Advances in research on gas-liquid interface toxicity of composite air pollutants in vitro

In February 2019, a number of scientists from the National Nano Center of the Chinese Academy of Sciences, the School of Environment and Resources of the Center for Environmental and Health Research of the University of Shanxi, and the University of Chinese Academy of Sciences published in the famous environmental journal Chemosphere entitled "Complex to simple: In vitro exposure Of particulate matter simulated at the air-liquid interface mask the health impacts of major air pollutants. Advances in the study of in vitro gas-liquid interface toxicity of composite air pollutants.

Air particulate matter (PM ):

The main inorganic constituents of PM include sulfates, nitrates, ammonium, chlorides and trace metals (Wang et al., 2013; Han et al., 2016), in which sulphate is more harmful to human health than other PM components ( Ueda et al., 2016), these sulfates are mainly formed by humans emitting SO2 into the atmosphere through complex redox reactions under certain conditions, while adsorbing onto the surface of aerosol particles and other substances together form complex synergistic toxic effects. . Silica (SiO ₂ ) is one of the main components of atmospheric aerosols and is used to simulate the core of atmospheric particles due to its stable structure, large specific surface area and relatively low toxicity (Wang et al., 2018). At the same time, with the development of nanotechnology, the application of silica nanoparticles is becoming more and more extensive. Previous studies have shown that sulfur dioxide in the air can be adsorbed to the surface of atmospheric particulate matter (Han et al., 2016). Therefore, aerosols formed by simulating the adsorption of sulfate on SiO ₂ can be used to study the toxic effects and health risks of air pollutants.

CULTEX gas- liquid interface exposure technology:

To date, no in vitro models have been used to study the synergistic toxicity of particulate matter with sulfur dioxide, primarily due to the lack of systems for the in vitro exposure of suitable particulate cells. In the traditional immersion exposure design, particles were added directly to the cell culture medium to assess particle toxicity. However, these methods have significant limitations, poor reproducibility, particle size changes due to aggregation, interaction of particles with media components (such as albumin), and dissolution of particles by the culture medium (Savi et al., 2008). ; Fatisson et al., 2012). In addition, the inhaled particles will first interact with the pulmonary surfactant, which is produced by epithelial type II cells, covering the alveolar area to prevent alveolar collapse and other functions. Surfactant coatings can alter the surface characteristics and subsequent toxicity of the inhaled particles. The traditional immersion exposure method obviously does not have the ability to simulate the real environment in the body. In contrast, the gas-liquid interface (ALI) model truly reflects the in vivo environment by providing a thin airway surface fluid for the exposed air surface of epithelial cells at the gas-interface (Jayaraman et al., 2001). . Furthermore, epithelial cells grown at the gas-liquid interface have a well-differentiated structure and function compared to cells immersed in the medium (Kameyama et al., 2003). Therefore, ALI can provide experimental conditions very similar to animal inhalation, although there are still many unresolved problems in its application, namely the interaction kinetics of particles with surface liquids in ALI or so-called in vivo surfactants, particle Physical and chemical changes and their impact on composition. In this study, the gas-liquid interface (ALI) exposure model was used to study the synergistic lung toxicity of HSO ₃ and SiO ₂ nanoparticles, revealing the pulmonary toxicity of complex air pollutants and possible lung diseases, especially inorganic and nanoparticle composite pollutants. Pulmonary toxicity is of great significance.

Thesis:

Particulate matter (PM) exposure has many adverse effects on human health. The air environment is composed of a variety of complex mixtures, however, it is very challenging to clarify the toxicity contribution of individual pollutants. The purpose of this study was to use aerosols composed of silica nanoparticles (SiO ₂ NPs) and bisulfite as simulated particle-related high sulfur contaminants. The health effects of sulfur dioxide were then assessed at the cellular level using an air-liquid interface (ALI) exposure chamber. BEAS-2B cells were exposed to nano silica, bisulfite aerosol, and bisulfite-coated silica (SiO ₂ -NH ₂ @HSO ₃ ) aerosol at the gas-liquid interface (ALI). 3 hours. The toxicity to cells was compared according to the exposure dose. Silica nanoparticles (SiO ₂ NPs) alone exposed to air did not produce significant cytotoxicity, but exposure to bisulfite-coated silica (SiO ₂ -NH ₂ @HSO ₃ ) aerosol significantly reduced cells Activity and enhanced cellular ROS production in a dose-dependent manner. Therefore, excessive oxidative stress leads to mitochondrial damage and apoptosis. The gas-liquid interface exposure method may reflect the actual physiological exposure of the human respiratory system. Sulfate, a derivative of air-contaminated sulphur dioxide, exacerbates the toxic effects of inhalable PMS. This result may be due to the large surface area of ​​the nanoparticles, which are capable of carrying more sulfite and reaching the target cells during aerosol exposure. Sulfate levels provide a meaningful complement to the current PM2.5 Air Pollution Index for better human health protection.

Experimental important data

All ALI exposure experiments in this study were performed in the German CLUTEX RFS COMPACT system. The RFS COMPACT system can simultaneously perform two groups of experiments in the control group and the experimental group.

The exposure concentrations of NM aerosols. The size distribution of aerosols of (A) SiO2-OH, (C) SiO2-NH2 and (E) SiO2-NH2@HSO3 in the 14.6e661.2 nm particle size range. The mass concentrations of aerosol particles Of (B) SiO2-OH, (D) SiO2-NH2 and (F) SiO2-NH2@HSO3 in the 14.6e661.2 nm particle size range after exposure on BEAS-2Bcells for 3 h at ALI.

Cellular toxicitiesdetected in BEAS-2B after ALI exposure to various PM aerosols. Cell viability(A) and cell membrane integrity analysis (B) after 3 h exposure. C1 is the ALI exposure control of filteredclean air; C2 is the normal cell control cultured in incubator The ROS levels(C) and ATP production (D) in BEAS-2B cells after ALI exposure for 3 h and withan extra incubation for 5 h. N = 3, Control group is the ALI exposure of filtered clean air. Onecandidate experiment result from at least three independent experiments. *P < 0.05, #P <0.01 vs the indicated groups.

The live and dead testing results of BEAS-2B cells after exposureto aerosols for 3 h at ALI and extra incubation in ALI chamber for 5 h. Thedata represent the mean of at least three independent experiments normalized tocontrols of ALI. C1 is the ALI exposure control Of filtered clean air; C2 is the normal cell controlcultured in incubator. *P <0.05, #P < 0.01 vs the indicated groups.

Expression levels of marker genes in BEAS-2Bcells after ALI exposure to different PM aerosols for 3 h and with an extraincubation for 5 h. (A) Bax; (B) Bcl-2; (C) Bcl-2/Baxratio; Caspase-3; (E) Chop; and (F) Xbp-1s. The data represents a candidate experiment result from at least three independent experiments. N = 5, Control group is the ALI exposure of clean air. *P < 0.05, #P <0.01 vs the indicated groups.

The research was funded by the Ministry of Science and Technology, the National Natural Science Foundation, the National Science Fund for Distinguished Young Scholars, and the Frontier Science Key Research Program of the Chinese Academy of Sciences.