Differences in cellular and molecular processes in exposure to PM2.5 and O3
Tingting Wu, Hao Liu, Rongrong Xu, Zhigang Li, Yongjie Wei
Abstract
• PM 2.5 infiltrates cells via endocytosis without causing damage to cell membranes. • O 3 induces lipid peroxidation at the cell surface. • PM 2.5 exposure increased the mitochondrial DNA copy number. • O 3 exposure decreased the mitochondrial DNA copy number. • PM 2.5 and O 3 damage the cell and mitochondria in different ways. Epidemiological and toxicological studies have shown that PM 2.5 and O 3 could pose significant risks to human health, such as an increased incidence of respiratory and cardiovascular diseases. Usually, the adverse health outcomes induced by PM 2.5 and O 3 exposure are similar. However, PM 2.5 and O 3 have distinct physical and chemical properties, with PM 2.5 being a solid–liquid mixture and O 3 being a strongly oxidizing gaseous pollutant. Therefore, we speculated that there are some differences in biological processes induced by PM 2.5 and O 3 exposure. In the present study, we investigated the differences induced by PM 2.5 and O 3 exposure from the perspective of cellular and molecular processes. Firstly, the pulmonary epithelial cells (BEAS-2B) were exposed to different concentrations of PM 2.5 or O 3 at different durations. Then, we chose experimental models with the concentrations and duration at which the cell survival rate was 50 % after exposure to PM 2.5 and O 3 , which were 100 μg/mL for 24 h for PM 2.5 , and 200 ppb for 4 h for O 3 . Our findings indicate that PM 2.5 infiltrates cells via endocytosis without causing significant damage to cell membranes, while O 3 induces lipid peroxidation at the cell surface. Moreover, the detection of mitochondrial function showed that the content of ATP was significantly reduced after exposure to both PM 2.5 and O 3 . However, we found a significant difference in mtDNA copy number. PM 2.5 exposure increased the mtDNA copy number by up-regulating the expression of fission genes ( Fis1 , Mff , Dnm1 ). O 3 exposure decreased it by up-regulating the expression of fusion gene ( Mfn1 , Mfn2 ) and down-regulating the expression of fission gene ( Fis1 , Dnm1 ). These results indicate that although both PM 2.5 and O 3 exposure induced almost exactly similar adverse health outcomes, significant differences do exist in cellular and molecular processes.