • Journal Article Kohl J, Baelder R, Lewkowich IP, Pandey MK, Hawlisch H, Wang L, Best J, Herman NS, Sproles AA, Zwirner J, Whitsett JA, Gerard C, Sfyroera G, Lambris JD, Wills-Karp M. A regulatory role for the C5a anaphylatoxin in type 2 immunity in asthma. Journal of Clinical Investigation 2006;116(3):783-796. R832139 (2007)
    R832139C003 (2006)
    R832139C003 (2007)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: Journal of Clinical Investigation HTML
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  • Abstract: Journal of Clinical Investigation
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  • Other: Journal of Clinical Investigation PDF
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  • Journal Article Lewkowich IP, Herman NS, Schleifer KW, Dance MP, Chen BL, Dienger KM, Sproles AA, Shah JS, Kohl J, Belkaid Y, Wills-Karp M. CD4+CD25+ T cells protect against experimentally induced asthma and alter pulmonary dendritic cell phenotype and function. Journal of Experimental Medicine 2005;202(11):1549-1561. R832139 (2006)
    R832139 (2007)
    R832139C003 (2006)
  • Full-text: Journal of Experimental Medicine PDF
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  • Abstract: Journal of Experimental Medicine
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  • Journal Article Wills-Karp M, Koehl J. New insights into the role of the complement pathway in allergy and asthma. Current Allergy and Asthma Reports 2005;5(5):362-369. R832139 (2007)
    R832139C003 (2006)
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  • Supplemental Keywords:

    RFA, Scientific Discipline, Health, Air, Geographic Area, HUMAN HEALTH, particulate matter, Health Risk Assessment, State, Health Effects, Allergens/Asthma, asthma, children's health, asthma triggers, air toxics, exposure, air pollution, children, air pollutant, human exposure, airborne pollutants, Maryland (MD), PM, allergens

    Progress and Final Reports:

    Original Abstract
  • 2004 Progress Report
  • 2005 Progress Report
  • 2007 Progress Report
  • 2008
  • 2009
  • Final Report

  • Main Center Abstract and Reports:

    R832139    Johns Hopkins Center for Childhood Asthma in the Urban Environment

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R832139C001 The Epidemiology of Susceptibility to Airborne Particulates and Allergens to Asthma in African Americans
    R832139C002 A Randomized Controlled Trial of Behavior Changes in Home Exposure Control
    R832139C003 Mechanisms of Particulate-Induced Allergic Asthma
    R832139C004 Dendritic Cell Activation by Particulate Matter and Allergen