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To investigate the damage of rat alveolar type II epithelial cells(RLE-6 TN) caused by air fine particulate matter(PM_(2.5)) and its related mechanism.PM_(2.5) in the atmosphere of Weifang City in 2020 was collected and cell culture medium was used to prepare particulate suspension. RLE-6 TN cells were exposed to different concentrations(25, 50, 100, 200, 400 μg/mL) of particulate matter suspensions for 24 h. The morphological changes of RLE-6 TN cells were observed under inverted microscope, and the cell viability was determined by MTT method. The concentration of lactate dehydrogenase(LDH) in cell supernatant was determined by microplate method. DCFH-DA, Annexin V-FITC/PI, JC-1 probe and laser confocal fluorescence intensity were used to determine the levels of reactive oxygen species(ROS), apoptosis and mitochondrial membrane potential. Total superoxide dismutase(T-SOD), glutathione(GSH) and malondialdehyde(MDA) contents and activity levels in cells were determined by colorimetric method. Caspase-3 and Caspase-9 kit were used to detect the relative expression activity of apoptosis proteins.PM_(2.5) could lead to morphological changes of RLE-6 TN cells, enlarged cell space and decreased cell viability. Compared with the control group, there were statistically significant differences in each dose group(Plt;0.05). LDH concentration in the supernatant of ≥50 μg/mL infected group increased, and LDH concentration was ≥(377.82±29.84), which was significantly different from that of the control group(278.51±23.76)(Plt;0.05). The result of laser confocal detection of ROS showed that the intracellular green fluorescence increased gradually in the ≥50 μg/mL group, and the relative fluorescence intensity was ≥(2.77±0.18), which was statistically significant compared with the control group(Plt;0.05). The level of apoptosis was significantly increased compared with the control group(Plt;0.05). The level of mitochondrial membrane potential decreased gradually, and the level of mitochondrial membrane potential in the ≥25 μg/mL group was ≤(4.22±0.45), which was statistically different from that in the control group(6.16±0.49)(Plt;0.05). PM_(2.5) could reduce the levels of T-SOD and GSH, and the levels of T-SOD and GSH in ≥50 μg/mL exposed group were ≤(14.67±0.49) and ≤(433.29±39.24), respectively, significantly lower than those in control group((16.58±0.60) and(542.90±45.06))(Plt;0.05). MDA level increased with the increase of PM_(2.5) concentration. Compared with the control group(1.15±0.19), MDA level in ≥50 μg/mL exposed group was ≥(1.72±0.13), with statistical significance(Plt;0.05). The activity levels of Caspase-3 and Caspase-9 increased in ≥100 μg/mL group, and the activity levels were ≥(1.62±0.27) and ≥(1.23±0.06), respectively, compared with the control group, the differences were statistically significant(Plt;0.05).Exposure to a certain concentration of PM_(2.5) can induce oxidative stress of rat alveolar type II epithelial cells, reduce the membrane potential, and eventually lead to cell apoptosis.

To investigate the protective effect of oleanolic acid(OA) on HgCl_2 induced liver injury.L02 cells were divided into four groups according to different treatment, control group(Con), oleanolic acid group(OA, 10 μmol/L), HgCl_2 group(HgCl_2, 40 μmol/L) and oleanolic acid + HgCl_2 group(OA + HgCl_2). Cells of control group were given serum-free medium, cells of OA group were pretreated with OA solution for 8 hours, cells of HgCl_2 group were exposed to HgCl_2 solution for 6 hours, cells of OA + HgCl_2 group were pretreated with OA solution for 8 hours, and then exposed to HgCl_2 solution for 6 hours. MTT assay was used to detect cell viability. Laser confocal scanning was used to detect JC-1 probe fluorescence intensity to determine mitochondrial membrane potential. DCFH-DA fluorescence probe combined with flow cytometry was used to detect reactive oxygen species(ROS) level. Annexin V/PI double staining method combined with flow cytometry was used to determine cell apoptosis rate. Catalase(CAT), total superoxide dismutase(T-SOD), glutathione(GSH), malondialdehyde(MDA), Caspase 3 and Caspase 9 kits combined with enzyme labeled instrument were used to determine their activity or content respectively.Compared with the control group, 40 μmol/L HgCl_2 could significantly reduce cell viability, the level was 0.52±0.03(Plt;0.05), OA pretreatment could significantly inhibit the decrease of cell viability induced by HgCl_2, the level was 0.86±0.05(Plt;0.05). The result of mitochondrial membrane potential detection showed that cell exposed to 40 μmol/L HgCl_2 significantly reduced the intensity of red fluorescence, and the ratio of red to green fluorescence was 0.23±0.02(Plt;0.05). OA pretreatment significantly increased red fluorescence, and the ratio of red fluorescence to green fluorescence was 1.32±0.08, which was significantly higher than that of HgCl_2(Plt;0.05). After exposure to 40 μmol/L HgCl_2, the relative fluorescence intensity of ROS was 1.21±0.07, the apoptosis rate was about 8%, the activity levels of Casepase 3 and Casepase 9 were 3.11±0.20 and 2.94±0.17, respectively, which were all significantly higher than those in the control group(Plt;0.05). OA pretreatment could significantly alleviate the changes of the above indexes, and the difference was statistically significant compared with HgCl_2 group(Plt;0.05). The level of T-SOD in HgCl_2 group was(7.68±0.39)U/mL, which was significantly lower than that in control group(Plt;0.05). Compared to the control group, the level of MDA was significantly increased to(4.99±0.26)nmol/mg(Plt;0.05). OA pretreatment significantly increased level of T-SOD and decreased the level of MDA, the levels were(13.97±0.71)U/mL and(3.01±0.17)nmol/mg, respectively(Plt;0.05).A certain concentration of HgCl_2 can induce hepatocyte damage. OA pretreatment may reduce cell damage by improving oxidative stress.

PM2.5 is a harmful air pollutant currently threatening public health. It has been closely linked to increased morbidity of bronchial asthma and lung cancer worldwide. Salidroside (Sal), an active component extracted from Rhodiola rosea, has been reported to ameliorate the progression of asthma. However, there are few studies on the protective effect of salidroside on PM2.5-induced bronchial epithelial cell injury, and the related molecular mechanism is not clear. Here, we aimed to explore the protective effect and related mechanism of Sal on PM2.5 bronchial injury. We chose 50 μg/mL PM2.5 for 24 h as a PM2.5-induced cell damage model. After that BEAS-2B cells were pretreated with 40, 80, 160 µM Sal for 24 h and then exposed to 50 μg/mL PM2.5 for 24 h. We found that Sal pretreatment significantly inhibited the decrease of cell viability induced by PM2.5. Sal was effective in preventing PM2.5-induced apoptotic features, including Ca2+ overload, the cleavages of caspase 3, and the increases in levels of caspase 9 and Bcl-2-associated X protein (Bax), ultimately, Sal significantly inhibited PM2.5-induced apoptosis. Sal improved mitochondrial membrane potential, inhibited the release of cytochrome c from the mitochondria to cytoplasm. Sal alleviated ROS production, decreased the level of MDA, prevented the reduction of CAT, SOD and GSH-Px and increased the expression of NF-E2-related factor 2 (Nrf2), HO-1 and superoxide dismutase 1 (SOD1) in cells exposed to PM2.5. Furthermore, Sal improved the decrease of SIRT1 and PGC-1 α expression levels caused by PM2.5. In addition, inhibition of SIRT1 by EX527 (SIRT1 inhibitor) reversed the protective effects of Sal, including the decrease of ROS level, the increase of membrane potential level and the decrease of apoptosis level. Thus, Sal may be regarded as a potential drug to prevent PM2.5-induced apoptosis of bronchial epithelial cells and other diseases with similar pathological mechanisms.

Gestational exposure to PM

Air pollution is a serious environmental health problem closely related to the occurrence of central nervous system diseases. Exposure to particulate matter with an aerodynamic diameter less than or equal to 2.5 µm (PM2.5) during pregnancy may affect the growth and development of infants. The present study was to investigate the effects of maternal exposure to PM2.5 during pregnancy on brain development in mice offspring. Pregnant mice were randomly divided into experimental groups of low-, medium-, or high-dosages of PM2.5, a mock-treated group which was treated with the same amount of phosphate buffer solution (PBS), and acontrol group which was untreated. The ethology of offspring mice on postnatal days 1, 7, 14, 21, and 30, along with neuronal development and apoptosis in the cerebral cortex were investigated. Compared with the control, neuronal mitochondrial cristae fracture, changed autophagy characteristics, significantly increased terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive cell rate, and mRNA levels of apoptosis-related caspase-8 and caspase-9 were found in cerebral cortex of mice offspring from the treatment groups, with mRNA levels of Bcl-2 and ratio of Bcl-2 to Bax decreased. Treatment groups also demonstrated enhanced protein expressions of apoptosis-related cleaved caspase-3, cleaved caspase-8 and cleaved caspase-9, along with declined proliferating cell nuclear antigen (PCNA), Bcl-2, and ratio of Bcl-2 to Bax. Open field experiments and tail suspension experiments showed that exposure to high dosage of PM2.5 resulted in decreased spontaneous activities but increased static accumulation time in mice offspring, indicating anxiety, depression, and social behavioral changes. Our results suggested that maternal exposure to PM2.5 during pregnancy might interfere with cerebral cortex development in mice offspring by affecting cell apoptosis.

Air pollution is a serious environmental health problem closely related to the occurrence of central nervous system diseases. Exposure to particulate matter with an aerodynamic diameter less than or equal to 2.5 µm (PM2.5) during pregnancy may affect the growth and development of infants. The present study was to investigate the effects of maternal exposure to PM2.5 during pregnancy on brain development in mice offspring. Pregnant mice were randomly divided into experimental groups of low-, medium-, or high-dosages of PM2.5, a mock-treated group which was treated with the same amount of phosphate buffer solution (PBS), and acontrol group which was untreated. The ethology of offspring mice on postnatal days 1, 7, 14, 21, and 30, along with neuronal development and apoptosis in the cerebral cortex were investigated. Compared with the control, neuronal mitochondrial cristae fracture, changed autophagy characteristics, significantly increased terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive cell rate, and mRNA levels of apoptosis-related caspase-8 and caspase-9 were found in cerebral cortex of mice offspring from the treatment groups, with mRNA levels of Bcl-2 and ratio of Bcl-2 to Bax decreased. Treatment groups also demonstrated enhanced protein expressions of apoptosis-related cleaved caspase-3, cleaved caspase-8 and cleaved caspase-9, along with declined proliferating cell nuclear antigen (PCNA), Bcl-2, and ratio of Bcl-2 to Bax. Open field experiments and tail suspension experiments showed that exposure to high dosage of PM2.5 resulted in decreased spontaneous activities but increased static accumulation time in mice offspring, indicating anxiety, depression, and social behavioral changes. Our results suggested that maternal exposure to PM2.5 during pregnancy might interfere with cerebral cortex development in mice offspring by affecting cell apoptosis.