Ozone is a powerful oxidant and respiratory irritant that leads to airway inflammation and pulmonary dysfunction. Although a greater susceptibility to inhaled ozone in children is not yet firmly established, rodent studies have shown neonates to be more sensitive than adults. Furthermore, previous mouse studies in my lab have shown clear and quantitative age and inter-strain differences in response to ozone inhalation. The current research sought to test the hypotheses that genetics plays an important role in the development of ozone sensitivity and that the underlying genes involved in this sensitivity are different in pups versus adult mice. Using classic intercross and in silico haplotype mapping linkage analyses, genome-wide searches for quantitative trait loci (QTLs) were conducted with data from inbred and F2 intercross neonatal mice (15 to 16d old) that were phenotyped for total protein and PMNs in lung lavage after exposure to 5h of 0.8 ppm ozone. Significant QTLs were identified on chromosomes (chrs) 3 and 14, with suggestive QTLs on 3, 5 and 14 for the protein phenotype, and significant QTLs were identified on chrs 2, 6, 7, 9 and 12, with suggestive QTLs on 2, 6 and 15 for the PMN phenotype. To investigate candidate genes that may be involved in the molecular mechanism(s) regulating ozone sensitivity, gene expression microarray data, collected from adult (15 wks) and neonatal mice from 2 resistant and 2 sensitive strains, were compared to QTL data. Significantly modulated genes were 3-7 times less in number in pups versus adults, and several significantly up- and down-regulated genes were identified exclusively in sensitive- or resistant-pup mouse strains. Using post-annotation of gene lists and comparison of gene locations with QTL results, 10 candidate genes were further analyzed using RT-RT-PCR and were related to oxidative stress (Cyp1a1, Hmox1), inflammation (Muc5ac), transcriptional regulation and development (Bmp4, Egr1, Fos, Foxp1, Ltk, Nfil3, Stat1). Overall, results from this study not only suggest a genetic component to age-related ozone-sensitivity, but also an involvement of multiple genes and overlapping mechanisms underlying this complex trait.
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