Published ahead of print on November 29, 2007, doi:10.1164/rccm.200706-863OC
© 2008 American Thoracic Society doi: 10.1164/rccm.200706-863OC
Ozone, Oxidant Defense Genes, and Risk of Asthma during Adolescence1 Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, California Correspondence and requests for reprints should be addressed to Frank Gilliland, M.D. Ph.D., Department of Preventive Medicine, USC Keck School of Medicine, 1540 Alcazar Street, CHP 236, Los Angeles, CA 90033. E-mail: gillilan{at}usc.edu Rationale: Although oxidative stress is a cardinal feature of asthma, the roles of oxidant air pollutants and antioxidant genes heme oxygenase 1 (HMOX-1), catalase (CAT), and manganese superoxide dismutase (MNSOD) in asthma pathogenesis have yet to be determined. Objectives: We hypothesized that the functional polymorphisms of HMOX-1 ([GT]n repeat), CAT (–262C>T –844C>T), and MNSOD (Ala-9Val) are associated with new-onset asthma, and the effects of these variants vary by exposure to ozone, a potent oxidant air pollutant. Methods: We assessed this hypothesis in a population-based cohort of non-Hispanic (n = 1,125) and Hispanic white (n = 586) children who resided in 12 California communities and who were followed annually for 8 years to ascertain new-onset asthma. Measurements and Main Results: Air pollutants were continuously measured in each of the study communities during the 8 years of study follow-up. HMOX-1 "short" alleles (<23 repeats) were associated with a reduced risk for new-onset asthma among non-Hispanic whites (hazard ratio [HR], 0.64; 95% confidence interval [CI], 0.41–0.99). This protective effect was largest in children residing in low-ozone communities (HR, 0.48; 95% CI, 0.25–0.91) (interaction P value = 0.003). Little evidence for an association with HMOX-1 was observed among Hispanic children. In contrast, Hispanic children with a variant of the CAT-262 "T" allele (CT or TT) had an increased risk for asthma (HR, 1.78; P value = 0.01). The effects of these polymorphisms were not modified by personal smoking or secondhand-smoke exposure. Conclusions: Functional promoter variants in CAT and HMOX-1 showed ethnicity-specific associations with new-onset asthma. Oxidant gene protection was restricted to children living in low-ozone communities.
Key Words: asthma • catalase • heme oxygenase-1 • MnSOD • oxidative stress • ozone
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