Effect Of Pulmonary Surfactants On The Toxicity And Transmembrane Efficiency Of Atmospheric Ultrafine Particles

Atmospheric ultrafine particulate matter（PM₁）is solid or liquid matter suspended in the air with an aerodynamic particle size of≤1μm,PM₁ is an important cause of air pollution.Current research has established that atmospheric particulate pollution,including PM₁,can have a number of harmful effects on the human health.PM₁ can break through the defence mechanisms of the respiratory system and will be deposited in the alveoli,Then it will cross the air-blood barrier and enter into the internal environment,causing noxious on other tissues properly.Pulmonary surfactant（PS）is widely present in the alveolar region under normal physiological conditions and is essential for the maintenance of the normal respiratory cycle;the main components of PS are lipids and proteins,which are produced by alveolar AT-II epithelial cells.When PM₁ reaches the alveolar region,it firstly interacts with PS,the PS will be adsorb to the surface of the PM₁particles,forming a typical“biomolecular corona”.The formation of a biomolecular corona can profoundly affect the biological effects of PM₁,and current studies have demonstrated that the toxicity and some biological effects of nanoparticular will be significantly altered following interaction with PS.However,fewer experiments have investigated the effects of atmospheric particulate matter and PS interactions on them,and many in vitro models have not even been constructed with PS as a key factor.This work focuses on the changes in the toxicity and transmembrane efficiency of PM₁ before and after its interaction with PS,provides more data to support the toxicological and biological effects of PM₁,and also provide a reference for the establishment of in vitro models about alveolar sites.Our study in this thesis is divided into the following main parts.（1）Collection processing and characterization of PM₁.We collected PM₁ samples in Beijing during the winter of 2018-2019,and the PM₁ samples were divided into two groups based on the aerodynamic particle size,i.e.,PM_0.5group（F1 group）and PM_0.5-1group（F2 group）,and the morphological characteristics of PM₁ samples were characterized using TEM and DLS,the elemental composition of PM₁ samples were characterized using ICP-MS and ICP-OES,and the OC and EC contents of PM₁samples were analyzed using total carbon analyzer.The results showed that the PM₁ fractions with different aerodynamic particle sizes were irregular in morphology,and after PM₁interacted with PS,it formed a significant biomolecular corona on its surface and even its morphology was partly changed.The elemental composition of the fractions with different AEDs also differed significantly,for example,the F2 sample had a significantly higher sulfur element than that in F1 sample.The ratio of total organic carbon to total carbon also showed significant differences depending on the AED,with higher OC/EC values in the F1 group（48.12）and lower OC/EC values in the F2 group（12.64）.（2）Effect of PM₁ on cytotoxicity and cellular lipid metabolism interacting with PS or not.The cytotoxicity of PM₁ and PM₁ after interaction with PS was measured using the CCK-8 assay,and the results showed that the cytotoxicity of PM₁ was significantly enhanced by its interaction with PS,and this effect was more pronounced in the fraction with smaller aerodynamic particle size（F1 group）.The enhanced toxicity was not related to the intracellular ROS content.The number of intracellular lipid droplets was observed by means of oil-red O sections,and it was found that PM₁ could cause an increase in the number of intracellular lipid droplets,which was further exacerbated after the interaction with PS.Further lipidomic study showed that the exposure to PM₁ samples significantly increased the intracellular Cer and SPH content,while the exposure after the interaction of PM₁ caused similar changes of intracellular Cer and SPH content compared to PM₁exposure alone.However,compared with PM₁ exposure alone,the exposure after its interaction with PS caused a significant increase of TG content.Taken together,we suggest that the PM₁ after interacting with PS might cause more serious abnormalities in cellular lipid metabolism and thus significantly increased the cytotoxicity of PM₁ samples.（3）Changes in transmembrane efficiency and changes in the damaging effect on the cellular barrier before and after the interaction between PM₁ and PS.The determination of some characteristic elements in the lower ventricular fluid of the alveolar model by ICP-MS（ICP-OES）showed no significant difference in the content of some characteristic elements.According to the barrier permeation assay and tight junction protein expression assay it indicated that there might be a limited effect on the function of the cell barrier after the interaction between PM₁and PS.In summary,the interaction between PM₁and PS had little effect on the efficiency of PM₁across the cell monolayer.In this thesis,we collected PM₁ samples from Beijing and characterized their elemental content and morphological characteristics,measured the morphological changes of PM₁ samples before and after interaction with PS,and confirmed the interaction between PS and PM₁.we measured the toxicity of PM₁ samples after interaction with PS,and confirmed that the interaction between PS and PM₁ significantly increased the cytotoxicity of PM₁,and this increase in toxicity was most likely related to the accumulation of lipid metabolites such as TG.This increase in toxicity was probably related to the abnormal accumulation of lipid metabolites such as TG.By measuring the transmembrane efficiency before and after the interaction between PM₁ and PS,we found that PS had a limited effect on the transmembrane efficiency of PM₁ after the interaction with PM₁.