The environmental pollutant pyrene induces the production of IL-4

Background: Epidemiologic studies and experiments with mouse models suggest that polyaromatic hydrocarbons contained in, among others, diesel exhaust particles can promote the development of allergy. Objective: Because IL-4 organizes allergic responses in vivo, we have investigated whether pyrene, a major compound of diesel exhaust particles, can affect the production of IL-4. Methods: IL-4 production by primary human T cells was assessed by ELISA and messenger RNA transcription was detected by Northern blotting. Activation of the IL-4 promoter was tested in reporter gene assays with transiently transfected cell lines. Results: Pyrene induced transcription of IL-4 messenger RNA and expression of IL-4 protein in primary human T cells. Pyrene, but not related polyaromatic hydrocarbons, enhanced basal transcription of the human and mouse IL-4 promoter. Conclusion: Our results suggest that pyrene may promote allergic diseases by inducing the production of IL-4.