Effects of diesel organic extracts on chemokine production by peripheral blood mononuclear cells

Background: Polyaromatic hydrocarbons (PAHs) associated with diesel exhaust particles (DEPs) are found in the atmospheric urban pollution. Such compounds have been shown to favor IgE production, bronchial hyperresponsiveness, and airway inflammation. Chemokines are a group of chemotactic cytokines involved in the recruitment of inflammatory cells. Objective: We investigated the effect of DEP-PAHs on the release and mRNA expression of IL-8, MCP-1, and RANTES by PBMCs obtained from healthy subjects. Methods: Protein production in supernatants was assessed by ELISA, and mRNA expression was evaluated by semiquantitative RT-PCR. Results: Secretion of IL-8 and RANTES increased in a dose-dependent manner with increasing concentrations of DEP-PAHs (range, 0.5 ng to 50 ng/mL). On the contrary, the release of MCP-1 was significantly inhibited, also in a dose-dependent manner. Messenger RNA production coding for IL-8, RANTES, and MCP-1 showed parallel variations to the production of the correspondent proteins. Effects of DEP-PAHs became significant at 7 hours and up to 48 hours time culture for MCP-1, and up to 24 hours time culture for IL-8 and RANTES. Moreover, supernatants from DEP-PAH-activated cells, compared with those of controls, exhibited a significantly enhanced chemotactic activity for neutrophils and eosinophils, which was significantly inhibited by pretreatment with anti-IL-8 and anti-RANTES neutralizing antibodies, respectively. Conclusion: These findings suggest that the chemokine pathways are modulated by DEP-PAHs at the transcriptional level, reinforcing the idea that the development of inflammatory reactions might be affected by diesel exhaust emission.