Grantee Research Project Results
Final Report: Genetic Basis of the Increased Susceptibility of Children to Inhaled Pollutants
EPA Grant Number: R830755Title: Genetic Basis of the Increased Susceptibility of Children to Inhaled Pollutants
Investigators: Gordon, Terry , Chen, Lung Chi , Gunnison, Albert F.
Institution: New York University School of Medicine
EPA Project Officer: Aja, Hayley
Project Period: January 31, 2003 through January 30, 2006 (Extended to January 30, 2007)
Project Amount: $749,175
RFA: Children's Vulnerability to Toxic Substances in the Environment (2002) RFA Text | Recipients Lists
Research Category: Children's Health , Human Health
Objective:
The objective of this study was to determine the biological mechanism underlying the increased susceptibility of children to inhaled pollutants. We hypothesized that there is a genetic basis for the differential response of neonatal and adult rodent lungs to inhaled pollutants. In testing this hypothesis, we: (1) compared the contribution of genetic versus environmental factors in the response to ozone; (2) identified candidate genes that may play a role in the molecular pathways leading to the increased susceptibility of the neonatal lung; and (3) compared these genes to those involved in adult lung toxicity. Our studies have demonstrated that ozone produces greater inflammation in neonatal lungs of some, but not all, inbred strains of mice.
Summary/Accomplishments (Outputs/Outcomes):
Aim I
To test the hypothesis that there is a genetic basis for the difference in response of neonate and adult mice to inhaled pollutants, eight inbred strains of neonatal and adult mice were exposed to ozone and examined for lung injury and inflammation. To ensure that strain differences in response were due to genetic factors, interstrain differences in dose, as measured by 18O in the lung, were assessed in neonatal and adult mice.
Aim I has been completed. Eight inbred strains of neonatal mice were exposed to ozone. Although we initially targeted the exposure to ozone to occur on day 18 after birth, a time-course study showed that the greatest response occurred at approximately 15 days of age, and therefore, all neonatal exposures to ozone were at 15 or 16 days of age.
Clear interstrain differences in response to ozone were observed in neonatal mice exposed to ozone at 15 or 16 days after birth. These changes were observed for the phenotypes used to study lung injury (protein) and inflammation (polymorphonuclear leukocytes [PMNs]) in lavage fluid. SJL, C3H/HeJ, and BALB/C mice were the most sensitive strains and AKR, A/J, and 129 mice were the most resistant.
This interstrain difference in response to ozone, suggested that there is a genetic component to the adverse pulmonary effects. Alternatively, as planned in the original grant application, it is possible that these interstrain differences were due to strain differences in the dose of ozone that reaches the surface fluid and epithelial cells that line the lung. Therefore, adult and neonatal mice from two sensitive and two resistant strains were exposed to ozone generated from 18-oxygen to examine the dose of ozone delivered to each strain. These studies were done in collaboration with Dr. G. Hatch (U.S. Environmental Protection Agency [EPA]) and demonstrated that the dose of ozone delivered to the lung was not important in the observed interstrain differences in lung injury and inflammation in neonatal mice. Moreover, the ozone dose did not account for the increased susceptibility of neonatal mice compared to adult mice of the same strain.
In addition, our studies have demonstrated that the increased susceptibility of neonatal mice to ozone-induced pulmonary inflammation does not extend to lung injury (total protein measured in lavage fluid as a marker of injury to the epithelial-endothelial cell barrier). Moreover, the adult mice experiments unexpectedly demonstrated a slight but statistically significant greater increase in lung response in female versus male adult mice.
Aim 2
To identify candidate genes that play a critical role in the differential response of neonatal and adult mice to ozone, we identified quantitative trait loci (QTL) that are associated with the response of neonatal mice to ozone by using both a classic genetic method and a state-of-the-art computational genomics method. To identify the most likely candidate genes within these chromosomal loci, the QTL results were cross-linked to microarray expression data.
The experiments proposed in Aim 2 are complete. An F2 generation of neonatal mice was bred from F1 mice generated from sensitive BALB/C and resistant A/J progenitor mice and then exposed to ozone using the protocol identical to that used to expose the eight strains of inbred neonatal and adult mice. The response of F1 neonatal mice suggested that the sensitivity/resistance of the mice to ozone-induced lung injury and inflammation was a heritable trait. The F2 mice have been phenotyped, their DNA isolated, and the genotyping is complete. A quantitative linkage analysis determined that suggestive quantitative linkage loci (QTL) are present on the proximal portions of chromosomes 7 and 14.
Because the genetic diversity of the F2 study was limited to two inbred strains of mice, a second F2 experiment (not part of the original study design) was conducted using two additional sensitive and resistant strains of mice. This second study will allow us to narrow our search for candidate genes within the proximal regions of chromosomes 7 and 14 from the first F2 study, as well as identify any additional linkage sites that may have been missed during the analysis of the results from a study limited to two strains. This second F2 study has been completed, although the genetic computations are still in progress. Follow-up work on this second F2 study will be completed in Dr. Gordon’s laboratory.
The second proposed experiment, to develop microarray expression data to compare to the significant loci identified by the quantitative linkage analysis study in the F2 mice, has been completed. The expression array data have been analyzed, and candidate genes that are highly up- or down-regulated within the QTLs observed in the first F2 linkage analysis study have been determined. Given the continual improvements in statistical analysis software, it is likely that the microarray expression data will be reanalyzed as new software becomes available and when the QTLs in the second F2 study are identified.
Conclusions:
Our studies have confirmed the hypothesis that the neonatal mammalian lung is more sensitive than the adult lung, at least in terms of the inflammatory response to inhaled ozone. The greater sensitivity of neonatal mice compared to adult mice occurred in seven of the eight strains tested, although the age-dependent effect was particularly strong for two strains. Because: (1) this susceptibility trait was inherited in F1 generation mice bred from sensitive and resistant strains; and (2) the 18O studies showed that dose was not involved, our findings suggest that a genetic factor plays a significant role in the age-dependent response to ozone. Finally, the F2 study delineated multiple linkage sites with trait contributions less than 25%, thus suggesting that this age-dependent effect is polygenic. Thus, this project has determined that multiple factors, including age and gender, play significant roles in the response of the mammalian lung to ambient ozone.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 2 publications | 1 publications in selected types | All 1 journal articles |
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Vancza EM, Galdanes K, Gunnison A, Hatch G, Gordon T. Age, strain, and gender as factors for increased sensitivity of the mouse lung to inhaled ozone. Toxicological Sciences 2009;107(2):535-543. |
R830755 (Final) |
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Supplemental Keywords:
ozone, children, ambient air, mice, genetic susceptibility,, RFA, Health, Scientific Discipline, INTERNATIONAL COOPERATION, ENVIRONMENTAL MANAGEMENT, Health Risk Assessment, Children's Health, Environmental Policy, Biology, Risk Assessment, sensitive populations, age-related differences, biological response, gene-environment interaction, genetic predisposition, air pollution, genetic mechanisms, ozone induced airway dysfunction, assessment of exposure, children's vulnerablity, genetic risk factors, inhalation, susceptibility, children's environmental health, exposure assessmentProgress and Final Reports:
Original AbstractThe 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.