Human Serum-derived Extracellular Vesicles Protect A549 from PM 2.5-induced Cell Apoptosis.

OBJECTIVE: Epidemiological studies reveal that exposure to fine particulate matter (aerodynamic diameter ≤ 2.5 µm, PM 2.5) increases the morbidity and mortality of respiratory diseases. Emerging evidence suggests that human circulating extracellular vesicles (EVs) may offer protective effects against injury caused by particulate matter. Currently, however, whether EVs attenuate PM 2.5-induced A549 cell apoptosis is unknown. METHODS: EVs were isolated from the serum of healthy subjects, quantified via nanoparticle tracking analysis, and qualified by the marker protein CD63. PM 2.5-exposed (50 µg/mL) A549 cells were pre-treated with 10 µg/mL EVs for 24 h. Cell viability, cell apoptosis, and AKT activation were assessed via Cell Counting Kit-8, flow cytometry, and Western blot, respectively. A rescue experiment was also performed using MK2206, an AKT inhibitor. RESULTS: PM 2.5 exposure caused a 100% increase in cell apoptosis. EVs treatment reduced cell apoptosis by 10%, promoted cell survival, and inhibited the PM 2.5-induced upregulation of Bax/Bcl2 and cleaved caspase 3/caspase 3 in PM 2.5-exposed A549 cells. Moreover, EVs treatment reversed PM 2.5-induced reductions in p-AKT Thr308 and p-AKT Ser473. AKT inhibition attenuated the anti-apoptotic effect of EVs treatment on PM 2.5-exposed A549 cells. CONCLUSIONS: EVs treatment promotes cell survival and attenuates PM 2.5-induced cell apoptosis via AKT phosphorylation. Human serum-derived EVs may be an efficacious novel therapeutic strategy in PM 2.5-induced lung injury.

PM2.5 induces liver fibrosis via triggering ROS-mediated mitophagy.

BACKGROUND: The increasing epidemic of fine particulate matter (PM2.5) is a serious threat to human health. It induces the occurrence of liver fibrosis, but its molecular mechanism is not yet clear. The molecular mechanisms of PM2.5 inducing liver fibrosis were investigated in this study. METHODS: The cell viability of LX-2 cells and primary hepatic stellate cells (HSCs) was detected using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In vitro enzyme-linked immune sorbent assay (ELISA) kits were used to detect the concentrations of antioxidant enzymes and reactive oxygen species (ROS). The mitochondrial transmembrane potential (MTP) was determined by JC-1 dye. Knockdown of Parkin was carried out by Parkin-specific siRNA transfection. Relative mRNA and protein expressions were evaluated by qRT-PCR, Western blotting, and immunofluorescence analysis. RESULTS: PM2.5 activated LX-2 cells and primary HSCs, inducing the liver fibrosis along with down-regulation of the gelatinases MMP-2, and up-regulation of myofibroblast markers collagen type I and α-SMA. The levels of ROS and reactive nitrogen species (RNS), as well as the lipid peroxidation marker malondialdehyde (MDA) were significantly up-regulated in LX-2 cells and primary HSCs treated with PM2.5. Also, the enzymatic antioxidants levels were disturbed by PM2.5. Furthermore, PM2.5 decreased the MTP, releasing cytochrome c from the mitochondria to the cytosol. The dynamics of mitochondria were regulated by PM2.5 via facilitating mitochondrial fission. The excess ROS induced by PM2.5 triggered the mitophagy by activating PINK1/Parkin pathway, and inhibition of mitophagy induced by PM2.5 diminished the liver fibrosis. CONCLUSION: PM2.5 may induce mitophagy via activating PINK1/Parking signal pathway by increasing ROS, thereby activating HSCs and causing liver fibrosis.