Association Between Antibiotic Exposure, Bronchiolitis, and TLR4 (rs1927911) Polymorphisms in Childhood Asthma

PURPOSE: The complex interplay between environmental and genetic factors plays an important role in the development of asthma. Several studies have yielded conflicting results regarding the 2 asthma-related risk factors: antibiotic usage during infancy and/or a history of bronchiolitis during early life and the development of asthma. In addition to these risk factors, we also explored the effects of Toll-like receptor 4 (TLR4) polymorphism on the development of childhood asthma. METHODS: This cross-sectional study involved 7,389 middle school students who were from 8 areas of Seoul, Korea, and completed the International Study of Asthma and Allergies in Childhood questionnaire. The TLR4 polymorphism rs1927911 was genotyped in 1,395 middle school students from two areas using the TaqMan assay. RESULTS: Bronchiolitis in the first 2 years of life, antibiotic exposure during the first year of life, and parental history of asthma were independent risk factors for the development of asthma. When combined, antibiotic use and a history of bronchiolitis increased the risk of asthma (adjusted odds ratio [aOR]: 4.64, 95% confidence interval [CI]: 3.09-6.97, P value for interaction=0.02). In subjects with CC genotype of TLR4, antibiotic exposure and a history of bronchiolitis during infancy, the risk of asthma was increased, compared to subjects without these risk factors (aOR: 5.72, 95% CI: 1.74-18.87). CONCLUSIONS: Early-life antibiotic exposures and a history of bronchiolitis are risk factors for asthma in young adolescents. Polymorphisms of TLR4 modified the influence of these environmental factors. Reducing antibiotic exposure and preventing bronchiolitis during infancy may prevent the development of asthma, especially in genetically susceptible subjects.

Association between Recent Acetaminophen Use and Asthma: Modification by Polymorphism at TLR4

The risk of asthma has been increasing in parallel with use of acetaminophen, which is a potential source of oxidative stress. Toll-like receptor 4 (TLR4) plays a critical role not only in innate immunity, but also in mediating reactive oxygen species induced inflammation. Therefore, we investigated associations between acetaminophen usage and TLR4 polymorphism on asthma and bronchial hyperresponsiveness (BHR). The number of 2,428 elementary school children in Seoul and Jeongeup cities was recruited. Subjects who used acetaminophen with a family history of asthma had an increased risk of both asthma diagnosis ever and current asthma. Individuals with CT+TT genotypes at the TLR4 polymorphism, in combination with acetaminophen usage, also demonstrated an increased risk of asthma diagnosis ever (aOR, 2.08; 95% confidence interval [CI], 1.10-3.92). Family history of asthma and acetaminophen usage were risk factors for BHR. Although TLR4 was not an independent risk factor for BHR, individuals with CT+TT genotypes at the TLR4 polymorphism had an increased risk of BHR when combined with acetaminophen usage (aOR, 1.74; 95% CI, 1.03-2.94). In conclusion, acetaminophen usage may be associated with asthma and BHR in genetically susceptible subjects. This effect may be modified by polymorphism at TLR4.

Gene-environment interaction between Toll-like receptor 4 and mold exposure in the development of atopic dermatitis in preschool children

PURPOSE: Genetic factors and environmental exposures are recognized as important risk factors for atopic dermatitis (AD) in children. Inflammatory responses by molds can be mediated via Toll-like receptor 4 (TLR4). The aims of this study were to investigate mold as risk factor of AD and gene-environment interaction on AD in preschool children. METHODS: We undertook a cross-sectional survey with 986 preschool children. We investigated five mold exposure measures (dampness stain, dampness damage, visible mold, mold odor, and house repair). The TLR4 polymorphism (rs1927911) was genotyped by TaqMan assay. RESULTS: The prevalence of AD was as follows: AD diagnosis by questionnaire, 35.1%; current AD (lifetime diagnosis together with symptoms in the last 12 months), 21.5%. When children with parental history of AD were exposed to mold odor during infancy and house repair during the last 12 months, the risk for current AD (adjusted odds ratio [aOR], 6.826; 95% confidence interval [CI], 2.511 to 18.554 vs. aOR, 6.143; 95% CI, 2.348 to 16.074) was further increased than only with parental history of AD. In children with the CC genotype of TLR4 polymorphism, the risk of AD was increased by mold exposure. CONCLUSION: This investigation identified that mold exposure is potential risk factor for AD in preschool children. Parental history of AD and mold exposure during infancy and the last 12 months had synergistic effect on high prevalence of AD. We identified that mold exposure and TLR4 polymorphism have an effect on the development of atopic dermatitis.