Greater susceptibility of girls to airborne Benzo[a]pyrene for obesity-associated childhood asthma

Children's exposure to polycyclic aromatic hydrocarbon (PAHs): a review on urinary 1-hydroxypyrene and associated health effects

This article reviewed the published studies on the environmental exposure to polycyclic aromatic hydrocarbons (PAHs) among children and assessed the urinary 1-hydroxypyrene (1-OHP) level as a biomarker of exposure to PAHs. The current knowledge of the potential health effects of increased 1-OHP in children was reviewed. Additionally, the influence of genetic polymorphism on the urinary 1-OHP level was discussed in this review. The assembled data showed that children who are attending schools or living close to industrial and polluted urban areas might have greater exposure to higher concentrations of PAHs with a higher level of urinary 1-OHP when compared to those children living in rural areas. Urinary 1-OHP may be a reliable biomarker for determining the genotoxic effects, oxidative stress and inflammation caused by exposure to PAHs. Strong research evidence indicated that the total body burden of PAHs should be evaluated by biomonitoring of 1-OHP in line with other urinary PAHs metabolites (with 2-3 rings) to evaluate recent total exposure to PAHs. Overall, the study suggests implementing a mitigation plan to combat air pollution to provide a cleaner environment for children.

Autocrine TGF-alpha is associated with Benzo(a)pyrene-induced mucus production and MUC5AC expression during allergic asthma

OBJECTS

Benzo(a)pyrene (BaP), an environmental pollutant, is present in high concentrations in urban smog and cigarette smoke and has been reported to promote high mucin 5AC (MUC5AC) expression. Epithelium-derived inflammatory cytokines are considered an important modulator of mucus oversecretion and MUC5AC overexpression. Here, we investigated whether the effect of BaP on MUC5AC overexpression was associated with cytokine autocrine activity in vivo and in vitro.

METHODS

In vivo, BALB/c mice were treated with ovalbumin (OVA) in the presence or absence of BaP. Allergy-induced mucus production was assessed by Alcian Blue Periodic acid Schiff (AB-PAS) staining. The human airway epithelial cell line NCI-H292 was used in vitro. MUC5AC and transforming growth factor (TGF)-α mRNA levels were assessed with real-time quantitative PCR. The concentration of cytokines was measured by ELISA. The MUC5AC, p-ERK, ERK, p-EGFR and EGFR proteins were detected by Western blotting in cells or by immunohistochemistry in mouse lungs. Small-interfering RNAs were used for gene silencing.

RESULTS

TGF-α was overproduced in the supernatant of NCI-H292 cells treated with BaP. Knockdown of TGF-α expression inhibited the BaP-induced increase in MUC5AC expression and subsequent activation of the EGFR-ERK signalling pathway. Knocking down aryl hydrocarbon receptor (AhR) expression or treatment with an ROS inhibitor (N-acetyl-L-cysteine) could relieve the TGF-α secretion induced by BaP in epithelial cells. In an animal study, coexposure to BaP with OVA increased mucus production, MUC5AC expression and ROS-EGFR-ERK activation in the lung as well as TGF-α levels in bronchoalveolar lavage fluid (BALF). Furthermore, the concentration of TGF-α in BALF was correlated with MUC5AC mRNA levels. Additionally, TGF-α expression was found to be positively correlated with MUC5AC expression in the airway epithelial cells of smokers. Compared with non-smoker asthma patients, TGF-α serum levels were also elevated in smoker asthma patients.

CONCLUSION

Autocrine TGF-α was associated with BaP-induced MUC5AC expression in vitro and in vivo. BaP induced TGF-α secretion by activating AhR and producing ROS, which led to activation of the EGFR-ERK pathway.

Combined adjuvant effects of ambient vapor-phase organic components and particulate matter potently promote allergic sensitization and Th2-skewing cytokine and chemokine milieux in mice: The importance of mechanistic multi-pollutant research

Although exposure to ambient particulate matter (PM) is linked to asthma, the health effects of co-existing vapor-phase organic pollutants (vapor) and their combined effects with PM on this disease are poorly understood. We used a murine asthma model to test the hypothesis that exposure to vapor would enhance allergic sensitization and this effect would be further strengthened by co-existing PM. We found that vapor and PM each individually exerted adjuvant effects on OVA sensitization. Co-exposure to vapor and PM during sensitization further enhanced allergic lung inflammation and OVA-specific antibody production which was accompanied by pulmonary cytokine/chemokine milieu that favored T-helper 2 immunity (i.e. increased IL-4, downregulation of Il12a and Ifng, and upregulation of Ccl11 and Ccl8). TNFα, IL-6, Ccl12, Cxcl1 and detoxification/antioxidant enzyme responses in the lung were pollutant-dependent. Inhibition of lipopolysaccharide-induced IL-12 secretion from primary antigen-presenting dendritic cells correlated positively with vapor's oxidant potential. In conclusion, concurrent exposure to vapor and PM led to significantly exaggerated adjuvant effects on allergic lung inflammation which were more potent than that of each pollutant type alone. These findings suggest that the effects of multi-component air pollution on asthma may be significantly underestimated if research only focuses on a single air pollutant (e.g., PM).

Airborne Benzo[a]Pyrene may contribute to divergent Pheno-Endotypes in children

BACKGROUND

Asthma represents a syndrome for which our understanding of the molecular processes underlying discrete sub-diseases (i.e., endotypes), beyond atopic asthma, is limited. The public health needs to characterize etiology-associated endotype risks is becoming urgent. In particular, the roles of polyaromatic hydrocarbon (PAH), globally distributed combustion by-products, toward the two known endotypes - T helper 2 cell high (Th2) or T helper 2 cell low (non-Th2) - warrants clarification.

OBJECTIVES

To explain ambient B[a]P association with non-atopic asthma (i.e., a proxy of non-Th2 endotype) is markedly different from that with atopic asthma (i.e., a proxy for Th2-high endotype).

METHODS

In a case-control study, we compare the non-atopic as well as atopic asthmatic boys and girls against their respective controls in terms of the ambient Benzo[a]pyrene concentration nearest to their home, plasma 15-Ft2-isoprostane (15-Ft2-isoP), urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), and lung function deficit. We repeated the analysis for i) dichotomous asthma outcome and ii) multinomial asthma-overweight/obese (OV/OB) combined outcomes.

RESULTS

The non-atopic asthma cases are associated with a significantly higher median B[a]P (11.16 ng/m3) compared to that in the non-atopic controls (3.83 ng/m3; P-value < 0.001). In asthma-OV/OB stratified analysis, the non-atopic girls with lean and OV/OB asthma are associated with a step-wisely elevated B[a]P (median,11.16 and 18.00 ng/m3, respectively), compared to the non-atopic lean control girls (median, 4.28 ng/m3, P-value < 0.001). In contrast, atopic asthmatic children (2.73 ng/m3) are not associated with a significantly elevated median B[a]P, compared to the atopic control children (2.60 ng/m3; P-value > 0.05). Based on the logistic regression model, on ln-unit increate in B[a]P is associated with 4.7-times greater odds (95% CI, 1.9-11.5, P = 0.001) of asthma among the non-atopic boys. The same unit increase in B[a]P is associated with 44.8-times greater odds (95% CI, 4.7-428.2, P = 0.001) among the non-atopic girls after adjusting for urinary Cotinine, lung function deficit, 15-Ft2-isoP, and 8-oxodG.

CONCLUSIONS

Ambient B[a]P is robustly associated with non-atopic asthma, while it has no clear associations with atopic asthma among lean children. Furthermore, lung function deficit, 15-Ft2-isoP, and 8-oxodG are associated with profound alteration of B[a]P-asthma associations among the non-atopic children.

Residential Links to Air Pollution and School Children with Asthma in Vilnius (Population Study)

Background and objectives: Many studies have been carried out on the negative health effects of exposure to PM₁₀, PM _2.5, NO₂, CO, SO₂ and B[a]P for small populations. The main purpose of this study was to explore the association of air pollution to diagnosis of asthma for the whole huge population of school children between 7–17 years in Vilnius (Lithuania) using geographical information system analysis tools. Material and Methods: In the research, a child population of 51,235 individuals was involved. From this large database, we identified children who had asthma diagnosis J45 (ICD-10 AM). Residential pollution concentrations and proximity to roads and green spaces were obtained using the ArcGIS spatial analysis tool from simulated air pollution maps. Multiple stepwise logistic regression was used to explore the relation between air pollution concentration and proximity between the roads and green spaces where children with asthma were living. Further, we explored the interaction between variables. Results: From 51,235 school children aged 7–17 years, 3065 children had asthma in 2017. We investigated significant associations, such as the likelihood of getting sick with age (odds ratio (OR) = 0.949, p < 0.001), gender (OR = 1.357, p = 0.003), NO₂ (OR = 1.013, p = 0.019), distance from the green spaces (OR = 1.327, p = 0.013) and interactions of age × gender (OR = 1.024, p = 0.051). The influence of gender on disease is partly explained by different age dependency slopes for boys and girls. Conclusions: According to our results, younger children are more likely to get sick, more cases appended on the lowest age group from 7 to 10 years (almost half cases (49.2%)) and asthma was respectively nearly twice more common in boys (64.1%) than in girls (35.9%). The risk of asthma is related to a higher concentration of NO₂ and residence proximity to green spaces.

Obesity may enhance the adverse effects of NO2 exposure in urban schools on asthma symptoms in children

BACKGROUND

Sparse data address the effects of nitrogen dioxide (NO₂) exposure in inner-city schools on obese students with asthma.

OBJECTIVE

We sought to evaluate relationships between classroom NO₂ exposure and asthma symptoms and morbidity by body mass index (BMI) category.

METHODS

The School Inner-City Asthma Study enrolled students aged 4 to 13 years with asthma from 37 inner-city schools. Students had baseline determination of BMI percentile. Asthma symptoms, morbidity, pulmonary inflammation, and lung function were monitored throughout the subsequent academic year. Classroom NO₂ data, linked to enrolled students, were collected twice per year. We determined the relationship between classroom NO₂ levels and asthma outcomes by BMI stratification.

RESULTS

A total of 271 predominantly black (35%) or Hispanic students (35%) were included in analyses. Fifty percent were normal weight (5-84th BMI percentile), 15% overweight (≥85-94th BMI percentile), and 35% obese (≥95th BMI percentile). For each 10-parts per billion increase in NO₂, obese students had a significant increase in the odds of having an asthma symptom day (odds ratio [OR], 1.86; 95% CI, 1.15-3.02) and in days caregiver changed plans (OR, 4.24; 95% CI, 2.33-7.70), which was significantly different than normal weight students who exhibited no relationship between NO₂ exposure and symptom days (OR, 0.90; 95% CI, 0.57-1.42; pairwise interaction P = .03) and change in caregiver plans (OR, 1.37; 95% CI, 0.67-2.82; pairwise interaction P = .02). Relationships between NO₂ levels and lung function and fractional exhaled nitric oxide did not differ by BMI category. If we applied a conservative Holm-Bonferroni correction for 16 comparisons (obese vs normal weight and overweight vs normal weight for 8 outcomes), these findings would not meet statistical significance (all P > .003).

CONCLUSIONS

Obese BMI status appears to increase susceptibility to classroom NO₂ exposure effects on asthma symptoms in inner-city children. Environmental interventions targeting indoor school NO₂ levels may improve asthma health for obese children. Although our findings would not remain statistically significant after adjustment for multiple comparisons, the large effect sizes warrant future study of the interaction of obesity and pollution in pediatric asthma.

Novel Insights on Sex-Related Differences in Asthma

PURPOSE OF REVIEW

Asthma, a common respiratory disease that affects about 10% of the US population, represents a significant public health issue. In the last decade, cumulative evidence has demonstrated sex disparities in asthma, including significant differences in epidemiology, clinical presentation, response to therapies, and health outcomes. Understanding sex-related differences in asthma enables clinicians to provide personalized asthma care and improve asthma outcome.

RECENT FINDINGS

Recent studies on sex-related differences in asthma inform us on mechanism underlying asthma pathogenesis across all age groups. Sex hormones directly modulate immune pathways crucial in asthma pathogenesis and affect individual's response to environmental triggers and medications, such as leukokotriene inhibitors. Not surprisingly, the use of external sex hormone supplementations appears to modulate asthma risk. Identification of sex-specific asthma risk loci through genome-wide association studies also provides supporting evidence on sex-related differences in asthma. There is an interaction between sex and obesity, an interaction that could place females at higher risk for systemic inflammation and, consequently, asthma. In this article, we review epidemiological and clinical studies on sex-related differences in asthma, with a special focus on the role of sex hormones, including hormonal therapies and the asthma-obesity interaction.