Bronchial and vascular effects induced by different diesel particles emission sources

Summary This study aims to compare the biological effects induced by three different diesel combustion particles (DEPs), focusing on their health hazard at both respiratory and vascular levels. In particular, DEP coming from a EuroIV engine, run under STOP&GO driving condition, resulted to be the more enriched in PAHs and more effective at all biological endpoints. Cell viability, oxidative stress, cell morphology, release of inflammatory mediators and genotoxic potential were investigated in the bronchial cell line BEAS-2B. The conditioned media, derived from these cells, were then used to treat human microvascular endothelial cells (HPMEC), in order to evaluate DEP-induced endothelial activation. DEPs with high content of PAHs, derived from an emission source of a high traffic area (DEP EuroIV) were responsible for both lung and vascular biological outcomes. Introduction The link between increased particles emissions and cardiovascular diseases has been well documented (e.g. Lee et al., 2014), but the mechanisms leading to these effects are still unknown, even if the activation of the respiratory endothelium seems to be involved. The release of mediators from the exposed epithelium has been suggested to be involved in this process and here investigated. Methodology and Results. Two in vitro models were used to compare the effects induced by the different DEPs: a conditioned media system and a co-culture in vitro model on Transwell inserts, mimicking the interplay between lung epithelium and pulmonary capillaries. Bronchial BEAS-2B cells were exposed to two standard reference DEP (1650b, 2975) and a DEP sampled from a EuroIV vehicle run over a chassis dyno. After DEPs exposure (5μg/cm2 for 20h), the expression of ROS species and the HO-1 oxidative stress marker were investigated by cytofluorimetric and Western Blot analyses, respectively. The release of cellular mediators (IL6, IL6R and VEGF) in BEAS-2B supernatants was assessed with ELISA. The genotoxic potential of DEPs was evaluated with the analysis of yH2AX expression, a biomarker of DNA double-strand breaks. Moreover, HPMEC lung microvascular endothelial cells were exposed for 24h to BEAS-2B conditioned media. The expression of endothelial adhesion molecules (ICAM-1 and VCAM-) was analyzed. Finally, a 3D in vitro air-blood barrier (ABB) was used: epithelial cells were treated with DEPs and after 24h the release of inflammatory mediators and endothelial activation were investigated. Among the different particles, only DEP EuroIV was able to induce oxidative stress, IL6 and IL6R release in BEAS cells and a consequent endothelial activation, as evidenced by the increased expression of ICAM-1 and VCAM-1 in HPMEC. These results are confirmed by the experiments on the co-culture model. Conclusions As traffic continues to increase in Europe, the emission of diesel combustion-derived particles will continue to contribute significantly to the atmospheric particles. Furthermore, these emissions include several substances with high toxicity to humans and the environment (e.g. metals and PAHs). DEP-induced cardiovascular effects may derive from the inflammatory response of lung epithelial cells and they are modulated by PAHs-enriched particles, whose physicochemical properties are more reactive and effective on the respiratory epithelium and endothelium. Acknowledgement This work was supported by Cariplo Foundation (Grant. N° 2013-1038) and MAECI project (ID PGR00786). References Lee, B.J., Kim, B., Lee, K., 2014. Air pollution exposure and cardiovascular disease. Toxicol. Res. 30, 71-75. http://dx.doi.org/10.5487/TR.2014.30.2.071. Fig.1 Morphology of cells exposed to three different DEPs: A) control cells, B) 1650b, C) 2975 and D) EuroIV. Fig.2 ICAM-1 expression in endothelial cells exposed to different conditioned media