Juan-Jose Sienra-Monge

GSTM1 and GSTP1 and respiratory health in asthmatic children exposed to ozone

Acute exposure to ozone has been related to a wide spectrum of health effects in susceptible individuals. Genetic factors may influence interindividual variation in ozone response. The current authors investigated the relationships between common polymorphisms in two genes involved in response to oxidative stress, i.e. glutathione S-transferases M1 (GSTM1) and P1 (GSTP1), and both respiratory symptoms and lung function in response to ozone among childhood asthmatics. A total of 151 asthmatic children, who were participants in a randomised controlled trial of antioxidant vitamin supplementation in Mexico City, were studied. Children were genotyped using PCR methods and followed from October 1998–April 2000. Increases in reported breathing difficulty were associated with ozone exposure in children with GSTM1 null (8%, 95% confidence interval (CI) 1–15%, per 20-ppb increase in 1-h maximum daily average over 7 days) or GSTP1 Valine/Valine (Val/Val) genotypes (14%, 95% CI 5–25%). In children with both GSTM1 null and GSTP1 Val/Val genotypes, the increase in breathing difficulty associated with a 20-ppb increase in ozone exposure was even greater (21%, 95% CI 5–39%). GSTP1 genotypes were not significantly associated with ozone-related lung function changes. In conclusion, asthmatic children with glutathione S-transferase M1 null and glutathione S-transferase P1 Valine/Valine genotypes appear more susceptible to developing respiratory symptoms related to ozone exposure.

Genetic variation in ORM1-like 3 (ORMDL3) and gasdermin-like (GSDML) and childhood asthma.

Background:  A genome‐wide association study identified ORM1‐like 3 (orosomucoid 1‐like 3, ORMDL3) as an asthma candidate gene. Single nucleotide polymorphisms (SNPs) in the region including ORMDL3 on chromosome 17q21 were related to childhood asthma risk and ORMDL3 expression levels in Europeans.

Evaluation of candidate genes in a genome-wide association study of childhood asthma in Mexicans.

BACKGROUND More than 200 asthma candidate genes have been examined in human association studies or identified with knockout mouse approaches. However, many have not been systematically replicated in human populations, especially those containing a large number of tagging single nucleotide polymorphisms (SNPs). OBJECTIVE We comprehensively evaluated the association of previously implicated asthma candidate genes with childhood asthma in a Mexico City population. METHODS From the literature, we identified candidate genes with at least 1 positive report of association with asthma phenotypes in human subjects or implicated in asthma pathogenesis using knockout mouse experiments. We performed a genome-wide association study in 492 asthmatic children aged 5 to 17 years and both parents using the Illumina HumanHap 550v3 BeadChip. Separate candidate gene analyses were performed for 2933 autosomal SNPs in the 237 selected genes by using the log-linear method with a log-additive risk model. RESULTS Sixty-one of the 237 genes had at least 1 SNP with a P value of less than .05 for association with asthma. The 9 most significant results were observed for rs2241715 in the gene encoding TGF-beta1 (TGFB1; P = 3.3 x 10(-5)), rs13431828 and rs1041973 in the gene encoding IL-1 receptor-like 1 (IL1RL1; P = 2 x 10(-4) and 3.5 x 10(-4)), 5 SNPs in the gene encoding dipeptidyl-peptidase 10 (DPP10; P = 1.6 x 10(-4) to 4.5 x 10(-4)), and rs17599222 in the gene encoding cytoplasmic FMR1 interacting protein 2 (CYFIP2; P = 4.1 x 10(-4)). False discovery rates were less than 0.1 for all 9 SNPs. Multimarker analysis identified TGFB1, IL1RL1, the gene encoding IL-18 receptor 1 (IL18R1), and DPP10 as the genes most significantly associated with asthma. CONCLUSIONS This comprehensive analysis of literature-based candidate genes suggests that SNPs in several candidate genes, including TGFB1, IL1RL1, IL18R1, and DPP10, might contribute to childhood asthma susceptibility in a Mexican population.

Antioxidant supplementation and nasal inflammatory responses among young asthmatics exposed to high levels of ozone

The inflammatory response to ozone in atopic asthma suggests that soluble mediators of inflammation are released in response to oxidant stress. Antioxidants may alleviate additional oxidative stress associated with photochemical oxidant pollution. This study investigates the impact of antioxidant supplementation on the nasal inflammatory response to ozone exposure in atopic asthmatic children. We conducted a randomized trial using a double‐blinded design. Children with asthma (n = 117), residents of Mexico City, were given randomly a daily supplement of vitamins (50 mg/day of vitamin E and 250 mg/day of vitamin C) or placebo. Nasal lavages were performed three times during the 4‐month follow‐up and analysed for content of interleukin‐6 (IL‐6), IL‐8, uric acid and glutathione (GSx). IL‐6 levels in the nasal lavage were increased significantly in the placebo group after ozone exposure while no increase was observed in the supplement group. The difference in response to ozone exposure between the two groups was significant (P = 0·02). Results were similar for IL‐8, but with no significant difference between the groups (P = 0·12). GSx decreased significantly in both groups. Uric acid decreased slightly in the placebo group. Our data suggest that vitamin C and E supplementation above the minimum dietary requirement in asthmatic children with a low intake of vitamin E might provide some protection against the nasal acute inflammatory response to ozone.

Traffic-related air pollution and respiratory symptoms among asthmatic children, resident in Mexico City: the EVA cohort study

BackgroundTaffic-related air pollution has been related to adverse respiratory outcomes; however, there is still uncertainty concerning the type of vehicle emission causing most deleterious effects.MethodsA panel study was conducted among 147 asthmatic and 50 healthy children, who were followed up for an average of 22 weeks. Incidence density of coughing, wheezing and breathing difficulty was assessed by referring to daily records of symptoms and childs medication. The association between exposure to pollutants and occurrence of symptoms was evaluated using mixed-effect models with binary response and poisson regression.ResultsWheezing was found to relate significantly to air pollutants: an increase of 17.4 μg/m3 (IQR) of PM2.5 (24-h average) was associated with an 8.8% increase (95% CI: 2.4% to 15.5%); an increase of 34 ppb (IQR) of NO2 (1-h maximum) was associated with an 9.1% increase (95% CI: 2.3% to16.4%) and an increase of 48 ppb (IQR) in O3 levels (1 hr maximum) to an increase of 10% (95% CI: 3.2% to 17.3%). Diesel-fueled motor vehicles were significantly associated with wheezing and bronchodilator use (IRR = 1.29; 95% CI: 1.03 to 1.62, and IRR = 1.32; 95% CI: 0.99 to 1.77, respectively, for an increase of 130 vehicles hourly, above the 24-hour average).ConclusionRespiratory symptoms in asthmatic children were significantly associated with exposure to traffic exhaust, especially from natural gas and diesel-fueled vehicles.

Parental Smoking Modifies the Relation between Genetic Variation in Tumor Necrosis Factor-[Alpha] (TNF) and Childhood Asthma

Background Polymorphisms in the proinflammatory cytokine genes tumor necrosis factor-α (TNF) and lymphotoxin-α (LTA, also called TNF-β) have been associated with asthma and atopy in some studies. Parental smoking is a consistent risk factor for childhood asthma. Secondhand smoke and ozone both stimulate TNF production. Objectives Our goal was to investigate whether genetic variation in TNF and LTA is associated with asthma and atopy and whether the association is modified by parental smoking in a Mexican population with high ozone exposure. Methods We genotyped six tagging single nucleotide polymorphisms (SNPs) in TNF and LTA, including functional variants, in 596 nuclear families consisting of asthmatics 4–17 years of age and their parents in Mexico City. Atopy was determined by skin prick tests. Results The A allele of the TNF-308 SNP was associated with increased risk of asthma [relative risk (RR) = 1.54; 95% confidence interval (CI), 1.04–2.28], especially among children of non-smoking parents (RR = 2.06; 95% CI, 1.19–3.55; p for interaction = 0.09). Similarly, the A allele of the TNF-238 SNP was associated with increased asthma risk among children of nonsmoking parents (RR = 2.21; 95% CI, 1.14–4.30; p for interaction = 0.01). LTA SNPs were not associated with asthma. Haplotype analyses reflected the single SNP findings in magnitude and direction. TNF and LTA SNPs were not associated with the degree of atopy. Conclusions Our results suggest that genetic variation in TNF may contribute to childhood asthma and that associations may be modified by parental smoking.

Obesity risk factors in the ISAAC (International Study of Asthma and Allergies in Childhood) in Mexico City

BACKGROUND The International Study of Asthma and Allergies in Childhood (ISAAC) has promoted surveys in asthma and allergic diseases using standardized methodologies including validated questionnaires. Many items in the questionnaires have also been implied in the overweight and obesity etiology. OBJECTIVE To describe the factors associated with obesity in subjects of 6-7 years and 13-14 years in the ISAAC survey in Mexico City. MATERIAL AND METHODS Data were obtained from questionnaires of children participating in a phase 3b ISAAC survey. Logistic regression was used to determine the obesity risks factors. RESULTS The factors related to obesity were weekly consumption of meat (+, positive relationship), vegetables, pasta, rice (+) and quartiles of birth weight (+) in boys of 6-7 years. Having suffered eczema at any time, weekly consumption of fruit, pasta, butter, nuts, potato (+), fast food (+), daily TV viewing (+) in girls of 6-7years. Having suffered eczema at any time, weekly consumption of pasta (+), butter, potato, weekly physical exercise in boys of 13-14 years; weekly consumption of pasta, margarine, milk, fast food (+), currently smoking in girls of 13-14 years. CONCLUSIONS There were not common factor patterns for the different groups, birth weight, fast food, TV viewing and lack of exercise have been previously related to pediatric obesity. Asthma was not associated with a higher risk of obesity but medical history of eczema was associated with lower risk of obesity in the 6-7 years girls, and 13-14 years boys. The present study provides the bases for future epidemiological studies and gives some clues on possible public health actions.

Elemental carbon exposure and lung function in schoolchildren from Mexico City

Though exposure to air pollution has a detrimental effect on respiratory health, few studies have examined the association between elemental carbon exposure and lung function among schoolchildren. The aim of the present study was to present the association between short-term elemental carbon exposure and lung function in schoolchildren from Mexico City. 55 asthmatic and 40 non-asthmatic children were followed for an average of 22 weeks. A spirometry test was performed every 15 days during follow-up. Portable air samplers collected particulate matter onto Teflon filters. Gravimetric analysis was conducted and elemental carbon was quantified using transmission densitometry. The association between the main variables was analysed using linear mixed effects models. The mean±sd of elemental carbon light absorption was 92.7±54.7 Mm−1. An increase of one interquartile range in the 24-h average of elemental carbon (100.93 Mm−1) was associated with a significant negative impact on forced expiratory volume in 1 s (FEV1) (-62.0 (95% CI -123.3– -1.2) mL) and forced expiratory flow at 25–75% of forced vital capacity (FVC) (FEF25–75%) (-111 (95% CI -228.3– -4.1) mL) among asthmatic children, equal to 3.3% and 5.5%, respectively; and on FEV1 (-95.0 (95% CI -182.3– -8.5) mL) and FVC (-105.0 (95% CI -197.0– -13.7) mL) among non-asthmatic children. Exposure to elemental carbon resulted in an important negative effect on lung function in atopic schoolchildren, regardless of asthma status.

STAT6 and LRP1 polymorphisms are associated with food allergen sensitization in Mexican children

To the Editor: Food allergy, affecting up to 8% of children in the United States,1 is most often mediated by allergen specific immunoglobulin E (IgE) antibodies in the blood. Food allergen sensitization is an intermediate phenotype measured by specific IgE blood tests or skin prick tests (SPTs) and used in the diagnosis of food allergy. Despite family history being a risk factor, no genetic variants have been conclusively identified for food sensitization or clinical food allergy.2 Using the Mexico City Childhood Asthma Study (MCCAS), we examined associations between food sensitization (based on SPTs) and single nucleotide polymorphisms (SNPs) spanning five autosomal candidate genes reviewed by Hong et al. [CD14 (cluster of differentiation 14), IL10 (interleukin 10), IL13 (interleukin 13), SPINK5 (serine peptidase inhibitor, Kazal type 5 isoform), and STAT6 (signal transducer and activator of transcription)].2 We previously conducted a genome-wide association study of asthma in MCCAS among 492 children with physician-diagnosed asthma (aged 5-17) and their parents, who were recruited from a pediatric allergy clinic in Mexico City.3 The children’s clinical evaluation included SPTs to six major food allergens that are common in the Mexican diet (milk, egg, wheat, soy, peanuts, and tree nuts). A SPT was declared positive if the largest diameter of the wheal exceeded 4mm. Testing was considered valid if the reaction to the positive control (histamine) exceeded 6 mm and also exceeded 4 mm above the negative control (glycerin).4 There were 162 trios having an asthmatic child with a positive SPT to at least one food allergen. We examined SNP associations with food sensitization in the five candidate genes in these 162 trios.2 As all probands are asthmatics, it is not possible to adjust for asthma. These associations are generalizable to the asthmatic population, but not necessarily to the general population. Genotyping was performed on the Illumina HumanHap 550v3 BeadChip, and standard quality control filters were applied.3 For this analysis, we selected SNPs spanning five candidate gene regions (20kb upstream of the 5′ end through 20kb downstream of the 3′ end), resulting in 343 SNPs (16 CD14, 52 IL10, 39 IL13, 28 STAT6, and 208 SPINK5 SNPs). SNPs were directly genotyped or imputed using MaCH (http://www.sph.umich.edu/csg/abecasis/MACH/index.html) with HapMap phase II release 21 reference haplotypes combined from CEU (European Americans), YRI (African Americans), and CHB+JPT (Chinese+Japanese). PBAT v3.61 (http://www.biostat.harvard.edu/~clange/default.htm) was used to conduct family-based association tests on additive SNP genotype dosage values (estimated reference allele counts with a fractional value ranging from 0 to 2.0). To correct for multiple testing, Bonferroni correction for the total number of SNPs (P<α/M, where M is the number of independent tests) is too conservative, given our observed correlation patterns among SNPs. Therefore, we applied the widely-used Nyholt correction (P<α/Meff), which adjusts for the effective number of independent tests (Meff) based on the correlation matrix of pairwise LD among the SNPs.5,6 This method gave a significance threshold of P<0.0011 A less conservative significance threshold based on the number of candidate genes examined is P<0.01. Association results and LD patterns were plotted together using SNAP (http://www.broadinstitute.org/mpg/snap/). In the 162 trios with a food allergen sensitized child, no SNP associations were statistically significant at P<0.0011. However, three genotyped SNPs in or near STAT6 were associated with food sensitization at P<0.01 (Table I), two intronic SNPs in the nearby LRP1 (low density lipoprotein receptor-related protein 1) gene and a 3′ untranslated STAT6 SNP. Their minor allele frequencies were lower in the food sensitized children (39.5% for the top SNP rs4759044) compared to the children with no sensitization to the six food allergens (42.2% for rs4759044). The STAT6 and LRP1 SNPs are in moderate LD in CEU (Figure 1, r2=0.34-0.37) and weaker LD in YRI (r2=0.08-0.24) and CHB+JPT (r2=0.12-0.13). Of 28 SNPs spanning the STAT6 region, none were associated with asthma at P<0.05, despite a three-fold greater sample size and thus more statistical power (Table I). There was minimal evidence for SNP associations with food sensitization across CD14, IL10, IL13 or SPINK5 (results not shown). Figure 1 Association results and linkage disequilibrium patterns of SNPs in or near STAT6 (±20kb). Correlations between the SNP with the lowest P value (rs4759044) and surrounding SNPs are shown with reference to the HapMap CEU population, with darker ... Table I Associations of the 28 SNPs examined in or near STAT6 (±20kb) in 492 trios with an asthmatic child and the subset of 162 trios with a food sensitized child (at least one positive skin prick test to six major food allergens). The flanking regions ... Another 3′ untranslated STAT6 SNP (rs324015) was previously associated with risk for, and severity of, nut allergy in white atopic children from the United Kingdom,7 but this association was not corroborated for severity of food allergy in Japanese children.8 In our study of Mexican children, rs324015 gave a P value of 0.072, but its adjacent SNP (rs703817) was associated with food sensitization at P=0.0076. The implicated SNPs may tag underlying functional or regulatory variants, and it is not surprising that association patterns vary across populations with dissimilar LD patterns. LRP1 and its protein product have been largely implicated in neurologic processes. STAT6 SNPs have been associated with food allergy,7,8 asthma,9 total IgE,10 and eosinophilic esophagitis.11 STAT6 plays a central role in mediating IL4 (interleukin 4) and IL13 signals for IgE antibody production.2 Given its biological role, STAT6 polymorphisms are more likely than LRP1 polymorphisms to influence food sensitization. Nonetheless, the association patterns between STAT6 and LRP1 SNPs reflect moderate LD with low recombination across the region (Figure 1). While our findings might not be generalizable to the general population, we provide evidence that STAT6 and LRP1 polymorphisms are associated with food sensitization in asthmatics, who are at particularly high risk for developing sensitization. Follow-up studies in Hispanics and other ethnicities could help to refine these associations with food sensitization and clinical food allergy.

Formoterol vs. Albuterol administered via Turbuhaler® System in the emergency treatment of acute asthma in children

BACKGROUND Formoterol is a new beta 2 agonist with a duration of 8-12 hours. Albuterol is a beta 2-agonist with rapid onset of action and a duration of approximately 6 hours. OBJECTIVE The aim of the present study was to compare the onset of action between formoterol and albuterol, both administered through a Turbohaler. MATERIAL AND METHOD In a double-blind, parallel-group study design 36 patients were randomly allocated to receive either formoterol 12 microg or salbutamol 200 microg. The two drugs were administered through a Turbohaler system. Response (% forced expiratory volume in one second [FEV1]) was evaluated 3, 30 and 60 minutes after drug administration. RESULTS The %FEV1 values at 3, 30 and 60 minutes were similar in both groups: 82 15.0 for formoterol and 82 14.4 for albuterol at 60 minutes (p > 0.05). CONCLUSIONS Formoterol 12 microg has a similar onset of action and potency to albuterol 200 microg when administered via a Turbuhaler in children with a mild acute asthma crisis.