Grantee Research Project Results
2015 Progress Report: Environmental Determinants of Early Host Response to RSV
EPA Grant Number: R834515C002Subproject: this is subproject number 002 , established and managed by the Center Director under grant R834515
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Denver Childrens Environmental Health Center - Environmental Determinants of Airway Disease in Children
Center Director: Guo, Yanbing
Title: Environmental Determinants of Early Host Response to RSV
Investigators: Schwartz, David A. , White, Carl W. , Dakhama, Azzeddine , Yang, Jing , Loader, Joan , Correll, Kelly , Gabehart, Kelsa
Institution: National Jewish Health , University of North Carolina at Charlotte , National Jewish Medical and Research Center , University of Colorado at Denver
Current Institution: National Jewish Health , National Jewish Medical and Research Center , University of Colorado at Denver , University of North Carolina at Charlotte
EPA Project Officer: Hahn, Intaek
Project Period: June 22, 2010 through June 21, 2015 (Extended to June 21, 2017)
Project Period Covered by this Report: June 22, 2015 through June 21,2016
RFA: Children's Environmental Health and Disease Prevention Research Centers (with NIEHS) (2009) RFA Text | Recipients Lists
Research Category: Children's Health , Human Health
Objective:
The pollutant ozone is suspected to play a significant role in the development and exacerbation of reactive airway diseases such as asthma. Ozone exposure may alter lung development and growth, especially in the early postnatal development phase, resulting in increased susceptibility to airway obstruction upon subsequent viral infection and allergen exposure. Ozone exposure also can influence the innate immune response by increasing Toll-like receptor (TLR)-4 expression, thereby increasing airway responsiveness to bacterial endotoxin (LPS). LPS also is known to mature dendritic cells, the primary immune cell subset that initiates T cell differentiation and directs the adaptive response. The overall hypothesis of this project is that ozone exposure, in the early postnatal phase, alters lung development and modifies the host immune response to early life viral infection and allergen exposure, thereby contributing to the development of reactive airway disease. In the presence of LPS, however, lung development will be sustained and the host immune response will mature and protect the newborn against the development of altered airway responses to viral infection and allergen exposure.
Specific Aim 1: To define the influence of ozone exposure on TLR expression and airway structure and function.
Specific Aim 2: To define the influence of ozone exposure on airway responsiveness to respiratory syncytial virus (RSV) and allergen.
Specific Aim 3: To determine if and how LPS can modify airway responsiveness to RSV infection and allergen, following postnatal exposure to ozone.
Progress Summary:
The overall objective of this project is to define the influence of ozone exposure on the developing postnatal lung. To obtain a better understanding of the neonatal lung response to ozone, we first used a genome-wide gene expression analysis approach. The results identified several novel genes and molecular pathways never associated before with ozone exposure. The pattern of gene expression and the molecular pathways perturbed by ozone in the neonatal lung also differed from those described previously for fully developed adult lungs. In particular, while tissue injury and inflammation are the predominant pathways induced by ozone exposure in the adult lung, it was mainly cell cycle-associated functions, including cell division/proliferation that were altered (mostly suppressed) after ozone exposure in the developing newborn lung. This suppression of cell cycle was further shown to be associated with significant inhibition of cell proliferation in the neonatal lung. This finding raised the important question as to whether such reduced cell proliferation could lead to permanent damage to the developing lung (altered lung growth or altered structure and function). Follow-up studies analyzing lung function 2 weeks after ozone exposure (when the mice were juvenile) showed no significant alteration in airway responsiveness to methacholine, but a small change was detected in other respiratory function parameters measured by whole body plethysmography (i.e., increased expiration time (Te), associated with decreased mid-expiratory flow at 50% volume (EF50)). Whether more sustained damage may occur under certain genetic susceptibilities is an important question to be addressed in the future.
An intriguing observation we have made in these studies was the attenuated inflammatory response that develops in the neonatal lung after ozone exposure. To understand the mechanisms underlying this apparent low responsiveness of newborns to ozone, we examined the response in various age groups of mice from neonates (1-week old) to adults (6-week old). The results demonstrated that neonatal mice, compared to adult mice, expressed low levels of pulmonary TLR-4 but responded with increased mucus production, and developed an attenuated response to ozone characterized by reduced albumin leakage and reduced neutrophils influx into the airways, associated with lower expression of the neutrophilic chemokines CXCL1 and CXCL2. Examination of the responses in TLR4-deficient mice further revealed that TLR-4 was required for the development of ozonemediated airway neutrophilia but not for albumin leakage or mucus production. This demonstrates that the response to ozone is determined by age and is partially dependent on TLR-4 signaling, and suggests that the reduced responsiveness of the neonatal lung to ozone could be due at least in part to insufficient expression of pulmonary TLR-4 in this early age.
The role of neutrophils in ozone-mediated injury is not established. To determine the role of neutrophils in the response to ozone, we depleted these cells with anti-Ly6G antibody and examined the responses at 6 and 24 h following a 3-h exposure to 1,000 ppb of ozone. Depletion was confirmed by flow cytometry and cytological analysis of blood smears and BAL cells. Because the neutrophilic response was too small in the neonatal lung, we used adult mice where the neutrophilic response to ozone is vigorous. In our studies, mice exposed to 1,000 ppb ozone for 3 h only developed a mild airway hyperresponsiveness (AHR) to methacholine that subsided by 24 h post-exposure. However, following depletion of neutrophils, AHR was slightly elevated at 6 h and was markedly enhanced by 24 h post-ozone exposure, suggesting a protective role for neutrophils in this response to ozone. Interestingly, albumin leakage was not altered following neutrophils depletion, indicating that this response is not dependent on, or regulated, by neutrophils. Further studies will be necessary to define the mechanisms whereby neutrophils may protect against the development of altered airway responsiveness following ozone exposure.
Ozone is suspected to promote the development of allergic asthma possibly by facilitating allergic sensitization. In our studies, acute postnatal ozone exposure did not increase allergic airway inflammation or antibody response to subsequent exposure to house dust mite allergen, indicating that ozone may not increase allergic sensitization in the developing neonatal mice. However, ozone exposure increased house dust mite-mediated AHR in these mice through a mechanism that remains to be defined.
We have recently completed studies examining the effects of postnatal ozone exposure on RSV infection. Preliminary analysis demonstrated that primary neonatal RSV infection induced a small but significant production of IL-4 and IL-5, but almost no IFN-g production from lung T cells. On re-infection, these mice developed an asthma-like phenotype with increased Th2 response and enhanced AHR, consistent with our previous studies (Dakhama et al. 2005, J Immunol 175:1876-83; Lee et al. 2008, AJRCCM 177:208-18). Following postnatal ozone exposure, the cytokine responses to either the primary or the secondary RSV infection were not altered significantly. However, despite a reduced airway eosinophilia, AHR was significantly increased following the secondary RSV infection in ozone-exposed mice, compared with FA-exposed mice. These findings are surprisingly similar to those obtained for HDM allergen exposure and further suggest that ozone may promote the development of reactive airway disease in response to common triggers (RSV or allergen) through a common pathway that does require increased sensitization or inflammation.
References:
Dakhama et al. 2005, J Immunol 175:1876-83
Lee et al. 2008, AJRCCM 177:208-18
Journal Articles on this Report : 2 Displayed | Download in RIS Format
| Other subproject views: | All 23 publications | 13 publications in selected types | All 13 journal articles |
|---|---|---|---|
| Other center views: | All 51 publications | 30 publications in selected types | All 30 journal articles |
Supplemental Keywords:
Endotoxin, exposure, children, asthma, risk, health effects, susceptibility, sensitive populations, genetic pre-disposition, genetic polymorphism, indoor air, dose-response, ozone, remediation, human health, health, health effects, biology, health risk assessment, children's health, allergens/asthma, asthma indices, intervention, Health, Scientific Discipline, HUMAN HEALTH, Health Risk Assessment, Allergens/Asthma, Health Effects, Biology, asthma, asthma triggers, sensitive populations, endotoxin, asthma indices, airway inflammation, children, allergic responseRelevant Websites:
Department of Biomedical Research | National Jewish Health Exit
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R834515 Denver Childrens Environmental Health Center - Environmental Determinants of Airway Disease in Children Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R834515C001 Endotoxin Exposure and Asthma in Children
R834515C002 Environmental Determinants of Early Host Response to RSV
R834515C003 Environmental Determinants of Host Defense
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
13 journal articles for this subproject
Main Center: R834515
51 publications for this center
30 journal articles for this center