Peroxisome proliferator-activated receptor gamma gene variants modify human airway and systemic responses to indoor dibutyl phthalate exposure

Background Single nucleotide polymorphisms (SNPs) of peroxisome proliferator-activated receptor gamma (PPAR-γ; gene: PPARG) and oxidative stress genes are associated with asthma risk. However, whether such variants modulate responses to dibutyl phthalate (DBP), a common plasticizer associated with increased asthma development, remains unknown. The purpose of this study is to investigate how SNPs in PPARG and oxidative stress genes , as represented by two separate genetic risk scores, modify the impact of DBP exposure on lung function and the airway and systemic response after an inhaled allergen challenge. Methods We conducted a double-blinded human crossover study with sixteen allergen-sensitized participants exposed for three hours to DBP and control air on distinct occasions separated by a 4-week washout. Each exposure was followed by an allergen inhalation challenge; subsequently, lung function was measured, and blood and bronchoalveolar lavage (BAL) were collected and analyzed for cell counts and allergen-specific immunoglobulin E (IgE). Genetic risk scores for PPAR-γ (P-GRS; weighted sum of PPARG SNPs rs10865710, rs709158, and rs3856806) and oxidative stress (OS-GRS; unweighted sum of 16 SNPs across multiple genes) were developed, and their ability to modify DBP effects were assessed using linear mixed-effects models. Results P-GRS and OS-GRS modified DBP effects on allergen-specific IgE in blood at 20 h (interaction effect [95% CI]: 1.43 [1.13 to 1.80], p = 0.005) and 3 h (0.99 [0.98 to 1], p = 0.03), respectively. P-GRS also modified DBP effects on Th2 cells in blood at 3 h (− 25.2 [− 47.7 to − 2.70], p = 0.03) and 20 h (− 39.1 [− 57.9 to − 20.3], p = 0.0005), and Th2 cells in BAL at 24 h (− 4.99 [− 8.97 to − 1.01], p = 0.02). An increasing P-GRS associated with reduced DBP effect on Th2 cells. Neither GRS significantly modified DBP effects on lung function parameters. Conclusions PPAR-γ variants modulated several airway and systemic immune responses to the ubiquitous chemical plasticizer DBP. Our results suggest that PPAR-γ variants may play a greater role than those in oxidative stress-related genes in airway allergic responses to DBP. Trial registration: This study reports results from The Phthalate-Allergen Immune Response Study that was registered on ClinicalTrials.gov with identification NCT02688478.