Effect of GST variants on lung function following diesel exhaust and allergen co-exposure in a controlled human crossover study

BACKGROUND: Isolated exposure to diesel exhaust (DE) or allergen can cause decrements in lung function that are impacted by the presence of genetic variants in the glutathione-S-transferase (GST) family but the effect of GST interactions with DE-allergen co-exposure on lung function is unknown. We aimed to assess the impact of DE and allergen co-exposure on lung function and the influence of GSTM1 or GSTT1 variation METHODS: We used a blinded crossover study design with 17 atopic subjects exposed to filtered air (FA; the control for DE) or DE for 2h. One hour following each exposure to DE or FA, bronchoscopy was performed to deliver a diluent-controlled segmental allergen challenge (SAC). Methacholine challenge and forced expiratory volume in 1s (FEV1) was performed pre-exposure (baseline airway responsiveness) and 24h post-exposure (effect of co-exposure). Additionally, FEV1 was performed hourly after DE/FA exposure and protein carbonyl content was measured in plasma as an oxidative stress marker. RESULTS: Changes in FEV1 from baseline were dependent on time following allergen exposure. DE, as opposed to FA, led to a significant change in FEV1 at 2h post-allergen exposure in GSTT1 variants only (24.5±19.6% reduction in GSTT1 null individuals vs. 9.2±7.3% reduction in GSTT1 present individuals). Moreover, plasma protein carbonyl level 4h after co-exposure was higher in the individuals who have the GSTT1 null genotype. CONCLUSIONS: This suggests a gene-environment interaction that endangers susceptible populations co-exposed to DE and allergen.