Immune impacts of fire smoke exposure

Exposure to fire smoke has become a global health concern and is associated with increased morbidity and mortality. There is a lack of understanding of the specific immune mechanisms involved in smoke exposure, with preventive and targeted interventions needed. After exposure to fire smoke, which includes PM_2.5, toxic metals and perfluoroalkyl and polyfluoroalkyl substances, epidemiology-based studies have demonstrated increases in respiratory (for example, asthma exacerbation), cardiac (for example, myocardial infarction, arrhythmias), neurological (for example, stroke) and pregnancy-related (for example, low birthweight, premature birth) outcomes. However, mechanistic studies exploring how smoke exposure disrupts cellular homeostasis are lacking. Therefore, we collected blood from smoke-exposed individuals (n = 31) and age-matched and sex-matched non-smoke-exposed controls (n = 29), and investigated these complex interactions using a single-cell exposomic approach based on both methylation and mass cytometry. Overall, our data demonstrated a strong association between smoke exposure and methylation at 133 disease-relevant gene loci, while immunophenotyping showed increased homing and activation biomarkers. We developed an application of mass cytometry to analyze single-cell/metal binding and found, for example, increased levels of mercury in dead cells and cadmium in the live and dead cell populations. Moreover, mercury levels were associated with years of smoke exposure. Several epigenetic sites across multiple chromosomes were associated with individual toxic metal isotopes in single immune cells. Our methods for detecting the effect of smoke exposure at the single-cell level and the study results may help to determine the timing of exposure and identify specific molecular targets that could be modified to prevent and manage exposure to smoke.