Whole Blood Cytokine Response to Local Traffic-Related Particulate Matter in Peruvian Children With and Without Asthma

Abstract

This study sought to investigate if acute phase immune responses of whole blood from Peruvian children with controlled and uncontrolled asthma differed from children without asthma, following exposure to traffic-related particulate matter (TRPM). TRPM, including particulate matter from diesel combustion, has been shown to stimulate acute airway inflammation in individuals with and without asthma. For this study, a whole blood assay (WBA) was used to test peripheral whole blood samples from 27 children with asthma, and 12 without asthma. Participant blood samples were stimulated, ex vivo, for 24-h with an aqueous extract of TRPM that was collected near study area highways in Lima, Peru. All participant blood samples were tested against the same TRPM extract, in addition to purified bacterial endotoxin and pyrogen-free water, which served as positive and negative WBA controls, respectively. The innate and adaptive cytokine responses were evaluated in cell-free supernatants of the whole blood incubations. Comparatively similar levels were recorded for nine out of the 10 cytokines measured [e.g., – Interleukin (IL)-1β, IL-6, IL-10], regardless of study participant asthma status. However, IL-8 levels in TRPM-stimulated blood from children with uncontrolled asthma were diminished, compared to subjects without asthma (633 pg/ml vs. 1,023 pg/ml, respectively; p < 0.01); IL-8 responses for subjects with controlled asthma were also reduced, but to a lesser degree (799 pg/ml vs. 1,023 pg/ml, respectively; p = 0.10). These relationships were present before, and after, adjusting for age, sex, obesity/overweight status, C-reactive protein levels, and residential proximity to the study area’s major roadway. For tests conducted with endotoxin, there were no discernible differences in cytokine response between groups, for all cytokines measured. The WBA testing conducted for this study highlighted the capacity of the TRPM extract to potently elicit the release of IL-8 from the human whole blood system. Although the small sample size of the study limits the capacity to draw definitive conclusions, the IL-8 responses suggest that that asthma control may be associated with the regulation of a key mediator in neutrophil chemotaxis, at a systemic level, following exposure to PM derived from traffic-related sources.

IL‐2 modulates Th2 cell responses to glucocorticosteroid: A cause of persistent type 2 inflammation?

“…The strong, super‐physiologic activation with PMA and ionomycin resulted in high production of IL‐2 from the patients’ peripheral blood cells in 1 mL of blood. This method has been published by others studying functional human immune responses, and showed a similar degree of variability in IL‐2 and tumor necrosis factor α production, whether cytokines levels were corrected for total cell numbers or not . In our in vitro system, we empirically developed a model of high and low IL‐2 based on typical concentrations used for Th2 cell cultures as well as functional readouts of resistance/susceptibility to GC‐induced apoptosis.…”

“…Whole blood (1 mL) from asthmatic patients was obtained, diluted 1:1 with RPMI-1640 and activated with mitogen (phorbol myristate acetate [PMA], 20 ng/mL; ionomycin, 1 μM) for 24 hours at 37⁰C, similar to methods developed to study human immune response. [32][33][34] IL-2 and IL-13 levels were measured in the supernatants with IL-2 (DY202-05; R&D Systems, Minneapolis, MN) and IL-13 (851.630.005; Diaclone, Besançon, France) enzyme-linked immunosorbent assay. All samples were run in duplicate, had low variability between replicates and were all within the standard curve of the assay.…”

Insights in particulate matter‐induced allergic airway inflammation: Focus on the epithelium

“…In contrast, most human studies investigate the effect of air pollution using blood, in which the identified cytokines can have either an epithelial or hematopoietic origin. Notably, exposure to PM has generally been related to an increased expression of IL‐1β in the blood of adults, children and during prenatal life . One study also observed a correlation between a joint increase in TSLP+IL‐33 cord blood levels and heavy street traffic during pregnancy (see Table for a detailed overview).…”

“…Notably, exposure to PM has generally been related to an increased expression of IL-1b in the blood of adults, children and during prenatal life. [160][161][162][163][164][165][166][167] One study also observed a correlation between a joint increase in TSLP+IL-33 cord blood levels and heavy street traffic during pregnancy 168 (see Table S2 for a detailed overview).…”

Long-Term Ambient Air Pollution Exposures and Circulating and Stimulated Inflammatory Mediators in a Cohort of Midlife Adults

“…There are very few prior studies combining air pollution exposures and stimulated cytokine measures, and those that have been performed used very different approaches, thereby complicating interpretability and comparability to our study. For example, Negherbon et al (2017) compared stimulated responses to trafficrelated particulate matter (TRPM) and LPS, respectively, among children with no asthma, controlled asthma, and uncontrolled asthma. The authors reported no significant differences among the groups in response to LPS-stimulation, but IL-8 responses following TRPM stimulation were lower among children with controlled or uncontrolled asthma than in nonasthmatic children.…”