A Novel Role of PM Extracts on the Post-Transcriptional Control of Pro-Inflammatory Mediators, IL-6 and CXCL8

Exposure to airborne particulate matter (PM) has been associated with the transcriptional up-regulation of pro-inflammatory mediators. However, the effect of PM on post-transcriptional regulation of pro-inflammatory mediators has not been fully explored. In this study, we examined the acute effect of organic extracts from urban PM, rural PM and diesel exhaust particles (DEP) on the post-transcriptional control of interleukin-6 (IL-6) and interleukin-8 (CXCL8) using a human bronchial epithelial cell line. Both PM and DEP extracts induced the release of IL-6 and CXCL8 after 24 h of exposure. Time-course experiments were conducted to examine changes in mRNA steady-state levels and half-lives. The steady-state levels of CXCL8 mRNA increase at 15 min on cells exposed to both PM and DEP extracts. Meanwhile only the urban extract induced significant increases of IL-6 mRNA levels at 15 min. Indirect measurements of IL-6 mRNA half-life showed a dramatic increase in cells exposed to the organic extracts. CXCL8 mRNA half-life increases in cells exposed to PM extracts and not DEP extract. Nuclear run-ons demonstrated that the urban PM and DEP extracts promoted an up-regulation in the transcription rate of CXCL8 at 15 min but not for IL-6. Urban and rural PM influences the post-transcriptional control of CXCL8.