Abstract
The biological effects induced by complete engine emissions in a 3D model of the human airway (MucilAirTM) and in human bronchial epithelial cells (BEAS-2B) grown at the air–liquid interface were compared. The cells were exposed for one or five days to emissions generated by a Euro 5 direct injection spark ignition engine. The general condition of the cells was assessed by the measurement of transepithelial electrical resistance and mucin production. The cytotoxic effects were evaluated by adenylate kinase (AK) and lactate dehydrogenase (LDH) activity. Phosphorylation of histone H2AX was used to detect double-stranded DNA breaks. The expression of the selected 370 relevant genes was analyzed using next-generation sequencing. The exposure had minimal effects on integrity and AK leakage in both cell models. LDH activity and mucin production in BEAS-2B cells significantly increased after longer exposures; DNA breaks were also detected. The exposure affected CYP1A1 and HSPA5 expression in MucilAirTM. There were no effects of this kind observed in BEAS-2B cells; in this system gene expression was rather affected by the time of treatment. The type of cell model was the most important factor modulating gene expression. In summary, the biological effects of complete emissions exposure were weak. In the specific conditions used in this study, the effects observed in BEAS-2B cells were induced by the exposure protocol rather than by emissions and thus this cell line seems to be less suitable for analyses of longer treatment than the 3D model.
Highlights
Road traffic is one of the major sources of air pollution, in large cities
In this study we aimed to compare the biological response in two different model systems: BEAS-2B cells, a typical cellular monoculture used in toxicological tests, and MucilAirTM, a commercial 3D model originating from bronchial epithelial tissue consisting of human basal, goblet, and ciliated cells [8]
The transepithelial electrical resistance (TEER) measurement results indicate that exposure to the complete emissions and/or the clean air had a minimal effect on the integrity of the MucilAirTM model
Summary
Road traffic is one of the major sources of air pollution, in large cities. Such monocultures have become part of a battery of tests recommended by the OECD These systems have numerous disadvantages, including limited genetic stability if cancer or immortalized cell lines are used, or a lack of inter- and intracellular signaling. 3D cultures have become an emerging platform of toxicity assessment [6] Various forms of these systems exist, including co-cultures consisting of two or more different cell types that mimic inter- and intracellular interactions found in in vivo conditions. They lack the typical 3D structure of organs/tissues. The models mimicking skin are most commonly used, but lung tissues for the purpose of inhalation toxicology are available [7,8]
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