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Johns Hopkins Center for Childhood Asthma in the Urban Environment
Principal Investigator: Patrick Breysse, PhD
| Overview | Community Partners |
| Exposures and Outcomes | Results |
| Research Projects | Selected Publications |
Results from the first two projects indicate that indoor PM and mouse allergen exposures are important targets for intervention, and suggest that current pollution regulations for ambient air alone may not be protective, so guidelines to reduce indoor-home air pollution levels may be needed.
Primary Exposures: Urban indoor air pollutants (including particulate matter [PM], ozone, nitrogen dioxide, and airborne allergens) and allergens in settled dust (including mouse, dust mite, cockroach, dog, and cat).
Primary Outcomes: Asthma, airway inflammation and respiratory disease in children
Original Projects: 1998-2003
Project 1: The Relationship of Airborne Pollutants and Allergens to Asthma Morbidity
The long-range goal of this epidemiologic study was to create a research infrastructure for the development and implementation of cost effective, community-based strategies to reduce asthma morbidity in the urban environment. The main hypothesis was that in children with asthma, exposure to both air pollutants and allergens results in respiratory morbidity that is greater than expected based on effects from independent exposures to air pollutants and allergens separately.
Project 2: A Randomized, Controlled
Trial of Home Exposure Control in Asthma
The intervention was designed to test the effectiveness (efficacy and feasibility) of home environmental treatment procedures that are currently recommended but have not been rigorously tested for their ability to affect asthma morbidity. Since indoor allergen and pollutant exposure has been shown to be extremely important risk factor for asthma morbidity, it is reasonable to expect that effective methods of reducing exposure will reduce asthma morbidity.
Project 3: Mechanisms of Particulate-Induced Allergic Asthma
The objective of this project was to examine the mechanisms by which ambient PM may exacerbate allergic airway disease, or play a role in the induction of an asthma-like phenotype in a mouse (murine) model. The studies show that a single exposure to ambient PM (0.5mg, <0.8 µm diameter) collected in inner-city Baltimore induces sustained airway hyperresponsiveness (AHR), and pulmonary inflammation (i.e. eosinophilia and neutrophilia). Conversely, these responses were not observed when animals were exposed to a reference source of fly ash.
Project 4: Genetic Mechanisms of Susceptibility to Inhaled Pollutants
The primary objective of this project was to utilize proven positional cloning
techniques to identify the gene or genes that determine differential susceptibility
to Ozone (O3)-induced pulmonary inflammation and injury in inbred mice, and
search for homologues in the human genome. Four specific aims were developed
to accomplish this objective:
(1) To generate high-resolution linkage maps for susceptibility to O3-induced
airway inflammation/epithelial injury; (2) To construct high-resolution
long-range physical maps of the regions of mouse chromosomes 17 and carrying
the O3 susceptibility loci; (3) To develop congenic strains of
mice that contain the genomic region that confers differential susceptibility
to O3-induced inflammation and epithelial injury; and (4) To characterize
the kinetics of lung response to O3 exposure in O3-resistant and
susceptible congenic mouse strains.
Current Projects: 2003-2008
Project 1: The Epidemiology of Susceptibility to Airborne Particulates and Allergens to Asthma in African Americans
Lead investigator: Greg Diette MD, MS
The long-range goal of this project is to examine the genetic basis of asthma in African-American children with specific attention to genetic modifiers involved in the enhanced susceptibility of certain patients to particulate matter (PM) and allergens. The strategy is to employ high-throughput genomic technologies to examine the (i) patterns of gene expression to identified candidate genes and (ii) the genetic basis for polymorphisms in genes which explain susceptibility to PM in an inner city African American population with asthma. Investigators are examining the relationship of genetic polymorphisms in genes encoding IL13, TLR4 and BADr to susceptibility to home pollutant and allergen exposure in asthmatic and control children.
The specific aims are (1) to obtain and prioritize and candidate genes for susceptibility to airborne particulate matter through gene expression profiling in human CD4+ T-lymphocytes; (2) to identify polymorphisms in candidate genes associated with susceptibility to PM exposures in asthma and with asthma severity; and (3) to identify polymorphisms in candidate genes associated with an interactive effect of cockroach allergen and PM10 exposures on asthma severity.
An important secondary goal is to complete the case-control study of home environments in inner city children with and without asthma and the nested longitudinal follow-up of the asthmatic cases from the first project period (1998-2003).
Current Funding Period (2003-2008): Abstract | 2004 | 2005 | 2006 | 2007
Project 2: A Randomized Controlled Trial of Behavior Changes in Home Exposure Control
Lead investigator: Arlene Butz, PhD
This randomized controlled clinical trial is testing methods to increase the effectiveness of current intervention strategies to reduce hazardous exposures and their adverse health effects.
Current Funding Period (2003-2008): Abstract | 2004 | 2005 | 2006 | 2007
Project 3: Mechanisms
of Particulate-Induced Allergic Asthma
Lead investigator: Marsha Wills-Karp, PhD
Dr. Wills-Karp’s project is examining the mechanisms by which particulate matter may exacerbate an allergen-driven inflammatory response in the airways. This project is using particulate matter collected from Baltimore city and from the homes of asthmatic children.
Current Funding Period (2003-2008): Abstract | 2004 | 2005 | 2006 | 2007
Project 4: Dendritic Cell Activation by Particulate Matter and Allergen
Lead investigator: Steven Georas, MD
This project is examining the effect of ambient particulate matter collected from Baltimore city on maturation of peripheral blood monocytes to dendritic cells (DCs).
In addition to these projects Johns Hopkins Children’s Center researchers continue to analyze data from the previously conducted cohort study of asthma morbidity and an exposure control intervention study which were completed during the first five years of funding.
Current Funding Period (2003-2008): Abstract | 2004 | 2005 | 2006 | 2007
Project 1 – Selected Results: Epidemiology of susceptibility to particulates and allergens in asthma
- Researchers at the Johns Hopkins Children’s Center found a strong and consistent relationship between mouse allergen exposure and asthma-related outcomes, including both symptoms and asthma-related health care use (Matsui et al. 2006).
- In the cohort study, children in the sensitized/higher exposure group experienced more symptoms than children in the other groups consistently across all symptom measures. In addition, the sensitized/higher exposure group had greater odds of asthma-related unscheduled doctor visits, emergency department visits, and hospitalization than children in the other groups.
- Elevated indoor particulate matter (PM) levels were significantly associated with increased respiratory symptoms and more frequent rescue medication use.
- For every 10 µg/m3 increase in PM10 (the coarse fraction of particulate matter with a diameter smaller than 10 microns), there were more days with asthma symptoms (cough, wheeze, chest tightness) in the previous 2 weeks [IRR 1.03 (95% CI, 1.0-1.05)]. Likewise, for every 10 µg/m3 increase in PM10, there were more nights with awakening with asthma symptoms [IRR 1.03 (95% CI, 1.0-1.06)] and more days with exercise symptoms [IRR 1.03 (95% CI, 1.0-1.06). For every 10 µg/m3 increase in PM10, there was a 7% (IRR 1.07 95% CI, 1.03-1.11) increase in wheezing severe enough to limit speech and a 5 % (IRR 1.05 95% CI, 1.03-1.08) increase in beta-agonist use in the previous 2-weeks. Similar relationships were found between health outcomes and fine particulate (PM2.5) levels, though not all were statistically significant.
- Parents of asthmatics reported that they had seen roaches in their home (43%), 54% had cats, 43% had dogs, and 82% had seen evidence of mice.
- Forty-five percent of asthmatic children were skin-test positive to cockroach allergens. The median level of bedroom cockroach allergen (Bla g 1) was 6.0 U/gm, a value slightly higher than seen in the intervention study. Children with the greatest symptom severity had the highest levels of bedroom PM. For example, 38% of children in the highest quartile of levels of PM2.5 (particulate matter with a diameter smaller than 2.5 microns) had moderate/severe persistent asthma vs. only 21% of those in the lowest quartile. Likewise, 28% of children in the highest quartile of coarse particulate matter (PM10) had moderate/severe persistent asthma vs. only 17% in the lowest quartile.
- Mouse (Mus m1) allergen was detected in settled dust samples from all bedrooms and was weakly correlated with levels of coarse particulate matter (PM10) but not with PM2.5. Mouse-sensitized children exposed to > 0.5 m g/g of Mus m were more likely to have had frequent asthma exacerbations. This study documents the importance of mouse allergen as a potential risk factor for asthma in asthma in inner city homes and establishes mouse allergen contamination as an important exposure to target for intervention (Matsui et al. 2005, Matsui et al. 2006)
- Sensitized and exposed children were more likely to wake from wheeze at least once a week than non-exposed and non-sensitized children. These data demonstrate that the intensity of exposure to mouse allergen that we documented in these homes is associated with increased chronic asthma morbidity.
Project 2 – Selected Results: A Randomized, Controlled Trial of Behavioral Changes in Home Exposure Control
- A randomized, controlled trial of home environmental interventions in inner-city asthmatics enrolled 100 children in Baltimore and demonstrated that placing air cleaners containing HEPA filters in children’s bedrooms resulted in a sustained PM reduction. Thus, we have shown that a simple, feasible intervention can achieve a substantial, sustained improvement in indoor PM levels.
- Results of the initial intervention study (Eggleston et al. 2005; Breysse et al. 2005) show that 2% of the PM10 values and 17% of the PM2.5 values exceeded the EPA’s proposed National Ambient Air Quality Standards (NAAQS). The most important indoor contributor to these high levels of indoor particulate matter was environmental tobacco smoke (ETS). The results suggest that almost half of indoor air particulates in homes of persons smoking cigarettes can be attributed to cigarette smoke. The intervention was successful at reducing allergen and particulate matter levels but did not produce a marked improvement in allergy symptoms. This may be due to the fact that the asthma severity in the recruited participants was low.
Project 3 – Selected Results: Mechanisms of Particulate-Induced Allergic Asthma
- 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, plasmacytoid 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.
- 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. 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 wild type 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.
Project 4 – Selected Results: Effects of Particulate Matter on Dendritic Cell Maturation
- Result indicate that PM induces a distinct form of DC maturation that shares some features with LPS but also has a unique signature including striking down regulation of the pattern recognition receptors TLR 2 and TLR4 and the production of IL-10. In addition, the production of the Th2-polarizing cytokine IL-6 was markedly up-regulated following stimulation of iDC with PM.
- One of the most important observations made from these experiments is that PM-primed dendritic cells promote an increase in the expression of both IL13 and IFN-gamma (with an increase in the IL-13 to IFN-gamma ratio) in co-culture with CD4+ T cells.
Thus, these studies firmly implicate PM as a novel agent acting on DC to promote pro-inflammatory Th2-like immune responses. Given that Th2 immune responses are a hallmark of allergic asthma, these studies open a new area of research into how environmental pollutants affect asthma immunology.
The Johns Hopkins Children’s Center works closely with its Community Advisory Committee, which includes community members from the Baltimore school system, community-based research and service organizations, local churches and families of asthmatic children.
Johns
Hopkins Center in Urban Environmental Health 
Johns Hopkins University Urban
Health Institute (UHI)
Breysse PN, Buckley TJ, Williams D, Beck CM, Jo SJ, Merriman B, Kanchanaraksa S, Swartz LJ, Callahan KA, Butz AM, Rand CS, Diette GB, Krishnan JA, Moseley AM, Curtin-Brosnan J, Durkin NB, Eggleston PA 2005. Indoor exposures to air pollutants and allergens in the homes of asthmatic children in inner-city Baltimore. Environ Res. 2005 Jun;98(2):167-76.
Eggleston PA, Butz A, Rand C, Curtin-Brosnan J, Kanchanaraksa S, Swartz L, Breysse P, Buckley T, Diette G, Merriman B, Krishnan JA 2005. Home environmental intervention in inner-city asthma: a randomized controlled clinical trial. Ann Allergy Asthma Immunol. 2005 Dec;95(6):518-24. Comment in:Ann Allergy Asthma Immunol. 2005 Dec;95(6):496-7.
Hansel NN, Rand CS Krishnan JA, Okelo S, Breysse PN, Eggleston PA, Matsui E, Curtin-Brosnan J, Diette GB 2006. Influence of caregivers’ health beliefs and experiences on their use of environmental control practices in homes of pre-school children with asthma. Pediatric Asthma, Allergy & Immunol. 2006 Dec;19(4):231-242.
Matsui EC, Eggleston PA, Buckley TJ, Krishnan JA, Breysse PN, Rand CS, Diette GB 2006. Household mouse allergen exposure and asthma morbidity in inner-city preschool children. Ann Allergy Asthma Immunol. 2006 Oct;97(4):514-20.
Matsui EC, Simons E, Rand C, Butz A, Buckley TJ, Breysse P, Eggleston PA 2005. Airborne mouse allergen in the homes of inner-city children with asthma. J Allergy Clin Immunol. 2005 Feb;115(2):358-63.
Walters DM, Breysse PN, Schofield B, Wills-Karp M 2002. Complement factor 3 mediates particulate matter-induced airway hyperresponsiveness. Am J Respir Cell Mol Biol 2002; 27:1-6.
Walters DM, Breysse PN, Wills-Karp M 2001. Ambient urban Baltimore particulate-induced airway hyperresponsiveness and inflammation in mice. Am J Respir Critical Care Med 2001; 164:1438-1443.
Full List of Publications | Publications List from NIEHS PubMed Database
Centers Funded By: 