Tumor cells expression of programmed death ligand-1 (PD-L1) is a major mechanism of immune escape and a predictor of therapeutic efficacy of immune checkpoint inhibitors. The expression of PD-L1 is regulated by a variety of mechanisms, among which epigenetic modifications such as DNA methylation, histone modification and non-coding RNA can promote the occurrence, development and drug resistance of tumors by regulating the expression of PD-L1. To clarify its regulation mechanism can bring new ideas for clinical immunotherapy of tumors.

OBJECTIVETo explore the possible mechanism and protective effect of BMSCs (bone mesenchymal stem cells) carrying superoxide dismutase (SOD) gene on mice with paraquat-induced acute lung injury.

METHODSTo establish the cell line of BMSCs bringing SOD gene, lentiviral vector bringing SOD gene was built and co-cultured with BMSCs. A total of 100 BALB/c mice were randomly divided into five groups, namely Control group, poisoning group (PQ group) , BMSCs therapy group (BMSC group) , BMSCs-Cherry therapy group (BMSC-Cherry group) , BMSCs-SOD therapy group (BMSC-SOD group) . PQ poisoning model was produced by stomach lavaged once with 1 ml of 25 mg/kg PQ solution, and the equal volume of normal saline (NS) was given to Control group mice instead of PQ. The corresponding BMSCs therapy cell lines were delivered to mice through the tail vein of mice 4h after PQ treatment.Five mice of each group were sacrificed 3 d, 7 d, 14 d and 21 days after corresponding BMSCs therapy cell lines administration, and lung tissues of mice were taken to make sections for histological analysis. The serum levels of glutathione (GSH) , malondialdehyde (MDA) , SOD, and the levels of transforming growth factor-β (TGF-β) and tumor necrosis factor-α (TNF-α) in lung tissue were determined. The level of SOD was assayed by Westen-blot.

RESULTSCompared with Control group, the early (3 days) levels of SOD protein in lung tissue of PQ group obviously decreased, and the late (21 days) levels of SOD obviously increased, while in therapy groups, that was higher than that in PQ group, and the BMSCs-SOD group showed most obvious (all P<0.05) . Compared with Control group, the levels of plasma GSH and SOD of PQ group and each therapy group wae significantly lower than those in Control group, while in therapy groups, those were higher than those of PQ group, and the BMSCs-SOD group showed most obvious (all P<0.05) .Compared with Control group, the level of plasma MDA, TNF-α and TGF-β in PQ group and therapy groups were significantly higher, while in therapy groups, that was lower than that in PQ group, and the BMSCs-SOD group showed most obvious (all P<0.05) . Lung biopsy showed that, the degree of lung tissue damage in each therapy group obviously reduced.

CONCLUSIONSOD is the key factor of the removal of reactive oxygen species (ROS) in cells, that can obviously inhibit the oxidative stress damage and the apoptosis induced by PQ, thus significantly increasing alveolar epithelial cell ability to fight outside harmful environment.

Acute Lung Injury ; chemically induced ; therapy ; Animals ; Antioxidants ; metabolism ; Cell Line ; Glutathione ; blood ; Lung ; pathology ; Malondialdehyde ; blood ; Mesenchymal Stem Cell Transplantation ; Mice ; Mice, Inbred BALB C ; Oxidative Stress ; Paraquat ; poisoning ; Superoxide Dismutase ; blood ; genetics ; Transforming Growth Factor beta ; metabolism ; Tumor Necrosis Factor-alpha ; metabolism