Defining the effects of traffic-related air pollution on the human plasma proteome using an aptamer proteomic array: A dose-dependent increase in atherosclerosis-related proteins

Traffic-related air pollution (TRAP) is a critical risk factor and major contributor to respiratory and cardiovascular disease (CVD). The effects of TRAP beyond the lungs can be related to changes in circulatory proteins. However, such TRAP-mediated changes have not been defined in an unbiased manner using a controlled human model. To detail global protein changes (the proteome) in plasma following exposure to inhaled diesel exhaust (DE), a paradigm of TRAP, using controlled human exposures. In one protocol, ex-smokers and never-smokers were exposed to filtered air (FA) and DE (300 μg PM₂.₅/m³), on order-randomized days, for 2 h. In a second protocol, independent never-smoking participants were exposed to lower concentrations of DE (20, 50 or 150 μg PM₂.₅/m³) and FA, for 4 h, on order-randomized days. Each exposure was separated by 4 weeks of washout. Plasma samples obtained 24 h post-exposure from ex-smokers (n = 6) were first probed using Slow off-rate modified aptamer proteomic array. Plasma from never-smokers (n = 11) was used for independent assessment of proteins selected from the proteomics study by immunoblotting. Proteomics analyses revealed that DE significantly altered 342 proteins in plasma of ex-smokers (n = 6). The top 20 proteins therein were primarily associated with inflammation and CVD. Plasma from never-smokers (n = 11) was used for independent assessment of 6 proteins, amongst the top 10 proteins increased by DE in the proteomics study, for immunoblotting. The abundance of all six proteins (fractalkine, apolipoproteins (APOB and APOM), IL18R1, MIP-3 and MMP-12) was significantly increased by DE in plasma of these never-smokers. DE-mediated increase was shown to be concentration-dependent for fractalkine, APOB and MMP-12, all biomarkers of atherosclerosis, which correlated with plasma levels of IL-6, a subclinical marker of CVD, in independent participants. This investigation details changes in the human plasma proteome due to TRAP. We identify specific atherosclerosis-related proteins that increase concentration-dependently across a range of TRAP levels applicable worldwide.