PM2.5-induced Lung Cellular Senescence And Lung Injury And The Underlying Mechanism

As an arising global threatening factor to public health,PM2.5(fine particulate matter,aerodynamic diameter≦2.5 μm)has proved to be one of the most harmful pollutants.Epidemiological investigations have demonstrated the correlation between PM2.5 and senescence-related chronic diseases such as respiratory diseases and nervous system diseases.Meanwhile,cellular senescence is one of the main performance factors resulting in lung inflammation and age-related diseases.The public’s health has been seriously affected in recent years by a variety of pollution and haze weather events that commonly occur throughout China and involve a wide range of locations,high intensity,and extended duration.However,the impacts of PM2.5 exposure in human beings and the specific mechanism of senescence induced by PM2.5 is unclear.This study investigated the effects of PM2.5 on lung cell senescence by mice,3D and 2D lung fibroblasts,and its mechanism.The PM2.5 samples were collected from Taiyuan City,Shanxi Province,a typical polluted city in China.The specific research results are as follows:1.PM2.5 exposure aggravated cellular senescence in 2D and 3D cultured fibroblasts and C57BL/6 mice.We explore the relationship between PM2.5 exposure and cellular senescence in 2D and 3D human lung fibroblasts and mice.In the study,mice were exposed to PM2.5 at different concentrations and the lung tissues of mice were sectioned after PM2.5 exposures and processed with β-Galactosidase and immunohistochemical staining.Results showed that PM2.5 exposure aggravated cellular senescence of mice lung cells,and the high-dose group was more serious.Immunohistochemical results showed that PM2.5 also caused lung inflammation,accompanied by fibrosis,and the toxic effects were related to the dose of PM2.5 exposure.Further study verified by 2D and 3D cultured cells,the results showed that the cellular senescence aggravated by PM2.5 was not only related with the dosage,but also related to the exposure duration.The above results mainly confirmed the senescence of lung cells caused by PM2.5 exposure in different levels(single cell,tissue,and individual),providing a new insight for the cytotoxicity detection of PM2.5 exposure.2.PM2.5 exposure induced senescence-related phenotypes in 2D and 3D cultured fibroblasts.We mainly focus on the changes in senescence-related phenotypes of 2D and 3D lung fibroblasts after PM2.5 exposure.The proliferation of cells decreased significantly under PM2.5 exposures,accompanied by G1 phase cell cycle arrest.Meanwhile,PM2.5 exposures caused serious DNA damage,including telomeric DNA damage.Through the morphological structure analysis of 3D cells after PM2.5 exposures,we found that PM2.5 exposure also interupt the growth of the 3D cell,and the structure was obviously damaged and collapsed with the increase of exposure time.These results proved that PM2.5 exposure caused the decrease of cell proliferation,the increase of cell genome instability,the disorder of cell cycle,which finally aggravated cellular senescence in vivo and in vitro.3.Study on the mechanism of cellular senescence aggravated by PM2.5Previous results have proved that PM2.5 exposure induced cellular senescence.In this study,we mainly explored the mechanism of cellular senescence caused by PM2.5.We found that PM2.5 exposure caused cGAS-STING pathway activation.After cGAS inhibition,the number of senescent cells caused by PM2.5 was decreased.The results confirmed that PM2.5 exposure aggravated cellular senescence in a cGAS dependent manner.Further exploration of cGAS activation,we found that PM2.5 caused a large amount of DNA damage on the micronuclei,and approximately 80%micronuclei accumulated cGAS,indicating that micronuclei was the trigger for cGAS activation.By labeling different kinds of lamina,we determined that the downregulation of lamin B1 led to the rupture of the nuclear membrane,which caused the loss of the integrity of the MN nuclear membrane,leading to recognization and gathering of cGAS in MN.In conclusion,we explored the potential toxicity of PM2.5 based on 2D,3D cultured fibroblasts and mice,and proved that PM2.5 caused cellular senescence.On the basis,we investigated the underlying mechanism of cellular senescence caused by PM2.5,revealed that PM2.5 induced-senescence was caused by cGAS activation through the formation and rupture of MN.These results provided experimental evidence for the necessity of air pollution management and health protection.