Assessment of lung cell toxicity of various gasoline engine exhausts using a versatile in vitro exposure system

Abstract

Adverse effect studies of gasoline exhaust are scarce, even though gasoline direct injection (GDI) vehicles can emit a high number of particles. The aim of this study was to conduct an in vitro hazard assessment of different GDI exhausts using two different cell culture models mimicking the human airway. In addition to gasoline particle filters (GPF), the effects of two lubrication oils with low and high ash content were assessed, since it is known that oils are important contributors to exhaust emissions. Complete exhausts from two gasoline driven cars (GDI1 and GDI2) were applied for 6 h (acute exposure) to a multi-cellular human lung model (16HBE14o-cell line, macrophages, and dendritic cells) and a primary human airway model (MucilAir™). GDI1 vehicle was driven unfiltered and filtered with an uncoated and a coated GPF. GDI2 vehicle was driven under four settings with different fuels: normal unleaded gasoline, 2% high and low ash oil in gasoline, and 2% high ash oil in gasoline with a GPF. GDI1 unfiltered was also used for a repeated exposure (3 times 6 h) to assess possible adverse effects. After 6 h exposure, no genes or proteins for oxidative stress or pro-inflammation were upregulated compared to the filtered air control in both cell systems, neither in GDI1 with GPFs nor in GDI2 with the different fuels. However, the repeated exposure led to a significant increase in HMOX1 and TNFa gene expression in the multi-cellular model, showing the responsiveness of the system towards gasoline engine exhaust upon prolonged exposure. The reduction of particles by GPFs is significant and no adverse effects were observed in vitro during a short-term exposure. On the other hand, more data comparing different lubrication oils and their possible adverse effects are needed. Future experiments also should, as shown here, focus on repeated exposures.

The Biological Effects of Complete Gasoline Engine Emissions Exposure in a 3D Human Airway Model (MucilAirTM) and in Human Bronchial Epithelial Cells (BEAS-2B)

“…The exposure to complete gasoline exhaust from engines with and without particle filters and using various fuels for 6 h followed by a 6-h post-incubation period had no effect on oxidative stress and inflammation-related genes in a multicellular human lung model and in MucilAir TM . However, the repeated 3 × 6 h exposure to an exhaust from an engine without the filter, followed by post-incubation periods, increased the expression of HMOX1 and TNFα genes in the multicellular model suggesting that longer exposure is required to induce the biological effects [14]. The effect of ethanol-containing fuels was tested in the multi-cellular human lung model consisting of three cells types.…”

“…Depending on the endpoints to be assessed, in vitro toxicity tests of vehicle emissions may be carried out in various settings. They include for example the exposure of the test system to complete emissions [9,10,11,12,13,14], suspended particles [15,16,17,18], or to extracts from particles [19,20,21,22]. Each of these approaches has its specific advantages and limitations.…”

“…Unlike cellular monocultures, 3D models have a greater potential for long-term exposure studies [25]. Regardless of this, the experiments with complete emissions reported so far have all been limited to short-term treatments, usually not exceeding 6 h [10,12,14,26,27].…”

Physical, chemical, and toxicological characteristics of particulate emissions from current technology gasoline direct injection vehicles

“…A number of studies have shown that exposure to primary PM emissions from mobile sources is linked directly to adverse health implications (Bisig et al, 2018;Tzamkiozis et al, 2010;Seagrave et al, 2002). Epidemiologic and toxicological studies have reported that elevated levels of PM are associated with cardiopulmonary mortality and morbidity (Araujo and Nel, 2009;Bates et al, 2015;Reed et al, 2008).…”

Is the particle deposition in a cell exposure facility comparable to the lungs? A computer model approach

“…Other ALI concepts (Phillips et al 2005;Savi et al 2008;Bisig et al 2018) choose different setups, for instance for minimum air velocity at the cell surface to mimic the situation in the alveolar space of the lungs more closely, thereby avoiding the cell stress from the radial shear flow in the stagnation point setup.…”