In vitro assessment of biological impact of volatile/semi-volatile primary and secondary emissions derived from vehicles

Primary particle emissions, and the formation of secondary aerosols through atmospheric processing, are believed to be the pollutant with the greatest public health impact. In general, it is known that exposure to emissions leads to increased pulmonary inflammation and respiratory symptoms aggravation due to oxidative stress and direct toxic injury. Within the AEROSOLS project, the biological impact of volatile/semi-volatile (V/S-V) primary and secondary compounds derived from the engine and exhaust systems of vehicles will be assessed. In particular, in vitro tests based on traditional cell cultures (i.e. submerged monolayer cultures) as well as human air-liquid-interface (ALI) organotypic airway tissue models derived from primary tracheobronchial epithelial cells will be performed to predict the effects of these compounds on animals and humans without ethical concerns. The ALI model is an alternative airway model in which differentiating primary airway cells cultured on microporous membrane scaffolds can be directly exposed to gases and aerosols at the air-liquid interface. Compared to submerged monolayer cultures, primary cells that undergo cellular differentiation can reproduce an in vivo–like transcriptional profile similar to that of human airway epithelium. Therefore, organotypic ALI airway models have a more realistic in vivo–like structure, as well as barrier properties and metabolic functions, similar to those found in vivo. In addition, ALI models can be dosed in a more human-relevant manner than that in submerged cultures. Within the AEROSOLS project, human alveolar adenocarcinoma A549 epithelial cells are initially used for the safety evaluation of the key V/S-V compounds on traditional cell cultures or on VITROCELL® Essentials ALI exposure system (VITROCELL SYSTEMS GmbH, Waldkirch, Germany). In vitro cytotoxicity of V/S-V compounds is assessed following standard protocols, while further studies on genotoxicity, mutagenicity/carcinogenicity and immunotoxicity are performed. Additionally, the potential of these compounds to induce oxidation stress and inflammation is studied as it is known that these parameters are strongly related to the development of respiratory diseases. These results will be helpful to categorize and prioritize the V/S-V compounds based on their health impact.

Acknowledgement: This research was funded by the European Union’s Horizon Europe research and innovation programme within the AEROSOLS project under grant agreement No. 101096912 and UK Research and Innovation (UKRI) under the UK government’s Horizon Europe funding guarantee [grant numbers 10092043 and 10100997].