Expression of programmed cell death factor 4 in pulmonary fibrosis model

AIM:To detect the expression of programmed cell death protein 4 (PDCD4) in pulmonary fibrosis model and its effect on cell viability and pulmonary fibrosis indicators, and to explore its mechanism. METHODS:The expression level of PDCD4, α-smooth muscle actin (α-SMA) and collagen type I (COL-I) in human embryonic lung fibroblasts cell line HFL-1 group and HFL-1+TGF-β1 group were detected by Western blot and RT-qPCR. The plasmid pEZ-M03-PDCD4 and empty vector pEZ-M03 were transfected into myofibroblasts (MB), and the protein expression level of PDCD4 was detected by Western blot. The protein levels of p-AKT and AKT in blank control group, pEZ-M03-PDCD4 group, pEZ-M03 group and LY294002 group and the expression of cell cycle-related proteins c-Myc and cyclin D1 were determined by Western blot. The effect of PDCD4 on the viability of MB was measured by CCK-8 assay. The hydroxyproline content in the culture supernatant of HFL-1 cells and transfected MB was detected by hydroxyproline digestion method. The expression of PDCD4 in the lung tissues of the mice in model group and control group was detected by Western blot. RESULTS:Compared with HFL-1 group, the expression of α-SMA and COL-I at mRNA and protein levels in HFL-1+TGF-β1 group was significantly increased (P<0.01), the mRNA expression of PDCD4 was not significantly changed, while PDCD4 protein was significantly down-regulated (P<0.01). Compared with blank control group and pEZ-M03 group, the protein expression of PDCD4 in pEZ-M03-PDCD4 group was significantly increased (P<0.05), the protein expression of c-Myc and cyclin D1 was significantly decreased (P<0.05), the cell viability was also significantly inhibited (P<0.01), and the content of hydroxyproline in the culture supernatant was significantly reduced (P<0.05). Compared with blank control group, the protein levels of p-AKT were significantly decreased in pEZ-M03-PDCD4 group and LY294002 group, and no significant difference between blank control group and pEZ-M03 control group was observed. Compared with control group, PDCD4 expression was decreased in model group (P<0.01).CONCLUSION:PDCD4 is low expressed in the process of pulmonary fibrosis. Over-expression of PDCD4 inhibits the viability of MB, decreases the content of hydroxyproline, and inhibits the PI3K/AKT signaling pathway.