Fig. 4.
Multiple interactions between air pollution, genetic polymorphism, and epigenetic markers. The NOS2A gene, which encodes inducible nitric oxide synthase, is known to modify the effect of air pollution on airway inflammation. NOS2A promoter haplotypes significantly influenced adjacent DNA methylation and high PM2.5 exposure associates with lower NOS2A methylation. These NOS2A genetic and epigenetic variations together with exposure to high levels of PM2.5 synergistically affect the levels of FeNO, which is an in-vivo airway inflammatory marker. FeNO, fractional exhaled nitric oxide; iNOS, inducible nitric oxide synthase; NOS2A, nitric oxide synthase 2A; PM, particulate matter.